Insight into the Li2CO3-K2CO3 eutectic mixture from classical molecular dynamics: Thermodynamics, structure, and dynamics

NASA Astrophysics Data System (ADS)

Corradini, Dario; Coudert, François-Xavier; Vuilleumier, Rodolphe

2016-03-01

We use molecular dynamics simulations to study the thermodynamics, structure, and dynamics of the Li2CO3-K2CO3 (62:38 mol. %) eutectic mixture. We present a new classical non-polarizable force field for this molten salt mixture, optimized using experimental and first principles molecular dynamics simulations data as reference. This simple force field allows efficient molecular simulations of phenomena at long time scales. We use this optimized force field to describe the behavior of the eutectic mixture in the 900-1100 K temperature range, at pressures between 0 and 5 GPa. After studying the equation of state in these thermodynamic conditions, we present molecular insight into the structure and dynamics of the melt. In particular, we present an analysis of the temperature and pressure dependence of the eutectic mixture's self-diffusion coefficients, viscosity, and ionic conductivity.

Insight into the Li2CO3-K2CO3 eutectic mixture from classical molecular dynamics: Thermodynamics, structure, and dynamics.

PubMed

Corradini, Dario; Coudert, François-Xavier; Vuilleumier, Rodolphe

2016-03-14

We use molecular dynamics simulations to study the thermodynamics, structure, and dynamics of the Li2CO3-K2CO3 (62:38 mol. %) eutectic mixture. We present a new classical non-polarizable force field for this molten salt mixture, optimized using experimental and first principles molecular dynamics simulations data as reference. This simple force field allows efficient molecular simulations of phenomena at long time scales. We use this optimized force field to describe the behavior of the eutectic mixture in the 900-1100 K temperature range, at pressures between 0 and 5 GPa. After studying the equation of state in these thermodynamic conditions, we present molecular insight into the structure and dynamics of the melt. In particular, we present an analysis of the temperature and pressure dependence of the eutectic mixture's self-diffusion coefficients, viscosity, and ionic conductivity.

Molecular simulation of disjoining-pressure isotherms for free liquid , Lennard-Jones thin films

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

Bhatt, Divesh; Newman, John; Radke, C.J.

2001-10-01

We present canonical-ensemble molecular-dynamics simulations of disjoining-pressure isotherms in Lennard-Jones free liquid films. Thermodynamics demands that the disjoining pressure is determined uniquely as a function of the chemical potential purely from the phase diagram of the fluid. Our results from molecular dynamics validate this argument. The inverse-sixth-power distance term in the Lennard-Jones intermolecular potential represents van der Waals dispersion forces. Hence, we compare our results with classical Hamaker theory that is based on dispersion forces but assumes a slab geometry for the density profile and completely neglects fluid structure and entropy. We find that the Hamaker constant obtained from ourmore » simulations is about an order of magnitude larger than that from classical theory. To investigate the origin of this discrepancy, we calculate the disjoining-pressure isotherm using a density-functional theory relaxing the inherent assumptions in the Hamaker theory and imparting to the fluid an approximate structure. For disjoining pressure as a function of chemical potential, the results of density-functional theory and molecular dynamics are very close. Even for disjoining-pressure isotherms, and the subsequently calculated Hamaker constant, results of the density-functional theory are closer to the molecular-dynamics simulations by about a factor of 4 compared to Hamaker theory. [References: 44]« less

Pressure measurements on a rectangular wing with a NACA0012 airfoil during conventional flutter

NASA Technical Reports Server (NTRS)

Rivera, Jose A., Jr.; Dansberry, Bryan E.; Durham, Michael H.; Bennett, Robert M.; Silva, Walter A.

1992-01-01

The Structural Dynamics Division at NASA LaRC has started a wind tunnel activity referred to as the Benchmark Models Program. The primary objective of the program is to acquire measured dynamic instability and corresponding pressure data that will be useful for developing and evaluating aeroelastic type CFD codes currently in use or under development. The program is a multi-year activity that will involve testing of several different models to investigate various aeroelastic phenomena. The first model consisted of a rigid semispan wing having a rectangular planform and a NACA 0012 airfoil shape which was mounted on a flexible two degree-of-freedom mount system. Two wind-tunnel tests were conducted with the first model. Several dynamic instability boundaries were investigated such as a conventional flutter boundary, a transonic plunge instability region near Mach = 0.90, and stall flutter. In addition, wing surface unsteady pressure data were acquired along two model chords located at the 60 to 95-percent span stations during these instabilities. At this time, only the pressure data for the conventional flutter boundary is presented. The conventional flutter boundary and the wing surface unsteady pressure measurements obtained at the conventional flutter boundary test conditions in pressure coefficient form are presented. Wing surface steady pressure measurements obtained with the model mount system rigidized are also presented. These steady pressure data were acquired at essentially the same dynamic pressure at which conventional flutter had been encountered with the mount system flexible.

Flight Tests of a 40-Foot Nominal Diameter Modified Ringsail Parachute Deployed at Mach 1.64 and Dynamic Pressure of 9.1 Pounds Per Square Foot

NASA Technical Reports Server (NTRS)

Eckstrom, Clinton V.; Murrow, Harold N.; Preisser, John S.

1967-01-01

A ringsail parachute, which had a nominal diameter of 40 feet (12.2 meters) and reference area of 1256 square feet (117 m(exp 2)) and was modified to provide a total geometric porosity of 15 percent of the reference area, was flight tested as part of the rocket launch portion of the NASA Planetary Entry Parachute Program. The payload for the flight test was an instrumented capsule from which the test parachute was ejected by a deployment mortar when the system was at a Mach number of 1.64 and a dynamic pressure of 9.1 pounds per square foot (43.6 newtons per m(exp 2)). The parachute deployed to suspension line stretch in 0.45 second with a resulting snatch force of 1620 pounds (7200 newtons). Canopy inflation began 0.07 second later and the parachute projected area increased slowly to a maximum of 20 percent of that expected for full inflation. During this test, the suspension lines twisted, primarily because the partially inflated canopy could not restrict the twisting to the attachment bridle and risers. This twisting of the suspension lines hampered canopy inflation at a time when velocity and dynamic-pressure conditions were more favorable.

Reference values for CSF outflow resistance and intracranial pressure in healthy elderly.

PubMed

Malm, Jan; Jacobsson, Johan; Birgander, Richard; Eklund, Anders

2011-03-08

The intracranial pressure (ICP) and CSF outflow resistance (R(out)) are essential to describe the dynamics of the CSF system. R(out) affects ICP, pulse amplitudes, CSF absorption, and the compliance of the system. The objective of this study was to determine the reference values in healthy elderly subjects. Elderly people (60-82 years), who considered themselves healthy, were recruited through an advertisement in the local newspaper. All were evaluated with a 3-T MRI. Subjects were eligible if they did not have any psychiatric or neurologic disorder or signs of advanced atherosclerotic disease. CSF resting pressure (ICP) and R(out) were determined by a constant pressure infusion method with the patient in the supine position. The study population consisted of 40 subjects (mean age 70 years; 23 women). The median ICP was 11.6 mm Hg (15.8 cmH(2)O) and the reference interval was ICP 7.8-14.3 mm Hg (10.6-19.4 cmH(2)O) (defined as 5th to 95th percentiles). The median R(out) was 8.6 mm Hg/mL/min. The variation in R(out) was large and not normally distributed. The 90th percentile of R(out) was 17.4 mm Hg/mL/min. This study reports reference values for ICP and R(out) and should be used for comparison when investigating disorders with suspected CSF dynamic disturbances in the elderly. ICP was in the same range as that reported in the young and middle-aged. The upper limit of R(out) was higher than previously believed to be the upper limit of normal for this age group.

NACA0012 benchmark model experimental flutter results with unsteady pressure distributions

NASA Technical Reports Server (NTRS)

Rivera, Jose A., Jr.; Dansberry, Bryan E.; Bennett, Robert M.; Durham, Michael H.; Silva, Walter A.

1992-01-01

The Structural Dynamics Division at NASA Langley Research Center has started a wind tunnel activity referred to as the Benchmark Models Program. The primary objective of this program is to acquire measured dynamic instability and corresponding pressure data that will be useful for developing and evaluating aeroelastic type computational fluid dynamics codes currently in use or under development. The program is a multi-year activity that will involve testing of several different models to investigate various aeroelastic phenomena. This paper describes results obtained from a second wind tunnel test of the first model in the Benchmark Models Program. This first model consisted of a rigid semispan wing having a rectangular planform and a NACA 0012 airfoil shape which was mounted on a flexible two degree of freedom mount system. Experimental flutter boundaries and corresponding unsteady pressure distribution data acquired over two model chords located at the 60 and 95 percent span stations are presented.

Cavitation erosion prediction based on analysis of flow dynamics and impact load spectra

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

Mihatsch, Michael S., E-mail: michael.mihatsch@aer.mw.tum.de; Schmidt, Steffen J.; Adams, Nikolaus A.

2015-10-15

Cavitation erosion is the consequence of repeated collapse-induced high pressure-loads on a material surface. The present paper assesses the prediction of impact load spectra of cavitating flows, i.e., the rate and intensity distribution of collapse events based on a detailed analysis of flow dynamics. Data are obtained from a numerical simulation which employs a density-based finite volume method, taking into account the compressibility of both phases, and resolves collapse-induced pressure waves. To determine the spectrum of collapse events in the fluid domain, we detect and quantify the collapse of isolated vapor structures. As reference configuration we consider the expansion ofmore » a liquid into a radially divergent gap which exhibits unsteady sheet and cloud cavitation. Analysis of simulation data shows that global cavitation dynamics and dominant flow events are well resolved, even though the spatial resolution is too coarse to resolve individual vapor bubbles. The inviscid flow model recovers increasingly fine-scale vapor structures and collapses with increasing resolution. We demonstrate that frequency and intensity of these collapse events scale with grid resolution. Scaling laws based on two reference lengths are introduced for this purpose. We show that upon applying these laws impact load spectra recorded on experimental and numerical pressure sensors agree with each other. Furthermore, correlation between experimental pitting rates and collapse-event rates is found. Locations of high maximum wall pressures and high densities of collapse events near walls obtained numerically agree well with areas of erosion damage in the experiment. The investigation shows that impact load spectra of cavitating flows can be inferred from flow data that captures the main vapor structures and wave dynamics without the need for resolving all flow scales.« less

A study to evaluate STS heads-up ascent trajectory performance employing a minimum-Hamiltonian optimization strategy

NASA Technical Reports Server (NTRS)

Sinha, Sujit

1988-01-01

A study was conducted to evaluate the performance implications of a heads-up ascent flight design for the Space Transportation System, as compared to the current heads-down flight mode. The procedure involved the use of the Minimum Hamiltonian Ascent Shuttle Trajectory Evaluation Program, which is a three-degree-of-freedom moment balance simulation of shuttle ascent. A minimum-Hamiltonian optimization strategy was employed to maximize injection weight as a function of maximum dynamic pressure constraint and Solid Rocket Motor burnrate. Performance Reference Mission Four trajectory groundrules were used for consistency. The major conclusions are that for heads-up ascent and a mission nominal design maximum dynamic pressure value of 680 psf, the optimum solid motor burnrate is 0.394 ips, which produces a performance enhancement of 4293 lbm relative to the baseline heads-down ascent, with 0.368 ips burnrate solid motors and a 680 psf dynamic pressure constraint. However, no performance advantage exists for heads-up flight if the current Solid Rocket Motor target burnrate of 0.368 ips is used. The advantage of heads-up ascent flight employing the current burnrate is that Space Shuttle Main Engine throttling for dynamic pressure control is not necessary.

The dynamics of double slab subduction

NASA Astrophysics Data System (ADS)

Holt, A. F.; Royden, L. H.; Becker, T. W.

2017-04-01

We use numerical models to investigate the dynamics of two interacting slabs with parallel trenches. Cases considered are: a single slab reference, outward dipping slabs (out-dip), inward dipping slabs (in-dip) and slabs dipping in the same direction (same-dip). Where trenches converge over time (same-dip and out-dip systems), large positive dynamic pressures in the asthenosphere are generated beneath the middle plate and large trench-normal extensional forces are transmitted through the middle plate. This results in slabs that dip away from the middle plate at depth, independent of trench geometry. The single slab, the front slab in the same-dip case and both out-dip slabs undergo trench retreat and exhibit stable subduction. However, slabs within the other double subduction systems tend to completely overturn at the base of the upper mantle, and exhibit either trench advance (rear slab in same-dip), or near-stationary trenches (in-dip). For all slabs, the net slab-normal dynamic pressure at 330 km depth is nearly equal to the slab-normal force induced by slab buoyancy. For double subduction, the net outward force on the slabs due to dynamic pressure from the asthenosphere is effectively counterbalanced by the net extensional force transmitted through the middle plate. Thus, dynamic pressure at depth, interplate coupling and lithospheric stresses are closely linked and their effects cannot be isolated. Our results provide insights into both the temporal evolution of double slab systems on Earth and, more generally, how the various components of subduction systems, from mantle flow/pressure to interplate coupling, are dynamically linked.

Dynamic pressure sensitivity determination with Mach number method

NASA Astrophysics Data System (ADS)

Sarraf, Christophe; Damion, Jean-Pierre

2018-05-01

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

Insight into the Li{sub 2}CO{sub 3}–K{sub 2}CO{sub 3} eutectic mixture from classical molecular dynamics: Thermodynamics, structure, and dynamics

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

Corradini, Dario; Vuilleumier, Rodolphe, E-mail: rodolphe.vuilleumier@ens.fr; Sorbonne Universités, UPMC Univ. Paris 06, PASTEUR, 75005 Paris

We use molecular dynamics simulations to study the thermodynamics, structure, and dynamics of the Li{sub 2}CO{sub 3}–K{sub 2}CO{sub 3} (62:38 mol. %) eutectic mixture. We present a new classical non-polarizable force field for this molten salt mixture, optimized using experimental and first principles molecular dynamics simulations data as reference. This simple force field allows efficient molecular simulations of phenomena at long time scales. We use this optimized force field to describe the behavior of the eutectic mixture in the 900–1100 K temperature range, at pressures between 0 and 5 GPa. After studying the equation of state in these thermodynamic conditions, wemore » present molecular insight into the structure and dynamics of the melt. In particular, we present an analysis of the temperature and pressure dependence of the eutectic mixture’s self-diffusion coefficients, viscosity, and ionic conductivity.« less

Experimental Investigation of Hysteretic Dynamic Capillarity Effect in Unsaturated Flow

PubMed Central

Zhuang, Luwen; Qin, Chao‐Zhong; de Waal, Arjen

2017-01-01

Abstract The difference between average pressures of two immiscible fluids is commonly assumed to be the same as macroscopic capillary pressure, which is considered to be a function of saturation only. However, under transient conditions, a dependence of this pressure difference on the time rate of saturation change has been observed by many researchers. This is commonly referred to as dynamic capillarity effect. As a first‐order approximation, the dynamic term is assumed to be linearly dependent on the time rate of change of saturation, through a material coefficient denoted by τ. In this study, a series of laboratory experiments were carried out to quantify the dynamic capillarity effect in an unsaturated sandy soil. Primary, main, and scanning drainage experiments, under both static and dynamic conditions, were performed on a sandy soil in a small cell. The value of the dynamic capillarity coefficient τ was calculated from the air‐water pressure differences and average saturation values during static and dynamic drainage experiments. We found a dependence of τ on saturation, which showed a similar trend for all drainage conditions. However, at any given saturation, the value of τ for primary drainage was larger than the value for main drainage and that was in turn larger than the value for scanning drainage. Each data set was fit a simple log‐linear equation, with different values of fitting parameters. This nonuniqueness of the relationship between τ and saturation and possible causes is discussed. PMID:29398729

Experimental Investigation of Hysteretic Dynamic Capillarity Effect in Unsaturated Flow

NASA Astrophysics Data System (ADS)

Zhuang, Luwen; Hassanizadeh, S. Majid; Qin, Chao-Zhong; de Waal, Arjen

2017-11-01

The difference between average pressures of two immiscible fluids is commonly assumed to be the same as macroscopic capillary pressure, which is considered to be a function of saturation only. However, under transient conditions, a dependence of this pressure difference on the time rate of saturation change has been observed by many researchers. This is commonly referred to as dynamic capillarity effect. As a first-order approximation, the dynamic term is assumed to be linearly dependent on the time rate of change of saturation, through a material coefficient denoted by τ. In this study, a series of laboratory experiments were carried out to quantify the dynamic capillarity effect in an unsaturated sandy soil. Primary, main, and scanning drainage experiments, under both static and dynamic conditions, were performed on a sandy soil in a small cell. The value of the dynamic capillarity coefficient τ was calculated from the air-water pressure differences and average saturation values during static and dynamic drainage experiments. We found a dependence of τ on saturation, which showed a similar trend for all drainage conditions. However, at any given saturation, the value of τ for primary drainage was larger than the value for main drainage and that was in turn larger than the value for scanning drainage. Each data set was fit a simple log-linear equation, with different values of fitting parameters. This nonuniqueness of the relationship between τ and saturation and possible causes is discussed.

Design principles for high–pressure force fields: Aqueous TMAO solutions from ambient to kilobar pressures

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

Hölzl, Christoph; Horinek, Dominik, E-mail: dominik.horinek@ur.de; Kibies, Patrick

Accurate force fields are one of the major pillars on which successful molecular dynamics simulations of complex biomolecular processes rest. They have been optimized for ambient conditions, whereas high-pressure simulations become increasingly important in pressure perturbation studies, using pressure as an independent thermodynamic variable. Here, we explore the design of non-polarizable force fields tailored to work well in the realm of kilobar pressures – while avoiding complete reparameterization. Our key is to first compute the pressure-induced electronic and structural response of a solute by combining an integral equation approach to include pressure effects on solvent structure with a quantum-chemical treatmentmore » of the solute within the embedded cluster reference interaction site model (EC-RISM) framework. Next, the solute’s response to compression is taken into account by introducing pressure-dependence into selected parameters of a well-established force field. In our proof-of-principle study, the full machinery is applied to N,N,N-trimethylamine-N-oxide (TMAO) in water being a potent osmolyte that counteracts pressure denaturation. EC-RISM theory is shown to describe well the charge redistribution upon compression of TMAO(aq) to 10 kbar, which is then embodied in force field molecular dynamics by pressure-dependent partial charges. The performance of the high pressure force field is assessed by comparing to experimental and ab initio molecular dynamics data. Beyond its broad usefulness for designing non-polarizable force fields for extreme thermodynamic conditions, a good description of the pressure-response of solutions is highly recommended when constructing and validating polarizable force fields.« less

Design principles for high-pressure force fields: Aqueous TMAO solutions from ambient to kilobar pressures.

PubMed

Hölzl, Christoph; Kibies, Patrick; Imoto, Sho; Frach, Roland; Suladze, Saba; Winter, Roland; Marx, Dominik; Horinek, Dominik; Kast, Stefan M

2016-04-14

Accurate force fields are one of the major pillars on which successful molecular dynamics simulations of complex biomolecular processes rest. They have been optimized for ambient conditions, whereas high-pressure simulations become increasingly important in pressure perturbation studies, using pressure as an independent thermodynamic variable. Here, we explore the design of non-polarizable force fields tailored to work well in the realm of kilobar pressures--while avoiding complete reparameterization. Our key is to first compute the pressure-induced electronic and structural response of a solute by combining an integral equation approach to include pressure effects on solvent structure with a quantum-chemical treatment of the solute within the embedded cluster reference interaction site model (EC-RISM) framework. Next, the solute's response to compression is taken into account by introducing pressure-dependence into selected parameters of a well-established force field. In our proof-of-principle study, the full machinery is applied to N,N,N-trimethylamine-N-oxide (TMAO) in water being a potent osmolyte that counteracts pressure denaturation. EC-RISM theory is shown to describe well the charge redistribution upon compression of TMAO(aq) to 10 kbar, which is then embodied in force field molecular dynamics by pressure-dependent partial charges. The performance of the high pressure force field is assessed by comparing to experimental and ab initio molecular dynamics data. Beyond its broad usefulness for designing non-polarizable force fields for extreme thermodynamic conditions, a good description of the pressure-response of solutions is highly recommended when constructing and validating polarizable force fields.

Measurements of Flow Turbulence in the NASA Langley Transonic Dynamics Tunnel

NASA Technical Reports Server (NTRS)

Wiesman, Carol D.; Sleeper, Robert K.

2005-01-01

An assessment of the flow turbulence in the NASA Langley Transonic Dynamics Tunnel (TDT) was conducted during calibration activities following the facility conversion from a Freon-12 heavy-gas test medium to an R134a heavy-gas test medium. Total pressure, static pressure, and acoustic pressure levels were measured at several locations on a stingmounted rake. The test measured wall static pressures at several locations although this paper presents only those from one location. The test used two data acquisition systems, one sampling at 1000 Hz and the second sampling at 125 000 Hz, for acquiring time-domain data. This paper presents standard deviations and power spectral densities of the turbulence points throughout the wind tunnel envelope in air and R134a. The objective of this paper is to present the turbulence characteristics for the test section. No attempt is made to assess the causes of the turbulence. The present paper looks at turbulence in terms of pressure fluctuations. Reference 1 looked at tunnel turbulence in terms of velocity fluctuations.

Dynamic response of Hovercraft lift fans

NASA Astrophysics Data System (ADS)

Moran, D. D.

1981-08-01

Hovercraft lift fans are subjected to varying back pressure due to wave action and craft motions when these vehicles are operating in a seaway. The oscillatory back pressure causes the fans to perform dynamically, exhibiting a hysteresis type of response and a corresponding degradation in mean performance. Since Hovercraft motions are influenced by variations in lift fan pressure and discharge, it is important to understand completely the nature of the dynamic performance of lift fans in order to completely solve the Hovercraft seakeeping problem. The present study was performed to determine and classify the instabilities encountered in a centrifugal fan operating against time-varying back pressure. A model-scale experiment was developed in which the fan discharge was directed into a flow-measuring device, terminating in a rotating valve which produced an oscillatory back pressure superimposed upon a mean aerodynamic resistance. Pressure and local velocity were measured as functions of time at several locations in the fan volute. The measurements permitted the identification of rotating (or propagating) stall in the impeller. One cell and two cell configurations were classified and the transient condition connecting these two configurations was observed. The mechanisms which lead to rotating stall in a centrifugal compressor are presented and discussed with specific reference to Hovercraft applications.

Intensity Biased PSP Measurement

NASA Technical Reports Server (NTRS)

Subramanian, Chelakara S.; Amer, Tahani R.; Oglesby, Donald M.; Burkett, Cecil G., Jr.

2000-01-01

The current pressure sensitive paint (PSP) technique assumes a linear relationship (Stern-Volmer Equation) between intensity ratio (I(sub 0)/I) and pressure ratio (P/P(sub 0)) over a wide range of pressures (vacuum to ambient or higher). Although this may be valid for some PSPs, in most PSPs the relationship is nonlinear, particularly at low pressures (less than 0.2 psia when the oxygen level is low). This non-linearity can be attributed to variations in the oxygen quenching (de-activation) rates (which otherwise is assumed constant) at these pressures. Other studies suggest that some paints also have non-linear calibrations at high pressures; because of heterogeneous (non-uniform) oxygen diffusion and c quenching. Moreover, pressure sensitive paints require correction for the output intensity due to light intensity variation, paint coating variation, model dynamics, wind-off reference pressure variation, and temperature sensitivity. Therefore to minimize the measurement uncertainties due to these causes, an in- situ intensity correction method was developed. A non-oxygen quenched paint (which provides a constant intensity at all pressures, called non-pressure sensitive paint, NPSP) was used for the reference intensity (I(sub NPSP)) with respect to which all the PSP intensities (I) were measured. The results of this study show that in order to fully reap the benefits of this technique, a totally oxygen impermeable NPSP must be available.

Intensity Biased PSP Measurement

NASA Technical Reports Server (NTRS)

Subramanian, Chelakara S.; Amer, Tahani R.; Oglesby, Donald M.; Burkett, Cecil G., Jr.

2000-01-01

The current pressure sensitive paint (PSP) technique assumes a linear relationship (Stern-Volmer Equation) between intensity ratio (I(sub o)/I) and pressure ratio (P/P(sub o)) over a wide range of pressures (vacuum to ambient or higher). Although this may be valid for some PSPs, in most PSPs the relationship is nonlinear, particularly at low pressures (less than 0.2 psia when the oxygen level is low). This non-linearity can be attributed to variations in the oxygen quenching (de-activation) rates (which otherwise is assumed constant) at these pressures. Other studies suggest that some paints also have non-linear calibrations at high pressures; because of heterogeneous (non-uniform) oxygen diffusion and quenching. Moreover, pressure sensitive paints require correction for the output intensity due to light intensity variation, paint coating variation, model dynamics, wind-off reference pressure variation, and temperature sensitivity. Therefore to minimize the measurement uncertainties due to these causes, an insitu intensity correction method was developed. A non-oxygen quenched paint (which provides a constant intensity at all pressures, called non-pressure sensitive paint, NPSP) was used for the reference intensity (I(sub NPSP) with respect to which all the PSP intensities (I) were measured. The results of this study show that in order to fully reap the benefits of this technique, a totally oxygen impermeable NPSP must be available.

In Situ Space Gas Dynamic Measurements by the ROSINA Comet Pressure Sensor COPS Onboard Rosetta Spacecraft

NASA Astrophysics Data System (ADS)

Tzou, Chia-Yu; Altwegg, Kathrin; Fiethe, Björn; Gasc, Sébastien; Rubin, Martin

2015-04-01

Rosetta is part of the cornerstone missions executed by the European Space Agency. It is the first space mission to orbit and also land on a comet. The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) is one of the core payloads on board of the Rosetta spacecraft [Balsiger et al, 2007]. ROSINA's main objective is to determine the major atmospheric and ionospheric composition in the coma and to investigate the gas dynamics around the comet. ROSINA consists of two mass spectrometers and a pressure sensor. The COmet Pressure Sensor (COPS) includes two gauges: the "nude gauge" measures total neutral density in the coma and the "ram gauge" measures the dynamic pressure of the cometary gas flux. The combination of these two gauges makes COPS capable to derive the gas dynamics (velocity and temperature) at the location of the spacecraft. Over several months Rosetta has been carrying out a close study of comet 67P/Churyumov-Gerasimenko. In early August 2014 COPS detected the faint and expanding atmosphere of the comet while it was still outside of 3.5 AU from the Sun. We will present ROSINA COPS observations of the evolution and gas dynamics of the cometary coma following these first observations until spring 2015. Reference: Balsiger, H. et al.: ROSINA-Rosetta Orbiter Spectrometer for Ion and Neutral Analysis, Space Science Reviews, Vol. 128, 745-801, 2007.

Ab initio molecular dynamic study of solid-state transitions of ammonium nitrate

PubMed Central

Yu, Hongyu; Duan, Defang; Liu, Hanyu; Yang, Ting; Tian, Fubo; Bao, Kuo; Li, Da; Zhao, Zhonglong; Liu, Bingbing; Cui, Tian

2016-01-01

High-pressure polymorphism and phase transitions have wide ranging consequences on the basic properties of ammonium nitrate. However, the phase diagram of ammonium nitrate at high pressure and high temperature is still under debate. This study systematically investigates the phase transitions and structural properties of ammonium nitrate at a pressure range of 5–60 GPa and temperature range of 250–400 K by ab initio molecular dynamics simulations. Two new phases are identified: one corresponds to the experimentally observed phase IV’ and the other is named AN-X. Simultaneously, the lattice strains play a significant role in the formation and stabilization of phase IV’, providing a reasonable explanation for experimental observation of phase IV-IV’ transition which only appears under nonhydrostatic pressure. In addition, 12 O atoms neighboring the NH (N atom in ammonium cation) atom are selected as reference system to clearly display the tanglesome rotation of ammonium cation. PMID:26754622

Dynamics of Geometrically Nonlinear Elastic Nonthin Anisotropic Shells of Variable Thickness

NASA Astrophysics Data System (ADS)

Marchuk, M. V.; Tuchapskii, R. I.

2017-11-01

A theory of dynamic elastic geometrically nonlinear deformation of nonthin anisotropic shells with variable thickness is constructed. Shells are assumed asymmetric about the reference surface. Functions are expanded into Legendre series. The basic equations are written in a coordinate system aligned with the lines of curvature of the reference surface. The equations of motion and appropriate boundary conditions are obtained using the Hamilton-Ostrogradsky variational principle. The change in metric across the thickness is taken into account. The theory assumes that the refinement process is regular and allows deriving equations including products of terms of Legendre series of unknown functions of arbitrary order. The behavior of a square metallic plate acted upon by a pressure pulse distributed over its face is studied.

Control integration concept for hypersonic cruise-turn maneuvers

NASA Technical Reports Server (NTRS)

Raney, David L.; Lallman, Frederick J.

1992-01-01

Piloting difficulties associated with conducting aircraft maneuvers in hypersonic flight are caused in part by the nonintuitive nature of the aircraft response and the stringent constraints anticipated on allowable angle of attack and dynamic pressure variations. An approach is documented that provides precise, coordinated maneuver control during excursions from a hypersonic cruise flight path and the necessary flight condition constraints. The approach is to achieve specified guidance commands by resolving altitude and cross range errors into a load factor and bank angle command by using a coordinate transformation that acts as an interface between outer and inner loop flight controls. This interface, referred to as a 'resolver', applies constraints on angle of attack and dynamic pressure perturbations while prioritizing altitude regulation over cross range. An unpiloted test simulation, in which the resolver was used to drive inner loop flight controls, produced time histories of responses to guidance commands and atmospheric disturbances at Mach numbers of 6, 10, 15, and 20. Angle of attack and throttle perturbation constraints, combined with high speed flight effects and the desire to maintain constant dynamic pressure, significantly impact the maneuver envelope for a hypersonic vehicle.

A calculation and uncertainty evaluation method for the effective area of a piston rod used in quasi-static pressure calibration

NASA Astrophysics Data System (ADS)

Gu, Tingwei; Kong, Deren; Shang, Fei; Chen, Jing

2018-04-01

This paper describes the merits and demerits of different sensors for measuring propellant gas pressure, the applicable range of the frequently used dynamic pressure calibration methods, and the working principle of absolute quasi-static pressure calibration based on the drop-weight device. The main factors affecting the accuracy of pressure calibration are analyzed from two aspects of the force sensor and the piston area. To calculate the effective area of the piston rod and evaluate the uncertainty between the force sensor and the corresponding peak pressure in the absolute quasi-static pressure calibration process, a method for solving these problems based on the least squares principle is proposed. According to the relevant quasi-static pressure calibration experimental data, the least squares fitting model between the peak force and the peak pressure, and the effective area of the piston rod and its measurement uncertainty, are obtained. The fitting model is tested by an additional group of experiments, and the peak pressure obtained by the existing high-precision comparison calibration method is taken as the reference value. The test results show that the peak pressure obtained by the least squares fitting model is closer to the reference value than the one directly calculated by the cross-sectional area of the piston rod. When the peak pressure is higher than 150 MPa, the percentage difference is less than 0.71%, which can meet the requirements of practical application.

[A simple model for describing pressure-volume curves in free balloon dilatation with reference the dynamics of inflation hydraulic aspects].

PubMed

Bloss, P; Werner, C

2000-06-01

We propose a simple model to describe pressure-time and pressure-volume curves for the free balloon (balloon in air) of balloon catheters, taking into account the dynamics of the inflation device. On the basis of our investigations of the flow rate-dependence of characteristic parameters of the pressure-time curves, the appropriateness of this simple model is demonstrated using a representative example. Basic considerations lead to the following assumptions: (1) the flow within the shaft of the catheter is laminar, and (ii) the volume decrease of the liquid used for inflation due to pressurization can be neglected if the liquid is carefully degassed prior to inflation, and if the total volume of the liquid in the system is less than 2 ml. Taking into account the dynamics of the inflation device used for pumping the liquid into the proximal end of the shaft during inflation, the inflation process can be subdivided into the following three phases: initial phase, filling phase and dilatation phase. For these three phases, the transformation of the time into the volume coordinates is given. On the basis of our model, the following parameters of the balloon catheter can be determined from a measured pressure-time curve: (1) the resistance to flow of the liquid through the shaft of the catheter and the resulting pressure drop across the shaft, (2) the residual volume and residual pressure of the balloon, and (3) the volume compliance of the balloon catheter with and without the inflation device.

The effect of a microscale fracture on dynamic capillary pressure of two-phase flow in porous media

NASA Astrophysics Data System (ADS)

Tang, Mingming; Lu, Shuangfang; Zhan, Hongbin; Wenqjie, Guo; Ma, Huifang

2018-03-01

Dynamic capillary pressure (DCP) effects, which is vital for predicting multiphase flow behavior in porous media, refers to the injection rate dependence capillary pressure observed during non-equilibrium displacement experiments. However, a clear picture of the effects of microscale fractures on DCP remains elusive. This study quantified the effects of microscale fractures on DCP and simulated pore-scale force and saturation change in fractured porous media using the multiphase lattice Boltzmann method (LBM). Eighteen simulation cases were carried out to calculate DCP as a function of wetting phase saturation. The effects of viscosity ratio and fracture orientation, aperture and length on DCP and DCP coefficient τ were investigated, where τ refers to the ratio of the difference of DCP and static capillary pressure (SCP) over the rate of wetting-phase saturation change versus time. Significant differences in τ values were observed between unfractured and fractured porous media. The τ values of fractured porous media were 1.1  × 104 Pa ms to 5.68 × 105 Pa ms, which were one or two orders of magnitude lower than those of unfractured porous media with a value of 4 × 106 Pa. ms. A horizontal fracture had greater effects on DCP and τ than a vertical fracture, given the same fracture aperture and length. This study suggested that a microscale fracture might result in large magnitude changes in DCP for two-phase flow.

Coarse-grained modeling of polyethylene melts: Effect on dynamics

DOE PAGES

Peters, Brandon L.; Salerno, K. Michael; Agrawal, Anupriya; ...

2017-05-23

The distinctive viscoelastic behavior of polymers results from a coupled interplay of motion on multiple length and time scales. Capturing the broad time and length scales of polymer motion remains a challenge. Using polyethylene (PE) as a model macromolecule, we construct coarse-grained (CG) models of PE with three to six methyl groups per CG bead and probe two critical aspects of the technique: pressure corrections required after iterative Boltzmann inversion (IBI) to generate CG potentials that match the pressure of reference fully atomistic melt simulations and the transferability of CG potentials across temperatures. While IBI produces nonbonded pair potentials thatmore » give excellent agreement between the atomistic and CG pair correlation functions, the resulting pressure for the CG models is large compared with the pressure of the atomistic system. We find that correcting the potential to match the reference pressure leads to nonbonded interactions with much deeper minima and slightly smaller effective bead diameter. However, simulations with potentials generated by IBI and pressure-corrected IBI result in similar mean-square displacements (MSDs) and stress autocorrelation functions G( t) for PE melts. While the time rescaling factor required to match CG and atomistic models is the same for pressure- and non-pressure-corrected CG models, it strongly depends on temperature. Furthermore, transferability was investigated by comparing the MSDs and stress autocorrelation functions for potentials developed at different temperatures.« less

Coarse-grained modeling of polyethylene melts: Effect on dynamics

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

Peters, Brandon L.; Salerno, K. Michael; Agrawal, Anupriya

The distinctive viscoelastic behavior of polymers results from a coupled interplay of motion on multiple length and time scales. Capturing the broad time and length scales of polymer motion remains a challenge. Using polyethylene (PE) as a model macromolecule, we construct coarse-grained (CG) models of PE with three to six methyl groups per CG bead and probe two critical aspects of the technique: pressure corrections required after iterative Boltzmann inversion (IBI) to generate CG potentials that match the pressure of reference fully atomistic melt simulations and the transferability of CG potentials across temperatures. While IBI produces nonbonded pair potentials thatmore » give excellent agreement between the atomistic and CG pair correlation functions, the resulting pressure for the CG models is large compared with the pressure of the atomistic system. We find that correcting the potential to match the reference pressure leads to nonbonded interactions with much deeper minima and slightly smaller effective bead diameter. However, simulations with potentials generated by IBI and pressure-corrected IBI result in similar mean-square displacements (MSDs) and stress autocorrelation functions G( t) for PE melts. While the time rescaling factor required to match CG and atomistic models is the same for pressure- and non-pressure-corrected CG models, it strongly depends on temperature. Furthermore, transferability was investigated by comparing the MSDs and stress autocorrelation functions for potentials developed at different temperatures.« less

Measurement correction method for force sensor used in dynamic pressure calibration based on artificial neural network optimized by genetic algorithm

NASA Astrophysics Data System (ADS)

Gu, Tingwei; Kong, Deren; Shang, Fei; Chen, Jing

2017-12-01

We present an optimization algorithm to obtain low-uncertainty dynamic pressure measurements from a force-transducer-based device. In this paper, the advantages and disadvantages of the methods that are commonly used to measure the propellant powder gas pressure, the applicable scope of dynamic pressure calibration devices, and the shortcomings of the traditional comparison calibration method based on the drop-weight device are firstly analysed in detail. Then, a dynamic calibration method for measuring pressure using a force sensor based on a drop-weight device is introduced. This method can effectively save time when many pressure sensors are calibrated simultaneously and extend the life of expensive reference sensors. However, the force sensor is installed between the drop-weight and the hammerhead by transition pieces through the connection mode of bolt fastening, which causes adverse effects such as additional pretightening and inertia forces. To solve these effects, the influence mechanisms of the pretightening force, the inertia force and other influence factors on the force measurement are theoretically analysed. Then a measurement correction method for the force measurement is proposed based on an artificial neural network optimized by a genetic algorithm. The training and testing data sets are obtained from calibration tests, and the selection criteria for the key parameters of the correction model is discussed. The evaluation results for the test data show that the correction model can effectively improve the force measurement accuracy of the force sensor. Compared with the traditional high-accuracy comparison calibration method, the percentage difference of the impact-force-based measurement is less than 0.6% and the relative uncertainty of the corrected force value is 1.95%, which can meet the requirements of engineering applications.

Field joint environmental protection system vibration/pressurization qualification

NASA Technical Reports Server (NTRS)

Cook, M.

1989-01-01

The procedures used and results obtained from vibration testing the redesigned solid rocket motor (RSRM) field joint environmental protection system (FJEPS), hereafter referred to as the joint protection system (JPS) are documented. The major purposes were to certify that the flight-designed JPS will withstand the dynamic environmental conditions of the redesigned solid rocket booster, and to certify that the cartridge check valve (vent valve) will relieve pressure build-up under the JPS during the initial 120 sec of flight. Also, an evaluation of the extruded cork insulation bonding was performed after the vibration testing.

Should care homes adopt a static-led approach to pressure ulcer prevention?

PubMed

Keen, Delia Catherine

A static-led approach refers to the provision of high-specification foam mattresses for the whole of a population at risk of pressure damage. Such mattresses have been found to reduce the risk of pressure ulceration and cost less overall than standard mattresses, even in populations where only 1 in 100 patients develops a pressure ulcer. Reduced pressure ulcer prevalence and reduced costs resulting from decreased expenditure on dynamic mattresses following the implementation of a static-led approach have been reported. Pressure ulcers cause pain, a reduced quality of life, loss of independence, depression and social isolation for those in whom they develop. Organizations are increasingly having to pay out large sums of money following litigation surrounding pressure ulcers. This article explains why NHS healthcare providers and private care organizations need to work together to consider implementing a static-led approach to pressure ulcer prevention within care homes in order to reduce pressure ulcer incidence cost-effectively within their local populations.

Ultra fast all-optical fiber pressure sensor for blast event evaluation

NASA Astrophysics Data System (ADS)

Wu, Nan; Wang, Wenhui; Tian, Ye; Niezrecki, Christopher; Wang, Xingwei

2011-05-01

Traumatic brain injury (TBI) is a great potential threat to soldiers who are exposed to explosions or athletes who receive cranial impacts. Protecting people from TBI has recently attracted a significant amount of attention due to recent military operations in the Middle East. Recording pressure transient data in a blast event is very critical to the understanding of the effects of blast events on TBI. However, due to the fast change of the pressure during blast events, very few sensors have the capability to effectively track the dynamic pressure transients. This paper reports an ultra fast, miniature and all-optical fiber pressure sensor which could be mounted at different locations of a helmet to measure the fast changing pressure simultaneously. The sensor is based on Fabry-Perot (FP) principle. The end face of the fiber is wet etched. A well controlled thickness silicon dioxide diaphragm is thermal bonded on the end face to form an FP cavity. A shock tube test was conducted at Natick Soldier Research Development and Engineering Center, where the sensors were mounted in a shock tube side by side with a reference sensor to measure the rapidly changing pressure. The results of the test demonstrated that the sensor developed had an improved rise time (shorter than 0.4 μs) when compared to a commercially available reference sensor.

Seismic variability of subduction thrust faults: Insights from laboratory models

NASA Astrophysics Data System (ADS)

Corbi, F.; Funiciello, F.; Faccenna, C.; Ranalli, G.; Heuret, A.

2011-06-01

Laboratory models are realized to investigate the role of interface roughness, driving rate, and pressure on friction dynamics. The setup consists of a gelatin block driven at constant velocity over sand paper. The interface roughness is quantified in terms of amplitude and wavelength of protrusions, jointly expressed by a reference roughness parameter obtained by their product. Frictional behavior shows a systematic dependence on system parameters. Both stick slip and stable sliding occur, depending on driving rate and interface roughness. Stress drop and frequency of slip episodes vary directly and inversely, respectively, with the reference roughness parameter, reflecting the fundamental role for the amplitude of protrusions. An increase in pressure tends to favor stick slip. Static friction is a steeply decreasing function of the reference roughness parameter. The velocity strengthening/weakening parameter in the state- and rate-dependent dynamic friction law becomes negative for specific values of the reference roughness parameter which are intermediate with respect to the explored range. Despite the simplifications of the adopted setup, which does not address the problem of off-fault fracturing, a comparison of the experimental results with the depth distribution of seismic energy release along subduction thrust faults leads to the hypothesis that their behavior is primarily controlled by the depth- and time-dependent distribution of protrusions. A rough subduction fault at shallow depths, unable to produce significant seismicity because of low lithostatic pressure, evolves into a moderately rough, velocity-weakening fault at intermediate depths. The magnitude of events in this range is calibrated by the interplay between surface roughness and subduction rate. At larger depths, the roughness further decreases and stable sliding becomes gradually more predominant. Thus, although interplate seismicity is ultimately controlled by tectonic parameters (velocity of the plates/trench and the thermal regime), the direct control is exercised by the resulting frictional properties of the plate interface.

Dynamic changes of the intraocular pressure and the pressure of cerebrospinal fluid in nonglaucomatous neurological patients.

PubMed

González-Camarena, Pedro Iván; San-Juan, Daniel; González-Olhovich, Irene; Rodríguez-Arévalo, David; Lozano-Elizondo, David; Trenado, Carlos; Anschel, David J

2017-03-01

To describe the dynamic changes of the intraocular pressure (IOP) and intracranial pressure (ICP) with normal or pathological values (intracranial hypertension) in nonglaucomatous neurological patients during lumbar punction (LP). Case-control study, prospective measurement of tonometry in both groups referred for LP. Intraocular pressure, ICP and translaminar pressure difference (TPD) were compared pre- and post-LP. Thirty-six patients (72 eyes) with mean age of 38.5 (16-64) years and BMI of 26.81 kg/m 2 were analysed. The initial mean ICP was 12.81 (± 6.6) mmHg. The mean TPD before and after the LP was 1.48 mmHg and 0.65 mmHg, respectively. The mean IOP of both eyes decreased to 0.8 mmHg post-LP in patients with pathological ICP (p = 0.0193) and normal ICP (p = 0.006). We found a statistically significant decrease of the IOP post-LP compared to the pre-LP in both groups, being higher in patients with pathological ICP. There were no significant differences of the IOP in patients with normal versus pathological ICP pre-LP/post-LP; neither was found a correlation between ICP and IOP. © 2016 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Computational fluid dynamics simulation of sound propagation through a blade row.

PubMed

Zhao, Lei; Qiao, Weiyang; Ji, Liang

2012-10-01

The propagation of sound waves through a blade row is investigated numerically. A wave splitting method in a two-dimensional duct with arbitrary mean flow is presented, based on which pressure amplitude of different wave mode can be extracted at an axial plane. The propagation of sound wave through a flat plate blade row has been simulated by solving the unsteady Reynolds average Navier-Stokes equations (URANS). The transmission and reflection coefficients obtained by Computational Fluid Dynamics (CFD) are compared with semi-analytical results. It indicates that the low order URANS scheme will cause large errors if the sound pressure level is lower than -100 dB (with as reference pressure the product of density, main flow velocity, and speed of sound). The CFD code has sufficient precision when solving the interaction of sound wave and blade row providing the boundary reflections have no substantial influence. Finally, the effects of flow Mach number, blade thickness, and blade turning angle on sound propagation are studied.

Understand rotating isothermal collapses yet

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

Tohline, J.E.

1985-01-01

A scalar virial equation is used to describe the dynamic properties of equilibrium gas clouds, taking into account the relative effects of surface pressure, rotation, self gravity and internal isothermal pressure. Details concerning the internal structure of the clouds are ignored in order to obtain a globalized analytical expression. The obtained solution to the equation is found to agree with the surface-pressure-dominated model of Stahler (1983), and the rotation-dominated model of Hayashi, Narita, and Miyama (1982). On the basis of the analytical expression of virial equilibrium in the clouds, some of the limiting properties of isothermal clouds are described, andmore » a realistic starting model for cloud collapse is proposed. 18 references.« less

Is a sequence of tests during urethral pressure profilometry correlated with symptoms assessment in women?

PubMed

Valentini, Françoise A; Robain, Gilberte; Marti, Brigitte G

2012-01-01

Our purpose was, applying a strictly defined protocol for urethral profilometry, 1) to test the repeatability of same session rest maximum urethral closure pressure (MUCP) and 2) to search for correlation between women complaint and the changes in MUCP value (rest and dynamic tests). A population of 140 consecutive women referred for evaluation of lower urinary tract dysfunction was stratified in 4 groups according with the urinary symptoms: stress, urge, mixed incontinence and continent and in each group in 3 age groups (young, middle age and old). The sequence of tests recorded in supine position was: urethral pressure profile at rest bladder empty, after bladder filling at 250 mL (reference test), stress profile, fatigability (before (rest) and after 10 successive strong coughs), then in standing position. In all groups, there was no significant difference between the two MUCP values at rest bladder filled. In the three incontinent groups, MUCP was higher bladder empty than bladder filled (p < 0.05) except in the young sub-group. Stress incontinence led to significant decrease of MUCP during dynamic tests in the young group. MUCP was not modified after fatigability test in women with urge complaint whatever age. When recorded following a strictly defined protocol, MUCP at rest bladder filled has a good repeatability in individual. However a complex sequence of tests during urethral pressure profilometry remains discussed in middle-age and old age-groups, it allows specifying the stress component of incontinence in young women and the urgency component in all age-groups.

Conceptual design of a pulsed-power accelerator optimized for megajoule-class 1-TPa dynamic-material-physics experiments

DOE PAGES

Stygar, William A.; Reisman, David B.; Stoltzfus, Brian S.; ...

2016-07-07

In this study, we have developed a conceptual design of a next-generation pulsed-power accelerator that is optmized for driving megajoule-class dynamic-material-physics experiments at pressures as high as 1 TPa. The design is based on an accelerator architecture that is founded on three concepts: single-stage electrical-pulse compression, impedance matching, and transit-time-isolated drive circuits. Since much of the accelerator is water insulated, we refer to this machine as Neptune. The prime power source of Neptune consists of 600 independent impedance-matched Marx generators. As much as 0.8 MJ and 20 MA can be delivered in a 300-ns pulse to a 16-mΩ physics load;more » hence Neptune is a megajoule-class 20-MA arbitrary waveform generator. Neptune will allow the international scientific community to conduct dynamic equation-of-state, phase-transition, mechanical-property, and other material-physics experiments with a wide variety of well-defined drive-pressure time histories. Because Neptune can deliver on the order of a megajoule to a load, such experiments can be conducted on centimeter-scale samples at terapascal pressures with time histories as long as 1 μs.« less

Breaking down barriers in cooperative fault management: Temporal and functional information displays

NASA Technical Reports Server (NTRS)

Potter, Scott S.; Woods, David D.

1994-01-01

At the highest level, the fundamental question addressed by this research is how to aid human operators engaged in dynamic fault management. In dynamic fault management there is some underlying dynamic process (an engineered or physiological process referred to as the monitored process - MP) whose state changes over time and whose behavior must be monitored and controlled. In these types of applications (dynamic, real-time systems), a vast array of sensor data is available to provide information on the state of the MP. Faults disturb the MP and diagnosis must be performed in parallel with responses to maintain process integrity and to correct the underlying problem. These situations frequently involve time pressure, multiple interacting goals, high consequences of failure, and multiple interleaved tasks.

FIR signature verification system characterizing dynamics of handwriting features

NASA Astrophysics Data System (ADS)

Thumwarin, Pitak; Pernwong, Jitawat; Matsuura, Takenobu

2013-12-01

This paper proposes an online signature verification method based on the finite impulse response (FIR) system characterizing time-frequency characteristics of dynamic handwriting features. First, the barycenter determined from both the center point of signature and two adjacent pen-point positions in the signing process, instead of one pen-point position, is used to reduce the fluctuation of handwriting motion. In this paper, among the available dynamic handwriting features, motion pressure and area pressure are employed to investigate handwriting behavior. Thus, the stable dynamic handwriting features can be described by the relation of the time-frequency characteristics of the dynamic handwriting features. In this study, the aforesaid relation can be represented by the FIR system with the wavelet coefficients of the dynamic handwriting features as both input and output of the system. The impulse response of the FIR system is used as the individual feature for a particular signature. In short, the signature can be verified by evaluating the difference between the impulse responses of the FIR systems for a reference signature and the signature to be verified. The signature verification experiments in this paper were conducted using the SUBCORPUS MCYT-100 signature database consisting of 5,000 signatures from 100 signers. The proposed method yielded equal error rate (EER) of 3.21% on skilled forgeries.

Analysis of laser shock experiments on precompressed samples using a quartz reference and application to warm dense hydrogen and helium

DOE PAGES

Brygoo, Stephanie; Millot, Marius; Loubeyre, Paul; ...

2015-11-16

Megabar (1 Mbar = 100 GPa) laser shocks on precompressed samples allow reaching unprecedented high densities and moderately high ~10 3–10 4 K temperatures. We describe in this paper a complete analysis framework for the velocimetry (VISAR) and pyrometry (SOP) data produced in these experiments. Since the precompression increases the initial density of both the sample of interest and the quartz reference for pressure-density, reflectivity, and temperature measurements, we describe analytical corrections based on available experimental data on warm dense silica and density-functional-theory based molecular dynamics computer simulations. Finally, using our improved analysis framework, we report a re-analysis of previouslymore » published data on warm dense hydrogen and helium, compare the newly inferred pressure, density, and temperature data with most advanced equation of state models and provide updated reflectivity values.« less

Kinematics and dynamics of green water on a fixed platform in a large wave basin in focusing wave and random wave conditions

NASA Astrophysics Data System (ADS)

Chuang, Wei-Liang; Chang, Kuang-An; Mercier, Richard

2018-06-01

Green water kinematics and dynamics due to wave impingements on a simplified geometry, fixed platform were experimentally investigated in a large, deep-water wave basin. Both plane focusing waves and random waves were employed in the generation of green water. The focusing wave condition was designed to create two consecutive plunging breaking waves with one impinging on the frontal vertical wall of the fixed platform, referred as wall impingement, and the other directly impinging on the deck surface, referred as deck impingement. The random wave condition was generated using the JONSWAP spectrum with a significant wave height approximately equal to the freeboard. A total of 179 green water events were collected in the random wave condition. By examining the green water events in random waves, three different flow types are categorized: collapse of overtopping wave, fall of bulk water, and breaking wave crest. The aerated flow velocity was measured using bubble image velocimetry, while the void fraction was measured using fiber optic reflectometry. For the plane focusing wave condition, measurements of impact pressure were synchronized with the flow velocity and void fraction measurements. The relationship between the peak pressures and the pressure rise times is examined. For the high-intensity impact in the deck impingement events, the peak pressures are observed to be proportional to the aeration levels. The maximum horizontal velocities in the green water events in random waves are well represented by the lognormal distribution. Ritter's solution is shown to quantitatively describe the green water velocity distributions under both the focusing wave condition and the random wave condition. A prediction equation for green water velocity distribution under random waves is proposed.

Mechanical impact of dynamic phenomena in Francis turbines at off design conditions

NASA Astrophysics Data System (ADS)

Duparchy, F.; Brammer, J.; Thibaud, M.; Favrel, A.; Lowys, P. Y.; Avellan, F.

2017-04-01

At partial load and overload conditions, Francis turbines are subjected to hydraulic instabilities that can potentially result in high dynamic solicitations of the turbine components and significantly reduce their lifetime. This study presents both experimental data and numerical simulations that were used as complementary approaches to study these dynamic solicitations. Measurements performed on a reduced scale physical model, including a special runner instrumented with on-board strain gauges and pressure sensors, were used to investigate the dynamic phenomena experienced by the runner. They were also taken as reference to validate the numerical simulation results. After validation, advantage was taken from the numerical simulations to highlight the mechanical response of the structure to the unsteady hydraulic phenomena, as well as their impact on the fatigue damage of the runner.

Circular dichroism and site-directed spin labeling reveal structural and dynamical features of high-pressure states of myoglobin

PubMed Central

Lerch, Michael T.; Horwitz, Joseph; McCoy, John; Hubbell, Wayne L.

2013-01-01

Excited states of proteins may play important roles in function, yet are difficult to study spectroscopically because of their sparse population. High hydrostatic pressure increases the equilibrium population of excited states, enabling their characterization [Akasaka K (2003) Biochemistry 42:10875–85]. High-pressure site-directed spin-labeling EPR (SDSL-EPR) was developed recently to map the site-specific structure and dynamics of excited states populated by pressure. To monitor global secondary structure content by circular dichroism (CD) at high pressure, a modified optical cell using a custom MgF2 window with a reduced aperture is introduced. Here, a combination of SDSL-EPR and CD is used to map reversible structural transitions in holomyoglobin and apomyoglobin (apoMb) as a function of applied pressure up to 2 kbar. CD shows that the high-pressure excited state of apoMb at pH 6 has helical content identical to that of native apoMb, but reversible changes reflecting the appearance of a conformational ensemble are observed by SDSL-EPR, suggesting a helical topology that fluctuates slowly on the EPR time scale. Although the high-pressure state of apoMb at pH 6 has been referred to as a molten globule, the data presented here reveal significant differences from the well-characterized pH 4.1 molten globule of apoMb. Pressure-populated states of both holomyoglobin and apoMb at pH 4.1 have significantly less helical structure, and for the latter, that may correspond to a transient folding intermediate. PMID:24248390

Significance of Dynamic Pore Pressure Variations - Comparison of Observations on Mud Volcanoes on the Costa Rica Margin and in the Gulf of Cadiz

NASA Astrophysics Data System (ADS)

Brueckmann, W.; Linke, P.; Pieper, M.; Hensen, C.; Tuerk, M.

2006-12-01

Research in the cooperative research center (SFB) 574 "Volatiles and Fluids in Subduction Zones" at the University Kiel focuses on volatile and fluid exchange processes at subduction zones. These have a significant impact on the long-term geochemical evolution of the hydrosphere and atmosphere. In the SFB 574 working area off Central America more than 120 mud volcanoes, mud diapirs and cold seeps have been identified and sampled. To better understand the internal dynamics of these structures and the temporal variability of fluid expulsion an in-situ tool for monitoring shallow pore pressure variations was devised. The tool (PWPL) monitors pore pressure variations along a 2m profile in the shallow subsurface using a stinger with 4 pressure ports. Positioned with a video-guided lander the stinger is gently pushed into the seafloor where it remains for several weeks or months in autonomous mode before being retrieved. While particular emphasis was placed on the convergent margin of Central America, mud volcanoes in other tectonic settings suitable for long-term observations of fluid flux are used for comparison. Here we will present data and interpretations from two mud volcanoes off Costa Rica and in the Gulf of Cadiz where we have conducted successful tests. Pore pressure data from short-term tests on Mound 11 on the continental slope off Costa Rica are compared with new results from a long-term (3-month) campaign on the Captain Arutjunov deep water mud volcano in the Gulf of Cadiz. Rates of fluid flow at both structures have been thoroughly characterized and quantified with geochemical methods providing a frame of reference for judging the significance of dynamic pore pressure variations.

In Situ Space Gas Dynamic Measurements by the ROSINA Comet Pressure Sensor COPS on the Rosetta Spacecraft

NASA Astrophysics Data System (ADS)

Tzou, C. Y.; Altwegg, K.; Fiethe, B.; Gasc, S.; Rubin, M.

2014-12-01

Rosetta is part of the cornerstone missions executed by the European Space Agency. It is the first space mission to orbit and also land on a comet. Starting in August 2014 Rosetta will be able to carry out a close study of comet 67P/Churyumov-Gerasimenko. The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) is one of the core payloads on board of the Rosetta spacecraft [Balsiger et al, 2007]. ROSINA's main objective is to determine the major atmospheric and ionospheric composition in the coma and to investigate the gas dynamics around the comet. ROSINA consists of two mass spectrometers and a pressure sensor. The Comet Pressure Sensor (COPS) includes two gauges: the "nude gauge" measures total neutral density in the coma and the "ram gauge" measures the dynamic pressure of the cometary gas flux to obtain the bulk velocity of the neutral gas. The combination of these two gauges makes COPS capable to derive the gas dynamics at the location of the spacecraft. We performed laboratory gas dynamic measurements with the identical flight-spare instrument of COPS. Using the Calibration System for The Mass Spectrometer Instrument ROSINA (CASYMIR) we produce neutral gas beams to model cometary gas jets with velocities from thermal up to 2 km/s. We expect that COPS will be able to detect the faint and expanding atmosphere of comet 67P/Churyumov-Gerasimenko as early as August 2014 when the comet is still farther than 3 AU from the Sun. We will present the first ROSINA COPS observations of the gas dynamics around the comet together with the corresponding laboratory measurements required for the interpretation of these data. Reference: Balsiger, H. et al.: ROSINA-Rosetta Orbiter Spectrometer for Ion and Neutral Analysis, Space Science Reviews, Vol. 128, 745-801, 2007.

Laboratory Gas Dynamic Measurements of the Comet Pressure Sensor COPS on the Rosetta Spacecraft

NASA Astrophysics Data System (ADS)

Tzou, Chia-Yu; Altwegg, Kathrin; Gasc, Sébastien; Rubin, Martin

2014-05-01

Rosetta is part of the cornerstone missions executed by the European Space Agency (ESA). It is the first space mission to orbit and also land on a comet. By the end of July 2014 Rosetta will be able to carry out a close study of comet 67P/Churyumov-Gerasimenko. The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) is one of the core payloads on board of the Rosetta spacecraft [Balsiger et al, 2007]. ROSINA's main objective is to determine the major atmospheric and ionospheric composition in the coma and to investigate the gas dynamics around the comet. ROSINA consists of two mass spectrometers and a pressure sensor. The Comet Pressure Sensor (COPS) is not only a pressure sensor but also plays the role of a safety instrument for Rosetta by providing high-density alerts to the other payload instruments. It includes two gauges: the "nude gauge" measures total neutral density in the coma and the "ram gauge" measures the dynamic pressure of the cometary gas flux to obtain the bulk velocity of the neutral gas. The combination of these two gauges makes COPS capable to derive the gas dynamics in the coma. We recently performed laboratory gas dynamic measurements with the identical flight-spare instrument of COPS. Using the Calibration System for The Mass Spectrometer Instrument ROSINA (CASYMIR) we produce neutral gas beams to model cometary gas jets with velocities from thermal to 2 km/s. For COPS calibration we measure gas beams with different incident angles to derive the velocity and the temperature of the gas using different mixtures expected at the comet. We demonstrate that COPS will be ready for the prime mission and it will be fascinating to compare COPS measurements with numerous observation results and computer models starting in summer 2014 to gain new insights into the gas dynamics around a comet. Reference: Balsiger, H. et al.: ROSINA-Rosetta Orbiter Spectrometer for Ion and Neutral Analysis, Space Science Reviews, Vol. 128, 745-801, 2007.

Continuous long-term measurements of the middle ear pressure in subjects without a history of ear disease.

PubMed

Tideholm, B; Carlborg, B; Jönsson, S; Bylander-Groth, A

1998-06-01

A new method was used for continuous measurement of the middle ear (ME) pressure during a 24-h period. In 10 subjects without a history of ear disease a small perforation was made through the tympanic membrane. A tight rubber stopper containing a small polyethylene tube was fitted into the external ear canal. Conventional tubal function tests were performed. The equipment was then carried by the subjects for 24 h of normal activity to monitor any slow or rapid dynamic pressure change in the ME. Body position was found to be the most important factor affecting ME pressure variation, during the 24-h continuous pressure measurements. A significant pressure rise occurred in the recumbent position in all but one subject. Few rapid pressure equilibrations were seen during the recordings, indicating few tubal openings. This implies that the pressure changes in the ME seen in this study were mainly the result of gas exchange over the mucosa. The investigation might be a base for reference when investigating different kinds of pathologic conditions in the ear.

3-D subduction dynamics in the western Pacific: Mantle pressure, plate kinematics, and dynamic topography.

NASA Astrophysics Data System (ADS)

Holt, A. F.; Royden, L.; Becker, T. W.; Faccenna, C.

2017-12-01

While it is well established that the slab pull of negatively buoyant oceanic plates is the primary driving force of plate tectonics, the dynamic "details" of subduction have proved difficult to pin down. We use the Philippine Sea Plate region of the western Pacific as a site to explore links between kinematic observables (e.g. topography and plate motions) and the dynamics of the subduction system (e.g. mantle flow, mantle pressure). To first order, the Philippine Sea Plate can be considered to be the central plate of a double slab system containing two slabs that dip in the same direction, to the west. This subduction configuration presents the opportunity to explore subduction dynamics in a setting where two closely spaced slabs interact via subduction-induced mantle flow and stresses transmitted through the intervening plate. We use a 3-D numerical approach (e.g. Holt et al., 2017), augmented by semi-analytical models (e.g. Jagoutz et al., 2017), to develop relationships between dynamic processes and kinematic properties, including plate velocities, lithospheric stress state, slab dip angles, and topography. When combined with subduction zone observables, this allows us to isolate the first order dynamic processes that are in operation in the Philippine Sea Plate region. Our results suggest that positive pressure build-up occurs in the asthenosphere between the two slabs (Izu-Bonin-Mariana and Ryukyu-Nankai), and that this is responsible for producing much of the observed kinematic variability in the region, including the steep dip of the Pacific slab at the Izu-Bonin-Mariana trench, as compared to the flat dip of the Pacific slab north of Japan. We then extend our understanding of the role of asthenospheric pressure to examine the forces responsible for the plate kinematics and dynamic topography of the entire Western Pacific subduction margin(s). References:Holt, A. F., Royden, L. H., Becker, T. W., 2017. Geophys. J. Int., 209, 250-265Jagoutz, O., Royden, L., Holt, A. F., Becker, T. W., 2015. Nature Geo., 8, doi:10.1038/ngeo2418

Space Shuttle propulsion performance reconstruction from flight data

NASA Technical Reports Server (NTRS)

Rogers, Robert M.

1989-01-01

The aplication of extended Kalman filtering to estimating Space Shuttle Solid Rocket Booster (SRB) performance, specific impulse, from flight data in a post-flight processing computer program. The flight data used includes inertial platform acceleration, SRB head pressure, and ground based radar tracking data. The key feature in this application is the model used for the SRBs, which represents a reference quasi-static internal ballistics model normalized to the propellant burn depth. Dynamic states of mass overboard and propellant burn depth are included in the filter model to account for real-time deviations from the reference model used. Aerodynamic, plume, wind and main engine uncertainties are included.

NASA low-speed centrifugal compressor for 3-D viscous code assessment and fundamental flow physics research

NASA Technical Reports Server (NTRS)

Hathaway, M. D.; Wood, J. R.; Wasserbauer, C. A.

1991-01-01

A low speed centrifugal compressor facility recently built by the NASA Lewis Research Center is described. The purpose of this facility is to obtain detailed flow field measurements for computational fluid dynamic code assessment and flow physics modeling in support of Army and NASA efforts to advance small gas turbine engine technology. The facility is heavily instrumented with pressure and temperature probes, both in the stationary and rotating frames of reference, and has provisions for flow visualization and laser velocimetry. The facility will accommodate rotational speeds to 2400 rpm and is rated at pressures to 1.25 atm. The initial compressor stage being tested is geometrically and dynamically representative of modern high-performance centrifugal compressor stages with the exception of Mach number levels. Preliminary experimental investigations of inlet and exit flow uniformly and measurement repeatability are presented. These results demonstrate the high quality of the data which may be expected from this facility. The significance of synergism between computational fluid dynamic analysis and experimentation throughout the development of the low speed centrifugal compressor facility is demonstrated.

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

Bhattacharyya, D.; Turton, R.; Zitney, S.

In this presentation, development of a plant-wide dynamic model of an advanced Integrated Gasification Combined Cycle (IGCC) plant with CO2 capture will be discussed. The IGCC reference plant generates 640 MWe of net power using Illinois No.6 coal as the feed. The plant includes an entrained, downflow, General Electric Energy (GEE) gasifier with a radiant syngas cooler (RSC), a two-stage water gas shift (WGS) conversion process, and two advanced 'F' class combustion turbines partially integrated with an elevated-pressure air separation unit (ASU). A subcritical steam cycle is considered for heat recovery steam generation. Syngas is selectively cleaned by a SELEXOLmore » acid gas removal (AGR) process. Sulfur is recovered using a two-train Claus unit with tail gas recycle to the AGR. A multistage intercooled compressor is used for compressing CO2 to the pressure required for sequestration. Using Illinois No.6 coal, the reference plant generates 640 MWe of net power. The plant-wide steady-state and dynamic IGCC simulations have been generated using the Aspen Plus{reg_sign} and Aspen Plus Dynamics{reg_sign} process simulators, respectively. The model is generated based on the Case 2 IGCC configuration detailed in the study available in the NETL website1. The GEE gasifier is represented with a restricted equilibrium reactor model where the temperature approach to equilibrium for individual reactions can be modified based on the experimental data. In this radiant-only configuration, the syngas from the Radiant Syngas Cooler (RSC) is quenched in a scrubber. The blackwater from the scrubber bottom is further cleaned in the blackwater treatment plant. The cleaned water is returned back to the scrubber and also used for slurry preparation. The acid gas from the sour water stripper (SWS) is sent to the Claus plant. The syngas from the scrubber passes through a sour shift process. The WGS reactors are modeled as adiabatic plug flow reactors with rigorous kinetics based on the mid-life activity of the shift-catalyst. The SELEXOL unit consists of the H2S and CO2 absorbers that are designed to meet the stringent environmental limits and requirements of other associated units. The model also considers the stripper for recovering H2S that is sent as a feed to a split-flow Claus unit. The tail gas from the Claus unit is recycled to the SELEXOL unit. The cleaned syngas is sent to the GE 7FB gas turbine. This turbine is modeled as per published data in the literature. Diluent N2 is used from the elevated-pressure ASU for reducing the NOx formation. The heat recovery steam generator (HRSG) is modeled by considering generation of high-pressure, intermediate-pressure, and low-pressure steam. All of the vessels, reactors, heat exchangers, and the columns have been sized. The basic IGCC process control structure has been synthesized by standard guidelines and existing practices. The steady-state simulation is solved in sequential-modular mode in Aspen Plus{reg_sign} and consists of more than 300 unit operations, 33 design specs, and 16 calculator blocks. The equation-oriented dynamic simulation consists of more than 100,000 equations solved using a multi-step Gear's integrator in Aspen Plus Dynamics{reg_sign}. The challenges faced in solving the dynamic model and key transient results from this dynamic model will also be discussed.« less

Thermal conductivity of tungsten: Effects of plasma-related structural defects from molecular-dynamics simulations

NASA Astrophysics Data System (ADS)

Hu, Lin; Wirth, Brian D.; Maroudas, Dimitrios

2017-08-01

We report results on the lattice thermal conductivities of tungsten single crystals containing nanoscale-sized pores or voids and helium (He) nanobubbles as a function of void/bubble size and gas pressure in the He bubbles based on molecular-dynamics simulations. For reference, we calculated lattice thermal conductivities of perfect tungsten single crystals along different crystallographic directions at room temperature and found them to be about 10% of the overall thermal conductivity of tungsten with a weak dependence on the heat flux direction. The presence of nanoscale voids in the crystal causes a significant reduction in its lattice thermal conductivity, which decreases with increasing void size. Filling the voids with He to form He nanobubbles and increasing the bubble pressure leads to further significant reduction of the tungsten lattice thermal conductivity, down to ˜20% of that of the perfect crystal. The anisotropy in heat conduction remains weak for tungsten single crystals containing nanoscale-sized voids and He nanobubbles throughout the pressure range examined. Analysis of the pressure and atomic displacement fields in the crystalline region that surrounds the He nanobubbles reveals that the significant reduction of tungsten lattice thermal conductivity in this region is due to phonon scattering from the nanobubbles, as well as lattice deformation around the nanobubbles and formation of lattice imperfections at higher bubble pressure.

Melting of Fe and Fe0.9Ni0.1 alloy at high pressures

NASA Astrophysics Data System (ADS)

Zhang, D.; Jackson, J. M.; Zhao, J.; Sturhahn, W.; Alp, E. E.; Hu, M. Y.; Toellner, T.

2014-12-01

Cosmochemical studies suggest that the cores of terrestrial planets are primarily composed of Fe alloyed with about 5 to 10 wt% Ni, plus some light elements (e.g., McDonough and Sun 1995). Thus, the high pressure melting curve of Fe0.9Ni0.1 is considered to be an important reference for characterizing the cores of terrestrial planets. We have determined the melting points of fcc-structured Fe and Fe0.9Ni0.1 up to 86 GPa using an in-situ method that monitors the atomic dynamics of the Fe atoms in the sample, synchrotron Mössbauer spectroscopy (Jackson et al. 2013). A laser heated diamond anvil cell is used to provide the high pressure-high temperature environmental conditions, and in-situ X-ray diffraction is used to constrain the pressure of the sample. To eliminate the influence of temperature fluctuations experienced by the sample on the determination of melting, we develop a Fast Temperature Readout (FasTeR) spectrometer. The FasTeR spectrometer features a fast reading rate (>100 Hz), a high sensitivity, a large dynamic range and a well-constrained focus. By combining the melting curve of fcc-structured Fe0.9Ni0.1 alloy determined in our study and the fcc-hcp phase boundary from Komabayashi et al. (2012), we calculate the fcc-hcp-liquid triple point of Fe0.9Ni0.1. Using this triple point and the thermophysical parameters from a nuclear resonant inelastic X-ray scattering study on hcp-Fe (Murphy et al. 2011), we compute the melting curve of hcp-structured Fe0.9Ni0.1. We will discuss our new experimental results with implications for the cores of Venus, Earth and Mars. Select references: McDonough & Sun (1995): The composition of the Earth. Chem. Geol. 120, 223-253. Jackson et al. (2013): Melting of compressed iron by monitoring atomic dynamics, EPSL, 362, 143-150. Komabayashi et al. (2012): In situ X-ray diffraction measurements of the fcc-hcp phase transition boundary of an Fe-Ni alloy in an internally heated diamond anvil cell, PCM, 39, 329-338. Murphy et al. (2011): Melting and thermal pressure of hcp-Fe from the phonon density of states, PEPI, 188, 114-120.

Fast optimization of glide vehicle reentry trajectory based on genetic algorithm

NASA Astrophysics Data System (ADS)

Jia, Jun; Dong, Ruixing; Yuan, Xuejun; Wang, Chuangwei

2018-02-01

An optimization method of reentry trajectory based on genetic algorithm is presented to meet the need of reentry trajectory optimization for glide vehicle. The dynamic model for the glide vehicle during reentry period is established. Considering the constraints of heat flux, dynamic pressure, overload etc., the optimization of reentry trajectory is investigated by utilizing genetic algorithm. The simulation shows that the method presented by this paper is effective for the optimization of reentry trajectory of glide vehicle. The efficiency and speed of this method is comparative with the references. Optimization results meet all constraints, and the on-line fast optimization is potential by pre-processing the offline samples.

A Zero Dimensional Time-Dependent Model of High-Pressure Ablative Capillary Discharge (Preprint)

DTIC Science & Technology

2008-06-01

comprehensive model of capillary discharge is important to understand the physics and engineering aspects of the capillary discharge thruster. A schematic...investigators since the mid-1980s see 1-11 and references therein, satisfy both of these conditions well. These studies investigated the dynamics of high...is a comprehensive description of the radiative heat transfer in the capillary discharge. It is worth noting that in other types of capillary

Molecular dynamics simulations of ejecta production from sinusoidal tin surfaces under supported and unsupported shocks

NASA Astrophysics Data System (ADS)

Wu, Bao; Wu, FengChao; Zhu, YinBo; Wang, Pei; He, AnMin; Wu, HengAn

2018-04-01

Micro-ejecta, an instability growth process, occurs at metal/vacuum or metal/gas interface when compressed shock wave releases from the free surface that contains surface defects. We present molecular dynamics (MD) simulations to investigate the ejecta production from tin surface shocked by supported and unsupported waves with pressures ranging from 8.5 to 60.8 GPa. It is found that the loading waveforms have little effect on spike velocity while remarkably affect the bubble velocity. The bubble velocity of unsupported shock loading remains nonzero constant value at late time as observed in experiments. Besides, the time evolution of ejected mass in the simulations is compared with the recently developed ejecta source model, indicating the suppressed ejection of unmelted or partial melted materials. Moreover, different reference positions are chosen to characterize the amount of ejecta under different loading waveforms. Compared with supported shock case, the ejected mass of unsupported shock case saturates at lower pressure. Through the analysis on unloading path, we find that the temperature of tin sample increases quickly from tensile stress state to zero pressure state, resulting in the melting of bulk tin under decaying shock. Thus, the unsupported wave loading exhibits a lower threshold pressure causing the solid-liquid phase transition on shock release than the supported shock loading.

Space shuttle propulsion estimation development verification

NASA Technical Reports Server (NTRS)

Rogers, Robert M.

1989-01-01

The application of extended Kalman filtering to estimating the Space Shuttle Propulsion performance, i.e., specific impulse, from flight data in a post-flight processing computer program is detailed. The flight data used include inertial platform acceleration, SRB head pressure, SSME chamber pressure and flow rates, and ground based radar tracking data. The key feature in this application is the model used for the SRB's, which is a nominal or reference quasi-static internal ballistics model normalized to the propellant burn depth. Dynamic states of mass overboard and propellant burn depth are included in the filter model to account for real-time deviations from the reference model used. Aerodynamic, plume, wind and main engine uncertainties are also included for an integrated system model. Assuming uncertainty within the propulsion system model and attempts to estimate its deviations represent a new application of parameter estimation for rocket powered vehicles. Illustrations from the results of applying this estimation approach to several missions show good quality propulsion estimates.

Arterial Pressure Variation in Elective Non-cardiac Surgery: Identifying Reference Distributions and Modifying Factors

PubMed Central

Mathis, Michael R.; Schechtman, Samuel A.; Engoren, Milo C.; Shanks, Amy M.; Thompson, Aleda; Kheterpal, Sachin; Tremper, Kevin K.

2016-01-01

Background Assessment of need for intravascular volume resuscitation remains challenging for anesthesiologists. Dynamic waveform indices, including systolic- and pulse-pressure variation (SPV/PPV), are demonstrated as reliable measures of fluid-responsiveness for mechanically ventilated patients. Despite widespread use, real-world reference distributions for SPV and PPV values have not been established for euvolemic intraoperative patients. The authors sought to establish SPV and PPV reference distributions and assess impact of modifying factors. Methods The authors evaluated adult patients undergoing general anesthetics for elective non-cardiac surgery. Median SPV and PPV over a 50-minute post-induction period were noted for each case. Modifying factors including body-mass index, age, ventilator settings, positioning, and hemodynamic management were studied via univariate and multivariable analyses. For SPV values, effects of data entry method (manually-entered versus automated recorded) were similarly studied. Results Among 1,791 cases, per-case median SPV and PPV values formed non-parametric distributions. For each distribution, median values, interquartile ranges, and reference intervals (2.5th-97.5th percentile) were respectively noted: these included manually-entered SPV (6.0, 5.0-7.0, 3.0-11.0 mmHg), automated SPV (4.7, 3.9-6.0, 2.2-10.4 mmHg), and automated PPV (7.0, 5.0-9.0, 2.0-16.0%). Non-supine positioning and preoperative beta blocker were independently associated with altered SPV and PPV, whereas ventilator tidal volume >8 mL/kg ideal body weight and peak inspiratory pressure >16 cm H2O demonstrated independent associations for SPV only. Conclusions This study establishes real-world SPV and PPV reference distributions absent in the current literature. Through a consideration of reference distributions and modifying factors, our study provides further evidence for assessing intraoperative volume status and fluid management therapies. PMID:27906705

Experiments and Analyses of Distributed Exhaust Nozzles

NASA Technical Reports Server (NTRS)

Kinzie, Kevin W.; Schein, David B.; Solomon, W. David, Jr.

2002-01-01

Experimental and analytical aeroacoustic properties of several distributed exhaust nozzle (DEN) designs are presented. Significant differences between the designs are observed and correlated back to Computational Fluid Dynamics (CFD) flowfield predictions. Up to 20 dB of noise reduction on a spectral basis and 10 dB on an overall sound pressure level basis are demonstrated from the DEN designs compared to a round reference nozzle. The most successful DEN designs acoustically show a predicted thrust loss of approximately 10% compared to the reference nozzle. Characteristics of the individual mini-jet nozzles that comprise the DEN such as jet-jet shielding and coalescence are shown to play a major role in the noise signature.

Main drivers of flood-risk dynamics along the Po River

NASA Astrophysics Data System (ADS)

Domeneghetti, Alessio; Carisi, Francesca; Castellarin, Attilio; Brath, Armando

2017-04-01

The increasing frequency with which floods damages are recorded, or reported by media, strengthen the common perception that the flood risk is dramatically increasing in Europe and other areas of the world, due to a combination of different causes, among which climate change is often described as the major factor. However, there is a growing awareness of how anthropogenic pressures, such as uncontrolled urban and industrial expansion on flood-prone areas, may strongly impact the evolution of flood-risk in a given area, increasing potential flood damages and losses. Starting from these considerations, our study aims at shedding some light on the impact and relative importance of different factors controlling the flood risk. Focusing in particular on the middle-lower portion of the River Po, we analyze the evolution of flood hazard in the last half century referring to long streamflow series for different gauging stations located along the study reach ( 450 km), while the modification of anthropogenic pressure is evaluated by referring to land-use and demographic dynamics observed from 1950s. Our study proposes simplified flood-vulnerability indices to be used for large scale flood-risk assessments and, on the basis of these indices, (1) we assess the importance of the different elements contributing to the definition of flood risk and (2) represent the evolution of flood risk in time along the middle and lower portion of the River Po.

Dynamic Determination of Oxygenation and Lung Compliance in Murine Pneumonectomy

PubMed Central

Gibney, Barry; Lee, Grace S.; Houdek, Jan; Lin, Miao; Miele, Lino; Chamoto, Kenji; Konerding, Moritz A.; Tsuda, Akira; Mentzer, Steven J.

2012-01-01

Thoracic surgical procedures in mice have been applied to a wide range of investigations, but little is known about the murine physiologic response to pulmonary surgery. Using continuous arterial oximetry monitoring and the FlexiVent murine ventilator, we investigated the effect of anesthesia and pneumonectomy on mouse oxygen saturation and lung mechanics. Sedation resulted in a dose-dependent decline of oxygen saturation that ranged from 55–82%. Oxygen saturation was restored by mechanical ventilation with increased rate and tidal volumes. In the mouse strain studied, optimal ventilatory rates were a rate of 200/minute and a tidal volume of 10ml/kg. Sustained inflation pressures, referred to as a "recruitment maneuver," improved lung volumes, lung compliance and arterial oxygenation. In contrast, positive end expiratory pressure (PEEP) had a detrimental effect on oxygenation; an effect that was ameliorated after pneumonectomy. Our results confirm that lung volumes in the mouse are dynamically determined and suggest a threshold level of mechanical ventilation to maintain perioperative oxygen saturation. PMID:21574875

A strategy to complete databases with parameters of refined line shapes and its test for CO in He, Ar and Kr

NASA Astrophysics Data System (ADS)

Ngo, N. H.; Hartmann, J.-M.

2017-12-01

We propose a strategy to generate parameters of the Hartmann-Tran profile (HTp) by simultaneously using first principle calculations and broadening coefficients deduced from Voigt/Lorentz fits of experimental spectra. We start from reference absorptions simulated, at pressures between 10 and 950 Torr, using the HTp with parameters recently obtained from high quality experiments for the P(1) and P(17) lines of the 3-0 band of CO in He, Ar and Kr. Using requantized Classical Molecular Dynamics Simulations (rCMDS), we calculate spectra under the same conditions. We then correct them using a single parameter deduced from Lorentzian fits of both reference and calculated absorptions at a single pressure. The corrected rCMDS spectra are then simultaneously fitted using the HTp, yielding the parameters of this model and associated spectra. Comparisons between the retrieved and input (reference) HTp parameters show a quite satisfactory agreement. Furthermore, differences between the reference spectra and those computed with the HT model fitted to the corrected-rCMDS predictions are much smaller than those obtained with a Voigt line shape. Their full amplitudes are in most cases smaller than 1%, and often below 0.5%, of the peak absorption. This opens the route to completing spectroscopic databases using calculations and the very numerous broadening coefficients available from Voigt fits of laboratory spectra.

Dynamic Vertical Mapping with Crowdsourced Smartphone Sensor Data

PubMed Central

Moslehi Rad, Omid Reza; Prehofer, Christian; Hugentobler, Urs

2018-01-01

In this paper, we present our novel approach for the crowdsourced dynamic vertical mapping of buildings. For achieving this, we use the barometric sensor of smartphones to estimate altitude differences and the moment of the outdoor to indoor transition to extract reference pressure. We have identified the outdoor–indoor transition (OITransition) via the fusion of four different sensors. Our approach has been evaluated extensively over a period of 6 months in different humidity, temperature, and cloud-coverage situations, as well as over different hours of the day, and it is found that it can always predict the correct number of floors, while it can approximate the altitude with an average error of 0.5 m. PMID:29415472

Indicator system provides complete data of engine cylinder pressure variation

NASA Technical Reports Server (NTRS)

Mc Jones, R. W.; Morgan, N. E.

1966-01-01

Varying reference pressure used together with a balanced pressure pickup /a diaphragm switch/ to switch the electric output of the pressure transducer in a reference pressure line obtains precise engine cylinder pressure data from a high speed internal combustion engine.

High-pressure effect on the dynamics of solvated peptides.

PubMed

Nellas, Ricky B; Glover, Mary M; Hamelberg, Donald; Shen, Tongye

2012-04-14

The dynamics of peptides has a direct connection to how quickly proteins can alter their conformations. The speed of exploring the free energy landscape depend on many factors, including the physical parameters of the environment, such as pressure and temperature. We performed a series of molecular dynamics simulations to investigate the pressure-temperature effects on peptide dynamics, especially on the torsional angle and peptide-water hydrogen bonding (H-bonding) dynamics. Here, we show that the dynamics of the omega angle and the H-bonding dynamics between water and the peptide are affected by pressure. At high temperature (500 K), both the dynamics of the torsional angle ω and H-bonding slow down significantly with increasing pressure, interestingly, at approximately the same rate. However, at a lower temperature of 300 K, the observed trend on H-bonding dynamics as a function of pressure reverses, i.e., higher pressure speeds up H-bonding dynamics.

FBG based high sensitive pressure sensor and its low-cost interrogation system with enhanced resolution

NASA Astrophysics Data System (ADS)

Pachava, Vengal Rao; Kamineni, Srimannarayana; Madhuvarasu, Sai Shankar; Putha, Kishore; Mamidi, Venkata Reddy

2015-12-01

A fiber Bragg grating (FBG) pressure sensor with high sensitivity and resolution has been designed and demonstrated. The sensor is configured by firmly fixing the FBG with a metal bellows structure. The sensor works by means of measuring the Bragg wavelength shift of the FBG with respect to pressure change. From the experimental results, the pressure sensitivity of the sensor is found to be 90.6 pm/psi, which is approximately 4000 times as that of a bare fiber Bragg grating. A very good linearity of 99.86% is observed between the Bragg wavelength of the FBG and applied pressure. The designed sensor shows good repeatability with a negligible hysteresis error of ± 0.29 psi. A low-cost interrogation system that includes a long period grating (LPG) and a photodiode (PD) accompanied with simple electronic circuitry is demonstrated for the FBG sensor, which enables the sensor to attain high resolution of up to 0.025 psi. Thermal-strain cross sensitivity of the FBG pressure sensor is compensated using a reference FBG temperature sensor. The designed sensor can be used for liquid level, specific gravity, and static/dynamic low pressure measurement applications.

Investigation of Spray Cooling Schemes for Dynamic Thermal Management

NASA Astrophysics Data System (ADS)

Yata, Vishnu Vardhan Reddy

This study aims to investigate variable flow and intermittent flow spray cooling characteristics for efficiency improvement in active two-phase thermal management systems. Variable flow spray cooling scheme requires control of pump input voltage (or speed), while intermittent flow spray cooling scheme requires control of solenoid valve duty cycle and frequency. Several testing scenarios representing dynamic heat load conditions are implemented to characterize the overall performance of variable flow and intermittent flow spray cooling cases in comparison with the reference, steady flow spray cooling case with constant flowrate, continuous spray cooling. Tests are conducted on a small-scale, closed loop spray cooling system featuring a pressure atomized spray nozzle. HFE-7100 dielectric liquid is selected as the working fluid. Two types of test samples are prepared on 10 mm x 10 mm x 2 mm copper substrates with matching size thick film resistors attached onto the opposite side, to generate heat and simulate high heat flux electronic devices. The test samples include: (i) plain, smooth surface, and (ii) microporous surface featuring 100 ?m thick copper-based coating prepared by dual stage electroplating technique. Experimental conditions involve HFE-7100 at atmospheric pressure and 30°C and 10°C subcooling. Steady flow spray cooling tests are conducted at flow rates of 2-5 ml/cm2.s, by controlling the heat flux in increasing steps, and recording the corresponding steady-state temperatures to obtain cooling curves in the form of surface superheat vs. heat flux. Variable flow and intermittent flow spray cooling tests are done at selected flowrate and subcooling conditions to investigate the effects of dynamic flow conditions on maintaining the target surface temperatures defined based on reference steady flow spray cooling performance.

The role of ICP monitoring in patients with persistent cerebrospinal fluid leak following spinal surgery: a case series.

PubMed

Craven, Claudia; Toma, Ahmed K; Khan, Akbar A; Watkins, Laurence D

2016-09-01

Cerebrospinal fluid (CSF) leak following spinal surgery is a relatively common surgical complication. A disturbance in the underlying CSF dynamics could be the causative factor in a small group of patients with refractory CSF leaks that require multiple surgical repairs and prolonged hospital admission. A retrospective case series of patients with persistent post spinal surgery CSF leak referred to the hydrocephalus service for continuous intracranial pressure (ICP) monitoring. Patients' notes were reviewed for medical history, ICP data, radiological data, and subsequent management and outcome. Five patients (two males/three females, mean age, 35.4 years) were referred for ICP monitoring over a 12-month period. These patients had prolonged CSF leak despite multiple repair attempts 252 ± 454 days (mean ± SD). On ICP monitoring, all five patients had abnormal results, with the mean ICP 8.95 ± 4.41 mmHg. Four had abnormal pulse amplitudes, mean 6.15 mmHg ± 1.22 mmHg. All five patients underwent an intervention. Three patients underwent insertion of ventriculoperitoneal (VP) shunts. One patient had venous sinus stent insertion and one patient underwent medical management with acetazolamide. All five of the patients' CSF leak resolved post intervention. The mean time to resolution of CSF leak post intervention was 10.8  ± 12.9 days. Abnormal cerebrospinal fluid dynamics could be the underlying factor in patients with a persistent and treatment-refractory CSF leak post spinal surgery. Treatments aimed at lowering ICP may be beneficial in this group of patients. Whether abnormal pressure and dynamics represent a pre-existing abnormality or is induced by spinal surgery should be a subject of further study.

Pressure gradients fail to predict diffusio-osmosis

NASA Astrophysics Data System (ADS)

Liu, Yawei; Ganti, Raman; Frenkel, Daan

2018-05-01

We present numerical simulations of diffusio-osmotic flow, i.e. the fluid flow generated by a concentration gradient along a solid-fluid interface. In our study, we compare a number of distinct approaches that have been proposed for computing such flows and compare them with a reference calculation based on direct, non-equilibrium molecular dynamics simulations. As alternatives, we consider schemes that compute diffusio-osmotic flow from the gradient of the chemical potentials of the constituent species and from the gradient of the component of the pressure tensor parallel to the interface. We find that the approach based on treating chemical potential gradients as external forces acting on various species agrees with the direct simulations, thereby supporting the approach of Marbach et al (2017 J. Chem. Phys. 146 194701). In contrast, an approach based on computing the gradients of the microscopic pressure tensor does not reproduce the direct non-equilibrium results.

Vectorcardiographic results from Skylab medical experiment M092: Lower body negative pressure

NASA Technical Reports Server (NTRS)

Hoffler, G. W.; Johnson, R. L.; Nicogossian, A. E.; Bergman, S. A., Jr.; Jackson, M. M.

1974-01-01

Vectorcardiograms were recorded via a modified Frank lead system from all crewmen of the three Skylab missions in conjuction with the Lower Body Negative Pressure - M092 Experiment. Data were analyzed by a specially developed computer program (VECTAN). Design of the test sequences allowed direct comparisons of supine resting, Earth based (reference) vectorcardiograms with those taken during lower body negative pressure stress and those obtained at rest in orbit, as well as combinations of these conditions. Results revealed several statistically significant space flight related changes; namely, increased testing and lower body negative pressure stressed heart rates, modestly increased PR interval and corrected QTC interval, and greatly increased P and QPS loop maximal amplitudes. In addition, orientation changes in the QRS maximum vector and the J-vector at rest in space seem quite consistent among crewmen and different from those caused by the application of lower body negative pressure. No clinical abnormalities were observed. Etiology of these findings is conjectured to be, at least in part, related to fluid mass shifts occurring in weightlessness and attendant alterations in cardiovascular dynamics and myocardial autonomic control mechanisms.

SI-traceable and dynamic reference gas mixtures for water vapour at polar and high troposphere atmospheric levels

NASA Astrophysics Data System (ADS)

Guillevic, Myriam; Pascale, Céline; Mutter, Daniel; Wettstein, Sascha; Niederhauser, Bernhard

2017-04-01

In the framework of METAS' AtmoChem-ECV project, new facilities are currently being developed to generate reference gas mixtures for water vapour at concentrations measured in the high troposphere and polar regions, in the range 1-20 µmol/mol (ppm). The generation method is dynamic (the mixture is produced continuously over time) and SI-traceable (i.e. the amount of substance fraction in mole per mole is traceable to the definition of SI-units). The generation process is composed of three successive steps. The first step is to purify the matrix gas, nitrogen or synthetic air. Second, this matrix gas is spiked with the pure substance using a permeation technique: a permeation device contains a few grams of pure water in liquid form and loses it linearly over time by permeation through a membrane. In a third step, to reach the desired concentration, the first, high concentration mixture exiting the permeation chamber is then diluted with a chosen flow of matrix gas with one or two subsequent dilution steps. All flows are piloted by mass flow controllers. All parts in contact with the gas mixture are passivated using coated surfaces, to reduce adsorption/desorption processes as much as possible. The mixture can eventually be directly used to calibrate an analyser. The standard mixture produced by METAS' dynamic setup was injected into a chilled mirror from MBW Calibration AG, the designated institute for absolute humidity calibration in Switzerland. The used chilled mirror, model 373LX, is able to measure frost point and sample pressure and therefore calculate the water vapour concentration. This intercomparison of the two systems was performed in the range 4-18 ppm water vapour in synthetic air, at two different pressure levels, 1013.25 hPa and 2000 hPa. We present here METAS' dynamic setup, its uncertainty budget and the first results of the intercomparison with MBW's chilled mirror.

The Dynamics of Chemical Reactions: Atomistic Visualizations of Organic Reactions, and Homage to van 't Hoff.

PubMed

Yang, Zhongyue; Houk, K N

2018-03-15

Jacobus Henricus van 't Hoff was the first Nobel Laureate in Chemistry. He pioneered in the study of chemical dynamics, which referred at that time to chemical kinetics and thermodynamics. The term has evolved in modern times to refer to the exploration of chemical transformations in a time-resolved fashion. Chemical dynamics has been driven by the development of molecular dynamics trajectory simulations, which provide atomic visualization of chemical processes and illuminate how dynamic effects influence chemical reactivity and selectivity. In homage to the legend of van 't Hoff, we review the development of the chemical dynamics of organic reactions, our area of research. We then discuss our trajectory simulations of pericyclic reactions, and our development of dynamic criteria for concerted and stepwise reaction mechanisms. We also describe a method that we call environment-perturbed transition state sampling, which enables trajectory simulations in condensed-media using quantum mechanics and molecular mechanics (QM/MM). We apply the method to reactions in solvent and in enzyme. Jacobus Henricus van 't Hoff (1852, Rotterdam-1911, Berlin) received the Nobel Prize for Chemistry in 1901 "in recognition of the extraordinary services he has rendered by the discovery of the laws of chemical dynamics and osmotic pressure in solutions". van 't Hoff was born the Netherlands, and earned his doctorate in Utrecht in 1874. In 1896 he moved to Berlin, where he was offered a position with more research and less teaching. van 't Hoff is considered one of the founders of physical chemistry. A key step in establishing this new field was the start of Zeitschrift für Physikalische Chemie in 1887. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pressure pulsation in Kaplan turbines: Prototype-CFD comparison

NASA Astrophysics Data System (ADS)

Rivetti, A.; Lucino1, C.; Liscia, S.; Muguerza, D.; Avellan, F.

2012-11-01

Pressure pulsation phenomena in a large Kaplan turbine are investigated by means of numerical simulations (CFD) and prototype measurements in order to study the dynamic behavior of flow due to the blade passage and its interaction with other components of the turbine. Numerical simulations are performed with the commercial software Ansys CFX code, solving the incompressible Unsteady Reynolds-Averaged-Navier Stokes equations under a finite volume scheme. The computational domain involves the entire machine at prototype scale. Special care is taken in the discretization of the wicket gate overhang and runner blade gap. Prototype measurements are performed using pressure transducers at different locations among the wicket gate outlet and the draft tube inlet. Then, CFD results are compared with temporary signals of prototype measurements at identical locations to validate the numerical model. A detailed analysis was focused on the tip gap flow and the pressure field at the discharge ring. From a rotating reference frame perspective, it is found that the mean pressure fluctuates accordingly the wicket gate passage. Moreover, in prototype measurements the pressure frequency that reveals the presence of modulated cavitation at the discharge ring is distinguished, as also verified from the shape of erosion patches in concordance with the number of wicket gates.

Evolution of Advection Upstream Splitting Method Schemes

NASA Technical Reports Server (NTRS)

Liou, Meng-Sing

2010-01-01

This paper focuses on the evolution of advection upstream splitting method(AUSM) schemes. The main ingredients that have led to the development of modern computational fluid dynamics (CFD) methods have been reviewed, thus the ideas behind AUSM. First and foremost is the concept of upwinding. Second, the use of Riemann problem in constructing the numerical flux in the finite-volume setting. Third, the necessity of including all physical processes, as characterised by the linear (convection) and nonlinear (acoustic) fields. Fourth, the realisation of separating the flux into convection and pressure fluxes. The rest of this review briefly outlines the technical evolution of AUSM and more details can be found in the cited references. Keywords: Computational fluid dynamics methods, hyperbolic systems, advection upstream splitting method, conservation laws, upwinding, CFD

STAPP: Spatiotemporal analysis of plantar pressure measurements using statistical parametric mapping.

PubMed

Booth, Brian G; Keijsers, Noël L W; Sijbers, Jan; Huysmans, Toon

2018-05-03

Pedobarography produces large sets of plantar pressure samples that are routinely subsampled (e.g. using regions of interest) or aggregated (e.g. center of pressure trajectories, peak pressure images) in order to simplify statistical analysis and provide intuitive clinical measures. We hypothesize that these data reductions discard gait information that can be used to differentiate between groups or conditions. To test the hypothesis of null information loss, we created an implementation of statistical parametric mapping (SPM) for dynamic plantar pressure datasets (i.e. plantar pressure videos). Our SPM software framework brings all plantar pressure videos into anatomical and temporal correspondence, then performs statistical tests at each sampling location in space and time. Novelly, we introduce non-linear temporal registration into the framework in order to normalize for timing differences within the stance phase. We refer to our software framework as STAPP: spatiotemporal analysis of plantar pressure measurements. Using STAPP, we tested our hypothesis on plantar pressure videos from 33 healthy subjects walking at different speeds. As walking speed increased, STAPP was able to identify significant decreases in plantar pressure at mid-stance from the heel through the lateral forefoot. The extent of these plantar pressure decreases has not previously been observed using existing plantar pressure analysis techniques. We therefore conclude that the subsampling of plantar pressure videos - a task which led to the discarding of gait information in our study - can be avoided using STAPP. Copyright © 2018 Elsevier B.V. All rights reserved.

Influence of mechanical rock properties and fracture healing rate on crustal fluid flow dynamics

NASA Astrophysics Data System (ADS)

Sachau, Till; Bons, Paul; Gomez-Rivas, Enrique; Koehn, Daniel; de Riese, Tamara

2016-04-01

Fluid flow in the Earth's crust is very slow over extended periods of time, during which it occurs within the connected pore space of rocks. If the fluid production rate exceeds a certain threshold, matrix permeability alone is insufficient to drain the fluid volume and fluid pressure builds up, thereby reducing the effective stress supported by the rock matrix. Hydraulic fractures form once the effective pressure exceeds the tensile strength of the rock matrix and act subsequently as highly effective fluid conduits. Once local fluid pressure is sufficiently low again, flow ceases and fractures begin to heal. Since fluid flow is controlled by the alternation of fracture permeability and matrix permeability, the flow rate in the system is strongly discontinuous and occurs in intermittent pulses. Resulting hydraulic fracture networks are largely self-organized: opening and subsequent healing of hydraulic fractures depends on the local fluid pressure and on the time-span between fluid pulses. We simulate this process with a computer model and describe the resulting dynamics statistically. Special interest is given to a) the spatially and temporally discontinuous formation and closure of fractures and fracture networks and b) the total flow rate over time. The computer model consists of a crustal-scale dual-porosity setup. Control parameters are the pressure- and time-dependent fracture healing rate, and the strength and the permeability of the intact rock. Statistical analysis involves determination of the multifractal properties and of the power spectral density of the temporal development of the total drainage rate and hydraulic fractures. References Bons, P. D. (2001). The formation of large quartz veins by rapid ascent of fluids in mobile hydrofractures. Tectonophysics, 336, 1-17. Miller, S. a., & Nur, A. (2000). Permeability as a toggle switch in fluid-controlled crustal processes. Earth and Planetary Science Letters, 183(1-2), 133-146. Sachau, T., Bons, P. D., & Gomez-Rivas, E. (2015). Transport efficiency and dynamics of hydraulic fracture networks. Frontiers in Physics, 3.

Method and Apparatus for Non-Invasive Measurement of Changes in Intracranial Pressure

NASA Technical Reports Server (NTRS)

Yost, William T. (Inventor); Cantrell, John H., Jr. (Inventor)

2004-01-01

A method and apparatus for measuring intracranial pressure. In one embodiment, the method comprises the steps of generating an information signal that comprises components (e.g., pulsatile changes and slow changes) that are related to intracranial pressure and blood pressure, generating a reference signal comprising pulsatile components that are solely related to blood pressure, processing the information and reference signals to determine the pulsatile components of the information signal that have generally the same phase as the pulsatile components of the reference signal, and removing from the information signal the pulsatile components determined to have generally the same phase as the pulsatile components of the reference signal so as to provide a data signal having components wherein substantially all of the components are related to intracranial pressure.

Gravitational vacuum energy in our recently accelerating universe

NASA Astrophysics Data System (ADS)

Bludman, Sidney

2009-04-01

We review current observations of the homogeneous cosmological expansion which, because they measure only kinematic variables, cannot determine the dynamics driving the recent accelerated expansion. The minimal fit to the data, the flat ACDM model, consisting of cold dark matter and a cosmological constant, interprets 4? geometrically as a classical spacetime curvature constant of nature, avoiding any reference to quantum vacuum energy. (The observed Uehling and Casimir effects measure forces due to QED vacuum polarization, but not any quantum material vacuum energies.) An Extended Anthropic Principle, that Dark Energy and Dark Gravity be indistinguishable, selects out flat ACDM. Prospective cosmic shear and galaxy clustering observations of the growth of fluctuations are intended to test whether the 'dark energy' driving the recent cosmological acceleration is static or moderately dynamic. Even if dynamic, observational differences between an additional negative-pressure material component within general relativity (Dark Energy) and low-curvature modifications of general relativity (Dark Gravity) will be extremely small.

Comparative experimental study of dynamic compressive strength of mortar with glass and basalt fibres

NASA Astrophysics Data System (ADS)

Kruszka, Leopold; Moćko, Wojciech; Fenu, Luigi; Cadoni, Ezio

2015-09-01

Specimen reinforced with glass and basalt fibers were prepared using Standard Portland cement (CEM I, 52.5 R as prescribed by EN 197-1) and standard sand, in accordance with EN 196-1. From this cementitious mixture, a reference cement mortar without fibers was first prepared. Compressive strength, modulus of elasticity, and mod of fracture were determined for all specimens. Static and dynamic properties were investigated using Instron testing machine and split Hopkinson pressure bar, respectively. Content of the glass fibers in the mortar does not influence the fracture stress at static loading conditions in a clearly observed way. Moreover at dynamic range 5% content of the fiber results in a significant drop of fracture stress. Analysis of the basalt fibers influence on the fracture stress shows that optimal content of this reinforcement is equal to 3% for both static and dynamic loading conditions. Further increase of the fiber share gives the opposite effect, i.e. drop of the fracture stress.

Literature search of publications concerning the prediction of dynamic inlet flow distortion and related topics

NASA Technical Reports Server (NTRS)

Schweikhhard, W. G.; Chen, Y. S.

1983-01-01

Publications prior to March 1981 were surveyed to determine inlet flow dynamic distortion prediction methods and to catalog experimental and analytical information concerning inlet flow dynamic distortion prediction methods and to catalog experimental and analytical information concerning inlet flow dynamics at the engine-inlet interface of conventional aircraft (excluding V/STOL). The sixty-five publications found are briefly summarized and tabulated according to topic and are cross-referenced according to content and nature of the investigation (e.g., predictive, experimental, analytical and types of tests). Three appendices include lists of references, authors, organizations and agencies conducting the studies. Also, selected materials summaries, introductions and conclusions - from the reports are included. Few reports were found covering methods for predicting the probable maximum distortion. The three predictive methods found are those of Melick, Jacox and Motycka. The latter two require extensive high response pressure measurements at the compressor face, while the Melick Technique can function with as few as one or two measurements.

Advanced Technical Data Study

DTIC Science & Technology

1975-01-29

will shut down automatically when condenser high pressure causes Pressure Limit Control high pressure switch to release. Press START switch (3...power cable (1) from facility pow- er. Troubleshoot cooling unit, for HI-LOW pressure switch repeated cutout. Refer to AGE ECU Cooling Unit...acti- vate when loss of air flow oc- curred, the pressure switch (3) failed to open circuit. Adjust or replace pressure switch . Refer to

An Assessment of Combustion Dynamics in a Low-Nox, Second-Generation Swirl-Venturi Lean Direct Injection Combustion Concept

NASA Technical Reports Server (NTRS)

Tacina, K. M.; Chang, C. T.; Lee, P.; Mongia, H.; Podboy, D. P.; Dam, B.

2015-01-01

Dynamic pressure measurements were taken during flame-tube emissions testing of three second-generation swirl-venturi lean direct injection (SV-LDI) combustor configurations. These measurements show that combustion dynamics were typically small. However, a small number of points showed high combustion dynamics, with peak-to-peak dynamic pressure fluctuations above 0.5 psi. High combustion dynamics occurred at low inlet temperatures in all three SV-LDI configurations, so combustion dynamics were explored further at low temperature conditions. A point with greater than 1.5 psi peak-to-peak dynamic pressure fluctuations was identified at an inlet temperature of 450!F, a pressure of 100 psia, an air pressure drop of 3%, and an overall equivalence ratio of 0.35. This is an off design condition: the temperature and pressure are typical of 7% power conditions, but the equivalence ratio is high. At this condition, the combustion dynamics depended strongly on the fuel staging. Combustion dynamics could be reduced significantly without changing the overall equivalence ratio by shifting the fuel distribution between stages. Shifting the fuel distribution also decreased NOx emissions.

Differential in vivo urodynamic measurement in a single thin catheter based on two optical fiber pressure sensors

NASA Astrophysics Data System (ADS)

Poeggel, Sven; Duraibabu, Dineshbabu; Tosi, Daniele; Leen, Gabriel; Lewis, Elfed; McGrath, Deirdre; Fusco, Ferdinando; Sannino, Simone; Lupoli, Laura; Ippolito, Juliet; Mirone, Vincenzo

2015-03-01

Urodynamic analysis is the predominant method for evaluating dysfunctions in the lower urinary tract. The exam measures the pressure during the filling and voiding process of the bladder and is mainly interested in the contraction of the bladder muscles. The data arising out of these pressure measurements enables the urologist to arrive at a precise diagnosis and prescribe an adequate treatment. A technique based on two optical fiber pressure and temperature sensors with a resolution of better than 0.1 cm H2O (˜10 Pa), a stability better than 1 cm H2O/hour, and a diameter of 0.2 mm in a miniature catheter with a diameter of only 5 Fr (1.67 mm), was used. This technique was tested in vivo on four patients with a real-time urodynamic measurement system. The optical system presented showed a very good correlation to two commercially available medical reference sensors. Furthermore, the optical urodynamic system demonstrated a higher dynamic and better sensitivity to detect small obstructions than both pre-existing medical systems currently in use in the urodynamic field.

Differential in vivo urodynamic measurement in a single thin catheter based on two optical fiber pressure sensors.

PubMed

Poeggel, Sven; Duraibabu, Dineshbabu; Tosi, Daniele; Leen, Gabriel; Lewis, Elfed; McGrath, Deirdre; Fusco, Ferdinando; Sannino, Simone; Lupoli, Laura; Ippolito, Juliet; Mirone, Vincenzo

2015-03-01

Urodynamic analysis is the predominant method for evaluating dysfunctions in the lower urinary tract. The exam measures the pressure during the filling and voiding process of the bladder and is mainly interested in the contraction of the bladder muscles. The data arising out of these pressure measurements enables the urologist to arrive at a precise diagnosis and prescribe an adequate treatment. A technique based on two optical fiber pressure and temperature sensors with a resolution of better than 0.1 cm H₂O (∼10 Pa), a stability better than 1 cm H₂O/hour, and a diameter of 0.2 mm in a miniature catheter with a diameter of only 5 Fr (1.67 mm), was used. This technique was tested in vivo on four patients with a real-time urodynamic measurement system. The optical system presented showed a very good correlation to two commercially available medical reference sensors. Furthermore, the optical urodynamic system demonstrated a higher dynamic and better sensitivity to detect small obstructions than both pre-existing medical systems currently in use in the urodynamic field.

Zero-Kelvin Compression Isotherms of the Elements 1 ≤ Z ≤ 92 to 100 GPa

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

Young, David A.; Cynn, Hyunchae; Söderlind, Per

2016-12-01

Most of the chemical elements have now been compressed close to or above 100 GPa (1 Mbar) pressure in diamond-anvil cells and the pressure–volume room-temperature isotherms have been measured. We collect these data and use simple lattice-dynamics models to reduce the isotherms to 0 K. We have extended the published work by making new diamond-anvil-cell measurements on Cr and Rh, and by conducting density-functional calculations on the elements Po, At, Rn, Fr, Ra, and Ac. The 0 K data are tabulated for all elements 1 ≤ Z ≤ 92 and 0 ≤ P ≤ 100 GPa. These data are usefulmore » for generating wide-range equation of state models and for studying the stability of chemical compounds at high pressure (“Megabar chemistry”). The tables presented here are intended to be reference thermodynamic tables for use in high-pressure research. Further experimental and theoretical work will be needed to extend the tables to higher pressure and to improve accuracy.« less

Characterization of Axial Inducer Cavitation Instabilities via High Speed Video Recordings

NASA Technical Reports Server (NTRS)

Arellano, Patrick; Peneda, Marinelle; Ferguson, Thomas; Zoladz, Thomas

2011-01-01

Sub-scale water tests were undertaken to assess the viability of utilizing high resolution, high frame-rate digital video recordings of a liquid rocket engine turbopump axial inducer to characterize cavitation instabilities. These high speed video (HSV) images of various cavitation phenomena, including higher order cavitation, rotating cavitation, alternating blade cavitation, and asymmetric cavitation, as well as non-cavitating flows for comparison, were recorded from various orientations through an acrylic tunnel using one and two cameras at digital recording rates ranging from 6,000 to 15,700 frames per second. The physical characteristics of these cavitation forms, including the mechanisms that define the cavitation frequency, were identified. Additionally, these images showed how the cavitation forms changed and transitioned from one type (tip vortex) to another (sheet cavitation) as the inducer boundary conditions (inlet pressures) were changed. Image processing techniques were developed which tracked the formation and collapse of cavitating fluid in a specified target area, both in the temporal and frequency domains, in order to characterize the cavitation instability frequency. The accuracy of the analysis techniques was found to be very dependent on target size for higher order cavitation, but much less so for the other phenomena. Tunnel-mounted piezoelectric, dynamic pressure transducers were present throughout these tests and were used as references in correlating the results obtained by image processing. Results showed good agreement between image processing and dynamic pressure spectral data. The test set-up, test program, and test results including H-Q and suction performance, dynamic environment and cavitation characterization, and image processing techniques and results will be discussed.

Periodic orbit-attitude solutions along planar orbits in a perturbed circular restricted three-body problem for the Earth-Moon system

NASA Astrophysics Data System (ADS)

Bucci, Lorenzo; Lavagna, Michèle; Guzzetti, Davide; Howell, Kathleen C.

2018-06-01

Interest on Large Space Structures (LSS), orbiting in strategic and possibly long-term stable locations, is nowadays increasing in the space community. LSS can serve as strategic outpost to support a variety of manned and unmanned mission, or may carry scientific payloads for astronomical observations. The paper focuses on analysing LSS in the Earth-Moon system, exploring dynamical structures that are available within a multi-body gravitational environment. Coupling between attitude and orbital dynamics is investigated, with particular interest on the gravity gradient torque exerted by the two massive attractors. First, natural periodic orbit-attitude solutions are obtained; a LSS that exploits such solutions would benefit of a naturally periodic body rotation synchronous with the orbital motion, easing the effort of the attitude control system to satisfy pointing requirements. Then, the solar radiation pressure is introduced into the fully coupled dynamical model and its effects investigated, discovering novel periodic attitude solutions. Benefits of periodic behaviours that incorporate solar radiation pressure are discussed, and analysed via the variation of some parameters (e.g reflection/absorption coefficients, position of the centre of pressure). As a final step to refine the current perturbed orbit-attitude model, a structure flexibility is also superimposed to a reference orbit-attitude rigid body motion via a simple, yet effective model. The coupling of structural vibrations and attitude motion is preliminarily explored, and allows identification of possible challenges, that may be faced to position a LSS in a periodic orbit within the Earth-Moon system.

Inducer Hydrodynamic Load Measurement Devices

NASA Technical Reports Server (NTRS)

Skelley, Stephen E.; Zoladz, Thomas F.

2002-01-01

Marshall Space Flight Center (MSFC) has demonstrated two measurement devices for sensing and resolving the hydrodynamic loads on fluid machinery. The first - a derivative of the six component wind tunnel balance - senses the forces and moments on the rotating device through a weakened shaft section instrumented with a series of strain gauges. This "rotating balance" was designed to directly measure the steady and unsteady hydrodynamic loads on an inducer, thereby defining both the amplitude and frequency content associated with operating in various cavitation modes. The second device - a high frequency response pressure transducer surface mounted on a rotating component - was merely an extension of existing technology for application in water. MSFC has recently completed experimental evaluations of both the rotating balance and surface-mount transducers in a water test loop. The measurement bandwidth of the rotating balance was severely limited by the relative flexibility of the device itself, resulting in an unexpectedly low structural bending mode and invalidating the higher frequency response data. Despite these limitations, measurements confirmed that the integrated loads on the four-bladed inducer respond to both cavitation intensity and cavitation phenomena. Likewise, the surface-mount pressure transducers were subjected to a range of temperatures and flow conditions in a non-rotating environment to record bias shifts and transfer functions between the transducers and a reference device. The pressure transducer static performance was within manufacturer's specifications and dynamic response accurately followed that of the reference.

Inducer Hydrodynamic Load Measurement Devices

NASA Technical Reports Server (NTRS)

Skelley, Stephen E.; Zoladz, Thomas F.; Turner, Jim (Technical Monitor)

2002-01-01

Marshall Space Flight Center (MSFC) has demonstrated two measurement devices for sensing and resolving the hydrodynamic loads on fluid machinery. The first - a derivative of the six-component wind tunnel balance - senses the forces and moments on the rotating device through a weakened shaft section instrumented with a series of strain gauges. This rotating balance was designed to directly measure the steady and unsteady hydrodynamic loads on an inducer, thereby defining both the amplitude and frequency content associated with operating in various cavitation modes. The second device - a high frequency response pressure transducer surface mounted on a rotating component - was merely an extension of existing technology for application in water. MSFC has recently completed experimental evaluations of both the rotating balance and surface-mount transducers in a water test loop. The measurement bandwidth of the rotating balance was severely limited by the relative flexibility of the device itself, resulting in an unexpectedly low structural bending mode and invalidating the higher-frequency response data. Despite these limitations, measurements confirmed that the integrated loads on the four-bladed inducer respond to both cavitation intensity and cavitation phenomena. Likewise, the surface-mount pressure transducers were subjected to a range of temperatures and flow conditions in a non-rotating environment to record bias shifts and transfer functions between the transducers and a reference device. The pressure transducer static performance was within manufacturer's specifications and dynamic response accurately followed that of the reference.

Comparison of three portable instruments to measure compression pressure.

PubMed

Partsch, H; Mosti, G

2010-10-01

Measurement of interface pressure between the skin and a compression device has gained practical importance not only for characterizing the efficacy of different compression products in physiological and clinical studies but also for the training of medical staff. A newly developed portable pneumatic pressure transducer (Picopress®) was compared with two established systems (Kikuhime® and SIGaT tester®) measuring linearity, variability and accuracy on a cylindrical model using a stepwise inflated sphygmomanometer as the reference. In addition the variation coefficients were measured by applying the transducers repeatedly under a blood pressure cuff on the distal lower leg of a healthy human subject with stepwise inflation. In the pressure range between 10 and 80 mmHg all three devices showed a linear association compared with the sphygmomanometer values (Pearson r>0.99). The best reproducibility (variation coefficients between 1.05-7.4%) and the highest degree of accuracy demonstrated by Bland-Altman plots was achieved with the Picopress® transducer. Repeated measurements of pressure in a human leg revealed average variation coefficients for the three devices of 4.17% (Kikuhime®), 8.52% (SIGaT®) and 2.79% (Picopress®). The results suggest that the Picopress® transducer, which also allows dynamic pressure tracing in connection with a software program and which may be left under a bandage for several days, is a reliable instrument for measuring the pressure under a compression device.

Ares I-X Test Flight Reference Trajectory Development

NASA Technical Reports Server (NTRS)

Starr, Brett R.; Gumbert, Clyde R.; Tartabini, Paul V.

2011-01-01

Ares I-X was the first test flight of NASA's Constellation Program's Ares I crew launch vehicle. Ares I is a two stage to orbit launch vehicle that provides crew access to low Earth orbit for NASA's future manned exploration missions. The Ares I first stage consists of a Shuttle solid rocket motor (SRM) modified to include an additional propellant segment and a liquid propellant upper stage with an Apollo J2X engine modified to increase its thrust capability. The modified propulsion systems were not available for the first test flight, thus the test had to be conducted with an existing Shuttle 4 segment reusable solid rocket motor (RSRM) and an inert Upper Stage. The test flight's primary objective was to demonstrate controllability of an Ares I vehicle during first stage boost and the ability to perform a successful separation. In order to demonstrate controllability, the Ares I-X ascent control algorithms had to maintain stable flight throughout a flight environment equivalent to Ares I. The goal of the test flight reference trajectory development was to design a boost trajectory using the existing RSRM that results in a flight environment equivalent to Ares I. A trajectory similarity metric was defined as the integrated difference between the Ares I and Ares I-X Mach versus dynamic pressure relationships. Optimization analyses were performed that minimized the metric by adjusting the inert upper stage weight and the ascent steering profile. The sensitivity of the optimal upper stage weight and steering profile to launch month was also investigated. A response surface approach was used to verify the optimization results. The analyses successfully defined monthly ascent trajectories that matched the Ares I reference trajectory dynamic pressure versus Mach number relationship to within 10% through Mach 3.5. The upper stage weight required to achieve the match was found to be feasible and varied less than 5% throughout the year. The paper will discuss the flight test requirements, provide Ares I-X vehicle background, discuss the optimization analyses used to meet the requirements, present analysis results, and compare the reference trajectory to the reconstructed flight trajectory.

Fluid relief and check valve

DOEpatents

Blaedel, K.L.; Lord, S.C.; Murray, I.

1986-07-17

A passive fluid pressure relief and check valve allows the relief pressure to be slaved to a reference pressure independently of the exhaust pressure. The pressure relief valve is embodied by a submerged vent line in a sealing fluid, the relief pressure being a function of the submerged depth. A check valve is embodied by a vertical column of fluid (the maximum back pressure being a function of the height of the column of fluid). The pressure is vented into an exhaust system which keeps the exhaust out of the area providing the reference pressure.

Vadose zone isobaric well

DOEpatents

Hubbell, Joel M.; Sisson, James B.

2001-01-01

A deep tensiometer is configured with an outer guide tube having a vented interval along a perforate section at its lower end, which is isolated from atmospheric pressure at or above grade. A transducer having a monitoring port and a reference port is located within a coaxial inner guide tube. The reference port of the transducer is open to the vented interval of the outer guide tube, which has the same gas pressure as in the sediment surrounding the tensiometer. The reference side of the pressure transducer is thus isolated from the effects of atmospheric pressure changes and relative to pressure changes in the material surrounding the tensiometer measurement location and so it is automatically compensated for such pressure changes.

Performance Characteristics of a New Generation Pressure Microsensor for Physiologic Applications

PubMed Central

Cottler, Patrick S.; Karpen, Whitney R.; Morrow, Duane A.; Kaufman, Kenton R.

2009-01-01

A next generation fiber-optic microsensor based on the extrinsic Fabry–Perot interferometric (EFPI) technique has been developed for pressure measurements. The basic physics governing the operation of these sensors makes them relatively tolerant or immune to the effects of high-temperature, high-EMI, and highly-corrosive environments. This pressure microsensor represents a significant improvement in size and performance over previous generation sensors. To achieve the desired overall size and sensitivity, numerical modeling of diaphragm deflection was incorporated in the design, with the desired dimensions and calculated material properties. With an outer diameter of approximately 250 µm, a dynamic operating range of over 250 mmHg, and a sampling frequency of 960 Hz, this sensor is ideal for the minimally invasive measurement of physiologic pressures and incorporation in catheter-based instrumentation. Nine individual sensors were calibrated and characterized by comparing the output to a U.S. National Institute of Standards and Technology (NIST) Traceable reference pressure over the range of 0–250 mmHg. The microsensor performance demonstrated accuracy of better than 2% full-scale output, and repeatability, and hysteresis of better than 1% full-scale output. Additionally, fatigue effects on five additional sensors were 0.25% full-scale output after over 10,000 pressure cycles. PMID:19495983

Restoration of the Potosi Dynamic Model 2010

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

Adushita, Yasmin; Leetaru, Hannes

2014-09-30

In topical Report DOE/FE0002068-1 [2] technical performance evaluations on the Cambrian Potosi Formation were performed through reservoir modeling. The data included formation tops from mud logs, well logs from the VW1 and the CCS1 wells, structural and stratigraphic formation from three dimensional (3D) seismic data, and field data from several waste water injection wells for Potosi Formation. Intention was for two million tons per annum (MTPA) of CO2 to be injected for 20 years. In this Task the 2010 Potosi heterogeneous model (referred to as the "Potosi Dynamic Model 2010" in this report) was re-run using a new injection scenario;more » 3.2 MTPA for 30 years. The extent of the Potosi Dynamic Model 2010, however, appeared too small for the new injection target. It was not sufficiently large enough to accommodate the evolution of the plume. Also, it might have overestimated the injection capacity by enhancing too much the pressure relief due to the relatively close proximity between the injector and the infinite acting boundaries. The new model, Potosi Dynamic Model 2013a, was built by extending the Potosi Dynamic Model 2010 grid to 30 miles x 30 miles (48 km by 48 km), while preserving all property modeling workflows and layering. This model was retained as the base case. Potosi Dynamic Model 2013.a gives an average CO2 injection rate of 1.4 MTPA and cumulative injection of 43 Mt in 30 years, which corresponds to 45% of the injection target. This implies that according to this preliminary model, a minimum of three (3) wells could be required to achieve the injection target. The injectivity evaluation of the Potosi formation will be revisited in topical Report 15 during which more data will be integrated in the modeling exercise. A vertical flow performance evaluation could be considered for the succeeding task to determine the appropriate tubing size, the required injection tubing head pressure (THP) and to investigate whether the corresponding well injection rate falls within the tubing erosional velocity limit. After 30 years, the plume extends 15 miles (24 km) in E-W and 14 miles (22 km) in N-S directions. After injection is completed, the plume continues to migrate laterally, mainly driven by the remaining pressure gradient. After 100 years post-injection, the plume extends 17 miles (27 km) in E-W and 15 miles (24 km) in N-S directions. The increase of reservoir pressure at the end of injection is approximately 370 psia around the injector and gradually decreases away from the well. The reservoir pressure increase is less than 30 psia beyond 14 miles (22 km) away from injector. The initial reservoir pressure is restored after approximately 20 years post-injection. This result, however, is associated with uncertainties on the boundary conditions, and a sensitivity analysis could be considered for the succeeding tasks. It is important to remember that the respective plume extent and areal pressure increase corresponds to an injection of 43 Mt CO2. Should the targeted cumulative injection of 96 Mt be achieved; a much larger plume extent and areal pressure increase could be expected. Re-evaluating the permeability modeling, vugs and heterogeneity distributions, and relative permeability input could be considered for the succeeding Potosi formation evaluations. A simulation using several injectors could also be considered to determine the required number of wells to achieve the injection target while taking into account the pressure interference.« less

SiO_{2} Glass Density to Lower-Mantle Pressures.

PubMed

Petitgirard, Sylvain; Malfait, Wim J; Journaux, Baptiste; Collings, Ines E; Jennings, Eleanor S; Blanchard, Ingrid; Kantor, Innokenty; Kurnosov, Alexander; Cotte, Marine; Dane, Thomas; Burghammer, Manfred; Rubie, David C

2017-11-24

The convection or settling of matter in the deep Earth's interior is mostly constrained by density variations between the different reservoirs. Knowledge of the density contrast between solid and molten silicates is thus of prime importance to understand and model the dynamic behavior of the past and present Earth. SiO_{2} is the main constituent of Earth's mantle and is the reference model system for the behavior of silicate melts at high pressure. Here, we apply our recently developed x-ray absorption technique to the density of SiO_{2} glass up to 110 GPa, doubling the pressure range for such measurements. Our density data validate recent molecular dynamics simulations and are in good agreement with previous experimental studies conducted at lower pressure. Silica glass rapidly densifies up to 40 GPa, but the density trend then flattens to become asymptotic to the density of SiO_{2} minerals above 60 GPa. The density data present two discontinuities at ∼17 and ∼60  GPa that can be related to a silicon coordination increase from 4 to a mixed 5/6 coordination and from 5/6 to sixfold, respectively. SiO_{2} glass becomes denser than MgSiO_{3} glass at ∼40  GPa, and its density becomes identical to that of MgSiO_{3} glass above 80 GPa. Our results on SiO_{2} glass may suggest that a variation of SiO_{2} content in a basaltic or pyrolitic melt with pressure has at most a minor effect on the final melt density, and iron partitioning between the melts and residual solids is the predominant factor that controls melt buoyancy in the lowermost mantle.

SiO2 Glass Density to Lower-Mantle Pressures

NASA Astrophysics Data System (ADS)

Petitgirard, Sylvain; Malfait, Wim J.; Journaux, Baptiste; Collings, Ines E.; Jennings, Eleanor S.; Blanchard, Ingrid; Kantor, Innokenty; Kurnosov, Alexander; Cotte, Marine; Dane, Thomas; Burghammer, Manfred; Rubie, David C.

2017-11-01

The convection or settling of matter in the deep Earth's interior is mostly constrained by density variations between the different reservoirs. Knowledge of the density contrast between solid and molten silicates is thus of prime importance to understand and model the dynamic behavior of the past and present Earth. SiO2 is the main constituent of Earth's mantle and is the reference model system for the behavior of silicate melts at high pressure. Here, we apply our recently developed x-ray absorption technique to the density of SiO2 glass up to 110 GPa, doubling the pressure range for such measurements. Our density data validate recent molecular dynamics simulations and are in good agreement with previous experimental studies conducted at lower pressure. Silica glass rapidly densifies up to 40 GPa, but the density trend then flattens to become asymptotic to the density of SiO2 minerals above 60 GPa. The density data present two discontinuities at ˜17 and ˜60 GPa that can be related to a silicon coordination increase from 4 to a mixed 5 /6 coordination and from 5 /6 to sixfold, respectively. SiO2 glass becomes denser than MgSiO3 glass at ˜40 GPa , and its density becomes identical to that of MgSiO3 glass above 80 GPa. Our results on SiO2 glass may suggest that a variation of SiO2 content in a basaltic or pyrolitic melt with pressure has at most a minor effect on the final melt density, and iron partitioning between the melts and residual solids is the predominant factor that controls melt buoyancy in the lowermost mantle.

Assessment of deep dynamic mechanical sensitivity in individuals with tension-type headache: The dynamic pressure algometry.

PubMed

Palacios-Ceña, M; Wang, K; Castaldo, M; Guerrero-Peral, Á; Caminero, A B; Fernández-de-Las-Peñas, C; Arendt-Nielsen, L

2017-09-01

To explore the validity of dynamic pressure algometry for evaluating deep dynamic mechanical sensitivity by assessing its association with headache features and widespread pressure sensitivity in tension-type headache (TTH). One hundred and eighty-eight subjects with TTH (70% women) participated. Deep dynamic sensitivity was assessed with a dynamic pressure algometry set (Aalborg University, Denmark © ) consisting of 11 different rollers including fixed levels from 500 g to 5300 g. Each roller was moved at a speed of 0.5 cm/s over a 60-mm horizontal line covering the temporalis muscle. Dynamic pain threshold (DPT-level of the first painful roller) was determined and pain intensity during DPT was rated on a numerical pain rate scale (NPRS, 0-10). Headache clinical features were collected on a headache diary. As gold standard, static pressure pain thresholds (PPT) were assessed over temporalis, C5/C6 joint, second metacarpal, and tibialis anterior muscle. Side-to-side consistency between DPT (r = 0.843, p < 0.001) and pain evoked (r = 0.712; p < 0.001) by dynamic algometer was observed. DPT was moderately associated with widespread PPTs (0.526 > r > 0.656, all p < 0.001). Furthermore, pain during DPT was negatively associated with widespread PPTs (-0.370 < r < -0.162, all p < 0.05). Dynamic pressure algometry was a valid tool for assessing deep dynamic mechanical sensitivity in TTH. DPT was associated with widespread pressure sensitivity independently of the frequency of headaches supporting that deep dynamic pressure sensitivity within the trigeminal area is consistent with widespread pressure sensitivity. Assessing deep static and dynamic somatic tissue pain sensitivity may provide new opportunities for differentiated diagnostics and possibly a new tool for assessing treatment effects. The current study found that dynamic pressure algometry in the temporalis muscle was associated with widespread pressure pain sensitivity in individuals with tension-type headache. The association was independent of the frequency of headaches. Assessing deep static and dynamic somatic tissue pain sensitivity may provide new opportunities for differentiated diagnostics and possibly a tool for assessing treatment effects. © 2017 European Pain Federation - EFIC®.

Prompt Disappearance and Emergence of Radiation Belt Magnetosonic Waves Induced by Solar Wind Dynamic Pressure Variations

NASA Astrophysics Data System (ADS)

Liu, Nigang; Su, Zhenpeng; Zheng, Huinan; Wang, Yuming; Wang, Shui

2018-01-01

Magnetosonic waves are highly oblique whistler mode emissions transferring energy from the ring current protons to the radiation belt electrons in the inner magnetosphere. Here we present the first report of prompt disappearance and emergence of magnetosonic waves induced by the solar wind dynamic pressure variations. The solar wind dynamic pressure reduction caused the magnetosphere expansion, adiabatically decelerated the ring current protons for the Bernstein mode instability, and produced the prompt disappearance of magnetosonic waves. On the contrary, because of the adiabatic acceleration of the ring current protons by the solar wind dynamic pressure enhancement, magnetosonic waves emerged suddenly. In the absence of impulsive injections of hot protons, magnetosonic waves were observable even only during the time period with the enhanced solar wind dynamic pressure. Our results demonstrate that the solar wind dynamic pressure is an essential parameter for modeling of magnetosonic waves and their effect on the radiation belt electrons.

Evaluation of atomic pressure in the multiple time-step integration algorithm.

PubMed

Andoh, Yoshimichi; Yoshii, Noriyuki; Yamada, Atsushi; Okazaki, Susumu

2017-04-15

In molecular dynamics (MD) calculations, reduction in calculation time per MD loop is essential. A multiple time-step (MTS) integration algorithm, the RESPA (Tuckerman and Berne, J. Chem. Phys. 1992, 97, 1990-2001), enables reductions in calculation time by decreasing the frequency of time-consuming long-range interaction calculations. However, the RESPA MTS algorithm involves uncertainties in evaluating the atomic interaction-based pressure (i.e., atomic pressure) of systems with and without holonomic constraints. It is not clear which intermediate forces and constraint forces in the MTS integration procedure should be used to calculate the atomic pressure. In this article, we propose a series of equations to evaluate the atomic pressure in the RESPA MTS integration procedure on the basis of its equivalence to the Velocity-Verlet integration procedure with a single time step (STS). The equations guarantee time-reversibility even for the system with holonomic constrants. Furthermore, we generalize the equations to both (i) arbitrary number of inner time steps and (ii) arbitrary number of force components (RESPA levels). The atomic pressure calculated by our equations with the MTS integration shows excellent agreement with the reference value with the STS, whereas pressures calculated using the conventional ad hoc equations deviated from it. Our equations can be extended straightforwardly to the MTS integration algorithm for the isothermal NVT and isothermal-isobaric NPT ensembles. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Novel blood pressure and pulse pressure estimation based on pulse transit time and stroke volume approximation.

PubMed

Lee, Joonnyong; Sohn, JangJay; Park, Jonghyun; Yang, SeungMan; Lee, Saram; Kim, Hee Chan

2018-06-18

Non-invasive continuous blood pressure monitors are of great interest to the medical community due to their value in hypertension management. Recently, studies have shown the potential of pulse pressure as a therapeutic target for hypertension, but not enough attention has been given to non-invasive continuous monitoring of pulse pressure. Although accurate pulse pressure estimation can be of direct value to hypertension management and indirectly to the estimation of systolic blood pressure, as it is the sum of pulse pressure and diastolic blood pressure, only a few inadequate methods of pulse pressure estimation have been proposed. We present a novel, non-invasive blood pressure and pulse pressure estimation method based on pulse transit time and pre-ejection period. Pre-ejection period and pulse transit time were measured non-invasively using electrocardiogram, seismocardiogram, and photoplethysmogram measured from the torso. The proposed method used the 2-element Windkessel model to model pulse pressure with the ratio of stroke volume, approximated by pre-ejection period, and arterial compliance, estimated by pulse transit time. Diastolic blood pressure was estimated using pulse transit time, and systolic blood pressure was estimated as the sum of the two estimates. The estimation method was verified in 11 subjects in two separate conditions with induced cardiovascular response and the results were compared against a reference measurement and values obtained from a previously proposed method. The proposed method yielded high agreement with the reference (pulse pressure correlation with reference R ≥ 0.927, diastolic blood pressure correlation with reference R ≥ 0.854, systolic blood pressure correlation with reference R ≥ 0.914) and high estimation accuracy in pulse pressure (mean root-mean-squared error ≤ 3.46 mmHg) and blood pressure (mean root-mean-squared error ≤ 6.31 mmHg for diastolic blood pressure and ≤ 8.41 mmHg for systolic blood pressure) over a wide range of hemodynamic changes. The proposed pulse pressure estimation method provides accurate estimates in situations with and without significant changes in stroke volume. The proposed method improves upon the currently available systolic blood pressure estimation methods by providing accurate pulse pressure estimates.

Velocity dependence of biphasic flow structuration: steady-state and oscillating flow effects

NASA Astrophysics Data System (ADS)

Tore Tallakstad, Ken; Jankov, Mihailo; Løvoll, Grunde; Toussaint, Renaud; Jørgen Mâløy, Knut; Grude Flekkøy, Eirik; Schmittbuhl, Jean; Schäfer, Gerhard; Méheust, Yves; Arendt Knudsen, Henning

2010-05-01

We study various types of biphasic flows in quasi-two-dimensional transparent porous models. These flows imply a viscous wetting fluid, and a lowly viscous one. The models are transparent, allowing the displacement process and structure to be monitored in space and time. Three different aspects will be presented: 1. In stationary biphasic flows, we study the relationship between the macroscopic pressure drop (related to relative permeability) and the average flow rate, and how this arises from the cluster size distribution of the lowly viscous fluid [1]. 2. In drainage situations, we study how the geometry of the invader can be explained, and how it gives rise to apparent dynamic capillary effects. We show how these can be explained by viscous effects on evolving geometries of invading fluid [2]. 3. We study the impact of oscillating pressure fields superimposed to a background flow over the flow regimes patterns [3]. Steady-State Two-Phase Flow in Porous Media: Statistics and Transport Properties. First, in stationary flow with a control of the flux of both fluids, we show how the pressure drop depends on the flow rate. We will show that the dynamics is dominated by the interplay between a viscous pressure field from the wetting fluid and bubble transport of a less viscous, nonwetting phase. In contrast with more studied displacement front systems, steady-state flow is in equilibrium, statistically speaking. The corresponding theoretical simplicity allows us to explain a data collapse in the cluster size distribution of lowly viscous fluid in the system, as well as the relation |?P|∞√Ca--. This allows to explain so called relative permeability effects by the morphological changes of the cluster size distribution. Influence of viscous fingering on dynamic saturation-pressure curves in porous media. Next, we study drainage in such models, and investigate the relationship between the pressure field and the morphology of the invading fluid. This allows to model the impact of the saturation changes in the system over the pressure difference between the wetting and non wetting phase. We show that the so-called dynamic effects referred in the hydrology literature of experimentally measured capillary pressure curves might be explained by the combined effect of capillary pressure along the invasion front of the gaseous phase and pressure changes caused by viscous effects. A detailed study of the structure optically followed shows that the geometry of the invader is self-similar with two different behaviors at small and large scales: the structure corresponds to the ones of invasion percolation models at small scales (capillary fingering structures with fractal dimension D=1.83), whereas at large scales, viscous pressure drops dominate over the capillary threshold variations, and the structures are self-similar fingering structures with a fractal dimension corresponding to Dielectric Breakdown Models (variants of the DLA model), with D ≠ƒ 1.5. The cross-over scale is set by the scale at which capillary fluctuations are of the order of the viscous pressure drops. This leads physically to the fact that cross-over scale between the two fingering dimensions, goes like the inverse of the capillary number. This study utilizes these geometrical characteristics of the viscous fingers forming in dynamic drainage, to obtain a meaningfull scaling law for the saturation-pressure curve at finite speed, i.e. the so-called dynamic capillary pressure relations. We thus show how the micromechanical interplay between viscous and capillary forces leads to some pattern formation, which results in a general form of dynamic capillary pressure relations. By combining these detailed informations on the displacement structure with global measures of pressure, saturation and controlling the capillary number Ca, a scaling relation relating pressure, saturation, system size and capillary number is developed. By applying this scaling relation, pressure-saturation curves for a wide range of capillary numbers can be collapsed. Effects of pressure oscillations on drainage in an elastic porous medium: The effects of seismic stimulation on the flow of two immiscible fluids in an elastic synthetic porous medium is experimentally investigated. A wetting fluid is slowly evacuated from the medium, while a pressure oscillation is applied on the injected non-wetting fluid. The amplitude and frequency of the pressure oscillations as well as the evacuation speed are kept constant throughout an experiment. The resulting morphology of the invading structure is found to be strongly dependent on the interplay between the amplitude and the frequency of the applied pressure oscillations and the elasticity of the porous medium. Different combinations of these properties yield morphologically similar structures, allowing a classification of structures that is found to depend on a proposed dimensionless number. [1] Tallakstad, K.T., H.A. Knudsen, T. Ramstad, G. Løvoll, K.J. Maløy, R. Toussaint and E.G. Flekkøy , Steady-state two-phase flow in porous media: statistics and transport properties, Phys. Rev. Lett. 102, 074502 (2009). doi:10.1103/PhysRevLett.102.074502 [2] Løvoll, G., M. Jankov, K.J. Maløy, R. Toussaint, J. Schmittbuhl, G. Schaefer and Y. Ḿ eheust, Influence of viscous fingering on dynamic saturation-pressure curves in porous media, submitted to Transport In Porous Media, (2010) [3] Jankov, M., G. Løvoll, H.A. Knudsen, K.J. Maløy, R. Planet, R. Toussaint and E.G. Flekkøy; Effects of pressure oscillations on drainage in an elastic porous medium, Transport In Porous Media, in press (2010).

Dynamic analysis of a 5-MW tripod offshore wind turbine by considering fluid-structure interaction

NASA Astrophysics Data System (ADS)

Zhang, Li-wei; Li, Xin

2017-10-01

Fixed offshore wind turbines usually have large underwater supporting structures. The fluid influences the dynamic characteristics of the structure system. The dynamic model of a 5-MW tripod offshore wind turbine considering the pile-soil system and fluid structure interaction (FSI) is established, and the structural modes in air and in water are obtained by use of ANSYS. By comparing low-order natural frequencies and mode shapes, the influence of sea water on the free vibration characteristics of offshore wind turbine is analyzed. On basis of the above work, seismic responses under excitation by El-Centro waves are calculated by the time-history analysis method. The results reveal that the dynamic responses such as the lateral displacement of the foundation and the section bending moment of the tubular piles increase substantially under the influence of the added-mass and hydrodynamic pressure of sea water. The method and conclusions presented in this paper can provide a theoretical reference for structure design and analysis of offshore wind turbines fixed in deep seawater.

Application of reference-modified density functional theory: Temperature and pressure dependences of solvation free energy.

PubMed

Sumi, Tomonari; Maruyama, Yutaka; Mitsutake, Ayori; Mochizuki, Kenji; Koga, Kenichiro

2018-02-05

Recently, we proposed a reference-modified density functional theory (RMDFT) to calculate solvation free energy (SFE), in which a hard-sphere fluid was introduced as the reference system instead of an ideal molecular gas. Through the RMDFT, using an optimal diameter for the hard-sphere reference system, the values of the SFE calculated at room temperature and normal pressure were in good agreement with those for more than 500 small organic molecules in water as determined by experiments. In this study, we present an application of the RMDFT for calculating the temperature and pressure dependences of the SFE for solute molecules in water. We demonstrate that the RMDFT has high predictive ability for the temperature and pressure dependences of the SFE for small solute molecules in water when the optimal reference hard-sphere diameter determined for each thermodynamic condition is used. We also apply the RMDFT to investigate the temperature and pressure dependences of the thermodynamic stability of an artificial small protein, chignolin, and discuss the mechanism of high-temperature and high-pressure unfolding of the protein. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

A data base and analysis program for shuttle main engine dynamic pressure measurements. Appendix B: Data base plots for SSME tests 901-290 through 901-414

NASA Technical Reports Server (NTRS)

Coffin, T.

1986-01-01

A dynamic pressure data base and data base management system developed to characterize the Space Shuttle Main Engine (SSME) dynamic pressure environment is described. The data base represents dynamic pressure measurements obtained during single engine hot firing tesets of the SSME. Software is provided to permit statistical evaluation of selected measurements under specified operating conditions. An interpolation scheme is also included to estimate spectral trends with SSME power level. Flow dynamic environments in high performance rocket engines are discussed.

A data base and analysis program for shuttle main engine dynamic pressure measurements. Appendix C: Data base plots for SSME tests 902-214 through 902-314

NASA Technical Reports Server (NTRS)

Coffin, T.

1986-01-01

A dynamic pressure data base and data base management system developed to characterize the Space Shuttle Main Engine (SSME) dynamic pressure environment is reported. The data base represents dynamic pressure measurements obtained during single engine hot firing tests of the SSME. Software is provided to permit statistical evaluation of selected measurements under specified operating conditions. An interpolation scheme is included to estimate spectral trends with SSME power level. Flow Dynamic Environments in High Performance Rocket Engines are described.

A data base and analysis program for shuttle main engine dynamic pressure measurements. Appendix F: Data base plots for SSME tests 750-120 through 750-200

NASA Technical Reports Server (NTRS)

Coffin, T.

1986-01-01

A dynamic pressure data base and data base management system developed to characterize the Space Shuttle Main Engine (SSME) dynamic pressure environment is presented. The data base represents dynamic pressure measurements obtained during single engine hot firing tests of the SSME. Software is provided to permit statistical evaluation of selected measurements under specified operating conditions. An interpolation scheme is also included to estimate spectral trends with SSME power level.

Laser Spectroscopy Monitoring of 13C18O16O and 12C17O16O of Atmospheric Carbon Dioxide

NASA Astrophysics Data System (ADS)

Shorter, J. H.; Nelson, D. D.; Ono, S.; McManus, J. B.; Zahniser, M. S.

2017-12-01

One of the main challenges to making accurate predictions of future changes in CO2 concentration is the capability to determine what fraction of human produced CO2 remains in the atmosphere. We present our progress in the application of Tunable Infrared Laser Direct Absorption Spectroscopy (TILDAS) to the measurement of the primary clumped (13C18O16O) as well as 17O (12C17O16O) isotopologues of atmospheric CO2, as a tracer of its sources and sinks. We expect unique isotopologue signals in CO2 from high-temperature combustion sources, plants, soils, and air-sea exchange processes. High sampling frequency (a few minutes for each sample vs. reference cycle) achieved by a TILDAS instrument is expected to enable us to document local heterogeneous sources and temporal variations. The TILDAS is equipped with a newly developed 400-meter absorption cell. We designed a dual pressure measurement technique in which the clumped isotopologue, 13C18O16O, and 13C16O16O are first measured at 30 torr cell pressure. This is followed by measurement of 12C17O16O, 12C18O16O and 12C16O16O at lower ( 5 torr) cell pressure. Isotopologue ratios are compared between reference and sample gases. Preliminary tests demonstrated a precision approaching 0.03 ‰ for the ratio 13C18O16O/13C16O16O and 0.08‰ for Δ13C18O16O value (1σ repeatability for 4 min sample vs. reference cycle). Sample size for a single analysis is approximately 100 mL of air (1.6μmol of CO2). Given the previously observed range of variations for Δ13C18O16O and Δ17O values as large as 0.6 to 0.3 ‰, respectively, TILDAS offers a novel approach for real time monitoring of atmospheric CO2 isotopologues. It was found that achieving better than 0.1‰ requires careful matching of CO2 mixing ratios between reference and sample air. A primary cause of pressure and mixing ratio dependence is inaccurate baseline fitting (analogous to abundance sensitivity or pressure baseline for IRMS). Given that mixing ratios of atmospheric CO2 can vary as much as 50% or more, a dynamic dilution scheme, where sample air is diluted by CO2 free air to match the reference mixing ratio, is being developed. An in-line calibration source of hot, equilibrated CO2 isotopologues is also being tested. We will discuss the current instrument performance, areas for improvement, and project future applications.

Voltage and Pressure Scaling of Streamer Dynamics in a Helium Plasma Jet With N2 CO-Flow (Postprint)

DTIC Science & Technology

2014-08-14

de Wetering, R. Blanc, E. M. van Veldhuizen , and U. Ebert, J. Phys. D: Appl. Phys. 43, 145204 (2010). 26T. M. P. Briels, J. Kos, G. J. J. Winands, E. M... van Veldhuizen , and U. Ebert, J. Phys. D: Appl. Phys. 41, 234004 (2008). 27See http://physics.nist.gov/PhysRefData/ASD for National Institute of...T. Briels, and E. van Velduizen, J. Geophys. Res. 115, A00E43, doi:10.1029/2009JA014867 (2010) and references therein. 25S. Nijdam, F. M. J. H. van

Modeling and control of a brushless DC axial flow ventricular assist device.

PubMed

Giridharan, Guruprasad A; Skliar, Mikhail; Olsen, Donald B; Pantalos, George M

2002-01-01

This article presents an integrated model of the human circulatory system that incorporates circulatory support by a brushless DC axial flow ventricular assist device (VAD), and a feedback VAD controller designed to maintain physiologically sufficient perfusion. The developed integrated model combines a network type model of the circulatory system with a nonlinear dynamic model of the brushless DC pump We show that maintaining a reference differential pressure between the left ventricle and aorta leads to adequate perfusion for different pathologic cases, ranging from normal heart to left heart asystole, and widely varying physical activity scenarios from rest to exercise.

Effects of pressure on the dynamics of a hyperthermophilic protein revealed by quasielastic neutron scattering

NASA Astrophysics Data System (ADS)

Shrestha, U. R.; Bhowmik, D.; Copley, J. R. D.; Tyagi, M.; Leao, J. B.; Chu, X.-Q.

Inorganic pyrophosphatase (IPPase) from Thermococcus thioreducens is a large oligomeric protein derived from hyperthermophilic microorganism that is found near hydrothermal vents deep under the sea, where the pressure is nearly 100 MPa. Here we study the effects of pressure on the conformational flexibility and relaxation dynamics of IPPase over a wide temperature range using quasielastic neutron scattering (QENS) technique. Two spectrometers were used to investigate the β-relaxation dynamics of proteins in time ranges from 2 to 25 ps, and from 100 ps to 2 ns. Our results reveal that, under the pressure of 100 MPa, IPPase displays much faster relaxation dynamics than a mesophilic model protein, hen egg white lysozyme (HEWL), opposite to what we observed previously under the ambient pressure. These contradictory observations imply that high pressure affects the dynamical properties of proteins by distorting their energy landscapes. Accordingly, we derived a general schematic denaturation phase diagram that can be used as a general picture to understand the effects of pressure on protein dynamics and activities Wayne State Univ Startup Fund.

Comparison of ambulatory blood pressure reference standards in children evaluated for hypertension.

PubMed

Jones, Deborah P; Richey, Phyllis A; Alpert, Bruce S

2009-06-01

The purpose of this study was to systematically compare methods for standardization of blood pressure levels obtained by ambulatory blood pressure monitoring (ABPM) in a group of 111 children studied at our institution. Blood pressure indices, blood pressure loads and standard deviation scores were calculated using the original ABPM and the modified reference standards. Bland-Altman plots and kappa statistics for the level of agreement were generated. Overall, the agreement between the two methods was excellent; however, approximately 5% of children were classified differently by one as compared with the other method. Depending on which version of the German Working Group's reference standards is used for interpretation of ABPM data, the classification of the individual as having hypertension or normal blood pressure may vary.

Comparison of ambulatory blood pressure reference standards in children evaluated for hypertension

PubMed Central

Jones, Deborah P.; Richey, Phyllis A.; Alpert, Bruce S.

2009-01-01

Objective The purpose of this study was to systematically compare methods for standardization of blood pressure levels obtained by ambulatory blood pressure monitoring (ABPM) in a group of 111 children studied at our institution. Methods Blood pressure indices, blood pressure loads and standard deviation scores were calculated using he original ABPM and the modified reference standards. Bland—Altman plots and kappa statistics for the level of agreement were generated. Results Overall, the agreement between the two methods was excellent; however, approximately 5% of children were classified differently by one as compared with the other method. Conclusion Depending on which version of the German Working Group’s reference standards is used for interpretation of ABPM data, the classification of the individual as having hypertension or normal blood pressure may vary. PMID:19433980

Influence of long-time stress relief treatments on the dynamic fracture toughness properties of ASME SA508 C1 2a and ASME SA533 GR B C12 pressure vessel steels

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

Logsdon, W.A.

1982-03-01

Dynamic fracture toughness tests were performed on materials which had been subjected to one of three long-time post weld type stress relief heat treatments: 48 hours at 1000/degree/F (538/degree/C), 24 hours at 1125/degree/F (607/degree/C), and 48 hours at 1125/degree/F (607/degree/C). Linear elastic K/sub Id/ results were obtained at low temperatures while J-integral techniques were utilized to evaluate dynamic fracture toughness over the transition and upper shelf temperature ranges. Tensile, Charpy impact, and drop weight nil-ductility transition tests as well as room temperature, air environment fatigue crack growth rate tests (SA508 Cl 2a only) were also performed. The fracture toughness ofmore » both materials exceeded the ASME specified minimum reference toughness K/sub IR/ curve. 17 refs.« less

Porous media fracturing dynamics: stepwise crack advancement and fluid pressure oscillations

NASA Astrophysics Data System (ADS)

Cao, Toan D.; Hussain, Fazle; Schrefler, Bernhard A.

2018-02-01

We present new results explaining why fracturing in saturated porous media is not smooth and continuous but is a distinct stepwise process concomitant with fluid pressure oscillations. All exact solutions and almost all numerical models yield smooth fracture advancement and fluid pressure evolution, while recent experimental results, mainly from the oil industry, observation from geophysics and a very few numerical results for the quasi-static case indeed reveal the stepwise phenomenon. We summarize first these new experiments and these few numerical solutions for the quasi-static case. Both mechanical loading and pressure driven fractures are considered because their behaviours differ in the direction of the pressure jumps. Then we explore stepwise crack tip advancement and pressure fluctuations in dynamic fracturing with a hydro-mechanical model of porous media based on the Hybrid Mixture Theory. Full dynamic analyses of examples dealing with both hydraulic fracturing and mechanical loading are presented. The stepwise fracture advancement is confirmed in the dynamic setting as well as in the pressure fluctuations, but there are substantial differences in the frequency contents of the pressure waves in the two loading cases. Comparison between the quasi-static and fully dynamic solutions reveals that the dynamic response gives much more information such as the type of pressure oscillations and related frequencies and should be applied whenever there is a doubt about inertia forces playing a role - the case in most fracturing events. In the absence of direct relevant dynamic tests on saturated media some experimental results on dynamic fracture in dry materials, a fast hydraulic fracturing test and observations from geophysics confirm qualitatively the obtained results such as the type of pressure oscillations and the substantial difference in the behaviour under the two loading cases.

Sandia Dynamic Materials Program Strategic Plan.

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

Flicker, Dawn Gustine; Benage, John F.; Desjarlais, Michael P.

2017-05-01

Materials in nuclear and conventional weapons can reach multi-megabar pressures and 1000s of degree temperatures on timescales ranging from microseconds to nanoseconds. Understanding the response of complex materials under these conditions is important for designing and assessing changes to nuclear weapons. In the next few decades, a major concern will be evaluating the behavior of aging materials and remanufactured components. The science to enable the program to underwrite decisions quickly and confidently on use, remanufacturing, and replacement of these materials will be critical to NNSA’s new Stockpile Responsiveness Program. Material response is also important for assessing the risks posed bymore » adversaries or proliferants. Dynamic materials research, which refers to the use of high-speed experiments to produce extreme conditions in matter, is an important part of NNSA’s Stockpile Stewardship Program.« less

Simulation Study on Missile Penetration Based on LS - DYNA

NASA Astrophysics Data System (ADS)

Tang, Jue; Sun, Xinli

2017-12-01

Penetrating the shell armor is an effective means of destroying hard targets with multiple layers of protection. The penetration process is a high-speed impact dynamics research category, involving high pressure, high temperature, high speed and internal material damage, including plugging, penetration, spalling, caving, splashing and other complex forms, therefore, Analysis is one of the difficulties in the study of impact dynamics. In this paper, the Lagrang algorithm and the SPH algorithm are used to analyze the penetrating steel plate, and the penetration model of the rocket penetrating the steel plate, the failure mode of the steel plate and the missile and the advantages and disadvantages of Lagrang algorithm and SPH algorithm in the simulation of high-speed collision problem are analyzed and compared, which provides a reference for the study of simulation collision problem.

Dynamic assessment of women pelvic floor function by using a fiber Bragg grating sensor system

NASA Astrophysics Data System (ADS)

Ferreira, Luis A.; Araújo, Francisco M.; Mascarenhas, Teresa; Natal Jorge, Renato M.; Fernandes, António A.

2006-02-01

We present a novel sensing system consisting of an intravaginal probe and an optoelectronic measurement unit, which allows an easy, comfortable and quantitative dynamic evaluation of women pelvic floor muscle strength. The sensing probe is based on a silicone cylinder that transduces radial muscle pressure into axial load applied to a fiber Bragg grating strain sensor. The performance of a first sensor probe prototype with temperature referentiation and of the autonomous, portable optoelectronic measurement unit with data logging capabilities and graphical user interface is disclosed. The presented results refer to an ongoing collaboration work between researchers from the Medical, Optoelectronics and Mechanical areas, directed to the development of equipment that can assist in medical practice and help in the research of primary mechanisms responsible for several pelvic floor disorders, in particular urogenital prolapses.

Patellofemoral Pressure Changes After Static and Dynamic Medial Patellofemoral Ligament Reconstructions.

PubMed

Rood, Akkie; Hannink, Gerjon; Lenting, Anke; Groenen, Karlijn; Koëter, Sander; Verdonschot, Nico; van Kampen, Albert

2015-10-01

Reconstructing the medial patellofemoral ligament (MPFL) has become a key procedure for stabilizing the patella. Different techniques to reconstruct the MPFL have been described: static techniques in which the graft is fixed rigidly to the bone or dynamic techniques with soft tissue fixation. Static MPFL reconstruction is most commonly used. However, dynamic reconstruction deforms more easily and presumably functions more like the native MPFL. The aim of the study was to evaluate the effect of the different MPFL fixation techniques on patellofemoral pressures compared with the native situation. The hypothesis was that dynamic reconstruction would result in patellofemoral pressures closer to those generated in an intact knee. Controlled laboratory study. Seven fresh-frozen knee specimens were tested in an in vitro knee joint loading apparatus. Tekscan pressure-sensitive films fixed to the retropatellar cartilage measured mean patellofemoral and peak pressures, contact area, and location of the center of force (COF) at fixed flexion angles from 0° to 110°. Four different conditions were tested: intact, dynamic, partial dynamic, and static MPFL reconstruction. Data were analyzed using linear mixed models. Static MPFL reconstruction resulted in higher peak and mean pressures from 60° to 110° of flexion (P < .001). There were no differences in pressure between the 2 different dynamic reconstructions and the intact situation (P > .05). The COF in the static reconstruction group moved more medially on the patella from 50° to 110° of flexion compared with the other conditions. The contact area showed no significant differences between the test conditions. After static MPFL reconstruction, the patellofemoral pressures in flexion angles from 60° to 110° were 3 to 5 times higher than those in the intact situation. The pressures after dynamic MPFL reconstruction were similar as compared with those in the intact situation, and therefore, dynamic MPFL reconstruction could be a safer option than static reconstruction for stabilizing the patella. This study showed that static MPFL reconstruction results in higher patellofemoral pressures and thus enhances the chance of osteoarthritis in the long term, while dynamic reconstruction results in more normal pressures. © 2015 The Author(s).

Error Propagation Dynamics of PIV-based Pressure Field Calculations: How well does the pressure Poisson solver perform inherently?

PubMed

Pan, Zhao; Whitehead, Jared; Thomson, Scott; Truscott, Tadd

2016-08-01

Obtaining pressure field data from particle image velocimetry (PIV) is an attractive technique in fluid dynamics due to its noninvasive nature. The application of this technique generally involves integrating the pressure gradient or solving the pressure Poisson equation using a velocity field measured with PIV. However, very little research has been done to investigate the dynamics of error propagation from PIV-based velocity measurements to the pressure field calculation. Rather than measure the error through experiment, we investigate the dynamics of the error propagation by examining the Poisson equation directly. We analytically quantify the error bound in the pressure field, and are able to illustrate the mathematical roots of why and how the Poisson equation based pressure calculation propagates error from the PIV data. The results show that the error depends on the shape and type of boundary conditions, the dimensions of the flow domain, and the flow type.

Instrumented urethral catheter and its ex vivo validation in a sheep urethra

NASA Astrophysics Data System (ADS)

Ahmadi, Mahdi; Rajamani, Rajesh; Timm, Gerald; Sezen, Serdar

2017-03-01

This paper designs and fabricates an instrumented catheter for instantaneous measurement of distributed urethral pressure profiles. Since the catheter enables a new type of urological measurement, a process for accurate ex vivo validation of the catheter is developed. A flexible sensor strip is first fabricated with nine pressure sensors and integrated electronic pads for an associated sensor IC chip. The flexible sensor strip and associated IC chip are assembled on a 7 Fr Foley catheter. A sheep bladder and urethra are extracted and used in an ex vivo set up for verification of the developed instrumented catheter. The bladder-urethra are suspended in a test rig and pressure cuffs placed to apply known static and dynamic pressures around the urethra. A significant challenge in the performance of the sensor system is the presence of parasitics that introduce large bias and drift errors in the capacitive sensor signals. An algorithm based on use of reference parasitic transducers is used to compensate for the parasitics. Extensive experimental results verify that the developed compensation method works effectively. Results on pressure variation profiles circumferentially around the urethra and longitudinally along the urethra are presented. The developed instrumented catheter will be useful in improved urodynamics to more accurately diagnose the source of urinary incontinence in patients.

Pressure dependence of excited-state charge-carrier dynamics in organolead tribromide perovskites

NASA Astrophysics Data System (ADS)

Liu, X. C.; Han, J. H.; Zhao, H. F.; Yan, H. C.; Shi, Y.; Jin, M. X.; Liu, C. L.; Ding, D. J.

2018-05-01

Excited-state charge-carrier dynamics governs the performance of organometal trihalide perovskites (OTPs) and is strongly influenced by the crystal structure. Characterizing the excited-state charge-carrier dynamics in OTPs under high pressure is imperative for providing crucial insights into structure-property relations. Here, we conduct in situ high-pressure femtosecond transient absorption spectroscopy experiments to study the excited-state carrier dynamics of CH3NH3PbBr3 (MAPbBr3) under hydrostatic pressure. The results indicate that compression is an effective approach to modulate the carrier dynamics of MAPbBr3. Across each pressure-induced phase, carrier relaxation, phonon scattering, and Auger recombination present different pressure-dependent properties under compression. Responsiveness is attributed to the pressure-induced variation in the lattice structure, which also changes the electronic band structure. Specifically, simultaneous prolongation of carrier relaxation and Auger recombination is achieved in the ambient phase, which is very valuable for excess energy harvesting. Our discussion provides clues for optimizing the photovoltaic performance of OTPs.

Zero-Kelvin compression isotherms of the elements 1 ≤ Z ≤ 92 to 100 GPa [Zero-Kelvin compression isotherms of the elements 1 ≤ Z ≤ 90 to 100 GPa (1 megabar)

DOE PAGES

Young, David A.; Cynn, Hyunchae; Soderlind, Per; ...

2016-10-24

Most of the chemical elements have now been compressed close to or above 100 GPa (1 Mbar) pressure in diamond-anvil cells and the pressure–volume room-temperature isotherms have been measured. We collect these data and use simple lattice-dynamics models to reduce the isotherms to 0 K. We have extended the published work by making new diamond-anvil-cell measurements on Cr and Rh, and by conducting density-functional calculations on the elements Po, At, Rn, Fr, Ra, and Ac. The 0 K data are tabulated for all elements 1 ≤ Z ≤ 92 and 0 ≤ P ≤ 100 GPa. These data are usefulmore » for generating wide-range equation of state models and for studying the stability of chemical compounds at high pressure (“Megabar chemistry”). As a result, the tables presented here are intended to be reference thermodynamic tables for use in high-pressure research. Further experimental and theoretical work will be needed to extend the tables to higher pressure and to improve accuracy.« less

Noncontact Monitoring of Respiration by Dynamic Air-Pressure Sensor.

PubMed

Takarada, Tohru; Asada, Tetsunosuke; Sumi, Yoshihisa; Higuchi, Yoshinori

2015-01-01

We have previously reported that a dynamic air-pressure sensor system allows respiratory status to be visually monitored for patients in minimally clothed condition. The dynamic air-pressure sensor measures vital information using changes in air pressure. To utilize this device in the field, we must clarify the influence of clothing conditions on measurement. The present study evaluated use of the dynamic air-pressure sensor system as a respiratory monitor that can reliably detect change in breathing patterns irrespective of clothing. Twelve healthy volunteers reclined on a dental chair positioned horizontally with the sensor pad for measuring air-pressure signals corresponding to respiration placed on the seat back of the dental chair in the central lumbar region. Respiratory measurements were taken under 2 conditions: (a) thinly clothed (subject lying directly on the sensor pad); and (b) thickly clothed (subject lying on the sensor pad covered with a pressure-reducing sheet). Air-pressure signals were recorded and time integration values for air pressure during each expiration were calculated. This information was compared with expiratory tidal volume measured simultaneously by a respirometer connected to the subject via face mask. The dynamic air-pressure sensor was able to receive the signal corresponding to respiration regardless of clothing conditions. A strong correlation was identified between expiratory tidal volume and time integration values for air pressure during each expiration for all subjects under both clothing conditions (0.840-0.988 for the thinly clothed condition and 0.867-0.992 for the thickly clothed condition). These results show that the dynamic air-pressure sensor is useful for monitoring respiratory physiology irrespective of clothing.

Dynamic Temperature and Pressure Measurements in the Core of a Propulsion Engine

NASA Technical Reports Server (NTRS)

Schuster, Bill; Gordon, Grant; Hultgren, Lennart S.

2015-01-01

Dynamic temperature and pressure measurements were made in the core of a TECH977 propulsion engine as part of a NASA funded investigation into indirect combustion noise. Dynamic temperature measurements were made in the combustor, the inter-turbine duct, and the mixer using ten two-wire thermocouple probes. Internal dynamic pressure measurements were made at the same locations using piezoresistive transducers installed in semi-infinite coils. Measurements were acquired at four steady state operating conditions covering the range of aircraft approach power settings. Fluctuating gas temperature spectra were computed from the thermocouple probe voltage measurements using a compensation procedure that was developed under previous NASA test programs. A database of simultaneously acquired dynamic temperature and dynamic pressure measurements was produced. Spectral and cross-spectral analyses were conducted to explore the characteristics of the temperature and pressure fluctuations inside the engine, with a particular focus on attempting to identify the presence of indirect combustion noise.

On the dynamic response of pressure transmission lines in the research of helium-charged free piston Stirling engines

NASA Technical Reports Server (NTRS)

Miller, Eric L.; Dudenhoefer, James E.

1989-01-01

In free piston Stirling engine research the integrity of both amplitude and phase of the dynamic pressure measurements is critical to the characterization of cycle dynamics and thermodynamics. It is therefore necessary to appreciate all possible sources of signal distortion when designing pressure measurement systems for this type of research. The signal distortion inherent to pressure transmission lines is discussed. Based on results from classical analysis, guidelines are formulated to describe the dynamic response properties of a volume-terminated transmission tube for applications involving helium-charged free piston Stirling engines. The scope and limitations of the dynamic response analysis are considered.

The pressure field of imploding lightbulbs

NASA Astrophysics Data System (ADS)

Czechanowski, M.; Ikeda, C.; Duncan, J. H.

2015-03-01

The implosion of A19 incandescent lightbulbs in a high-pressure water environment is studied in a 1.77-m-diameter steel tank. Underwater blast sensors are used to measure the dynamic pressure field near the lightbulbs and the implosions are photographed with a high-speed movie camera at a frame rate of 24,000 pps. The movie camera and the pressure signal recording system are synchronized to enable correlation of features in the movie frames with those in the pressure records. It is found that the gross dimensions and weight of the bulbs are very similar from one bulb to another, but the ambient water pressure at which a given bulb implodes (, called the implosion pressure) varies from 6.29 to 11.98 atmospheres, probably due to inconsistencies in the glass wall thickness and perhaps other detailed characteristics of the bulbs. The dynamic pressures (the local pressure minus , as measured by the sensors) first drop during the implosion and then reach a strong positive peak at about the time that the bulb reaches minimum volume. The peak dynamic pressure varies from 3.61 to 28.66 atmospheres. In order to explore the physics of the implosion process, the dynamic pressure signals are compared to calculations of the pressure field generated by the collapse of a spherical bubble in a weakly compressible liquid. The wide range of implosion pressures is used in combination with the calculations to explore the effect of the relative liquid compressibility and the bulb itself on the dynamic pressure field.

Effect of reference conditions on flow rate, modifier fraction and retention in supercritical fluid chromatography.

PubMed

De Pauw, Ruben; Shoykhet Choikhet, Konstantin; Desmet, Gert; Broeckhoven, Ken

2016-08-12

When using compressible mobile phases such as fluidic CO2, the density, the volumetric flow rates and volumetric fractions are pressure dependent. The pressure and temperature definition of these volumetric parameters (referred to as the reference conditions) may alter between systems, manufacturers and operating conditions. A supercritical fluid chromatography system was modified to operate in two modes with different definition of the eluent delivery parameters, referred to as fixed and variable mode. For the variable mode, the volumetric parameters are defined with reference to the pump operating pressure and actual pump head temperature. These conditions may vary when, e.g. changing the column length, permeability, flow rate, etc. and are thus variable reference conditions. For the fixed mode, the reference conditions were set at 150bar and 30°C, resulting in a mass flow rate and mass fraction of modifier definition which is independent of the operation conditions. For the variable mode, the mass flow rate of carbon dioxide increases with system pump operating pressure, decreasing the fraction of modifier. Comparing the void times and retention factor shows that the deviation between the two modes is almost independent of modifier percentage, but depends on the operating pressure. Recalculating the set volumetric fraction of modifier to the mass fraction results in the same retention behaviour for both modes. This shows that retention in SFC can be best modelled using the mass fraction of modifier. The fixed mode also simplifies method scaling as it only requires matching average column pressure. Copyright © 2016 Elsevier B.V. All rights reserved.

Elasticity-Driven Backflow of Fluid-Driven Cracks

NASA Astrophysics Data System (ADS)

Lai, Ching-Yao; Dressaire, Emilie; Ramon, Guy; Huppert, Herbert; Stone, Howard A.

2016-11-01

Fluid-driven cracks are generated by the injection of pressurized fluid into an elastic medium. Once the injection pressure is released, the crack closes up due to elasticity and the fluid in the crack drains out of the crack through an outlet, which we refer to as backflow. We experimentally study the effects of crack size, elasticity of the matrix, and fluid viscosity on the backflow dynamics. During backflow, the volume of liquid remaining in the crack as a function of time exhibits a transition from a fast decay at early times to a power law behavior at late times. Our results at late times can be explained by scaling arguments balancing elastic and viscous stresses in the crack. This work may relate to the environmental issue of flowback in hydraulic fracturing. This work is supported by National Science Foundation via Grant CBET-1509347 and partially supported by Andlinger Center for Energy and the Environment at Princeton University.

Determination of hydrocarbon abundances and the strength of eddy mixing in the stratosphere of Neptune: Analysis of UVS solar occultation lightcurves

NASA Technical Reports Server (NTRS)

Bishop, James

1995-01-01

Work on completing our analysis of the Voyager UVS solar occultation data acquired during Neptune encounter is essentially complete, as testified by the attached poster materials. The photochemical modeling addresses the recent revision in branching ratios for radical production in the photolysis of methane at H Lyman alpha implied by the lab measurements of Mordaunt et al. (1993). The software generated in this effort has been useful for checking the degree to which photochemical models addressing other datasets (mainly infrared) are consistent with the UVS data. This work complements the UVS modeling results in that the IR data refer to deeper pressure levels; as regards the modeling of UVS data, the most significant result is the convincing support for the presence of a stagnant lower stratosphere. Evidence for strong dynamical (mixing) transport of minor constituents at shallower pressures is provided by the UVS data analysis.

Laser velocimeter and total pressure measurements in circular-to-rectangular transition ducts

NASA Technical Reports Server (NTRS)

Patrick, William P.; Mccormick, Duane C.

1988-01-01

A comprehensive set of total pressure and three-component laser velocimetry (LV) data were obtained within two circular-to-rectangular transition ducts at low subsonic speeds. This set of reference data was acquired for use in identifying secondary flow mechanisms and for assessing the accuracy of computational procedures for calculating such flows. Data were obtained at the inlet and exit planes of an aspect ratio three duct having a length-to-diameter ratio of one (AR310) and an aspect ratio six duct having a length-to-diameter ratio of three (AR630). Each duct was unseparated throughout its transition section. It is therefore concluded that secondary flows can play an important part in the fluid dynamics of transition ducts and needs to be addressed in computational analysis. The strength of the secondary flows depends on both the aspect ratio and relative axial duct length.

Comparison of Modal Analysis Methods Applied to a Vibro-Acoustic Test Article

NASA Technical Reports Server (NTRS)

Pritchard, Jocelyn; Pappa, Richard; Buehrle, Ralph; Grosveld, Ferdinand

2001-01-01

Modal testing of a vibro-acoustic test article referred to as the Aluminum Testbed Cylinder (ATC) has provided frequency response data for the development of validated numerical models of complex structures for interior noise prediction and control. The ATC is an all aluminum, ring and stringer stiffened cylinder, 12 feet in length and 4 feet in diameter. The cylinder was designed to represent typical aircraft construction. Modal tests were conducted for several different configurations of the cylinder assembly under ambient and pressurized conditions. The purpose of this paper is to present results from dynamic testing of different ATC configurations using two modal analysis software methods: Eigensystem Realization Algorithm (ERA) and MTS IDEAS Polyreference method. The paper compares results from the two analysis methods as well as the results from various test configurations. The effects of pressurization on the modal characteristics are discussed.

Rotating pressure measurement system using an on board calibration standard

NASA Technical Reports Server (NTRS)

Senyitko, Richard G.; Blumenthal, Philip Z.; Freedman, Robert J.

1991-01-01

A computer-controlled multichannel pressure measurement system was developed to acquire detailed flow field measurements on board the Large Low Speed Centrifugal Compressor Research Facility at the NASA Lewis Research Center. A pneumatic slip ring seal assembly is used to transfer calibration pressures to a reference standard transducer on board the compressor rotor in order to measure very low differential pressures with the high accuracy required. A unique data acquisition system was designed and built to convert the analog signal from the reference transducer to the variable frequency required by the multichannel pressure measurement system and also to provide an output for temperature control of the reference transducer. The system also monitors changes in test cell barometric pressure and rotating seal leakage and provides an on screen warning to the operator if limits are exceeded. The methods used for the selection and testing of the the reference transducer are discussed, and the data acquisition system hardware and software design are described. The calculated and experimental data for the system measurement accuracy are also presented.

Calibrated acoustic emission system records M -3.5 to M -8 events generated on a saw-cut granite sample

USGS Publications Warehouse

McLaskey, Gregory C.; Lockner, David A.

2016-01-01

Acoustic emission (AE) analyses have been used for decades for rock mechanics testing, but because AE systems are not typically calibrated, the absolute sizes of dynamic microcrack growth and other physical processes responsible for the generation of AEs are poorly constrained. We describe a calibration technique for the AE recording system as a whole (transducers + amplifiers + digitizers + sample + loading frame) that uses the impact of a 4.76-mm free-falling steel ball bearing as a reference source. We demonstrate the technique on a 76-mm diameter cylinder of westerly granite loaded in a triaxial deformation apparatus at 40 MPa confining pressure. The ball bearing is dropped inside a cavity within the sample while inside the pressure vessel. We compare this reference source to conventional AEs generated during loading of a saw-cut fault in a second granite sample. All located AEs occur on the saw-cut surface and have moment magnitudes ranging from M −5.7 down to at least M −8. Dynamic events rupturing the entire simulated fault surface (stick–slip events) have measurable stress drop and macroscopic slip and radiate seismic waves similar to those from a M −3.5 earthquake. The largest AE events that do not rupture the entire fault are M −5.7. For these events, we also estimate the corner frequency (200–300 kHz), and we assume the Brune model to estimate source dimensions of 4–6 mm. These AE sources are larger than the 0.2 mm grain size and smaller than the 76 × 152 mm fault surface.

The Potosi Reservoir Model 2013c, Property Modeling Update

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

Adushita, Yasmin; Smith, Valerie; Leetaru, Hannes

2014-09-30

As part of a larger project co-funded by the United States Department of Energy (US DOE) to evaluate the potential of formations within the Cambro-Ordovician strata above the Mt. Simon as potential targets for carbon sequestration in the Illinois and Michigan Basins, the Illinois Clean Coal Institute (ICCI) requested Schlumberger to evaluate the potential injectivity and carbon dioxide (CO2) plume size of the Cambrian Potosi Formation. The evaluation of this formation was accomplished using wireline data, core data, pressure data, and seismic data from this project as well as two other separately funded projects: the US DOE-funded Illinois Basin–Decatur Projectmore » (IBDP) being conducted by the Midwest Geological Sequestration Consortium (MGSC) in Macon County, Illinois, and the Illinois Industrial Carbon Capture and Sequestration (ICCS) project funded through the American Recovery and Reinvestment Act. In 2010, technical performance evaluations on the Cambrian Potosi Formation were performed through reservoir modeling. The data included formation tops from mud logs, well logs from the Verification Well #1 (VW1) and the Injection Well (CCS1), structural and stratigraphic formation from three dimensional (3D) seismic data, and field data from several waste water injection wells for Potosi Formation. The intention was for 2.2 million tons per annum (2 million tonnes per annum [MTPA]) of CO2 to be injected for 20 years. In the Task Error! Reference source not found., the 2010 Potosi heterogeneous model (referred to as the "Potosi Dynamic Model 2010") was re-run using a new injection scenario of 3.5 million tons per annum (3.2 MTPA) for 30 years. The extent of the Potosi Dynamic Model 2010, however, appeared too small for the new injection target. The models size was insufficient to accommodate the evolution of the plume. The new model, Potosi Dynamic Model 2013a, was built by extending the Potosi Dynamic Model 2010 grid to 30 by 30 mi (48 by 48 km), while preserving all property modeling workflows and layering. This model was retained as the base case. In the preceding Task [1], the Potosi reservoir model was updated to take into account the new data from the Verification Well #2 (VW2) which was drilled in 2012. The porosity and permeability modeling was revised to take into account the log data from the new well. Revisions of the 2010 modeling assumptions were also done on relative permeability, capillary pressures, formation water salinity, and the maximum allowable well bottomhole pressure. Dynamic simulations were run using the injection target of 3.5 million tons per annum (3.2 MTPA) for 30 years. This dynamic model was named Potosi Dynamic Model 2013b. In this Task, a new property modeling workflow was applied, where seismic inversion data guided the porosity mapping and geobody extraction. The static reservoir model was fully guided by PorosityCube interpretations and derivations coupled with petrophysical logs from three wells. The two main assumptions are: porosity features in the PorosityCube that correlate with lost circulation zones represent vugular zones, and that these vugular zones are laterally continuous. Extrapolation was done carefully to populate the vugular facies and their corresponding properties outside the seismic footprint up to the boundary of the 30 by 30 mi (48 by 48 km) model. Dynamic simulations were also run using the injection target of 3.5 million tons per annum (3.2 MTPA) for 30 years. This new dynamic model was named Potosi Dynamic Model 2013c. Reservoir simulation with the latest model gives a cumulative injection of 43 million tons (39 MT) in 30 years with a single well, which corresponds to 40% of the injection target. The injection rate is approx. 3.2 MTPA in the first six months as the well is injecting into the surrounding vugs, and declines rapidly to 1.8 million tons per annum (1.6 MTPA) in year 3 once the surrounding vugs are full and the CO2 start to reach the matrix. After, the injection rate declines gradually to 1.2 million tons per annum (1.1 MTPA) in year 18 and stays constant. This implies that a minimum of three (3) wells could be required in the Potosi to reach the injection target. The injectivity evaluated in this Task was higher compared to the preceding Task, since the current facies modeling (guided by the porosity map from the seismic inversion) indicated a higher density of vugs within the vugular zones. 5 As the CO2 follows the paths where vugs interconnection exists, a reasonably large and irregular plume extent was created. After 30 years of injection, the plume extends 13.7 mi (22 km) in E-W and 9.7 mi (16 km) in N-S directions. After injection finishes, the plume continues to migrate laterally, mainly driven by the remaining pressure gradient. After 60 years post-injection, the plume extends 14.2 mi (22.8 km) in E-W and 10 mi (16 km) in N-S directions, and remains constant as the remaining pressure gradient has become very low. Should the targeted cumulative injection of 106 million tons (96 MT) be achieved; a much larger plume extent could be expected. The increase of reservoir pressure at the end of injection is approximately 1,200 psia (8,274 kPa) around the injector and gradually decreases away from the well. The reservoir pressure increase is less than 10 psia (69 kPa) beyond 14 mi (23 km) away from injector. Should the targeted cumulative injection of 106 million tons (96 MT) be achieved; a much larger areal pressure increase could be expected. The reservoir pressure declines rapidly during the first 30 years post injection and the initial reservoir pressure is nearly restored after 100 years post-injection. The present evaluation is mainly associated with uncertainty on the vugs permeability and interconnectivity. The use of porosity mapping from seismic inversion might have reduced the uncertainty on the lateral vugs body distributions. However, major uncertainties on the Potosi vugs permeability remains. Therefore, injection test and pressure interference test among the wells could be considered to evaluate the local vugs permeability, extent, and interconnectivity. Facies modeling within the Potosi has yet to be thoroughly addressed. The carbonates during the time of deposition are believed to be regionally extensive. However, it may be worth delineating the reservoir with other regional wells or modern day analogues to understand the extent of the Potosi. More specifically, the model could incorporate lateral changes or trends if deemed necessary to represent facies transition. Data acquisitions to characterize the fracture pressure gradient, the formation water properties, the relative permeability, and the capillary pressure could also be considered in order to allow a more rigorous evaluation of the Potosi storage performance. A simulation using several injectors could also be considered to determine the required number of wells and appropriate spacing to achieve the injection target while taking into account the pressure interference.« less

A dynamic pressure source for the calibration of pressure transducers

NASA Technical Reports Server (NTRS)

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

1976-01-01

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

Lagrangian dynamics of the mistral during the HyMeX SOP2

NASA Astrophysics Data System (ADS)

Drobinski, P.; Alonzo, B.; Basdevant, C.; Cocquerez, P.; Doerenbecher, A.; Fourrié, N.; Nuret, M.

2017-02-01

The mistral refers to a severe wind blowing over the Gulf of Lions after being channeled in the Rhone valley. It influences the western Mediterranean climate as it brings cold and dry continental air over the warm western Mediterranean, generating intense air-sea heat exchanges and sea surface cooling, inducing the formation of the western Mediterranean deep water that moves into the Atlantic Ocean. The mistral is frequently observed to extend as far as a few hundred kilometers from the coast, and its fine-scale dynamics over the sea is still only partially understood as finely resolved observations in time and space are lacking. The boundary layer pressurized balloons (BLPB) developed by the Centre National d'Etudes Spatiales and deployed during HyMeX SOP2 allowed the Lagrangian documentation of the mistral events that occurred between beginning of February to mid-March 2013. Analyzed in synergy with the AROME-WMED weather forecast model, all the terms of the Lagrangian formulation of the momentum conservation equation could be quantified showing three different regions: (1) an injection zone where the mistral flow is directed toward the center of the Genoa cyclone due to a strong zonal pressure gradient, enhanced friction, and entrainment in the mountain wake; (2) an ejection zone where the flow is deflected outward of the cyclone due to either the nonnegligible inertia pseudoforce or an inertial oscillation caused by a sudden friction decrease; and (3) a region of geostrophic deceleration due to the weakening of the pressure gradient.

Lagrangian dynamics of the mistral during the HyMeX SOP2

NASA Astrophysics Data System (ADS)

Drobinski, Philippe; Alonzo, Bastien; Basdevant, Claude; Cocquerez, Philippe; Fourrié, Nadia; Nuret, Mathieu

2017-04-01

The mistral refers to a severe wind blowing over the Gulf of Lions after being channeled in the Rhone valley. It influences the western Mediterranean climate as it brings cold and dry continental air over the warm western Mediterranean, generating intense air-sea heat exchanges and sea surface cooling, inducing the formation of the western Mediterranean deep water that moves into the Atlantic Ocean. The mistral is frequently observed to extend as far as a few hundred kilometers from the coast, and its fine-scale dynamics over the sea is still only partially understood as finely resolved observations in time and space are lacking. The boundary layer pressurized balloons (BLPB) developed by the Centre National d'Etudes Spatiales and deployed during HyMeX SOP2 allowed the Lagrangian documentation of the mistral events that occurred between beginning of February to mid-March 2013. Analyzed in synergy with the AROME-WMED weather forecast model, all the terms of the Lagrangian formulation of the momentum conservation equation could be quantified showing three different regions: (1) an injection zone where the mistral flow is directed toward the center of the Genoa cyclone due to a strong zonal pressure gradient, enhanced friction, and entrainment in the mountain wake; (2) an ejection zone where the flow is deflected outward of the cyclone due to either the nonnegligible inertia pseudoforce or an inertial oscillation caused by a sudden friction decrease; and (3) a region of geostrophic deceleration due to the weakening of the pressure gradient.

Modeling Dynamic Anisotropic Behaviour and Spall Failure in Commercial Aluminium Alloys AA7010

NASA Astrophysics Data System (ADS)

Mohd Nor, M. K.; Ma'at, N.; Ho, C. S.

2018-04-01

This paper presents a finite strain constitutive model to predict a complex elastoplastic deformation behaviour involves very high pressures and shockwaves in orthotropic materials of aluminium alloys. The previous published constitutive model is used as a reference to start the development in this work. The proposed formulation that used a new definition of Mandel stress tensor to define Hill's yield criterion and a new shock equation of state (EOS) of the generalised orthotropic pressure is further enhanced with Grady spall failure model to closely predict shockwave propagation and spall failure in the chosen commercial aluminium alloy. This hyperelastic-plastic constitutive model is implemented as a new material model in the Lawrence Livermore National Laboratory (LLNL)-DYNA3D code of UTHM's version, named Material Type 92 (Mat92). The implementations of a new EOS of the generalised orthotropic pressure including the spall failure are also discussed in this paper. The capability of the proposed constitutive model to capture the complex behaviour of the selected material is validated against range of Plate Impact Test data at 234, 450 and 895 ms-1 impact velocities.

Study of blood flow inside the stenosis vessel under the effect of solenoid magnetic field using ferrohydrodynamics principles

NASA Astrophysics Data System (ADS)

Badfar, Homayoun; Motlagh, Saber Yekani; Sharifi, Abbas

2017-10-01

In this paper, biomagnetic blood flow in the stenosis vessel under the effect of the solenoid magnetic field is studied using the ferrohydrodynamics (FHD) model. The parabolic profile is considered at an inlet of the axisymmetric stenosis vessel. Blood is modeled as electrically non-conducting, Newtonian and homogeneous fluid. Finite volume and the SIMPLE (Semi-Implicit Method for Pressure Linked Equations) algorithm are utilized to discretize governing equations. The investigation is studied at different magnetic numbers ( MnF=164, 328, 1640 and 3280) and the number of the coil loops (three, five and nine loops). Results indicate an increase in heat transfer, wall shear stress and energy loss (pressure drop) with an increment in the magnetic number (ratio of Kelvin force to dynamic pressure force), arising from the FHD, and the number of solenoid loops. Furthermore, the flow pattern is affected by the magnetic field, and the temperature of blood can be decreased up to 1.48 {}°C under the effect of the solenoid magnetic field with nine loops and reference magnetic field ( B0) of 2 tesla.

Effect of temperature and pressure on the dynamics of nanoconfined propane

NASA Astrophysics Data System (ADS)

Gautam, Siddharth; Liu, Tingting; Rother, Gernot; Jalarvo, Niina; Mamontov, Eugene; Welch, Susan; Cole, David

2014-04-01

We report the effect of temperature and pressure on the dynamical properties of propane confined in nanoporous silica aerogel studied using quasielastic neutron scattering (QENS). Our results demonstrate that the effect of a change in the pressure dominates over the effect of temperature variation on the dynamics of propane nano-confined in silica aerogel. At low pressures, most of the propane molecules are strongly bound to the pore walls, only a small fraction is mobile. As the pressure is increased, the fraction of mobile molecules increases. A change in the mechanism of motion, from continuous diffusion at low pressures to jump diffusion at higher pressures has also been observed.

Vortex, ULF wave and Aurora Observation after Solar Wind Dynamic Pressure Change

NASA Astrophysics Data System (ADS)

Shi, Q.

2017-12-01

Here we will summarize our recent study and show some new results on the Magnetosphere and Ionosphere Response to Dynamic Pressure Change/disturbances in the Solar Wind and foreshock regions. We study the step function type solar wind dynamic pressure change (increase/decrease) interaction with the magnetosphere using THEMIS satellites at both dayside and nightside in different geocentric distances. Vortices generated by the dynamic pressure change passing along the magnetopause are found and compared with model predictions. ULF waves and vortices are excited in the dayside and nightside plasma sheet when dynamic pressure change hit the magnetotail. The related ionospheric responses, such as aurora and TCVs, are also investigated. We compare Global MHD simulations with the observations. We will also show some new results that dayside magnetospheric FLRs might be caused by foreshock structures.Shi, Q. Q. et al. (2013), THEMIS observations of ULF wave excitation in the nightside plasma sheet during sudden impulse events, J. Geophys. Res. Space Physics, 118, doi:10.1029/2012JA017984. Shi, Q. Q. et al. (2014), Solar wind pressure pulse-driven magnetospheric vortices and their global consequences, J. Geophys. Res. Space Physics, 119, doi:10.1002/2013JA019551. Tian, A.M. et al.(2016), Dayside magnetospheric and ionospheric responses to solar wind pressure increase: Multispacecraft and ground observations, J. Geophys. Res., 121, doi:10.1002/2016JA022459. Shen, X.C. et al.(2015), Magnetospheric ULF waves with increasing amplitude related to solar wind dynamic pressure changes: THEMIS observations, J. Geophys. Res., 120, doi:10.1002/2014JA020913Zhao, H. Y. et al. (2016), Magnetospheric vortices and their global effect after a solar wind dynamic pressure decrease, J. Geophys. Res. Space Physics, 121, doi:10.1002/2015JA021646. Shen, X. C., et al. (2017), Dayside magnetospheric ULF wave frequency modulated by a solar wind dynamic pressure negative impulse, J. Geophys. Res., 122, doi:10.1002/2016JA023351.

An overview of the dynamic calibration of piezoelectric pressure transducers

NASA Astrophysics Data System (ADS)

Theodoro, F. R. F.; Reis, M. L. C. C.; d’ Souto, C.

2018-03-01

Dynamic calibration is a research area that is still under development and is of great interest to aerospace and automotive industries. This study discusses some concepts regarding dynamic measurements of pressure quantities and presents an overview of dynamic calibration of pressure transducers. Studies conducted by the Institute of Aeronautics and Space focusing on research regarding piezoelectric pressure transducer calibration in shock tube are presented. We employed the Guide to the Expression of Uncertainty and a Monte Carlo Method in the methodology. The results show that both device and methodology employed are adequate to calibrate the piezoelectric sensor.

Intracellular Pressure Dynamics in Blebbing Cells

PubMed Central

Strychalski, Wanda; Guy, Robert D.

2016-01-01

Blebs are pressure-driven protrusions that play an important role in cell migration, particularly in three-dimensional environments. A bleb is initiated when the cytoskeleton detaches from the cell membrane, resulting in the pressure-driven flow of cytosol toward the area of detachment and local expansion of the cell membrane. Recent experiments involving blebbing cells have led to conflicting hypotheses regarding the timescale of intracellular pressure propagation. The interpretation of one set of experiments supports a poroelastic model of the cytoplasm that leads to slow pressure equilibration when compared to the timescale of bleb expansion. A different study concludes that pressure equilibrates faster than the timescale of bleb expansion. To address this discrepancy, a dynamic computational model of the cell was developed that includes mechanics of and the interactions among the cytoplasm, the actin cortex, the cell membrane, and the cytoskeleton. The model results quantify the relationship among cytoplasmic rheology, pressure, and bleb expansion dynamics, and provide a more detailed picture of intracellular pressure dynamics. This study shows the elastic response of the cytoplasm relieves pressure and limits bleb size, and that both permeability and elasticity of the cytoplasm determine bleb expansion time. Our model with a poroelastic cytoplasm shows that pressure disturbances from bleb initiation propagate faster than the timescale of bleb expansion and that pressure equilibrates slower than the timescale of bleb expansion. The multiple timescales in intracellular pressure dynamics explain the apparent discrepancy in the interpretation of experimental results. PMID:26958893

Reference values for physical performance measures in the aging working population.

PubMed

Cote, Mark P; Kenny, Anne; Dussetschleger, Jeffrey; Farr, Dana; Chaurasia, Ashok; Cherniack, Martin

2014-02-01

The aim of this study was to determine reference physical performance values in older aging workers. Cross-sectional physical performance measures were collected for 736 manufacturing workers to assess effects of work and nonwork factors on age-related changes in musculoskeletal function and health. Participants underwent surveys and physical testing that included bioelectrical impedance analysis, range-of-motion measures, exercise testing, and dynamic assessment. Physical characteristics, such as blood pressure and body fat percentage, were comparable to published values. Dynamic and range-of-motion measurements differed from published normative results. Women had age-related decreases in cervical extension and lateral rotation. Older men had better spinal flexion than expected. Predicted age-related decline in lower-extremity strength and shoulder strength in women was not seen. Men declined in handgrip, lower-extremity strength, and knee extension strength, but not trunk strength, across age groups. There was no appreciable decline in muscle fatigue at the trunk, shoulder, and knee with aging for either gender, except for the youngest age group of women. Normative values may underestimate physical performance in "healthy" older workers, thereby underappreciating declines in less healthy older workers. Work may be preservative of function for a large group of selected individuals. A "healthy worker effect" may be greater for musculoskeletal disease and function than for heart disease and mortality. Clinicians and researchers studying musculoskeletal function in older workers can use a more specific set of reference values.

Diffusivity anomaly in modified Stillinger-Weber liquids

NASA Astrophysics Data System (ADS)

Sengupta, Shiladitya; Vasisht, Vishwas V.; Sastry, Srikanth

2014-01-01

By modifying the tetrahedrality (the strength of the three body interactions) in the well-known Stillinger-Weber model for silicon, we study the diffusivity of a series of model liquids as a function of tetrahedrality and temperature at fixed pressure. Previous work has shown that at constant temperature, the diffusivity exhibits a maximum as a function of tetrahedrality, which we refer to as the diffusivity anomaly, in analogy with the well-known anomaly in water upon variation of pressure at constant temperature. We explore to what extent the structural and thermodynamic changes accompanying changes in the interaction potential can help rationalize the diffusivity anomaly, by employing the Rosenfeld relation between diffusivity and the excess entropy (over the ideal gas reference value), and the pair correlation entropy, which provides an approximation to the excess entropy in terms of the pair correlation function. We find that in the modified Stillinger-Weber liquids, the Rosenfeld relation works well above the melting temperatures but exhibits deviations below, with the deviations becoming smaller for smaller tetrahedrality. Further we find that both the excess entropy and the pair correlation entropy at constant temperature go through maxima as a function of the tetrahedrality, thus demonstrating the close relationship between structural, thermodynamic, and dynamical anomalies in the modified Stillinger-Weber liquids.

Tropospheric- Stratospheric Measurement Studies Summary

NASA Technical Reports Server (NTRS)

Browen, Stuart W.

1998-01-01

The two high altitude aircraft, ER-2 NASA #706 and 709 and the DC-8 NASA #717 are in active use in several programs of upper atmospheric research to study polar ozone changes, stratospheric-tropospheric exchange processes and atmospheric effects of aviation aircraft. The ER-2 has participated in seven major missions which mainly concentrated on vortex dynamics and the large losses of Ozone in the Polar regions (Ozone hole) observed in the spring. One mission verified the complex dynamical chemical and physical processes that occur during sunrise and sunset. Stratospheric Tracers of Atmospheric Transport (STRAT) obtained background measurements using the full ER-2 suite of instruments. Photochemistry of Ozone Loss in the Arctic Region in Summer (POLARIS) in 1997 assisted in understanding the mid-latitude and Arctic Ozone losses during the Northern Summer. The DC-8 with the Meteorological Measurement System (MMS) has participated in the Subsonic Aircraft: Cloud and Contrail Effects Special Study (SUCCESS), in 1996 and the Subsonic assessment Ozone and Nitrogen oxide experiment (SONEX) in 1997 missions. The MMS with its sophisticated software accurately measures ground speed and attitude, in-situ static and dynamic pressure total temperature, which are used to calculate the three dimensional wind fields, static pressure, temperature and turbulence values to meteorological accuracy. The meteorological data is not only of interest for its own sake in atmospheric dynamical processes such as mountain waves and flux measurements; but is also required by other ER-2 experiments that simultaneously measure water vapor, O3, aerosols, NO, HCl, CH4, N2O, ClO, BrO, CO2, NOy, HOx and temperature gradients. MMS products are extensively used to assist in the interpretation of their results in understanding the importance of convective effects relative to in-situ chemical changes, as may be noted by examining the list of references attached. The MMS consists of three subsystems: (a) aircraft instrumentation, inertial navigation system (INS), static and dynamic pressure taps, (b) additional dedicated instrumentation measuring angle of attack, yaw, total temperature, and a GPS which on the DC-8 measures position, velocity and attitude (c) an on board data, storage and computing acquisition system. This instrumentation and the associated software requires both an on-going laboratory ground calibration procedure for the total air temperature, static and total pressure inputs, verification of the INS dynamic response and also extensive air measurements and intercomparisons which ultimately verify and calibrate the complete system and its software. More than the usual accuracy is required because of the near cancellation occurring in the difference between the ground speed and true airspeed vectors used to give the wind vector. In the past year we have redesigned, recalibrated and used the MMS system on the NASA DC-8 that was previously used in the SUCCESS mission for the SONEX mission. Two papers were co-authored based on SUCCESS flights. Several reports and handouts were written for SONEX. Calibrations of the DC-8 pressure transducer temperature measuring thermistors was completed and an extensive analysis spanning several years of data files of the DC-8 Rosemount pressure transducer calibrations was done.

Boiling regimes of impacting drops on a heated substrate under reduced pressure

NASA Astrophysics Data System (ADS)

van Limbeek, Michiel A. J.; Hoefnagels, Paul B. J.; Shirota, Minori; Sun, Chao; Lohse, Detlef

2018-05-01

We experimentally investigate the boiling behavior of impacting ethanol drops on a heated smooth sapphire substrate at pressures ranging from P =0.13 bar to atmospheric pressure. We employ frustrated total internal reflection imaging to study the wetting dynamics of the contact between the drop and the substrate. The spreading drop can be in full contact (contact boiling), it can partially touch (transition boiling), or the drop can be fully levitated (Leidenfrost boiling). We show that the temperature of the boundary between contact and transition boiling shows at most a weak dependence on the impact velocity, but a significant decrease with decreasing ambient gas pressure. A striking correspondence is found between the temperature of this boundary and the static Leidenfrost temperature for all pressures. We therefore conclude that both phenomena share the same mechanism and are dominated by the dynamics taking place at the contact line. On the other hand, the boundary between transition boiling and Leidenfrost boiling, i.e., the dynamic Leidenfrost temperature, increases for increasing impact velocity for all ambient gas pressures. Moreover, the dynamic Leidenfrost temperature coincides for pressures between P =0.13 and 0.54 bar, whereas for atmospheric pressure the dynamic Leidenfrost temperature is slightly elevated. This indicates that the dynamic Leidenfrost temperature is at most weakly dependent on the enhanced evaporation by the lower saturation temperature of the liquid.

Electron dynamics and potential jump across slow mode shocks

NASA Technical Reports Server (NTRS)

Schwartz, Steven J.; Douglas, Fraser T.; Thomsen, Michelle F.; Feldman, William C.

1987-01-01

In the de Hoffmann-Teller reference frame, the cross-shock electric field is simply the thermoelectric field responsible for preserving charge neutrality. As such, it gives information regarding the heating and dissipation occurring within the shock. The total cross-shock potential can be determined by integrating a weighted electron pressure gradient through the shock, but this requires knowledge of the density and temperature profiles. Here, a recently proposed alternative approach relying on particle dynamics is exploited to provide an independent estimate of this potential. Both determinations are applied to slow mode shocks which form the plasma sheet boundary in the deep geomagnetic tail as observed by ISEE 3. The two methods correlate well. There is no indication of the expected transition from resistive to viscous shocks, although the highest Mach number shocks show the highest potentials. The implications of these results for the electron dissipation mechanisms and turbulence at the shock are discussed.

The 14 month wind stressed residual circulation (pole tide) in the North Sea

NASA Technical Reports Server (NTRS)

Oconnor, W. P.

1986-01-01

From published research it is known that a quasi-periodic 14 month atmospheric pressure oscillation of a few tenths of a millibar exists in the region of the North and Baltic Seas. At some time in the cycle the associated wind stress has a westerly component that drives a circulation in the North Sea. The results of a dynamical model and comparisons with several North Sea residual circulation studies show that a large sea level gradient results along the Dutch coast. It is this feature that has been referred to as the enhanced pole tide. The dynamical similarity of this pole tide in the North and Baltic Seas to the annual and seasonal wind forced circulations is considered. It is inferred that the large deviations of the pole tide from equilibrium at coastal stations are the result of this sea level set up forces by the 14 month wind stress cycle.

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.

Advancing a smart air cushion system for preventing pressure ulcers using projection Moiré for large deformation measurements

NASA Astrophysics Data System (ADS)

Cheng, Sheng-Lin; Tsai, Tsung-Heng; Lee, Carina Jean-Tien; Hsu, Yu-Hsiang; Lee, Chih-Kung

2016-03-01

A pressure ulcer is one of the most important concerns for wheelchair bound patients with spinal cord injuries. A pressure ulcer is a localized injury near the buttocks that bear ischial tuberosity oppression over a long period of time. Due to elevated compression to blood vessels, the surrounding tissues suffer from a lack of oxygen and nutrition. The ulcers eventually lead to skin damage followed by tissue necrosis. The current medical strategy is to minimize the occurrence of pressure ulcers by regularly helping patients change their posture. However, these methods do not always work effectively or well. As a solution to fundamentally prevent pressure ulcers, a smart air cushion system was developed to detect and control pressure actively. The air cushion works by automatically adjusting a patient's sitting posture to effectively relieve the buttock pressure. To analyze the correlation between the dynamic pressure profiles of an air cell with a patient's weight, a projection Moiré system was adopted to measure the deformation of an air cell and its associated stress distribution. Combining a full-field deformation imaging with air pressure measured within an air cell, the patient's weight and the stress distribution can be simultaneously obtained. By integrating a full-field optical metrology with a time varying pressure sensor output coupled with different active air control algorithms for various designs, we can tailor the ratio of the air cells. Our preliminary data suggests that this newly developed smart air cushion has the potential to selectively reduce localized compression on the tissues at the buttocks. Furthermore, it can take a patient's weight which is an additional benefit so that medical personnel can reference it to prescribe the correct drug dosages.

Determination of Water Vapor Pressure Over Corrosive Chemicals Versus Temperature Using Raman Spectroscopy as Exemplified with 85.5% Phosphoric Acid.

PubMed

Rodier, Marion; Li, Qingfeng; Berg, Rolf Willestofte; Bjerrum, Niels Janniksen

2016-07-01

A method to determine the water vapor pressure over a corrosive substance was developed and tested with 85.5 ± 0.4% phosphoric acid. The water vapor pressure was obtained at a range of temperatures from ∼25 ℃ to ∼200 ℃ using Raman spectrometry. The acid was placed in an ampoule and sealed with a reference gas (either hydrogen or methane) at a known pressure (typically ∼0.5 bar). By comparing the Raman signals from the water vapor and the references, the water pressure was determined as a function of temperature. A considerable amount of data on the vapor pressure of phosphoric acid are available in the literature, to which our results could successfully be compared. A record value of the vapor pressure, 3.40 bar, was determined at 210 ℃. The method required a determination of the precise Raman scattering ratios between the substance, water, and the used reference gas, hydrogen or methane. In our case the scattering ratios between water and reference ν1 Q-branches were found to be 1.20 ± 0.03 and 0.40 ± 0.02 for H2 and CH4, respectively. © The Author(s) 2016.

Selected Gravity Models in Terms of the fit to the GOCE Kinematic Orbit in the Dynamic Orbit Determination Process

NASA Astrophysics Data System (ADS)

Bobojć, Andrzej; Drożyner, Andrzej; Rzepecka, Zofia

2017-04-01

The work includes the comparison of performance of selected geopotential models in the dynamic orbit estimation of the satellite of the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) mission. This was realized by fitting estimated orbital arcs to the official centimeter-accuracy GOCE kinematic orbit which is provided by the European Space Agency. The Cartesian coordinates of kinematic orbit were treated as observations in the orbit estimation. The initial satellite state vector components were corrected in an iterative process with respect to the J2000.0 inertial reference frame using the given geopotential model, the models describing the remaining gravitational perturbations and the solar radiation pressure. Taking the obtained solutions into account, the RMS values of orbital residuals were computed. These residuals result from the difference between the determined orbit and the reference one - the GOCE kinematic orbit. The performance of selected gravity models was also determined using various orbital arc lengths. Additionally, the RMS fit values were obtained for some gravity models truncated at given degree and order of spherical harmonic coefficients. The advantage of using the kinematic orbit is its independence from any a priori dynamical models. For the research such GOCE-independent gravity models as HUST-Grace2016s, ITU_GRACE16, ITSG-Grace2014s, ITSG-Grace2014k, GGM05S, Tongji-GRACE01, ULUX_CHAMP2013S, ITG-GRACE2010S, EIGEN-51C, EIGEN5S, EGM2008 and EGM96 were adopted.

Application of the coplanar principle to dynamic epidural pressure measurements.

PubMed

Beck, J; Schettini, A; Salton, R

1984-10-01

The application of the coplanar principle to dynamic epidural pressure measurements was investigated in vitro. The authors used a coplanar pressure-displacement transducer, commonly employed to measure the viscoelastic properties of brain tissue in vivo. The present studies were performed using canine dura and a specially constructed fluid-filled chamber. The accuracy of the technique was assessed by comparing the pressure in the chamber recorded by the coplanar transducer to the pressure measured by a transducer directly vented to the chamber. The results show that the coplanar principle remained valid for dynamic measurements with the transducer under a variety of conditions.

Dynamism or Disorder at High Pressures?

NASA Astrophysics Data System (ADS)

Angel, R. J.; Bismayer, U.; Marshall, W. G.

2002-12-01

Phase transitions in minerals at elevated temperatures typically involve dynamics as a natural consequence of the increase in thermal energy available to the system. Classic examples include quartz, cristobalite, and carbonates in which the high-temperature, high symmetry phase is dynamically disordered. This disorder has important thermodynamic consequences, including displacement and curvature of phase boundaries (e.g. calcite-aragonite). In other minerals such as clinopyroxenes and anorthite feldspar, the dynamic behaviour is restricted to the neighbourhood of the phase transition. The fundamental question is whether increasing pressure generally suppresses such dynamic behaviour (as in anorthite; Angel, 1988), or not. In the latter case it must be included in thermodynamic models of high-pressure phase equilibria and seismological modelling of the mantle; the potential dynamics and softening in stishovite may provide the critical observational constraint on the presence or otherwise of free silica in the lower mantle. We have continued to use the lead phosphate as a prototype ferroelastic in which to understand dynamic behaviour, simply because its dynamics and transition behaviour is far better characterised than any mineral. Furthermore, the phase transition is at a pressure where experimental difficulties do not dominate the experimental results. Our previous neutron diffraction study (Angel et al., 2001) revealed that some disorder, either dynamic or static, is retained in the high-symmetry, high-pressure phase just above the phase transition. New neutron diffraction data on the pure material now suggests that this disorder slowly decreases with increasing pressure until at twice the transition pressure it is ordered. Further data for doped material provides insights into the nature of this disorder. Angel (1988) Amer. Mineral. 73:1114. Angel et al (2001) J PhysC 13: 5353.

Research on calibration method of downhole optical fiber temperature measurement and its application in SAGD well

NASA Astrophysics Data System (ADS)

Lu, Zhiwei; Han, Li; Hu, Chengjun; Pan, Yong; Duan, Shengnan; Wang, Ningbo; Li, Shijian; Nuer, Maimaiti

2017-10-01

With the development of oil and gas fields, the accuracy and quantity requirements of real-time dynamic monitoring data needed for well dynamic analysis and regulation are increasing. Permanent, distributed downhole optical fiber temperature and pressure monitoring and other online real-time continuous data monitoring has become an important data acquisition and transmission technology in digital oil field and intelligent oil field construction. Considering the requirement of dynamic analysis of steam chamber developing state in SAGD horizontal wells in F oil reservoir in Xinjiang oilfield, it is necessary to carry out real-time and continuous temperature monitoring in horizontal section. Based on the study of the principle of optical fiber temperature measurement, the factors that cause the deviation of optical fiber temperature sensing are analyzed, and the method of fiber temperature calibration is proposed to solve the problem of temperature deviation. Field application in three wells showed that it could attain accurate measurement of downhole temperature by temperature correction. The real-time and continuous downhole distributed fiber temperature sensing technology has higher application value in the reservoir management of SAGD horizontal wells. It also has a reference for similar dynamic monitoring in reservoir production.

First principles investigation of structural, mechanical, dynamical and thermodynamic properties of AgMg under pressure

NASA Astrophysics Data System (ADS)

Cui, Rong Hua; Chao Dong, Zheng; Gui Zhong, Chong

2017-12-01

The effects of pressure on the structural, mechanical, dynamical and thermodynamic properties of AgMg have been investigated using first principles based on density functional theory. The optimized lattice constants agree well with previous experimental and theoretical results. The bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio and Debye temperature under pressures were calculated. The calculated results of Cauchy pressure and B/G ratio indicate that AgMg shows ductile nature. Phonon dispersion curves suggest the dynamical stability of AgMg. The pressure dependent behavior of thermodynamic properties are calculated, the Helmholtz free energy and internal energy increase with increase of pressure, while entropy and heat capacity decrease.

Fluid-structure interaction dynamic simulation of spring-loaded pressure relief valves under seismic wave

NASA Astrophysics Data System (ADS)

Lv, Dongwei; Zhang, Jian; Yu, Xinhai

2018-05-01

In this paper, a fluid-structure interaction dynamic simulation method of spring-loaded pressure relief valve was established. The dynamic performances of the fluid regions and the stress and strain of the structure regions were calculated at the same time by accurately setting up the contact pairs between the solid parts and the coupling surfaces between the fluid regions and the structure regions. A two way fluid-structure interaction dynamic simulation of a simplified pressure relief valve model was carried out. The influence of vertical sinusoidal seismic waves on the performance of the pressure relief valve was preliminarily investigated by loading sine waves. Under vertical seismic waves, the pressure relief valve will flutter, and the reseating pressure was affected by the amplitude and frequency of the seismic waves. This simulation method of the pressure relief valve under vertical seismic waves can provide effective means for investigating the seismic performances of the valves, and make up for the shortcomings of the experiment.

Preliminary characterization of an expanding flow of siloxane vapor MDM

NASA Astrophysics Data System (ADS)

Spinelli, A.; Cozzi, F.; Cammi, G.; Zocca, M.; Gaetani, P.; Dossena, V.; Guardone, A.

2017-03-01

The early experimental results on the characterization of expanding flows of siloxane vapor MDM (C8H24O2Si3, octamethyltrisiloxane) are presented. The measurements were performed on the Test Rig for Organic VApors (TROVA) at the CREA Laboratory of Politecnico di Milano. The TROVA test-rig was built in order to investigate the non-ideal compressible-fluid behavior of typical expanding flows occurring within organic Rankine cycles (ORC) turbine passages. The test rig implements a batch Rankine cycle where a planar converging-diverging nozzle replaces the turbine and represents a test section. Investigations related to both fields of non-ideal compressible-fluid dynamics fundamentals and turbomachinery are allowed. The nozzle can be operated with different working fluids and operating conditions aiming at measuring independently the pressure, the temperature and the velocity field and thus providing data to verify the thermo-fluid dynamic models adopted to predict the behavior of these flows. The limiting values of pressure and temperature are 50 bar and 400 °C respectively. The early measurements are performed along the nozzle axis, where an isentropic process is expected to occur. In particular, the results reported here refer to the nozzle operated in adapted conditions using the siloxane vapor MDM as working fluid in thermodynamic regions where mild to medium non-ideal compressible-fluid effects are present. Both total temperature and total pressure of the nozzle are measured upstream of the test section, while static pressure are measured along the nozzle axis. Schlieren visualizations are also carried out in order to complement the pressure measurement with information about the 2D density gradient field. The Laser Doppler Velocimetry technique is planned to be used in the future for velocity measurements. The measured flow field has also been interpreted by resorting to the quasi-one-dimensional theory and two dimensional CFD viscous calculation. In both cases state-of-the-art thermodynamic models were applied.

Molecular dynamics simulations of shock waves in hydroxyl-terminated polybutadiene melts: Mechanical and structural responses

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

Fröhlich, Markus G., E-mail: FroehlichM@missouri.edu, E-mail: ThompsonDon@missouri.edu; Sewell, Thomas D., E-mail: SewellT@missouri.edu; Thompson, Donald L., E-mail: FroehlichM@missouri.edu, E-mail: ThompsonDon@missouri.edu

2014-01-14

The mechanical and structural responses of hydroxyl-terminated cis-1,4-polybutadiene melts to shock waves were investigated by means of all-atom non-reactive molecular dynamics simulations. The simulations were performed using the OPLS-AA force field but with the standard 12-6 Lennard-Jones potential replaced by the Buckingham exponential-6 potential to better represent the interactions at high compression. Monodisperse systems containing 64, 128, and 256 backbone carbon atoms were studied. Supported shock waves were generated by impacting the samples onto stationary pistons at impact velocities of 1.0, 1.5, 2.0, and 2.5 km s{sup −1}, yielding shock pressures between approximately 2.8 GPa and 12.5 GPa. Single-molecule structuralmore » properties (squared radii of gyration, asphericity parameters, and orientational order parameters) and mechanical properties (density, shock pressure, shock temperature, and shear stress) were analyzed using a geometric binning scheme to obtain spatio-temporal resolution in the reference frame centered on the shock front. Our results indicate that while shear stress behind the shock front is relieved on a ∼0.5 ps time scale, a shock-induced transition to a glass-like state occurs with a concomitant increase of structural relaxation times by several orders of magnitude.« less

20 plus Years of Computational Fluid Dynamics for the Space Shuttle

NASA Technical Reports Server (NTRS)

Gomez, Reynaldo J., III

2011-01-01

This slide presentation reviews the use of computational fluid dynamics in performing analysis of the space shuttle with particular reference to the return to flight analysis and other shuttle problems. Slides show a comparison of pressure coefficient with the shuttle ascent configuration between the wind tunnel test and the computed values. the evolution of the grid system for the space shuttle launch vehicle (SSLv) from the early 80's to one in 2004, the grid configuration of the bipod ramp redesign from the original design to the current configuration, charts with the computations showing solid rocket booster surface pressures from wind tunnel data, calculated over two grid systems (i.e., the original 14 grid system, and the enhanced 113 grid system), and the computed flight orbiter wing loads are compared with strain gage data on STS-50 during flight. The loss of STS-107 initiated an unprecedented review of all external environments. The current SSLV grid system of 600+ grids, 1.8 Million surface points and 95+ million volume points is shown. The inflight entry analyses is shown, and the use of Overset CFD as a key part to many external tank redesign and debris assessments is discussed. The work that still remains to be accomplished for future shuttle flights is discussed.

The Dynamic Gait Index in Evaluating Patients with Normal Pressure Hydrocephalus for Cerebrospinal Fluid Diversion.

PubMed

Chivukula, Srinivas; Tempel, Zachary J; Zwagerman, Nathan T; Newman, W Christopher; Shin, Samuel S; Chen, Ching-Jen; Gardner, Paul A; McDade, Eric M; Ducruet, Andrew F

2015-12-01

Diagnosing normal pressure hydrocephalus (NPH) remains challenging. Most clinical tests currently used to evaluate suspected NPH patients for shunt surgery are invasive, require inpatient admission, and are not without complications. An objective, noninvasive, and low-cost alternative would be ideal. A retrospective review was performed of prospectively collected dynamic gait index (DGI) scores, obtained at baseline and on every day of a 3- to 5-day lumbar cerebrospinal fluid (CSF) drainage trial on patients with suspected NPH at our institution. Between 2003 and 2014, 170 patients were suspected to have primary NPH (166, 97.6%) or secondary NPH (4, 2.4%). Using responsiveness to lumbar CSF drainage and subsequent shunting as the reference standard, we found that a baseline DGI ≥ 7 was found to have significant ability in selecting patients for permanent CSF diverting shunt surgery: sensitivity of 84.2% (95% confidence interval [95% CI]: 75.6%-90.2%), specificity of 80.6% (95% CI 70.0%-88.0%), and diagnostic odds ratio of 22.1 (95% CI 9.9-49.3). A baseline DGI ≥ 7 appears to provide an objective, low-cost, noninvasive measure to select patients with suspected NPH for a positive response to CSF diversion with high sensitivity, specificity and diagnostic odds ratio. Copyright © 2015 Elsevier Inc. All rights reserved.

Dynamic Pressure Probes Developed for Supersonic Flow-Field Measurements

NASA Technical Reports Server (NTRS)

Porro, A. Robert

2001-01-01

A series of dynamic flow-field pressure probes were developed for use in large-scale supersonic wind tunnels at the NASA Glenn Research Center. These flow-field probes include pitot and static pressure probes that can capture fast-acting flow-field pressure transients occurring on a millisecond timescale. The pitot and static probes can be used to determine local Mach number time histories during a transient event. The flow-field pressure probe contains four major components: 1) Static pressure aerodynamic tip; 2) Pressure-sensing cartridge assembly; 3) Pitot pressure aerodynamic tip; 4) Mounting stem. This modular design allows for a variety of probe tips to be used for a specific application. Here, the focus is on flow-field pressure measurements in supersonic flows, so we developed a cone-cylinder static pressure tip and a pitot pressure tip. Alternatively, probe tips optimized for subsonic and transonic flows could be used with this design. The pressure-sensing cartridge assembly allows the simultaneous measurement of steady-state and transient pressure which allows continuous calibration of the dynamic pressure transducer.

The Dynamic Compression Brace for Pectus Carinatum: Intermediate Results in 286 Patients.

PubMed

de Beer, Sjoerd A; Gritter, Martin; de Jong, Justin R; van Heurn, Ernst L W

2017-06-01

Dynamic brace compression is a novel treatment for patients with pectus carinatum. The dynamic compression system contains a device to measure the flexibility of the thoracic wall and regulate the pressure of the brace. Patients referred to our pediatric surgical center were screened for treatment with the dynamic compression brace. Patients with a pressure of initial correction (PIC) of 10.0 pounds per square inch or less were offered treatment with the brace. Patients with a PIC above 10.0 pounds per square inch were offered surgical correction. Between March 2013 and April 2016, 286 patients were treated with the brace; 260 were male (91%) and 26 were female (9%). Their mean age was 14 years (range, 4 to 21 years). Seventy-eight patients completed brace treatment; the mean treatment time was 14 months. Twenty-seven patients abandoned treatment because of lack of motivation, loss to follow-up, persistent protrusion of the sternal bone or flaring that required surgical correction, failure of treatment because of a bifid rib, fear of locking the brace, and delayed correction. One hundred eighty-one patients are still wearing the brace, either in the active or in the retainer phase. Patients with a high PIC also showed improvement when they were compliant. Adverse events were minor and included skin lesions (n = 4, 1%) and vasovagal reactions at the start of therapy (n = 3, 1%). These data show that brace therapy can be considered a valuable treatment option to correct pectus carinatum in patients with a flexible thorax. Copyright © 2017 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

High Pressure Oxidizer Turbopump (HPOTP) inducer dynamic design environment

NASA Technical Reports Server (NTRS)

Herda, D. A.; Gross, R. S.

1995-01-01

The dynamic environment must be known to evaluate high pressure oxidizer turbopump inducer fatigue life. This report sets the dynamic design loads for the alternate turbopump inducer as determined by water-flow rig testing. Also, guidelines are given for estimating the dynamic environment for other inducer and impeller applications.

On the possibility to develop an advanced non-equilibrium model of depressurisation in two-phase fluids

NASA Astrophysics Data System (ADS)

Duc, Linh Do; Horák, Vladimír; Kulish, Vladimir; Lukáč, Tomáš

2017-01-01

Carbon dioxide is widely used as the power gas in the gas guns community due to its ease of handling, storability at room temperature, and high vapor pressure depending only upon temperature, but not a tank size, as long as some liquid carbon dioxide remains in the tank. This high vapor pressure can be used as the pressurant, making it what is referred to as a self-pressurising propellant. However, as a two-phase substance, carbon dioxide does have its drawbacks: (1) vaporization of liquefied CO2 inside a tank when shooting rapidly or a lot causes the tank to get cool, resulting in pressure fluctuations that makes the gun's performance and accuracy worse, (2) solid carbon dioxide that is also known as dry ice can appear on the output valve of the tank while shooting and it can cause damage or slow the gun's performance down, if it works its way into some control components, including the barrel of the gun. Hence, it is crucial to obtain a scientific understanding of carbon dioxide behavior and further the discharge characteristics of a wide range of pressure-tank configurations. For the purpose of satisfying this goal, a comprehensive discharge mathematical model for carbon dioxide tank dynamics is required. In this paper, the possibility to develop an advanced non-equilibrium model of depressurization in two-phase fluids is discussed.

Rambling and trembling in response to body loading.

PubMed

Tahayor, Behdad; Riley, Zachary A; Mahmoudian, Armaghan; Koceja, David M; Hong, Siang Lee

2012-04-01

Various studies have suggested that postural sway is controlled by at least two subsystems. Rambling-Trembling analysis is a widely accepted methodology to dissociate the signals generated by these two hypothetical subsystems. The core assumption of this method is based on the equilibrium point hypothesis which suggests that the central nervous system preserves upright standing by transiently shifting the center of pressure (COP) from one equilibrium point to another. The trajectory generated by this shifting is referred to as rambling and its difference from the original COP signal is referred to as trembling. In this study we showed that these two components of COP are differentially affected when standing with external loads. Using Detrended Fluctuation analysis, we compared the pattern of these two signals in different configurations of body loading. Our findings suggest that by applying an external load, the dynamics of the trembling component is altered independently of the area of postural sway and also independently of the rambling component. The dynamics of rambling changed only during the backloading condition in which the postural sway area also substantially increased. It can be suggested that during loaded standing, the trembling mechanism (which is suggested to be activated by peripheral mechanisms and reflexes) is altered without affecting the central influence on the shifts of the equilibrium point.

Measuring acoustic impedances using a semi-infinite waveguide reference: Applications to wind instruments and vocal tracts

NASA Astrophysics Data System (ADS)

Wolfe, Joe; Smith, John; Tann, John; France, Ryan

2002-11-01

Acoustic pressures may generally be measured with much greater sensitivity, dynamic range, and frequency response than acoustic currents. Consequently, most measurements of acoustic impedance consist of comparison with standard impedances. The method reported here uses a semi-infinite waveguide as the reference because its impedance is purely resistive, frequency independent and accurately known, independent of theories of the boundary layer. Waveguides are effectively infinite for pulses shorter than the echo return time, or if the attenuation due to wall losses (typically 80 dB) exceeds the dynamic range of the experiment. The measurement signal from a high output impedance source is calibrated to have Fourier components proportional to fn, where n may be 1 for convenience or chosen to improve the signal:noise ratio. The method has been used on diverse systems over the range 50 Hz to 13 kHz. When applied to systems with simple geometries, the technique yields results with a little higher wall losses than those expected from the calculations of Rayleigh and Benade. Discontinuities introduce further losses as well as the expected departures from simple one-dimensional models. Measurements on musical wind instruments and on the human vocal tract are reported. [Work supported by the Australian Research Council.

Monitoring intracranial pressure based on F-P

NASA Astrophysics Data System (ADS)

Cai, Ting; Tong, Xinglin; Chen, Guangxi

2013-09-01

Intracranial pressure is an important monitoring indicator of neurosurgery. In this paper we adopt all-fiber FP fiber optic sensor, using a minimally invasive operation to realize real-time dynamic monitoring intracranial pressure of the hemorrhage rats, and observe their intracranial pressure regularity of dynamic changes. Preliminary results verify the effectiveness of applications and feasibility, providing some basis for human brain minimally invasive intracranial pressure measurement.

Measurement of the True Dynamic and Static Pressures in Flight

NASA Technical Reports Server (NTRS)

Kiel, Georg

1939-01-01

In this report, two reliable methods are presented, with the aid of which the undisturbed flight dynamic pressure and the true static pressure may be determined without error. These problems were solved chiefly through practical flight tests.

Asymmetric Fuzzy Control of a Positive and Negative Pneumatic Pressure Servo System

NASA Astrophysics Data System (ADS)

Yang, Gang; Du, Jing-Min; Fu, Xiao-Yun; Li, Bao-Ren

2017-11-01

The pneumatic pressure control systems have been used in some fields. However, the researches on pneumatic pressure control mainly focus on constant pressure regulation. Poor dynamic characteristics and strong nonlinearity of such systems limit its application in the field of pressure tracking control. In order to meet the demand of generating dynamic pressure signal in the application of the hardware-in-the-loop simulation of aerospace engineering, a positive and negative pneumatic pressure servo system is provided to implement dynamic adjustment of sealed chamber pressure. A mathematical model is established with simulation and experiment being implemented afterwards to discuss the characteristics of the system, which shows serious asymmetry in the process of charging and discharging. Based on the analysis of the system dynamics, a fuzzy proportional integral derivative (PID) controller with asymmetric fuzzy compensator is proposed. Different from conventional adjusting mechanisms employing the error and change in error of the controlled variable as input parameters, the current chamber pressure and charging or discharging state are chosen as inputs of the compensator, which improves adaptability. To verify the effectiveness and performance of the proposed controller, the comparison experiments tracking sinusoidal and square wave commands are conducted. Experimental results show that the proposed controller can obtain better dynamic performance and relatively consistent control performance across the scope of work (2-140 kPa). The research proposes a fuzzy control method to overcome asymmetry and enhance adaptability for the positive and negative pneumatic pressure servo system.

Implanted Blood-Pressure-Measuring Device

NASA Technical Reports Server (NTRS)

Fischell, Robert E.

1988-01-01

Arterial pressure compared with ambient bodily-fluid pressure. Implanted apparatus, capable of measuring blood pressure of patient, includes differential-pressure transducer connected to pressure sensor positioned in major artery. Electrical signal is function of differential pressure between blood-pressure sensor and reference-pressure sensor transmitted through skin of patient to recorder or indicator.

Toward a mineral physics reference model for the Moon's core.

PubMed

Antonangeli, Daniele; Morard, Guillaume; Schmerr, Nicholas C; Komabayashi, Tetsuya; Krisch, Michael; Fiquet, Guillaume; Fei, Yingwei

2015-03-31

The physical properties of iron (Fe) at high pressure and high temperature are crucial for understanding the chemical composition, evolution, and dynamics of planetary interiors. Indeed, the inner structures of the telluric planets all share a similar layered nature: a central metallic core composed mostly of iron, surrounded by a silicate mantle, and a thin, chemically differentiated crust. To date, most studies of iron have focused on the hexagonal closed packed (hcp, or ε) phase, as ε-Fe is likely stable across the pressure and temperature conditions of Earth's core. However, at the more moderate pressures characteristic of the cores of smaller planetary bodies, such as the Moon, Mercury, or Mars, iron takes on a face-centered cubic (fcc, or γ) structure. Here we present compressional and shear wave sound velocity and density measurements of γ-Fe at high pressures and high temperatures, which are needed to develop accurate seismic models of planetary interiors. Our results indicate that the seismic velocities proposed for the Moon's inner core by a recent reanalysis of Apollo seismic data are well below those of γ-Fe. Our dataset thus provides strong constraints to seismic models of the lunar core and cores of small telluric planets. This allows us to propose a direct compositional and velocity model for the Moon's core.

Historical changes of the Mediterranean Sea ecosystem: modelling the role and impact of primary productivity and fisheries changes over time

NASA Astrophysics Data System (ADS)

Piroddi, Chiara; Coll, Marta; Liquete, Camino; Macias, Diego; Greer, Krista; Buszowski, Joe; Steenbeek, Jeroen; Danovaro, Roberto; Christensen, Villy

2017-03-01

The Mediterranean Sea has been defined “under siege” because of intense pressures from multiple human activities; yet there is still insufficient information on the cumulative impact of these stressors on the ecosystem and its resources. We evaluate how the historical (1950-2011) trends of various ecosystems groups/species have been impacted by changes in primary productivity (PP) combined with fishing pressure. We investigate the whole Mediterranean Sea using a food web modelling approach. Results indicate that both changes in PP and fishing pressure played an important role in driving species dynamics. Yet, PP was the strongest driver upon the Mediterranean Sea ecosystem. This highlights the importance of bottom-up processes in controlling the biological characteristics of the region. We observe a reduction in abundance of important fish species (~34%, including commercial and non-commercial) and top predators (~41%), and increases of the organisms at the bottom of the food web (~23%). Ecological indicators, such as community biomass, trophic levels, catch and diversity indicators, reflect such changes and show overall ecosystem degradation over time. Since climate change and fishing pressure are expected to intensify in the Mediterranean Sea, this study constitutes a baseline reference for stepping forward in assessing the future management of the basin.

The effect of a dynamic PCL brace on patellofemoral compartment pressures in PCL-and PCL/PLC-deficient knees.

PubMed

Welch, Tyler; Keller, Thomas; Maldonado, Ruben; Metzger, Melodie; Mohr, Karen; Kvitne, Ronald

2017-12-01

The natural history of posterior cruciate ligament (PCL) deficiency includes the development of arthrosis in the patellofemoral joint (PFJ). The purpose of this biomechanical study was to evaluate the hypothesis that dynamic bracing reduces PFJ pressures in PCL- and combined PCL/posterolateral corner (PLC)-deficient knees. Controlled Laboratory Study. Eight fresh frozen cadaveric knees with intact cruciate and collateral ligaments were included. PFJ pressures and force were measured using a pressure mapping system via a lateral arthrotomy at knee flexion angles of 30°, 60°, 90°, and 120° in intact, PCL-deficient, and PCL/PLC-deficient knees under a combined quadriceps/hamstrings load of 400 N/200 N. Testing was then repeated in PCL- and PCL/PLC-deficient knees after application of a dynamic PCL brace. Application of a dynamic PCL brace led to a reduction in peak PFJ pressures in PCL-deficient knees. In addition, the brace led to a significant reduction in peak pressures in PCL/PLC-deficient knees at 60°, 90°, and 120° of flexion. Application of the dynamic brace also led to a reduction in total PFJ force across all flexion angles for both PCL- and PCL/PLC-deficient knees. Dynamic bracing reduces PFJ pressures in PCL- and combined PCL/PLC-deficient knees, particularly at high degrees of knee flexion.

Experimental Combustion Dynamics Behavior of a Multi-Element Lean Direct Injection (LDI) Gas Turbine Combustor

NASA Technical Reports Server (NTRS)

Acosta, Waldo A.; Chang, Clarence T.

2016-01-01

An experimental investigation of the combustion dynamic characteristics of a research multi-element lean direct injection (LDI) combustor under simulated gas turbine conditions was conducted. The objective was to gain a better understanding of the physical phenomena inside a pressurized flametube combustion chamber under acoustically isolated conditions. A nine-point swirl venturi lean direct injection (SV-LDI) geometry was evaluated at inlet pressures up to 2,413 kPa and non-vitiated air temperatures up to 867 K. The equivalence ratio was varied to obtain adiabatic flame temperatures between 1388 K and 1905 K. Dynamic pressure measurements were taken upstream of the SV-LDI, in the combustion zone and downstream of the exit nozzle. The measurements showed that combustion dynamics were fairly small when the fuel was distributed uniformly and mostly due to fluid dynamics effects. Dynamic pressure fluctuations larger than 40 kPa at low frequencies were measured at 653 K inlet temperature and 1117 kPa inlet pressure when fuel was shifted and the pilot fuel injector equivalence ratio was increased to 0.72.

Ventilation-Induced Modulation of Pulse Oximeter Waveforms: A Method for the Assessment of Early Changes in Intravascular Volume During Spinal Fusion Surgery in Pediatric Patients.

PubMed

Alian, Aymen A; Atteya, Gourg; Gaal, Dorothy; Golembeski, Thomas; Smith, Brian G; Dai, Feng; Silverman, David G; Shelley, Kirk

2016-08-01

Scoliosis surgery is often associated with substantial blood loss, requiring fluid resuscitation and blood transfusions. In adults, dynamic preload indices have been shown to be more reliable for guiding fluid resuscitation, but these indices have not been useful in children undergoing surgery. The aim of this study was to introduce frequency-analyzed photoplethysmogram (PPG) and arterial pressure waveform variables and to study the ability of these parameters to detect early bleeding in children during surgery. We studied 20 children undergoing spinal fusion. Electrocardiogram, arterial pressure, finger pulse oximetry (finger PPG), and airway pressure waveforms were analyzed using time domain and frequency domain methods of analysis. Frequency domain analysis consisted of calculating the amplitude density of PPG and arterial pressure waveforms at the respiratory and cardiac frequencies using Fourier analysis. This generated 2 measurements: The first is related to slow mean arterial pressure modulation induced by ventilation (also known as DC modulation when referring to the PPG), and the second corresponds to pulse pressure modulation (AC modulation or changes in the amplitude of pulse oximeter plethysmograph when referring to the PPG). Both PPG and arterial pressure measurements were divided by their respective cardiac pulse amplitude to generate DC% and AC% (normalized values). Standard hemodynamic data were also recorded. Data at baseline and after bleeding (estimated blood loss about 9% of blood volume) were presented as median and interquartile range and compared using Wilcoxon signed-rank tests; a Bonferroni-corrected P value <0.05 was considered statistically significant. There were significant increases in PPG DC% (median [interquartile range] = 359% [210 to 541], P = 0.002), PPG AC% (160% [87 to 251], P = 0.003), and arterial DC% (44% [19 to 84], P = 0.012) modulations, respectively, whereas arterial AC% modulations showed nonsignificant increase (41% [1 to 85], P = 0.12). The change in PPG DC% was significantly higher than that in PPG AC%, arterial DC%, arterial AC%, and systolic blood pressure with P values of 0.008, 0.002, 0.003, and 0.002, respectively. Only systolic blood pressure showed significant changes (11% [4 to 21], P = 0.003) between bleeding phase and baseline. Finger PPG and arterial waveform parameters (using frequency analysis) can track changes in blood volume during the bleeding phase, suggesting the potential for a noninvasive monitor for tracking changes in blood volume in pediatric patients. PPG waveform baseline modulation (PPG DC%) was more sensitive to changes in venous blood volume when compared with respiration-induced modulation seen in the arterial pressure waveform.

Copper nanocluster growth at experimental conditions using temperature accelerated dynamics

NASA Astrophysics Data System (ADS)

Dias, C. S.; Cadilhe, A. C.; Voter, A. F.

2009-03-01

We study the dynamics of vapor phase cluster growth near experimental conditions of pressure at temperatures below 200K. To this end, we carried out temperature accelerated dynamics (TAD) simulations at different vapor pressures to characterize the morphology of the resulting nanoparticles, which leads to a range of values of the flux of impinging atoms at fixed vapor temperature. At typical experimental pressures of 10-3-10-4 bar TAD provides substantial boost over regular Molecular Dynamics (MD). TAD is also advantageous over MD, regarding the sampling of the network of visited states, which provides a deeper understanding of the evolution of the system. We characterize the growth of such clusters at different vapor pressures.

Numerical research of dynamic characteristics in tower solar cavity receiver based on step-change radiation flux

NASA Astrophysics Data System (ADS)

Chen, Zhengwei; Wang, Yueshe; Hao, Yun; Wang, Qizhi

2013-07-01

The solar cavity receiver is an important light-energy to thermal-energy convector in the tower solar thermal power plant system. The heat flux in the inner surface of the cavity will show the characteristics of non-continuous step change especially in non-normal and transient weather conditions, which may result in a continuous dynamic variation of the characteristic parameters. Therefore, the research of dynamic characteristics of the receiver plays a very important role in the operation and the control safely in solar cavity receiver system. In this paper, based on the non-continuous step change of radiation flux, a non-linear dynamic model is put forward to obtain the effects of the non-continuous step change radiation flux and step change feed water flow on the receiver performance by sequential modular approach. The subject investigated in our study is a 1MW solar power station constructed in Yanqing County, Beijing. This study has obtained the dynamic responses of the characteristic parameters in the cavity receiver, such as drum pressure, drum water level, main steam flow and main steam enthalpy under step change radiation flux. And the influence law of step-change feed water flow to the dynamic characteristics in the receiver also has been analyzed. The results have a reference value for the safe operation and the control in solar cavity receiver system.

CLINICAL AVIATION MEDICINE RESEARCH: COMPARISON OF SIMULTANEOUS MEASUREMENTS OF INTRA-AORTIC AND AUSCULTATORY BLOOD PRESSURES WITH PRESSURE-FLOW DYNAMICS DURING REST AND EXERCISE,

DTIC Science & Technology

recorded simultaneously by auscultation of the brachial artery; and (2) to study the pattern of pressure and flow dynamics during bicycle work at moderate...strenuous and maximal intensities. In most instances systolic pressures measured by auscultation were in close agreement with the directly recorded

Tracking a Solar Wind Dynamic Pressure Pulses' Impact Through the Magnetosphere Using the Heliophysics System Observatory

NASA Astrophysics Data System (ADS)

Vidal-Luengo, S.; Moldwin, M.

2017-12-01

During northward Interplanetary Magnetic Field (IMF) Bz conditions, the magnetosphere acts as a closed "cavity" and reacts to solar wind dynamic pressure pulses more simply than during southward IMF conditions. Effects of solar wind dynamic pressure have been observed as geomagnetic lobe compressions depending on the characteristics of the pressure pulse and the spacecraft location. One of the most important aspects of this study is the incorporation of simultaneous observations by different missions, such as WIND, CLUSTER, THEMIS, MMS, Van Allen Probes and GOES as well as magnetometer ground stations that allow us to map the magnetosphere response at different locations during the propagation of a pressure pulse. In this study we used the SYM-H as an indicator of dynamic pressure pulses occurrence from 2007 to 2016. The selection criteria for events are: (1) the increase in the index must be bigger than 10 [nT] and (2) the rise time must be in less than 5 minutes. Additionally, the events must occur under northward IMF and at the same time at least one spacecraft has to be located in the magnetosphere nightside. Using this methodology we found 66 pressure pulse events for analysis. Most of them can be classified as step function pressure pulses or as sudden impulses (increase followed immediately by a decrease of the dynamic pressure). Under these two categories the results show some systematic signatures depending of the location of the spacecraft. For both kind of pressure pulse signatures, compressions are observed on the dayside. However, on the nightside compressions and/or South-then-North magnetic signatures can be observed for step function like pressure pulses, meanwhile for the sudden impulse kind of pressure pulses the magnetospheric response seems to be less global and more dependent on the local conditions.

Control algorithms for aerobraking in the Martian atmosphere

NASA Technical Reports Server (NTRS)

Ward, Donald T.; Shipley, Buford W., Jr.

1991-01-01

The Analytic Predictor Corrector (APC) and Energy Controller (EC) atmospheric guidance concepts were adapted to control an interplanetary vehicle aerobraking in the Martian atmosphere. Changes are made to the APC to improve its robustness to density variations. These changes include adaptation of a new exit phase algorithm, an adaptive transition velocity to initiate the exit phase, refinement of the reference dynamic pressure calculation and two improved density estimation techniques. The modified controller with the hybrid density estimation technique is called the Mars Hybrid Predictor Corrector (MHPC), while the modified controller with a polynomial density estimator is called the Mars Predictor Corrector (MPC). A Lyapunov Steepest Descent Controller (LSDC) is adapted to control the vehicle. The LSDC lacked robustness, so a Lyapunov tracking exit phase algorithm is developed to guide the vehicle along a reference trajectory. This algorithm, when using the hybrid density estimation technique to define the reference path, is called the Lyapunov Hybrid Tracking Controller (LHTC). With the polynomial density estimator used to define the reference trajectory, the algorithm is called the Lyapunov Tracking Controller (LTC). These four new controllers are tested using a six degree of freedom computer simulation to evaluate their robustness. The MHPC, MPC, LHTC, and LTC show dramatic improvements in robustness over the APC and EC.

Dynamics of phenotypic switching of bacterial cells with temporal fluctuations in pressure

NASA Astrophysics Data System (ADS)

Nepal, Sudip; Kumar, Pradeep

2018-05-01

Phenotypic switching is one of the mechanisms by which bacteria thrive in ever changing environmental conditions around them. Earlier studies have shown that the application of steady high hydrostatic pressure leads to stochastic switching of mesophilic bacteria from a cellular phenotype having a normal cell cycle to another phenotype lacking cell division. Here, we have studied the dynamics of this phenotypic switching with fluctuating periodic pressure using a set of experiments and a theoretical model. Our results suggest that the phenotypic switching rate from high-pressure phenotype to low-pressure phenotype in the reversible regime is larger as compared to the switching rate from low-pressure phenotype to high-pressure phenotype. Furthermore, we find that even though the cell division and elongation are presumably regulated by a large number of genes the underlying physics of the dynamics of stochastic switching at high pressure is captured reasonably well by a simple two-state model.

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

NASA Technical Reports Server (NTRS)

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

1976-01-01

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

Lattice dynamics, elasticity and magnetic abnormality in ordered crystalline alloys Fe3Pt at high pressures

NASA Astrophysics Data System (ADS)

Cheng, Tai-min; Yu, Guo-Liang; Su, Yong; Ge, Chong-Yuan; Zhang, Xin-Xin; Zhu, Lin; Li, Lin

2018-05-01

The ordered crystalline Invar alloy Fe3Pt is in a special magnetic critical state, under which the lattice dynamic stability of the system is extremely sensitive to external pressures. We studied the pressure dependence of enthalpy and magnetism of Fe3Pt in different crystalline alloys by using the first-principles projector augmented-wave method based on the density functional theory. Results show that the P4/mbm structure is the ground state structure and is more stable relative to other structures at pressures below 18.54 GPa. The total magnetic moments of L12, I4/mmm and DO22 structures decrease rapidly with pressure and oscillate near the ferromagnetic collapse critical pressure. At the pressure of 43 GPa, the ferrimagnetic property in DO22 structure becomes apparently strengthened and its volume increases rapidly. The lattice dynamics calculation for L12 structures at high pressures shows that the spontaneous magnetization of the system in ferromagnetic states induces the softening of the transverse acoustic phonon TA1 (M), and there exists a strong spontaneous volume magnetostriction at pressures below 26.95 GPa. Especially, the lattice dynamics stability is sensitive to pressure, in the pressure range between the ferromagnetic collapse critical pressure (41.9 GPa) and the magnetism completely disappearing pressure (57.25 GPa), and near the pressure of phase transition from L12 to P4/mbm structure (27.27 GPa). Moreover, the instability of magnetic structure leads to a prominent elastic modulus oscillation, and the spin polarizability of electrons near the Fermi level is very sensitive to pressures in that the pressure range. The pressure induces the stability of the phonon spectra of the system at pressures above 57.25 GPa.

Diastolic viscous properties of the intact canine left ventricle.

PubMed

Nikolic, S D; Tamura, K; Tamura, T; Dahm, M; Frater, R W; Yellin, E L

1990-08-01

The viscoelastic model of the ventricle predicts that the rate of change of volume (strain rate) is a determinant of the instantaneous pressure in the ventricle during diastole. Because relaxation is not complete before the onset of filling, one cannot distinguish the individual effects of relaxation and viscosity unless the passive and active components that determine the ventricular pressure are separated. To overcome this problem, we used the method of ventricular volume clamping to compare the pressures in the fully relaxed ventricle at a given volume at zero strain rate (static pressure) and high strain rate (dynamic pressure). Six open-chest, fentanyl-anesthetized dogs were instrumented with micromanometers and an electronically controlled mitral valve occluder in series with the electromagnetic flow probe. We reasoned as follows: If there were significant viscosity, then the dynamic pressure would be higher than the static pressure. The static pressure was measured when the ventricle was completely relaxed following a mitral valve occlusion after an arbitrary filling volume had been achieved. The dynamic pressure was determined by delaying the onset of filling until relaxation was complete and then measuring the pressure at the same volume that was achieved when the static pressure was measured. In 19 different hemodynamic situations, the dynamic and static pressures were identical (mean difference, 0.1 +/- 0.8 mm Hg), indicating that in the passive ventricle viscoelastic effects are insignificant and do not contribute to the left ventricular diastolic pressure under normal filling rates.

A Novel Strategy for Selection and Validation of Reference Genes in Dynamic Multidimensional Experimental Design in Yeast

PubMed Central

Cankorur-Cetinkaya, Ayca; Dereli, Elif; Eraslan, Serpil; Karabekmez, Erkan; Dikicioglu, Duygu; Kirdar, Betul

2012-01-01

Background Understanding the dynamic mechanism behind the transcriptional organization of genes in response to varying environmental conditions requires time-dependent data. The dynamic transcriptional response obtained by real-time RT-qPCR experiments could only be correctly interpreted if suitable reference genes are used in the analysis. The lack of available studies on the identification of candidate reference genes in dynamic gene expression studies necessitates the identification and the verification of a suitable gene set for the analysis of transient gene expression response. Principal Findings In this study, a candidate reference gene set for RT-qPCR analysis of dynamic transcriptional changes in Saccharomyces cerevisiae was determined using 31 different publicly available time series transcriptome datasets. Ten of the twelve candidates (TPI1, FBA1, CCW12, CDC19, ADH1, PGK1, GCN4, PDC1, RPS26A and ARF1) we identified were not previously reported as potential reference genes. Our method also identified the commonly used reference genes ACT1 and TDH3. The most stable reference genes from this pool were determined as TPI1, FBA1, CDC19 and ACT1 in response to a perturbation in the amount of available glucose and as FBA1, TDH3, CCW12 and ACT1 in response to a perturbation in the amount of available ammonium. The use of these newly proposed gene sets outperformed the use of common reference genes in the determination of dynamic transcriptional response of the target genes, HAP4 and MEP2, in response to relaxation from glucose and ammonium limitations, respectively. Conclusions A candidate reference gene set to be used in dynamic real-time RT-qPCR expression profiling in yeast was proposed for the first time in the present study. Suitable pools of stable reference genes to be used under different experimental conditions could be selected from this candidate set in order to successfully determine the expression profiles for the genes of interest. PMID:22675547

Effect of inlet-air humidity, temperature, pressure, and reference Mach number on the formation of oxides of nitrogen in a gas turbine combustor

NASA Technical Reports Server (NTRS)

Marchionna, N. R.; Diehl, L. A.; Trout, A. M.

1973-01-01

Tests were conducted to determine the effect of inlet air humidity on the formation of oxides of nitrogen (NOx) from a gas turbine combustor. Combustor inlet air temperature ranged from 506 K (450 F) to 838 K (1050 F). The tests were primarily run at a constant pressure of 6 atmospheres and reference Mach number of 0.065. The NOx emission index was found to decrease with increasing inlet air humidity at a constant exponential rate: NOx = NOx0e-19H (where H is the humidity and the subscript 0 denotes the value at zero humidity). the emission index increased exponentially with increasing normalized inlet air temperature to the 1.14 power. Additional tests made to determine the effect of pressure and reference Mach number on NOx showed that the NOx emission index varies directly with pressure to the 0.5 power and inversely with reference Mach number.

Simple electrolyte solutions: Comparison of DRISM and molecular dynamics results for alkali halide solutions

PubMed Central

Joung, In Suk; Luchko, Tyler; Case, David A.

2013-01-01

Using the dielectrically consistent reference interaction site model (DRISM) of molecular solvation, we have calculated structural and thermodynamic information of alkali-halide salts in aqueous solution, as a function of salt concentration. The impact of varying the closure relation used with DRISM is investigated using the partial series expansion of order-n (PSE-n) family of closures, which includes the commonly used hypernetted-chain equation (HNC) and Kovalenko-Hirata closures. Results are compared to explicit molecular dynamics (MD) simulations, using the same force fields, and to experiment. The mean activity coefficients of ions predicted by DRISM agree well with experimental values at concentrations below 0.5 m, especially when using the HNC closure. As individual ion activities (and the corresponding solvation free energies) are not known from experiment, only DRISM and MD results are directly compared and found to have reasonably good agreement. The activity of water directly estimated from DRISM is nearly consistent with values derived from the DRISM ion activities and the Gibbs-Duhem equation, but the changes in the computed pressure as a function of salt concentration dominate these comparisons. Good agreement with experiment is obtained if these pressure changes are ignored. Radial distribution functions of NaCl solution at three concentrations were compared between DRISM and MD simulations. DRISM shows comparable water distribution around the cation, but water structures around the anion deviate from the MD results; this may also be related to the high pressure of the system. Despite some problems, DRISM-PSE-n is an effective tool for investigating thermodynamic properties of simple electrolytes. PMID:23387564

Towards DMD-Based Estimation and Control of Flow Separation using an Array of Surface Pressure Sensors

NASA Astrophysics Data System (ADS)

Deem, Eric; Cattafesta, Louis; Zhang, Hao; Rowley, Clancy

2016-11-01

Closed-loop control of flow separation requires the spatio-temporal states of the flow to be fed back through the controller in real time. Previously, static and dynamic estimation methods have been employed that provide reduced-order model estimates of the POD-coefficients of the flow velocity using surface pressure measurements. However, this requires a "learning" dataset a priori. This approach is effective as long as the dynamics during control do not stray from the learning dataset. Since only a few dynamical features are required for feedback control of flow separation, many of the details provided by full-field snapshots are superfluous. This motivates a state-observation technique that extracts key dynamical features directly from surface pressure, without requiring PIV snapshots. The results of identifying DMD modes of separated flow through an array of surface pressure sensors in real-time are presented. This is accomplished by employing streaming DMD "on the fly" to surface pressure snapshots. These modal characteristics exhibit striking similarities to those extracted from PIV data and the pressure field obtained via solving Poisson's equation. Progress towards closed-loop separation control based on the dynamic modes of surface pressure will be discussed. Supported by AFOSR Grant FA9550-14-1-0289.

Non-Invasive Method of Determining Absolute Intracranial Pressure

NASA Technical Reports Server (NTRS)

Yost, William T. (Inventor); Cantrell, John H., Jr. (Inventor); Hargens, Alan E. (Inventor)

2004-01-01

A method is presented for determining absolute intracranial pressure (ICP) in a patient. Skull expansion is monitored while changes in ICP are induced. The patient's blood pressure is measured when skull expansion is approximately zero. The measured blood pressure is indicative of a reference ICP value. Subsequently, the method causes a known change in ICP and measured the change in skull expansion associated therewith. The absolute ICP is a function of the reference ICP value, the known change in ICP and its associated change in skull expansion; and a measured change in skull expansion.

Muscle blood flow at onset of dynamic exercise in humans.

PubMed

Rådegran, G; Saltin, B

1998-01-01

To evaluate the temporal relationship between blood flow, blood pressure, and muscle contractions, we continuously measured femoral arterial inflow with ultrasound Doppler at onset of passive exercise and voluntary, one-legged, dynamic knee-extensor exercise in humans. Blood velocity and inflow increased (P < 0.006) with the first relaxation of passive and voluntary exercise, whereas the arterial-venous pressure difference was unaltered [P = not significant (NS)]. During steady-state exercise, and with arterial pressure as a superimposed influence, blood velocity was affected by the muscle pump, peaking (P < 0.001) at approximately 2.5 +/- 0.3 m/s as the relaxation coincided with peak systolic arterial blood pressure; blood velocity decreased (P < 0.001) to 44.2 +/- 8.6 and 28.5 +/- 5.5% of peak velocity at the second dicrotic and diastolic blood pressure notches, respectively. Mechanical hindrance occurred (P < 0.001) during the contraction phase at blood pressures less than or equal to that at the second dicrotic notch. The increase in blood flow (Q) was characterized by a one-component (approximately 15% of peak power output), two-component (approximately 40-70% of peak power output), or three-component exponential model (> or = 75% of peak power output), where Q(t) = Qpassive + delta Q1.[1 - e-(t - TD1/tau 1)]+ delta Q2.[1 - e-(t - TD2/tau 2)]+ delta Q3.[1 - e-(t - TD3/tau 3)]; Qpassive, the blood flow during passive leg movement, equals 1.17 +/- 0.11 l/min; TD is the onset latency; tau is the time constant; delta Q is the magnitude of blood flow rise; and subscripts 1-3 refer to the first, second, and third components of the exponential model, respectively. The time to reach 50% of the difference between passive and voluntary asymptotic blood flow was approximately 2.2-8.9 s. The blood flow leveled off after approximately 10-150 s, related to the power outputs. It is concluded that the elevation in blood flow with the first duty cycle(s) is due to muscle mechanical factors, but vasodilators initiate a more potent amplification within the second to fourth contraction.

High-resolution dynamic pressure sensor array based on piezo-phototronic effect tuned photoluminescence imaging.

PubMed

Peng, Mingzeng; Li, Zhou; Liu, Caihong; Zheng, Qiang; Shi, Xieqing; Song, Ming; Zhang, Yang; Du, Shiyu; Zhai, Junyi; Wang, Zhong Lin

2015-03-24

A high-resolution dynamic tactile/pressure display is indispensable to the comprehensive perception of force/mechanical stimulations such as electronic skin, biomechanical imaging/analysis, or personalized signatures. Here, we present a dynamic pressure sensor array based on pressure/strain tuned photoluminescence imaging without the need for electricity. Each sensor is a nanopillar that consists of InGaN/GaN multiple quantum wells. Its photoluminescence intensity can be modulated dramatically and linearly by small strain (0-0.15%) owing to the piezo-phototronic effect. The sensor array has a high pixel density of 6350 dpi and exceptional small standard deviation of photoluminescence. High-quality tactile/pressure sensing distribution can be real-time recorded by parallel photoluminescence imaging without any cross-talk. The sensor array can be inexpensively fabricated over large areas by semiconductor product lines. The proposed dynamic all-optical pressure imaging with excellent resolution, high sensitivity, good uniformity, and ultrafast response time offers a suitable way for smart sensing, micro/nano-opto-electromechanical systems.

Vapor pressures of a homologous series of polyethylene glycols as a reference data set for validating vapor pressure measurement techniques.

NASA Astrophysics Data System (ADS)

Krieger, Ulrich; Marcolli, Claudia; Siegrist, Franziska

2015-04-01

The production of secondary organic aerosol (SOA) by gas-to-particle partitioning is generally represented by an equilibrium partitioning model. A key physical parameter which governs gas-particle partitioning is the pure component vapor pressure, which is difficult to measure for low- and semivolatile compounds. For typical atmospheric compounds like e.g. citric acid or tartaric acid, vapor pressures have been reported in the literature which differ by up to six orders of magnitude [Huisman et al., 2013]. Here, we report vapor pressures of a homologous series of polyethylene glycols (triethylene glycol to octaethylene glycol) determined by measuring the evaporation rate of single, levitated aerosol particles in an electrodynamic balance. We propose to use those as a reference data set for validating different vapor pressure measurement techniques. With each addition of a (O-CH2-CH2)-group the vapor pressure is lowered by about one order of magnitude which makes it easy to detect the lower limit of vapor pressures accessible with a particular technique down to a pressure of 10-8 Pa at room temperature. Reference: Huisman, A. J., Krieger, U. K., Zuend, A., Marcolli, C., and Peter, T., Atmos. Chem. Phys., 13, 6647-6662, 2013.

Experimental and Computational Studies of Molecular and Lattice Symmetries of Energetic Materials at High Pressure

DTIC Science & Technology

2002-01-01

Prescribed by ANSI Std Z39-18 Research and Technology Department Dynamics and Diagnostics Division, Static High- Pressure Group Overall Research...Department Dynamics and Diagnostics Division, Static High- Pressure Group Impact of this Basic Research • This research generates phase and density...Static High- Pressure Group Experimental Methodology Use Diamond Anvil Cells (DAC) with coil Heaters (HDAC) to achieve • High pressures (P) to 10 GPa

Modeling the Effect of Fluid-Structure Interaction on the Impact Dynamics of Pressurized Tank Cars

DOT National Transportation Integrated Search

2009-11-13

This paper presents a computational framework that : analyzes the effect of fluid-structure interaction (FSI) on the : impact dynamics of pressurized commodity tank cars using the : nonlinear dynamic finite element code ABAQUS/Explicit. : There exist...

Integration of piezo-capacitive and piezo-electric nanoweb based pressure sensors for imaging of static and dynamic pressure distribution.

PubMed

Jeong, Y J; Oh, T I; Woo, E J; Kim, K J

2017-07-01

Recently, highly flexible and soft pressure distribution imaging sensor is in great demand for tactile sensing, gait analysis, ubiquitous life-care based on activity recognition, and therapeutics. In this study, we integrate the piezo-capacitive and piezo-electric nanowebs with the conductive fabric sheets for detecting static and dynamic pressure distributions on a large sensing area. Electrical impedance tomography (EIT) and electric source imaging are applied for reconstructing pressure distribution images from measured current-voltage data on the boundary of the hybrid fabric sensor. We evaluated the piezo-capacitive nanoweb sensor, piezo-electric nanoweb sensor, and hybrid fabric sensor. The results show the feasibility of static and dynamic pressure distribution imaging from the boundary measurements of the fabric sensors.

Analysis of the cycle-to-cycle pressure distribution variations in dynamic stall

NASA Astrophysics Data System (ADS)

Harms, Tanner; Nikoueeyan, Pourya; Naughton, Jonathan

2017-11-01

Dynamic stall is an unsteady flow phenomenon observed on blades and wings that, despite decades of focused study, remains a challenging problem for rotorcraft and wind turbine applications. Traditionally, dynamic stall has been studied on pitch-oscillating airfoils by measuring the unsteady pressure distribution that is phase-averaged, by which the typical flow pattern may be observed and quantified. In cases where light to deep dynamic stall are observed, pressure distributions with high levels of variance are present in regions of separation. It was recently observed that, under certain conditions, this scatter may be the result of a two-state flow solution - as if there were a bifurcation in the unsteady pressure distribution behavior on the suction side of the airfoil. This is significant since phase-averaged dynamic stall data are often used to tune dynamic stall models and for validation of simulations of dynamic stall. In order to better understand this phenomenon, statistical analysis of the pressure data using probability density functions (PDFs) and other statistical approaches has been carried out for the SC 1094R8, DU97-W-300, and NACA 0015 airfoil geometries. 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.

Osmosis-Based Pressure Generation: Dynamics and Application

PubMed Central

Li, Suyi; Billeh, Yazan N.; Wang, K. W.; Mayer, Michael

2014-01-01

This paper describes osmotically-driven pressure generation in a membrane-bound compartment while taking into account volume expansion, solute dilution, surface area to volume ratio, membrane hydraulic permeability, and changes in osmotic gradient, bulk modulus, and degree of membrane fouling. The emphasis lies on the dynamics of pressure generation; these dynamics have not previously been described in detail. Experimental results are compared to and supported by numerical simulations, which we make accessible as an open source tool. This approach reveals unintuitive results about the quantitative dependence of the speed of pressure generation on the relevant and interdependent parameters that will be encountered in most osmotically-driven pressure generators. For instance, restricting the volume expansion of a compartment allows it to generate its first 5 kPa of pressure seven times faster than without a restraint. In addition, this dynamics study shows that plants are near-ideal osmotic pressure generators, as they are composed of many small compartments with large surface area to volume ratios and strong cell wall reinforcements. Finally, we demonstrate two applications of an osmosis-based pressure generator: actuation of a soft robot and continuous volume delivery over long periods of time. Both applications do not need an external power source but rather take advantage of the energy released upon watering the pressure generators. PMID:24614529

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

PubMed

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

2017-11-29

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

Structure and dynamics of water confined in a graphene nanochannel under gigapascal high pressure: dependence of friction on pressure and confinement.

PubMed

Yang, Lei; Guo, Yanjie; Diao, Dongfeng

2017-05-31

Recently, water flow confined in nanochannels has become an interesting topic due to its unique properties and potential applications in nanofluidic devices. The trapped water is predicted to experience high pressure in the gigapascal regime. Theoretical and experimental studies have reported various novel structures of the confined water under high pressure. However, the role of this high pressure on the dynamic properties of water has not been elucidated to date. In the present study, the structure evolution and interfacial friction behavior of water constrained in a graphene nanochannel were investigated via molecular dynamics simulations. Transitions of the confined water to different ice phases at room temperature were observed in the presence of lateral pressure at the gigapascal level. The friction coefficient at the water/graphene interface was found to be dependent on the lateral pressure and nanochannel height. Further theoretical analyses indicate that the pressure dependence of friction is related to the pressure-induced change in the structure of water and the confinement dependence results from the variation in the water/graphene interaction energy barrier. These findings provide a basic understanding of the dynamics of the nanoconfined water, which is crucial in both fundamental and applied science.

Intracellular fluid flow in rapidly moving cells

PubMed Central

Keren, Kinneret; Yam, Patricia T.; Kinkhabwala, Anika; Mogilner, Alex; Theriot, Julie A.

2010-01-01

Cytosolic fluid dynamics have been implicated in cell motility1–5 because of the hydrodynamic forces they induce and because of their influence on transport of components of the actin machinery to the leading edge. To investigate the existence and the direction of fluid flow in rapidly moving cells, we introduced inert quantum dots into the lamellipodia of fish epithelial keratocytes and analysed their distribution and motion. Our results indicate that fluid flow is directed from the cell body towards the leading edge in the cell frame of reference, at about 40% of cell speed. We propose that this forward-directed flow is driven by increased hydrostatic pressure generated at the rear of the cell by myosin contraction, and show that inhibition of myosin II activity by blebbistatin reverses the direction of fluid flow and leads to a decrease in keratocyte speed. We present a physical model for fluid pressure and flow in moving cells that quantitatively accounts for our experimental data. PMID:19767741

Active load control during rolling maneuvers. [performed in the Langley Transonic Dynamics Tunnel

NASA Technical Reports Server (NTRS)

Woods-Vedeler, Jessica A.; Pototzky, Anthony S.; Hoadley, Sherwood T.

1994-01-01

A rolling maneuver load alleviation (RMLA) system has been demonstrated on the active flexible wing (AFW) wind tunnel model in the Langley Transonic Dynamics Tunnel (TDT). The objective was to develop a systematic approach for designing active control laws to alleviate wing loads during rolling maneuvers. Two RMLA control laws were developed that utilized outboard control-surface pairs (leading and trailing edge) to counteract the loads and that used inboard trailing-edge control-surface pairs to maintain roll performance. Rolling maneuver load tests were performed in the TDT at several dynamic pressures that included two below and one 11 percent above open-loop flutter dynamic pressure. The RMLA system was operated simultaneously with an active flutter suppression system above open-loop flutter dynamic pressure. At all dynamic pressures for which baseline results were obtained, torsion-moment loads were reduced for both RMLA control laws. Results for bending-moment load reductions were mixed; however, design equations developed in this study provided conservative estimates of load reduction in all cases.

Asymmetric bubble collapse and jetting in generalized Newtonian fluids

NASA Astrophysics Data System (ADS)

Shukla, Ratnesh K.; Freund, Jonathan B.

2017-11-01

The jetting dynamics of a gas bubble near a rigid wall in a non-Newtonian fluid are investigated using an axisymmetric simulation model. The bubble gas is assumed to be homogeneous, with density and pressure related through a polytropic equation of state. An Eulerian numerical description, based on a sharp interface capturing method for the shear-free bubble-liquid interface and an incompressible Navier-Stokes flow solver for generalized fluids, is developed specifically for this problem. Detailed simulations for a range of rheological parameters in the Carreau model show both the stabilizing and destabilizing non-Newtonian effects on the jet formation and impact. In general, for fixed driving pressure ratio, stand-off distance and reference zero-shear-rate viscosity, shear-thinning and shear-thickening promote and suppress jet formation and impact, respectively. For a sufficiently large high-shear-rate limit viscosity, the jet impact is completely suppressed. Thresholds are also determined for the Carreau power-index and material time constant. The dependence of these threshold rheological parameters on the non-dimensional driving pressure ratio and wall stand-off distance is similarly established. Implications for tissue injury in therapeutic ultrasound will be discussed.

Non-hydrostatic semi-elastic hybrid-coordinate SISL extension of HIRLAM. Part I: numerical scheme

NASA Astrophysics Data System (ADS)

Rõõm, Rein; Männik, Aarne; Luhamaa, Andres

2007-10-01

Two-time-level, semi-implicit, semi-Lagrangian (SISL) scheme is applied to the non-hydrostatic pressure coordinate equations, constituting a modified Miller-Pearce-White model, in hybrid-coordinate framework. Neutral background is subtracted in the initial continuous dynamics, yielding modified equations for geopotential, temperature and logarithmic surface pressure fluctuation. Implicit Lagrangian marching formulae for single time-step are derived. A disclosure scheme is presented, which results in an uncoupled diagnostic system, consisting of 3-D Poisson equation for omega velocity and 2-D Helmholtz equation for logarithmic pressure fluctuation. The model is discretized to create a non-hydrostatic extension to numerical weather prediction model HIRLAM. The discretization schemes, trajectory computation algorithms and interpolation routines, as well as the physical parametrization package are maintained from parent hydrostatic HIRLAM. For stability investigation, the derived SISL model is linearized with respect to the initial, thermally non-equilibrium resting state. Explicit residuals of the linear model prove to be sensitive to the relative departures of temperature and static stability from the reference state. Relayed on the stability study, the semi-implicit term in the vertical momentum equation is replaced to the implicit term, which results in stability increase of the model.

EDIN design study alternate space shuttle booster replacement concepts. Volume 1: Engineering analysis

NASA Technical Reports Server (NTRS)

Demakes, P. T.; Hirsch, G. N.; Stewart, W. A.; Glatt, C. R.

1976-01-01

The use of a recoverable liquid rocket booster (LRB) system to replace the existing solid rocket booster (SRB) system for the shuttle was studied. Historical weight estimating relationships were developed for the LRB using Saturn technology and modified as required. Mission performance was computed using February 1975 shuttle configuration groundrules to allow reasonable comparison of the existing shuttle with the study designs. The launch trajectory was constrained to pass through both the RTLS/AOA and main engine cut off points of the shuttle reference mission 1. Performance analysis is based on a point design trajectory model which optimizes initial tilt rate and exoatmospheric pitch profile. A gravity turn was employed during the boost phase in place of the shuttle angle of attack profile. Engine throttling add/or shutdown was used to constrain dynamic pressure and/or longitudinal acceleration where necessary. Four basic configurations were investigated: a parallel burn vehicle with an F-1 engine powered LRB; a parallel burn vehicle with a high pressure engine powered LRB; a series burn vehicle with a high pressure engine powered LRB. The relative sizes of the LRB and the ET are optimized to minimize GLOW in most cases.

Streamline curvature in supersonic shear layers

NASA Technical Reports Server (NTRS)

Kibens, V.

1992-01-01

Results of an experimental investigation in which a curved shear layer was generated between supersonic flow from a rectangular converging/diverging nozzle and the freestream in a series of open channels with varying radii of curvature are reported. The shear layers exhibit unsteady large-scale activity at supersonic pressure ratios, indicating increased mixing efficiency. This effect contrasts with supersonic flow in a straight channel, for which no large-scale vortical structure development occurs. Curvature must exceed a minimum level before it begins to affect the dynamics of the supersonic shear layer appreciably. The curved channel flows are compared with reference flows consisting of a free jet, a straight channel, and wall jets without sidewalls on a flat and a curved plate.

Unifying role of dissipative action in the dynamic failure of solids

NASA Astrophysics Data System (ADS)

Grady, Dennis E.

2015-04-01

A fourth-power law underlying the steady shock-wave structure and solid viscosity of condensed material has been observed for a wide range of metals and non-metals. The fourth-power law relates the steady-wave Hugoniot pressure to the fourth power of the strain rate during passage of the material through the structured shock wave. Preceding the fourth-power law was the observation in a shock transition that the product of the shock dissipation energy and the shock transition time is a constant independent of the shock pressure amplitude. Invariance of this energy-time product implies the fourth-power law. This property of the shock transition in solids was initially identified as a shock invariant. More recently, it has been referred to as the dissipative action, although no relationship to the accepted definitions of action in mechanics has been demonstrated. This same invariant property has application to a wider range of transient failure phenomena in solids. Invariance of this dissipation action has application to spall fracture, failure through adiabatic shear, shock compaction of granular media, and perhaps others. Through models of the failure processes, a clearer picture of the physics underlying the observed invariance is emerging. These insights in turn are leading to a better understanding of the shock deformation processes underlying the fourth-power law. Experimental result and material models encompassing the dynamic failure of solids are explored for the purpose of demonstrating commonalities leading to invariance of the dissipation action. Calculations are extended to aluminum and uranium metals with the intent of predicting micro-scale dynamics and spatial structure in the steady shock wave.

Large-eddy simulation of cavitating nozzle flow and primary jet break-up

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

Örley, F., E-mail: felix.oerley@aer.mw.tum.de; Trummler, T.; Mihatsch, M. S.

We employ a barotropic two-phase/two-fluid model to study the primary break-up of cavitating liquid jets emanating from a rectangular nozzle, which resembles a high aspect-ratio slot flow. All components (i.e., gas, liquid, and vapor) are represented by a homogeneous mixture approach. The cavitating fluid model is based on a thermodynamic-equilibrium assumption. Compressibility of all phases enables full resolution of collapse-induced pressure wave dynamics. The thermodynamic model is embedded into an implicit large-eddy simulation (LES) environment. The considered configuration follows the general setup of a reference experiment and is a generic reproduction of a scaled-up fuel injector or control valve asmore » found in an automotive engine. Due to the experimental conditions, it operates, however, at significantly lower pressures. LES results are compared to the experimental reference for validation. Three different operating points are studied, which differ in terms of the development of cavitation regions and the jet break-up characteristics. Observed differences between experimental and numerical data in some of the investigated cases can be caused by uncertainties in meeting nominal parameters by the experiment. The investigation reveals that three main mechanisms promote primary jet break-up: collapse-induced turbulent fluctuations near the outlet, entrainment of free gas into the nozzle, and collapse events inside the jet near the liquid-gas interface.« less

Non-hydrostatic semi-elastic hybrid-coordinate SISL extension of HIRLAM. Part II: numerical testing

NASA Astrophysics Data System (ADS)

Rõõm, Rein; Männik, Aarne; Luhamaa, Andres; Zirk, Marko

2007-10-01

The semi-implicit semi-Lagrangian (SISL), two-time-level, non-hydrostatic numerical scheme, based on the non-hydrostatic, semi-elastic pressure-coordinate equations, is tested in model experiments with flow over given orography (elliptical hill, mountain ridge, system of successive ridges) in a rectangular domain with emphasis on the numerical accuracy and non-hydrostatic effect presentation capability. Comparison demonstrates good (in strong primary wave generation) to satisfactory (in weak secondary wave reproduction in some cases) consistency of the numerical modelling results with known stationary linear test solutions. Numerical stability of the developed model is investigated with respect to the reference state choice, modelling dynamics of a stationary front. The horizontally area-mean reference temperature proves to be the optimal stability warrant. The numerical scheme with explicit residual in the vertical forcing term becomes unstable for cross-frontal temperature differences exceeding 30 K. Stability is restored, if the vertical forcing is treated implicitly, which enables to use time steps, comparable with the hydrostatic SISL.

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

DTIC Science & Technology

2007-06-01

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

Trajectory optimization and guidance law development for national aerospace plane applications

NASA Technical Reports Server (NTRS)

Calise, A. J.; Flandro, G. A.; Corban, J. E.

1988-01-01

The work completed to date is comprised of the following: a simple vehicle model representative of the aerospace plane concept in the hypersonic flight regime, fuel-optimal climb profiles for the unconstrained and dynamic pressure constrained cases generated using a reduced order dynamic model, an analytic switching condition for transition to rocket powered flight as orbital velocity is approached, simple feedback guidance laws for both the unconstrained and dynamic pressure constrained cases derived via singular perturbation theory and a nonlinear transformation technique, and numerical simulation results for ascent to orbit in the dynamic pressure constrained case.

Implications of Dynamic Pressure Transducer Mounting Variations on Measurements in Pyrotechnic Test Apparatus

NASA Technical Reports Server (NTRS)

Dibbern, Andreas; Crisafulli, Jeffrey; Hagopia, Michael; McDougle, Stephen H.; Saulsberry, Regor L.

2009-01-01

Accurate dynamic pressure measurements are often difficult to make within small pyrotechnic devices, and transducer mounting difficulties can cause data anomalies that lead to erroneous conclusions. Delayed initial pressure response followed by data ringing has been observed when using miniaturized pressure transducer mounting adapters required to interface transducers to small test chambers. This delayed pressure response and ringing, combined with a high data acquisition rate, has complicated data analysis. This paper compares the output signal characteristics from different pressure transducer mounting options, where the passage distance from the transducer face to the pyrotechnic chamber is varied in length and diameter. By analyzing the data and understating the associated system dynamics, a more realistic understanding of the actual dynamic pressure variations is achieved. Three pressure transducer mounting configurations (elongated, standard, and face/flush mount) were simultaneously tested using NASA standard initiators in closed volume pressure bombs. This paper also presents results of these pressure transducer mounting configurations as a result of a larger NASA Engineering and Safety Center pyrovalve test project. Results from these tests indicate the improved performance of using face/flush mounted pressure transducers in this application. This type of mounting improved initial pressure measurement response time by approximately 19 s over standard adapter mounting, eliminating most of the lag time; provided a near step-function type initial pressure increase; and greatly reduced data ringing in high data acquisition rate systems. The paper goes on to discuss other issues associated with the firing and instrumentation that are important for the tester to understand.

Analysis of the intraocular jet flows and pressure gradients induced by air and fluid infusion: mechanism of focal chorioretinal damage.

PubMed

Kim, Yong Joon; Jo, Sungkil; Moon, Daruchi; Joo, Youngcheol; Choi, Kyung Seek

2014-05-01

To comprehend the mechanism of focal chorioretinal damage by analysis of the pressure distribution and dynamic pressure induced by infused air during fluid-air exchange. A precise simulation featuring a model eye and a fluid circuit was designed to analyze fluid-air exchange. The pressure distribution, flow velocity, and dynamic pressure induced by infusion of air into an air-filled eye were analyzed using an approach based on fluid dynamics. The size of the port and the infusion pressure were varied during simulated iterations. We simulated infusion of an air-filled eye with balanced salt solution (BSS) to better understand the mechanism of chorioretinal damage induced by infused air. Infused air was projected straight toward a point on the retina contralateral to the infusion port (the "vulnerable point"). The highest pressure was evident at the vulnerable point, and the lowest pressure was recorded on most retinal areas. Simulations using greater infusion pressure and a port of larger size were associated with elevations in dynamic pressure and the pressure gradient. The pressure gradients were 2.8 and 5.1 mm Hg, respectively, when infusion pressures of 30 and 50 mm Hg were delivered through a 20-gauge port. The pressure gradient associated with BSS infusion was greater than that created by air, but lasted for only a moment. Our simulation explains the mechanism of focal chorioretinal damage in numerical terms. Infused air induces a prolonged increase in focal pressure on the vulnerable point, and this may be responsible for visual field defects arising after fluid-air exchange. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

Fiber-Optic Pressure Sensor With Dynamic Demodulation Developed

NASA Technical Reports Server (NTRS)

Lekki, John D.

2002-01-01

Researchers at the NASA Glenn Research Center developed in-house a method to detect pressure fluctuations using a fiber-optic sensor and dynamic signal processing. This work was in support of the Intelligent Systems Controls and Operations project under NASA's Information Technology Base Research Program. We constructed an optical pressure sensor by attaching a fiber-optic Bragg grating to a flexible membrane and then adhering the membrane to one end of a small cylinder. The other end of the cylinder was left open and exposed to pressure variations from a pulsed air jet. These pressure variations flexed the membrane, inducing a strain in the fiber-optic grating. This strain was read out optically with a dynamic spectrometer to record changes in the wavelength of light reflected from the grating. The dynamic spectrometer was built in-house to detect very small wavelength shifts induced by the pressure fluctuations. The spectrometer is an unbalanced interferometer specifically designed for maximum sensitivity to wavelength shifts. An optimum pathlength difference, which was determined empirically, resulted in a 14-percent sensitivity improvement over theoretically predicted path-length differences. This difference is suspected to be from uncertainty about the spectral power difference of the signal reflected from the Bragg grating. The figure shows the output of the dynamic spectrometer as the sensor was exposed to a nominally 2-kPa peak-to-peak square-wave pressure fluctuation. Good tracking, sensitivity, and signal-to-noise ratios are evident even though the sensor was constructed as a proof-of-concept and was not optimized in any way. Therefore the fiber-optic Bragg grating, which is normally considered a good candidate as a strain or temperature sensor, also has been shown to be a good candidate for a dynamic pressure sensor.

Portable Dynamic Pressure Calibrator

NASA Technical Reports Server (NTRS)

Wright, Morgan S.; Maynard, Everett (Technical Monitor)

1996-01-01

A portable, dynamic pressure calibrator was fabricated for use on wind tunnel models at NASA-Ames Research Center. The calibrator generates sine wave pressures at levels up to 1 PSIG P-P(168dB) at frequencies from 10Hz to 6KHz and .5 PSIG P.P (162dB) at frequencies from 6KHz to 20KHz. The calibrator consists of two units connected by a single cable. The handheld unit contains a pressure transducer, speaker, and deadman switch. This unit allows application of dynamic pressure to transducers/ports on installed wind tunnel models. The base unit contains all of power supplies, controls and displays. This unit allows amplitude and frequency to be set and verified at a safe location off of the model.

High pressure study of molecular dynamics of protic ionic liquid lidocaine hydrochloride.

PubMed

Swiety-Pospiech, A; Wojnarowska, Z; Pionteck, J; Pawlus, S; Grzybowski, A; Hensel-Bielowka, S; Grzybowska, K; Szulc, A; Paluch, M

2012-06-14

In this paper, we investigate the effect of pressure on the molecular dynamics of protic ionic liquid lidocaine hydrochloride, a commonly used pharmaceutical, by means of dielectric spectroscopy and pressure-temperature-volume methods. We observed that near T(g) the pressure dependence of conductivity relaxation times reveals a peculiar behavior, which can be treated as a manifestation of decoupling between ion migration and structural relaxation times. Moreover, we discuss the validity of thermodynamic scaling in lidocaine HCl. We also employed the temperature-volume Avramov model to determine the value of pressure coefficient of glass transition temperature, dT(g)/dP|(P = 0.1). Finally, we investigate the role of thermal and density fluctuations in controlling of molecular dynamics of the examined compound.

Experimental studies on the tripping behavior of narrow T-stiffened flat plates subjected to hydrostatic pressure and underwater shock

NASA Technical Reports Server (NTRS)

Budweg, H. L.; Shin, Y. S.

1987-01-01

An experimental investigation was conducted to determine the static and dynamic responses of a specific stiffened flat plate design. The air-backed rectangular flat plates of 6061-T6 aluminum with an externally machined longitudinal narrow-flanged T-stiffener and clamped boundary conditions were subjected to static loading by water hydropump pressure and shock loading from an eight pound TNT charge detonated underwater. The dynamic test plate was instrumented to measure transient strains and free field pressure. The static test plate was instrumented to measure transient strains, plate deflection, and pressure. Emphasis was placed upon forcing static and dynamic stiffener tripping, obtaining relevant strain and pressure data, and studying the associated plate-stiffener behavior.

Analysis of oscillatory pressure data including dynamic stall effects

NASA Technical Reports Server (NTRS)

Carta, F. O.

1974-01-01

The dynamic stall phenomenon was examined in detail by analyzing an existing set of unsteady pressure data obtained on an airfoil oscillating in pitch. Most of the data were for sinusoidal oscillations which penetrated the stall region in varying degrees, and here the effort was concentrated on the chordwise propagation of pressure waves associated with the dynamic stall. It was found that this phenomenon could be quantified in terms of a pressure wave velocity which is consistently much less than free-stream velocity, and which varies directly with frequency. It was also found that even when the stall region has been deeply penetrated and a substantial dynamic stall occurs during the downstroke, stall recovery near minimum incidence will occur, followed by a potential flow behavior up to stall inception.

Ultrafast Dynamic Pressure Sensors Based on Graphene Hybrid Structure.

PubMed

Liu, Shanbiao; Wu, Xing; Zhang, Dongdong; Guo, Congwei; Wang, Peng; Hu, Weida; Li, Xinming; Zhou, Xiaofeng; Xu, Hejun; Luo, Chen; Zhang, Jian; Chu, Junhao

2017-07-19

Mechanical flexible electronic skin has been focused on sensing various physical parameters, such as pressure and temperature. The studies of material design and array-accessible devices are the building blocks of strain sensors for subtle pressure sensing. Here, we report a new and facile preparation of a graphene hybrid structure with an ultrafast dynamic pressure response. Graphene oxide nanosheets are used as a surfactant to prevent graphene restacking in aqueous solution. This graphene hybrid structure exhibits a frequency-independent pressure resistive sensing property. Exceeding natural skin, such pressure sensors, can provide transient responses from static up to 10 000 Hz dynamic frequencies. Integrated by the controlling system, the array-accessible sensors can manipulate a robot arm and self-rectify the temperature of a heating blanket. This may pave a path toward the future application of graphene-based wearable electronics.

Evaluation of the Environmental Instruments, Incorporated Series 200 Dual Component Wind Set.

DTIC Science & Technology

1980-09-01

elements is sensed to derive the sign (+ or -), which indicates the wind direction across the element pair. The reference arm of the Wheatstone bridge...Csine a for the crosswind axis, r and PF=a Vw Sine a for the headwind axis, r where Pa is the ambient air density, Pr is reference density at standard...pressure transducer is a hybrid linear silicon device which consists of a diaphragm and pressure reference , piezoresistive sensor, signal discriminator

Acoustic Database for Turbofan Engine Core-Noise Sources. I; Volume

NASA Technical Reports Server (NTRS)

Gordon, Grant

2015-01-01

In this program, a database of dynamic temperature and dynamic pressure measurements were acquired inside the core of a TECH977 turbofan engine to support investigations of indirect combustion noise. Dynamic temperature and pressure measurements were recorded for engine gas dynamics up to temperatures of 3100 degrees Fahrenheit and transient responses as high as 1000 hertz. These measurements were made at the entrance of the high pressure turbine (HPT) and at the entrance and exit of the low pressure turbine (LPT). Measurements were made at two circumferential clocking positions. In the combustor and inter-turbine duct (ITD), measurements were made at two axial locations to enable the exploration of time delays. The dynamic temperature measurements were made using dual thin-wire thermocouple probes. The dynamic pressure measurements were made using semi-infinite probes. Prior to the engine test, a series of bench, oven, and combustor rig tests were conducted to characterize the performance of the dual wire temperature probes and to define and characterize the data acquisition systems. A measurement solution for acquiring dynamic temperature and pressure data on the engine was defined. A suite of hardware modifications were designed to incorporate the dynamic temperature and pressure instrumentation into the TECH977 engine. In particular, a probe actuation system was developed to protect the delicate temperature probes during engine startup and transients in order to maximize sensor life. A set of temperature probes was procured and the TECH977 engine was assembled with the suite of new and modified hardware. The engine was tested at four steady state operating speeds, with repeats. Dynamic pressure and temperature data were acquired at each condition for at least one minute. At the two highest power settings, temperature data could not be obtained at the forward probe locations since the mean temperatures exceeded the capability of the probes. The temperature data were processed using software that accounts for the effects of convective and conductive heat transfer. The software was developed under previous NASA sponsored programs. Compensated temperature spectra and compensated time histories corresponding to the dynamic temperature of the gas stream were generated. Auto-spectral and cross-spectral analyses of the data were performed to investigate spectral features, acoustic circumferential mode content, signal coherence, and time delays. The dynamic temperature data exhibit a wideband and fairly flat spectral content. The temperature spectra do not change substantially with operating speed. The pressure spectra in the combustor and ITD exhibit generally similar shapes and amplitudes, making it difficult to identify any features that suggest the presence of indirect combustion noise. Cross-spectral analysis reveal a strong correlation between pressure and temperature fluctuations in the ITD, but little correlation between temperature fluctuations at the entrance of the HPT and pressure fluctuations downstream of it. Temperature fluctuations at the entrance of the low pressure turbine were an order of magnitude smaller than those at the entrance to the high pressure turbine. Time delay analysis of the temperature fluctuations in the combustor was inconclusive, perhaps due to the substantial mixing that occurs between the upstream and downstream locations. Time delay analysis of the temperature fluctuations in the ITD indicate that they convect at the mean flow speed. Analysis of the data did not reveal any convincing indications of the presence of indirect combustion noise. However, this analysis has been preliminary and additional exploration of the data is recommended including the use of more sophisticated signal processing to explore subtle issues that have been revealed but which are not yet fully understood or explained.

[Age- and sex-specific reference intervals for 10 health examination items: mega-data from a Japanese Health Service Association].

PubMed

Suka, Machi; Yoshida, Katsumi; Kawai, Tadashi; Aoki, Yoshikazu; Yamane, Noriyuki; Yamauchi, Kuniaki

2005-07-01

To determine age- and sex-specific reference intervals for 10 health examination items in Japanese adults. Health examination data were accumulated from 24 different prefectural health service associations affiliated with the Japan Association of Health Service. Those who were non-smokers, drank less than 7 days/week, and had a body mass index of 18.5-24.9kg/m2 were sampled as a reference population (n = 737,538; 224,947 men and 512,591 women). After classified by age and sex, reference intervals for 10 health examination items (systolic blood pressure, diastolic blood pressure, total cholesterol, triglyceride, glucose, uric acid, AST, ALT, gamma-GT, and hemoglobin) were estimated using the parametric and nonparametric methods. In every item except for hemoglobin, men had higher reference intervals than women. Systolic blood pressure, total cholesterol, and glucose showed an upward trend in values with increasing age. Hemoglobin showed a downward trend in values with increasing age. Triglyceride, ALT, and gamma-GT reached a peak in middle age. Overall, parametric estimates showed narrower reference intervals than non-parametric estimates. Reference intervals vary with age and sex. Age- and sex-specific reference intervals may contribute to better assessment of health examination data.

Formulation of blade-flutter spectral analyses in stationary reference frame

NASA Technical Reports Server (NTRS)

Kurkov, A. P.

1984-01-01

Analytic representations are developed for the discrete blade deflection and the continuous tip static pressure fields in a stationary reference frame. Considered are the sampling rates equal to the rotational frequency, equal to blade passing frequency, and for the pressure, equal to a multiple of the blade passing frequency. For the last two rates the expressions for determining the nodal diameters from the spectra are included. A procedure is presented for transforming the complete unsteady pressure field into a rotating frame of reference. The determination of the true flutter frequency by using two sensors is described. To illustrate their use, the developed procedures are used to interpret selected experimental results.

Monitoring localized cracks on under pressure concrete nuclear containment wall using linear and nonlinear ultrasonic coda wave interferometry

NASA Astrophysics Data System (ADS)

Legland, J.-B.; Abraham, O.; Durand, O.; Henault, J.-M.

2018-04-01

Civil engineering is constantly demanding new methods for evaluation and non-destructive testing (NDT), particularly to prevent and monitor serious damage to concrete structures. Tn this work, experimental results are presented on the detection and characterization of cracks using nonlinear modulation of coda waves interferometry (NCWT) [1]. This method consists in mixing high-amplitude low-frequency acoustic waves with multi-scattered probe waves (coda) and analyzing their effects by interferometry. Unlike the classic method of coda analysis (CWT), the NCWT does not require the recording of a coda as a reference before damage to the structure. Tn the framework of the PTA-ENDE project, a 1/3 model of a preconstrained concrete containment (EDF VeRCoRs mock-up) is placed under pressure to study the leakage of the structure. During this evaluation protocol, specific areas are monitored by the NCWT (during 5 days, which correspond to the protocol of nuclear power plant pressurization under maintenance test). The acoustic nonlinear response due to the high amplitude of the acoustic modulation gives pertinent information about the elastic and dissipative nonlinearities of the concrete. Tts effective level is evaluated by two nonlinear observables extracted from the interferometry. The increase of nonlinearities is in agreement with the creation of a crack with a network of microcracks located at its base; however, a change in the dynamics of the evolution of the nonlinearities may indicate the opening of a through crack. Tn addition, as during the experimental campaign, reference codas have been recorded. We used CWT to follow the stress evolution and the gas leaks ratio of the structure. Both CWT and NCWT results are presented in this paper.

Concept of a self-pressurized feed system for liquid rocket engines and its fundamental experiment results

NASA Astrophysics Data System (ADS)

Matsumoto, Jun; Okaya, Shunichi; Igoh, Hiroshi; Kawaguchi, Junichiro

2017-04-01

A new propellant feed system referred to as a self-pressurized feed system is proposed for liquid rocket engines. The self-pressurized feed system is a type of gas-pressure feed system; however, the pressurization source is retained in the liquid state to reduce tank volume. The liquid pressurization source is heated and gasified using heat exchange from the hot propellant using a regenerative cooling strategy. The liquid pressurization source is raised to critical pressure by a pressure booster referred to as a charger in order to avoid boiling and improve the heat exchange efficiency. The charger is driven by a part of the generated pressurization gas using a closed-loop self-pressurized feed system. The purpose of this study is to propose a propellant feed system that is lighter and simpler than traditional gas pressure feed systems. The proposed system can be applied to all liquid rocket engines that use the regenerative cooling strategy. The concept and mathematical models of the self-pressurized feed system are presented first. Experiment results for verification are then shown and compared with the mathematical models.

A quasi-dynamic nonlinear finite element model to investigate prosthetic interface stresses during walking for trans-tibial amputees.

PubMed

Jia, Xiaohong; Zhang, Ming; Li, Xiaobing; Lee, Winson C C

2005-07-01

To predict the interface pressure between residual limb and prosthetic socket for trans-tibial amputees during walking. A quasi-dynamic finite element model was built based on the actual geometry of residual limb, internal bones and socket liner. To simulate the friction/slip boundary conditions between the skin and liner, automated surface-to-surface contact was used. Besides variable external loads and material inertia, the coupling between the large rigid displacement of knee joint and small elastic deformation of residual limb and prosthetic components were also considered. Interface pressure distribution was found to have the same profile during walking. The high pressures fall over popliteal depression, middle patella tendon, lateral tibia and medial tibia regions. Interface pressure predicted by static or quasi-dynamic analysis had the similar double-peaked waveform shape in stance phase. The consideration of inertial effects and motion of knee joint cause 210% average variation of the area between the pressure curve and the horizontal line of pressure threshold between two cases, even though there is only a small change in the peak pressure. The findings in this paper show that the coupling dynamic effects of inertial loads and knee flexion must be considered to study interface pressure between residual limb and prosthetic socket during walking.

46 CFR 64.5 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-10-01

... SYSTEMS General § 64.5 Definitions. As used in this part: (a) Marine portable tank or MPT means a liquid... consisting of the absolute vapor pressure of the product at 122 °F added to the dynamic pressure, based on... maximum allowable working pressure. (f) Dynamic loading conditions means the following: (1) A loading in...

A Proposed Dynamic Pressure and Temperature Primary Standard

PubMed Central

Rosasco, Gregory J.; Bean, Vern E.; Hurst, Wilbur S.

1990-01-01

Diatomic gas molecules have a fundamental vibrational motion whose frequency is affected by pressure in a simple way. In addition, these molecules have well defined rotational energy levels whose populations provide a reliable measure of the thermodynamic temperature. Since information concerning the frequency of vibration and the relative populations can be determined by laser spectroscopy, the gas molecules themselves can serve as sensors of pressure and temperature. Through measurements under static conditions, the pressure and temperature dependence of the spectra of selected molecules is now understood. As the time required for the spectroscopic measurement can be reduced to nanoseconds, the diatomic gas molecule is an excellent candidate for a dynamic pressure/temperature primary standard. The temporal response in this case will be limited by the equilibration time for the molecules to respond to changes in local thermodynamic variables. Preliminary feasibility studies suggest that by using coherent anti-Stokes Raman spectroscopy we will be able to measure dynamic pressure up to 108 Pa and dynamic temperature up to 1500 K with an uncertainty of 5%. PMID:28179756

Demodulation System for Fiber Optic Bragg Grating Dynamic Pressure Sensing

NASA Technical Reports Server (NTRS)

Lekki, John D.; Adamovsky, Grigory; Floyd, Bertram

2001-01-01

Fiber optic Bragg gratings have been used for years to measure quasi-static phenomena. In aircraft engine applications there is a need to measure dynamic signals such as variable pressures. In order to monitor these pressures a detection system with broad dynamic range is needed. This paper describes an interferometric demodulator that was developed and optimized for this particular application. The signal to noise ratio was maximized through temporal coherence analysis. The demodulator was incorporated in a laboratory system that simulates conditions to be measured. Several pressure sensor configurations incorporating a fiber optic Bragg grating were also explored. The results of the experiments are reported in this paper.

40 CFR 63.705 - Performance test methods and procedures to determine initial compliance.

Code of Federal Regulations, 2014 CFR

2014-07-01

... per gram-mole. Pi = Barometric pressure at the time of sample analysis, millimeters mercury absolute. 760 = Reference or standard pressure, millimeters mercury absolute. 293 = Reference or standard...: ER15DE94.005 (i) The value of RSi is zero unless the owner or operator submits the following information to...

40 CFR 63.705 - Performance test methods and procedures to determine initial compliance.

Code of Federal Regulations, 2012 CFR

2012-07-01

... per gram-mole. Pi = Barometric pressure at the time of sample analysis, millimeters mercury absolute. 760 = Reference or standard pressure, millimeters mercury absolute. 293 = Reference or standard...: ER15DE94.005 (i) The value of RSi is zero unless the owner or operator submits the following information to...

40 CFR 63.705 - Performance test methods and procedures to determine initial compliance.

Code of Federal Regulations, 2010 CFR

2010-07-01

... per gram-mole. Pi = Barometric pressure at the time of sample analysis, millimeters mercury absolute. 760 = Reference or standard pressure, millimeters mercury absolute. 293 = Reference or standard...: ER15DE94.005 (i) The value of RSi is zero unless the owner or operator submits the following information to...

40 CFR 63.705 - Performance test methods and procedures to determine initial compliance.

Code of Federal Regulations, 2013 CFR

2013-07-01

... per gram-mole. Pi = Barometric pressure at the time of sample analysis, millimeters mercury absolute. 760 = Reference or standard pressure, millimeters mercury absolute. 293 = Reference or standard...: ER15DE94.005 (i) The value of RSi is zero unless the owner or operator submits the following information to...

40 CFR 63.705 - Performance test methods and procedures to determine initial compliance.

Code of Federal Regulations, 2011 CFR

2011-07-01

... per gram-mole. Pi = Barometric pressure at the time of sample analysis, millimeters mercury absolute. 760 = Reference or standard pressure, millimeters mercury absolute. 293 = Reference or standard...: ER15DE94.005 (i) The value of RSi is zero unless the owner or operator submits the following information to...

Increases in intramuscular pressure raise arterial blood pressure during dynamic exercise

NASA Technical Reports Server (NTRS)

Gallagher, K. M.; Fadel, P. J.; Smith, S. A.; Norton, K. H.; Querry, R. G.; Olivencia-Yurvati, A.; Raven, P. B.

2001-01-01

This investigation was designed to determine the role of intramuscular pressure-sensitive mechanoreceptors and chemically sensitive metaboreceptors in affecting the blood pressure response to dynamic exercise in humans. Sixteen subjects performed incremental (20 W/min) cycle exercise to fatigue under four conditions: control, exercise with thigh cuff occlusion of 90 Torr (Cuff occlusion), exercise with lower body positive pressure (LBPP) of 45 Torr, and a combination of thigh cuff occlusion and LBPP (combination). Indexes of central command (heart rate, oxygen uptake, ratings of perceived exertion, and electromyographic activity), cardiac output, stroke volume, and total peripheral resistance were not significantly different between the four conditions. Mechanical stimulation during LBPP and combination conditions resulted in significant elevations in intramuscular pressure and mean arterial pressure from control at rest and throughout the incremental exercise protocol (P < 0.05). Conversely, there existed no significant changes in mean arterial pressure when the metaboreflex was stimulated by cuff occlusion. These findings suggest that under normal conditions the mechanoreflex is tonically active and is the primary mediator of exercise pressor reflex-induced alterations in arterial blood pressure during submaximal dynamic exercise in humans.

Dynamic Leidenfrost temperature on micro-textured surfaces: Acoustic wave absorption into thin vapor layer

NASA Astrophysics Data System (ADS)

Jerng, Dong Wook; Kim, Dong Eok

2018-01-01

The dynamic Leidenfrost phenomenon is governed by three types of pressure potentials induced via vapor hydrodynamics, liquid dynamic pressure, and the water hammer effect resulting from the generation of acoustic waves at the liquid-vapor interface. The prediction of the Leidenfrost temperature for a dynamic droplet needs quantitative evaluation and definition for each of the pressure fields. In particular, the textures on a heated surface can significantly affect the vapor hydrodynamics and the water hammer pressure. We present a quantitative model for evaluating the water hammer pressure on micro-textured surfaces taking into account the absorption of acoustic waves into the thin vapor layer. The model demonstrates that the strength of the acoustic flow into the liquid droplet, which directly contributes to the water hammer pressure, depends on the magnitude of the acoustic resistance (impedance) in the droplet and the vapor region. In consequence, the micro-textures of the surface and the increased spacing between them reduce the water hammer coefficient ( kh ) defined as the ratio of the acoustic flow into the droplet to total generated flow. Aided by numerical calculations that solve the laminar Navier-Stokes equation for the vapor flow, we also predict the dynamic Leidenfrost temperature on a micro-textured surface with reliable accuracy consistent with the experimental data.

Molecular dynamics and residual entropy in the soft crystal, SmE phase, of 4-butyl-4'-isothiocyano-1,1'-biphenyl.

PubMed

Ishimaru, Shin'ichi; Saito, Kazuya; Ikeuchi, Satoaki; Massalska-Arodz, Maria; Witko, Waclaw

2005-05-26

Molecular dynamics and resulting disorder in the soft crystal, smectic E (SmE) phase, were studied in detail for the title compound, 4-butyl-4'-isothiocyano-1,1'-biphenyl (4TCB), by (1)H NMR spectroscopy and adiabatic calorimetry. The ordered crystal phase of 4TCB was realized for the first time under ambient pressure after long two-step annealing and used as the reference state in the analysis of the experimental results. Four motional modes were identified in the SmE phase through the analysis of the (1)H NMR T(1). The residual entropy was determined as ca. 6 J K(-1) mol(-1). This magnitude implies that most of the disorder in the SmE phase at high temperatures is removed on cooling except for the head-to-tail disorder of the rod-shaped 4TCB molecule. Standard thermodynamic functions are tabulated below 375 K.

Deployment Simulation Methods for Ultra-Lightweight Inflatable Structures

NASA Technical Reports Server (NTRS)

Wang, John T.; Johnson, Arthur R.

2003-01-01

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

Flight Test of 31.2 Diameter Modified Ringsail Parachute Deployed at Mach 1.39, Dynamic Pressure 11 Pounds per Square Foot

NASA Technical Reports Server (NTRS)

Preisser, John S.; Eckstrom, Clinton V.; Murrow, Harold N.

1967-01-01

A 31.2-foot (9.51 meter) nominal diameter (reference area 764 ft(exp 2) (71.0 m(exp 2)) ringsail parachute modified to provide 15-percent geometric porosity was flight tested while attached to a 201-pound mass (91.2 kilogram) instrumented payload as part of the rocket launch portion of the NASA Planetary Entry Parachute Program (PEPP). The parachute deployment was initiated by the firing of a mortar at a Mach number of 1.39 and a dynamic pressure of 11.0 lb/ft(exp 2) (527 newtons/m(exp 2)) at an altitude of 122,500 feet (37.3 kilometers). The parachute deployed to suspension-line stretch (snatch force) in 0.35 second, and 0.12 second later the drag force increase associated with parachute inflation began. The parachute inflated in 0.24 second to the full-open condition for a total elapsed opening time of 0.71 second. The maximum opening load of 3970 pounds (17,700 newtons) came at the time the parachute was just fully opened. During the deceleration period, the parachute exhibited an average drag coefficient of 0.52 and oscillations of the parachute canopy were less than 5 degrees. During the steady-state terminal descent portion of the test period, the average effective drag coefficient (based on vertical descent velocity) was 0.52.

They CAN and They SHOULD: Undergraduates Providing Peer Reference and Instruction

ERIC Educational Resources Information Center

Bodemer, Brett B.

2014-01-01

Peer learning dynamics have proven powerful in collegiate contexts. These dynamics should be leveraged at the undergraduate level in academic libraries for reference provision and basic information literacy instruction. Drawing on the literature of peer learning, documented examples of peer reference and instruction in academic libraries, and…

Investigation on the radial micro-motion about piston of axial piston pump

NASA Astrophysics Data System (ADS)

Xu, Bing; Zhang, Junhui; Yang, Huayong; Zhang, Bin

2013-03-01

The limit working parameters and service life of axial piston pump are determined by the carrying ability and lubrication characteristic of its key friction pairs. Therefore, the design and optimization of the key friction pairs are always a key and difficult problem in the research on axial piston pump. In the traditional research on piston/cylinder pair, the assembly relationship of piston and cylinder bore is simplified into ideal cylindrical pair, which can not be used to analyze the influences of radial micro-motion of piston on the distribution characteristics of oil-film thickness and pressure in details. In this paper, based on the lubrication theory of the oil film, a numerical simulation model is built, taking the influences of roughness, elastic deformation of piston and pressure-viscosity effect into consideration. With the simulation model, the dynamic characteristics of the radial micro-motion and pressure distribution are analyzed, and the relationships between radial micro-motion and carrying ability, lubrication condition, and abrasion are discussed. Furthermore, a model pump for pressure distribution measurement of oil film between piston and cylinder bore is designed. The comparison of simulation and experimental results of pressure distribution shows that the simulation model has high accuracy. The experiment and simulation results demonstrate that the pressure distribution has peak values that are much higher than the boundary pressure in the piston chamber due to the radial micro-motion, and the abrasion of piston takes place mainly on the hand close to piston ball. In addition, improvement of manufacturing roundness and straightness of piston and cylinder bore is helpful to improve the carrying ability of piston/cylinder pair. The proposed research provides references for designing piston/cylinder pair, and helps to prolong the service life of axial piston pump.

On-line calibration of high-response pressure transducers during jet-engine testing

NASA Technical Reports Server (NTRS)

Armentrout, E. C.

1974-01-01

Jet engine testing is reported concerned with the effect of inlet pressure and temperature distortions on engine performance and involves the use of numerous miniature pressure transducers. Despite recent improvements in the manufacture of miniature pressure transducers, they still exhibit sensitivity change and zero-shift with temperature and time. To obtain meaningful data, a calibration system is needed to determine these changes. A system has been developed which provides for computer selection of appropriate reference pressures selected from nine different sources to provide a two- or three-point calibration. Calibrations are made on command, before and sometimes after each data point. A unique no leak matrix valve design is used in the reference pressure system. Zero-shift corrections are measured and the values are automatically inserted into the data reduction program.

Study of methods of improving the performance of the Langley Research Center Transonic Dynamics Tunnel (TDT)

NASA Technical Reports Server (NTRS)

1973-01-01

A study has been made of possible ways to improve the performance of the Langley Research Center's Transonic Dynamics Tunnel (TDT). The major effort was directed toward obtaining increased dynamic pressure in the Mach number range from 0.8 to 1.2, but methods to increase Mach number capability were also considered. Methods studied for increasing dynamic pressure capability were higher total pressure, auxiliary suction, reducing circuit losses, reduced test medium temperature, smaller test section and higher molecular weight test medium. Increased Mach number methods investigated were nozzle block inserts, variable geometry nozzle, changes in test section wall configuration, and auxiliary suction.

Reference Canopy Stomatal Conductance Explains Spatiotemporal Patterns of Tree Transpiration

NASA Astrophysics Data System (ADS)

Loranty, M. M.; Mackay, D. S.; Ewers, B. E.; Kruger, E. L.; Traver, E.

2007-12-01

Increased heterogeneity in patterns of whole tree transpiration (EC) with increasing atmospheric vapor pressure deficit (D) suggests a dynamic response of sap flow velocity (JS) to environmental drivers. We hypothesized that differences in reference stomatal conductance (GSref), stomatal conductance at D = 1kPa, would explain the spatiotemporal dynamics of JS. Using a coupled model of plant hydraulic and biochemical processes we tested this hypothesis with sap flux data for 106 aspen ( Populus tremuloides) and 108 sugar maple ( Acer saccharum) trees collected from plots using in 2-D cyclic sampling scheme during the summer of 2005 in northern Wisconsin. Inverse modeling is used to estimate GSref for each tree. For each species, trees from across the ranges of JS and diameter distributions are compared. GSref explained temporal variability in spatial patterns of EC We explore several possible mechanistic explanations for differences in GSref among trees. Topoedaphic factors are considered to determine if location within a stand has an effect. We also consider competition with neighboring individuals as a possible explanation. Variations in GSref in aspen were explained in part by competition for light between neighboring individuals, while competition for light was not a significant factor for sugar maple. Based on simulation analysis we identify possible biochemical feedbacks as drivers of the variability in plant hydraulics. Other factors examined included micro-topography within both sites.

Bilateral key comparison CCM.P-K3.1 for absolute pressure measurements from 3 × 10-6 Pa to 9 × 10-4 Pa

NASA Astrophysics Data System (ADS)

Fedchak, J. A.; Bock, Th; Jousten, K.

2014-01-01

This report describes the bilateral key comparison CCM.P-K3.1 between the National Institute of Standards and Technology (NIST) and Physikalisch-Technische Bundesanstalt (PTB) for absolute pressure in the range from 3 × 10-6 Pa to 9 × 10-4 Pa. This comparison was a follow-up to the comparison CCM.P-K3. Two ionization gauges and two spinning rotor gauges (SRGs) were used as the transfer standards for the comparison. The SRGs were used to compare the standards at a pressure of 9 × 10-4 Pa and to normalize the ionization gauge readings. The two ionization gauges were used to compare the standards in the pressure range of from 3 × 10-6 Pa to 3 × 10-4 Pa. Both laboratories used dynamic expansion chambers as standards in the comparison. The two labs showed excellent agreement with each other and with the CCM.P-K3 key comparison reference value (KCRV) over the entire range. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Toward a mineral physics reference model for the Moon’s core

PubMed Central

Antonangeli, Daniele; Morard, Guillaume; Schmerr, Nicholas C.; Komabayashi, Tetsuya; Krisch, Michael; Fiquet, Guillaume; Fei, Yingwei

2015-01-01

The physical properties of iron (Fe) at high pressure and high temperature are crucial for understanding the chemical composition, evolution, and dynamics of planetary interiors. Indeed, the inner structures of the telluric planets all share a similar layered nature: a central metallic core composed mostly of iron, surrounded by a silicate mantle, and a thin, chemically differentiated crust. To date, most studies of iron have focused on the hexagonal closed packed (hcp, or ε) phase, as ε-Fe is likely stable across the pressure and temperature conditions of Earth’s core. However, at the more moderate pressures characteristic of the cores of smaller planetary bodies, such as the Moon, Mercury, or Mars, iron takes on a face-centered cubic (fcc, or γ) structure. Here we present compressional and shear wave sound velocity and density measurements of γ-Fe at high pressures and high temperatures, which are needed to develop accurate seismic models of planetary interiors. Our results indicate that the seismic velocities proposed for the Moon’s inner core by a recent reanalysis of Apollo seismic data are well below those of γ-Fe. Our dataset thus provides strong constraints to seismic models of the lunar core and cores of small telluric planets. This allows us to propose a direct compositional and velocity model for the Moon’s core. PMID:25775531

Molecular dynamics of liquid SiO2 under high pressure

NASA Technical Reports Server (NTRS)

Rustad, James R.; Yuen, David A.; Spera, Frank J.

1990-01-01

The molecular dynamics of pure SiO2 liquids was investigated up to pressures of 20 GPa at 4000 K using 252, 498, 864, and 1371 particles. The results obtained suggest that the pressure-induced maxima in the self-diffusion coefficients of both oxygen and silicon are dependent on the system size. In the case of larger systems, the maximum decreases and shifts to lower pressures. Changes in the velocity autocorrelation function with increasing pressure are described. The populations of anomalously coordinated silicon and oxygen are then discussed as a function of pressure and system size.

Dynamic Pressure Calibration Standard

NASA Technical Reports Server (NTRS)

Schutte, P. C.; Cate, K. H.; Young, S. D.

1986-01-01

Vibrating columns of fluid used to calibrate transducers. Dynamic pressure calibration standard developed for calibrating flush diaphragm-mounted pressure transducers. Pressures up to 20 kPa (3 psi) accurately generated over frequency range of 50 to 1,800 Hz. System includes two conically shaped aluminum columns one 5 cm (2 in.) high for low pressures and another 11 cm (4.3 in.) high for higher pressures, each filled with viscous fluid. Each column mounted on armature of vibration exciter, which imparts sinusoidally varying acceleration to fluid column. Signal noise low, and waveform highly dependent on quality of drive signal in vibration exciter.

Real-time combustion control and diagnostics sensor-pressure oscillation monitor

DOEpatents

Chorpening, Benjamin T [Morgantown, WV; Thornton, Jimmy [Morgantown, WV; Huckaby, E David [Morgantown, WV; Richards, George A [Morgantown, WV

2009-07-14

An apparatus and method for monitoring and controlling the combustion process in a combustion system to determine the amplitude and/or frequencies of dynamic pressure oscillations during combustion. An electrode in communication with the combustion system senses hydrocarbon ions and/or electrons produced by the combustion process and calibration apparatus calibrates the relationship between the standard deviation of the current in the electrode and the amplitudes of the dynamic pressure oscillations by applying a substantially constant voltage between the electrode and ground resulting in a current in the electrode and by varying one or more of (1) the flow rate of the fuel, (2) the flow rate of the oxidant, (3) the equivalence ratio, (4) the acoustic tuning of the combustion system, and (5) the fuel distribution in the combustion chamber such that the amplitudes of the dynamic pressure oscillations in the combustion chamber are calculated as a function of the standard deviation of the electrode current. Thereafter, the supply of fuel and/or oxidant is varied to modify the dynamic pressure oscillations.

Dynamic analysis of solid propellant grains subjected to ignition pressurization loading

NASA Astrophysics Data System (ADS)

Chyuan, Shiang-Woei

2003-11-01

Traditionally, the transient analysis of solid propellant grains subjected to ignition pressurization loading was not considered, and quasi-elastic-static analysis was widely adopted for structural integrity because the analytical task gets simplified. But it does not mean that the dynamic effect is not useful and could be neglected arbitrarily, and this effect usually plays a very important role for some critical design. In order to simulate the dynamic response for solid rocket motor, a transient finite element model, accompanied by concepts of time-temperature shift principle, reduced integration and thermorheologically simple material assumption, was used. For studying the dynamic response, diverse ignition pressurization loading cases were used and investigated in the present paper. Results show that the dynamic effect is important for structural integrity of solid propellant grains under ignition pressurization loading. Comparing the effective stress of transient analysis and of quasi-elastic-static analysis, one can see that there is an obvious difference between them because of the dynamic effect. From the work of quasi-elastic-static and transient analyses, the dynamic analysis highlighted several areas of interest and a more accurate and reasonable result could be obtained for the engineer.

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 effectiveness of vane-aileron excitation in the experimental determination of flutter speed by parameter identification

NASA Technical Reports Server (NTRS)

Nissim, Eli

1990-01-01

The effectiveness of aerodynamic excitation is evaluated analytically in conjunction with the experimental determination of flutter dynamic pressure by parameter identification. Existing control surfaces were used, with an additional vane located at the wingtip. The equations leading to the identification of the equations of motion were reformulated to accommodate excitation forces of aerodynamic origin. The aerodynamic coefficients of the excitation forces do not need to be known since they are determined by the identification procedure. The 12 degree-of-freedom numerical example treated in this work revealed the best wingtip vane locations, and demonstrated the effectiveness of the aileron-vane excitation system. Results from simulated data gathered at much lower dynamic pressures (approximately half the value of flutter dynamic pressure) predicted flutter dynamic pressures with 2-percent errors.

Options for Dealing with Pressure Dependence of Pulse Wave Velocity as a Measure of Arterial Stiffness: An Update of Cardio-Ankle Vascular Index (CAVI) and CAVI0.

PubMed

Spronck, Bart; Delhaas, Tammo; Butlin, Mark; Reesink, Koen D; Avolio, Alberto P

2018-03-01

Pulse wave velocity (PWV), a marker of arterial stiffness, is known to change instantaneously with changes in blood pressure. In this mini-review, we discuss two main approaches for handling the blood pressure dependence of PWV: (1) converting PWV into a pressure-independent index, and (2) correcting PWV per se for the pressure dependence. Under option 1, we focus on cardio-ankle vascular index (CAVI). CAVI is essentially a form of stiffness index β - CAVI is estimated for a (heart-to-ankle) trajectory, whereas β is estimated for a single artery from pressure and diameter measurements. Stiffness index β, and therefore also CAVI, have been shown to theoretically exhibit a slight residual blood pressure dependence due to the use of diastolic blood pressure instead of a fixed reference blood pressure. Additionally, CAVI exhibits pressure dependence due to the use of an estimated derivative of the pressure-diameter relationship. In this mini-review, we will address CAVI's blood pressure dependence theoretically, but also statistically. Furthermore, we review corrected indices (CAVI 0 and β 0 ) that theoretically do not show a residual blood pressure dependence. Under option 2, three ways of correcting PWV are reviewed: (1) using an exponential relationship between pressure and cross-sectional area, (2) by statistical model adjustment, and (3) through reference values or rule of thumb. Method 2 requires a population to be studied to characterise the statistical model, and method 3 requires a representative reference study. Given these limitations, method 1 seems preferable for correcting PWV per se for its blood pressure dependence. In summary, several options are available to handle the blood pressure dependence of PWV. If a blood pressure-independent index is sought, CAVI 0 is theoretically preferable over CAVI. If correcting PWV per se is required, using an exponential pressure-area relationship provides the user with a method to correct PWV on an individual basis.

Dynamic diamond anvil cell (dDAC): A novel device for studying the dynamic-pressure properties of materials

NASA Astrophysics Data System (ADS)

Evans, William J.; Yoo, Choong-Shik; Lee, Geun Woo; Cynn, Hyunchae; Lipp, Magnus J.; Visbeck, Ken

2007-07-01

We have developed a unique device, a dynamic diamond anvil cell (dDAC), which repetitively applies a time-dependent load/pressure profile to a sample. This capability allows studies of the kinetics of phase transitions and metastable phases at compression (strain) rates of up to 500GPa/s (˜0.16s-1 for a metal). Our approach adapts electromechanical piezoelectric actuators to a conventional diamond anvil cell design, which enables precise specification and control of a time-dependent applied load/pressure. Existing DAC instrumentation and experimental techniques are easily adapted to the dDAC to measure the properties of a sample under the varying load/pressure conditions. This capability addresses the sparsely studied regime of dynamic phenomena between static research (diamond anvil cells and large volume presses) and dynamic shock-driven experiments (gas guns, explosive, and laser shock). We present an overview of a variety of experimental measurements that can be made with this device.

First-principles molecular dynamics simulations of anorthite (CaAl2Si2O8) glass at high pressure

NASA Astrophysics Data System (ADS)

Ghosh, Dipta B.; Karki, Bijaya B.

2018-06-01

We report first-principles molecular dynamics study of the equation of state, structural, and elastic properties of CaAl2Si2O8 glass at 300 K as a function of pressure up to 155 GPa. Our results for the ambient pressure glass show that: (1) as with other silicates, Si atoms remain mostly (> 95%) under tetrahedral oxygen surroundings; (2) unlike anorthite crystal, presence of high-coordination (> 4) Al atoms with 30% abundance; (3) and significant presence of both non-bridging (8%) and triply (17%) coordinated oxygen. To achieve the glass configurations at various pressures, we use two different simulation schedules: cold and hot compression. Cold compression refers to sequential compression at 300 K. Compression at 3000 K and subsequent isochoric quenching to 300 K is considered as hot compression. At the initial stages of compression (0-10 GPa), smooth increase in bond distance and coordination occurs in the hot-compressed glass. Whereas in cold compression, Si (also Al to some extent) displays mainly topological changes (without significantly affecting the average bond distance or coordination) in this pressure interval. Further increase in pressure results in gradual increases in mean coordination, with Si-O (Al-O) coordination eventually reaching and remaining 6 (6.5) at the highest compression. Similarly, the ambient pressure Ca-O coordination of 5.9 increases to 9.5 at 155 GPa. The continuous pressure-induced increase in the proportion of oxygen triclusters along with the appearance and increasing abundance of tetrahedral oxygens results in mean O-T (T = Si and Al) coordination of > 3 from a value of 2.1 at ambient pressure. Due to the absence of kinetic barrier, the hot-compressed glasses consistently produce greater densities and higher coordination numbers than the cold compression cases. Decompressed glasses show irreversible compaction along with retention of high-coordination species when decompressed from pressure ≥ 10 GPa. The different density retention amounts (12, 17, and 20% when decompressed from 12, 40, and 155 GPa, respectively) signifies that the degree of irreversibility depends on the peak pressure of decompression. The calculated compressional and shear wave velocities (5 and 3 km/s at 0 GPa) for the cold-compressed case display sluggish pressure response in the 0-10 GPa interval as opposed to smooth increase in the hot-compressed one. Shear velocity saturates rather rapidly with a value of 5 km/s, whereas compressional wave velocity displays continuous increase, reaching/exceeding 12.5 km/s at 155 GPa. These structural details suggest that the pressure response of the cold-compressed glasses is not only inherently different at the 0-10 GPa interval, the density, coordination, and wave velocity data are consistently lower than the hot-compressed glasses. Hot-compressed glasses may, therefore, be the better analog in the study of high-pressure silicate melts.

Pre-Test Assessment of the Use Envelope of the Normal Force of a Wind Tunnel Strain-Gage Balance

NASA Technical Reports Server (NTRS)

Ulbrich, N.

2016-01-01

The relationship between the aerodynamic lift force generated by a wind tunnel model, the model weight, and the measured normal force of a strain-gage balance is investigated to better understand the expected use envelope of the normal force during a wind tunnel test. First, the fundamental relationship between normal force, model weight, lift curve slope, model reference area, dynamic pressure, and angle of attack is derived. Then, based on this fundamental relationship, the use envelope of a balance is examined for four typical wind tunnel test cases. The first case looks at the use envelope of the normal force during the test of a light wind tunnel model at high subsonic Mach numbers. The second case examines the use envelope of the normal force during the test of a heavy wind tunnel model in an atmospheric low-speed facility. The third case reviews the use envelope of the normal force during the test of a floor-mounted semi-span model. The fourth case discusses the normal force characteristics during the test of a rotated full-span model. The wind tunnel model's lift-to-weight ratio is introduced as a new parameter that may be used for a quick pre-test assessment of the use envelope of the normal force of a balance. The parameter is derived as a function of the lift coefficient, the dimensionless dynamic pressure, and the dimensionless model weight. Lower and upper bounds of the use envelope of a balance are defined using the model's lift-to-weight ratio. Finally, data from a pressurized wind tunnel is used to illustrate both application and interpretation of the model's lift-to-weight ratio.

A flatness-based control approach to drug infusion for cardiac function regulation

NASA Astrophysics Data System (ADS)

Rigatos, Gerasimos; Zervos, Nikolaos; Melkikh, Alexey

2016-12-01

A new control method based on differential flatness theory is developed in this article, aiming at solving the problem of regulation of haemodynamic parameters, Actually control of the cardiac output (volume of blood pumped out by heart per unit of time) and of the arterial blood pressure is achieved through the administered infusion of cardiovascular drugs, such as dopamine and sodium nitroprusside. Time delays between the control inputs and the system's outputs are taken into account. Using the principle of dynamic extension, which means that by considering certain control inputs and their derivatives as additional state variables, a state-space description for the heart's function is obtained. It is proven that the dynamic model of the heart is a differentially flat one. This enables its transformation into a linear canonical and decoupled form, for which the design of a stabilizing feedback controller becomes possible. The proposed feedback controller is of proven stability and assures fast and accurate tracking of the reference setpoints by the outputs of the heart's dynamic model. Moreover, by using a Kalman Filter-based disturbances' estimator, it becomes possible to estimate in real-time and compensate for the model uncertainty and external perturbation inputs that affect the heart's model.

Simulating shock-bubble interactions at water-gelatin interfaces

NASA Astrophysics Data System (ADS)

Adami, Stefan; Kaiser, Jakob; Bermejo-Moreno, Ivan; Adams, Nikolaus

2016-11-01

Biomedical problems are often driven by fluid dynamics, as in vivo organisms are usually composed of or filled with fluids that (strongly) affected their physics. Additionally, fluid dynamical effects can be used to enhance certain phenomena or destroy organisms. As examples, we highlight the benign potential of shockwave-driven kidney-stone lithotripsy or sonoporation (acoustic cavitation of microbubbles) to improve drug delivery into cells. During the CTR SummerProgram 2016 we have performed axisymmetric three-phase simulations of a shock hitting a gas bubble in water near a gelatin interface mimicking the fundamental process during sonoporation. We used our multi-resolution finite volume method with sharp interface representation (level-set), WENO-5 shock capturing and interface scale-separation and compared the results with a diffuse-interface method. Qualitatively our simulation results agree well with the reference. Due to the interface treatment the pressure profiles are sharper in our simulations and bubble collapse dynamics are predicted at shorter time-scales. Validation with free-field collapse (Rayleigh collapse) shows very good agreement. The project leading to this application has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (Grant agreement No 667483).

Dynamic pressure sensor calibration techniques offering expanded bandwidth with increased resolution

NASA Astrophysics Data System (ADS)

Wisniewiski, David

2015-03-01

Advancements in the aerospace, defense and energy markets are being made possible by increasingly more sophisticated systems and sub-systems which rely upon critical information to be conveyed from the physical environment being monitored through ever more specialized, extreme environment sensing components. One sensing parameter of particular interest is dynamic pressure measurement. Crossing the boundary of all three markets (i.e. aerospace, defense and energy) is dynamic pressure sensing which is used in research and development of gas turbine technology, and subsequently embedded into a control loop used for long-term monitoring. Applications include quantifying the effects of aircraft boundary layer ingestion into the engine inlet to provide a reliable and robust design. Another application includes optimization of combustor dynamics by "listening" to the acoustic signature so that fuel-to-air mixture can be adjusted in real-time to provide cost operating efficiencies and reduced NOx emissions. With the vast majority of pressure sensors supplied today being calibrated either statically or "quasi" statically, the dynamic response characterization of the frequency dependent sensitivity (i.e. transfer function) of the pressure sensor is noticeably absent. The shock tube has been shown to be an efficient vehicle to provide frequency response of pressure sensors from extremely high frequencies down to 500 Hz. Recent development activity has lowered this starting frequency; thereby augmenting the calibration bandwidth with increased frequency resolution so that as the pressure sensor is used in an actual test application, more understanding of the physical measurement can be ascertained by the end-user.

Spontaneous ignition temperature limits of jet A fuel in research-combustor segment

NASA Technical Reports Server (NTRS)

Ingebo, R. D.

1974-01-01

The effects of inlet-air pressure and reference velocity on the spontaneous-ignition temperature limits of Jet A fuel were determined in a combustor segment with a primary-zone length of 0.076 m (3 in.). At a constant reference velocity of 21.4 m/sec (170 ft/sec), increasing the inlet-air pressure from 21 to 207 N/sq cm decreased the spontaneous-ignition temperature limit from approximately 700 to 555 K. At a constant inlet-air pressure of 41 N/sq cm, increasing the reference velocity from 12.2 to 30.5 m/sec increased the spontaneous-ignition temperature limit from approximately 575 to 800 K. Results are compared with other data in the literature.

Liquid gating elastomeric porous system with dynamically controllable gas/liquid transport.

PubMed

Sheng, Zhizhi; Wang, Honglong; Tang, Yongliang; Wang, Miao; Huang, Lizhi; Min, Lingli; Meng, Haiqiang; Chen, Songyue; Jiang, Lei; Hou, Xu

2018-02-01

The development of membrane technology is central to fields ranging from resource harvesting to medicine, but the existing designs are unable to handle the complex sorting of multiphase substances required for many systems. Especially, the dynamic multiphase transport and separation under a steady-state applied pressure have great benefits for membrane science, but have not been realized at present. Moreover, the incorporation of precisely dynamic control with avoidance of contamination of membranes remains elusive. We show a versatile strategy for creating elastomeric microporous membrane-based systems that can finely control and dynamically modulate the sorting of a wide range of gases and liquids under a steady-state applied pressure, nearly eliminate fouling, and can be easily applied over many size scales, pressures, and environments. Experiments and theoretical calculation demonstrate the stability of our system and the tunability of the critical pressure. Dynamic transport of gas and liquid can be achieved through our gating interfacial design and the controllable pores' deformation without changing the applied pressure. Therefore, we believe that this system will bring new opportunities for many applications, such as gas-involved chemical reactions, fuel cells, multiphase separation, multiphase flow, multiphase microreactors, colloidal particle synthesis, and sizing nano/microparticles.

Liquid gating elastomeric porous system with dynamically controllable gas/liquid transport

PubMed Central

Sheng, Zhizhi; Wang, Honglong; Tang, Yongliang; Wang, Miao; Huang, Lizhi; Min, Lingli; Meng, Haiqiang; Chen, Songyue; Jiang, Lei; Hou, Xu

2018-01-01

The development of membrane technology is central to fields ranging from resource harvesting to medicine, but the existing designs are unable to handle the complex sorting of multiphase substances required for many systems. Especially, the dynamic multiphase transport and separation under a steady-state applied pressure have great benefits for membrane science, but have not been realized at present. Moreover, the incorporation of precisely dynamic control with avoidance of contamination of membranes remains elusive. We show a versatile strategy for creating elastomeric microporous membrane-based systems that can finely control and dynamically modulate the sorting of a wide range of gases and liquids under a steady-state applied pressure, nearly eliminate fouling, and can be easily applied over many size scales, pressures, and environments. Experiments and theoretical calculation demonstrate the stability of our system and the tunability of the critical pressure. Dynamic transport of gas and liquid can be achieved through our gating interfacial design and the controllable pores’ deformation without changing the applied pressure. Therefore, we believe that this system will bring new opportunities for many applications, such as gas-involved chemical reactions, fuel cells, multiphase separation, multiphase flow, multiphase microreactors, colloidal particle synthesis, and sizing nano/microparticles. PMID:29487906

Method and apparatus for monitoring oxygen partial pressure in air masks

NASA Technical Reports Server (NTRS)

Kelly, Mark E. (Inventor); Pettit, Donald R. (Inventor)

2006-01-01

Method and apparatus are disclosed for monitoring an oxygen partial pressure in an air mask and providing a tactile warning to the user. The oxygen partial pressure in the air mask is detected using an electrochemical sensor, the output signal from which is provided to a comparator. The comparator compares the output signal with a preset reference value or range of values representing acceptable oxygen partial pressures. If the output signal is different than the reference value or outside the range of values, the air mask is vibrated by a vibrating motor to alert the user to a potentially hypoxic condition.

Dynamic Characteristics of The DSI-Type Constant-Flow Valves

NASA Astrophysics Data System (ADS)

Kang, Yuan; Hu, Sheng-Yan; Chou, Hsien-Chin; Lee, Hsing-Han

Constant flow valves have been presented in industrial applications or academic studies, which compensate recess pressures of a hydrostatic bearing to resist load fluctuating. The flow rate of constant-flow valves can be constant in spite of the pressure changes in recesses, however the design parameters must be specified. This paper analyzes the dynamic responses of DSI-type constant-flow valves that is designed as double pistons on both ends of a spool with single feedback of working pressure and regulating restriction at inlet. In this study the static analysis presents the specific relationships among design parameters for constant flow rate and the dynamic analyses give the variations around the constant flow rate as the working pressure fluctuates.

Pressure calculation in hybrid particle-field simulations

NASA Astrophysics Data System (ADS)

Milano, Giuseppe; Kawakatsu, Toshihiro

2010-12-01

In the framework of a recently developed scheme for a hybrid particle-field simulation techniques where self-consistent field (SCF) theory and particle models (molecular dynamics) are combined [J. Chem. Phys. 130, 214106 (2009)], we developed a general formulation for the calculation of instantaneous pressure and stress tensor. The expressions have been derived from statistical mechanical definition of the pressure starting from the expression for the free energy functional in the SCF theory. An implementation of the derived formulation suitable for hybrid particle-field molecular dynamics-self-consistent field simulations is described. A series of test simulations on model systems are reported comparing the calculated pressure with those obtained from standard molecular dynamics simulations based on pair potentials.

CIELO-A GIS integrated model for climatic and water balance simulation in islands environments

NASA Astrophysics Data System (ADS)

Azevedo, E. B.; Pereira, L. S.

2003-04-01

The model CIELO (acronym for "Clima Insular à Escala Local") is a physically based model that simulates the climatic variables in an island using data from a single synoptic reference meteorological station. The reference station "knows" its position in the orographic and dynamic regime context. The domain of computation is a GIS raster grid parameterised with a digital elevation model (DEM). The grid is oriented following the direction of the air masses circulation through a specific algorithm named rotational terrain model (RTM). The model consists of two main sub-models. One, relative to the advective component simulation, assumes the Foehn effect to reproduce the dynamic and thermodynamic processes occurring when an air mass moves through the island orographic obstacle. This makes possible to simulate the air temperature, air humidity, cloudiness and precipitation as influenced by the orography along the air displacement. The second concerns the radiative component as affected by the clouds of orographic origin and by the shadow produced by the relief. The initial state parameters are computed starting from the reference meteorological station across the DEM transept until the sea level at the windward side. Then, starting from the sea level, the model computes the local scale meteorological parameters according to the direction of the air displacement, which is adjusted with the RTM. The air pressure, temperature and humidity are directly calculated for each cell in the computational grid, while several algorithms are used to compute the cloudiness, net radiation, evapotranspiration, and precipitation. The model presented in this paper has been calibrated and validated using data from some meteorological stations and a larger number of rainfall stations located at various elevations in the Azores Islands.

A unifying model for elongational flow of polymer melts and solutions based on the interchain tube pressure concept

NASA Astrophysics Data System (ADS)

Wagner, Manfred Hermann; Rolón-Garrido, Víctor Hugo

2015-04-01

An extended interchain tube pressure model for polymer melts and concentrated solutions is presented, based on the idea that the pressures exerted by a polymer chain on the walls of an anisotropic confinement are anisotropic (M. Doi and S. F. Edwards, The Theory of Polymer Dynamics, Oxford University Press, New York, 1986). In a tube model with variable tube diameter, chain stretch and tube diameter reduction are related, and at deformation rates larger than the inverse Rouse time τR, the chain is stretched and its confining tube becomes increasingly anisotropic. Tube diameter reduction leads to an interchain pressure in the lateral direction of the tube, which is proportional to the 3rd power of stretch (G. Marrucci and G. Ianniruberto. Macromolecules 37, 3934-3942, 2004). In the extended interchain tube pressure (EIP) model, it is assumed that chain stretch is balanced by interchain tube pressure in the lateral direction, and by a spring force in the longitudinal direction of the tube, which is linear in stretch. The scaling relations established for the relaxation modulus of concentrated solutions of polystyrene in oligomeric styrene (M. H. Wagner, Rheol. Acta 53, 765-777, 2014, M. H. Wagner, J. Non-Newtonian Fluid Mech. http://dx.doi.org/10.1016/j.jnnfm.2014.09.017, 2014) are applied to the solutions of polystyrene (PS) in diethyl phthalate (DEP) investigated by Bhattacharjee et al. (P. K. Bhattacharjee et al., Macromolecules 35, 10131-10148, 2002) and Acharya et al. (M. V. Acharya et al. AIP Conference Proceedings 1027, 391-393, 2008). The scaling relies on the difference ΔTg between the glass-transition temperatures of the melt and the glass-transition temperatures of the solutions. ΔTg can be inferred from the reported zero-shear viscosities, and the BSW spectra of the solutions are obtained from the BSW spectrum of the reference melt with good accuracy. Predictions of the EIP model are compared to the steady-state elongational viscosity data of PS/DEP solutions. Except for a possible influence of solvent quality, linear and nonlinear viscoelasticity of entangled polystyrene solutions can thus be obtained from the linear-viscoelastic characteristics of a reference polymer melt and the shift of the glass transition temperature between melt and solution.

Scale Dependence of Dark Energy Antigravity

NASA Astrophysics Data System (ADS)

Perivolaropoulos, L.

2002-09-01

We investigate the effects of negative pressure induced by dark energy (cosmological constant or quintessence) on the dynamics at various astrophysical scales. Negative pressure induces a repulsive term (antigravity) in Newton's law which dominates on large scales. Assuming a value of the cosmological constant consistent with the recent SnIa data we determine the critical scale $r_c$ beyond which antigravity dominates the dynamics ($r_c \\sim 1Mpc $) and discuss some of the dynamical effects implied. We show that dynamically induced mass estimates on the scale of the Local Group and beyond are significantly modified due to negative pressure. We also briefly discuss possible dynamical tests (eg effects on local Hubble flow) that can be applied on relatively small scales (a few $Mpc$) to determine the density and equation of state of dark energy.

On the dynamic response of pressure transmission lines in the research of helium-charged free piston Stirling engines

NASA Technical Reports Server (NTRS)

Miller, Eric L.; Dudenhoefer, James E.

1989-01-01

The signal distortion inherent to pressure transmission lines in free-piston Stirling engine research is discussed. Based on results from classical analysis, guidelines are formulated to describe the dynamic response properties of a volume-terminated transmission tube for applications involving the helium-charged free-piston Stirling engines. The underdamped flow regime is described, the primary resonance frequency is derived, and the pressure phase and amplitude distortion are discussed. The scope and limitation of the dynamic response analysis are considered.

Unsteady-Pressure and Dynamic-Deflection Measurements on an Aeroelastic Supercritical Wing

NASA Technical Reports Server (NTRS)

Seidel, David A.; Sandford, Maynard C.; Eckstrom, Clinton V.

1991-01-01

Transonic steady and unsteady pressure tests were conducted on a large elastic wing. The wing has a supercritical airfoil, a full span aspect ratio of 10.3, a leading edge sweepback angle of 28.8 degrees, and two inboard and one outboard trailing edge control surfaces. Only the outboard control surface was deflected statically and dynamically to generate steady and unsteady flow over the wing. The unsteady surface pressure and dynamic deflection measurements of this elastic wing are presented to permit correlations of the experimental data with theoretical predictions.

Fluid Dynamic Mechanisms and Interactions within Separated Flows.

DTIC Science & Technology

1986-07-01

Vol. 42, Series E, No., pp. 197, pp. 387-39S. b5-bD, March N95, 18. Warpinski , N. R., and Chow, W. L., "Base Pres- 27. Chow, W. L., "Base Pressure of a...lied Rocket/Plume Fluid Dynamic Interactions, Vol. Mechanics, Vol. 46, No. 3, Sept. 197. 1, Base Flows, Fluid Dynamic Lab Report 63-101, 19. Warpinski ...34Surface Pressure Measurements ’" Warpinski , N. R. and Chow, W. L., "Base Pressure Associated on a Boattailed Projectile Shape at Transonic Speeds," ARBRL

Microenvironment is involved in cellular response to hydrostatic pressures during chondrogenesis of mesenchymal stem cells.

PubMed

Ye, Rui; Hao, Jin; Song, Jinlin; Zhao, Zhihe; Fang, Shanbao; Wang, Yating; Li, Juan

2014-06-01

Chondrocytes integrate numerous microenvironmental cues to mount physiologically relevant differentiation responses, and the regulation of mechanical signaling in chondrogenic differentiation is now coming into intensive focus. To facilitate tissue-engineered chondrogenesis by mechanical strategy, a thorough understanding about the interactional roles of chemical factors under mechanical stimuli in regulating chondrogenesis is in great need. Therefore, this study attempts to investigate the interaction of rat MSCs with their microenvironment by imposing dynamic and static hydrostatic pressure through modulating gaseous tension above the culture medium. Under dynamic pressure, chemical parameters (pH, pO2, and pCO2) were kept in homeostasis. In contrast, pH was remarkably reduced due to increased pCO2 under static pressure. MSCs under the dynamically pressured microenvironment exhibited a strong accumulation of GAG within and outside the alginate beads, while cells under the statically pressured environment lost newly synthesized GAG into the medium with a speed higher than its production. In addition, the synergic influence on expression of chondrogenic genes was more persistent under dynamic pressure than that under static pressure. This temporal contrast was similar to that of activation of endogenous TGF-β1. Taken altogether, it indicates that a loading strategy which can keep a homeostatic chemical microenvironment is preferred, since it might sustain the stimulatory effects of mechanical stimuli on chondrogenesis via activation of endogenous TGF-β1. © 2013 Wiley Periodicals, Inc.

Autonomic neural control of dynamic cerebral autoregulation in humans

NASA Technical Reports Server (NTRS)

Zhang, Rong; Zuckerman, Julie H.; Iwasaki, Kenichi; Wilson, Thad E.; Crandall, Craig G.; Levine, Benjamin D.

2002-01-01

BACKGROUND: The purpose of the present study was to determine the role of autonomic neural control of dynamic cerebral autoregulation in humans. METHODS AND RESULTS: We measured arterial pressure and cerebral blood flow (CBF) velocity in 12 healthy subjects (aged 29+/-6 years) before and after ganglion blockade with trimethaphan. CBF velocity was measured in the middle cerebral artery using transcranial Doppler. The magnitude of spontaneous changes in mean blood pressure and CBF velocity were quantified by spectral analysis. The transfer function gain, phase, and coherence between these variables were estimated to quantify dynamic cerebral autoregulation. After ganglion blockade, systolic and pulse pressure decreased significantly by 13% and 26%, respectively. CBF velocity decreased by 6% (P<0.05). In the very low frequency range (0.02 to 0.07 Hz), mean blood pressure variability decreased significantly (by 82%), while CBF velocity variability persisted. Thus, transfer function gain increased by 81%. In addition, the phase lead of CBF velocity to arterial pressure diminished. These changes in transfer function gain and phase persisted despite restoration of arterial pressure by infusion of phenylephrine and normalization of mean blood pressure variability by oscillatory lower body negative pressure. CONCLUSIONS: These data suggest that dynamic cerebral autoregulation is altered by ganglion blockade. We speculate that autonomic neural control of the cerebral circulation is tonically active and likely plays a significant role in the regulation of beat-to-beat CBF in humans.

Temperature and pressure effects on GFP mutants: explaining spectral changes by molecular dynamics simulations and TD-DFT calculations.

PubMed

Jacchetti, Emanuela; Gabellieri, Edi; Cioni, Patrizia; Bizzarri, Ranieri; Nifosì, Riccardo

2016-05-14

By combining spectroscopic measurements under high pressure with molecular dynamics simulations and quantum mechanics calculations we investigate how sub-angstrom structural perturbations are able to tune protein function. We monitored the variations in fluorescence output of two green fluorescent protein mutants (termed Mut2 and Mut2Y, the latter containing the key T203Y mutation) subjected to pressures up to 600 MPa, at various temperatures in the 280-320 K range. By performing 150 ns molecular dynamics simulations of the protein structures at various pressures, we evidenced subtle changes in conformation and dynamics around the light-absorbing chromophore. Such changes explain the measured spectral tuning in the case of the sizable 120 cm(-1) red-shift observed for pressurized Mut2Y, but absent in Mut2. Previous work [Barstow et al., Proc. Natl. Acad. Sci. U. S. A., 2008, 105, 13362] on pressure effects on GFP also involved a T203Y mutant. On the basis of cryocooling X-ray crystallography, the pressure-induced fluorescence blue shift at low temperature (77 K) was attributed to key changes in relative conformation of the chromophore and Tyr203 phenol ring. At room temperature, however, a red shift was observed at high pressure, analogous to the one we observe in Mut2Y. Our investigation of structural variations in compressed Mut2Y also explains their result, bridging the gap between low-temperature and room-temperature high-pressure effects.

Dynamics of Choice: A Tutorial

ERIC Educational Resources Information Center

Baum, William M.

2010-01-01

Choice may be defined as the allocation of behavior among activities. Since all activities take up time, choice is conveniently thought of as the allocation of time among activities, even if activities like pecking are most easily measured by counting. Since dynamics refers to change through time, the dynamics of choice refers to change of…

Latitudinal Dependence of the Radial IMF Component: Coronal Imprint

NASA Technical Reports Server (NTRS)

Suess, S. T.; Smith, E. J.

1996-01-01

Measurements by Ulysses have confirmed that there is no significant gradient with respect to heliomagnetic latitude in the radial component, B(sub r,) of the interplanetary magnetic field. In the corona, the plasma, beta is much less than 1, except directly above streamers, so longitudinal and latitudinal gradients in field strength will relax due to the transverse magnetic pressure gradient force as the solar wind carries magnetic flux away from the Sun. This happens quickly enough so that the field is essentially uniform by 5 - 10 solar radius, apparently remaining so as it is carried to beyond 1 AU. Here, we illustrate the coronal relaxation with a qualitative physical argument and by reference to a detailed Magneto HydroDynamics (MHD) simulation.

Molecular dynamics modelling of solidification in metals

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

Boercker, D.B.; Belak, J.; Glosli, J.

1997-12-31

Molecular dynamics modeling is used to study the solidification of metals at high pressure and temperature. Constant pressure MD is applied to a simulation cell initially filled with both solid and molten metal. The solid/liquid interface is tracked as a function of time, and the data are used to estimate growth rates of crystallites at high pressure and temperature in Ta and Mg.

Dynamic tire pressure sensor for measuring ground vibration.

PubMed

Wang, Qi; McDaniel, James Gregory; Wang, Ming L

2012-11-07

This work presents a convenient and non-contact acoustic sensing approach for measuring ground vibration. This approach, which uses an instantaneous dynamic tire pressure sensor (DTPS), possesses the capability to replace the accelerometer or directional microphone currently being used for inspecting pavement conditions. By measuring dynamic pressure changes inside the tire, ground vibration can be amplified and isolated from environmental noise. In this work, verifications of the DTPS concept of sensing inside the tire have been carried out. In addition, comparisons between a DTPS, ground-mounted accelerometer, and directional microphone are made. A data analysis algorithm has been developed and optimized to reconstruct ground acceleration from DTPS data. Numerical and experimental studies of this DTPS reveal a strong potential for measuring ground vibration caused by a moving vehicle. A calibration of transfer function between dynamic tire pressure change and ground acceleration may be needed for different tire system or for more accurate application.

Dynamic Tire Pressure Sensor for Measuring Ground Vibration

PubMed Central

Wang, Qi; McDaniel, James Gregory; Wang, Ming L.

2012-01-01

This work presents a convenient and non-contact acoustic sensing approach for measuring ground vibration. This approach, which uses an instantaneous dynamic tire pressure sensor (DTPS), possesses the capability to replace the accelerometer or directional microphone currently being used for inspecting pavement conditions. By measuring dynamic pressure changes inside the tire, ground vibration can be amplified and isolated from environmental noise. In this work, verifications of the DTPS concept of sensing inside the tire have been carried out. In addition, comparisons between a DTPS, ground-mounted accelerometer, and directional microphone are made. A data analysis algorithm has been developed and optimized to reconstruct ground acceleration from DTPS data. Numerical and experimental studies of this DTPS reveal a strong potential for measuring ground vibration caused by a moving vehicle. A calibration of transfer function between dynamic tire pressure change and ground acceleration may be needed for different tire system or for more accurate application. PMID:23202206

Report of the panel on earth rotation and reference frames, section 7

NASA Technical Reports Server (NTRS)

Dickey, Jean O.; Dickman, Steven R.; Eubanks, Marshall T.; Feissel, Martine; Herring, Thomas A.; Mueller, Ivan I.; Rosen, Richard D.; Schutz, Robert E.; Wahr, John M.; Wilson, Charles R.

1991-01-01

Objectives and requirements for Earth rotation and reference frame studies in the 1990s are discussed. The objectives are to observe and understand interactions of air and water with the rotational dynamics of the Earth, the effects of the Earth's crust and mantle on the dynamics and excitation of Earth rotation variations over time scales of hours to centuries, and the effects of the Earth's core on the rotational dynamics and the excitation of Earth rotation variations over time scales of a year or longer. Another objective is to establish, refine and maintain terrestrial and celestrial reference frames. Requirements include improvements in observations and analysis, improvements in celestial and terrestrial reference frames and reference frame connections, and improved observations of crustal motion and mass redistribution on the Earth.

Association of Severe Traumatic Brain Injury Patient Outcomes With Duration of Cerebrovascular Autoregulation Impairment Events.

PubMed

Preiksaitis, Aidanas; Krakauskaite, Solventa; Petkus, Vytautas; Rocka, Saulius; Chomskis, Romanas; Dagi, Teodoro Forcht; Ragauskas, Arminas

2016-07-01

Cerebrovascular autoregulation (CA) is an important hemodynamic mechanism that protects the brain against inappropriate fluctuations in cerebral blood flow in the face of changing cerebral perfusion pressure. Temporal CA failure is associated with worse outcomes in various acute neurological diseases. An integrative approach is presently used according to the existing paradigm for the association of series of temporal CA impairments with the outcomes of patients with traumatic brain injury (TBI). To explore the influence of the duration of CA impairment events on severe TBI patient outcomes. Patient age was also included in the analysis of the prospectively collected clinical data. CA monitoring included 33 prospective severe TBI patients. The pressure reactivity index [PRx(t)] was continuously monitored to collect information on the dynamics of CA status and to analyze associations between the duration of the longest CA impairment event and patient outcomes. The Glasgow outcome scale and the duration of the longest CA impairment were negatively correlated. The duration of autoregulation impairment significantly correlated with worse outcomes. Multidimensional representation of Glasgow outcome scale plots showed that better outcomes were obtained for younger patients (age < 47 years) and those whose longest CA impairment event was shorter than 40 minutes if PRx(t) was above 0.7 in the CA impairment event. Unfavorable outcomes for TBI patients are more significantly associated with the duration of the single longest CA impairment episode at a high PRx(t) value, rather than with averaged PRx(t) values or the average time of all CA impairment episodes. ABP, arterial blood pressureABP(t), continuous reference arterial blood pressureCA, cerebrovascular autoregulationCBF, cerebral blood flowCPP, cerebral perfusion pressureGOS, Glasgow outcome scaleGOSHD, Glasgow outcome scale after hospital dischargeGOS6M, Glasgow outcome scale at 6 months after dischargeICP, intracranial pressureICP(t), continuously monitored intracranial pressureLCAI, longest CA impairmentoptCPP, optimal cerebral perfusion pressurePRx(t), pressure reactivity indexTBI, traumatic brain injury.

Pressure effect on phonon frequencies in some transition metals: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Kazanc, S.; Ozgen, S.

2005-08-01

It is important to determine the atomic lattice vibrations of metallic materials, under high-pressure conditions, due to its effects on material properties such as thermal, electrical and optical conductions. In this work, we have investigated the changes of acoustic phonon frequencies with hydrostatic pressure for Cu, Ni, Al, Ag and Au transition metals, using molecular dynamics (MD) simulations based on embedded atom method (EAM). For this aim, we have adopted the embedded atom potential proposed by Sutton and Chen. The phonon frequencies have been calculated from the dynamical matrix for [1 0 0], [1 1 0] and [1 1 1] high symmetry directions of the Brillouin zone. The obtained results show that the hydrostatic pressure causes an increment in phonon frequencies, and this rising do not depend linearly on the increasing pressure.

Effect of thermal pressurization on dynamic rupture propagation under depth-dependent stress

NASA Astrophysics Data System (ADS)

Urata, Y.; Kuge, K.; Kase, Y.

2009-12-01

Fluid and pore pressure evolution can affect dynamic propagation of earthquake ruptures owing to thermal pressurization (e.g., Mase and Smith, 1985). We investigate dynamic rupture propagation with thermal pressurization on a fault subjected to depth-dependent stress, on the basis of 3-D numerical simulations for spontaneous dynamic ruptures. We put a vertical strike-slip rectangular fault in a semi-infinite, homogenous, and elastic medium. The length and width of the fault are 8 and 3 km, respectively. We assume a depth-dependent stress estimated by Yamashita et al. (2004). The numerical algorithm is based on the finite-difference method by Kase and Kuge (2001). A rupture is initiated by increasing shear stress in a small patch at the bottom of the fault, and then proceeds spontaneously, governed by a slip-weakening law with the Coulomb failure criteria. Coefficients of friction and Dc are homogeneous on the fault. On a fault with thermal pressurization, we allow effective normal stress to vary with pore pressure change due to frictional heating by the formulation of Bizzarri and Cocco (2006). When thermal pressurization does not work, tractions drop in the same way everywhere and rupture velocity is subshear except near the free surface. Due to thermal pressurization, dynamic friction on the fault decreases and is heterogeneous not only vertically but horizontally, slip increases, and rupture velocity along the strike direction becomes supershear. As a result, plural peaks of final slip appear, as observed in the case of undrained dip-slip fault by Urata et al. (2008). We found in this study that the early stage of rupture growth under the depth-dependent stress is affected by the location of an initial crack. When a rupture is initiated at the center of the fault without thermal pressurization, the rupture cannot propagate and terminates. Thermal pressurization can help such a powerless rupture to keep propagating.

Noninvasive monitoring of blood pressure using optical Ballistocardiography and Photoplethysmograph approaches.

PubMed

Chen, Zhihao; Yang, Xiufeng; Teo, Ju Teng; Ng, Soon Huat

2013-01-01

A new all optical method for long term and continuous blood pressure measurement and monitoring without using cuffs is proposed by using Ballistocardiography (BCG) and Photoplethysmograph (PPG). Based on BCG signal and PPG signal, a time delay between these two signals is obtained to calculate both systolic blood pressure and diastolic blood pressure via linear regression analysis. The fabricated noninvasive blood pressure monitoring device consists of a fiber sensor mat to measure BCG signal and a SpO2 sensor to measure PPG signal. A commercial digital oscillometric blood pressure meter is used to obtain reference values and for calibration. It has been found that by comparing with the reference device, our prototype has typical means and standard deviations of 9+/-5.6 mmHg for systolic blood pressure, 1.8+/-1.3 mmHg for diastolic blood pressure and 0.6+/-0.9 bpm for pulse rate, respectively. If the fiber optic SpO2 probe is used, this new all fiber cuffless noninvasive blood pressure monitoring device will truly be a MRI safe blood pressure measurement and monitoring device.

75 FR 61432 - Takes of Marine Mammals Incidental to Specified Activities; Construction of the Parsons Slough...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-05

... a medium, such as air or water. Sound levels are compared to a reference sound pressure to identify the medium. For air and water, these reference pressures are ``re 20 microPa'' and ``re 1 microPa... produce a wide range of social signals, most occurring at relatively low frequencies (Southall et al...

Changing the "Normal Range" for Blood Pressure from 140/90 to 130/Any Improves Risk Assessment.

PubMed

Fulks, Michael; Stout, Robert L; Dolan, Vera F

2015-01-01

Objective .- Redefine the "normal" reference range for blood pressure from <140/90 to one that more effectively identifies individuals with increased mortality risk. Method .- Data from the recently published 2014 CRL blood pressure study was used. It includes 2,472,706 life insurance applicants tested by Clinical Reference Laboratory from 1993 to 2007 with follow-up for vital status using the September 2011 Social Security Death Master File. Various upper limits of blood pressure (BP in mm Hg) were evaluated to determine if any was superior to the current, commonly used limit of 140/90 in identifying individuals with increased mortality risk. Results .- An alternative reference range using a systolic BP (SBP) <130 with any diastolic BP (DBP) included 84% of life insurance applicants. It had a lower mortality rate and narrower range of relative risk than <140/90, including 89% as many applicants but only 68% as many deaths. This pattern of lives and deaths was consistent across age and sex. Conclusion .- Switching to a "normal" reference range of SBP <130 offers superior risk assessment relative to using BP <140/90 while still including a sufficient percentage of the population.

Design and development of a cost effective plantar pressure distribution analysis system for the dynamically moving feet.

PubMed

Karkokli, R; McConville, K M Valter

2006-01-01

This paper portrays the design and instrumentation of a low cost plantar pressure analysis system, suitable for clinical podiatry. The system measures plantar pressure between the foot and shoe during dynamic movement in real-time, which can be used in clinical gait analysis. It contains a pressure sensing insole which the patient can insert in his/her shoe, and user-friendly software to graph and analyze the data. Applications include occupational health and safety, research and private practice.

Dynamic pressure probe response tests for robust measurements in periodic flows close to probe resonating frequency

NASA Astrophysics Data System (ADS)

Ceyhun Şahin, Fatma; Schiffmann, Jürg

2018-02-01

A single-hole probe was designed to measure steady and periodic flows with high fluctuation amplitudes and with minimal flow intrusion. Because of its high aspect ratio, estimations showed that the probe resonates at a frequency two orders of magnitude lower than the fast response sensor cut-off frequencies. The high fluctuation amplitudes cause a non-linear behavior of the probe and available models are neither adequate for a quantitative estimation of the resonating frequencies nor for predicting the system damping. Instead, a non-linear data correction procedure based on individual transfer functions defined for each harmonic contribution is introduced for pneumatic probes that allows to extend their operating range beyond the resonating frequencies and linear dynamics. This data correction procedure was assessed on a miniature single-hole probe of 0.35 mm inner diameter which was designed to measure flow speed and direction. For the reliable use of such a probe in periodic flows, its frequency response was reproduced with a siren disk, which allows exciting the probe up to 10 kHz with peak-to-peak amplitudes ranging between 20%-170% of the absolute mean pressure. The effect of the probe interior design on the phase lag and amplitude distortion in periodic flow measurements was investigated on probes with similar inner diameters and different lengths or similar aspect ratios (L/D) and different total interior volumes. The results suggest that while the tube length consistently sets the resonance frequency, the internal total volume affects the non-linear dynamic response in terms of varying gain functions. A detailed analysis of the introduced calibration methodology shows that the goodness of the reconstructed data compared to the reference data is above 75% for fundamental frequencies up to twice the probe resonance frequency. The results clearly suggest that the introduced procedure is adequate to capture non-linear pneumatic probe dynamics and to reproduce time-resolved data far above probe resonant frequency.

Quantifying patterns of change in marine ecosystem response to multiple pressures.

PubMed

Large, Scott I; Fay, Gavin; Friedland, Kevin D; Link, Jason S

2015-01-01

The ability to understand and ultimately predict ecosystem response to multiple pressures is paramount to successfully implement ecosystem-based management. Thresholds shifts and nonlinear patterns in ecosystem responses can be used to determine reference points that identify levels of a pressure that may drastically alter ecosystem status, which can inform management action. However, quantifying ecosystem reference points has proven elusive due in large part to the multi-dimensional nature of both ecosystem pressures and ecosystem responses. We used ecological indicators, synthetic measures of ecosystem status and functioning, to enumerate important ecosystem attributes and to reduce the complexity of the Northeast Shelf Large Marine Ecosystem (NES LME). Random forests were used to quantify the importance of four environmental and four anthropogenic pressure variables to the value of ecological indicators, and to quantify shifts in aggregate ecological indicator response along pressure gradients. Anthropogenic pressure variables were critical defining features and were able to predict an average of 8-13% (up to 25-66% for individual ecological indicators) of the variation in ecological indicator values, whereas environmental pressures were able to predict an average of 1-5 % (up to 9-26% for individual ecological indicators) of ecological indicator variation. Each pressure variable predicted a different suite of ecological indicator's variation and the shapes of ecological indicator responses along pressure gradients were generally nonlinear. Threshold shifts in ecosystem response to exploitation, the most important pressure variable, occurred when commercial landings were 20 and 60% of total surveyed biomass. Although present, threshold shifts in ecosystem response to environmental pressures were much less important, which suggests that anthropogenic pressures have significantly altered the ecosystem structure and functioning of the NES LME. Gradient response curves provide ecologically informed transformations of pressure variables to explain patterns of ecosystem structure and functioning. By concurrently identifying thresholds for a suite of ecological indicator responses to multiple pressures, we demonstrate that ecosystem reference points can be evaluated and used to support ecosystem-based management.

Dynamics of Oxidation of Aluminum Nanoclusters using Variable Charge Molecular-Dynamics Simulations on Parallel Computers

NASA Astrophysics Data System (ADS)

Campbell, Timothy; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya; Ogata, Shuji; Rodgers, Stephen

1999-06-01

Oxidation of aluminum nanoclusters is investigated with a parallel molecular-dynamics approach based on dynamic charge transfer among atoms. Structural and dynamic correlations reveal that significant charge transfer gives rise to large negative pressure in the oxide which dominates the positive pressure due to steric forces. As a result, aluminum moves outward and oxygen moves towards the interior of the cluster with the aluminum diffusivity 60% higher than that of oxygen. A stable 40 Å thick amorphous oxide is formed; this is in excellent agreement with experiments.

Selective serotonin reuptake inhibitors and intraoperative blood pressure.

PubMed

van Haelst, Ingrid M M; van Klei, Wilton A; Doodeman, Hieronymus J; Kalkman, Cor J; Egberts, Toine C G

2012-02-01

The influence of selective serotonin reuptake inhibitors (SSRIs) on blood pressure is poorly understood. We hypothesized that if SSRIs have an influence on blood pressure, this might become manifest in changes in intraoperative blood pressure. We aimed to study the association between perioperative use of SSRIs and changes in intraoperative blood pressure by measuring the occurrence of intraoperative hyper- and hypotension. We conducted a retrospective observational follow-up study among patients who underwent elective primary total hip arthroplasty. The index group included users of SSRIs. The reference group included a random sample (ratio 1:3) of nonusers of an antidepressant agent. The outcome was the occurrence of intraoperative hypo- and hypertensive episodes (number, mean and total duration, and area under the curve (AUC)). The outcome was adjusted for confounding factors using regression techniques. The index group included 20 users of an SSRI. The reference group included 60 nonusers. Users of SSRIs showed fewer intraoperative hypotensive episodes, a shorter mean and total duration, and a smaller AUC when compared to the reference group. After adjustment for confounders, SSRI use was associated with a significantly shorter total duration of hypotension: mean difference of -29.4 min (95% confidence interval (CI) -50.4 to -8.3). Two users of an SSRI and two patients in the reference group had a hypertensive episode. Continuation of treatment with SSRIs before surgery was associated with a briefer duration of intraoperative hypotension.

A recurrence network approach for the analysis of skin blood flow dynamics in response to loading pressure.

PubMed

Liao, Fuyuan; Jan, Yih-Kuen

2012-06-01

This paper presents a recurrence network approach for the analysis of skin blood flow dynamics in response to loading pressure. Recurrence is a fundamental property of many dynamical systems, which can be explored in phase spaces constructed from observational time series. A visualization tool of recurrence analysis called recurrence plot (RP) has been proved to be highly effective to detect transitions in the dynamics of the system. However, it was found that delay embedding can produce spurious structures in RPs. Network-based concepts have been applied for the analysis of nonlinear time series recently. We demonstrate that time series with different types of dynamics exhibit distinct global clustering coefficients and distributions of local clustering coefficients and that the global clustering coefficient is robust to the embedding parameters. We applied the approach to study skin blood flow oscillations (BFO) response to loading pressure. The results showed that global clustering coefficients of BFO significantly decreased in response to loading pressure (p<0.01). Moreover, surrogate tests indicated that such a decrease was associated with a loss of nonlinearity of BFO. Our results suggest that the recurrence network approach can practically quantify the nonlinear dynamics of BFO.

Closed-loop control of renal perfusion pressure in physiological experiments.

PubMed

Campos-Delgado, D U; Bonilla, I; Rodríguez-Martínez, M; Sánchez-Briones, M E; Ruiz-Hernández, E

2013-07-01

This paper presents the design, experimental modeling, and control of a pump-driven renal perfusion pressure (RPP)-regulatory system to implement precise and relatively fast RPP regulation in rats. The mechatronic system is a simple, low-cost, and reliable device to automate the RPP regulation process based on flow-mediated occlusion. Hence, the regulated signal is the RPP measured in the left femoral artery of the rat, and the manipulated variable is the voltage applied to a dc motor that controls the occlusion of the aorta. The control system is implemented in a PC through the LabView software, and a data acquisition board NI USB-6210. A simple first-order linear system is proposed to approximate the dynamics in the experiment. The parameters of the model are chosen to minimize the error between the predicted and experimental output averaged from eight input/output datasets at different RPP operating conditions. A closed-loop servocontrol system based on a pole-placement PD controller plus dead-zone compensation was proposed for this purpose. First, the feedback structure was validated in simulation by considering parameter uncertainty, and constant and time-varying references. Several experimental tests were also conducted to validate in real time the closed-loop performance for stepwise and fast switching references, and the results show the effectiveness of the proposed automatic system to regulate the RPP in the rat, in a precise, accurate (mean error less than 2 mmHg) and relatively fast mode (10-15 s of response time).

Development of a primary diffusion source of organic vapors for gas analyzer calibration

NASA Astrophysics Data System (ADS)

Lecuna, M.; Demichelis, A.; Sassi, G.; Sassi, M. P.

2018-03-01

The generation of reference mixtures of volatile organic compounds (VOCs) at trace levels (10 ppt-10 ppb) is a challenge for both environmental and clinical measurements. The calibration of gas analyzers for trace VOC measurements requires a stable and accurate source of the compound of interest. The dynamic preparation of gas mixtures by diffusion is a suitable method for fulfilling these requirements. The estimation of the uncertainty of the molar fraction of the VOC in the mixture is a key step in the metrological characterization of a dynamic generator. The performance of a dynamic generator was monitored over a wide range of operating conditions. The generation system was simulated by a model developed with computational fluid dynamics and validated against experimental data. The vapor pressure of the VOC was found to be one of the main contributors to the uncertainty of the diffusion rate and its influence at 10-70 kPa was analyzed and discussed. The air buoyancy effect and perturbations due to the weighing duration were studied. The gas carrier flow rate and the amount of liquid in the vial were found to play a role in limiting the diffusion rate. The results of sensitivity analyses were reported through an uncertainty budget for the diffusion rate. The roles of each influence quantity were discussed. A set of criteria to minimize the uncertainty contribution to the primary diffusion source (25 µg min-1) were estimated: carrier gas flow rate higher than 37.7 sml min-1, a maximum VOC liquid mass decrease in the vial of 4.8 g, a minimum residual mass of 1 g and vial weighing times of 1-3 min. With this procedure a limit uncertainty of 0.5% in the diffusion rate can be obtained for VOC mixtures at trace levels (10 ppt-10 ppb), making the developed diffusion vials a primary diffusion source with potential to become a new reference material for trace VOC analysis.

Pulse Wave Velocity as Marker of Preclinical Arterial Disease: Reference Levels in a Uruguayan Population Considering Wave Detection Algorithms, Path Lengths, Aging, and Blood Pressure

PubMed Central

Farro, Ignacio; Bia, Daniel; Zócalo, Yanina; Torrado, Juan; Farro, Federico; Florio, Lucía; Olascoaga, Alicia; Alallón, Walter; Lluberas, Ricardo; Armentano, Ricardo L.

2012-01-01

Carotid-femoral pulse wave velocity (PWV) has emerged as the gold standard for non-invasive evaluation of aortic stiffness; absence of standardized methodologies of study and lack of normal and reference values have limited a wider clinical implementation. This work was carried out in a Uruguayan (South American) population in order to characterize normal, reference, and threshold levels of PWV considering normal age-related changes in PWV and the prevailing blood pressure level during the study. A conservative approach was used, and we excluded symptomatic subjects; subjects with history of cardiovascular (CV) disease, diabetes mellitus or renal failure; subjects with traditional CV risk factors (other than age and gender); asymptomatic subjects with atherosclerotic plaques in carotid arteries; patients taking anti-hypertensives or lipid-lowering medications. The included subjects (n = 429) were categorized according to the age decade and the blood pressure levels (at study time). All subjects represented the “reference population”; the group of subjects with optimal/normal blood pressures levels at study time represented the “normal population.” Results. Normal and reference PWV levels were obtained. Differences in PWV levels and aging-associated changes were obtained. The obtained data could be used to define vascular aging and abnormal or disease-related arterial changes. PMID:22666551

High Strain Rate Testing of Rocks using a Split-Hopkinson-Pressure Bar

NASA Astrophysics Data System (ADS)

Zwiessler, Ruprecht; Kenkmann, Thomas; Poelchau, Michael; Nau, Siegfried; Hess, Sebastian

2016-04-01

Dynamic mechanical testing of rocks is important to define the onset of rate dependency of brittle failure. The strain rate dependency occurs through the propagation velocity limit (Rayleigh wave speed) of cracks and their reduced ability to coalesce, which, in turn, significantly increases the strength of the rock. We use a newly developed pressurized air driven Split-Hopkinson-Pressure Bar (SHPB), that is specifically designed for the investigation of high strain rate testing of rocks, consisting of several 10 to 50 cm long strikers and bar components of 50 mm in diameter and 2.5 meters in length each. The whole set up, composed of striker, incident- and transmission bar is available in aluminum, titanium and maraging steel to minimize the acoustic impedance contrast, determined by the change of density and speed of sound, to the specific rock of investigation. Dynamic mechanical parameters are obtained in compression as well as in spallation configuration, covering a wide spectrum from intermediate to high strain rates (100-103 s-1). In SHPB experiments [1] one-dimensional longitudinal compressive pulses of diverse shapes and lengths - formed with pulse shapers - are used to generate a variety of loading histories under 1D states of stress in cylindrical rock samples, in order to measure the respective stress-strain response at specific strain rates. Subsequent microstructural analysis of the deformed samples is aimed at quantification fracture orientation, fracture pattern, fracture density, and fracture surface properties as a function of the loading rate. Linking mechanical and microstructural data to natural dynamic deformation processes has relevance for the understanding of earthquakes, landslides, impacts, and has several rock engineering applications. For instance, experiments on dynamic fragmentation help to unravel super-shear rupture events that pervasively pulverize rocks up to several hundred meters from the fault core [2, 3, 4]. The dynamic, strain rate dependent behavior with strongly increasing strength and changing fracturing process has not been consequently considered in modeling of geo-hazards such as earthquakes, rock falls, landslides or even meteorite impacts [5]. Incorporation of dynamic material data therefore will contribute to improvements of forecast models and the understanding of fast geodynamic processes. References [1] Zhang, Q. B. & Zhao, J. (2013). A Review of Dynamic Experimental Techniques and Mechanical Behaviour of Rock Materials. Rock Mech Rock Eng. DOI 10.1007/s00603-013-0463-y [2] Doan, M. L., & Gary, G. (2009). Rock pulverization at high strain rate near the San Andreas fault. Nature Geosci., 2, 709-712. [3] Reches, Z. E., & Dewers, T. A. (2005). Gouge formation by dynamic pulverization during earthquake rupture. Earth Planet. Sci. Lett., 235, 361-374. [4] Fondriest, M., Aretusini, S., Di Toro, G., & Smith, S. A. (2015). Fracturing and rock pulverization along an exhumed seismogenic fault zone in dolostones: The Foiana Fault Zone (Southern Alps, Italy). Tectonophys.654, 56-74. [5] Kenkmann, T., Poelchau, M. H., & Wulf, G. (2014). Structural Geology of impact craters. J. .Struct. Geol., 62, 156-182.

Pressure Relief Devices

NASA Astrophysics Data System (ADS)

Manha, William D.

2010-09-01

Pressure relief devices are used in pressure systems and on pressure vessels to prevent catastrophic rupture or explosion from excessive pressure. Pressure systems and pressure vessels have manufacturers maximum rated operating pressures or maximum design pressures(MDP) for which there are relatively high safety factors and minimum risk of rupture or explosion. Pressure systems and pressure vessels that have a potential to exceed the MDP by being connected to another higher pressure source, a compressor, or heat to water(boiler) are required to have over-pressure protecting devices. Such devices can be relief valves and/or burst discs to safely relieve potentially excessive pressure and prevent unacceptable ruptures and explosions which result in fail-safe pressure systems and pressure vessels. Common aerospace relief valve and burst disc requirements and standards will be presented. This will include the NASA PSRP Interpretation Letter TA-88-074 Fault Tolerance of Systems Using Specially Certified Burst Disks that dictates burst disc requirements for payloads on Shuttle. Two recent undesirable manned space payloads pressure relief devices and practices will be discussed, as well as why these practices should not be continued. One example for discussion is the use of three burst discs that have been placed in series to comply with safety requirements of three controls to prevent a catastrophic hazard of the over-pressurization and rupture of pressure system and/or vessels. The cavities between the burst discs are evacuated and are the reference pressures for activating the two upstream burst discs. If the upstream burst disc leaks into the reference cavity, the reference pressure increases and it can increase the burst disc activating pressure and potentially result in the burst disc assembly being ineffective for over pressure protection. The three burst discs-in-series assembly was found acceptable because the burst discs are designed for minimum risk(DFMR) of leakage into the reference cavity. Since the burst discs are DFMR, a single burst disc would suffice, without adding the two leak-into-reference cavity failure modes. A single DFMR burst disc is preferable. An Alpha Magnetic Spectrometer - 02 burst disc assembly, with three-in-series burst discs test failure, necessitated the deletion of one of the burst discs, will be presented. Payload relief valves require periodic retests were extended significantly beyond the normal one year retest period because of the reduced ISS down mass capability which followed the Columbia accident. The acceptability of the extended retest period was determined by analysis, materials stability, benign environment, relatively inert fluid exposure, etc.(The policy letter, NC4-02-205 Guidelines for Certification and Verification of Pressure System Control Hardware, that permitted this action will be provided even though this application is not recommended for extending relief valve annual retest requirements.) The first crack pressure of a relief valve after an extended inactive period can be higher than the set crack pressure. Extrapolation of the extended inactive period and increased crack pressure could result in ineffective over pressure protection. Thus, relief valves with a ring or lever for activation are recommended so the relief valve can periodically be verified to open, functionality verified and the extended relief valve retest period should be discouraged. Stainless Steel cylindrical poppet-in-cylindrical housing check valves should never be used in a fluid with ions for an extended period of time, because the poppet is vulnerable to seizing or not functioning as a relief valve, even though the specifications, crack pressure, reseat pressure, maximum flow, and reseat leak look very much like the specifications for a relief valve. The technical reasons for this avoidance of using check valves as a relief valve will be discussed. The presentation will be summarized and recommendations made.

How the Toughest Inorganic Fullerene Cages Absorb Shockwave Pressures in a Protective Nanocomposite: Experimental Evidence from Two In Situ Investigations.

PubMed

Xu, Fang; Kobayashi, Takamichi; Yang, Zhuxian; Sekine, Toshimori; Chang, Hong; Wang, Nannan; Xia, Yongde; Zhu, Yanqiu

2017-08-22

Nanocomposites fabricated using the toughest caged inorganic fullerene WS 2 (IF-WS 2 ) nanoparticles could offer ultimate protection via absorbing shockwaves; however, if the IF-WS 2 nanomaterials really work, how they behave and what they experience within the nanocomposites at the right moment of impact have never been investigated effectively, due to the limitations of existing investigation techniques that are unable to elucidate the true characteristics of high-speed impacts in composites. We first fabricated Al matrix model nanocomposites and then unlocked the exact roles of IF-WS 2 in it at the exact moment of impact, at a time resolution that has never been attempted before, using two in situ techniques. We find that the presence of IF-WS 2 reduced the impact velocity by over 100 m/s and in pressure by at least 2 GPa against those Al and hexagonal WS 2 platelet composites at an impact speed of 1000 m/s. The IF-WS 2 composites achieved an intriguing inelastic impact and outperformed other reference composites, all originating from the "balloon effect" by absorbing the shockwave pressures. This study not only provides fundamental understanding for the dynamic performance of composites but also benefits the development of protective nanocomposite engineering.

Pressure-based high-order TVD methodology for dynamic stall control

NASA Astrophysics Data System (ADS)

Yang, H. Q.; Przekwas, A. J.

1992-01-01

The quantitative prediction of the dynamics of separating unsteady flows, such as dynamic stall, is of crucial importance. This six-month SBIR Phase 1 study has developed several new pressure-based methodologies for solving 3D Navier-Stokes equations in both stationary and moving (body-comforting) coordinates. The present pressure-based algorithm is equally efficient for low speed incompressible flows and high speed compressible flows. The discretization of convective terms by the presently developed high-order TVD schemes requires no artificial dissipation and can properly resolve the concentrated vortices in the wing-body with minimum numerical diffusion. It is demonstrated that the proposed Newton's iteration technique not only increases the convergence rate but also strongly couples the iteration between pressure and velocities. The proposed hyperbolization of the pressure correction equation is shown to increase the solver's efficiency. The above proposed methodologies were implemented in an existing CFD code, REFLEQS. The modified code was used to simulate both static and dynamic stalls on two- and three-dimensional wing-body configurations. Three-dimensional effect and flow physics are discussed.

Increasing blood flow to exercising muscle attenuates systemic cardiovascular responses during dynamic exercise in humans

PubMed Central

Ichinose-Kuwahara, Tomoko; Kondo, Narihiko; Nishiyasu, Takeshi

2015-01-01

Reducing blood flow to working muscles during dynamic exercise causes metabolites to accumulate within the active muscles and evokes systemic pressor responses. Whether a similar cardiovascular response is elicited with normal blood flow to exercising muscles during dynamic exercise remains unknown, however. To address that issue, we tested whether cardiovascular responses are affected by increases in blood flow to active muscles. Thirteen healthy subjects performed dynamic plantarflexion exercise for 12 min at 20%, 40%, and 60% of peak workload (EX20, EX40, and EX60) with their lower thigh enclosed in a negative pressure box. Under control conditions, the box pressure was the same as the ambient air pressure. Under negative pressure conditions, beginning 3 min after the start of the exercise, the box pressure was decreased by 20, 45, and then 70 mmHg in stepwise fashion with 3-min step durations. During EX20, the negative pressure had no effect on blood flow or the cardiovascular responses measured. However, application of negative pressure increased blood flow to the exercising leg during EX40 and EX60. This increase in blood flow had no significant effect on systemic cardiovascular responses during EX40, but it markedly attenuated the pressor responses otherwise seen during EX60. These results demonstrate that during mild exercise, normal blood flow to exercising muscle is not a factor eliciting cardiovascular responses, whereas it elicits an important pressor effect during moderate exercise. This suggests blood flow to exercising muscle is a major determinant of cardiovascular responses during dynamic exercise at higher than moderate intensity. PMID:26377556

High-speed motion picture camera experiments of cavitation in dynamically loaded journal bearings

NASA Technical Reports Server (NTRS)

Jacobson, B. O.; Hamrock, B. J.

1982-01-01

A high-speed camera was used to investigate cavitation in dynamically loaded journal bearings. The length-diameter ratio of the bearing, the speeds of the shaft and bearing, the surface material of the shaft, and the static and dynamic eccentricity of the bearing were varied. The results reveal not only the appearance of gas cavitation, but also the development of previously unsuspected vapor cavitation. It was found that gas cavitation increases with time until, after many hundreds of pressure cycles, there is a constant amount of gas kept in the cavitation zone of the bearing. The gas can have pressures of many times the atmospheric pressure. Vapor cavitation bubbles, on the other hand, collapse at pressures lower than the atmospheric pressure and cannot be transported through a high-pressure zone, nor does the amount of vapor cavitation in a bearing increase with time. Analysis is given to support the experimental findings for both gas and vapor cavitation.

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

NASA Astrophysics Data System (ADS)

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

2018-01-01

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

Pressure effect on micellization of non-ionic surfactant Triton X-100

NASA Astrophysics Data System (ADS)

Espinosa, Yanis R.; Caffarena, Ernesto R.; Martínez, Yanina Berrueta; Grigera, J. Raúl

2018-02-01

Micellar aggregates can be arranged in new types of conformational assemblies when they are isotropically compressed. Thus, the pressure effects in the underlying fundamental interactions leading to self-assembly of micellar aggregates can be represented by changes in the phase boundaries with increasing pressure. In this paper, we have employed molecular dynamics simulations to study the self-assembly of micelles composed of the non-ionic surfactant Triton X-100 at the atomic scale, monitoring the changes in the solvation dynamics when the micelles are subjected to a wide range of hydrostatic pressures. The computational molecular model was capable of self-assembling and forming a non-ionic micelle, which subsequently was coupled to a high-pressure barostat producing a geometric transition of the micelle due to changes in the solvation dynamics. Accordingly, under a high pressure regime, the hydrogen bonds are redistributed, the water density is modified, and water acts as an unstructured liquid, capable of penetrating into the micelle.

Computational Fluid Dynamics Analysis of High Injection Pressure Blended Biodiesel

NASA Astrophysics Data System (ADS)

Khalid, Amir; Jaat, Norrizam; Faisal Hushim, Mohd; Manshoor, Bukhari; Zaman, Izzuddin; Sapit, Azwan; Razali, Azahari

2017-08-01

Biodiesel have great potential for substitution with petrol fuel for the purpose of achieving clean energy production and emission reduction. Among the methods that can control the combustion properties, controlling of the fuel injection conditions is one of the successful methods. The purpose of this study is to investigate the effect of high injection pressure of biodiesel blends on spray characteristics using Computational Fluid Dynamics (CFD). Injection pressure was observed at 220 MPa, 250 MPa and 280 MPa. The ambient temperature was kept held at 1050 K and ambient pressure 8 MPa in order to simulate the effect of boost pressure or turbo charger during combustion process. Computational Fluid Dynamics were used to investigate the spray characteristics of biodiesel blends such as spray penetration length, spray angle and mixture formation of fuel-air mixing. The results shows that increases of injection pressure, wider spray angle is produced by biodiesel blends and diesel fuel. The injection pressure strongly affects the mixture formation, characteristics of fuel spray, longer spray penetration length thus promotes the fuel and air mixing.

Interstellar Pickup Ion Observations to 38 au

NASA Astrophysics Data System (ADS)

McComas, D. J.; Zirnstein, E. J.; Bzowski, M.; Elliott, H. A.; Randol, B.; Schwadron, N. A.; Sokół, J. M.; Szalay, J. R.; Olkin, C.; Spencer, J.; Stern, A.; Weaver, H.

2017-11-01

We provide the first direct observations of interstellar H+ and He+ pickup ions in the solar wind from 22 to 38 au. We use the Vasyliunas and Siscoe model functional form to quantify the pickup ion distributions, and while the fit parameters generally lie outside their physically expected ranges, this form allows fits that quantify variations in the pickup H+ properties with distance. By ˜20 au, the pickup ions already provide the dominant internal pressure in the solar wind. We determine the radial trends and extrapolate them to the termination shock at ˜90 au, where the pickup H+ to core solar wind density reaches ˜0.14. The pickup H+ temperature and thermal pressure increase from 22 to 38 au, indicating additional heating of the pickup ions. This produces very large extrapolated ratios of pickup H+ to solar wind temperature and pressure, and an extrapolated ratio of the pickup ion pressure to the solar wind dynamic pressure at the termination shock of ˜0.16. Such a large ratio has profound implications for moderating the termination shock and the overall outer heliospheric interaction. We also identify suprathermal tails in the H+ spectra and complex features in the He+ spectra, likely indicating variations in the pickup ion history and processing. Finally, we discover enhancements in both H+ and He+ populations just below their cutoff energies, which may be associated with enhanced local pickup. This study serves to document the release and serves as a citable reference of these pickup ion data for broad community use and analysis.

Structural integrated sensor and actuator systems for active flow control

NASA Astrophysics Data System (ADS)

Behr, Christian; Schwerter, Martin; Leester-Schädel, Monika; Wierach, Peter; Dietzel, Andreas; Sinapius, Michael

2016-04-01

An adaptive flow separation control system is designed and implemented as an essential part of a novel high-lift device for future aircraft. The system consists of MEMS pressure sensors to determine the flow conditions and adaptive lips to regulate the mass flow and the velocity of a wall near stream over the internally blown Coanda flap. By the oscillating lip the mass flow in the blowing slot changes dynamically, consequently the momentum exchange of the boundary layer over a high lift flap required mass flow can be reduced. These new compact and highly integrated systems provide a real-time monitoring and manipulation of the flow conditions. In this context the integration of pressure sensors into flow sensing airfoils of composite material is investigated. Mechanical and electrical properties of the integrated sensors are investigated under mechanical loads during tensile tests. The sensors contain a reference pressure chamber isolated to the ambient by a deformable membrane with integrated piezoresistors connected as a Wheatstone bridge, which outputs voltage signals depending on the ambient pressure. The composite material in which the sensors are embedded consists of 22 individual layers of unidirectional glass fiber reinforced plastic (GFRP) prepreg. The results of the experiments are used for adapting the design of the sensors and the layout of the laminate to ensure an optimized flux of force in highly loaded structures primarily for future aeronautical applications. It can be shown that the pressure sensor withstands the embedding process into fiber composites with full functional capability and predictable behavior under stress.

Dynamic behaviors of cavitation bubble for the steady cavitating flow

NASA Astrophysics Data System (ADS)

Cai, Jun; Huai, Xiulan; Li, Xunfeng

2009-12-01

In this paper, by introducing the flow velocity item into the classical Rayleigh-Plesset dynamic equation, a new equation, which does not involve the time term and can describe the motion of cavitation bubble in the steady cavitating flow, has been obtained. By solving the new motion equation using Runge-Kutta fourth order method with adaptive step size control, the dynamic behaviors of cavitation bubble driven by the varying pressure field downstream of a venturi cavitation reactor are numerically simulated. The effects of liquid temperature (corresponding to the saturated vapor pressure of liquid), cavitation number and inlet pressure of venturi on radial motion of bubble and pressure pulse due to the radial motion are analyzed and discussed in detail. Some dynamic behaviors of bubble different from those in previous papers are displayed. In addition, the internal relationship between bubble dynamics and process intensification is also discussed. The simulation results reported in this work reveal the variation laws of cavitation intensity with the flow conditions of liquid, and will lay a foundation for the practical application of hydrodynamic cavitation technology.

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

Burkholder, Michael B.; Litster, Shawn, E-mail: litster@andrew.cmu.edu

In this study, we analyze the stability of two-phase flow regimes and their transitions using chaotic and fractal statistics, and we report new measurements of dynamic two-phase pressure drop hysteresis that is related to flow regime stability and channel water content. Two-phase flow dynamics are relevant to a variety of real-world systems, and quantifying transient two-phase flow phenomena is important for efficient design. We recorded two-phase (air and water) pressure drops and flow images in a microchannel under both steady and transient conditions. Using Lyapunov exponents and Hurst exponents to characterize the steady-state pressure fluctuations, we develop a new, measurablemore » regime identification criteria based on the dynamic stability of the two-phase pressure signal. We also applied a new experimental technique by continuously cycling the air flow rate to study dynamic hysteresis in two-phase pressure drops, which is separate from steady-state hysteresis and can be used to understand two-phase flow development time scales. Using recorded images of the two-phase flow, we show that the capacitive dynamic hysteresis is related to channel water content and flow regime stability. The mixed-wettability microchannel and in-channel water introduction used in this study simulate a polymer electrolyte fuel cell cathode air flow channel.« less

The National Expert Standard Pressure Ulcer Prevention in Nursing and pressure ulcer prevalence in German health care facilities: a multilevel analysis.

PubMed

Wilborn, Doris; Grittner, Ulrike; Dassen, Theo; Kottner, Jan

2010-12-01

The objective of this study was to describe the relationship between the German National Expert Standard Pressure Ulcer Prevention and the pressure ulcer prevalence in German nursing homes and hospitals. The patient outcome pressure ulcer does not only depend on individual characteristics of patients, but also on institutional factors. In Germany, National Expert Standards are evidence-based instruments that build the basis of continuing improvement in health care quality. It is expected that after having implemented the National Expert Standard Pressure Ulcer Prevention, the number of pressure ulcers should decrease in health care institutions. The analysed data were obtained from two cross-sectional studies from 2004-2005. A multilevel analysis was performed to show the impact of the National Expert Standard Pressure Ulcer Prevention on pressure ulcer prevalence. A total of 41.5% of hospitals and 38.8% of the nursing homes claimed to use the National Expert Standard in the process of developing their local protocols. The overall pressure ulcer prevalence grade 2-4 was 4.7%. Adjusted for hospital departments, survey year and individual characteristics, there was no significant difference in the prevalence of pressure ulcers between institutions that refer to the National Expert Standard or those referring to other sources in developing their local protocols (OR=1.14, 95% CI=0.90-1.44). There was no empirical evidence demonstrating that local protocols of pressure ulcer prevention based on the National Expert Standard were superior to local protocols which refer other sources of knowledge with regard to the pressure ulcer prevalence. The use of the National Expert Standard Pressure Ulcer Prevention can neither be recommended nor be refused. The recent definition of implementation of Expert Standards should be mandatory for all health care institutions which introduce Expert Standards. © 2010 Blackwell Publishing Ltd.

Dynamics of large-diameter water pipes in hydroelectric power plants

NASA Astrophysics Data System (ADS)

Pavić, G.; Chevillotte, F.; Heraud, J.

2017-04-01

An outline is made of physical behaviour of water - filled large pipes. The fluid-wall coupling, the key factor governing the pipe dynamics, is discussed in some detail. Different circumferential pipe modes and the associated cut-on frequencies are addressed from a theoretical as well as practical point of view. Major attention is paid to the breathing mode in view of its importance regarding main dynamic phenomena, such as water hammer. Selected measurement results done at EDF are presented to demonstrate how an external, non-intrusive sensor can detect pressure pulsations of the breathing mode in a pressure pipe. Differences in the pressure measurement using intrusive and non-intrusive sensors reveal the full complexity of large-diameter pipe dynamics.

First-Principles Study of the Structural, Optical, Dynamical and Thermodynamic Properties of BaZnO2 Under Pressure

NASA Astrophysics Data System (ADS)

Wang, Yi-Xian; Hu, Cui-E.; Chen, Yang-Mei; Cheng, Yan; Ji, Guang-Fu

2016-11-01

The structural, optical, dynamical, and thermodynamic properties of BaZnO2 under pressure are studied based on the density functional theory. The calculated structural parameters are consistent with the available experimental data. In the ground state, the electronic band structure and density of states indicate that BaZnO2 is an insulator with a direct gap of 2.2 eV. The Mulliken charges are also analyzed to characterize the bonding property. After the structural relaxation, the optical properties are studied. It is found that the dielectric function of E Vert x and EVert y are isotropic, whereas the EVert x and EVert z are anisotropic. The effect of pressure on the energy-loss function in the ultraviolet region becomes more obvious as the pressure increases. Furthermore, the dynamical properties under different pressures are investigated using the finite displacement method. We find that the P3121 phase of BaZnO2 is dynamically stable under the pressure ranging from 0 GPa to 30 GPa. The phonon dispersion curves, phonon density of states, vibrational modes and atoms that contribute to these vibrations at {{\\varvec{Γ }}} point under different pressures are also reported in this work. Finally, by employing the quasi-harmonic approximation, the thermodynamic properties such as the temperature dependence of the thermal expansion coefficient, specific heat, entropy and Gibbs free energy under different pressures are investigated. It is found that the influences of the temperature on the heat capacity are much more significant than that of the pressure on it.

A National Trial on Differences in Cerebral Perfusion Pressure Values by Measurement Location.

PubMed

McNett, Molly M; Bader, Mary Kay; Livesay, Sarah; Yeager, Susan; Moran, Cristina; Barnes, Arianna; Harrison, Kimberly R; Olson, DaiWai M

2018-04-01

Cerebral perfusion pressure (CPP) is a key parameter in management of brain injury with suspected impaired cerebral autoregulation. CPP is calculated by subtracting intracranial pressure (ICP) from mean arterial pressure (MAP). Despite consensus on importance of CPP monitoring, substantial variations exist on anatomical reference points used to measure arterial MAP when calculating CPP. This study aimed to identify differences in CPP values based on measurement location when using phlebostatic axis (PA) or tragus (Tg) as anatomical reference points. The secondary study aim was to determine impact of differences on patient outcomes at discharge. This was a prospective, repeated measures, multi-site national trial. Adult ICU patients with neurological injury necessitating ICP and CPP monitoring were consecutively enrolled from seven sites. Daily MAP/ICP/CPP values were gathered with the arterial transducer at the PA, followed by the Tg as anatomical reference points. A total of 136 subjects were enrolled, resulting in 324 paired observations. There were significant differences for CPP when comparing values obtained at PA and Tg reference points (p < 0.000). Differences remained significant in repeated measures model when controlling for clinical factors (mean CPP-PA = 80.77, mean CPP-Tg = 70.61, p < 0.000). When categorizing CPP as binary endpoint, 18.8% of values were identified as adequate with PA values, yet inadequate with CPP values measured at the Tg. Findings identify numerical differences for CPP based on anatomical reference location and highlight importance of a standard reference point for both clinical practice and future trials to limit practice variations and heterogeneity of findings.

Experimental study on a comparison of typical premixed combustible gas-air flame propagation in a horizontal rectangular closed duct.

PubMed

Jin, Kaiqiang; Duan, Qiangling; Liew, K M; Peng, Zhongjing; Gong, Liang; Sun, Jinhua

2017-04-05

Research surrounding premixed flame propagation in ducts has a history of more than one hundred years. Most previous studies focus on the tulip flame formation and flame acceleration in pure gas fuel-air flame. However, the premixed natural gas-air flame may show different behaviors and pressure dynamics due to its unique composition. Natural gas, methane and acetylene are chosen here to conduct a comparison study on different flame behaviors and pressure dynamics, and to explore the influence of different compositions on premixed flame dynamics. The characteristics of flame front and pressure dynamics are recorded using high-speed schlieren photography and a pressure transducer, respectively. The results indicate that the compositions of the gas mixture greatly influence flame behaviors and pressure. Acetylene has the fastest flame tip speed and the highest pressure, while natural gas has a faster flame tip speed and higher pressure than methane. The Bychkov theory for predicting the flame skirt motion is verified, and the results indicate that the experimental data coincide well with theory in the case of equivalence ratios close to 1.00. Moreover, the Bychkov theory is able to predict flame skirt motion for acetylene, even outside of the best suitable expansion ratio range of 6

Lane-Emden equation with inertial force and general polytropic dynamic model for molecular cloud cores

NASA Astrophysics Data System (ADS)

Li, DaLei; Lou, Yu-Qing; Esimbek, Jarken

2018-01-01

We study self-similar hydrodynamics of spherical symmetry using a general polytropic (GP) equation of state and derive the GP dynamic Lane-Emden equation (LEE) with a radial inertial force. In reference to Lou & Cao, we solve the GP dynamic LEE for both polytropic index γ = 1 + 1/n and the isothermal case n → +∞; our formalism is more general than the conventional polytropic model with n = 3 or γ = 4/3 of Goldreich & Weber. For proper boundary conditions, we obtain an exact constant solution for arbitrary n and analytic variable solutions for n = 0 and n = 1, respectively. Series expansion solutions are derived near the origin with the explicit recursion formulae for the series coefficients for both the GP and isothermal cases. By extensive numerical explorations, we find that there is no zero density at a finite radius for n ≥ 5. For 0 ≤ n < 5, we adjust the inertial force parameter c and find the range of c > 0 for monotonically decreasing density from the origin and vanishing at a finite radius for c being less than a critical value Ccr. As astrophysical applications, we invoke our solutions of the GP dynamic LEE with central finite boundary conditions to fit the molecular cloud core Barnard 68 in contrast to the static isothermal Bonnor-Ebert sphere by Alves et al. Our GP dynamic model fits appear to be sensibly consistent with several more observations and diagnostics for density, temperature and gas pressure profiles.

Quality classification of Spanish olive oils by untargeted gas chromatography coupled to hybrid quadrupole-time of flight mass spectrometry with atmospheric pressure chemical ionization and metabolomics-based statistical approach.

PubMed

Sales, C; Cervera, M I; Gil, R; Portolés, T; Pitarch, E; Beltran, J

2017-02-01

The novel atmospheric pressure chemical ionization (APCI) source has been used in combination with gas chromatography (GC) coupled to hybrid quadrupole time-of-flight (QTOF) mass spectrometry (MS) for determination of volatile components of olive oil, enhancing its potential for classification of olive oil samples according to their quality using a metabolomics-based approach. The full-spectrum acquisition has allowed the detection of volatile organic compounds (VOCs) in olive oil samples, including Extra Virgin, Virgin and Lampante qualities. A dynamic headspace extraction with cartridge solvent elution was applied. The metabolomics strategy consisted of three different steps: a full mass spectral alignment of GC-MS data using MzMine 2.0, a multivariate analysis using Ez-Info and the creation of the statistical model with combinations of responses for molecular fragments. The model was finally validated using blind samples, obtaining an accuracy in oil classification of 70%, taking the official established method, "PANEL TEST", as reference. Copyright © 2016 Elsevier Ltd. All rights reserved.

Acidified pressurized hot water for the continuous extraction of cadmium and lead from plant materials prior to ETAAS

NASA Astrophysics Data System (ADS)

Morales-Muñoz, S.; Luque-García, J. L.; Luque de Castro, M. D.

2003-01-01

Acidified and pressurized hot water is proposed for the continuous leaching of Cd and Pb from plants prior to determination by electrothermal atomic absorption spectrometry. Beech leaves (a certified reference material—CRM 100—where the analytes were not certified) were used for optimizing the method by a multivariate approach. The samples (0.5 g) were subjected to dynamic extraction with water modified with 1% v/v HNO 3 at 250 °C as leachant. A kinetics study was performed in order to know the pattern of the extraction process. The method was validated with a CRM (olive leaves, 062 from the BCR) where the analytes had been certified. The agreement between the certified values and those found using the proposed method demonstrates its usefulness. The repeatability and within-laboratory reproducibility were 3.7 and 2.3% for Cd and 1.04% and 6.3% for Pb, respectively. The precision of the method, together with its efficiency, rapidity, and environmental acceptability, makes it a good alternative for the determination of trace metals in plant material.

Optical nucleation of bubble clouds in a high pressure spherical resonator.

PubMed

Anderson, Phillip; Sampathkumar, A; Murray, Todd W; Gaitan, D Felipe; Glynn Holt, R

2011-11-01

An experimental setup for nucleating clouds of bubbles in a high-pressure spherical resonator is described. Using nanosecond laser pulses and multiple phase gratings, bubble clouds are optically nucleated in an acoustic field. Dynamics of the clouds are captured using a high-speed CCD camera. The images reveal cloud nucleation, growth, and collapse and the resulting emission of radially expanding shockwaves. These shockwaves are reflected at the interior surface of the resonator and then reconverge to the center of the resonator. As the shocks reconverge upon the center of the resonator, they renucleate and grow the bubble cloud. This process is repeated over many acoustic cycles and with each successive shock reconvergence, the bubble cloud becomes more organized and centralized so that subsequent collapses give rise to stronger, better defined shockwaves. After many acoustic cycles individual bubbles cannot be distinguished and the cloud is then referred to as a cluster. Sustainability of the process is ultimately limited by the detuning of the acoustic field inside the resonator. The nucleation parameter space is studied in terms of laser firing phase, laser energy, and acoustic power used.

The Numerical Simulation of the Shock Wave of Coal Gas Explosions in Gas Pipe*

NASA Astrophysics Data System (ADS)

Chen, Zhenxing; Hou, Kepeng; Chen, Longwei

2018-03-01

For the problem of large deformation and vortex, the method of Euler and Lagrange has both advantage and disadvantage. In this paper we adopt special fuzzy interface method(volume of fluid). Gas satisfies the conditions of conservation equations of mass, momentum, and energy. Based on explosion and three-dimension fluid dynamics theory, using unsteady, compressible, inviscid hydrodynamic equations and state equations, this paper considers pressure gradient’s effects to velocity, mass and energy in Lagrange steps by the finite difference method. To minimize transport errors of material, energy and volume in Finite Difference mesh, it also considers material transport in Euler steps. Programmed with Fortran PowerStation 4.0 and visualized with the software designed independently, we design the numerical simulation of gas explosion with specific pipeline structure, check the key points of the pressure change in the flow field, reproduce the gas explosion in pipeline of shock wave propagation, from the initial development, flame and accelerate the process of shock wave. This offers beneficial reference and experience to coal gas explosion accidents or safety precautions.

Characteristics of tip-leakage flow in an axial fan

NASA Astrophysics Data System (ADS)

Park, Keuntae; Choi, Haecheon; Choi, Seokho; Sa, Yongcheol

2014-11-01

An axial fan with a shroud generates complicated vortical structures by the interaction of the axial flow with the fan blades and shroud near the blade tips. Large eddy simulation (LES) is performed for flow through a forward-swept axial fan, operating at the design condition of Re = 547,000 based on the radius of blade tip and the tip velocity. A dynamic global model (Lee et al. 2010) is used for a subgrid-scale model, and an immersed boundary method in a non-inertial reference frame (Kim & Choi 2006) is adopted for the present simulation. It is found that two vortical structures are formed near the blade tip: the main tip leakage vortex (TLV) and the auxiliary TLV. The main TLV is initiated near the leading edge, develops downstream, and impinges on the pressure surface of the next blade, where the pressure fluctuations and turbulence intensity become high. On the other hand, the auxiliary TLV is initiated at the aft part of the blade but is relatively weak such that it merges with the main TLV. Supported by the KISTI Supercomputing Center (KSC-2014-C2-014).

Distribution of physical properties and timing of relative uplift in upper plate off Costa Rica: IODP Expedition 344

NASA Astrophysics Data System (ADS)

Saiki, A.; Hashimoto, Y.

2015-12-01

Evolution of physical properties in subduction zone is a key to understand lithification processes, location of decollement, and stress distribution. In this study, we examined the physical properties of sediments using on-board data and laboratory experimental data on sediments obtained off Costa Rica margin. Target sites are in the Integrate Ocean Drilling Program (IODP) Expedition 344 off Costa Rica, including reference sites (U1381 and U1414), mid-slope site (U1378, U1380) and upper-slope site (U1413). Seven samples from reference sites were analyzed. Laboratory experiments for velocity and porosity measurements were conducted with variation of effective pressure. Velocity-porosity relationships from on-board data and from laboratory experiments are comparable. The porosity-effective pressure curves under isotropic condition were converted to the curves under uniaxial condition (Teeuw, 1971). Using the normal consolidation curves under uniaxial stress conditions, we converted onboard porosity to effective pressure and fluid pressure. In reference sites, hydrostatic fluid pressure was estimated as expected as a reference sites, suggesting that porosity-effective pressure relationship was obtained correctly by experiments and it can be adapted to estimation of fluid pressure for the wedge sites. The porosity-effective pressure relationship under isotropic conditions were used for the estimation in wedge sites. In wedge sites, estimated pore pressures show lower than hydrostatic pressure, suggesting that onboard porosity was lower than that under normal compaction. The lower porosity can be caused by relative uplift from deeper portion. The amount of relative uplift can be estimated by differences in porosity-depth relationships between onboard data and experimental data. The amount of relative uplift for each site shows more than ~1000m up to ~5000m. The small error in porosity depth curve from experimental data makes relative uplift larger or smaller exponentially in the deeper portion. The increment of relative uplift, however, starts from about 1Ma in each site, suggesting some events were occurred at the timing. Laboratory experiments under differential stress should be conducted in the near future because smaller porosity is expected under differential stress conditions.

Quantitative sensory testing in the German Research Network on Neuropathic Pain (DFNS): reference data for the trunk and application in patients with chronic postherpetic neuralgia.

PubMed

Pfau, Doreen B; Krumova, Elena K; Treede, Rolf-Detlef; Baron, Ralf; Toelle, Thomas; Birklein, Frank; Eich, Wolfgang; Geber, Christian; Gerhardt, Andreas; Weiss, Thomas; Magerl, Walter; Maier, Christoph

2014-05-01

Age- and gender-matched reference values are essential for the clinical use of quantitative sensory testing (QST). To extend the standard test sites for QST-according to the German Research Network on Neuropathic Pain-to the trunk, we collected QST profiles on the back in 162 healthy subjects. Sensory profiles for standard test sites were within normal interlaboratory differences. QST revealed lower sensitivity on the upper back than the hand, and higher sensitivity on the lower back than the foot, but no systematic differences between these trunk sites. Age effects were significant for most parameters. Females exhibited lower pressure pain thresholds (PPT) than males, which was the only significant gender difference. Values outside the 95% confidence interval of healthy subjects (considered abnormal) required temperature changes of >3.3-8.2 °C for thermal detection. For cold pain thresholds, confidence intervals extended mostly beyond safety cutoffs, hence only relative reference data (left-right differences, hand-trunk differences) were sufficiently sensitive. For mechanical detection and pain thresholds, left-right differences were 1.5-2.3 times more sensitive than absolute reference data. The most sensitive parameter was PPT, where already side-to-side differences >35% were abnormal. Compared to trunk reference data, patients with postherpetic neuralgia exhibited thermal and tactile deficits and dynamic mechanical allodynia, mostly without reduced mechanical pain thresholds. This pattern deviates from other types of neuropathic pain. QST reference data for the trunk will also be useful for patients with postthoracotomy pain or chronic back pain. Copyright © 2014 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

Challenge for the accurate CMT estimation of the offshore earthquakes using ocean bottom pressure gauges as seismometers

NASA Astrophysics Data System (ADS)

Kubota, T.; Saito, T.; Suzuki, W.; Hino, R.

2017-12-01

When an earthquake occurs in offshore region, ocean bottom pressure gauges (OBP) observe the low-frequency (> 400s) pressure change due to tsunami and also high-frequency (< 200 s) pressure change due to seismic waves (e.g. Filloux 1983; Matsumoto et al. 2012). When the period of the seafloor motion is sufficiently long (> 20 s), the relation between seafloor dynamic pressure change p and seafloor vertical acceleration az is approximately given as p=ρ0h0az (ρ0: seawater density, h0: sea depth) (e.g., Bolshakova et al. 2011; Matsumoto et al.,2012; Saito and Tsushima, 2016, JGR; Saito, 2017, GJI). Based on this relation, it is expected that OBP can be used as vertical accelerometers. If we use OBP deployed in offshore region as seismometer, the station coverage is improved and then the accuracy of the earthquake location is also improved. In this study, we analyzed seismograms together with seafloor dynamic pressure change records to estimate the CMT of the interplate earthquakes occurred at off the coast of Tohoku on 9 March, 2011 (Mw 7.3 and 6.5) (Kubota et al., 2017, EPSL), and discussed the estimation accuracy of the centroid horizontal location. When the dynamic pressure change recorded by OBP is used in addition to the seismograms, the horizontal location of CMT was reliably constrained. The centroid was located in the center of the rupture area estimated by the tsunami inversion analysis (Kubota et al., 2017). These CMTs had reverse-fault mechanisms consistent with the interplate earthquakes and well reproduces the dynamic pressure signals in the OBP records. Meanwhile, when we used only the inland seismometers, the centroids were estimated to be outside the rupture area. This study proved that the dynamic pressure change in OBP records are available as seismic-wave records, which greatly helped to investigate the source process of offshore earthquakes far from the coast.

Challenge for the accurate CMT estimation of the offshore earthquakes using ocean bottom pressure gauges as seismometers

NASA Astrophysics Data System (ADS)

Kubota, T.; Saito, T.; Suzuki, W.; Hino, R.

2016-12-01

When an earthquake occurs in offshore region, ocean bottom pressure gauges (OBP) observe the low-frequency (> 400s) pressure change due to tsunami and also high-frequency (< 200 s) pressure change due to seismic waves (e.g. Filloux 1983; Matsumoto et al. 2012). When the period of the seafloor motion is sufficiently long (> 20 s), the relation between seafloor dynamic pressure change p and seafloor vertical acceleration az is approximately given as p=ρ0h0az (ρ0: seawater density, h0: sea depth) (e.g., Bolshakova et al. 2011; Matsumoto et al.,2012; Saito and Tsushima, 2016, JGR; Saito, 2017, GJI). Based on this relation, it is expected that OBP can be used as vertical accelerometers. If we use OBP deployed in offshore region as seismometer, the station coverage is improved and then the accuracy of the earthquake location is also improved. In this study, we analyzed seismograms together with seafloor dynamic pressure change records to estimate the CMT of the interplate earthquakes occurred at off the coast of Tohoku on 9 March, 2011 (Mw 7.3 and 6.5) (Kubota et al., 2017, EPSL), and discussed the estimation accuracy of the centroid horizontal location. When the dynamic pressure change recorded by OBP is used in addition to the seismograms, the horizontal location of CMT was reliably constrained. The centroid was located in the center of the rupture area estimated by the tsunami inversion analysis (Kubota et al., 2017). These CMTs had reverse-fault mechanisms consistent with the interplate earthquakes and well reproduces the dynamic pressure signals in the OBP records. Meanwhile, when we used only the inland seismometers, the centroids were estimated to be outside the rupture area. This study proved that the dynamic pressure change in OBP records are available as seismic-wave records, which greatly helped to investigate the source process of offshore earthquakes far from the coast.

Prediction of new high pressure structural sequence in thorium carbide: A first principles study

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

Sahoo, B. D., E-mail: bdsahoo@barc.gov.in; Joshi, K. D.; Gupta, Satish C.

2015-05-14

In the present work, we report the detailed electronic band structure calculations on thorium monocarbide. The comparison of enthalpies, derived for various phases using evolutionary structure search method in conjunction with first principles total energy calculations at several hydrostatic compressions, yielded a high pressure structural sequence of NaCl type (B1) → Pnma → Cmcm → CsCl type (B2) at hydrostatic pressures of ∼19 GPa, 36 GPa, and 200 GPa, respectively. However, the two high pressure experimental studies by Gerward et al. [J. Appl. Crystallogr. 19, 308 (1986); J. Less-Common Met. 161, L11 (1990)] one up to 36 GPa and other up to 50 GPa, onmore » substoichiometric thorium carbide samples with carbon deficiency of ∼20%, do not report any structural transition. The discrepancy between theory and experiment could be due to the non-stoichiometry of thorium carbide samples used in the experiment. Further, in order to substantiate the results of our static lattice calculations, we have determined the phonon dispersion relations for these structures from lattice dynamic calculations. The theoretically calculated phonon spectrum reveal that the B1 phase fails dynamically at ∼33.8 GPa whereas the Pnma phase appears as dynamically stable structure around the B1 to Pnma transition pressure. Similarly, the Cmcm structure also displays dynamic stability in the regime of its structural stability. The B2 phase becomes dynamically stable much below the Cmcm to B2 transition pressure. Additionally, we have derived various thermophysical properties such as zero pressure equilibrium volume, bulk modulus, its pressure derivative, Debye temperature, thermal expansion coefficient and Gruneisen parameter at 300 K and compared these with available experimental data. Further, the behavior of zero pressure bulk modulus, heat capacity and Helmholtz free energy has been examined as a function temperature and compared with the experimental data of Danan [J. Nucl. Mater. 57, 280 (1975)].« less

Dynamics of High Pressure Reacting Shear Flows

DTIC Science & Technology

2015-10-02

liquid rockets, future gas turbines • When the combustion systems are for propulsion, limited tankage dictates that on-board propellants be stored in...system dynamics • Combustion dynamics always includes acoustic waves, which in enclosed systems can sometimes reach detrimental amplitudes – eg...a high pressure, chemically reacting, multiphase, acoustically driven, shear flow in the form of a coaxial jet flame • Explore how the presence of

Elastic Nonlinear Response in Granular Media Under Resonance Conditions

NASA Astrophysics Data System (ADS)

Jia, X.; Johnson, P. A.

2004-12-01

We are studying the elastic linear and nonlinear behavior of granular media using dynamic wave methods. In the work presented here, our goal is to quantify the elastic nonlinear response by applying wave resonance. Resonance studies are desirable because they provide the means to easily study amplitude dependencies of elastic nonlinear behavior and thus to characterize the physical nature of the elastic nonlinearity. This work has implications for a variety of topics, in particular, the in situ nonlinear response of surface sediments. For this work we constructed an experimental cell in which high sensitivity dynamic resonance studies were conducted using granular media under controlled effective pressure. We limit our studies here to bulk modes but have the capability to employ shear waves as well. The granular media are composed of glass beads held under pressure by a piston, while applying resonance waves from transducers as both the excitation and the material probe. The container is closed with two fitted pistons and a normal load is applied to the granular sample across the top piston. Force and displacement are measured directly. Resonant frequency sweeps with frequencies corresponding to the fundamental bulk mode are applied to the longitudinal source transducer. The pore pressure in the system is 1 atm. The glass beads used in our experiments are of diameter 0.5 mm, randomly deposited in a duralumin cylinder of diameter 30 mm and height of 15 mm. This corresponds to a granular skeleton acoustic wave velocity of v ª 750m/s under 50 N of force [0.07 Mpa]. The loaded system gives fundamental mode resonances in the audio frequency band at half a wavelength where resonance frequency is effective-pressure dependent. The volume fraction of glass beads thus obtained is found to be 0.63 ± 0.01. Plane-wave generating and detecting transducers of diameter 30 mm are placed on axis at the top and bottom of the cylindrical container in direct contact with the glass beads. The wave signals are detected using a lock-in amplifier, and frequency and amplitude are recorded on computer. Drive frequency is swept from below to above the resonance mode. A typical frequency sweep is 3 kHz in width with a frequency sampling of 6 Hz. Frequency sweeps are applied at progressively increasing drive voltages to test for nonlinear-dynamical induced modulus softening. The resonance frequency at peak amplitude corresponds directly to modulus. We find significant elastic nonlinearity at all effective pressures, manifest by the fundamental-mode resonance curves decreasing progressively, at progressively increasing drive level. This is equivalent to progressive material softening with wave amplitude, meaning the wavespeed and modulus diminish. The wave dissipation simultaneously increases (Johnson and Sutin 2004). For example, at 0.11 Mpa effective pressure the observed change in resonance frequency of about 2.6% corresponds to a material bulk modulus decrease of about 5.2%. Strain amplitudes are 10-7-10-6. Thus, we would predict that surface sediments should have significant elastic nonlinear response beginning at about 10-6 strain amplitude. reference: Johnson, P. and A. Sutin, Slow dynamics in diverse solids, J. Acoust. Soc Am., in press (2004).

On the AU Microscopii debris disk. Density profiles, grain properties, and dust dynamics

NASA Astrophysics Data System (ADS)

Augereau, J.-C.; Beust, H.

2006-09-01

Context: . AU Mic is a young M-type star surrounded by an edge-on optically thin debris disk that shares many common observational properties with the disk around β Pictoris. In particular, the scattered light surface brightness profile falls off as ˜ r-5 outside 120 AU for β Pictoris and 35 AU for AU Mic. In both cases, the disk color rises as the distance increases beyond these reference radii. Aims: . In this paper, we present the first comprehensive analysis of the AU Mic disk properties since the system was resolved by Kalas et al. (2004, Science, 303, 1990). We explore whether the dynamical model, which successfully reproduces the β Pictoris brightness profile (e.g., Augereau et al. 2001, A&A, 370, 447), could apply to AU Mic. Methods: . We calculate the surface density profile of the AU Mic disk by performing the inversion of the near-IR and visible scattered light brightness profiles measured by Liu (2004, Science, 305, 1442) and Krist et al. (2005, AJ, 129, 1008), respectively. We discuss the grain properties by analysing the blue color of the disk in the visible (Krist et al. 2005) and by fitting the disk spectral energy distribution. Finally, we evaluate the radiation and wind forces on the grains. The impact of the recurrent X-ray and UV-flares on the dust dynamics is also discussed. Results: . We show that irrespective of the mean scattering asymmetry factor of the grains, most of the emission arises from an asymmetric, collisionally-dominated region that peaks close to the surface brightness break around 35 AU. The elementary scatterers at visible wavelengths are found to be sub-micronic, but the inferred size distribution underestimates the number of large grains, resulting in sub-millimeter emissions that are too low compared to the observations. From our inversion procedure, we find that the V- to H-band scattering cross sections ratio increases outside 40 AU, in line with the observed color gradient of the disk. This behavior is expected if the grains have not been produced locally, but placed in orbits of high eccentricity by a size-dependent pressure force, resulting in a paucity of large grains beyond the outer edge of the parent bodies' disk. Because of the low luminosity of AU Mic, radiation pressure is inefficient to diffuse the smallest grains in the outer disk, even when the flares are taken into account. Conversely, we show that a standard, solar-like stellar wind generates a pressure force onto the dust particles that behaves much like a radiation pressure force. With an assumed dot{M} ≃ 3×102 dot{M}⊙, the wind pressure overcomes the radiation pressure, and this effect is enhanced by the stellar flares. This greatly contributes to populating the extended AU Mic debris disk and explains the similarity between the β Pictoris and AU Mic brightness profiles. In both cases, the color gradient beyond 120 AU for β Pictoris and 35 AU for AU Mic, is believed to be a direct consequence of the dust dynamics.

Book review: Estimating groundwater recharge

USGS Publications Warehouse

Stonestrom, David A.

2011-01-01

Groundwater recharge is the entry of fresh water into the saturated portion of the subsurface part of the hydrologic cycle, the modifier “saturated” indicating that the pressure of the pore water is greater than atmospheric. Briefly stated, recharge is downward flux across the water table. The term “groundwater recharge” can refer either to the multiple interacting processes generating and controlling the flux or to the fluxR itself. When referring to flux, R can represent either (1) a value integrated over large areas and long periods of time or (2) a point value, or instantaneous flux density, that varies erratically as well as continuously in time and space. Knowing how R is distributed through space and time is required for understanding the dynamics of groundwater flow and transport in any watershed, aquifer, or selected domain of interest and for understanding heads, flow paths, and discharges to streams, wetlands, and other surface water bodies. Clearly among the most important of hydrologic fluxes, R is also one of the most difficult to measure. Advancements in hydrologic science have proceeded surprisingly in lockstep with advances in determining R.

Expansion of a compressible gas bubble in Stokes flow

NASA Astrophysics Data System (ADS)

Pozrikidis, C.

2001-09-01

The flow-induced deformation of an inviscid bubble occupied by a compressible gas and suspended in an ambient viscous liquid is considered at low Reynolds numbers with particular reference to the pressure developing inside the bubble. Ambient fluid motion alters the bubble pressure with respect to that established in the quiescent state, and requires the bubble to expand or contract according to an assumed equation of state. When changes in the bubble volume are prohibited by a global constraint on the total volume of the flow, the ambient pressure is modified while the bubble pressure remains constant during the deformation. A numerical method is developed for evaluating the pressure inside a two-dimensional bubble in an ambient Stokes flow on the basis of the normal component of the interfacial force balance involving the capillary pressure, the normal viscous stress, and the pressure at the free surface on the side of the liquid; the last is computed by evaluating a strongly singular integral. Dynamical simulations of bubble deformation are performed using the boundary integral method properly implemented to remove the multiplicity of solutions due to the a priori unknown rate of expansion, and three particular problems are discussed in detail: the shrinkage of a bubble at a specified rate, the deformation of a bubble subject to simple shear flow, and the deformation of a bubble subject to a purely elongational flow. In the case of shrinkage, it is found that the surface tension plays a critical role in determining the behaviour of the bubble pressure near the critical time when the bubble disappears. In the case of shear or elongational flow, it is found that the bubble contracts during an initial period of deformation from the circular shape, and then it expands to obtain a stationary shape whose area is higher than that assumed in the quiescent state. Expansion may destabilize the bubble by raising the capillary number above the critical threshold under which stationary shapes can be found.

Molecular-dynamic simulations of the thermophysical properties of hexanitrohexaazaisowurtzitane single crystal at high pressures and temperatures

NASA Astrophysics Data System (ADS)

Kozlova, S. A.; Gubin, S. A.; Maklashova, I. V.; Selezenev, A. A.

2017-11-01

Molecular dynamic simulations of isothermal compression parameters are performed for a hexanitrohexaazaisowurtzitane single crystal (C6H6O12N12) using a modified ReaxFF-log reactive force field. It is shown that the pressure-compression ratio curve for a single C6H6O12N12 crystal at constant temperature T = 300 K in pressure range P = 0.05-40 GPa is in satisfactory agreement with experimental compression isotherms obtained for a single C6H6O12N12 crystal. Hugoniot molecular-dynamic simulations of the shock-wave hydrostatic compression of a single C6H6O12N12 crystal are performed. Along with Hugoniot temperature-pressure curves, calculated shock-wave pressure-compression ratios for a single C6H6O12N12 crystal are obtained for a wide pressure range of P = 1-40 GPa. It is established that the percussive adiabat obtained for a single C6H6O12N12 crystal is in a good agreement with the experimental data. All calculations are performed using a LAMMPS molecular dynamics simulation software package that provides a ReaxFF-lg reactive force field to support the approach.

Dynamic Changes of Pulmonary Arterial Pressure and Ductus Arteriosus in Human Newborns From Birth to 72 Hours of Age

PubMed Central

Kang, Chunmiao; Zhao, Enfa; Zhou, Yinghua; Zhao, Huayun; Liu, Yunyao; Gao, Ningning; Huang, Xiaoxin; Liu, Baomin

2016-01-01

Abstract Normal pulmonary artery pressure and pulmonary hypertension assessment of newborns is rarely reported. The aim of the study is to explore dynamic changes of pulmonary arterial pressure and ductus arteriosus in human newborns from birth to 72 h of age with echocardiography. A total of 76 cases of normal newborns were prospectively detected by echocardiography after birth of 2 h, 6 h, 12 h, 24 h, 48 h, and 72 h, respectively. Ductus arteriosus diameter, blood shunt direction, blood flow velocity, and pressure gradient were recorded. The brachial artery blood pressure were measured to estimate the pulmonary artery systolic pressure (PASP) and pulmonary artery diastolic pressure (PADP) using patent ductus arteriosus pressure gradient method. The mean pulmonary artery pressure (PAMP) were calculated by equation of PAMP = PADP + 1/3(PASP-PADP). (1) There were 76 cases of normal newborns. Among them, 29 cases (38%) ductus arteriosus closed within 24 h, 59 cases (78%) closed within 48 h, 72 cases (95%) closed within 72 h, and 4 cases (5%) ductus arteriosus not closed within 72 h. (2) The ductus arteriosus diameter of 2 h, 6 h, 12 h, 24 h, 48 h, and 72 h after birth was 4.60 ± 0.59 mm, 3.37 ± 0.59 mm, 2.47 ± 0.49 mm, 1.89 ± 0.41 mm, 1.61 ± 0.35 mm, and 1.20 ± 0.24 mm, respectively. Compared all of the ductus arteriosus diameter of the above time periods, there were statistically differences with P < 0.05, respectively. (3) The mean PASP in 2 h, 6 h, 12 h, 24 h, 48 h, 72 h after birth were 76.58 ± 7.28 mm Hg, 65.53 ± 9.25mm Hg, 52.51 ± 9.07 mm Hg, 43.83 ± 7.90 mm Hg, 38.07 ± 8.26 mm Hg, and 36 ± 6.48 mm Hg, respectively. The PADP of the above time period were 37.88 ± 5.56 mm Hg, 29.93 ± 7.91 mm Hg, 23.43 ± 7.37 mm Hg, 19.70 ± 8.51 mm Hg, 13.85 ± 5.58 mm Hg, 13.25 ± 6.18 mm Hg, respectively. The PAMP of the above time period were 63.41 ± 7.03 mm Hg, 51.78 ± 9.82 mm Hg, 40.94 ± 9.32 mm Hg, 34.39 ± 9.89 mm Hg, 26.23 ± 7.49 mm Hg, 25.25 ± 8.29 mm Hg, respectively. There were statistically differences with P < 0.05 between each time periods of PASP, PADP, and PAMP. (4) The upper 95% limit reference range of PASP of normal newborns of 72 h after birth were 39.97 mm Hg. (1) Normal newborns ductus arteriosus diameter gradually decreased after birth, and 95% of them spontaneous closed within 24 to 72 h. (2) Normal newborns pulmonary artery pressure showed a gradually decline after birth, the upper 95% limit reference range for PASP measured in normal newborns <72 h of age was 39.97 mm Hg. Therefore, the diagnostic criteria of newborns pulmonary hypertension may be >40.00 mm Hg according to our limited study. PMID:26817918

Botulinum Toxin Type A Injection for Spastic Equinovarus Foot in Children with Spastic Cerebral Palsy: Effects on Gait and Foot Pressure Distribution

PubMed Central

Choi, Ja Young; Jung, Soojin; Rha, Dong-wook

2016-01-01

Purpose To investigate the effect of intramuscular Botulinum toxin type A (BoNT-A) injection on gait and dynamic foot pressure distribution in children with spastic cerebral palsy (CP) with dynamic equinovarus foot. Materials and Methods Twenty-five legs of 25 children with CP were investigated in this study. BoNT-A was injected into the gastrocnemius (GCM) and tibialis posterior (TP) muscles under the guidance of ultrasonography. The effects of the toxin were clinically assessed using the modified Ashworth scale (MAS) and modified Tardieu scale (MTS), and a computerized gait analysis and dynamic foot pressure measurements using the F-scan system were also performed before injection and at 1 and 4 months after injection. Results Spasticity of the ankle plantar-flexor in both the MAS and MTS was significantly reduced at both 1 and 4 months after injection. On dynamic foot pressure measurements, the center of pressure index and coronal index, which represent the asymmetrical weight-bearing of the medial and lateral columns of the foot, significantly improved at both 1 and 4 months after injection. The dynamic foot pressure index, total contact area, contact length and hind foot contact width all increased at 1 month after injection, suggesting better heel contact. Ankle kinematic data were significantly improved at both 1 and 4 months after injection, and ankle power generation was significantly increased at 4 months after injection compared to baseline data. Conclusion Using a computerized gait analysis and foot scan, this study revealed significant benefits of BoNT-A injection into the GCM and TP muscles for dynamic equinovarus foot in children with spastic CP. PMID:26847306

Influence of cerebrovascular resistance on the dynamic relationship between blood pressure and cerebral blood flow in humans.

PubMed

Smirl, J D; Tzeng, Y C; Monteleone, B J; Ainslie, P N

2014-06-15

We examined the hypothesis that changes in the cerebrovascular resistance index (CVRi), independent of blood pressure (BP), will influence the dynamic relationship between BP and cerebral blood flow in humans. We altered CVRi with (via controlled hyperventilation) and without [via indomethacin (INDO, 1.2 mg/kg)] changes in PaCO2. Sixteen subjects (12 men, 27 ± 7 yr) were tested on two occasions (INDO and hypocapnia) separated by >48 h. Each test incorporated seated rest (5 min), followed by squat-stand maneuvers to increase BP variability and improve assessment of the pressure-flow dynamics using linear transfer function analysis (TFA). Beat-to-beat BP, middle cerebral artery velocity (MCAv), posterior cerebral artery velocity (PCAv), and end-tidal Pco2 were monitored. Dynamic pressure-flow relations were quantified using TFA between BP and MCAv/PCAv in the very low and low frequencies through the driven squat-stand maneuvers at 0.05 and 0.10 Hz. MCAv and PCAv reductions by INDO and hypocapnia were well matched, and CVRi was comparably elevated (P < 0.001). During the squat-stand maneuvers (0.05 and 0.10 Hz), the point estimates of absolute gain were universally reduced, and phase was increased under both conditions. In addition to an absence of regional differences, our findings indicate that alterations in CVRi independent of PaCO2 can alter cerebral pressure-flow dynamics. These findings are consistent with the concept of CVRi being a key factor that should be considered in the correct interpretation of cerebral pressure-flow dynamics as indexed using TFA metrics. Copyright © 2014 the American Physiological Society.

Best-estimate coupled RELAP/CONTAIN analysis of inadvertent BWR ADS valve opening transient

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

Feltus, M.A.; Muftuoglu, A.K.

1993-01-01

Noncondensible gases may become dissolved in boiling water reactor (BWR) water-level instrumentation during normal operations. Any dissolved noncondensible gases inside these water columns may come out of solution during rapid depressurization events and displace water from the reference leg piping, resulting in a false high level. Significant errors in water-level indication are not expected to occur until the reactor pressure vessel (RPV) pressure has dropped below [approximately]450 psig. These water level errors may cause a delay or failure in emergency core cooling system (ECCS) actuation. The RPV water level is monitored using the pressure of a water column having amore » varying height (reactor water level) that is compared to the pressure of a water column maintained at a constant height (reference level). The reference legs have small-diameter pipes with varying lengths that provide a constant head of water and are located outside the drywell. The amount of noncondensible gases dissolved in each reference leg is very dependent on the amount of leakage from the reference leg and its geometry and interaction of the reactor coolant system with the containment, i.e., torus or suppression pool, and reactor building. If a rapid depressurization causes an erroneously high water level, preventing automatic ECCS actuation, it becomes important to determine if there would be other adequate indications for operator response. In the postulated inadvertent opening of all seven automatic depressurization system (ADS) valves, the ECCS signal on high drywell pressure would be circumvented because the ADS valves discharge directly into the suppression pool. A best-estimate analysis of such an inadvertent opening of all ADS valves would have to consider the thermal-hydraulic coupling between the pool, drywell, reactor building, and RPV.« less

Simultaneous pressure measurement and high-speed photography study of cavitation in a dynamically loaded journal bearing

NASA Technical Reports Server (NTRS)

Sun, D. C.; Brewe, D. E.; Abel, P. B.

1993-01-01

Cavitation of the oil film in a dynamically loaded journal bearing was studied using high-speed photography and pressure measurement simultaneously. Comparison of the visual and pressure data provided considerable insight into the occurence and non-occurrence of cavitation. It was found that (1), cavitation typically occurred in the form of one bubble with the pressure in the cavitation bubble close to the absolute zero; and (2), for cavitation-producing operating conditions, cavitation did not always occur; with the oil film then supporting a tensile stress.

Aqueous Humor Dynamics of the Brown-Norway Rat

PubMed Central

Ficarrotta, Kayla R.; Bello, Simon A.; Mohamed, Youssef H.; Passaglia, Christopher L.

2018-01-01

Purpose The study aimed to provide a quantitative description of aqueous humor dynamics in healthy rat eyes. Methods One eye of 26 anesthetized adult Brown-Norway rats was cannulated with a needle connected to a perfusion pump and pressure transducer. Pressure-flow data were measured in live and dead eyes by varying pump rate (constant-flow technique) or by modulating pump duty cycle to hold intraocular pressure (IOP) at set levels (modified constant-pressure technique). Data were fit by the Goldmann equation to estimate conventional outflow facility (\\begin{document}\

A simple, stable, and accurate linear tetrahedral finite element for transient, nearly, and fully incompressible solid dynamics: A dynamic variational multiscale approach [A simple, stable, and accurate tetrahedral finite element for transient, nearly incompressible, linear and nonlinear elasticity: A dynamic variational multiscale approach

DOE PAGES

Scovazzi, Guglielmo; Carnes, Brian; Zeng, Xianyi; ...

2015-11-12

Here, we propose a new approach for the stabilization of linear tetrahedral finite elements in the case of nearly incompressible transient solid dynamics computations. Our method is based on a mixed formulation, in which the momentum equation is complemented by a rate equation for the evolution of the pressure field, approximated with piece-wise linear, continuous finite element functions. The pressure equation is stabilized to prevent spurious pressure oscillations in computations. Incidentally, it is also shown that many stabilized methods previously developed for the static case do not generalize easily to transient dynamics. Extensive tests in the context of linear andmore » nonlinear elasticity are used to corroborate the claim that the proposed method is robust, stable, and accurate.« less

A simple, stable, and accurate linear tetrahedral finite element for transient, nearly, and fully incompressible solid dynamics: A dynamic variational multiscale approach [A simple, stable, and accurate tetrahedral finite element for transient, nearly incompressible, linear and nonlinear elasticity: A dynamic variational multiscale approach

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

Scovazzi, Guglielmo; Carnes, Brian; Zeng, Xianyi

Here, we propose a new approach for the stabilization of linear tetrahedral finite elements in the case of nearly incompressible transient solid dynamics computations. Our method is based on a mixed formulation, in which the momentum equation is complemented by a rate equation for the evolution of the pressure field, approximated with piece-wise linear, continuous finite element functions. The pressure equation is stabilized to prevent spurious pressure oscillations in computations. Incidentally, it is also shown that many stabilized methods previously developed for the static case do not generalize easily to transient dynamics. Extensive tests in the context of linear andmore » nonlinear elasticity are used to corroborate the claim that the proposed method is robust, stable, and accurate.« less

Wind loads on flat plate photovoltaic array fields (nonsteady winds)

NASA Technical Reports Server (NTRS)

Miller, R. D.; Zimmerman, D. K.

1981-01-01

Techniques to predict the dynamic response and the structural dynamic loads of flat plate photovoltaic arrays due to wind turbulence were analyzed. Guidelines for use in predicting the turbulent portion of the wind loading on future similar arrays are presented. The dynamic response and the loads dynamic magnification factor of the two array configurations are similar. The magnification factors at a mid chord and outer chord location on the array illustrated and at four points on the chord are shown. The wind tunnel test experimental rms pressure coefficient on which magnification factors are based is shown. It is found that the largest response and dynamic magnification factor occur at a mid chord location on an array and near the trailing edge. A technique employing these magnification factors and the wind tunnel test rms fluctuating pressure coefficients to calculate design pressure loads due to wind turbulence is presented.

Flight Test of a 30-Foot Nominal Diameter Cross Parachute Deployed at a Mach Number of 1.57 and a Dynamic Pressure of 9.7 Pounds per Square Foot

NASA Technical Reports Server (NTRS)

Eckstrom, Clinton V.; Preisser, John S.

1968-01-01

A 30-foot (9.1-meter) nominal-diameter cross-type parachute with a cloth area (reference area) of 709 square feet (65.9 square meters) was flight tested in the rocket-launched portion of the NASA Planetary Entry Parachute Program (PEPP). The test parachute was ejected from an instrumented payload by means of a mortar when the system was at a Mach number of 1.57 and a dynamic pressure of 9.7 psf. The parachute deployed to suspension-line stretch in 0.44 second with a resulting snatch-force loading of 1100 pounds (4900 newtons), Canopy inflation began at 0.58 second and a first full inflation was achieved at approximately 0.77 second. The maximum opening load occurred at 0.81 second and was 4255 pounds (18,930 newtons). Thereafter, the test item exhibited a canopy-shape instability in that the four panel arms experienced fluctuations, a "scissoring" type of motion predominating throughout the test period. Calculated values of axial-force coefficient during the deceleration portion of the test varied between 0.35 and 1.05, with an average value of 0.69. During descent, canopy-shape variations had reduced to small amplitudes and resultant pitch-yaw angles of the payload with respect to the local vertical averaged less than 10 degrees. The effective drag coefficient, based on the vertical components of velocity and acceleration during system descent, was 0.78.

Evaluation of friction heating in cavitating high pressure Diesel injector nozzles

NASA Astrophysics Data System (ADS)

Salemi, R.; Koukouvinis, P.; Strotos, G.; McDavid, R.; Wang, Lifeng; Li, Jason; Marengo, M.; Gavaises, M.

2015-12-01

Variation of fuel properties occurring during extreme fuel pressurisation in Diesel fuel injectors relative to those under atmospheric pressure and room temperature conditions may affect significantly fuel delivery, fuel injection temperature, injector durability and thus engine performance. Indicative results of flow simulations during the full injection event of a Diesel injector are presented. In addition to the Navier-Stokes equations, the enthalpy conservation equation is considered for predicting the fuel temperature. Cavitation is simulated using an Eulerian-Lagrangian cavitation model fully coupled with the flow equations. Compressible bubble dynamics based on the R-P equation also consider thermal effects. Variable fuel properties function of the local pressure and temperature are taken from literature and correspond to a reference so-called summer Diesel fuel. Fuel pressurisation up to 3000bar pressure is considered while various wall temperature boundary conditions are tested in order to compare their effect relative to those of the fuel heating caused during the depressurisation of the fuel as it passes through the injection orifices. The results indicate formation of strong temperature gradients inside the fuel injector while heating resulting from the extreme friction may result to local temperatures above the fuel's boiling point. Predictions indicate bulk fuel temperature increase of more than 100°C during the opening phase of the needle valve. Overall, it is concluded that such effects are significant for the injector performance and should be considered in relevant simulation tools.

Intrathoracic and venous pressure relationships during responses to changes in body position

NASA Technical Reports Server (NTRS)

Avasthey, P.; Wood, E. H.

1974-01-01

Simultaneous end-expiratory pressures, referred to midthoracic level, in the superior and abdominal venae cavae, pericardial space, and right and left heart, were recorded without thoracotomy in three anesthetized dogs during sudden changes from supine to vertical head-up or head-down body positions. Intrathoracic and dependent great vein pressures referred to midchest level (sixth thoracic vertebra) decreased and showed simple hydrostatic gradients in either vertical position. However, a discontinuity in the large vein hydrostatic gradient occurred just distal to the superior margin of the thorax in either body position and was resumed again above this level. It is concluded that, just as the cerebrospinal fluid and intraperitoneal pressures minimize the effects of gravitational and inertial forces on the cerebral and visceral circulations, the pericardial and pleural pressures have a similar role for the heart proper.

Conformational changes in human Hsp70 induced by high hydrostatic pressure produce oligomers with ATPase activity but without chaperone activity.

PubMed

Araujo, Thaís L S; Borges, Julio Cesar; Ramos, Carlos H; Meyer-Fernandes, José Roberto; Oliveira Júnior, Reinaldo S; Pascutti, Pedro G; Foguel, Debora; Palhano, Fernando L

2014-05-13

We investigated the folding of the 70 kDa human cytosolic inducible protein (Hsp70) in vitro using high hydrostatic pressure as a denaturing agent. We followed the structural changes in Hsp70 induced by high hydrostatic pressure using tryptophan fluorescence, molecular dynamics, circular dichroism, high-performance liquid chromatography gel filtration, dynamic light scattering, ATPase activity, and chaperone activity. Although monomeric, Hsp70 is very sensitive to hydrostatic pressure; after pressure had been removed, the protein did not return to its native sate but instead formed oligomeric species that lost chaperone activity but retained ATPase activity.

Pressure Regulators as Valves for Saving Compressed Air and their Influence on System Dynamics

NASA Astrophysics Data System (ADS)

Dvořák, Lukáš; Fojtášek, Kamil

2015-05-01

Pressure regulators in the field of pneumatic mechanisms can be used as valves for saving compressed air. For example it can be used to reduce the pressure when the piston rod is retracting unloaded and thus it is possible to save some energy. However the problem is that saving valve can significantly affect the dynamics of the pneumatic system. The lower pressure in the piston rod chamber causes extension of time for retraction of the piston rod. This article compare the air consumption experimentally determined and calculated, measured curves of pressure in cylinder chambers and piston speed when saving valve is set up differently.

Bubble dynamics in a standing sound field: the bubble habitat.

PubMed

Koch, P; Kurz, T; Parlitz, U; Lauterborn, W

2011-11-01

Bubble dynamics is investigated numerically with special emphasis on the static pressure and the positional stability of the bubble in a standing sound field. The bubble habitat, made up of not dissolving, positionally and spherically stable bubbles, is calculated in the parameter space of the bubble radius at rest and sound pressure amplitude for different sound field frequencies, static pressures, and gas concentrations of the liquid. The bubble habitat grows with static pressure and shrinks with sound field frequency. The range of diffusionally stable bubble oscillations, found at positive slopes of the habitat-diffusion border, can be increased substantially with static pressure.

Physics of Non-Inertial Reference Frames

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

Kamalov, Timur F.

2010-12-22

Physics of non-inertial reference frames is a generalizing of Newton's laws to any reference frames. It is the system of general axioms for classical and quantum mechanics. The first, Kinematics Principle reads: the kinematic state of a body free of forces conserves and equal in absolute value to an invariant of the observer's reference frame. The second, Dynamics Principle extended Newton's second law to non-inertial reference frames and also contains additional variables there are higher derivatives of coordinates. Dynamics Principle reads: a force induces a change in the kinematic state of the body and is proportional to the rate ofmore » its change. It is mean that if the kinematic invariant of the reference frame is n-th derivative with respect the time, then the dynamics of a body being affected by the force F is described by the 2n-th differential equation. The third, Statics Principle reads: the sum of all forces acting a body at rest is equal to zero.« less

Redistribution Principle Approach for Evaluation of Seismic Active Earth Pressure Behind Retaining Wall

NASA Astrophysics Data System (ADS)

Maskar, A. D.; Madhekar, S. N.; Phatak, D. R.

2017-11-01

The knowledge of seismic active earth pressure behind the rigid retaining wall is very essential in the design of retaining wall in earthquake prone regions. Commonly used Mononobe-Okabe (MO) method considers pseudo-static approach. Recently there are many pseudo-dynamic methods used to evaluate the seismic earth pressure. However, available pseudo-static and pseudo-dynamic methods do not incorporate the effect of wall movement on the earth pressure distribution. Dubrova (Interaction between soils and structures, Rechnoi Transport, Moscow, 1963) was the first, who considered such effect and till date, it is used for cohesionless soil, without considering the effect of seismicity. In this paper, Dubrova's model based on redistribution principle, considering the seismic effect has been developed. It is further used to compute the distribution of seismic active earth pressure, in a more realistic manner, by considering the effect of wall movement on the earth pressure, as it is displacement based method. The effects of a wide range of parameters like soil friction angle (ϕ), wall friction angle (δ), horizontal and vertical seismic acceleration coefficients (kh and kv); on seismic active earth pressure (Kae) have been studied. Results are presented for comparison of pseudo-static and pseudo-dynamic methods, to highlight the realistic, non-linearity of seismic active earth pressure distribution. The current study results in the variation of Kae with kh in the same manner as that of MO method and Choudhury and Nimbalkar (Geotech Geol Eng 24(5):1103-1113, 2006) study. To increase in ϕ, there is a reduction in static as well as seismic earth pressure. Also, by keeping constant ϕ value, as kh increases from 0 to 0.3, earth pressure increases; whereas as δ increases, active earth pressure decreases. The seismic active earth pressure coefficient (Kae) obtained from the present study is approximately same as that obtained by previous researchers. Though seismic earth pressure obtained by pseudo-dynamic approach and seismic earth pressure obtained by redistribution principle have different background of formulation, the final earth pressure distribution is approximately same.

Comparison of ionospheric convection and the transpolar potential before and after solar wind dynamic pressure fronts: implications for magnetospheric reconnection

NASA Astrophysics Data System (ADS)

Boudouridis, A.; Zesta, E.; Lyons, L. R.; Kim, H.-J.; Lummerzheim, D.; Wiltberger, M.; Weygand, J. M.; Ruohoniemi, J. M.; Ridley, A. J.

2012-04-01

The solar wind dynamic pressure, both through its steady state value and through its variations, plays an important role in the determination of the state of the terrestrial magnetosphere and ionosphere, its effects being only secondary to those of the Interplanetary Magnetic Field (IMF). Recent studies have demonstrated the significant effect solar wind dynamic pressure enhancements have on ionospheric convection and the transpolar potential. Further studies have shown a strong response of the polar cap boundary and thus the open flux content of the magnetosphere. These studies clearly illustrate the strong coupling of solar wind dynamic pressure fronts to the terrestrial magnetosphere-ionosphere system. We present statistical studies of the response of Super Dual Auroral Radar Network (SuperDARN) flows, and Assimilative Mapping of Ionospheric Electrodynamics (AMIE) transpolar potentials to sudden enhancements in solar wind dynamic pressure. The SuperDARN results show that the convection is enhanced within both the dayside and nightside ionosphere. The dayside response is more clear and immediate, while the response on the nightside is slower and more evident for low IMF By values. AMIE results show that the overall convection, represented by the transpolar potential, has a strong response immediately after an increase in pressure, with magnitude and duration modulated by the background IMF Bz conditions. We compare the location of the SuperDARN convection enhancements with the location and motion of the polar cap boundary, as determined by POLAR Ultra-Violet Imager (UVI) images and runs of the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamic model for specific events. We find that the boundary exhibits a poleward motion after the increase in dynamic pressure. The enhanced ionospheric flows and the poleward motion of the boundary on the nightside are both signatures of enhanced tail reconnection, a conclusion that is reinforced by the observation of the enhanced flows crossing the polar cap boundary in selected case studies when simultaneous measurements are available.

Predictor-Based Model Reference Adaptive Control

NASA Technical Reports Server (NTRS)

Lavretsky, Eugene; Gadient, Ross; Gregory, Irene M.

2009-01-01

This paper is devoted to robust, Predictor-based Model Reference Adaptive Control (PMRAC) design. The proposed adaptive system is compared with the now-classical Model Reference Adaptive Control (MRAC) architecture. Simulation examples are presented. Numerical evidence indicates that the proposed PMRAC tracking architecture has better than MRAC transient characteristics. In this paper, we presented a state-predictor based direct adaptive tracking design methodology for multi-input dynamical systems, with partially known dynamics. Efficiency of the design was demonstrated using short period dynamics of an aircraft. Formal proof of the reported PMRAC benefits constitute future research and will be reported elsewhere.

Optimal dynamic pricing for deteriorating items with reference-price effects

NASA Astrophysics Data System (ADS)

Xue, Musen; Tang, Wansheng; Zhang, Jianxiong

2016-07-01

In this paper, a dynamic pricing problem for deteriorating items with the consumers' reference-price effect is studied. An optimal control model is established to maximise the total profit, where the demand not only depends on the current price, but also is sensitive to the historical price. The continuous-time dynamic optimal pricing strategy with reference-price effect is obtained through solving the optimal control model on the basis of Pontryagin's maximum principle. In addition, numerical simulations and sensitivity analysis are carried out. Finally, some managerial suggestions that firm may adopt to formulate its pricing policy are proposed.

Aspirator increases relief valve poppet stroke

NASA Technical Reports Server (NTRS)

Biddle, M. E.

1967-01-01

Addition of an aspirator to a relief valve increases the valve poppet stroke under dynamic flow conditions. The aspirator allows poppet inlet dynamic forces to overcome relief valve spring force. It reduces the fluid pressure in the skirt cavity by providing a low pressure sense probe.

Irrigation dynamics associated with positive pressure, apical negative pressure and passive ultrasonic irrigations: a computational fluid dynamics analysis.

PubMed

Chen, José Enrique; Nurbakhsh, Babak; Layton, Gillian; Bussmann, Markus; Kishen, Anil

2014-08-01

Complexities in root canal anatomy and surface adherent biofilm structures remain as challenges in endodontic disinfection. The ability of an irrigant to penetrate into the apical region of a canal, along with its interaction with the root canal walls, will aid in endodontic disinfection. The aim of this study was to qualitatively examine the irrigation dynamics of syringe irrigation with different needle tip designs (open-ended and closed-ended), apical negative pressure irrigation with the EndoVac® system, and passive ultrasonic-assisted irrigation, using a computational fluid dynamics model. Syringe-based irrigation with a side-vented needle showed a higher wall shear stress than the open-ended but was localised to a small region of the canal wall. The apical negative pressure mode of irrigation generated the lowest wall shear stress, while the passive-ultrasonic irrigation group showed the highest wall shear stress along with the greatest magnitude of velocity. © 2013 The Authors. Australian Endodontic Journal © 2013 Australian Society of Endodontology.

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

NASA Technical Reports Server (NTRS)

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

1977-01-01

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

X-ray scattering measurements of dissociation-induced metallization of dynamically compressed deuterium

DOE PAGES

Davis, P.; Döppner, T.; Rygg, J. R.; ...

2016-04-18

Hydrogen, the simplest element in the universe, has a surprisingly complex phase diagram. Because of applications to planetary science, inertial confinement fusion and fundamental physics, its high-pressure properties have been the subject of intense study over the past two decades. While sophisticated static experiments have probed hydrogen’s structure at ever higher pressures, studies examining the higher-temperature regime using dynamic compression have mostly been limited to optical measurement techniques. Here we present spectrally resolved x-ray scattering measurements from plasmons in dynamically compressed deuterium. Combined with Compton scattering, and velocity interferometry to determine shock pressure and mass density, this allows us tomore » extract ionization state as a function of compression. Furthermore, the onset of ionization occurs close in pressure to where density functional theory-molecular dynamics (DFT-MD) simulations show molecular dissociation, suggesting hydrogen transitions from a molecular and insulating fluid to a conducting state without passing through an intermediate atomic phase.« less

Repeatability Modeling for Wind-Tunnel Measurements: Results for Three Langley Facilities

NASA Technical Reports Server (NTRS)

Hemsch, Michael J.; Houlden, Heather P.

2014-01-01

Data from extensive check standard tests of seven measurement processes in three NASA Langley Research Center wind tunnels are statistically analyzed to test a simple model previously presented in 2000 for characterizing short-term, within-test and across-test repeatability. The analysis is intended to support process improvement and development of uncertainty models for the measurements. The analysis suggests that the repeatability can be estimated adequately as a function of only the test section dynamic pressure over a two-orders- of-magnitude dynamic pressure range. As expected for low instrument loading, short-term coefficient repeatability is determined by the resolution of the instrument alone (air off). However, as previously pointed out, for the highest dynamic pressure range the coefficient repeatability appears to be independent of dynamic pressure, thus presenting a lower floor for the standard deviation for all three time frames. The simple repeatability model is shown to be adequate for all of the cases presented and for all three time frames.

Bayes to the Rescue: Continuous Positive Airway Pressure Has Less Mortality Than High-Flow Oxygen.

PubMed

Modesto I Alapont, Vicent; Khemani, Robinder G; Medina, Alberto; Del Villar Guerra, Pablo; Molina Cambra, Alfred

2017-02-01

The merits of high-flow nasal cannula oxygen versus bubble continuous positive airway pressure are debated in children with pneumonia, with suggestions that randomized controlled trials are needed. In light of a previous randomized controlled trial showing a trend for lower mortality with bubble continuous positive airway pressure, we sought to determine the probability that a new randomized controlled trial would find high-flow nasal cannula oxygen superior to bubble continuous positive airway pressure through a "robust" Bayesian analysis. Sample data were extracted from the trial by Chisti et al, and requisite to "robust" Bayesian analysis, we specified three prior distributions to represent clinically meaningful assumptions. These priors (reference, pessimistic, and optimistic) were used to generate three scenarios to represent the range of possible hypotheses. 1) "Reference": we believe bubble continuous positive airway pressure and high-flow nasal cannula oxygen are equally effective with the same uninformative reference priors; 2) "Sceptic on high-flow nasal cannula oxygen": we believe that bubble continuous positive airway pressure is better than high-flow nasal cannula oxygen (bubble continuous positive airway pressure has an optimistic prior and high-flow nasal cannula oxygen has a pessimistic prior); and 3) "Enthusiastic on high-flow nasal cannula oxygen": we believe that high-flow nasal cannula oxygen is better than bubble continuous positive airway pressure (high-flow nasal cannula oxygen has an optimistic prior and bubble continuous positive airway pressure has a pessimistic prior). Finally, posterior empiric Bayesian distributions were obtained through 100,000 Markov Chain Monte Carlo simulations. In all three scenarios, there was a high probability for more death from high-flow nasal cannula oxygen compared with bubble continuous positive airway pressure (reference, 0.98; sceptic on high-flow nasal cannula oxygen, 0.982; enthusiastic on high-flow nasal cannula oxygen, 0.742). The posterior 95% credible interval on the difference in mortality identified a future randomized controlled trial would be extremely unlikely to find a mortality benefit for high-flow nasal cannula oxygen over bubble continuous positive airway pressure, regardless of the scenario. Interpreting these findings using the "range of practical equivalence" framework would recommend rejecting the hypothesis that high-flow nasal cannula oxygen is superior to bubble continuous positive airway pressure for these children. For children younger than 5 years with pneumonia, high-flow nasal cannula oxygen has higher mortality than bubble continuous positive airway pressure. A future randomized controlled trial in this population is unlikely to find high-flow nasal cannula oxygen superior to bubble continuous positive airway pressure.

Transdisciplinary unifying implications of circadian findings in the 1950s

PubMed Central

Halberg, Franz; Cornélissen, Germaine; Katinas, George; Syutkina, Elena V; Sothern, Robert B; Zaslavskaya, Rina; Halberg, Francine; Watanabe, Yoshihiko; Schwartzkopff, Othild; Otsuka, Kuniaki; Tarquini, Roberto; Frederico, Perfetto; Siggelova, Jarmila

2003-01-01

A few puzzles relating to a small fraction of my endeavors in the 1950s are summarized herein, with answers to a few questions of the Editor-in-Chief, to suggest that the rules of variability in time complement the rules of genetics as a biological variability in space. I advocate to replace truisms such as a relative constancy or homeostasis, that have served bioscience very well for very long. They were never intended, however, to lower a curtain of ignorance over everyday physiology. In raising these curtains, we unveil a range of dynamics, resolvable in the data collection and as-one-goes analysis by computers built into smaller and smaller devices, for a continued self-surveillance of the normal and for an individualized detection of the abnormal. The current medical art based on spotchecks interpreted by reference to a time-unqualified normal range can become a science of time series with tests relating to the individual in inferential statistical terms. This is already doable for the case of blood pressure, but eventually should become possible for many other variables interpreted today only based on the quicksand of clinical trials on groups. These ignore individual differences and hence the individual's needs. Chronomics (mapping time structures) with the major aim of quantifying normalcy by dynamic reference values for detecting earliest risk elevation, also yields the dividend of allowing molecular biology to focus on the normal as well as on the grossly abnormal. PMID:14728726

The Propulsive Small Expendable Deployer System (ProSEDS)

NASA Technical Reports Server (NTRS)

Lorenzini, Enrico C.; Cosmo, Mario L.; Estes, Robert D.; Sanmartin, Juan; Pelaez, Jesus; Ruiz, Manuel

2003-01-01

This Final Report covers the following main topics: 1) Brief Description of ProSEDS; 2) Mission Analysis; 3) Dynamics Reference Mission; 4) Dynamics Stability; 5) Deployment Control; 6) Updated System Performance; 7) Updated Mission Analysis; 8) Updated Dynamics Reference Mission; 9) Updated Deployment Control Profiles and Simulations; 10) Updated Reference Mission; 11) Evaluation of Power Delivered by the Tether; 12) Deployment Control Profile Ref. #78 and Simulations; 13) Kalman Filters for Mission Estimation; 14) Analysis/Estimation of Deployment Flight Data; 15) Comparison of ED Tethers and Electrical Thrusters; 16) Dynamics Analysis for Mission Starting at a Lower Altitude; 17) Deployment Performance at a Lower Altitude; 18) Satellite Orbit after a Tether Cut; 19) Deployment with Shorter Dyneema Tether Length; 20) Interactive Software for ED Tethers.

Increasing blood flow to exercising muscle attenuates systemic cardiovascular responses during dynamic exercise in humans.

PubMed

Ichinose, Masashi; Ichinose-Kuwahara, Tomoko; Kondo, Narihiko; Nishiyasu, Takeshi

2015-11-15

Reducing blood flow to working muscles during dynamic exercise causes metabolites to accumulate within the active muscles and evokes systemic pressor responses. Whether a similar cardiovascular response is elicited with normal blood flow to exercising muscles during dynamic exercise remains unknown, however. To address that issue, we tested whether cardiovascular responses are affected by increases in blood flow to active muscles. Thirteen healthy subjects performed dynamic plantarflexion exercise for 12 min at 20%, 40%, and 60% of peak workload (EX20, EX40, and EX60) with their lower thigh enclosed in a negative pressure box. Under control conditions, the box pressure was the same as the ambient air pressure. Under negative pressure conditions, beginning 3 min after the start of the exercise, the box pressure was decreased by 20, 45, and then 70 mmHg in stepwise fashion with 3-min step durations. During EX20, the negative pressure had no effect on blood flow or the cardiovascular responses measured. However, application of negative pressure increased blood flow to the exercising leg during EX40 and EX60. This increase in blood flow had no significant effect on systemic cardiovascular responses during EX40, but it markedly attenuated the pressor responses otherwise seen during EX60. These results demonstrate that during mild exercise, normal blood flow to exercising muscle is not a factor eliciting cardiovascular responses, whereas it elicits an important pressor effect during moderate exercise. This suggests blood flow to exercising muscle is a major determinant of cardiovascular responses during dynamic exercise at higher than moderate intensity. Copyright © 2015 the American Physiological Society.

Dynamic behaviour of the soft palate during nasal positive pressure ventilation under anaesthesia and paralysis: comparison between patients with and without obstructive sleep-disordered breathing.

PubMed

Okuyama, M; Kato, S; Sato, S; Okazaki, J; Kitamura, Y; Ishikawa, T; Sato, Y; Isono, S

2018-01-01

Difficult mask ventilation is common and is known to be associated with sleep-disordered breathing (SDB). It is our hypothesis that the incidence of expiratory retropalatal (RP) airway closure (primary outcome) during nasal positive pressure ventilation (PPV) is more frequent in patients with SDB (apnea hypopnea index ≥5 h -1 ) than non-SDB subjects. The severity of SDB was assessed before surgery using a portable sleep monitor. In anaesthetized and paralysed patients with (n=11) and without SDB (n=9), we observed the behaviour of the RP airway endoscopically during nasal PPV with the mouth closed and determined the dynamic RP closing pressure, which was defined as the highest airway pressure above which the RP airway closure was reversed. The static RP closing pressure was obtained during cessation of mechanical ventilation in patients with dynamic RP closure during nasal PPV. The expiratory RP airway closure accompanied by expiratory flow limitation occurred more frequently in SDB patients (9/11, 82%) than in non-SDB subjects (2/9, 22%; exact logistic regression analysis: P=0.022, odds ratio 3.6, 95% confidence interval 1.1-15.4). Receiver operating characteristic curve analyses indicated AHI >10h -1 and presence of habitual snoring as clinically useful predictors for the occurrence of RP closure during PPV. Dynamic RP closing pressure was greater than the static RP closing pressure by approximately 4-5 cm H 2 O. Valve-like dynamic RP closure that limits expiratory flow during nasal PPV occurs more frequently in SDB patients. Copyright © 2017. Published by Elsevier Ltd.

Pressure-induced emergence of unusually high-frequency transverse excitations in a liquid alkali metal: Evidence of two types of collective excitations contributing to the transverse dynamics at high pressures

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

Bryk, Taras; Lviv Polytechnic National University, 12 S. Bandera Street, UA-79013 Lviv; Ruocco, G.

Unlike phonons in crystals, the collective excitations in liquids cannot be treated as propagation of harmonic displacements of atoms around stable local energy minima. The viscoelasticity of liquids, reflected in transition from the adiabatic to elastic high-frequency speed of sound and in absence of the long-wavelength transverse excitations, results in dispersions of longitudinal (L) and transverse (T) collective excitations essentially different from the typical phonon ones. Practically, nothing is known about the effect of high pressure on the dispersion of collective excitations in liquids, which causes strong changes in liquid structure. Here dispersions of L and T collective excitations inmore » liquid Li in the range of pressures up to 186 GPa were studied by ab initio simulations. Two methodologies for dispersion calculations were used: direct estimation from the peak positions of the L/T current spectral functions and simulation-based calculations of wavenumber-dependent collective eigenmodes. It is found that at ambient pressure, the longitudinal and transverse dynamics are well separated, while at high pressures, the transverse current spectral functions, density of vibrational states, and dispersions of collective excitations yield evidence of two types of propagating modes that contribute strongly to transverse dynamics. Emergence of the unusually high-frequency transverse modes gives evidence of the breakdown of a regular viscoelastic theory of transverse dynamics, which is based on coupling of a single transverse propagating mode with shear relaxation. The explanation of the observed high-frequency shift above the viscoelastic value is given by the presence of another branch of collective excitations. With the pressure increasing, coupling between the two types of collective excitations is rationalized within a proposed extended viscoelastic model of transverse dynamics.« less

The effect of pressure on the hydration structure around hydrophobic solute: A molecular dynamics simulation study

NASA Astrophysics Data System (ADS)

Sarma, Rahul; Paul, Sandip

2012-03-01

Molecular dynamics simulations are performed to study the effects of pressure on the hydrophobic interactions between neopentane molecules immersed in water. Simulations are carried out for five different pressure values ranging from 1 atm to 8000 atm. From potential of mean force calculations, we find that with enhancement of pressure, there is decrease in the well depth of contact minimum (CM) and the relative stability of solvent separated minimum over CM increases. Lower clustering of neopentane at high pressure is also observed in association constant and cluster-structure analysis. Selected site-site radial distribution functions suggest efficient packing of water molecules around neopentane molecules at elevated pressure. The orientational profile calculations of water molecules show that the orientation of water molecules in the vicinity of solute molecule is anisotropic and this distribution becomes flatter as we move away from the solute. Increasing pressure slightly changes the water distribution. Our hydrogen bond properties and dynamics calculations reveal pressure-induced formation of more and more number of water molecules with five and four hydrogen bond at the expense of breaking of two and three hydrogen bonded water molecules. We also find lowering of water-water continuous hydrogen bond lifetime on application of pressure. Implication of these results for relative dispersion of hydrophobic molecules at high pressure are discussed.

Connection Between the ICRF and the Dynamical Reference Frame for the Outer Planets

NASA Astrophysics Data System (ADS)

da Silva Neto, D. N.; Assafin, M.; Andrei, A. H.; Vieira Martins, R.

2005-01-01

This work brings an approach intending to improve the connection between the Dynamical Reference Frame and the Extragalactic Reference Frame. For that, close encounters of outer Solar System objects and quasars are used. With this goal, Uranus, Neptune and two quasars were observed at Laborat´orio Nacional de Astrof´ısica (LNA), Brazil. The optical reference frame is the HCRF, as given by the UCAC2 catalogue. The first results show an accuracy of 45 mas - 50 mas in the optical positions. The optical minus radio offsets give the local orientation between the catalogue and radio frame. From this, it is possible to place the optical planet coordinates on the extragalactic frame. A comparison between the new corrected optical coordinates and the respective DE ephemeris to these planets can give the instant orientations of the Dynamical Reference Frame with regard to the ICRS, for this zone of outer Solar System.

A range of newly developed mobile generators to dynamically produce SI-traceable reference gas mixtures for reactive compounds at atmospheric concentrations

NASA Astrophysics Data System (ADS)

Leuenberger, Daiana; Pascale, Céline; Guillevic, Myriam; Ackermann, Andreas; Niederhauser, Bernhard

2017-04-01

Three new mobile facilities have been developed at METAS to dynamically generate SI-traceable reference gas mixtures for a variety of reactive compounds at atmospheric amount of substance fractions and at very low levels of uncertainty (Ux < 3%). We present three new portable "Reactive Gas Standard ReGaS" reference gas generators for the realisation of the following substances: ReGaS1: Ammonia and nitrogen dioxide in the nmol/mol (ppb) range ReGaS2: Volatile organic compounds (VOCs), e.g. limonene, alpha-pinene, MVK, MEK in the nmol/mol (ppb) range ReGaS-3: Fluorinated gases (F-gases, i.e. containing fluorine atoms) in the pmol/mol (ppt) range These three mobile generators have been designed and manufactured at METAS in the framework of the three EMRP projects MetNH3, KEY-VOCs and HIGHGAS. The method is based on permeation and subsequent dynamic dilution: A permeation tube containing the pure substance (e.g. NH3) is stored in the permeation chamber at constant temperature, pressure and matrix gas flow (N2, purified air, synthetic air). Under such conditions the pure substance permeates at constant rate into the matrix gas and can be diluted thereafter to the desired amount fractions in one or two subsequent steps. The permeation rate (mass loss over time) of the permeation tube is precisely calibrated in a fully traceable magnetic suspension balance. The carrier gas is previously purified from the compounds of interest using commercially available purification cartridges. The permeation chambers of ReGaS2 and ReGaS3 have multiple individual cells allowing for the generation of mixtures containing up to 5 different components if required. ReGaS1 allows for the generation of one-component mixtures only. These primary mixtures are then diluted to the required amount of substance fractions using thermal mass flow controllers for full flexibility and adaptability of the generation process over the entire range of possible concentrations. In order to considerably reduce adsorption/desorption processes and thus stabilisation time, all electro-polished stainless steel parts of ReGaS1 and ReGaS2 in contact with the reference gas mixtures are passivated with SilcoNert2000® surface coating. These three state-of-the-art mobile reference gas generators are applicable under both, laboratory and field conditions. Moreover the dynamic generation method can be adapted and applied to a large variety of molecules (e.g. BTEX, CFCs, HCFCs, HFCs and other refrigerants) and is particularly suitable for reactive gas species and/or at concentration ranges which are unstable when stored in pressurised cylinders. Acknowledgement: This work was supported by the European Metrology Research Programme (EMRP). The EMRP is jointly funded by the EMRP participating countries within EURAMET and the European Union

Relationship between ultrasonically detected phasic antral contractions and antral pressure.

PubMed

Hveem, K; Sun, W M; Hebbard, G; Horowitz, M; Doran, S; Dent, J

2001-07-01

The relationships between gastric wall motion and intraluminal pressure are believed to be major determinants of flows within and from the stomach. Gastric antral wall motion and intraluminal pressures were monitored in five healthy subjects by concurrent antropyloroduodenal manometry and transabdominal ultrasound for 60 min after subjects drank 500 ml of clear soup. We found that 99% of antral contractions detected by ultrasound were propagated aborally, and 68% of contractions became lumen occlusive at the site of the ultrasound marker. Of the 203 contractions detected by ultrasound, 53% were associated with pressure events in the manometric reference channel; 86% of contractions had corresponding pressure events detectable somewhere in the antrum. Contractions that occluded the lumen were more likely to be associated with a pressure event in the manometric reference channel (P < 0.01) and to be of greater amplitude (P < 0.01) than non-lumen-occlusive contractions. We conclude that heterogeneous pressure event patterns in the antrum occur despite a stereotyped pattern of contraction propagation seen on ultrasound. Lumen occlusion is more likely to be associated with higher peak antral pressure events.

Dynamic Analysis of Hammer Mechanism "Twin Hammer" of Impact Wrench

NASA Astrophysics Data System (ADS)

Konečný, M.; Slavík, J.

This paper describes function of the hammer mechanism "Twin hammer" the impact wrench, calculation of dynamic forces exerted on the mechanism and determining the contact pressures between the parts of the mechanism. The modelling of parts was performed in system Pro ENGINEER—standard. The simulation and finding dynamic forces was performed in advanced module Pro ENGINEER—mechanism design and finding contacts pressures in modul Pro ENGENEER—mechanica.

Bubbles are responsive materials interesting for nonequilibrium physics

NASA Astrophysics Data System (ADS)

Andreeva, Daria; Granick, Steve

Understanding of nature and conditions of non-equilibrium transformations of bubbles, droplets, polysomes and vesicles in a gradient filed is a breath-taking question that dissipative systems raise. We ask: how to establish a dynamic control of useful characteristics, for example dynamic control of morphology and composition modulation in soft matter. A possible answer is to develop a new generation of dynamic impactors that can trigger spatiotemporal oscillations of structures and functions. We aim to apply acoustic filed for development of temperature and pressure oscillations at a microscale area. We demonstrate amazing dynamic behavior of gas-filled bubbles in pressure gradient field using a unique technique combining optical imaging, high intensity ultrasound and high speed camera. We find that pressure oscillations trigger continuous phase transformations that are considered to be impossible in physical systems.

Modeling Ullage Dynamics of Tank Pressure Control Experiment during Jet Mixing in Microgravity

NASA Technical Reports Server (NTRS)

Kartuzova, O.; Kassemi, M.

2016-01-01

A CFD model for simulating the fluid dynamics of the jet induced mixing process is utilized in this paper to model the pressure control portion of the Tank Pressure Control Experiment (TPCE) in microgravity1. The Volume of Fluid (VOF) method is used for modeling the dynamics of the interface during mixing. The simulations were performed at a range of jet Weber numbers from non-penetrating to fully penetrating. Two different initial ullage positions were considered. The computational results for the jet-ullage interaction are compared with still images from the video of the experiment. A qualitative comparison shows that the CFD model was able to capture the main features of the interfacial dynamics, as well as the jet penetration of the ullage.

Prediction of the reference evapotranspiration using a chaotic approach.

PubMed

Wang, Wei-guang; Zou, Shan; Luo, Zhao-hui; Zhang, Wei; Chen, Dan; Kong, Jun

2014-01-01

Evapotranspiration is one of the most important hydrological variables in the context of water resources management. An attempt was made to understand and predict the dynamics of reference evapotranspiration from a nonlinear dynamical perspective in this study. The reference evapotranspiration data was calculated using the FAO Penman-Monteith equation with the observed daily meteorological data for the period 1966-2005 at four meteorological stations (i.e., Baotou, Zhangbei, Kaifeng, and Shaoguan) representing a wide range of climatic conditions of China. The correlation dimension method was employed to investigate the chaotic behavior of the reference evapotranspiration series. The existence of chaos in the reference evapotranspiration series at the four different locations was proved by the finite and low correlation dimension. A local approximation approach was employed to forecast the daily reference evapotranspiration series. Low root mean square error (RSME) and mean absolute error (MAE) (for all locations lower than 0.31 and 0.24, resp.), high correlation coefficient (CC), and modified coefficient of efficiency (for all locations larger than 0.97 and 0.8, resp.) indicate that the predicted reference evapotranspiration agrees well with the observed one. The encouraging results indicate the suitableness of chaotic approach for understanding and predicting the dynamics of the reference evapotranspiration.

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

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

Dynamic Nucleation of Ice Induced by a Single Stable Cavitation Bubble

NASA Technical Reports Server (NTRS)

Ohsaka, Kenichi; Trinh, Eugene H.

1997-01-01

Dynamic nucleation of ice induced by caviation bubble in undercooled water is observed using an acoustic levitation technique. The observation indicates that a high pressure pulse associated with a collapsing bubble is indeed responsible for the nucleation of a high pressure phase of ice.

Raman spectroscopy and lattice dynamics of MgSiO3-perovskite at high pressure

NASA Astrophysics Data System (ADS)

Hemley, R. J.; Cohen, R. E.; Yeganeh-Haeri, A.; Mao, H. K.; Weidner, D. J.; Ito, E.

Vibrational Raman spectra have been obtained for 50 to 100 μm single crystals of MgSiO3 perovskite in situ at high pressure. Seven bands were tracked as a function of pressure to 26 GPa using a diamond-anvil high-pressure cell with rare-gas pressure-transmitting media. The frequency shifts with pressure are positive, and no soft modes were observed, in agreement with the present and previous lattice dynamics calculations. Zero-pressure frequency shifts (dυi/dP)0 vary between 1.7 and 4.2 cm-1/GPa, which contrasts with the uniform shift of 2.6 cm-1/GPa for modes measured in high-pressure mid-infrared spectra. The mode-Grüneisen parameters γi, determined from the present data span the range 1.6-1.9, and are generally higher than those reported in the infrared study. The Raman data are interpreted using the lattice dynamics calculated from the potential-induced breathing (PIB) model, a Gordon-Kim approach that includes the effects of charge relaxation on the dynamics. Good agreement with the experimentally determined frequencies is obtained, particularly in the lower frequency range, in comparison with previous rigid-ion results. The high thermal expansivity for MgSiO3-perovskite is shown to be due to the comparatively high values for γi associated with the lower frequency modes. Thermal weighting of the individual γi is required for an accurate calculation of the thermal Grüneisen parameter γTH and thermal expansivity.

The Pneumatic Actuators As Vertical Dynamic Load Simulators On Medium Weighted Wheel Suspension Mechanism

NASA Astrophysics Data System (ADS)

Ka'ka, Simon; Himran, Syukri; Renreng, Ilyas; Sutresman, Onny

2018-02-01

Almost all of road damage can be caused by dynamic loads of vehicles that fluctuate according to the type of vehicle that passes through. This study aims to calculate the vertical dynamic load of the vehicle actually occurs on road construction by the mechanism of vehicle wheel suspension. Pneumatic cylinders driven by pressurized air directly load the spring and shock absorber installed on the wheels of the vehicle. The load fluctuations of the medium weight categorized vehicles are determined by the regulation of the amount of pressurized air that enters into the pneumatic cylinder chamber, pushing the piston and connecting rods. The displacement that occurs during compression on the spring and shock absorber, is substituted into the equation of vehicle dynamic load while taking into account the spring stiffness constant, and the fluid or damper gas coefficient. The results show that the magnitude of the displacement when the compression force works has significant influences to the amount of vertical dynamic load of the vehicle that overlies the road construction. The presence of dynamic load of vehicles that fluctuates and repeats, also affects on the reduction of road ability to receive the load. Experimental results using pneumatic actuators instead of real dynamic vehicle loads illustrate the characteristics of the relationship between work pressure and dynamic load. If the working pressure of P2 (bar) is greater, the vertical dynamic load Ft (N) that overloads the road structure is also greater. The associate graphs show that the shock absorber has a greater ability to reduce dynamic load vertically that burden the road structure when compared with the ability of screw spring.

The Precise Orbit and the Challenge of Long Term Stability

NASA Technical Reports Server (NTRS)

Lemoine, Frank G.; Cerri, Luca; Otten, Michiel; Bertiger, William; Zelensky, Nikita; Willis, Pascal

2012-01-01

The computation of a precise orbit reference is a fundamental component of the altimetric measurement. Since the dawn of the modern altimeter age, orbit accuracy has been determined by the quality of the GPS, SLR, and DORIS tracking systems, the fidelity of the measurement and force models, and the choice of parameterization for the orbit solutions, and whether a dynamic or a reduced-dynamic strategy is used to calculate the orbits. At the start of the TOPEX mission, the inaccuracies in the modeling of static gravity, dynamic ocean tides, and the nonconservative forces dominated the orbit error budget. Much of the error due to dynamic mismodeling can be compensated by reduced-dynamic tracking techniques depending on the measurement system strength. In the last decade, the launch of the GRACE mission has eliminated the static gravity field as a concern, and the background force models and the terrestrial reference frame have been systematically refined. GPS systems have realized many improvements, including better modeling of the forces on the GPS spacecraft, large increases in the ground tracking network, and improved modeling of the GPS measurements. DORIS systems have achieved improvements through the use of new antennae, more stable monumentation, and of satellite receivers that can track multiple beacons, and as well as through improved modeling of the nonconservative forces. Many of these improvements have been applied in the new reprocessed time series of orbits produced for the ERS satellites, Envisat, TOPEX/Poseidon and the Jason satellites, and as well as for the most recent Cryosat-2 and HY2A. We now face the challenge of maintaining a stable orbit reference for these altimetric satellites. Changes in the time-variable gravity field of the Earth and how these are modelled have been shown to affect the orbit evolution, and the calibration of the altimetric data with tide gauges. The accuracy of the reference frame realizations, and their projection into the future remains a source of error. Other sources of omission error include the geocenter for which no consensus model is as of yet applied. Although progress has been made in nonconservative force modeling through the use of detailed satellite-specific models, radiation pressure modeling, and atmospheric density modeling remain a potential source of orbit error. The longer term influence of variations in the solar and terrestrial radiation fields over annual and solar cycles remains principally untested. Also the long term variation in optical and thermal properties of the space vehicle surfaces would contribute to biases in the orbital frame if ignored. We review the status of altimetric precision orbit determination as exemplified by the recent computations undertaken by the different analysis centers for ERS, Envisat, TOPEX/Poseidon, Jason, Cryosat2 and HY2A, and we provide a perspective on the challenges for future missions such as the Jason-3, SENTINEL-3 and SWOT.

Response of the coupled M-I-T system to the March 17, 2015 solar wind dynamic pressure enhancement event

NASA Astrophysics Data System (ADS)

Ozturk, D. S.; Zou, S.; Slavin, J. A.; Ridley, A. J.

2017-12-01

When the solar wind dynamic pressure is enhanced, it could perturb the global magnetosphere-ionosphere-thermosphere (M-I-T) system. The most notable indicators of such disruptions are changes in Field-Aligned Currents (FACs), ionospheric convection patterns and magnetic perturbations observed by ground magnetometers. The link between dynamic pressure enhancements and FACs has been well established, but studies on how these FACs affect the ionosphere-thermosphere system are very limited. In order to understand the large-scale dynamic processes in the M-I-T system due to the solar wind dynamic pressure enhancement, we study the 17 March 2015 event in detail. This is one of the most geoeffective events of the solar cycle 24 with Dst minimum of -222 nT. The Wind spacecraft recorded a two-step increment in the solar wind dynamic pressure, from 2 nPa to 12 nPa within 3 minutes, while the IMF Bz stayed northward. We used the University of Michigan Block Adaptive Tree Solarwind Roe Upwind Scheme (BATS'R'US), global MHD code to study the generation and propagation of perturbations associated with the compression of the magnetosphere. To effectively represent the coupled magnetosphere-ionosphere system, we included the Global Magnetosphere (GM), Inner Magnetosphere (IM) and Ionospheric electrodynamic (IE) modules. 600 uniformly distributed virtual magnetometers are included in the simulation to identify the magnetic perturbations associated with the FAC pairs as well as their temporal and spatial variations. In addition, we used the IE module output to drive the University of Michigan Global Ionosphere Thermosphere Model (GITM) to study how the I-T system responds to dynamic pressure enhancement. We show that as a result of the solar wind dynamic pressure enhancement, two pair of perturbation FACs develop in addition to the NBZ current system. These FACs significantly alter the ionospheric convection profile and create elongated vortices that propagate from dayside to nightside. The ion temperature at the location of these vortices is significantly and immediately enhanced. We analyzed the altitude profiles of plasma temperature, electron density and joule heating to quantitatively understand energy deposition during this process, and compare them with observations from ground-based incoherent scatter radar.

The measurement of dynamic radii for passenger car tyre

NASA Astrophysics Data System (ADS)

Anghelache, G.; Moisescu, R.

2017-10-01

The tyre dynamic rolling radius is an extremely important parameter for vehicle dynamics, for operation of safety systems as ESP, ABS, TCS, etc., for road vehicle research and development, as well as for validation or as an input parameter of automotive simulations and models. The paper investigates the dynamic rolling radii of passenger car tyre and the influence of rolling speed and inflation pressure on their magnitude. The measurement of dynamic rolling radii has been performed on a chassis dynamometer test rig. The dynamic rolling radii have been measured indirectly, using longitudinal rolling speed and angular velocity of wheel. Due to the subtle effects that the parameters have on rolling radius magnitude, very accurate equipment has to be used. Two different methods have been chosen for measuring the wheel angular velocity: the stroboscopic lamp and the incremental rotary encoder. The paper shows that the stroboscopic lamp has an insufficient resolution, therefore it was no longer used for experimental investigation. The tyre dynamic rolling radii increase with rolling speed and with tyre inflation pressure, but the effect of pressure is more significant. The paper also makes considerations on the viability of simplified formulae from literature for calculating the tyre dynamic rolling radius.

Modeling of anaerobic degradation of solid slaughterhouse waste: inhibition effects of long-chain fatty acids or ammonia.

PubMed

Lokshina, L Y; Vavilin, V A; Salminen, E; Rintala, J

2003-01-01

The anaerobic bioconversion of solid poultry slaughterhouse wastes was kinetically investigated. The modified version of simulation model was applied for description of experimental data in mesophilic laboratory digester and assays. Additionally, stages of formation and consumption of long chain fatty acids (LCFA) were included in the model. Batch data on volatile solids, ammonium, acetate, butyrate, propionate, LCFA concentrations, pH level, cumulative volume, and methane partial pressure were used for model calibration. As a reference, the model was used to describe digestion of solid sorted household waste. Simulation results showed that an inhibition of polymer hydrolysis by volatile fatty acids and acetogenesis by NH3 or LCFA could be responsible for the complex system dynamics during degradation of lipid- and protein-rich wastes.

High Fidelity Modeling of SRP and Its Effect on the Relative Motion of Starshade and WFIRST

NASA Technical Reports Server (NTRS)

Farres, Ariadna; Webster, Cassandra; Folta, Dave

2018-01-01

In this paper we perform a detailed analysis of how Solar Radiation Pressure (SRP) affects the relative motion of two spacecrafts, the Wide-Field Infrared Survey Telescope (WFIRST) and Starshade, orbiting in the vicinity of the Sun-Earth L2. While WFIRST orbits about its own Libration Point Orbit (LPO), Starshade will fly a specific trajectory to align with WFIRST and observe a Design Reference Mission of pre-determined target stars. In this analysis, we focus on the transfer orbit for Starshade from one observation to the other. We will describe how SRP affects the dynamics of the Starshade relative to WFIRSTand how relevant this effect is in order to get an accurate estimate of the total difference in velocity (delta v).

Cell Surface Mechanochemistry and the Determinants of Bleb Formation, Healing, and Travel Velocity

PubMed Central

Manakova, Kathryn; Yan, Huaming; Lowengrub, John; Allard, Jun

2016-01-01

Blebs are pressure-driven cell protrusions implicated in cellular functions such as cell division, apoptosis, and cell motility, including motility of protease-inhibited cancer cells. Because of their mechanical nature, blebs inform us about general cell-surface mechanics, including membrane dynamics, pressure propagation throughout the cytoplasm, and the architecture and dynamics of the actin cortex. Mathematical models including detailed fluid dynamics have previously been used to understand bleb expansion. Here, we develop mathematical models in two and three dimensions on longer timescales that recapitulate the full bleb life cycle, including both expansion and healing by cortex reformation, in terms of experimentally accessible biophysical parameters such as myosin contractility, osmotic pressure, and turnover of actin and ezrin. The model provides conditions under which blebbing occurs, and naturally gives rise to traveling blebs. The model predicts conditions under which blebs travel or remain stationary, as well as the bleb traveling velocity, a quantity that has remained elusive in previous models. As previous studies have used blebs as reporters of membrane tension and pressure dynamics within the cell, we have used our system to investigate various pressure equilibration models and dynamic, nonuniform membrane tension to account for the shape of a traveling bleb. We also find that traveling blebs tend to expand in all directions unless otherwise constrained. One possible constraint could be provided by spatial heterogeneity in, for example, adhesion density. PMID:27074688

High-pressure phase transitions of α-quartz under nonhydrostatic dynamic conditions: A reconnaissance study at PETRA III

NASA Astrophysics Data System (ADS)

Carl, Eva-Regine; Mansfeld, Ulrich; Liermann, Hanns-Peter; Danilewsky, Andreas; Langenhorst, Falko; Ehm, Lars; Trullenque, Ghislain; Kenkmann, Thomas

2017-07-01

Hypervelocity collisions of solid bodies occur frequently in the solar system and affect rocks by shock waves and dynamic loading. A range of shock metamorphic effects and high-pressure polymorphs in rock-forming minerals are known from meteorites and terrestrial impact craters. Here, we investigate the formation of high-pressure polymorphs of α-quartz under dynamic and nonhydrostatic conditions and compare these disequilibrium states with those predicted by phase diagrams derived from static experiments under equilibrium conditions. We create highly dynamic conditions utilizing a mDAC and study the phase transformations in α-quartz in situ by synchrotron powder X-ray diffraction. Phase transitions of α-quartz are studied at pressures up to 66.1 and different loading rates. At compression rates between 0.14 and 1.96 GPa s-1, experiments reveal that α-quartz is amorphized and partially converted to stishovite between 20.7 GPa and 28.0 GPa. Therefore, coesite is not formed as would be expected from equilibrium conditions. With the increasing compression rate, a slight increase in the transition pressure occurs. The experiments show that dynamic compression causes an instantaneous formation of structures consisting only of SiO6 octahedra rather than the rearrangement of the SiO4 tetrahedra to form a coesite. Although shock compression rates are orders of magnitude faster, a similar mechanism could operate in impact events.

Fire testing and computer modelling of rail tank-cars engulfed in fires : literature review

DOT National Transportation Integrated Search

2006-03-01

This literature review contains important references relating to fire effects on pressure : vessels. The specific pressure vessels of interest are rail tank-cars carrying pressure : liquefied gases such as LPG and anhydrous ammonia. The literature id...

The effects of plantar flexor static stretching and dynamic stretching using an aero-step on foot pressure during gait in healthy adults: a preliminary study.

PubMed

Shim, Je-Myung; Jung, Ju-Hyeon; Kim, Hwan-Hee

2015-07-01

[Purpose] The aim of this study was to examine whether plantar flexor static stretching and dynamic stretching using an Aero-Step results in changes in foot pressure during gait in healthy adults. [Subjects] Eighteen normal adults were randomly allocated to either a dynamic stretching using an Aero-Step group (DSUAS) group (n = 8) or a static stretching (SS) group (n = 10). [Methods] The DSUAS and SS participants took part in an exercise program for 15 minutes. Outcome measures were foot plantar pressure, which was measured during the subject's gait stance phase; the asymmetric ratio of foot pressure for both feet; and the visual analogue scale (VAS) measured during the interventions. [Results] There were significant differences in the asymmetric ratio of foot pressure for both feet and VAS between the two groups after intervention. However, there were no significant differences in foot plantar pressure during the gait stance phase within both groups. [Conclusion] DSUSAS is an effective stretching method, as pain during it is lower than that with SS, which can minimize the asymmetric ratio of foot pressure for both feet during gait due to asymmetric postural alignment.

Pressure-Drop Considerations in the Characterization of Dew-Point Transfer Standards at High Temperatures

NASA Astrophysics Data System (ADS)

Mitter, H.; Böse, N.; Benyon, R.; Vicente, T.

2012-09-01

During calibration of precision optical dew-point hygrometers (DPHs), it is usually necessary to take into account the pressure drop induced by the gas flow between the "point of reference" and the "point of use" (mirror or measuring head of the DPH) either as a correction of the reference dew-point temperature or as part of the uncertainty estimation. At dew-point temperatures in the range of ambient temperature and below, it is sufficient to determine the pressure drop for the required gas flow, and to keep the volumetric flow constant during the measurements. In this case, it is feasible to keep the dry-gas flow into the dew-point generator constant or to measure the flow downstream the DPH at ambient temperature. In normal operation, at least one DPH in addition to the monitoring DPH are used, and this operation has to be applied to each instrument. The situation is different at high dew-point temperatures up to 95 °C, the currently achievable upper limit reported in this paper. With increasing dew-point temperatures, the reference gas contains increasing amounts of water vapour and a constant dry-gas flow will lead to a significant enhanced volume flow at the conditions at the point of use, and therefore, to a significantly varying pressure drop depending on the applied dew-point temperature. At dew-point temperatures above ambient temperature, it is also necessary to heat the reference gas and the mirror head of the DPH sufficiently to avoid condensation which will additionally increase the volume flow and the pressure drop. In this paper, a method is provided to calculate the dry-gas flow rate needed to maintain a known wet-gas flow rate through a chilled mirror for a range of temperature and pressures.

Dynamic Shock Compression of Copper to Multi-Megabar Pressure

NASA Astrophysics Data System (ADS)

Haill, T. A.; Furnish, M. D.; Twyeffort, L. L.; Arrington, C. L.; Lemke, R. W.; Knudson, M. D.; Davis, J.-P.

2015-11-01

Copper is an important material for a variety of shock and high energy density applications and experiments. Copper is used as a standard reference material to determine the EOS properties of other materials. The high conductivity of copper makes it useful as an MHD driver layer in high current dynamic materials experiments on Sandia National Laboratories Z machine. Composite aluminum/copper flyer plates increase the dwell time in plate impact experiments by taking advantage of the slower wave speeds in copper. This presentation reports on recent efforts to reinstate a composite Al/Cu flyer capability on Z and to extend the range of equation-of-state shock compression data through the use of hyper-velocity composite flyers and symmetric planar impact with copper targets. We will present results from multi-dimensional ALEGRA MHD simulations, as well as experimental designs and methods of composite flyer fabrication. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. DOE's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Afterbody Heating Predictions for a Mars Science Laboratory Entry Vehicle

NASA Technical Reports Server (NTRS)

Edquist, Karl T.

2005-01-01

The Mars Science Laboratory mission intends to deliver a large rover to the Martian surface within 10 km of its target site. One candidate entry vehicle aeroshell consists of a 3.75-m diameter, 70-deg sphere-cone forebody and a biconic afterbody similar to that of Viking. This paper presents computational fluid dynamics predictions of laminar afterbody heating rates for this configuration and a 2010 arrival at Mars. Computational solutions at flight conditions used an 8-species Mars gas model in chemical and thermal non-equilibrium. A grid resolution study examined the effects of mesh spacing on afterbody heating rates and resulted in grids used for heating predictions on a reference entry trajectory. Afterbody heating rate reaches its maximum value near 0.6 W/sq cm on the first windward afterbody cone at the time of peak freestream dynamic pressure. Predicted afterbody heating rates generally are below 3% of the forebody laminar nose cap heating rate throughout the design trajectory. The heating rates integrated over time provide total heat load during entry, which drives thermal protection material thickness.

Large dynamic range pressure sensor based on two semicircle-holes microstructured fiber.

PubMed

Liu, Zhengyong; Htein, Lin; Lee, Kang-Kuen; Lau, Kin-Tak; Tam, Hwa-Yaw

2018-01-08

This paper presents a sensitive and large dynamic range pressure sensor based on a novel birefringence microstructured optical fiber (MOF) deployed in a Sagnac interferometer configuration. The MOF has two large semicircle holes in the cladding and a rectangular strut with germanium-doped core in the center. The fiber structure permits surrounding pressure to induce large effective index difference between the two polarized modes. The calculated and measured group birefringence of the fiber are 1.49 × 10 -4 , 1.23 × 10 -4 , respectively, at the wavelength of 1550 nm. Experimental results shown that the pressure sensitivity of the sensor varied from 45,000 pm/MPa to 50,000 pm/MPa, and minimum detectable pressure of 80 Pa and dynamic range of better than 116 dB could be achieved with the novel fiber sensor. The proposed sensor could be used in harsh environment and is an ideal candidate for downhole applications where high pressure measurement at elevated temperature up to 250 °C is needed.

Water Dynamics in Shewanella oneidensis at Ambient and High Pressure using Quasi-Elastic Neutron Scattering

NASA Astrophysics Data System (ADS)

Foglia, Fabrizia; Hazael, Rachael; Simeoni, Giovanna G.; Appavou, Marie-Sousai; Moulin, Martine; Haertlein, Michael; Trevor Forsyth, V.; Seydel, Tilo; Daniel, Isabelle; Meersman, Filip; McMillan, Paul F.

2016-01-01

Quasielastic neutron scattering (QENS) is an ideal technique for studying water transport and relaxation dynamics at pico- to nanosecond timescales and at length scales relevant to cellular dimensions. Studies of high pressure dynamic effects in live organisms are needed to understand Earth’s deep biosphere and biotechnology applications. Here we applied QENS to study water transport in Shewanella oneidensis at ambient (0.1 MPa) and high (200 MPa) pressure using H/D isotopic contrast experiments for normal and perdeuterated bacteria and buffer solutions to distinguish intracellular and transmembrane processes. The results indicate that intracellular water dynamics are comparable with bulk diffusion rates in aqueous fluids at ambient conditions but a significant reduction occurs in high pressure mobility. We interpret this as due to enhanced interactions with macromolecules in the nanoconfined environment. Overall diffusion rates across the cell envelope also occur at similar rates but unexpected narrowing of the QENS signal appears between momentum transfer values Q = 0.7-1.1 Å-1 corresponding to real space dimensions of 6-9 Å. The relaxation time increase can be explained by correlated dynamics of molecules passing through Aquaporin water transport complexes located within the inner or outer membrane structures.

Water Dynamics in Shewanella oneidensis at Ambient and High Pressure using Quasi-Elastic Neutron Scattering.

PubMed

Foglia, Fabrizia; Hazael, Rachael; Simeoni, Giovanna G; Appavou, Marie-Sousai; Moulin, Martine; Haertlein, Michael; Trevor Forsyth, V; Seydel, Tilo; Daniel, Isabelle; Meersman, Filip; McMillan, Paul F

2016-01-07

Quasielastic neutron scattering (QENS) is an ideal technique for studying water transport and relaxation dynamics at pico- to nanosecond timescales and at length scales relevant to cellular dimensions. Studies of high pressure dynamic effects in live organisms are needed to understand Earth's deep biosphere and biotechnology applications. Here we applied QENS to study water transport in Shewanella oneidensis at ambient (0.1 MPa) and high (200 MPa) pressure using H/D isotopic contrast experiments for normal and perdeuterated bacteria and buffer solutions to distinguish intracellular and transmembrane processes. The results indicate that intracellular water dynamics are comparable with bulk diffusion rates in aqueous fluids at ambient conditions but a significant reduction occurs in high pressure mobility. We interpret this as due to enhanced interactions with macromolecules in the nanoconfined environment. Overall diffusion rates across the cell envelope also occur at similar rates but unexpected narrowing of the QENS signal appears between momentum transfer values Q = 0.7-1.1 Å(-1) corresponding to real space dimensions of 6-9 Å. The relaxation time increase can be explained by correlated dynamics of molecules passing through Aquaporin water transport complexes located within the inner or outer membrane structures.

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

NASA Astrophysics Data System (ADS)

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

2016-11-01

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

Water dynamics and retrogradation of ultrahigh pressurized wheat starch.

PubMed

Doona, Christopher J; Feeherry, Florence E; Baik, Moo-Yeol

2006-09-06

The water dynamics and retrogradation kinetics behavior of gelatinized wheat starch by either ultrahigh pressure (UHP) processing or heat are investigated. Wheat starch completely gelatinized in the condition of 90, 000 psi at 25 degrees C for 30 min (pressurized gel) or 100 degrees C for 30 min (heated gel). The physical properties of the wheat starches were characterized in terms of proton relaxation times (T2 times) measured using time-domain nuclear magnetic resonance spectroscopy and evaluated using commercially available continuous distribution modeling software. Different T2 distributions in both micro- and millisecond ranges between pressurized and heated wheat starch gels suggest distinctively different water dynamics between pressurized and heated wheat starch gels. Smaller water self-diffusion coefficients were observed for pressurized wheat starch gels and are indicative of more restricted translational proton mobility than is observed with heated wheat starch gels. The physical characteristics associated with changes taking place during retrogradation were evaluated using melting curves obtained with differential scanning calorimetry. Less retrogradation was observed in pressurized wheat starch, and it may be related to a smaller quantity of freezable water in pressurized wheat starch. Starches comprise a major constituent of many foods proposed for commercial potential using UHP, and the present results furnish insight into the effect of UHP on starch gelatinization and the mechanism of retrogradation during storage.

Spectral calculations for pressure-velocity and pressure-strain correlations in homogeneous shear turbulence

NASA Astrophysics Data System (ADS)

Dutta, Kishore

2018-02-01

Theoretical analyses of pressure related turbulent statistics are vital for a reliable and accurate modeling of turbulence. In the inertial subrange of turbulent shear flow, pressure-velocity and pressure-strain correlations are affected by anisotropy imposed at large scales. Recently, Tsuji and Kaneda (2012 J. Fluid Mech. 694 50) performed a set of experiments on homogeneous shear flow, and estimated various one-dimensional pressure related spectra and the associated non-dimensional universal numbers. Here, starting from the governing Navier-Stokes dynamics for the fluctuating velocity field and assuming the anisotropy at inertial scales as a weak perturbation of an otherwise isotropic dynamics, we analytically derive the form of the pressure-velocity and pressure-strain correlations. The associated universal numbers are calculated using the well-known renormalization-group results, and are compared with the experimental estimates of Tsuji and Kaneda. Approximations involved in the perturbative calculations are discussed.

Investigation of space shuttle vehicle 140C configuration orbiter (model 16-0) wheel well pressure loads in the Rockwell International 7.75 x 11 foot wind tunnel (OA143)

NASA Technical Reports Server (NTRS)

Mennell, R. C.

1975-01-01

Experimental aerodynamic investigations were conducted on a sting mounted .0405-scale representation of the 140C outer mold line space shuttle orbiter configuration in the Rockwell International 7.75 x 11.00 foot low speed wind tunnel. The primary test objectives were to define the orbiter wheel well pressure loading and its effects on landing gear thermal insulation and to investigate the pressure environment experienced by both the horizontal flight nose probe and air vent door probes. Steady state and dynamic pressure values were recorded in the orbiter nose gear well, left main landing gear well, horizontal flight nose probe, and both left and right air vent door probe. All steady state pressure levels were measured by Statham differential pressure transducers while dynamic pressure levels were recorded by Kulite high frequency response pressure sensors.

A seal test facility for the measurement of isotropic and anisotropic linear rotordynamic characteristics

NASA Technical Reports Server (NTRS)

Adams, M. L.; Yang, T.; Pace, S. E.

1989-01-01

A new seal test facility for measuring high-pressure seal rotor-dynamic characteristics has recently been made operational at Case Western Reserve University (CWRU). This work is being sponsored by the Electric Power Research Institute (EPRI). The fundamental concept embodied in this test apparatus is a double-spool-shaft spindle which permits independent control over the spin speed and the frequency of an adjustable circular vibration orbit for both forward and backward whirl. Also, the static eccentricity between the rotating and non-rotating test seal parts is easily adjustable to desired values. By accurately measuring both dynamic radial displacement and dynamic radial force signals, over a wide range of circular orbit frequency, one is able to solve for the full linear-anisotropic model's 12 coefficients rather than the 6 coefficients of the more restrictive isotropic linear model. Of course, one may also impose the isotropic assumption in reducing test data, thereby providing a valid qualification of which seal configurations are well represented by the isotropic model and which are not. In fact, as argued in reference (1), the requirement for maintaining a symmetric total system mass matrix means that the resulting isotropic model needs 5 coefficients and the anisotropic model needs 11 coefficients.

Contributions of the NASA Langley Transonic Dynamics Tunnel to Launch Vehicle and Spacecraft Development

NASA Technical Reports Server (NTRS)

Cole, Stanley R.; Keller, Donald F.; Piatak, David J.

2000-01-01

The NASA Langley Transonic Dynamics Tunnel (TDT) has provided wind-tunnel experimental validation and research data for numerous launch vehicles and spacecraft throughout its forty year history. Most of these tests have dealt with some aspect of aeroelastic or unsteady-response testing, which is the primary purpose of the TDT facility. However, some space-related test programs that have not involved aeroelasticity have used the TDT to take advantage of specific characteristics of the wind-tunnel facility. In general. the heavy gas test medium, variable pressure, relatively high Reynolds number and large size of the TDT test section have made it the preferred facility for these tests. The space-related tests conducted in the TDT have been divided into five categories. These categories are ground wind loads, launch vehicle dynamics, atmospheric flight of space vehicles, atmospheric reentry. and planetary-probe testing. All known TDT tests of launch vehicles and spacecraft are discussed in this report. An attempt has been made to succinctly summarize each wind-tunnel test, or in the case of multiple. related tests, each wind-tunnel program. Most summaries include model program discussion, description of the physical wind-tunnel model, and some typical or significant test results. When available, references are presented to assist the reader in further pursuing information on the tests.

46 CFR 154.407 - Cargo tank internal pressure head.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Equipment Cargo Containment Systems § 154.407 Cargo tank internal pressure head. (a) For the calculation..., resulting from the combined effects of gravity and dynamic accelerations of a full tank)=aβ Zβ Y; where: aβ=dimensionless acceleration relative to the acceleration of gravity resulting from gravitational and dynamic...

CFD Investigation of Effect of Depth to Diameter Ratio on Dimple Flow Dynamics

DTIC Science & Technology

2007-06-01

contained dynamic vortical flow structures with behavior varying between each dimple studied. This dynamic vortex activity was observed to be linked... 1 1.1 Research Goals . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Motivation for Research . . . . . . . . . . . . . . . . . . 1 1.3...59 F. 1 . Pressure tap for ReD 20500 Rex 5000 0.05 h/D dimple . . . . . 66 F.2. Pressure tap for ReD 20500 Rex 77000 0.05 h/D dimple

Pressure Studies of Protein Dynamics.

DTIC Science & Technology

1987-02-20

applicable ) Office of Naval Research ONR N00014-86-K-0270 kc. ADDRESS (City, State,and ZIP Code) 10. SOURCE OF FUNDING NUMBERS - PROGRAM PROJECT I TASK IWORK...Pressure Studies of Protein Dynamics 12. PERSONAL AUTHOR(S) Hans Frauenfelder and Robert D. Young 13a. TYPE OF REPORT |13b. TIME COVERED 114 DATE OF...relatioihbetween dynamic structure and function of protein protein dyna -bsey observing the phenomena induced by flash photolysis using near ultravfilet

Pressure effects on structural, electronic, elastic and lattice dynamical properties of XSi2 (X = Cr, Mo, W) from first principles

NASA Astrophysics Data System (ADS)

Zhu, Haiyan; Shi, Liwei; Li, Shuaiqi; Zhang, Shaobo; Xia, Wangsuo

2018-04-01

First-principles calculations have been performed to study the structure, elastic and lattice dynamical properties of C40 XSi2 (X=Cr, Mo, W) under hydrostatic pressure. The obtained structural parameters are in line with existing experimental and theoretical data. The evolutions of fundamental bandgap energies, elastic moduli, IR absorption spectra with pressure have been investigated in detail. Our results indicate that the energy gaps of XSi2 (X=Cr, Mo, W) show different trends as the pressure increases. Larger BH/GH ratio and Poisson’s ratio are achieved with pressure, suggesting an improved ductility for XSi2 (X=Cr, Mo, W). Moreover, a large elastic anisotropy under pressure is exhibited in Young’s anisotropic factors. The infrared-active phonon frequencies exhibit substantial blueshifts under pressure.

[Study on the correlation between adolescents' emotional and behavioral problems and life events].

PubMed

Huang, Xue-zhu; Guo, Lan-ting; Tang, Guang-zheng

2006-03-01

To study the life events which are correlated with adolescent's emotion and behavior problems, and to provide evidence for clinicians and school staff to develop intervention for those problems. Youth's Self Report (YSR) and Adolescent Self-Rating Life Events Check List (ASLEC) were used to assess adolescent's emotional and behavioral problems and life events by 'spot' study. The referred group consisted of 585 patients from 11 to 18 years old in a Mental Health Centre of West China Hospital of Sichuan University from July in 2002 to March in 2004. Level of IQ was above 5th grade of primary school among the study subjects who were willing to fill in the YSR and ASLEC. The non-referred group was selected in a 1280 students cluster-sample from the schools of Chengdu city, whose sex, age and father's career were matched with the referred group. Variance inflation factor (VIF) was used to verify that there was no collinearity to each other in the 6 factors of ASLEC: interpersonal relationship, learning pressure, being punished, losing good adaptation and other. Linear stepwise regression was adopted. The YSR scores in referred group were higher than those in non-referred group, and the referred group had more emotional and behavioral problems than the non-referred one. Partial correlations ranged from 0.124 to 0.418 in referred group, and from 0.104 to 0.388 in non-referred group. Unsatisfied interpersonal relationship, heavy learning pressure, having been punished and poor adaptation were likely to increase the risk of youth's emotional and behavioral problems. More attention should be paid to help adolescents in the following areas: solving intrapersonal affairs, relieving pressure from learning, avoiding punishment, and improving ability to fit themselves to their surroundings.

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.

Measuring Tissue Perfusion During Pressure Relief Maneuvers: Insights Into Preventing Pressure Ulcers

PubMed Central

Makhsous, Mohsen; Priebe, Michael; Bankard, James; Rowles, Diana; Zeigler, Mary; Chen, David; Lin, Fang

2007-01-01

Background/Objective: To study the effect on tissue perfusion of relieving interface pressure using standard wheelchair pushups compared with a mechanical automated dynamic pressure relief system. Design: Repeated measures in 2 protocols on 3 groups of subjects. Participants: Twenty individuals with motor-complete paraplegia below T4, 20 with motor-complete tetraplegia, and 20 able-bodied subjects. Methods: Two 1-hour sitting protocols: dynamic protocol, sitting configuration alternated every 10 minutes between a normal sitting configuration and an off-loading configuration; wheelchair pushup protocol, normal sitting configuration with standard wheelchair pushup once every 20 minutes. Main Outcome Measures: Transcutaneous partial pressures of oxygen and carbon dioxide measured from buttock overlying the ischial tuberosity and interface pressure measured at the seat back and buttocks. Perfusion deterioration and recovery times were calculated during changes in interface pressures. Results: In the off-loading configuration, concentrated interface pressure during the normal sitting configuration was significantly diminished, and tissue perfusion was significantly improved. Wheelchair pushups showed complete relief of interface pressure but incomplete recovery of tissue perfusion. Conclusions: Interface pressure analysis does not provide complete information about the effectiveness of pressure relief maneuvers. Measures of tissue perfusion may help establish more effective strategies. Relief achieved by standard wheelchair pushups may not be sufficient to recover tissue perfusion compromised during sitting; alternate maneuvers may be necessary. The dynamic seating system provided effective pressure relief with sustained reduction in interface pressure adequate for complete recovery of tissue perfusion. Differences in perfusion recovery times between subjects with spinal cord injury (SCI) and controls raise questions about the importance of changes in vascular responses to pressure after SCI. PMID:18092567

On the role and value of β in incompressible MHD simulations

NASA Astrophysics Data System (ADS)

Chahine, Robert; Bos, Wouter J. T.

2018-04-01

The parameter β, defined as the ratio of the pressure to the square of the magnetic field, is widely used to characterize astrophysical and fusion plasmas. However, in the dynamics of a plasma flow, it is the pressure gradient which is important rather than the value of the pressure itself. It is shown that if one is interested in the influence of the pressure gradient on the dynamics of a plasma, it is not the quantity β which should be considered, but a similar quantity depending on the pressure gradient. The scaling of this newly defined quantity is investigated using incompressible magnetohydrodynamic simulations in a periodic cylinder in the Reversed Field Pinch flow regime.

Multi-modal anatomical optical coherence tomography and CT for in vivo dynamic upper airway imaging

NASA Astrophysics Data System (ADS)

Balakrishnan, Santosh; Bu, Ruofei; Price, Hillel; Zdanski, Carlton; Oldenburg, Amy L.

2017-02-01

We describe a novel, multi-modal imaging protocol for validating quantitative dynamic airway imaging performed using anatomical Optical Coherence Tomography (aOCT). The aOCT system consists of a catheter-based aOCT probe that is deployed via a bronchoscope, while a programmable ventilator is used to control airway pressure. This setup is employed on the bed of a Siemens Biograph CT system capable of performing respiratory-gated acquisitions. In this arrangement the position of the aOCT catheter may be visualized with CT to aid in co-registration. Utilizing this setup we investigate multiple respiratory pressure parameters with aOCT, and respiratory-gated CT, on both ex vivo porcine trachea and live, anesthetized pigs. This acquisition protocol has enabled real-time measurement of airway deformation with simultaneous measurement of pressure under physiologically relevant static and dynamic conditions- inspiratory peak or peak positive airway pressures of 10-40 cm H2O, and 20-30 breaths per minute for dynamic studies. We subsequently compare the airway cross sectional areas (CSA) obtained from aOCT and CT, including the change in CSA at different stages of the breathing cycle for dynamic studies, and the CSA at different peak positive airway pressures for static studies. This approach has allowed us to improve our acquisition methodology and to validate aOCT measurements of the dynamic airway for the first time. We believe that this protocol will prove invaluable for aOCT system development and greatly facilitate translation of OCT systems for airway imaging into the clinical setting.

An ultra-fast fiber optic pressure sensor for blast event measurements

NASA Astrophysics Data System (ADS)

Wu, Nan; Zou, Xiaotian; Tian, Ye; Fitek, John; Maffeo, Michael; Niezrecki, Christopher; Chen, Julie; Wang, Xingwei

2012-05-01

Soldiers who are exposed to explosions are at risk of suffering traumatic brain injury (TBI). Since the causal relationship between a blast and TBI is poorly understood, it is critical to have sensors that can accurately quantify the blast dynamics and resulting wave propagation through a helmet and skull that are imparted onto and inside the brain. To help quantify the cause of TBI, it is important to record transient pressure data during a blast event. However, very few sensors feature the capabilities of tracking the dynamic pressure transients due to the rapid change of the pressure during blast events, while not interfering with the physical material layers or wave propagation. In order to measure the pressure transients efficiently, a pressure sensor should have a high resonant frequency and a high spatial resolution. This paper describes an ultra-fast fiber optic pressure sensor based on the Fabry-Perot principle for the application of measuring the rapid pressure changes in a blast event. A shock tube experiment performed in US Army Natick Soldier Research, Development and Engineering Center has demonstrated that the resonant frequency of the sensor is 4.12 MHz, which is relatively close to the designed theoretical value of 4.113 MHz. Moreover, the experiment illustrated that the sensor has a rise time of 120 ns, which demonstrates that the sensor is capable of observing the dynamics of the pressure transient during a blast event.

Elevation effects in volcano applications of the COSPEC

USGS Publications Warehouse

Gerlach, T.M.

2003-01-01

Volcano applications commonly involve sizeable departures from the reference pressure and temperature of COSPEC calibration cells. Analysis shows that COSPEC SO2 column abundances and derived mass emission rates are independent of pressure and temperature, and thus unaffected by elevation effects related to deviations from calibration cell reference state. However, path-length concentrations are pressure and temperature dependent. Since COSPEC path-length concentration data assume the reference pressure and temperature of calibration cells, they can lead to large errors when used to calculate SO2 mixing ratios of volcanic plumes. Correction factors for COSPEC path-length concentrations become significant (c.10%) at elevations of about 1 km (e.g. Kilauea volcano) and rise rapidly to c.80% at 6 km (e.g. Cotopaxi volcano). Calculating SO2 mixing ratios for volcanic plumes directly from COSPEC path-length concentrations always gives low results. Corrections can substantially increase mixing ratios; for example, corrections increase SO2 ppm concentrations reported for the Mount St Helens, Colima, and Erebus plumes by 25-50%. Several arguments suggest it would be advantageous to calibrate COSPEC measurements in column abundance units rather than path-length concentration units.

Simultaneous pressure measurement and high-speed photography study of cavitation in a dynamically loaded journal bearing

NASA Technical Reports Server (NTRS)

Sun, D. C.; Brewe, David E.; Abel, Philip B.

1994-01-01

Cavitation of the oil film in a dynamically loaded journal bearing was studied using high-speed photography and pressure measurement simultaneously. Comparison of the visual and pressure data provided considerable insight into the occurrence and nonoccurrence of cavitation. It was found that (1) for the submerged journal bearing, cavitation typically occurred in the form of one bubble with the pressure in the cavitation bubble close to the absolute zero; and (2) for cavitation-producing operating conditions, cavitation did not always occur; with the oil film then supporting a tensile stress.

Development of a dynamic pressure calibration technique

NASA Technical Reports Server (NTRS)

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

1975-01-01

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

Steady- and unsteady-pressure measurements on a supercritical-wing model with oscillating control surfaces at subsonic and transonic speeds

NASA Technical Reports Server (NTRS)

Sandford, M. C.; Ricketts, R. H.

1983-01-01

A high aspect ratio supercritical wing with oscillating control surfaces is described. The semispan wing model was instrumented with 252 static pressure orifices and 164 in situ dynamic pressure gages for studying the effects of control surface position and sinusoidal motion on steady and unsteady pressures. Results from the present test (the third in a series of tests on this model) were obtained in the Langley Transonic Dynamics Tunnel at Mach numbers of 0.60, 0.78, and 0.86 and are presented in tabular form.

Pressure effects on collective density fluctuations in water and protein solutions

PubMed Central

Russo, Daniela; Laloni, Alessio; Filabozzi, Alessandra; Heyden, Matthias

2017-01-01

Neutron Brillouin scattering and molecular dynamics simulations have been used to investigate protein hydration water density fluctuations as a function of pressure. Our results show significant differences between the pressure and density dependence of collective dynamics in bulk water and in concentrated protein solutions. Pressure-induced changes in the tetrahedral order of the water HB network have direct consequences for the high-frequency sound velocity and damping coefficients, which we find to be a sensitive probe for changes in the HB network structure as well as the wetting of biomolecular surfaces. PMID:29073065

Fiber-linked interferometric pressure sensor

NASA Technical Reports Server (NTRS)

Beheim, G.; Fritsch, K.; Poorman, R. N.

1987-01-01

A fiber-optic pressure sensor is described which uses a diaphragm to modulate the mirror separation of a Fabry-Perot cavity (the sensing cavity). A multimode optical fiber delivers broadband light to the sensing cavity and returns the spectrally modulated light which the cavity reflects. The sensor's output spectrum is analyzed using a tunable Fabry-Perot cavity (the reference cavity) to determine the mismatch in the mirror separations of the two cavities. An electronic servo control uses this result to cause the mirror separation of the reference cavity to equal that of the sensing cavity. The displacement of the pressure-sensing diaphragm is then obtained by measuring the capacitance of the reference cavity's metal-coated mirrors. Relative to other fiber-optic sensors, an important advantage of this instrument is its high immunity to the effects of variations in both the transmissivity of the fiber link and the wavelength of the optical source.

Investigation of Dynamics in BMIM TFSA Ionic Liquid through Variable Temperature and Pressure NMR Relaxometry and Diffusometry

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

Pilar, Kartik; Rua, Armando; Suarez, Sophia N.

A comprehensive variable temperature, pressure and frequency multinuclear ( 1H, 2H, and 19F) magnetic resonance study was undertaken on selectively deuterated 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (BMIM TFSA) ionic liquid isotopologues. This study builds on our earlier investigation of the effects of increasing alkyl chain length on diffusion and dynamics in imidazolium-based TFSA ionic liquids. Fast field cycling 1H T 1 data revealed multiple modes of motion. Through calculation of diffusion coefficient (D) values and activation energies, the low- and high-field regimes were assigned to the translational and reorientation dynamics respectively. Variable-pressure 2H T 1 measurements reveal site-dependent interactions in the cation withmore » strengths in the order MD 3 > CD 3 > CD 2, indicating dissimilarities in the electric field gradients along the alkyl chain, with the CD 2 sites having the largest gradient. Additionally, the α saturation effect in T 1 vs. P was observed for all three sites, suggesting significant reduction of the short-range rapid reorientational dynamics. This reduction was also deduced from the variable pressure 1H T 1 data, which showed an approach to saturation for both the methyl and butyl group terminal methyl sites. Pressure-dependent D measurements show independent motions for both cations and anions, with the cations having greater D values over the entire pressure range.« less

Volcano infrasonic signals and magma degassing: First-order experimental insights and application to Stromboli

NASA Astrophysics Data System (ADS)

Lane, Stephen J.; James, Mike R.; Corder, Steven B.

2013-09-01

We demonstrate the rise and expansion of a gas slug as a fluid dynamic source mechanism for infrasonic signals generated by gas puffing and impulsive explosions at Stromboli. The fluid dynamics behind the rise, expansion and burst of gas slugs in the confines of an experimental tube can be characterised into different regimes. Passive expansion occurs for small gas masses, where negligible dynamic gas over-pressure develops during bubble ascent and, prior to burst, meniscus oscillation forms an important infrasonic source. With increasing gas mass, a transition regime emerges where dynamic gas over-pressure is significant. For larger gas masses, this regime transforms to fully explosive behaviour, where gas over-pressure dominates as an infrasonic source and bubble bursting is not a critical factor. The rate of change of excess pressure in the experimental tube was used to generate synthetic infrasonic waveforms. Qualitatively, the waveforms compare well to infrasonic waveforms measured from a range of eruptions at Stromboli. Assuming pressure continuity during flow through the vent, and applying dimensionless arguments from the first-order experiments, allows estimation of eruption metrics from infrasonic signals measured at Stromboli. Values of bubble length, gas mass and over-pressure calculated from infrasonic signals are in excellent agreement with those derived by independent means for eruptions at Stromboli, therefore providing a method of estimating eruption metrics from infrasonic measurement.

Investigation of Dynamics in BMIM TFSA Ionic Liquid through Variable Temperature and Pressure NMR Relaxometry and Diffusometry

DOE PAGES

Pilar, Kartik; Rua, Armando; Suarez, Sophia N.; ...

2017-05-11

A comprehensive variable temperature, pressure and frequency multinuclear ( 1H, 2H, and 19F) magnetic resonance study was undertaken on selectively deuterated 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (BMIM TFSA) ionic liquid isotopologues. This study builds on our earlier investigation of the effects of increasing alkyl chain length on diffusion and dynamics in imidazolium-based TFSA ionic liquids. Fast field cycling 1H T 1 data revealed multiple modes of motion. Through calculation of diffusion coefficient (D) values and activation energies, the low- and high-field regimes were assigned to the translational and reorientation dynamics respectively. Variable-pressure 2H T 1 measurements reveal site-dependent interactions in the cation withmore » strengths in the order MD 3 > CD 3 > CD 2, indicating dissimilarities in the electric field gradients along the alkyl chain, with the CD 2 sites having the largest gradient. Additionally, the α saturation effect in T 1 vs. P was observed for all three sites, suggesting significant reduction of the short-range rapid reorientational dynamics. This reduction was also deduced from the variable pressure 1H T 1 data, which showed an approach to saturation for both the methyl and butyl group terminal methyl sites. Pressure-dependent D measurements show independent motions for both cations and anions, with the cations having greater D values over the entire pressure range.« less

Modelling cavitation erosion using fluid–material interaction simulations

PubMed Central

Chahine, Georges L.; Hsiao, Chao-Tsung

2015-01-01

Material deformation and pitting from cavitation bubble collapse is investigated using fluid and material dynamics and their interaction. In the fluid, a novel hybrid approach, which links a boundary element method and a compressible finite difference method, is used to capture non-spherical bubble dynamics and resulting liquid pressures efficiently and accurately. The bubble dynamics is intimately coupled with a finite-element structure model to enable fluid/structure interaction simulations. Bubble collapse loads the material with high impulsive pressures, which result from shock waves and bubble re-entrant jet direct impact on the material surface. The shock wave loading can be from the re-entrant jet impact on the opposite side of the bubble, the fast primary collapse of the bubble, and/or the collapse of the remaining bubble ring. This produces high stress waves, which propagate inside the material, cause deformation, and eventually failure. A permanent deformation or pit is formed when the local equivalent stresses exceed the material yield stress. The pressure loading depends on bubble dynamics parameters such as the size of the bubble at its maximum volume, the bubble standoff distance from the material wall and the pressure driving the bubble collapse. The effects of standoff and material type on the pressure loading and resulting pit formation are highlighted and the effects of bubble interaction on pressure loading and material deformation are preliminarily discussed. PMID:26442140

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

NASA Technical Reports Server (NTRS)

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

2000-01-01

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

Intraocular pressure reduction and regulation system

NASA Technical Reports Server (NTRS)

Baehr, E. F.; Burnett, J. E.; Felder, S. F.; Mcgannon, W. J.

1979-01-01

An intraocular pressure reduction and regulation system is described and data are presented covering performance in: (1) reducing intraocular pressure to a preselected value, (2) maintaining a set minimum intraocular pressure, and (3) reducing the dynamic increases in intraocular pressure resulting from external loads applied to the eye.

Rapid, optical measurement of the atmospheric pressure on a fast research aircraft using open-path TDLAS

NASA Astrophysics Data System (ADS)

Buchholz, B.; Afchine, A.; Ebert, V.

2014-05-01

Because of the high travel speed, the complex flow dynamics around an aircraft and the complex dependency of the fluid dynamics on numerous airborne parameters, it is quite difficult to obtain accurate pressure values at a specific instrument location of an aircraft's fuselage. Complex simulations using computational fluid dynamics (CFD) models can in theory computationally "transfer" pressure values from one location to another. However, for long flight patterns, this process is inconvenient and cumbersome. Furthermore these CFD transfer models require a local experimental validation, which is rarely available. In this paper, we describe an integrated approach for a spectroscopic, calibration-free, in-flight pressure determination in an open-path White cell on an aircraft fuselage using ambient, atmospheric water vapour as the "sensor species". The presented measurements are realized with the HAI (Hygrometer for Atmospheric Investigations) instrument, built for multiphase water detection via calibration-free TDLAS (tunable diode laser absorption spectroscopy). The pressure determination is based on raw data used for H2O concentration measurement, but with a different post-flight evaluation method, and can therefore be conducted at deferred time intervals on any desired flight track. The spectroscopic pressure is compared in-flight with the static ambient pressure of the aircraft avionic system and a micro-mechanical pressure sensor, located next to the open-path cell, over a pressure range from 150 hPa to 800 hPa, and a water vapour concentration range of more than three orders of magnitude. The correlation between the micro-mechanical pressure sensor measurements and the spectroscopic pressure measurements show an average deviation from linearity of only 0.14% and a small offset of 9.5 hPa. For the spectroscopic pressure evaluation we derive measurement uncertainties under laboratory conditions of 3.2% and 5.1% during in flight operation on the HALO airplane. Under certain flight conditions we quantified for the first time stalling-induced, dynamic pressure deviations of up to 30% (at 200 hPa) between the avionic sensor and the optical and mechanical pressure sensors integrated in HAI. Such severe local pressure deviations from the usually used avionic pressure are important to take into account for other airborne sensors employed on such fast flying platforms as the HALO aircraft.

Rapid, optical measurement of the atmospheric pressure on a fast research aircraft using open-path TDLAS

NASA Astrophysics Data System (ADS)

Buchholz, B.; Afchine, A.; Ebert, V.

2014-11-01

Because of the high travel speed, the complex flow dynamics around an aircraft, and the complex dependency of the fluid dynamics on numerous airborne parameters, it is quite difficult to obtain accurate pressure values at a specific instrument location of an aircraft's fuselage. Complex simulations using computational fluid dynamics (CFD) models can in theory computationally "transfer" pressure values from one location to another. However, for long flight patterns, this process is inconvenient and cumbersome. Furthermore, these CFD transfer models require a local experimental validation, which is rarely available. In this paper, we describe an integrated approach for a spectroscopic, calibration-free, in-flight pressure determination in an open-path White cell on an aircraft fuselage using ambient, atmospheric water vapour as the "sensor species". The presented measurements are realised with the HAI (Hygrometer for Atmospheric Investigations) instrument, built for multiphase water detection via calibration-free TDLAS (tunable diode laser absorption spectroscopy). The pressure determination is based on raw data used for H2O concentration measurement, but with a different post-flight evaluation method, and can therefore be conducted at deferred time intervals on any desired flight track. The spectroscopic pressure is compared in-flight with the static ambient pressure of the aircraft avionic system and a micro-mechanical pressure sensor, located next to the open-path cell, over a pressure range from 150 to 800 hPa, and a water vapour concentration range of more than 3 orders of magnitude. The correlation between the micro-mechanical pressure sensor measurements and the spectroscopic pressure measurements shows an average deviation from linearity of only 0.14% and a small offset of 9.5 hPa. For the spectroscopic pressure evaluation we derive measurement uncertainties under laboratory conditions of 3.2 and 5.1% during in-flight operation on the HALO airplane. Under certain flight conditions we quantified, for the first time, stalling-induced, dynamic pressure deviations of up to 30% (at 200 hPa) between the avionic sensor and the optical and mechanical pressure sensors integrated in HAI. Such severe local pressure deviations from the typically used avionic pressure are important to take into account for other airborne sensors employed on such fast flying platforms as the HALO aircraft.

Simultaneous disappearances of plasmaspheric hiss, exohiss, and chorus waves triggered by a sudden decrease in solar wind dynamic pressure

DOE PAGES

Liu, Nigang; Su, Zhenpeng; Gao, Zhonglei; ...

2016-12-29

Magnetospheric whistler mode waves are of great importance in the radiation belt electron dynamics. In this paper, on the basis of the analysis of a rare event with the simultaneous disappearances of whistler mode plasmaspheric hiss, exohiss, and chorus triggered by a sudden decrease in the solar wind dynamic pressure, we provide evidences for the following physical scenarios: (1) nonlinear generation of chorus controlled by the geomagnetic field inhomogeneity, (2) origination of plasmaspheric hiss from chorus, and (3) leakage of plasmaspheric hiss into exohiss. Finally, following the reduction of the solar wind dynamic pressure, the dayside geomagnetic field configuration withmore » the enhanced inhomogeneity became unfavorable for the generation of chorus, and the quenching of chorus directly caused the disappearances of plasmaspheric hiss and then exohiss.« less

Simultaneous disappearances of plasmaspheric hiss, exohiss, and chorus waves triggered by a sudden decrease in solar wind dynamic pressure

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

Liu, Nigang; Su, Zhenpeng; Gao, Zhonglei

Magnetospheric whistler mode waves are of great importance in the radiation belt electron dynamics. In this paper, on the basis of the analysis of a rare event with the simultaneous disappearances of whistler mode plasmaspheric hiss, exohiss, and chorus triggered by a sudden decrease in the solar wind dynamic pressure, we provide evidences for the following physical scenarios: (1) nonlinear generation of chorus controlled by the geomagnetic field inhomogeneity, (2) origination of plasmaspheric hiss from chorus, and (3) leakage of plasmaspheric hiss into exohiss. Finally, following the reduction of the solar wind dynamic pressure, the dayside geomagnetic field configuration withmore » the enhanced inhomogeneity became unfavorable for the generation of chorus, and the quenching of chorus directly caused the disappearances of plasmaspheric hiss and then exohiss.« less

Nonlinear vocal fold dynamics resulting from asymmetric fluid loading on a two-mass model of speech

NASA Astrophysics Data System (ADS)

Erath, Byron D.; Zañartu, Matías; Peterson, Sean D.; Plesniak, Michael W.

2011-09-01

Nonlinear vocal fold dynamics arising from asymmetric flow formations within the glottis are investigated using a two-mass model of speech with asymmetric vocal fold tensioning, representative of unilateral vocal fold paralysis. A refined theoretical boundary-layer flow solver is implemented to compute the intraglottal pressures, providing a more realistic description of the flow than the standard one-dimensional, inviscid Bernoulli flow solution. Vocal fold dynamics are investigated for subglottal pressures of 0.6 < ps < 1.5 kPa and tension asymmetries of 0.5 < Q < 0.8. As tension asymmetries become pronounced the asymmetric flow incites nonlinear behavior in the vocal fold dynamics at subglottal pressures that are associated with normal speech, behavior that is not captured with standard Bernoulli flow solvers. Regions of bifurcation, coexistence of solutions, and chaos are identified.

The Convergence of the Twain or Titanic Collision? BI and Reference in the 1990s' Sea of Change.

ERIC Educational Resources Information Center

Rettig, James

1995-01-01

The future role, scope, and nature of bibliographic instruction (BI) and reference services at academic libraries is unresolved. Both have felt internal pressures and challenges during the past decade. It is suggested that BI and reference share tasks and become a single service. (92 references) (Author/DGM)

Pulmonary artery wave propagation and reservoir function in conscious man: impact of pulmonary vascular disease, respiration and dynamic stress tests.

PubMed

Su, Junjing; Manisty, Charlotte; Simonsen, Ulf; Howard, Luke S; Parker, Kim H; Hughes, Alun D

2017-10-15

Wave travel plays an important role in cardiovascular physiology. However, many aspects of pulmonary arterial wave behaviour remain unclear. Wave intensity and reservoir-excess pressure analyses were applied in the pulmonary artery in subjects with and without pulmonary hypertension during spontaneous respiration and dynamic stress tests. Arterial wave energy decreased during expiration and Valsalva manoeuvre due to decreased ventricular preload. Wave energy also decreased during handgrip exercise due to increased heart rate. In pulmonary hypertension patients, the asymptotic pressure at which the microvascular flow ceases, the reservoir pressure related to arterial compliance and the excess pressure caused by waves increased. The reservoir and excess pressures decreased during Valsalva manoeuvre but remained unchanged during handgrip exercise. This study provides insights into the influence of pulmonary vascular disease, spontaneous respiration and dynamic stress tests on pulmonary artery wave propagation and reservoir function. Detailed haemodynamic analysis may provide novel insights into the pulmonary circulation. Therefore, wave intensity and reservoir-excess pressure analyses were applied in the pulmonary artery to characterize changes in wave propagation and reservoir function during spontaneous respiration and dynamic stress tests. Right heart catheterization was performed using a pressure and Doppler flow sensor tipped guidewire to obtain simultaneous pressure and flow velocity measurements in the pulmonary artery in control subjects and patients with pulmonary arterial hypertension (PAH) at rest. In controls, recordings were also obtained during Valsalva manoeuvre and handgrip exercise. The asymptotic pressure at which the flow through the microcirculation ceases, the reservoir pressure related to arterial compliance and the excess pressure caused by arterial waves increased in PAH patients compared to controls. The systolic and diastolic rate constants also increased, while the diastolic time constant decreased. The forward compression wave energy decreased by ∼8% in controls and ∼6% in PAH patients during expiration compared to inspiration, while the wave speed remained unchanged throughout the respiratory cycle. Wave energy decreased during Valsalva manoeuvre (by ∼45%) and handgrip exercise (by ∼27%) with unaffected wave speed. Moreover, the reservoir and excess pressures decreased during Valsalva manoeuvre but remained unaltered during handgrip exercise. In conclusion, reservoir-excess pressure analysis applied to the pulmonary artery revealed distinctive differences between controls and PAH patients. Variations in the ventricular preload and afterload influence pulmonary arterial wave propagation as demonstrated by changes in wave energy during spontaneous respiration and dynamic stress tests. © 2017 The Authors. The Journal of Physiology © 2017 The Physiological Society.

Developing Dynamic Reference Models and a Decision Support Framework for Southeastern Ecosystems: An Integrated Approach

DTIC Science & Technology

2015-06-01

the contents be construed as reflecting the official policy or position of the Department of Defense. Reference herein to any specific commercial ...the number of territories occupied by either a solitary male or a breeding pair at Eglin AFB from 2000 to 2013 ............................. 55...in the context of a dynamic target. The reference sites in this study became more species rich, achieved greater abundance of understory plants , and

Cardiovascular and Metabolic Health of 74 Children From Women Previously Diagnosed With Polycystic Ovary Syndrome in Comparison With a Population-Based Reference Cohort.

PubMed

de Wilde, Marlieke A; Eising, Jacobien B; Gunning, Marlise N; Koster, Maria P H; Evelein, Annemieke M V; Dalmeijer, Geertje W; Uiterwaal, Cuno S P M; Eijkemans, Marinus J C; van der Ent, Cornelis K; Meijboom, Folkert J; Fauser, Bart C J M

2018-01-01

Women with polycystic ovary syndrome (PCOS) have compromised cardiovascular health profiles and an increased risk of pregnancy complications. In order to evaluate potential consequences, we aim to compare the cardiovascular and metabolic health of the children from women with PCOS with a population-based reference cohort. We included children from women with PCOS between the age of 2.5 to 4 years (n = 42) and 6 to 8 years (n = 32). The reference groups consisted of 168 (3-4 years old) and 130 children (7-8 years old). In an extensive cardiovascular screening program, we measured anthropometrics and blood pressure (all children), heart function and vascular rigidity (young children), metabolic laboratory assessment and carotid intima thickness (old age-group). Results showed that young PCOS offspring have a significantly lower diastolic blood pressure (β = 2.3 [95% confidence interval, CI: 0.5-4.0]) and higher aortic pulse pressure (β = -1.4 [95% CI: -2.5 to -0.2]), compared to the reference population. Furthermore, a higher left ventricle internal diameter but a lower tissue Doppler imaging of the right wall in systole compared to the reference group was found. Older offspring of women with PCOS presented with a significantly lower breast and abdominal circumference, but higher triglycerides (β = -0.1 [95% CI: -0.2 to -0.1]), LDL-cholesterol (β = -0.4 [95% CI: -0.6 to -0.1]), and higher carotid intima-media thickness (β = -31.7 [95% CI: -46.6 to -16.9]) compared to the reference group. In conclusion, we observe subtle but distinct cardiovascular and metabolic abnormalities already at an early age in PCOS offspring compared to a population-based reference group, despite a lower diastolic blood pressure, breast, and abdominal circumference. These preliminary findings require confirmation in independent data sets.

Transient response of a liquid injector to a steep-fronted transverse pressure wave

NASA Astrophysics Data System (ADS)

Lim, D.; Heister, S.; Stechmann, D.; Kan, B.

2017-12-01

Motivated by the dynamic injection environment posed by unsteady pressure gain combustion processes, an experimental apparatus was developed to visualize the dynamic response of a transparent liquid injector subjected to a single steep-fronted transverse pressure wave. Experiments were conducted at atmospheric pressure with a variety of acrylic injector passage designs using water as the working fluid. High-speed visual observations were made of the injector exit near field, and the extent of backflow and the time to refill the orifice passage were characterized over a range of injection pressures. A companion transient one-dimensional model was developed for interpretation of the results and to elucidate the trends with regard to the strength of the transverse pressure wave. Results from the model were compared with the experimental observations.

Investigations of High Pressure Acoustic Waves in Resonators with Seal-like Features

NASA Technical Reports Server (NTRS)

Daniels, Christopher; Steinetz, Bruce; Finkbeiner, Joshua

2003-01-01

A conical resonator (having a dissonant acoustic design) was tested in four configurations: (1) baseline resonator with closed ends and no blockage, (2) closed resonator with internal blockage, (3) ventilated resonator with no blockage, and (4) ventilated resonator with an applied pressure differential. These tests were conducted to investigate the effects of blockage and ventilation holes on dynamic pressurization. Additionally, the investigation was to determine the ability of acoustic pressurization to impede flow through the resonator. In each of the configurations studied, the entire resonator was oscillated at the gas resonant frequency while dynamic pressure, static pressure, and temperature of the fluid were measured. In the final configuration, flow through the resonator was recorded for three oscillation conditions. Ambient condition air was used as the working fluid.

Transient response of a liquid injector to a steep-fronted transverse pressure wave

NASA Astrophysics Data System (ADS)

Lim, D.; Heister, S.; Stechmann, D.; Kan, B.

2018-07-01

Motivated by the dynamic injection environment posed by unsteady pressure gain combustion processes, an experimental apparatus was developed to visualize the dynamic response of a transparent liquid injector subjected to a single steep-fronted transverse pressure wave. Experiments were conducted at atmospheric pressure with a variety of acrylic injector passage designs using water as the working fluid. High-speed visual observations were made of the injector exit near field, and the extent of backflow and the time to refill the orifice passage were characterized over a range of injection pressures. A companion transient one-dimensional model was developed for interpretation of the results and to elucidate the trends with regard to the strength of the transverse pressure wave. Results from the model were compared with the experimental observations.

Application of active control landing gear technology to the A-10 aircraft

NASA Technical Reports Server (NTRS)

Ross, I.; Edson, R.

1983-01-01

Two concepts which reduce the A-10 aircraft's wing/gear interface forces as a result of applying active control technology to the main landing gear are described. In the first concept, referred to as the alternate concept a servovalve in a closed pressure control loop configuration effectively varies the size of the third stage spool valve orifice which is embedded in the strut. This action allows the internal energy in the strut to shunt hydraulic flow around the metering orifice. The command signal to the loop is reference strut pressure which is compared to the measured strut pressure, the difference being the loop error. Thus, the loop effectively varies the spool valve orifice size to maintain the strut pressure, and therefore minimizes the wing/gear interface force referenced.

Experimental Results of the 2.7% Reference H Nacelle Airframe Interference High Speed Civil Transport Model

NASA Technical Reports Server (NTRS)

Cappuccio, Gelsomina

1999-01-01

Experiments were conducted in the NASA Ames 9-Ft by 7-Ft Supersonic and 11-Ft by 11-Ft Transonic Wind Tunnels of a 2.7% Reference H (Ref. H) Nacelle Airframe Interference (NAI) High Speed Civil Transport (HSCT) model. NASA Ames did the experiment with the cooperation and assistance of Boeing and McDonnell Douglas. The Ref. H geometry was designed by Boeing. The model was built and tested by NASA under a license agreement with Boeing. Detailed forces and pressures of individual components of the configuration were obtained to assess nacelle airframe interference through the transonic and supersonic flight regime. The test apparatus was capable of measuring forces and pressures of the Wing body (WB) and nacelles. Axisymmetric and 2-D inlet nacelles were tested with the WB in both the in-proximity and captive mode. The in-proximity nacelles were mounted to a nacelle support system apparatus and were individually positioned. The right hand nacelles were force instrumented with flow through strain-gauged balances and the left hand nacelles were pressure instrumented. Mass flow ratio was varied to get steady state inlet unstart data. In addition, supersonic spillage data was taken by testing the 2-D inlet nacelles with ramps and the axisymmetric inlet nacelles with an inlet centerbody for the Mach condition of interest. The captive nacelles, both axisymmetric and 2-D, were attached to the WB via diverters. The captive 2-D inlet nacelle was also tested with ramps to get supersonic spillage data. Boeing analyzed the data and showed a drag penalty of four drag counts for the 2-D compared with the axisymmetric inlet nacelle. Two of the four counts were attributable to the external bevel designed into the 2-D inlet contour. Boeing and McDonnell Douglas used these data for evaluating Computational Fluid Dynamic (CFD) codes and for evaluation of nacelle airframe integration problems and solutions.

Experimental Verification of Buffet Calculation Procedure Using Unsteady PSP

NASA Technical Reports Server (NTRS)

Panda, Jayanta

2016-01-01

Typically a limited number of dynamic pressure sensors are employed to determine the unsteady aerodynamic forces on large, slender aerospace structures. The estimated forces are known to be very sensitive to the number of the dynamic pressure sensors and the details of the integration scheme. This report describes a robust calculation procedure, based on frequency-specific correlation lengths, that is found to produce good estimation of fluctuating forces from a few dynamic pressure sensors. The validation test was conducted on a flat panel, placed on the floor of a wind tunnel, and was subjected to vortex shedding from a rectangular bluff-body. The panel was coated with fast response Pressure Sensitive Paint (PSP), which allowed time-resolved measurements of unsteady pressure fluctuations on a dense grid of spatial points. The first part of the report describes the detail procedure used to analyze the high-speed, PSP camera images. The procedure includes steps to reduce contamination by electronic shot noise, correction for spatial non-uniformities, and lamp brightness variation, and finally conversion of fluctuating light intensity to fluctuating pressure. The latter involved applying calibration constants from a few dynamic pressure sensors placed at selective points on the plate. Excellent comparison in the spectra, coherence and phase, calculated via PSP and dynamic pressure sensors validated the PSP processing steps. The second part of the report describes the buffet validation process, for which the first step was to use pressure histories from all PSP points to determine the "true" force fluctuations. In the next step only a selected number of pixels were chosen as "virtual sensors" and a correlation-length based buffet calculation procedure was applied to determine "modeled" force fluctuations. By progressively decreasing the number of virtual sensors it was observed that the present calculation procedure was able to make a close estimate of the "true" unsteady forces only from four sensors. It is believed that the present work provides the first validation of the buffet calculation procedure which has been used for the development of many space vehicles.

Optimal right heart filling pressure in acute respiratory distress syndrome determined by strain echocardiography.

PubMed

Garcia-Montilla, Romel; Imam, Faryal; Miao, Mi; Stinson, Kathryn; Khan, Akram; Heitner, Stephen

2017-06-01

Right ventricular (RV) systolic dysfunction is common in acute respiratory distress syndrome (ARDS). While preload optimization is crucial in its management, dynamic fluid responsiveness indices lack reliability, and there is no consensus on target central venous pressure (CVP). We analyzed the utility of RV free wall longitudinal strain (RVFWS) in the estimation of optimal RV filling pressure in ARDS. A retrospective cross-sectional analysis of clinical data and echocardiograms of patients with ARDS was performed. Tricuspid annular plane systolic excursion (TAPSE), tricuspid peak systolic velocity (S'), RV fractional area change (RVFAC), RVFWS, CVP, systolic pulmonary artery pressure (SPAP), and left ventricular ejection fraction (LVEF) were measured. Fifty-one patients with moderate-severe ARDS were included. There were inverse correlations between CVP and TAPSE, S', RVFAC, RVFWS, and LVEF. The most significant was with RVFWS (r:.74, R 2 :.55, P:.00001). Direct correlations with creatinine and lactate were noted. Receiver operating characteristic analysis showed that RVFWS -21% (normal reference value) was associated with CVP: 13 mm Hg (AUC: 0.92, 95% CI: 0.83-1.00). Regression model analysis of CVP, and RVFWS interactions established an RVFWS range from -18% to -24%. RVFWS -24% corresponded to CVP: 11 mm Hg and RVFWS -18% to CVP: 15 mm Hg. Beyond a CVP of 15 mm Hg, biventricular systolic dysfunction rapidly ensues. Our data are the first to show that an RV filling pressure of 13±2 mm Hg-as by CVP-correlates with optimal RV mechanics as evaluated by strain echocardiography in patients with moderate-severe ARDS. © 2017, Wiley Periodicals, Inc.

Discussion of pore pressure transmission under rain infiltration in a soil layer

NASA Astrophysics Data System (ADS)

Yang, S. Y.; Jan, C. D.

2017-12-01

The vadose zone (or unsaturated zone) denotes the geologic media between ground surface and the water table in situ where the openings, or pores, in the soil (rock) layers are partially filled with water and air. In this landscape, rainwater infiltrates into soils advancing through this vadose zone and could generates a shallow saturation zone at soil bedrock boundary due to permeability contrast. This saturation zone leads to downslope shallow subsurface storm runoff that contributes to a part of saturation overland flow, dominating water reaching river channels. Hence, unsaturated processes (e.g., rain infiltration) is an important issue that can determine the timing and magnitude of positive pore pressure and discharge peaks, and the characteristics of runoff, water chemistry, hillslope stability is also tie to the processes. In this study, we investigated the transmission of pore pressure evolution in the vadose zone for diverse soil materials based on poroelasticity theory. Commonly, a traditional way is to utilize the Richard's equation to predict pore pressure evolution under unsaturated rain infiltration, ignoring the inertial effect on the process. Here we relax this limitation and propose two reference time tk and tep that can represent the arriving time at a certain depth of wave propagation and dissipation, respectively. Form ground surface to a depth of 1 m, tk has significant differences under nearly unsaturated conditions for diverse soil properties; however, no evident variations in tk can be observed under nearly saturated conditions. Values of tep for loose, cohesionless soils are much greater but decreases to the smallest one (within 1 day) than those for other soil properties under a nearly saturated condition. Results indicate that transient pore pressure transmission is mainly dominated by dynamic wave propagation but the effect of dissipation could become more important with increase in water saturation.

Aerodynamic Design of Axial-flow Compressors. Volume 2

NASA Technical Reports Server (NTRS)

1956-01-01

Available experimental two-dimensional-cascade data for conventional compressor blade sections are correlated. The two-dimensional cascade and some of the principal aerodynamic factors involved in its operation are first briefly described. Then the data are analyzed by examining the variation of cascade performance at a reference incidence angle in the region of minimum loss. Variations of reference incidence angle, total-pressure loss, and deviation angle with cascade geometry, inlet Mach number, and Reynolds number are investigated. From the analysis and the correlations of the available data, rules and relations are evolved for the prediction of the magnitude of the reference total-pressure loss and the reference deviation and incidence angles for conventional blade profiles. These relations are developed in simplified forms readily applicable to compressor design procedures.

Models of Cerebral-Body Perfusion and Cerebral Chemical Transport.

DTIC Science & Technology

1988-03-01

Pressure Waves 22 Conchusion 23 References 36 A Compartmental Brain Model for Chemical Transport and CO2 Controlled Blood Flow Abstract 37 Introduction 38...surrounding the body, e.g., atmospheric pressure , pressure al high and low altitudes, high underwater pressure , vacuum and excessive gravity acceleration...Resistance of the AreriolarNenous capillary, accounting for the pressure drop observed between them. RCB Resistance of the Blood -Brain barrier (between

Laboratory Simulation and Measurement of Instrument Drift in Quartz-Resonant Pressure Gauges

NASA Astrophysics Data System (ADS)

Sasagawa, G. S.; Zumberge, M. A.

2017-12-01

Marine geodesy uses ocean bottom pressure sensors to measure vertical deformation of the sea floor, including that due to volcanic inflation and subsidence, episodic tremor and slip, plate subduction, and deformation due to hydrocarbon extraction at offshore reservoirs. Instrumental drift is inherent in existing pressure sensors and introduce uncertainties in data interpretation. Different methods have been developed to control drift, using varying techniques and instrumentation. Laboratory measurements of sensor drift, under controlled conditions that simulate seafloor pressures and temperatures, would allow for evaluating pressure gauge drift and the efficacy of new drift control methods. We have constructed and operated a laboratory system to monitor the drift of 15 quartz resonant pressure gauges over a year. The temperature and pressure are maintained and controlled at approximately 5 °C and 1900 dbar. A deadweight tester was used to provide a reference signal at frequent intervals; the time series of reference pressure signals is a direct measure of each gauge's drift. Several other tests were conducted, including a) evaluation of a custom outgassing sensor used as proxy for instrument drift, b) determination of the oscillator drift in the pressure gauge signal conditioning electronics, and c) a test of ambient air pressure calibration, also known as the A-0-A method. First results will be presented.

Self-Organized Information Processing in Neuronal Networks: Replacing Layers in Deep Networks by Dynamics

NASA Astrophysics Data System (ADS)

Kirst, Christoph

It is astonishing how the sub-parts of a brain co-act to produce coherent behavior. What are mechanism that coordinate information processing and communication and how can those be changed flexibly in order to cope with variable contexts? Here we show that when information is encoded in the deviations around a collective dynamical reference state of a recurrent network the propagation of these fluctuations is strongly dependent on precisely this underlying reference. Information here 'surfs' on top of the collective dynamics and switching between states enables fast and flexible rerouting of information. This in turn affects local processing and consequently changes in the global reference dynamics that re-regulate the distribution of information. This provides a generic mechanism for self-organized information processing as we demonstrate with an oscillatory Hopfield network that performs contextual pattern recognition. Deep neural networks have proven to be very successful recently. Here we show that generating information channels via collective reference dynamics can effectively compress a deep multi-layer architecture into a single layer making this mechanism a promising candidate for the organization of information processing in biological neuronal networks.

A Study of the Development of Steady and Periodic Unsteady Turbulent Wakes Through Curved Channels at Positive, Zero, and Negative Streamwise Pressure Gradients, Part 1

NASA Technical Reports Server (NTRS)

Schobeiri, M. T.; John, J.

1996-01-01

The turbomachinery wake flow development is largely influenced by streamline curvature and streamwise pressure gradient. The objective of this investigation is to study the development of the wake under the influence of streamline curvature and streamwise pressure gradient. The experimental investigation is carried out in two phases. The first phase involves the study of the wake behind a stationary circular cylinder (steady wake) in curved channels at positive, zero, and negative streamwise pressure gradients. The mean velocity and Reynolds stress components are measured using a X-hot-film probe. The measured quantities obtained in probe coordinates are transformed to a curvilinear coordinate system along the wake centerline and are presented in similarity coordinates. The results of the steady wakes suggest strong asymmetry in velocity and Reynolds stress components. However, the velocity defect profiles in similarity coordinates are almost symmetrical and follow the same distribution as the zero pressure gradient straight wake. The results of Reynolds stress distributions show higher values on the inner side of the wake than the outer side. Other quantities, including the decay of maximum velocity defect, growth of wake width, and wake integral parameters, are also presented for the three different pressure gradient cases of steady wake. The decay rate of velocity defect is fastest for the negative streamwise pressure gradient case and slowest for the positive pressure gradient case. Conversely, the growth of the wake width is fastest for the positive streamwise pressure gradient case and slowest for the negative streamwise pressure gradient. The second phase studies the development of periodic unsteady wakes generated by the circular cylinders of the rotating wake generator in a curved channel at zero streamwise pressure gradient. Instantaneous velocity components of the periodic unsteady wakes, measured with a stationary X-hot-film probe, are analyzed by the phase averaging techniques. The temporal distribution of velocity and Reynolds stress components obtained in a stationary frame of reference are transformed to a spatial distribution in a relative frame of reference. Profiles of phase-averaged velocity and Reynolds stress distributions in the relative frame of reference and similarity coordinates are presented. The velocity defect and Reynolds stress distributions agree with the results of the wake development behind a stationary cylinder in the curved channel at zero streamwise pressure gradient. The phase-averaged third-order correlations, presented in the relative frame of reference and similarity coordinates, show pronounced asymmetric features.

High-pressure microscopy for tracking dynamic properties of molecular machines.

PubMed

Nishiyama, Masayoshi

2017-12-01

High-pressure microscopy is one of the powerful techniques to visualize the effects of hydrostatic pressures on research targets. It could be used for monitoring the pressure-induced changes in the structure and function of molecular machines in vitro and in vivo. This review focuses on the dynamic properties of the assemblies and machines, analyzed by means of high-pressure microscopy measurement. We developed a high-pressure microscope that is optimized both for the best image formation and for the stability to hydrostatic pressure up to 150 MPa. Application of pressure could change polymerization and depolymerization processes of the microtubule cytoskeleton, suggesting a modulation of the intermolecular interaction between tubulin molecules. A novel motility assay demonstrated that high hydrostatic pressure induces counterclockwise (CCW) to clockwise (CW) reversals of the Escherichia coli flagellar motor. The present techniques could be extended to study how molecular machines in complicated systems respond to mechanical stimuli. Copyright © 2017 Elsevier B.V. All rights reserved.

[Pressure control in medical gas distribution systems].

PubMed

Bourgain, J L; Benayoun, L; Baguenard, P; Haré, G; Puizillout, J M; Billard, V

1997-01-01

To assess whether the pressure gauges at the downstream part of pressure regulators are accurate enough to ensure that pressure in O2 pipeline is always higher than in Air pipeline and that pressure in the latter is higher than pressure in N2O pipeline. A pressure difference of at least 0.4 bar between two medical gas supply systems is recommended to avoid the reflow of either N2O or Air into the O2 pipeline, through a faulty mixer or proportioning device. Prospective technical comparative study. Readings of 32 Bourdon gauges were compared with data obtained with a calibrated reference transducer. Two sets of measurements were performed at a one month interval. Pressure differences between Bourdon gauges and reference transducer were 8% (0.28 bar) in average for a theoretical maximal error less than 2.5%. During the first set of measurements, Air pressure was higher than O2 pressure in one place and N2O pressure higher than Air pressure in another. After an increase in the O2 pipeline pressure and careful setting of pressure regulators, this problem was not observed at the second set of measurements. Actual accuracy of Bourdon gauges was not convenient enough to ensure that O2 pressure was always above Air pressure. Regular controls of these pressure gauges are therefore essential. Replacement of the faulty Bourdon gauges by more accurate transducers should be considered. As an alternative, the increase in pressure difference between O2 and Air pipelines to at least 0.6 bar is recommended.

Non-Ideal Compressible-Fluid Dynamics of Fast-Response Pressure Probes for Unsteady Flow Measurements in Turbomachinery

NASA Astrophysics Data System (ADS)

Gori, G.; Molesini, P.; Persico, G.; Guardone, A.

2017-03-01

The dynamic response of pressure probes for unsteady flow measurements in turbomachinery is investigated numerically for fluids operating in non-ideal thermodynamic conditions, which are relevant for e.g. Organic Rankine Cycles (ORC) and super-critical CO2 applications. The step response of a fast-response pressure probe is investigated numerically in order to assess the expected time response when operating in the non-ideal fluid regime. Numerical simulations are carried out exploiting the Non-Ideal Compressible Fluid-Dynamics (NICFD) solver embedded in the open-source fluid dynamics code SU2. The computational framework is assessed against available experimental data for air in dilute conditions. Then, polytropic ideal gas (PIG), i.e. constant specific heats, and Peng-Robinson Stryjek-Vera (PRSV) models are applied to simulate the flow field within the probe operating with siloxane fluid octamethyltrisiloxane (MDM). The step responses are found to depend mainly on the speed of sound of the working fluid, indicating that molecular complexity plays a major role in determining the promptness of the measurement devices. According to the PRSV model, non-ideal effects can increase the step response time with respect to the acoustic theory predictions. The fundamental derivative of gas-dynamic is confirmed to be the driving parameter for evaluating non-ideal thermodynamic effects related to the dynamic calibration of fast-response aerodynamic pressure probes.

Compensated vibrating optical fiber pressure measuring device

DOEpatents

Fasching, George E.; Goff, David R.

1987-01-01

A microbending optical fiber is attached under tension to a diaphragm to se a differential pressure applied across the diaphragm which it causes it to deflect. The fiber is attached to the diaphragm so that one portion of the fiber, attached to a central portion of the diaphragm, undergoes a change in tension; proportional to the differential pressure applied to the diaphragm while a second portion attached at the periphery of the diaphragm remains at a reference tension. Both portions of the fiber are caused to vibrate at their natural frequencies. Light transmitted through the fiber is attenuated by both portions of the tensioned sections of the fiber by an amount which increases with the curvature of fiber bending so that the light signal is modulated by both portions of the fiber at separate frequencies. The modulated light signal is transduced into a electrical signal. The separate modulation signals are detected to generate separate signals having frequencies corresponding to the reference and measuring vibrating sections of the continuous fiber, respectively. A signal proportional to the difference between these signals is generated which is indicative of the measured pressure differential across the diaphragm. The reference portion of the fiber is used to compensate the pressure signal for zero and span changes resulting from ambient temperature and humidity effects upon the fiber and the transducer fixture.

Coupled dynamics of translation and collapse of acoustically driven microbubbles.

PubMed

Reddy, Anil J; Szeri, Andrew J

2002-10-01

Pressure gradients drive the motion of microbubbles relative to liquids in which they are suspended. Examples include the hydrostatic pressure due to a gravitational field, and the pressure gradients in a sound field, useful for acoustic levitation. In this paper, the equations describing the coupled dynamics of radial oscillation and translation of a microbubble are given. The formulation is based on a recently derived expression for the hydrodynamic force on a bubble of changing size in an incompressible liquid [J. Magnaudet and D. Legendre, Phys. Fluids 10, 550-556 (1998)]. The complex interaction between radial and translation dynamics is best understood by examination of the added momentum associated with the liquid motion caused by the moving bubble. Translation is maximized when the bubble collapses violently. The new theory for coupled collapse and translation dynamics is compared to past experiments and to previous theories for decoupled translation dynamics. Special attention is paid to bubbles of relevance in biomedical applications.

Starvation effects on the hydrodynamic lubrication of rigid nonconformal contacts in combined rolling and normal motion

NASA Technical Reports Server (NTRS)

Ghosh, M. K.; Hamrock, B. J.; Brewe, D. E.

1986-01-01

The effect of inlet starvation on the hydrodynamic lubrication of lightly loaded rigid nonconformal contacts in combined rolling and normal motion is determined through a numerical solution of the Reynolds' equation for an isoviscous, incompressible lubricant. Starvation is effected by systematically reducing the fluid inlet level. The pressures are taken to be ambient at the inlet meniscus boundary and Reynolds' boundary condition is applied for film rupture in the exit region. Results are presented for the dynamic performance of the starved contacts in combined rolling and normal motion for both normal approach and separation. During normal approach the dynamic load ratio (i.e. ratio of dynamic to steady state load capacity) increases considerably with increase in the inlet starvation. The effect of starvation on the dynamic peak pressure ratio is relatively small. Further, it has been observed that with increasing starvation, film thickness effects become significant in the dynamic behavior of the nonconformal contacts. For significantly starved contacts the dynamic load ratio increases with increase in film thickness during normal approach and a similar reduction is observed during separation. A similar effect is noted for the dynamic peak pressure ratio.

Prediction of the Reference Evapotranspiration Using a Chaotic Approach

PubMed Central

Wang, Wei-guang; Zou, Shan; Luo, Zhao-hui; Zhang, Wei; Kong, Jun

2014-01-01

Evapotranspiration is one of the most important hydrological variables in the context of water resources management. An attempt was made to understand and predict the dynamics of reference evapotranspiration from a nonlinear dynamical perspective in this study. The reference evapotranspiration data was calculated using the FAO Penman-Monteith equation with the observed daily meteorological data for the period 1966–2005 at four meteorological stations (i.e., Baotou, Zhangbei, Kaifeng, and Shaoguan) representing a wide range of climatic conditions of China. The correlation dimension method was employed to investigate the chaotic behavior of the reference evapotranspiration series. The existence of chaos in the reference evapotranspiration series at the four different locations was proved by the finite and low correlation dimension. A local approximation approach was employed to forecast the daily reference evapotranspiration series. Low root mean square error (RSME) and mean absolute error (MAE) (for all locations lower than 0.31 and 0.24, resp.), high correlation coefficient (CC), and modified coefficient of efficiency (for all locations larger than 0.97 and 0.8, resp.) indicate that the predicted reference evapotranspiration agrees well with the observed one. The encouraging results indicate the suitableness of chaotic approach for understanding and predicting the dynamics of the reference evapotranspiration. PMID:25133221

Advanced High Pressure O2/H2 Technology

NASA Technical Reports Server (NTRS)

Morea, S. F. (Editor); Wu, S. T. (Editor)

1985-01-01

Activities in the development of advanced high pressure oxygen-hydrogen stage combustion rocket engines are reported. Particular emphasis is given to the Space Shuttle main engine. The areas of engine technology discussed include fracture and fatigue in engine components, manufacturing and producibility engineering, materials, bearing technology, structure dynamics, fluid dynamics, and instrumentation technology.

Mass loading in the solar wind interaction with Venus and Mars

NASA Astrophysics Data System (ADS)

Breus, T. K.; Bauer, S. J.; Krymskii, A. M.; Mitnitskii, V. Ya.

1989-03-01

An analysis of available experimental data and theoretical concepts indicates that the interaction of the solar wind (SW) on the subsolar side with Venus, which has no intrinsic magnetic field, and with Mars, which has a small intrinsic magnetic field, is determined by the solar wind dynamic pressure with a contribution from the neutral planetary atmosphere to this interaction. The pattern of the SW interaction with these planets is different in principle for high and low dynamic pressures of the SW and is related to the varying intensity of ion formation processes (the SW Mass loading effect) in the vicinity of the SW obstacle boundary, which moves for different SW dynamic pressures into regions of different neutral atmosphere density. For moderate or high SW dynamic pressures, the subsolar Martian magnetosphere is also affected by this process. Results of numerical simulations of the SW-Mars interaction for a magnetospheric obstacle boundary at an altitude of 300 km are presented. To estimate the relative role of photoionization and charge exchange processes and their effect on the shock front position, different versions of the mass loading effect were separately calculated.

Non-equilibrium dynamics in disordered materials: Ab initio molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Ohmura, Satoshi; Nagaya, Kiyonobu; Shimojo, Fuyuki; Yao, Makoto

2015-08-01

The dynamic properties of liquid B2O3 under pressure and highly-charged bromophenol molecule are studied by using molecular dynamics (MD) simulations based on density functional theory (DFT). Diffusion properties of covalent liquids under high pressure are very interesting in the sense that they show unexpected pressure dependence. It is found from our simulation that the magnitude relation of diffusion coefficients for boron and oxygen in liquid B2O3 shows the anomalous pressure dependence. The simulation clarified the microscopic origin of the anomalous diffusion properties. Our simulation also reveals the dissociation mechanism in the coulomb explosion of the highly-charged bromophenol molecule. When the charge state n is 6, hydrogen atom in the hydroxyl group dissociates at times shorter than 20 fs while all hydrogen atoms dissociate when n is 8. After the hydrogen dissociation, the carbon ring breaks at about 100 fs. There is also a difference on the mechanism of the ring breaking depending on charge states, in which the ring breaks with expanding (n = 6) or shrink (n = 8).

[Effects of acupuncture on circadian rhythm of blood pressure in patients with essential hypertension].

PubMed

Lei, Yun; Jin, Jiu; Ban, Haipeng; Du, Yuzheng

2017-11-12

To observe the effects of acupuncture combined with medication on circadian rhythm of blood pressure in patients with essential hypertension. Sixty-four patients of essential hypertension were randomly divided into an observation group and a control group, 32 cases in each group. All the patients maintained original treatment (taking antihypertensive medication); the patients in the observation group were treated with acupuncture method of " Huoxue Sanfeng , Shugan Jianpi ", once a day, five times per week, for totally 6 weeks (30 times). The circadian rhythm of blood pressure and related dynamic parameters were observed before and after treatment in the two groups. (1) The differences of daytime average systolic blood pressure (dASBP), daytime average diastolic blood pressure (dADBP), nighttime average systolic blood pressure (nASBP) and circadian rhythm of systolic blood pressure before and after treatment were significant in the observation group (all P <0.05); the differences of circadian rhythm of blood pressure and related dynamic parameters before and after treatment were insignificant in the control group (all P >0.05). The nASBP and circadian rhythm of systolic blood pressure in the observation group were significantly different from those in the control group (all P <0.05). (2) After the treatment, the spoon-shaped rate of circadian rhythm of blood pressure in the observation group was higher than that in the control group ( P <0.05). The acupuncture combined with medication could effectively improve the circadian rhythm of blood pressure and related dynamic parameters in patients with essential hypertension.

Transonic steady- and unsteady-pressure measurements on a high-aspect-ratio supercritical-wing model with oscillating control surfaces

NASA Technical Reports Server (NTRS)

Sandford, M. C.; Ricketts, R. H.; Cazier, F. W., Jr.

1980-01-01

A supercritical wing with an aspect ratio of 10.76 and with two trailing-edge oscillating control surfaces is described. The semispan wing is instrumented with 252 static orifices and 164 in situ dynamic-pressure gages for studying the effects of control-surface position and motion on steady- and unsteady-pressures at transonic speeds. Results from initial tests conducted in the Langley Transonic Dynamics Tunnel at two Reynolds numbers are presented in tabular form.

Experimental Analysis of the Vorticity and Turbulent Flow Dynamics of a Pitching Airfoil at Realistic Flight Conditions

DTIC Science & Technology

2007-08-31

Element type Hex, independent meshing, Linear 3D stress Hex, independent meshing, Linear 3D stress 1 English Units were used in ABAQUS The NACA...Flow Freestream Condition Instrumentation Test section conditions were measured using a Druck DPI 203 digital pressure gage and an Omega Model 199...temperature gage. The Druck pressure gage measures the set dynamic pressure within 0.08%± of full scale, and the Omega thermometer is accurate to

Observations on Bubble Dynamics at High Pressures and Bubble Dynamics in Stagnation Flow.

DTIC Science & Technology

1982-11-30

reverse side It nocooeuAn aifdentifly by block mt..bet) S 1 Cavitation, High Speed Photography, Ruby Laser . 20. AFSTAACT Co.nflno on revere side Of...AT NIGH ASIE3r.T PRESSUrES A.T. Ellis and J.E. Starrect University of California, San Diego Recent developsent by the authors of a unique ruby laser ...1,000,300 frames per second with exposure clue of approximately 2vl0- seconds. The coherent nature of the laser illuminacion revealed shock waves

A review of factors that influence adult handwriting performance.

PubMed

van Drempt, Nadege; McCluskey, Annie; Lannin, Natasha A

2011-10-01

Handwriting is an important activity for people of all ages. Handwriting is frequently affected after stroke and other neurological conditions. However, research on the handwriting of healthy adults is difficult to find. This review aims to advance the development of evidence-informed handwriting assessment and retraining. The aim of this paper was to review factors that influence the handwriting performance of unimpaired adults, some of which are amenable to intervention. Searches were conducted of eight electronic databases up to April 2009 and again in November 2010. Reference lists were also used to identify potential studies of interest. No limits were placed on study design.  Age: Younger adults write more legibly and faster than older adults. Gender: Women write faster and more legibly than men. Pengrip: Grips other than the traditional dynamic tripod are functional, producing legible text in an acceptable time. Pen pressure: Pressure varies with different letters, words, text size, speed and across a page of text. Error corrections and a mixed writing style occur in healthy adult handwriting. Research was inconclusive about the association between speed, pressure and upper limb movements on handwriting performance. Other factors able to predict adult handwriting legibility have been largely unexplored. A number of knowledge and research gaps about adult handwriting were identified, including the need for more contemporary normative data. © 2011 The Authors. Australian Occupational Therapy Journal © 2011 Occupational Therapy Australia.

Simulation on a car interior aerodynamic noise control based on statistical energy analysis

NASA Astrophysics Data System (ADS)

Chen, Xin; Wang, Dengfeng; Ma, Zhengdong

2012-09-01

How to simulate interior aerodynamic noise accurately is an important question of a car interior noise reduction. The unsteady aerodynamic pressure on body surfaces is proved to be the key effect factor of car interior aerodynamic noise control in high frequency on high speed. In this paper, a detail statistical energy analysis (SEA) model is built. And the vibra-acoustic power inputs are loaded on the model for the valid result of car interior noise analysis. The model is the solid foundation for further optimization on car interior noise control. After the most sensitive subsystems for the power contribution to car interior noise are pointed by SEA comprehensive analysis, the sound pressure level of car interior aerodynamic noise can be reduced by improving their sound and damping characteristics. The further vehicle testing results show that it is available to improve the interior acoustic performance by using detailed SEA model, which comprised by more than 80 subsystems, with the unsteady aerodynamic pressure calculation on body surfaces and the materials improvement of sound/damping properties. It is able to acquire more than 2 dB reduction on the central frequency in the spectrum over 800 Hz. The proposed optimization method can be looked as a reference of car interior aerodynamic noise control by the detail SEA model integrated unsteady computational fluid dynamics (CFD) and sensitivity analysis of acoustic contribution.

Effective Use of Weld Metal Yield Strength for HY-Steels

DTIC Science & Technology

1983-01-01

Boiler and Pressure Vessel Code The ASME Boiler and Pressure Vessel Code (B&PV Code) is divided...As noted earlier, the ASME Boiler and Pressure Vessel Code makes only one exception to its overall philosophy of matching weld-metal strength and...material where toughness is of primary importance. REFERENCES American Society of Mechanical Engineers, Boiler and Pressure Vessel

The Influence of Shaping Air Pressure of Pneumatic Spray Gun

NASA Astrophysics Data System (ADS)

Chen, Wenzhuo; Chen, Yan; Pan, Haiwei; Zhang, Weiming; Li, Bo

2018-02-01

The shaping air pressure is a very important parameter in the application of pneumatic spray gun, and studying its influence on spray flow field and film thickness distribution has practical values. In this paper, Euler-Lagrangian method is adopted to describe the two-phase spray flow of pneumatic painting process, and the air flow fields, spray patterns and dynamic film thickness distributions were obtained with the help of the computational fluid dynamics code—ANSYS Fluent. Results show that with the increase of the shaping air pressure, the air phase flow field spreads in the plane perpendicular to the shaping air hole plane, the spray pattern becomes narrower and flatter, and the width of the dynamic film increases with the reduced maximum value of the film thickness. But the film thickness distribution seems to change little with the shaping air pressure decreasing from 0.6bar to 0.9bar.

Earthquake dynamics. Mapping pressurized volcanic fluids from induced crustal seismic velocity drops.

PubMed

Brenguier, F; Campillo, M; Takeda, T; Aoki, Y; Shapiro, N M; Briand, X; Emoto, K; Miyake, H

2014-07-04

Volcanic eruptions are caused by the release of pressure that has accumulated due to hot volcanic fluids at depth. Here, we show that the extent of the regions affected by pressurized fluids can be imaged through the measurement of their response to transient stress perturbations. We used records of seismic noise from the Japanese Hi-net seismic network to measure the crustal seismic velocity changes below volcanic regions caused by the 2011 moment magnitude (M(w)) 9.0 Tohoku-Oki earthquake. We interpret coseismic crustal seismic velocity reductions as related to the mechanical weakening of the pressurized crust by the dynamic stress associated with the seismic waves. We suggest, therefore, that mapping seismic velocity susceptibility to dynamic stress perturbations can be used for the imaging and characterization of volcanic systems. Copyright © 2014, American Association for the Advancement of Science.

Cavitation propagation in water under tension

NASA Astrophysics Data System (ADS)

Noblin, Xavier; Yip Cheung Sang, Yann; Pellegrin, Mathieu; Materials and Complex Fluids Team

2012-11-01

Cavitation appears when pressure decreases below vapor pressure, generating vapor bubbles. It can be obtain in dynamical ways (acoustic, hydraulic) but also in quasi-static conditions. This later case is often observed in nature, in trees, or during the ejection of ferns spores. We study the cavitation bubbles nucleation dynamics and its propagation in a confined microfabricated media. This later is an ordered array of microcavities made in hydrogel filled with water. When the system is put into dry air, it dehydrates, water leaves the cavities and tension (negative pressure) builds in the cavities. This can be sustained up to a critical pressure (of order -20 MPa), then cavitation bubbles appear. We follow the dynamics using ultra high speed imaging. Events with several bubbles cavitating in a few microseconds could be observed along neighboring cells, showing a propagation phenomenon that we discuss. ANR CAVISOFT 2010-JCJC-0407 01.

Flexible Piezoelectric-Induced Pressure Sensors for Static Measurements Based on Nanowires/Graphene Heterostructures.

PubMed

Chen, Zefeng; Wang, Zhao; Li, Xinming; Lin, Yuxuan; Luo, Ningqi; Long, Mingzhu; Zhao, Ni; Xu, Jian-Bin

2017-05-23

The piezoelectric effect is widely applied in pressure sensors for the detection of dynamic signals. However, these piezoelectric-induced pressure sensors have challenges in measuring static signals that are based on the transient flow of electrons in an external load as driven by the piezopotential arisen from dynamic stress. Here, we present a pressure sensor with nanowires/graphene heterostructures for static measurements based on the synergistic mechanisms between strain-induced polarization charges in piezoelectric nanowires and the caused change of carrier scattering in graphene. Compared to the conventional piezoelectric nanowire or graphene pressure sensors, this sensor is capable of measuring static pressures with a sensitivity of up to 9.4 × 10 -3 kPa -1 and a fast response time down to 5-7 ms. This demonstration of pressure sensors shows great potential in the applications of electronic skin and wearable devices.

Experimental investigation on the effects of non-cyclical frequency and amplitude variation on dynamic stall

NASA Astrophysics Data System (ADS)

Heintz, Kyle C.

An experimental study of a cambered airfoil undergoing non-cyclical, transient pitch trajectories and the resulting effects on the dynamic stall phenomenon is presented. Surface pressure measurements and airfoil incidence angle are acquired simultaneously to resolve instantaneous aerodynamic load coefficients at Mach numbers ranging from 0.2 to 0.4. Derived from these coefficients are various formulations of the aerodynamic damping factor, referred to copiously throughout. Using a two-motor mechanism, each providing independent frequency and amplitude input to the airfoil, unique pitch motions can be implemented by actively controlling the phase between inputs. This work primarily focuses on three pitch motion schemas, the first of which is a "chirp" style trajectory featuring concurrent exponential frequency growth and amplitude decay. Second, these parameters are tested separately to determine their individual contributions. Lastly, a novel dual harmonic pitch motion is devised which rapidly traverses dynamic stall regimes on an inter-cycle basis by modulating the static-stall penetration angle. Throughout all results presented, there is evidence that for consecutive pitch-cycles, the process of dynamic stall is affected when prior oscillations prior have undergone deeper stall-penetration angles. In other words when stall-penetration is descending, retreating from a regime of light or deep stall, statistics of load coefficients, such as damping coefficient, maximum lift, minimum quarter-chord moment, and their phase relationships, do not match the values seen when stall-penetration was growing. The outcomes herein suggest that the airfoil retains some memory of previous flow separation which has the potential to change the influence of the dynamic stall vortex.

Entry vehicle performance analysis and atmospheric guidance algorithm for precision landing on Mars. M.S. Thesis - Massachusetts Inst. of Technology

NASA Technical Reports Server (NTRS)

Dieriam, Todd A.

1990-01-01

Future missions to Mars may require pin-point landing precision, possibly on the order of tens of meters. The ability to reach a target while meeting a dynamic pressure constraint to ensure safe parachute deployment is complicated at Mars by low atmospheric density, high atmospheric uncertainty, and the desire to employ only bank angle control. The vehicle aerodynamic performance requirements and guidance necessary for 0.5 to 1.5 lift drag ratio vehicle to maximize the achievable footprint while meeting the constraints are examined. A parametric study of the various factors related to entry vehicle performance in the Mars environment is undertaken to develop general vehicle aerodynamic design requirements. The combination of low lift drag ratio and low atmospheric density at Mars result in a large phugoid motion involving the dynamic pressure which complicates trajectory control. Vehicle ballistic coefficient is demonstrated to be the predominant characteristic affecting final dynamic pressure. Additionally, a speed brake is shown to be ineffective at reducing the final dynamic pressure. An adaptive precision entry atmospheric guidance scheme is presented. The guidance uses a numeric predictor-corrector algorithm to control downrange, an azimuth controller to govern crossrange, and analytic control law to reduce the final dynamic pressure. Guidance performance is tested against a variety of dispersions, and the results from selected tests are presented. Precision entry using bank angle control only is demonstrated to be feasible at Mars.

High-pressure phase transitions of α-quartz under nonhydrostatic dynamic conditions: A reconnaissance study at PETRA III

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

Carl, Eva-Regine; Mansfeld, Ulrich; Liermann, Hanns-Peter

Hypervelocity collisions of solid bodies occur frequently in the solar system and affect rocks by shock waves and dynamic loading. A range of shock metamorphic effects and high-pressure polymorphs in rock-forming minerals are known from meteorites and terrestrial impact craters. In this paper, we investigate the formation of high-pressure polymorphs of α-quartz under dynamic and nonhydrostatic conditions and compare these disequilibrium states with those predicted by phase diagrams derived from static experiments under equilibrium conditions. We create highly dynamic conditions utilizing a mDAC and study the phase transformations in α-quartz in situ by synchrotron powder X-ray diffraction. Phase transitions ofmore » α-quartz are studied at pressures up to 66.1 and different loading rates. At compression rates between 0.14 and 1.96 GPa s -1, experiments reveal that α-quartz is amorphized and partially converted to stishovite between 20.7 GPa and 28.0 GPa. Therefore, coesite is not formed as would be expected from equilibrium conditions. With the increasing compression rate, a slight increase in the transition pressure occurs. The experiments show that dynamic compression causes an instantaneous formation of structures consisting only of SiO 6 octahedra rather than the rearrangement of the SiO 4 tetrahedra to form a coesite. Although shock compression rates are orders of magnitude faster, a similar mechanism could operate in impact events.« less

High-pressure phase transitions of α-quartz under nonhydrostatic dynamic conditions: A reconnaissance study at PETRA III

DOE PAGES

Carl, Eva-Regine; Mansfeld, Ulrich; Liermann, Hanns-Peter; ...

2017-03-27

Hypervelocity collisions of solid bodies occur frequently in the solar system and affect rocks by shock waves and dynamic loading. A range of shock metamorphic effects and high-pressure polymorphs in rock-forming minerals are known from meteorites and terrestrial impact craters. In this paper, we investigate the formation of high-pressure polymorphs of α-quartz under dynamic and nonhydrostatic conditions and compare these disequilibrium states with those predicted by phase diagrams derived from static experiments under equilibrium conditions. We create highly dynamic conditions utilizing a mDAC and study the phase transformations in α-quartz in situ by synchrotron powder X-ray diffraction. Phase transitions ofmore » α-quartz are studied at pressures up to 66.1 and different loading rates. At compression rates between 0.14 and 1.96 GPa s -1, experiments reveal that α-quartz is amorphized and partially converted to stishovite between 20.7 GPa and 28.0 GPa. Therefore, coesite is not formed as would be expected from equilibrium conditions. With the increasing compression rate, a slight increase in the transition pressure occurs. The experiments show that dynamic compression causes an instantaneous formation of structures consisting only of SiO 6 octahedra rather than the rearrangement of the SiO 4 tetrahedra to form a coesite. Although shock compression rates are orders of magnitude faster, a similar mechanism could operate in impact events.« less

Neurogenic bladder

MedlinePlus

... cause skin to break down and lead to pressure sores Kidney damage if the bladder becomes too full, ... dysfunction; NBSD Patient Instructions Multiple sclerosis - discharge Preventing pressure ulcers Images Voiding cystourethrogram References Chapple CR, Osman NI. ...

Measurement of Dynamic Urethral Pressures with a High Resolution Manometry System in Continent and Incontinent Women

PubMed Central

Kirby, Anna C; Tan-Kim, Jasmine; Nager, Charles W.

2015-01-01

Objectives Female stress urinary incontinence (SUI) is caused by urethral dysfunction during dynamic conditions, but current technology has limitations in measuring urethral pressures under dynamic conditions. An 8-French high resolution manometry catheter (HRM) currently in clinical use in gastroenterology may accurately measure urethral pressures under dynamic conditions because it has a 25ms response rate and circumferential pressure sensors along the length of the catheter (ManoScan® ESO, Given Imaging). We evaluated the concordance, repeatability, and tolerability of this catheter. Methods We measured resting, cough, and strain maximum urethral closure pressures (MUCPs) using HRM and measured resting MUCPs with water perfusion side-hole catheter urethral pressure profilometry (UPP) in 37 continent and 28 stress incontinent subjects. Maneuvers were repeated after moving the HRM catheter along the urethral length to evaluate whether results depend on catheter positioning. Visual analog pain scores evaluated the comfort of HRM compared to UPP. Results The correlation coefficient for resting MUCPs measured by HRM vs. UPP was high (r = 0.79, p<0.001). Repeatability after catheter repositioning was high for rest, cough, and strain with HRM: r= 0.92, 0.89, and 0.89. Mean MUCPs (rest, cough, strain) were higher in continent than incontinent subjects (all p < 0.001) and decreased more in incontinent subjects than continent subjects during cough and strain maneuvers compared to rest. Conclusions This preliminary study shows that HRM is concordant with standard technology, repeatable, and well tolerated in the urethra. Incontinent women have more impairment of their urethral closure pressures during cough and strain than continent women. PMID:25185595

The influence of tobacco smoking on the relationship between pressure and flow in the middle cerebral artery in humans.

PubMed

Peebles, Karen C; Horsman, Helen; Tzeng, Yu-Chieh

2013-01-01

Cigarette smoking is associated with an increased risk of stroke but the mechanism is unclear. The study examined whether acute and chronic cigarette smoking alters the dynamic relationship between blood pressure and cerebral blood flow. We hypothesised that acute and chronic smoking would result in a cerebral circulation that was less capable of buffering against dynamic fluctuations in blood pressure. Further, these changes would be accompanied by a reduction in baroreflex sensitivity, which is reduced after smoking (acute smoking). We recruited 17 non-smokers and 15 habitual smokers (13 ± 5 pack years). Continuous measurements of mean cerebral blood flow velocity (transcranial Doppler ultrasound), blood pressure (finger photoplethysmography) and heart rate enabled transfer function analysis of the dynamic relationship between pressure and flow (gain, normalised gain, phase and coherence) and baroreflex sensitivity during supine rest before and after smoking a single cigarette (acute smoking). There were no between-group differences in gain, phase or coherence before acute smoking. However, both groups showed a reduction in gain and coherence, associated with a reduction in baroreflex sensitivity, and increase in phase after acute smoking. Contrary to our hypothesis, these findings suggest that in the face of a reduction in baroreflex sensitivity acute smoking may potentially improve the ability of the cerebral circulation to buffer against changes in blood pressure. However, chronic smoking did not alter the dynamic relationship between blood pressure and cerebral blood flow velocity. These results have implications on understanding mechanisms for attenuating stroke risk.

Effect of compression rate on ice VI crystal growth using dDAC

NASA Astrophysics Data System (ADS)

Lee, Yun-Hee; Kim, Yong-Jae; Lee, Sooheyong; Cho, Yong Chan; Lee, Geun Woo; Frontier in Extreme Physics Team

It is well known that static and dynamic pressure give different results in many aspects. Understanding of crystal growth under such different pressure condition is one of the crucial issues for the formation of materials in the earth and planets. To figure out the crystal growth under the different pressure condition, we should control compression rate from static to dynamic pressurization. Here, we use a dynamic diamond anvil cell (dDAC) technique to study the effect of compression rate of ice VI crystal growth. Using dDAC with high speed camera, we monitored growth of a single crystal ice VI. A rounded ice crystal with rough surface was selected in the phase boundary of water and ice VI and then, its repetitive growth and melting has been carried out by dynamic operation of the pressure cell. The roughened crystal showed interesting growth transition with compression rate from three dimensional to two dimensional growth as well as faceting process. We will discuss possible mechanism of the growth change by compression rate with diffusion mechanism of water. This research was supported by the Converging Research Center Program through the Ministry of Science, ICT and Future Planning, Korea (NRF-2014M1A7A1A01030128).

Dynamical contibution of Mean Potential Vorticity pseudo-observations derived from MetOp/GOME2 Ozone data into weather forecast, a Mediterranean High Precipitation Event study.

NASA Astrophysics Data System (ADS)

Sbii, Siham; Zazoui, Mimoun; Semane, Noureddine

2015-04-01

In the absence of observations covering the upper troposphere - lower stratophere, headquarters of several disturbances, and knowing that satellites are uniquely capable of providing uniform data coverage globally, a methodology is followed [1] to convert Total Column Ozone, observed by MetOp/GOME2, into pseudo-observations of Mean Potential Vorticity (MPV). The aim is to study the dynamical impact of Ozone data in the prediction of a Mediterranean Heavy Precipitation Event observed during 28-29 September 2012 in the context of HYMEX1. This study builds on a previously described methodology [2] that generates numerical weather prediction model initial conditions from ozone data. Indeed, the assimilation of MPV in a 3D-var framework is based on a linear regression between observed Ozone and vertical integrated Ertel PV. The latter is calculated using dynamical fields from the moroccan operational limited area model ALADIN-MAROC according to [3]: δθ fp p0 -R δU δV P V = - gξaδp- g-R-(p )Cp [(δp-)2 + (δp-)2] (1) Where ξa is the vertical component of the absolute vorticity, U and V the horizontal wind components, θ the potential temperature, R gas constant, Cp specific heat at constant pressure, p the pressure, p0 a reference pressure, g the gravity and f is the Coriolis parameter. The MPV is estimated using the following expression: --1--∫ P2 M PV = P1 - P2 P P V.δp 1 (2) With P1 = 500hPa and P2 = 100hPa In the present study, the linear regression is performed over September 2012 with a correlation coefficient of 0.8265 and is described as follows: M P V = 5.314610- 2 *O3 - 13.445 (3) where O3 and MPV are given in Dobson Unit (DU) and PVU (1 PV U = 10-6 m2 K kg-1 s-1), respectively. It is found that the ozone-influenced upper-level initializing fields affect the precipitation forecast, as diagnosed by a comparison with the ECMWF model. References [1] S. Sbii, N. Semane, Y. Michel, P. Arbogast and M. Zazoui (2012). Using METOP/GOME-2 data and MSG ozone data as Potential Vorticity pseudo-observations, Geophysical Research Abstracts Vol. 14, EGU2012-8926, EGU General Assembly. [2] S. Sbii, M. Zazoui, N. Semane, Y. Michel and P. Arbogast (2013). Exploring the Potential Application of MetOp/GOME2 Ozone Data to Weather Analysis.IJCSI, Vol. 10, Issue 2, No 3, March 2013: 260-263. [3] Guerin, R., Desroziers, G. and Arbogast, P. (2006). 4D-Var analysis of potential vorticity pseudo-observations. Q.J.R. Meteorol. Soc., 132: 1283-1298.

Pressure Ulcers in Adults: Prediction and Prevention. Clinical Practice Guideline Number 3.

ERIC Educational Resources Information Center

Agency for Health Care Policy and Research (DHHS/PHS), Rockville, MD.

This package includes a clinical practice guideline, quick reference guide for clinicians, and patient's guide to predicting and preventing pressure ulcers in adults. The clinical practice guideline includes the following: overview of the incidence and prevalence of pressure ulcers; clinical practice guideline (introduction, risk assessment tools…

49 CFR 192.191 - Design pressure of plastic fittings.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 3 2010-10-01 2010-10-01 false Design pressure of plastic fittings. 192.191... Components § 192.191 Design pressure of plastic fittings. (a) Thermosetting fittings for plastic pipe must conform to ASTM D 2517, (incorporated by reference, see § 192.7). (b) Thermoplastic fittings for plastic...

49 CFR 192.191 - Design pressure of plastic fittings.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 3 2012-10-01 2012-10-01 false Design pressure of plastic fittings. 192.191... Components § 192.191 Design pressure of plastic fittings. (a) Thermosetting fittings for plastic pipe must conform to ASTM D 2517, (incorporated by reference, see § 192.7). (b) Thermoplastic fittings for plastic...

49 CFR 192.191 - Design pressure of plastic fittings.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 3 2014-10-01 2014-10-01 false Design pressure of plastic fittings. 192.191... Components § 192.191 Design pressure of plastic fittings. (a) Thermosetting fittings for plastic pipe must conform to ASTM D 2517, (incorporated by reference, see § 192.7). (b) Thermoplastic fittings for plastic...

In-Flight Aeroelastic Stability of the Thermal Protection System on the NASA HIAD, Part II: Nonlinear Theory and Extended Aerodynamics

NASA Technical Reports Server (NTRS)

Goldman, Benjamin D.; Dowell, Earl H.; Scott, Robert C.

2015-01-01

Conical shell theory and a supersonic potential flow aerodynamic theory are used to study the nonlinear pressure buckling and aeroelastic limit cycle behavior of the thermal protection system for NASA's Hypersonic Inflatable Aerodynamic Decelerator. The structural model of the thermal protection system consists of an orthotropic conical shell of the Donnell type, resting on several circumferential elastic supports. Classical Piston Theory is used initially for the aerodynamic pressure, but was found to be insufficient at low supersonic Mach numbers. Transform methods are applied to the convected wave equation for potential flow, and a time-dependent aerodynamic pressure correction factor is obtained. The Lagrangian of the shell system is formulated in terms of the generalized coordinates for all displacements and the Rayleigh-Ritz method is used to derive the governing differential-algebraic equations of motion. Aeroelastic limit cycle oscillations and buckling deformations are calculated in the time domain using a Runge-Kutta method in MATLAB. Three conical shell geometries were considered in the present analysis: a 3-meter diameter 70 deg. cone, a 3.7-meter 70 deg. cone, and a 6-meter diameter 70 deg. cone. The 6-meter configuration was loaded statically and the results were compared with an experimental load test of a 6-meter HIAD. Though agreement between theoretical and experimental strains was poor, the circumferential wrinkling phenomena observed during the experiments was captured by the theory and axial deformations were qualitatively similar in shape. With Piston Theory aerodynamics, the nonlinear flutter dynamic pressures of the 3-meter configuration were in agreement with the values calculated using linear theory, and the limit cycle amplitudes were generally on the order of the shell thickness. The effect of axial tension was studied for this configuration, and increasing tension was found to decrease the limit cycle amplitudes when the circumferential elastic supports were neglected, but resulted in more complex behavior when the supports were included. The nominal flutter dynamic pressure of the 3.7-meter configuration was significantly lower than that of the 3-meter, and it was found that two sets of natural modes coalesce to flutter modes near the same dynamic pressure. This resulted in a significant drop in the limit cycle frequencies at higher dynamic pressures, where the flutter mode with the lower frequency becomes more critical. Pre-buckling pressure loads and the aerodynamic pressure correction factor were studied for all geometries, and these effects resulted in significantly lower flutter boundaries compared with Piston Theory alone. The maximum dynamic pressure predicted by aerodynamic simulations of a proposed 3.7-meter HIAD vehicle was still lower than any of the calculated flutter dynamic pressures, suggesting that aeroelastic effects for this vehicle are of little concern.

Development of model reference adaptive control theory for electric power plant control applications

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

Mabius, L.E.

1982-09-15

The scope of this effort includes the theoretical development of a multi-input, multi-output (MIMO) Model Reference Control (MRC) algorithm, (i.e., model following control law), Model Reference Adaptive Control (MRAC) algorithm and the formulation of a nonlinear model of a typical electric power plant. Previous single-input, single-output MRAC algorithm designs have been generalized to MIMO MRAC designs using the MIMO MRC algorithm. This MRC algorithm, which has been developed using Command Generator Tracker methodologies, represents the steady state behavior (in the adaptive sense) of the MRAC algorithm. The MRC algorithm is a fundamental component in the MRAC design and stability analysis.more » An enhanced MRC algorithm, which has been developed for systems with more controls than regulated outputs, alleviates the MRC stability constraint of stable plant transmission zeroes. The nonlinear power plant model is based on the Cromby model with the addition of a governor valve management algorithm, turbine dynamics and turbine interactions with extraction flows. An application of the MRC algorithm to a linearization of this model demonstrates its applicability to power plant systems. In particular, the generated power changes at 7% per minute while throttle pressure and temperature, reheat temperature and drum level are held constant with a reasonable level of control. The enhanced algorithm reduces significantly control fluctuations without modifying the output response.« less

The effects of backpack loads and spinal stabilization exercises on the dynamic foot pressure of elementary school children with idiopathic scoliosis

PubMed Central

Lee, Suemin; Shim, Jemyung

2015-01-01

[Purpose] The purpose of this study was to measure and observe the changes in dynamic plantar pressures when school children carried specific bag loads, and to determine whether improved physical balance after an eight-week spinal stabilization exercise program can influences plantar pressures. [Subjects] The subjects were 10 school students with Cobb angles of 10° or greater. [Methods] Gait View Pro 1.0 (Alfoots, Korea) was were based on to measure the pressure of the participants’ feet. Spinal stabilization exercises used TOGU Multi-roll Functional (TOGU, Germany) training. Dynamic plantar pressures were measured with bag loads of 0% no bag and 15% of subjects’ body weight. The independent t test was performed to analyze changes in plantar pressures. [Results] The plantar pressure measurements of bag load of 0% of subjects’ body weight before and after the spinal stabilization exercise program were not significantly different, but those of two foot areas with a 15% load were statistically significant (mt5, 67.32±24.25 and 51.77±25.52 kPa; lat heel, 126.00±20.46 and 102.08±23.87 kPa). [Conclusion] After performance of the spinal stabilization exercises subjects’ overall plantar pressures were reduced, which may suggest that physical balance improved. PMID:26311964