Development of a 3D Filling Model of Low-Pressure Die-Cast Aluminum Alloy Wheels

NASA Astrophysics Data System (ADS)

Duan, Jianglan; Maijer, Daan; Cockcroft, Steve; Reilly, Carl

2013-12-01

A two-phase computational fluid dynamics model of the low-pressure die-cast process for the production of A356 aluminum alloy wheels has been developed to predict the flow conditions during die filling. The filling model represents a 36-deg section of a production wheel, and was developed within the commercial finite-volume package, ANSYS CFX, assuming isothermal conditions. To fully understand the behavior of the free surface, a novel technique was developed to approximate the vent resistances as they impact on the development of a backpressure within the die cavity. The filling model was first validated against experimental data, and then was used to investigate the effects of venting conditions and pressure curves during die filling. It was found that vent resistance and vent location strongly affected die filling time, free surface topography, and air entrainment for a given pressure fill-curve. With regard to the pressure curve, the model revealed a strong relation between the pressure curve and the flow behavior in the hub, which is an area prone to defect formation.

Surface spectroscopy studies of the oxidation behavior of uranium

NASA Astrophysics Data System (ADS)

Bloch, J.; Atzmony, U.; Dariel, M. P.; Mintz, M. H.; Shamir, N.

1982-02-01

Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) techniques were utilized to study the oxidation behavior of clean uranium surfaces, at very low pressures of various atmospheres (UHV, H 2, O 2, and CO 2), at room temperature. Both for O 2 and CO 2, a precursor chemisorbed oxygen species has been identified at the very initial stage of the oxidation reaction. This chemisorbed oxygen transforms to the oxide form at a rate which depends on the pressure of the oxidizing atmosphere. Residual gaseous carbon compounds which are present even under UHV conditions result in the simultaneous formation of surface carbide which accompanies the initial stage of oxidation. This carbide however decomposes later as oxidation proceeds. Adventitious hydrocarbon adsorption occurs on the formed oxide layer.

Fluctuating pressures in flow fields of jets

NASA Technical Reports Server (NTRS)

Schroeder, J. C.; Haviland, J. K.

1976-01-01

The powered lift configurations under present development for STOL aircraft are the externally blown flap (EBF), involving direct jet impingement on the aircraft flaps, and the upper surface blown (USB), where the jet flow is attached on the upper surface of the wing and directed downwards. Towards the goal of developing scaling laws to predict unsteady loads imposed on the structural components of these STOL aircraft from small model tests, the near field fluctuating pressure behavior for the simplified cases of a round free cold jet and the same jet impinging on a flat plate was investigated. Examples are given of coherences, phase lags (giving convection velocities), and overall fluctuating pressure levels measured. The fluctuating pressure levels measured on the flat plate are compared to surface fluctuating pressure levels measured on full-scale powered-lift configuration models.

Effect of working pressure on corrosion behavior of nitrogen doped diamond-like carbon thin films deposited by DC magnetron sputtering.

PubMed

Khun, N W; Liu, E

2011-06-01

Nitrogen doped diamond-like carbon thin films were deposited on highly conductive p-silicon(100) substrates using a DC magnetron sputtering deposition system by varying working pressure in the deposition chamber. The bonding structure, adhesion strength, surface roughness and corrosion behavior of the films were investigated by using X-ray photoelectron spectroscopy, micro-Raman spectroscopy, micro-scratch test, atomic force microscopy and potentiodynamic polarization test. A 0.6 M NaCl electrolytic solution was used for the corrosion tests. The optimum corrosion resistance of the films was found at a working pressure of 7 mTorr at which a good balance between the kinetics of the sputtered ions and the surface mobility of the adatoms promoted a microstructure of the films with fewer porosities.

Hybrid surface design for robust superhydrophobicity.

PubMed

Dash, Susmita; Alt, Marie T; Garimella, Suresh V

2012-06-26

Surfaces may be rendered superhydrophobic by engineering the surface morphology to control the extent of the liquid-air interface and by the use of low-surface-energy coatings. The droplet state on a superhydrophobic surface under static and dynamic conditions may be explained in terms of the relative magnitudes of the wetting and antiwetting pressures acting at the liquid-air interface on the substrate. In this paper, we discuss the design and fabrication of hollow hybrid superhydrophobic surfaces which incorporate both communicating and noncommunicating air gaps. The surface design is analytically shown to exhibit higher capillary (or nonwetting) pressure compared to solid pillars with only communicating air gaps. Six hybrid surfaces are fabricated with different surface parameters selected such that the Cassie state of a droplet is energetically favorable. The robustness of the surfaces is tested under dynamic impingement conditions, and droplet dynamics are explained using pressure-based transitions between Cassie and Wenzel states. During droplet impingement, the effective water hammer pressure acting due to the sudden change in the velocity of the droplet is determined experimentally and is found to be at least 2 orders of magnitude less than values reported in the literature. The experiments show that the water hammer pressure depends on the surface morphology and capillary pressure of the surface. We propose that the observed reduction in shock pressure may be attributed to the presence of air gaps in the substrate. This feature allows liquid deformation and hence avoids the sudden stoppage of the droplet motion as opposed to droplet behavior on smooth surfaces.

Study of the air-water interfacial properties of biodegradable polyesters and their block copolymers with poly(ethylene glycol).

PubMed

Park, Hae-Woong; Choi, Je; Ohn, Kimberly; Lee, Hyunsuk; Kim, Jin Woong; Won, You-Yeon

2012-08-07

It has been reported that the surface pressure-area isotherm of poly(D,L-lactic acid-ran-glycolic acid) (PLGA) at the air-water interface exhibits several interesting features: (1) a plateau at intermediate compression levels, (2) a sharp rise in surface pressure upon further compression, and (3) marked surface pressure-area hysteresis during compression-expansion cycles. To investigate the molecular origin of this behavior, we conducted an extensive set of surface pressure and AFM imaging measurements with PLGA materials having several different molecular weights and also a poly(D,L-lactic acid-ran-glycolic acid-ran-caprolactone) (PLGACL) material in which the caprolactone monomers were incorporated as a plasticizing component. The results suggest that (i) the plateau in the surface pressure-area isotherm of PLGA (or PLGACL) occurs because of the formation (and collapse) of a continuous monolayer of the polymer under continuous compression; (ii) the PLGA monolayer becomes significantly resistant to compression at high compression because under that condition the collapsed domains become large enough to become glassy (such behavior was not observed in the nonglassy PLGACL sample); and (iii) the isotherm hysteresis is due to a coarsening of the collapsed domains that occurs under high-compression conditions. We also investigated the monolayer properties of PEG-PLGA and PEG-PLGACL diblock copolymers. The results demonstrate that the tendency of PLGA (or PLGACL) to spread on water allows the polymer to be used as an anchoring block to form a smooth biodegradable monolayer of block copolymers at the air-water interface. These diblock copolymer monolayers exhibit protein resistance.

Flight testing of a luminescent surface pressure sensor

NASA Technical Reports Server (NTRS)

Mclachlan, B. G.; Bell, J. H.; Espina, J.; Gallery, J.; Gouterman, M.; Demandante, C. G. N.; Bjarke, L.

1992-01-01

NASA ARC has conducted flight tests of a new type of aerodynamic pressure sensor based on a luminescent surface coating. Flights were conducted at the NASA ARC-Dryden Flight Research Facility. The luminescent pressure sensor is based on a surface coating which, when illuminated with ultraviolet light, emits visible light with an intensity dependent on the local air pressure on the surface. This technique makes it possible to obtain pressure data over the entire surface of an aircraft, as opposed to conventional instrumentation, which can only make measurements at pre-selected points. The objective of the flight tests was to evaluate the effectiveness and practicality of a luminescent pressure sensor in the actual flight environment. A luminescent pressure sensor was installed on a fin, the Flight Test Fixture (FTF), that is attached to the underside of an F-104 aircraft. The response of one particular surface coating was evaluated at low supersonic Mach numbers (M = 1.0-1.6) in order to provide an initial estimate of the sensor's capabilities. This memo describes the test approach, the techniques used, and the pressure sensor's behavior under flight conditions. A direct comparison between data provided by the luminescent pressure sensor and that produced by conventional pressure instrumentation shows that the luminescent sensor can provide quantitative data under flight conditions. However, the test results also show that the sensor has a number of limitations which must be addressed if this technique is to prove useful in the flight environment.

Preliminary Investigation of Cyclic Behavior at SHADOZ Sites Between the Equator and 5 deg S Latitude

NASA Technical Reports Server (NTRS)

Schmidlin, F. J.

2009-01-01

Investigation of cyclic behavior of temperature and ozone data from five SHADOZ sites between the Equator and 5degS Latitude (Nairobi, Ascension Island, Natal, San Crystobal, and Watukoset) reveal an amazing array of oscillations. In particular, eight years of measurements (1998-2007) reveal changes such as decreasing amounts of ozone at some pressure levels and/or sites, while other levels and/or sites experience increasing ozone. Temperature changes of 1-2 C occur that also experience irregular oscillations. This study is preliminary and only concentrates on the 250-, 200-, 100-, 70-, and 50-hPa pressure surfaces. Surfaces existing below and above the tropopause behave differently.

Understanding the Hydromechanical Behavior of a Fault Zone From Transient Surface Tilt and Fluid Pressure Observations at Hourly Time Scales

NASA Astrophysics Data System (ADS)

Schuite, Jonathan; Longuevergne, Laurent; Bour, Olivier; Burbey, Thomas J.; Boudin, Frédérick; Lavenant, Nicolas; Davy, Philippe

2017-12-01

Flow through reservoirs such as fractured media is powered by head gradients which also generate measurable poroelastic deformation of the rock body. The combined analysis of surface deformation and subsurface pressure provides valuable insights of a reservoir's structure and hydromechanical properties, which are of interest for deep-seated CO2 or nuclear waste storage for instance. Among all surveying tools, surface tiltmeters offer the possibility to grasp hydraulically induced deformations over a broad range of time scales with a remarkable precision. Here we investigate the information content of transient surface tilt generated by the pressurization a kilometer scale subvertical fault zone. Our approach involves the combination of field data and results of a fully coupled poromechanical model. The signature of pressure changes in the fault zone due to pumping cycles is clearly recognizable in field tilt data and we aim to explain the peculiar features that appear in (1) tilt time series alone from a set of four instruments and 2) the ratio of tilt over pressure. We evidence that the shape of tilt measurements on both sides of a fault zone is sensitive to its diffusivity and its elastic modulus. The ratio of tilt over pressure predominantly encompasses information about the system's dynamic behavior and extent of the fault zone and allows separating contributions of flow in the different compartments. Hence, tiltmeters are well suited to characterize hydromechanical processes associated with fault zone hydrogeology at short time scales, where spaceborne surveying methods fail to recognize any deformation signal.

Lipid and Lipid-Polymer Mixtures at an Interface

NASA Astrophysics Data System (ADS)

Kim, Joon Heon; Kim, Mahn Won

2000-03-01

The surface pressure (Π) and surface area/molecule (A) isotherms of a mixture of DMPC (DL-α-phosphatidylcholine,Dimyristoyl) and PEG-DMPE (1,2-Diacyl-sn-Glycero-3-Phosphoethanolamine-N-[Poly(ethylene glycol)5000]) system were measured at various compositions by the Langmuir surface balance technique at an air/water interface. In the range where the surface pressure is less than about 8 dynes/cm, a PEG polymer chain of PEG-DMPE molecules remains on the surface and the isotherm can be explained by the 2-D power law behavior of chains in a good solvent. In the range above 8 dynes/cm, a part of the PEG polymer segment is dissolved into the water phase, and the surface pressure can be explained as the sum of the 2-D component and 3-D component. Furthermore, the mixing energy is negative, which indicates an attractive interaction between DMPC and PEG-DMPE.

Lipid and lipid-polymer mixtures at an interface

NASA Astrophysics Data System (ADS)

Kim, Joon Heon; Kim, Mahn Won

2000-06-01

The surface pressure (Π) and surface area/molecule (A) isotherms of a mixture of DMPC (DL-α-phosphatidylcholine, Dimyristoyl) and PEG-DMPE (1,2-Diacyl-sn-Glycero-3-Phosphoethanolamine-N-[Poly(ethylene glycol)5000]) system were measured at various compositions by the Langmuir surface balance technique at an air/water interface. In the range where the surface pressure is less than about 8 dynes/cm, a PEG polymer chain of PEG-DMPE molecules remains on the surface and the isotherm can be explained by the 2-D power law behavior of chains in a good solvent. In the range above 8 dynes/cm, a part of the PEG polymer segment is dissolved into the water phase, and the surface pressure can be explained as the sum of the 2-D component and 3-D component. Furthermore, the mixing energy is negative, which indicates an attractive interaction between DMPC and PEG-DMPE. .

Unsteady surface pressure measurements on a slender delta wing undergoing limit cycle wing rock

NASA Technical Reports Server (NTRS)

Arena, Andrew S., Jr.; Nelson, Robert C.

1991-01-01

An experimental investigation of slender wing limit cycle motion known as wing rock was investigated using two unique experimental systems. Dynamic roll moment measurements and visualization data on the leading edge vortices were obtained using a free to roll apparatus that incorporates an airbearing spindle. In addition, both static and unsteady surface pressure data was measured on the top and bottom surfaces of the model. To obtain the unsteady surface pressure data a new computer controller drive system was developed to accurately reproduce the free to roll time history motions. The data from these experiments include, roll angle time histories, vortex trajectory data on the position of the vortices relative to the model's surface, and surface pressure measurements as a function of roll angle when the model is stationary or undergoing a wing rock motion. The roll time history data was numerically differentiated to determine the dynamic roll moment coefficient. An analysis of these data revealed that the primary mechanism for the limit cycle behavior was a time lag in the position of the vortices normal to the wing surface.

Modeling of wave-coherent pressures in the turbulent boundary layer above water waves

NASA Technical Reports Server (NTRS)

Papadimitrakis, Yiannis ALEX.

1988-01-01

The behavior of air pressure fluctuations induced by progressive water waves generated mechanically in a laboratory tank was simulated by solving a modified Orr-Sommerfeld equation in a transformed Eulerian wave-following frame of reference. Solution is obtained by modeling the mean and wave-coherent turbulent Reynolds stresses, the behavior of which in the turbulent boundary layer above the waves was simulated using a turbulent kinetic energy-dissipation model, properly modified to account for free-surface proximity and favorable pressure gradient effects. The distribution of both the wave-coherent turbulent Reynolds stress and pressure amplitudes and their corresponding phase lags was found to agree reasonably well with available laboratory data.

Impact of air and water vapor environments on the hydrophobicity of surfaces.

PubMed

Weisensee, Patricia B; Neelakantan, Nitin K; Suslick, Kenneth S; Jacobi, Anthony M; King, William P

2015-09-01

Droplet wettability and mobility play an important role in dropwise condensation heat transfer. Heat exchangers and heat pipes operate at liquid-vapor saturation. We hypothesize that the wetting behavior of liquid water on microstructures surrounded by pure water vapor differs from that for water droplets in air. The static and dynamic contact angles and contact angle hysteresis of water droplets were measured in air and pure water vapor environments inside a pressure vessel. Pressures ranged from 60 to 1000 mbar, with corresponding saturation temperatures between 36 and 100°C. The wetting behavior was studied on four hydrophobic surfaces: flat Teflon-coated, micropillars, micro-scale meshes, and nanoparticle-coated with hierarchical micro- and nanoscale roughness. Static advancing contact angles are 9° lower in the water vapor environment than in air on a flat surface. One explanation for this reduction in contact angles is water vapor adsorption to the Teflon. On microstructured surfaces, the vapor environment has little effect on the static contact angles. In all cases, variations in pressure and temperature do not influence the wettability and mobility of the water droplets. In most cases, advancing contact angles increase and contact angle hysteresis decreases when the droplets are sliding or rolling down an inclined surface. Copyright © 2015 Elsevier Inc. All rights reserved.

Interfacial layers from the protein HFBII hydrophobin: dynamic surface tension, dilatational elasticity and relaxation times.

PubMed

Alexandrov, Nikola A; Marinova, Krastanka G; Gurkov, Theodor D; Danov, Krassimir D; Kralchevsky, Peter A; Stoyanov, Simeon D; Blijdenstein, Theodorus B J; Arnaudov, Luben N; Pelan, Eddie G; Lips, Alex

2012-06-15

The pendant-drop method (with drop-shape analysis) and Langmuir trough are applied to investigate the characteristic relaxation times and elasticity of interfacial layers from the protein HFBII hydrophobin. Such layers undergo a transition from fluid to elastic solid films. The transition is detected as an increase in the error of the fit of the pendant-drop profile by means of the Laplace equation of capillarity. The relaxation of surface tension after interfacial expansion follows an exponential-decay law, which indicates adsorption kinetics under barrier control. The experimental data for the relaxation time suggest that the adsorption rate is determined by the balance of two opposing factors: (i) the barrier to detachment of protein molecules from bulk aggregates and (ii) the attraction of the detached molecules by the adsorption layer due to the hydrophobic surface force. The hydrophobic attraction can explain why a greater surface coverage leads to a faster adsorption. The relaxation of surface tension after interfacial compression follows a different, square-root law. Such behavior can be attributed to surface diffusion of adsorbed protein molecules that are condensing at the periphery of interfacial protein aggregates. The surface dilatational elasticity, E, is determined in experiments on quick expansion or compression of the interfacial protein layers. At lower surface pressures (<11 mN/m) the experiments on expansion, compression and oscillations give close values of E that are increasing with the rise of surface pressure. At higher surface pressures, E exhibits the opposite tendency and the data are scattered. The latter behavior can be explained with a two-dimensional condensation of adsorbed protein molecules at the higher surface pressures. The results could be important for the understanding and control of dynamic processes in foams and emulsions stabilized by hydrophobins, as well as for the modification of solid surfaces by adsorption of such proteins. Copyright © 2012 Elsevier Inc. All rights reserved.

Composite Behavior of Insulated Concrete Sandwich Wall Panels Subjected to Wind Pressure and Suction.

PubMed

Choi, Insub; Kim, JunHee; Kim, Ho-Ryong

2015-03-19

A full-scale experimental test was conducted to analyze the composite behavior of insulated concrete sandwich wall panels (ICSWPs) subjected to wind pressure and suction. The experimental program was composed of three groups of ICSWP specimens, each with a different type of insulation and number of glass-fiber-reinforced polymer (GFRP) shear grids. The degree of composite action of each specimen was analyzed according to the load direction, type of the insulation, and number of GFRP shear grids by comparing the theoretical and experimental values. The failure modes of the ICSWPs were compared to investigate the effect of bonds according to the load direction and type of insulation. Bonds based on insulation absorptiveness were effective to result in the composite behavior of ICSWP under positive loading tests only, while bonds based on insulation surface roughness were effective under both positive and negative loading tests. Therefore, the composite behavior based on surface roughness can be applied to the calculation of the design strength of ICSWPs with continuous GFRP shear connectors.

Influence of Oxidation Treatments and Surface Finishing on the Electrochemical Behavior of Ni-20Cr HVOF Coatings

NASA Astrophysics Data System (ADS)

Ruiz-Luna, H.; Porcayo-Calderon, J.; Alvarado-Orozco, J. M.; Mora-García, A. G.; Martinez-Gomez, L.; Trápaga-Martínez, L. G.; Muñoz-Saldaña, J.

2017-12-01

The low-temperature electrochemical behavior of HVOF Ni-20Cr coatings was assessed. The coatings were evaluated in different conditions including as-sprayed, as-ground, and heat-treated in air and argon atmospheres. A detailed analysis of the coatings was carried out by means of XRD, SEM, and EPMA, prior and after the corrosion test. The corrosion rate was analyzed in a NaCl solution saturated with CO2. Results demonstrate that the use of a low-oxygen partial pressure favors the formation of a Cr2O3 layer on the surface of the coatings. According to the electrochemical results, the lower corrosion rates were obtained for the heat-treated coatings irrespective of the surface finishing, being the ground and argon heat-treated condition that shows the best corrosion performance. This behavior is due to the synergistic effect of the low-pressure heat treatment and the grinding processes. The grinding promotes a more homogeneous reaction area without surface heterogeneities such as voids, and the pre-oxidation treatment decreases the porosity content of the coating and also allows the growing of a Cr-rich oxide scale which acts as a barrier against the ions of the aqueous solution.

Application of sound and temperature to control boundary-layer transition

NASA Technical Reports Server (NTRS)

Maestrello, Lucio; Parikh, Paresh; Bayliss, A.; Huang, L. S.; Bryant, T. D.

1987-01-01

The growth and decay of a wave packet convecting in a boundary layer over a concave-convex surface and its active control by localized surface heating are studied numerically using direct computations of the Navier-Stokes equations. The resulting sound radiations are computed using linearized Euler equations with the pressure from the Navier-Stokes solution as a time-dependent boundary condition. It is shown that on the concave portion the amplitude of the wave packet increases and its bandwidth broadens while on the convex portion some of the components in the packet are stabilized. The pressure field decays exponentially away from the surface and then algebraically, exhibiting a decay characteristic of acoustic waves in two dimensions. The far-field acoustic behavior exhibits a super-directivity type of behavior with a beaming downstream. Active control by surface heating is shown to reduce the growth of the wave packet but have little effect on acoustic far field behavior for the cases considered. Active control by sound emanating from the surface of an airfoil in the vicinity of the leading edge is experimentally investigated. The purpose is to control the separated region at high angles of attack. The results show that injection of sound at shedding frequency of the flow is effective in an increase of lift and reduction of drag.

Three-dimensional multi-physics coupled simulation of ignition transient in a dual pulse solid rocket motor

NASA Astrophysics Data System (ADS)

Li, Yingkun; Chen, Xiong; Xu, Jinsheng; Zhou, Changsheng; Musa, Omer

2018-05-01

In this paper, numerical investigation of ignition transient in a dual pulse solid rocket motor has been conducted. An in-house code has been developed in order to solve multi-physics governing equations, including unsteady compressible flow, heat conduction and structural dynamic. The simplified numerical models for solid propellant ignition and combustion have been added. The conventional serial staggered algorithm is adopted to simulate the fluid structure interaction problems in a loosely-coupled manner. The accuracy of the coupling procedure is validated by the behavior of a cantilever panel subjected to a shock wave. Then, the detailed flow field development, flame propagation characteristics, pressure evolution in the combustion chamber, and the structural response of metal diaphragm are analyzed carefully. The burst-time and burst-pressure of the metal diaphragm are also obtained. The individual effects of the igniter's mass flow rate, metal diaphragm thickness and diameter on the ignition transient have been systemically compared. The numerical results show that the evolution of the flow field in the combustion chamber, the temperature distribution on the propellant surface and the pressure loading on the metal diaphragm surface present a strong three-dimensional behavior during the initial ignition stage. The rupture of metal diaphragm is not only related to the magnitude of pressure loading on the diaphragm surface, but also to the history of pressure loading. The metal diaphragm thickness and diameter have a significant effect on the burst-time and burst-pressure of metal diaphragm.

An experimental evaluation of the application of the Kirchhoff formulation for sound radiation from an oscillating airfoil

NASA Technical Reports Server (NTRS)

Brooks, T. F.

1977-01-01

The Kirchhoff integral formulation is evaluated for its effectiveness in quantitatively predicting the sound radiated from an oscillating airfoil whose chord length is comparable with the acoustic wavelength. A rigid airfoil section was oscillated at samll amplitude in a medium at rest to produce the sound field. Simultaneous amplitude and phase measurements were made of surface pressure and surface velocity distributions and the acoustic free field. Measured surface pressure and motion are used in applying the theory, and airfoil thickness and contour are taken into account. The result was that the theory overpredicted the sound pressure level by 2 to 5, depending on direction. Differences are also noted in the sound field phase behavior.

Intermittent Behavior of the Separated Boundary Layer along the Suction Surface of a Low Pressure Turbine Blade under Periodic Unsteady Flow Conditions

NASA Technical Reports Server (NTRS)

Oeztuerk, B; Schobeiri, M. T.; Ashpis, David E.

2005-01-01

The paper experimentally and theoretically studies the effects of periodic unsteady wake flow and aerodynamic characteristics on boundary layer development, separation and re-attachment along the suction surface of a low pressure turbine blade. The experiments were carried out at Reynolds number of 110,000 (based on suction surface length and exit velocity). For one steady and two different unsteady inlet flow conditions with the corresponding passing frequencies, intermittency behaviors were experimentally and theoretically investigated. The current investigation attempts to extend the intermittency unsteady boundary layer transition model developed in previously to the LPT cases, where separation occurs on the suction surface at a low Reynolds number. The results of the unsteady boundary layer measurements and the intermittency analysis were presented in the ensemble-averaged and contour plot forms. The analysis of the boundary layer experimental data with the flow separation, confirms the universal character of the relative intermittency function which is described by a Gausssian function.

Pressure driven currents near magnetic islands in 3D MHD equilibria: Effects of pressure variation within flux surfaces and of symmetry

NASA Astrophysics Data System (ADS)

Reiman, Allan H.

2016-07-01

In toroidal, magnetically confined plasmas, the heat and particle transport is strongly anisotropic, with transport along the field lines sufficiently strong relative to cross-field transport that the equilibrium pressure can generally be regarded as constant on the flux surfaces in much of the plasma. The regions near small magnetic islands, and those near the X-lines of larger islands, are exceptions, having a significant variation of the pressure within the flux surfaces. It is shown here that the variation of the equilibrium pressure within the flux surfaces in those regions has significant consequences for the pressure driven currents. It is further shown that the consequences are strongly affected by the symmetry of the magnetic field if the field is invariant under combined reflection in the poloidal and toroidal angles. (This symmetry property is called "stellarator symmetry.") In non-stellarator-symmetric equilibria, the pressure-driven currents have logarithmic singularities at the X-lines. In stellarator-symmetric MHD equilibria, the singular components of the pressure-driven currents vanish. These equilibria are to be contrasted with equilibria having B ṡ∇p =0 , where the singular components of the pressure-driven currents vanish regardless of the symmetry. They are also to be contrasted with 3D MHD equilibrium solutions that are constrained to have simply nested flux surfaces, where the pressure-driven current goes like 1 /x near rational surfaces, where x is the distance from the rational surface, except in the case of quasi-symmetric flux surfaces. For the purpose of calculating the pressure-driven currents near magnetic islands, we work with a closed subset of the MHD equilibrium equations that involves only perpendicular force balance, and is decoupled from parallel force balance. It is not correct to use the parallel component of the conventional MHD force balance equation, B ṡ∇p =0 , near magnetic islands. Small but nonzero values of B ṡ∇p are important in this region, and small non-MHD contributions to the parallel force balance equation cannot be neglected there. Two approaches are pursued to solve our equations for the pressure driven currents. First, the equilibrium equations are applied to an analytically tractable magnetic field with an island, obtaining explicit expressions for the rotational transform and magnetic coordinates, and for the pressure-driven current and its limiting behavior near the X-line. The second approach utilizes an expansion about the X-line to provide a more general calculation of the pressure-driven current near an X-line and of the rotational transform near a separatrix. The study presented in this paper is motivated, in part, by tokamak experiments with nonaxisymmetric magnetic perturbations, where significant differences are observed between the behavior of stellarator-symmetric and non-stellarator-symmetric configurations with regard to stabilization of edge localized modes by resonant magnetic perturbations. Implications for the coupling between neoclassical tearing modes, and for magnetic island stability calculations, are also discussed.

Deformation of volcanic materials by pore pressurization: analog experiments with simplified geometry

NASA Astrophysics Data System (ADS)

Hyman, David; Bursik, Marcus

2018-03-01

The pressurization of pore fluids plays a significant role in deforming volcanic materials; however, understanding of this process remains incomplete, especially scenarios accompanying phreatic eruptions. Analog experiments presented here use a simple geometry to study the mechanics of this type of deformation. Syrup was injected into the base of a sand medium, simulating the permeable flow of fluids through shallow volcanic systems. The experiments examined surface deformation over many source depths and pressures. Surface deformation was recorded using a Microsoft® Kinect™ sensor, generating high-spatiotemporal resolution lab-scale digital elevation models (DEMs). The behavior of the system is controlled by the ratio of pore pressure to lithostatic loading (λ =p/ρ g D). For λ <10, deformation was accommodated by high-angle, reversed-mechanism shearing along which fluid preferentially flowed, leading to a continuous feedback between deformation and pressurization wherein higher pressure ratios yielded larger deformations. For λ >10, fluid expulsion from the layer was much faster, vertically fracturing to the surface with larger pressure ratios yielding less deformation. The temporal behavior of deformation followed a characteristic evolution that produced an approximately exponential increase in deformation with time until complete layer penetration. This process is distinguished from magmatic sources in continuous geodetic data by its rapidity and characteristic time evolution. The time evolution of the experiments compares well with tilt records from Mt. Ontake, Japan, in the lead-up to the deadly 2014 phreatic eruption. Improved understanding of this process may guide the evolution of magmatic intrusions such as dikes, cone sheets, and cryptodomes and contribute to caldera resurgence or deformation that destabilizes volcanic flanks.

Roles of additives and surface control in slurry atomization

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

Tsai, S.C.

1990-01-01

This report focuses on the effects of interparticle forces on the rheology and airblast atomization of micronized coal water slurry (CWS). We found that the CWS flow behavior index is determined by the relative importance of the interparticle van der Waals attraction and the interparticle electrostatic repulsion. The former intensifies as the Hamaker constant increases and the interparticle distance reduces while the latter increases as the particle surface charge density increases. The interparticle attraction causes particle aggregation, which breaks down at high shear rates, and thus leads to slurry pseudoplastic behavior. In contrast, the interparticle repulsion prevents particle aggregation andmore » thus leads to Newtonian behavior. Both atomized at low atomizing air pressures (less than 270 kPa) using twin-fluid jet atomizers of various distributor designs. We found that the atomized drop sizes of micronized coal water slurries substantially decrease as the atomizing air pressure exceeds a threshold value. The effects of coal volume fraction, coal particle surface charge, liquid composition and liquid viscosity on slurry atomization can be accounted for by their effects on slurry rheology. 26 refs.« less

Novel cavitation fluid jet polishing process based on negative pressure effects.

PubMed

Chen, Fengjun; Wang, Hui; Tang, Yu; Yin, Shaohui; Huang, Shuai; Zhang, Guanghua

2018-04-01

Traditional abrasive fluid jet polishing (FJP) is limited by its high-pressure equipment, unstable material removal rate, and applicability to ultra-smooth surfaces because of the evident air turbulence, fluid expansion, and a large polishing spot in high-pressure FJP. This paper presents a novel cavitation fluid jet polishing (CFJP) method and process based on FJP technology. It can implement high-efficiency polishing on small-scale surfaces in a low-pressure environment. CFJP uses the purposely designed polishing equipment with a sealed chamber, which can generate a cavitation effect in negative pressure environment. Moreover, the collapse of cavitation bubbles can spray out a high-energy microjet and shock wave to enhance the material removal. Its feasibility is verified through researching the flow behavior and the cavitation results of the negative pressure cavitation machining of pure water in reversing suction flow. The mechanism is analyzed through a computational fluid dynamics simulation. Thus, its cavitation and surface removal mechanisms in the vertical CFJP and inclined CFJP are studied. A series of polishing experiments on different materials and polishing parameters are conducted to validate its polishing performance compared with FJP. The maximum removal depth increases, and surface roughness gradually decreases with increasing negative outlet pressures. The surface becomes smooth with the increase of polishing time. The experimental results confirm that the CFJP process can realize a high material removal rate and smooth surface with low energy consumption in the low-pressure environment, together with compatible surface roughness to FJP. Copyright © 2017 Elsevier B.V. All rights reserved.

Lateral Diffusion in a DMPC:DMPE-EO Binary Monolayer at the Air/Water Interface

NASA Astrophysics Data System (ADS)

Adalsteinsson, Thorsteinn; Porter, Ryan; Yu, Hyuk

2002-03-01

Polyethylene glycol tethered phospholipids (lipo-polymers) have recently attracted attention for improving the stability of liposomes and other bilayer delivery systems. Here, we report a study of surface pressure measurement and diffusion measurements of a probe lipid (NBD-DMPC) in a binary monolayer of DMPC and DMPE-EO at the Air/Water interface. Our findings are that the DMPE-EO lipo-polymer desorbs from the interface at intermediate surface pressures if the EO tail is sufficiently large (i.e. EO_45) and does not interfere with the diffusion of the probe thereafter. In the case where the EO tail is short (i.e. EO_17) the lipo-polymer retards the diffusion of the probe, but as the surface pressure increases, the diffusion behavior approaches that of pure DMPC monolayer independent of lipo-polymer. Thus, we conclude that the surface pressure and EO molar mass dependent desorption of the lipo-polymer modulates the probe diffusion retardation.

Wavelet analysis of hemispheroid flow separation toward understanding human vocal fold pathologies

NASA Astrophysics Data System (ADS)

Plesniak, Daniel H.; Carr, Ian A.; Bulusu, Kartik V.; Plesniak, Michael W.

2014-11-01

Physiological flows observed in human vocal fold pathologies, such as polyps and nodules, can be modeled by flow over a wall-mounted protuberance. The experimental investigation of flow separation over a surface-mounted hemispheroid was performed using particle image velocimetry (PIV) and measurements of surface pressure in a low-speed wind tunnel. This study builds on the hypothesis that the signatures of vortical structures associated with flow separation are imprinted on the surface pressure distributions. Wavelet decomposition methods in one- and two-dimensions were utilized to elucidate the flow behavior. First, a complex Gaussian wavelet was used for the reconstruction of surface pressure time series from static pressure measurements acquired from ports upstream, downstream, and on the surface of the hemispheroid. This was followed by the application of a novel continuous wavelet transform algorithm (PIVlet 1.2) using a 2D-Ricker wavelet for coherent structure detection on instantaneous PIV-data. The goal of this study is to correlate phase shifts in surface pressure with Strouhal numbers associated with the vortex shedding. Ultimately, the wavelet-based analytical framework will be aimed at addressing pulsatile flows. This material is based in part upon work supported by the National Science Foundation under Grant Number CBET-1236351, and GW Center for Biomimetics and Bioinspired Engineering (COBRE).

Reactive Behavior of Explosive Billets in Deflagration Tube of Varied Confinements

NASA Astrophysics Data System (ADS)

Hu, Haibo; Guo, Yingwen; Li, Tao; Fu, Hua; Shang, Hailin; Wen, Shanggang; Qiu, Tian; LaboratoryShock Wave; Detonation Physics Research Team

2017-06-01

The deflagration process of small size cylinder billets of pressed HMX-based explosive JO-9159 and the deflagration tube wall deformation is recorded by combined pressure velocity-meter high-speed frame photographic and radiographic diagnostic system. The influence of confinement structure strength on deflagration evolution behavior is compared with analysis of convective flame propagation along the slot between explosive billet and confinement wall.The follow-up reaction inside the cracks on the initiation site end surface on the side surfaces and between the end surfaces of explosive billets is restored with the analysis results of post experimental explosive billet remains.

Simulation and evaluation of rupturable coated capsules by finite element method.

PubMed

Yang, Yan; Fang, Jie; Shen, Lian; Shan, Weiguang

2017-03-15

The objective of this study was to simulate and evaluate the burst behavior of rupturable coated capsules by finite element method (FEM). Film and coated capsules were prepared by dip-coating method and their dimensions were determined by stereomicroscope. Mechanical properties of the film were measured by tensile test and used as material properties of FEM models. Swelling pressure was determined by restrained expansion method and applied to the internal surface of FEM models. Water uptake of coated capsules was determined to study the formation of internal pressure. Burst test and in vitro dissolution was used to verify the FEM models, which were used to study and predict the coating burst behavior. Simulated results of coating burst behavior were well agreed with the experiment results. Swelling pressure, material properties and dimensions of coating had influence on the maximum stress. Burst pressure and critical L-HPC content were calculated for burst prediction and formulation optimization. FEM simulation was a feasible way to simulate and evaluate the burst behavior of coated capsules. Copyright © 2017 Elsevier B.V. All rights reserved.

Martian thermal tides from the surface to the atmosphere

NASA Astrophysics Data System (ADS)

Holstein-Rathlou, C.; Withers, P.

2017-12-01

The presence of observational platforms both in orbit and on the surface of Mars today provides a unique opportunity to simultaneously study the effects of thermal tides at the surface, above that surface location and in the atmosphere. Thermal tides are an important aspect of the atmospheric dynamics on Mars and the unique opportunity to unify landed and orbital measurements can provide a comprehensive understanding of thermal tides. Ideally, pressure measurements from the Curiosity lander and atmospheric temperature profiles from the Mars Climate Sounder (MCS) onboard Mars Reconnaissance Orbiter provide a complimentary pair of surface and atmospheric observations to study. However, the unique landing site of Curiosity, in Gale crater, introduces several complicating factors to the analysis of tidal behavior, two of which are crater circulation and the impact of the dichotomy boundary topography. In order to achieve a baseline understanding of thermal tidal behavior another complimentary pair of observations is necessary. For this purpose, the equatorial and relatively topographically flat landing site of the Viking 1 (VIK1) lander, along with its lengthy record of surface pressures, is the candidate surface dataset. There are no concurrent atmospheric observational data, so atmospheric profiles were obtained from the Mars Climate Database to ensure maximum coverage in space and time. 2-dimensional Fourier analysis in local time and longitude has yielded amplitude and phases for the four major tidal modes on Mars (diurnal and semidiurnal migrating tides, DK1 and DK2). We will present current results regarding amplitude and phase dependence on season and altitude at the VIK1 landing site. These results will (in time) be tied to tidal amplitude and phase behavior from observed MCS atmospheric temperature profiles from "appropriately quiet" Mars years (years without major dust storms). The understanding gathered from this approach will then allow us to return to the pressure measurements from Curiosity in Gale Crater, and assess to what degree the "pure" tidal signatures are muddled by various complicating factors, e.g. topography.

Martian thermal tides from the surface to the atmosphere

NASA Astrophysics Data System (ADS)

Holstein-Rathlou, Christina; Withers, Paul

2017-10-01

The presence of observational platforms both in orbit and on the surface of Mars today provides a unique opportunity to simultaneously study the effects of thermal tides at the surface, above that surface location and in the atmosphere. Thermal tides are an important aspect of the atmospheric dynamics on Mars and the unique opportunity to unify landed and orbital measurements can provide a comprehensive understanding of thermal tides.Ideally, pressure measurements from the Curiosity lander and atmospheric temperature profiles from the Mars Climate Sounder (MCS) onboard Mars Reconnaissance Orbiter provide a complimentary pair of surface and atmospheric observations to study. However, the unique landing site of Curiosity, in Gale crater, introduces several complicating factors to the analysis of tidal behavior, two of which are crater circulation and the impact of the dichotomy boundary topography.In order to achieve a baseline understanding of thermal tidal behavior another complimentary pair of observations is necessary. For this purpose, the equatorial and relatively topographically flat landing site of the Viking 1 (VIK1) lander, along with its lengthy record of surface pressures, is the candidate surface dataset. There are no concurrent atmospheric observational data, so atmospheric profiles were obtained from the Mars Climate Database to ensure maximum coverage in space and time.2-dimensional Fourier analysis in local time and longitude has yielded amplitude and phases for the four major tidal modes on Mars (diurnal and semidiurnal migrating tides, DK1 and DK2). We will present current results regarding amplitude and phase dependence on season and altitude at the VIK1 landing site. These results will (in time) be tied to tidal amplitude and phase behavior from observed MCS atmospheric temperature profiles from “appropriately quiet” Mars years (years without major dust storms). The understanding gathered from this approach will then allow us to return to the pressure measurements from Curiosity in Gale Crater, and assess to what degree the “pure” tidal signatures are muddled by various complicating factors, e.g. topography.

Control of Hydrogen Environment Embrittlement of Ultra-High Strength Steel for Naval Application

DTIC Science & Technology

2005-07-01

load cracking behavior of maraging steels in hydrogen. Corrosion , 29, 1973, 299-304. D.A. Jones, A.F. Jankowski and G.A. Davidson, "Diffusion of...short crack case. This behavior is relevant to small surface cracks in coated UHSS components such as a landing gear. IV.B. Effect of Steel Composition ...PRESSURE (k N /m 2) Figure 26. The effect of H2 pressure on the HEAC growth rate for a ultra-high strength 18Ni Maraging steel stressed in a highly

Composite Behavior of Insulated Concrete Sandwich Wall Panels Subjected to Wind Pressure and Suction

PubMed Central

Choi, Insub; Kim, JunHee; Kim, Ho-Ryong

2015-01-01

A full-scale experimental test was conducted to analyze the composite behavior of insulated concrete sandwich wall panels (ICSWPs) subjected to wind pressure and suction. The experimental program was composed of three groups of ICSWP specimens, each with a different type of insulation and number of glass-fiber-reinforced polymer (GFRP) shear grids. The degree of composite action of each specimen was analyzed according to the load direction, type of the insulation, and number of GFRP shear grids by comparing the theoretical and experimental values. The failure modes of the ICSWPs were compared to investigate the effect of bonds according to the load direction and type of insulation. Bonds based on insulation absorptiveness were effective to result in the composite behavior of ICSWP under positive loading tests only, while bonds based on insulation surface roughness were effective under both positive and negative loading tests. Therefore, the composite behavior based on surface roughness can be applied to the calculation of the design strength of ICSWPs with continuous GFRP shear connectors. PMID:28788001

Behavior of neutral solutes in pressurized flow driven electrochromatography using a mixed stationary phase of ODS and anion-exchange.

PubMed

Kitagawa, Shinya; Tsuda, Takao

2003-05-02

The behavior of neutral sample solutes in pressurized flow driven electrochromatography using a mixed stationary phase, which consisted of ODS and anion-exchange (ODS-SAX), was studied. Applications of both positive and negative voltage on a column induced increases in retention factors of sample solutes. The direction of an electroosmotic flow under applications of positive and negative voltage were the same, therefore, the sign of the surface charge density under positive and negative voltage was opposite. We proposed a new equation for the relationship between applied voltage and surface charge density, and the practical electroosmotic flow conformed to this equation. Studying the electroosmotic flow using our proposed equation revealed that the applied negative voltage accelerates the protonation of the quaternary ammonium group and dissociation of the silanol group on packing materials. The retention behavior of a neutral solute was affected by the existence of the charged functional groups. We propose that this phenomenon is applicable to the control of the retention behavior of a sample solute using an electric field.

Tribological Behavior of Aqueous Copolymer Lubricant in Mixed Lubrication Regime.

PubMed

Ta, Thi D; Tieu, A Kiet; Zhu, Hongtao; Zhu, Qiang; Kosasih, Prabouno B; Zhang, Jie; Deng, Guanyu

2016-03-02

Although a number of experiments have been attempted to investigate the lubrication of aqueous copolymer lubricant, which is applied widely in metalworking operations, a comprehensive theoretical investigation at atomistic level is still lacking. This study addresses the influence of loading pressure and copolymer concentration on the structural properties and tribological performance of aqueous copolymer solution of poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) (PPO-PEO-PPO) at mixed lubrication using a molecular dynamic (MD) simulation. An effective interfacial potential, which has been derived from density functional theory (DFT) calculations, was employed for the interactions between the fluid's molecules and iron surface. The simulation results have indicated that the triblock copolymer is physisorption on iron surface. Under confinement by iron surfaces, the copolymer molecules form lamellar structure in aqueous solution and behave differently from its bulk state. The lubrication performance of aqueous copolymer lubricant increases with concentration, but the friction reduction is insignificant at high loading pressure. Additionally, the plastic deformation of asperity is dependent on both copolymer concentration and loading pressure, and the wear behavior shows a linear dependence of friction force on the number of transferred atoms between contacting asperities.

Simulating regolith ejecta due to gas impingement

NASA Astrophysics Data System (ADS)

Chambers, Wesley Allen; Metzger, Philip; Dove, Adrienne; Britt, Daniel

2016-10-01

Space missions operating at or near the surface of a planet or small body must consider possible gas-regolith interactions, as they can cause hazardous effects or, conversely, be employed to accomplish mission goals. They are also directly related to a body's surface properties; thus understanding these interactions could provide an additional tool to analyze mission data. The Python Regolith Interaction Calculator (PyRIC), built upon a computational technique developed in the Apollo era, was used to assess interactions between rocket exhaust and an asteroid's surface. It focused specifically on threshold conditions for causing regolith ejecta. To improve this model, and learn more about the underlying physics, we have begun ground-based experiments studying the interaction between gas impingement and regolith simulant. Compressed air, initially standing in for rocket exhaust, is directed through a rocket nozzle at a bed of simulant. We assess the qualitative behavior of various simulants when subjected to a known maximum surface pressure, both in atmosphere and in a chamber initially at vacuum. These behaviors are compared to prior computational results, and possible flow patterns are inferred. Our future work will continue these experiments in microgravity through the use of a drop tower. These will use several simulant types and various pressure levels to observe the effects gas flow can have on target surfaces. Combining this with a characterization of the surface pressure distribution, tighter bounds can be set on the cohesive threshold necessary to maintain regolith integrity. This will aid the characterization of actual regolith distributions, as well as informing the surface operation phase of mission design.

Cell-to-Cell Heterogeneity in Cortical Tension Specifies Curvature of Contact Surfaces in Caenorhabditis elegans Embryos

PubMed Central

Fujita, Masashi; Onami, Shuichi

2012-01-01

In the two-cell stage embryos of Caenorhabditis elegans, the contact surface of the two blastomeres forms a curve that bulges from the AB blastomere to the P1 blastomere. This curve is a consequence of the high intracellular hydrostatic pressure of AB compared with that of P1. However, the higher pressure in AB is intriguing because AB has a larger volume than P1. In soap bubbles, which are a widely used model of cell shape, a larger bubble has lower pressure than a smaller bubble. Here, we reveal that the higher pressure in AB is mediated by its higher cortical tension. The cell fusion experiments confirmed that the curvature of the contact surface is related to the pressure difference between the cells. Chemical and genetic interferences showed that the pressure difference is mediated by actomyosin. Fluorescence imaging indicated that non-muscle myosin is enriched in the AB cortex. The cell killing experiments provided evidence that AB but not P1 is responsible for the pressure difference. Computer simulation clarified that the cell-to-cell heterogeneity of cortical tensions is indispensable for explaining the pressure difference. This study demonstrates that heterogeneity in surface tension results in significant deviations of cell behavior compared to simple soap bubble models, and thus must be taken into consideration in understanding cell shape within embryos. PMID:22253922

Phase behavior of Langmuir monolayers with ionic molecular heads: Molecular simulations

NASA Astrophysics Data System (ADS)

González-Castro, Carlos A.; Ramírez-Santiago, Guillermo

2015-03-01

We carried out Monte Carlo simulations in the N ,Π,T ensemble of a Langmuir monolayer coarse-grained molecular model. Considering that the hydrophilic groups can be ionized by modulating acid-base interactions, here we study the phase behavior of a model that incorporates the short-range steric and long-range ionic interactions. The simulations were carried out in the reduced temperature range 0.1 ≤T*<4.0 , where there is a competition of these interactions. Different order parameters were calculated and analyzed for several values of the reduced surface pressure in the interval, 1 ≤Π*≤40. For most of the surface pressures two directions of molecular tilt were found: (i) towards the nearest neighbor (NN) at low temperatures, T*<0.7, and most of the values of Π* and (ii) towards next-nearest neighbors (NNN) in the temperature interval 0.7 ≤T*<1.1 for Π*<25. We also found the coexistence of the NN and NNN at intermediate temperatures and Π*>25 . A low-temperature reentrant disorder-order-disorder transition in the positions of the molecular heads and in the collective tilt of the tails was found for all the surface pressure values. It was also found that the molecular tails arranged forming "rotating patterns" in the temperature interval, 0.5

Pressure mapping and performance of the compression bandage/garment for venous leg ulcer treatment.

PubMed

Ghosh, S; Mukhopadhyay, A; Sikka, M; Nagla, K S

2008-08-01

A study has been conducted on the commercially available compression bandages as regards their performance with time. Pressure mapping of these bandages has been done using a fabricated pressure-measuring device on a mannequin leg to see the effect on pressure due to creep, fabric friction and angle of bandaging. The results show that the creep behavior, frictional behavior and the angle of bandaging have a significant effect on the pressure profile generated by the bandages during application. The regression analysis shows that the surface friction restricts the slippage in a multilayer system. Also the diameters of the limb and the amount of stretch given to the bandage during application have definite impact on the bandage pressure. In case of compression garments, washing improves the pressure generated but not to the extent of the pressure of a virgin garment. Comparing the two compression materials i.e. bandage and garment, it is found that the presence of higher percentage of elastomeric material and a highly close construction in case of garment provides better holding power and a more homogeneous pressure distribution.

Measuring the surface tension of soap bubbles

NASA Technical Reports Server (NTRS)

Sorensen, Carl D.

1992-01-01

The objectives are for students to gain an understanding of surface tension, to see that pressure inside a small bubble is larger than that inside a large bubble. These concepts can be used to explain the behavior of liquid foams as well as precipitate coarsening and grain growth. Equipment, supplies, and procedures are explained.

Measuring the surface tension of soap bubbles

NASA Astrophysics Data System (ADS)

Sorensen, Carl D.

1992-06-01

The objectives are for students to gain an understanding of surface tension, to see that pressure inside a small bubble is larger than that inside a large bubble. These concepts can be used to explain the behavior of liquid foams as well as precipitate coarsening and grain growth. Equipment, supplies, and procedures are explained.

Abrasion behavior of aluminum and composite skin coupons, stiffened skins and stiffened panels representative of transport airplane structures

NASA Technical Reports Server (NTRS)

Jackson, K. E.

1985-01-01

A three-phase investigation was conducted to compare the friction and wear response of aluminum and graphite-epoxy composite materials when subjected to loading conditions similar to those experienced by the skin panels on the underside of a transport airplane during an emergency belly landing on a runway surface. The first phase involved a laboratory test which used a standard belt sander to provide the sliding abrasive surface. Small skin-coupon test specimens were abraded over a range of pressures and velocities to determine the effects of these variables on the coefficient of friction and wear rate. The second phase involved abrading I-beam stiffened skins on actual runway surface over the same range of pressures and velocities used in the first phase. In the third phase, large stiffened panels which most closely resembled transport fuelage skin construction were abraded on a runway surface. This report presents results from each phase of the investigation and shows comparisons between the friction and wear behavior of the aluminum and graphite-epoxy composite materials.

Engineering plasmonic nanostructured surfaces by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Ghidelli, Matteo; Mascaretti, Luca; Bricchi, Beatrice Roberta; Zapelli, Andrea; Russo, Valeria; Casari, Carlo Spartaco; Li Bassi, Andrea

2018-03-01

The synthesis and the optical response of gold nanoparticles (NPs) and thin nanostructured films grown by pulsed laser deposition (PLD) are here studied. Different PLD process parameters - including background gas pressure and the number of laser shots as well as post-deposition annealing treatments - have been varied to control the growth of Au NPs and films, thus tuning the surface plasmon characteristics. The mechanisms of NPs and film growth have been explored performing a morphological characterization by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM), and the correlation with the optical behavior is investigated. We show that the size distribution and the morphology of the as deposited Au NPs depend on growth mechanisms which are controlled by tuning the deposition process, while the optical behavior is strongly affected by the average size and surface density of NPs or by the length of percolated Au domains. Furthermore, nucleation in gas phase has been reported at high (1000 Pa Ar) background pressures, enabling independent control of NP size and coverage, contrary to surface driven NP growth by diffusion and aggregation on substrate.

Analysis of a two row hydrostatic journal bearing with variable properties, inertia effects and surface roughness

NASA Technical Reports Server (NTRS)

Braun, M. J.; Adams, M. L.; Mullen, R. L.

1985-01-01

A computer algorithm for simulation of hydrostatic journal bearing pressure-flow behavior has been generated. The effects taken into account are inertia, cavitation, variable properties (isothermal bearing) and roughness. The program has been specifically tailored for simulation of the hybrid bearing of the cryogenic turbopumps of the main shuttle engine. Due to the high pressure (515 psia) of the supply line no cavitation has been found. The influence of the roughness effects have been found to become important only when the surface-roughness order of magnitude is comparable with that of the bearing clearance itself. Pocket edge inertia and variable properties have been found to have quite an important influence upon the pocket pressure, field pressure distribution and lubricant mass flow.

Effect of the barometric phase transition of a DMPA bilayer on the lipid/water interface. An atomistic description by molecular dynamics simulation.

PubMed

Casares, J J Giner; Camacho, L; Romero, M T Martín; Cascales, J J López

2007-12-13

Understanding the structure and dynamics of phospholipid bilayers is of fundamental relevance in biophysics, biochemistry, and chemical physics. Lipid Langmuir monolayers are used as a model of lipid bilayers, because they are much more easily studied experimentally, although some authors question the validity of this model. With the aim of throwing light on this debate, we used molecular dynamics simulations to obtain an atomistic description of a membrane of dimyristoylphosphatidic acid under different surface pressures. Our results show that at low surface pressure the interdigitation between opposite lipids (that is, back-to-back interactions) controls the system structure. In this setting and due to the absence of this effect in the Langmuir monolayers, the behavior between these two systems differs considerably. However, when the surface pressure increases the lipid interdigitation diminishes and so monolayer and bilayer behavior converges. In this work, four computer simulations were carried out, subjecting the phospholipids to lateral pressures ranging from 0.17 to 40 mN/m. The phospholipids were studied in their charged state because this approach is closer to the experimental situation. Special attention was paid to validating our simulation results by comparison with available experimental data, therebeing in general excellent agreement between experimental and simulation data. In addition, the properties of the lipid/solution interface associated with the lipid barometric phase transition were studied.

Pulmonary Surfactant Model Systems Catch the Specific Interaction of an Amphiphilic Peptide with Anionic Phospholipid

PubMed Central

Nakahara, Hiromichi; Lee, Sannamu; Shibata, Osamu

2009-01-01

Interfacial behavior was studied in pulmonary surfactant model systems containing an amphiphilic α-helical peptide (Hel 13-5), which consists of 13 hydrophobic and five hydrophilic amino acid residues. Fully saturated phospholipids of dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG) were utilized to understand specific interactions between anionic DPPG and cationic Hel 13-5 for pulmonary functions. Surface pressure (π)-molecular area (A) and surface potential (ΔV)-A isotherms of DPPG/Hel 13-5 and DPPC/DPPG (4:1, mol/mol)/Hel 13-5 preparations were measured to obtain basic information on the phase behavior under compression and expansion processes. The interaction leads to a variation in squeeze-out surface pressures against a mole fraction of Hel 13-5, where Hel 13-5 is eliminated from the surface on compression. The phase behavior was visualized by means of Brewster angle microscopy, fluorescence microscopy, and atomic force microscopy. At low surface pressures, the formation of differently ordered domains in size and shape is induced by electrostatic interactions. The domains independently grow upon compression to high surface pressures, especially in the DPPG/Hel 13-5 system. Under the further compression process, protrusion masses are formed in AFM images in the vicinity of squeeze-out pressures. The protrusion masses, which are attributed to the squeezed-out Hel 13-5, grow larger in lateral size with increasing DPPG content in phospholipid compositions. During subsequent expansion up to 35 mN m−1, the protrusions retain their height and lateral diameter for the DPPG/Hel 13-5 system, whereas the protrusions become smaller for the DPPC/Hel 13-5 and DPPC/DPPG/Hel 13-5 systems due to a reentrance of the ejected Hel 13-5 into the surface. In this work we detected for the first time, to our knowledge, a remarkably large hysteresis loop for cyclic ΔV-A isotherms of the binary DPPG/Hel 13-5 preparation. This exciting phenomenon suggests that the specific interaction triggers two completely independent processes for Hel 13-5 during repeated compression and expansion: 1), squeezing-out into the subsolution; and 2), and close packing as a monolayer with DPPG at the interface. These characteristic processes are also strongly supported by atomic force microscopy observations. The data presented here provide complementary information on the mechanism and importance of the specific interaction between the phosphatidylglycerol headgroup and the polarized moiety of native surfactant protein B for biophysical functions of pulmonary surfactants. PMID:19217859

Modeling of edge effect in subaperture tool influence functions of computer controlled optical surfacing.

PubMed

Wan, Songlin; Zhang, Xiangchao; He, Xiaoying; Xu, Min

2016-12-20

Computer controlled optical surfacing requires an accurate tool influence function (TIF) for reliable path planning and deterministic fabrication. Near the edge of the workpieces, the TIF has a nonlinear removal behavior, which will cause a severe edge-roll phenomenon. In the present paper, a new edge pressure model is developed based on the finite element analysis results. The model is represented as the product of a basic pressure function and a correcting function. The basic pressure distribution is calculated according to the surface shape of the polishing pad, and the correcting function is used to compensate the errors caused by the edge effect. Practical experimental results demonstrate that the new model can accurately predict the edge TIFs with different overhang ratios. The relative error of the new edge model can be reduced to 15%.

Investigation of Surface Phenomena in Shocked Tin in Converging Geometry

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

Rousculp, Christopher L.; Oro, David Michael; Margolin, Len G.

2015-08-06

There is great interest in the behavior of the free surface of tin under shock loading. While it is known that meso-scale surface imperfections can seed the Richtmyer-Meshkov Instability (RMI) for a surface that is melted on release, much less is known about a tin surface that is solid, but plastically deforming. Here material properties such as shear and yield strength come into play especially in converging geometry. Previous experiments have been driven by direct contact HE. Usually a thin, flat target coupon is fielded with various single-mode, sinusoidal, machined, profiles on the free surface. The free surface is adjacentmore » to either vacuum or an inert receiver gas. Most of these previous driver/target configurations have been nominal planer geometry. With modern HE it has been straightforward to shock tin into melt on release. However it has been challenging to achieve a low enough pressure for solid state on release. Here we propose to extend the existing base of knowledge to include the behavior of the free surface of tin in cylindrical converging geometry. By shock loading a cylindrical tin shell with a magnetically driven cylindrical liner impactor, the free surface evolution can be diagnosed with proton radiography. With the PHELIX capacitor bank, the drive can easily be varied to span the pressure range to achieve solid, mixed, and liquid states on release.« less

Thermocapillary flow with evaporation and condensation and its effect on liquid retention in low-G fluid acquisition devices

NASA Technical Reports Server (NTRS)

Schmidt, George R.

1994-01-01

The steady motion, thermal and free surface behavior of a volatile, wetting liquid in microgravity are studied using scaling and numerical techniques. The objective is to determine whether the thermocapillary and two-phase convection arising from thermodynamic nonequilibrium along the porous surfaces of spacecraft liquid acquisition devices could cause the retention failures observed with liquid hydrogen and heated vapor pressurant. Why these devices seem immune to retention loss when pressurized with heated helium or heated directly through the porous structure was also examined. Results show that highly wetting fluids exhibit large negative and positive dynamic pressure gradients towards the meniscus interline when superheated and subcooled, respectively. With superheating, the pressure variation and recoil force arising from liquid/vapor phase change exert the same influence on surface morphology and promote retention. With subcooling, however, the pressure distribution produces a suction that degrades mechanical equilibrium of the surface. This result indicates that thermocapillary-induced deformation arising from subcooling and condensation is the likely cause for retention loss. In addition, increasing the level of nonequilibrium by reducing accommodation coefficient suppresses deformation and explains why this failure mode does not occur in instances of direct screen heating or pressurization with a heated inert gas.

A new theoretical approach to adsorption desorption behavior of Ga on GaAs surfaces

NASA Astrophysics Data System (ADS)

Kangawa, Y.; Ito, T.; Taguchi, A.; Shiraishi, K.; Ohachi, T.

2001-11-01

We propose a new theoretical approach for studying adsorption-desorption behavior of atoms on semiconductor surfaces. The new theoretical approach based on the ab initio calculations incorporates the free energy of gas phase; therefore we can calculate how adsorption and desorption depends on growth temperature and beam equivalent pressure (BEP). The versatility of the new theoretical approach was confirmed by the calculation of Ga adsorption-desorption transition temperatures and transition BEPs on the GaAs(0 0 1)-(4×2)β2 Ga-rich surface. This new approach is feasible to predict how adsorption and desorption depend on the growth conditions.

Thermogravimetric study of vapor pressure of TATP synthesized without recrystallization.

PubMed

Mbah, Jonathan; Knott, Debra; Steward, Scott

2014-11-01

This study aims at characterizing the vapor pressure signatures generated by triacetone triperoxide (TATP) that was synthesized without recrystallization by thermogravimmetric analysis (TGA) for exploitation by standoff detection technologies of explosive devices. The thermal behavior of the nonrecrystallized sample was compared with reported values. Any phase change, melting point and decomposition identification were studied by differential scanning calorimeter. Vapor pressures were estimated by the Langmuir method of evaporation from an open surface in a vacuum. Vapor pressures of TATP at different temperatures were calculated using the linear logarithmic relationship obtained from benzoic acid reference standard. Sublimation of TATP was found to follow apparent zero-order kinetics and sublimes at steady rates at 298 K and above. While the enthalpy of sublimation found, 71.7 kJ mol(-1), is in agreement with reported values the vapor pressures deviated significantly. The differences in the vapor pressures behavior are attributable to the synthesis pathway chosen in this study. Copyright © 2014 Elsevier B.V. All rights reserved.

Evolution of surface structure in laser-preheated, perturbed materials

DOE PAGES

Di Stefano, Carlos; Merritt, Elizabeth Catherine; Doss, Forrest William; ...

2017-02-03

Here, we report an experimental and computational study investigating the effects of laser preheat on the hydrodynamic behavior of a material layer. In particular, we find that perturbation of the surface of the layer results in a complex interaction, in which the bulk of the layer develops density, pressure, and temperature structure and in which the surface experiences instability-like behavior, including mode coupling. A uniform one-temperature preheat model is used to reproduce the experimentally observed behavior, and we find that this model can be used to capture the evolution of the layer, while also providing evidence of complexities in themore » preheat behavior. Lastly, this result has important consequences for inertially confined fusion plasmas, which can be difficult to diagnose in detail, as well as for laser hydrodynamics experiments, which generally depend on assumptions about initial conditions in order to interpret their results.« less

Thermoelasticity and anomalies in the pressure dependence of phonon velocities in niobium

NASA Astrophysics Data System (ADS)

Zou, Yongtao; Li, Ying; Chen, Haiyan; Welch, David; Zhao, Yusheng; Li, Baosheng

2018-01-01

Compressional and shear wave velocities of polycrystalline niobium have been measured at simultaneously high pressures and temperatures up to 5.8 GPa and 1073 K, respectively, using ultrasonic interferometry in conjunction with synchrotron x-ray techniques. An anomalous pressure-induced softening behavior in the phonon velocities, probably owing to the topological change in the Fermi surface, has been observed at ˜4.8 GPa during cold compression, which is supported by the elasticity data from our first-principles calculations. In contrast, both the bulk (BS) and shear (G) moduli increase with pressures but decrease with temperatures upon compression at extreme P-T up to 5.8 GPa and 1073 K. Using finite strain equation-of-state approaches, the elasticity of bulk and shear moduli and their pressure and temperature dependences are derived from the directly measured velocities and densities, yielding BS0 = 174.9(3.2) GPa, G0 = 37.1(3) GPa, ∂BS/∂P = 3.97(9), ∂G/∂P = 0.83(5), ∂BS/∂T = -0.064(7) GPa/K, and ∂G/∂T = -0.012(3) GPa/K. On the basis of the current thermoelasticity data, Debye temperature and the high-pressure melting curve of Nb are derived. The origin of the anomalies in shear behavior at high pressure might be attributed to the progressive s-d electron-transfer-induced topological changes of the Fermi surface upon compression.

Pressure sensitive microparticle adhesion through biomimicry of the pollen-stigma interaction.

PubMed

Lin, Haisheng; Qu, Zihao; Meredith, J Carson

2016-03-21

Many soft biomimetic synthetic adhesives, optimized to support macroscopic masses (∼kg), have been inspired by geckos, insects and other animals. Far less work has investigated bioinspired adhesion that is tuned to micro- and nano-scale sizes and forces. However, such adhesive forces are extremely important in the adhesion of micro- and nanoparticles to surfaces, relevant to a wide range of industrial and biological systems. Pollens, whose adhesion is critical to plant reproduction, are an evolutionary-optimized system for biomimicry to engineer tunable adhesion between particles and micro-patterned soft matter surfaces. In addition, the adhesion of pollen particles is relevant to topics as varied as pollinator ecology, transport of allergens, and atmospheric phenomena. We report the first observation of structurally-derived pressure-sensitive adhesion of a microparticle by using the sunflower pollen and stigma surfaces as a model. This strong, pressure-sensitive adhesion results from interlocking between the pollen's conical spines and the stigma's receptive papillae. Inspired by this behavior, we fabricated synthetic polymeric patterned surfaces that mimic the stigma surface's receptivity to pollen. These soft mimics allow the magnitude of the pressure-sensitive response to be tuned by adjusting the size and spacing of surface features. These results provide an important new insight for soft material adhesion based on bio-inspired principles, namely that ornamented microparticles and micro-patterned surfaces can be designed with complementarity that enable a tunable, pressure-sensitive adhesion on the microparticle size and length scale.

Structural investigation of Langmuir and Langmuir-Blodgett monolayers of semifluorinated alkanes.

PubMed

Dynarowicz Łatka, Patrycja; Pérez-Morales, Marta; Muñoz, Eulogia; Broniatowski, Marcin; Martín-Romero, María T; Camacho, Luis

2006-03-30

The behavior of a semi-fluorinated alkane (C(10)F(21)C(19)H(39)) has been studied at the air-water interface by using surface pressure and surface potential-area isotherms as well as infrared spectroscopy for the Langmuir-Blodgett films. In addition, based on the quantum chemical PM3 semiempirical approach, the dimer structure was investigated, and the double helix was found to be the most stable conformation of the dimer. The obtained results allow us to imply that the phase transition observed in the course of the surface pressure/area isotherm is due to a conformational change originating from the double helix to a vertical, single helix configuration.

Cren(ulation)-­1,2 Preshot Report

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

Rousculp, Christopher L.; Oro, David Michael; Griego, Jeffrey Randall

2015-12-21

There is great interest in the behavior of the free surface of tin under shock loading. While it is known that meso-scale surface imperfections can seed the RichtmyerMeshkov Instability (RMI) for a surface that is melted on release, much less is known about a tin surface that is solid, but plastically deforming. Here material properties such as shear and yield strength come into play especially in converging geometry. Previous experiments have been driven by direct contact HE. Usually a thin, flat target coupon is fielded with various single-mode, sinusoidal, machined, profiles on the free surface. The free surface is adjacentmore » to either vacuum or an inert receiver gas. Most of these previous driver/target configurations have been nominal planer geometry. With modern HE it has been straightforward to shock tin into melt on release. However it has been challenging to achieve a low enough pressure for solid state on release. Here we propose to extend the existing base of knowledge to include the behavior of the free surface of tin in cylindrical converging geometry. By shock loading a cylindrical tin shell with a magnetically driven cylindrical liner impactor, the free surface evolution can be diagnosed with proton radiography. With the PHELIX capacitor bank, the drive can easily be varied to span the pressure range to achieve solid, mixed, and liquid states on release.« less

Planar shock reflection on a wedged concave reflector

NASA Astrophysics Data System (ADS)

Yu, Fan-Ming; Sheu, Kuen-Dong

2001-04-01

The investigation of shock reflection and shock diffraction phenomena upon a wedged concave reflector produced by a planar incident shock wave has been done in the shock tube facility of Institute of Aeronautics and Astronautics, National Cheng- Kung University. The experiment proceeds upon three wedged concave reflectors models the upper and lower wedge angles arrangement of them are (50 degrees, 50 degrees) - 35 degrees, 35 degrees) and (50 degrees, 35 degrees), respectively. They were tested at Mach numbers of 1.2 - 1.65 and 2.0. On the first reflector, following the regular reflection on the 50 degree-wedged surface by the incident shock wave, a Mach shock diffraction behavior has been observed as shock moves outward from the apex of the reflector. On the apex of the reflector, it behaviors as a sector of the blast shock moving on a diverging channel. On the shadowgraph pictures it has been observed there exists a pattern of gas dynamics focus upon the second reflector. The Mach reflection from the 35 degree- wedged surface as being generated by the planar incident shock wave, on which the overlapping of the two triple points from both wedged surface offers the focusing mechanism. The shock interference, which proceeds by the Mach shock reflection and the regular shock diffraction from the reflector, generates a very complicate rolling-up of slip lines system. On the third reflector, the mixed shock interference behavior has been observed of which two diffraction shocks from concave 50 degree-wedged surface and 35 degree-wedged surface interfere with each other. The measurement of the peak pressure along a ray from the model apex parallel to incident shock direction indicates that the measured maximum pressure rising is larger near the apex of the reflector. Considering the measured maximum pressure increment due to the reflection shocks indicate that the wave strength upon large apex angle reflector is greater than it is upon small apex angle reflector. However, as considering the measured maximum pressure increment following the diffraction shocks, the results show that due to the focusing process upon (35 degree, 35 degree) reflector, it is of the largest increment.

The Effect of O2, H2O, and N2 on the Fatigue Crack Growth Behavior of an Alpha + Beta Titanium Alloy at 24 C and 177 C

NASA Technical Reports Server (NTRS)

Smith, Stephen W.; Piascik, Robert S.

2001-01-01

To study the effects of atmospheric species on the fatigue crack growth behavior of an a+B titanium alloy (Ti 6-2-2-2-2) at room temperature and 177 C, fatigue tests were performed in laboratory air, ultrahigh vacuum, and high purity water vapor, oxygen, nitrogen and helium at various partial pressures. Accelerated fatigue crack growth rates in laboratory air compared to ultrahigh vacuum are linked to the damaging effects of both water vapor and oxygen. Observations of the fatigue crack growth behavior in ultrahigh purity environments, along with surface film analysis using X-ray photoelectron spectroscopy (XPS), suggest that multiple crack-tip processes govern the damaging effects of air. Three possible mechanisms are proposed: 1) at low pressure (less than 10(exp -1) Pa), accelerated da/dN is likely due to monolayer adsorption on crack-tip surfaces presumably resulting in decreased bond strengths at the fatigue crack tip, 2) for pressures greater than 10(exp -1) Pa, accelerated da/dN in oxygen may result from oxidation at the crack tip limiting reversible slip, and 3) in water vapor, absorption of atomic hydrogen at the reactive crack tip resulting in process zone embrittlement.

Realistic multisite lattice-gas modeling and KMC simulation of catalytic surface reactions: Kinetics and multiscale spatial behavior for CO-oxidation on metal (1 0 0) surfaces

NASA Astrophysics Data System (ADS)

Liu, Da-Jiang; Evans, James W.

2013-12-01

A realistic molecular-level description of catalytic reactions on single-crystal metal surfaces can be provided by stochastic multisite lattice-gas (msLG) models. This approach has general applicability, although in this report, we will focus on the example of CO-oxidation on the unreconstructed fcc metal (1 0 0) or M(1 0 0) surfaces of common catalyst metals M = Pd, Rh, Pt and Ir (i.e., avoiding regimes where Pt and Ir reconstruct). These models can capture the thermodynamics and kinetics of adsorbed layers for the individual reactants species, such as CO/M(1 0 0) and O/M(1 0 0), as well as the interaction and reaction between different reactant species in mixed adlayers, such as (CO + O)/M(1 0 0). The msLG models allow population of any of hollow, bridge, and top sites. This enables a more flexible and realistic description of adsorption and adlayer ordering, as well as of reaction configurations and configuration-dependent barriers. Adspecies adsorption and interaction energies, as well as barriers for various processes, constitute key model input. The choice of these energies is guided by experimental observations, as well as by extensive Density Functional Theory analysis. Model behavior is assessed via Kinetic Monte Carlo (KMC) simulation. We also address the simulation challenges and theoretical ramifications associated with very rapid diffusion and local equilibration of reactant adspecies such as CO. These msLG models are applied to describe adsorption, ordering, and temperature programmed desorption (TPD) for individual CO/M(1 0 0) and O/M(1 0 0) reactant adlayers. In addition, they are also applied to predict mixed (CO + O)/M(1 0 0) adlayer structure on the nanoscale, the complete bifurcation diagram for reactive steady-states under continuous flow conditions, temperature programmed reaction (TPR) spectra, and titration reactions for the CO-oxidation reaction. Extensive and reasonably successful comparison of model predictions is made with experimental data. Furthermore, we discuss the possible transition from traditional mean-field-type bistability and reaction kinetics for lower-pressure to multistability and enhanced fluctuation effects for moderate- or higher-pressure. Behavior in the latter regime reflects a stronger influence of adspecies interactions and also lower diffusivity in the higher-coverage mixed adlayer. We also analyze mesoscale spatiotemporal behavior including the propagation of reaction-diffusion fronts between bistable reactive and inactive states, and associated nucleation-mediated transitions between these states. This behavior is controlled by complex surface mass transport processes, specifically chemical diffusion in mixed reactant adlayers for which we provide a precise theoretical formulation. The msLG models together with an appropriate treatment of chemical diffusivity enable equation-free heterogeneous coupled lattice-gas (HCLG) simulations of spatiotemporal behavior. In addition, msLG + HCLG modeling can describe coverage variations across polycrystalline catalysts surfaces, pressure variations across catalyst surfaces in microreactors, and could be incorporated into a multiphysics framework to describe mass and heat transfer limitations for high-pressure catalysis.

Realistic multisite lattice-gas modeling and KMC simulation of catalytic surface reactions: Kinetics and multiscale spatial behavior for CO-oxidation on metal (100) surfaces

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

Liu, Dajiang; Evans, James W.

2013-12-01

A realistic molecular-level description of catalytic reactions on single-crystal metal surfaces can be provided by stochastic multisite lattice-gas (msLG) models. This approach has general applicability, although in this report, we will focus on the example of CO-oxidation on the unreconstructed fcc metal (100) or M(100) surfaces of common catalyst metals M = Pd, Rh, Pt and Ir (i.e., avoiding regimes where Pt and Ir reconstruct). These models can capture the thermodynamics and kinetics of adsorbed layers for the individual reactants species, such as CO/M(100) and O/M(100), as well as the interaction and reaction between different reactant species in mixed adlayers,more » such as (CO + O)/M(100). The msLG models allow population of any of hollow, bridge, and top sites. This enables a more flexible and realistic description of adsorption and adlayer ordering, as well as of reaction configurations and configuration-dependent barriers. Adspecies adsorption and interaction energies, as well as barriers for various processes, constitute key model input. The choice of these energies is guided by experimental observations, as well as by extensive Density Functional Theory analysis. Model behavior is assessed via Kinetic Monte Carlo (KMC) simulation. We also address the simulation challenges and theoretical ramifications associated with very rapid diffusion and local equilibration of reactant adspecies such as CO. These msLG models are applied to describe adsorption, ordering, and temperature programmed desorption (TPD) for individual CO/M(100) and O/M(100) reactant adlayers. In addition, they are also applied to predict mixed (CO + O)/M(100) adlayer structure on the nanoscale, the complete bifurcation diagram for reactive steady-states under continuous flow conditions, temperature programmed reaction (TPR) spectra, and titration reactions for the CO-oxidation reaction. Extensive and reasonably successful comparison of model predictions is made with experimental data. Furthermore, we discuss the possible transition from traditional mean-field-type bistability and reaction kinetics for lower-pressure to multistability and enhanced fluctuation effects for moderate- or higher-pressure. Behavior in the latter regime reflects a stronger influence of adspecies interactions and also lower diffusivity in the higher-coverage mixed adlayer. We also analyze mesoscale spatiotemporal behavior including the propagation of reaction diffusion fronts between bistable reactive and inactive states, and associated nucleation-mediated transitions between these states. This behavior is controlled by complex surface mass transport processes, specifically chemical diffusion in mixed reactant adlayers for which we provide a precise theoretical formulation. The msLG models together with an appropriate treatment of chemical diffusivity enable equation-free heterogeneous coupled lattice-gas (HCLG) simulations of spatiotemporal behavior. In addition, msLG + HCLG modeling can describe coverage variations across polycrystalline catalysts surfaces, pressure variations across catalyst surfaces in microreactors, and could be incorporated into a multiphysics framework to describe mass and heat transfer limitations for high-pressure catalysis. (C) 2013 Elsevier Ltd. All rights reserved.« less

Spectral analysis of unsteady surface pressure on a pusher propeller

NASA Technical Reports Server (NTRS)

Farokhi, Saeed

1992-01-01

A propeller of an advanced turboprop testbed aircraft in pusher configuration is instrumented with 22 miniature blade-mounted transducers (BMTs) at two radii. Upstream pylon wake interaction with the propeller is the source of a one-per-cycle excitation for the blades in flight. The time history of fluctuating pressure signals over 26 flight conditions is statistically analyzed in the frequency domain. The rms amplitude of fluctuating pressure signals measured by suction surface BMTs indicates a very strong presence of the fundamental frequency over most of the upper surface. The pylon wake pressure signature on the propeller trailing edge, i.e., x/c not less than 0.80, shows predominantly random turbulence; hence, the amplitude of the fundamental frequency wave is fairly small. The resurgence of a large amplitude fundamental harmonic with coherent pylon wake signature further downstream, say at 90 percent chord, is unexpected behavior. The appearance of a dominating second propeller shaft order in the spectra of the rms pressure in transonic flight conditions identifies the presence of a two-per-cycle excitation source in the azimuthal direction. This is due to the presence of a shock wave, as evidenced by the pressure-time history plots.

Strong coupling electrostatics for randomly charged surfaces: antifragility and effective interactions.

PubMed

Ghodrat, Malihe; Naji, Ali; Komaie-Moghaddam, Haniyeh; Podgornik, Rudolf

2015-05-07

We study the effective interaction mediated by strongly coupled Coulomb fluids between dielectric surfaces carrying quenched, random monopolar charges with equal mean and variance, both when the Coulomb fluid consists only of mobile multivalent counterions and when it consists of an asymmetric ionic mixture containing multivalent and monovalent (salt) ions in equilibrium with an aqueous bulk reservoir. We analyze the consequences that follow from the interplay between surface charge disorder, dielectric and salt image effects, and the strong electrostatic coupling that results from multivalent counterions on the distribution of these ions and the effective interaction pressure they mediate between the surfaces. In a dielectrically homogeneous system, we show that the multivalent counterions are attracted towards the surfaces with a singular, disorder-induced potential that diverges logarithmically on approach to the surfaces, creating a singular but integrable counterion density profile that exhibits an algebraic divergence at the surfaces with an exponent that depends on the surface charge (disorder) variance. This effect drives the system towards a state of lower thermal 'disorder', one that can be described by a renormalized temperature, exhibiting thus a remarkable antifragility. In the presence of an interfacial dielectric discontinuity, the singular behavior of counterion density at the surfaces is removed but multivalent counterions are still accumulated much more strongly close to randomly charged surfaces as compared with uniformly charged ones. The interaction pressure acting on the surfaces displays in general a highly non-monotonic behavior as a function of the inter-surface separation with a prominent regime of attraction at small to intermediate separations. This attraction is caused directly by the combined effects from charge disorder and strong coupling electrostatics of multivalent counterions, which dominate the surface-surface repulsion due to the (equal) mean charges on the two surfaces and the osmotic pressure of monovalent ions residing between them. These effects can be quite significant even with a small degree of surface charge disorder relative to the mean surface charge. The strong coupling, disorder-induced attraction is typically much stronger than the van der Waals interaction between the surfaces, especially within a range of several nanometers for the inter-surface separation, where such effects are predicted to be most pronounced.

Effects of Discrete Charge Clustering in Simulations of Charged Interfaces.

PubMed

Grime, John M A; Khan, Malek O

2010-10-12

A system of counterions between charged surfaces is investigated, with the surfaces represented by uniform charged planes and three different arrangements of discrete surface charges - an equispaced grid and two different clustered arrangements. The behaviors of a series of systems with identical net surface charge density are examined, with particular emphasis placed on the long ranged corrections via the method of "charged slabs" and the effects of the simulation cell size. Marked differences are observed in counterion distributions and the osmotic pressure dependent on the particular representation of the charged surfaces; the uniformly charged surfaces and equispaced grids of discrete charge behave in a broadly similar manner, but the clustered systems display a pronounced decrease in osmotic pressure as the simulation size is increased. The influence of the long ranged correction is shown to be minimal for all but the very smallest of system sizes.

Investigation of the surface free energy of the ITO thin films deposited under different working pressure

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

Özen, Soner, E-mail: osoner@ogu.edu.tr; Pat, Suat; Korkmaz, Şadan

This study discusses the influence of working pressure on the surface energy of the ITO thin films produced by radio frequency magnetron sputtering method. Optical tensiometer (Attension Theta Lite) is used for evaluating wetting behavior of the water droplet on the film surface and Equation of State method was selected to determine surface free energy for this study. Equation of state method does not divide the surface tension into different components such as polar, dispersive, acid-base. It is calculated the surfaces’ free energy measuring the contact angle with a single liquid. The surface free energy value was in the rangemore » of 15-31 mN/m. Also, the transmittances were determined in the wavelength range between 200 and 1000 nm using the UNICO 4802 UV-Vis double beam spectrophotometer. Transmittances of the produced ITO thin films are greater than %70 in the visible range.« less

Unsteady blade pressure measurements for the SR-7A propeller at cruise conditions

NASA Technical Reports Server (NTRS)

Heidelberg, L. J.; Nallasamy, M.

1990-01-01

The unsteady blade surface pressures were measured on the SR-7A propeller. The freestream Mach no., inflow angle, and advance ratio were varied while measurements were made at nine blade stations. At a freestream Mach no. of 0.8, the data in terms of unsteady pressure coefficient vs. azimuth angle are compared to an unsteady 3-D Euler solution, yielding very encouraging results. The code predicts the shape (phase) of the waveform very well, while the magnitude is over-predicted in many cases. At tunnel Mach nos. below 0.6, an unusually large response on the suction surface at 0.15 chord and 0.88 radius was observed. The behavior of this response suggests the presence of a leading edge vortex. The midchord measuring stations on the suction surface exhibit a response that leads the forcing function while most other locations show a phase lag.

Flame surface statistics of constant-pressure turbulent expanding premixed flames

NASA Astrophysics Data System (ADS)

Saha, Abhishek; Chaudhuri, Swetaprovo; Law, Chung K.

2014-04-01

In this paper we investigate the local flame surface statistics of constant-pressure turbulent expanding flames. First the statistics of local length ratio is experimentally determined from high-speed planar Mie scattering images of spherically expanding flames, with the length ratio on the measurement plane, at predefined equiangular sectors, defined as the ratio of the actual flame length to the length of a circular-arc of radius equal to the average radius of the flame. Assuming isotropic distribution of such flame segments we then convolute suitable forms of the length-ratio probability distribution functions (pdfs) to arrive at the corresponding area-ratio pdfs. It is found that both the length ratio and area ratio pdfs are near log-normally distributed and shows self-similar behavior with increasing radius. Near log-normality and rather intermittent behavior of the flame-length ratio suggests similarity with dissipation rate quantities which stimulates multifractal analysis.

Identification of Control Parameters for Brass Player’s Embouchure by Measuring Contact Pressure on the Teeth Buccal Surface

NASA Astrophysics Data System (ADS)

Kourakata, Itaru; Moriyama, Kozo; Hara, Toshiaki

For the technical improvement for brass instrument players it is important to obtain the detailed control parameters for embouchure building. While many investigators have reported the preliminary data on the muscle behavior, the precise aspects are unrevealed so far. The purpose of the present paper is to study dynamic perioral muscle behavior of French horn players and to investigate their lip valve function by measuring the contact pressure on teeth buccal surface during playing. It was shown from the experimental results that the advanced players contracted depressor angulioris and levator angulioris especially for high tone playing. It is considered that the combined contraction by these muscles contributes to forming smaller lip aperture being suitable to produce higher tones. Inversely a strong contraction of m. buccinator, which is widely believed to work to give hard tension to player’s lip, was observed insignificantly in the advanced players.

Ultrasonic and metallographic studies on AISI 4140 steel exposed to hydrogen at high pressure and temperature

NASA Astrophysics Data System (ADS)

Oruganti, Malavika

This thesis conducts an investigation to study the effects of hydrogen exposure at high temperature and pressure on the behavior of AISI 4140 steel. Piezoelectric ultrasonic technique was primarily used to evaluate surface longitudinal wave velocity and defect geometry variations, as related to time after exposure to hydrogen at high temperature and pressure. Critically refracted longitudinal wave technique was used for the former and pulse-echo technique for the latter. Optical microscopy and scanning electron microscopy were used to correlate the ultrasonic results with the microstructure of the steel and to provide better insight into the steel behavior. The results of the investigation indicate that frequency analysis of the defect echo, determined using the pulse-echo technique at regular intervals of time, appears to be a promising tool for monitoring defect growth induced by a high temperature and high pressure hydrogen-related attack.

Pressure-Induced Amorphization and a New High Density Amorphous Metallic Phase in Matrix-Free Ge Nanoparticles.

PubMed

Corsini, Niccolo R C; Zhang, Yuanpeng; Little, William R; Karatutlu, Ali; Ersoy, Osman; Haynes, Peter D; Molteni, Carla; Hine, Nicholas D M; Hernandez, Ignacio; Gonzalez, Jesus; Rodriguez, Fernando; Brazhkin, Vadim V; Sapelkin, Andrei

2015-11-11

Over the last two decades, it has been demonstrated that size effects have significant consequences for the atomic arrangements and phase behavior of matter under extreme pressure. Furthermore, it has been shown that an understanding of how size affects critical pressure-temperature conditions provides vital guidance in the search for materials with novel properties. Here, we report on the remarkable behavior of small (under ~5 nm) matrix-free Ge nanoparticles under hydrostatic compression that is drastically different from both larger nanoparticles and bulk Ge. We discover that the application of pressure drives surface-induced amorphization leading to Ge-Ge bond overcompression and eventually to a polyamorphic semiconductor-to-metal transformation. A combination of spectroscopic techniques together with ab initio simulations were employed to reveal the details of the transformation mechanism into a new high density phase-amorphous metallic Ge.

Experimental study of elliptical jet from sub to supercritical conditions

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

Muthukumaran, C. K.; Vaidyanathan, Aravind, E-mail: aravind7@iist.ac.in

2014-04-15

The jet mixing at supercritical conditions involves fluid dynamics as well as thermodynamic phenomena. All the jet mixing studies at critical conditions to the present date have focused only on axisymmetric jets. When the liquid jet is injected into supercritical environment, the thermodynamic transition could be well understood by considering one of the important fluid properties such as surface tension since it decides the existence of distinct boundary between the liquid and gaseous phase. It is well known that an elliptical liquid jet undergoes axis-switching phenomena under atmospheric conditions due to the presence of surface tension. The experimental investigations weremore » carried out with low speed elliptical jet under supercritical condition. Investigation of the binary component system with fluoroketone jet and N{sub 2} gas as environment shows that the surface tension force dominates for a large downstream distance, indicating delayed thermodynamic transition. The increase in pressure to critical state at supercritical temperature is found to expedite the thermodynamic transition. The ligament like structures has been observed rather than droplets for supercritical pressures. However, for the single component system with fluoroketone jet and fluoroketone environment shows that the jet disintegrates into droplets as it is subjected to the chamber conditions even for the subcritical pressures and no axis switching phenomenon is observed. For a single component system, as the pressure is increased to critical state, the liquid jet exhibits gas-gas like mixing behavior and that too without exhibiting axis-switching behavior.« less

Transonic buffet behavior of Northrop F-5A aircraft

NASA Technical Reports Server (NTRS)

Hwang, C.; Pi, W. S.

1974-01-01

Flight tests were performed on an F-5A aircraft to investigate the dynamic buffet pressure distribution on the wing surfaces and the responses during a series of transonic maneuvers called wind-up turns. The conditions under which the tests were conducted are defined. The fluctuating buffet pressure data on the right wing of the aircraft were acquired by miniaturized semiconductor-type pressure transducers flush mounted on the wing. Processing of the fluctuating pressures and responses included the generation of the auto- and cross-power spectra, and of the spatial correlation functions. An analytical correlation procedure was introduced to compute the aircraft response spectra based on the measured buffet pressures.

Evidence of alloy formation during reduction of platinized tin oxide surfaces

NASA Technical Reports Server (NTRS)

Gardner, Steven D.; Hoflund, Gar B.; Davidson, Mark R.; Schryer, David R.

1989-01-01

Ion scattering spectroscopy, Auger electron spectroscopy, and electron spectroscopy for chemical analysis have been used to examine a platinized tin oxide catalyst surface before, during, and after reduction by annealing under vacuum at 250 to 450 C. These techniques were then used to examine the reduced surface after a room-temperature, low-pressure oxygen exposure. The spectral results and the behavior of the reduced surface toward oxygen exposure both indicate that a Pt/Sn alloy is produced during reduction.

Semiconductor Clathrates: In Situ Studies of Their High Pressure, Variable Temperature and Synthesis Behavior

NASA Astrophysics Data System (ADS)

Machon, D.; McMillan, P. F.; San-Miguel, A.; Barnes, P.; Hutchins, P. T.

In situ studies have provided valuable new information on the synthesis mechanisms, low temperature properties and high pressure behavior of semiconductor clathrates. Here we review work using synchrotron and laboratory X-ray diffraction and Raman scattering used to study mainly Si-based clathrates under a variety of conditions. During synthesis of the Type I clathrate Na8Si46 by metastable thermal decomposition from NaSi in vacuum, we observe an unusual quasi-epitaxial process where the clathrate structure appears to nucleate and grow directly from the Na-deficient Zintl phase surface. Low temperature X-ray studies of the guest-free Type II clathrate framework Si136 reveal a region of negative thermal expansion behavior as predicted theoretically and analogous to that observed for diamond-structured Si. High pressure studies of Si136 lead to metastable production of the β-Sn structured Si-II phase as well as perhaps other metastable crystalline materials. High pressure investigations of Type I clathrates show evidence for a new class of apparently isostructural densification transformations followed by amorphization in certain cases.

Lubricant Rheology in Concentrated Contacts

NASA Technical Reports Server (NTRS)

Jacobson, B. O.

1984-01-01

Lubricant behavior in highly stressed situtations shows that a Newtonian model for lubricant rheology is insufficient for explanation of traction behavior. The oil film build up is predicted by using a Newtonian lubricant model except at high slide to roll ratios and at very high loads, where the nonNewtonian behavior starts to be important already outside the Hertzian contact area. Static and dynamic experiments are reported. In static experiments the pressure is applied to the lubricant more than a million times longer than in an EHD contact. Depending on the pressure-temperature history of the experiment the lubricant will become a crystallized or amorphous solid at high pressures. In dynamic experiments, the oil is in an amorphous solid state. Depending on the viscosity, time scale, elasticity of the oil and the bearing surfaces, the oil film pressure, shear strain rate and the type of lubricant, different properties of the oil are important for prediction of shear stresses in the oil. The different proposed models for the lubricant, which describe it to a Newtonian liquid, an elastic liquid, a plastic liquid and an elastic-plastic solid.

A micro-machined piezoelectric flexural-mode hydrophone with air backing: a hydrostatic pressure-balancing mechanism for integrity preservation.

PubMed

Choi, Sungjoon; Lee, Haksue; Moon, Wonkyu

2010-09-01

Although an air-backed thin plate is an effective sound receiver structure, it is easily damaged via pressure unbalance caused by external hydrostatic pressure. To overcome this difficulty, a simple pressure-balancing module is proposed. Despite its small size and relative simplicity, with proper design and operation, micro-channel structure provides a solution to the pressure-balancing problem. If the channel size is sufficiently small, the gas-liquid interface may move back and forth without breach by the hydrostatic pressure since the surface tension can retain the interface surface continuously. One input port of the device is opened to an intermediate liquid, while the other port is connected to the air-backing chamber. As the hydrostatic pressure increases, the liquid in the micro-channel compresses the air, and the pressure in the backing chamber is then equalized to match the external hydrostatic pressure. To validate the performance of the proposed mechanism, a micro-channel prototype is designed and integrated with the piezoelectric micro-machined flexural sensor developed in our previous work. The working principle of the mechanism is experimentally verified. In addition, the effect of hydrostatic pressure on receiving sensitivity is evaluated and compared with predicted behavior.

Surface tension effects on the behavior of a cavity growing, collapsing, and rebounding near a rigid wall.

PubMed

Zhang, Zhen-yu; Zhang, Hui-sheng

2004-11-01

Surface tension effects on the behavior of a pure vapor cavity or a cavity containing some noncondensible contents, which is growing, collapsing, and rebounding axisymmetrically near a rigid wall, are investigated numerically by the boundary integral method for different values of dimensionless stand-off parameter gamma, buoyancy parameter delta, and surface tension parameter beta. It is found that at the late stage of the collapse, if the resultant action of the Bjerknes force and the buoyancy force is not small, surface tension will not have significant effects on bubble behavior except that the bubble collapse time is shortened and the liquid jet becomes wider. If the resultant action of the two force is small enough, surface tension will have significant and in some cases substantial effects on bubble behavior, such as changing the direction of the liquid jet, making a new liquid jet appear, in some cases preventing the bubble from rebound before jet impact, and in other cases causing the bubble to rebound or even recollapse before jet impact. The mechanism of surface tension effects on the collapsing behavior of a cavity has been analyzed. The mechanisms of some complicated phenomena induced by surface tension effects are illustrated by analysis of the computed velocity fields and pressure contours of the liquid flow outside the bubble at different stages of the bubble evolution.

Surface Mechanical and Rheological Behaviors of Biocompatible Poly((D,L-lactic acid-ran-glycolic acid)-block-ethylene glycol) (PLGA-PEG) and Poly((D,L-lactic acid-ran-glycolic acid-ran-ε-caprolactone)-block-ethylene glycol) (PLGACL-PEG) Block Copolymers at the Air-Water Interface

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

Kim, Hyun Chang; Lee, Hoyoung; Khetan, Jawahar

Air–water interfacial monolayers of poly((d,l-lactic acid-ran-glycolic acid)-block-ethylene glycol) (PLGA–PEG) exhibit an exponential increase in surface pressure under high monolayer compression. In order to understand the molecular origin of this behavior, a combined experimental and theoretical investigation (including surface pressure–area isotherm, X-ray reflectivity (XR) and interfacial rheological measurements, and a self-consistent field (SCF) theoretical analysis) was performed on air–water monolayers formed by a PLGA–PEG diblock copolymer and also by a nonglassy analogue of this diblock copolymer, poly((d,l-lactic acid-ran-glycolic acid-ran-caprolactone)-block-ethylene glycol) (PLGACL–PEG). The combined results of this study show that the two mechanisms, i.e., the glass transition of the collapsed PLGA filmmore » and the lateral repulsion of the PEG brush chains that occur simultaneously under lateral compression of the monolayer, are both responsible for the observed PLGA–PEG isotherm behavior. Upon cessation of compression, the high surface pressure of the PLGA–PEG monolayer typically relaxes over time with a stretched exponential decay, suggesting that in this diblock copolymer situation, the hydrophobic domain formed by the PLGA blocks undergoes glass transition in the high lateral compression state, analogously to the PLGA homopolymer monolayer. In the high PEG grafting density regime, the contribution of the PEG brush chains to the high monolayer surface pressure is significantly lower than what is predicted by the SCF model because of the many-body attraction among PEG segments (referred to in the literature as the “n-cluster” effects). The end-grafted PEG chains were found to be protein resistant even under the influence of the “n-cluster” effects.« less

High Pressure Cosmochemistry of Major Planetary Interiors: Laboratory Studies of the Water-rich Region of the System Ammonia-water

NASA Technical Reports Server (NTRS)

Nicol, M.; Johnson, M.; Koumvakalis, A. S.

1985-01-01

The behavior of gas-ice mixtures in major planets at very high pressures was studied. Some relevant pressure-temperature-composition (P-T-X) regions of the hydrogen (H2)-helium (He)-water (H2O-ammonia (NH3)-methane (CH4) phase diagram were determined. The studies, and theoretical model, of the relevant phases, are needed to interpret the compositions of ice-gas systems at conditions of planetary interest. The compositions and structures of a multiphase, multicomponent system at very high pressures care characterized, and the goal is to characterize this system over a wide range of low and high temperatures. The NH3-H2O compositions that are relevant to planetary problems yet are easy to prepare were applied. The P-T surface of water was examined and the corresponding surface for NH3 was determined. The T-X diagram of ammonia-water at atmospheric pressure was studied and two water-rich phases were found, NH3-2H2O (ammonia dihydrate), which melts incongruently, and NH3.H2O (ammonia monohydrate), which is nonstoichiometric and melts at a higher temperature than the dihydrate. It is suggested that a P-T surface at approximately the monohydrate composition and the P-X surface at room temperature is determined.

Investigation of Surface Phenomena in Shocked Tin in Converging Geometry

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

Rousculp, Christopher L.; Oro, David Michael; Griego, Jeffrey Randall

2016-03-21

There is great interest in the behavior of the free surface of tin under shock loading. While it is known that meso-scale surface imperfections can seed the Richtmyer- Meshkov Instability (RMI) for a surface that is melted on release, much less is known about a tin surface that is solid, but plastically deforming. Here material properties such as shear and yield strength come into play especially in converging geometry. Previous experiments have been driven by direct contact HE. Usually a thin, flat target coupon is fielded with various single-mode, sinusoidal, machined, profiles on the free surface. The free surface ismore » adjacent to either vacuum or an inert receiver gas. Most of these previous driver/target configurations have been nominal planer geometry. With modern HE it has been straightforward to shock tin into melt on release. However it has been challenging to achieve a low enough pressure for solid state on release. Here we propose to extend the existing base of knowledge to include the behavior of the free surface of tin in cylindrical converging geometry. By shock loading a cylindrical tin shell with a magnetically driven cylindrical liner impactor, the free surface evolution can be diagnosed with proton radiography. With the PHELIX capacitor bank, the drive can easily be varied to span the pressure range to achieve solid, mixed, and liquid states on release. A conceptual cylindrical liner and target is shown in Figure 1.« less

Mixing-induced fluid destratification and ullage condensation

NASA Technical Reports Server (NTRS)

Meserole, Jere S.; Jones, Ogden S.; Fortini, Anthony F.

1987-01-01

In many applications, on-orbit storage and transfer of cryogens will require forced mixing to control tank pressure without direct venting to space. During a no-vent transfer or during operation of a thermodynamic vent system in a cryogen storage tank, pressure control is achieved by circulating cool liquid to the liquid-vapor interface to condense some of the ullage vapor. To measure the pressure and temperature response rates in mixing-induced condensation, an experiment has been developed using Freon 11 to simulate the two-phase behavior of a cryogen. A thin layer at the liquid surface is heated to raise the tank pressure, and then a jet mixer is turned on to circulate the liquid, cool the surface, and reduce the pressure. Many nozzle configurations and flow rates are used. Tank pressure and the temperature profiles in the ullage and the liquid are measured. Initial data from this ground test are shown correlated with normal-gravity and drop-tower dye-mixing data. Pressure collapse times are comparable to the dye-mixing times, whereas the times needed for complete thermal mixing are much longer than the dye-mixing times.

Experimental Study of the Effects of Periodic Unsteady Wakes on Flow Separation in Low Pressure Turbines

NASA Technical Reports Server (NTRS)

Ozturk, Burak; Schobeiri, Meinhard T.

2009-01-01

The present study, which is the first of a series of investigations of low pressure turbine (LPT) boundary layer aerodynamics, is aimed at providing detailed unsteady boundary layer flow information to understand the underlying physics of the inception, onset, and extent of the separation zone. A detailed experimental study on the behavior of the separation zone on the suction surface of a highly loaded LPT-blade under periodic unsteady wake flow is presented. Experimental investigations were performed on a large-scale, high-subsonic unsteady turbine cascade research facility with an integrated wake generator and test section unit. Blade Pak B geometry was used in the cascade. The wakes were generated by continuously moving cylindrical bars device. Boundary layer investigations were performed using hot wire anemometry at Reynolds number of 110,000, based on the blade suction surface length and the exit velocity, for one steady and two unsteady inlet flow conditions, with the corresponding passing frequencies, wake velocities, and turbulence intensities. The reduced frequencies cover the entire operation range of LP-turbines. In addition to the unsteady boundary layer measurements, blade surface pressure measurements were performed at Re = 50,000, 75,000, 100,000, 110,000, and 125,000. For each Reynolds number, surface pressure measurements are carried out at one steady and two periodic unsteady inlet flow conditions. Detailed unsteady boundary layer measurement identifies the onset and extension of the separation zone as well as its behavior under unsteady wake flow. The results, presented in ensemble-averaged and contour plot forms, help to understand the physics of the separation phenomenon under periodic unsteady wake flow.

Rupture of thin liquid films on structured surfaces

NASA Astrophysics Data System (ADS)

Ajaev, Vladimir S.; Gatapova, Elizaveta Ya.; Kabov, Oleg A.

2011-10-01

We investigate stability and breakup of a thin liquid film on a solid surface under the action of disjoining pressure. The solid surface is structured by parallel grooves. Air is trapped in the grooves under the liquid film. Our mathematical model takes into account the effect of slip due to the presence of menisci separating the liquid film from the air inside the grooves, the deformation of these menisci due to local variations of pressure in the liquid film, and nonuniformities of the Hamaker constant which measures the strength of disjoining pressure. Both linear stability and strongly nonlinear evolution of the film are analyzed. Surface structuring results in decrease of the fastest growing instability wavelength and the rupture time. It is shown that a simplified description of film dynamics based on the standard formula for effective slip leads to significant deviations from the behavior seen in our simulations. Self-similar decay over several orders of magnitude of the film thickness near the rupture point is observed. We also show that the presence of the grooves can lead to instability in otherwise stable films if the relative groove width is above a critical value, found as a function of disjoining pressure parameters.

The atmosphere of 2060 Chiron

NASA Technical Reports Server (NTRS)

Meech, Karen J.; Belton, Michael J. S.

1990-01-01

An explanation for 2060 Chiron's behavior, which focuses on the influence of Chiron's mass on the development of its dust coma, is presented. It is suggested that dust is entrained by the flow of CO or another gas of similar volatility from an active region. It remains gravitationally bound on orbits confined to a region, roughly 5000 km in extent, that lies between the surface and an exopause imposed by radiation pressure forces. The influence of radiation pressure transforms the initial particle trajectories into satellite orbits with a characteristic period of 20 days and orbital residence time of about 25 revolutions. The particle population in the coma slowly increases, explaining Chiron's photometric behavior.

Demixing, surface nematization, and competing adsorption in binary mixtures of hard rods and hard spheres under confinement

NASA Astrophysics Data System (ADS)

Wu, Liang; Malijevský, Alexandr; Avendaño, Carlos; Müller, Erich A.; Jackson, George

2018-04-01

A molecular simulation study of binary mixtures of hard spherocylinders (HSCs) and hard spheres (HSs) confined between two structureless hard walls is presented. The principal aim of the work is to understand the effect of the presence of hard spheres on the entropically driven surface nematization of hard rod-like particles at surfaces. The mixtures are studied using a constant normal-pressure Monte Carlo algorithm. The surface adsorption at different compositions is examined in detail. At moderate hard-sphere concentrations, preferential adsorption of the spheres at the wall is found. However, at moderate to high pressure (density), we observe a crossover in the adsorption behavior with nematic layers of the rods forming at the walls leading to local demixing of the system. The presence of the spherical particles is seen to destabilize the surface nematization of the rods, and the degree of demixing increases on increasing the hard-sphere concentration.

Demixing, surface nematization, and competing adsorption in binary mixtures of hard rods and hard spheres under confinement.

PubMed

Wu, Liang; Malijevský, Alexandr; Avendaño, Carlos; Müller, Erich A; Jackson, George

2018-04-28

A molecular simulation study of binary mixtures of hard spherocylinders (HSCs) and hard spheres (HSs) confined between two structureless hard walls is presented. The principal aim of the work is to understand the effect of the presence of hard spheres on the entropically driven surface nematization of hard rod-like particles at surfaces. The mixtures are studied using a constant normal-pressure Monte Carlo algorithm. The surface adsorption at different compositions is examined in detail. At moderate hard-sphere concentrations, preferential adsorption of the spheres at the wall is found. However, at moderate to high pressure (density), we observe a crossover in the adsorption behavior with nematic layers of the rods forming at the walls leading to local demixing of the system. The presence of the spherical particles is seen to destabilize the surface nematization of the rods, and the degree of demixing increases on increasing the hard-sphere concentration.

The structure of untwisted magnetic flux tubes. [solar magnetic field distribution

NASA Technical Reports Server (NTRS)

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

1982-01-01

While most previous investigations have concentrated on slender flux tubes, the present study of the equilibrium structure of an axisymmetric magnetic flux tube, confined by an external pressure that varies along the length of the tube, explores the properties of thick tubes in order to establish the degree to which slender tube theory is valid. It is found that slender flux tube results may in some cases give no indication of thick tube behavior in a nonuniform atmosphere. Depending on boundary conditions applied at the ends of the tube, it may expand or contract upon entering a region of increasing pressure. Rather than expanding indefinitely, the tube surface may form a cusped shape when a point of external pressure on the tube surface falls to equality with the internal pressure. Numerical solutions for an initially uniform tube give smaller expansions than would be expected from slender tube theory.

Behavior of HfB2-SiC Materials in Simulated Re-Entry Environments

NASA Technical Reports Server (NTRS)

Ellerby, Don; Beckman, Sarah; Irby, Edward; Johnson, Sylvia M.; Gunsman, Michael; Gasch, Matthew; Ridge, Jerry; Martinez, Ed; Squire, Tom; Olejniczak, Joe

2003-01-01

The objectives of this research are to: 1) Investigate the oxidation/ablation behavior of HfB2/SiC materials in simulated re-entry environments; 2) Use the arc jet test results to define appropriate use environments for these materials for use in vehicle design. The parameters to be investigated include: surface temperature, stagnation pressure, duration, number of cycles, and thermal stresses.

[Establishment and application of mechanical strain loading system of multi-channel cells].

PubMed

Li, Yongming; Wang, Hua; Zhang, Xiaodong; Tang, Lin

2012-02-01

Based on single-chip microcomputer, we have established a mechanical strain loading system with multi-channel to study the biological behavior of cultured cells in vitro under mechanical strain. We developed a multi-channel cell strain loading device controlled by single-chip microcomputer. We controlled the vacuum pump with vacuum chamber to make negative pressure changing periodically in the vacuum chamber. The tested cells were seeded on the surface of an elastic membrane mounted on the vacuum chamber, and could be strained or relaxed by cyclic pressure. Since the cells are attached to the surface of the membrane, they presumably experience the same deformation as that was applied to the membrane. The system was easy to carry and to operate, with deformation rate (1%-21%) and frequency (0-0. 5Hz) which could be adjusted correctly according to experimental requirement, and could compare different deformation rate of three channels at the same time. The system ran stably and completely achieved design aims, and provided a method to study the biological behavior of cultured cells attached to the surface of the elastic membrane under mechanical strain in vitro.

SPH for impact force and ricochet behavior of water-entry bodies

NASA Astrophysics Data System (ADS)

Omidvar, Pourya; Farghadani, Omid; Nikeghbali, Pooyan

The numerical modeling of fluid interaction with a bouncing body has many applications in scientific and engineering application. In this paper, the problem of water impact of a body on free-surface is investigated, where the fixed ghost boundary condition is added to the open source code SPHysics2D1 to rectify the oscillations in pressure distributions with the repulsive boundary condition. First, after introducing the methodology of SPH and the option of boundary conditions, the still water problem is simulated using two types of boundary conditions. It is shown that the fixed ghost boundary condition gives a better result for a hydrostatics pressure. Then, the dam-break problem, which is a bench mark test case in SPH, is simulated and compared with available data. In order to show the behavior of the hydrostatics forces on bodies, a fix/floating cylinder is placed on free surface looking carefully at the force and heaving profile. Finally, the impact of a body on free-surface is successfully simulated for different impact angles and velocities.

Surface tension of dilute alcohol-aqueous binary fluids: n-Butanol/water, n-Pentanol/water, and n-Hexanol/water solutions

NASA Astrophysics Data System (ADS)

Cheng, Kuok Kong; Park, Chanwoo

2017-07-01

Surface tension of pure fluids, inherently decreasing with regard to temperature, creates a thermo-capillary-driven (Marangoni) flow moving away from a hot surface. It has been known that few high-carbon alcohol-aqueous solutions exhibit an opposite behavior of the surface tension increasing with regard to temperature, such that the Marangoni flow moves towards the hot surface (self-rewetting effect). We report the surface tensions of three dilute aqueous solutions of n-Butanol, n-Pentanol and n-Hexanol as self-rewetting fluids measured for ranges of alcohol concentration (within solubility limits) and fluid temperatures (25-85 °C). A maximum bubble pressure method using a leak-tight setup was used to measure the surface tension without evaporation losses of volatile components. It was found from this study that the aqueous solutions with higher-carbon alcohols exhibit a weak self-rewetting behavior, such that the surface tensions remain constant or slightly increases above about 60 °C. These results greatly differ from the previously reported results showing a strong self-rewetting behavior, which is attributed to the measurement errors associated with the evaporation losses of test fluids during open-system experiments.

Humidity-dependent compression-induced glass transition of the air–water interfacial Langmuir films of poly(D,L-lactic acid- ran-glycolic acid) (PLGA)

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

Kim, Hyun Chang; Lee, Hoyoung; Jung, Hyunjung

2015-08-26

Constant rate compression isotherms of the air–water interfacial Langmuir films of poly(D,L-lactic acid- ran-glycolic acid) (PLGA)show a distinct feature of an exponential increase in surface pressure in the high surface polymer concentration regime. We have previously demonstrated that this abrupt increase in surface pressure is linked to the glass transition of the polymer film, but the detailed mechanism of this process is not understood. In order to obtain a molecular-level understanding of this behavior, we performed extensive characterizations of the surface mechanical, structural and rheological properties of Langmuir PLGA films at the air–water interface, using combined experimental techniques including themore » Langmuir film balance, X-ray reflectivity and double-wall-ring interfacial rheometry methods.« less

Reconstruction of instantaneous surface normal velocity of a vibrating structure using interpolated time-domain equivalent source method

NASA Astrophysics Data System (ADS)

Geng, Lin; Bi, Chuan-Xing; Xie, Feng; Zhang, Xiao-Zheng

2018-07-01

Interpolated time-domain equivalent source method is extended to reconstruct the instantaneous surface normal velocity of a vibrating structure by using the time-evolving particle velocity as the input, which provides a non-contact way to overall understand the instantaneous vibration behavior of the structure. In this method, the time-evolving particle velocity in the near field is first modeled by a set of equivalent sources positioned inside the vibrating structure, and then the integrals of equivalent source strengths are solved by an iterative solving process and are further used to calculate the instantaneous surface normal velocity. An experiment of a semi-cylindrical steel plate impacted by a steel ball is investigated to examine the ability of the extended method, where the time-evolving normal particle velocity and pressure on the hologram surface measured by a Microflown pressure-velocity probe are used as the inputs of the extended method and the method based on pressure measurements, respectively, and the instantaneous surface normal velocity of the plate measured by a laser Doppler vibrometry is used as the reference for comparison. The experimental results demonstrate that the extended method is a powerful tool to visualize the instantaneous surface normal velocity of a vibrating structure in both time and space domains and can obtain more accurate results than that of the method based on pressure measurements.

Phase transition of a DPPC bilayer induced by an external surface pressure: from bilayer to monolayer behavior. a molecular dynamics simulation study.

PubMed

López Cascales, J J; Otero, T F; Fernandez Romero, A J; Camacho, L

2006-06-20

Understanding the lipid phase transition of lipid bilayers is of great interest from biophysical, physicochemical, and technological points of view. With the aim of elucidating the structural changes that take place in a DPPC phospholipid bilayer induced by an external isotropic surface pressure, five computer simulations were carried out in a range from 0.1 to 40 mN/m. Molecular dynamics simulations provided insight into the structural changes that took place in the lipid structure. It was seen that low pressures ranging from 0.1 to 1 mN/m had hardly any effect on the structure, electrical properties, or hydration of the lipid bilayer. However, for pressures above 40 mN/m, there was a sharp change in the lipid-lipid interactions, hydrocarbon lipid fluidity, and electrostatic potential, corresponding to the mesomorphic transition from a liquid crystalline state (L(alpha)) to its gel state (P'(beta)). The head lipid orientation remained almost unaltered, parallel to the lipid layer, as the surface pressure was increased, although a noticeable change in its angular distribution function was evident with the phase transition.

Control of sound radiation from a wavepacket over a curved surface

NASA Technical Reports Server (NTRS)

Maestrello, Lucio; El Hady, Nabil M.

1989-01-01

Active control of acoustic pressure in the far field resulting from the growth and decay of a wavepacket convecting in a boundary layer over a concave-convex surface is investigated numerically using direct computations of the Navier-Stokes equations. The resulting sound radiation is computed using linearized Euler equations with the pressure from the Navier-Stokes solution as a time-dependent boundary condition. The acoustic far field exhibits directivity type of behavior that points upstream to the flow direction. A fixed control algorithm is used where the attenuation signal is synthesized by a filter which actively adapt it to the amplitude-time response of the outgoing acoustic wave.

Three-Dimensional Digital Image Correlation of a Composite Overwrapped Pressure Vessel During Hydrostatic Pressure Tests

NASA Technical Reports Server (NTRS)

Revilock, Duane M., Jr.; Thesken, John C.; Schmidt, Timothy E.

2007-01-01

Ambient temperature hydrostatic pressurization tests were conducted on a composite overwrapped pressure vessel (COPV) to understand the fiber stresses in COPV components. Two three-dimensional digital image correlation systems with high speed cameras were used in the evaluation to provide full field displacement and strain data for each pressurization test. A few of the key findings will be discussed including how the principal strains provided better insight into system behavior than traditional gauges, a high localized strain that was measured where gages were not present and the challenges of measuring curved surfaces with the use of a 1.25 in. thick layered polycarbonate panel that protected the cameras.

VTOL in ground effect flows for closely spaced jets. [to predict pressure and upwash forces on aircraft structures

NASA Technical Reports Server (NTRS)

Migdal, D.; Hill, W. G., Jr.; Jenkins, R. C.

1979-01-01

Results of a series of in ground effect twin jet tests are presented along with flow models for closely spaced jets to help predict pressure and upwash forces on simulated aircraft surfaces. The isolated twin jet tests revealed unstable fountains over a range of spacings and jet heights, regions of below ambient pressure on the ground, and negative pressure differential in the upwash flow field. A separate computer code was developed for vertically oriented, incompressible jets. This model more accurately reflects fountain behavior without fully formed wall jets, and adequately predicts ground isobars, upwash dynamic pressure decay, and fountain lift force variation with height above ground.

Headgroup effects of template monolayers on the adsorption behavior and conformation of glucose oxidase adsorbed at air/liquid interfaces.

PubMed

Wang, Ke-Hsuan; Syu, Mei-Jywan; Chang, Chien-Hsiang; Lee, Yuh-Lang

2011-06-21

Stearic acid (SA) and octadecylamine (ODA) monolayers at the air/liquid interface were used as template layers to adsorb glucose oxidase (GOx) from aqueous solution. The effect of the template monolayers on the adsorption behavior of GOx was studied in terms of the variation of surface pressure, the evolution of surface morphology observed by BAM and AFM, and the conformation of adsorbed GOx. The results show that the presence of a template monolayer can enhance the adsorption rate of GOx; furthermore, ODA has a higher ability, compared to SA, to adsorb GOx, which is attributed to the electrostatic attractive interaction between ODA and GOx. For adsorption performed on a bare surface or on an SA monolayer, the surface pressure approaches an equilibrium value (ca. 8 mN/m) after 2 to 3 h of adsorption and remains nearly constant in the following adsorption process. For the adsorption on an ODA monolayer, the surface pressure will increase further 1 to 2 h after approaching the first equilibrium pressure, which is termed the second adsorption stage. The measurement of circular dichroism (CD) spectroscopy indicates that the Langmuir-Blodgett films of adsorbed GOx transferred at the first equilibrium state (π = 8 mN/m) have mainly a β-sheet conformation, which is independent of the type of template monolayers. However, the ODA/GOx LB film transferred at the second adsorption stage has mainly an α-helix conformation. It is concluded that the specific interaction between ODA and GOx not only leads to a higher adsorption rate and adsorbed amount of GOx but also induces a conformation change in adsorbed GOx from β-sheet to α-helix. The present results indicate that is possible to control the conformation of adsorbed protein by selecting the appropriate template monolayer. © 2011 American Chemical Society

Investigation of blown boundary layers with an improved wall jet system. Ph.D. Thesis. Final Technical Report, 1 Jul. 1978 - Dec. 1979; [to prevent turbulent boundary layer separation

NASA Technical Reports Server (NTRS)

Saripalli, K. R.; Simpson, R. L.

1979-01-01

The behavior of two dimensional incompressible turbulent wall jets submerged in a boundary layer when they are used to prevent boundary layer separation on plane surfaces is investigated. The experimental set-up and instrumentation are described. Experimental results of zero pressure gradient flow and adverse pressure gradient flow are presented. Conclusions are given and discussed.

Non-Gaussian PDF Modeling of Turbulent Boundary Layer Fluctuating Pressure Excitation

NASA Technical Reports Server (NTRS)

Steinwolf, Alexander; Rizzi, Stephen A.

2003-01-01

The purpose of the study is to investigate properties of the probability density function (PDF) of turbulent boundary layer fluctuating pressures measured on the exterior of a supersonic transport aircraft. It is shown that fluctuating pressure PDFs differ from the Gaussian distribution even for surface conditions having no significant discontinuities. The PDF tails are wider and longer than those of the Gaussian model. For pressure fluctuations upstream of forward-facing step discontinuities and downstream of aft-facing step discontinuities, deviations from the Gaussian model are more significant and the PDFs become asymmetrical. Various analytical PDF distributions are used and further developed to model this behavior.

Effects of coarse grain size distribution and fine particle content on pore fluid pressure and shear behavior in experimental debris flows

NASA Astrophysics Data System (ADS)

Kaitna, Roland; Palucis, Marisa C.; Yohannes, Bereket; Hill, Kimberly M.; Dietrich, William E.

2016-02-01

Debris flows are typically a saturated mixture of poorly sorted particles and interstitial fluid, whose density and flow properties depend strongly on the presence of suspended fine sediment. Recent research suggests that grain size distribution (GSD) influences excess pore pressures (i.e., pressure in excess of predicted hydrostatic pressure), which in turn plays a governing role in debris flow behaviors. We report a series of controlled laboratory experiments in a 4 m diameter vertically rotating drum where the coarse particle size distribution and the content of fine particles were varied independently. We measured basal pore fluid pressures, pore fluid pressure profiles (using novel sensor probes), velocity profiles, and longitudinal profiles of the flow height. Excess pore fluid pressure was significant for mixtures with high fines fraction. Such flows exhibited lower values for their bulk flow resistance (as measured by surface slope of the flow), had damped fluctuations of normalized fluid pressure and normal stress, and had velocity profiles where the shear was concentrated at the base of the flow. These effects were most pronounced in flows with a wide coarse GSD distribution. Sustained excess fluid pressure occurred during flow and after cessation of motion. Various mechanisms may cause dilation and contraction of the flows, and we propose that the sustained excess fluid pressures during flow and once the flow has stopped may arise from hindered particle settling and yield strength of the fluid, resulting in transfer of particle weight to the fluid. Thus, debris flow behavior may be strongly influenced by sustained excess fluid pressures controlled by particle settling rates.

Morphology-Patterned Anisotropic Wetting Surface for Fluid Control and Gas-Liquid Separation in Microfluidics.

PubMed

Wang, Shuli; Yu, Nianzuo; Wang, Tieqiang; Ge, Peng; Ye, Shunsheng; Xue, Peihong; Liu, Wendong; Shen, Huaizhong; Zhang, Junhu; Yang, Bai

2016-05-25

This article shows morphology-patterned stripes as a new platform for directing flow guidance of the fluid in microfluidic devices. Anisotropic (even unidirectional) spreading behavior due to anisotropic wetting of the underlying surface is observed after integrating morphology-patterned stripes with a Y-shaped microchannel. The anisotropic wetting flow of the fluid is influenced by the applied pressure, dimensions of the patterns, including the period and depth of the structure, and size of the channels. Fluids with different surface tensions show different flowing anisotropy in our microdevice. Moreover, the morphology-patterned surfaces could be used as a microvalve, and gas-water separation in the microchannel was realized using the unidirectional flow of water. Therefore, benefiting from their good performance and simple fabrication process, morphology-patterned surfaces are good candidates to be applied in controlling the fluid behavior in microfluidics.

Magnetic anisotropy at material interfaces

NASA Astrophysics Data System (ADS)

Greene, Peter Kevin

In this dissertation, a comprehensive set of depth dependent magnetic measurements, as well as structural characterizations, were carried out on the Co/Pd multilayer system. The first-order reversal curve (FORC) technique is applied extensively to identify reversal mechanisms and different reversal phases within the material. In particular, the extension of the FORC technique to x-ray magnetic circular dichroism (XMCD) as a surface sensitive technique that identifies reversible magnetization change was performed for the first time. Polarized neutron reflectivity (PNR) was also used to directly measure the magnetization as a function of depth. The effects of deposition pressure grading within the Co/Pd multilayers were investigated. Structures were graded with three distinct pressure regions. FORC analysis shows that not only does increasing the deposition pressure increase the coercivity and effective anisotropy within that region, but also the order in which the pressure is changed also affects the entire structure. Layers grown at high sputtering pressures tend to reverse via domain wall pinning and rotation while those grown at lower pressures reverse via rapid domain wall propagation laterally across the film. Having high pressure layers underneath low pressure layers causes disorder to vertically propagate and lessen the induced anisotropy gradient. This analysis is confirmed by depth dependent magnetization profiles obtain from PNR. Continuously pressure-graded Co/Pd multilayers were then sputtered at two incident angles onto porous aluminum oxide templates with different pore aspect ratios. The effects of pressure grading versus uniform low pressure deposition is studied, as well as the effect of the angle of the incident deposition flux. The coercivity of the pressure graded perpendicular flux sample is compared to the low pressure sample. Additionally the effect of deposition angle and pore sidewall deposition is investigated. It is shown that sidewall deposition strongly affects the reversal behavior. As another way to induce a vertical anisotropy gradient, Co/Pd multilayers were bombarded with Ar+ ions at different energies and fluences. The effects of the depth dependent structural damage as a function of irradiation conditions were investigated. It is shown that the structural damage weakens the perpendicular anisotropy of the surface layers, causing a tilting of the surface magnetic moment into the plane of the film. The surface behavior is explicitly measured and shown to have a significant tilting angle in the top 5 nm depending on irradiation energy and fluence. Continuing the study of vertical anisotropy gradients in Co/Pd multilayers, multilayers with varied Co thickness were studied. Four films with varying Co thickness profiles were created and then patterned into nanodot arrays with diameters between 700 nm and 70 nm. The different films were graded continuously, or in stacks with varying Co thicknesses. An anisotropy gradient is shown to be established in the graded samples, and the switching field is lowered as a result. Furthermore, in the continuously graded samples the magnetization reversal behavior is fundamentally different from all other samples. The thermal energy barriers are measured in the uniform and continuously graded samples, yielding similar results. Finally, the establishment of exchange anisotropy at the ferromagnet / antiferromagnet (FM/AFM) interface in the epitaxial Fe/CoO system is investigated as a function of AFM thickness. The establishment of frozen AFM moments is analyzed using the FORC technique. The FORC technique combined with vector coil measurements also shows the transition from rotatable AFM to pinned AFM moments and suggests a mechanism of winding domain walls within the bulk AFM. (Abstract shortened by UMI.).

Ejection of Particles from the Free Surface of Shock-Loaded Lead into Vacuum and Gas Medium

NASA Astrophysics Data System (ADS)

Ogorodnikov, V. A.; Mikhailov, A. L.; Erunov, S. V.; Antipov, M. V.; Fedorov, A. V.; Syrunin, M. A.; Kulakov, E. V.; Kleshchevnikov, O. A.; Yurtov, I. V.; Utenkov, A. A.; Finyushin, S. A.; Chudakov, E. A.; Kalashnikov, D. A.; Pupkov, A. S.; Chapaev, A. V.; Mishanov, A. V.; Glushikhin, V. V.; Fedoseev, A. V.; Tagirov, R. R.; Kostyukov, S. A.; Tagirova, I. Yu.; Saprykina, E. V.

2017-12-01

The presence and behavior of a gas-metal interfacial layer at the free surface of shock-wave driven flying vehicles in gases of various compositions and densities has not been sufficiently studied so far. We present new comparative data on "dusting" from the free surface of lead into vacuum and gas as dependent on the surface roughness, pressure amplitude at the shock-wave front, and phase state of the material. Methods of estimating the mass flux of ejected particles in the presence of a gas medium at the free metal surface are proposed.

Surface processing and ageing behavior of silk fabrics treated with atmospheric-pressure plasma for pigment-based ink-jet printing

NASA Astrophysics Data System (ADS)

Zhang, Chunming; Wang, Libing; Yu, Miao; Qu, Lijun; Men, Yajing; Zhang, Xiangwu

2018-03-01

Pigment inkjet printing has highlighted the advantages of cost-effective, short production cycle and environment-friendly. However, patterns directly printed with pigment inks usually have low color yields and blurry images which are caused by bleeding phenomenon. This work presents an atmospheric-pressure plasma method for improving the pigment-based ink-jet printing performance of silk fabrics. The effects of surface changes induced are discussed, with data derived from morphological study by atomic force microscopy (AFM), chemical analysis using X-ray photoelectron spectroscopy (XPS) and contact angle measurement. Ink-jet printing experiments were conducted to study the influence of measured changes on anti-bleeding property and color strength of treated and original samples. The ageing experiment indicates that the modified silk fabrics should be printed within 24 h after plasma processing for maximum color yields. This study explores an effective approach for the atmospheric-pressure plasma, which can provide its significant use in improving the surface properties and ink-jet printing performance of fabrics.

Surface phase behavior and microstructure of lipid/PEG-emulsifier monolayer-coated microbubbles.

PubMed

Borden, Mark A; Pu, Gang; Runner, Gabriel J; Longo, Marjorie L

2004-06-01

Langmuir trough methods and fluorescence microscopy were combined to investigate the phase behavior and microstructure of monolayer shells coating micron-scale bubbles (microbubbles) typically used in biomedical applications. The monolayer shell consisted of a homologous series of saturated acyl chain phospholipids and an emulsifier containing a single hydrophobic stearate chain and polyethylene glycol (PEG) head group. PEG-emulsifier was fully miscible with expanded phase lipids and phase separated from condensed phase lipids. Phase coexistence was observed in the form of dark condensed phase lipid domains surrounded by a sea of bright, emulsifier-rich expanded phase. A rich assortment of condensed phase area fractions and domain morphologies, including networks and other novel structures, were observed in each batch of microbubbles. Network domains were reproduced in Langmuir monolayers under conditions of heating-cooling followed by compression-expansion, as well as in microbubble shells that underwent surface flow with slight compression. Domain size decreased with increased cooling rate through the phase transition temperature, and domain branching increased with lipid acyl chain length at high cooling rates. Squeeze-out of the emulsifier at a surface pressure near 35 mN/m was indicated by a plateau in Langmuir isotherms and directly visualized with fluorescence microscopy, although collapse of the solid lipid domains occurred at much higher surface pressures. Compression of the monolayer past the PEG-emulsifier squeeze-out surface pressure resulted in a dark shell composed entirely of lipid. Under certain conditions, the PEG-emulsifier was reincorporated upon subsequent expansion. Factors that affect shell formation and evolution, as well as implications for the rational design of microbubbles in medical applications, are discussed.

Thermal-hydraulic behaviors of vapor-liquid interface due to arrival of a pressure wave

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

Inoue, Akira; Fujii, Yoshifumi; Matsuzaki, Mitsuo

In the vapor explosion, a pressure wave (shock wave) plays a fundamental role for triggering, propagation and enhancement of the explosion. Energy of the explosion is related to the magnitude of heat transfer rate from hot liquid to cold volatile one. This is related to an increasing rate of interface area and to an amount of transient heat flux between the liquids. In this study, the characteristics of transient heat transfer and behaviors of vapor film both on the platinum tube and on the hot melt tin drop, under same boundary conditions have been investigated. It is considered that theremore » exists a fundamental mechanism of the explosion in the initial expansion process of the hot liquid drop immediately after arrival of pressure wave. The growth rate of the vapor film is much faster on the hot liquid than that on the solid surface. Two kinds of roughness were observed, one due to the Taylor instability, by rapid growth of the explosion bubble, and another, nucleation sites were observed at the vapor-liquid interface. Based on detailed observation of early stage interface behaviors after arrival of a pressure wave, the thermal fragmentation mechanism is proposed.« less

Dynamic stall characterization using modal analysis of phase-averaged pressure distributions

NASA Astrophysics Data System (ADS)

Harms, Tanner; Nikoueeyan, Pourya; Naughton, Jonathan

2017-11-01

Dynamic stall characterization by means of surface pressure measurements can simplify the time and cost associated with experimental investigation of unsteady airfoil aerodynamics. A unique test capability has been developed at University of Wyoming over the past few years that allows for time and cost efficient measurement of dynamic stall. A variety of rotorcraft and wind turbine airfoils have been tested under a variety of pitch oscillation conditions resulting in a range of dynamic stall behavior. Formation, development and separation of different flow structures are responsible for the complex aerodynamic loading behavior experienced during dynamic stall. These structures have unique signatures on the pressure distribution over the airfoil. This work investigates the statistical behavior of phase-averaged pressure distribution for different types of dynamic stall by means of modal analysis. The use of different modes to identify specific flow structures is being investigated. The use of these modes for different types of dynamic stall can provide a new approach for understanding and categorizing these flows. This work uses airfoil data acquired under Army contract W911W60160C-0021, DOE Grant DE-SC0001261, and a gift from BP Alternative Energy North America, Inc.

The atmosphere of 2060 Chiron

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

Meech, K.J.; Belton, M.J.S.

An explanation for 2060 Chiron's behavior, which focuses on the influence of Chiron's mass on the development of its dust coma, is presented. It is suggested that dust is entrained by the flow of CO or another gas of similar volatility from an active region. It remains gravitationally bound on orbits confined to a region, roughly 5000 km in extent, that lies between the surface and an exopause imposed by radiation pressure forces. The influence of radiation pressure transforms the initial particle trajectories into satellite orbits with a characteristic period of 20 days and orbital residence time of about 25more » revolutions. The particle population in the coma slowly increases, explaining Chiron's photometric behavior. 74 refs.« less

Surface temperatures and glassy state investigations in tribology, part 2

NASA Technical Reports Server (NTRS)

Bair, S. S.; Winer, W. O.

1979-01-01

Measurements of lubricant shear rheological behavior in the amorphous solid region and near the liquid solid transition are reported. Elastic, plastic and viscous behavior was observed. The maximum yield shear stress (limiting shear stress) is a function of temperature and pressure and is believed to be the property which determines the maximum traction in elastohydrodynamic contacts such as traction drives. A shear rheological model based on primary laboratory data is proposed for concentrated contact lubrication. The model is Maxwell model modified with a limiting shear stress. Three material properties are required: low shear stress viscosity, limiting elastic shear modulus, and the limiting shear stress the material can withstand. All three are functions of temperature and pressure.

Influence of aramid fiber moisture regain during atmospheric plasma treatment on aging of treatment effects on surface wettability and bonding strength to epoxy

NASA Astrophysics Data System (ADS)

Ren, Yu; Wang, Chunxia; Qiu, Yiping

2007-09-01

One of the main differences between a low-pressure plasma treatment and an atmospheric pressure plasma treatment is that in atmosphere, the substrate material may absorb significant amount of water which may potentially influence the plasma treatment effects. This paper investigates how the moisture absorbed by aramid fibers during the atmospheric pressure plasma treatment influences the aging behavior of the modified surfaces. Kevlar 49 fibers with different moisture regains (MR) (0.5, 3.5 and 5.5%, respectively) are treated with atmospheric pressure plasma jet (APPJ) with helium as the carrier gas and oxygen as the treatment gas. Surface wettability and chemical compositions, and interfacial shear strengths (IFSS) to epoxy for the aramid fibers in all groups are determined using water contact angle measurements, X-ray photoelectron spectroscopy (XPS), and micro-bond pull out tests, respectively. Immediately after the plasma treatment, the treated fibers have substantially lower water contact angles, higher surface oxygen and nitrogen contents, and larger IFSS to epoxy than those of the control group. At the end of 30 day aging period, the fibers treated with 5.5% moisture regain had a lower water contact angle and more polar groups on the fiber surface, leading to 75% improvement of IFSS over the control fibers, while those for the 0.5 and 3.5% moisture regain groups were only 30%.

Space and surface charge behavior analysis of charge-eliminated polymer films

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

Oda, Tetsuji; Takashima, Kazunori; Ichiyama, Shinichiro

1995-12-31

Charge behavior of corona-charged or charge eliminated polymer films being dipped in the city water were studied. They were polytetrafluoroethylene (PTFE teflon{trademark}), polypropylene (PP), low density or high density polyethylene (LDPE or HDPE) thin films which are as grown (native) or plasma-processed. The plasma processing at low pressure was tested as antistatic processing. Charge elimination was done by being dipped in alcohol or city water. TSDC analysis and surface charge profile measurement were done for both charged and charge eliminated polymer films. Surface charge density of plasma processed polymer films just after corona charging is roughly the same as thatmore » of an original film. There is little difference between surface charge density profile of a native film and that of a plasma processed film. A large hetero current peak of TSDC was observed at room temperature for a processed film. It was found that the hetero peak disappears after charge elimination process. A pressure pulse wave method by using a pulse-driven piezoelectric PVDF polymer film as a piezoelectric actuator was newly developed to observe real space charge distribution. A little difference of internal space charge distribution between the plasma processed film and the native one after corona charging is found.« less

Asp-Gly based peptides confined at the surface of cationic gemini surfactant aggregates.

PubMed

Brizard, Aurélie; Dolain, Christel; Huc, Ivan; Oda, Reiko

2006-04-11

Cationic gemini surfactants complexed with anionic oligoglycine-aspartate (called gemini peptides hereafter) were synthesized, and their aggregation behaviors were studied. The effects of the hydrophobic chain length (C10-C22) and the length of the oligoglycine (0-4) were investigated, and it was clearly shown by critical micellar concentration, Krafft temperature, and isothermal surface pressure measurements that the hydrophobic effect and interpeptidic interaction influence the aggregation behavior in a cooperative manner. Below their Krafft temperatures, some of them formed both hydro- and organogels with three-dimensional networks and the Fourier transform infrared measurements show the presence of interpeptidic hydrogen bonds.

An example of slip instability resulting from displacement-varying strength

USGS Publications Warehouse

Lockner, D.; Byerlee, J.

1990-01-01

A rock cylinder, containing a clay-filled sawcut making an angle of 30?? to the sample axis, was deformed at constant confining and pore pressures and constant remote shortening rate. The sawcut surfaces contained a series of regularly spaced ridges and grooves oriented perpendicular to the direction of shear. The interaction of these grooved surfaces resulted in a sliding strength which varied periodically with displacement. By varying the effective machine stiffness through the use of an electronic feedback circuit, a range of stable and unstable slip behavior was achieved. In this way, we examined fault slip behavior which was dominated by displacement-dependent strength. ?? 1990 Birkha??user Verlag.

Surface ozone concentrations in Europe: Links with the regional-scale atmospheric circulation

NASA Astrophysics Data System (ADS)

Davies, T. D.; Kelly, P. M.; Low, P. S.; Pierce, C. E.

1992-06-01

Daily surface ozone observations from 1978 (1976 for some analyses) to 1988 for Bottesford (United Kingdom), Cabauw, Kloosterburen (The Netherlands), Hohenpeissenberg, Neuglobsow, Hamburg, and Arkona (Germany) are used to analyze links between surface ozone variations and the atmospheric circulation. A daily Europe-wide synoptic classification highlights marked differences between surface ozone/meteorology relationships in summer and winter. These relationships are characterized by correlations between daily surface ozone concentrations at each station and a local subregional surface pressure gradient (a wind speed index). Although there are geographical variations, which are explicable in terms of regional climatology, there are distinct annual cycles. In summer, the surface ozone/wind speed relationship exhibits the expected negative sign; however, in winter, the relationship is, in the main, strongly positive, especially at those stations which are more influenced by the vigorous westerlies. Spring and autumn exhibit negative, positive, or transitional (between summer and winter) behavior, depending on geographical position. It is suggested that these relationships reflect the importance of vertical exchange from the free troposphere to the surface in the nonsummer months. Composite surface pressure patterns and surface pressure anomaly (from the long-term mean) patterns associated with high surface ozone concentrations on daily and seasonal time scales are consistent with the surface ozone/wind speed relationships. Moreover, they demonstrate that high surface ozone concentrations, in a climatological time frame, can be associated with mean surface pressure patterns which have a synoptic reality and are robust. Such an approach may be useful in interpreting past variations in surface ozone and may help to isolate the effect of human activity. It is also possible that assessments can be made of the effect of projected future changes in the atmospheric circulation. This potential is illustrated by the fact that up to 65% of the interannual variance in 6-month mean surface ozone concentrations can be explained by the subregional wind speed index.

A review of recent theoretical and computational studies on pinned surface nanobubbles

NASA Astrophysics Data System (ADS)

Liu, Yawei; Zhang, Xianren

2018-01-01

The findings of long-lived surface nanobubbles in various experiments brought a puzzle in theory, as they were supposed to be dissolved in microseconds due to the high Laplace pressure. However, an increasing number of studies suggest that the pinning of contact line, together with certain levels of oversaturation, is responsible for the anomalous stability of surface nanobubble. This mechanism can interpret most characteristics of surface nanobubbles. Here we summarize recent theoretical and computational work to explain how the surface nanobubbles become stable with the pinning of contact line. Other related work devoted to understand the unusual behaviors of pinned surface nanobubbles are also reviewed here.

Sleep state classification using pressure sensor mats.

PubMed

Baran Pouyan, M; Nourani, M; Pompeo, M

2015-08-01

Sleep state detection is valuable in assessing patient's sleep quality and in-bed general behavior. In this paper, a novel classification approach of sleep states (sleep, pre-wake, wake) is proposed that uses only surface pressure sensors. In our method, a mobility metric is defined based on successive pressure body maps. Then, suitable statistical features are computed based on the mobility metric. Finally, a customized random forest classifier is employed to identify various classes including a new class for pre-wake state. Our algorithm achieves 96.1% and 88% accuracies for two (sleep, wake) and three (sleep, pre-wake, wake) class identification, respectively.

Environmental crack-growth behavior of high strength pressure vessel alloys

NASA Technical Reports Server (NTRS)

Forman, R. G.

1975-01-01

Results of sustained-load environmental crack growth threshold tests performed on six spacecraft pressure vessel alloys are presented. The alloys were Inconel 718, 6Al-4V titanium, A-286 steel, AM-350 stainless steel, cryoformed AISI 301 stainless steel; and cryoformed AISI 304L steel. The test environments for the program were air, pressurized gases of hydrogen, oxygen, nitrogen, and carbon dioxide, and liquid environments of distilled water, sea water, nitrogen tetroxide, hydrazine, aerozine 50, monomethyl hydrazine, and hydrogen peroxide. Surface flaw type specimens were used with flaws located in both base metal and weld metal.

Aerodynamics Via Acoustics: Application of Acoustic Formulas for Aerodynamic Calculations

NASA Technical Reports Server (NTRS)

Farassat, F.; Myers, M. K.

1986-01-01

Prediction of aerodynamic loads on bodies in arbitrary motion is considered from an acoustic point of view, i.e., in a frame of reference fixed in the undisturbed medium. An inhomogeneous wave equation which governs the disturbance pressure is constructed and solved formally using generalized function theory. When the observer is located on the moving body surface there results a singular linear integral equation for surface pressure. Two different methods for obtaining such equations are discussed. Both steady and unsteady aerodynamic calculations are considered. Two examples are presented, the more important being an application to propeller aerodynamics. Of particular interest for numerical applications is the analytical behavior of the kernel functions in the various integral equations.

Survival of marine heterotrophic flagellates isolated from the surface and the deep sea at high hydrostatic pressure: Literature review and own experiments

NASA Astrophysics Data System (ADS)

Živaljić, Suzana; Schoenle, Alexandra; Nitsche, Frank; Hohlfeld, Manon; Piechocki, Julia; Reif, Farina; Shumo, Marwa; Weiss, Alexandra; Werner, Jennifer; Witt, Madeleine; Voss, Janine; Arndt, Hartmut

2018-02-01

Although the abyssal seafloor represents the most common benthic environment on Earth, eukaryotic microbial life at abyssal depths is still an uncharted territory. This is in striking contrast to their potential importance regarding the material flux and bacteria consumption in the deep sea. Flagellate genotypes determined from sedimentary DNA deep-sea samples might originate from vital deep-sea populations or from cysts of organisms sedimented down from surface waters. The latter one may have never been active under deep-sea conditions. We wanted to analyze the principal ability of cultivable heterotrophic flagellates of different phylogenetic groups (choanoflagellates, ancyromonads, euglenids, kinetoplastids, bicosoecids, chrysomonads, and cercozoans) to survive exposure to high hydrostatic pressure (up to 670 bar). We summarized our own studies and the few available data from literature on pressure tolerances of flagellates isolated from different marine habitats. Our results demonstrated that many different flagellate species isolated from the surface waters and deep-sea sediments survived drastic changes in hydrostatic pressure. Barophilic behavior was also recorded for several species isolated from the deep sea indicating their possible genetic adaptation to high pressures. This is in accordance with records of heterotrophic flagellates present in environmental DNA surveys based on clone libraries established for deep-sea environments.

Amine-Rich Organic Thin Films for Cell Culture: Possible Electrostatic Effects in Cell-Surface Interactions

NASA Astrophysics Data System (ADS)

Wertheimer, Michael R.; St-Georges-Robillard, Amélie; Lerouge, Sophie; Mwale, Fackson; Elkin, Bentsian; Oehr, Christian; Wirges, Werner; Gerhard, Reimund

2012-11-01

In recent communications from these laboratories, we observed that amine-rich thin organic layers are very efficient surfaces for the adhesion of mammalian cells. We prepare such deposits by plasma polymerization at low pressure, atmospheric pressure, or by vacuum-ultraviolet photo-polymerization. More recently, we have also investigated a commercially available material, Parylene diX AM. In this article we first briefly introduce literature relating to electrostatic interactions between cells, proteins, and charged surfaces. We then present certain selected cell-response results that pertain to applications in orthopedic and cardiovascular medicine: we discuss the influence of surface properties on the observed behaviors of two particular cell lines, human U937 monocytes, and Chinese hamster ovary cells. Particular emphasis is placed on possible electrostatic attractive forces due to positively charged R-NH3+ groups and negatively charged proteins and cells, respectively. Experiments carried out with electrets, polymers with high positive or negative surface potentials are added for comparison.

Evaporation of LOX under supercritical and subcritical conditions

NASA Technical Reports Server (NTRS)

Yang, A. S.; Hsieh, W. H.; Kuo, K. K.; Brown, J. J.

1993-01-01

The evaporation of LOX under supercritical and subcritical conditions was studied experimentally and theoretically. In experiments, the evaporation rate and surface temperature were measured for LOX strand vaporizing in helium environments at pressures ranging from 5 to 68 atmospheres. Gas sampling and chromatography analysis were also employed to profile the gas composition above the LOX surface for the purpose of model validation. A comprehensive theoretical model was formulated and solved numerically to simulate the evaporation process of LOX at high pressures. The model was based on the conservation equations of mass, momentum, energy, and species concentrations for a multicomponent system, with consideration of gravitational body force, solubility of ambient gases in liquid, and variable thermophysical properties. Good agreement between predictions and measured oxygen mole fraction profiles was obtained. The effect of pressure on the distribution of the Lewis number, as well as the effect of variable diffusion coefficient, were further examined to elucidate the high-pressure transport behavior exhibited in the LOX vaporization process.

Computer-Generated Phase Diagrams for Binary Mixtures.

ERIC Educational Resources Information Center

Jolls, Kenneth R.; And Others

1983-01-01

Computer programs that generate projections of thermodynamic phase surfaces through computer graphics were used to produce diagrams representing properties of water and steam and the pressure-volume-temperature behavior of most of the common equations of state. The program, program options emphasizing thermodynamic features of interest, and…

A literature review and inventory of the effects of environment on the fatigue behavior of metals

NASA Technical Reports Server (NTRS)

Hudson, C. M.; Seward, S. K.

1976-01-01

The current state of knowledge of the effects of gas environments (at atmospheric pressure and below) on the fatigue behavior of metals is reviewed. Among the topics considered are the mechanisms proposed to explain the differences observed in the fatigue behavior of vacuum- and air-tested specimens, the effects of environment on the surface topography of fatigue cycled specimens, the effect of environment on the various phases of the fatigue phenomenon, the effect of prolonged exposure to vacuum on fatigue life, the variation of fatigue life with decreasing gas pressure, and gas evolution during fatigue cycling. Analysis of the findings of this review indicates that hydrogen embrittlement is primarily responsible for decreased fatigue resistance in humid environments, and that dislocations move more easily during tests in vacuum than during test in air. It was found that fatigue cracks generally initiated and propagated more rapidly in air than in vacuum. Prolonged exposure to vacuum does not adversely affect fatigue resistance. The variation of fatigue life with decreasing gas pressure is sometimes stepped and sometimes continuous.

On the turbulent friction layer for rising pressure

NASA Technical Reports Server (NTRS)

Wieghardt, K; Tillmann, W

1951-01-01

Among the information presented are included displacement, momentum, and kinetic energy thicknesses, shearing stress distributions across boundary layer, and surface friction coefficients. The Gruschwitz method and its modifications are examined and tested. An energy theorem for the turbulent boundary layer is introduced and discussed but does not lead to a method for the prediction of the behavior of the turbulent boundary layer because relations for the shearing stress and the surface friction are lacking.

XPS and UPS studies on electronic structure of Li 2O

NASA Astrophysics Data System (ADS)

Tanaka, Satoru; Taniguchi, Masaki; Tanigawa, Hisashi

2000-12-01

The adsorption behavior of H 2O on Li 2O was studied by X-ray photo electron spectroscopy (XPS) and ultraviolet photo electron spectroscopy (UPS). XPS and UPS spectra of Li 2O single crystals which were exposed to different pressure of H 2O vapor were observed. In O(1s) region, two peaks were observed and they were assigned to O(1s) in precipitated LiOH on the surface and O(1s) in Li 2O. After H 2O exposure, a peak broadening and an appearance of a new peak were observed at the higher binding energy region than O(1s) in Li 2O. They were attributed to surface -OH and H 2O molecule adsorbed on the surface. The adsorption behavior of H 2O was discussed from the observation of electronic structure in Li 2O surface.

Effect of surface tension on the behavior of adhesive contact based on Lennard-Jones potential law

NASA Astrophysics Data System (ADS)

Zhu, Xinyao; Xu, Wei

2018-02-01

The present study explores the effect of surface tension on adhesive contact behavior where the adhesion is interpreted by long-range intermolecular forces. The adhesive contact is analyzed using the equivalent system of a rigid sphere and an elastic half space covered by a membrane with surface tension. The long-range intermolecular forces are modeled with the Lennard‒Jones (L‒J) potential law. The current adhesive contact issue can be represented by a nonlinear integral equation, which can be solved by Newton‒Raphson method. In contrast to previous studies which consider intermolecular forces as short-range, the present study reveals more details of the features of adhesive contact with surface tension, in terms of jump instabilities, pull-off forces, pressure distribution within the contact area, etc. The transition of the pull-off force is not only consistent with previous studies, but also presents some new interesting characteristics in the current situation.

Extreme high temperature redox kinetics in ceria: exploration of the transition from gas-phase to material-kinetic limitations

DOE PAGES

Ji, Ho-Il; Davenport, Timothy C.; Gopal, Chirranjeevi Balaji; ...

2016-07-18

The redox kinetics of undoped ceria (CeO 2-δ) are investigated by the electrical conductivity relaxation method in the oxygen partial pressure range of -4.3 ≤ log(pO 2/atm) ≤ -2.0 at 1400 °C. It is demonstrated that extremely large gas flow rates, relative to the mass of the oxide, are required in order to overcome gas phase limitations and access the material kinetic properties. Using these high flow rate conditions, the surface reaction rate constant k chem is found to obey the correlation log(k chem/cm s -1) = (0.84 ± 0.02) × log(pO 2/atm) - (0.99 ± 0.05) and increases withmore » oxygen partial pressure. This increase contrasts the known behavior of the dominant defect species, oxygen vacancies and free electrons, which decrease in concentration with increasing oxygen partial pressure. For the sample geometries employed, diffusion was too fast to be detected. At low gas flow rates, the relaxation process becomes limited by the capacity of the sweep gas to supply/remove oxygen to/from the oxide. An analytical expression is derived for the relaxation in the gas-phase limited regime, and the result reveals an exponential decay profile, identical in form to that known for a surface reaction limited process. Thus, measurements under varied gas flow rates are required to differentiate between surface reaction limited and gas flow limited behavior.« less

Extreme high temperature redox kinetics in ceria: exploration of the transition from gas-phase to material-kinetic limitations.

PubMed

Ji, Ho-Il; Davenport, Timothy C; Gopal, Chirranjeevi Balaji; Haile, Sossina M

2016-08-03

The redox kinetics of undoped ceria (CeO2-δ) are investigated by the electrical conductivity relaxation method in the oxygen partial pressure range of -4.3 ≤ log(pO2/atm) ≤ -2.0 at 1400 °C. It is demonstrated that extremely large gas flow rates, relative to the mass of the oxide, are required in order to overcome gas phase limitations and access the material kinetic properties. Using these high flow rate conditions, the surface reaction rate constant kchem is found to obey the correlation log(kchem/cm s(-1)) = (0.84 ± 0.02) × log(pO2/atm) - (0.99 ± 0.05) and increases with oxygen partial pressure. This increase contrasts the known behavior of the dominant defect species, oxygen vacancies and free electrons, which decrease in concentration with increasing oxygen partial pressure. For the sample geometries employed, diffusion was too fast to be detected. At low gas flow rates, the relaxation process becomes limited by the capacity of the sweep gas to supply/remove oxygen to/from the oxide. An analytical expression is derived for the relaxation in the gas-phase limited regime, and the result reveals an exponential decay profile, identical in form to that known for a surface reaction limited process. Thus, measurements under varied gas flow rates are required to differentiate between surface reaction limited and gas flow limited behavior.

Behavior of lysozyme adsorbed onto biological liquid crystal lipid monolayer at the air/water interface

NASA Astrophysics Data System (ADS)

Lu, Xiaolong; Shi, Ruixin; Hao, Changchun; Chen, Huan; Zhang, Lei; Li, Junhua; Xu, Guoqing; Sun, Runguang

2016-09-01

The interaction between proteins and lipids is one of the basic problems of modern biochemistry and biophysics. The purpose of this study is to compare the penetration degree of lysozyme into 1,2-diapalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphoethano-lamine (DPPE) by analyzing the data of surface pressure-area (π-A) isotherms and surface pressure-time (π-T) curves. Lysozyme can penetrate into both DPPC and DPPE monolayers because of the increase of surface pressure at an initial pressure of 15 mN/m. However, the changes of DPPE are larger than DPPC, indicating stronger interaction of lysozyme with DPPE than DPPC. The reason may be due to the different head groups and phase state of DPPC and DPPE monolayers at the surface pressure of 15 mN/m. Atomic force microscopy reveals that lysozyme was absorbed by DPPC and DPPE monolayers, which leads to self-aggregation and self-assembly, forming irregular multimers and conical multimeric. Through analysis, we think that the process of polymer formation is similar to the aggregation mechanism of amyloid fibers. Project supported by the National Natural Science Foundation of China (Grant Nos. 21402114 and 11544009), the Natural Science Basic Research Plan in Shaanxi Province of China (Grant No. 2016JM2010), the Fundamental Research Funds for the Central Universities of China (Grant No. GK201603026), and the National University Science and Technology Innovation Project of China (Grant No. 201610718013).

The jump-off velocity of an impulsively loaded spherical shell

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

Chabaud, Brandon M.; Brock, Jerry S.

2012-04-13

We consider a constant temperature spherical shell of isotropic, homogeneous, linearly elastic material with density {rho} and Lame coefficients {lambda} and {mu}. The inner and outer radii of the shell are r{sub i} and r{sub o}, respectively. We assume that the inside of the shell is a void. On the outside of the shell, we apply a uniform, time-varying pressure p(t). We also assume that the shell is initially at rest. We want to compute the jump-off time and velocity of the pressure wave, which are the first time after t = 0 at which the pressure wave from themore » outer surface reaches the inner surface. This analysis computes the jump-off velocity and time for both compressible and incompressible materials. This differs substantially from [3], where only incompressible materials are considered. We will consider the behavior of an impulsively loaded, exponentially decaying pressure wave p(t) = P{sub 0{sup e}}{sup -{alpha}t}, where {alpha} {ge} 0. We notice that a constant pressure wave P(t) = P{sub 0} is a special case ({alpha} = 0) of a decaying pressure wave. Both of these boundary conditions are considered in [3].« less

Deformation analysis of vesicles in an alternating-current electric field.

PubMed

Tang, Yu-Gang; Liu, Ying; Feng, Xi-Qiao

2014-08-01

In this paper the shape equation for axisymmetric vesicles subjected to an ac electric field is derived on the basis of the liquid-crystal model. The equilibrium morphology of a lipid vesicle is determined by the minimization of its free energy in coupled mechanical and ac electric fields. Besides elastic bending, the effects of the osmotic pressure difference, surface tension, Maxwell pressure, and flexoelectric and dielectric properties of phospholipid membrane as well are taken into account. The influences of elastic bending, osmotic pressure difference, and surface tension on the frequency-dependent behavior of a vesicle membrane in an ac electric field are examined. The singularity of the ac electric field is also investigated. Our theoretical results of vesicle deformation agree well with previous experimental and numerical results. The present study provides insights into the physical mechanisms underpinning the frequency-dependent morphological evolution of vesicles in the electric and mechanical fields.

Study of Mechano-Chemical Machining of Ceramics and the Effect on Thin Film Behavior.

DTIC Science & Technology

1983-01-01

with Fe2O3 Under Various Pressures 9 7 Nomarski Micrographs of an Si N Substrate (a) Before *. and (b) After Mechanochemical Polishing 11 8 -Surface...the entire polished surface did not reveal any scratches. Figure 7 com- pares the Nomarski micrographs of an Si3 N4 substrate before (in the as...mechanochemically polished Si3N4 substrates, using an interferometric technique. The surface figure of a 2.5 x 2.5 cm Si 3N4 substrate is shown in Figure 9. This fig

Melting of the Dipalmitoylphosphatidylcholine Monolayer.

PubMed

Xu, Lu; Bosiljevac, Gordon; Yu, Kyle; Zuo, Yi Y

2018-04-17

Langmuir monolayer self-assembled at the air-water interface represents an excellent model for studying phase transition and lipid polymorphism in two dimensions. Compared with numerous studies of phospholipid phase transitions induced by isothermal compression, there are very scarce reports on two-dimensional phase transitions induced by isobaric heating. This is mainly due to technical difficulties of continuously regulating temperature variations while maintaining a constant surface pressure in a classical Langmuir-type film balance. Here, with technological advances in constrained drop surfactometry and closed-loop axisymmetric drop shape analysis, we studied the isobaric heating process of the dipalmitoylphosphatidylcholine (DPPC) monolayer. It is found that temperature and surface pressure are two equally important intensive properties that jointly determine the phase behavior of the phospholipid monolayer. We have determined a critical point of the DPPC monolayer at a temperature of 44 °C and a surface pressure of 57 mN/m. Beyond this critical point, no phase transition can exist in the DPPC monolayer, either by isothermal compression or by isobaric heating. The melting process of the DPPC monolayer studied here provides novel insights into the understanding of a wide range of physicochemical and biophysical phenomena, such as surface thermodynamics, critical phenomena, and biophysical study of pulmonary surfactants.

High-temperature friction and wear studies of Fe-Cu-Sn alloy with graphite as solid lubricant under dry sliding conditions

NASA Astrophysics Data System (ADS)

Mushtaq, Shuhaib; Wani, M. F.

2018-02-01

Solid lubricants are particularly used in the advanced mechanical motion systems with extreme conditions such as (high temperature, vacuum, radiation, extreme contact pressure, etc). The main focus of this paper is to study the dry sliding friction and wear behavior of Fe-Cu-Sn alloy with varying wt% of graphite at high temperature up to 423 K. The influence of temperature, sliding distance and load on friction and wear behavior of Fe-Cu-Sn alloy against EN8 steel was studied using ball (EN8) on disc (Fe-Cu-Sn alloy). Lower wear and lower friction of Fe-Cu-Sn alloy were observed at high temperature, as compared to room temperature. Surface morphological and surface analytical studies of fresh and worn surfaces were carried out using optical microscopy, 3D profilometer, scanning electron microscope, energy dispersive x-ray spectroscopy, XRD, and Raman spectroscopy to understand the friction and wear behavior.

Experimental studies of hypersonic shock-wave boundary-layer interactions

NASA Technical Reports Server (NTRS)

Lu, Frank K.

1992-01-01

Two classes of shock-wave boundary-layer interactions were studied experimentally in a shock tunnel in which a low Reynolds number, turbulent flow at Mach 8 was developed on a cold, flat test surface. The two classes of interactions were: (1) a swept interaction generated by a wedge ('fin') mounted perpendicularly on the flat plate; and (2) a two-dimensional, unseparated interaction induced by a shock impinging near an expansion corner. The swept interaction, with wedge angles of 5-20 degrees, was separated and there was also indication that the strongest interactions prossessed secondary separation zones. The interaction spread out extensively from the inviscid shock location although no indication of quasi-conical symmetry was evident. The surface pressure from the upstream influence to the inviscid shock was relatively low compared to the inviscid downstream value but it rose rapidly past the inviscid shock location. However, the surface pressure did not reach the downstream inviscid value and reasons were proposed for this anomalous behavior compared to strongly separated, supersonic interactions. The second class of interactions involved weak shocks impinging near small expansion corners. As a prelude to studying this interaction, a hypersonic similarity parameter was identified for the pure, expansion corner flow. The expansion corner severely damped out surface pressure fluctuations. When a shock impinged upstream of the corner, no significant changes to the surface pressure were found as compared to the case when the shock impinged on a flat plate. But, when the shock impinged downstream of the corner, a close coupling existed between the two wave systems, unlike the supersonic case. This close coupling modified the upstream influence. Regardless of whether the shock impinged ahead or behind the corner, the downstream region was affected by the close coupling between the shock and the expansion. Not only was the mean pressure distribution modified but the unsteadiness in the surface pressure was reduced compared to the flat-plate case.

Surface thermodynamic analysis of fluid confined in a cone and comparison with the sphere-plate and plate-plate geometries.

PubMed

Zargarzadeh, Leila; Elliott, Janet A W

2013-10-22

The behavior of pure fluid confined in a cone is investigated using thermodynamic stability analysis. Four situations are explained on the basis of the initial confined phase (liquid/vapor) and its pressure (above/below the saturation pressure). Thermodynamic stability analysis (a plot of the free energy of the system versus the size of the new potential phase) reveals whether the phase transition is possible and, if so, the number and type (unstable/metastable/stable) of equilibrium states in each of these situations. Moreover we investigated the effect of the equilibrium contact angle and the cone angle (equivalent to the confinement's surface separation distance) on the free energy (potential equilibrium states). The results are then compared to our previous study of pure fluid confined in the gap between a sphere and a flat plate and the gap between two flat plates.1 Confined fluid behavior of the four possible situations (for these three geometries) can be explained in a unified framework under two categories based on only the meniscus shape (concave/convex). For systems with bulk-phase pressure imposed by a reservoir, the stable coexistence of pure liquid and vapor is possible only when the meniscus is concave.

Effect of wettability of a porous stainless steel on thermally induced liquid-vapor interface behavior

NASA Astrophysics Data System (ADS)

Oka, C.; Odagiri, K.; Nagano, H.

2017-12-01

Control of thermally induced liquid-vapor interface behavior at the contact surface of porous media is crucial for development of two-phase heat transfer devices such as loop heat pipes. The behavior experiences three modes with increase of heat flux, and the middle mode possesses the highest heat transfer performance. In this paper, the effect of improving wettability of the porous media is demonstrated experimentally and numerically for the first time, in particular with regard to the effect on a domain of the middle mode. Ethanol wettability of a porous stainless steel was improved via a facile method, which was a simple acid treatment. As a result, the domain of the middle mode was extended as a consequence of the wettability improvement. The mode transfers from the middle to the last one when the pressure drop in the liquid supply exceeds the capillary pressure of liquid bridges formed between the heating plate and the porous medium. Hence, the extension of the domain suggested that the capillary pressure was increased by the wettability improvement. This was verified via numerical calculation. The calculated capillary pressure was increased by 7% after improving wettability, which resulted in the extension of the domain of the middle mode.

The Pascal Mars Scout Mission

NASA Technical Reports Server (NTRS)

Haberle, R. M.; Fonda, Mark (Technical Monitor)

2002-01-01

Except for Earth, Mars is the planet most amenable to surface-based climate studies. Its surface is accessible, and the kind of observations that are needed, such as meteorological measurements from a long-lived global network, are readily achievable. Weather controls the movement of dust, the exchange of water between the surface and atmosphere, and the cycling of CO2 between the poles. We know there is a weather signal, we know how to measure it, and we know how to interpret it. Pascal seeks to understand the long-term global behavior of near-surface weather systems on Mars, how they interact with its surface, and, therefore, how they control its climate system. To achieve this, Pascal delivers 18 Science Stations to the surface of the planet that operate for three Mars years (5.6 Earth years). The network has stations operating in the tropics, midlatitudes, and polar regions of both hemispheres. During entry, descent, and landing, each Pascal probe acquires deceleration measurements to determine thermal structure, and descent images to characterize local terrain. On the surface, each Science Station takes daily measurements of pressure, opacity, temperature, wind speed, and water vapor concentration and monthly panoramic images of the landing environment. These data will characterize the planet's climate system and how atmosphere-surface interactions control it. The Pascal mission is named after 17th century French Scientist, Blaise Pascal, who pioneered measurements of atmospheric pressure. Pressure is the most critical measurement because it records the "heartbeat" of the planet's general circulation and climate system.

A Systematic Procedure to Describe Shale Gas Permeability Evolution during the Production Process

NASA Astrophysics Data System (ADS)

Jia, B.; Tsau, J. S.; Barati, R.

2017-12-01

Gas flow behavior in shales is complex due to the multi-physics nature of the process. Pore size reduces as the in-situ stress increases during the production process, which will reduce intrinsic permeability of the porous media. Slip flow/pore diffusion enhances gas apparent permeability, especially under low reservoir pressures. Adsorption not only increases original gas in place but also influences gas flow behavior because of the adsorption layer. Surface diffusion between free gas and adsorption phase enhances gas permeability. Pore size reduction and the adsorption layer both have complex impacts on gas apparent permeability and non-Darcy flow might be a major component in nanopores. Previously published literature is generally incomplete in terms of coupling of all these four physics with fluid flow during gas production. This work proposes a methodology to simultaneously take them into account to describe a permeability evolution process. Our results show that to fully describe shale gas permeability evolution during gas production, three sets of experimental data are needed initially: 1) intrinsic permeability under different in-situ stress, 2) adsorption isotherm under reservoir conditions and 3) surface diffusivity measurement by the pulse-decay method. Geomechanical effects, slip flow/pore diffusion, adsorption layer and surface diffusion all play roles affecting gas permeability. Neglecting any of them might lead to misleading results. The increasing in-situ stress during shale gas production is unfavorable to shale gas flow process. Slip flow/pore diffusion is important for gas permeability under low pressures in the tight porous media. They might overwhelm the geomechanical effect and enhance gas permeability at low pressures. Adsorption layer reduces the gas permeability by reducing the effective pore size, but the effect is limited. Surface diffusion increases gas permeability more under lower pressures. The total gas apparent permeability might keep increasing during the gas production process when the surface diffusivity is larger than a critical value. We believe that our workflow proposed in this study will help describe shale gas permeability evolution considering all the underlying physics altogether.

Proof test criteria for thin-walled 2219 aluminum pressure vessels. Volume 1: Program summary and data analysis

NASA Technical Reports Server (NTRS)

Finger, R. W.

1976-01-01

This experimental program was undertaken to investigate the crack growth behavior of deep surface flaws in 2219 aluminum. The program included tests of uniaxially loaded surface flaw and center crack panels at temperatures ranging from 20K (-423 F) to ambient. The tests were conducted on both the base metal and as-welded weld metal material. The program was designed to provide data on the mechanisms of failure by ligament penetration, and the residual cyclic life, after proof-testing, of a vessel which has been subjected to incipient penetration by the proof test. The results were compared and analyzed with previously developed data to develop guidelines for the proof testing of thin walled 2219 pressure vessels.

Graphite pellicles, methods of formation and properties

NASA Astrophysics Data System (ADS)

Topala, P.; Marin, L.; Besliu, V.; Stoicev, P.; Ojegov, A.; Cosovschii, P.

2015-11-01

The paper presents the results of experimental investigations aimed at the establishing the composition and the functional properties of the graphite pellicles formed on the metal surfaces by the action of plasma in the air media at normal pressure applying electrical discharges in impulse (EDI). It shows that they have the same behavior characteristics as fullerene, avoiding the stick effect between metal surfaces and between metal and liquid glass at temperatures of the order of 400-1200 °C.

Fouling behavior of poly(ether)sulfone ultrafiltration membrane during concentration of whey proteins: Effect of hydrophilic modification using atmospheric pressure argon jet plasma.

PubMed

Damar Huner, Irem; Gulec, Haci Ali

2017-12-01

The aim of the study was to investigate the effects of hydrophilic surface modification via atmospheric pressure jet plasma (ApJPls) on the fouling propensity of polyethersulfone (PES) ultrafiltration (UF) membranes during concentration of whey proteins. The distance from nozzle to substrate surface of 30mm and the exposure period of 5 times were determined as the most effective parameters enabling an increase in ΔG iwi value of the plain membrane from (-) 14.92±0.89mJ/m 2 to (+) 17.57±0.67mJ/m 2 . Maximum hydrophilicity and minimum surface roughness achieved by argon plasma action resulted in better antifouling behavior, while the hydraulic permeability and the initial permeate flux were decreased sharply due to the plasma-induced surface cross-linking. A quite steady state flux was obtained throughout the UF with the ApJPls modified PES membrane. The contribution of R frev to R t , which was 94% for the UF through the plain membrane, decreased to 43% after the plasma treatment. The overall results of this study highlighted the ApJPls modification decreased the fouling propensity of PES membrane without affecting the original protein rejection capability and improved the recovery of initial permeate flux after chemical cleaning. Copyright © 2017 Elsevier B.V. All rights reserved.

Delphinid behavioral responses to incidental mid-frequency active sonar.

PubMed

Henderson, E Elizabeth; Smith, Michael H; Gassmann, Martin; Wiggins, Sean M; Douglas, Annie B; Hildebrand, John A

2014-10-01

Opportunistic observations of behavioral responses by delphinids to incidental mid-frequency active (MFA) sonar were recorded in the Southern California Bight from 2004 through 2008 using visual focal follows, static hydrophones, and autonomous recorders. Sound pressure levels were calculated between 2 and 8 kHz. Surface behavioral responses were observed in 26 groups from at least three species of 46 groups out of five species encountered during MFA sonar incidents. Responses included changes in behavioral state or direction of travel, changes in vocalization rates and call intensity, or a lack of vocalizations while MFA sonar occurred. However, 46% of focal groups not exposed to sonar also changed their behavior, and 43% of focal groups exposed to sonar did not change their behavior. Mean peak sound pressure levels when a behavioral response occurred were around 122 dB re: 1 μPa. Acoustic localizations of dolphin groups exhibiting a response gave insight into nighttime movement patterns and provided evidence that impacts of sonar may be mediated by behavioral state. The lack of response in some cases may indicate a tolerance of or habituation to MFA sonar by local populations; however, the responses that occur at lower received levels may point to some sensitization as well.

(Quasi-) 2D aggregation of polystyrene-b-dextran at the air-water interface.

PubMed

Bosker, Wouter T E; Cohen Stuart, Martien A; Norde, Willem

2013-02-26

Polystyrene-b-dextran (PS-b-Dextran) copolymers can be used to prepare dextran brushes at solid surfaces, applying Langmuir-Blodgett deposition. When recording the interfacial pressure versus area isotherms of a PS-b-Dextran monolayer, time-dependent hysteresis was observed upon compression and expansion. We argue that this is due to (quasi-) 2D aggregation of the copolymer at the air-water surface, with three contributions. First, at large area per molecule, a zero surface pressure is measured; we ascribe this to self-assembly of block copolymers into surface micelles. At intermediate area we identify a second regime ("desorption regime") where aggregation into large patches occurs due to van der Waals attraction between PS blocks. At high surface pressure ("brush regime") we observe hysteretic behavior attributed to H-bonding between dextran chains. When compared to hysteresis of other amphiphilic diblock copolymers (also containing PS, e.g., polystyrene-b-poly(ethylene oxide)) a general criterion can be formulated concerning the extent of hysteresis: when the hydrophobic (PS) block is of equal size as (or bigger than) the hydrophilic block, the hysteresis is maximal. The (quasi-) 2D aggregation of PS-b-Dextran has significant implications for the preparation of dextran brushes at solid surfaces using Langmuir-Blodgett deposition. For each grafting density the monolayer needs to relax, up to several hours, prior to transfer.

Conformational changes of a calix[8]arene derivative at the air-water interface.

PubMed

de Miguel, Gustavo; Pedrosa, José M; Martín-Romero, María T; Muñoz, Eulogia; Richardson, Tim H; Camacho, Luis

2005-03-10

The particular behavior of a p-tert-butyl calix[8]arene derivative (C8A) has been studied at the air-water interface using surface pressure-area isotherms, surface potential-area isotherms, film relaxation measurements, Brewster angle microscopy (BAM), and infrared spectroscopy for Langmuir-Blodgett films. Thus, it is observed that the properties of the film, for example, isotherms, domain formation, and FTIR spectra, recorded during the first compression cycle differ appreciably from those during the second compression and following cycles. The results obtained are interpreted on the basis of the conformational changes of the C8A molecules by surface pressure, allowing us to inquire into the inter- and intramolecular interactions (hydrogen bonds) of those molecules. Thus, the compression induces changes in the kind of hydrogen bonds from intra- and intermolecular with other C8A molecules to hydrogen bonds with water molecules.

Devolatilization Analysis in a Twin Screw Extruder by using the Flow Analysis Network (FAN) Method

NASA Astrophysics Data System (ADS)

Tomiyama, Hideki; Takamoto, Seiji; Shintani, Hiroaki; Inoue, Shigeki

We derived the theoretical formulas for three mechanisms of devolatilization in a twin screw extruder. These are flash, surface refreshment and forced expansion. The method for flash devolatilization is based on the equation of equilibrium concentration which shows that volatiles break off from polymer when they are relieved from high pressure condition. For surface refreshment devolatilization, we applied Latinen's model to allow estimation of polymer behavior in the unfilled screw conveying condition. Forced expansion devolatilization is based on the expansion theory in which foams are generated under reduced pressure and volatiles are diffused on the exposed surface layer after mixing with the injected devolatilization agent. Based on these models, we developed the simulation software of twin-screw extrusion by the FAN method and it allows us to quantitatively estimate volatile concentration and polymer temperature with a high accuracy in the actual multi-vent extrusion process for LDPE + n-hexane.

Closed-loop Separation Control Using Oscillatory Flow Excitation

NASA Technical Reports Server (NTRS)

Allan, Brian G.; Juang, Jer-Nan; Raney, David L.; Seifert, Avi; Pack, latunia G.; Brown, Donald E.

2000-01-01

Design and implementation of a digital feedback controller for a flow control experiment was performed. The experiment was conducted in a cryogenic pressurized wind tunnel on a generic separated configuration at a chord Reynolds number of 16 million and a Mach number of 0.25. The model simulates the upper surface of a 20% thick airfoil at zero angle-of-attack. A moderate favorable pressure gradient, up to 55% of the chord, is followed by a severe adverse pressure gradient which is relaxed towards the trailing edge. The turbulent separation bubble, behind the adverse pressure gradient, is then reduced by introducing oscillatory flow excitation just upstream of the point of flow separation. The degree of reduction in the separation region can be controlled by the amplitude of the oscillatory excitation. A feedback controller was designed to track a given trajectory for the desired degree of flow reattachment and to improve the transient behavior of the flow system. Closed-loop experiments demonstrated that the feedback controller was able to track step input commands and improve the transient behavior of the open-loop response.

Non-Gaussian Analysis of Turbulent Boundary Layer Fluctuating Pressure on Aircraft Skin Panels

NASA Technical Reports Server (NTRS)

Rizzi, Stephen A.; Steinwolf, Alexander

2005-01-01

The purpose of the study is to investigate the probability density function (PDF) of turbulent boundary layer fluctuating pressures measured on the outer sidewall of a supersonic transport aircraft and to approximate these PDFs by analytical models. Experimental flight results show that the fluctuating pressure PDFs differ from the Gaussian distribution even for standard smooth surface conditions. The PDF tails are wider and longer than those of the Gaussian model. For pressure fluctuations in front of forward-facing step discontinuities, deviations from the Gaussian model are more significant and the PDFs become asymmetrical. There is a certain spatial pattern of the skewness and kurtosis behavior depending on the distance upstream from the step. All characteristics related to non-Gaussian behavior are highly dependent upon the distance from the step and the step height, less dependent on aircraft speed, and not dependent on the fuselage location. A Hermite polynomial transform model and a piecewise-Gaussian model fit the flight data well both for the smooth and stepped conditions. The piecewise-Gaussian approximation can be additionally regarded for convenience in usage after the model is constructed.

Analysis of a deflating soap bubble

NASA Astrophysics Data System (ADS)

Jackson, David P.; Sleyman, Sarah

2010-10-01

A soap bubble on the end of a cylindrical tube is seen to deflate as the higher pressure air inside the bubble escapes through a tube. We perform an experiment to measure the radius of the slowly deflating bubble and observe that the radius decreases to a minimum before quickly increasing. This behavior reflects the fact that the bubble ends up as a flat surface over the end of the tube. A theoretical analysis reproduces this behavior and compares favorably with the experimental data.

Modeling interface shear behavior of granular materials using micro-polar continuum approach

NASA Astrophysics Data System (ADS)

Ebrahimian, Babak; Noorzad, Ali; Alsaleh, Mustafa I.

2018-01-01

Recently, the authors have focused on the shear behavior of interface between granular soil body and very rough surface of moving bounding structure. For this purpose, they have used finite element method and a micro-polar elasto-plastic continuum model. They have shown that the boundary conditions assumed along the interface have strong influences on the soil behavior. While in the previous studies, only very rough bounding interfaces have been taken into account, the present investigation focuses on the rough, medium rough and relatively smooth interfaces. In this regard, plane monotonic shearing of an infinite extended narrow granular soil layer is simulated under constant vertical pressure and free dilatancy. The soil layer is located between two parallel rigid boundaries of different surface roughness values. Particular attention is paid to the effect of surface roughness of top and bottom boundaries on the shear behavior of granular soil layer. It is shown that the interaction between roughness of bounding structure surface and the rotation resistance of bounding grains can be modeled in a reasonable manner through considered Cosserat boundary conditions. The influence of surface roughness is investigated on the soil shear strength mobilized along the interface as well as on the location and evolution of shear localization formed within the layer. The obtained numerical results have been qualitatively compared with experimental observations as well as DEM simulations, and acceptable agreement is shown.

Effect of Reynolds Number and Periodic Unsteady Wake Flow Condition on Boundary Layer Development, Separation, and Intermittency Behavior Along the Suction Surface of a Low Pressure Turbine Blade

NASA Technical Reports Server (NTRS)

Schobeiri, M. T.; Ozturk, B.; Ashpis, David E.

2007-01-01

The paper experimentally studies the effects of periodic unsteady wake flow and different Reynolds numbers on boundary layer development, separation and re-attachment along the suction surface of a low pressure turbine blade. The experimental investigations were performed on a large scale, subsonic unsteady turbine cascade research facility at Turbomachinery Performance and Flow Research Laboratory (TPFL) of Texas A&M University. The experiments were carried out at Reynolds numbers of 110,000 and 150,000 (based on suction surface length and exit velocity). One steady and two different unsteady inlet flow conditions with the corresponding passing frequencies, wake velocities, and turbulence intensities were investigated. The reduced frequencies chosen cover the operating range of LP turbines. In addition to the unsteady boundary layer measurements, surface pressure measurements were performed. The inception, onset, and the extent of the separation bubble information collected from the pressure measurements were compared with the hot wire measurements. The results presented in ensemble-averaged, and the contour plot forms help to understand the physics of the separation phenomenon under periodic unsteady wake flow and different Reynolds number. It was found that the suction surface displayed a strong separation bubble for these three different reduced frequencies. For each condition, the locations defining the separation bubble were determined carefully analyzing and examining the pressure and mean velocity profile data. The location of the boundary layer separation was dependent of the Reynolds number. It is observed that starting point of the separation bubble and the re-attachment point move further downstream by increasing Reynolds number from 110,000 to 150,000. Also, the size of the separation bubble is smaller when compared to that for Re=110,000.

Study of the interaction of lactoferricin B with phospholipid monolayers and bilayers.

PubMed

Arseneault, Marjolaine; Bédard, Sarah; Boulet-Audet, Maxime; Pézolet, Michel

2010-03-02

Bovine lactoferricin (LfcinB) is an antimicrobial peptide obtained from the pepsin cleavage of lactoferrin. The activity of LfcinB has been extensively studied on diverse pathogens, but its mechanism of action still has to be elucidated. Because of its nonspecificity, its mode of action is assumed to be related to interactions with membranes. In this study, the interaction of LfcinB with a negatively charged monolayer of dipalmitoylphosphatidylglycerol has been investigated as a function of the surface pressure of the lipid film using in situ Brewster angle and polarization modulation infrared reflection absorption spectroscopy and on transferred monolayers by atomic force microscopy and polarized attenuated total reflection infrared spectroscopy. The data show clearly that LfcinB forms stable films at the air-water interface. They also reveal that the interaction of LfcinB with the lipid monolayer is modulated by the surface pressure. At low surface pressure, LfcinB inserts within the lipid film with its long molecular axis oriented mainly parallel to the acyl chains, while at high surface pressure, LfcinB is adsorbed under the lipid film, the hairpin being preferentially aligned parallel to the plane of the interface. The threshold for which the behavior changes is 20 mN/m. At this critical surface pressure, LfcinB interacts with the monolayer to form discoidal lipid-peptide assemblies. This structure may actually represent the mechanism of action of this peptide. The results obtained on monolayers are correlated by fluorescent probe release measurements of dye-containing vesicles made of lipids in different phases and support the important role of the lipid fluidity and packing on the activity of LfcinB.

High-pressure structural parameters and equation of state of osmium to 207 GPa

DOE PAGES

Perreault, Christopher S.; Velisavljevic, Nenad; Vohra, Yogesh K.; ...

2017-09-08

We studied the most incompressible transition metal osmium (Os) under high pressure. There is significant interest in Os because of the structural anomalies attributed to topological transitions in the Fermi surface for valence electrons in the hexagonal close-packed phase. We report on measurements of structural parameters and equation of state on Os metal to a pressure of 207 GPa at ambient temperature using platinum as a pressure standard. We also obtained angle-dispersive X-ray diffraction data at a synchrotron source with closely spaced pressure intervals to observe any discontinuities or anomalies in the axial c/a ratio at high pressures. Rietveld refinementsmore » of X-ray diffraction data show a slowly varying axial ratio (c/a) with a broad minimum at 75 GPa. Our data do not provide any evidence of anomalous behavior in the c/a ratio in Os at 25 or 150 GPa as have been reported in previous studies. These experimental results are in agreement with theoretical calculations that do not predict any anomalous behavior in c/a ratio in Os under extreme conditions. We present an equation of state for Os to 207 GPa (V/V 0 = 0.761) at ambient temperature and compare our results with the previously published data.« less

High-pressure structural parameters and equation of state of osmium to 207 GPa

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

Perreault, Christopher S.; Velisavljevic, Nenad; Vohra, Yogesh K.

We studied the most incompressible transition metal osmium (Os) under high pressure. There is significant interest in Os because of the structural anomalies attributed to topological transitions in the Fermi surface for valence electrons in the hexagonal close-packed phase. We report on measurements of structural parameters and equation of state on Os metal to a pressure of 207 GPa at ambient temperature using platinum as a pressure standard. We also obtained angle-dispersive X-ray diffraction data at a synchrotron source with closely spaced pressure intervals to observe any discontinuities or anomalies in the axial c/a ratio at high pressures. Rietveld refinementsmore » of X-ray diffraction data show a slowly varying axial ratio (c/a) with a broad minimum at 75 GPa. Our data do not provide any evidence of anomalous behavior in the c/a ratio in Os at 25 or 150 GPa as have been reported in previous studies. These experimental results are in agreement with theoretical calculations that do not predict any anomalous behavior in c/a ratio in Os under extreme conditions. We present an equation of state for Os to 207 GPa (V/V 0 = 0.761) at ambient temperature and compare our results with the previously published data.« less

Global surface pressure measurements of static and dynamic stall on a wind turbine airfoil at low Reynolds number

NASA Astrophysics Data System (ADS)

Disotell, Kevin J.; Nikoueeyan, Pourya; Naughton, Jonathan W.; Gregory, James W.

2016-05-01

Recognizing the need for global surface measurement techniques to characterize the time-varying, three-dimensional loading encountered on rotating wind turbine blades, fast-responding pressure-sensitive paint (PSP) has been evaluated for resolving unsteady aerodynamic effects in incompressible flow. Results of a study aimed at demonstrating the laser-based, single-shot PSP technique on a low Reynolds number wind turbine airfoil in static and dynamic stall are reported. PSP was applied to the suction side of a Delft DU97-W-300 airfoil (maximum thickness-to-chord ratio of 30 %) at a chord Reynolds number of 225,000 in the University of Wyoming open-return wind tunnel. Static and dynamic stall behaviors are presented using instantaneous and phase-averaged global pressure maps. In particular, a three-dimensional pressure topology driven by a stall cell pattern is detected near the maximum lift condition on the steady airfoil. Trends in the PSP-measured pressure topology on the steady airfoil were confirmed using surface oil visualization. The dynamic stall case was characterized by a sinusoidal pitching motion with mean angle of 15.7°, amplitude of 11.2°, and reduced frequency of 0.106 based on semichord. PSP images were acquired at selected phase positions, capturing the breakdown of nominally two-dimensional flow near lift stall, development of post-stall suction near the trailing edge, and a highly three-dimensional topology as the flow reattaches. Structural patterns in the surface pressure topologies are considered from the analysis of the individual PSP snapshots, enabled by a laser-based excitation system that achieves sufficient signal-to-noise ratio in the single-shot images. The PSP results are found to be in general agreement with observations about the steady and unsteady stall characteristics expected for the airfoil.

Acoustic Behavior of Vapor Bubbles

NASA Technical Reports Server (NTRS)

Prosperetti, Andrea; Oguz, Hasan N.

1996-01-01

In a microgravity environment vapor bubbles generated at a boiling surface tend to remain near it for a long time. This affects the boiling heat transfer and in particular promotes an early transition to the highly inefficient film boiling regime. This paper describes the physical basis underlying attempts to remove the bubbles by means of pressure radiation forces.

Studies in Cup Drawing Behavior of Polymer Laminated Sheet Metal

NASA Astrophysics Data System (ADS)

Elnagmi, M.; Jain, M.; Bruhis, M.; Nielsen, K.

2011-08-01

Axisymmetric deep drawing behavior of a polymer laminated sheet metal (PLSM) is investigated using an axisymmetric cup drawing test. PLSMs are of interest as a replacement for painted finishes for automotive applications as they have the potential to achieve good quality long lasting and aesthetically appealing surfaces on stamped parts. However, there is limited understanding of PLSMs in automotive deep drawing situations to produce complex 3-D parts. The tests are carried out using well-controlled, laboratory-based, dual-action, servo-hydraulic forming presses under blank-holder force and punch displacement control conditions. An optical strain mapping system is used to measure the surface strains (and to construct 3D strain maps) from the film side of the deformed samples for a range of forming conditions. Deep drawing characteristics such as punch load versus punch displacement traces, strain distribution along the cup profile, flange wrinkling and fracture characteristics are experimentally assessed for stainless steel-plastic film laminated sheet materials. Also the effect of lamination pressure on wrinkling and delamination is investigated for a decorative pressure sensitive adhesive film affixed to the stainless steel sheet.

Effects of spoiler surfaces on the aeroelastic behavior of a low-aspect-ratio rectangular wing

NASA Technical Reports Server (NTRS)

Cole, Stanley R.

1990-01-01

An experimental research study to determine the effectiveness of spoiler surfaces in suppressing flutter onset for a low-aspect-ratio, rectangular wing was conducted in the Langley Transonic Dynamics Tunnel (TDT). The wing model used in this flutter test consisted of a rigid wing mounted to the wind-tunnel wall by a flexible, rectangular beam. The flexible beam was connected to the wing root and cantilever mounted to the wind-tunnel wall. The wing had a 1.5 aspect ratio based on wing semispan and a NACA 64A010 airfoil shape. The spoiler surfaces consisted of thin, rectangular aluminum plates that were vertically mounted to the wing surface. The spoiler surface geometry and location on the wing surface were varied to determine the effects of these parameters on the classical flutter of the wing model. Subsonically, the experiment showed that spoiler surfaces increased the flutter dynamic pressure with each successive increase in spoiler height or width. This subsonic increase in flutter dynamic pressure was approximately 15 percent for the maximum height spoiler configuration and for the maximum width spoiler configuration. At transonic Mach numbers, the flutter dynamic pressure conditions were increased even more substantially than at subsonic Mach numbers for some of the smaller spoiler surfaces. But greater than a certain spoiler size (in terms of either height or width) the spoilers forced a torsional instability in the transonic regime that was highly Mach number dependent. This detrimental torsional instability was found at dynamic pressures well below the expected flutter conditions. Variations in the spanwise location of the spoiler surfaces on the wing showed little effect on flutter. Flutter analysis was conducted for the basic configuration (clean wing with all spoiler surface mass properties included). The analysis correlated well with the clean wing experimental flutter results.

Xylem Surfactants Introduce a New Element to the Cohesion-Tension Theory1[OPEN

PubMed Central

Espino, Susana; Nima, Neda; Do, Aissa Y.T.; Michaud, Joseph M.; Papahadjopoulos-Sternberg, Brigitte; Yang, Jinlong; Steppe, Kathy

2017-01-01

Vascular plants transport water under negative pressure without constantly creating gas bubbles that would disable their hydraulic systems. Attempts to replicate this feat in artificial systems almost invariably result in bubble formation, except under highly controlled conditions with pure water and only hydrophilic surfaces present. In theory, conditions in the xylem should favor bubble nucleation even more: there are millions of conduits with at least some hydrophobic surfaces, and xylem sap is saturated or sometimes supersaturated with atmospheric gas and may contain surface-active molecules that can lower surface tension. So how do plants transport water under negative pressure? Here, we show that angiosperm xylem contains abundant hydrophobic surfaces as well as insoluble lipid surfactants, including phospholipids, and proteins, a composition similar to pulmonary surfactants. Lipid surfactants were found in xylem sap and as nanoparticles under transmission electron microscopy in pores of intervessel pit membranes and deposited on vessel wall surfaces. Nanoparticles observed in xylem sap via nanoparticle-tracking analysis included surfactant-coated nanobubbles when examined by freeze-fracture electron microscopy. Based on their fracture behavior, this technique is able to distinguish between dense-core particles, liquid-filled, bilayer-coated vesicles/liposomes, and gas-filled bubbles. Xylem surfactants showed strong surface activity that reduces surface tension to low values when concentrated as they are in pit membrane pores. We hypothesize that xylem surfactants support water transport under negative pressure as explained by the cohesion-tension theory by coating hydrophobic surfaces and nanobubbles, thereby keeping the latter below the critical size at which bubbles would expand to form embolisms. PMID:27927981

Xylem Surfactants Introduce a New Element to the Cohesion-Tension Theory.

PubMed

Schenk, H Jochen; Espino, Susana; Romo, David M; Nima, Neda; Do, Aissa Y T; Michaud, Joseph M; Papahadjopoulos-Sternberg, Brigitte; Yang, Jinlong; Zuo, Yi Y; Steppe, Kathy; Jansen, Steven

2017-02-01

Vascular plants transport water under negative pressure without constantly creating gas bubbles that would disable their hydraulic systems. Attempts to replicate this feat in artificial systems almost invariably result in bubble formation, except under highly controlled conditions with pure water and only hydrophilic surfaces present. In theory, conditions in the xylem should favor bubble nucleation even more: there are millions of conduits with at least some hydrophobic surfaces, and xylem sap is saturated or sometimes supersaturated with atmospheric gas and may contain surface-active molecules that can lower surface tension. So how do plants transport water under negative pressure? Here, we show that angiosperm xylem contains abundant hydrophobic surfaces as well as insoluble lipid surfactants, including phospholipids, and proteins, a composition similar to pulmonary surfactants. Lipid surfactants were found in xylem sap and as nanoparticles under transmission electron microscopy in pores of intervessel pit membranes and deposited on vessel wall surfaces. Nanoparticles observed in xylem sap via nanoparticle-tracking analysis included surfactant-coated nanobubbles when examined by freeze-fracture electron microscopy. Based on their fracture behavior, this technique is able to distinguish between dense-core particles, liquid-filled, bilayer-coated vesicles/liposomes, and gas-filled bubbles. Xylem surfactants showed strong surface activity that reduces surface tension to low values when concentrated as they are in pit membrane pores. We hypothesize that xylem surfactants support water transport under negative pressure as explained by the cohesion-tension theory by coating hydrophobic surfaces and nanobubbles, thereby keeping the latter below the critical size at which bubbles would expand to form embolisms. © 2017 American Society of Plant Biologists. All Rights Reserved.

Gas-phase formaldehyde adsorption isotherm studies on activated carbon: correlations of adsorption capacity to surface functional group density.

PubMed

Carter, Ellison M; Katz, Lynn E; Speitel, Gerald E; Ramirez, David

2011-08-01

Formaldehyde (HCHO) adsorption isotherms were developed for the first time on three activated carbons representing one activated carbon fiber (ACF) cloth, one all-purpose granular activated carbon (GAC), and one GAC commercially promoted for gas-phase HCHO removal. The three activated carbons were evaluated for HCHO removal in the low-ppm(v) range and for water vapor adsorption from relative pressures of 0.1-0.9 at 26 °C where, according to the IUPAC isotherm classification system, the adsorption isotherms observed exhibited Type V behavior. A Type V adsorption isotherm model recently proposed by Qi and LeVan (Q-L) was selected to model the observed adsorption behavior because it reduces to a finite, nonzero limit at low partial pressures and it describes the entire range of adsorption considered in this study. The Q-L model was applied to a polar organic adsorbate to fit HCHO adsorption isotherms for the three activated carbons. The physical and chemical characteristics of the activated carbon surfaces were characterized using nitrogen adsorption isotherms, X-ray photoelectron spectroscopy (XPS), and Boehm titrations. At low concentrations, HCHO adsorption capacity was most strongly related to the density of basic surface functional groups (SFGs), while water vapor adsorption was most strongly influenced by the density of acidic SFGs.

Cloud Forcing and the Earth's Radiation Budget: New Ideas and New Observations

NASA Technical Reports Server (NTRS)

Barkstrom, Bruce R.

1997-01-01

1. NEW PERSPECTIVES ON CLOUD-RADIATIVE FORCING. When the Earth Radiation Budget Experiment (ERBE) produced the first measurements of cloud-radiative forcing, the climate community interpreted the results from a context in which the atmosphere was a single column, strongly coupled to the Earth's surface. 2. NEW PERSPECTIVES ON CLOUD-RADIATION OBSERVATIONS. The climate community is also on the verge of adding a new dimension to its observational capability. In classic thinking about atmospheric circulation and climate, surface pressure was a readily available quantity. As meteorology developed, it was possible to develop quantitative predictions of future weather by bringing together a network of surface pressure observations and then of profiles of temperature and humidity obtained from balloons. 3. ON COMBINING OBSERVATIONS AND THE - ORY. With this new capability, it is natural to seek recognizable features in the observations we make of the Earth. There are techniques we can use to group the remotely sensed data in the individual footprints into objects that we can track. We will present one such image-processing application to radiation budget data, showing how we can interpret the radiation budget data in terms of cloud systems that are organized into systematic patterns of behavior - an ecosystem-like view of cloud behavior.

Burning mechanism and regression rate of RX-35-AU and RX-35-AV as a function of HMX particle size measured by the hybrid closed bomb-strand burner

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

Tao, W.C.; Costantino, M.S.; Ornellas, D.L.

1990-04-01

In this study, the average surface regression rate of two HMX-based cast explosives, RX-35-AU and RX-35-AV, is measured to pressures above 750 MPa using a hybrid closed bomb-strand burner. The hybrid design allows the simultaneous measurement of pressure and regression rate over a large range of pressures in each experiment. Nitroglycerin/Triacetin (75/25) and polyethylene glycol (PEG) are used as the energetic plasticizer and polymeric binder, respectively, in both formulations. The HMX solids loading in each formulation is 50 wt %, consisting of a narrow particle size distribution of 6--8 {mu}m for RX-35-AU and 150--177 {mu}m for RX-35-AV. Of special interestmore » are the regression rate and burning mechanism as a function of the initial particle size distribution and the mechanical properties fo the cast explosives. In general, the regression rate for the larger particle size formulation, RX-35-AV, is two to three times faster compared to that for RX-35-AU. Up to 750 MPa and independent of the initial confinement pressure, RX-35-AU exhibits a planar burning mechanism with the regression rate obeying the classical aP{sup n} formalism. For RX-35-AV, however, the burning behavior is erratic for samples ignited at 200 MPa confinement pressure. At confinement pressures above 400 MPa, the regression exhibits more of a planar burning mechanism. The unstable combustion behavior for RX-35-AV at lower confinement pressures is related to several mechanisms: (1) an abrupt increase in surface area due to particle fracture and subsequent translation and rotation, resulting in debonding and creating porosity, (2) thixotropic'' separation of the binder and nitramine, causing the significantly greater fracture damage to the nitramine during the loading cycle, (3) microscopic damage to the nitramine crystals that increase its intrinsic burning rate. 12 refs., 8 figs., 2 tabs.« less

Studies of friction and wear characteristics of various wires for wire-brush skids

NASA Technical Reports Server (NTRS)

Dreher, R. C.

1977-01-01

The friction and wear characteristics of 22 types and sizes of wires for potential use in wire-brush skids were studied. These characteristics were determined by placing brushes made from candidate wires on a belt sander whose moving belt simulated landing roll-out distance. At the same time, the drag force and wear behavior were monitored. Data were obtained over distances up to 3048 m (10,000 ft) at preselected bearing pressures of 172 to 1034 kPa (25 to 150 psi). In general, the friction coefficient developed by the candidate wires was found to be independent of bearing pressure and ranged between 0.4 and 0.6 under the test conditions of this investigation. The friction coefficient was not degraded when the surface was wetted and appears to be independent of wire diameter except perhaps when wire size is relatively large compared with the surface asperities. Generally, the high friction demonstrated by the soft materials was accompanied by high wear rates; conversely, the hard materials provided greater wear resistance but offered lower friction. For all test wires, the wear was shown to increase with increasing bearing pressure, in general, for the same bearing pressure, wear increased with increasing wire diameter and decreased when the surface was wetted.

Nonequilibrium 2-Hydroxyoctadecanoic Acid Monolayers: Effect of Electrolytes

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

Lendrum, Conrad D.; Ingham, Bridget; Lin, Binhua

2012-02-06

2-Hydroxyacids display complex monolayer phase behavior due to the additional hydrogen bonding afforded by the presence of the second hydroxy group. The placement of this group at the position {alpha} to the carboxylic acid functionality also introduces the possibility of chelation, a utility important in crystallization including biomineralization. Biomineralization, like many biological processes, is inherently a nonequilibrium process. The nonequilibrium monolayer phase behavior of 2-hydroxyoctadecanoic acid was investigated on each of pure water, calcium chloride, sodium bicarbonate and calcium carbonate crystallizing subphases as a precursor study to a model calcium carbonate biomineralizing system, each at a pH of {approx}6. Themore » role of the bicarbonate co-ion in manipulating the monolayer structure was determined by comparison with monolayer phase behavior on a sodium chloride subphase. Monolayer phase behavior was probed using surface pressure/area isotherms, surface potential, Brewster angle microscopy, and synchrotron-based grazing incidence X-ray diffraction and X-ray reflectivity. Complex phase behavior was observed for all but the sodium chloride subphase with hydrogen bonding, electrostatic and steric effects defining the symmetry of the monolayer. On a pure water subphase hydrogen bonding dominates with three phases coexisting at low pressures. Introduction of calcium ions into the aqueous subphase ensures strong cation binding to the surfactant head groups through chelation. The monolayer becomes very unstable in the presence of bicarbonate ions within the subphase due to short-range hydrogen bonding interactions between the monolayer and bicarbonate ions facilitated by the sodium cation enhancing surfactant solubility. The combined effects of electrostatics and hydrogen bonding are observed on the calcium carbonate crystallizing subphase.« less

[Significance of the glenoid labrum for stability of the glenohumeral joint. An experimental study].

PubMed

Habermeyer, P; Schuller, U

1990-01-01

In human cadavers we were able to show that the glenohumeral joint is comparable to the model of a physical piston. The labrum glenoidale functions like a valve against atmospheric pressure. It is possible to characterize the behavior of intraarticular negative pressure by the equation (formula; see text). The calculations of the force F of atmospheric pressure tending to resist distraction of the joint surfaces leads to a 95% confidence interval from 6.9 to 22.9 kp. Under a general anesthetic, distraction of the healthy glenohumeral joint also produces negative intraarticular pressure in the area of the fossa glenoidalis in vivo. Joints with a labral tear (Bankart defect) and a chronic instability are not characterized by this phenomenon. A change in intraarticular pressure might stimulate intraarticular pressure receptors. This could be important in functioning as a neuromuscular protection reflex for the joint.

Investigation of the Martian environment by infrared spectroscopy on Mariner 9

NASA Technical Reports Server (NTRS)

Conrath, H. R.; Conrath, B. J.; Novis, W.; Kunde, V. G.; Lowman, P.; Maguire, W.; Pearl, J. C.; Pirraglia, J.; Prabhakara, C.; Schlachman, B.

1972-01-01

Measurements obtained during and after the planet-wide dust storm indicate that large diurnal variations in atmospheric temperature existed up to at least 30 km; winds inferred from the temperature fields show a strong tidal component and significant ageostrophic behavior. With the dissipation of the dust, the daily maximum in the atmospheric temperature field moved from approximately latitude -60 and late afternoon local time to near the subsolar point in latitude and time. Analysis of spectral features due to the atmospheric dust indicates as SIO2 content of 60 ? 10%, implying that substantial geochemical differentiation has occurred. Water vapor estimates indicate abundances of 10 to 20 precipitable micrometers. Between November 1971 and April 1972 no gross latitudinal or temporal dependence in the water vapor distribution was detected from the south polar region to the equator. Water vapor was not detected over the north polar regions. Surface pressure mapping was carried out from which topographic relief of nearly two pressure scale heights is inferred. Extensive regions were found where the surface pressure exceeds the triple point pressure of water.

Surface Roughness Investigation of Ultrafine-Grained Aluminum Alloy Subjected to High-Speed Erosion

NASA Astrophysics Data System (ADS)

Kazarinov, N. A.; Evstifeev, A. D.; Petrov, Y. V.; Atroshenko, S. A.; Lashkov, V. A.; Valiev, R. Z.; Bondarenko, A. S.

2016-09-01

This study is the first attempt to investigate the influence of severe plastic deformation (SPD) treatment on material surface behavior under intensive erosive conditions. Samples of aluminum alloy 1235 (99.3 Al) before and after high-pressure torsion (HPT) were subjected to intensive erosion by corundum particles accelerated via air flow in a small-scale wind tunnel. Velocity of particles varied from 40 to 200 m/s, while particle average diameter was around 100 μm. Surface roughness measurements provided possibility to compare surface properties of both materials after erosion tests. Moreover, SPD processing appeared to increase noticeably the threshold velocity of the surface damaging process. Additionally, structural analysis of the fracture surfaces of the tested samples was carried out.

A model of Martian surface chemistry

NASA Technical Reports Server (NTRS)

Oyama, V. I.; Berdahl, B. J.

1979-01-01

Alkaline earth and alkali metal superoxides and peroxides, gamma-Fe2O3 and carbon suboxide polymer, are proposed to be constituents of the Martian surface material. These reactive substances explain the water modified reactions and thermal behaviors of the Martian samples demonstrated by all of the Viking Biology Experiments. It is also proposed that the syntheses of these substances result mainly from electrical discharges between wind-mobilized particles at Martian pressures; plasmas are initiated and maintained by these discharges. Active species in the plasma either combine to form or react with inorganic surfaces to create the reactive constituents.

Plasma variables and tribological properties of coatings in low pressure (0.1 - 10.0 torr) plasma systems

NASA Technical Reports Server (NTRS)

Avni, R.; Spalvins, T.

1984-01-01

A detailed treatment is presented of the dialog known as plasma surface interactions (PSI) with respect to the coating process and its tribological behavior. Adsorption, morphological changes, defect formation, sputtering, chemical etching, and secondary electron emission are all discussed as promoting and enhancing the surface chemistry, thus influencing the tribological properties of the deposited flux. Phenomenological correlations of rate of deposition, flux composition, microhardness, and wear with the plasma layer variables give an insight to the formation of chemical bonding between the deposited flux and the substrate surface.

Effects of high hydrostatic pressure on secondary structure and emulsifying behavior of sweet potato protein

NASA Astrophysics Data System (ADS)

Mehmood Khan, Nasir; Mu, Tai-Hua; Sun, Hong-Nan; Zhang, Miao; Chen, Jing-Wang

2015-04-01

In this study, secondary structures of sweet potato protein (SPP) after high hydrostatic pressure (HHP) treatment (200-600 MPa) were evaluated and emulsifying properties of emulsions with HHP-treated SPP solutions in different pH values (3, 6, and 9) were investigated. Circular dichroism analysis confirmed the modification of the SPP secondary structure. Surface hydrophobicity increased at pH 3 and decreased at 6 and 9. Emulsifying activity index at pH 6 increased with an increase in pressure, whereas emulsifying stability index increased at pH 6 and 9. Oil droplet sizes decreased, while volume frequency distribution of the smaller droplets increased at pH 3 and 6 with the HHP treatment. Emulsion viscosity increased at pH 6 and 9 and pseudo-plastic flow behaviors were not altered for all emulsions produced with HHP-treated SPP. These results suggested that HHP could modify the SPP structure for better emulsifying properties, which could increase the use of SPP emulsion in the food industry.

Behavior of aircraft antiskid braking systems on dry and wet runway surfaces - A velocity-rate-controlled, pressure-bias-modulated system

NASA Technical Reports Server (NTRS)

Stubbs, S. M.; Tanner, J. A.

1976-01-01

During maximum braking the average ratio of drag-force friction coefficient developed by the antiskid system to maximum drag-force friction coefficient available at the tire/runway interface was higher on dry surfaces than on wet surfaces. The gross stopping power generated by the brake system on the dry surface was more than twice that obtained on the wet surfaces. With maximum braking applied, the average ratio of side-force friction coefficient developed by the tire under antiskid control to maximum side-force friction available at the tire/runway interface of a free-rolling yawed tire was shown to decrease with increasing yaw angle. Braking reduced the side-force friction coefficient on a dry surface by 75 percent as the wheel slip ratio was increased to 0.3; on a flooded surface the coefficient dropped to near zero for the same slip ratio. Locked wheel skids were observed when the tire encountered a runway surface transition from dry to flooded, due in part to the response time required for the system to sense abrupt changes in the runway friction; however, the antiskid system quickly responded by reducing brake pressure and cycling normally during the remainder of the run on the flooded surface.

Modeling the Buildup of Annular Pressure in Cased and Uncased Annuli of Faulty Wellbores

NASA Astrophysics Data System (ADS)

Lackey, G.; Rajaram, H.

2017-12-01

Structurally sound wellbores are essential to oil and gas production, natural gas storage, and carbon dioxide sequestration operations. Wellbore integrity is easily assessed at the wellhead by the presence of pressure or gas flow in the outer annuli of a well, as it indicates the uncontrolled vertical migration of fluids outside the production casing. This phenomenon is typically referred to as sustained casing pressure (SCP), sustained annular pressure, or surface casing vent flow. Of particular concern is the buildup of pressure in the surface casing annulus. If the surface casing is sealed at the wellhead and cement is not brought into the bottom of the casing, annular pressure that builds induces gas migration when the fluid and entry pressure of the formation at the bottom of the surface casing is exceeded. Multiple incidents of stray gas migration from oil and gas operations have contaminated water wells in Colorado, Pennsylvania, and Ohio through this mechanism. Natural gas escaping the #25 Standard Senson well at the Aliso Gas storage facility in California, the largest accidental release of greenhouse gases in US history, also followed this pathway. Previous studies have modeled the buildup of SCP in faulty wells with fully-cased annuli that are isolated from the surrounding formation. However, the majority of onshore oil and gas wells in the US are constructed with uncased outermost annuli that are hydraulically connected to the surrounding subsurface. In this study, we adapt current approaches of modeling SCP to include the regulation of annular liquid level by formation fluid pressure, dissolution of gas into the annular liquids, the transport of aqueous gas by crossflow into deep formations, and gas migration away from the well, when the entry pressure of the formations or fractures along the uncased annulus is exceeded, to compare the buildup behavior of SCP in both uncased and fully-cased annuli. We consider well construction and subsurface geology representative of the Wattenberg Field in Colorado and interpret observations of sustained casing pressure collected by the Colorado Oil and Gas Conservation Commission. We demonstrate that the potential negative consequences of integrity loss are much greater for an uncased well than for fully-cased well.

Superhydrophobic copper tubes with possible flow enhancement and drag reduction.

PubMed

Shirtcliffe, Neil J; McHale, Glen; Newton, Michael I; Zhang, Yong

2009-06-01

The transport of a Newtonian liquid through a smooth pipe or tube is dominated by the frictional drag on the liquid against the walls. The resistance to flow against a solid can, however, be reduced by introducing a layer of gas at or near the boundary between the solid and liquid. This can occur by the vaporization of liquid at a surface at a temperature above the Leidenfrost point, by a cushion of air (e.g. below a hovercraft), or by producing bubbles at the interface. These methods require a continuous energy input, but a more recent discovery is the possibility of using a superhydrophobic surface. Most reported research uses small sections of lithographically patterned surfaces and rarely considers pressure differences or varying flow rates. In this work we present a method for creating a uniform superhydrophobic nanoribbon layer on the inside of round copper tubes of millimetric internal radius. Two types of experiments are described, with the first involving a simultaneous comparison of four tubes with different surface finishes (as received, as received with hydrophobic coating, nanoribbon, and nanoribbon with a hydrophobic coating) under constant flow rate conditions using water and water-glycerol mixtures. The results show that the superhydrophobic nanoribbon with a hydrophobic coating surface finish allows greater flow at low pressure differences but that the effect disappears as the pressure at the inlet of the tube is increased. The second experiment is a simple visual demonstration of the low-pressure behavior using two nominally identical tubes in terms of length and cross-section, but with one tube possessing a superhydrophobic internal surface finish. In this experiment a reservoir is allowed to feed the two tubes with open ends via a T-piece and it is observed that, once flow commences, it preferentially occurs down the superhydrophobic tube.

CO Adsorption on Reconstructed Ir(100) Surfaces from UHV to mbar Pressure: A LEED, TPD, and PM-IRAS Study

PubMed Central

2016-01-01

Clean and stable surface modifications of an iridium (100) single crystal, i.e., the (1 × 1) phase, the (5 × 1) reconstruction, and the oxygen-terminated (2 × 1)-O surface, were prepared and characterized by low energy electron diffraction (LEED), temperature-programmed desorption (TPD), infrared reflection absorption spectroscopy (IRAS) and polarization modulation IRAS (PM-IRAS). The adsorption of CO in UHV and at elevated (mbar) pressure/temperature was followed both ex situ and in situ on all three surface modifications, with a focus on mbar pressures of CO. The Ir(1 × 1) surface exhibited c(4 × 2)/c(2 × 2) and c(6 × 2) CO structures under low pressure conditions, and remained stable up to 100 mbar and 700 K. For the (2 × 1)-O reconstruction CO adsorption induced a structural change from (2 × 1)-O to (1 × 1), as confirmed by LEED, TPD, and IR. For Ir (2 × 1)-O TPD indicated that CO reacted with surface oxygen forming CO2. The (5 × 1) reconstruction featured a reversible and dynamic behavior upon CO adsorption, with a local lifting of the reconstruction to (1 × 1). After CO desorption, the (5 × 1) structure was restored. All three reconstructions exhibited CO adsorption with on-top geometry, as evidenced by IR. With increasing CO exposure the resonances shifted to higher wavenumber, due to adsorbate–adsorbate and adsorbate–substrate interactions. The largest wavenumber shift (from 2057 to 2100 cm–1) was observed for Ir(5 × 1) upon CO dosing from 1 L to 100 mbar. PMID:27257467

Synthesis and improved explosion behaviors of aluminum powders coated with nano-sized nickel film

NASA Astrophysics Data System (ADS)

Kim, Kyung Tae; Kim, Dong Won; Kim, Soo Hyung; Kim, Chang Kee; Choi, Yoon Jeong

2017-09-01

Nickel (Ni) materials with a thickness of a few hundred nm were homogeneously coated on the surfaces of aluminum (Al) powders by an electroless plating process. The Ni-coated Al powders show characteristic interfacial structures mixed of Ni, Al and O instead of densely packed Al oxide at the surface. The explosion test of the Ni-coated Al powders utilizing flame ignition showed that the powders had a 3.6 times enhanced pressurization rate of 405 kPa/ms compared to 111 kPa/ms of uncoated Al powders. It was found that this is due to a feasible diffusion of oxygen atoms into the Al powders through the thin and rough interfacial layers present at the Ni/Al interface. These results clearly indicate that nano-sized Ni film introduced instead of surface oxide acts as a very profitable layer to achieve efficient combustion behaviors by a rapid oxidation of Al powders.

Asphaltene-laden interfaces form soft glassy layers in contraction experiments: a mechanism for coalescence blocking.

PubMed

Pauchard, Vincent; Rane, Jayant P; Banerjee, Sanjoy

2014-11-04

In previous studies, the adsorption kinetics of asphaltenes at the water-oil interface were interpreted utilizing a Langmuir equation of state (EOS) based on droplet expansion experiments.1-3 Long-term adsorption kinetics followed random sequential adsorption (RSA) theory predictions, asymptotically reaching ∼85% limiting surface coverage, which is similar to limiting random 2D close packing of disks. To extend this work beyond this slow adsorption process, we performed rapid contractions and contraction-expansions of asphaltene-laden interfaces using the pendant drop experiment to emulate a Langmuir trough. This simulates the rapid increase in interfacial asphaltene concentration that occurs during coalescence events. For the contraction of droplets aged in asphaltene solutions, deviation from the EOS consistently occurs at a surface pressure value ∼21 mN/m corresponding to a surface coverage ∼80%. At this point droplets lose the shape required for validity of the Laplace-Young equation, indicating solidlike surface behavior. On further contraction wrinkles appear, which disappear when the droplet is held at constant volume. Surface pressure also decreases down to an equilibrium value near that measured for slow adsorption experiments. This behavior appears to be due to a transition to a glassy interface on contraction past the packing limit, followed by relaxation toward equilibrium by desorption at constant volume. This hypothesis is supported by cycling experiments around the close-packed limit where the transition to and from a solidlike state appears to be both fast and reversible, with little hysteresis. Also, the soft glass rheology model of Sollich is shown to capture previously reported shear behavior during adsorption. The results suggest that the mechanism by which asphaltenes stabilize water-in-oil emulsions is by blocking coalescence due to rapid formation of a glassy interface, in turn caused by interfacial asphaltenes rapidly increasing in concentration beyond the glass transition point.

Self-Similar Taylor Cone Formation in Conducting Viscous Films: Computational Study of the Influence of Reynolds Number

NASA Astrophysics Data System (ADS)

Albertson, Theodore; Troian, Sandra

2017-11-01

Previous studies by Zubarev (2001) and Suvorov and Zubarev (2004) have shown that above a critical field strength, an ideal (inviscid) conducting fluid film will deform into a singular profile characterized by a conic cusp. The governing equations for the electrohydrodynamic response beneath the cusp admit self-similar solutions leading to so-called blow-up behavior in the Maxwell pressure, capillary pressure and kinetic energy density. The runaway behavior in these variables reflects divergence in time characterized by an exponent of -2/3. Here we extend the physical system to include viscous effects and conduct a computational study of the cusp region as a function of increasing electrical Reynolds number ReE . We employ a finite element, moving mesh algorithm to examine the behavior of the film shape, Maxwell pressure and capillary pressure upon approach to the blow-up event. Our study indicates that self-similarity establishes at relatively low ReE despite the presence of vorticity, which is localized to the cusp surface region. With increasing ReE , the period of self-similiarity extends further in time as the exponent changes from about -4/5 to the ideal value of -2/3, with slightly different values distinguishing the Maxwell and capillary stresses. T. Albertson gratefully acknowledges support from a NASA Space Technology Research Fellowship.

Constraining geometrical, hydrodynamical and mechanical properties of a fault zone at hourly time scales from ground surface tilt data

NASA Astrophysics Data System (ADS)

Schuite, Jonathan; Longuevergne, Laurent; Bour, Olivier; Burbey, Thomas J.; Boudin, Frédéric

2017-04-01

Flow through reservoirs such as fractured media is powered by pressure gradients which also generate measurable poroelastic deformation of the rock body. The combined analysis of ground surface deformation and sub-surface fluid pressure provides valuable insights of a reservoir's structure and hydromechanical properties, which are of interest for deep-seated CO2 or nuclear waste storage for instance. Amongst all surveying tools, surface tiltmeters offer the possibility to grasp hydraulically-induced deformation over a broad range of time scales with a remarkable precision (1 nanoradian). Here, we investigate the information content of transient surface tilt generated by flow in a kilometer scale sub-vertical fault zone and its surrounding fractured rock matrix. Our approach involves the combined analysis of field data and results of a fully coupled poroelastic model, where fault and matrix are represented as equivalent homogeneous domains. The signature of pressure changes in the fault zone due to pumping cycles is clearly recognizable in field tilt data and we aim to explain the peculiar features that appear in: 1) tilt time series alone from a set of 4 instruments; 2) the ratio of tilt over pressure. With the model, we evidence that the shape of tilt measurements on both sides of a fault zone is sensitive to its diffusivity and its elastic modulus. In particular, we show a few well placed tiltmeters (on each side of a fault) give more information on the medium's properties than well spatialized surface displacement maps. Furthermore, the ratio of tilt over pressure predominantly encompasses information about the system's dynamic behavior and extent of the fault zone, and allows separating contributions of flow in the different compartments. Hence, tiltmeters are well suited to characterize hydromechanical processes associated to fault zone hydrogeology at short time scales, where space-borne surveying methods fail to seize any deformation signal.

Time and space variability of spectral estimates of atmospheric pressure

NASA Technical Reports Server (NTRS)

Canavero, Flavio G.; Einaudi, Franco

1987-01-01

The temporal and spatial behaviors of atmospheric pressure spectra over the northern Italy and the Alpine massif were analyzed using data on surface pressure measurements carried out at two microbarograph stations in the Po Valley, one 50 km south of the Alps, the other in the foothills of the Dolomites. The first 15 days of the study overlapped with the Alpex Intensive Observation Period. The pressure records were found to be intrinsically nonstationary and were found to display substantial time variability, implying that the statistical moments depend on time. The shape and the energy content of spectra depended on different time segments. In addition, important differences existed between spectra obtained at the two stations, indicating a substantial effect of topography, particularly for periods less than 40 min.

Charge and pressure-tuned surface patterning of surfactant-encapsulated polyoxometalate complexes at the air-water interface.

PubMed

Xu, Miao; Li, Haolong; Zhang, Liying; Wang, Yizhan; Yuan, Yuan; Zhang, Jianming; Wu, Lixin

2012-10-16

In this paper, four organic-inorganic hybrid complexes were prepared using a cationic surfactant dimethyldioctadecylammonium (DODA) to replace the counter cations of four Keggin-type polyoxometalate (POM) clusters with gradually increased negative charges, PW(12)O(40)(3-), SiW(12)O(40)(4-), BW(12)O(40)(5-), and CoW(12)O(40)(6-). The formed surfactant-encapsulated POM (SEP) complexes showed typical amphiphilic properties and can be spread onto the air-water interface to form Langmuir monolayers. The interfacial behavior of the SEP monolayer films was systemically studied by multiple in situ and ex situ characterization methods including Brewster angle microscopy (BAM), atomic force microscopy (AFM), reflection-absorption infrared (RAIR), and X-ray photoelectron spectroscopy (XPS). We found that the increasing alkyl chain density of SEPs leads to an enhanced stability and a higher collapse pressure of SEP Langmuir monolayers. Moreover, a second layer evolved as patterns from the initial monolayers of all the SEPs, when the surface pressures approached the collapse values. The rational combination of alkyl chain density and surface pressure can precisely control the size and the morphology of SEP patterns transforming from disk-like to leaf-like structures on a micrometer scale. The pattern formation was demonstrated to be driven by the self-optimized surface energy of SEP monolayers. This finding can direct a new strategy for the fabrication of POM-hybrid films with controllable patterns, which should be instructive for designing POM-based thin film devices.

Effect of surface oxide films on the properties of pulse electric-current sintered metal powders

NASA Astrophysics Data System (ADS)

Xie, Guoqiang; Ohashi, Osamu; Yamaguchi, Norio; Wang, Airu

2003-11-01

Metallic powders with various thermodynamic stability oxide films (Ag, Cu, and Al powders) were sintered using a pulse electric-current sintering (PECS) process. Behavior of oxide films at powder surfaces and their effect on the sintering properties were investigated. The results showed that the sintering properties of metallic powders in the PECS process were subject to the thermodynamic stability of oxide films at particles surfaces. The oxide films at Ag powder surfaces are decomposed during sintering with the contact region between the particles being metal/metal bond. The oxide films at Cu powder surfaces are mainly broken via loading pressure at a low sintering temperature. At a high sintering temperature, they are mainly dissolved in the parent metal, and the contact regions turn into the direct metal/metal bonding. Excellent sintering properties can be received. The oxide films at Al powder surfaces are very stable, and cannot be decomposed and dissolved, but broken by plastic deformation of particles under loading pressure at experimental temperatures. The interface between particles is partially bonded via the direct metal/metal bonding making it difficult to achieve good sintered properties.

Uniaxial low cycle fatigue behavior for pre-corroded 16MND5 bainitic steel in simulated pressurized water reactor environment

NASA Astrophysics Data System (ADS)

Chen, Xu; Ren, Bin; Yu, Dunji; Xu, Bin; Zhang, Zhe; Chen, Gang

2018-06-01

The effects of uniaxial tension properties and low cycle fatigue behavior of 16MND5 bainitic steel cylinder pre-corroded in simulated pressurized water reactor (PWR) were investigated by fatigue at room temperature in air and immersion test system, scanning electron microscopy (SEM), energy disperse spectroscopy (EDS). The experimental results indicated that the corrosion fatigue lives of 16MND5 specimen were significantly affected by the strain amplitude and simulated PWR environments. The compositions of corrosion products were complexly formed in simulated PWR environments. The porous corrosion surface of pre-corroded materials tended to generate pits as a result of promoting contact area to the fresh metal, which promoted crack initiation. For original materials, the fatigue cracks initiated at inclusions imbedded in the micro-cracks. Moreover, the simulated PWR environments degraded the mechanical properties and low cycle fatigue behavior of 16MND5 specimens remarkably. Pre-corrosion of 16MND5 specimen mainly affected the plastic term of the Coffin-Manson equation.

Effects of high hydrostatic pressure on the functional and rheological properties of the protein fraction extracted from pine nuts.

PubMed

Cao, Baiying; Fang, Li; Liu, Chunlei; Min, Weihong; Liu, Jingsheng

2018-01-01

High hydrostatic pressure treatments could increase the protein solubility (200 MPa), water holding capacity (400 MPa), and oil holding capacity (400 MPa) of pine nuts protein fractions, respectively. The exposed sufhydryl content for albumin was highest at 100 MPa while for other fractions it was 400 MPa, contrary for total sufhydryl content-generally it was at 100 MPa, except glutelin (400 MPa). Pine nuts protein fractions demonstrated the typical behavior of weak gels (G' > G″). After the treatments of high hydrostatic pressure the specific surface area of pine nuts protein particle was increased upon pressure, and the surface of protein became rough which increased the particle size. The functional groups of protein were found to be unchanged, but the characteristic peaks of pine nuts protein moved to a low-band displacement and the value of peaks was amplified accordingly to the pressure. The high hydrostatic pressure treatments were found to improve the functional properties of pine nuts protein isolates by enhancing the heat-induced gel strength of pine nuts protein isolates which make proteins more stretchable. These results suggest that high hydrostatic pressure treatments can increase the functional properties and alter the rheological properties of pine nuts protein fractions which will broaden its applications in food industry.

Lubrication theory for a random fibrous medium

NASA Astrophysics Data System (ADS)

Mirbod, Parisa; Andreopoulos, Yiannis; Weinbaum, Sheldon

2007-11-01

In the classical theory for a slipper bearing one examines the relative motion of an inclined planar surface and a horizontal planar surface. The solution for the pressure distribution and lift force are independent of which boundary is moving and there is an optimum tilt k=h1/h2=2.2 for maximum lift. This symmetry is lost if the intervening space is filled with a soft porous fibrous material. In this paper the generalized Reynolds equation derived in Feng and Weinbaum (2000) J. Fluid Mech. 422:281 is extended to treat a random fiber matrix satisfying the widely used Carman-Kozeny equation. We show that the solutions are strikingly different depending on whether a) the inclined upper boundary moves or b) the upper boundary is stationary and the horizontal lower boundary moves beneath it. The behavior depends critically on the value of the dimensionless fiber interaction layer thickness α=H/√Kp . In a) the pressure and lift force increase as 2̂ and asymptotically approach a limiting behavior for large values of α since the fluid is pushed forward by the tilt of the upper boundary. In b) the pressure and lift force decay as &-2circ; since the fiber interaction layer thickness decreases and the amount of fluid dragged though the fluid gap decreases as α increases and vanishes for α>> 1.

A modeling study of the effect of runoff variability on the effective pressure beneath Russell Glacier, West Greenland

NASA Astrophysics Data System (ADS)

de Fleurian, Basile; Morlighem, Mathieu; Seroussi, Helene; Rignot, Eric; van den Broeke, Michiel R.; Kuipers Munneke, Peter; Mouginot, Jeremie; Smeets, Paul C. J. P.; Tedstone, Andrew J.

2016-10-01

Basal sliding is a main control on glacier flow primarily driven by water pressure at the glacier base. The ongoing increase in surface melting of the Greenland Ice Sheet warrants an examination of its impact on basal water pressure and in turn on basal sliding. Here we examine the case of Russell Glacier, in West Greenland, where an extensive set of observations has been collected. These observations suggest that the recent increase in melt has had an equivocal impact on the annual velocity, with stable flow on the lower part of the drainage basin but accelerated flow above the Equilibrium Line Altitude (ELA). These distinct behaviors have been attributed to different evolutions of the subglacial draining system during and after the melt season. Here we use a high-resolution subglacial hydrological model forced by reconstructed surface runoff for the period 2008 to 2012 to investigate the cause of these distinct behaviors. We find that the increase in meltwater production at low elevation yields a more efficient drainage system compatible with the observed stagnation of the mean annual flow below the ELA. At higher elevation, the model indicates that the drainage system is mostly inefficient and is therefore strongly sensitive to an increase in meltwater availability, which is consistent with the observed increase in ice velocity.

Origins of extreme boundary lubrication by phosphatidylcholine liposomes.

PubMed

Sorkin, Raya; Kampf, Nir; Dror, Yael; Shimoni, Eyal; Klein, Jacob

2013-07-01

Phosphatidylcholine (PC) vesicles have been shown to have remarkable boundary lubricating properties under physiologically-high pressures. Here we carry out a systematic study, using a surface force balance, of the normal and shear (frictional) forces between two opposing surfaces bearing different PC vesicles across water, to elucidate the origin of these properties. Small unilamellar vesicles (SUVs, diameters < 100 nm) of the symmetric saturated diacyl PCs DMPC (C(14)), DPPC (C(16)) and DSPC (C(18)) attached to mica surfaces were studied in their solid-ordered (SO) phase on the surface. Overall liposome lubrication ability improves markedly with increasing acyl chain length, and correlates strongly with the liposomes' structural integrity on the substrate surface: DSPC-SUVs were stable on the surface, and provided extremely efficient lubrication (friction coefficient μ ≈ 10(-4)) at room temperature at pressures up to at least 18 MPa. DMPC-SUVs ruptured following adsorption, providing poor high-pressure lubrication, while DPPC-SUVs behavior was intermediate between the two. These results can be well understood in terms of the hydration-lubrication paradigm, but suggest that an earlier conjecture, that highly-efficient lubrication by PC-SUVs depended simply on their being in the SO rather than in the liquid-disordered phase, should be more nuanced. Our results indicate that the resistance of the SUVs to mechanical deformation and rupture is the dominant factor in determining their overall boundary lubrication efficiency in our system. Copyright © 2013 Elsevier Ltd. All rights reserved.

Transient heat transfer behavior of water spray evaporative cooling on a stainless steel cylinder with structured surface for safety design application in high temperature scenario

NASA Astrophysics Data System (ADS)

Aamir, Muhammad; Liao, Qiang; Hong, Wang; Xun, Zhu; Song, Sihong; Sajid, Muhammad

2017-02-01

High heat transfer performance of spray cooling on structured surface might be an additional measure to increase the safety of an installation against any threat caused by rapid increase in the temperature. The purpose of present experimental study is to explore heat transfer performance of structured surface under different spray conditions and surface temperatures. Two cylindrical stainless steel samples were used, one with pyramid pins structured surface and other with smooth surface. Surface heat flux of 3.60, 3.46, 3.93 and 4.91 MW/m2 are estimated for sample initial average temperature of 600, 700, 800 and 900 °C, respectively for an inlet pressure of 1.0 MPa. A maximum cooling rate of 507 °C/s was estimated for an inlet pressure of 0.7 MPa at 900 °C for structured surface while for smooth surface maximum cooling rate of 356 °C/s was attained at 1.0 MPa for 700 °C. Structured surface performed better to exchange heat during spray cooling at initial sample temperature of 900 °C with a relative increase in surface heat flux by factor of 1.9, 1.56, 1.66 and 1.74 relative to smooth surface, for inlet pressure of 0.4, 0.7, 1.0 and 1.3 MPa, respectively. For smooth surface, a decreasing trend in estimated heat flux is observed, when initial sample temperature was increased from 600 to 900 °C. Temperature-based function specification method was utilized to estimate surface heat flux and surface temperature. Limited published work is available about the application of structured surface spray cooling techniques for safety of stainless steel structures at very high temperature scenario such as nuclear safety vessel and liquid natural gas storage tanks.

Fundamental Ice Crystal Accretion Physics Studies

NASA Technical Reports Server (NTRS)

Struk, Peter M.; Broeren, Andy P.; Tsao, Jen-Ching; Vargas, Mario; Wright, William B.; Currie, Tom; Knezevici, Danny; Fuleki, Dan

2012-01-01

Due to numerous engine power-loss events associated with high-altitude convective weather, ice accretion within an engine due to ice crystal ingestion is being investigated. The National Aeronautics and Space Administration (NASA) and the National Research Council (NRC) of Canada are starting to examine the physical mechanisms of ice accretion on surfaces exposed to ice-crystal and mixed-phase conditions. In November 2010, two weeks of testing occurred at the NRC Research Altitude Facility utilizing a single wedge-type airfoil designed to facilitate fundamental studies while retaining critical features of a compressor stator blade or guide vane. The airfoil was placed in the NRC cascade wind tunnel for both aerodynamic and icing tests. Aerodynamic testing showed excellent agreement compared with CFD data on the icing pressure surface and allowed calculation of heat transfer coefficients at various airfoil locations. Icing tests were performed at Mach numbers of 0.2 to 0.3, total pressures from 93 to 45 kPa, and total temperatures from 5 to 15 C. Ice and liquid water contents ranged up to 20 and 3 g/m3, respectively. The ice appeared well adhered to the surface in the lowest pressure tests (45 kPa) and, in a particular case, showed continuous leading-edge ice growth to a thickness greater than 15 mm in 3 min. Such widespread deposits were not observed in the highest pressure tests, where the accretions were limited to a small area around the leading edge. The suction surface was typically ice-free in the tests at high pressure, but not at low pressure. The icing behavior at high and low pressure appeared to be correlated with the wet-bulb temperature, which was estimated to be above 0 C in tests at 93 kPa and below 0 C in tests at lower pressure, the latter enhanced by more evaporative cooling of water. The authors believe that the large ice accretions observed in the low pressure tests would undoubtedly cause the aerodynamic performance of a compressor component such as a stator blade to degrade significantly, and could damage downstream components if shed.

Dynamic relationship between ocean bottom pressure and bathymetry around northern part of Hikurangi

NASA Astrophysics Data System (ADS)

Muramoto, T.; Inazu, D.; Ito, Y.; Hino, R.; Suzuki, S.

2017-12-01

In recent years, observation using ocean bottom pressure recorders for the purpose of the evaluation of sea floor crustal deformation is in great vogue. The observation network set up for the observation of sea floor is densely spaced compared with the instrument network for the observation of ocean. Therefore, it has the characteristic that it can observe phenomena on a local scale. In this study, by using these in situ data, we discuss ocean phenomena on a local scale. In this study, we use a high-resolution ocean model (Inazu Ocean Model) driven by surface air pressure and surface wind vector published by the Japan Meteorological Agency. We perform a hindcast experiment for ocean bottom pressure anomaly from April 2013 to June 2017. Then, we compare these results with in situ data. In this study, we use observed pressure records which were recorded by autonomous type instrument spanning a period from April 2013 to June 2017 off the coast of North Island in New Zealand. Consequently, we found this model can simulate not only the amplitude but also phase of non-tidal oceanic variation of East Cape Current (ECC) off the coast of North Island of New Zealand. Then, we calculate cross-correlation coefficient between the data at the OBP sites. We revealed that the ocean bottom pressure shows different behavior on the west side from the east side of edge of the continental shelf. This result implies that the submarine slope induces a dynamic effect and contributes to the seasonal variation of ocean bottom pressure. In addition, we calculate the velocity of the surface current in this area using our model, and consider the relationship between it and ocean bottom pressure variation. Taken together, we can say that the barotropic flow in the direction of south-west extends to the bottom of the sea in this area. Therefore, the existence of local cross-isobath currents is suggested. Our result indicates bathymetry has dynamic effect to ocean circulation on local scale and at the same time the surface ocean circulation contributes to ocean bottom pressure considerably.

Fundamental Ice Crystal Accretion Physics Studies

NASA Technical Reports Server (NTRS)

Currie, Tom; Knezevici, Danny; Fuleki, Dan; Struk, Peter M.; Broeren, Andy P.; Tsao, Jen-ching; Vargas, Mario; Wright, William

2011-01-01

Due to numerous engine power-loss events associated with high-altitude convective weather, ice accretion within an engine due to ice-crystal ingestion is being investigated. The National Aeronautics and Space Administration (NASA) and the National Research Council (NRC) of Canada are starting to examine the physical mechanisms of ice accretion on surfaces exposed to ice-crystal and mixed-phase conditions. In November 2010, two weeks of testing occurred at the NRC Research Altitude Facility utilizing a single wedge-type airfoil designed to facilitate fundamental studies while retaining critical features of a compressor stator blade or guide vane. The airfoil was placed in the NRC cascade wind tunnel for both aerodynamic and icing tests. Aerodynamic testing showed excellent agreement compared with CFD data on the icing pressure surface and allowed calculation of heat transfer coefficients at various airfoil locations. Icing tests were performed at Mach numbers of 0.2 to 0.3, total pressures from 93 to 45 kPa, and total temperatures from 5 to 15 C. Ice and liquid water contents ranged up to 20 and 3 grams per cubic meter, respectively. The ice appeared well adhered to the surface in the lowest pressure tests (45 kPa) and, in a particular case, showed continuous leading-edge ice growth to a thickness greater than 15 millimeters in 3 minutes. Such widespread deposits were not observed in the highest pressure tests, where the accretions were limited to a small area around the leading edge. The suction surface was typically ice-free in the tests at high pressure, but not at low pressure. The icing behavior at high and low pressure appeared to be correlated with the wet-bulb temperature, which was estimated to be above 0 C in tests at 93 kPa and below 0 C in tests at lower pressure, the latter enhanced by more evaporative cooling of water. The authors believe that the large ice accretions observed in the low pressure tests would undoubtedly cause the aerodynamic performance of a compressor component such as a stator blade to degrade significantly, and could damage downstream components if shed.

Fluid surface behavior in low gravity. Center discretionary fund no. 83-21

NASA Technical Reports Server (NTRS)

Leslie, F.; Gans, R. F.; Schafer, C.

1985-01-01

Measurements of rotating equilibrium bubble shapes in the low-gravity environment of a free-falling aircraft are presented. Emphasis is placed on bubbles which intersect the container boundaries. These data are compared with theoretical profiles derived from Laplace's formula and are in good agreement with the measurements. Two types of instability are explored. The first occurs when the baffle spacing is too large for the bubble to intersect both the top and bottom boundaries. The second occurs when the hydrostatic pressure beneath a displaced free surface does not compensate for pressure change due to capillary forces. The interface shape depends on the contact angle, the radius of intersection with container, and the parameter F which is a measure of the relative importance of centrifugal force to surface tension. For isolated bubbles, F has a maximum value of 1/2. A further increase in F causes the bubble to break contact with the axis of rotation. For large values of F, the bubble becomes more cylindrical and the capillary rise occurs over a thinner layer so that the small radius of curvature can generate enough pressure drop to balance the increased hydrostatic contribution.

Deformation and electrical properties of magnetic and vertically conductive composites with a chain-of-spheres structure

NASA Astrophysics Data System (ADS)

Choi, Chulmin; Hong, Soonkook; Chen, Li-Han; Liu, Chin-Hung; Choi, Duyoung; Kuru, Cihan; Jin, Sungho

2014-05-01

Vertically anisotropically conductive composites with aligned chain-of-spheres of 20-75 mm Ni particles in an elastomer matrix have been prepared by curing the mixture at 100°C-150°C under an applied magnetic field of ˜300-1000 Oe. The particles are coated with a ˜120 nm thick Au layer for enhanced electrical conductivity. The resultant vertically aligned but laterally isolated columns of conductive particles extend through the whole composite thickness and the end of the Ni columns protrude from the surface, contributing to enhanced electrical contact on the composite surface. The stress-strain curve on compressive deformation exhibits a nonlinear behavior with a rapidly increasing Young's modulus with stress (or pressure). The electrical contact resistance Rc decreases rapidly when the applied pressure is small and then more gradually after the applied pressure reaches 500 psi (˜3.4 MPa), corresponding to a 30% deformation. The directionally conductive elastomer composite material with metal pads and conductive electrodes on the substrate surface can be used as a convenient tactile shear sensor for applications involving artificial limbs, robotic devices, and other visual communication devices such as touch sensitive screens.

Langmuir-Blodgett Films of Supported Polyester Dendrimers

PubMed Central

Redón, Rocío; Carreón-Castro, M. Pilar; Mendoza-Martínez, F. J.

2012-01-01

Amphiphiles with a dendritic structure are attractive materials as they combine the features of dendrimers with the self-assembling properties and interfacial behavior of water-air affinities. We have synthesized three generations of polyester dendrimers and studied their interfacial properties on the Langmuir films. The behavior obtained was, as a rule, the lowest generation dendrimers behaving like traditional amphiphiles and the larger molecules presenting complicated isotherms. The Langmuir films of these compounds have been characterized by their surface pressure versus molecular area (π/A) and Brewster angle microscopy (BAM) observations. PMID:24052855

The COSIMA experiments and their verification, a data base for the validation of two phase flow computer codes

NASA Astrophysics Data System (ADS)

Class, G.; Meyder, R.; Stratmanns, E.

1985-12-01

The large data base for validation and development of computer codes for two-phase flow, generated at the COSIMA facility, is reviewed. The aim of COSIMA is to simulate the hydraulic, thermal, and mechanical conditions in the subchannel and the cladding of fuel rods in pressurized water reactors during the blowout phase of a loss of coolant accident. In terms of fuel rod behavior, it is found that during blowout under realistic conditions only small strains are reached. For cladding rupture extremely high rod internal pressures are necessary. The behavior of fuel rod simulators and the effect of thermocouples attached to the cladding outer surface are clarified. Calculations performed with the codes RELAP and DRUFAN show satisfactory agreement with experiments. This can be improved by updating the phase separation models in the codes.

Corrosion and stress corrosion cracking of ferritic/martensitic steel in super critical pressurized water

NASA Astrophysics Data System (ADS)

Hirose, T.; Shiba, K.; Enoeda, M.; Akiba, M.

2007-08-01

A water-cooled solid breeder (WCSB) blanket cooled by high temperature SCPW (super critical pressurized water) is a practical option of DEMO reactor. Therefore, it is necessary to check the compatibility of the steel with SCPW. In this work, reduced activation ferritic/martensitic steel, F82H has been tested through slow strain rate tests (SSRT) in 23.5 MPa SCPW. And weight change behavior was measured up to 1000 h. F82H did not demonstrated stress corrosion cracking and its weight simply increased with surface oxidation. The weight change of F82H was almost same as commercial 9%-Cr steels. According to a cross-sectional analysis and weight change behavior, corrosion rate of F82H in the 823 K SCPW is estimated to be 0.04 mm/yr.

Preferential interactions of trehalose, L-arginine.HCl and sodium chloride with therapeutically relevant IgG1 monoclonal antibodies.

PubMed

Sudrik, Chaitanya; Cloutier, Theresa; Pham, Phuong; Samra, Hardeep S; Trout, Bernhardt L

2017-10-01

Preferential interactions of weakly interacting formulation excipients govern their effect on the equilibrium and kinetics of several reactions of protein molecules in solution. Using vapor pressure osmometry, we characterized the preferential interactions of commonly used excipients trehalose, L-arginine.HCl and NaCl with three therapeutically-relevant, IgG1 monoclonal antibodies that have similar size and shape, but differ in their surface hydrophobicity and net charge. We further characterized the effect of these excipients on the reversible self-association, aggregation and viscosity behavior of these antibody molecules. We report that trehalose, L-arginine.HCl and NaCl are all excluded from the surface of the three IgG1 monoclonal antibodies, and that the exclusion behavior is linearly related to the excipient molality in the case of trehalose and NaCl, whereas a non-linear behavior is observed for L-arginine.HCl. Interestingly, we find that the magnitude of trehalose exclusion depends upon the nature of the protein surface. Such behavior is not observed in case of NaCl and L-arginine.HCl as they are excluded to the same extent from the surface of all three antibody molecules tested in this study. Analysis of data presented in this study provides further insight into the mechanisms governing excipient-mediated stabilization of mAb formulations.

Phonon triggered rhombohedral lattice distortion in vanadium at high pressure

DOE PAGES

Antonangeli, Daniele; Farber, Daniel L.; Bosak, Alexei; ...

2016-08-19

In spite of the simple body-centered-cubic crystal structure, the elements of group V, vanadium, niobium and tantalum, show strong interactions between the electronic properties and lattice dynamics. Further, these interactions can be tuned by external parameters, such as pressure and temperature. We used inelastic x-ray scattering to probe the phonon dispersion of single-crystalline vanadium as a function of pressure to 45 GPa. Our measurements show an anomalous high-pressure behavior of the transverse acoustic mode along the (100) direction and a softening of the elastic modulus C44 that triggers a rhombohedral lattice distortion occurring between 34 and 39 GPa. Lastly, ourmore » results provide the missing experimental confirmation of the theoretically predicted shear instability arising from the progressive intra-band nesting of the Fermi surface with increasing pressure, a scenario common to all transition metals of group V.« less

Carbon nanohorns under cold compression to 40 GPa: Raman scattering and X-ray diffraction experiments

NASA Astrophysics Data System (ADS)

Li, Bo; Nan, Yanli; Zhao, Xiang; Song, Xiaolong; Li, Haining; Wu, Jie; Su, Lei

2017-11-01

We report a high-pressure behavior of carbon nanohorns (CNHs) to 40 GPa at ambient temperature by in situ Raman spectroscopy and synchrotron radiation x-ray diffraction (XRD) in a diamond anvil cell. In Raman measurement, multiple structural transitions are observed. In particular, an additional band at ˜1540 cm-1 indicative of sp3 bonding is shown above 35 GPa, but it reverses upon releasing pressure, implying the formation of a metastable carbon phase having both sp2 and sp3 bonds. Raman frequencies of all bands (G, 2D, D + G, and 2D') are dependent upon pressure with respective pressure coefficients, among which the value for the G band is as small as ˜2.65 cm-1 GPa-1 above 10 GPa, showing a superior high-pressure structural stability. Analysis based on mode Grüneisen parameter demonstrates the similarity of high-pressure behavior between CNHs and single-walled carbon nanotubes. Furthermore, the bulk modulus and Grüneisen parameter for the G band of CNHs are calculated to be ˜33.3 GPa and 0.1, respectively. In addition, XRD data demonstrate that the structure of post-graphite phase derives from surface nanohorns. Based on topological defects within conical graphene lattice, a reasonable transformation route from nanohorns to the post-graphite phase is proposed.

Effect of vesicle size on the prodan fluorescence in diheptadecanoylphosphatidylcholine bilayer membrane under atmospheric and high pressures.

PubMed

Goto, Masaki; Sawaguchi, Hiroshi; Tamai, Nobutake; Matsuki, Hitoshi; Kaneshina, Shoji

2010-08-17

The bilayer phase behavior of diheptadecanoylphosphatidylcholine (C17PC) with different vesicle sizes (large multilamellar vesicle (LMV) and giant multilamellar vesicle (GMV)) was investigated by fluorescence spectroscopy using a polarity-sensitive fluorescent probe Prodan under atmospheric and high pressures. The difference in phase transitions and thermodynamic quantities of the transition was hardly observed between LMV and GMV used here. On the contrary, the Prodan fluorescence in the bilayer membranes changed depending on the size of vesicles as well as on the phase states. From the second derivative of fluorescence spectra, the three-dimensional image plots in which we can see the location of Prodan in the bilayer membrane as blue valleys were constructed for LMV and GMV under atmospheric pressure. The following characteristic behavior was found: (1) the Prodan molecules in GMV can be distributed to not only adjacent glycerol backbone region, but also near bulk-water region in the lamellar gel or ripple gel phase; (2) the blue valleys of GMV became deeper than those of LMV because of the greater surface density of the Prodan molecules per unit area of GMV than LMV; (3) the liquid crystalline phase of the bilayer excludes the Prodan molecules to a more hydrophilic region at the membrane surface with an increase in vesicle size; (4) the accurate information as to the phase transitions is gradually lost with increasing vesicle size. Under the high-pressure condition, the difference in Prodan fluorescence between LMV and GMV was essentially the same as the difference under atmospheric pressure except for the existence of the pressure-induced interdigitated gel phase. Further, we found that Prodan fluorescence spectra in the interdigitated gel phase were especially affected by the size of vesicles. This study revealed that the Prodan molecules can move around the headgroup region by responding not only to the phase state but also to the vesicle size, and they become a useful membrane probe, detecting important membrane properties such as the packing stress.

Variability of in situ sediment strength and pore pressure behavior of tidal estuary surface sediments

NASA Astrophysics Data System (ADS)

Lucking, Greg; Stark, Nina; Lippmann, Thomas; Smyth, Stephen

2017-10-01

Tidal estuaries feature spatially and temporally varying sediment dynamics and characteristics. Particularly, the variability of geotechnical sediment parameters is still poorly understood, limiting the prediction of long-term sediment stability and dynamics. This paper presents results from an in situ investigation of surficial sediments (≤50 cm) in a tidal estuary in New Hampshire (USA), using a portable free fall penetrometer. The aim is to investigate variations in sediment strength and pore pressure behavior with regard to sediment type and seabed morphology. The study also provides a detailed analysis of high velocity impact pore pressure data to derive information about sediment type and permeability. The penetrometer was deployed 227 times, and the findings are correlated to 78 sediment samples. Differences in sediment strength and type were found when transitioning from tidal flats to the deeper channels. Finer-grained sediments located predominantly on the tidal flats appeared well consolidated with noticeable and spatially consistent sediment strength (reflected in an estimate of quasi-static bearing capacity qsbcmax 10 kPa). Sediments with higher sand content (>75%) showed more variations in strength relating to differences in gradation, and likely represent loose and poorly consolidated sands (qsbcmax 10-55 kPa). The rate at which the recorded excess pore pressures approached equilibrium after penetration was classified and related to sediment type. The data indicate that the development of excess pore pressures upon impact and during penetration may provide additional insight into the nature and layering of bed material, such as identifying a desiccated or over-consolidated dilative surficial layer. In summary, with varying sediment grain size distributions, bulk densities and morphology, sediment strength and pore pressure behavior can vary significantly within a tidal estuary.

Racial variations in interfacial behavior of lipids extracted from worn soft contact lenses.

PubMed

Svitova, Tatyana F; Lin, Meng C

2013-12-01

To explore interfacial behaviors and effects of temperature and dilatation on dynamic properties of multilayered human tear lipids extracted from silicone hydrogel (SiH) lenses worn by asymptomatic Asian and white subjects. Interfacial properties of lipids extracted from Focus N&D lenses worn by 14 subjects continuously for 1 month were studied. The lipids were deposited on an air bubble immersed in a model tear electrolyte (MTE) solution to form 100 ± 20-nm-thick films. Surface pressure was recorded during slow expansion/contraction cycles to evaluate compressibility and hysteresis of lipid films. Films were also subjected to fast step-strain dilatations at temperatures of 22 to 45°C for their viscoelastic property assessment. Isocycles for Asian and white lipids were similar at low surface pressures but had distinctly different compressibility and hysteresis at dynamic pressures exceeding 30 mN/m. Rheological parameters of reconstituted lipids were also dissimilar between Asian and white. The elastic modulus E∞ for white lipids was 1.5 times higher than that for Asian lipids, whereas relaxation time (t) was on average 1.3 times higher for Asian. No significant changes were observed in rheological properties of both Asian and white lipids when temperature increased from 22.0 to 36.5°C. However, for white lipids, E∞ reduced considerably at temperatures higher than 42.0°C, whereas t remained unchanged. For Asian lipids, both E∞ and t started to decline as temperature increased to 38°C and higher. Higher elastic modulus of white lipids and elasticity threshold at certain deformations indicate stronger structure and intermolecular interactions as compared with more viscous Asian lipids. The differences in interfacial behaviors between Asian and white lipids may be associated with the differences in their chemical compositions.

Micropattern array with gradient size (µPAGS) plastic surfaces fabricated by PDMS (polydimethylsiloxane) mold-based hot embossing technique for investigation of cell-surface interaction.

PubMed

Choi, Min Jin; Park, Ju Young; Cha, Kyoung Je; Rhie, Jong-Won; Cho, Dong-Woo; Kim, Dong Sung

2012-12-01

Recently, it was found that the variations of physical environment significantly affect cell behaviors including cell proliferation, migration and differentiation. Through a plastic surface with controlled mechanical properties such as stiffness, one can change the orientation and migration of cells in a particular direction, thereby determining cell behaviors. In this study, we demonstrate a polydimethylsiloxane (PDMS) mold-based hot embossing technique for rapid, simple and low-cost replication of polystyrene (PS) surfaces having micropatterns. The PDMS mold was fabricated by UV-photolithography followed by PDMS casting; the elastomeric properties of PDMS enabled us to obtain conformal contact of the PDMS mold to a PS surface and to create high transcription quality of micropatterns on the PS surface. Two different types of circular micropillar and microwell arrays were successfully replicated on the PS surfaces based on the suggested technique. The micropatterns were designed to have various diameters (2-150 µm), spacings (2-160 µm) and heights (1.4, 2.4, 8.2 and 14.9 µm), so as to generate the gradient of physical properties on the surface. Experimental parametric studies indicated that (1) the embossing temperature became a critical processing parameter as the aspect ratio of micropattern increased and (2) the PDMS mold-based hot embossing could successfully replicate micropatterns, even having an aspect ratio of 2.7 for micropattern diameter of 6 µm, with an optimal processing condition (embossing pressure and temperature of 0.4 MPa and 130 °C, respectively) in this study. We carried out cell experiments with adipose-derived stem cells on the replicated PS surface with the height of 1.4 µm to investigate cellular behaviors in response to the micropattern array with gradient size. Cellular experiment results showed that the micropillar-arrayed surface improved cell proliferation as compared with the microwell-arrayed surface. We could also estimate the ranges of pattern sizes having the desired effects on the cellular behaviors.

Airfoil modification effects on subsonic and transonic pressure distributions and performance for the EA-6B airplane

NASA Technical Reports Server (NTRS)

Allison, Dennis O.; Sewall, William G.

1995-01-01

Longitudinal characteristics and wing-section pressure distributions are compared for the EA-6B airplane with and without airfoil modifications. The airfoil modifications were designed to increase low-speed maximum lift for maneuvering, while having a minimal effect on transonic performance. Section contour changes were confined to the leading-edge slat and trailing-edge flap regions of the wing. Experimental data are analyzed from tests in the Langley 16-Foot Transonic Tunnel on the baseline and two modified wing-fuselage configurations with the slats and flaps in their retracted positions. Wing modification effects on subsonic and transonic performance are seen in wing-section pressure distributions of the various configurations at similar lift coefficients. The modified-wing configurations produced maximum lift coefficients which exceeded those of the baseline configuration at low-speed Mach numbers (0.300 and 0.400). This benefit was related to the behavior of the wing upper surface leading-edge suction peak and the behavior of the trailing-edge pressure. At transonic Mach numbers (0.725 to 0.900), the wing modifications produced a somewhat stronger nose-down pitching moment, a slightly higher drag at low-lift levels, and a lower drag at higher lift levels.

Influence of Particle Morphology on 3D Kinematic Behavior and Strain Localization of Sheared Sand

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

Alshibli, Khalid A.; Jarrar, Maha F.; Druckrey, Andrew M.

The constitutive behavior of sheared sand is highly influenced by particle morphology, gradation, mineralogy, specimen density, loading condition, stress path, and boundary conditions. The current literature lacks a three-dimensional (3D) systematic experimental study that investigates the influence of particle morphology, confining pressure, and specimen density on the failure mode of sheared sand. In this paper, surface texture, roundness, and sphericity of three uniform sands and glass beads with similar grain size were quantified by using 3D images of particles. In situ nondestructive 3D synchrotron microcomputed tomography (SMT) was used to monitor the deformation of medium-dense and very dense dry sandmore » specimens that were tested under axisymmetric triaxial loading condition at 15 and 400 kPa confining pressures. The particles were identified and tracked in 3D as shearing progressed within the specimens, and maps of incremental particle translation and rotation were developed and used to uncover the relationship between particle morphology, specimen density, and confining pressure on the deformation and failure mode of sheared sand. This paper discusses the relationship between the failure mode and particle morphology, specimen density, and confining pressure.« less

Interactions between self-assembled monolayers and an organophosphonate: A detailed study using surface acoustic wave-based mass analysis, polarization modulation-FTIR spectroscopy, and ellipsometry

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

Crooks, R.M.; Yang, H.C.; McEllistrem, L.J.

Self-assembled monolayers (SAMs) having surfaces terminated in the following functional groups: -CH{sub 3}, -OH, -COOH, and (COO{sup -}){sub 2}Cu{sup 2+} (MUA-Cu{sup 2+}) have been prepared and examined as potential chemically sensitive interfaces. Mass measurements made using surface acoustic wave (SAW) devices indicate that these surfaces display different degrees of selectivity and sensitivity to a range of analytes. The response of the MUA-Cu{sup 2+} SAM to the nerve-agent simulant diisopropyl methylphosphonate (DIMP) is particularly intriguing. Exposure of this surface to 50%-of-saturation DIMP yields a surface concentration equivalent to about 20 DIMP monolayers. Such a high surface concentration in equilibrium with amore » much lower-than-saturation vapor pressure has not previously been observed. Newly developed analytical tools have made it possible to measure the infrared spectrum of the chemically receptive surface during analyte dosing. Coupled with in-situ SAW/ellipsometry measurements, which permit simultaneous measurement of mass and thickness with nanogram and Angstrom resolution, respectively, it has been possibly to develop a model for the surface chemistry leading to the unusual behavior of this system. The results indicate that DIMP interacts strongly with surface-confined Cu{sup 2+} adduct that nucleates growth of semi-ordered crystallites having substantially lower vapor pressure than the liquid.« less

Mechanical behavior and localized failure modes in a porous basalt from the Azores

NASA Astrophysics Data System (ADS)

Loaiza, S.; Fortin, J.; Schubnel, A.; Gueguen, Y.; Vinciguerra, S.; Moreira, M.

2012-10-01

Basaltic rocks are the main component of the oceanic upper crust, thus of potential interest for water and geothermal resources, storage of CO2 and volcanic edifice stability. In this work, we investigated experimentally the mechanical behavior and the failure modes of a porous basalt, with an initial connected porosity of 18%. Results were acquired under triaxial compression experiments at confining pressure in the range of 25-200 MPa on water saturated samples. In addition, a purely hydrostatic test was also performed to reach the pore collapse critical pressure P*. During hydrostatic loading, our results show that the permeability is highly pressure dependent, which suggests that the permeability is mainly controlled by pre-existing cracks. When the sample is deformed at pressure higher than the pore collapse pressure P*, some very small dilatancy develops due to microcracking, and an increase in permeability is observed. Under triaxial loading, two modes of deformation can be highlighted. At low confining pressure (Pc < 50 MPa), the samples are brittle and shear localization occurs. For confining pressure > 50 MPa, the stress-strain curves are characterized by strain hardening and volumetric compaction. Stress drops are also observed, suggesting that compaction may be localized. The presence of compaction bands is confirmed by our microstructure analysis. In addition, the mechanical data allows us to plot the full yield surface for this porous basalt, which follows an elliptic cap as previously observed in high porosity sandstones and limestones.

Importance of correlation effects in hcp iron revealed by a pressure-induced electronic topological transition.

PubMed

Glazyrin, K; Pourovskii, L V; Dubrovinsky, L; Narygina, O; McCammon, C; Hewener, B; Schünemann, V; Wolny, J; Muffler, K; Chumakov, A I; Crichton, W; Hanfland, M; Prakapenka, V B; Tasnádi, F; Ekholm, M; Aichhorn, M; Vildosola, V; Ruban, A V; Katsnelson, M I; Abrikosov, I A

2013-03-15

We discover that hcp phases of Fe and Fe(0.9)Ni(0.1) undergo an electronic topological transition at pressures of about 40 GPa. This topological change of the Fermi surface manifests itself through anomalous behavior of the Debye sound velocity, c/a lattice parameter ratio, and Mössbauer center shift observed in our experiments. First-principles simulations within the dynamic mean field approach demonstrate that the transition is induced by many-electron effects. It is absent in one-electron calculations and represents a clear signature of correlation effects in hcp Fe.

Stable and Metastable InGaAs/GaAs Island Shapes and Surfactant-like Suppression of the Wetting Transformation

NASA Technical Reports Server (NTRS)

Leon, R.; Lobo, C.; Zou, J.; Romeo, T.; Cockayne, D. J. H.

1998-01-01

Diverging behaviors are observed in the InGaAs/GaAs Stranski-Krastanow (S-K) island formation during vapor phase epitaxy: varying group V partial pressures gives different critical thicknesses for the onset of the S-K transformation, island surface coverages, ratios between coherent and incoherent islands, and dissimilar morphologies upon annealing.

Atmospheric-pressure plasma jets: Effect of gas flow, active species, and snake-like bullet propagation

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

Wu, S.; Wang, Z.; Huang, Q.

2013-02-15

Cold atmospheric-pressure plasma jets have recently attracted enormous interest owing to numerous applications in plasma biology, health care, medicine, and nanotechnology. A dedicated study of the interaction between the upstream and downstream plasma plumes revealed that the active species (electrons, ions, excited OH, metastable Ar, and nitrogen-related species) generated by the upstream plasma plume enhance the propagation of the downstream plasma plume. At gas flows exceeding 2 l/min, the downstream plasma plume is longer than the upstream plasma plume. Detailed plasma diagnostics and discharge species analysis suggest that this effect is due to the electrons and ions that are generatedmore » by the upstream plasma and flow into the downstream plume. This in turn leads to the relatively higher electron density in the downstream plasma. Moreover, high-speed photography reveals a highly unusual behavior of the plasma bullets, which propagate in snake-like motions, very differently from the previous reports. This behavior is related to the hydrodynamic instability of the gas flow, which results in non-uniform distributions of long-lifetime active species in the discharge tube and of surface charges on the inner surface of the tube.« less

The Influence of Upward Groundwater between Joints on the Stability and the Behavior of Dip Slope Failures

NASA Astrophysics Data System (ADS)

Weng, C. H.; Lin, M. L.; Hsieh, P. C.

2016-12-01

In recent years, landslides have attracted much attention in the engineering field in Taiwan. As previous studies, landslides are induced by earthquakes, rainfall, and groundwater. That groundwater flows into upper layer through vertical joints, upward groundwater, erodes the slope and reduces its stability. Nevertheless, in the literature, the impact of upward groundwater to the location of sliding surface and the behaviors of dip slope failure has not be investigated. In this study, physical model tests with water flow inclinometers are used to investigate the kinematics of dip slope failures under various conditions and to identify the failure modes of specimens (Fig. 1). Besides, the mechanics of one landslide case owing to upward groundwater is studied by numerical simulation. In the physical tests, the effects of upward groundwater on slope stability are investigated with different angles of inclinometers, different position of joints on specimens and different locations of upward seepage. The test results suggest that the upward water pressure becomes lower when the number of joints increases. As the water pressure increases to 3.8 times the weight of one block of the specimen, the block will slide. Another, when the specimen is covered by one granular content layer (see Fig. 2), the failure surface tends to develop at the granular content layer, and its kinematics is similar to debris slide; when the clay seam is below of the specimen, the translational slide occurs along the bottom of the blocks. Moreover, one dip slope case, Taiwan's National Highway No. 3 landslide event, are studied by numerical simulation. According to the results, some points are concluded: water pressure makes tension cracks on the top of the vertical joints on weathered sandstones; with anchor attenuation, the sandstone moves downslope, which makes the shear strain of the slope toe region increases (see Fig. 3). If friction angle of the slope decreases, the slide surface occurs along the weak surface, and it develops to the toe of the slope.

Phase diagrams of nonionic foam films: construction by means of disjoining pressure versus thickness curves.

PubMed

Stubenrauch, Cosima; Kashchiev, Dimo; Strey, Reinhard

2004-12-01

The thickness h of foam films can be measured as a function of the disjoining pressure Pi using a thin film pressure balance. Experimental Pi-h curves of foam films stabilized with nonionic surfactants measured at various concentrations resemble the p-V(m) isotherms of real gases measured at various temperatures (p is the pressure and V(m) is the molar volume of the gas). This observation led us to adopt the van der Waals approach for describing real gases to thin foam films, where the thickness h takes the role of V(m) and the disjoining pressure Pi replaces the ordinary pressure p. Our analysis results in a phase diagram for a thin foam film with spinodal, binodal as well as a critical point. The thicker common black film corresponds to the gas phase and the compact Newton black film for which the two surfaces are in direct contact corresponds to the dense liquid. We show that the tuning parameter for the phase behavior of the film is the surface charge density, which means that Pi-h curves should not be referred to as isotherms. In addition to the equilibrium properties the driving force for the phase transition from a common black film to a Newton black film or vice versa is calculated. We discuss how this transition can be controlled experimentally.

Fabrication characteristics and hydrogenation behavior of hydrogen storage alloys for sealed Ni-MH batteries

NASA Astrophysics Data System (ADS)

Kim, Ho-Sung; Kim, Jeon Min; Kim, Tae-Won; Oh, Ik-Hyun; Choi, Jeon; Park, Choong Nyeon

2008-08-01

Hydrogen storage alloys based on LmNi4.2Co0.2Mn0.3Al0.3 were fabricated to study the equilibrium hydrogen pressure and electrochemical performance. The surface morphology and structure of the alloys were analyzed by SEM and XRD, and then the hydrogenation behaviors of all alloys were evaluated by PCT and electrochemical half-cell. We studied the hydrogenation behavior of the Lm-based alloy with changes in composition elements such as Mn, Al, and Co and investigated the optimal design for Lm-based alloy in a sealed battery system. As a result of studying the hydrogenation characterization of alloys with the substitution elements, hydrogen storage alloys such as LmNi3.75Co0.15Mn0.5Al0.3 and LmNi3.5Co0.5Mn0.5Al0.5 were obtained to correspond with the characteristics of a sealed battery with a higher capacity, long life cycle, lower internal pressure, and lower battery cost. The capacity preservation rate of LmNi3.5Co0.5Mn0.5Al0.5 was greatly improved to 92.7% (255 mAh/g) at 60 cycles, indicating a low equilibrium hydrogen pressure of 0.03 atm in PCT devices.

Understanding the external pressure and behavior of commercial banks' environmental risk management: an empirical study undertaken in the Yangtze River delta of China.

PubMed

Liu, Yong; Lin, Zhongguo

2014-04-01

The present study employed a quantitative survey to ascertain whether the external pressure of environmental risk management (ERM) on commercial banks was a contributing factor to their ERM behavior. Data was obtained using questionnaires from 204 branches of commercial banks located in the Yangtze River Delta of China. The relationship between external pressure and behavior was tested using a linear structural relations model through path analysis. The results revealed that external pressure of ERM was significantly and positively related to the behavior and that pressure from governmental regulations was the most important contributing factor in the passive feedback behavior and preventive behavior of commercial banks. The pressure from markets was the most important contributing factor in banks' active participation behavior; the pressure from community and NGOs was the most important contributing factor in their enthusiastic behavior.

Noninvasive estimation of assist pressure for direct mechanical ventricular actuation

NASA Astrophysics Data System (ADS)

An, Dawei; Yang, Ming; Gu, Xiaotong; Meng, Fan; Yang, Tianyue; Lin, Shujing

2018-02-01

Direct mechanical ventricular actuation is effective to reestablish the ventricular function with non-blood contact. Due to the energy loss within the driveline of the direct cardiac compression device, it is necessary to acquire the accurate value of assist pressure acting on the heart surface. To avoid myocardial trauma induced by invasive sensors, the noninvasive estimation method is developed and the experimental device is designed to measure the sample data for fitting the estimation models. By examining the goodness of fit numerically and graphically, the polynomial model presents the best behavior among the four alternative models. Meanwhile, to verify the effect of the noninvasive estimation, the simplified lumped parameter model is utilized to calculate the pre-support and the post-support left ventricular pressure. Furthermore, by adjusting the driving pressure beyond the range of the sample data, the assist pressure is estimated with the similar waveform and the post-support left ventricular pressure approaches the value of the adult healthy heart, indicating the good generalization ability of the noninvasive estimation method.

Deformation Behavior and TExture Evolution of Steel Alloys under Axial-Torsional Loading

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

Siriruk, A.; Kant, M.; Penumadu, D.

2011-06-01

Using hollow cylinder samples with suitable geometry obtained from round bar stock, the deformation behavior of bcc Fe based 12L14 steel alloy is evaluated under multi-axial conditions. A stacked strain gage rosette and extensometer mounted on the cylindrical surface at the mid height of the specimen provided strain tensor as a function of applied stress for pure tensile and torsion tests prior to yielding. This study examines elastic and yield behavior and effects of these with respect to texture evolution. Hollow cylinder specimen geometry (tubes) with small wall thickness and relatively (to its thickness) large inner diameter is used. Themore » variation of observed yield surface in deviatoric plane and the effect on mode of deformation (tension versus torsion versus its combination) on stress-strain behavior is discussed. Bulk texture was studied using neutron time-of-flight diffractometer at High-Pressure-Preferred Orientation (HIPPO) - Los Alamos Neutron Science Center (LANSCE) instrument and the evolution of texture and related anisotropy for pure tension versus torsion are also included.« less

A finite difference model for free surface gravity drainage

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

Couri, F.R.; Ramey, H.J. Jr.

1993-09-01

The unconfined gravity flow of liquid with a free surface into a well is a classical well test problem which has not been well understood by either hydrologists or petroleum engineers. Paradigms have led many authors to treat an incompressible flow as compressible flow to justify the delayed yield behavior of a time-drawdown test. A finite-difference model has been developed to simulate the free surface gravity flow of an unconfined single phase, infinitely large reservoir into a well. The model was verified with experimental results in sandbox models in the literature and with classical methods applied to observation wells inmore » the Groundwater literature. The simulator response was also compared with analytical Theis (1935) and Ramey et al. (1989) approaches for wellbore pressure at late producing times. The seepage face in the sandface and the delayed yield behavior were reproduced by the model considering a small liquid compressibility and incompressible porous medium. The potential buildup (recovery) simulated by the model evidenced a different- phenomenon from the drawdown, contrary to statements found in the Groundwater literature. Graphs of buildup potential vs time, buildup seepage face length vs time, and free surface head and sand bottom head radial profiles evidenced that the liquid refills the desaturating cone as a flat moving surface. The late time pseudo radial behavior was only approached after exaggerated long times.« less

Heavy fermion behavior in the quasi-one-dimensional Kondo lattice CeCo 2Ga 8

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

Wang, Le; Fu, Zhaoming; Sun, Jianping

Dimensionality plays an essential role in determining the anomalous non-Fermi liquid properties in heavy fermion systems. So far most heavy fermion compounds are quasi-two-dimensional or three-dimensional. Here we report the synthesis and systematic investigations of the single crystals of the quasi-one-dimensional Kondo lattice CeCo 2Ga 8. Resistivity measurements at ambient pressure reveal the onset of coherence at T * ≈ 20 K and non-Fermi liquid behavior with linear temperature dependence over a decade in temperature from 2 to 0.1 K. The specific heat increases logarithmically with lowering temperature between 10 and 2 K and reaches 800 mJ/mol K 2 atmore » 1 K, suggesting that CeCo 2Ga 8 is a heavy fermion compound in the close vicinity of a quantum critical point. Resistivity measurements under pressure further confirm the non-Fermi liquid behavior in a large temperature–pressure range. The magnetic susceptibility is found to follow the typical behavior for a one-dimensional spin chain from 300 K down to T *, and first-principles calculations predict flat Fermi surfaces for the itinerant f-electron bands. These suggest that CeCo 2Ga 8 is a rare example of the quasi-one-dimensional Kondo lattice, but its non-Fermi liquid behaviors resemble those of the quasi-two-dimensional YbRh 2Si 2 family. The study of the quasi-one-dimensional CeCo 2Ga 8 family may therefore help us to understand the role of dimensionality on heavy fermion physics and quantum criticality.« less

Heavy fermion behavior in the quasi-one-dimensional Kondo lattice CeCo2Ga8

NASA Astrophysics Data System (ADS)

Wang, Le; Fu, Zhaoming; Sun, Jianping; Liu, Min; Yi, Wei; Yi, Changjiang; Luo, Yongkang; Dai, Yaomin; Liu, Guangtong; Matsushita, Yoshitaka; Yamaura, Kazunari; Lu, Li; Cheng, Jin-Guang; Yang, Yi-feng; Shi, Youguo; Luo, Jianlin

2017-07-01

Dimensionality plays an essential role in determining the anomalous non-Fermi liquid properties in heavy fermion systems. So far most heavy fermion compounds are quasi-two-dimensional or three-dimensional. Here we report the synthesis and systematic investigations of the single crystals of the quasi-one-dimensional Kondo lattice CeCo2Ga8. Resistivity measurements at ambient pressure reveal the onset of coherence at T * ≈ 20 K and non-Fermi liquid behavior with linear temperature dependence over a decade in temperature from 2 to 0.1 K. The specific heat increases logarithmically with lowering temperature between 10 and 2 K and reaches 800 mJ/mol K2 at 1 K, suggesting that CeCo2Ga8 is a heavy fermion compound in the close vicinity of a quantum critical point. Resistivity measurements under pressure further confirm the non-Fermi liquid behavior in a large temperature-pressure range. The magnetic susceptibility is found to follow the typical behavior for a one-dimensional spin chain from 300 K down to T *, and first-principles calculations predict flat Fermi surfaces for the itinerant f-electron bands. These suggest that CeCo2Ga8 is a rare example of the quasi-one-dimensional Kondo lattice, but its non-Fermi liquid behaviors resemble those of the quasi-two-dimensional YbRh2Si2 family. The study of the quasi-one-dimensional CeCo2Ga8 family may therefore help us to understand the role of dimensionality on heavy fermion physics and quantum criticality.

Heavy fermion behavior in the quasi-one-dimensional Kondo lattice CeCo 2Ga 8

DOE PAGES

Wang, Le; Fu, Zhaoming; Sun, Jianping; ...

2017-07-04

Dimensionality plays an essential role in determining the anomalous non-Fermi liquid properties in heavy fermion systems. So far most heavy fermion compounds are quasi-two-dimensional or three-dimensional. Here we report the synthesis and systematic investigations of the single crystals of the quasi-one-dimensional Kondo lattice CeCo 2Ga 8. Resistivity measurements at ambient pressure reveal the onset of coherence at T * ≈ 20 K and non-Fermi liquid behavior with linear temperature dependence over a decade in temperature from 2 to 0.1 K. The specific heat increases logarithmically with lowering temperature between 10 and 2 K and reaches 800 mJ/mol K 2 atmore » 1 K, suggesting that CeCo 2Ga 8 is a heavy fermion compound in the close vicinity of a quantum critical point. Resistivity measurements under pressure further confirm the non-Fermi liquid behavior in a large temperature–pressure range. The magnetic susceptibility is found to follow the typical behavior for a one-dimensional spin chain from 300 K down to T *, and first-principles calculations predict flat Fermi surfaces for the itinerant f-electron bands. These suggest that CeCo 2Ga 8 is a rare example of the quasi-one-dimensional Kondo lattice, but its non-Fermi liquid behaviors resemble those of the quasi-two-dimensional YbRh 2Si 2 family. The study of the quasi-one-dimensional CeCo 2Ga 8 family may therefore help us to understand the role of dimensionality on heavy fermion physics and quantum criticality.« less

Effects of surface pressure and internal friction on the dynamics of shear-driven supported lipid bilayers.

PubMed

Jönsson, Peter; Höök, Fredrik

2011-02-15

Supported lipid bilayers (SLBs) are one of the most common model systems for cell membrane studies. We have previously found that when applying a bulk flow of liquid above an SLB the lipid bilayer and its constituents move in the direction of the bulk flow in a rolling type of motion, with the lower monolayer being essentially stationary. In this study, a theoretical platform is developed to model the dynamic behavior of a shear-driven SLB. In most regions of the moving SLB, the dynamics of the lipid bilayer is well explained by a balance between the hydrodynamic shear force arising from the bulk flow above the lipid bilayer and the friction between the upper and lower monolayers of the SLB. These two forces result in a drift velocity profile for the lipids in the upper monolayer of the SLB that is highest at the center of the channel and decreases to almost zero at the corners of the channel. However, near the front of an advancing SLB a very different flow behavior is observed, showing an almost constant drift velocity of the lipids over the entire bilayer front. In this region, the motion of the SLB is significantly influenced by gradients in the surface pressure as well as internal friction due to molecules that have accumulated at the front of the SLB. It is shown that even a modest surface fraction of accumulated molecules (∼1%) can drastically affect the behavior of the SLB near the bilayer front, forcing the advancing lipids in the SLB away from the center of the channel out toward the sides.

Analysis of unswept and swept wing chordwise pressure data from an oscillating NACA 0012 airfoil experiment. Volume 1: Technical Report

NASA Technical Reports Server (NTRS)

St.hilaire, A. O.; Carta, F. O.

1983-01-01

The unsteady chordwise force response on the airfoil surface was investigated and its sensitivity to the various system parameters was examined. A further examination of unsteady aerodynamic data on a tunnel spanning wing (both swept and unswept), obtained in a wind tunnel, was performed. The main body of this data analysis was carried out by analyzing the propagation speed of pressure disturbances along the chord and by studying the behavior of the unsteady part of the chordwise pressure distribution at various points of the airfoil pitching cycle. It was found that Mach number effects dominate the approach to and the inception of both static and dynamic stall. The stall angle decreases as the Mach number increases. However, sweep dominates the load behavior within the stall regime. Large phase differences between unswept and swept responses, that do not exist at low lift coefficient, appear once the stall boundary is penetrated. It was also found that reduced frequency is not a reliable indicator of the unsteady aerodynamic response in the high angle of attack regime.

Inflation-predictable behavior and co-eruption deformation at Axial Seamount.

PubMed

Nooner, Scott L; Chadwick, William W

2016-12-16

Deformation of the ground surface at active volcanoes provides information about magma movements at depth. Improved seafloor deformation measurements between 2011 and 2015 documented a fourfold increase in magma supply and confirmed that Axial Seamount's eruptive behavior is inflation-predictable, probably triggered by a critical level of magmatic pressure. A 2015 eruption was successfully forecast on the basis of this deformation pattern and marked the first time that deflation and tilt were captured in real time by a new seafloor cabled observatory, revealing the timing, location, and volume of eruption-related magma movements. Improved modeling of the deformation suggests a steeply dipping prolate-spheroid pressure source beneath the eastern caldera that is consistent with the location of the zone of highest melt within the subcaldera magma reservoir determined from multichannel seismic results. Copyright © 2016, American Association for the Advancement of Science.

Experimental investigation of flow-induced fabrics in rocks at upper-mantle pressures: Application to understanding mantle dynamics and seismic anisotropy

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

Kohlstedt, David L.

2016-04-26

The goal of this collaborative research effort between W.B. Durham at the Massachusetts Institute of Technology (MIT) and D.L. Kohlstedt and S. Mei at the University of Minnesota (UMN) was to exploit a newly developed technology for high-pressure, high-temperature deformation experimentation, namely, the deformation DIA (D-DIA) to determine the deformation behavior of a number of important upper mantle rock types including olivine, garnet, enstatite, and periclase. Experiments were carried out under both hydrous and anhydrous conditions and at both lithospheric and asthenospheric stress and temperature conditions. The result was a group of flow laws for Earth’s upper mantle that quantitativelymore » describe the viscosity of mantle rocks from shallow depths (the lithosphere) to great depths (the asthenosphere). These flow laws are fundamental for modeling the geodynamic behavior and heat transport from depth to Earth’s surface.« less

Experimental investigation of flow-induced fabrics in rocks at upper-mantle pressures. Application to understanding mantle dynamics and seismic anisotropy

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

Durham, William B.

2016-05-02

The goal of this collaborative research effort between W.B. Durham at the Massachusetts Institute of Technology (MIT) and D.L. Kohlstedt and S. Mei at the University of Minnesota (UMN) was to exploit a newly developed technology for high-pressure, high-temperature deformation experimentation, namely, the deformation DIA (D-DIA), to determine the deformation behavior of a number of important upper mantle rock types including olivine, garnet, enstatite, and periclase. Experiments were carried out under both hydrous and anhydrous conditions and at both lithospheric and asthenospheric stress and temperature conditions. The result was a group of flow laws for Earth’s upper mantle that quantitativelymore » describe the viscosity of mantle rocks from shallow depths (the lithosphere) to great depths (the asthenosphere). These flow laws are fundamental for modeling the geodynamic behavior and heat transport from depth to Earth’s surface.-« less

Asymmetric Yield Function Based on the Stress Invariants for Pressure Sensitive Metals

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

Jeong Wahn Yoon; Yanshan Lou; Jong Hun Yoon

A general asymmetric yield function is proposed with dependence on the stress invariants for pressure sensitive metals. The pressure sensitivity of the proposed yield function is consistent with the experimental result of Spitzig and Richmond (1984) for steel and aluminum alloys while the asymmetry of the third invariant is preserved to model strength differential (SD) effect of pressure insensitive materials. The proposed yield function is transformed in the space of the stress triaxaility, the von Mises stress and the normalized invariant to theoretically investigate the possible reason of the SD effect. The proposed plasticity model is further extended to characterizemore » the anisotropic behavior of metals both in tension and compression. The extension of the yield function is realized by introducing two distinct fourth-order linear transformation tensors of the stress tensor for the second and third invariants, respectively. The extended yield function reasonably models the evolution of yield surfaces for a zirconium clock-rolled plate during in-plane and through-thickness compression reported by Plunkett et al. (2007). The extended yield function is also applied to describe the orthotropic behavior of a face-centered cubic metal of AA 2008-T4 and two hexagonal close-packed metals of high-purity-titanium and AZ31 magnesium alloy. The orthotropic behavior predicted by the generalized model is compared with experimental results of these metals. The comparison validates that the proposed yield function provides sufficient predictability on SD effect and anisotropic behavior both in tension and compression. When it is necessary to consider r-value anisotropy, the proposed function is efficient to be used with nonassociated flow plasticity by introducing a separate plastic potential for the consideration of r-values as shown in Stoughton & Yoon (2004, 2009).« less

Spray Characteristics and Tribo-Mechanical Properties of High-Velocity Arc-Sprayed WC-W2C Iron-Based Coatings

NASA Astrophysics Data System (ADS)

Tillmann, W.; Hagen, L.; Kokalj, D.

2017-10-01

In terms of arc-sprayed coatings, the lamellar coating microstructure is mainly affected by the atomization behavior of the molten electrode tips. When using compressed air, oxide formations occur during atomization, across the particle-laden spray plume and when the molten droplets splash onto the substrate. Within the scope of this study, the potential of a high-velocity arc-spraying process due to elevated atomization gas pressures and its effect on the spray and coating characteristics was analyzed using a cast tungsten carbide (CTC)-reinforced FeCMnSi cored wire. Since the atomization behavior corresponds with the electrode phenomena, the power spectrum and the droplet formation were observed during spraying. The tribo-mechanical properties of CTC-FeCMnSi coatings were examined in dry sliding experiments and indentation tests. In addition, adhesion tests and metallographic investigations were carried out to analyze the bonding strength, cohesive behavior, and lamellar microstructure. The occurrence of oxide phases was evaluated by x-ray diffraction and electron microscopy. Moreover, the oxygen content was determined by using glow discharge optical emission spectroscopy as well as energy-dispersive x-ray spectroscopy. With respect to elevated atomization gas pressures, a dense microstructure with improved adhesion to the substrate and reduced surface roughness was observed. Dry sliding experiments revealed an advanced wear behavior of specimens, when using above average increased atomization gas pressures. Analytic methods verified the existence of oxide phases, which were generated during spraying. A significant change of the extent and type of oxides, when applying an increased flow rate of the atomization gas, cannot be observed. Besides an enhanced coating quality, the use of increased atomization gas pressure exhibited good process stability.

Surface-bonded ionic liquid stationary phases in high-performance liquid chromatography--a review.

PubMed

Pino, Verónica; Afonso, Ana M

2012-02-10

Ionic liquids (ILs) are a class of ionic, nonmolecular solvents which remain in liquid state at temperatures below 100°C. ILs possess a variety of properties including low to negligible vapor pressure, high thermal stability, miscibility with water or a variety of organic solvents, and variable viscosity. IL-modified silica as novel high-performance liquid chromatography (HPLC) stationary phases have attracted considerable attention for their differential behavior and low free-silanol activity. Indeed, around 21 surface-confined ionic liquids (SCIL) stationary phases have been developed in the last six years. Their chromatographic behavior has been studied, and, despite the presence of a positive charge on the stationary phase, they showed considerable promise for the separation of neutral solutes (not only basic analytes), when operated in reversed phase mode. This aspect points to the potential for truly multimodal stationary phases. This review attempts to summarize the state-of-the-art about SCIL phases including their preparation, chromatographic behavior, and analytical performance. Copyright © 2011 Elsevier B.V. All rights reserved.

Wetting state and maximum spreading factor of microdroplets impacting on superhydrophobic textured surfaces with anisotropic arrays of pillars

NASA Astrophysics Data System (ADS)

Kwon, Dae Hee; Huh, Hyung Kyu; Lee, Sang Joon

2013-07-01

The dynamic behaviors of microdroplets that impact on textured surfaces with various patterns of microscale pillars are experimentally investigated in this study. A piezoelectric inkjet is used to generate the microdroplets that have a diameter of less than 46 μm and a controlled Weber number. The impact and spreading dynamics of an individual droplet are captured by using a high-speed imaging system. The anisotropic and directional wettability and the wetting states on the textured surfaces with anisotropically arranged pillars are revealed for the first time in this study. The impalement transition from the Cassie-Baxter state to the partially impaled state is evaluated by balancing the wetting pressure P wet and the capillary pressure P C even on the anisotropic textured surfaces. The maximum spreading factor is measured and compared with the theoretical prediction to elucidate the wettability of the textured surfaces. For a given Weber number, the maximum spreading factor decreases as the texture area fraction of the textured surface decreases. In addition, the maximum spreading factors along the direction of longer inter-pillar spacing always have smaller values than those along the direction of shorter inter-pillar spacing when a droplet impacts on the anisotropic arrays of pillars.

Electronic structure and the van Hove singularity scenario in high-T(sub c)H(g)Ba2CuO(4+delta) superconductors

NASA Technical Reports Server (NTRS)

Agrawal, Bal K.; Agrawal, Savitri

1995-01-01

The electronic structure and the hole concentrations in the high Tc superconductor HgBa2CuO(4+delta) (delta = O, 1) has been investigated by employing a first principles full potential self-consistent LMTO method with the local density functional theory. The scalar relativistic effects have been considered. The hole concentrations of the Cu-d and O-p(x,y) orbitals are seen to be larger for the HgBaCuO5 system than those of the HgBaCuO4 solid. However, the van Hove singularity (vHs) induced Cu-d and O-p peak which is seen to lie comparatively away and above the Fermi level in the delta = 1 system shifts towards the Fermi level in the delta = 0 system. Thus, the superconducting behavior appears to originate from the occurrence of the vHs peak at the Fermi level. The Fermi surface nesting area in the delta = 0 compound is seen to be larger than in the delta = 1 compound. The calculation reveals that the increase in pressure on the crystal enhances the hole concentrations but without showing any optimum value, On the other hand, the vHs peak approaches to-wards the Fermi level with pressure and crosses the Fermi surface near V/Vo approximately equals 0.625 (V and Vo are the crystal volumes at high and normal pressures, respectively). Our calculated value of the bulk modulus equal to 0.626 Mbar predicts the occurrence of this crossover at about 24 GPa which is in complete agreement with the experimental value. At this pressure the compound has maximum nesting area and self-doped behavior.

Liquid-Vapor Equilibrium of Multicomponent Cryogenic Systems

NASA Technical Reports Server (NTRS)

Thompson, W. Reid; Calado, Jorge C. G.; Zollweg, John A.

1990-01-01

Liquid-vapor and solid-vapor equilibria at low to moderate pressures and low temperatures are important in many solar system environments, including the surface and clouds of Titan, the clouds of Uranus and Neptune, and the surfaces of Mars and Triton. The familiar cases of ideal behavior are limiting cases of a general thermodynamic representation for the vapor pressure of each component in a homogeneous multicomponent system. The fundamental connections of laboratory measurements to thermodynamic models are through the Gibbs-Duhem relation and the Gibbs-Helmholtz relation. Using laboratory measurements of the total pressure, temperature, and compositions of the liquid and vapor phases at equilibrium, the values of these parameters can be determined. The resulting model for vapor-liquid equilibrium can then conveniently and accurately be used to calculate pressures, compositions, condensation altitudes, and their dependencies on changing climatic conditions. A specific system being investigated is CH4-C2H6-N2, at conditions relevant to Titan's surface and atmosphere. Discussed are: the modeling of existing data on CH4-N2, with applications to the composition of Titan's condensate clouds; some new measurements on the CH4-C2H6 binary, using a high-precision static/volumetric system, and on the C2H6-N2 binary, using the volumetric system and a sensitive cryogenic flow calorimeter; and describe a new cryogenic phase-equilibrium vessel with which we are beginning a detailed, systematic study of the three constituent binaries and the ternary CH4-C2H6-N2 system at temperatures ranging from 80 to 105 K and pressures from 0.1 to 7 bar.

Friction and wear behavior of aluminum and composite airplane skins

NASA Technical Reports Server (NTRS)

Jackson, K. E.

1984-01-01

Friction and wear behavior was determined for small skin specimens under abrasive loading conditions typical of those occurring on the underside of a transport airplane during emergency belly landing. A test apparatus consisting of a standard belt sander provided the sliding surface. Small test specimens constructed of aluminum, standard graphite-epoxy composite, aramid-epoxy composite, and toughened-resin composites were tested undar a range of pressures, belt velocities, and belt-surface textures. The effects of these test variables on the wear rate and the coefficient of friction are discussed and comparisons are made between the composite materials and aluminum. The effect of fiber orientation in the composite materials on wear rate was also investigated. In addition, tests were performed in which thermocouples were imbedded into the various test specimens to obtain temperature-time histories during abrasion.

Direct Observation of Domain-Wall Surface Tension by Deflating or Inflating a Magnetic Bubble

NASA Astrophysics Data System (ADS)

Zhang, Xueying; Vernier, Nicolas; Zhao, Weisheng; Yu, Haiming; Vila, Laurent; Zhang, Yue; Ravelosona, Dafiné

2018-02-01

The surface energy of a magnetic domain wall (DW) strongly affects its static and dynamic behaviors. However, this effect is seldom directly observed, and some of the related phenomena are not well understood. Moreover, a reliable method to quantify the DW surface energy is still absent. Here, we report a series of experiments in which the DW surface energy becomes a dominant parameter. We observe that a semicircular magnetic domain bubble can spontaneously collapse under the Laplace pressure induced by DW surface energy. We further demonstrate that the surface energy can lead to a geometrically induced pinning when the DW propagates in a Hall cross or from a nanowire into a nucleation pad. Based on these observations, we develop two methods to quantify the DW surface energy, which can be very helpful in the estimation of intrinsic parameters such as Dzyaloshinskii-Moriya interactions or exchange stiffness in magnetic ultrathin films.

Effects of Phase Transformations and Dynamic Material Strength on Hydrodynamic Instability Evolution in Metals

NASA Astrophysics Data System (ADS)

Opie, Saul

Hydrodynamic phenomena such as the Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instabilities can be described by exponential/linear growth of surface perturbations at a bimaterial interface when subjected to constant/impulsive acceleration. A challenge in designing systems to mitigate or exploit these effects is the lack of accurate material models at large dynamic strain rates and pressures. In particular, little stress-strain constitutive information at large strain rates and pressures is available for transient material phases formed at high pressures, and the continuum effect the phase transformation process has on the instability evolution. In this work, a phase-aware isotropic strength model is developed and partially validated with a novel RM-based instability experiment in addition to existing data from the literature. With the validated material model additional simulations are performed to provide insight into to the role that robust material constitutive behavior (e.g., pressure, temperature, rate dependence) has on RM instability and how RM instability experiments can be used to characterize and validated expected material behavior. For phase aware materials, particularly iron in this work, the simulations predict a strong dependence on the Atwood number that single phase materials do not have. At Atwood numbers close to unity, and pressures in the high pressure stability region, the high pressure phase dominates the RM evolution. However, at Atwood numbers close to negative one, the RM evolution is only weakly affected by the high-pressure phase even for shocks well above the phase transformation threshold. In addition to RM evolution this work looks at the closely related shock front perturbation evolution. Existing analytical models for isentropic processes in gases and liquids are modified for metal equation of states and plastic behavior for the first time. It is found that the presence of a volume collapsing phase transformation with increased pressure causes shock front perturbations to decay sooner, while plastic strength has the opposite effect which is significantly different from the effect viscosity has. These results suggest additional experimental setups to validate material models, or relevant material parameters that can be optimized for system design objectives, e.g., minimize feed through perturbations in inertial confinement fusion capsules.

Role of infrasound pressure waves in atherosclerotic plaque rupture: a theoretical approach.

PubMed

Tsatsaris, Athanasios; Koukounaris, Efstathios; Motsakos, Theodoros; Perrea, Despina

2007-01-01

To investigate the role of infrasound aortic pressure waves (IPW) in atherosclerotic plaque rupture. Atherosclerotic plaques have been simulated partly, in two dimensions, as being short or long Conical Intersections (CIS), that is to say elliptic, parabolic or hyperbolic surfaces. Consequently, the course and reflection of the generated aortic pressure wave (infrasound domain-less than 20Hz) has been examined around the simulated plaques. The incidence of IPW on plaque surface results both in reflection and "refraction" of the wave. The IPW course within tissue, seems to be enhanced by high Cu-level presence at these areas according to recent evidence (US2003000388213). The "refracted", derived wave travels through plaque tissue and is eventually accumulated to the foci of the respective CIS-plaque geometry. The foci location within or underneath atheroma declares zones where infrasound energy is mostly absorbed. This process, among other mechanisms may contribute to plaque rupture through the development of local hemorrhage and inflammation in foci areas. In future, detection of foci areas and repair (i.e. via Laser Healing Microtechnique) may attenuate atherosclerotic plaque rupture behavior.

Selective Oxidation and Reactive Wetting during Galvanizing of a CMnAl TRIP-Assisted Steel

NASA Astrophysics Data System (ADS)

Bellhouse, E. M.; McDermid, J. R.

2011-09-01

A transformation induced plasticity (TRIP)-assisted steel with 0.2 pct C, 1.5 pct Mn, and 1.5 pct Al was successfully galvanized using a thermal cycle previously shown to produce an excellent combination of strength and ductility. The steel surface chemistry and oxide morphology were determined as a function of process atmosphere oxygen partial pressure. For the 220 K (-53 °C) dew point (dp) + 20 pct H2 atmosphere, the oxide morphology was a mixture of films and nodules. For the 243 K (-30 °C) dp + 5 pct H2 atmosphere, nodules of MnO were found primarily at grain boundaries. For the 278 K (+5 °C) dp + 5 pct H2 atmosphere, nodules of metallic Fe were found on the surface as a result of alloy element internal oxidation. The steel surface chemistry and oxide morphology were then related to the reactive wetting behavior during continuous hot dip galvanizing. Good wetting was obtained using the two lower oxygen partial pressure process atmospheres [220 K dp and 243 K dp (-53 °C dp and -30 °C dp)]. An increase in the number of bare spots was observed when using the higher oxygen partial pressure process atmosphere (+5 °C dp) due to the increased thickness of localized oxide films.

Confinement Correction to Mercury Intrusion Capillary Pressure of Shale Nanopores

PubMed Central

Wang, Sen; Javadpour, Farzam; Feng, Qihong

2016-01-01

We optimized potential parameters in a molecular dynamics model to reproduce the experimental contact angle of a macroscopic mercury droplet on graphite. With the tuned potential, we studied the effects of pore size, geometry, and temperature on the wetting of mercury droplets confined in organic-rich shale nanopores. The contact angle of mercury in a circular pore increases exponentially as pore size decreases. In conjunction with the curvature-dependent surface tension of liquid droplets predicted from a theoretical model, we proposed a technique to correct the common interpretation procedure of mercury intrusion capillary pressure (MICP) measurement for nanoporous material such as shale. Considering the variation of contact angle and surface tension with pore size improves the agreement between MICP and adsorption-derived pore size distribution, especially for pores having a radius smaller than 5 nm. The relative error produced in ignoring these effects could be as high as 44%—samples that contain smaller pores deviate more. We also explored the impacts of pore size and temperature on the surface tension and contact angle of water/vapor and oil/gas systems, by which the capillary pressure of water/oil/gas in shale can be obtained from MICP. This information is fundamental to understanding multiphase flow behavior in shale systems. PMID:26832445

Reproducing Kernel Particle Method in Plasticity of Pressure-Sensitive Material with Reference to Powder Forming Process

NASA Astrophysics Data System (ADS)

Khoei, A. R.; Samimi, M.; Azami, A. R.

2007-02-01

In this paper, an application of the reproducing kernel particle method (RKPM) is presented in plasticity behavior of pressure-sensitive material. The RKPM technique is implemented in large deformation analysis of powder compaction process. The RKPM shape function and its derivatives are constructed by imposing the consistency conditions. The essential boundary conditions are enforced by the use of the penalty approach. The support of the RKPM shape function covers the same set of particles during powder compaction, hence no instability is encountered in the large deformation computation. A double-surface plasticity model is developed in numerical simulation of pressure-sensitive material. The plasticity model includes a failure surface and an elliptical cap, which closes the open space between the failure surface and hydrostatic axis. The moving cap expands in the stress space according to a specified hardening rule. The cap model is presented within the framework of large deformation RKPM analysis in order to predict the non-uniform relative density distribution during powder die pressing. Numerical computations are performed to demonstrate the applicability of the algorithm in modeling of powder forming processes and the results are compared to those obtained from finite element simulation to demonstrate the accuracy of the proposed model.

A path analysis model for explaining unsafe behavior in workplaces: the effect of perceived work pressure.

PubMed

Ghasemi, Fakhradin; Kalatpour, Omid; Moghimbeigi, Abbas; Mohhamadfam, Iraj

2018-06-01

Unsafe behavior is closely related to occupational accidents. Work pressure is one the main factors affecting employees' behavior. The aim of the present study was to provide a path analysis model for explaining how work pressure affects safety behavior. Using a self-administered questionnaire, six variables supposed to affect safety employees' behavior were measured. The path analysis model was constructed based on several hypotheses. The goodness of fit of the model was assessed using both absolute and comparative fit indices. Work pressure was determined not to influence safety behavior directly. However, it negatively influenced other variables. Group attitude and personal attitude toward safety were the main factors mediating the effect of work pressure on safety behavior. Among the variables investigated in the present study, group attitude, personal attitude and work pressure had the strongest effects on safety behavior. Managers should consider that in order to improve employees' safety behavior, work pressure should be reduced to a reasonable level, and concurrently a supportive environment, which ensures a positive group attitude toward safety, should be provided. Replication of the study is recommended.

On the Resistance to Transpiration of the Sites of Evaporation within the Leaf 1

PubMed Central

Farquhar, Graham D.; Raschke, Klaus

1978-01-01

The rates of transpiration from the upper and lower surfaces of leaves of Gossypium hirsutum, Xanthium strumarium, and Zea mays were compared with the rates at which helium diffused across those leaves. There was no evidence for effects of CO2 concentration or rate of evaporation on the resistance to water loss from the evaporating surface (“resistance of the mesophyll wall to transpiration”) and no evidence for any significant wall resistance in turgid tissues. The possible existence of a wall resistance was also tested in leaves of Commelina communis and Tulipa gesneriana whose epidermis could be easily peeled. Only when an epidermis was removed from a leaf, evaporation from the mesophyll tissue declined. We conclude that under conditions relevant to studies of stomatal behavior, the water vapor pressure at the sites of evaporation is equal to the saturation vapor pressure. PMID:16660404

A fast and accurate Langmuir-type polymer microtensiometer.

PubMed

Gijsenbergh, Pieter; Puers, Robert

2018-05-01

A semi-flexible polymer microtensiometer for local surface pressure measurements of Langmuir monolayers is presented. The current device geometry and read-out method via image analysis result in a theoretical accuracy of ±0.02mN⋅m -1 for a dynamic range between 0 and 75mN⋅m -1 . The tensiometer sensitivity and dynamic range are easily tunable as they are solely based on the tensiometer spring dimensions. Finite element simulations are used to determine the response time of 20ms for a subphase viscosity of 1mPa⋅s. A poroviscomechanical model of the sensor is composed and the subphase viscosity is shown to dominate the transient behavior. The tensiometer performance is verified in a Langmuir trough by applying rapid local surface pressure oscillations. A Wilhelmy plate is used as an independent measurement tool and the results of both techniques correlate well. Copyright © 2017 Elsevier B.V. All rights reserved.

The pressure is all in your head: A cilia-driven high-pressure pump in the head of a deep-sea animal

NASA Astrophysics Data System (ADS)

Nawroth, Janna; Katija, Kakani; Shelley, Michael; Kanso, Eva

2017-11-01

Motile cilia are microscopic, hair-like structures on the cell surface that can sense and propel the extracellular fluid environment. In many ciliated systems found in nature, such as the mammalian airways and marine sponges, the organization and collective behavior of the cilia favors the pumping of fluids at low pressures and high volumes. We recently discovered an alternate design located in the head of a deep-sea animal called Larvacean. Here, cilia morphology, kinematics and flow indicate a role in maintaining the hydrostatic skeleton of the animal by generating a high-pressure flow. We describe our empirical and computational approaches toward understanding the design principles and dynamic range of this newly discovered pumping mechanism. In ongoing work, we further explore the fluid dynamic constraints on the morphological diversity of cilia and the resulting categories of fluid transport functions.

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

Mohaghegh, Shahab D.

apability of underground carbon dioxide storage to confine and sustain injected CO2 for a very long time is the main concern for geologic CO2 sequestration. If a leakage from a geological CO2 sequestration site occurs, it is crucial to find the approximate amount and the location of the leak in order to implement proper remediation activity. An overwhelming majority of research and development for storage site monitoring has been concentrated on atmospheric, surface or near surface monitoring of the sequestered CO2. This study aims to monitor the integrity of CO2 storage at the reservoir level. This work proposes developing in-situmore » CO2 Monitoring and Verification technology based on the implementation of Permanent Down-hole Gauges (PDG) or “Smart Wells” along with Artificial Intelligence and Data Mining (AI&DM). The technology attempts to identify the characteristics of the CO2 leakage by de-convolving the pressure signals collected from Permanent Down-hole Gauges (PDG). Citronelle field, a saline aquifer reservoir, located in the U.S. was considered for this study. A reservoir simulation model for CO2 sequestration in the Citronelle field was developed and history matched. The presence of the PDGs were considered in the reservoir model at the injection well and an observation well. High frequency pressure data from sensors were collected based on different synthetic CO2 leakage scenarios in the model. Due to complexity of the pressure signal behaviors, a Machine Learning-based technology was introduced to build an Intelligent Leakage Detection System (ILDS). The ILDS was able to detect leakage characteristics in a short period of time (less than a day) demonstrating the capability of the system in quantifying leakage characteristics subject to complex rate behaviors. The performance of ILDS was examined under different conditions such as multiple well leakages, cap rock leakage, availability of an additional monitoring well, presence of pressure drift and noise in the pressure sensor and uncertainty in the reservoir model.« less

Achieving Zero Stress in Iridium, Chromium, and Nickel Thin Films

NASA Technical Reports Server (NTRS)

Broadway, David M.; Weimer, Jeffrey; Gurgew, Danielle; Lis, Tomasz; Ramsey, Brian D.; O'Dell, Stephen L.; Ames, A.; Bruni, R.

2015-01-01

We examine a method for achieving zero intrinsic stress in thin films of iridium, chromium, and nickel deposited by magnetron sputter deposition. The examination of the stress in these materials is motivated by efforts to advance the optical performance of light-weight x-ray space telescopes into the regime of sub-arc second resolution that rely on control of the film stress to values within 10-100 MPa. A characteristic feature of the intrinsic stress behavior in chromium and nickel is their sensitivity to the magnitude and sign of the intrinsic stress with argon gas pressure, including the existence of a critical pressure that results in zero film stress. This critical pressure scales linearly with the film's density. While the effect of stress reversal with argon pressure has been previously reported by Hoffman and others for nickel and chromium, we have discovered a similar behavior for iridium. Additionally, we have identified zero stress in iridium shortly after island coalescence. This feature of film growth is used for achieving a total internal stress of -2.89 MPa for a 15.8 nm thick iridium film. The surface roughness of this low-stress film was examined using scanning probe microscopy (SPM) and x-ray reflectivity (XRR) at CuKa and these results presented and discussed.

Influence of the perceived taste intensity of chemesthetic stimuli on swallowing parameters given age and genetic taste differences in healthy adult women.

PubMed

Pelletier, Cathy A; Steele, Catriona M

2014-02-01

This study examined whether the perceived taste intensity of liquids with chemesthetic properties influenced lingua-palatal pressures and submental surface electromyography (sEMG) in swallowing, compared with water. Swallowing was studied in 80 healthy women, stratified by age group and genetic taste status. General Labeled Magnitude Scale ratings of taste intensity were collected for deionized water; carbonated water; 2.7% w/v citric acid; and diluted ethanol. These stimuli were swallowed, with measurement of tongue-palate pressures and submental sEMG. Path analysis differentiated stimulus, genetic taste status, age, and perceived taste intensity effects on swallowing. Signal amplitude during effortful saliva swallowing served as a covariate representing participant strength. Significant differences (p < .05) in taste intensity were seen across liquids: citric acid > ethanol > carbonated water > water. Supertasters perceived greater taste intensity than did nontasters. Lingua-palatal pressure and sEMG amplitudes were correlated with the strength covariate. Anterior palate pressures and sEMG amplitudes were significantly higher for the citric acid stimulus. Perceived taste intensity was a significant mediator of stimulus differences. These data provide confirmatory evidence that high-intensity sour stimuli do influence swallowing behaviors. In addition, taste genetics influence the perception of taste intensity for stimuli with chemesthetic properties, which modulates behavioral responses.

The structural properties of Zr-based bulk metallic glasses subjected to high pressure torsion at different temperatures

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

Boltynjuk, E. V., E-mail: boltynjuk@gmail.com; Ubyivovk, E. V.; Kshumanev, A. M.

2016-06-17

The structural properties of a Zr{sub 62}Cu{sub 22}Al{sub 10}Fe{sub 5}Dy{sub 1} bulk metallic glasses were investigated. Cylindrical rods of the Zr{sub 62}Cu{sub 22}Al{sub 10}Fe{sub 5}Dy{sub 1} BMG were subjected to high pressure torsion at temperatures of 20°C and 150°C. X-ray diffraction, transmission electron microscopy were used to determine peculiarities of the modified structure. Analysis of fracture surfaces, nanohardness measurements were conducted to investigate the influence of structural changes on mechanical behavior of processed samples.

Chemical surface, diffusional, electrical and elastic characterizations of two different dense regenerated cellulose membranes.

PubMed

Vázquez, M I; de Lara, R; Benavente, J

2008-12-15

A comparison of NaCl transport across two dense cellulosic membranes from different suppliers is presented. Hydraulic and diffusional permeabilities were determined from volume flow-applied pressure and concentration-time relationships, while cation transport number and membrane conductivity were determined from electromotrice force and impedance spectroscopy measurements, respectively. Chemical surface differences between both membranes are correlated to transport parameters and morphology, but differences in elastic properties of both membranes might also be considered in order to get a more complete picture of membrane behaviors and to obtain structural-transport parameters correlations.

Stability analysis for capillary channel flow: 1d and 3d computations

NASA Astrophysics Data System (ADS)

Grah, Aleksander; Klatte, Jörg; Dreyer, Michael E.

The subject of the presentation are numerical studies on capillary channel flow, based on results of the sounding rocket TEXUS experiments. The flow through a capillary channel is established by a gear pump at the outlet. The channel, consists of two parallel glass plates with a width of 25 mm, a gap of 10 mm and a length of 12 mm. The meniscus of a compensation tube maintains a constant system pressure. Steady and dynamic pressure effects in the system force the surfaces to bend inwards. A maximum flow rate is achieved when the free surface collapses and gas ingestion occurs at the outlet. This critical flow rate depends on the channel geometry, the flow regime and the liquid properties. The aim of the experiments is the determination of the free surface shape and to find the maximum flow rate. In order to study the unsteady liquid loop behavior, a dimensionless one-dimensional model and a corresponding three-dimensional model were developed. The one-dimensional model is based on the unsteady Bernoulli equation, the unsteady continuity equation and geometrical conditions for the surface curvature and the flow cross-section. The experimental and evaluated contour data show good agreement for a sequence of transient flow rate perturbations. In the case of steady flow at maximum flow rate, when the "choking" effect occurs, the surfaces collapse and cause gas ingestion into the channel. This effect is related to the Speed Index. At the critical flow rate the Speed Index reaches the value 1, in analogy to the Mach Number. Unsteady choking does not necessarily cause surface collapse. We show, that temporarily Speed Index values exceeding One may be achieved for a perfectly stable supercritical dynamic flow. As a supercritical criterion for the dynamic free surface stability we define a Dynamic Index considering the local capillary pressure and the convective pressure, which is a function of the local velocity. The Dynamic Index is below One for stable flow while D = 1 indicates surface collapse. This studies lead to a stability diagram, which defines the limits of flow dynamics and the maximum unsteady flow rate.

Influence of hydrostatic pressure on dynamics and spatial distribution of protein partial molar volume: time-resolved surficial Kirkwood-Buff approach.

PubMed

Yu, Isseki; Tasaki, Tomohiro; Nakada, Kyoko; Nagaoka, Masataka

2010-09-30

The influence of hydrostatic pressure on the partial molar volume (PMV) of the protein apomyoglobin (AMb) was investigated by all-atom molecular dynamics (MD) simulations. Using the time-resolved Kirkwood-Buff (KB) approach, the dynamic behavior of the PMV was identified. The simulated time average value of the PMV and its reduction by 3000 bar pressurization correlated with experimental data. In addition, with the aid of the surficial KB integral method, we obtained the spatial distributions of the components of PMV to elucidate the detailed mechanism of the PMV reduction. New R-dependent PMV profiles identified the regions that increase or decrease the PMV under the high pressure condition. The results indicate that besides the hydration in the vicinity of the protein surface, the outer space of the first hydration layer also significantly influences the total PMV change. These results provide a direct and detailed picture of pressure induced PMV reduction.

Anisotropic lattice compression of α- and β-CePdZn

NASA Astrophysics Data System (ADS)

Oomi, Gendo; Eto, Tetsujiro; Okada, Taku; Uwatoko, Yoshiya

2018-05-01

The lattice constants of ZrNiAl type α-CePdZn and TiNiSi type β-CePdZn were measured at high pressure up to 14 GPa at room temperature using X-ray diffraction (XRD) and a diamond anvil cell. The pressure dependence of lattice constants and volume of α-CePdZn were found to be smooth without any discontinuity, and having a bulk modulus, B0, and its pressure derivative, B0‧, of 67 GPa and 5.1, respectively. On the other hand, the a and b axes as well as volume of β-CePdZn were found to show anomalous pressure dependence at around 8 GPa. B0 and B0‧ of β-CePdZn were 90 GPa and 2.1, respectively. These results suggest that a crossover in the electronic states is induced by applying pressure to β-CePdZn. The origins of these anomalous behaviors are discussed in connection with crossover and change in the topology of Fermi surface.

Critical capillary channel flow

NASA Astrophysics Data System (ADS)

Grah, Aleksander; Klatte, Jörg; Dreyer, Michael E.

The main subject are numerical studies on capillary channel flow, based on results of the sounding rocket experiments TEXUS 41/42. The flow through a capillary channel is established by a gear pump at the outlet. The channel, consists of two parallel glass plates with a width of 25 mm, a gap of 10 mm and a length of 12 mm. The meniscus of a compensation tube maintains a constant system pressure. Steady and dynamic pressure effects in the system force the surfaces to bend inwards. A maximum flow rate is achieved when the free surface collapses and gas ingestion occurs at the outlet. This critical flow rate depends on the channel geometry, the flow regime and the liquid properties. The aim of the experiments is the determination of the free surface shape and to find the maximum flow rate. In order to study the unsteady liquid loop behaviour, a dimensionless transient model was developed. It is based on the unsteady Bernoulli equation, the unsteady continuity equation and geometrical conditions for the surface curvature and the flow cross-section. The pressure is related to the curvature of the free liquid surface by the dimensionless Gauss-Laplace equation with two principal radii. The experimental and evaluated contour data shows good agreement for a sequence of transient flow rate perturbations. The surface oscillation frequencies and amplitudes can be predicted with quite high accuracy. The dynamic of the pump is defined by the increase of the flow rate in a time period. To study the unsteady system behavior in the "worst case", we use a perturbations related to the natural frequency of the oscillating liquid. In the case of steady flow at maximum flow rate, when the "choking" effect occurs, the surfaces collapse and cause gas ingestion into the channel. This effect is related to the Speed Index. At the critical flow rate the Speed Index reaches the value Sca = 1, in analogy to the Mach Number. Unsteady choking does not necessarily cause surface collapse. We show, that temporarily Speed Index values exceeding One may be achieved for a perfectly stable supercritical dynamic flow. As a supercritical criterion for the dynamic free surface stability we define a Dynamic Index D considering the local capillary pressure and the convective pressure, which is a function of the local velocity. The Dynamic Index is below One for stable flow while D = 1 indicates surface collapse. This studies result in a stability diagram, which defines the limits of flow dynamics and the maximum unsteady flow rate. It may serve as a road map for open capillary channel flow control.

Learning to detect vocal hyperfunction from ambulatory neck-surface acceleration features: initial results for vocal fold nodules.

PubMed

Ghassemi, Marzyeh; Van Stan, Jarrad H; Mehta, Daryush D; Zañartu, Matías; Cheyne, Harold A; Hillman, Robert E; Guttag, John V

2014-06-01

Voice disorders are medical conditions that often result from vocal abuse/misuse which is referred to generically as vocal hyperfunction. Standard voice assessment approaches cannot accurately determine the actual nature, prevalence, and pathological impact of hyperfunctional vocal behaviors because such behaviors can vary greatly across the course of an individual's typical day and may not be clearly demonstrated during a brief clinical encounter. Thus, it would be clinically valuable to develop noninvasive ambulatory measures that can reliably differentiate vocal hyperfunction from normal patterns of vocal behavior. As an initial step toward this goal we used an accelerometer taped to the neck surface to provide a continuous, noninvasive acceleration signal designed to capture some aspects of vocal behavior related to vocal cord nodules, a common manifestation of vocal hyperfunction. We gathered data from 12 female adult patients diagnosed with vocal fold nodules and 12 control speakers matched for age and occupation. We derived features from weeklong neck-surface acceleration recordings by using distributions of sound pressure level and fundamental frequency over 5-min windows of the acceleration signal and normalized these features so that intersubject comparisons were meaningful. We then used supervised machine learning to show that the two groups exhibit distinct vocal behaviors that can be detected using the acceleration signal. We were able to correctly classify 22 of the 24 subjects, suggesting that in the future measures of the acceleration signal could be used to detect patients with the types of aberrant vocal behaviors that are associated with hyperfunctional voice disorders.

Characterization and corrosion behavior of F6NM stainless steel treated in high temperature water

NASA Astrophysics Data System (ADS)

Li, Zheng-yang; Cai, Zhen-bing; Yang, Wen-jin; Shen, Xiao-yao; Xue, Guo-hong; Zhu, Min-hao

2018-03-01

F6NM martensitic stainless steel was exposed to 350 °C water condition for 500, 1500, and 2500 h to simulate pressurized water reactor (PWR) condition. The characterization and corrosion behavior of the oxide film were investigated. Results indicate that the exposed steel surface formed a double-layer oxide film. The outer oxide film is Fe-rich and contains two type oxide particles. However, the inner oxide film is Cr-rich, and two oxide films, whose thicknesses increase with increasing exposure time. The oxide film reduces the corrosion behavior because the outer oxide film has many crack and pores. Finally, the mechanism and factors affecting the formation of the oxide film were investigated.

A trough for improved SFG spectroscopy of lipid monolayers.

PubMed

Franz, Johannes; van Zadel, Marc-Jan; Weidner, Tobias

2017-05-01

Lipid monolayers are indispensable model systems for biological membranes. The main advantage over bilayer model systems is that the surface pressure within the layer can be directly and reliably controlled. The sensitive interplay between surface pressure and temperature determines the molecular order within a model membrane and consequently determines the membrane phase behavior. The lipid phase is of crucial importance for a range of membrane functions such as protein interactions and membrane permeability. A very reliable method to probe the structure of lipid monolayers is sum frequency generation (SFG) vibrational spectroscopy. Not only is SFG extremely surface sensitive but it can also directly access critical parameters such as lipid order and orientation, and it can provide valuable information about protein interactions along with interfacial hydration. However, recent studies have shown that temperature gradients caused by high power laser beams perturb the lipid layers and potentially obscure the spectroscopic results. Here we demonstrate how the local heating problem can be effectively reduced by spatially distributing the laser pulses on the sample surface using a translating Langmuir trough for SFG experiments at lipid monolayers. The efficiency of the trough is illustrated by the detection of enhanced molecular order due to reduced heat load.

A trough for improved SFG spectroscopy of lipid monolayers

NASA Astrophysics Data System (ADS)

Franz, Johannes; van Zadel, Marc-Jan; Weidner, Tobias

2017-05-01

Lipid monolayers are indispensable model systems for biological membranes. The main advantage over bilayer model systems is that the surface pressure within the layer can be directly and reliably controlled. The sensitive interplay between surface pressure and temperature determines the molecular order within a model membrane and consequently determines the membrane phase behavior. The lipid phase is of crucial importance for a range of membrane functions such as protein interactions and membrane permeability. A very reliable method to probe the structure of lipid monolayers is sum frequency generation (SFG) vibrational spectroscopy. Not only is SFG extremely surface sensitive but it can also directly access critical parameters such as lipid order and orientation, and it can provide valuable information about protein interactions along with interfacial hydration. However, recent studies have shown that temperature gradients caused by high power laser beams perturb the lipid layers and potentially obscure the spectroscopic results. Here we demonstrate how the local heating problem can be effectively reduced by spatially distributing the laser pulses on the sample surface using a translating Langmuir trough for SFG experiments at lipid monolayers. The efficiency of the trough is illustrated by the detection of enhanced molecular order due to reduced heat load.

Interdependency of Subsurface Carbon Distribution and Graphene–Catalyst Interaction

PubMed Central

2014-01-01

The dynamics of the graphene–catalyst interaction during chemical vapor deposition are investigated using in situ, time- and depth-resolved X-ray photoelectron spectroscopy, and complementary grand canonical Monte Carlo simulations coupled to a tight-binding model. We thereby reveal the interdependency of the distribution of carbon close to the catalyst surface and the strength of the graphene–catalyst interaction. The strong interaction of epitaxial graphene with Ni(111) causes a depletion of dissolved carbon close to the catalyst surface, which prevents additional layer formation leading to a self-limiting graphene growth behavior for low exposure pressures (10–6–10–3 mbar). A further hydrocarbon pressure increase (to ∼10–1 mbar) leads to weakening of the graphene–Ni(111) interaction accompanied by additional graphene layer formation, mediated by an increased concentration of near-surface dissolved carbon. We show that growth of more weakly adhered, rotated graphene on Ni(111) is linked to an initially higher level of near-surface carbon compared to the case of epitaxial graphene growth. The key implications of these results for graphene growth control and their relevance to carbon nanotube growth are highlighted in the context of existing literature. PMID:25188018

Van der Waals model for phase transitions in thermoresponsive surface films.

PubMed

McCoy, John D; Curro, John G

2009-05-21

Phase transitions in polymeric surface films are studied with a simple model based on the van der Waals equation of state. Each chain is modeled by a single bead attached to the surface by an entropic-Hooke's law spring. The surface coverage is controlled by adjusting the chemical potential, and the equilibrium density profile is calculated with density functional theory. The interesting feature of this model is the multivalued nature of the density profile seen at low temperature. This van der Waals loop behavior is resolved with a Maxwell construction between a high-density phase near the wall and a low-density phase in a "vertical" phase transition. Signatures of the phase transition in experimentally measurable quantities are then found. Numerical calculations are presented for isotherms of surface pressure, for the Poisson ratio, and for the swelling ratio.

A Synchrotron Mössbauer Spectroscopy Study of a Hydrated Iron-Sulfate at High Pressures

NASA Astrophysics Data System (ADS)

Perez, T. M.; Finkelstein, G. J.; Solomatova, N. V.; Jackson, J. M.

2017-12-01

Szomolnokite is a monohydrated ferrous iron sulfate mineral, FeSO4*H2O, where the ferrous iron atoms are in octahedral coordination with four corners shared with SO4 and two with H2O. While somewhat rare on Earth, szomolnokite has been detected on the surface of Mars along with several other hydrated sulfates and suggested to occur near the surface of Venus [1,2]. It is not clear if these sulfates are a result of reactions occurring at depth driven by changes in the behavior of iron in the sulfate. To date, only a few high-pressure studies have been conducted on hydrated iron sulfates using Mössbauer spectroscopy. Our study represents a first step towards understanding of the electronic environment of iron in a monohydrated sulfate at pressure. Using a hydrostatic helium pressure-transmitting medium, the pressure dependence of iron's site-specific behavior in a synthetic szomolnokite powdered sample was explored up to about 100 GPa with time-resolved synchrotron Mössbauer spectroscopy at the Advanced Photon Source of Argonne National Laboratory. At 1 bar, the Mössbauer spectrum is well described by three Fe2+-like sites, consistent with conventional Mössbauer spectra reported in Dyar et al. [3]. At pressures up to 20 GPa, changes in the hyperfine parameters are most likely due to a structural phase transition. Above this pressure, a fourth site is required to explain the time-spectra. Changes in the electronic configuration of iron, such as those due to a phase transition and/or a spin crossover, will affect the material's compressibility and transport properties. We will compare our high-pressure trends with those of other iron-bearing phases and discuss the relative influence on the dynamics of terrestrial planetary interiors. 1. Bishop et al. (2014) What Lurks in the Martian Rocks and Soil? Investigations of Sulfates, Phosphates, and Perchlorates. Spectral and thermal properties of perchlorate salts and implications for Mars. Am. Min. 99(8-9), 1580-1592. Wendt et al. (2011) Sulfates and iron oxides in Ophir Chasma, Mars, based on OMEGA and CRISM observations. Icarus 213(1). 86-103. 2. Barsukov et al. (1982) The crust of Venus: theoretical models of chemical and mineral composition. JGR, 87(S01). 3. Dyar et al. (2013) Mössbauer parameters of iron in sulfate minerals. Am. Min. DOI: 10.2138/am.2013.4604.

3-D analysis of a containment equipment hatch

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

Greimann, L.; Fanous, F.

1985-01-01

There are at least two models used to characterize the possible leakage of a containment during a severe accident: (1) the threshold model in which the containment is assumed to be leak-tight until certain pressure/temperature conditions are reached and a very large rupture occurs; and (2) the leak-before-break model in which small leak paths are hypothesized to develop at levels below the threshold. The objective of this work is to investigate the leak-before-break potential of a typical equipment hatch seal. The relative deformations of the sealing surfaces during pressurization are of interest, especially if any buckling of the hatch occurs.more » A three-dimensional finite element model of the equipment hatch assembly was developed. The model included: shell elements for the containment shell, containment stiffeners, penetration sleeve and hatch shell; prestressed bar elements for the swing bolts which hold the hatch closed; and interface elements for the sliding or opening which can occur at the seal surfaces. The nonlinear material properties were approximated by a piecewise linear curve with a proportional limit equal to one-half the yield strength. Geometric nonlinearities were also included in the model. As pressure increments were added to the finite element model, the seal surfaces tended to move together initially. The dominate observable behavior in this range was ''ovaling'' of the penetration sleeve relative to the hatch cover. Since the hatch itself tended to remain circular, there was a mismatch at the sealing surface. Friction reduces but does not eliminate this relative motion. As the containment reached a higher pressure level, the hatch began to buckle at the idealized imperfection. The finite element solution was incremented through the snapthrough. As this postbuckling occurred, additional seal interface distortion was observed.« less

Stability of faults with heterogeneous friction properties and effective normal stress

NASA Astrophysics Data System (ADS)

Luo, Yingdi; Ampuero, Jean-Paul

2018-05-01

Abundant geological, seismological and experimental evidence of the heterogeneous structure of natural faults motivates the theoretical and computational study of the mechanical behavior of heterogeneous frictional fault interfaces. Fault zones are composed of a mixture of materials with contrasting strength, which may affect the spatial variability of seismic coupling, the location of high-frequency radiation and the diversity of slip behavior observed in natural faults. To develop a quantitative understanding of the effect of strength heterogeneity on the mechanical behavior of faults, here we investigate a fault model with spatially variable frictional properties and pore pressure. Conceptually, this model may correspond to two rough surfaces in contact along discrete asperities, the space in between being filled by compressed gouge. The asperities have different permeability than the gouge matrix and may be hydraulically sealed, resulting in different pore pressure. We consider faults governed by rate-and-state friction, with mixtures of velocity-weakening and velocity-strengthening materials and contrasts of effective normal stress. We systematically study the diversity of slip behaviors generated by this model through multi-cycle simulations and linear stability analysis. The fault can be either stable without spontaneous slip transients, or unstable with spontaneous rupture. When the fault is unstable, slip can rupture either part or the entire fault. In some cases the fault alternates between these behaviors throughout multiple cycles. We determine how the fault behavior is controlled by the proportion of velocity-weakening and velocity-strengthening materials, their relative strength and other frictional properties. We also develop, through heuristic approximations, closed-form equations to predict the stability of slip on heterogeneous faults. Our study shows that a fault model with heterogeneous materials and pore pressure contrasts is a viable framework to reproduce the full spectrum of fault behaviors observed in natural faults: from fast earthquakes, to slow transients, to stable sliding. In particular, this model constitutes a building block for models of episodic tremor and slow slip events.

Turbulent boundary layer on a convex, curved surface

NASA Technical Reports Server (NTRS)

Gillis, J. C.; Johnston, J. P.; Kays, W. M.; Moffat, R. J.

1980-01-01

The effects of strong convex curvature on boundary layer turbulence were investigated. The data gathered on the behavior of Reynolds stress suggested the formulation of a simple turbulence model. Three sets of data were taken on two separate facilities. Both rigs had flow from a flat surface, over a convex surface with 90 deg of turning, and then onto a flat recovery surface. The geometry was adjusted so that, for both rigs, the pressure gradient along the test surface was zero - thus avoiding any effects of streamwise acceleration on the wall layers. Results show that after a sudden introduction of curvature, the shear stress in the outer part of the boundary layer is sharply diminished and is even slightly negative near the edge. The wall shear also drops off quickly downstream. In contrast, when the surface suddenly becomes flat again, the wall shear and shear stress profiles recover very slowly towards flat wall conditions.

Surface water and groundwater water interaction model in catastrophic floods and mudslides in the beds of mountain rivers

NASA Astrophysics Data System (ADS)

Tulenev, Nikita

2014-05-01

Catastrophic floods and mudslides / mudflows are very dangerous disaster. Water volumes appear suddenly and continuously increasing in intensity and can spread with great speed, leading to catastrophic consequences - destruction and casualties [1]. These phenomena are typically nonlinear processes occurring in an open system with spatially distributed feedback [2]. Currently, most researchers consider as causes of such powerful water flows seasonal rapid melting of glaciers and intense rain showers. However, their localization is often in line with a separate small mountain river and dynamics of development raises a number of issues, primarily in connection with the justification of the amounts of water that are distributed on the surface and demonstrate the complex hydrodynamic behavior with obvious elements of self-organization. Highlights in this project we consider the interaction of groundwater and surface water by means of the transport system 3D - cracks. In this case there are, two types of emissions to the surface of groundwater - the flash and relatively protracted continuous replenishment of surface runoff due to smooth outpouring of underground streams. We rely on the concept, in which groundwater and surface water are not isolated systems, and is closely related to each other in the territory of a single watershed in the functioning of the overall transport system - 3D-network of cracks in the rock (visible manifestation of which is on the surface and the riverbed itself [3]). Evaluative analysis of groundwater discharge into the river channel can hold a first approximation, by analogy with the artesian well, working in a mode of self-flowing. And in a similar way as it is possible to calculate the pressure at the bottom of the well based on its flow rate, we can estimate the pressure in the aquifer based on the amount obtained by mudflow or flood. In the case of a violent release according to our calculations, such pressure can reach tens of atmospheres. Such pressure may be due to various external factors (including seismic character). In the event of a sharp increase in pressure under the influence of external factors, may occur short and violent eruption, which in mountainous terrain can form a mudflow. If pressure builds up gradually, which is more typical of the plains, the release can develop into increasing recharge the riverbed, which in turn may lead to flooding. Thus, even if a catastrophic flood / mudflow originally formed for other reasons - because of melting glaciers or intensive / heavy rains, the presence on its way sectors fed by groundwater can significantly strengthen it. If we talk about the comparison of these two models with the actual events taking place, the first time that may be associated with catastrophic flooding in Krymsk (July 2012.), And the second - the floods in the Amur River basin (September 2013) in Russia. It is necessary to take into account the spatial extent of these dynamic phenomena. Groundwater resources are essentially spatially distributed. For example, the size of many artesian basins, ranging from hundreds to hundreds of thousands of square kilometers. Thus, the influence on the behavior of groundwater can have events that occur from them at a considerable distance. In particular, are essential earthquake. Consideration of these tasks within the approaches of nonlinear physics can be very

Tracking coherent structures in massively-separated and turbulent flows

NASA Astrophysics Data System (ADS)

Rockwood, Matthew; Huang, Yangzi; Green, Melissa

2018-01-01

Coherent vortex structures are tracked in simulations of massively-separated and turbulent flows. Topological Lagrangian saddle points are found using intersections of the positive and negative finite-time Lyapunov exponent ridges, and these points are then followed in order to track individual coherent structure motion both in a complex interacting three-dimensional flow (turbulent channel) and during vortex formation (two-dimensional bluff body shedding). For a simulation of wall-bounded turbulence in a channel flow, tracking Lagrangian saddles shows that the average structure convection speed exhibits a similar trend as a previously published result based on velocity and pressure correlations, giving validity to the method. When this tracking method is applied in a study of a circular cylinder in cross-flow it shows that Lagrangian saddles rapidly accelerate away from the cylinder surface as the vortex sheds. This saddle behavior is compared with the time-resolved static pressure distribution on the circular cylinder, yielding locations on a cylinder surface where common sensors could detect this phenomenon, which is not available from force measurements or vortex circulation calculations. The current method of tracking coherent structures yields insight into the behavior of the coherent structures in both of the diverse flows presented, highlighting the breadth of its potential application.

Effect of laser beam on temperature distribution on artificial cylindrical shaped hard tissue bones

NASA Astrophysics Data System (ADS)

Al-Akhras, M.-Ali H.; Qaseer, Mohammad-Khair; Albiss, B. A.; Gezawa, Umar S.

2018-02-01

Samples from fresh lamb chest bones were made in cylindrical shapes to study the time variation of temperature T as functions of the cylindrical radius and depth when its front surface exposed to a laser beam of 110Mw power and 642nm wavelength. The laser beam was directed at the center of the front surface of the horizontal cylinder. The measurements were done in vacuum and at atmospheric pressure. Our data reveal the linear variation of T with time, followed by a gradual increase before it reaches a plateau value at higher time. This sort of behavior independent of the radius or the depth where the temperature was measured. Moreover, the maximum variation occurs on the front surface where the laser beam was hitting and diminishes gradually with depth deep inside the cylinder. Data at atmospheric pressure showed less changes in temperature. The temperature distribution in bone due to laser irradiation is very important for a rational use of laser therapy as well as in the surgery to minimizes the thermal tissue damage.

Influence of atmospheric plasma on physicochemical properties of vapor-grown graphite nanofibers.

PubMed

Seo, Min-Kang; Park, Soo-Jin; Lee, Sang-Kwan

2005-05-01

Vapor-grown graphite nanofibers (GNFs) were modified by plasma treatments using low-pressure plasmas with different gases (Ar gas only and/or Ar/O2 gases), flow rates, pressures, and powers. Surface characterizations and morphologies of the GNFs after plasma treatment were investigated by X-ray photoelectron spectroscopy (XPS), contact angle, titration, and transmission electron microscopy (TEM) measurements. Also, the investigation of thermomechanical behavior and impact strengths of the GNFs/epoxy composites was performed by dynamic-mechanical thermal analysis (DMTA) and Izod impact testing, respectively. The plasma treatment of the fibers changed the surface morphologies by forming a layer with a thickness on the order of 1 nm, mainly consisting of oxygen functional groups such as hydroxyl, carbonyl, and carboxyl groups. After functionalization of the complete surfaces, further plasma treatment did not enhance the superficial oxygen content but slightly changed the portions of the functional groups. Also, the composites with plasma-treated GNFs showed an increase in T(g) and impact strength compared to the composites containing the same amount of plasma-untreated GNFs.

Elimination of diazinon insecticide from cucumber surface by atmospheric pressure air-dielectric barrier discharge plasma.

PubMed

Dorraki, Naghme; Mahdavi, Vahideh; Ghomi, Hamid; Ghasempour, Alireza

2016-12-06

The food industry is in a constant search for new technologies to improve the commercial sterilization process of agricultural commodities. Plasma treatment may offer a novel and efficient method for pesticide removal from agricultural product surfaces. To study the proposed technique of plasma food treatment, the degradation behavior of diazinon insecticide by air-dielectric barrier discharge (DBD) plasma was investigated. The authors studied the effect of different plasma powers and treatment times on pesticide concentration in liquid form and coated on the surface of cucumbers, where the diazinon residue was analyzed with mass spectroscopy gas chromatography. Our results suggest that atmospheric pressure air-DBD plasma is potentially effective for the degradation of diazinon insecticide, and mainly depends on related operating parameters, including plasma treatment time, discharge power, and pesticide concentrations. Based on the interaction between reactive oxygen species and electrons in the plasma with the diazinon molecule, two degradation pathway of diazinon during plasma treatment are proposed. It was also found that produced organophosphate pesticides are harmless and less hazardous compounds than diazinon.

From Red Cells to Soft Porous Lubrication

NASA Astrophysics Data System (ADS)

Gacka, T.; Nathan, R.; Wu, L.; Wu, Q.; Cbmss Laboratory Team; Chinese Academy Of Sci. Team

2011-11-01

Feng and Weinbaum (J. Fluid. Mech., 422, 282, 2000), inspired by the enhanced lift phenomena in downhill skiing, developed a new lubrication theory for highly compressible porous media where significantly increased lifting force was predicted as a planing surface glided over a soft porous layer; suggesting superior potential use of porous media for soft lubrication. In this study, we experimentally examine the lift generation phenomena by developing a novel soft porous bearing that consists of a running conveyer belt covered with a soft, 100% polyester, porous sheet, and a stationary, fully instrumented, inclined, planar, upper board. Pore pressure was generated as the upper boundary glides over the soft porous bearing and was measured by pressure sensors. One observed that the pore pressure distribution is consistent with predictions by Feng and Weinbaum (2000), and is a function of the relative velocity between the planing surface and the running belt, the mechanical properties (e.g. porosity, permeability and stiffness) and thickness of the porous layer, as well as the compression ratios at the leading and trailing edges. A load cell is used to characterize the performance of the porous bearing, by comparing pore pressure to total lifting forces. The study presented herein significantly improves our understanding of the behavior of highly compressible porous media under fast compression.

Porous Media Approach for Modeling Closed Cell Foam

NASA Technical Reports Server (NTRS)

Ghosn, Louis J.; Sullivan, Roy M.

2006-01-01

In order to minimize boil off of the liquid oxygen and liquid hydrogen and to prevent the formation of ice on its exterior surface, the Space Shuttle External Tank (ET) is insulated using various low-density, closed-cell polymeric foams. Improved analysis methods for these foam materials are needed to predict the foam structural response and to help identify the foam fracture behavior in order to help minimize foam shedding occurrences. This presentation describes a continuum based approach to modeling the foam thermo-mechanical behavior that accounts for the cellular nature of the material and explicitly addresses the effect of the internal cell gas pressure. A porous media approach is implemented in a finite element frame work to model the mechanical behavior of the closed cell foam. The ABAQUS general purpose finite element program is used to simulate the continuum behavior of the foam. The soil mechanics element is implemented to account for the cell internal pressure and its effect on the stress and strain fields. The pressure variation inside the closed cells is calculated using the ideal gas laws. The soil mechanics element is compatible with an orthotropic materials model to capture the different behavior between the rise and in-plane directions of the foam. The porous media approach is applied to model the foam thermal strain and calculate the foam effective coefficient of thermal expansion. The calculated foam coefficients of thermal expansion were able to simulate the measured thermal strain during heat up from cryogenic temperature to room temperature in vacuum. The porous media approach was applied to an insulated substrate with one inch foam and compared to a simple elastic solution without pore pressure. The porous media approach is also applied to model the foam mechanical behavior during subscale laboratory experiments. In this test, a foam layer sprayed on a metal substrate is subjected to a temperature variation while the metal substrate is stretched to simulate the structural response of the tank during operation. The thermal expansion mismatch between the foam and the metal substrate and the thermal gradient in the foam layer causes high tensile stresses near the metal/foam interface that can lead to delamination.

Isostructural solid-solid phase transition in monolayers of soft core-shell particles at fluid interfaces: structure and mechanics.

PubMed

Rey, Marcel; Fernández-Rodríguez, Miguel Ángel; Steinacher, Mathias; Scheidegger, Laura; Geisel, Karen; Richtering, Walter; Squires, Todd M; Isa, Lucio

2016-04-21

We have studied the complete two-dimensional phase diagram of a core-shell microgel-laden fluid interface by synchronizing its compression with the deposition of the interfacial monolayer. Applying a new protocol, different positions on the substrate correspond to different values of the monolayer surface pressure and specific area. Analyzing the microstructure of the deposited monolayers, we discovered an isostructural solid-solid phase transition between two crystalline phases with the same hexagonal symmetry, but with two different lattice constants. The two phases corresponded to shell-shell and core-core inter-particle contacts, respectively; with increasing surface pressure the former mechanically failed enabling the particle cores to come into contact. In the phase-transition region, clusters of particles in core-core contacts nucleate, melting the surrounding shell-shell crystal, until the whole monolayer moves into the second phase. We furthermore measured the interfacial rheology of the monolayers as a function of the surface pressure using an interfacial microdisk rheometer. The interfaces always showed a strong elastic response, with a dip in the shear elastic modulus in correspondence with the melting of the shell-shell phase, followed by a steep increase upon the formation of a percolating network of the core-core contacts. These results demonstrate that the core-shell nature of the particles leads to a rich mechanical and structural behavior that can be externally tuned by compressing the interface, indicating new routes for applications, e.g. in surface patterning or emulsion stabilization.

The dewetting properties of lotus leaves.

PubMed

Zhang, Jihua; Sheng, Xianliang; Jiang, Lei

2009-02-03

The high dewetting abilities of lotus leaves can be transited to a complete wetting state by soaking the leaves in water at a depth of 50 cm for 2 h. However, after being dried by N2 gas, the high dewetting behavior of lotus leaves may be mostly restored. This indicates that experimental procedure might considerably affect the dewetting abilities of lotus leaves. To discover the mechanism underlying this interesting dewetting phenomena, the dewetting force was used to characterize the dewetting abilities of surfaces, and model studies to mimic the papillae were done. Surface hydrophobicity, sizes, rise angles, and secondary structures of the models' sides affected their dewetting force with water. So we suggested that the dewetting states, Cassie or Wenzel's state, of lotus surfaces depend much on the depth of water, i.e., the hydraulic pressure. On the other hand, the primary structures of papillae in Cassie's state led to a high receding angle with respect to the plane of the leaf during the dewetting measurement. The secondary structures and micro/nano arrays of papillae increased the dewetting abilities of lotus leaves, since no water intruded between papillae. However, the structures of papillae in Wenzle's state significantly reduced the dewetting abilities of lotus leaves after being soaked at a depth of 50 cm for 2 h. Therefore, as for novel designs of microdevices floating on water, including the use of the high dewetting properties of suphydrophobic materials, surface (primary or secondary) microstructure and external pressure, such as static hydraulic pressure, must be taken into account.

Effect of drop volume and surface statistics on the superhydrophobicity of randomly rough substrates

NASA Astrophysics Data System (ADS)

Afferrante, L.; Carbone, G.

2018-01-01

In this paper, a simple theoretical approach is developed with the aim of evaluating shape, interfacial pressure, apparent contact angle and contact area of liquid drops gently deposed on randomly rough surfaces. This method can be useful to characterize the superhydrophobic properties of rough substrates, and to investigate the contact behavior of impacting drops. We assume that (i) the size of the apparent liquid-solid contact area is much larger than the micromorphology of the substrate, and (ii) a composite interface is always formed at the microscale. Results show apparent contact angle and liquid-solid area fraction are slightly influenced by the drop volume only at relatively high values of the root mean square roughness h rms, whereas the effect of volume is practically negligible at small h rms. The main statistical quantity affecting the superhydrophobic properties is found to be the Wenzel roughness parameter r W, which depends on the average slope of the surface heights. Moreover, transition from the Cassie-Baxter state to the Wenzel one is observed when r W reduces below a certain critical value, and theoretical predictions are found to be in good agreement with experimental data. Finally, the present method can be conveniently exploited to evaluate the occurrence of pinning phenomena in the case of impacting drops, as the Wenzel critical pressure for liquid penetration gives an estimation of the maximum impact pressure tolerated by the surface without pinning occurring.

Temperature, pressure, and compositional effects on anomalous or "self" preservation of gas hydrates

USGS Publications Warehouse

Stern, L.A.; Circone, S.; Kirby, S.H.; Durham, W.B.

2003-01-01

We previously reported on a thermal regime where pure, polycrystalline methane hydrate is preserved metastably in bulk at up to 75 K above its nominal temperature stability limit of 193 K at 0.1 MPa, following rapid release of the sample pore pressure. Large fractions (>50 vol.%) of methane hydrate can be preserved for 2-3 weeks by this method, reflecting the greatly suppressed rates of dissociation that characterize this "anomalous preservation" regime. This behavior contrasts that exhibited by methane hydrate at both colder (193-240 K) and warmer (272-290 K) isothermal test conditions, where dissociation rates increase monotonically with increasing temperature. Here, we report on recent experiments that further investigate the effects of temperature, pressure, and composition on anomalous preservation behavior. All tests conducted on sI methane hydrate yielded self-consistent results that confirm the highly temperature-sensitive but reproducible nature of anomalous preservation behavior. Temperature-stepping experiments conducted between 250 and 268 K corroborate the relative rates measured previously in isothermal preservation tests, and elevated pore-pressure tests showed that, as expected, dissociation rates are further reduced with increasing pressure. Surprisingly, sII methane-ethane hydrate was found to exhibit no comparable preservation effect when rapidly depressurized at 268 K, even though it is thermodynamically stable at higher temperatures and lower pressures than sI methane hydrate. These results, coupled with SEM imaging of quenched sample material from a variety of dissociation tests, strongly support our earlier arguments that ice-"shielding" effects provided by partial dissociation along hydrate grain surfaces do not serve as the primary mechanism for anomalous preservation. The underlying physical-chemistry mechanism(s) of anomalous preservation remains elusive, but appears to be based more on textural or morphological changes within the hydrate material itself, rather than on compositional zoning or ice-rind development.

Pool boiling of water on nano-structured micro wires at sub-atmospheric conditions

NASA Astrophysics Data System (ADS)

Arya, Mahendra; Khandekar, Sameer; Pratap, Dheeraj; Ramakrishna, S. Anantha

2016-09-01

Past decades have seen active research in enhancement of boiling heat transfer by surface modifications. Favorable surface modifications are expected to enhance boiling efficiency. Several interrelated mechanisms such as capillarity, surface energy alteration, wettability, cavity geometry, wetting transitions, geometrical features of surface morphology, etc., are responsible for change in the boiling behavior of modified surfaces. Not much work is available on pool boiling at low pressures on microscale/nanoscale geometries; low pressure boiling is attractive in many applications wherein low operating temperatures are desired for a particular working fluid. In this background, an experimental setup was designed and developed to investigate the pool boiling performance of water on (a) plain aluminum micro wire (99.999 % pure) and, (b) nano-porous alumina structured aluminum micro wire, both having diameter of 250 µm, under sub-atmospheric pressure. Nano-structuring on the plain wire surface was achieved via anodization. Two samples, A and B of anodized wires, differing by the degree of anodization were tested. The heater length scale (wire diameter) was much smaller than the capillary length scale. Pool boiling characteristics of water were investigated at three different sub-atmospheric pressures of 73, 123 and 199 mbar (corresponding to T sat = 40, 50 and 60 °C). First, the boiling characteristics of plain wire were measured. It was noticed that at sub-atmospheric pressures, boiling heat transfer performance for plain wire was quite low due to the increased bubble sizes and low nucleation site density. Subsequently, boiling performance of nano-structured wires (both Sample A and Sample B) was compared with plain wire and it was noted that boiling heat transfer for the former was considerably enhanced as compared to the plain wire. This enhancement is attributed to increased nucleation site density, change in wettability and possibly due to enhanced pore scale evaporation. A preliminary estimation of the bubble growth rates, measured by high speed videography, was undertaken and compared with classical bubble growth rate correlations. It was observed that the average bubble departure sizes on Sample B were larger as compared to plain wire, due to larger surface forces holding the bubble before departure. Bubble condensation in the thermal boundary layer was also captured.

Near-ambient pressure XPS of high-temperature surface chemistry in Sr2Co2O5 thin films

DOE PAGES

Hong, Wesley T.; Stoerzinger, Kelsey; Crumlin, Ethan J.; ...

2016-02-11

Transition metal perovskite oxides are promising electrocatalysts for the oxygen reduction reaction (ORR) in fuel cells, but a lack of fundamental understanding of oxide surfaces impedes the rational design of novel catalysts with improved device efficiencies. In particular, understanding the surface chemistry of oxides is essential for controlling both catalytic activity and long-term stability. Thus, elucidating the physical nature of species on perovskite surfaces and their catalytic enhancement would generate new insights in developing oxide electrocatalysts. In this article, we perform near-ambient pressure XPS of model brownmillerite Sr 2Co 2O 5 (SCO) epitaxial thin films with different crystallographic orientations. Detailedmore » analysis of the Co 2p spectra suggests that the films lose oxygen as a function of temperature. Moreover, deconvolution of the O 1s spectra shows distinct behavior for (114)-oriented SCO films compared to (001)-oriented SCO films, where an additional bulk oxygen species is observed. These findings indicate a change to a perovskite-like oxygen chemistry that occurs more easily in (114) SCO than (001) SCO, likely due to the orientation of oxygen vacancy channels out-of-plane with respect to the film surface. This difference in surface chemistry is responsible for the anisotropy of the oxygen surface exchange coefficient of SCO and may contribute to the enhanced ORR kinetics of La 0.8Sr 0.2CoO 3-δ thin films by SCO surface particles observed previously.« less

Secular Climate Change on Mars: An Update Using One Mars Year of MSL Pressure Data

NASA Astrophysics Data System (ADS)

Haberle, R. M.; Gómez-Elvira, J.; De La Torre Juarez, M.; Harri, A. M.; Hollingsworth, J. L.; Kahanpää, H.; Kahre, M. A.; Lemmon, M. T.; Martín-Torres, J.; Mischna, M. A.; Moores, J.; Newman, C. E.; Rafkin, S. C.; Renno, N. O.; Richardson, M. I.; Rodriguez-Manfredi, J. A.; Thomas, P. C.; Vasavada, A. R.; Wong, M. H.; Zorzano, M. P.

2014-12-01

The South Polar Residual Cap (SPRC) on Mars is an icy reservoir of CO2. If all the CO2 trapped in the SPRC were released to the atmosphere the mean annual global surface pressure would rise by ~20 Pa. Repeated MOC and HiRISE imaging of scarp retreat within the SPRC led to suggestions that the SPRC is losing mass. Estimates for the loss rate vary between 0. 5 Pa per Mars Decade to 13 Pa per Mars Decade. Assuming 80% of this loss goes directly into the atmosphere, an estimate based on some modeling (Haberle and Kahre, 2010), and that the loss is monotonic, the global annual mean surface pressure should have increased between ~1-20 Pa since the Viking mission (~20 Mars years ago). Surface pressure measurements by the Phoenix Lander only 2.5 Mars years ago were found to be consistent with these loss rates. Last year at this meeting we compared surface pressure data from the MSL mission through sol 360 with that from Viking Lander 2 (VL-2) for the same period to determine if the trend continues. The results were ambiguous. This year we have a full Mars year of MSL data to work with. Using the Ames GCM to compensate for dynamics and environmental differences, our analysis suggests that the mean annual pressure has decreased by ~ 8 Pa since Viking. This result implies that the SPRC has gained (not lost) mass since Viking. However, the estimated uncertainties in our analysis are easily at the 10 Pa level and possibly higher. Chief among these are the hydrostatic adjustment of surface pressure from grid point elevations to actual elevations and the simulated regional environmental conditions at the lander sites. For these reasons, the most reasonable conclusion is that there is no significant difference in the size of the atmosphere between now and Viking. This implies, but does not demand, that the mass of the SPRC has not changed since Viking. Of course, year-to-year variations are possible as implied by the Phoenix data. Given that there has been no unusual behavior in the climate system as observed by a variety of spacecraft at Mars since Phoenix, its seems more likely that the Phoenix data simply did not have a long enough record to accurately determine annual mean pressure changes as Haberle and Kahre (2010) cautioned. In the absence of a strong signal in the MSL data, we conclude that if the SPRC is loosing mass it is not going into the atmosphere reservoir.

Secular Climate Change on Mars: An Update Using One Mars Year of MSL Pressure Data

NASA Technical Reports Server (NTRS)

Haberle, R. M.; Gomez-Elvira, J.; de la Torre Juarez, M.; Harri, A-M.; Hollingsworth, J. L.; Kahanpaa, H.; Kahre, M. A.; Lemmon, M.; Martin-Torres, F. J.; Mischna, M.;

Wetting of silicone oil onto a cell-seeded substrate

NASA Astrophysics Data System (ADS)

Lu, Yongjie; Chan, Yau Kei; Chao, Youchuang; Shum, Ho Cheung

2017-11-01

Wetting behavior of solid substrates in three-phase systems containing two immiscible liquids are widely studied. There exist many three-phase systems in biological environments, such as droplet-based microfluidics or tamponade of silicone oil for eye surgery. However, few studies focus on wetting behavior of biological surfaces with cells. Here we investigate wetting of silicone oil onto cell-seeded PMMA sheet immersed in water. Using a simple parallel-plate cell, we show the effect of cell density, viscosity of silicone oil, morphology of silicone oil drops and interfacial tension on the wetting phenomenon. The dynamics of wetting is also observed by squeezing silicone oil drop using two parallel plates. Experimental results are explained based on disjoining pressure which is dependent on the interaction of biological surfaces and liquid used. These findings are useful for explaining emulsification of silicone oil in ophthalmological applications.

The compression behavior of blödite at low and high temperature up to ~10GPa: Implications for the stability of hydrous sulfates on icy planetary bodies

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

Comodi, Paola; Stagno, Vincenzo; Zucchini, Azzurra

Recent satellite inferences of hydrous sulfates as recurrent minerals on the surface of icy planetary bodies link with the potential mineral composition of their interior. Blödite, a mixed Mg-Na sulfate, is here taken as representative mineral of icy satellites surface to investigate its crystal structure and stability at conditions of the interior of icy bodies. To this aim we performed in situ synchrotron angle-dispersive X-ray powder diffraction experiments on natural blödite at pressures up to ~10.4 GPa and temperatures from ~118.8 K to ~490.0 K using diamond anvil cell technique to investigate the compression behavior and establish a low-to-high temperaturemore » equation of state that can be used as reference when modeling the interior of sulfate-rich icy satellites such as Ganymede.« less

The climate of Mars

NASA Astrophysics Data System (ADS)

Haberle, R. M.

1986-05-01

The composition of the primitive Martian atmosphere and its development into the present environment are described. The primitive atmosphere consisted of water vapor, carbon dioxide, and nitrogen released from rocks; the greenhouse effect which maintained the surface temperature above the frost point of water is examined. Volcanic activity reduced the greenhouse effect and along with CO2 removal from the atmosphere caused a lowering of the planet temperature. The global circulation patterns on earth and Mars are compared; the similarities in the circulation patterns and Mars' seasonal variations are studied. The carbon dioxide and water cycles on Mars are analyzed; the carbon dioxide cycle determines seasonal variations in surface pressure and the behavior of the water cycle. The behavior of the atmospheric dust and the relationship between the seasonal dust cycle and Hadley circulation are investigated. The periodic variations in the three orbital parameters of Mars, which affect the climate by changing the seasonal and latitudinal distribution of incoming solar energy are discussed

Friction and wear behavior of aluminum and composite I-beam stiffened airplane skins

NASA Technical Reports Server (NTRS)

Jackson, K. E.

1985-01-01

Friction and wear behavior was determined for I-beam stiffened skins constructed of aluminum, graphite-epoxy composite, and glass hybrid composite under abrasive loading conditions typical of those occurring on the underside of a transport airplane during an emergency belly landing. A test apparatus was developed to abrade the test specimens on actual runway surface under a range of pressures (2-5 psi) and velocities (16-50 mph). These parameters were chosen to fall within the range of conditions typical of an airframe sliding on a runway surface. The effects of the test variables on the wear rate and the coefficient of friction are discussed and comparisons are made between the composite materials and aluminum. In addition, the test apparatus was equipped to monitor the temperature variations on the backside of the skins during abrasion and these results are presented.

Barium versus nonbarium stimuli: differences in taste intensity, chemesthesis, and swallowing behavior in healthy adult women.

PubMed

Nagy, Ahmed; Steele, Catriona M; Pelletier, Cathy A

2014-06-01

The authors examined the impact of barium on the perceived taste intensity of 7 different liquid tastant stimuli and the modulatory effect that these differences in perceived taste intensity have on swallowing behaviors. Participants were 80 healthy women, stratified by age group (<40; >60) and genetic taste status (supertasters; nontasters). Perceived taste intensity and chemesthetic properties (fizziness; burning-stinging) were rated for 7 tastant solutions (each prepared with and without barium) using the general Labeled Magnitude Scale. Tongue-palate pressures and submental surface electromyography (sEMG) were simultaneously measured during swallowing of these same randomized liquids. Path analysis differentiated the effects of stimulus, genetic taste status, age, barium condition, taste intensity, and an effortful saliva swallow strength covariate on swallowing. Barium stimuli were rated as having reduced taste intensity compared with nonbarium stimuli. Barium also dampened fizziness but did not influence burning-stinging sensation. The amplitudes of tongue-palate pressure or submental sEMG did not differ when swallowing barium versus nonbarium stimuli. Despite impacting taste intensity, the addition of barium to liquid stimuli does not appear to alter behavioral parameters of swallowing. Barium solutions can be considered to elicit behaviors that are similar to those used with nonbarium liquids outside the assessment situation.

History of respiratory mechanics prior to World War II.

PubMed

West, John B

2012-01-01

The history of respiratory mechanics is reviewed over a period of some 2,500 years from the ancient Greeks to World War II. A cardinal early figure was Galen (130-199 AD) who made remarkably perceptive statements on the diaphragm and the anatomy of the phrenic nerves. The polymath Leonardo da Vinci (1452-1519) contributed observations on pulmonary mechanics including the pleural space and bronchial airflow that still make good reading. Vesalius (1514-1564) produced magnificent illustrations of the lung, ribcage, and diaphragm. In the 17th century, the Oxford School including Boyle, Hooke, Lower, and Mayow were responsible for many contributions on mechanical functions including the intercostal muscles and the pleura. Hales (1677-1761) calculated the size and surface area of the alveoli, the time spent by the blood in the pulmonary capillaries, and intrathoracic pressures. Poiseuille (1799-1869) carried out classical studies of fluid mechanics including one of the first demonstrations of flow limitation in collapsible vessels. The culmination of the pre-World War II period was the outstanding contributions of Rohrer (1888-1926) and his two Swiss countrymen, Wirz (1896-1978) and von Neergaard (1887-1947). Rohrer developed the first comprehensive, quantitative treatment of respiratory mechanics in the space of 10 years including an analysis of flow in airways, and the pressure-volume behavior of the respiratory system. von Neergaard performed landmark studies on the effects of surface tension on pressure-volume behavior. Progress over the 2,500 years was slow and erratic at times, but by 1940 the stage was set for the spectacular developments of the next 70 years. © 2012 American Physiological Society

Investigations of inorganic and organic fouling behaviors, antifouling and cleaning strategies for pressure retarded osmosis (PRO) membrane using seawater desalination brine and wastewater.

PubMed

Han, Gang; Zhou, Jieliang; Wan, Chunfeng; Yang, Tianshi; Chung, Tai-Shung

2016-10-15

By employing seawater desalination brine (SWBr) and wastewater brine (WWBr) as the feed pair, membrane fouling behaviors as well as antifouling and cleaning strategies for the state-of-the-art thin-film composite polyethersulfone (TFC-PES) hollow fiber membrane have been systematically investigated under pressure retarded osmosis (PRO) operations. Fouling on the polyamide selective layer induced by the SWBr draw solution is relatively mild because of the outstanding membrane rejection and the hydration antifouling layer formed by the permeating water. However, using WWBr as the feed causes fast and severe internal concentration polarization (ICP) and fouling within the porous PES substrate, which result in dramatic flux and power density declines. In addition, the PRO fouling upon and within the porous substrate is highly irreversible. Experimental data show that both anti-scalant pretreatment and pH adjustment of WWBr could effectively mitigate inorganic fouling, while increasing feed flow velocity along the substrate surface is ineffective for fouling control. To clean the fouled membranes, hydraulic-pressure induced backwash and flushing with alkaline and NaOCl solutions on the fouled surface are effective strategies to remove foulants and regenerate membranes with a flux recovery of 83-90%. However, osmotic backwash shows low cleaning efficiency in PRO. In summary, a proper combination of feed pretreatment and membrane cleaning strategies has been demonstrated in this study to sustain PRO operations with a high water flux and power density. Copyright © 2016 Elsevier Ltd. All rights reserved.

Racial Variations in Interfacial Behavior of Lipids Extracted from Worn Soft Contact Lenses

PubMed Central

Svitova, Tatyana F.; Lin, Meng C.

2014-01-01

Purpose To explore interfacial behaviors and effect of temperature and dilatation on dynamic properties of multilayered human tear lipids extracted from silicone hydrogel (SiH) lenses worn by asymptomatic Asian and Caucasian subjects. Methods Interfacial properties of lipids extracted from Focus® N&D lenses worn by 14 subjects continuously for 1 month were studied. The lipids were deposited on an air bubble immersed in a model tear electrolytes (MTE) solution to form 100 ± 20 nm-thick films. Surface pressure was recorded during slow expansion/contraction cycles to evaluate compressibility and hysteresis of lipid films. Films were also subjected to fast step-strain dilatations at temperatures 22°–45° C for their visco-elastic properties assessment. Results Iso-cycles for Asian and Caucasian lipids were similar at low surface pressures, but had distinctly different compressibility and hysteresis at dynamic pressures exceeding 30 mN/m. Rheological parameters of reconstituted lipids were also dissimilar between Asian and Caucasian. The elastic modulusE∞ for Caucasian lipids was 1.5 times higher than that for Asian lipids, whereas relaxation time (t) was on average 1.3 times higher for Asian. No significant changes were observed in rheological properties of both Asian and Caucasian lipids when temperature increased from 22.0° to 36.5° C. However, for Caucasian lipids, E∞ reduced considerably at temperatures above 42.0° C, while t remained unchanged. For Asian lipids, both E∞ and t started to decline as temperature increased to 38° C and higher. Conclusions Higher elastic modulus of Caucasian lipids and elasticity threshold at certain deformations indicate stronger structure and intermolecular interactions as compared with more viscous Asian lipids. The differences in interfacial behaviors between Asian and Caucasian lipids may be associated with the differences in their chemical compositions. PMID:24270592

A Stability Analysis for a Hydrodynamic Three-Wave Journal Bearing

NASA Technical Reports Server (NTRS)

Ene, Nicoleta M.; Dimofte, Florin; Keith, Theo G., Jr.

2007-01-01

The influence of the wave amplitude and oil supply pressure on the dynamic behavior of a hydrodynamic three-wave journal bearing is presented. Both, a transient and a small perturbation technique, were used to predict the threshold to fractional frequency whirl (FFW). In addition, the behavior of the rotor after FFW appeared was determined from the transient analysis. The turbulent effects were also included in the computations. Bearings having a diameter of 30 mm, a length of 27.5 mm, and a clearance of 35 microns were analyzed. Numerical results were compared to experimental results obtained at the NASA GRC. Numerical and experimental results showed that the above-mentioned wave bearing with a wave amplitude ratio of 0.305 operates stably at rotational speeds up to 60,000 rpm, regardless of the oil supply pressure. For smaller wave amplitude ratios, a threshold of stability was found. It was observed that the threshold of stability for lower wave amplitude strongly depends on the oil supply pressure and on the wave amplitude. When the FFW occurs, the journal center maintains its trajectory inside the bearing clearance and therefore the rotor can be run safely without damaging the bearing surfaces.

Using a Virtual Environment to Study Pedestrian Behaviors: How Does Time Pressure Affect Children's and Adults' Street Crossing Behaviors?

PubMed

Morrongiello, Barbara A; Corbett, Michael; Switzer, Jessica; Hall, Tom

2015-08-01

The aim of this study was to examine how crossing under time pressure influences the pedestrian behaviors of children and adults. Using a highly immersive virtual reality system interfaced with a 3D movement measurement system, various indices of children's and adults' crossing behaviors were measured under time-pressure and no time-pressure conditions. Pedestrians engaged in riskier crossing behaviors on time-pressure trials as indicated by appraising traffic for a shorter period before initiating their crossing, selecting shorter more hazardous temporal gaps to cross into, and having the car come closer to them (less time to spare). There were no age or sex differences in how time pressure affected crossing behaviors. The current findings indicate that, at all ages, pedestrians experience greater exposure to traffic dangers when they cross under time pressure. © The Author 2015. Published by Oxford University Press on behalf of the Society of Pediatric Psychology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Emerging Applications of Liquid Metals Featuring Surface Oxides

PubMed Central

2014-01-01

Gallium and several of its alloys are liquid metals at or near room temperature. Gallium has low toxicity, essentially no vapor pressure, and a low viscosity. Despite these desirable properties, applications calling for liquid metal often use toxic mercury because gallium forms a thin oxide layer on its surface. The oxide interferes with electrochemical measurements, alters the physicochemical properties of the surface, and changes the fluid dynamic behavior of the metal in a way that has, until recently, been considered a nuisance. Here, we show that this solid oxide “skin” enables many new applications for liquid metals including soft electrodes and sensors, functional microcomponents for microfluidic devices, self-healing circuits, shape-reconfigurable conductors, and stretchable antennas, wires, and interconnects. PMID:25283244

Effect of oxygen, methyl mercaptan, and methyl chloride on friction behavior of copper-iron contacts

NASA Technical Reports Server (NTRS)

Buckley, D. H.

1978-01-01

Sliding friction experiments were conducted with an iron rider on a copper disk and a copper rider on an iron disk. The sputter cleaned iron and copper disk surfaces were saturated with oxygen, methyl mercaptan, and methyl chloride at atmospheric pressure. Auger emission spectroscopy was used to monitor the surfaces. Lower friction was obtained in all experiments with the copper rider sliding on the iron disk than when the couple was reversed. For both iron and copper disks, methyl mercaptan gave the best surface coverage and was most effective in reducing friction. For both iron and copper disks, methyl chloride was the least effective in reducing friction. With sliding, copper transferred to iron and iron to copper.

Exploring the effect of oxygen coverage on the electronic, magnetic and chemical properties of Ni(111) supported h-BN sheet: A density functional study

NASA Astrophysics Data System (ADS)

Wasey, A. H. M. Abdul; Das, G. P.; Majumder, C.

2017-05-01

Traditionally, h-BN is used as coating material to prevent corrosion on the metal surface. In sharp contrast to this, here we show catalytic behavior of h-BN monolayer deposited on Ni(111) surface, clearly demonstrating the influence of the support in modulation of h-BN electronic structure. Using first principles density functional theory we have studied the interaction of O2 molecules with the h-BN/Ni(111) surface. The activation of Osbnd O bond, which is the most important step for oxidative catalysis, showed dependence on the O2 coverage. Thus this study is extremely important to predict the optimum O2 pressure in reaction chamber for efficient catalysis.

Active control of Boundary Layer Separation & Flow Distortion in Adverse Pressure Gradient Flows via Supersonic Microjets

NASA Technical Reports Server (NTRS)

Alvi, Farrukh S.; Gorton, Susan (Technical Monitor)

2005-01-01

Inlets to aircraft propulsion systems must supply flow to the compressor with minimal pressure loss, flow distortion or unsteadiness. Flow separation in internal flows such as inlets and ducts in aircraft propulsion systems and external flows such as over aircraft wings, is undesirable as it reduces the overall system performance. The aim of this research has been to understand the nature of separation and more importantly, to explore techniques to actively control this flow separation. In particular, the use of supersonic microjets as a means of controlling boundary layer separation was explored. The geometry used for the early part of this study was a simple diverging Stratford ramp, equipped with arrays of supersonic microjets. Initial results, based on the mean surface pressure distribution, surface flow visualization and Planar Laser Scattering (PLS) indicated a reverse flow region. We implemented supersonic microjets to control this separation and flow visualization results appeared to suggest that microjets have a favorable effect, at least to a certain extent. However, the details of the separated flow field were difficult to determine based on surface pressure distribution, surface flow patterns and PLS alone. It was also difficult to clearly determine the exact influence of the supersonic microjets on this flow. In the latter part of this study, the properties of this flow-field and the effect of supersonic microjets on its behavior were investigated in further detail using 2-component (planar) Particle Image Velocimetry (PIV). The results clearly show that the activation of microjets eliminated flow separation and resulted in a significant increase in the momentum of the fluid near the ramp surface. Also notable is the fact that the gain in momentum due to the elimination of flow separation is at least an order of magnitude larger (two orders of magnitude larger in most cases) than the momentum injected by the microjets and is accomplished with very little mass flow through the microjets.

Feedback Regulation of Intracellular Hydrostatic Pressure in Surface Cells of the Lens

PubMed Central

Gao, Junyuan; Sun, Xiurong; White, Thomas W.; Delamere, Nicholas A.; Mathias, Richard T.

2015-01-01

In wild-type lenses from various species, an intracellular hydrostatic pressure gradient goes from ∼340 mmHg in central fiber cells to 0 mmHg in surface cells. This gradient drives a center-to-surface flow of intracellular fluid. In lenses in which gap-junction coupling is increased, the central pressure is lower, whereas if gap-junction coupling is reduced, the central pressure is higher but surface pressure is always zero. Recently, we found that surface cell pressure was elevated in PTEN null lenses. This suggested disruption of a feedback control system that normally maintained zero surface cell pressure. Our purpose in this study was to investigate and characterize this feedback control system. We measured intracellular hydrostatic pressures in mouse lenses using a microelectrode/manometer-based system. We found that all feedback went through transport by the Na/K ATPase, which adjusted surface cell osmolarity such that pressure was maintained at zero. We traced the regulation of Na/K ATPase activity back to either TRPV4, which sensed positive pressure and stimulated activity, or TRPV1, which sensed negative pressure and inhibited activity. The inhibitory effect of TRPV1 on Na/K pumps was shown to signal through activation of the PI3K/AKT axis. The stimulatory effect of TRPV4 was shown in previous studies to go through a different signal transduction path. Thus, there is a local two-legged feedback control system for pressure in lens surface cells. The surface pressure provides a pedestal on which the pressure gradient sits, so surface pressure determines the absolute value of pressure at each radial location. We speculate that the absolute value of intracellular pressure may set the radial gradient in the refractive index, which is essential for visual acuity. PMID:26536260

Water is a poor solvent for densely grafted poly(ethylene oxide) chains: a conclusion drawn from a self-consistent field theory-based analysis of neutron reflectivity and surface pressure-area isotherm data.

PubMed

Lee, Hoyoung; Kim, Dae Hwan; Witte, Kevin N; Ohn, Kimberly; Choi, Je; Akgun, Bulent; Satija, Sushil; Won, You-Yeon

2012-06-21

By use of a combined experimental and theoretical approach, a model poly(ethylene oxide) (PEO) brush system, prepared by spreading a poly(ethylene oxide)-poly(n-butyl acrylate) (PEO-PnBA) amphiphilic diblock copolymer onto an air-water interface, was investigated. The polymer segment density profiles of the PEO brush in the direction normal to the air-water interface under various grafting density conditions were determined by using the neutron reflectivity (NR) measurement technique. To achieve a theoretically sound analysis of the reflectivity data, we used a data analysis method that utilizes the self-consistent field (SCF) theoretical modeling as a tool for predicting expected reflectivity results for comparison with the experimental data. Using this data analysis technique, we discovered that the effective Flory-Huggins interaction parameter of the PEO brush chains is significantly greater than that corresponding to the θ condition in Flory-Huggins solutions (i.e., χ(PEO-water)(brush chains)/χ(PEO-water)(θ condition) ≈ 1.2), suggesting that contrary to what is more commonly observed for PEO in normal situations (χ(PEO-water)(free chains)/χ(PEO-water)(θ condition) ≈ 0.92), the PEO chains are actually not "hydrophilic" when they exist as polymer brush chains, because of the many body interactions that are forced to be effective in the brush situation. This result is further supported by the fact that the surface pressures of the PEO brush calculated on the basis of the measured χ(PEO-water) value are in close agreement with the experimental surface pressure-area isotherm data. The SCF theoretical analysis of the surface pressure behavior of the PEO brush also suggests that even though the grafted PEO chains experience a poor solvent environment, the PEO brush layer exhibits positive surface pressures, because the hydrophobicity of the PEO brush chains (which favors compression) is insufficient to overcome the opposing effect of the chain conformational entropy (which resists compression).

Ground effect for V/STOL aircraft configurations and its simulation in the wind tunnel. Part 1: Introduction and theoretical studies

NASA Technical Reports Server (NTRS)

Hackett, J. E.; Praytor, E. B.

1972-01-01

Theoretical studies are made of three dimensional turbulent boundary layer behavior on fixed grounds and on moving grounds of the type used in wind tunnel tests. It is shown that, for several widely-varying STOL configurations, the ground static pressure distributions possess a remarkable degree of fore-aft symmetry about the center of lift. At low Renolds number, corresponding to small-tunnel testing, the boundary layer displacement surface reflects to a large degree the symmetry of the pressure distribution. For this reason, induced incidence at the model is small for unseparated ground flow. At high Reynolds number, the displacement thickness decrease aft of the static pressure maximum is noticeably more rapid than the corresponding rise. This is attributed to trailing-vortex-induced spanwise pumping within the boundary layer.

An improved source model for aircraft interior noise studies

NASA Technical Reports Server (NTRS)

Mahan, J. R.; Fuller, C. R.

1985-01-01

There is concern that advanced turboprop engines currently being developed may produce excessive aircraft cabin noise levels. This concern has stimulated renewed interest in developing aircraft interior noise reduction methods that do not significantly increase take off weight. An existing analytical model for noise transmission into aircraft cabins was utilized to investigate the behavior of an improved propeller source model for use in aircraft interior noise studies. The new source model, a virtually rotating dipole, is shown to adequately match measured fuselage sound pressure distributions, including the correct phase relationships, for published data. The virtually rotating dipole is used to study the sensitivity of synchrophasing effectiveness to the fuselage sound pressure trace velocity distribution. Results of calculations are presented which reveal the importance of correctly modeling the surface pressure phase relations in synchrophasing and other aircraft interior noise studies.

An improved source model for aircraft interior noise studies

NASA Technical Reports Server (NTRS)

Mahan, J. R.; Fuller, C. R.

1985-01-01

There is concern that advanced turboprop engines currently being developed may produce excessive aircraft cabin noise level. This concern has stimulated renewed interest in developing aircraft interior noise reduction methods that do not significnatly increase take off weight. An existing analytical model for noise transmission into aircraft cabins was utilized to investigate the behavior of an improved propeller source model for use in aircraft interior noise studies. The new source model, a virtually rotating dipole, is shown to adequately match measured fuselage sound pressure distributions, including the correct phase relationships, for published data. The virtually rotating dipole is used to study the sensitivity of synchrophasing effectiveness to the fuselage sound pressure trace velocity distribution. Results of calculations are presented which reveal the importance of correctly modeling the surface pressure phase relations in synchrophasing and other aircraft interior noise studies.

Bovine insulin-phosphatidylcholine mixed Langmuir monolayers: behavior at the air-water interface.

PubMed

Pérez-López, S; Blanco-Vila, N M; Vila-Romeu, N

2011-08-04

The behavior of the binary mixed Langmuir monolayers of bovine insulin (INS) and phosphatidylcholine (PC) spread at the air-water interface was investigated under various subphase conditions. Pure and mixed monolayers were spread on water, on NaOH and phosphate-buffered solutions of pH 7.4, and on Zn(2+)-containing solutions. Miscibility and interactions between the components were studied on the basis of the analysis of the surface pressure (π)-mean molecular area (A) isotherms, surface compression modulus (C(s)(-1))-π curves, and plots of A versus mole fraction of INS (X(INS)). Our results indicate that intermolecular interactions between INS and PC depend on both the monolayer state and the structural characteristics of INS at the interface, which are strongly influenced by the subphase pH and salt content. Brewster angle microscopy (BAM) was applied to investigate the peptide aggregation pattern at the air-water interface in the presence of the studied lipid under any experimental condition investigated. The influence of the lipid on the INS behavior at the interface strongly depends on the subphase conditions.

Effect of surface state on the oxidation behavior of welded 308L in simulated nominal primary water of PWR

NASA Astrophysics Data System (ADS)

Ming, Hongliang; Zhang, Zhiming; Wang, Jiazhen; Zhu, Ruolin; Ding, Jie; Wang, Jianqiu; Han, En-Hou; Ke, Wei

2015-05-01

The oxidation behavior of 308L weld metal (WM) with different surface state in the simulated nominal primary water of pressurized water reactor (PWR) was studied by scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) analyzer and X-ray photoelectron spectroscopy (XPS). After 480 h immersion, a duplex oxide film composed of a Fe-rich outer layer (Fe3O4, Fe2O3 and a small amount of NiFe2O4, Ni(OH)2, Cr(OH)3 and (Ni, Fe)Cr2O4) and a Cr-rich inner layer (FeCr2O4 and NiCr2O4) can be formed on the 308L WM samples with different surface state. The surface state has no influence on the phase composition of the oxide films but obviously affects the thickness of the oxide films and the morphology of the oxides (number & size). With increasing the density of dislocations and subgrain boundaries in the cold-worked superficial layer, the thickness of the oxide film, the number and size of the oxides decrease.

Ionic-Liquid-Infused Nanostructures as Repellent Surfaces.

PubMed

Galvan, Yaraset; Phillips, Katherine R; Haumann, Marco; Wasserscheid, Peter; Zarraga, Ramon; Vogel, Nicolas

2018-06-12

In order to prepare lubricant-infused repellent coatings on silica nanostructures using low vapor pressure ionic liquids as lubricants, we study the wetting behavior of a set of imidazolium-based ionic liquids with different alkyl side chains as a function of the applied surface functionalities. We take advantage of the structural color of inverse opals prepared from a colloidal coassembly technique to study the infiltration of ionic liquids into these nanoporous structures. We find that the more hydrophobic ionic liquids with butyl and hexyl side chains can completely infiltrate inverse opals functionalized with mixed self-assembled monolayers composed of imidazole groups and aliphatic hydrocarbon chains, which we introduce via silane chemistry. These molecular species reflect the chemical nature of the ionic liquid, thereby increasing the affinity between the liquid and solid surface. The mixed surface chemistry provides sufficiently small contact angles with the ionic liquid to infiltrate the nanopores while maximizing the contact angle with water. As a result, the mixed monolayers enable the design of a stable ionic liquid/solid interface that is able to repel water as a test liquid. Our results underline the importance of matching chemical affinities to predict and control the wetting behavior in complex, multiphase systems.

Flocculation of deformable emulsion droplets. 2: Interaction energy

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

Petsev, D.N.; Denkov, N.D.; Kralchevsky, P.A.

1995-12-01

The effect of different factors (drop radius, interfacial tension, Hamaker constant, electrolyte, micellar concentrations, etc.) on the interaction energy of emulsion droplets is studied theoretically. It is demonstrated that the deformation of the colliding droplets considerably affects the interaction energy. The contributions of the electrostatic, van der Waals, depletion, steric, and oscillatory surface forces, as well as for the surface stretching and bending energies, are estimated and discussed. The calculations show that the droplets interact as nondeformed spheres when the attractive interactions are weak. At stronger attractions an equilibrium plane parallel film is formed between the droplets, corresponding to minimummore » interaction energy of the system. For droplets in concentrated micellar surfactant solutions the oscillatory surface forces become operative and one can observe several minima of the energy surface,each corresponding to a metastable state with a different number of micellar layers inside the film formed between the droplets. The present theoretical analysis can find applications in predicting the behavior and stability of miniemulsions (containing micrometer and submicrometer droplets), as well as in interpretation of data obtained by light scattering, phase behavior, rheological and osmotic pressure measurements, etc.« less

On the Physics of Flow Separation Along a Low Pressure Turbine Blade Under Unsteady Flow Conditions

NASA Technical Reports Server (NTRS)

Schobeiri, Meinhard T.; Ozturk, Burak; Ashpis, David E.

2005-01-01

The present study, which is the first of a series of investigations dealing with specific issues of low pressure turbine (LPT) boundary layer aerodynamics, is aimed at providing detailed unsteady boundary flow information to understand the underlying physics of the inception, onset, and extent of the separation zone. A detailed experimental study on the behavior of the separation zone on the suction surface of a highly loaded LPT-blade under periodic unsteady wake flow is presented. Experimental investigations were performed at Texas A&M Turbomachinery Performance and Flow Research Laboratory using a large-scale unsteady turbine cascade research facility with an integrated wake generator and test section unit. To account for a high flow deflection of LPT-cascades at design and off-design operating points, the entire wake generator and test section unit including the traversing system is designed to allow a precise angle adjustment of the cascade relative to the incoming flow. This is done by a hydraulic platform, which simultaneously lifts and rotates the wake generator and test section unit. The unit is then attached to the tunnel exit nozzle with an angular accuracy of better than 0.05 , which is measured electronically. Utilizing a Reynolds number of 110,000 based on the blade suction surface length and the exit velocity, one steady and two different unsteady inlet flow conditions with the corresponding passing frequencies, wake velocities and turbulence intensities are investigated using hot-wire anemometry. In addition to the unsteady boundary layer measurements, blade surface pressure measurements were performed at Re=50,000, 75,000, 100,000, and 125,000 at one steady and two periodic unsteady inlet flow conditions. Detailed unsteady boundary layer measurement identifies the onset and extent of the separation zone as well as its behavior under unsteady wake flow. The results presented in ensemble-averaged and contour plot forms contribute to understanding the physics of the separation phenomenon under periodic unsteady wake flow. Several physical mechanisms are discussed.

Poole-Frenkel effect on electrical characterization of Al-doped ZnO films deposited on p-type GaN

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

Huang, Bohr-Ran; Liao, Chung-Chi; Ke, Wen-Cheng, E-mail: wcke@saturn.yzu.edu.tw

2014-03-21

This paper presents the electrical properties of Al-doped ZnO (AZO) films directly grown on two types of p-type GaN thin films. The low-pressure p-GaN thin films (LP-p-GaN) exhibited structural properties of high-density edge-type threading dislocations (TDs) and compensated defects (i.e., nitrogen vacancy). Compared with high-pressure p-GaN thin films (HP-p-GaN), X-ray photoemission spectroscopy of Ga 3d core levels indicated that the surface Fermi-level shifted toward the higher binding-energy side by approximately 0.7 eV. The high-density edge-type TDs and compensated defects enabled surface Fermi-level shifting above the intrinsic Fermi-level, causing the surface of LP-p-GaN thin films to invert to n-type semiconductor. A highlymore » nonlinear increase in leakage current regarding reverse-bias voltage was observed for AZO/LP-p-GaN. The theoretical fits for the reverse-bias voltage region indicated that the field-assisted thermal ionization of carriers from defect associated traps, which is known as the Poole-Frenkel effect, dominated the I-V behavior of AZO/LP-p-GaN. The fitting result estimated the trap energy level at 0.62 eV below the conduction band edge. In addition, the optical band gap increased from 3.50 eV for as-deposited AZO films to 3.62 eV for 300 °C annealed AZO films because of the increased carrier concentration. The increasing Fermi-level of the 300 °C annealed AZO films enabled the carrier transport to move across the interface into the LP-p-GaN thin films without any thermal activated energy. Thus, the Ohmic behavior of AZO contact can be achieved directly on the low-pressure p-GaN films at room temperature.« less

Poole-Frenkel effect on electrical characterization of Al-doped ZnO films deposited on p-type GaN

NASA Astrophysics Data System (ADS)

Huang, Bohr-Ran; Liao, Chung-Chi; Ke, Wen-Cheng; Chang, Yuan-Ching; Huang, Hao-Ping; Chen, Nai-Chuan

2014-03-01

This paper presents the electrical properties of Al-doped ZnO (AZO) films directly grown on two types of p-type GaN thin films. The low-pressure p-GaN thin films (LP-p-GaN) exhibited structural properties of high-density edge-type threading dislocations (TDs) and compensated defects (i.e., nitrogen vacancy). Compared with high-pressure p-GaN thin films (HP-p-GaN), X-ray photoemission spectroscopy of Ga 3d core levels indicated that the surface Fermi-level shifted toward the higher binding-energy side by approximately 0.7 eV. The high-density edge-type TDs and compensated defects enabled surface Fermi-level shifting above the intrinsic Fermi-level, causing the surface of LP-p-GaN thin films to invert to n-type semiconductor. A highly nonlinear increase in leakage current regarding reverse-bias voltage was observed for AZO/LP-p-GaN. The theoretical fits for the reverse-bias voltage region indicated that the field-assisted thermal ionization of carriers from defect associated traps, which is known as the Poole-Frenkel effect, dominated the I-V behavior of AZO/LP-p-GaN. The fitting result estimated the trap energy level at 0.62 eV below the conduction band edge. In addition, the optical band gap increased from 3.50 eV for as-deposited AZO films to 3.62 eV for 300 °C annealed AZO films because of the increased carrier concentration. The increasing Fermi-level of the 300 °C annealed AZO films enabled the carrier transport to move across the interface into the LP-p-GaN thin films without any thermal activated energy. Thus, the Ohmic behavior of AZO contact can be achieved directly on the low-pressure p-GaN films at room temperature.

On the Physics of Flow Separation Along a Low Pressure Turbine Blade Under Unsteady Flow Conditions

NASA Technical Reports Server (NTRS)

Schobeiri, Meinhard T.; Ozturk, Burak; Ashpis, David E.

2003-01-01

The present study, which is the first of a series of investigations dealing with specific issues of low pressure turbine (LPT) boundary layer aerodynamics, is aimed at providing detailed unsteady boundary flow information to understand the underlying physics of the inception, onset, and extent of the separation zone. A detailed experimental study on the behavior of the separation zone on the suction surface of a highly loaded LPT-blade under periodic unsteady wake flow is presented. Experimental investigations were performed at Texas A&M Turbomachinery Performance and Flow Research Laboratory using a large-scale unsteady turbine cascade research facility with an integrated wake generator and test section unit. To account for a high flow deflection of LPT-cascades at design and off-design operating points, the entire wake generator and test section unit including the traversing system is designed to allow a precise angle adjustment of the cascade relative to the incoming flow. This is done by a hydraulic platform, which simultaneously lifts and rotates the wake generator and test section unit. The unit is then attached to the tunnel exit nozzle with an angular accuracy of better than 0.05 , which is measured electronically. Utilizing a Reynolds number of 110,000 based on the blade suction surface length and the exit velocity, one steady and two different unsteady inlet flowconditions with the corresponding passing frequencies, wake velocities and turbulence intensities are investigated using hot-wire anemometry. In addition to the unsteady boundary layer measurements, blade surface pressure measurements were performed at Re=50,000, 75,000, 100,000, and 125,000 at one steady and two periodic unsteady inlet flow conditions. Detailed unsteady boundary layer measurement identifies the onset and extent of the separation zone as well as its behavior under unsteady wake flow. The results presented in ensemble-averaged and contour plot forms contribute to understanding the physics of the separation phenomenon under periodic unsteady wake flow. Several physical mechanisms are discussed.

Structure, electronic properties, and aggregation behavior of hydroxylated carbon nanotubes

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

López-Oyama, A. B.; Silva-Molina, R. A.; Ruíz-García, J.

2014-11-07

We present a combined experimental and theoretical study to analyze the structure, electronic properties, and aggregation behavior of hydroxylated multiwalled carbon nanotubes (OH–MWCNT). Our MWCNTs have average diameters of ∼2 nm, lengths of approximately 100–300 nm, and a hydroxyl surface coverage θ∼0.1. When deposited on the air/water interface the OH–MWCNTs are partially soluble and the floating units interact and link with each other forming extended foam-like carbon networks. Surface pressure-area isotherms of the nanotube films are performed using the Langmuir balance method at different equilibration times. The films are transferred into a mica substrate and atomic force microscopy images showmore » that the foam like structure is preserved and reveals fine details of their microstructure. Density functional theory calculations performed on model hydroxylated carbon nanotubes show that low energy atomic configurations are found when the OH groups form molecular islands on the nanotube's surface. This patchy behavior for the OH species is expected to produce nanotubes having reduced wettabilities, in line with experimental observations. OH doping yields nanotubes having small HOMO–LUMO energy gaps and generates a nanotube → OH direction for the charge transfer leading to the existence of more hole carriers in the structures. Our synthesized OH–MWCNTs might have promising applications.« less

Structure, electronic properties, and aggregation behavior of hydroxylated carbon nanotubes.

PubMed

López-Oyama, A B; Silva-Molina, R A; Ruíz-García, J; Gámez-Corrales, R; Guirado-López, R A

2014-11-07

We present a combined experimental and theoretical study to analyze the structure, electronic properties, and aggregation behavior of hydroxylated multiwalled carbon nanotubes (OH-MWCNT). Our MWCNTs have average diameters of ~2 nm, lengths of approximately 100-300 nm, and a hydroxyl surface coverage θ~0.1. When deposited on the air/water interface the OH-MWCNTs are partially soluble and the floating units interact and link with each other forming extended foam-like carbon networks. Surface pressure-area isotherms of the nanotube films are performed using the Langmuir balance method at different equilibration times. The films are transferred into a mica substrate and atomic force microscopy images show that the foam like structure is preserved and reveals fine details of their microstructure. Density functional theory calculations performed on model hydroxylated carbon nanotubes show that low energy atomic configurations are found when the OH groups form molecular islands on the nanotube's surface. This patchy behavior for the OH species is expected to produce nanotubes having reduced wettabilities, in line with experimental observations. OH doping yields nanotubes having small HOMO-LUMO energy gaps and generates a nanotube → OH direction for the charge transfer leading to the existence of more hole carriers in the structures. Our synthesized OH-MWCNTs might have promising applications.

Influence of chemistry on wetting dynamics of nanotextured hydrophobic surfaces.

PubMed

Di Mundo, Rosa; Palumbo, Fabio; d'Agostino, Riccardo

2010-04-06

In this work, the role of a chemical parameter, such as the degree of fluorination, on the wetting behavior of nanotextured hydrophobic surfaces is investigated. Texture and chemistry tuning of the surfaces has been accomplished with single batch radiofrequency low-pressure plasma processes. Polystyrene substrates have been textured by CF(4) plasma etching and subsequently covered by thin films with a tunable F-to-C ratio, obtained in discharges fed with C(4)F(8)-C(2)H(4). Measurements of wetting dynamics reveal a regime transition from adhesive-hydrophobic to slippery-superhydrophobic, i.e., from wet to non wet states, as the F-to-C rises at constant topography. Such achievements are strengthened by calculation of the solid fraction of surface water contact area applying Cassie-Baxter advancing and receding equations to water contact angle data of textured and flat reference surfaces.

Surface plasmon oscillations in a semi-bounded semiconductor plasma

NASA Astrophysics Data System (ADS)

M, SHAHMANSOURI; A, P. MISRA

2018-02-01

We study the dispersion properties of surface plasmon (SP) oscillations in a semi-bounded semiconductor plasma with the effects of the Coulomb exchange (CE) force associated with the spin polarization of electrons and holes as well as the effects of the Fermi degenerate pressure and the quantum Bohm potential. Starting from a quantum hydrodynamic model coupled to the Poisson equation, we derive the general dispersion relation for surface plasma waves. Previous results in this context are recovered. The dispersion properties of the surface waves are analyzed in some particular cases of interest and the relative influence of the quantum forces on these waves are also studied for a nano-sized GaAs semiconductor plasma. It is found that the CE effects significantly modify the behaviors of the SP waves. The present results are applicable to understand the propagation characteristics of surface waves in solid density plasmas.

Internal Surface Adsorption of Methane in the Microporous and the Mesoporous Montmorillonite Models

NASA Astrophysics Data System (ADS)

Shao, Changjin; Nie, Dakai; Zhai, Zengqiang; Yang, Zhenqing

2018-05-01

Due to the rising worldwide energy demands and the shortage of natural gas resources, the development of shale gas has become the new research focus in the field of novel energy resources. To understand the adsorption mechanism of shale gas in the reservoir, we use grand canonical Monte Carlo (GCMC) method to investigate the internal surface adsorption behavior of methane (main component of shale gas) in microporous and mesoporous montmorillonite materials for changing pressure, temperature and surface spacing. The results show that the adsorption capacity of methane decreases with increasing temperature while increasing as the surface spacing increases. Especially, the adsorption isotherm of the microporous model has a mutation when the surface spacing is about 10 ˚A. According to the trend for the change in the adsorption capacity, the best scheme for the exploitation of shale gas can be selected so that the mining efficiency is greatly improved.

Manufacturing of Liquid-Embedded Elastomers for Stretchable Electronics

NASA Astrophysics Data System (ADS)

Kramer, Rebecca; Majidi, Carmel; Weaver, James; Wood, Robert

2013-03-01

Future generations of robots, electronics, and assistive medical devices will include systems that are soft, elastically deformable, and may adapt their functionality in unstructured environments. This will require soft active materials for power circuits and sensing of deformation and contact pressure. As the demand for increased elasticity of electrical components heightens, the challenges for functionality revert to basic questions of fabrication, materials, and design. Several designs for soft sensory skins (including strain, pressure and curvature sensors) based on a liquid-embedded-elastomer approach have been developed. This talk will highlight new ``soft MEMS'' manufacturing techniques based on wetting behavior between gallium-indium alloys and elastomers with varying microtextured surface topography. Supported by Harvard MRSEC and the Wyss Institute

Silicone Liner-Free Pressure Sensitive Adhesive Labels

NASA Astrophysics Data System (ADS)

Empereur, Johanne; Chaussy, Didier; Belgacem, Mohamed Naceur

2008-08-01

Pressure sensitive adhesives (PSA) were microencapsulated using simple and complex coacervation and aminoplaste. The microcapsules thus prepared were characterized by FTIR spectroscopy, particle size distribution, rheological behavior and peeling tests. The microcapsules were isolated and found to be out of sticky indicating that the PSAs were indeed encapsulated. The prepared suspensions were deposited at the surface of a paper sheets and the dried labels were then pressed against each other. The ensuing complex was then characterized in terms of peeling forces and showed that the encapsulation using aminoplaste technique of a commercial PSA yielded peel energy of 170 J/m2, which constitutes the recovering of about 68% of the adhesive power of the original non encapsulated PSA.

Experimental Nanofluidics in an individual Nanotube

NASA Astrophysics Data System (ADS)

Siria, Alessandro; Poncharal, Philippe; Biance, Anne Laure; Fulcrand, Remy; Purcell, Stephen; Bocquet, Lyderic

2012-11-01

Building new devices that benefit from the strange transport behavior of fluids at nanoscales is an open and worthy challenge that may lead to new scientific and technological paradigms. We present here a new class of nanofluidic device, made of individual Boron-Nitride (BN) nanotube inserted in a pierced membrane and connecting two macroscopic reservoirs. We explore fluidic transport inside a single BN nanotube under electric fields, pressure drops, chemical gradients, and combinations of these. We show that in this transmembrane geometry, the pressure-driven streaming current is voltage gated, with an apparent electro-osmotic zeta potential raising up to one volt. Further, we measured the current induced by ion concentration gradients and show its dependency on the surface charge.

Vibration studies of a lightweight three-sided membrane suitable for space application

NASA Technical Reports Server (NTRS)

Sewell, J. L.; Miserentino, R.; Pappa, R. S.

1983-01-01

Vibration studies carried out in a vacuum chamber are reported for a three-sided membrane with inwardly curved edges. Uniform tension was transmitted by thin steel cables encased in the edges. Variation of ambient air pressure from atmospheric to near vacuum resulted in increased response frequencies and amplitudes. The first few vibration modes measured in a near vacuum are shown to be predictable by a finite element structural analysis over a range of applied tension loads. The complicated vibration mode behavior observed during tests at various air pressures is studied analytically with a nonstructural effective air-mass approximation. The membrane structure is a candidate for reflective surfaces in space antennas.

[Synthesis and monolayer behaviors of 4-methyl-5-hydroxy-ethyl isothiazole stearic ester].

PubMed

Shen, Yu-hua; Kong, Lin; Yang, Jia-xiang; Xie, An-jian; Qian, Jia-sheng; Ouyang, Jian-ming; Xia, Bing

2002-12-01

4-methyl-5-hydroxy-ethyl isothiazole stearic ester (HISE) was synthesized and characterized by FTIR spectroscopy, 1H NMR and MS. The monolayer-forming ability of HISE was studied in subphases with different pH values using isotherms of surface pressure-area per molecule (pi-A). It was observed that the collapse pressure and the film-forming ability of the monolayers of HISE increased gradually as pH values ascended. Research of differentiated pi-A curves (d pi(/dA-A) indicated that there were one or two phase change points during the compressing process, and the incompressibility and the stability of HISE monolayers on alkalescent subphases were better than on acid subphases.

Oxidation Behavior of HfB2-SiC Materials in Dissociated Environments

NASA Technical Reports Server (NTRS)

Ellerby, Don; Irby, Edward; Johnson, Sylvia M.; Beckman, Sarah; Gusman, Michael; Gasch, Matthew

2002-01-01

Hafnium diboride based materials have shown promise for use in extremely high temperature applications, such as sharp leading edges on future reentry vehicles. During reentry, the oxygen and nitrogen in the atmosphere are dissociated by the shock layer ahead of the sharp leading edge such that surface reactions are determined by reactions of monatomic oxygen and nitrogen rather than O2, and N2. Simulation of the reentry environment on the ground requires the use of arc jet (plasma jet) facilities that provide monatomic species and are the closest approximation to actual flight conditions. Simple static or flowing oxidation studies under ambient pressures and atmospheres are not adequate to develop an understanding of a materials behavior in flight. Arc jet testing is required to provide the appropriate stagnation pressures, heat fluxes, enthalpies, heat loads and atmospheres encountered during flight. This work looks at the response of HfB2/SiC materials exposed to various simulated reentry environments.

Measurement of behavior of secondary sealing areas of rotary engine apex seals - Two-piece nonsplit and three-piece slanted horizontal split types

NASA Astrophysics Data System (ADS)

Matsuura, Kenji; Terasaki, Kazuo; Yamane, Katsuki

1992-12-01

Behavior measurements have been made with two displacement sensors and an underseal pressure sensor, using an overhanging eccentric shaft-type single-rotor research engine equipped with a packaged multichannel slip ring. The two-piece seal was tilted to the leading and trailing sides of a seal slot during its travel along the rotor housing surface and vibrated on the top end of the leading side of the slot as a fulcrum after the shift from the trailing to the leading side of the slot after the minor axis on the spark plug side. As for the three-piece seal, its top part was also tilted in all operating conditions, although its bottom part made effective area contact with the side of the slot under light load conditions up to medium engine speeds. The working chamber pressure was induced in the underseal in the same manner as with the two-piece type.

Understanding the Fundamental Roles of Momentum and Vorticity Injections in Flow Control

DTIC Science & Technology

2016-09-02

production by pitched and skewed jets in a turbulent boundary layer . AIAA Journal 30, 640–647. DISTRIBUTION A: Distribution approved for public release...adverse pressure gradient along the suction surface, which ultimately results in a separated boundary layer . Such behavior of the boundary layer can... boundary layer either directly or by utilizing free stream momentum to energize the boundary layer (Gad-el-Hak, 2000a). Directly adding momentum to the

Linear and nonlinear 2D finite element analysis of sloshing modes and pressures in rectangular tanks subject to horizontal harmonic motions

NASA Astrophysics Data System (ADS)

Virella, Juan C.; Prato, Carlos A.; Godoy, Luis A.

2008-05-01

The influence of nonlinear wave theory on the sloshing natural periods and their modal pressure distributions are investigated for rectangular tanks under the assumption of two-dimensional behavior. Natural periods and mode shapes are computed and compared for both linear wave theory (LWT) and nonlinear wave theory (NLWT) models, using the finite element package ABAQUS. Linear wave theory is implemented in an acoustic model, whereas a plane strain problem with large displacements is used in NLWT. Pressure distributions acting on the tank walls are obtained for the first three sloshing modes using both linear and nonlinear wave theory. It is found that the nonlinearity does not have significant effects on the natural sloshing periods. For the sloshing pressures on the tank walls, different distributions were found using linear and nonlinear wave theory models. However, in all cases studied, the linear wave theory conservatively estimated the magnitude of the pressure distribution, whereas larger pressures resultant heights were obtained when using the nonlinear theory. It is concluded that the nonlinearity of the surface wave does not have major effects in the pressure distribution on the walls for rectangular tanks.

On the mechanical interaction between a fluid-filled fracture and the earth's surface

USGS Publications Warehouse

Pollard, D.D.; Holzhausen, G.

1979-01-01

The mechanical interaction between a fluid-filled fracture (e.g., hydraulic fracture joint, or igneous dike) and the earth's surface is analyzed using a two-dimensional elastic solution for a slit of arbitrary inclination buried beneath a horizontal free surface and subjected to an arbitrary pressure distribution. The solution is obtained by iteratively superimposing two fundamental sets of analytical solutions. For uniform internal pressure the slit behaves essentially as if it were in an infinite region if the depth-to-center is three times greater than the half-length. For shallower slits interaction with the free surface is pronounced: stresses and displacements near the slit differ by more than 10% from values for the deeply buried slit. The following changes are noted as the depth-to-center decreases: 1. (1) the mode I stress intensity factor increases for both ends of the slit, but more rapidly at the upper end; 2. (2) the mode II stress-intensity factor is significantly different from zero (except for vertical slits) suggesting propagation out of the original plane of the slit; 3. (3) displacements of the slit wall are asymmetric such that the slit gaps open more widely near the upper end. Similar changes are noted if fluid density creates a linear pressure gradient that is smaller than the lithostatic gradient. Under such conditions natural fractures should propagate preferentially upward toward the earth's surface requiring less pressure as they grow in length. If deformation near the surface is of interest, the model should account explicitly for the free surface. Stresses and displacements at the free surface are not approximated very well by values calculated along a line in an infinite region, even when the slit is far from the line. As depth-to-center of a shallow pressurized slit decreases, the following changes are noted: 1. (1) displacements of the free surface increase to the same order of magnitude as the displacements of the slit walls, 2. (2) tensile stresses of magnitude greater than the pressure in the slit are concentrated along the free surface. The relative surface displacements over a shallow vertical slit are downward over the slit and upward to both sides of this area. The tensile stress acting parallel to the free surface over a shallow vertical slit is concentrated in two maxima adjacent to a point of very low stress immediately over the slit. The solution is used to estimate the length-to-depth ratio at which igneous sills have gained sufficient leverage on overlying strata to bend these strata upward and form a laccolith. The pronounced mode II stress intensity associated with shallow horizontal slits explains the tendency for some sills to climb to higher stratigraphie horizons as they grow in length. The bimodal tensile stress concentration over shallow vertical slits correlates qualitatively with the distribution of cracks and normal faults which flank fissure eruptions on volcanoes. The solution may be used to analyze surface displacements and tilts over massive hydraulic fractures in oil fields and to understand the behavior of hydraulic fractures in granite quarries. ?? 1979.

Multiaxial behavior of foams - Experiments and modeling

NASA Astrophysics Data System (ADS)

Maheo, Laurent; Guérard, Sandra; Rio, Gérard; Donnard, Adrien; Viot, Philippe

2015-09-01

Cellular materials are strongly related to pressure level inside the material. It is therefore important to use experiments which can highlight (i) the pressure-volume behavior, (ii) the shear-shape behavior for different pressure level. Authors propose to use hydrostatic compressive, shear and combined pressure-shear tests to determine cellular materials behavior. Finite Element Modeling must take into account these behavior specificities. Authors chose to use a behavior law with a Hyperelastic, a Viscous and a Hysteretic contributions. Specific developments has been performed on the Hyperelastic one by separating the spherical and the deviatoric part to take into account volume change and shape change characteristics of cellular materials.

Tactile Perception of Roughness and Hardness to Discriminate Materials by Friction-Induced Vibration

PubMed Central

Zhao, Xuezeng

2017-01-01

The human fingertip is an exquisitely powerful bio-tactile sensor in perceiving different materials based on various highly-sensitive mechanoreceptors distributed all over the skin. The tactile perception of surface roughness and material hardness can be estimated by skin vibrations generated during a fingertip stroking of a surface instead of being maintained in a static position. Moreover, reciprocating sliding with increasing velocities and pressures are two common behaviors in humans to discriminate different materials, but the question remains as to what the correlation of the sliding velocity and normal load on the tactile perceptions of surface roughness and hardness is for material discrimination. In order to investigate this correlation, a finger-inspired crossed-I beam structure tactile tester has been designed to mimic the anthropic tactile discrimination behaviors. A novel method of characterizing the fast Fourier transform integral (FFT) slope of the vibration acceleration signal generated from fingertip rubbing on surfaces at increasing sliding velocity and normal load, respectively, are defined as kv and kw, and is proposed to discriminate the surface roughness and hardness of different materials. Over eight types of materials were tested, and they proved the capability and advantages of this high tactile-discriminating method. Our study may find applications in investigating humanoid robot perceptual abilities. PMID:29182538

Mechanism of gas saturated oil viscosity anomaly near to phase transition point

NASA Astrophysics Data System (ADS)

Suleimanov, Baghir A.; Abbasov, Elkhan M.; Sisenbayeva, Marziya R.

2017-01-01

The article presents experimental studies of the phase behavior by the flash liberation test and of the viscosity of the live oil at different pressures. Unlike the typical studies at the pressure near the saturation pressure, the measurements were conducted at a relatively small pressure increment of 0.08-0.25 MPa. The viscosity anomaly was discovered experimentally near to the phase transition point in the range of the pressure levels P/Pb = 1-1.14 (Pb—bubble point pressure) and shows that it decreases about 70 times in comparison to the viscosity at the reservoir pressure. It was found that the bubble point pressure decreases significantly (up to 36%) with surfactant addition. Furthermore, the viscosity of the live oil at the surfactant concentration of 5 wt. % decreases almost 37 times in comparison to the viscosity at the reservoir pressure. The mechanism of observed effects was suggested based on the formation of the stable subcritical gas nuclei and associated slippage effect. The mechanism for the stabilization of the subcritical nuclei by the combined action of the surface and electrical forces, as well as the morphology of the formed nanobubbles, was considered. The model for determining the oil viscosity taking into account the slippage effect was suggested.

Change in Frictional Behavior during Olivine Serpentinization

NASA Astrophysics Data System (ADS)

Xing, T.; Zhu, W.; French, M. E.; Belzer, B.

2017-12-01

Hydration of mantle peridotites (serpentinization) is pervasive at plate boundaries. It is widely accepted that serpentinization is intrinsically linked to hydromechanical processes within the sub-seafloor, where the interplay between cracking, fluid supply and chemical reactions is responsible for a spectrum of fault slip, from earthquake swarms at the transform faults, to slow slip events at the subduction zone. Previous studies demonstrate that serpentine minerals can either promote slip or creep depend on many factors that include sliding velocity, temperature, pressure, interstitial fluids, etc. One missing link from the experimental investigation of serpentine to observations of tectonic faults is the extent of alteration necessary for changing the frictional behaviors. We quantify changes in frictional behavior due to serpentinization by conducting experiments after in-situ serpentinization of olivine gouge. In the sample configuration a layer of powder is sandwiched between porous sandstone blocks with 35° saw-cut surface. The starting material of fine-grained (63 120 µm) olivine powder is reacted with deionized water for 72 hours at 150°C before loading starts. Under the conventional triaxial configuration, the sample is stressed until sliding occurs within the gouge. A series of velocity-steps is then performed to measure the response of friction coefficient to variations of sliding velocity from which the rate-and-state parameters are deduced. For comparison, we measured the frictional behavior of unaltered olivine and pure serpentine gouges.Our results confirm that serpentinization causes reduced frictional strength and velocity weakening. In unaltered olivine gouge, an increase in frictional resistance with increasing sliding velocity is observed, whereas the serpentinized olivine and serpentine gouges favor velocity weakening behaviors at the same conditions. Furthermore, we observed that high pore pressures cause velocity weakening in olivine but velocity strengthening in serpentine. The alteration of frictional behavior is considerable even though the fraction of altered olivine is miniscule. Contrasting frictional responses between olivine and serpentine gouges in response to high pore pressure shed some light on faulting in ultramafic chemical environments.

Process parameter and surface morphology of pineapple leaf electrospun nanofibers (PALF)

NASA Astrophysics Data System (ADS)

Surip, S. N.; Aziz, F. M. A.; Bonnia, N. N.; Sekak, K. A.; Zakaria, M. N.

2017-09-01

In recent times, nanofibers have attracted the attention of researchers due to their pronounced micro and nano structural characteristics that enable the development of advanced materials that have sophisticated applications. The production of nanofibers by the electrospinning process is influenced both by the electrostatic forces and the viscoelastic behavior of the polymer. Process parameters, like solution feed rate, applied voltage, nozzle-collector distance, and spinning environment, and material properties, like solution concentration, viscosity, surface tension, conductivity, and solvent vapor pressure, influence the structure and properties of electrospun nanofibers. Significant work has been done to characterize the properties of PALF nanofibers as a function of process and material parameters.

Microstructure and Corrosion Characterization of Squeeze Cast AM50 Magnesium Alloys

NASA Astrophysics Data System (ADS)

Sachdeva, Deepika; Tiwari, Shashank; Sundarraj, Suresh; Luo, Alan A.

2010-12-01

Squeeze casting of magnesium alloys potentially can be used in lightweight chassis components such as control arms and knuckles. This study documents the microstructural analysis and corrosion behavior of AM50 alloys squeeze cast at different pressures between 40 and 120 MPa and compares them with high-pressure die cast (HPDC) AM50 alloy castings and an AM50 squeeze cast prototype control arm. Although the corrosion rates of the squeeze cast samples are slightly higher than those observed for the HPDC AM50 alloy, the former does produce virtually porosity-free castings that are required for structural applications like control arms and wheels. This outcome is extremely encouraging as it provides an opportunity for additional alloy and process development by squeeze casting that has remained relatively unexplored for magnesium alloys compared with aluminum. Among the microstructural parameters analyzed, it seems that the β-phase interfacial area, indicating a greater degree of β network, leads to a lower corrosion rate. Weight loss was the better method for determining corrosion behavior in these alloys that contain a large fraction of second phase, which can cause perturbations to an overall uniform surface corrosion behavior.

Anomalous compression behavior of ˜12 nm nanocrystalline TiO2

NASA Astrophysics Data System (ADS)

Wang, Qiming; Li, Shourui; Peng, Fang; Lei, Li; Hu, Qiwei; Wang, Pei; Nan, Xiaolong; Liu, Jing; Zhu, Wenjun; He, Duanwei

2017-06-01

When the grain size decreases, there inevitably exists a critical size (dc) where the contribution of surface atoms to the physical properties is competitive with that of the interior atoms, giving rise to a wide variety of new phenomena. The behavior of granular materials near dc is particularly interesting because of the crossover, a continuous transition from one type of mechanism to another. In situ high-pressure x-ray diffraction experiments showed that the compression curve of nanocrystalline anatase TiO2 with grain size near dc reached a platform after about 5%-6% of deformation under hydrostatic compression. Eventually, the unit cell volume of anatase expanded at ˜14-16 GPa. We propose that the anomalous compression behavior is attributed to the formation and thickening of the stiff high density amorphous shell under high pressure, giving rise to a great arching effect at the grain boundary at the nanolevel. This process results in a remarkable difference in stress between inside and outside of the shell, generating the illusions of the hardening and the negative compressibility. This study offers a new insight into the mechanical properties of nanomaterials under extreme conditions.

Investigation on single walled carbon nanotube thin films deposited by Langmuir Blodgett method

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

Vishalli,, E-mail: vishalli-2008@yahoo.com; Dharamvir, Keya; Kaur, Ramneek

2015-05-15

Langmuir Blodgett is a technique to deposit a homogeneous film with a fine control over thickness and molecular organization. Thin films of functionalized SWCNTs have been prepared by Langmuir Blodgett method. The good surface spreading properties of SWCNTs at air/water interface are indicated by surface pressure-area isotherm and the monolayer formed on water surface is transferred onto the quartz substrate by vertical dipping. A multilayer film is thus obtained in a layer by layer manner. The film is characterized by Atomic Force Microscope (AFM), UV-Vis-NIR spectroscopy and FTIR.AFM shows the surface morphology of the deposited film. UV-Vis-NIR spectroscopy shows themore » characteristic peaks of semiconducting SWCNTs. The uniformity of LB film can be used further in understanding the optical and electrical behavior of these materials.« less

Physical and chemical behavior of flowing endothermic jet fuels

NASA Astrophysics Data System (ADS)

Ward, Thomas Arthur

Hydrocarbon fuels have been used as cooling media for aircraft jet engines for decades. However, modern aircraft engines are reaching a practical heat transfer limit beyond which the convective heat transfer provided by fuels is no longer adequate. One solution is to use an endothermic fuel that absorbs heat through a series of pyrolytic chemical reactions. However, many of the physical and chemical processes involved in endothermic fuel degradation are not well understood. The purpose of this dissertation is to study different characteristics of endothermic fuels using experiments and computational models. In the first section, data from three flow experiments using heated Jet-A fuel and additives were analyzed (with the aid of CFD calculations) to study the effects of treated surfaces on surface deposition. Surface deposition is the primary impediment in creating an operational endothermic fuel heat exchanger system, because deposits can obstruct fuel pathways causing a catastrophic system failure. As heated fuel flows through a fuel system, trace species within the fuel react with dissolved O2 to form surface deposits. At relatively higher fuel temperatures, the dissolved O2 is depleted, and pyrolytic chemistry becomes dominant (at temperatures greater than ˜500 °C). In the first experiment, the dissolved O2 consumption of heated fuel was measured on different surface types over a range of temperatures. It is found that use of treated tubes significantly delays oxidation of the fuel. In the second experiment, the treated length of tubing was progressively increased, which varied the characteristics of the thermal-oxidative deposits formed. In the third experiment, pyrolytic surface deposition in either fully treated or untreated tubes is studied. It is found that the treated surface significantly reduced the formation of surface deposits for both thermal oxidative and pyrolytic degradation mechanisms. Moreover, it is found that the chemical reactions resulting in pyrolytic deposition on the untreated surface are more sensitive to pressure level than those causing pyrolytic deposition on the treated surface. The second section describes the development of a two-dimensional computational model of the heat and mass transport associated with a flowing fuel using a unique global chemical kinetics model. This model calculates the changing flow properties of a supercritical reacting fuel by use of experimentally derived proportional product distributions. The third section studies the effects of pressure on flowing; mildly-cracked, supercritical n-decane. The experimental results are studied with the aid of the computational model described in section 2, expanded to deal with variable pressures. The experiments indicate that increasing pressure enhances the processes in which n-decane converts to (C5--C9) n-alkane products instead of decomposing into lower molecular weight products (C1--C4): Increasing pressure also increases the overall conversion rate of supercritical n-decane flowing through a reactor. Computational modeling of the experiment shows how the flow properties are influenced by pressure. (Abstract shortened by UMI.)

Numerical Simulation of Thin Film Breakup on Nonwettable Surfaces

NASA Astrophysics Data System (ADS)

Suzzi, N.; Croce, G.

2017-01-01

When a continuous film flows on a nonwettable substrate surface, it may break up, with the consequent formation of a dry-patch. The actual shape of the resulting water layer is of great interest in several engineering applications, from in-flight icing simulation to finned dehumidifier behavior modeling. Here, a 2D numerical solver for the prediction of film flow behavior is presented. The effect of the contact line is introduced via the disjoining pressure terms, and both gravity and shear are included in the formulation. The code is validated with literature experimental data for the case of a stationary dry-patch on an inclined plane. Detailed numerical results are compared with literature simplified model prediction. Numerical simulation are then performed in order to predict the threshold value of the film thickness allowing for film breakup and to analyze the dependence of the dynamic contact angle on film velocity and position along the contact line. Those informations will be useful in order to efficiently predict more complex configuration involving multiple breakups on arbitrarily curved substrate surfaces (as those involved in in-flight icing phenomena on aircraft).

Effect of Ionic Soil Stabilizers on Soil-Water Characteristic of Special Clay

NASA Astrophysics Data System (ADS)

Cui, D.; Xiang, W.

2011-12-01

The engineering properties of special clay are conventionally improved through the use of chemical additive such as ionic soil stabilizer (ISS). Such special clays are often referred to as stabilized or treated clays. The soil-water characteristic curves (SWCC) of special clays from Henan province and Hubei province were measured both in natural and stabilized conditions using the pressure plate apparatus in the suction range of 0-500 kPa. The SWCC results are used to interpret the special clays behavior due to stabilizer treatment. In addition, relationships were developed between the basic clay and stabilized properties such as specific surface area and pore size distribution. The analysis showed that specific surface area decreases, cumulative pore volume and average pore size diameter decrease, dehydration rate slows and the thickness of water film thins after treatment with Ionic Soil Stabilizer. The research data and interpretation analysis presented here can be extended to understand the water film change behaviors influencing the mechanical and physical properties of stabilized special clay soils. KEY WORDS: ionic soil stabilizer, special clay, pore size diameter, specific surface area, soil water characteristic curve, water film

Physically-Based Modelling and Real-Time Simulation of Fluids.

NASA Astrophysics Data System (ADS)

Chen, Jim Xiong

1995-01-01

Simulating physically realistic complex fluid behaviors presents an extremely challenging problem for computer graphics researchers. Such behaviors include the effects of driving boats through water, blending differently colored fluids, rain falling and flowing on a terrain, fluids interacting in a Distributed Interactive Simulation (DIS), etc. Such capabilities are useful in computer art, advertising, education, entertainment, and training. We present a new method for physically-based modeling and real-time simulation of fluids in computer graphics and dynamic virtual environments. By solving the 2D Navier -Stokes equations using a CFD method, we map the surface into 3D using the corresponding pressures in the fluid flow field. This achieves realistic real-time fluid surface behaviors by employing the physical governing laws of fluids but avoiding extensive 3D fluid dynamics computations. To complement the surface behaviors, we calculate fluid volume and external boundary changes separately to achieve full 3D general fluid flow. To simulate physical activities in a DIS, we introduce a mechanism which uses a uniform time scale proportional to the clock-time and variable time-slicing to synchronize physical models such as fluids in the networked environment. Our approach can simulate many different fluid behaviors by changing the internal or external boundary conditions. It can model different kinds of fluids by varying the Reynolds number. It can simulate objects moving or floating in fluids. It can also produce synchronized general fluid flows in a DIS. Our model can serve as a testbed to simulate many other fluid phenomena which have never been successfully modeled previously.

Surface Interactions and Confinement of Methane: A High Pressure Magic Angle Spinning NMR and Computational Chemistry Study

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

Ok, Salim; Hoyt, David W.; Andersen, Amity

Characterization and modeling of the molecular-level behavior of simple hydrocarbon gases, such as methane, in the presence of both nonporous and nanoporous mineral matrices allows for predictive understanding of important processes in engineered and natural systems. In this study, we observed changes in local electromagnetic environments of the carbon atoms in methane under conditions of high pressure (up to 130 bar) and moderate temperature (up to 346 K) with 13C magic-angle spinning (MAS) NMR spectroscopy while the methane gas was mixed with two model solid substrates: a fumed nonporous, 12 nm particle size silica and a mesoporous silica with 200more » nm particle size and 4 nm average pore diameter. Examination of the interactions between methane and the silica systems over temperatures and pressures that include the supercritical regime was allowed by a novel high pressure MAS sample containment system, which provided high resolution spectra collected under in situ conditions. There was no significant thermal effects were found for the observed 13C chemical shifts at all pressures studied here (28.2, 32.6, 56.4, 65.1, 112.7, and 130.3 bar) for pure methane. However, the 13C chemical shifts of resonances arising from confined methane changed slightly with changes in temperature in mixtures with mesoporous silica. The chemical shift values of 13C nuclides in methane change measurably as a function of pressure both in the pure state and in mixtures with both silica matrices, with a more pronounced shift when meso-porous silica is present. Molecular-level simulations utilizing GCMC, MD, and DFT confirm qualitatively that the experimentally measured changes are attributed to interactions of methane with the hydroxylated silica surfaces as well as densification of methane within nanopores and on pore surfaces.« less

Surface Interactions and Confinement of Methane: A High Pressure Magic Angle Spinning NMR and Computational Chemistry Study

DOE PAGES

Ok, Salim; Hoyt, David W.; Andersen, Amity; ...

2017-01-18

Characterization and modeling of the molecular-level behavior of simple hydrocarbon gases, such as methane, in the presence of both nonporous and nanoporous mineral matrices allows for predictive understanding of important processes in engineered and natural systems. In this study, we observed changes in local electromagnetic environments of the carbon atoms in methane under conditions of high pressure (up to 130 bar) and moderate temperature (up to 346 K) with 13C magic-angle spinning (MAS) NMR spectroscopy while the methane gas was mixed with two model solid substrates: a fumed nonporous, 12 nm particle size silica and a mesoporous silica with 200more » nm particle size and 4 nm average pore diameter. Examination of the interactions between methane and the silica systems over temperatures and pressures that include the supercritical regime was allowed by a novel high pressure MAS sample containment system, which provided high resolution spectra collected under in situ conditions. There was no significant thermal effects were found for the observed 13C chemical shifts at all pressures studied here (28.2, 32.6, 56.4, 65.1, 112.7, and 130.3 bar) for pure methane. However, the 13C chemical shifts of resonances arising from confined methane changed slightly with changes in temperature in mixtures with mesoporous silica. The chemical shift values of 13C nuclides in methane change measurably as a function of pressure both in the pure state and in mixtures with both silica matrices, with a more pronounced shift when meso-porous silica is present. Molecular-level simulations utilizing GCMC, MD, and DFT confirm qualitatively that the experimentally measured changes are attributed to interactions of methane with the hydroxylated silica surfaces as well as densification of methane within nanopores and on pore surfaces.« less

Surface Interactions and Confinement of Methane: A High Pressure Magic Angle Spinning NMR and Computational Chemistry Study

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

Ok, Salim; Hoyt, David W.; Andersen, Amity

Characterization and modeling of the molecular-level behavior of simple hydrocarbon gases, such as methane, in the presence of both nonporous and nano-porous mineral matrices allows for predictive understanding of important processes in engineered and natural systems. In this study, changes in local electromagnetic environments of the carbon atoms in methane under conditions of high pressure (up to 130 bar) and moderate temperature (up to 346 K) were observed with 13C magic-angle spinning (MAS) NMR spectroscopy while the methane gas was mixed with two model solid substrates: a fumed non-porous, 12 nm particle size silica and a mesoporous silica with 200more » nm particle size and 4 nm average pore diameter. Examination of the interactions between methane and the silica systems over temperatures and pressures that include the supercritical regime was allowed by a novel high pressure MAS sample containment system, which provided high resolution spectra collected under in situ conditions. For pure methane, no significant thermal effects were found for the observed 13C chemical shifts at all pressures studied here (28.2 bar, 32.6 bar, 56.4 bar, 65.1 bar, 112.7 bar, and 130.3 bar). However, the 13C chemical shifts of resonances arising from confined methane changed slightly with changes in temperature in mixtures with mesoporous silica. The chemical shift values of 13C nuclides in methane change measurably as a function of pressure both in the pure state and in mixtures with both silica matrices, with a more pronounced shift when meso-porous silica is present. Molecular-level simulations utilizing GCMC, MD and DFT confirm qualitatively that the experimentally measured changes are attributed to interactions of methane with the hydroxylated silica surfaces as well as densification of methane within nanopores and on pore surfaces.« less

Investigation into Behavior of a Steam-Water Mixture Flow Through Holes in a Submerged Perforated Sheet at High Void Fractions

NASA Astrophysics Data System (ADS)

Melikhov, V. I.; Melikhov, O. I.; Nerovnov, A. A.; Nikonov, S. M.

2018-01-01

Processing of experimental data on the pressure difference across a submerged perforated sheet (SPS) revealed that, at sufficiently high void fractions under SPS, the pressure difference across it became less than the pressure difference for the pure steam stream with the same flowrate. To find the cause of this, the effect of a liquid film, which can be formed on the SPS upstream surface as a result of water droplets' impact and can smooth over sharp edges of holes in SDS, was examined. This can decrease the pressure drop across the sharp edges of holes. This assumption was checked through numerical solution to several model problems in the axisymmetric formulation for a steam flow in a round pipe with an orifice. The flow of steam and water was modeled using the viscous incompressible liquid approximation, while the turbulence was described by the k-ɛ model. The evolution of the interfacial area was modeled using the VOF model. The following model problems of steam flow through an orifice were studied: a single-phase flow, a flow through the orifice with a liquid film on its upstream surface, a flow through a chamfered hole, and a flow through the orifice with a liquid film on its upstream surface without liquid supply to the film. The predictions demonstrate that even the approximate account of the liquid film effect on the steam flow yields a considerable decrease in the pressure drop across the hole (from 8 to 24%) due to smoothing its sharp outlet edges over. This makes it possible to make a conclusion that the cause of a decrease in the pressure drop across SPS observed in the experiments at high void fractions is the formation of a liquid film, which smooths the sharp edges of the hole.

Experimental study of combustion in hydrogen peroxide hybrid rockets

NASA Astrophysics Data System (ADS)

Wernimont, Eric John

Combustion behavior in a hydrogen peroxide oxidized hybrid rocket motor is investigated with a series of experiments. Hybrid chemical rocket propulsion is presently of interest due to reduced system complexity compared to classical chemical propulsion systems. Reduced system complexity, by use of a storable oxidizer and a hybrid configuration, is expected to reduce propulsive costs. The fuel in this study is polyethylene which has the potential of continuous manufacture leading to further reduced system costs. The study investigated parameters of interest for nominal design of a full scale hydrogen peroxide oxidized hybrid rocket. Amongst these parameters is the influence of chamber pressure, mass flux, fuel molecular weight and fuel density on fuel regression rate. Effects of chamber pressure and aft combustion length on combustion efficiency and non-acoustic combustion oscillations are also examined. The fuel regression behavior is found to be strongly influenced by both chamber pressure and mass flux. Combustion efficiencies in the upper 90% range are attained by simple changes to the aft combustion chamber length as well as increased combustion pressure. Fuel burning surface is found to be influenced by the density of the polyethylene polymer as well as molecular weight. The combustion is observed to be exceptionally smooth (oscillations less than 5% zero-to-peak of mean) in all motors tested in this program. Tests using both a single port fuel gain and a novel radial flow hybrid are also performed.

Improvement of the Laser-Induced Breakdown Spectroscopy method sensitivity by the usage of combination of Ag-nanoparticles and vacuum conditions

NASA Astrophysics Data System (ADS)

Sládková, Lucia; Prochazka, David; Pořízka, Pavel; Škarková, Pavlína; Remešová, Michaela; Hrdlička, Aleš; Novotný, Karel; Čelko, Ladislav; Kaiser, Jozef

2017-01-01

In this work we studied the effect of vacuum (low pressure) conditions on the behavior of laser-induced plasma (LIP) created on a sample surface covered with silver nanoparticles (Ag-NPs), i.e. Nanoparticles-Enhanced Laser-Induced Breakdown Spectroscopy (NELIBS) experiment in a vacuum. The focus was put on the step by step optimization of the measurement parameters, such as energy of the laser pulse, temporally resolved detection, ambient pressure, and different content of Ag-NPs applied on the sample surface. The measurement parameters were optimized in order to achieve the greatest enhancement represented as the signal-to-noise ratio (SNR) of NELIBS signal to the SNR of LIBS signal. The presence of NPs involved in the ablation process enhances LIP intensity; hence the improvement in the analytical sensitivity was yielded. A leaded brass standard was analyzed with the emphasis on the signal enhancement of Pb traces. We gained enhancement by a factor of four. Although the low pressure had no significant influence on the LIP signal enhancement compared to that under ambient conditions, the SNR values were noticeably improved with the implementation of the NPs.

Cavitation during wire brushing

NASA Astrophysics Data System (ADS)

Li, Bo; Zou, Jun; Ji, Chen

2016-11-01

In our daily life, brush is often used to scrub the surface of objects, for example, teeth, pots, shoes, pool, etc. And cleaning rust and stripping paint are accomplished using wire brush. Wire brushes also can be used to clean the teeth for large animals, such as horses, crocodiles. By observing brushing process in water, we capture the cavitation phenomenon on the track of moving brush wire. It shows that the cavitation also can affect the surface. In order to take clear and entire pictures of cavity, a simplified model of one stainless steel wire brushing a boss is adopted in our experiment. A transparent organic tank filled with deionized water is used as a view box. And a high speed video camera is used to record the sequences. In experiment, ambient pressure is atmospheric pressure and deionized water temperature is kept at home temperature. An obvious beautiful flabellate cavity zone appears behind the moving steel wire. The fluctuation of pressure near cavity is recorded by a hydrophone. More movies and pictures are used to show the behaviors of cavitation bubble following a restoring wire. Beautiful tracking cavitation bubble cluster is captured and recorded to show.

Scaling behavior of columnar structure during physical vapor deposition

NASA Astrophysics Data System (ADS)

Meese, W. J.; Lu, T.-M.

2018-02-01

The statistical effects of different conditions in physical vapor deposition, such as sputter deposition, have on thin film morphology has long been the subject of interest. One notable effect is that of column development due to differential chamber pressure in the well-known empirical model called the Thornton's Structure Zone Model. The model is qualitative in nature and theoretical understanding with quantitative predictions of the morphology is still lacking due, in part, to the absence of a quantitative description of the incident flux distribution on the growth front. In this work, we propose an incident Gaussian flux model developed from a series of binary hard-sphere collisions and simulate its effects using Monte Carlo methods and a solid-on-solid growth scheme. We also propose an approximate cosine-power distribution for faster Monte Carlo sampling. With this model, it is observed that higher chamber pressures widen the average deposition angle, and similarly increase the growth of column diameters (or lateral correlation length) and the column-to-column separation (film surface wavelength). We treat both the column diameter and the surface wavelength as power laws. It is seen that both the column diameter exponent and the wavelength exponent are very sensitive to changes in pressure for low pressures (0.13 Pa to 0.80 Pa); meanwhile, both exponents saturate for higher pressures (0.80 Pa to 6.7 Pa) around a value of 0.6. These predictions will serve as guides to future experiments for quantitative description of the film morphology under a wide range of vapor pressure.

CALIBRATION AND TESTING OF SONIC STIMULATION TECHNOLOGIES

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

Roger Turpening; Wayne Pennington; Christopher Schmidt

2005-03-01

In conjunction with Baker Atlas Inc. Michigan Technological University devised a system capable of recording the earth motion and pressure due to downhole and surface seismic sources. The essential elements of the system are (1) a borehole test site that will remain constant and is available all the time and for any length of time, (2) a downhole sonde that will itself remain constant and, because of its downhole digitization feature, does not require the wireline or surface recording components to remain constant, and (3) a set of procedures that ensures that the amplitude and frequency parameters of a widemore » range of sources can be compared with confidence. This system was used to record four seismic sources, three downhole sources and one surface source. A single activation of each of the downhole sources was not seen on time traces above the ambient noise, however, one sweep of the surface source, a small vertical vibrator, was easily seen in a time trace. One of the downhole sources was seen by means of a spike in its spectrum and a second downhole source was clearly seen after correlation and stacking. The surface vibrator produced a peak to peak particle motion signal of approximately 4.5 x 10{sup -5} cm/sec and a peak to peak pressure of approx. 2.5 x 10{sup -7} microPascals at a depth of 1,485 ft. Theoretical advances were made with our partner, Dr. Igor Beresnev at Iowa State University. A theory has been developed to account for the behavior of oil ganglia trapped in pore throats, and their ultimate release through the additional incremental pressure associated with sonic stimulation.« less

Redox variations in Mauna Kea lavas, the oxygen fugacity of the Hawaiian plume, and the role of volcanic gases in Earth’s oxygenation

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

Brounce, Maryjo; Stolper, Edward; Eiler, John

The behavior of C, H, and S in the solid Earth depends on their oxidation states, which are related to oxygen fugacity (fO2). Volcanic degassing is a source of these elements to Earth’s surface; therefore, variations in mantle fO2 may influence the fO2 at Earth’s surface. However, degassing can impact magmatic fO2 before or during eruption, potentially obscuring relationships between the fO2 of the solid Earth and of emitted gases and their impact on surface fO2. We show that low-pressure degassing resulted in reduction of the fO2 of Mauna Kea magmas by more than an order of magnitude. The leastmore » degassed magmas from Mauna Kea are more oxidized than midocean ridge basalt (MORB) magmas, suggesting that the upper mantle sources of Hawaiian magmas have higher fO2 than MORB sources. One explanation for this difference is recycling of material from the oxidized surface to the deep mantle, which is then returned to the surface as a component of buoyant plumes. It has been proposed that a decreasing pressure of volcanic eruptions led to the oxygenation of the atmosphere. Extension of our findings via modeling of degassing trends suggests that a decrease in eruption pressure would not produce this effect. If degassing of basalts were responsible for the rise in oxygen, it requires that Archean magmas had at least two orders of magnitude lower fO2 than modern magmas. Estimates of fO2 of Archean magmas are not this low, arguing for alternative explanations for the oxygenation of the atmosphere.« less

Redox variations in Mauna Kea lavas, the oxygen fugacity of the Hawaiian plume, and the role of volcanic gases in Earth's oxygenation.

PubMed

Brounce, Maryjo; Stolper, Edward; Eiler, John

2017-08-22

The behavior of C, H, and S in the solid Earth depends on their oxidation states, which are related to oxygen fugacity ( f O 2 ). Volcanic degassing is a source of these elements to Earth's surface; therefore, variations in mantle f O 2 may influence the f O 2 at Earth's surface. However, degassing can impact magmatic f O 2 before or during eruption, potentially obscuring relationships between the f O 2 of the solid Earth and of emitted gases and their impact on surface f O 2 We show that low-pressure degassing resulted in reduction of the f O 2 of Mauna Kea magmas by more than an order of magnitude. The least degassed magmas from Mauna Kea are more oxidized than midocean ridge basalt (MORB) magmas, suggesting that the upper mantle sources of Hawaiian magmas have higher f O 2 than MORB sources. One explanation for this difference is recycling of material from the oxidized surface to the deep mantle, which is then returned to the surface as a component of buoyant plumes. It has been proposed that a decreasing pressure of volcanic eruptions led to the oxygenation of the atmosphere. Extension of our findings via modeling of degassing trends suggests that a decrease in eruption pressure would not produce this effect. If degassing of basalts were responsible for the rise in oxygen, it requires that Archean magmas had at least two orders of magnitude lower f O 2 than modern magmas. Estimates of f O 2 of Archean magmas are not this low, arguing for alternative explanations for the oxygenation of the atmosphere.

Redox variations in Mauna Kea lavas, the oxygen fugacity of the Hawaiian plume, and the role of volcanic gases in Earth’s oxygenation

PubMed Central

Stolper, Edward; Eiler, John

2017-01-01

The behavior of C, H, and S in the solid Earth depends on their oxidation states, which are related to oxygen fugacity (fO2). Volcanic degassing is a source of these elements to Earth’s surface; therefore, variations in mantle fO2 may influence the fO2 at Earth’s surface. However, degassing can impact magmatic fO2 before or during eruption, potentially obscuring relationships between the fO2 of the solid Earth and of emitted gases and their impact on surface fO2. We show that low-pressure degassing resulted in reduction of the fO2 of Mauna Kea magmas by more than an order of magnitude. The least degassed magmas from Mauna Kea are more oxidized than midocean ridge basalt (MORB) magmas, suggesting that the upper mantle sources of Hawaiian magmas have higher fO2 than MORB sources. One explanation for this difference is recycling of material from the oxidized surface to the deep mantle, which is then returned to the surface as a component of buoyant plumes. It has been proposed that a decreasing pressure of volcanic eruptions led to the oxygenation of the atmosphere. Extension of our findings via modeling of degassing trends suggests that a decrease in eruption pressure would not produce this effect. If degassing of basalts were responsible for the rise in oxygen, it requires that Archean magmas had at least two orders of magnitude lower fO2 than modern magmas. Estimates of fO2 of Archean magmas are not this low, arguing for alternative explanations for the oxygenation of the atmosphere. PMID:28784788

Redox variations in Mauna Kea lavas, the oxygen fugacity of the Hawaiian plume, and the role of volcanic gases in Earth's oxygenation

NASA Astrophysics Data System (ADS)

Brounce, Maryjo; Stolper, Edward; Eiler, John

2017-08-01

The behavior of C, H, and S in the solid Earth depends on their oxidation states, which are related to oxygen fugacity (fO2). Volcanic degassing is a source of these elements to Earth’s surface; therefore, variations in mantle fO2 may influence the fO2 at Earth’s surface. However, degassing can impact magmatic fO2 before or during eruption, potentially obscuring relationships between the fO2 of the solid Earth and of emitted gases and their impact on surface fO2. We show that low-pressure degassing resulted in reduction of the fO2 of Mauna Kea magmas by more than an order of magnitude. The least degassed magmas from Mauna Kea are more oxidized than midocean ridge basalt (MORB) magmas, suggesting that the upper mantle sources of Hawaiian magmas have higher fO2 than MORB sources. One explanation for this difference is recycling of material from the oxidized surface to the deep mantle, which is then returned to the surface as a component of buoyant plumes. It has been proposed that a decreasing pressure of volcanic eruptions led to the oxygenation of the atmosphere. Extension of our findings via modeling of degassing trends suggests that a decrease in eruption pressure would not produce this effect. If degassing of basalts were responsible for the rise in oxygen, it requires that Archean magmas had at least two orders of magnitude lower fO2 than modern magmas. Estimates of fO2 of Archean magmas are not this low, arguing for alternative explanations for the oxygenation of the atmosphere.

Pressure and partial wetting effects on superhydrophobic friction reduction in microchannel flow

NASA Astrophysics Data System (ADS)

Kim, Tae Jin; Hidrovo, Carlos

2012-11-01

Friction reduction in microchannel flows can help alleviate the inherently taxing pumping power requirements associated with the dimensions involved. One possible way of achieving friction reduction is through the introduction of surface microtexturing that can lead to a superhydrophobic Cassie-Baxter state. The Cassie-Baxter state is characterized by the presence of air pockets within the surface microtexturing believed to act as an effective "shear free" (or at least shear reduced) layer, decreasing the overall friction characteristics of the surface. Most work in this area has concentrated on optimizing the surface microtexturing geometry to maximize the friction reduction effects and overall stability of the Cassie-Baxter state. However, less attention has been paid to the effects of partially wetted conditions induced by pressure and the correlation between the liquid-gas interface location within the surface microtexturing and the microchannel flow characteristics. This is mainly attributed to the difficulty in tracking the interface shape and location within the microtexturing in the typical top-down view arrangements used in most studies. In this paper, a rectangular microchannel with regular microtexturing on the sidewalls is used to visualize and track the location of the air-water interface within the roughness elements. While visually tracking the wetting conditions in the microtextures, pressure drops versus flow rates for each microchannel are measured and analyzed in terms of the non-dimensional friction coefficient. The frictional behavior of the Poiseuille flow suggests that (1) the air-water interface more closely resembles a no-slip boundary rather than a shear-free one, (2) the friction is rather insensitive to the degree of microtexturing wetting, and (3) the fully wetted (Wenzel state) microtexturing provides lower friction than the non-wetted one (Cassie state), in corroboration with observations (1) and (2).

Texture discrimination and multi-unit recording in the rat vibrissal nerve

PubMed Central

Albarracín, Ana L; Farfán, Fernando D; Felice, Carmelo J; Décima, Emilio E

2006-01-01

Background Rats distinguish objects differing in surface texture by actively moving their vibrissae. In this paper we characterized some aspects of texture sensing in anesthetized rats during active touch. We analyzed the multifiber discharge from a deep vibrissal nerve when the vibrissa sweeps materials (wood, metal, acrylic, sandpaper) having different textures. We polished these surfaces with sandpaper (P1000) to obtain close degrees of roughness and we induced vibrissal movement with two-branch facial nerve stimulation. We also consider the change in pressure against the vibrissa as a way to improve the tactile information acquisition. The signals were compared with a reference signal (control) – vibrissa sweeping the air – and were analyzed with the Root Mean Square (RMS) and the Power Spectrum Density (PSD). Results We extracted the information about texture discrimination hidden in the population activity of one vibrissa innervation, using the RMS values and the PSD. The pressure level 3 produced the best differentiation for RMS values and it could represent the "optimum" vibrissal pressure for texture discrimination. The frequency analysis (PSD) provided information only at low-pressure levels and showed that the differences are not related to the roughness of the materials but could be related to other texture parameters. Conclusion Our results suggest that the physical properties of different materials could be transduced by the trigeminal sensory system of rats, as are shown by amplitude and frequency changes. Likewise, varying the pressure could represent a behavioral strategy that improves the information acquisition for texture discrimination. PMID:16719904

Texture discrimination and multi-unit recording in the rat vibrissal nerve.

PubMed

Albarracín, Ana L; Farfán, Fernando D; Felice, Carmelo J; Décima, Emilio E

2006-05-23

Rats distinguish objects differing in surface texture by actively moving their vibrissae. In this paper we characterized some aspects of texture sensing in anesthetized rats during active touch. We analyzed the multifiber discharge from a deep vibrissal nerve when the vibrissa sweeps materials (wood, metal, acrylic, sandpaper) having different textures. We polished these surfaces with sandpaper (P1000) to obtain close degrees of roughness and we induced vibrissal movement with two-branch facial nerve stimulation. We also consider the change in pressure against the vibrissa as a way to improve the tactile information acquisition. The signals were compared with a reference signal (control)--vibrissa sweeping the air--and were analyzed with the Root Mean Square (RMS) and the Power Spectrum Density (PSD). We extracted the information about texture discrimination hidden in the population activity of one vibrissa innervation, using the RMS values and the PSD. The pressure level 3 produced the best differentiation for RMS values and it could represent the "optimum" vibrissal pressure for texture discrimination. The frequency analysis (PSD) provided information only at low-pressure levels and showed that the differences are not related to the roughness of the materials but could be related to other texture parameters. Our results suggest that the physical properties of different materials could be transduced by the trigeminal sensory system of rats, as are shown by amplitude and frequency changes. Likewise, varying the pressure could represent a behavioral strategy that improves the information acquisition for texture discrimination.

In Vivo Measurement of Surface Pressures and Retraction Distances Applied on Abdominal Organs During Surgery.

PubMed

Shah, Dignesh; Alderson, Andrew; Corden, James; Satyadas, Thomas; Augustine, Titus

2018-02-01

This study undertook the in vivo measurement of surface pressures applied by the fingers of the surgeon during typical representative retraction movements of key human abdominal organs during both open and hand-assisted laparoscopic surgery. Surface pressures were measured using a flexible thin-film pressure sensor for 35 typical liver retractions to access the gall bladder, 36 bowel retractions, 9 kidney retractions, 8 stomach retractions, and 5 spleen retractions across 12 patients undergoing open and laparoscopic abdominal surgery. The maximum and root mean square surface pressures were calculated for each organ retraction. The maximum surface pressures applied to these key abdominal organs are in the range 1 to 41 kPa, and the average maximum surface pressure for all organs and procedures was 14 ± 3 kPa. Surface pressure relaxation during the retraction hold period was observed. Generally, the surface pressures are higher, and the rate of surface pressure relaxation is lower, in the more confined hand-assisted laparoscopic procedures than in open surgery. Combined video footage and pressure sensor data for retraction of the liver in open surgery enabled correlation of organ retraction distance with surface pressure application. The data provide a platform to design strategies for the prevention of retraction injuries. They also form a basis for the design of next-generation organ retraction and space creation surgical devices with embedded sensors that can further quantify intraoperative retraction forces to reduce injury or trauma to organs and surrounding tissues.

Contact Behavior of Composite CrTiSiN Coated Dies in Compressing of Mg Alloy Sheets under High Pressure

PubMed Central

Yang, T.S.; Yao, S.H.; Chang, Y.Y.; Deng, J.H.

2018-01-01

Hard coatings have been adopted in cutting and forming applications for nearly two decades. The major purpose of using hard coatings is to reduce the friction coefficient between contact surfaces, to increase strength, toughness and anti-wear performance of working tools and molds, and then to obtain a smooth work surface and an increase in service life of tools and molds. In this report, we deposited a composite CrTiSiN hard coating, and a traditional single-layered TiAlN coating as a reference. Then, the coatings were comparatively studied by a series of tests. A field emission SEM was used to characterize the microstructure. Hardness was measured using a nano-indentation tester. Adhesion of coatings was evaluated using a Rockwell C hardness indentation tester. A pin-on-disk wear tester with WC balls as sliding counterparts was used to determine the wear properties. A self-designed compression and friction tester, by combining a Universal Testing Machine and a wear tester, was used to evaluate the contact behavior of composite CrTiSiN coated dies in compressing of Mg alloy sheets under high pressure. The results indicated that the hardness of composite CrTiSiN coating was lower than that of the TiAlN coating. However, the CrTiSiN coating showed better anti-wear performance. The CrTiSiN coated dies achieved smooth surfaces on the Mg alloy sheet in the compressing test and lower friction coefficient in the friction test, as compared with the TiAlN coating. PMID:29316687

Contact Behavior of Composite CrTiSiN Coated Dies in Compressing of Mg Alloy Sheets under High Pressure.

PubMed

Yang, T S; Yao, S H; Chang, Y Y; Deng, J H

2018-01-08

Hard coatings have been adopted in cutting and forming applications for nearly two decades. The major purpose of using hard coatings is to reduce the friction coefficient between contact surfaces, to increase strength, toughness and anti-wear performance of working tools and molds, and then to obtain a smooth work surface and an increase in service life of tools and molds. In this report, we deposited a composite CrTiSiN hard coating, and a traditional single-layered TiAlN coating as a reference. Then, the coatings were comparatively studied by a series of tests. A field emission SEM was used to characterize the microstructure. Hardness was measured using a nano-indentation tester. Adhesion of coatings was evaluated using a Rockwell C hardness indentation tester. A pin-on-disk wear tester with WC balls as sliding counterparts was used to determine the wear properties. A self-designed compression and friction tester, by combining a Universal Testing Machine and a wear tester, was used to evaluate the contact behavior of composite CrTiSiN coated dies in compressing of Mg alloy sheets under high pressure. The results indicated that the hardness of composite CrTiSiN coating was lower than that of the TiAlN coating. However, the CrTiSiN coating showed better anti-wear performance. The CrTiSiN coated dies achieved smooth surfaces on the Mg alloy sheet in the compressing test and lower friction coefficient in the friction test, as compared with the TiAlN coating.

Multiscale Hierarchical Design of a Flexible Piezoresistive Pressure Sensor with High Sensitivity and Wide Linearity Range.

PubMed

Shi, Jidong; Wang, Liu; Dai, Zhaohe; Zhao, Lingyu; Du, Mingde; Li, Hongbian; Fang, Ying

2018-05-30

Flexible piezoresistive pressure sensors have been attracting wide attention for applications in health monitoring and human-machine interfaces because of their simple device structure and easy-readout signals. For practical applications, flexible pressure sensors with both high sensitivity and wide linearity range are highly desirable. Herein, a simple and low-cost method for the fabrication of a flexible piezoresistive pressure sensor with a hierarchical structure over large areas is presented. The piezoresistive pressure sensor consists of arrays of microscale papillae with nanoscale roughness produced by replicating the lotus leaf's surface and spray-coating of graphene ink. Finite element analysis (FEA) shows that the hierarchical structure governs the deformation behavior and pressure distribution at the contact interface, leading to a quick and steady increase in contact area with loads. As a result, the piezoresistive pressure sensor demonstrates a high sensitivity of 1.2 kPa -1 and a wide linearity range from 0 to 25 kPa. The flexible pressure sensor is applied for sensitive monitoring of small vibrations, including wrist pulse and acoustic waves. Moreover, a piezoresistive pressure sensor array is fabricated for mapping the spatial distribution of pressure. These results highlight the potential applications of the flexible piezoresistive pressure sensor for health monitoring and electronic skin. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Patterning of graphene for flexible electronics with remote atmospheric-pressure plasma using dielectric barrier

NASA Astrophysics Data System (ADS)

Kim, Duk Jae; Park, Jeongwon; Geon Han, Jeon

2016-08-01

We show results of the patterning of graphene layers on poly(ethylene terephthalate) (PET) films through remote atmospheric-pressure dielectric barrier discharge plasma. The size of plasma discharge electrodes was adjusted for large-area and role-to-role-type substrates. Optical emission spectroscopy (OES) was used to analyze the characteristics of charge species in atmospheric-pressure plasma. The OES emission intensity of the O2* peaks (248.8 and 259.3 nm) shows the highest value at the ratio of \\text{N}2:\\text{clean dry air (CDA)} = 100:1 due to the highest plasma discharge. The PET surface roughness and hydrophilic behavior were controlled with CDA flow rate during the process. Although the atmospheric-pressure plasma treatment of the PET film led to an increase in the FT-IR intensity of C-O bonding at 1240 cm-1, the peak intensity at 1710 cm-1 (C=O bonding) decreased. The patterning of graphene layers was confirmed by scanning electron microscopy and Raman spectroscopy.

Condensation heat transfer and pressure drop of R-410A in a 7.0 mm O.D. microfin tube at low mass fluxes

NASA Astrophysics Data System (ADS)

Kim, Nae-Hyun

2016-12-01

R-410A condensation heat transfer and pressure drop data are provided for a 7.0 mm O.D. microfin tube at low mass fluxes (50-250 kg/m2 s). The heat transfer coefficient of the microfin tube shows a minimum behavior with the mass flux. At a low mass flux, where flow pattern is stratified, condensation induced by surface tension by microfins overwhelms condensation induced by shear, and the heat transfer coefficient decreases as mass flux increases. At a high mass flux, where flow pattern is annular, condensation induced by shear governs the heat transfer, and the heat transfer coefficient increases as mass flux increases. The pressure drop of the microfin tube is larger than that of the smooth tube at the annular flow regime. On the contrary, the pressure drop of the smooth tube is larger than that of the microfin tube at the stratified flow regime.

Preparation and physicochemical characterization of spray-dried and jet-milled microparticles containing bosentan hydrate for dry powder inhalation aerosols.

PubMed

Lee, Hyo-Jung; Kang, Ji-Hyun; Lee, Hong-Goo; Kim, Dong-Wook; Rhee, Yun-Seok; Kim, Ju-Young; Park, Eun-Seok; Park, Chun-Woong

2016-01-01

The objectives of this study were to prepare bosentan hydrate (BST) microparticles as dry powder inhalations (DPIs) via spray drying and jet milling under various parameters, to comprehensively characterize the physicochemical properties of the BST hydrate microparticles, and to evaluate the aerosol dispersion performance and dissolution behavior as DPIs. The BST microparticles were successfully prepared for DPIs by spray drying from feeding solution concentrations of 1%, 3%, and 5% (w/v) and by jet milling at grinding pressures of 2, 3, and 4 MPa. The physicochemical properties of the spray-dried (SD) and jet-milled (JM) microparticles were determined via scanning electron microscopy, atomic force microscopy, dynamic light scattering particle size analysis, Karl Fischer titration, surface analysis, pycnometry, differential scanning calorimetry, powder X-ray diffraction, and Fourier transform infrared spectroscopy. The in vitro aerosol dispersion performance and drug dissolution behavior were evaluated using an Anderson cascade impactor and a Franz diffusion cell, respectively. The JM microparticles exhibited an irregular corrugated surface and a crystalline solid state, while the SD microparticles were spherical with a smooth surface and an amorphous solid state. Thus, the in vitro aerosol dispersion performance and dissolution behavior as DPIs were considerably different due to the differences in the physicochemical properties of the SD and JM microparticles. In particular, the highest grinding pressures under jet milling exhibited excellent aerosol dispersion performance with statistically higher values of 56.8%±2.0% of respirable fraction and 33.8%±2.3% of fine particle fraction and lower mass median aerodynamic diameter of 5.0±0.3 μm than the others ( P <0.05, analysis of variance/Tukey). The drug dissolution mechanism was also affected by the physicochemical properties that determine the dissolution kinetics of the SD and JM microparticles, which were well fitted into the Higuchi and zero-order models, respectively.

Blood Pressure, Emotional Dampening, and Risk Behavior: Implications for Hypertension Development.

PubMed

McCubbin, James A; Nathan, Aaron; Hibdon, Melissa A; Castillo, Anastasia M; Graham, Jack G; Switzer, Fred S

2018-05-07

Elevated resting blood pressure (BP) is associated with risk for hypertension and emotional dampening, including reduced responses to emotionally meaningful stimuli. Perception of threat is a critical motivator in avoidance of risky health-damaging behavior. We hypothesize that BP-associated dampening of threat appraisal may increase risk-taking behavior. We measured resting BP, perception of affect, and risk behavior in 92 healthy, women (n=49) and men (n=43) recruited from university students and staff, and members of the surrounding community. Mean age +/- standard deviation for the sample was 21.5 +/- 4.3 year. Blood pressure was measured using an automated blood pressure monitor, and risk behavior was assessed with a modified National College Health Risk Behavior Survey. We also measured recognition of affect using the Perception of Affect Task (PAT). Risk-taking behavior was positively correlated with both systolic (SBP; r(89)=.278, p=.008) and diastolic blood pressure (DBP; r(89)=.309, p<.003). Regression analysis indicated that the association between risk-taking behavior and blood pressure was not mediated by PAT scores. Results show that persons with higher resting BP levels report increased risk-taking behavior. PAT scores, while correlated with SBP, did not mediate the relationship between BP and risk. The relationship between BP and risk behavior reflects the potential involvement of CNS regulation of both BP and emotional responsivity, and its relationship to health damaging behavior and risk for hypertension.

Assessing the Behavior of Typically Lithophile Elements Under Highly Reducing Conditions Relevant to the Planet Mercury

NASA Technical Reports Server (NTRS)

Rowland, Rick, II; Vander Kaaden, Kathleen E.; McCubbin, Francis M.; Danielson, Lisa R.

2017-01-01

With the data returned from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission, there are now numerous constraints on the physical and chemical properties of Mercury, including its surface composition (e.g., Evans et al. 2012; Nittler et al. 201 l; Peplowski et al. 2012; Weider et al. 2012). The high Sand low FeO contents observed from MESSENGER on the planet's surface suggests a low oxygen fugacity of the present planetary materials. Estimates of the oxygen fugacity for Mercurian magmas are approximately 3- 7 log units below the Iron-Wiistite (Fe-FeO) oxygen buffer (McCubbin et al. 2012; Zolotov et al. 2013), several orders of magnitude more reducing than other terrestrial bodies we have data from such as the Earth, Moon, or Mars (Herd 2008; Sharp, McCubbin, and Shearer 2013; Wadhwa 2008). Most of our understanding of elemental partitioning behavior comes from observations made on terrestrial rocks, but Mercury's oxygen fugacity is far outside the conditions of those samples. With limited oxygen available, lithophile elements may instead exhibit chalcophile, halophile, or siderophile behaviors. Furthermore, very few natural samples of rocks that formed under reducing conditions are available in our collections (e.g., enstatite chondrites, achondrites, aubrites). The goal of this study is to conduct experiments at high pressure and temperature conditions to determine the elemental partitioning behavior of typically lithophile elements as a function of decreasing oxygen fugacity.

Network structure control of binary mixed langmuir monolayers of homo-PS and PS-b-P2VP.

PubMed

Wen, Gangyao

2010-03-25

Our recent work showed there existed a composition window for mixed Langmuir monolayers of homopolystyrene (h-PS) and a symmetric diblock copolymer polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) to form necklace-network structures at the air/water interface. In order to study further the possible mechanism and control the network structure (i.e., surface coverage and nanoaggregate diameter), effects of spreading solution concentration and volume, subphase temperature, and transfer pressure on the network structure were studied by the Langmuir monolayer technique and tapping mode atomic force microscopy. With the increase of transfer pressure, there existed a novel nonlinear behavior for the nanoaggregate diameter first to increase, then to decrease, and finally to increase again, while the surface coverage tended to increase step by step. Moreover, with the elevation of temperature, chain motion between the adjoining nanoaggregates tended to be improved and thus the nanoaggregate diameter tended to be more uniform.

Friction of hard surfaces and its application in earthquakes and rock slope stability

NASA Astrophysics Data System (ADS)

Sinha, Nitish; Singh, Arun K.; Singh, Trilok N.

2018-05-01

In this article, we discuss the friction models for hard surfaces and their applications in earth sciences. The rate and state friction (RSF) model, which is basically modified form of the classical Amontons-Coulomb friction laws, is widely used for explaining the crustal earthquakes and the rock slope failures. Yet the RSF model has further been modified by considering the role of temperature at the sliding interface known as the rate, state and temperature friction (RSTF) model. Further, if the pore pressure is also taken into account then it is stated as the rate, state, temperature and pore pressure friction (RSTPF) model. All the RSF models predict a critical stiffness as well as a critical velocity at which sliding behavior becomes stable/unstable. The friction models are also used for predicting time of failure of the rock mass on an inclined plane. Finally, the limitation and possibilities of the proposed friction models are also highlighted.

Global Characteristics of Porosity and Density Stratification Within the Lunar Crust from GRAIL Gravity and Lunar Orbiter Laser Altimeter Topography Data

NASA Technical Reports Server (NTRS)

Han, Shin-Chan; Schmerr, Nicholas; Neumann, Gregory; Holmes, Simon

2014-01-01

The Gravity Recovery and Interior Laboratory (GRAIL) mission is providing unprecedentedly high-resolution gravity data. The gravity signal in relation to topography decreases from 100 km to 30 km wavelength, equivalent to a uniform crustal density of 2450 kg/cu m that is 100 kg/cu m smaller than the density required at 100 km. To explain such frequency-dependent behavior, we introduce rock compaction models under lithostatic pressure that yield radially stratified porosity (and thus density) and examine the depth extent of porosity. Our modeling and analysis support the assertion that the crustal density must vary from surface to deep crust by up to 500 kg/cu m. We found that the surface density of mega regolith is around 2400 kg/cu m with an initial porosity of 10-20%, and this porosity is eliminated at 10-20 km depth due to lithostatic overburden pressure. Our stratified density models provide improved fits to both GRAIL primary and extended mission data.

Finite-size versus interface-proximity effects in thin-film epitaxial SrTiO3

NASA Astrophysics Data System (ADS)

De Souza, R. A.; Gunkel, F.; Hoffmann-Eifert, S.; Dittmann, R.

2014-06-01

The equilibrium electrical conductivity of epitaxial SrTiO3 (STO) thin films was investigated as a function of temperature, 950≤ T/K ≤1100, and oxygen partial pressure, 10-23≤ pO2/bar ≤1. Compared with single-crystal STO, nanoscale thin-film STO exhibited with decreasing film thickness an increasingly enhanced electronic conductivity under highly reducing conditions, with a corresponding decrease in the activation enthalpy of conduction. This implies substantial modification of STO's point-defect thermodynamics for nanoscale film thicknesses. We argue, however, against such a finite-size effect and for an interface-proximity effect. Indeed, assuming trapping of oxygen vacancies at the STO surface and concomitant depletion of oxygen vacancies—and accumulation of electrons—in an equilibrium surface space-charge layer, we are able to predict quantitatively the conductivity as a function of temperature, oxygen partial pressure, and film thickness. Particularly complex behavior is predicted for ultrathin films that are consumed entirely by space charge.

Nitramine smokeless propellant research

NASA Technical Reports Server (NTRS)

Cohen, N. S.; Strand, L. P.

1977-01-01

A transient ballistics and combustion model is derived to represent the closed vessel experiment that is widely used to characterize propellants. A computer program is developed to solve the time-dependent equations, and is applied to explain aspects of closed vessel behavior. In the case of nitramine propellants the cratering of the burning surface associated with combustion above break-point pressures augments the effective burning rate as deduced from the closed vessel experiment. Low pressure combustion is significantly affected by the ignition process and, in the case of nitramine propellants, by the developing and changing surface structure. Thus, burning rates deduced from the closed vessel experiment may or may not agree with those measured in the equilibrium strand burner. Series of T burner experiments are performed to compare the combustion instability characteristics of nitramine (HMX) containing propellants and ammonium perchlorate (AP)propellants. Although ash produced by more fuel rich propellants could have provided mechanical suppression, results from clean-burning propellants permit the conclusion that HMX reduces the acoustic driving.

Behavior of MHD Instabilities of the Large Helical Device near the Effective Plasma Boundary in the Magnetic Stochastic Region

NASA Astrophysics Data System (ADS)

Ohdachi, S.; Suzuki, Y.; Sakakibara, S.; Watanabe, K. Y.; Ida, K.; Goto, M.; Du, X. D.; Narushima, Y.; Takemura, Y.; Yamada, H.

In the high beta experiments of the Large Helical Device (LHD), the plasma tends to expand from the last closed flux surface (LCFS) determined by the vacuum magnetic field. The pressure/temperature gradient in the external region is finite. The scale length of the pressure profile does not change so much even when the mean free path of electrons exceeds the connection length of the magnetic field line to the wall. There appear MHD instabilities with amplitude of 10-4 of the toroidal magnetic field. From the mode number of the activities (m/n = 2/3, 1/2, 2/4), the location of the corresponding rational surface is outside the vacuum LCFS. The location of the mode is consistent with the fluctuation measurement, e.g., soft X-ray detector arrays. The MHD mode localized in the magnetic stochastic region is affected by the magnetic field structure estimated by the connection length to the wall using 3D equilibrium calculation.

Self-similar assemblies of globular whey proteins at the air-water interface: effect of the structure.

PubMed

Mahmoudi, Najet; Gaillard, Cédric; Boué, François; Axelos, Monique A V; Riaublanc, Alain

2010-05-01

We investigated the structure of heat-induced assemblies of whey globular proteins using small angle neutron scattering (SANS), static and dynamic light scattering (SLS and DLS), and cryogenic transmission electron microscopy (Cryo-TEM). Whey protein molecules self-assemble in fractal aggregates with a structure density depending on the electrostatic interactions. We determined the static and dynamic properties of interfacial layer formed by the protein assemblies, upon adsorption and spreading at the air-water interface using surface film balance and interfacial dilatational rheology. Upon spreading, all whey protein systems show a power-law scaling behavior of the surface pressure versus concentration in the semi-dilute surface concentration regime, with an exponent ranging from 5.5 to 9 depending on the electrostatic interactions and the aggregation state. The dilatational modulus derived from surface pressure isotherms shows a main peak at 6-8 mN/m, generally considered to be the onset of a conformational change in the monolayer, and a second peak or a shoulder at 15 mN/m. Long-time adsorption kinetics give similar results for both the native whey proteins and the corresponding self-similar assemblies, with a systematic effect of the ionic strength. Copyright 2010 Elsevier Inc. All rights reserved.

Morphological variation of stimuli-responsive polypeptide at air-water interface

NASA Astrophysics Data System (ADS)

Shin, Sungchul; Ahn, Sungmin; Cheng, Jie; Chang, Hyejin; Jung, Dae-Hong; Hyun, Jinho

2016-12-01

The morphological variation of stimuli-responsive polypeptide molecules at the air-water interface as a function of temperature and compression was described. The surface pressure-area (π-A) isotherms of an elastin-like polypeptide (ELP) monolayer were obtained under variable external conditions, and Langmuir-Blodgett (LB) monolayers were deposited onto a mica substrate for characterization. As the compression of the ELP monolayer increased, the surface pressure increased gradually, indicating that the ELP monolayer could be prepared with high stability at the air-water interface. The temperature in the subphase of the ELP monolayer was critical in the preparation of LB monolayers. The change in temperature induced a shift in the π-A isotherms as well as a change in ELP secondary structures. Surprisingly, the compression of the ELP monolayer influenced the ELP secondary structure due to the reduction in the phase transition temperature with decreasing temperature. The change in the ELP secondary structure formed at the air-water interface was investigated by surface-enhanced Raman scattering. Moreover, the morphology of the ELP monolayer was subsequently imaged using atomic force microscopy. The temperature responsive behavior resulted in changes in surface morphology from relatively flat structures to rugged labyrinth structures, which suggested conformational changes in the ELP monolayers.

Hydrophobic properties of a wavy rough substrate.

PubMed

Carbone, G; Mangialardi, L

2005-01-01

The wetting/non-wetting properties of a liquid drop in contact with a chemically hydrophobic rough surface (thermodynamic contact angle theta(e)>pi/2) are studied for the case of an extremely idealized rough profile: the liquid drop is considered to lie on a simple sinusoidal profile. Depending on surface geometry and pressure values, it is found that the Cassie and Wenzel states can coexist. But if the amplitude h of the substrate is sufficiently large the only possible stable state is the Cassie one, whereas if h is below a certain critical value hcr a transition to the Wenzel state occurs. Since in many potential applications of such super-hydrophobic surfaces, liquid drops often collide with the substrate (e.g. vehicle windscreens), in the paper the critical drop pressure pW is calculated at which the Cassie state is no longer stable and the liquid jumps into full contact with the substrate (Wenzel state). By analyzing the asymptotic behavior of the systems in the limiting case of a large substrate corrugation, a simple criterion is also proposed to calculate the minimum height asperity h necessary to prevent the Wenzel state from being formed, to preserve the super-hydrophobic properties of the substrate, and, hence, to design a robust super-hydrophobic surface.

Break the electron- hole balance and pressure induced superconductivity in Tungsten Ditelluride

NASA Astrophysics Data System (ADS)

Song, Fengqi; Pan, Xing-Chen

Tungsten ditelluride has garnered immense interest due to the recent discovery of titanic unsaturated magnetoresistance up to 60 Tesla and its possible topological metal nature. The titanic unsaturated magnetoresistance is attributed to the perfect compensation between the opposite carriers in this material. Motivated by the small and sensitive Fermi surface of 5d electronic orbitals, we break the electron-hole balance by the application of high pressure. Superconductivity sharply appears at the pressure of 2.5 GPa, quickly reaching a maximum critical temperature of 7 K at around 16.8 GPa, and followed by a monotonic decrease in Tc with increasing pressure exhibiting the typical dome-shaped superconducting phase. What's more, linear magnetoresistance dominates the transport behavior under high pressure instead of semi-classical parabolic magnetoresistance, like in other topological metals. Refence: Nature Commun. 6, 7805 (2015), arXiv 1505, 07968. The authors would like to thank the National Key Projects for Basic Research in China, the National Natural Science Foundation of China , the NSF of Jiangsu Province, the PAPD project, and the Fundamental Research Funds for the Central Universities.

Geomechanical behavior of the reservoir and caprock system at the In Salah CO2 storage project.

PubMed

White, Joshua A; Chiaramonte, Laura; Ezzedine, Souheil; Foxall, William; Hao, Yue; Ramirez, Abelardo; McNab, Walt

2014-06-17

Almost 4 million metric tons of CO2 were injected at the In Salah CO2 storage site between 2004 and 2011. Storage integrity at the site is provided by a 950-m-thick caprock that sits above the injection interval. This caprock consists of a number of low-permeability units that work together to limit vertical fluid migration. These are grouped into main caprock units, providing the primary seal, and lower caprock units, providing an additional buffer and some secondary storage capacity. Monitoring observations at the site indirectly suggest that pressure, and probably CO2, have migrated upward into the lower portion of the caprock. Although there are no indications that the overall storage integrity has been compromised, these observations raise interesting questions about the geomechanical behavior of the system. Several hypotheses have been put forward to explain the measured pressure, seismic, and surface deformation behavior. These include fault leakage, flow through preexisting fractures, and the possibility that injection pressures induced hydraulic fractures. This work evaluates these hypotheses in light of the available data. We suggest that the simplest and most likely explanation for the observations is that a portion of the lower caprock was hydrofractured, although interaction with preexisting fractures may have played a significant role. There are no indications, however, that the overall storage complex has been compromised, and several independent data sets demonstrate that CO2 is contained in the confinement zone.

Dimethyl methylphosphonate adsorption and decomposition on MoO2 as studied by ambient pressure x-ray photoelectron spectroscopy and DFT calculations

NASA Astrophysics Data System (ADS)

Head, Ashley R.; Tsyshevsky, Roman; Trotochaud, Lena; Yu, Yi; Karslıoǧlu, Osman; Eichhorn, Bryan; Kuklja, Maija M.; Bluhm, Hendrik

2018-04-01

Organophosphonates range in their toxicity and are used as pesticides, herbicides, and chemical warfare agents (CWAs). Few laboratories are equipped to handle the most toxic molecules, thus simulants such as dimethyl methylphosphonate (DMMP), are used as a first step in studying adsorption and reactivity on materials. Benchmarked by combined experimental and theoretical studies of simulants, calculations offer an opportunity to understand how molecular interactions with a surface changes upon using a CWA. However, most calculations of DMMP and CWAs on surfaces are limited to adsorption studies on clusters of atoms, which may differ markedly from the behavior on bulk solid-state materials with extended surfaces. We have benchmarked our solid-state periodic calculations of DMMP adsorption and reactivity on MoO2 with ambient pressure x-ray photoelectron spectroscopy studies (APXPS). DMMP is found to interact strongly with a MoO2 film, a model system for the MoO x component in the ASZM-TEDA© gas filtration material. Density functional theory modeling of several adsorption and decomposition mechanisms assist the assignment of APXPS peaks. Our results show that some of the adsorbed DMMP decomposes, with all the products remaining on the surface. The rigorous calculations benchmarked with experiments pave a path to reliable and predictive theoretical studies of CWA interactions with surfaces.

Atmospheric-pressure plasma activation and surface characterization on polyethylene membrane separator

NASA Astrophysics Data System (ADS)

Tseng, Yu-Chien; Li, Hsiao-Ling; Huang, Chun

2017-01-01

The surface hydrophilic activation of a polyethylene membrane separator was achieved using an atmospheric-pressure plasma jet. The surface of the atmospheric-pressure-plasma-treated membrane separator was found to be highly hydrophilic realized by adjusting the plasma power input. The variations in membrane separator chemical structure were confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Chemical analysis showed newly formed carbonyl-containing groups and high surface concentrations of oxygen-containing species on the atmospheric-pressure-plasma-treated polymeric separator surface. It also showed that surface hydrophilicity primarily increased from the polar component after atmospheric-pressure plasma treatment. The surface and pore structures of the polyethylene membrane separator were examined by scanning electron microscopy, revealing a slight alteration in the pore structure. As a result of the incorporation of polar functionalities by atmospheric-pressure plasma activation, the electrolyte uptake and electrochemical impedance of the atmospheric-pressure-plasma-treated membrane separator improved. The investigational results show that the separator surface can be controlled by atmospheric-pressure plasma surface treatment to tailor the hydrophilicity and enhance the electrochemical performance of lithium ion batteries.

Kinematically irreversible particle motion in 2D suspensions due to surface-pressure-dependent surface rheology

NASA Astrophysics Data System (ADS)

Manikantan, Harishankar; Squires, Todd

2017-11-01

The surface viscosity of many insoluble surfactants depends strongly on the surface pressure (or surface tension) of that surfactant. Surface pressure gradients naturally arise in interfacial flows, and surface-pressure-dependent surface rheology alters 2D suspension dynamics in significant ways. We use the Lorentz reciprocal theorem to asymptotically quantify the irreversible dynamics that break Newtonian symmetries. We first show that a particle embedded in a surfactant-laden interface and translating parallel to or rotating near an interfacial boundary experiences a force in the direction perpendicular to the boundary. Building on this, we extend the theory to compute the first effects of pressure-dependent surface viscosity on 2D particle pairs in suspension. The fore-aft symmetry of pair trajectories in a Newtonian interface is lost, leading to well-separated (when pressure-thickening) or aggregated (when pressure-thinning) particles. Notably, the relative motion is kinematically irreversible, and pairs steadily evolve toward a particular displacement. Based on these irreversible pair interactions, we hypothesize that pressure-thickening (or -thinning) leads to shear-thinning (or -thickening) in 2D suspensions.

Dependence of Non-Prestonian Behavior of Ceria Slurry with Anionic Surfactant on Abrasive Concentration and Size in Shallow Trench Isolation Chemical Mechanical Polishing

NASA Astrophysics Data System (ADS)

Kang, Hyun‑Goo; Kim, Dae‑Hyeong; Katoh, Takeo; Kim, Sung‑Jun; Paik, Ungyu; Park, Jea‑Gun

2006-05-01

The dependencies of the non-Prestonian behavior of ceria slurry with anionic surfactant on the size and concentration of abrasive particles were investigated by performing chemical mechanical polishing (CMP) experiments using blanket wafers. We found that not only the abrasive size but also the abrasive concentration with surfactant addition influences the non-Prestonian behavior. Such behavior is clearly exhibited with small abrasive sizes and a higher concentrations of abrasives with surfactant addition, because the abrasive particles can locally contact the film surface more effectively with applied pressure. We introduce a factor to quantify these relations with the non-Prestonian behavior of a slurry. For ceria slurry, this non-Prestonian factor, βNP, was determined to be almost independent of the abrasive concentration for a larger size and a smaller weight conentration of abrasive particles, but it increased with the surfactant concentration for a smaller size and a higher concentration of abrasives with surfactant addition.

Estimation of turgor pressure through comparison between single plant cell and pressurized shell mechanics

NASA Astrophysics Data System (ADS)

Durand-Smet, P.; Gauquelin, E.; Chastrette, N.; Boudaoud, A.; Asnacios, A.

2017-10-01

While plant growth is well known to rely on turgor pressure, it is challenging to quantify the contribution of turgor pressure to plant cell rheology. Here we used a custom-made micro-rheometer to quantify the viscoelastic behavior of isolated plant cells while varying their internal turgor pressure. To get insight into how plant cells adapt their internal pressure to the osmolarity of their medium, we compared the mechanical behavior of single plant cells to that of a simple, passive, pressurized shell: a soccer ball. While both systems exhibited the same qualitative behavior, a simple mechanical model allowed us to quantify turgor pressure regulation at the single cell scale.

An Electrochemical, Microtopographical and Ambient Pressure X-Ray Photoelectron Spectroscopic Investigation of Si/TiO 2/Ni/Electrolyte Interfaces

DOE PAGES

Lichterman, Michael F.; Richter, Matthias H.; Hu, Shu; ...

2015-12-05

The electrical and spectroscopic properties of the TiO 2/Ni protection layer system, which enables stabilization of otherwise corroding photoanodes, have been investigated in contact with electrolyte solutions by scanning-probe microscopy, electrochemistry and in-situ ambient pressure X-ray photoelectron spectroscopy (AP-XPS). Specifically, the energy-band relations of the p +-Si/ALD-TiO 2/Ni interface have been determined for a selected range of Ni thicknesses. AP-XPS measurements using tender X-rays were performed in a three-electrode electrochemical arrangement under potentiostatic control to obtain information from the semiconductor near-surface region, the electrochemical double layer (ECDL) and the electrolyte beyond the ECDL. The degree of conductivity depended on themore » chemical state of the Ni on the TiO 2 surface. At low loadings of Ni, the Ni was present primarily as an oxide layer and the samples were not conductive, although the TiO 2 XPS core levels nonetheless displayed behavior indicative of a metal-electrolyte junction. In contrast, as the Ni thickness increased, the Ni phase was primarily metallic and the electrochemical behavior became highly conductive, with the AP-XPS data indicative of a metal-electrolyte junction. Electrochemical and microtopographical methods have been employed to better define the nature of the TiO 2/Ni electrodes and to contextualize the AP-XPS results.« 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.

Spontaneous deswelling of pNIPAM microgels at high concentrations

NASA Astrophysics Data System (ADS)

Gasser, Urs; Scotti, Andrea; Herman, Emily S.; Pelaez-Fernandez, Miguel; Han, Jun; Menzel, Andreas; Lyon, L. Andrew; Fernandez-Nieves, Alberto

Polydisperse suspensions of pNIPAM microgel particles show a unique, spontaneous particle deswelling behavior. Beyond a critical concentration, the largest microgels deswell and thereby reduce the polydispersity of the suspension. We have recently unraveled the mechanism of this spontaneous, selective deswelling. pNIPAM microgels carry charged sulfate groups originating from the ammonium persulfate starter used in particle synthesis. Most of the ammonium counterions are trapped close to the microgel surface, but a fraction of them escapes the electrostatic attraction and contributes to the osmotic pressure of the suspension. The counterion clouds of neighboring particles progressively overlap with increasing volume fraction, leading to an increase of free counterions and the osmotic pressure outside but not inside the microgel particles. We find particles to deswell when the resulting osmotic pressure difference between the inside and the outside becomes larger their bulk modulus. For pNIPAM microgels synthesized with the same protocol, the largest particles are the softest and deswell first.

Wind ripples in low density atmospheres

NASA Technical Reports Server (NTRS)

Miller, J. S.; Marshall, J. R.; Greeley, R.

1987-01-01

The effect of varying fluid density (rho) on particle transport was examined by conducting tests at atmospheric pressures between 1 and 0.004 bar in the Martian Surface Wind Tunnel (MARSWIT). This study specifically concerns the effect of varying rho on the character of wind ripples, and elicits information concerning generalized ripple models as well as specific geological circumstances for ripple formation such as those prevailing on Mars. Tests were conducted primarily with 95 micron quartz sand, and for each atmospheric pressure chosen, tests were conducted at two freestream wind speeds: 1.1 U*(t) and 1.5 U*(t), where U*(t) is saltation threshold. Preliminary analysis of the data suggests: (1) ballistic ripple wavelength is not at variance with model predictions; (2) an atmospheric pressure of approximately 0.2 bar could represent a discontinuity in ripple behavior; and (4) ripple formation on Mars may not be readily predicted by extrapolation of terrestrial observations.

Optical and mechanical properties of nanocrystalline ZrC thin films grown by pulsed laser deposition.

DOE PAGES

Craciun, D.; Socol, G.; Lambers, E.; ...

2015-01-17

Thin ZrC films (<500 nm) were grown on (100) Si substrates at a substrate temperature of 500 °C by the pulsed laser deposition (PLD) technique using a KrF excimer laser under different CH 4 pressures. Glancing incidence X-ray diffraction showed that films were nanocrystalline, while X-ray reflectivity studies found out films were very dense and exhibited a smooth surface morphology. Optical spectroscopy data shows that the films have high reflectivity (>90%) in the infrared region, characteristic of metallic behavior. Nanoindentation results indicated that films deposited under lower CH 4 pressures exhibited slightly higher nanohardness and Young modulus values than filmsmore » deposited under higher pressures. As a result, tribological characterization revealed that these films exhibited relatively high wear resistance and steady-state friction coefficients on the order of μ = 0.4.« less

Liquid oxygen LOX compatibility evaluations of aluminum lithium (Al-Li) alloys: Investigation of the Alcoa 2090 and MMC weldalite 049 alloys

NASA Technical Reports Server (NTRS)

Diwan, Ravinder M.

1989-01-01

The behavior of liquid oxygen (LOX) compatibility of aluminum lithium (Al-Li) alloys is investigated. Alloy systems of Alcoa 2090, vintages 1 to 3, and of Martin Marietta Corporation (MMC) Weldalite 049 were evaluated for their behavior related to the LOX compatibility employing liquid oxygen impact test conditions under ambient pressures and up to 1000 psi. The developments of these aluminum lithium alloys are of critical and significant interest because of their lower densities and higher specific strengths and improved mechanical properties at cryogenic temperatures. Of the different LOX impact tests carried out at the Marshall Space Flight Center (MSFC), it is seen that in certain test conditions at higher pressures, not all Al-Li alloys are LOX compatible. In case of any reactivity, it appears that lithium makes the material more sensitive at grain boundaries due to microstructural inhomogeneities and associated precipitate free zones (PFZ). The objectives were to identify and rationalize the microstructural mechanisms that could be relaxed to LOX compatibility behavior of the alloy system in consideration. The LOX compatibility behavior of Al-Li 2090 and Weldalite 049 is analyzed in detail using microstructural characterization techniques with light optical metallography, scanning electron microscopy (SEM), electron microprobe analysis, and surface studies using secondary ion mass spectrometry (SIMS), electron spectroscopy in chemical analysis (ESCA) and Auger electron spectroscopy (AES). Differences in the behavior of these aluminum lithium alloys are assessed and related to their chemistry, heat treatment conditions, and microstructural effects.

Failure Behavior of Granite Affected by Confinement and Water Pressure and Its Influence on the Seepage Behavior by Laboratory Experiments.

PubMed

Cheng, Cheng; Li, Xiao; Li, Shouding; Zheng, Bo

2017-07-14

Failure behavior of granite material is paramount for host rock stability of geological repositories for high-level waste (HLW) disposal. Failure behavior also affects the seepage behavior related to transportation of radionuclide. Few of the published studies gave a consistent analysis on how confinement and water pressure affect the failure behavior, which in turn influences the seepage behavior of the rock during the damage process. Based on a series of laboratory experiments on NRG01 granite samples cored from Alxa area, a candidate area for China's HLW disposal, this paper presents some detailed observations and analyses for a better understanding on the failure mechanism and seepage behavior of the samples under different confinements and water pressure. The main findings of this study are as follows: (1) Strength reduction properties were found for the granite under water pressure. Besides, the complete axial stress-strain curves show more obvious yielding process in the pre-peak region and a more gradual stress drop in the post-peak region; (2) Shear fracturing pattern is more likely to form in the granite samples with the effect of water pressure, even under much lower confinements, than the predictions from the conventional triaxial compressive results; (3) Four stages of inflow rate curves are divided and the seepage behaviors are found to depend on the failure behavior affected by the confinement and water pressure.

Nanoscale roughness contact in a slider-disk interface.

PubMed

Hua, Wei; Liu, Bo; Yu, Shengkai; Zhou, Weidong

2009-07-15

The nanoscale roughness contact between molecularly smooth surfaces of a slider-disk interface in a hard disk drive is analyzed, and the lubricant behavior at very high shear rate is presented. A new contact model is developed to study the nanoscale roughness contact behavior by classifying various forms of contact into slider-lubricant contact, slider-disk elastic contact and plastic contact. The contact pressure and the contact probabilities of the three types of contact are investigated. The new contact model is employed to explain and provide insight to an interesting experimental result found in a thermal protrusion slider. The protrusion budget for head surfing in the lubricant, which is the ideal state for contact recording, is also discussed.

Rolling-element fatigue life with two synthetic cycloaliphatic traction fluids

NASA Technical Reports Server (NTRS)

Loewenthal, S. H.; Parker, R. J.

1976-01-01

The life potential of two synthetic cycloaliphatic hydrocarbon traction fluids in rolling element fatigue was evaluated in a five ball fatigue tester. Life comparisons with a MIL-L-23699 qualified tetraester oil showed that the traction test oils had good fatigue life performance, comparable to that of the tetraester oil. No statistically significant life differences between the traction fluids and the tetraester oil were exhibited under the accelerated fatigue test conditions. Erratic operating behavior was occasionally encountered during tests with the antiwear additive containing traction fluid for reasons thought to be related to excessive chemical activity under high contact pressure. This behavior occasionally resulted in premature test termination due to excessive surface distress and overheating.

Active fluids at circular boundaries: swim pressure and anomalous droplet ripening.

PubMed

Jamali, Tayeb; Naji, Ali

2018-06-13

We investigate the swim pressure exerted by non-chiral and chiral active particles on convex or concave circular boundaries. Active particles are modeled as non-interacting and non-aligning self-propelled Brownian particles. The convex and concave circular boundaries are used to model a fixed inclusion immersed in an active bath and a cavity (or container) enclosing the active particles, respectively. We first present a detailed analysis of the role of convex versus concave boundary curvature and of the chirality of active particles in their spatial distribution, chirality-induced currents, and the swim pressure they exert on the bounding surfaces. The results will then be used to predict the mechanical equilibria of suspended fluid enclosures (generically referred to as 'droplets') in a bulk with active particles being present either inside the bulk fluid or within the suspended droplets. We show that, while droplets containing active particles behave in accordance with standard capillary paradigms when suspended in a normal bulk, those containing a normal fluid exhibit anomalous behaviors when suspended in an active bulk. In the latter case, the excess swim pressure results in non-monotonic dependence of the inside droplet pressure on the droplet radius; hence, revealing an anomalous regime of behavior beyond a threshold radius, in which the inside droplet pressure increases upon increasing the droplet size. Furthermore, for two interconnected droplets, mechanical equilibrium can occur also when the droplets have different sizes. We thus identify a regime of anomalous droplet ripening, where two unequal-sized droplets can reach a final state of equal size upon interconnection, in stark contrast with the standard Ostwald ripening phenomenon, implying shrinkage of the smaller droplet in favor of the larger one.

Simulation of river plume behaviors in a tropical region: Case study of the Upper Gulf of Thailand

NASA Astrophysics Data System (ADS)

Yu, Xiaojie; Guo, Xinyu; Morimoto, Akihiko; Buranapratheprat, Anukul

2018-02-01

River plumes are a general phenomenon in coastal regions. Most previous studies focus on river plumes in middle and high latitudes with few studies examining those in low latitude regions. Here, we apply a numerical model to the Upper Gulf of Thailand (UGoT) to examine a river plume in low latitudes. Consistent with observational data, the modeled plume has seasonal variation dependent on monsoon conditions. During southwesterly monsoons, the plume extends northeastward to the head of the gulf; during northeasterly monsoons, it extends southwestward to the mouth of the gulf. To examine the effects of latitude, wind and river discharge on the river plume, we designed several numerical experiments. Using a middle latitude for the UGoT, the bulge close to the river mouth becomes smaller, the downstream current flows closer to the coast, and the salinity in the northern UGoT becomes lower. The reduction in the size of the bulge is consistent with the relationship between the offshore distance of a bulge and the Coriolis parameter. Momentum balance of the coastal current is maintained by advection, the Coriolis force, pressure gradient and internal stresses in both low and middle latitudes, with the Coriolis force and pressure gradient enlarged in the middle latitude. The larger pressure gradient in the middle latitude is induced by more offshore freshwater flowing with the coastal current, which induces lower salinity. The influence of wind on the river plume not only has the advection effects of changing the surface current direction and increasing the surface current speed, but also decreases the current speed due to enhanced vertical mixing. Changes in river discharge influence stratification in the UGoT but have little effect on the behavior of the river plume.

Effect of SiC Content on the Ablation and Oxidation Behavior of ZrB2-Based Ultra High Temperature Ceramic Composites

PubMed Central

Hu, Ping; Gui, Kaixuan; Yang, Yang; Dong, Shun; Zhang, Xinghong

2013-01-01

The ablation and oxidation of ZrB2-based ultra high temperature ceramic (UHTC) composites containing 10%, 15% and 30% v/v SiC were tested under different heat fluxes in a high frequency plasma wind tunnel. Performance was significantly affected by the surface temperature, which was strongly dependent on the composition. Composites containing 10% SiC showed the highest surface temperature (>2300 °C) and underwent a marked degradation under both conditions. In contrast, composites with 30% SiC exhibited the lowest surface temperature (<2000 °C) and demonstrated excellent ablation resistance. The surface temperature of UHTCs in aerothermal testing was closely associated with the dynamic evolution of the surface and bulk oxide properties, especially for the change in chemical composition on the exposed surface, which was strongly dependent on the material composition and testing parameters (i.e., heat flux, enthalpy, pressure and test time), and in turn affected its oxidation performance. PMID:28809239

Effect of SiC Content on the Ablation and Oxidation Behavior of ZrB₂-Based Ultra High Temperature Ceramic Composites.

PubMed

Hu, Ping; Gui, Kaixuan; Yang, Yang; Dong, Shun; Zhang, Xinghong

2013-04-29

The ablation and oxidation of ZrB₂-based ultra high temperature ceramic (UHTC) composites containing 10%, 15% and 30% v/v SiC were tested under different heat fluxes in a high frequency plasma wind tunnel. Performance was significantly affected by the surface temperature, which was strongly dependent on the composition. Composites containing 10% SiC showed the highest surface temperature (>2300 °C) and underwent a marked degradation under both conditions. In contrast, composites with 30% SiC exhibited the lowest surface temperature (<2000 °C) and demonstrated excellent ablation resistance. The surface temperature of UHTCs in aerothermal testing was closely associated with the dynamic evolution of the surface and bulk oxide properties, especially for the change in chemical composition on the exposed surface, which was strongly dependent on the material composition and testing parameters ( i.e. , heat flux, enthalpy, pressure and test time), and in turn affected its oxidation performance.

Damage Tolerance Behavior of Friction Stir Welds in Aluminum Alloys

NASA Technical Reports Server (NTRS)

McGill, Preston; Burkholder, Jonathan

2012-01-01

Friction stir welding is a solid state welding process used in the fabrication of various aerospace structures. Self-reacting and conventional friction stir welding are variations of the friction stir weld process employed in the fabrication of cryogenic propellant tanks which are classified as pressurized structure in many spaceflight vehicle architectures. In order to address damage tolerance behavior associated with friction stir welds in these safety critical structures, nondestructive inspection and proof testing may be required to screen hardware for mission critical defects. The efficacy of the nondestructive evaluation or the proof test is based on an assessment of the critical flaw size. Test data describing fracture behavior, residual strength capability, and cyclic mission life capability of friction stir welds at ambient and cryogenic temperatures have been generated and will be presented in this paper. Fracture behavior will include fracture toughness and tearing (R-curve) response of the friction stir welds. Residual strength behavior will include an evaluation of the effects of lack of penetration on conventional friction stir welds, the effects of internal defects (wormholes) on self-reacting friction stir welds, and an evaluation of the effects of fatigue cycled surface cracks on both conventional and selfreacting welds. Cyclic mission life capability will demonstrate the effects of surface crack defects on service load cycle capability. The fracture data will be used to evaluate nondestructive inspection and proof test requirements for the welds.

YZ (Y = V, Cr; Z = Al, Ga) under pressure: a DFT study

NASA Astrophysics Data System (ADS)

Seema, K.; Kumar, Ranjan

2014-09-01

The structural, electronic and magnetic properties of Co-based Heusler compounds Co2YZ (Y = V, Cr; Z = Al, Ga) under pressure are studied using first principles density functional theory. The calculations are performed within generalized gradient approximation. The total magnetic moment decreases slightly on compression. Under application of external pressure, the valence band and conduction band are shifted downward which leads to the modification of electronic structure. There exists an indirect band gap along Г- X for all the alloys studied. Co2CrAl shows half-metallic nature up to 85 GPa. After this pressure transition from true half-metallic behavior to nearly half-metallic behavior is observed and at 90 GPa it shows metallic behavior. Co2CrGa shows nearly half-metallic behavior at ambient pressure, but true half-metallic behavior is observed as pressure is increased to 100 GPa. For Co2VGa, true half-metallic to nearly half-metallic transition is observed at 40 GPa and around 100 GPa, Co2VGa shows metallic behavior. For Co2VAl, true half-metallic behavior is not observed at ambient as well as higher pressures. The half metal-to-metal transition in Co2VAl and Co2CrAl is accompanied by quenching of magnetic moment.

Monitoring transient changes within overpressured regions of subduction zones using ambient seismic noise.

PubMed

Chaves, Esteban J; Schwartz, Susan Y

2016-01-01

In subduction zones, elevated pore fluid pressure, generally linked to metamorphic dehydration reactions, has a profound influence on the mechanical behavior of the plate interface and forearc crust through its control on effective stress. We use seismic noise-based monitoring to characterize seismic velocity variations following the 2012 Nicoya Peninsula, Costa Rica earthquake [M w (moment magnitude) 7.6] that we attribute to the presence of pressurized pore fluids. Our study reveals a strong velocity reduction (~0.6%) in a region where previous work identified high forearc pore fluid pressure. The depth of this velocity reduction is constrained to be below 5 km and therefore not the result of near-surface damage due to strong ground motions; rather, we posit that it is caused by fracturing of the fluid-pressurized weakened crust due to dynamic stresses. Although pressurized fluids have been implicated in causing coseismic velocity reductions beneath the Japanese volcanic arc, this is the first report of a similar phenomenon in a subduction zone setting. It demonstrates the potential to identify pressurized fluids in subduction zones using temporal variations of seismic velocity inferred from ambient seismic noise correlations.

Synthesis and characterization of Co3O4 prepared from atmospheric pressure acid leach liquors of nickel laterite ores

NASA Astrophysics Data System (ADS)

Meng, Long; Guo, Zhan-cheng; Qu, Jing-kui; Qi, Tao; Guo, Qiang; Hou, Gui-hua; Dong, Peng-yu; Xi, Xin-guo

2018-01-01

A chemical precipitation-thermal decomposition method was developed to synthesize Co3O4 nanoparticles using cobalt liquor obtained from the atmospheric pressure acid leaching process of nickel laterite ores. The effects of the precursor reaction temperature, the concentration of Co2+, and the calcination temperature on the specific surface area, morphology, and the electrochemical behavior of the obtained Co3O4 particles were investigated. The precursor basic cobaltous carbonate and cobaltosic oxide products were characterized and analyzed by Fourier transform infrared spectroscopy, thermogravimetric differential thermal analysis, X-ray diffraction, field-emission scanning electron microscopy, specific surface area analysis, and electrochemical analysis. The results indicate that the specific surface area of the Co3O4 particles with a diameter of 30 nm, which were obtained under the optimum conditions of a precursor reaction temperature of 30°C, 0.25 mol/L Co2+, and a calcination temperature of 350°C, was 48.89 m2/g. Electrodes fabricated using Co3O4 nanoparticles exhibited good electrochemical properties, with a specific capacitance of 216.3 F/g at a scan rate of 100 mV/s.

A level set method for determining critical curvatures for drainage and imbibition.

PubMed

Prodanović, Masa; Bryant, Steven L

2006-12-15

An accurate description of the mechanics of pore level displacement of immiscible fluids could significantly improve the predictions from pore network models of capillary pressure-saturation curves, interfacial areas and relative permeability in real porous media. If we assume quasi-static displacement, at constant pressure and surface tension, pore scale interfaces are modeled as constant mean curvature surfaces, which are not easy to calculate. Moreover, the extremely irregular geometry of natural porous media makes it difficult to evaluate surface curvature values and corresponding geometric configurations of two fluids. Finally, accounting for the topological changes of the interface, such as splitting or merging, is nontrivial. We apply the level set method for tracking and propagating interfaces in order to robustly handle topological changes and to obtain geometrically correct interfaces. We describe a simple but robust model for determining critical curvatures for throat drainage and pore imbibition. The model is set up for quasi-static displacements but it nevertheless captures both reversible and irreversible behavior (Haines jump, pore body imbibition). The pore scale grain boundary conditions are extracted from model porous media and from imaged geometries in real rocks. The method gives quantitative agreement with measurements and with other theories and computational approaches.

Phase-field modeling of chemical control of polarization stability and switching dynamics in ferroelectric thin films

DOE PAGES

Cao, Ye; Kalinin, Sergei V.

2016-12-15

Phase-field simulation (PFS) has revolutionized the understanding of domain structure and switching behavior in ferroelectric thin films and ceramics. Generally, PFS is based on the solution of (a set of) Landau-Ginzburg-Devonshire equations for a defined order parameter field(s) under physical boundary conditions (BCs) of fixed potential or charge. While well matched to the interfaces in bulk materials and devices, these BCs are generally not applicable to free ferroelectric surfaces. Here, we developed a self-consistent phase-field model with BCs based on electrochemical equilibria. We chose Pb(Zr 0.2Ti 0.8)O 3 ultrathin film consisting of (001) oriented single tetragonal domain ( Pz) asmore » a model system and systematically studied the effects of oxygen partial pressure, temperature, and surface ions on the ferroelectric state and compared it with the case of complete screening. We have further explored the polarization switching induced by the oxygen partial pressure and observed pronounced size effect induced by chemical screening. Finally, our paper thus helps to understand the emergent phenomena in ferroelectric thin films brought about by the electrochemical ionic surface compensations.« less

Phase-field modeling of chemical control of polarization stability and switching dynamics in ferroelectric thin films

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

Cao, Ye; Kalinin, Sergei V.

Phase-field simulation (PFS) has revolutionized the understanding of domain structure and switching behavior in ferroelectric thin films and ceramics. Generally, PFS is based on the solution of (a set of) Landau-Ginzburg-Devonshire equations for a defined order parameter field(s) under physical boundary conditions (BCs) of fixed potential or charge. While well matched to the interfaces in bulk materials and devices, these BCs are generally not applicable to free ferroelectric surfaces. Here, we developed a self-consistent phase-field model with BCs based on electrochemical equilibria. We chose Pb(Zr 0.2Ti 0.8)O 3 ultrathin film consisting of (001) oriented single tetragonal domain ( Pz) asmore » a model system and systematically studied the effects of oxygen partial pressure, temperature, and surface ions on the ferroelectric state and compared it with the case of complete screening. We have further explored the polarization switching induced by the oxygen partial pressure and observed pronounced size effect induced by chemical screening. Finally, our paper thus helps to understand the emergent phenomena in ferroelectric thin films brought about by the electrochemical ionic surface compensations.« less

An improved weakly compressible SPH method for simulating free surface flows of viscous and viscoelastic fluids

NASA Astrophysics Data System (ADS)

Xu, Xiaoyang; Deng, Xiao-Long

2016-04-01

In this paper, an improved weakly compressible smoothed particle hydrodynamics (SPH) method is proposed to simulate transient free surface flows of viscous and viscoelastic fluids. The improved SPH algorithm includes the implementation of (i) the mixed symmetric correction of kernel gradient to improve the accuracy and stability of traditional SPH method and (ii) the Rusanov flux in the continuity equation for improving the computation of pressure distributions in the dynamics of liquids. To assess the effectiveness of the improved SPH algorithm, a number of numerical examples including the stretching of an initially circular water drop, dam breaking flow against a vertical wall, the impact of viscous and viscoelastic fluid drop with a rigid wall, and the extrudate swell of viscoelastic fluid have been presented and compared with available numerical and experimental data in literature. The convergent behavior of the improved SPH algorithm has also been studied by using different number of particles. All numerical results demonstrate that the improved SPH algorithm proposed here is capable of modeling free surface flows of viscous and viscoelastic fluids accurately and stably, and even more important, also computing an accurate and little oscillatory pressure field.

In Situ Determination of the Water Condensation Mechanisms on Superhydrophobic and Superhydrophilic Titanium Dioxide Nanotubes.

PubMed

Macias-Montero, Manuel; Lopez-Santos, Carmen; Filippin, A Nicolas; Rico, Victor J; Espinos, Juan P; Fraxedas, Jordi; Perez-Dieste, Virginia; Escudero, Carlos; Gonzalez-Elipe, Agustin R; Borras, Ana

2017-07-05

One-dimensional (1D) nanostructured surfaces based on high-density arrays of nanowires and nanotubes of photoactive titanium dioxide (TiO 2 ) present a tunable wetting behavior from superhydrophobic to superhydrophilic states. These situations are depicted in a reversible way by simply irradiating with ultraviolet light (superhydrophobic to superhydrophilic) and storage in dark. In this article, we combine in situ environmental scanning electron microscopy (ESEM) and near ambient pressure photoemission analysis (NAPP) to understand this transition. These experiments reveal complementary information at microscopic and atomic level reflecting the surface wettability and chemical state modifications experienced by these 1D surfaces upon irradiation. We pay special attention to the role of the water condensation mechanisms and try to elucidate the relationship between apparent water contact angles of sessile drops under ambient conditions at the macroscale with the formation of droplets by water condensation at low temperature and increasing humidity on the nanotubes' surfaces. Thus, for the as-grown nanotubes, we reveal a metastable and superhydrophobic Cassie state for sessile drops that tunes toward water dropwise condensation at the microscale compatible with a partial hydrophobic Wenzel state. For the UV-irradiated surfaces, a filmwise wetting behavior is observed for both condensed water and sessile droplets. NAPP analyses show a hydroxyl accumulation on the as-grown nanotubes surfaces during the exposure to water condensation conditions, whereas the water filmwise condensation on a previously hydroxyl enriched surface is proved for the superhydrophilic counterpart.

Impact of Exposure to Pressure of 50 MPa on the Specific Surface Area of Clay

NASA Astrophysics Data System (ADS)

Koszela-Marek, Ewa

2017-12-01

The paper presents results of laboratory tests conducted to determine the impact of pressure of 50 MPa on specific surface area of clay. These tests were carried out in an original, high-pressure test stand. The specific surface area of clay extracted directly from an open pit mine was compared with the specific surface area of the same clay subjected to the pressure of 50 MPa in a high-pressure chamber. The study found that the specific surface area of the clay subjected to the pressure of 50 MPa increased distinctly by over 35 %. The increase in specific surface can be a result of changes in the microstructure of clay particles and microstructural alteration in the soil skeleton, caused by the pressure.

Experimental observations of pressure oscillations and flow regimes in an analogue volcanic system

USGS Publications Warehouse

Lane, S.J.; Chouet, B.A.; Phillips, J.C.; Dawson, P.; Ryan, G.A.; Hurst, E.

2001-01-01

Gas-liquid flows, designed to be analogous to those in volcanic conduits, are generated in the laboratory using organic gas-gum rosin mixtures expanding in a vertically mounted tube. The expanding fluid shows a range of both flow and pressure oscillation behaviors. Weakly supersaturated source liquids produce a low Reynolds number flow with foam expanding from the top surface of a liquid that exhibits zero fluid velocity at the tube wall; i.e., the conventional "no-slip" boundary condition. Pressure oscillations, often with strong long-period characteristics and consistent with longitudinal and radial resonant oscillation modes, are detected in these fluids. Strongly supersaturated source liquids generate more energetic flows that display a number of flow regimes. These regimes include a static liquid source, viscous flow, detached flow (comprising gas-pockets-at-wall and foam-in-gas annular flow, therefore demonstrating strong radial heterogeneity), and a fully turbulent transonic fragmented or mist flow. Each of these flow regimes displays characteristic pressure oscillations that can be related to resonance of flow features or wall impact phenomena. The pressure oscillations are produced by the degassing processes without the need of elastic coupling to the confining medium or flow restrictors and valvelike features. The oscillatory behavior of the experimental flows is compared to seismoacoustic data from a range of volcanoes where resonant oscillation of the fluid within the conduit is also often invoked as controlling the observed oscillation frequencies. On the basis of the experimental data we postulate on the nature of seismic signals that may be measured during large-scale explosive activity. Copyright 2001 by the American Geophysical Union.

Restraint of Liquid Jets by Surface Tension in Microgravity Modeled

NASA Technical Reports Server (NTRS)

Chato, David J.

2001-01-01

Tension in Microgravity Modeled Microgravity poses many challenges to the designer of spacecraft tanks. Chief among these are the lack of phase separation and the need to supply vapor-free liquid or liquidfree vapor to the spacecraft processes that require fluid. One of the principal problems of phase separation is the creation of liquid jets. A jet can be created by liquid filling, settling of the fluid to one end of the tank, or even closing a valve to stop the liquid flow. Anyone who has seen a fountain knows that jets occur in normal gravity also. However, in normal gravity, the gravity controls and restricts the jet flow. In microgravity, with gravity largely absent, jets must be contained by surface tension forces. Recent NASA experiments in microgravity (Tank Pressure Control Experiment, TPCE, and Vented Tank Pressure Experiment, VTRE) resulted in a wealth of data about jet behavior in microgravity. VTRE was surprising in that, although it contained a complex geometry of baffles and vanes, the limit on liquid inflow was the emergence of a liquid jet from the top of the vane structure. Clearly understanding the restraint of liquid jets by surface tension is key to managing fluids in low gravity. To model this phenomenon, we need a numerical method that can track the fluid motion and the surface tension forces. The fluid motion is modeled with the Navier-Stokes equation formulated for low-speed incompressible flows. The quantities of velocity and pressure are placed on a staggered grid, with velocity being tracked at cell faces and pressure at cell centers. The free surface is tracked via the introduction of a color function that tracks liquid as 1/2 and gas as -1/2. A phase model developed by Jacqmin is used. This model converts the discrete surface tension force into a barrier function that peaks at the free surface and decays rapidly. Previous attempts at this formulation have been criticized for smearing the interface. However, by sharpening the phase function, double gridding the fluid function, and using a higher order solution for the fluid function, interface smearing is avoided. These equations can be rewritten as two coupled Poisson equations that also include the velocity. The method of solution is as follows: first, the phase equations are solved from this solution, a velocity field is generated, then a successive overrelaxation scheme is used to solve for a pressure field consistent with the velocity solution. After the code was implemented in axisymmetric form and verified by several test cases, the drop tower runs of Aydelott were modeled. The model handed the free-surface deformation quite nicely, even to the point of modeling geyser growth in the regime where the free surface was no longer restrained. A representative run is shown.

An alternative to reduction of surface pressure to sea level

NASA Technical Reports Server (NTRS)

Deardorff, J. W.

1982-01-01

The pitfalls of the present method of reducing surface pressure to sea level are reviewed, and an alternative, adjusted pressure, P, is proposed. P is obtained from solution of a Poisson equation over a continental region, using the simplest boundary condition along the perimeter or coastline where P equals the sea level pressure. The use of P would avoid the empiricisms and disadvantages of pressure reduction to sea level, and would produce surface pressure charts which depict the true geostrophic wind at the surface.

Recollections of pressure to eat during childhood, but not picky eating, predict young adult eating behavior.

PubMed

Ellis, Jordan M; Galloway, Amy T; Webb, Rose Mary; Martz, Denise M; Farrow, Claire V

2016-02-01

Picky eating is a childhood behavior that vexes many parents and is a symptom in the newer diagnosis of Avoidant/Restrictive Food Intake Disorder (ARFID) in adults. Pressure to eat, a parental controlling feeding practice aimed at encouraging a child to eat more, is associated with picky eating and a number of other childhood eating concerns. Low intuitive eating, an insensitivity to internal hunger and satiety cues, is also associated with a number of problem eating behaviors in adulthood. Whether picky eating and pressure to eat are predictive of young adult eating behavior is relatively unstudied. Current adult intuitive eating and disordered eating behaviors were self-reported by 170 college students, along with childhood picky eating and pressure through retrospective self- and parent reports. Hierarchical regression analyses revealed that childhood parental pressure to eat, but not picky eating, predicted intuitive eating and disordered eating symptoms in college students. These findings suggest that parental pressure in childhood is associated with problematic eating patterns in young adulthood. Additional research is needed to understand the extent to which parental pressure is a reaction to or perhaps compounds the development of problematic eating behavior. Copyright © 2015 Elsevier Ltd. All rights reserved.

Surface-initiated phase transition in solid hydrogen under the high-pressure compression

NASA Astrophysics Data System (ADS)

Lei, Haile; Lin, Wei; Wang, Kai; Li, Xibo

2018-03-01

The large-scale molecular dynamics simulations have been performed to understand the microscopic mechanism governing the phase transition of solid hydrogen under the high-pressure compression. These results demonstrate that the face-centered-cubic-to-hexagonal close-packed phase transition is initiated first at the surfaces at a much lower pressure than in the volume and then extends gradually from the surface to volume in the solid hydrogen. The infrared spectra from the surface are revealed to exhibit a different pressure-dependent feature from those of the volume during the high-pressure compression. It is thus deduced that the weakening intramolecular H-H bonds are always accompanied by hardening surface phonons through strengthening the intermolecular H2-H2 coupling at the surfaces with respect to the counterparts in the volume at high pressures. This is just opposite to the conventional atomic crystals, in which the surface phonons are softening. The high-pressure compression has further been predicted to force the atoms or molecules to spray out of surface to degrade the pressure. These results provide a glimpse of structural properties of solid hydrogen at the early stage during the high-pressure compression.

Surface temperatures and glassy state investigations in tribology

NASA Technical Reports Server (NTRS)

Bair, S.; Winer, W. O.

1979-01-01

The limiting shear stress shear rheological model was applied to property measurements pursuant to the use of the constitutive equation and the application of the constitutive equation to elastrohydrodynamic (EHD) traction. Experimental techniques were developed to subject materials to isothermal compression which is similar to the history the materials were subjected to in EHD contacts. In addition, an apparatus was developed for measuring the shear stress-strain behavior of solid lubricating materials. Four commercially available materials were examined under pressure. They exhibit elastic and limiting shear stress behavior similar to that of liquid lubricants. The application of the limiting shear stress model to traction predictions was extended employing the primary materials properties measured in the laboratory. The shear rheological model was also applied to a Grubin-like EHD inlet analysis for predicting film thicknesses when employing the limiting shear stress model material behavior.

Volcanoes Behave as Composite Materials: Implications for Modeling Magma Chambers, Dikes, and Surface Deformation

NASA Astrophysics Data System (ADS)

Leiss, B.; Gudmundsson, A.; Philipp, S. L.

2005-12-01

By definition, composite volcanoes are composed of numerous alternating material units or layers such as lavas, sediments, and pyroclastics. Commonly, these layers have widely different mechanical properties. In particular, some lava flows and welded pyroclastic flows may be stiff (with a high Young's modulus), whereas others, such as non-welded pyroclastic units and sediments, may be soft (with a low Young's modulus). As a consequence, even if the loading (tectonic stress, magmatic pressure, or displacement) is uniform, the stresses within the composite volcano will vary widely. In this sense, the behavior of composite volcanoes is similar to that of general composite materials. The deformation of the surface of a volcano during an unrest period results from stresses generated by processes and parameters such as fluid pressure in a geothermal field or a magma chamber, a regional tectonic event, and a dike injection. Here we present new numerical models on mechanics of magma chambers and dikes, and the associated surface deformation of composite volcanoes. The models show that the surface deformation during magma-chamber inflation and deflation depends much on the chamber geometry, the loading conditions, and the mechanical properties of the rock units that constitute the volcano. The models also indicate that the surface deformation induced by a propagating dike depends much on the mechanical properties of the layers between the dike tip and the surface. In particular, the numerical results show that soft layers and weak contacts between layers may suppress the dike-induced tensile stresses and the associated surface deformation. Many dikes may therefore become injected and arrested at shallow depths in a volcano while giving rise to little or no surface deformation. Traditional analytical surface-deformation models such as a point source (Mogi model) for a magma-chamber pressure change and a dislocation for a dike normally assume the volcano to behave as a homogeneous, isotropic half space. The present numerical results, combined with field studies, indicate that such analytical models may yield results that have little similarity with the actual structure being modeled.

Fate of a perched crystal layer in a magma ocean

NASA Technical Reports Server (NTRS)

Morse, S. A.

1992-01-01

The pressure gradients and liquid compressibilities of deep magma oceans should sustain the internal flotation of native crystals owing to a density crossover between crystal and liquid. Olivine at upper mantle depths near 250 km is considered. The behavior of a perched crystal layer is part of the general question concerning the fate of any transient crystal carried away from a cooling surface, whether this be a planetary surface or the roof of an intrusive magma body. For magma bodies thicker than a few hundred meters at modest crustal depths, the major cooling surface is the roof even when most solidification occurs at the floor. Importation of cool surroundings must also be invoked for the generation of a perched crystal layer in a magma ocean, but in this case the perched layer is deeply embedded in the hot part of the magma body, and far away from any cooling surface. Other aspects of this study are presented.

Molar volume and adsorption isotherm dependence of capillary forces in nanoasperity contacts.

PubMed

Asay, David B; Kim, Seong H

2007-11-20

The magnitude of the capillary force at any given temperature and adsorbate partial pressure depends primarily on four factors: the surface tension of the adsorbate, its liquid molar volume, its isothermal behavior, and the contact geometry. At large contacting radii, the adsorbate surface tension and the contact geometry are dominating. This is the case of surface force apparatus measurements and atomic force microscopy (AFM) experiments with micrometer-size spheres. However, as the size of contacting asperities decreases to the nanoscale as in AFM experiments with sharp tips, the molar volume and isotherm of the adsorbate become very important to capillary formation as well as capillary adhesion. This effect is experimentally and theoretically explored with simple alcohol molecules (ethanol, 1-butanol, and 1-pentanol) which have comparable surface tensions but differing liquid molar volumes. Adsorption isotherms for these alcohols on silicon oxide are also reported.

Nickel adsorption on chalk and calcite

NASA Astrophysics Data System (ADS)

Belova, D. A.; Lakshtanov, L. Z.; Carneiro, J. F.; Stipp, S. L. S.

2014-12-01

Nickel uptake from solution by two types of chalk and calcite was investigated in batch sorption studies. The goal was to understand the difference in sorption behavior between synthetic and biogenic calcite. Experiments at atmospheric partial pressure of CO2, in solutions equilibrated with calcite and chalk and pH ranging from 7.7 to 8.8, explored the influence of initial concentration and the amount and type of sorbent on Ni uptake. Adsorption increases with increased surface area and pH. A surface complexation model describes the data well. Stability constants for the Ni surface complex are log KNi = - 1.12 on calcite and log KNi = - 0.43 and - 0.50 on the two chalk samples. The study confirms that synthetic calcite and chalk both take up nickel, but Ni binds more strongly on the biogenic calcite than on inorganically precipitated, synthetic powder, because of the presence of trace amounts of polysaccharides and clay nanoparticles on the chalk surface.

Friction and wear behavior of single-crystal silicon carbide in contact with titanium

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1977-01-01

Sliding friction experiments were conducted with single crystal silicon carbide in sliding contact with titanium. Results indicate that the friction coefficient is greater in vacuum than in argon and that this is due to the greater adhesion or adhesive transfer in vacuum. Thin films of silicon carbide transferred to titanium also adhered to silicon carbide both in argon at atmospheric pressure and in high vacuum. Cohesive bonds fractured on both the silicon carbide and titanium surfaces. The wear debris of silicon carbide created by fracture plowed the silicon carbide surface in a plastic manner. The friction characteristics of titanium in contact with silicon carbide were sensitive to the surface roughness of silicon carbide, and the friction coefficients were higher for a rough surface of silicon carbide than for a smooth one. The difference in friction results was due to plastic deformation (plowing of titanium).

Self-regulating galaxy formation. Part 1: HII disk and Lyman alpha pressure

NASA Technical Reports Server (NTRS)

Cox, D. P.

1983-01-01

Assuming a simple but physically based prototype for behavior of interstellar material during formation of a disk galaxy, coupled with the lowest order description of infall, a scenario is developed for self-regulated disk galaxy formation. Radiation pressure, particularly that of Lyman depha (from fluorescence conversion Lyman continuum), is an essential component, maintaining an inflated disk and stopping infall when only a small fraction of the overall perturbation has joined the disk. The resulting galaxies consist of a two dimensional family whose typical scales and surface density are expressable in terms of fundamental constants. The model leads naturally to galaxies with a rich circumgalactic environment and flat rotation curves (but is weak in its analysis of the subsequent evolution of halo material).

Surface pressure field mapping using luminescent coatings

NASA Technical Reports Server (NTRS)

Mclachlan, B. G.; Kavandi, J. L.; Callis, J. B.; Gouterman, M.; Green, E.; Khalil, G.; Burns, D.

1993-01-01

In recent experiments we demonstrated the feasibility of using the oxygen dependence of luminescent molecules for surface pressure measurement in aerodynamic testing. This technique is based on the observation that for many luminescent molecules the light emitted increases as the oxygen partial pressure, and thus the air pressure, the molecules see decreases. In practice the surface to be observed is coated with an oxygen permeable polymer containing a luminescent molecule and illuminated with ultraviolet radiation. The airflow induced surface pressure field is seen as a luminescence intensity distribution which can be measured using quantitative video techniques. Computer processing converts the video data into a map of the surface pressure field. The experiments consisted of evaluating a trial luminescent coating in measuring the static surface pressure field over a two-dimensional NACA-0012 section model airfoil for Mach numbers ranging from 0.3 and 0.66. Comparison of the luminescent coating derived pressures were made to those obtained from conventional pressure taps. The method along with the experiment and its results will be described.

The effect of multiple layers of linens on surface interface pressure: results of a laboratory study.

PubMed

Williamson, Rachel; Lachenbruch, Charlie; Vangilder, Catherine

2013-06-01

Underpads and layers of linens are frequently placed under patients who are incontinent, have other moisture-related issues, and/or are immobile and cannot reposition independently. Many of these patients are also at risk for pressure ulcers and placed on pressure-redistribution surfaces. The purpose of this study was to measure the effects of linens and incontinence pads on interface pressure. Interface sacral pressures were measured (mm Hg) using a mannequinlike pelvic indenter that has pressure transducers integrated into the unit and is covered with a soft flesh-like elastomer. The indenter was loaded to simulate a median-weight male (80 kg/176 lb), and the testing was performed at head-of bed (HOB) angles of 0°, 30°, and 45°. Two different surfaces, a high performance low-air-loss support (LAL) surface and a standard foam support surface, were used and covered with a fitted sheet (FS) only or a combination of the FS and various incontinence pads and transfer sheets. Linen combinations typically used for relatively immobile patients (n = 4), moisture management (n = 4), and moisture management and immobility (n = 1) were tested, as was the heavy use of linens/pads (nine layers, n = 1). All combinations were tested 10 times at HOB angles of 0°, 30°, and 45°. The highest pressure observed was recorded (peak pressure). Ninety five percent (95%) confidence interval (CI) surrounding the mean of the 10 trials for each combination was calculated using the t-distribution; differences between means for all surface combinations were determined using one-way ANOVA with follow-up Fisher Hayter test. Results indicated that each incontinence pad, transfer sheet, or combination of linens significantly increased the mean peak sacral pressure when compared to a single FS on both the low-air-loss surface and the foam surface, regardless of the head-of-bed angle. The magnitude of peak sacral interface pressure increase for the LAL surface at 30° head-of-bed angle was 20% to 64% depending on the linen combination. At 30°, the foam surface showed increases 6% to 29% (P <0.0001) compared with a FS baseline. If linens were wet, peak interface sacral pressures were equivalent to or less than pressures measured on the same pads when measured dry. The presence of linens on both surface types adversely affected the pressure redistribution capabilities of the surfaces; added layers increased pressure proportionally. The effect on interface pressure from the linen layers was more pronounced on the LAL than the foam surface. The study results illustrate that significant increases in peak interface pressure occur in a laboratory setting when linen layers are added to pressure redistribution surfaces. Results also indicated wetting incontinence pads on a support surface did not significantly increase interface pressure. Although additional preclinical and clinical studies are needed to guide practice, excessive linen usage for patients on therapeutic support surfaces should be discouraged.

In situ measurements of hydraulic fracture behavior, PTE-3. Final report

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

Warpinski, N.R.

Measurements of width and pressure in a propagating hydraulic fracture have been made in tests conducted at DOE`s Nevada Test Site. This was accomplished by creating an "instrumented fracture" at a tunnel complex (at a depth of 1400 ft) where realistic in situ conditions prevail, particularly with respect to stress and geologic features such as natural fractures and material anisotropy. Analyses of these data show that the pressure drop along the fracture length is much larger than predicted by viscous theory currently in use in models today. This is apparently due to the tortuosity of the fracture path, multiple fracturemore » strands, roughness, and sharp turns (corners) in the flow path due to natural fractures and rock property variations. It suggests that fracture design models need to be updated to include a more realistic friction factor so that fracture lengths are not overestimated. The width and pressure profiles near the crack tip have been investigated in some detail, including the length of the unwetted region and the tapering of the crack tip. The overall fracture behavior has been compared with published fracture models. Mineback of the fracture provided evidence of the geometry of the fracture and details of surface features. 35 refs., 89 figs., 30 tabs.« less

Investigation of the Influence of Shapes-Texture on Surface Deformation of UHMWPE as a Bearing Material in Static Normal Load and Rolling Contact

NASA Astrophysics Data System (ADS)

Lestari, W. D.; Ismail, R.; Jamari, J.; Bayuseno, A. P.

2017-05-01

Surface texture is a common method for improving wear properties of a tribo-pair of soft and hard bearing material. The reduction of wear rates on the contacting surface material is becoming important issues. In the present study, analysis of the contact pressure on the flat surface of UHMWPE (Ultra High Molecular Weight Polyethylene) under the static- and rolling motion with the surface of steel ball used the 3D finite element method (FEM) (the ABAQUS software version 6.12). Five shaped-texture models (square, circle, ellipse, triangle, and chevron) were presented on the flat surface for analysis. The normal load of 17, 30 and 50 N was deliberately set-up for static and rolling contact analysis. The contact pressure was determined to predict the wear behavior of the shaped-texture on the flat surface of UHMWPE. The results have shown that the static normal load yielded the lowest von-Mises stress distribution on the shaped-texture of the ellipse for all values applied a load, while the square shape experienced the highest stress distribution. Under rolling contact, however, the increasing load yielded the increasing von Mises stress distribution for the texture with a triangle shape. Moreover, the texture shapes for circle, ellipse, and chevron respectively, may undergo the lowest stress distribution for all load. The wear calculation provided that the circle and square shape may undergo the highest wear rates. Obviously, the surface texture of circle, ellipse, and chevron may experience the lowest wear rates and is potential for use in the surface engineering of bearing materials.

Enhancing the Bioactivity of Yttria-Stabilized Tetragonal Zirconia Ceramics via Grain-Boundary Activation.

PubMed

Ke, Jinhuan; He, Fupo; Ye, Jiandong

2017-05-17

Yttria-stabilized tetragonal zirconia (Y-TZP) has been proposed as a potential dental implant because of its good biocompatibility, excellent mechanical properties, and distinctive aesthetic effect. However, Y-TZP cannot form chemical bonds with bone tissue because of its biological inertness, which affects the reliability and long-term efficacy of Y-TZP implants. In this study, to improve the bioactivity of Y-TZP ceramics while maintaining their good mechanical performance, Y-TZP was modified by grain-boundary activation via the infiltration of a bioactive glass (BG) sol into the surface layers of Y-TZP ceramics under different negative pressures (atmospheric pressure, -0.05 kPa, and -0.1 kPa), followed by gelling and sintering. The in vitro bioactivity, mechanical properties, and cell behavior of the Y-TZP with improved bioactivity were systematically investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), electron probe microanalysis (EPMA), and Raman spectroscopy. The results of the bioactivity test conducted by immersing Y-TZP in simulated body fluid (SBF) showed that a bonelike apatite layer was produced on the entire surface. The mechanical properties of the modified Y-TZP decreased as the negative pressure in the BG-infiltration process increased relative to those of the Y-TZP blank group. However, the samples infiltrated with the BG sol under -0.05 kPa and atmospheric pressure still retained good mechanical performance. The cell-culture results revealed that the bioactive surface modification of Y-TZP could promote cell adhesion and differentiation. The present work demonstrates that the bioactivity of Y-TZP can be enhanced by grain-boundary activation, and the bioactive Y-TZP is expected to be a potential candidate for use as a dental implant material.

Multivariate optimum interpolation of surface pressure and winds over oceans

NASA Technical Reports Server (NTRS)

Bloom, S. C.

1984-01-01

The observations of surface pressure are quite sparse over oceanic areas. An effort to improve the analysis of surface pressure over oceans through the development of a multivariate surface analysis scheme which makes use of surface pressure and wind data is discussed. Although the present research used ship winds, future versions of this analysis scheme could utilize winds from additional sources, such as satellite scatterometer data.

High pressure Raman spectroscopy of H2O-CH3OH mixtures.

PubMed

Hsieh, Wen-Pin; Chien, Yu-Hsiang

2015-02-23

Complex intra-molecular interactions and the hydrogen-bonding network in H2O-volatile mixtures play critical roles in many dynamics processes in physical chemistry, biology, and Earth and planetary sciences. We used high pressure Raman spectroscopy to study the pressure evolution of vibrational frequencies and bonding behavior in H2O-CH3OH mixtures. We found that the presence of low CH3OH content in H2O increases the transition pressure where water crystallizes to ice VI, but does not significantly change the pressure where ice VI transforms to ice VII. Furthermore, the stiffening rates of C-H stretching frequencies dω/dP in CH3OH significantly decrease upon the crystallization of water, and the softening rates of the O-H stretching frequencies of ice VII are suppressed over a narrow pressure range, after which the frequencies of these modes shift with pressure in ways similar to pure CH3OH and ice VII, respectively. Such complex pressure evolution of Raman frequencies along with pronounced variations in Raman intensities of CH3OH within the sample, and the hysteresis of the water-ice VI phase transition suggest pressure-induced segregation of low content CH3OH from ice VII. These findings indicate the significant influence of volatiles on the crystallization of sub-surface ocean and thermal evolution within large icy planets and satellites.

On the use of electrokinetic phenomena of the second kind for probing electrode kinetic properties of modified electron-conducting surfaces.

PubMed

Duval, Jérôme F L; Sorrenti, Estelle; Waldvogel, Yves; Görner, Tatiana; De Donato, Philippe

2007-04-14

The electrokinetic features of electron-conducting substrates, as measured in a conventional thin-layer electrokinetic cell, strongly depend on the extent of bipolar faradaic depolarisation of the interface formed with the adjacent electrolytic solution. Streaming potential versus applied pressure data obtained for metallic substrates must generally be interpreted on the basis of a modified Helmholtz-Smoluchowski equation corrected by an electronic conduction term-non linear with respect to the lateral potential and applied pressure gradient-that stems from the bipolar electrodic behavior of the metallic surface. In the current study, streaming potential measurements have been performed in KNO(3) solutions on porous plugs made of electron-conducting grains of pyrite (FeS(2)) covered by humic acids. For zero coverage, the extensive bipolar electronic conduction taking place in the plug-depolarized by concomitant and spatially distributed oxidation and reduction reactions of Fe(2+) and Fe(3+) species-leads to the complete extinction of the streaming potential over the entire range of applied pressure examined. For low to intermediate coverage, the local electron-transfer kinetics on the covered regions of the plug becomes more sluggish. The overall bipolar electronic conduction is then diminished which leads to an increase in the streaming potential with a non-linear dependence on the pressure. For significant coverage, a linear response is observed which basically reflects the interfacial double layer properties of the humics surface layer. A tractable, semi-analytical model is presented that reproduces the electrokinetic peculiarities of the complex and composite system FeS(2)/humics investigated. The study demonstrates that the streaming potential technique is a fast and valuable tool for establishing how well the electron transfer kinetics at a partially or completely depolarised bare electron-conducting substrate/electrolyte solution interface is either promoted (catalysis) or blocked (passivation) by the presence of a discontinuous surface layer.

Correlation models for waste tank sludges and slurries

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

Mahoney, L.A.; Trent, D.S.

This report presents the results of work conducted to support the TEMPEST computer modeling under the Flammable Gas Program (FGP) and to further the comprehension of the physical processes occurring in the Hanford waste tanks. The end products of this task are correlation models (sets of algorithms) that can be added to the TEMPEST computer code to improve the reliability of its simulation of the physical processes that occur in Hanford tanks. The correlation models can be used to augment, not only the TEMPEST code, but other computer codes that can simulate sludge motion and flammable gas retention. This reportmore » presents the correlation models, also termed submodels, that have been developed to date. The submodel-development process is an ongoing effort designed to increase our understanding of sludge behavior and improve our ability to realistically simulate the sludge fluid characteristics that have an impact on safety analysis. The effort has employed both literature searches and data correlation to provide an encyclopedia of tank waste properties in forms that are relatively easy to use in modeling waste behavior. These properties submodels will be used in other tasks to simulate waste behavior in the tanks. Density, viscosity, yield strength, surface tension, heat capacity, thermal conductivity, salt solubility, and ammonia and water vapor pressures were compiled for solutions and suspensions of sodium nitrate and other salts (where data were available), and the data were correlated by linear regression. In addition, data for simulated Hanford waste tank supernatant were correlated to provide density, solubility, surface tension, and vapor pressure submodels for multi-component solutions containing sodium hydroxide, sodium nitrate, sodium nitrite, and sodium aluminate.« less

The behavior of osmium and other siderophile elements during impacts: Insights from the Ries impact structure and central European tektites

NASA Astrophysics Data System (ADS)

Ackerman, Lukáš; Magna, Tomáš; Žák, Karel; Skála, Roman; Jonášová, Šárka; Mizera, Jiří; Řanda, Zdeněk

2017-08-01

Impact processes are natural phenomena that contribute to a variety of physico-chemical mechanisms over an extreme range of shock pressures and temperatures, otherwise seldomly achieved in the Earth's crust through other processes. Under these extreme conditions with transient temperatures and pressures ≥3000 K and ≥100 GPa, followed by their rapid decrease, the behavior of elements has remained poorly understood. Distal glassy ejecta (tektites) were produced in early phases of contact between the Earth's surface and an impacting body. Here we provide evidence for a complex behavior of Os and other highly siderophile elements (HSE; Ir, Ru, Pt, Pd, and Re) during tektite production related to a hyper-velocity impact that formed the Ries structure in Germany. Instead of simple mixing between the surface materials, which are thought to form the major source of central European tektites (moldavites), and impactor matter, the patterns of HSE contents and 187Re/188Os - 187Os/188Os ratios in moldavites, target sediments and impact-related breccias (suevites) can be explained by several sequential and/or contemporary processes. These involve (i) evaporative loss of partially oxidized HSE from the overheated tektite melt, (ii) mixing of target-derived and impactor-derived HSE vapor (plasma) phases, and (iii) early (high-temperature) condensation of a part of the mixed vapor phase back to silicate melt droplets. An almost complete loss of terrestrial Os from the tektite melt and its replacement with extra-terrestrial Os are indicated by low 187Os/188Os ratios in tektites (<0.163) relative to precursor materials (>0.69). This is paralleled by a co-variation between Os and Ni contents in tektites but not in suevites formed later in the impact process.

Room contamination, patient colonization pressure, and the risk of vancomycin-resistant Enterococcus colonization on a unit dedicated to the treatment of hematologic malignancies and hematopoietic stem cell transplantation.

PubMed

Ford, Clyde D; Lopansri, Bert K; Gazdik, Michaela A; Webb, Brandon; Snow, Gregory L; Hoda, Daanish; Adams, Barbara; Petersen, Finn Bo

2016-10-01

Contaminated surfaces and colonization pressure are risk factors for vancomycin-resistant Enterococcus (VRE) colonization in intensive care units (ICUs). Whether these apply to modern units dedicated to the care of hematologic malignancies and hematopoietic stem cell transplant (HSCT) procedures is unknown. We reviewed the records of 780 consecutive admissions for acute leukemia, autologous HSCT, or allogeneic HSCT in which the patient was at risk for hospital-acquired VRE and underwent weekly surveillance. We also obtained staff and room cultures, observed staff behavior, and performed VRE molecular strain typing on selected isolates. The overall rate of VRE colonization was 11.4 cases/1,000 patient days. Cultures of room surfaces revealed VRE isolates in 10% of terminally cleaned rooms. A prior VRE-colonized room occupant did not increase risk, and paired isolates from 20 patients and prior occupants were indistinguishable on molecular typing in only 1 pair. VRE colonization pressure was significantly associated with acquisition. Cultures of unit personnel and shared equipment were negative except for weighing scales. Observation of unit clinical personnel showed high compliance for hand sanitation and but less so for gowns. Conversely, ancillary staff showed poor compliance. Transmission of VRE from room surfaces seems to be an infrequent event. Encouraging adherence to surveillance, disinfection, and contact isolation protocols may decrease VRE colonization rates. Copyright © 2016. Published by Elsevier Inc.

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

K., S C; M., T C

Plastic bonded explosives (PBX) generally consist of 85 - 95 % by weight energetic material, such as HMX, and 5 - 15 % polymeric binder. Understanding of the structure and morphology at elevated temperatures and pressures is important for predicting of PBX behavior in accident scenarios. The crystallographic behavior of pure HMX has been measured as functions of temperature and grain size. The investigation is extended to the high temperature behavior of PBX 9501 (95% HMX, 2.5 % Estane, 2.5 % BDNPA/F). The results show that the HMX {beta}-phase to {delta}-phase transition in PBX 9501 is similar to that inmore » neat HMX. However, in the presence of the PBX 9501 binder, {delta}-phase HMX readily converts back to {beta}-phase during cooling. Using the same temperature profile, the conversion rate decreases for each subsequent heating and cooling cycle. As observed in earlier experiments, no reverse conversion is observed without the polymer binder. It is proposed that the reversion of {delta}-phase to {beta}-phase is due to changes in the surface molecular potential caused by the influence of the polymer binder on the surface molecules of the {delta}-phase. Upon thermal cycling, the polymer binder segregates from the HMX particles and thus reduces the influence of the binder on the surface molecules. This segregation increases the resistance for the {delta}-phase to {beta}-phase transition, as demonstrated in an aged PBX 9501 material for which the reversion is not observed.« less

Failure Behavior of Granite Affected by Confinement and Water Pressure and Its Influence on the Seepage Behavior by Laboratory Experiments

PubMed Central

Cheng, Cheng; Li, Xiao; Li, Shouding; Zheng, Bo

2017-01-01

Failure behavior of granite material is paramount for host rock stability of geological repositories for high-level waste (HLW) disposal. Failure behavior also affects the seepage behavior related to transportation of radionuclide. Few of the published studies gave a consistent analysis on how confinement and water pressure affect the failure behavior, which in turn influences the seepage behavior of the rock during the damage process. Based on a series of laboratory experiments on NRG01 granite samples cored from Alxa area, a candidate area for China’s HLW disposal, this paper presents some detailed observations and analyses for a better understanding on the failure mechanism and seepage behavior of the samples under different confinements and water pressure. The main findings of this study are as follows: (1) Strength reduction properties were found for the granite under water pressure. Besides, the complete axial stress–strain curves show more obvious yielding process in the pre-peak region and a more gradual stress drop in the post-peak region; (2) Shear fracturing pattern is more likely to form in the granite samples with the effect of water pressure, even under much lower confinements, than the predictions from the conventional triaxial compressive results; (3) Four stages of inflow rate curves are divided and the seepage behaviors are found to depend on the failure behavior affected by the confinement and water pressure. PMID:28773157

Statistical behavior of post-shock overpressure past grid turbulence

NASA Astrophysics Data System (ADS)

Sasoh, Akihiro; Harasaki, Tatsuya; Kitamura, Takuya; Takagi, Daisuke; Ito, Shigeyoshi; Matsuda, Atsushi; Nagata, Kouji; Sakai, Yasuhiko

2014-09-01

When a shock wave ejected from the exit of a 5.4-mm inner diameter, stainless steel tube propagated through grid turbulence across a distance of 215 mm, which is 5-15 times larger than its integral length scale , and was normally incident onto a flat surface; the peak value of post-shock overpressure, , at a shock Mach number of 1.0009 on the flat surface experienced a standard deviation of up to about 9 % of its ensemble average. This value was more than 40 times larger than the dynamic pressure fluctuation corresponding to the maximum value of the root-mean-square velocity fluctuation, . By varying and , the statistical behavior of was obtained after at least 500 runs were performed for each condition. The standard deviation of due to the turbulence was almost proportional to . Although the overpressure modulations at two points 200 mm apart were independent of each other, we observed a weak positive correlation between the peak overpressure difference and the relative arrival time difference.

Falling Barometer--Failing Behavior.

ERIC Educational Resources Information Center

Scagliotta, Edward G.

1980-01-01

Observations of 127 boys with behavior problems (ages 9 to 13) were made to study the correlation between air pressure and adverse behavior in the Ss. Results showed that, with each change in barometric pressure, there was an obvious change in the Ss' behavior. (PHR)

Exploring the Role of Habitat on the Wettability of Cicada Wings.

PubMed

Oh, Junho; Dana, Catherine E; Hong, Sungmin; Román, Jessica K; Jo, Kyoo Dong; Hong, Je Won; Nguyen, Jonah; Cropek, Donald M; Alleyne, Marianne; Miljkovic, Nenad

2017-08-16

Evolutionary pressure has pushed many extant species to develop micro/nanostructures that can significantly affect wettability and enable functionalities such as droplet jumping, self-cleaning, antifogging, antimicrobial, and antireflectivity. In particular, significant effort is underway to understand the insect wing surface structure to establish rational design tools for the development of novel engineered materials. Most studies, however, have focused on superhydrophobic wings obtained from a single insect species, in particular, the Psaltoda claripennis cicada. Here, we investigate the relationship between the spatially dependent wing wettability, topology, and droplet jumping behavior of multiple cicada species and their habitat, lifecycle, and interspecies relatedness. We focus on cicada wings of four different species: Neotibicen pruinosus, N. tibicen, Megatibicen dorsatus, and Magicicada septendecim and take a comparative approach. Using spatially resolved microgoniometry, scanning electron microscopy, atomic force microscopy, and high speed optical microscopy, we show that within cicada species, the wettability of wings is spatially homogeneous across wing cells. All four species were shown to have truncated conical pillars with widely varying length scales ranging from 50 to 400 nm in height. Comparison of the wettability revealed three cicada species with wings that are superhydrophobic (>150°) with low contact angle hysteresis (<5°), resulting in stable droplet jumping behavior. The fourth, more distantly related species (Ma. septendecim) showed only moderate hydrophobic behavior, eliminating some of the beneficial surface functional aspects for this cicada. Correlation between cicada habitat and wing wettability yielded little connection as wetter, swampy environments do not necessarily equate to higher measured wing hydrophobicity. The results, however, do point to species relatedness and reproductive strategy as a closer proxy for predicting wettability and surface structure and resultant enhanced wing surface functionality. This work not only elucidates the differences between inter- and intraspecies cicada wing topology, wettability, and water shedding behavior but also enables the development of rational design tools for the manufacture of artificial surfaces for energy and water applications.

The Influence of Oil Contamination on the Nucleate Pool-Boiling Behavior of R-114 from a Structured Surface.

DTIC Science & Technology

1985-03-01

1 7015 IF Pu-a THEN PRINT "PA" Y,"PO" 70Ze IF Pu-) THEN PRINT "PA" .,Y. "PU" 702S NEXT Xa 7038 PRINT "PU" 783S Ian.-Ion+ I 7848 COTO 6540 7845 END IF...Heat Transfer over the wide Range of Pressure," Proceedinqs of the Seventh International Heat Transfer CencYne-,Mun- ch -vI-, �, pp. 19. Webb, R. L

Jumping Mechanism of Self-Propelled Droplet

NASA Astrophysics Data System (ADS)

Lian, Yongsheng; Chen, Yan

2017-11-01

The self-propelled behavior of coalesced droplets can be utilized to enhance heat transfer performance of dropwise condensation. It has been recognized that the droplet self-propelling is the combined result of the conversion of surface energy to kinetic energy and the unsymmetrical boundary conditions imposed on the droplets. However, the roles of boundary conditions, which largely determine the conversion ratio of surface energy to the effective jumping kinetic energy, are not well understood. In this paper we use a numerical approach to investigate the boundary condition effect on the self-propelling behavior. A Navier-Stokes equation solver for multiphase flows is used to describe the flow field. The moment of fluid interface reconstruction technique is applied to resolute the interfaces. A direction splitting method is applied to advect the interface. And an approximate projection method is used to decouple the calculation of velocity and pressure. Comparisons are made with experimental results and show the simulation can accurately capture self-propelling behavior. Our simulation show the vertical flow velocity inside the coalesced droplet can increase the normalized jumping velocity but the contact area between droplets and substrate can decrease jumping velocity. High viscous dissipation is observed at the beginning of the coalescence which reduces jumping velocity.

Study of the corrosion behaviors of 304 austenite stainless steel specimens exposed to static liquid lithium at 600 K

NASA Astrophysics Data System (ADS)

Meng, Xiancai; Zuo, Guizhong; Ren, Jun; Xu, Wei; Sun, Zhen; Huang, Ming; Hu, Wangyu; Hu, Jiansheng; Deng, Huiqiu

2016-11-01

Investigation of corrosion behavior of stainless steel served as one kind of structure materials exposed to liquid lithium (Li) is one of the keys to apply liquid Li as potential plasma facing materials (PFM) or blanket coolant in the fusion device. Corrosion experiments of 304 austenite stainless steel (304 SS) were carried out in static liquid Li at 600 K and up to1584 h at high vacuum with pressure less than 4 × 10-4 Pa. After exposure to liquid Li, it was found that the weight of 304 SS slightly decreased with weight loss rate of 5.7 × 10-4 g/m2/h and surface hardness increased by about 50 HV. Lots of spinel-like grains and holes were observed on the surface of specimens measured by SEM. By further EDS, XRD and metallographic analyzing, it was confirmed that the main compositions of spinel-like grains were M23C6 carbides, and 304 SS produced a non-uniform corrosion behavior by preferential grain boundary attack, possibly due to the easy formation of M23C6 carbides and/or formation of Li compound at grain boundaries.

Modeling the stochastic dynamics of moving turbulent spots over a slender cone at Mach 5 during laminar-turbulent transition

NASA Astrophysics Data System (ADS)

Robbins, Brian; Field, Rich; Grigoriu, Mircea; Jamison, Ryan; Mesh, Mikhail; Casper, Katya; Dechant, Lawrence

2016-11-01

During reentry, a hypersonic vehicle undergoes a period in which the flow about the vehicle transitions from laminar to turbulent flow. During this transitional phase, the flow is characterized by intermittent formations of localized turbulent behavior. These localized regions of turbulence are born at the onset of transition and grow as they move to the aft end of the flight vehicle. Throughout laminar-turbulent transition, the moving turbulent spots cause pressure fluctuations on the outer surface of the vehicle, which leads to the random vibration of the structure and its internal components. In light of this, it is of great interest to study the dynamical response of a flight vehicle undergoing transitional flow so that aircraft can be better designed to prevent structural failure. In this talk, we present a statistical model that calculates the birth, evolution, and pressure field of turbulent spots over a generic slender cone structure. We then illustrate that the model appropriately quantifies intermittency behavior and pressure loading by comparing the intermittency and root-mean-square pressure fluctuations produced by the model with theory and experiment. Finally, we present results pertaining to the structural response of a housing panel on the slender cone. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

An experimental study of the effects of adsorbing and non-adsorbing gases on friction and permeability evolution in clay-rich fault gouge

NASA Astrophysics Data System (ADS)

Lisabeth, H. P.; Zoback, M. D.

2017-12-01

Understanding the flow of fluids through fractures in clay-rich rocks is fundamental to a number of geoengineering enterprises, including development of unconventional hydrocarbon resources, nuclear waste storage and geological carbon sequestration. High clay content tends to make rocks plastic, low-porosity and anisotropic. In addition, some gasses adsorb to clay mineral surfaces, resulting in swelling and concomitant changes in physical properties. These complexities can lead to coupled behaviors that render prediction of fluid behavior in the subsurface difficult. We present the results of a suite of triaxial experiments on binary mixtures of quartz and illite grains to separate and quantify the effects of hydrostatic pressure, differential stress, clay content and gas chemistry on the evolution of mechanical and hydraulic characteristics of the gouge material during deformation. Tests are run on saw-cut samples prepared with gouge at 20 MPa confining pressure, 10 MPa pore pressure and at room temperature. Argon or carbon dioxide is used as pore fluid. Sample permeability, stress and strain are monitored continuously during hydrostatic and axial deformation. We find that pressure and shearing both lead to reductions in permeability. Adsorbing gas leads to swelling and promotes permeability reduction, but appears to have no effect on frictional properties. These results indicate that the seal integrity of clay-rich caprocks may not be compromised by shear deformation, and that depletion and shear deformation of unconventional reservoirs is expected to result in production declines.

Leading-Edge Flow Sensing for Aerodynamic Parameter Estimation

NASA Astrophysics Data System (ADS)

Saini, Aditya

The identification of inflow air data quantities such as airspeed, angle of attack, and local lift coefficient on various sections of a wing or rotor blade provides the capability for load monitoring, aerodynamic diagnostics, and control on devices ranging from air vehicles to wind turbines. Real-time measurement of aerodynamic parameters during flight provides the ability to enhance aircraft operating capabilities while preventing dangerous stall situations. This thesis presents a novel Leading-Edge Flow Sensing (LEFS) algorithm for the determination of the air -data parameters using discrete surface pressures measured at a few ports in the vicinity of the leading edge of a wing or blade section. The approach approximates the leading-edge region of the airfoil as a parabola and uses pressure distribution from the exact potential-ow solution for the parabola to _t the pressures measured from the ports. Pressures sensed at five discrete locations near the leading edge of an airfoil are given as input to the algorithm to solve the model using a simple nonlinear regression. The algorithm directly computes the inflow velocity, the stagnation-point location, section angle of attack and lift coefficient. The performance of the algorithm is assessed using computational and experimental data in the literature for airfoils under different ow conditions. The results show good correlation between the actual and predicted aerodynamic quantities within the pre-stall regime, even for a rotating blade section. Sensing the deviation of the aerodynamic behavior from the linear regime requires additional information on the location of ow separation on the airfoil surface. Bio-inspired artificial hair sensors were explored as a part of the current research for stall detection. The response of such artificial micro-structures can identify critical ow characteristics, which relate directly to the stall behavior. The response of the microfences was recorded via an optical microscope for ow over a at plate at different freestream velocities in the NCSU subsonic wind tunnel. Experiments were also conducted to characterize the directional sensitivity of the microstructures by creating ow reversal at the sensor location to assess the sensor response. The results show that the direction of microfence deflection correctly reflects the local ow behavior as the ow direction is reversed at the sensor location and the magnitude of deflection correlates qualitatively to an increase in the freestream velocity. The knowledge of the ow-separation location integrated with the LEFS algorithm allows the possibility of extending the LEFS analysis to post-stall flight regimes, which is explored in the current work. Finally, the application of the LEFS algorithm to unsteady aerodynamics is investigated to identify the critical sequence of events associated with the formation of leading-edge vortices. Signatures of vortex formation on the airfoil surface can be captured in the surface-pressure measurements. Real-time knowledge of the unsteady ow phenomena holds significant potential for exploiting the enhanced-lift characteristics related to vortex formation and inhibiting the detrimental effects of dynamic stall in engineering applications such as helicopters, wind turbines, bio-inspired flight, and energy harvesting devices. Computational data was used to assess the capability of the LEFS outputs to identity the signatures associated with vortex formation, i.e. onset of vortex shedding, detachment, and termination. The results demonstrate useful correlation between the LEFS outputs and the LEV signatures.

Aerodynamic performance of transonic and subsonic airfoils: Effects of surface roughness, turbulence intensity, Mach number, and streamline curvature-airfoil shape

NASA Astrophysics Data System (ADS)

Zhang, Qiang

The effects of surface roughness, turbulence intensity, Mach number, and streamline curvature-airfoil shape on the aerodynamic performance of turbine airfoils are investigated in compressible, high speed flows. The University of Utah Transonic Wind Tunnel is employed for the experimental part of the study. Two different test sections are designed to produce Mach numbers, Reynolds numbers, passage mass flow rates, and physical dimensions, which match values along turbine blades in operating engines: (i) a nonturning test section with a symmetric airfoil, and (ii) a cascade test section with a cambered turbine vane. The nonuniform, irregular, three-dimensional surface roughness is characterized using the equivalent sand grain roughness size. Changing the airfoil surface roughness condition has a substantial effect on wake profiles of total pressure loss coefficients, normalized Mach number, normalized kinetic energy, and on the normalized and dimensional magnitudes of Integrated Aerodynamic Losses produced by the airfoils. Comparisons with results for a symmetric airfoil and a cambered vane show that roughness has more substantial effects on losses produced by the symmetric airfoil than the cambered vane. Data are also provided that illustrate the larger loss magnitudes are generally present with flow turning and cambered airfoils, than with symmetric airfoils. Wake turbulence structure of symmetric airfoils and cambered vanes are also studied experimentally. The effects of surface roughness and freestream turbulence levels on wake distributions of mean velocity, turbulence intensity, and power spectral density profiles and vortex shedding frequencies are quantified one axial chord length downstream of the test airfoils. As the level of surface roughness increases, all wake profile quantities broaden significantly and nondimensional vortex shedding frequencies decrease. Wake profiles produced by the symmetric airfoil are more sensitive to variations of surface roughness and freestream turbulence, compared with data from the cambered vane airfoil. Stanton numbers, skin friction coefficients, aerodynamic losses, and Reynolds analogy behavior are numerically predicted for a turbine vane using the FLUENT with a k-epsilon RNG model to show the effects of Mach number, mainstream turbulence level, and surface roughness. Comparisons with wake aerodynamic loss experimental data are made. Numerically predicted skin friction coefficients and Stanton numbers are also used to deduce Reynolds analogy behavior on the vane suction and pressure sides.

Corrosion Behavior of FBR Structural Materials in High Temperature Supercritical Carbon Dioxide

NASA Astrophysics Data System (ADS)

Furukawa, Tomohiro; Inagaki, Yoshiyuki; Aritomi, Masanori

A key problem in the application of a supercritical carbon dioxide (CO2) turbine cycle to a fast breeder reactor (FBR) is the corrosion of structural material by supercritical CO2 at high temperature. In this study, corrosion test of high-chromium martensitic steel (12Cr-steel) and FBR grade type 316 stainless steel (316FR), which are candidate materials for FBRs, were performed at 400-600°C in supercritical CO2 pressurized at 20MPa. Corrosion due to the high temperature oxidation in exposed surface was measured up to approximately 2000h in both steels. In the case of 12Cr-steel, the weight gain showed parabolic growth with exposure time at each temperature. The oxidation coefficient could be estimated by the Arrhenius function. The specimens were covered by two successive oxide layers, an Fe-Cr-O layer (inside) and an Fe-O layer (outside). A partial thin oxide diffusion layer appeared between the base metal and the Fe-Cr-O layer. The corrosion behavior was equivalent to that in supercritical CO2 at 10MPa, and no effects of CO2 pressure on oxidation were observed in this study. In the case of 316FR specimens, the weight gain was significantly lower than that of 12Cr-steel. Dependency of neither temperature nor exposed time on oxidation was not observed, and the value of all tested specimens was within 2g/m2. Nodule shape oxides which consisted of two structures, Fe-Cr-O and Fe-O were observed on the surface of the 316FR specimen. Carburizing, known as a factor in the occurrence of breakaway corrosion and/or the degradation of ductility, was observed on the surface of both steels.

A new approach for crystallization of copper(ii) oxide hollow nanostructures with superior catalytic and magnetic response

NASA Astrophysics Data System (ADS)

Singh, Inderjeet; Landfester, Katharina; Chandra, Amreesh; Muñoz-Espí, Rafael

2015-11-01

We report the synthesis of copper(ii) oxide hollow nanostructures at ambient pressure and close to room temperature by applying the soft templating effect provided by the confinement of droplets in miniemulsion systems. Particle growth can be explained by considering a mechanism that involves both diffusion and reaction control. The catalytic reduction of p-nitrophenol in aqueous media is used as a model reaction to prove the catalytic activity of the materials: the synthesized hollow structures show nearly 100 times higher rate constants than solid CuO microspheres. The kinetic behavior and the order of the reduction reaction change due to the increase of the surface area of the hollow structures. The synthesis also leads to modification of physical properties such as magnetism.We report the synthesis of copper(ii) oxide hollow nanostructures at ambient pressure and close to room temperature by applying the soft templating effect provided by the confinement of droplets in miniemulsion systems. Particle growth can be explained by considering a mechanism that involves both diffusion and reaction control. The catalytic reduction of p-nitrophenol in aqueous media is used as a model reaction to prove the catalytic activity of the materials: the synthesized hollow structures show nearly 100 times higher rate constants than solid CuO microspheres. The kinetic behavior and the order of the reduction reaction change due to the increase of the surface area of the hollow structures. The synthesis also leads to modification of physical properties such as magnetism. Electronic supplementary information (ESI) available: Associated structural and morphological analysis, XPS characterization, BET surface area, catalytic measurements, recycle tests of the catalyst, and magnetic characterizations. See DOI: 10.1039/c5nr05579b

Scuffing Characteristics of High-Load Rolling/Sliding Contacts Operating in Liquid Oxygen: Effects of Materials and Surface Roughness

NASA Technical Reports Server (NTRS)

Chang, L.; Hall, P. B.; Thom, R.

1996-01-01

This research reports on an experimental study of the effects of materials and surface roughness on the scuffing characteristics of rolling/sliding contacts cooled and lubricated with liquid oxygen. Experiments were carried out under heavy loading with a Hertzian pressure in the range of 2.0 GPa to 3.0 GPa and with a high rolling velocity of up to 48 m/s. For contacts between AISI 440 C stainless-steel elements, the results showed that the scuffing behavior of the system was fairly consistent under a wide range of rolling velocity. Scuffing commenced at a small slide-to-roll ratio of around 0.02, and the scuffing behavior of the contact was not sensitive to surface roughness for the test-sample RMS roughness ranging from 0.02 microns to 0.10 microns. For contacts between 440 C and Si3N4 elements, on the other hand, the scuffing behavior of the system was not very consistent and somewhat unpredictable. The results were sensitive to surface roughness particularly that of the Si3N4 test sample. With well polished test samples, consistent results were obtained; the level of traction was lower than that with a 440 C toroid and scuffing did not take place up to a slide-to-roll ratio of near 0.03. The results strongly suggest that significant hydrodynamic effect can be generated by liquid oxygen under heavy loading and high velocity conditions. The results also suggest that the hydrodynamic action is likely generated by the conventional viscous mechanism as it can be largely destroyed by a narrow circumferential surface scratch running through the central region of the contact.

Multilayer adsorption of C2H4 and CF4 on graphite: Grand Canonical Monte Carlo simulation

NASA Astrophysics Data System (ADS)

Abdelatif, H.; Drir, M.

2016-11-01

We study the phase transitions in adsorbed multilayers by Grand Canonical Monte Carlo simulations (GCMC) of the lattice-gas model. The focus will be on ethylene (C2H4) and tetrafluoromethane (CF4) on a homogeneous graphite surface. Earlier simulations of these systems investigated structural properties, dynamical behaviors of adsorbed films and thermodynamic quantities such as isosteric heat. The main purpose of this study is to consider the adsorbed multilayers by the evaluation of the layering behavior, the wetting phenomena and the critical temperatures. The isotherms obtained for temperature from 50 K to 170 K reproduce a number of interesting features observed experimentally: (i) we observe an important number of layers in contrast with previous simulations, (ii) a finite number of layers at saturated pressure for low temperatures are found, (iii) the isotherms present vertical steps typical of layer-by-layer growth, at higher temperatures these distinct layers tend to disappear signifying that the film thickness increases continuously, (iv) a thin film to thick film transition near the triple point temperature is noticed. In addition to this qualitative description, quantitative information are determined including temperatures and relative pressures of layers formation, layer-critical-point temperatures and phase diagrams. Comparing the two systems, ethylene/graphite and tetrafluoromethane/graphite, we observe a qualitatively similar behavior.

Nonlinear Acoustics at the Air-Water Free Surface

NASA Astrophysics Data System (ADS)

Pree, Seth; Naranjo, Brian; Putterman, Seth

2016-11-01

According to linear acoustics, airborne sound incident on a water surface transmits only a tenth of a percent of its energy. This difficulty of transmitting energy across the water surface limits the feasibility of standoff ultrasound imaging. We propose to overcome this long standing problem by developing new methods of coupling into the medium at standoff. In particular, we believe that the acoustic nonlinearity of both the air and the medium may yield a range of effects in the vicinity of the surface permitting an efficient transmission of ultrasound from the air into the medium. The recent commercial availability of parametric speakers that deliver modulated 100kHz ultrasound at 135dB to nonlinearly generate music at 95dB provides an interesting platform with which to revisit the transmission of sound across acoustic impedance mismatches. We show results of experimental studies of the behavior of the air-water free surface when subjected to large amplitude acoustic pressures from the air. This work was supported by the ARO STIR program.

Physical properties and application in the confined geometrical systems

NASA Astrophysics Data System (ADS)

Pak, Hunkyun

Surface viscoelasticity of a vitamin E modified polyethylene glycol (vitamin E-TPGS) monolayers at the air/water interface is deduced by the surface light scattering method and Wilhelmy plate method. It was found that the viscoelasticity of vitamin E-TPGS monolayer is similar to that of PEO monolayer at the surface pressure lower than the collapse pressure of the polyethylene oxide (PEO). However, at higher surface pressure than the collapse pressure of PEO, it deviates from the viscoelastic behavior of PEO. Lateral diffusion constants of a probe lipid (NBD-PC) in a binary monolayer of L-a-dilauroylphosphatidylcholine (DLPC) and poly-(di-isobutylene-alt-maleic acid) (PDIBMA) were determined by the fluorescence recovery after photobleaching (FRAP) method at the air/pH 7 buffer interface as a function of composition. The diffusion constant is found to retard down to less than one hundredth to that at pure DLPC monolayers as the mole fraction of PDIBMA increased. The free area model was used to interpret the probe diffusion retardation. Translational diffusion constants of a probe molecule, 4-octadecylamino-7-nitrobenzo-2-oxa-1,3-diazole (C18-NBD), in thin polyisoprene (PI) and polydimethyl siloxane (PDMS) films, spin coated on methylated and propylyaminated silicon wafers, are studied by the FRAP method as a function of film thickness. Reduction of the diffusion constant is observed as thickness of the films is decreased. Two empirical models, the two-layer model and the continuous layer model are proposed to account for the diffusion constant dependence on the film thickness vs. thickness. It was observed that the diffusion profiles in the films are dependet on the nature of the substrate surfaces. Self-assembled patterns of magnetic particles were made and fixed by applying magnetic field on the particles dispersed at the air/liquid interface, followed by gelling of the liquid subphase. With this method, the large patterns with controllable lattice constant can be made. The fixation of the subphase enhances the stability of the patterns. Further, three-dimensional self-assembled patterns can be made by this method when the fixation process is incorporated.

Triboelectric, Corona, and Induction Charging of Insulators as a Function of Pressure

NASA Technical Reports Server (NTRS)

Hogue, Michael D.; Mucciolo, Eduardo R.; Calle, Carlos I.

2006-01-01

Theoretical and experimental research has been performed that shows that the surface charge on an insulator after triboelectric charging with another insulator is rapidly dissipated with lowered atmospheric pressure. This pressure discharge is consistent with surface ions being evaporated off the surface once their vapor pressure is attained. In this paper we will report on the results of three different charging techniques (triboelectric, corona, and induction) performed on selected polymers with varying atmospheric pressure. This data will show that ion exchange between the polymer samples is the mechanism responsible for most of the surface charge on the polymer surfaces.

In-Situ Electrochemical Corrosion Behavior of Nickel-Base 718 Alloy Under Various CO2 Partial Pressures at 150 and 205 °C in NaCl Solution

NASA Astrophysics Data System (ADS)

Zhang, Yubi; Zhao, Yongtao; Tang, An; Yang, Wenjie; Li, Enzuo

2018-07-01

The electrochemical corrosion behavior of nickel-base alloy 718 was investigated using electrochemical impedance spectroscopy and potentiodynamic polarization techniques at various partial pressures of CO2 (P_{{{CO}2 }}s) in a 25 wt% NaCl solution at 150 and 205 °C. The passive films composed of FeCO3 exhibit good corrosion resistance with a feature of Warburg impedance, Tafel plots show a complete passivation and the anodic reactions was dominated by a diffusion process at low P_{{{CO}2 }}s (1.8-9.8 MPa) at 150 °C. While numerous dented corrosion areas appeared on the sample surface for the P_{{{CO}2 }} of 11.6 MPa at 205 °C, the Tafel plot with three anodic peaks and the Nyquist diagram with an atrophied impedance arc were present. This dented corrosion attribute to the synergistic effects of stress, temperature, P_{{{CO}2 }} and Cl-, the temperature and stress could play crucial roles on the corrosion of the alloy 718.

Jumping hoops on water

NASA Astrophysics Data System (ADS)

Yang, Eunjin; Kim, Ho-Young

2015-11-01

Small aquatic arthropods, such as water striders and fishing spiders, are able to jump off water to a height several times their body length. Inspired by the unique biological motility on water, we study a simple model using a flexible hoop to provide fundamental understanding and a mimicking principle of small jumpers on water. Behavior of a hoop on water, which is coated with superhydrophobic particles and initially bent into an ellipse from an equilibrium circular shape, is visualized with a high speed camera upon launching it into air by releasing its initial elastic strain energy. We observe that jumping of our hoops is dominated by the dynamic pressure of water rather than surface tension, and thus it corresponds to the dynamic condition experienced by fishing spiders. We calculate the reaction forces provided by water adopting the unsteady Bernoulli equation as well as the momentum loss into liquid inertia and viscous friction. Our analysis allows us to predict the jumping efficiency of the hoop on water in comparison to that on ground, and to discuss the evolutionary pressure rendering fishing spiders select such dynamic behavior.

In-Situ Electrochemical Corrosion Behavior of Nickel-Base 718 Alloy Under Various CO2 Partial Pressures at 150 and 205 °C in NaCl Solution

NASA Astrophysics Data System (ADS)

Zhang, Yubi; Zhao, Yongtao; Tang, An; Yang, Wenjie; Li, Enzuo

2018-03-01

The electrochemical corrosion behavior of nickel-base alloy 718 was investigated using electrochemical impedance spectroscopy and potentiodynamic polarization techniques at various partial pressures of CO2 (P_{{{CO}2 }} s) in a 25 wt% NaCl solution at 150 and 205 °C. The passive films composed of FeCO3 exhibit good corrosion resistance with a feature of Warburg impedance, Tafel plots show a complete passivation and the anodic reactions was dominated by a diffusion process at low P_{{{CO}2 }} s (1.8-9.8 MPa) at 150 °C. While numerous dented corrosion areas appeared on the sample surface for the P_{{{CO}2 }} of 11.6 MPa at 205 °C, the Tafel plot with three anodic peaks and the Nyquist diagram with an atrophied impedance arc were present. This dented corrosion attribute to the synergistic effects of stress, temperature, P_{{{CO}2 }} and Cl-, the temperature and stress could play crucial roles on the corrosion of the alloy 718.

Aero-thermal performances of leakage flows injection from the endwall slot in linear cascade of high-pressure turbine

NASA Astrophysics Data System (ADS)

Ghopa, Wan Aizon W.; Harun, Zambri; Funazaki, Ken-ichi; Miura, Takemitsu

2015-02-01

The existence of a gap between combustor and turbine endwall in the real gas turbine induces to the leakages phenomenon. However, the leakages could be used as a coolant to protect the endwall surfaces from the hot gas since it could not be completely prevented. Thus, present study investigated the potential of leakage flows as a function of film cooling. In present study, the flow field at the downstream of high-pressure turbine blade has been investigated by 5-holes pitot tube. This is to reveal the aerodynamic performances under the influenced of leakage flows while the temperature measurement was conducted by thermochromic liquid crystal (TLC). Experimental has significantly captured theaerodynamics effect of leakage flows near the blade downstream. Furthermore, TLC measurement illustrated that the film cooling effectiveness contours were strongly influenced by the secondary flows behavior on the endwall region. Aero-thermal results were validated by the numerical simulation adopted by commercial software, ANSYS CFX 13. Both experimental and numerical simulation indicated almost similar trendinaero and also thermal behavior as the amount of leakage flows increases.

Nonlinear acoustic techniques for landmine detection.

PubMed

Korman, Murray S; Sabatier, James M

2004-12-01

Measurements of the top surface vibration of a buried (inert) VS 2.2 anti-tank plastic landmine reveal significant resonances in the frequency range between 80 and 650 Hz. Resonances from measurements of the normal component of the acoustically induced soil surface particle velocity (due to sufficient acoustic-to-seismic coupling) have been used in detection schemes. Since the interface between the top plate and the soil responds nonlinearly to pressure fluctuations, characteristics of landmines, the soil, and the interface are rich in nonlinear physics and allow for a method of buried landmine detection not previously exploited. Tuning curve experiments (revealing "softening" and a back-bone curve linear in particle velocity amplitude versus frequency) help characterize the nonlinear resonant behavior of the soil-landmine oscillator. The results appear to exhibit the characteristics of nonlinear mesoscopic elastic behavior, which is explored. When two primary waves f1 and f2 drive the soil over the mine near resonance, a rich spectrum of nonlinearly generated tones is measured with a geophone on the surface over the buried landmine in agreement with Donskoy [SPIE Proc. 3392, 221-217 (1998); 3710, 239-246 (1999)]. In profiling, particular nonlinear tonals can improve the contrast ratio compared to using either primary tone in the spectrum.

Log-Normality and Multifractal Analysis of Flame Surface Statistics

NASA Astrophysics Data System (ADS)

Saha, Abhishek; Chaudhuri, Swetaprovo; Law, Chung K.

2013-11-01

The turbulent flame surface is typically highly wrinkled and folded at a multitude of scales controlled by various flame properties. It is useful if the information contained in this complex geometry can be projected onto a simpler regular geometry for the use of spectral, wavelet or multifractal analyses. Here we investigate local flame surface statistics of turbulent flame expanding under constant pressure. First the statistics of local length ratio is experimentally obtained from high-speed Mie scattering images. For spherically expanding flame, length ratio on the measurement plane, at predefined equiangular sectors is defined as the ratio of the actual flame length to the length of a circular-arc of radius equal to the average radius of the flame. Assuming isotropic distribution of such flame segments we convolute suitable forms of the length-ratio probability distribution functions (pdfs) to arrive at corresponding area-ratio pdfs. Both the pdfs are found to be near log-normally distributed and shows self-similar behavior with increasing radius. Near log-normality and rather intermittent behavior of the flame-length ratio suggests similarity with dissipation rate quantities which stimulates multifractal analysis. Currently at Indian Institute of Science, India.

Temperature-dependent residual shear strength characteristics of smectite-rich landslide soils

NASA Astrophysics Data System (ADS)

Shibasaki, Tatsuya; Matsuura, Sumio; Okamoto, Takashi

2015-04-01

On gentle clayey slopes in weathered argillaceous rock areas, there exist many landslides which repeatedly reactivate with slow movement. The slip surface soils of these landslides are sometimes composed dominantly of swelling clay mineral (smectite) which is well known to show extremely low residual friction angle. From field data monitored at landslide sites in Japan, it has become clear that some landslides with relatively shallow slip surface begin to move and become active in late autumn or early winter every year. In such cases, the triggering mechanisms of landslides have not been understood well enough, because landslide initiation and movement are not always clearly linked with rises in pore water pressures (ground water levels). In this study, we focus on the influence of seasonal variation in ground temperature on slope stability and have investigated the effect of temperature on the shear strength of slip surface soils. Undisturbed soil samples were collected by boring from the Busuno landslide in Japan. We performed box shear experiments on undisturbed slip surface soils at low temperature ranges (approximately 5-25 °C). XRD analysis revealed that these soils contain high fraction of smectite. Slickensided slip surface within test specimen was coincided with the shearing plane of the shear box and shear displacement was applied precisely along the localized slip surface. Experiments were performed under slow shearing rate condition (0.005mm/min) and the results showed that shear strength decreased with decreasing temperature. Temperature effect was rather significant on frictional angle than on cohesion. Ring shear experiments were also performed on normally-consolidated remoulded samples. Under residual strength condition, temperature-change experiments (cooling-event tests) ranging approximately from 5 to 25 °C were performed on smectite-rich landslide soils and commercial bentonites. As well as the results by box shear test, shear weakening behaviors were also recognized during cooling-event tests. Shear stress fluctuations, which were obtained by 1 Hz data sampling, showed that shear behavior characteristically changed in response to temperature conditions. Stick-slip behavior prevailed under room temperature conditions, whereas shear behavior gradually changed into stable sliding behavior as temperature decreased. SEM (Scanning Electric Microscope) observation on shear surfaces indicated that silt- and sand-size asperities in the vicinity of the shear surface influence the occurrence of stick-slip behavior. It is also characteristically noted that rod-shaped smectitic clays, here called "roll", developed on shear surfaces and are arrayed densely perpendicular to the shearing direction in a micrometer scale. We assume that these rolls are probably rotating slowly within shear zone and acting as a lubricant which affects the temperature-dependent frictional properties of the shearing plane. These experimental results show that residual strength characteristics of smectite-rich soils are sensitive to temperature conditions. Our findings imply that if slip surface soils contain a high fraction of smectite, a decrease in ground temperature can lead to lowered shear resistance of the slip surface and triggering of slow landslide movement.

A rolling-sliding bench test for investigating rear axle lubrication

DOE PAGES

Stump, Benjamin C.; Zhou, Yan; Viola, Michael B.; ...

2018-02-07

An automotive rear axle is composed of a set of hypoid gears, whose contact surfaces experience a complex combination of rolling contact fatigue damage and sliding wear. Full-scale rear axle dynamometer tests are used in the industry for efficiency and durability assessment. Here, this study developed a bench-scale rolling-sliding test protocol by simulating the contact pressure, oil temperature, and lubrication regime experienced in a dynamometer duty cycle test. Initial bench results have demonstrated the ability of generating both rolling contact-induced micropitting and sliding wear and the feasibility of investigating the impact of slide-to-roll ratio, surface roughness, test duration, and oilmore » temperature on the friction behavior, vibration noise, and surface damage. Finally, this bench test will allow studying candidate rear axle lubricants and materials under relevant conditions.« less

A rolling-sliding bench test for investigating rear axle lubrication

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

Stump, Benjamin C.; Zhou, Yan; Viola, Michael B.

An automotive rear axle is composed of a set of hypoid gears, whose contact surfaces experience a complex combination of rolling contact fatigue damage and sliding wear. Full-scale rear axle dynamometer tests are used in the industry for efficiency and durability assessment. Here, this study developed a bench-scale rolling-sliding test protocol by simulating the contact pressure, oil temperature, and lubrication regime experienced in a dynamometer duty cycle test. Initial bench results have demonstrated the ability of generating both rolling contact-induced micropitting and sliding wear and the feasibility of investigating the impact of slide-to-roll ratio, surface roughness, test duration, and oilmore » temperature on the friction behavior, vibration noise, and surface damage. Finally, this bench test will allow studying candidate rear axle lubricants and materials under relevant conditions.« less

High-frequency pressure variations in the vicinity of a surface CO2 flux chamber

Treesearch

Eugene S. Takle; James R. Brandle; R. A. Schmidt; Rick Garcia; Irina V. Litvina; William J. Massman; Xinhua Zhou; Geoffrey Doyle; Charles W. Rice

2003-01-01

We report measurements of 2Hz pressure fluctuations at and below the soil surface in the vicinity of a surface-based CO2 flux chamber. These measurements were part of a field experiment to examine the possible role of pressure pumping due to atmospheric pressure fluctuations on measurements of surface fluxes of CO2. Under the moderate wind speeds, warm temperatures,...

Investigation of unsteady, hypersonic, laminar separated flows over a double cone geometry using a kinetic approach

NASA Astrophysics Data System (ADS)

Tumuklu, Ozgur; Levin, Deborah A.; Theofilis, Vassilis

2018-04-01

Shock-dominated hypersonic laminar flows over a double cone are investigated using time accurate direct simulation Monte Carlo combined with the residuals algorithm for unit Reynolds numbers gradually increasing from 9.35 × 104 to 3.74 × 105 m-1 at a Mach number of about 16. The main flow features, such as the strong bow-shock, location of the separation shock, the triple point, and the entire laminar separated region, show a time-dependent behavior. Although the separation shock angle is found to be similar for all Re numbers, the effects of Reynolds number on the structure and extent of the separation region are profound. As the Reynolds number is increased, larger pressure values in the under-expanded jet region due to strong shock interactions form more prominent λ-shocklets in the supersonic region between two contact surfaces. Likewise, the surface parameters, especially on the second cone surface, show a strong dependence on the Reynolds number, with skin friction, pressure, and surface heating rates increasing and velocity slip and temperature jump values decreasing for increasing Re number. A Kelvin-Helmholtz instability arising at the shear layer results in an unsteady flow for the highest Reynolds number. These findings suggest that consideration of experimental measurement times is important when it comes to determining the steady state surface parameters even for a relatively simple double cone geometry at moderately large Reynolds numbers.

Characterization of fuels for second-generation PFBC

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

Zevenhoven, C.A.P.; Hupa, M.

1997-12-31

In second-generation PFBC technology a solid fuel is partly converted in a devolatilization step (in a carbonizer) to produce a char and a pressurized fuel gas, followed by PFB combustion of the char. The fuel gas is led to the combustion chamber of a gas turbine after it is mixed with the PFBC off-gas, thus increasing the temperature at the inlet of the expansion turbine. Clearly, the optimization of the carbonizer design and operation is essential to the process. Detailed information on the behavior of solid fuels under pressurized conditions is, however, largely limited to steam and/or carbon dioxide gasificationmore » reactivities, obtained at a different combination of process parameters, such as temperature, pressure, heating rate, particle size and gas atmosphere. In the present work, the effect of temperature, pressure and heating rates on the yields of volatiles and char residue reactivity has been measured for a set of fuels ranging from bituminous coal to wood. Laboratory conditions were typical for the carbonizer and combustion reactors in a second-generation PFBC system. A pressurized thermogravimetric reactor (PTGR) operated at heating rates of around 250 K/s and a pressurized grid heater (PGH) operated at heating rates up to 3,000 K/s were used to analyze fuel devolatilization and char reactivity against carbon dioxide or steam at temperatures between 800 and 1,100 C, and 1, 10 or 25 bar total pressure. For comparison, a few experiments were repeated without a separate devolatilization step. The behavior of the various fuels were compared and related to proximate and ultimate fuel analysis. Several empirical, engineering equations are given. A simple 2-parameter model which separates intrinsic surface reactivity and physical, structure effects, very well describes the time-conversion data of the char. It was found that the fuel O/C molar ratio is a very good index for char reactivity, when the char O/C ratio itself is unknown.« less

In-situ monitoring of etching of bovine serum albumin using low-temperature atmospheric plasma jet

NASA Astrophysics Data System (ADS)

Kousal, J.; Shelemin, A.; Kylián, O.; Slavínská, D.; Biederman, H.

2017-01-01

Bio-decontamination of surfaces by means of atmospheric pressure plasma is nowadays extensively studied as it represents promising alternative to commonly used sterilization/decontamination techniques. The non-equilibrium atmospheric pressure plasmas were already reported to be highly effective in removal of a wide range of biological residual from surfaces. Nevertheless the kinetics of removal of biological contamination from surfaces is still not well understood as the majority of performed studies were based on ex-situ evaluation of etching rates, which did not allow investigating details of plasma action on biomolecules. This study therefore presents a real-time, in-situ ellipsometric characterization of removal of bovine serum albumin (BSA) from surfaces by low-temperature atmospheric plasma jet operated in argon. Non-linear and at shorter distances between treated samples and nozzle of the plasma jet also non-monotonic dependence of the removal rate on the treatment duration was observed. According to additional measurements focused on the determination of chemical changes of treated BSA as well as temperature measurements, the observed behavior is most likely connected with two opposing effects: the formation of a thin layer on the top of BSA deposit enriched in inorganic compounds, whose presence causes a gradual decrease of removal efficiency, and slight heating of BSA that facilitates its degradation and volatilization induced by chemically active radicals produced by the plasma.

Microstructure and corrosion behavior of die-cast AM60B magnesium alloys in a complex salt solution. A slow positron beam study

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

Liu, Y. F.; Yang, W.; Qin, Q. L.

2013-12-15

The microstructure and corrosion behavior of high pressure die-cast (HPDC) and super vacuum die-cast (SVDC) AM60B magnesium alloys were investigated in a complex salt solution using slow positron beam technique and potentiodynamic polarization tests. The experiments revealed that a CaCO 3 film was formed on the surface of the alloys and that the rate of CaCO 3 formation for the SVDC alloy with immersion time was slower than that of the HPDC alloy. The larger volume fraction of b-phase in the skin layer of the SVDC alloy than that of the HPDC alloy was responsible for the better corrosion resistance.

Pressure Relief Behaviors and Weight Shifting Activities to Prevent Pressure Ulcers in Persons with SCI

DTIC Science & Technology

2016-10-01

pressures and increased blood flow. This level of off-loading is achieved by postural changes during sustained reaching, leaning and other...wheelchair cushions and pressure relief maneuvers on ischial interface pressure and blood flow in people with spinal cord injury”, Archives of Physical Medicine and Rehabilitation, Vol. 95 no.7, pp. 1350-1357, July 2014. ...0 AWARD NUMBER: W81XWH-13-1-0387 TITLE: Pressure Relief Behaviors and Weight-Shifting Activities to Prevent Pressure Ulcers in

The manual pressures of stone tool behaviors and their implications for the evolution of the human hand.

PubMed

Williams-Hatala, Erin Marie; Hatala, Kevin G; Gordon, McKenzie; Key, Alastair; Kasper, Margaret; Kivell, Tracy L

2018-06-01

It is widely agreed that biomechanical stresses imposed by stone tool behaviors influenced the evolution of the human hand. Though archaeological evidence suggests that early hominins participated in a variety of tool behaviors, it is unlikely that all behaviors equally influenced modern human hand anatomy. It is more probable that a behavior's likelihood of exerting a selective pressure was a weighted function of the magnitude of stresses associated with that behavior, the benefits received from it, and the amount of time spent performing it. Based on this premise, we focused on the first part of that equation and evaluated magnitudes of stresses associated with stone tool behaviors thought to have been commonly practiced by early hominins, to determine which placed the greatest loads on the digits. Manual pressure data were gathered from 39 human subjects using a Novel Pliance ® manual pressure system while they participated in multiple Plio-Pleistocene tool behaviors: nut-cracking, marrow acquisition with a hammerstone, flake production with a hammerstone, and handaxe and flake use. Manual pressure distributions varied significantly according to behavior, though there was a tendency for regions of the hand subject to the lowest pressures (e.g., proximal phalanges) to be affected less by behavior type. Hammerstone use during marrow acquisition and flake production consistently placed the greatest loads on the digits collectively, on each digit and on each phalanx. Our results suggest that, based solely on the magnitudes of stresses, hammerstone use during marrow acquisition and flake production are the most likely of the assessed behaviors to have influenced the anatomical and functional evolution of the human hand. Copyright © 2018 Elsevier Ltd. All rights reserved.

In-situ neutron imaging of hydrogenous fuels in combustion generated porous carbons under dynamic and steady state pressure conditions

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

Ossler, Frederik; Santodonato, Louis J.; Bilheux, Hassina Z.

Here, we report results from experiments where we characterize the surface properties of soot particles interacting with high-pressure methane. We also found considerable differences in behavior of the soot material between static and dynamic pressure conditions that can be explained by multiscale correlations in the dynamics, from the micro to macro of the porous fractal-like carbon matrix. The measurements were possible utilizing cold neutron imaging of methane mixed with combustion generated carbon (soot) inside steel cells. The studies were performed under static and dynamic pressure conditions in the range 10-90 bar, and are of interest for applications of energy storagemore » of hydrogenous fuels. The very high cross sections for neutrons compared to hard X-ray photons, enabled us to find considerable amounts of native hydrogen in the soot and to see and quantify the presence of hydrogen atoms in the carbon soot matrix under different pressure conditions. Our work lays the base for more detailed in-situ investigations on the interaction of porous carbon materials with hydrogen in practical environments for hydrogen and methane storage.« less

Highly Stable and Flexible Pressure Sensors with Modified Multi-Walled Carbon Nanotube/Polymer Composites for Human Monitoring

PubMed Central

He, Yin; Ming, Yue; Li, Wei; Li, Yafang; Wu, Maoqi; Song, Jinzhong; Li, Xiaojiu; Liu, Hao

2018-01-01

A facile method for preparing an easy processing, repeatable and flexible pressure sensor was presented via the synthesis of modified multi-walled carbon nanotubes (m-MWNTs) and polyurethane (PU) films. The surface modification of multi-walled carbon nanotubes (MWNTs) simultaneously used a silane coupling agent (KH550) and sodium dodecyl benzene sulfonate (SDBS) to improve the dispersibility and compatibility of the MWNTs in a polymer matrix. The electrical property and piezoresistive behavior of the m-MWNT/PU composites were compared with raw multi-walled carbon nanotube (raw MWNT)/PU composites. Under linear uniaxial pressure, the m-MWNT/PU composite exhibited 4.282%kPa−1 sensitivity within the pressure of 1 kPa. The nonlinear error, hysteresis error and repeatability error of the piezoresistivity of m-MWNT/PU decreased 9%, 16.72% and 54.95% relative to raw MWNT/PU respectively. Therefore, the piezoresistive response of m-MWNT/PU had better stability than that of raw MWNT/PU composites. The m-MWNT/PU sensors could be utilized in wearable devices for body movement detection, monitoring of respiration and pressure detection in garments. PMID:29701643

In-situ neutron imaging of hydrogenous fuels in combustion generated porous carbons under dynamic and steady state pressure conditions

DOE PAGES

Ossler, Frederik; Santodonato, Louis J.; Bilheux, Hassina Z.

2017-02-12

Here, we report results from experiments where we characterize the surface properties of soot particles interacting with high-pressure methane. We also found considerable differences in behavior of the soot material between static and dynamic pressure conditions that can be explained by multiscale correlations in the dynamics, from the micro to macro of the porous fractal-like carbon matrix. The measurements were possible utilizing cold neutron imaging of methane mixed with combustion generated carbon (soot) inside steel cells. The studies were performed under static and dynamic pressure conditions in the range 10-90 bar, and are of interest for applications of energy storagemore » of hydrogenous fuels. The very high cross sections for neutrons compared to hard X-ray photons, enabled us to find considerable amounts of native hydrogen in the soot and to see and quantify the presence of hydrogen atoms in the carbon soot matrix under different pressure conditions. Our work lays the base for more detailed in-situ investigations on the interaction of porous carbon materials with hydrogen in practical environments for hydrogen and methane storage.« less

Highly Stable and Flexible Pressure Sensors with Modified Multi-Walled Carbon Nanotube/Polymer Composites for Human Monitoring.

PubMed

He, Yin; Ming, Yue; Li, Wei; Li, Yafang; Wu, Maoqi; Song, Jinzhong; Li, Xiaojiu; Liu, Hao

2018-04-26

A facile method for preparing an easy processing, repeatable and flexible pressure sensor was presented via the synthesis of modified multi-walled carbon nanotubes (m-MWNTs) and polyurethane (PU) films. The surface modification of multi-walled carbon nanotubes (MWNTs) simultaneously used a silane coupling agent (KH550) and sodium dodecyl benzene sulfonate (SDBS) to improve the dispersibility and compatibility of the MWNTs in a polymer matrix. The electrical property and piezoresistive behavior of the m-MWNT/PU composites were compared with raw multi-walled carbon nanotube (raw MWNT)/PU composites. Under linear uniaxial pressure, the m-MWNT/PU composite exhibited 4.282%kPa −1 sensitivity within the pressure of 1 kPa. The nonlinear error, hysteresis error and repeatability error of the piezoresistivity of m-MWNT/PU decreased 9%, 16.72% and 54.95% relative to raw MWNT/PU respectively. Therefore, the piezoresistive response of m-MWNT/PU had better stability than that of raw MWNT/PU composites. The m-MWNT/PU sensors could be utilized in wearable devices for body movement detection, monitoring of respiration and pressure detection in garments.

Unconventional resistivity at the border of metallic antiferromagnetism in NiS2

NASA Astrophysics Data System (ADS)

Niklowitz, P. G.; Alireza, P. L.; Steiner, M. J.; Lonzarich, G. G.; Braithwaite, D.; Knebel, G.; Flouquet, J.; Wilson, J. A.

2008-03-01

We report low-temperature and high-pressure measurements of the electrical resistivity ρ(T) of the antiferromagnetic compound NiS2 in its high-pressure metallic state. The form of ρ(T,p) suggests the presence of a quantum phase transition at a critical pressure pc=76±5kbar . Near pc , the temperature variation of ρ(T) is similar to that observed in NiS2-xSex near the critical composition x=1 , where metallic antiferromagnetism is suppressed at ambient pressure. In both cases, ρ(T) varies approximately as T1.5 over a wide range below 100K . This lets us assume that the high-pressure metallic phase of stoichiometric NiS2 also develops itinerant antiferromagnetism, which becomes suppressed at pc . However, on closer analysis, the resistivity exponent in NiS2 exhibits an undulating variation with temperature not seen in NiSSe (x=1) . This difference in behavior may be due to the effects of spin-fluctuation scattering of charge carriers on cold and hot spots of the Fermi surface in the presence of quenched disorder, which is higher in NiSSe than in stoichiometric NiS2 .

Pressure potential and stability analysis in an acoustical noncontact transportation

NASA Astrophysics Data System (ADS)

Li, J.; Liu, C. J.; Zhang, W. J.

2017-01-01

Near field acoustic traveling wave is one of the most popular principles in noncontact manipulations and transportations. The stability behavior is a key factor in the industrial applications of acoustical noncontact transportation. We present here an in-depth analysis of the transportation stability of a planar object levitated in near field acoustic traveling waves. To more accurately describe the pressure distributions on the radiation surface, a 3D nonlinear traveling wave model is presented. A closed form solution is derived based on the pressure potential to quantitatively calculate the restoring forces and moments under small disturbances. The physical explanations of the effects of fluid inertia and the effects of non-uniform pressure distributions are provided in detail. It is found that a vibration rail with tapered cross section provides more stable transportation than a rail with rectangular cross section. The present study sheds light on the issue of quantitative evaluation of stability in acoustic traveling waves and proposes three main factors that influence the stability: (a) vibration shape, (b) pressure distribution and (c) restoring force/moment. It helps to provide a better understanding of the physics behind the near field acoustic transportation and provide useful design and optimization tools for industrial applications.

A Study Of High Speed Friction Behavior Under Elastic Loading Conditions

NASA Astrophysics Data System (ADS)

Crawford, P. J.; Hammerberg, J. E.

2005-03-01

The role of interfacial dynamics under high strain-rate conditions is an important constitutive relationship in modern modeling and simulation studies of dynamic events (<100 μs in length). The frictional behavior occurring at the interface between two metal surfaces under high elastic loading and sliding speed conditions is studied using the Rotating Barrel Gas Gun (RBGG) facility. The RBGG utilizes a low-pressure gas gun to propel a rotating annular projectile towards an annular target rod. Upon striking the target, the projectile imparts both an axial and a torsional impulse into the target. Resulting elastic waves are measured using strain gauges attached to the target rod. The kinetic coefficient of friction is obtained through an analysis of the resulting strain wave data. Experiments performed using Cu/Cu, Cu/Stainless steel and Cu/Al interfaces provide some insight into the kinetic coefficient of friction behavior at varying sliding speeds and impact loads.

Support surfaces for pressure ulcer prevention: A network meta-analysis

PubMed Central

Dumville, Jo C.; Cullum, Nicky

2018-01-01

Background Pressure ulcers are a prevalent and global issue and support surfaces are widely used for preventing ulceration. However, the diversity of available support surfaces and the lack of direct comparisons in RCTs make decision-making difficult. Objectives To determine, using network meta-analysis, the relative effects of different support surfaces in reducing pressure ulcer incidence and comfort and to rank these support surfaces in order of their effectiveness. Methods We conducted a systematic review, using a literature search up to November 2016, to identify randomised trials comparing support surfaces for pressure ulcer prevention. Two reviewers independently performed study selection, risk of bias assessment and data extraction. We grouped the support surfaces according to their characteristics and formed evidence networks using these groups. We used network meta-analysis to estimate the relative effects and effectiveness ranking of the groups for the outcomes of pressure ulcer incidence and participant comfort. GRADE was used to assess the certainty of evidence. Main results We included 65 studies in the review. The network for assessing pressure ulcer incidence comprised evidence of low or very low certainty for most network contrasts. There was moderate-certainty evidence that powered active air surfaces and powered hybrid air surfaces probably reduce pressure ulcer incidence compared with standard hospital surfaces (risk ratios (RR) 0.42, 95% confidence intervals (CI) 0.29 to 0.63; 0.22, 0.07 to 0.66, respectively). The network for comfort suggested that powered active air-surfaces are probably slightly less comfortable than standard hospital mattresses (RR 0.80, 95% CI 0.69 to 0.94; moderate-certainty evidence). Conclusions This is the first network meta-analysis of the effects of support surfaces for pressure ulcer prevention. Powered active air-surfaces probably reduce pressure ulcer incidence, but are probably less comfortable than standard hospital surfaces. Most prevention evidence was of low or very low certainty, and more research is required to reduce these uncertainties. PMID:29474359

Support surfaces for pressure ulcer prevention: A network meta-analysis.

PubMed

Shi, Chunhu; Dumville, Jo C; Cullum, Nicky

2018-01-01

Pressure ulcers are a prevalent and global issue and support surfaces are widely used for preventing ulceration. However, the diversity of available support surfaces and the lack of direct comparisons in RCTs make decision-making difficult. To determine, using network meta-analysis, the relative effects of different support surfaces in reducing pressure ulcer incidence and comfort and to rank these support surfaces in order of their effectiveness. We conducted a systematic review, using a literature search up to November 2016, to identify randomised trials comparing support surfaces for pressure ulcer prevention. Two reviewers independently performed study selection, risk of bias assessment and data extraction. We grouped the support surfaces according to their characteristics and formed evidence networks using these groups. We used network meta-analysis to estimate the relative effects and effectiveness ranking of the groups for the outcomes of pressure ulcer incidence and participant comfort. GRADE was used to assess the certainty of evidence. We included 65 studies in the review. The network for assessing pressure ulcer incidence comprised evidence of low or very low certainty for most network contrasts. There was moderate-certainty evidence that powered active air surfaces and powered hybrid air surfaces probably reduce pressure ulcer incidence compared with standard hospital surfaces (risk ratios (RR) 0.42, 95% confidence intervals (CI) 0.29 to 0.63; 0.22, 0.07 to 0.66, respectively). The network for comfort suggested that powered active air-surfaces are probably slightly less comfortable than standard hospital mattresses (RR 0.80, 95% CI 0.69 to 0.94; moderate-certainty evidence). This is the first network meta-analysis of the effects of support surfaces for pressure ulcer prevention. Powered active air-surfaces probably reduce pressure ulcer incidence, but are probably less comfortable than standard hospital surfaces. Most prevention evidence was of low or very low certainty, and more research is required to reduce these uncertainties.

Synchronous Measuring Techniques in Parallel to MRE: Study of Pressure, Pre-Tension, and Surface Dynamics

NASA Astrophysics Data System (ADS)

Brinker, Spencer Thomas

The contents of this dissertation include investigations in Magnetic Resonance Elastography (MRE) using a preclinical 9.4 Tesla small animal Magnetic Resonance Imaging (MRI) system along with synthetic materials that mimic the mechanical properties of soft human tissue. MRE is used for studying the mechanical behavior of soft tissue particularly applicable to medical applications. Wave motion induced by a mechanical driver is measured with MRI to acquire internal displacement fields over time and space within a material media. Complex shear modulus of the media is calculated from the response of mechanical wave transmission through the material. Changes in soft tissue stiffness is associated with disease progression and thus, is why assessing tissue mechanical properties with MRE has powerful diagnostic potential due to the noninvasive procedure of MRI. The experiments performed in this dissertation used elastic phantoms and specimens to observe the influence of pre-stress on MRE derived mechanical properties while additional mechanical measurements from other related material testing methods were synchronously collected alongside MRI scanning. An organ simulating phantom was used to explore changes in MRE stiffness in response to gas and liquid cyclic pressure loading. MRE stiffness increased with pressure and hysteresis was observed in cyclic pressure loading. The results suggest MRE is applicable to pressure related disease assessment. In addition, an interconnected porosity pressure phantom was constructed for future porous media investigations. A custom system was also built to demonstrate concurrent tensile testing during MRE for investigating homogeneous soft material media undergoing pre-tension. Stiffness increased with uniaxial tensile stress and strain. The tension and stiffness relationship explored can be related to the stress analysis of voluntary muscle. The results also offer prospective experimental strategies for community wide standards on MRE calibration methods. Lastly, a novel platform was developed for synchronous acquisition of Scanning Laser Doppler Vibrometry (SLDV) and MRE for examining surface wave dynamics related to internal media wave propagation in soft material experiencing sinusoidal mechanical excitation. The results indicate that optical displacement measurements of media on the surface are similar in nature to internal displacement measured from MRE. It is concluded that optical and MRI based elastography yield similar values of complex shear modulus.

High Temperature Corrosion and Heat Transfer Studies of Zirconium-Silicide Coatings for Light Water Reactor Cladding Applications

NASA Astrophysics Data System (ADS)

Yeom, Hwasung

Experimental results investigating the feasibility of zirconium-silicide coating for accident tolerance of LWR fuel cladding coating was presented. The oxidation resistance of ZrSi2 appeared to be superior to bare Zircaloy-4 in high temperature air. It was shown that micro- and nanostructures consisting of alternating SiO2 and ZrO2 evolved during transient oxidation of ZrSi2, which was explained by spinodal phase decomposition of Zr-Si-O oxide. Coating optimization regarding oxidation resistance was performed mainly using magnetron sputter deposition method. ZrSi 2 coatings ( 3.9 microm) showed improvement of almost two orders of magnitude when compared to bare Zircaloy-4 after air-oxidation at 700 °C for 20-hours. Pre-oxidation of ZrSi2 coating at 700 °C for 5 h significantly mitigated oxygen diffusion in air-oxidation tests at 1000 °C for 1-hour and 1200 °C for 10-minutes. The ZrSi2 coating with the pre-oxidation was found to be the best condition to prevent oxide formation in Zircaloy-4 substrate in the steam condition even if the top surface of the coating was degraded by formation of zirconium-rich oxide layer. Only the ZrSiO4 phase, formed by exposing the ZrSi2 coating at 1400 °C in air, allowed for immobilization of silicon species in the oxide scale in the aqueous environments. A quench test facility was designed and built to study transient boiling heat transfer of modified Zircaloy-4 surfaces (e.g., roughened surfaces, oxidized surfaces, ZrSi2 coated surfaces) at various system conditions (e.g., elevated pressures and water subcooling). The minimum film boiling temperature increased with increasing system pressure and water subcooling, consistent with past literature. Quenching behavior was affected by the types of surface modification regardless of the environmental conditions. Quenching heat transfer was improved by the ZrSi 2 coating, a degree of surface oxidation (deltaox = 3 to 50 microm), and surface roughening (Ra 20 microm). A plausible hypothesis based on transient heat conduction models for liquid-solid contact in quenching process was proposed to explain the enhanced quenching performance. The theoretical model incorporated localized temperature behavior on superheated surface and elucidated bubble dynamics qualitatively, and predicts minimum film boiling temperature of oxidized Zirc-4 surfaces, which were in good agreement with experimental data.

Response of Simple, Model Systems to Extreme Conditions

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

Ewing, Rodney C.; Lang, Maik

2015-07-30

The focus of the research was on the application of high-pressure/high-temperature techniques, together with intense energetic ion beams, to the study of the behavior of simple oxide systems (e.g., SiO 2, GeO 2, CeO 2, TiO 2, HfO 2, SnO 2, ZnO and ZrO 2) under extreme conditions. These simple stoichiometries provide unique model systems for the analysis of structural responses to pressure up to and above 1 Mbar, temperatures of up to several thousands of kelvin, and the extreme energy density generated by energetic heavy ions (tens of keV/atom). The investigations included systematic studies of radiation- and pressure-induced amorphizationmore » of high P-T polymorphs. By studying the response of simple stoichiometries that have multiple structural “outcomes”, we have established the basic knowledge required for the prediction of the response of more complex structures to extreme conditions. We especially focused on the amorphous state and characterized the different non-crystalline structure-types that result from the interplay of radiation and pressure. For such experiments, we made use of recent technological developments, such as the perforated diamond-anvil cell and in situ investigation using synchrotron x-ray sources. We have been particularly interested in using extreme pressures to alter the electronic structure of a solid prior to irradiation. We expected that the effects of modified band structure would be evident in the track structure and morphology, information which is much needed to describe theoretically the fundamental physics of track-formation. Finally, we investigated the behavior of different simple-oxide, composite nanomaterials (e.g., uncoated nanoparticles vs. core/shell systems) under coupled, extreme conditions. This provided insight into surface and boundary effects on phase stability under extreme conditions.« less

Experiment Evaluation of Bifurcation in Sands

NASA Technical Reports Server (NTRS)

Alshibi, Khalid A.; Sture, Stein

2000-01-01

The basic principles of bifurcation analysis have been established by several investigators, however several issues remain unresolved, specifically how do stress level, grain size distribution, and boundary conditions affect general bifurcation phenomena in pressure sensitive and dilatant materials. General geometrical and kinematics conditions for moving surfaces of discontinuity was derived and applied to problems of instability of solids. In 1962, the theoretical framework of bifurcation by studying the acceleration waves in elasto-plastic (J2) solids were presented. Bifurcation analysis for more specific forms of constitutive behavior was examined by studying localization in pressure-sensitive, dilatant materials, however, analyses were restricted to plane deformation states only. Bifurcation analyses were presented and applied to predict shear band formations in sand under plane strain condition. The properties of discontinuous bifurcation solutions for elastic-plastic solids under axisymmetric and plane strain loading conditions were studied. The study focused on theory, but also references and comparisons to experiments were made. The current paper includes a presentation of a summary of bifurcation analyses for biaxial and triaxial (axisymmetric) loading conditions. The Coulomb model is implemented using incremental piecewise scheme to predict the constitutive relations and shear band inclination angles. Then, a comprehensive evaluation of bifurcation phenomena is presented based on data from triaxial experiments performed under microgravity conditions aboard the Space Shuttle under very low effective confining pressure (0.05 to 1.30 kPa), in which very high peak friction angles (47 to 75 degrees) and dilatancy angles (30 to 31 degrees) were measured. The evaluation will be extended to include biaxial experiments performed on the same material under low (10 kPa) and moderate (100 kPa) confining pressures. A comparison between the behavior under biaxial and triaxial loading conditions will be presented, and related issues concerning influence of confining pressure will be discussed.

The Impact of a Deepwater Wave on a Wall with Finite Vertical Extent

NASA Astrophysics Data System (ADS)

Wang, An; Duncan, James H.

2016-11-01

The impact of a dispersively focused 2D plunging breaker (average wave frequency 1.15 Hz) on a 2D wall that is 45 cm high and 30 cm thick is studied experimentally. The temporal evolution of the water surface profile upstream of the wall is measured with a cinematic LIF technique using frame rates up to 4,500 Hz. Impact pressures on the wall are measured simultaneously at sample rates up to 900 kHz. The wall is located horizontally 6.41 m from the wave maker in all cases and the submergence of the bottom surface of the wall is varied. It is found that the impact behavior varies dramatically with the wall submergence. When the bottom is submerged by 13.3 cm, a flip-through impact occurs. In this case, the impact evolves without wave breaking and a vertical jet is formed. When the wall is submerged by less than 4.5 cm, small-amplitude components in the wave packet interact with the bottom of the wall before the main crest arrives. Ripples reflected during this interaction modify the behavior of the incoming breaker significantly. When the bottom of the wall is located sufficiently high above the mean water level, the first interaction occurs when the undisturbed wave crest collides with the wall. The highest pressures are observed in this case. The support of the Office of Naval Research is gratefully acknowledged.

Wake measurements in a strong adverse pressure gradient

NASA Technical Reports Server (NTRS)

Hoffenberg, R.; Sullivan, John P.; Schneider, S. P.

1994-01-01

The behavior of wakes in adverse pressure gradients is critical to the performance of high-lift systems for transport aircraft. Wake deceleration is known to lead to sudden thickening and the onset of reversed flow; this 'wake bursting' phenomenon can occur while surface flows remain attached. Although 'wake bursting' is known to be important for high-lift systems, no detailed measurements of 'burst' wakes have ever been reported. Wake bursting has been successfully achieved in the wake of a flat plate as it decelerated in a two-dimensional diffuser, whose sidewalls were forced to remain attached by use of slot blowing. Pilot probe surveys, L.D.V. measurements, and flow visualization have been used to investigate the physics of this decelerated wake, through the onset of reversed flow.

Freezing behavior as a response to sexual visual stimuli as demonstrated by posturography.

PubMed

Mouras, Harold; Lelard, Thierry; Ahmaidi, Said; Godefroy, Olivier; Krystkowiak, Pierre

2015-01-01

Posturographic changes in motivational conditions remain largely unexplored in the context of embodied cognition. Over the last decade, sexual motivation has been used as a good canonical working model to study motivated social interactions. The objective of this study was to explore posturographic variations in response to visual sexual videos as compared to neutral videos. Our results support demonstration of a freezing-type response in response to sexually explicit stimuli compared to other conditions, as demonstrated by significantly decreased standard deviations for (i) the center of pressure displacement along the mediolateral and anteroposterior axes and (ii) center of pressure's displacement surface. These results support the complexity of the motor correlates of sexual motivation considered to be a canonical functional context to study the motor correlates of motivated social interactions.

Surface Pressure Dependencies in the GEOS-Chem-Adjoint System and the Impact of the GEOS-5 Surface Pressure on CO2 Model Forecast

NASA Technical Reports Server (NTRS)

Lee, Meemong; Weidner, Richard

2016-01-01

In the GEOS-Chem Adjoint (GCA) system, the total (wet) surface pressure of the GEOS meteorology is employed as dry surface pressure, ignoring the presence of water vapor. The Jet Propulsion Laboratory (JPL) Carbon Monitoring System (CMS) research team has been evaluating the impact of the above discrepancy on the CO2 model forecast and the CO2 flux inversion. The JPL CMS research utilizes a multi-mission assimilation framework developed by the Multi-Mission Observation Operator (M2O2) research team at JPL extending the GCA system. The GCA-M2O2 framework facilitates mission-generic 3D and 4D-variational assimilations streamlining the interfaces to the satellite data products and prior emission inventories. The GCA-M2O2 framework currently integrates the GCA system version 35h and provides a dry surface pressure setup to allow the CO2 model forecast to be performed with the GEOS-5 surface pressure directly or after converting it to dry surface pressure.

Surface Pressure Dependencies in the Geos-Chem-Adjoint System and the Impact of the GEOS-5 Surface Pressure on CO2 Model Forecast

NASA Technical Reports Server (NTRS)

Lee, Meemong; Weidner, Richard

2016-01-01

In the GEOS-Chem Adjoint (GCA) system, the total (wet) surface pressure of the GEOS meteorology is employed as dry surface pressure, ignoring the presence of water vapor. The Jet Propulsion Laboratory (JPL) Carbon Monitoring System (CMS) research team has been evaluating the impact of the above discrepancy on the CO2 model forecast and the CO2 flux inversion. The JPL CMS research utilizes a multi-mission assimilation framework developed by the Multi-Mission Observation Operator (M2O2) research team at JPL extending the GCA system. The GCA-M2O2 framework facilitates mission-generic 3D and 4D-variational assimilations streamlining the interfaces to the satellite data products and prior emission inventories. The GCA-M2O2 framework currently integrates the GCA system version 35h and provides a dry surface pressure setup to allow the CO2 model forecast to be performed with the GEOS-5 surface pressure directly or after converting it to dry surface pressure.

Structural and shear characteristics of adsorbed sodium caseinate and monoglyceride mixed monolayers at the air-water interface.

PubMed

Rodríguez Patino, Juan M; Cejudo Fernández, Marta; Carrera Sánchez, Cecilio; Rodríguez Niño, Ma Rosario

2007-09-01

The structural and shear characteristics of mixed monolayers formed by an adsorbed Na-caseinate film and a spread monoglyceride (monopalmitin or monoolein) on the previously adsorbed protein film have been analyzed. Measurements of the surface pressure (pi)-area (A) isotherm and surface shear viscosity (eta(s)) were obtained at 20 degrees C and at pH 7 in a modified Wilhelmy-type film balance. The structural and shear characteristics of the mixed films depend on the surface pressure and on the composition of the mixed film. At surface pressures lower than the equilibrium surface pressure of Na-caseinate (at pipi(e)(CS) have important repercussions on the shear characteristics of the mixed films.

Dynamics and Instabilities of Acoustically Stressed Interfaces

NASA Astrophysics Data System (ADS)

Shi, William Tao

An intense sound field exerts acoustic radiation pressure on a transitional layer between two continuous fluid media, leading to the unconventional dynamical behavior of the interface in the presence of the sound field. An understanding of this behavior has applications in the study of drop dynamics and surface rheology. Acoustic fields have also been utilized in the generation of interfacial instability, which may further encourage the dispersion or coalescence of liquids. Therefore, the study of the dynamics of the acoustically stressed interfaces is essential to infer the mechanism of the various phenomena related to interfacial dynamics and to acquire the properties of liquid surfaces. This thesis studies the dynamics of acoustically stressed interfaces through a theoretical model of surface interactions on both closed and open interfaces. Accordingly, a boundary integral method is developed to simulate the motions of a stressed interface. The method has been employed to determine the deformation, oscillation and instability of acoustically levitated drops. The generalized computations are found to be in good agreement with available experimental results. The linearized theory is also derived to predict the instability threshold of the flat interface, and is then compared with experiments conducted to observe and measure the unstable motions of the horizontal interface. This thesis is devoted to describing and classifying the simplest mechanisms by which acoustic fields provide a surface interaction with a fluid. A physical picture of the competing processes introduced by the evolution of an interface in a sound field is presented. The development of an initial small perturbation into a sharp form is observed on either a drop surface or a horizontal interface, indicating a strong focusing of acoustic energy at certain spots of the interface. Emphasis is placed on understanding the basic coupling mechanisms, rather than on particular applications that may involve this coupling. The dynamical behavior of a stressed drop can be determined in terms of a given form of an incident sound field and three dimensionless quantities. Thus, the behavior of a complex dynamic system has been clarified, permitting the exploration and interpretation of the nature of liquid surface phenomena.

Surface pressure maps from scatterometer data

NASA Technical Reports Server (NTRS)

Brown, R. A.; Levy, Gad

1991-01-01

The ability to determine surface pressure fields from satellite scatterometer data was shown by Brown and Levy (1986). The surface winds are used to calculate the gradient winds above the planetary boundary layer, and these are directly related to the pressure gradients. There are corrections for variable stratification, variable surface roughness, horizontal inhomogeneity, humidity and baroclinity. The Seasat-A Satellite Scatterometer (SASS) data have been used in a systematic study of 50 synoptic weather events (regions of approximately 1000 X 1000 km). The preliminary statistics of agreement with national weather service surface pressure maps are calculated. The resulting surface pressure maps can be used together with SASS winds and Scanning Multichannel Microwave Radiometer (SMMR) water vapor and liquid water analyses to provide good front and storm system analyses.

Determination of tropical cyclone surface pressure and winds from satellite microwave data

NASA Technical Reports Server (NTRS)

Kidder, S. Q.

1979-01-01

An approach to the problem of deducing wind speed and pressure around tropical cyclones is presented. The technique, called the Surface Wind Inference from Microwave data (SWIM technique, uses satellites microwave sounder data to measure upper tropospheric temperature anomalies which may then be related to surface pressure anomalies through the hydrostatic and radiative transfer equations. Surface pressure gradients outside of the radius of maximum wind are estimated for the first time. Future instruments may be able to estimate central pressure with + or - 0/1 kPa accuracy.

High-pressure liquid-monopropellant strand combustion.

NASA Technical Reports Server (NTRS)

Faeth, G. M.

1972-01-01

Examination of the influence of dissolved gases on the state of the liquid surface during high-pressure liquid-monopropellant combustion through the use of a strand burning experiment. Liquid surface temperatures were measured, using fine-wire thermocouples, during the strand combustion of ethyl nitrate, normal propyl nitrate, and propylene glycol dinitrate at pressures up to 81 atm. These measurements were compared with the predictions of a variable-property gas-phase analysis assuming an infinite activation energy for the decomposition reaction. The state of the liquid surface was estimated using a conventional low-pressure phase equilibrium model, as well as a high-pressure version that considered the presence of dissolved combustion-product gases in the liquid phase. The high-pressure model was found to give a superior prediction of measured liquid surface temperatures. Computed total pressures required for the surface to reach its critical mixing point during strand combustion were found to be in the range from 2.15 to 4.62 times the critical pressure of the pure propellant. Computed dissolved gas concentrations at the liquid surface were in the range from 35 to 50% near the critical combustion condition.

Correlation between mechanical behavior of protein films at the air/water interface and intrinsic stability of protein molecules.

PubMed

Martin, Anneke H; Cohen Stuart, Martien A; Bos, Martin A; van Vliet, Ton

2005-04-26

The relation between mechanical film properties of various adsorbed protein layers at the air/water interface and intrinsic stability of the corresponding proteins is discussed. Mechanical film properties were determined by surface deformation in shear and dilation. In shear, fracture stress, sigma(f), and fracture strain, gamma(f), were determined, as well as the relaxation behavior after macroscopic fracture. The dilatational measurements were performed in a Langmuir trough equipped with an infra-red reflection absorption spectroscopy (IRRAS) accessory. During compression and relaxation of the surface, the surface pressure, Pi, and adsorbed amount, Gamma (determined from the IRRAS spectra), were determined simultaneously. In addition, IRRAS spectra revealed information on conformational changes in terms of secondary structure. Possible correlations between macroscopic film properties and intrinsic stability of the proteins were determined and discussed in terms of molecular dimensions of single proteins and interfacial protein films. Molecular properties involved the area per protein molecule at Pi approximately 0 mN/m (A(0)), A(0)/M (M = molecular weight) and the maximum slope of the Pi-Gamma curves (dPi/dGamma). The differences observed in mechanical properties and relaxation behavior indicate that the behavior of a protein film subjected to large deformation may vary widely from predominantly viscous (yielding) to more elastic (fracture). This transition is also observed in gradual changes in A(0)/M. It appeared that in general protein layers with high A(0)/M have a high gamma(f) and behave more fluidlike, whereas solidlike behavior is characterized by low A(0)/M and low gamma(f). Additionally, proteins with a low A(0)/M value have a low adaptability in changing their conformation upon adsorption at the air/water interface. Both results support the conclusion that the hardness (internal cohesion) of protein molecules determines predominantly the mechanical behavior of adsorbed protein layers.

Flush Airdata Sensing (FADS) System Calibration Procedures and Results for Blunt Forebodies

NASA Technical Reports Server (NTRS)

Cobleigh, Brent R.; Whitmore, Stephen A.; Haering, Edward A., Jr.; Borrer, Jerry; Roback, V. Eric

1999-01-01

Blunt-forebody pressure data are used to study the behavior of the NASA Dryden Flight Research Center flush airdata sensing (FADS) pressure model and solution algorithm. The model relates surface pressure measurements to the airdata state. Spliced from the potential flow solution for uniform flow over a sphere and the modified Newtonian impact theory, the model was shown to apply to a wide range of blunt-forebody shapes and Mach numbers. Calibrations of a sphere, spherical cones, a Rankine half body, and the F-14, F/A-18, X-33, X-34, and X-38 configurations are shown. The three calibration parameters are well-behaved from Mach 0.25 to Mach 5.0, an angle-of-attack range extending to greater than 30 deg, and an angle-of-sideslip range extending to greater than 15 deg. Contrary to the sharp calibration changes found on traditional pitot-static systems at transonic speeds, the FADS calibrations are smooth, monotonic functions of Mach number and effective angles of attack and sideslip. Because the FADS calibration is sensitive to pressure port location, detailed measurements of the actual pressure port locations on the flight vehicle are required and the wind-tunnel calibration model should have pressure ports in similar locations. The procedure for calibrating a FADS system is outlined.

The Effect of Landing Surface on the Plantar Kinetics of Chinese Paratroopers Using Half-Squat Landing

PubMed Central

Li, Yi; Wu, Ji; Zheng, Chao; Huang, Rong Rong; Na, Yuhong; Yang, Fan; Wang, Zengshun; Wu, Di

2013-01-01

The objective of the study was to determine the effect of landing surface on plantar kinetics during a half-squat landing. Twenty male elite paratroopers with formal parachute landing training and over 2 years of parachute jumping experience were recruited. The subjects wore parachuting boots in which pressure sensing insoles were placed. Each subject was instructed to jump off a platform with a height of 60 cm, and land on either a hard or soft surface in a half-squat posture. Outcome measures were maximal plantar pressure, time to maximal plantar pressure (T-MPP), and pressure-time integral (PTI) upon landing on 10 plantar regions. Compared to a soft surface, hard surface produced higher maximal plantar pressure in the 1st to 4th metatarsal and mid-foot regions, but lower maximal plantar pressure in the 5th metatarsal region. Shorter T- MPP was found during hard surface landing in the 1st and 2nd metatarsal and medial rear foot. Landing on a hard surface landing resulted in a lower PTI than a soft surface in the 1stphalangeal region. For Chinese paratroopers, specific foot prosthesis should be designed to protect the1st to 4thmetatarsal region for hard surface landing, and the 1stphalangeal and 5thmetatarsal region for soft surface landing. Key Points Understanding plantar kinetics during the half-squat landing used by Chinese paratroopers can assist in the design of protective footwear. Compared to landing on a soft surface, a hard surface produced higher maximal plantar pressure in the 1st to 4th metatarsal and mid-foot regions, but lower maximal plantar pressure in the 5th metatarsal region. A shorter time to maximal plantar pressure was found during a hard surface landing in the 1st and 2nd metatarsals and medial rear foot. Landing on a hard surface resulted in a lower pressure-time integral than landing on a soft surface in the 1st phalangeal region. For Chinese paratroopers, specific foot prosthesis should be designed to protect the 1st to 4th metatarsal region for a hard surface landing, and the 1st phalangeal and 5th metatarsal region for a soft surface landing. PMID:24149145

Lunar soil properties and soil mechanics. Flow in porous media under rarefied gas conditions. Research phase: Fluid conductivity of lunar surface materials

NASA Technical Reports Server (NTRS)

Hurlbut, F. C.; Jih, C. R.

1972-01-01

Theoretical and experimental research on fluid conductivity of lunar surface materials is summarized. Theoretical methods were developed for the analysis of transitional and free-molecular flows, and for analysis of lunar permeability probe data in general. Experimental studies of rarefied flows under conditions of a large pressure gradient show flows in the continuum regime to be responsible for the largest portion of the pressure drop between source and sink for one dimensional flow, provided the entrance Knudsen number is sufficiently small. The concept of local similarity leading to a universal nondimensional function of Knudsen number was shown to have approximate validity; flows in all regimes may be described in terms of an area fraction and a single length parameter. Synthetic porous media prepared from glass beads exhibited flow behavior similar in many regards to that of a natural sandstone; studies using artificial stones with known pore configurations may lead to new insight concerning the structure of natural materials. The experimental method involving the use of segmented specimens of large permeability is shown to be fruitful.

Accelerated aging studies of UHMWPE. II. Virgin UHMWPE is not immune to oxidative degradation.

PubMed

Edidin, A A; Villarraga, M L; Herr, M P; Muth, J; Yau, S S; Kurtz, S M

2002-08-01

In Part I of this series, we showed that aging at elevated oxygen pressure is more successful at increasing the depth to which degradation occurs although it, too, generally causes greater degradation at the surface than at the subsurface. Therefore we hypothesized that thermal degradation alone, in the absence of free radicals, could be sufficient to artificially age UHMWPE in a manner analogous to natural aging. In the present study, virgin and air-irradiated UHMWPE (extruded GUR 1050 and compression-molded 1900) were aged up to 4 weeks at elevated oxygen pressure, and the mechanical behavior at the surface and subsurface was examined. All the materials were substantially degraded following 4 weeks of aging, but the spatial variations in the nonirradiated materials more closely mimicked the previously observed subsurface peak of degradation seen in naturally aged UHMWPE following irradiation in air. This aged material could provide a more realistic model for subsurface mechanical degradation, making it suitable for further mechanical testing in venues such as wear simulation. Copyright 2002 Wiley Periodicals, Inc.