The Real-Time Wall Interference Correction System of the NASA Ames 12-Foot Pressure Wind Tunnel

NASA Technical Reports Server (NTRS)

Ulbrich, Norbert

1998-01-01

An improved version of the Wall Signature Method was developed to compute wall interference effects in three-dimensional subsonic wind tunnel testing of aircraft models in real-time. The method may be applied to a full-span or a semispan model. A simplified singularity representation of the aircraft model is used. Fuselage, support system, propulsion simulator, and separation wake volume blockage effects are represented by point sources and sinks. Lifting effects are represented by semi-infinite line doublets. The singularity representation of the test article is combined with the measurement of wind tunnel test reference conditions, wall pressure, lift force, thrust force, pitching moment, rolling moment, and pre-computed solutions of the subsonic potential equation to determine first order wall interference corrections. Second order wall interference corrections for pitching and rolling moment coefficient are also determined. A new procedure is presented that estimates a rolling moment coefficient correction for wings with non-symmetric lift distribution. Experimental data obtained during the calibration of the Ames Bipod model support system and during tests of two semispan models mounted on an image plane in the NASA Ames 12 ft. Pressure Wind Tunnel are used to demonstrate the application of the wall interference correction method.

Estimating Engine Airflow in Gas-Turbine Powered Aircraft with Clean and Distorted Inlet Flows

NASA Technical Reports Server (NTRS)

Williams, J. G.; Steenken, W. G.; Yuhas, A. J.

1996-01-01

The P404-GF-400 Powered F/A-18A High Alpha Research Vehicle (HARV) was used to examine the impact of inlet-generated total-pressure distortion on estimating levels of engine airflow. Five airflow estimation methods were studied. The Reference Method was a fan corrected airflow to fan corrected speed calibration from an uninstalled engine test. In-flight airflow estimation methods utilized the average, or individual, inlet duct static- to total-pressure ratios, and the average fan-discharge static-pressure to average inlet total-pressure ratio. Correlations were established at low distortion conditions for each method relative to the Reference Method. A range of distorted inlet flow conditions were obtained from -10 deg. to +60 deg. angle of attack and -7 deg. to +11 deg. angle of sideslip. The individual inlet duct pressure ratio correlation resulted in a 2.3 percent airflow spread for all distorted flow levels with a bias error of -0.7 percent. The fan discharge pressure ratio correlation gave results with a 0.6 percent airflow spread with essentially no systematic error. Inlet-generated total-pressure distortion and turbulence had no significant impact on the P404-GE400 engine airflow pumping. Therefore, a speed-flow relationship may provide the best airflow estimate for a specific engine under all flight conditions.

Potential Energy Surface for Large Barrierless Reaction Systems: Application to the Kinetic Calculations of the Dissociation of Alkanes and the Reverse Recombination Reactions.

PubMed

Yao, Qian; Cao, Xiao-Mei; Zong, Wen-Gang; Sun, Xiao-Hui; Li, Ze-Rong; Li, Xiang-Yuan

2018-05-31

The isodesmic reaction method is applied to calculate the potential energy surface (PES) along the reaction coordinates and the rate constants of the barrierless reactions for unimolecular dissociation reactions of alkanes to form two alkyl radicals and their reverse recombination reactions. The reaction class is divided into 10 subclasses depending upon the type of carbon atoms in the reaction centers. A correction scheme based on isodesmic reaction theory is proposed to correct the PESs at UB3LYP/6-31+G(d,p) level. To validate the accuracy of this scheme, a comparison of the PESs at B3LYP level and the corrected PESs with the PESs at CASPT2/aug-cc-pVTZ level is performed for 13 representative reactions, and it is found that the deviations of the PESs at B3LYP level are up to 35.18 kcal/mol and are reduced to within 2 kcal/mol after correction, indicating that the PESs for barrierless reactions in a subclass can be calculated meaningfully accurately at a low level of ab initio method using our correction scheme. High-pressure limit rate constants and pressure dependent rate constants of these reactions are calculated based on their corrected PESs and the results show the pressure dependence of the rate constants cannot be ignored, especially at high temperatures. Furthermore, the impact of molecular size on the pressure-dependent rate constants of decomposition reactions of alkanes and their reverse reactions has been studied. The present work provides an effective method to generate meaningfully accurate PESs for large molecular system.

Measurement of unsteady pressures in rotating systems

NASA Technical Reports Server (NTRS)

Kienappel, K.

1978-01-01

The principles of the experimental determination of unsteady periodic pressure distributions in rotating systems are reported. An indirect method is discussed, and the effects of the centrifugal force and the transmission behavior of the pressure measurement circuit were outlined. The required correction procedures are described and experimentally implemented in a test bench. Results show that the indirect method is suited to the measurement of unsteady nonharmonic pressure distributions in rotating systems.

A Study on Micropipetting Detection Technology of Automatic Enzyme Immunoassay Analyzer.

PubMed

Shang, Zhiwu; Zhou, Xiangping; Li, Cheng; Tsai, Sang-Bing

2018-04-10

In order to improve the accuracy and reliability of micropipetting, a method of micro-pipette detection and calibration combining the dynamic pressure monitoring in pipetting process and quantitative identification of pipette volume in image processing was proposed. Firstly, the normalized pressure model for the pipetting process was established with the kinematic model of the pipetting operation, and the pressure model is corrected by the experimental method. Through the pipetting process pressure and pressure of the first derivative of real-time monitoring, the use of segmentation of the double threshold method as pipetting fault evaluation criteria, and the pressure sensor data are processed by Kalman filtering, the accuracy of fault diagnosis is improved. When there is a fault, the pipette tip image is collected through the camera, extract the boundary of the liquid region by the background contrast method, and obtain the liquid volume in the tip according to the geometric characteristics of the pipette tip. The pipette deviation feedback to the automatic pipetting module and deviation correction is carried out. The titration test results show that the combination of the segmented pipetting kinematic model of the double threshold method of pressure monitoring, can effectively real-time judgment and classification of the pipette fault. The method of closed-loop adjustment of pipetting volume can effectively improve the accuracy and reliability of the pipetting system.

Improved Correction of Atmospheric Pressure Data Obtained by Smartphones through Machine Learning

PubMed Central

Kim, Yong-Hyuk; Ha, Ji-Hun; Kim, Na-Young; Im, Hyo-Hyuc; Sim, Sangjin; Choi, Reno K. Y.

2016-01-01

A correction method using machine learning aims to improve the conventional linear regression (LR) based method for correction of atmospheric pressure data obtained by smartphones. The method proposed in this study conducts clustering and regression analysis with time domain classification. Data obtained in Gyeonggi-do, one of the most populous provinces in South Korea surrounding Seoul with the size of 10,000 km2, from July 2014 through December 2014, using smartphones were classified with respect to time of day (daytime or nighttime) as well as day of the week (weekday or weekend) and the user's mobility, prior to the expectation-maximization (EM) clustering. Subsequently, the results were analyzed for comparison by applying machine learning methods such as multilayer perceptron (MLP) and support vector regression (SVR). The results showed a mean absolute error (MAE) 26% lower on average when regression analysis was performed through EM clustering compared to that obtained without EM clustering. For machine learning methods, the MAE for SVR was around 31% lower for LR and about 19% lower for MLP. It is concluded that pressure data from smartphones are as good as the ones from national automatic weather station (AWS) network. PMID:27524999

An efficient method for computing unsteady transonic aerodynamics of swept wings with control surfaces

NASA Technical Reports Server (NTRS)

Liu, D. D.; Kao, Y. F.; Fung, K. Y.

1989-01-01

A transonic equivalent strip (TES) method was further developed for unsteady flow computations of arbitrary wing planforms. The TES method consists of two consecutive correction steps to a given nonlinear code such as LTRAN2; namely, the chordwise mean flow correction and the spanwise phase correction. The computation procedure requires direct pressure input from other computed or measured data. Otherwise, it does not require airfoil shape or grid generation for given planforms. To validate the computed results, four swept wings of various aspect ratios, including those with control surfaces, are selected as computational examples. Overall trends in unsteady pressures are established with those obtained by XTRAN3S codes, Isogai's full potential code and measured data by NLR and RAE. In comparison with these methods, the TES has achieved considerable saving in computer time and reasonable accuracy which suggests immediate industrial applications.

Aerodynamics of Supersonic Lifting Bodies

DTIC Science & Technology

1981-02-01

Correction Velocity Ratio, y = 1.4 .. ......... . . . . 38 9 Perturbation Pressure Coefficient on the Body Surface .... 41 10 Pressure Coefficient on...Secant Method and Exper.1ent ... ....... 119 40 Geometrica . :onfinmration anl 7ro)r;1Tnate Systens ....... 125 41 1pheri. •a. 1-rinites...due to pitching p contribution due to plunging 8 shock wave w wedge z contribution due to pitching about Ln 0 free stream Superscripts (c) correction

Tire pressure special study : interview data

DOT National Transportation Integrated Search

2001-08-01

Although 85% of the population of drivers are : concerned about maintaining proper tire inflation in : their vehicles, only 25% use the correct method to : determine the manufacturers recommended tire : pressure for their tires. In addition, 43% o...

Design of the micro pressure multi-node measuring system for micro-fluidic chip

NASA Astrophysics Data System (ADS)

Mu, Lili; Guo, Shuheng; Rong, Li; Yin, Ke

2016-01-01

An online multi-node microfludic pressure measuring system was designed in the paper. The research focused on the design of pressure test circuit system and methods on dealing with pressure data collecting. The MPXV7002 micro-pressure sensor was selected to measure the chip inside channel pressure and installed by a silicone tube on different micro-channel measured nodes. The pressure transmission loss was estimated in the paper, and corrected by the filtering and smoothing method. The pressure test experiment was carried out and the data were analyzed. Finally, the measuring system was calibrated. The results showed that the measuring system had high testing precision.

Correction of static pressure on a research aircraft in accelerated flight using differential pressure measurements

NASA Astrophysics Data System (ADS)

Rodi, A. R.; Leon, D. C.

2012-05-01

Geometric altitude data from a combined Global Navigation Satellite System (GNSS) and inertial measurement unit (IMU) system on the University of Wyoming King Air research aircraft are used to estimate acceleration effects on static pressure measurement. Using data collected during periods of accelerated flight, comparison of measured pressure with that derived from GNSS/IMU geometric altitude show that errors exceeding 150 Pa can occur which is significant in airspeed and atmospheric air motion determination. A method is developed to predict static pressure errors from analysis of differential pressure measurements from a Rosemount model 858 differential pressure air velocity probe. The method was evaluated with a carefully designed probe towed on connecting tubing behind the aircraft - a "trailing cone" - in steady flight, and shown to have a precision of about ±10 Pa over a wide range of conditions including various altitudes, power settings, and gear and flap extensions. Under accelerated flight conditions, compared to the GNSS/IMU data, this algorithm predicts corrections to a precision of better than ±20 Pa. Some limiting factors affecting the precision of static pressure measurement on a research aircraft are examined.

A simplified fourwall interference assessment procedure for airfoil data obtained in the Langley 0.3-meter transonic cryogenic tunnel

NASA Technical Reports Server (NTRS)

Murthy, A. V.

1987-01-01

A simplified fourwall interference assessment method has been described, and a computer program developed to facilitate correction of the airfoil data obtained in the Langley 0.3-m Transonic Cryogenic Tunnel (TCT). The procedure adopted is to first apply a blockage correction due to sidewall boundary-layer effects by various methods. The sidewall boundary-layer corrected data are then used to calculate the top and bottom wall interference effects by the method of Capallier, Chevallier and Bouinol, using the measured wall pressure distribution and the model force coefficients. The interference corrections obtained by the present method have been compared with other methods and found to give good agreement for the experimental data obtained in the TCT with slotted top and bottom walls.

Helicopter Noise Reduction Design Trade-Off Study

DTIC Science & Technology

1977-01-01

level, A-weighted sound pressure level, perceived noise level and tone corrected perceived noise level time histories, and are further analyzed to...DATA ---------------------------- 101 10 BASELINE VEHICLE EFFECTIVE PERCEIVED NOISE LEVELS (EPiII.) AND RANGE FOR MAXIMIJM TONE CORRECTED PERCEIVED...and tone corrected perceived noise level (PNLT) units. All noise level calculation methods have been computerized in FORTRAN language for use on the

Combination volumetric and gravimetric sorption instrument for high accuracy measurements of methane adsorption

NASA Astrophysics Data System (ADS)

Burress, Jacob; Bethea, Donald; Troub, Brandon

2017-05-01

The accurate measurement of adsorbed gas up to high pressures (˜100 bars) is critical for the development of new materials for adsorbed gas storage. The typical Sievert-type volumetric method introduces accumulating errors that can become large at maximum pressures. Alternatively, gravimetric methods employing microbalances require careful buoyancy corrections. In this paper, we present a combination gravimetric and volumetric system for methane sorption measurements on samples between ˜0.5 and 1 g. The gravimetric method described requires no buoyancy corrections. The tandem use of the gravimetric method allows for a check on the highest uncertainty volumetric measurements. The sources and proper calculation of uncertainties are discussed. Results from methane measurements on activated carbon MSC-30 and metal-organic framework HKUST-1 are compared across methods and within the literature.

Combination volumetric and gravimetric sorption instrument for high accuracy measurements of methane adsorption.

PubMed

Burress, Jacob; Bethea, Donald; Troub, Brandon

2017-05-01

The accurate measurement of adsorbed gas up to high pressures (∼100 bars) is critical for the development of new materials for adsorbed gas storage. The typical Sievert-type volumetric method introduces accumulating errors that can become large at maximum pressures. Alternatively, gravimetric methods employing microbalances require careful buoyancy corrections. In this paper, we present a combination gravimetric and volumetric system for methane sorption measurements on samples between ∼0.5 and 1 g. The gravimetric method described requires no buoyancy corrections. The tandem use of the gravimetric method allows for a check on the highest uncertainty volumetric measurements. The sources and proper calculation of uncertainties are discussed. Results from methane measurements on activated carbon MSC-30 and metal-organic framework HKUST-1 are compared across methods and within the literature.

Analysis of stress-strain state of a human eye by the method of elastotonometry after the surgical correction of hyperopia

NASA Astrophysics Data System (ADS)

Bauer, S. M.; Venatovskaya, L. A.

2018-05-01

The mathematical model of measuring of the intraocular pressure (IOP) by Maklakoff tonometer in the software package ANSYS, Inc. is presented. The dependence of the tonometric pressure on the weight of the tonometer before and after LASIK and Femto LASIK surgical corrections of hyperopia is analized. Cornea-scleral eye shell is modeled as two thin transversely isotropic joint spherical shells with different radii of curvature and biomechanical properties. To analyze the biomechanical state of the corneoscleral shell of the eye after the surgery the elastotonometry method is used. Firstly sequential measurements of intraocular pressure by Maklakoff tonometers weighting 5; 7.5; 10 and 15 g is carried out, then the dependence curve of tonometric IOP vs. tonometer weight is plotted and analyzed. The results of the calculations are compared with the clinical data.

A Rotational Pressure-Correction Scheme for Incompressible Two-Phase Flows with Open Boundaries

PubMed Central

Dong, S.; Wang, X.

2016-01-01

Two-phase outflows refer to situations where the interface formed between two immiscible incompressible fluids passes through open portions of the domain boundary. We present several new forms of open boundary conditions for two-phase outflow simulations within the phase field framework, as well as a rotational pressure correction based algorithm for numerically treating these open boundary conditions. Our algorithm gives rise to linear algebraic systems for the velocity and the pressure that involve only constant and time-independent coefficient matrices after discretization, despite the variable density and variable viscosity of the two-phase mixture. By comparing simulation results with theory and the experimental data, we show that the method produces physically accurate results. We also present numerical experiments to demonstrate the long-term stability of the method in situations where large density contrast, large viscosity contrast, and backflows occur at the two-phase open boundaries. PMID:27163909

Intra-Ocular Pressure Measurement in a Patient with a Thin, Thick or Abnormal Cornea.

PubMed

Clement, Colin I; Parker, Douglas G A; Goldberg, Ivan

2016-01-01

Accurate measurement of intra-ocular pressure is a fundamental component of the ocular examination. The most common method of measuring IOP is by Goldmann applanation tonometry, the accuracy of which is influenced by the thickness and biomechanical properties of the cornea. Algorithms devised to correct for corneal thickness to estimate IOP oversimplify the effects of corneal biomechanics. The viscous and elastic properties of the cornea influence IOP measurements in unpredictable ways, a finding borne out in studies of patients with inherently abnormal and surgically altered corneal biomechanics. Dynamic contour tonometry, rebound tonometry and the ocular response analyzer provide useful alternatives to GAT in patients with abnormal corneas, such as those who have undergone laser vision correction or keratoplasty. This article reviews the various methods of intra-ocular pressure measurement available to the clinician and the ways in which their utility is influenced by variations in corneal thickness and biomechanics.

Frequency Response of Pressure Sensitive Paints

NASA Technical Reports Server (NTRS)

Winslow, Neal A.; Carroll, Bruce F.; Setzer, Fred M.

1996-01-01

An experimental method for measuring the frequency response of Pressure Sensitive Paints (PSP) is presented. These results lead to the development of a dynamic correction technique for PSP measurements which is of great importance to the advancement of PSP as a measurement technique. The ability to design such a dynamic corrector is most easily formed from the frequency response of the given system. An example of this correction technique is shown. In addition to the experimental data, an analytical model for the frequency response is developed from the one dimensional mass diffusion equation.

Accurate pressure gradient calculations in hydrostatic atmospheric models

NASA Technical Reports Server (NTRS)

Carroll, John J.; Mendez-Nunez, Luis R.; Tanrikulu, Saffet

1987-01-01

A method for the accurate calculation of the horizontal pressure gradient acceleration in hydrostatic atmospheric models is presented which is especially useful in situations where the isothermal surfaces are not parallel to the vertical coordinate surfaces. The present method is shown to be exact if the potential temperature lapse rate is constant between the vertical pressure integration limits. The technique is applied to both the integration of the hydrostatic equation and the computation of the slope correction term in the horizontal pressure gradient. A fixed vertical grid and a dynamic grid defined by the significant levels in the vertical temperature distribution are employed.

Implementation of the WICS Wall Interference Correction System at the National Transonic Facility

NASA Technical Reports Server (NTRS)

Iyer, Venkit; Everhart, Joel L.; Bir, Pamela J.; Ulbrich, Norbert

2000-01-01

The Wall Interference Correction System (WICS) is operational at the National Transonic Facility (NTF) of NASA Langley Research Center (NASA LaRC) for semispan and full span tests in the solid wall (slots covered) configuration. The method is based on the wall pressure signature method for computing corrections to the measured parameters. It is an adaptation of the WICS code operational at the 12 ft pressure wind tunnel (12ft PWT) of NASA Ames Research Center (NASA ARC). This paper discusses the details of implementation of WICS at the NTF including tunnel calibration, code modifications for tunnel and support geometry, changes made for the NTF wall orifices layout, details of interfacing with the tunnel data processing system, and post-processing of results. Example results of applying WICS to a semispan test and a full span test are presented. Comparison with classical correction results and an analysis of uncertainty in the corrections are also given. As a special application of the code, the Mach number calibration data from a centerline pipe test was computed by WICS. Finally, future work for expanding the applicability of the code including online implementation is discussed.

Implementation of the WICS Wall Interference Correction System at the National Transonic Facility

NASA Technical Reports Server (NTRS)

Iyer, Venkit; Martin, Lockheed; Everhart, Joel L.; Bir, Pamela J.; Ulbrich, Norbert

2000-01-01

The Wall Interference Correction System (WICS) is operational at the National Transonic Facility (NTF) of NASA Langley Research Center (NASA LaRC) for semispan and full span tests in the solid wall (slots covered) configuration, The method is based on the wall pressure signature method for computing corrections to the measured parameters. It is an adaptation of the WICS code operational at the 12 ft pressure wind tunnel (12ft PWT) of NASA Ames Research Center (NASA ARC). This paper discusses the details of implementation of WICS at the NTF including, tunnel calibration, code modifications for tunnel and support geometry, changes made for the NTF wall orifices layout, details of interfacing with the tunnel data processing system, and post-processing of results. Example results of applying WICS to a semispan test and a full span test are presented. Comparison with classical correction results and an analysis of uncertainty in the corrections are also given. As a special application of the code, the Mach number calibration data from a centerline pipe test was computed by WICS. Finally, future work for expanding the applicability of the code including online implementation is discussed.

Blood pressure measurement in obese patients: comparison between upper arm and forearm measurements.

PubMed

Pierin, Angela M G; Alavarce, Débora C; Gusmão, Josiane L; Halpern, Alfredo; Mion, Décio

2004-06-01

It is well known that blood pressure measurement with a standard 12-13 cm wide cuff is erroneous for large arms. To compare arm blood pressure measurements with an appropriate cuff and forearm blood pressure measurements (BPM) with a standard cuff, and both measurements by the Photopletismography (Finapres) method. One hundred and twenty-nine obese patients were studied (body mass index=40+/-7 kg/m2). The patients had three arm BPM taken by an automatic oscillometric device using an appropriate cuff and three forearm BPM with a standard cuff in the sitting position after a five-minute rest. Data were analysed by the analysis of variance. The correction values were obtained by the linear regression test. Systolic and diastolic arm BPM with an appropriate cuff were significantly lower (p<0.05) than forearm BPM with a standard cuff. The measurements obtained by Finapres were significantly lower (p<0.05) than those found for forearm systolic and diastolic blood pressures and upper arm diastolic blood pressure. The equation to correct BPM in forearm in obese patients with arm circumference between 32-44 cm was: systolic BPM=33.2+/-0.68 x systolic forearm BPM, and diastolic BPM=25.2+0.59 x forearm diastolic BPM. This study showed that forearm blood pressure measurement overestimates the values of arm blood pressure measurement. In addition, it is possible to correct forearm BPM with an equation.

Experimental aspects of buoyancy correction in measuring reliable high-pressure excess adsorption isotherms using the gravimetric method

NASA Astrophysics Data System (ADS)

Nguyen, Huong Giang T.; Horn, Jarod C.; Thommes, Matthias; van Zee, Roger D.; Espinal, Laura

2017-12-01

Addressing reproducibility issues in adsorption measurements is critical to accelerating the path to discovery of new industrial adsorbents and to understanding adsorption processes. A National Institute of Standards and Technology Reference Material, RM 8852 (ammonium ZSM-5 zeolite), and two gravimetric instruments with asymmetric two-beam balances were used to measure high-pressure adsorption isotherms. This work demonstrates how common approaches to buoyancy correction, a key factor in obtaining the mass change due to surface excess gas uptake from the apparent mass change, can impact the adsorption isotherm data. Three different approaches to buoyancy correction were investigated and applied to the subcritical CO2 and supercritical N2 adsorption isotherms at 293 K. It was observed that measuring a collective volume for all balance components for the buoyancy correction (helium method) introduces an inherent bias in temperature partition when there is a temperature gradient (i.e. analysis temperature is not equal to instrument air bath temperature). We demonstrate that a blank subtraction is effective in mitigating the biases associated with temperature partitioning, instrument calibration, and the determined volumes of the balance components. In general, the manual and subtraction methods allow for better treatment of the temperature gradient during buoyancy correction. From the study, best practices specific to asymmetric two-beam balances and more general recommendations for measuring isotherms far from critical temperatures using gravimetric instruments are offered.

Supercooled liquid vapour pressures and related thermodynamic properties of polycyclic aromatic hydrocarbons determined by gas chromatography.

PubMed

Haftka, Joris J H; Parsons, John R; Govers, Harrie A J

2006-11-24

A gas chromatographic method using Kováts retention indices has been applied to determine the liquid vapour pressure (P(i)), enthalpy of vaporization (DeltaH(i)) and difference in heat capacity between gas and liquid phase (DeltaC(i)) for a group of polycyclic aromatic hydrocarbons (PAHs). This group consists of 19 unsubstituted, methylated and sulphur containing PAHs. Differences in log P(i) of -0.04 to +0.99 log units at 298.15K were observed between experimental values and data from effusion and gas saturation studies. These differences in log P(i) have been fitted with multilinear regression resulting in a compound and temperature dependent correction. Over a temperature range from 273.15 to 423.15K, differences in corrected log P(i) of a training set (-0.07 to +0.03 log units) and a validation set (-0.17 to 0.19 log units) were within calculated error ranges. The corrected vapour pressures also showed a good agreement with other GC determined vapour pressures (average -0.09 log units).

SU-E-T-123: Anomalous Altitude Effect in Permanent Implant Brachytherapy Seeds

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

Watt, E; Spencer, DP; Meyer, T

Purpose: Permanent seed implant brachytherapy procedures require the measurement of the air kerma strength of seeds prior to implant. This is typically accomplished using a well-type ionization chamber. Previous measurements (Griffin et al., 2005; Bohm et al., 2005) of several low-energy seeds using the air-communicating HDR 1000 Plus chamber have demonstrated that the standard temperature-pressure correction factor, P{sub TP}, may overcompensate for air density changes induced by altitude variations by up to 18%. The purpose of this work is to present empirical correction factors for two clinically-used seeds (IsoAid ADVANTAGE™ {sup 103}Pd and Nucletron selectSeed {sup 125}I) for which empiricalmore » altitude correction factors do not yet exist in the literature when measured with the HDR 1000 Plus chamber. Methods: An in-house constructed pressure vessel containing the HDR 1000 Plus well chamber and a digital barometer/thermometer was pumped or evacuated, as appropriate, to a variety of pressures from 725 to 1075 mbar. Current measurements, corrected with P{sub TP}, were acquired for each seed at these pressures and normalized to the reading at ‘standard’ pressure (1013.25 mbar). Results: Measurements in this study have shown that utilization of P{sub TP} can overcompensate in the corrected current reading by up to 20% and 17% for the IsoAid Pd-103 and the Nucletron I-125 seed respectively. Compared to literature correction factors for other seed models, the correction factors in this study diverge by up to 2.6% and 3.0% for iodine (with silver) and palladium respectively, indicating the need for seed-specific factors. Conclusion: The use of seed specific altitude correction factors can reduce uncertainty in the determination of air kerma strength. The empirical correction factors determined in this work can be applied in clinical quality assurance measurements of air kerma strength for two previously unpublished seed designs (IsoAid ADVANTAGE™ {sup 103}Pd and Nucletron selectSeed {sup 125}I) with the HDR 1000 Plus well chamber.« less

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

Anikovsky, V.V.; Karzov, G.P.; Timofeev, B.T.

The paper demonstrates an insufficiency of some requirements native Norms (when comparing them with the foreign requirements for the consideration of calculating situations): (1) leak before break (LBB); (2) short cracks; (3) preliminary loading (warm prestressing). In particular, the paper presents (1) Comparison of native and foreign normative requirements (PNAE G-7-002-86, Code ASME, BS 1515, KTA) on permissible stress levels and specifically on the estimation of crack initiation and propagation; (2) comparison of RF and USA Norms of pressure vessel material acceptance and also data of pressure vessel hydrotests; (3) comparison of Norms on the presence of defects (RF andmore » USA) in NPP vessels, developments of defect schematization rules; foundation of a calculated defect (semi-axis correlation a/b) for pressure vessel and piping components: (4) sequence of defect estimation (growth of initial defects and critical crack sizes) proceeding from the concept LBB; (5) analysis of crack initiation and propagation conditions according to the acting Norms (including crack jumps); (6) necessity to correct estimation methods of ultimate states of brittle an ductile fracture and elastic-plastic region as applied to calculating situation: (a) LBB and (b) short cracks; (7) necessity to correct estimation methods of ultimate states with the consideration of static and cyclic loading (warm prestressing effect) of pressure vessel; estimation of the effect stability; (8) proposals on PNAE G-7-002-86 Norm corrections.« less

Dynamic compression of copper to over 450 GPa: A high-pressure standard

DOE PAGES

Kraus, R. G.; Davis, J. -P.; Seagle, C. T.; ...

2016-04-12

We obtained an absolute stress-density path for shocklessly compressed copper to over 450 GPa. A magnetic pressure drive is temporally tailored to generate shockless compression waves through over 2.5-mm-thick copper samples. Furthermore, the free-surface velocity data is analyzed for Lagrangian sound velocity using the iterative Lagrangian analysis (ILA) technique, which relies upon the method of characteristics. We correct for the effects of strength and plastic work heating to determine an isentropic compression path. By assuming a Debye model for the heat capacity, we can further correct the isentrope to an isotherm. Finally, our determination of the isentrope and isotherm ofmore » copper represents a highly accurate pressure standard for copper to over 450 GPa.« less

Nanoscale simulation of shale transport properties using the lattice Boltzmann method: Permeability and diffusivity

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

Chen, Li; Zhang, Lei; Kang, Qinjun

Here, porous structures of shales are reconstructed using the markov chain monte carlo (MCMC) method based on scanning electron microscopy (SEM) images of shale samples from Sichuan Basin, China. Characterization analysis of the reconstructed shales is performed, including porosity, pore size distribution, specific surface area and pore connectivity. The lattice Boltzmann method (LBM) is adopted to simulate fluid flow and Knudsen diffusion within the reconstructed shales. Simulation results reveal that the tortuosity of the shales is much higher than that commonly employed in the Bruggeman equation, and such high tortuosity leads to extremely low intrinsic permeability. Correction of the intrinsicmore » permeability is performed based on the dusty gas model (DGM) by considering the contribution of Knudsen diffusion to the total flow flux, resulting in apparent permeability. The correction factor over a range of Knudsen number and pressure is estimated and compared with empirical correlations in the literature. We find that for the wide pressure range investigated, the correction factor is always greater than 1, indicating Knudsen diffusion always plays a role on shale gas transport mechanisms in the reconstructed shales. Specifically, we found that most of the values of correction factor fall in the slip and transition regime, with no Darcy flow regime observed.« less

Nanoscale simulation of shale transport properties using the lattice Boltzmann method: Permeability and diffusivity

DOE PAGES

Chen, Li; Zhang, Lei; Kang, Qinjun; ...

2015-01-28

Here, porous structures of shales are reconstructed using the markov chain monte carlo (MCMC) method based on scanning electron microscopy (SEM) images of shale samples from Sichuan Basin, China. Characterization analysis of the reconstructed shales is performed, including porosity, pore size distribution, specific surface area and pore connectivity. The lattice Boltzmann method (LBM) is adopted to simulate fluid flow and Knudsen diffusion within the reconstructed shales. Simulation results reveal that the tortuosity of the shales is much higher than that commonly employed in the Bruggeman equation, and such high tortuosity leads to extremely low intrinsic permeability. Correction of the intrinsicmore » permeability is performed based on the dusty gas model (DGM) by considering the contribution of Knudsen diffusion to the total flow flux, resulting in apparent permeability. The correction factor over a range of Knudsen number and pressure is estimated and compared with empirical correlations in the literature. We find that for the wide pressure range investigated, the correction factor is always greater than 1, indicating Knudsen diffusion always plays a role on shale gas transport mechanisms in the reconstructed shales. Specifically, we found that most of the values of correction factor fall in the slip and transition regime, with no Darcy flow regime observed.« less

Nanoscale simulation of shale transport properties using the lattice Boltzmann method: permeability and diffusivity

PubMed Central

Chen, Li; Zhang, Lei; Kang, Qinjun; Viswanathan, Hari S.; Yao, Jun; Tao, Wenquan

2015-01-01

Porous structures of shales are reconstructed using the markov chain monte carlo (MCMC) method based on scanning electron microscopy (SEM) images of shale samples from Sichuan Basin, China. Characterization analysis of the reconstructed shales is performed, including porosity, pore size distribution, specific surface area and pore connectivity. The lattice Boltzmann method (LBM) is adopted to simulate fluid flow and Knudsen diffusion within the reconstructed shales. Simulation results reveal that the tortuosity of the shales is much higher than that commonly employed in the Bruggeman equation, and such high tortuosity leads to extremely low intrinsic permeability. Correction of the intrinsic permeability is performed based on the dusty gas model (DGM) by considering the contribution of Knudsen diffusion to the total flow flux, resulting in apparent permeability. The correction factor over a range of Knudsen number and pressure is estimated and compared with empirical correlations in the literature. For the wide pressure range investigated, the correction factor is always greater than 1, indicating Knudsen diffusion always plays a role on shale gas transport mechanisms in the reconstructed shales. Specifically, we found that most of the values of correction factor fall in the slip and transition regime, with no Darcy flow regime observed. PMID:25627247

Reconstructing ice-age palaeoclimates: Quantifying low-CO2 effects on plants

NASA Astrophysics Data System (ADS)

Prentice, I. C.; Cleator, S. F.; Huang, Y. H.; Harrison, S. P.; Roulstone, I.

2017-02-01

We present a novel method to quantify the ecophysiological effects of changes in CO2 concentration during the reconstruction of climate changes from fossil pollen assemblages. The method does not depend on any particular vegetation model. Instead, it makes use of general equations from ecophysiology and hydrology that link moisture index (MI) to transpiration and the ratio of leaf-internal to ambient CO2 (χ). Statistically reconstructed MI values are corrected post facto for effects of CO2 concentration. The correction is based on the principle that e, the rate of water loss per unit carbon gain, should be inversely related to effective moisture availability as sensed by plants. The method involves solving a non-linear equation that relates e to MI, temperature and CO2 concentration via the Fu-Zhang relation between evapotranspiration and MI, Monteith's empirical relationship between vapour pressure deficit and evapotranspiration, and recently developed theory that predicts the response of χ to vapour pressure deficit and temperature. The solution to this equation provides a correction term for MI. The numerical value of the correction depends on the reconstructed MI. It is slightly sensitive to temperature, but primarily sensitive to CO2 concentration. Under low LGM CO2 concentration the correction is always positive, implying that LGM climate was wetter than it would seem from vegetation composition. A statistical reconstruction of last glacial maximum (LGM, 21±1 kyr BP) palaeoclimates, based on a new compilation of modern and LGM pollen assemblage data from Australia, is used to illustrate the method in practice. Applying the correction brings pollen-reconstructed LGM moisture availability in southeastern Australia better into line with palaeohydrological estimates of LGM climate.

Comparison of 2 correction methods for absolute values of esophageal pressure in subjects with acute hypoxemic respiratory failure, mechanically ventilated in the ICU.

PubMed

Guérin, Claude; Richard, Jean-Christophe

2012-12-01

A recent trial showed that setting PEEP according to end-expiratory transpulmonary pressure (P(pl,ee)) in acute lung injury/acute respiratory distress syndrome (ALI/ARDS) might improve patient outcome. P(pl,ee) was obtained by subtracting the absolute value of esophageal pressure (P(es)) from airway pressure an invariant value of 5 cm H(2)O. The goal of the present study was to compare 2 methods for correcting absolute P(es) values in terms of resulting P(pl,ee) and recommended PEEP. Measurements collected prospectively from 42 subjects with various forms of acute hypoxemic respiratory failure receiving mechanical ventilation in ICU were analyzed. P(es) was measured at PEEP (P(es,ee)) and at relaxation volume of the respiratory system Vr (P(es,Vr)), obtained by allowing the subject to exhale into the atmosphere (zero PEEP). Two methods for correcting P(es) were compared: Talmor method (P(pl,ee,Talmor) = P(es,ee) - 5 cm H(2)O), and Vr method (P(es,ee,Vr) = P(es,ee) - P(es,Vr)). The rationale was that P(es,Vr) was a more physiologically based correction factor than an invariant value of 5 cm H(2)O applied to all subjects. Over the 42 subjects, median and interquartile range of P(es,ee) and P(es,Vr) were 11 (7-14) cm H(2)O and 8 (4-11) cm H(2)O, respectively. P(pl,ee,Talmor) was 6 (1-8) cm H(2)O, and P(es,ee,Vr) was 2 (1-5) cm H(2)O (P = .008). Two groups of subjects were defined, based on the difference between the 2 corrected values. In 28 subjects P(pl,ee,Talmor) was ≥ P(es,ee,Vr) (7 [5-9] cm H(2)O vs 2 [1-5] cm H(2)O, respectively), while in 14 subjects P(es,ee,Vr) was > P(pl,ee,Talmor) (2 [0-4] cm H(2)O vs -1 [-3 to 2] cm H(2)O, respectively). P(pl,ee,Vr) was significantly greater than P(pl,ee,Talmor) (7 [5-11] cm H(2)O vs 5 [2-7] cm H(2)O) in the former, and significantly lower in the latter (1 [-2 to 6] cm H(2)O vs 6 [4-9] cm H(2)O). Referring absolute P(es) values to Vr rather than to an invariant value would be better adapted to a patient's physiological background. Further studies are required to determine whether this correction method might improve patient outcome.

Preventing collapse of external auditory meatus during audiometry.

PubMed

Pearlman, R C

1975-11-01

Occlusion of the external auditory meatus resulting from earphone pressure can produce a pseudoconductive hearing loss. I describe a method for detecting ear canal collapse by otoscopy and I suggest a method of correcting the problem with a polyethylene tube prosthesis.

A conservative, thermodynamically consistent numerical approach for low Mach number combustion. Part I: Single-level integration

NASA Astrophysics Data System (ADS)

Nonaka, Andrew; Day, Marcus S.; Bell, John B.

2018-01-01

We present a numerical approach for low Mach number combustion that conserves both mass and energy while remaining on the equation of state to a desired tolerance. We present both unconfined and confined cases, where in the latter the ambient pressure changes over time. Our overall scheme is a projection method for the velocity coupled to a multi-implicit spectral deferred corrections (SDC) approach to integrate the mass and energy equations. The iterative nature of SDC methods allows us to incorporate a series of pressure discrepancy corrections naturally that lead to additional mass and energy influx/outflux in each finite volume cell in order to satisfy the equation of state. The method is second order, and satisfies the equation of state to a desired tolerance with increasing iterations. Motivated by experimental results, we test our algorithm on hydrogen flames with detailed kinetics. We examine the morphology of thermodiffusively unstable cylindrical premixed flames in high-pressure environments for confined and unconfined cases. We also demonstrate that our algorithm maintains the equation of state for premixed methane flames and non-premixed dimethyl ether jet flames.

Analysis and comparison of sleeping posture classification methods using pressure sensitive bed system.

PubMed

Hsia, C C; Liou, K J; Aung, A P W; Foo, V; Huang, W; Biswas, J

2009-01-01

Pressure ulcers are common problems for bedridden patients. Caregivers need to reposition the sleeping posture of a patient every two hours in order to reduce the risk of getting ulcers. This study presents the use of Kurtosis and skewness estimation, principal component analysis (PCA) and support vector machines (SVMs) for sleeping posture classification using cost-effective pressure sensitive mattress that can help caregivers to make correct sleeping posture changes for the prevention of pressure ulcers.

Water-level measurements in Dauphin Island, Alabama, from the 2013 Hurricane Season

USGS Publications Warehouse

Dickhudt, Patrick J.; Sherwood, Christopher R.; DeWitt, Nancy T.

2015-01-01

This report describes the instrumentation, field measurements, and processing methods used by the U.S. Geological Survey to measure atmospheric pressure, water levels, and waves on Dauphin Island, Alabama, in 2013 at part of the Barrier Island Evolution Research project. Simple, inexpensive pressure sensors mounted in shallow wells were buried in the beach and left throughout the hurricane season. Additionally, an atmospheric pressure sensor was mounted on the porch of a private residence to provide a local atmospheric pressure measurement for correcting the submerged pressure records.

Effect of the lithospheric thermal state on the Moho interface: A case study in South America

NASA Astrophysics Data System (ADS)

Bagherbandi, Mohammad; Bai, Yongliang; Sjöberg, Lars E.; Tenzer, Robert; Abrehdary, Majid; Miranda, Silvia; Alcacer Sanchez, Juan M.

2017-07-01

Gravimetric methods applied for Moho recovery in areas with sparse and irregular distribution of seismic data often assume only a constant crustal density. Results of latest studies, however, indicate that corrections for crustal density heterogeneities could improve the gravimetric result, especially in regions with a complex geologic/tectonic structure. Moreover, the isostatic mass balance reflects also the density structure within the lithosphere. The gravimetric methods should therefore incorporate an additional correction for the lithospheric mantle as well as deeper mantle density heterogeneities. Following this principle, we solve the Vening Meinesz-Moritz (VMM) inverse problem of isostasy constrained by seismic data to determine the Moho depth of the South American tectonic plate including surrounding oceans, while taking into consideration the crustal and mantle density heterogeneities. Our numerical result confirms that contribution of sediments significantly modifies the estimation of the Moho geometry especially along the continental margins with large sediment deposits. To account for the mantle density heterogeneities we develop and apply a method in order to correct the Moho geometry for the contribution of the lithospheric thermal state (i.e., the lithospheric thermal-pressure correction). In addition, the misfit between the isostatic and seismic Moho models, attributed mainly to deep mantle density heterogeneities and other geophysical phenomena, is corrected for by applying the non-isostatic correction. The results reveal that the application of the lithospheric thermal-pressure correction improves the RMS fit of the VMM gravimetric Moho solution to the CRUST1.0 (improves ∼ 1.9 km) and GEMMA (∼1.1 km) models and the point-wise seismic data (∼0.7 km) in South America.

A rapid and non-invasive method for measuring the peak positive pressure of HIFU fields by a laser beam.

PubMed

Wang, Hua; Zeng, Deping; Chen, Ziguang; Yang, Zengtao

2017-04-12

Based on the acousto-optic interaction, we propose a laser deflection method for rapidly, non-invasively and quantitatively measuring the peak positive pressure of HIFU fields. In the characterization of HIFU fields, the effect of nonlinear propagation is considered. The relation between the laser deflection length and the peak positive pressure is derived. Then the laser deflection method is assessed by comparing it with the hydrophone method. The experimental results show that the peak positive pressure measured by laser deflection method is little higher than that obtained by the hydrophone, confirming that they are in reasonable agreement. Considering that the peak pressure measured by hydrophones is always underestimated, the laser deflection method is assumed to be more accurate than the hydrophone method due to the absence of the errors in hydrophone spatial-averaging measurement and the influence of waveform distortion on hydrophone corrections. Moreover, noting that the Lorentz formula still remains applicable to high-pressure environments, the laser deflection method exhibits a great potential for measuring HIFU field under high-pressure amplitude. Additionally, the laser deflection method provides a rapid way for measuring the peak positive pressure, without the scan time, which is required by the hydrophones.

Preliminary Results of an Altitude-Wind-Tunnel Investigation of a TG-100A Gas Turbine-Propeller Engine. V; Combustion-Chamber Characteristics

NASA Technical Reports Server (NTRS)

Gensenheyner, Robert M.; Berdysz, Joseph J.

1947-01-01

An investigation to determine the performance and operational characteristics of the TG-1OOA gas turbine-propeller engine was conducted in the Cleveland altitude wind tunnel. As part of this investigation, the combustion-chamber performance was determined at pressure altitudes from 5000 to 35,000 feet, compressor-inlet rm-pressure ratios of 1.00 and 1.09, and engine speeds from 8000 to 13,000 rpm. Combustion-chamber performance is presented as a function of corrected engine speed and.correcte& horsepower. For the range of corrected engine speeds investigated, over-all total-pressure-loss ratio, cycle efficiency, ana the frac%ional loss in cycle efficiency resulting from pressure losses in the combustion chambers were unaffected by a change in altitude or compressor-inlet ram-pressure ratio. The scatter of combustion- efficiency data tended to obscure any effect of altitude or ram-pressure ratio. For the range of corrected horse-powers investigated, the total-pressure-loss ratio an& the fractional loss in cycle efficiency resulting from pressure losses in the combustion chambers decreased with an increase in corrected horsepower at a constant corrected engine speed. The combustion efficiency remained constant for the range of corrected horse-powers investigated at all corrected engine speeds.

[Research on the method of interference correction for nondispersive infrared multi-component gas analysis].

PubMed

Sun, You-Wen; Liu, Wen-Qing; Wang, Shi-Mei; Huang, Shu-Hua; Yu, Xiao-Man

2011-10-01

A method of interference correction for nondispersive infrared multi-component gas analysis was described. According to the successive integral gas absorption models and methods, the influence of temperature and air pressure on the integral line strengths and linetype was considered, and based on Lorentz detuning linetypes, the absorption cross sections and response coefficients of H2O, CO2, CO, and NO on each filter channel were obtained. The four dimension linear regression equations for interference correction were established by response coefficients, the absorption cross interference was corrected by solving the multi-dimensional linear regression equations, and after interference correction, the pure absorbance signal on each filter channel was only controlled by the corresponding target gas concentration. When the sample cell was filled with gas mixture with a certain concentration proportion of CO, NO and CO2, the pure absorbance after interference correction was used for concentration inversion, the inversion concentration error for CO2 is 2.0%, the inversion concentration error for CO is 1.6%, and the inversion concentration error for NO is 1.7%. Both the theory and experiment prove that the interference correction method proposed for NDIR multi-component gas analysis is feasible.

40 CFR 146.64 - Corrective action for wells in the area of review.

Code of Federal Regulations, 2012 CFR

2012-07-01

... requiring corrective action other than pressure limitations shall include a compliance schedule requiring... require observance of appropriate pressure limitations under paragraph (d)(3) until all other corrective... have been taken. (3) The Director may require pressure limitations in lieu of plugging. If pressure...

Preliminary Results of an Altitude-Wind-Tunnel Investigation of an Axial-Flow Gas Turbine-Propeller Engine. 5; Combustion-Chamber Characterisitcs

NASA Technical Reports Server (NTRS)

Geisenheyner, Robert M.; Berdysz, Joseph J.

1948-01-01

An investigation to determine the performance and operational characteristics of an axial-flow gas turbine-propeller engine was conducted in the Cleveland altitude wind tunnel. As part of this investigation, the combustion-chamber performance was determined at pressure altitudes from 5000 to 35,000 feet, compressor-inlet ram-pressure ratios of 1.00 and 1.09, and engine speeds from 8000 to 13,000 rpm. Combustion-chamber performance is presented as a function of corrected engine speed and corrected horsepower. For the range of corrected engine speeds investigated, overall total-pressure-loss ratio, cycle efficiency, and the fractional loss in cycle efficiency resulting from pressure losses in the combustion chambers were unaffected by a change in altitude or compressor-inlet ram-pressure ratio. For the range of corrected horsepowers investigated, the total-pressure-loss ratio and the fractional loss in cycle efficiency resulting from pressure losses in the combustion chambers decreased with an increase in corrected horsepower at a constant corrected engine speed. The combustion efficiency remained constant for the range of corrected horsepowers investigated at all corrected engine speeds.

Atmospheric Pressure Corrections in Geodesy and Oceanography: a Strategy for Handling Air Tides

NASA Technical Reports Server (NTRS)

Ponte, Rui M.; Ray, Richard D.

2003-01-01

Global pressure data are often needed for processing or interpreting modern geodetic and oceanographic measurements. The most common source of these data is the analysis or reanalysis products of various meteorological centers. Tidal signals in these products can be problematic for several reasons, including potentially aliased sampling of the semidiurnal solar tide as well as the presence of various modeling or timing errors. Building on the work of Van den Dool and colleagues, we lay out a strategy for handling atmospheric tides in (re)analysis data. The procedure also offers a method to account for ocean loading corrections in satellite altimeter data that are consistent with standard ocean-tide corrections. The proposed strategy has immediate application to the on-going Jason-1 and GRACE satellite missions.

An experimental investigation of clocking effects on turbine aerodynamics using a modern 3-D one and one-half stage high pressure turbine for code verification and flow model development

NASA Astrophysics Data System (ADS)

Haldeman, Charles Waldo, IV

2003-10-01

This research uses a modern 1 and 1/2 stage high-pressure (HP) turbine operating at the proper design corrected speed, pressure ratio, and gas to metal temperature ratio to generate a detailed data set containing aerodynamic, heat-transfer and aero-performance information. The data was generated using the Ohio State University Gas Turbine Laboratory Turbine Test Facility (TTF), which is a short-duration shock tunnel facility. The research program utilizes an uncooled turbine stage for which all three airfoils are heavily instrumented at multiple spans and on the HPV and LPV endwalls and HPB platform and tips. Heat-flux and pressure data are obtained using the traditional shock-tube and blowdown facility operational modes. Detailed examination show that the aerodynamic (pressure) data obtained in the blowdown mode is the same as obtained in the shock-tube mode when the corrected conditions are matched. Various experimental conditions and configurations were performed, including LPV clocking positions, off-design corrected speed conditions, pressure ratio changes, and Reynolds number changes. The main research for this dissertation is concentrated on the LPV clocking experiments, where the LPV was clocked relative to the HPV at several different passage locations and at different Reynolds numbers. Various methods were used to evaluate the effect of clocking on both the aeroperformance (efficiency) and aerodynamics (pressure loading) on the LPV, including time-resolved measurements, time-averaged measurements and stage performance measurements. A general improvement in overall efficiency of approximately 2% is demonstrated and could be observed using a variety of independent methods. Maximum efficiency is obtained when the time-average pressures are highest on the LPV, and the time-resolved data both in the time domain and frequency domain show the least amount of variation. The gain in aeroperformance is obtained by integrating over the entire airfoil as the three-dimensional effects on the LPV surface are significant.

Path correction of free flight projectiles by cross firing of subsidiary projectiles

NASA Astrophysics Data System (ADS)

Stroem, L.

1982-10-01

Terminal guidance of gun-fired shells is described. The path is corrected by shooting out throw-bodies from the shell casing. The drawbacks of the method, e.g., casing deformation, were eliminated. Using deflagrating substances instead of explosives, higher impulses were obtained, and at lower pressure levels. At acceleration distances of only 10 to 15 mm throw-body speeds of 400 to 500 m/sec were noted, allowing this method to be applied to rotation-stabilized shells.

Simulating the electrohydrodynamics of a viscous droplet

NASA Astrophysics Data System (ADS)

Theillard, Maxime; Saintillan, David

2016-11-01

We present a novel numerical approach for the simulation of viscous drop placed in an electric field in two and three spatial dimensions. Our method is constructed as a stable projection method on Quad/Octree grids. Using a modified pressure correction we were able to alleviate the standard time step restriction incurred by capillary forces. In weak electric fields, our results match remarkably well with the predictions from the Taylor-Melcher leaky dielectric model. In strong electric fields the so-called Quincke rotation is correctly reproduced.

Clock genes explain large proportion of phenotypic variance in systolic blood pressure and this control is not modified by environmental temperature

USDA-ARS?s Scientific Manuscript database

BACKGROUND: Diurnal variation in blood pressure (BP) is regulated, in part, by an endogenous circadian clock; however, few human studies have identified associations between clock genes and BP. Accounting for environmental temperature may be necessary to correct for seasonal bias. METHODS: We examin...

Calculation of Derivative Thermodynamic Hydration and Aqueous Partial Molar Properties of Ions Based on Atomistic Simulations.

PubMed

Dahlgren, Björn; Reif, Maria M; Hünenberger, Philippe H; Hansen, Niels

2012-10-09

The raw ionic solvation free energies calculated on the basis of atomistic (explicit-solvent) simulations are extremely sensitive to the boundary conditions and treatment of electrostatic interactions used during these simulations. However, as shown recently [Kastenholz, M. A.; Hünenberger, P. H. J. Chem. Phys.2006, 124, 224501 and Reif, M. M.; Hünenberger, P. H. J. Chem. Phys.2011, 134, 144104], the application of an appropriate correction scheme allows for a conversion of the methodology-dependent raw data into methodology-independent results. In this work, methodology-independent derivative thermodynamic hydration and aqueous partial molar properties are calculated for the Na(+) and Cl(-) ions at P° = 1 bar and T(-) = 298.15 K, based on the SPC water model and on ion-solvent Lennard-Jones interaction coefficients previously reoptimized against experimental hydration free energies. The hydration parameters considered are the hydration free energy and enthalpy. The aqueous partial molar parameters considered are the partial molar entropy, volume, heat capacity, volume-compressibility, and volume-expansivity. Two alternative calculation methods are employed to access these properties. Method I relies on the difference in average volume and energy between two aqueous systems involving the same number of water molecules, either in the absence or in the presence of the ion, along with variations of these differences corresponding to finite pressure or/and temperature changes. Method II relies on the calculation of the hydration free energy of the ion, along with variations of this free energy corresponding to finite pressure or/and temperature changes. Both methods are used considering two distinct variants in the application of the correction scheme. In variant A, the raw values from the simulations are corrected after the application of finite difference in pressure or/and temperature, based on correction terms specifically designed for derivative parameters at P° and T(-). In variant B, these raw values are corrected prior to differentiation, based on corresponding correction terms appropriate for the different simulation pressures P and temperatures T. The results corresponding to the different calculation schemes show that, except for the hydration free energy itself, accurate methodological independence and quantitative agreement with even the most reliable experimental parameters (ion-pair properties) are not yet reached. Nevertheless, approximate internal consistency and qualitative agreement with experimental results can be achieved, but only when an appropriate correction scheme is applied, along with a careful consideration of standard-state issues. In this sense, the main merit of the present study is to set a clear framework for these types of calculations and to point toward directions for future improvements, with the ultimate goal of reaching a consistent and quantitative description of single-ion hydration thermodynamics in molecular dynamics simulations.

Ab initio studies of 1,3,5,7-tetranitro-1,3,5,7-tetrazocine/1,3-dimethyl-2-imidazolidinone cocrystal under high pressure using dispersion corrected density functional theory

NASA Astrophysics Data System (ADS)

Gu, Bang-Ming; Lin, He; Zhu, Shun-Guan

2014-04-01

A detailed study of structural, electronic, and thermodynamic properties of 1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)/1,3-dimethyl-2-imidazolidinone (DMI) cocrystal under the hydrostatic pressure of 0-100 GPa was performed by using dispersion-corrected density functional theory (DFT-D) method. The calculated crystal structure is in reasonable agreement with the experimental data at the ambient pressure. Based on the analysis of lattice constants, bond lengths, bond angles, and dihedral angles under compression, it is found that HMX molecules in HMX/DMI cocrystal are seriously distorted. In addition, as the pressure increases, the band gap decreases gradually, which suggests that HMX/DMI cocrystal is becoming more metallic. Some important intermolecular interactions between HMX and DMI are also observed in the density of states spectrum. Finally, its thermodynamic properties were characterized, and the results show that HMX/DMI cocrystal is more easily formed in the low pressure.

Simulation Analysis of Computer-Controlled pressurization for Mixture Ratio Control

NASA Technical Reports Server (NTRS)

Alexander, Leslie A.; Bishop-Behel, Karen; Benfield, Michael P. J.; Kelley, Anthony; Woodcock, Gordon R.

2005-01-01

A procedural code (C++) simulation was developed to investigate potentials for mixture ratio control of pressure-fed spacecraft rocket propulsion systems by measuring propellant flows, tank liquid quantities, or both, and using feedback from these measurements to adjust propellant tank pressures to set the correct operating mixture ratio for minimum propellant residuals. The pressurization system eliminated mechanical regulators in favor of a computer-controlled, servo- driven throttling valve. We found that a quasi-steady state simulation (pressure and flow transients in the pressurization systems resulting from changes in flow control valve position are ignored) is adequate for this purpose. Monte-Carlo methods are used to obtain simulated statistics on propellant depletion. Mixture ratio control algorithms based on proportional-integral-differential (PID) controller methods were developed. These algorithms actually set target tank pressures; the tank pressures are controlled by another PID controller. Simulation indicates this approach can provide reductions in residual propellants.

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.

Comparison of analytical and experimental steadyand unsteady-pressure distributions at Mach number 0.78 for a high-aspect-ratio supercritical wing model with oscillating control surfaces

NASA Technical Reports Server (NTRS)

Mccain, W. E.

1984-01-01

The unsteady aerodynamic lifting surface theory, the Doublet Lattice method, with experimental steady and unsteady pressure measurements of a high aspect ratio supercritical wing model at a Mach number of 0.78 were compared. The steady pressure data comparisons were made for incremental changes in angle of attack and control surface deflection. The unsteady pressure data comparisons were made at set angle of attack positions with oscillating control surface deflections. Significant viscous and transonic effects in the experimental aerodynamics which cannot be predicted by the Doublet Lattice method are shown. This study should assist development of empirical correction methods that may be applied to improve Doublet Lattice calculations of lifting surface aerodynamics.

Numerical simulations of incompressible laminar flows using viscous-inviscid interaction procedures

NASA Astrophysics Data System (ADS)

Shatalov, Alexander V.

The present method is based on Helmholtz velocity decomposition where velocity is written as a sum of irrotational (gradient of a potential) and rotational (correction due to vorticity) components. Substitution of the velocity decomposition into the continuity equation yields an equation for the potential, while substitution into the momentum equations yields equations for the velocity corrections. A continuation approach is used to relate the pressure to the gradient of the potential through a modified Bernoulli's law, which allows the elimination of the pressure variable from the momentum equations. The present work considers steady and unsteady two-dimensional incompressible flows over an infinite cylinder and NACA 0012 airfoil shape. The numerical results are compared against standard methods (stream function-vorticity and SMAC methods) and data available in literature. The results demonstrate that the proposed formulation leads to a good approximation with some possible benefits compared to the available formulations. The method is not restricted to two-dimensional flows and can be used for viscous-inviscid domain decomposition calculations.

Correction of Non-Linear Propagation Artifact in Contrast-Enhanced Ultrasound Imaging of Carotid Arteries: Methods and in Vitro Evaluation.

PubMed

Yildiz, Yesna O; Eckersley, Robert J; Senior, Roxy; Lim, Adrian K P; Cosgrove, David; Tang, Meng-Xing

2015-07-01

Non-linear propagation of ultrasound creates artifacts in contrast-enhanced ultrasound images that significantly affect both qualitative and quantitative assessments of tissue perfusion. This article describes the development and evaluation of a new algorithm to correct for this artifact. The correction is a post-processing method that estimates and removes non-linear artifact in the contrast-specific image using the simultaneously acquired B-mode image data. The method is evaluated on carotid artery flow phantoms with large and small vessels containing microbubbles of various concentrations at different acoustic pressures. The algorithm significantly reduces non-linear artifacts while maintaining the contrast signal from bubbles to increase the contrast-to-tissue ratio by up to 11 dB. Contrast signal from a small vessel 600 μm in diameter buried in tissue artifacts before correction was recovered after the correction. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

A Semi-implicit Method for Time Accurate Simulation of Compressible Flow

NASA Astrophysics Data System (ADS)

Wall, Clifton; Pierce, Charles D.; Moin, Parviz

2001-11-01

A semi-implicit method for time accurate simulation of compressible flow is presented. The method avoids the acoustic CFL limitation, allowing a time step restricted only by the convective velocity. Centered discretization in both time and space allows the method to achieve zero artificial attenuation of acoustic waves. The method is an extension of the standard low Mach number pressure correction method to the compressible Navier-Stokes equations, and the main feature of the method is the solution of a Helmholtz type pressure correction equation similar to that of Demirdžić et al. (Int. J. Num. Meth. Fluids, Vol. 16, pp. 1029-1050, 1993). The method is attractive for simulation of acoustic combustion instabilities in practical combustors. In these flows, the Mach number is low; therefore the time step allowed by the convective CFL limitation is significantly larger than that allowed by the acoustic CFL limitation, resulting in significant efficiency gains. Also, the method's property of zero artificial attenuation of acoustic waves is important for accurate simulation of the interaction between acoustic waves and the combustion process. The method has been implemented in a large eddy simulation code, and results from several test cases will be presented.

Dependence with air density of the response of the PTW SourceCheck ionization chamber for low energy brachytherapy sources

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

Tornero-López, Ana M.; Guirado, Damián; Ruiz-Arrebola, Samuel

2013-12-15

Purpose: Air-communicating well ionization chambers are commonly used to assess air kerma strength of sources used in brachytherapy. The signal produced is supposed to be proportional to the air density within the chamber and, therefore, a density-independent air kerma strength is obtained when the measurement is corrected to standard atmospheric conditions using the usual temperature and pressure correction factor. Nevertheless, when assessing low energy sources, the ionization chambers may not fulfill that condition and a residual density dependence still remains after correction. In this work, the authors examined the behavior of the PTW 34051 SourceCheck ionization chamber when measuring themore » air kerma strength of {sup 125}I seeds.Methods: Four different SourceCheck chambers were analyzed. With each one of them, two series of measurements of the air kerma strength for {sup 125}I selectSeed{sup TM} brachytherapy sources were performed inside a pressure chamber and varying the pressure in a range from 747 to 1040 hPa (560 to 780 mm Hg). The temperature and relative humidity were kept basically constant. An analogous experiment was performed by taking measurements at different altitudes above sea level.Results: Contrary to other well-known ionization chambers, like the HDR1000 PLUS, in which the temperature-pressure correction factor overcorrects the measurements, in the SourceCheck ionization chamber they are undercorrected. At a typical atmospheric situation of 933 hPa (700 mm Hg) and 20 °C, this undercorrection turns out to be 1.5%. Corrected measurements show a residual linear dependence on the density and, as a consequence, an additional density dependent correction must be applied. The slope of this residual linear density dependence is different for each SourceCheck chamber investigated. The results obtained by taking measurements at different altitudes are compatible with those obtained with the pressure chamber.Conclusions: Variations of the altitude and changes in the weather conditions may produce significant density corrections, and that effect should be taken into account. This effect is chamber-dependent, indicating that a specific calibration is necessary for each particular chamber. To our knowledge, this correction has not been considered so far for SourceCheck ionization chambers, but its magnitude cannot be neglected in clinical practice. The atmospheric pressure and temperature at which the chamber was calibrated need to be taken into account, and they should be reported in the calibration certificate. In addition, each institution should analyze the particular response of its SourceCheck ionization chamber and compute the adequate correction factors. In the absence of a suitable pressure chamber, a possibility for this assessment is to take measurements at different altitudes, spanning a wide enough air density range.« less

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.

InSAR Tropospheric Correction Methods: A Statistical Comparison over Different Regions

NASA Astrophysics Data System (ADS)

Bekaert, D. P.; Walters, R. J.; Wright, T. J.; Hooper, A. J.; Parker, D. J.

2015-12-01

Observing small magnitude surface displacements through InSAR is highly challenging, and requires advanced correction techniques to reduce noise. In fact, one of the largest obstacles facing the InSAR community is related to tropospheric noise correction. Spatial and temporal variations in temperature, pressure, and relative humidity result in a spatially-variable InSAR tropospheric signal, which masks smaller surface displacements due to tectonic or volcanic deformation. Correction methods applied today include those relying on weather model data, GNSS and/or spectrometer data. Unfortunately, these methods are often limited by the spatial and temporal resolution of the auxiliary data. Alternatively a correction can be estimated from the high-resolution interferometric phase by assuming a linear or a power-law relationship between the phase and topography. For these methods, the challenge lies in separating deformation from tropospheric signals. We will present results of a statistical comparison of the state-of-the-art tropospheric corrections estimated from spectrometer products (MERIS and MODIS), a low and high spatial-resolution weather model (ERA-I and WRF), and both the conventional linear and power-law empirical methods. We evaluate the correction capability over Southern Mexico, Italy, and El Hierro, and investigate the impact of increasing cloud cover on the accuracy of the tropospheric delay estimation. We find that each method has its strengths and weaknesses, and suggest that further developments should aim to combine different correction methods. All the presented methods are included into our new open source software package called TRAIN - Toolbox for Reducing Atmospheric InSAR Noise (Bekaert et al., in review), which is available to the community Bekaert, D., R. Walters, T. Wright, A. Hooper, and D. Parker (in review), Statistical comparison of InSAR tropospheric correction techniques, Remote Sensing of Environment

Optical measurement of isolated canine lung filtration coefficients at normal hematocrits.

PubMed

Klaesner, J W; Pou, N A; Parker, R E; Finney, C; Roselli, R J

1997-12-01

In this study, lung filtration coefficient (Kfc) values were measured in eight isolated canine lung preparations at normal hematocrit values using three methods: gravimetric, blood-corrected gravimetric, and optical. The lungs were kept in zone 3 conditions and subjected to an average venous pressure increase of 10.24 +/- 0.27 (SE) cmH2O. The resulting Kfc (ml . min-1 . cmH2O-1 . 100 g dry lung wt-1) measured with the gravimetric technique was 0.420 +/- 0.017, which was statistically different from the Kfc measured by the blood-corrected gravimetric method (0.273 +/- 0.018) or the product of the reflection coefficient (sigmaf) and Kfc measured optically (0. 272 +/- 0.018). The optical method involved the use of a Cellco filter cartridge to separate red blood cells from plasma, which allowed measurement of the concentration of the tracer in plasma at normal hematocrits (34 +/- 1.5). The permeability-surface area product was measured using radioactive multiple indicator-dilution methods before, during, and after venous pressure elevations. Results showed that the surface area of the lung did not change significantly during the measurement of Kfc. These studies suggest that sigmafKfc can be measured optically at normal hematocrits, that this measurement is not influenced by blood volume changes that occur during the measurement, and that the optical sigmafKfc agrees with the Kfc obtained via the blood-corrected gravimetric method.

An improved source model for aircraft interior noise studies

NASA Technical Reports Server (NTRS)

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

1985-01-01

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

An improved source model for aircraft interior noise studies

NASA Technical Reports Server (NTRS)

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

1985-01-01

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

Correction to the gas phase pressure term in the continuum model for partially saturated granular media presented by Pietruszczak and co-workers

NASA Astrophysics Data System (ADS)

Iveson, Simon M.

2003-06-01

Pietruszczak and coworkers (Internat. J. Numer. Anal. Methods Geomech. 1994; 18(2):93-105; Comput. Geotech. 1991; 12( ):55-71) have presented a continuum-based model for predicting the dynamic mechanical response of partially saturated granular media with viscous interstitial liquids. In their model they assume that the gas phase is distributed uniformly throughout the medium as discrete spherical air bubbles occupying the voids between the particles. However, their derivation of the air pressure inside these gas bubbles is inconsistent with their stated assumptions. In addition the resultant dependence of gas pressure on liquid saturation lies outside of the plausible range of possible values for discrete air bubbles. This results in an over-prediction of the average bulk modulus of the void phase. Corrected equations are presented.

The digital compensation technology system for automotive pressure sensor

NASA Astrophysics Data System (ADS)

Guo, Bin; Li, Quanling; Lu, Yi; Luo, Zai

2011-05-01

Piezoresistive pressure sensor be made of semiconductor silicon based on Piezoresistive phenomenon, has many characteristics. But since the temperature effect of semiconductor, the performance of silicon sensor is also changed by temperature, and the pressure sensor without temperature drift can not be produced at present. This paper briefly describe the principles of sensors, the function of pressure sensor and the various types of compensation method, design the detailed digital compensation program for automotive pressure sensor. Simulation-Digital mixed signal conditioning is used in this dissertation, adopt signal conditioning chip MAX1452. AVR singlechip ATMEGA128 and other apparatus; fulfill the design of digital pressure sensor hardware circuit and singlechip hardware circuit; simultaneously design the singlechip software; Digital pressure sensor hardware circuit is used to implementing the correction and compensation of sensor; singlechip hardware circuit is used to implementing to controll the correction and compensation of pressure sensor; singlechip software is used to implementing to fulfill compensation arithmetic. In the end, it implement to measure the output of sensor, and contrast to the data of non-compensation, the outcome indicates that the compensation precision of compensated sensor output is obviously better than non-compensation sensor, not only improving the compensation precision but also increasing the stabilization of pressure sensor.

Perspectives for a new realization of the pascal by optical methods

NASA Astrophysics Data System (ADS)

Jousten, Karl; Hendricks, Jay; Barker, Daniel; Douglas, Kevin; Eckel, Steve; Egan, Patrick; Fedchak, James; Flügge, Jens; Gaiser, Christof; Olson, Douglas; Ricker, Jacob; Rubin, Tom; Sabuga, Wladimir; Scherschligt, Julia; Schödel, Rene; Sterr, Uwe; Stone, Jack; Strouse, Gregory

2017-12-01

Since the beginning of measurement of pressure in the 17th century, the unit of pressure has been defined by the relationship of force per unit area. The present state of optical technology now offers the possibility of using a thermodynamic definition—specifically the ideal gas law—for the realization of the pressure unit, in the vacuum regime and slightly above, with an accuracy comparable to or better than the traditional methods of force per area. The changes planned for the SI in 2018 support the application of this thermodynamic definition that is based on the ideal gas law with the necessary corrections for real-gas effects. The paper reviews the theoretical and experimental foundations of those optical methods that are considered to be most promising to realize the unit of pressure at the highest level of metrology.

Apparatus for controlling air/fuel ratio for internal combustion engine

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

Kato, K.; Mizuno, T.

1986-07-08

This patent describes an apparatus for controlling air-fuel ratio of an air-fuel mixture to be supplied to an internal combustion engine having an intake passage, an exhaust passage, an an exhaust gas recirculation passage for recirculating exhaust gases in the exhaust passage to the intake passage therethrough. The apparatus consists of: (a) means for sensing rotational speed of the engine; (b) means for sensing intake pressure in the intake passage; (c) means for sensing atmospheric pressure; (d) means for enabling and disabling exhaust gas recirculation through the exhaust gas recirculation passage in accordance with operating condition of the engine; (e)more » means for determining required amount of fuel in accordance with the sensed rotational speed and the sensed intake pressure; (f) means for determining, when the exhaust gas recirculation is enabled, a first correction value in accordance with the sensed rotational speed, the sensed intake pressure and the sensed atmospheric pressure, the first correction factor being used for correcting fuel amount so as to compensate for the decrease of fuel due to the performance of exhaust gas recirculation and also to compensate for the change in atmospheric pressure; (g) means for determining, when the exhaust gas recirculation is disabled, a second correction value in accordance with the atmospheric pressure, the second correction factor being used so as to compensate for the change in atmospheric pressure; (h) means for correcting the required amount of fuel by the first correction value and the second correction value when the exhaust gas recirculation is enabled and disabled respectively; and (i) means for supplying the engine with the corrected amount of fuel.« less

Biomechanical Analysis of Cuboid Osteotomy Lateral Column Lengthening for Stage II B Adult-Acquired Flatfoot Deformity: A Cadaveric Study.

PubMed

Zhou, Haichao; Ren, Haoyang; Li, Chunguang; Xia, Jiang; Yu, Guangrong; Yang, Yunfeng

2017-01-01

Purpose . To investigate the effect of cuboid osteotomy lateral column lengthening (LCL) for the correction of stage II B adult-acquired flatfoot deformity in cadaver. Methods . Six cadaver specimens were loaded to 350 N. Flatfoot models were established and each was evaluated radiographically and pedobarographically in the following conditions: (1) intact foot, (2) flatfoot, and (3) cuboid osteotomy LCL (2, 3, 4, and 5 mm). Results . Compared with the flatfoot model, the LCLs showed significant correction of talonavicular coverage on anteroposterior radiographs and talus-first metatarsal angle on both anteroposterior and lateral radiographs ( p < .05). Compared with the intact foot, the above angles of the LCLs showed no significant difference except the 2 mm LCL. In terms of forefoot pressure, medial pressure of the 2 mm LCL ( p = .044) and lateral pressure of the 3, 4, and 5 mm LCLs showed statistical differences ( p < .05), but lateral pressure of the 3 mm LCL was not more than the intact foot as compared to the 4 and 5 mm LCLs, which was less than medial pressure. Conclusion . Cuboid osteotomy LCL procedure avoids damage to subtalar joint and has a good effect on correction of stage II B adult-acquired flatfoot deformity with a 3 mm lengthening in cadavers.

Biomechanical Analysis of Cuboid Osteotomy Lateral Column Lengthening for Stage II B Adult-Acquired Flatfoot Deformity: A Cadaveric Study

PubMed Central

Zhou, Haichao; Ren, Haoyang; Li, Chunguang; Xia, Jiang; Yu, Guangrong

2017-01-01

Purpose. To investigate the effect of cuboid osteotomy lateral column lengthening (LCL) for the correction of stage II B adult-acquired flatfoot deformity in cadaver. Methods. Six cadaver specimens were loaded to 350 N. Flatfoot models were established and each was evaluated radiographically and pedobarographically in the following conditions: (1) intact foot, (2) flatfoot, and (3) cuboid osteotomy LCL (2, 3, 4, and 5 mm). Results. Compared with the flatfoot model, the LCLs showed significant correction of talonavicular coverage on anteroposterior radiographs and talus-first metatarsal angle on both anteroposterior and lateral radiographs (p < .05). Compared with the intact foot, the above angles of the LCLs showed no significant difference except the 2 mm LCL. In terms of forefoot pressure, medial pressure of the 2 mm LCL (p = .044) and lateral pressure of the 3, 4, and 5 mm LCLs showed statistical differences (p < .05), but lateral pressure of the 3 mm LCL was not more than the intact foot as compared to the 4 and 5 mm LCLs, which was less than medial pressure. Conclusion. Cuboid osteotomy LCL procedure avoids damage to subtalar joint and has a good effect on correction of stage II B adult-acquired flatfoot deformity with a 3 mm lengthening in cadavers. PMID:28497049

Analysis of pressure distortion testing

NASA Technical Reports Server (NTRS)

Koch, K. E.; Rees, R. L.

1976-01-01

The development of a distortion methodology, method D, was documented, and its application to steady state and unsteady data was demonstrated. Three methodologies based upon DIDENT, a NASA-LeRC distortion methodology based upon the parallel compressor model, were investigated by applying them to a set of steady state data. The best formulation was then applied to an independent data set. The good correlation achieved with this data set showed that method E, one of the above methodologies, is a viable concept. Unsteady data were analyzed by using the method E methodology. This analysis pointed out that the method E sensitivities are functions of pressure defect level as well as corrected speed and pattern.

Ab initio studies of 1,3,5,7-tetranitro-1,3,5,7-tetrazocine/1,3-dimethyl-2-imidazolidinone cocrystal under high pressure using dispersion corrected density functional theory

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

Gu, Bang-Ming; Lin, He; Zhu, Shun-Guan, E-mail: zhusguan@yahoo.com

A detailed study of structural, electronic, and thermodynamic properties of 1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)/1,3-dimethyl-2-imidazolidinone (DMI) cocrystal under the hydrostatic pressure of 0–100 GPa was performed by using dispersion-corrected density functional theory (DFT-D) method. The calculated crystal structure is in reasonable agreement with the experimental data at the ambient pressure. Based on the analysis of lattice constants, bond lengths, bond angles, and dihedral angles under compression, it is found that HMX molecules in HMX/DMI cocrystal are seriously distorted. In addition, as the pressure increases, the band gap decreases gradually, which suggests that HMX/DMI cocrystal is becoming more metallic. Some important intermolecular interactions between HMXmore » and DMI are also observed in the density of states spectrum. Finally, its thermodynamic properties were characterized, and the results show that HMX/DMI cocrystal is more easily formed in the low pressure.« less

An Eulerian/Lagrangian coupling procedure for three-dimensional vortical flows

NASA Technical Reports Server (NTRS)

Felici, Helene M.; Drela, Mark

1993-01-01

A coupled Eulerian/Lagrangian method is presented for the reduction of numerical diffusion observed in solutions of 3D vortical flows using standard Eulerian finite-volume time-marching procedures. A Lagrangian particle tracking method, added to the Eulerian time-marching procedure, provides a correction of the Eulerian solution. In turn, the Eulerian solution is used to integrate the Lagrangian state-vector along the particles trajectories. While the Eulerian solution ensures the conservation of mass and sets the pressure field, the particle markers describe accurately the convection properties and enhance the vorticity and entropy capturing capabilities of the Eulerian solver. The Eulerian/Lagrangian coupling strategies are discussed and the combined scheme is tested on a constant stagnation pressure flow in a 90 deg bend and on a swirling pipe flow. As the numerical diffusion is reduced when using the Lagrangian correction, a vorticity gradient augmentation is identified as a basic problem of this inviscid calculation.

Brady's Geothermal Field - Analysis of Pressure Data

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

Lim, David

*This submission provides corrections to GDR Submissions 844 and 845* Poroelastic Tomography (PoroTomo) by Adjoint Inverse Modeling of Data from Hydrology. The 3 *csv files containing pressure data are the corrected versions of the pressure dataset found in Submission 844. The dataset has been corrected in the sense that the atmospheric pressure has been subtracted from the total pressure measured in the well. Also, the transducers used at wells 56A-1 and SP-2 are sensitive to surface temperature fluctuations. These temperature effects have been removed from the corrected datasets. The 4th *csv file contains corrected version of the pumping data foundmore » in Submission 845. The data has been corrected in the sense that the data from several wells that were used during the PoroTomo deployment pumping tests that were not included in the original dataset has been added. In addition, several other minor changes have been made to the pumping records due to flow rate instrument calibration issues that were discovered.« less

The thermodynamic properties of nitrogen from 65 to 2000 K with pressures to 10,000 atmospheres. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Jacobsen, R. T.

1972-01-01

An equation of state is presented for liquid and gaseous nitrogen for temperatures from 65 degrees K to 2000 degrees K and pressures to 10,000 atmospheres. All the pressure-density-temperature data available from published literature have been corrected and applied to bring experimental temperatures into accord with the International Practical Temperature Scale of 1968. The coefficients of the equation of state were determined by a weighted least squares fit to selected published pressure-density-temperature data. The methods of weighting the various data for simultaneous fitting are presented and discussed.

Managing endotracheal tube cuff pressure at altitude: a comparison of four methods.

PubMed

Britton, Tyler; Blakeman, Thomas C; Eggert, John; Rodriquez, Dario; Ortiz, Heather; Branson, Richard D

2014-09-01

Ascent to altitude results in the expansion of gases in closed spaces. The management of overinflation of the endotracheal tube (ETT) cuff at altitude is critical to prevent mucosal injury. We continuously measured ETT cuff pressures during a Critical Care Air Transport Team training flight to 8,000-ft cabin pressure using four methods of cuff pressure management. ETTs were placed in a tracheal model, and mechanical ventilation was performed. In the control ETT, the cuff was inflated to 20 mm Hg to 22 mm Hg and not manipulated. The manual method used a pressure manometer to adjust pressure at cruising altitude and after landing. A PressureEasy device was connected to the pilot balloon of the third tube and set to a pressure of 20 mm Hg to 22 mm Hg. The final method filled the balloon with 10 mL of saline. Both size 8.0-mm and 7.5-mm ETT were studied during three flights. In the control tube, pressure exceeded 70 mm Hg at cruising altitude. Manual management corrected for pressure at altitude but resulted in low cuff pressures upon landing (<10 mm Hg). The PressureEasy reduced the pressure change to a maximum of 36 mm Hg, but on landing, cuff pressures were less than 15 mm Hg. Saline inflation ameliorated cuff pressure changes at altitude, but initial pressures were 40 mm Hg. None of the three methods using air inflation managed to maintain cuff pressures below those associated with tracheal damage at altitude or above pressures associated with secretion aspiration during descent. Saline inflation minimizes altitude-related alteration in cuff pressure but creates excessive pressures at sea level. New techniques need to be developed.

Tandem Gravimetric and Volumetric Apparatus for Methane Sorption Measurements

NASA Astrophysics Data System (ADS)

Burress, Jacob; Bethea, Donald

Concerns about global climate change have driven the search for alternative fuels. Natural gas (NG, methane) is a cleaner fuel than gasoline and abundantly available due to hydraulic fracturing. One hurdle to the adoption of NG vehicles is the bulky cylindrical storage vessels needed to store the NG at high pressures (3600 psi, 250 bar). The adsorption of methane in microporous materials can store large amounts of methane at low enough pressures for the allowance of conformable, ``flat'' pressure vessels. The measurement of the amount of gas stored in sorbent materials is typically done by measuring pressure differences (volumetric, manometric) or masses (gravimetric). Volumetric instruments of the Sievert type have uncertainties that compound with each additional measurement. Therefore, the highest-pressure measurement has the largest uncertainty. Gravimetric instruments don't have that drawback, but can have issues with buoyancy corrections. An instrument will be presented with which methane adsorption measurements can be performed using both volumetric and gravimetric methods in tandem. The gravimetric method presented has no buoyancy corrections and low uncertainty. Therefore, the gravimetric measurements can be performed throughout an entire isotherm or just at the extrema to verify the results from the volumetric measurements. Results from methane sorption measurements on an activated carbon (MSC-30) and a metal-organic framework (Cu-BTC, HKUST-1, MOF-199) will be shown. New recommendations for calculations of gas uptake and uncertainty measurements will be discussed.

A stable and high-order accurate discontinuous Galerkin based splitting method for the incompressible Navier-Stokes equations

NASA Astrophysics Data System (ADS)

Piatkowski, Marian; Müthing, Steffen; Bastian, Peter

2018-03-01

In this paper we consider discontinuous Galerkin (DG) methods for the incompressible Navier-Stokes equations in the framework of projection methods. In particular we employ symmetric interior penalty DG methods within the second-order rotational incremental pressure correction scheme. The major focus of the paper is threefold: i) We propose a modified upwind scheme based on the Vijayasundaram numerical flux that has favourable properties in the context of DG. ii) We present a novel postprocessing technique in the Helmholtz projection step based on H (div) reconstruction of the pressure correction that is computed locally, is a projection in the discrete setting and ensures that the projected velocity satisfies the discrete continuity equation exactly. As a consequence it also provides local mass conservation of the projected velocity. iii) Numerical results demonstrate the properties of the scheme for different polynomial degrees applied to two-dimensional problems with known solution as well as large-scale three-dimensional problems. In particular we address second-order convergence in time of the splitting scheme as well as its long-time stability.

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

Winter, J.R.; Keywood, S.S.

PTFE-based gaskets in chemical plant service typically fail in an extrusion mode, sometimes referred to as blowout. Test work previously published by Monsanto indicated that correctly installed PTFE-based gaskets have pressure performance far exceeding system pressure ratings. These results have since been confirmed by extensive testing at the Montreal based Ecole Polytechnique Tightness Testing and Research Laboratory (TTRL), funded by a consortium of gasket users and manufacturers. With the knowledge that properly installed gaskets can withstand system pressures in excess of 1,000 psig [6,894 kPa], failures at two chemical plants were re-examined. This analysis indicates that extrusion type failures canmore » be caused by excessive internal pressures, associated with sections of pipe having an external source of heat coincident with a blocked flow condition. This results in high system pressures which explain the extrusion type failures observed. The paper discusses details of individual failures and examines methods to prevent them. Other causes for extrusion failures are reviewed, with a recommendation that stronger gasket materials not be utilized to correct problems until it is verified that excessive pressure build-up is not the problem. Also summarized are the requirements for proper installation to achieve the potential blowout resistance found in these gaskets.« less

Experimental demonstration of passive acoustic imaging in the human skull cavity using CT-based aberration corrections

PubMed Central

Jones, Ryan M.; O’Reilly, Meaghan A.; Hynynen, Kullervo

2015-01-01

Purpose: Experimentally verify a previously described technique for performing passive acoustic imaging through an intact human skull using noninvasive, computed tomography (CT)-based aberration corrections Jones et al. [Phys. Med. Biol. 58, 4981–5005 (2013)]. Methods: A sparse hemispherical receiver array (30 cm diameter) consisting of 128 piezoceramic discs (2.5 mm diameter, 612 kHz center frequency) was used to passively listen through ex vivo human skullcaps (n = 4) to acoustic emissions from a narrow-band fixed source (1 mm diameter, 516 kHz center frequency) and from ultrasound-stimulated (5 cycle bursts, 1 Hz pulse repetition frequency, estimated in situ peak negative pressure 0.11–0.33 MPa, 306 kHz driving frequency) Definity™ microbubbles flowing through a thin-walled tube phantom. Initial in vivo feasibility testing of the method was performed. The performance of the method was assessed through comparisons to images generated without skull corrections, with invasive source-based corrections, and with water-path control images. Results: For source locations at least 25 mm from the inner skull surface, the modified reconstruction algorithm successfully restored a single focus within the skull cavity at a location within 1.25 mm from the true position of the narrow-band source. The results obtained from imaging single bubbles are in good agreement with numerical simulations of point source emitters and the authors’ previous experimental measurements using source-based skull corrections O’Reilly et al. [IEEE Trans. Biomed. Eng. 61, 1285–1294 (2014)]. In a rat model, microbubble activity was mapped through an intact human skull at pressure levels below and above the threshold for focused ultrasound-induced blood–brain barrier opening. During bursts that led to coherent bubble activity, the location of maximum intensity in images generated with CT-based skull corrections was found to deviate by less than 1 mm, on average, from the position obtained using source-based corrections. Conclusions: Taken together, these results demonstrate the feasibility of using the method to guide bubble-mediated ultrasound therapies in the brain. The technique may also have application in ultrasound-based cerebral angiography. PMID:26133635

Transonic pressure measurements and comparison of theory to experiment for an arrow-wing configuration. Volume 1: Experimental data report, base configuration and effects of wing twist and leading-edge configuration. [wind tunnel tests, aircraft models

NASA Technical Reports Server (NTRS)

Manro, M. E.; Manning, K. J. R.; Hallstaff, T. H.; Rogers, J. T.

1975-01-01

A wind tunnel test of an arrow-wing-body configuration consisting of flat and twisted wings, as well as a variety of leading- and trailing-edge control surface deflections, was conducted at Mach numbers from 0.4 to 1.1 to provide an experimental pressure data base for comparison with theoretical methods. Theory-to-experiment comparisons of detailed pressure distributions were made using current state-of-the-art attached and separated flow methods. The purpose of these comparisons was to delineate conditions under which these theories are valid for both flat and twisted wings and to explore the use of empirical methods to correct the theoretical methods where theory is deficient.

Analysis of Arterial and Venous Blood Gases in Healthy Gyr Falcons ( Falco rusticolus ) Under Anesthesia.

PubMed

Raghav, Raj; Middleton, Rachael; BSc, Rinshiya Ahamed; Arjunan, Raji; Caliendo, Valentina

2015-12-01

Arterial and venous blood gas analysis is useful in the assessment of tissue oxygenation and ventilation and in diagnosis of metabolic and respiratory derangements. It can be performed with a relatively small volume of blood in avian patients under emergency situations. Arterial and venous blood gas analysis was performed in 30 healthy gyr falcons ( Falco rusticolus ) under anaesthesia to establish temperature-corrected reference intervals for arterial blood gas values and to compare them to temperature-corrected venous blood gas values with a portable point-of-care blood gas analyzer (i-STAT 1, Abbott Laboratories, Abbott Park, IL, USA). Statistically significant differences were observed between the temperature-corrected values of pH, partial pressure of carbon dioxide (Pco2), and partial pressure of oxygen (Po2) and the corresponding nontemperature-corrected values of these parameters in both arterial and venous blood. Values of temperature-corrected pH, temperature-corrected Pco2, bicarbonate concentrations, and base excess of extra cellular fluid did not differ significantly between arterial and venous blood, suggesting that, in anesthetized gyr falcons, venous blood gas analysis can be used in place of arterial blood gas analysis in clinical situations. Values for hematocrit, measured by the point-of-care analyzer, were significantly lower compared with those obtained by the microhematocrit method.

A Non-Invasive Assessment of Cardiopulmonary Hemodynamics with MRI in Pulmonary Hypertension

PubMed Central

Bane, Octavia; Shah, Sanjiv J.; Cuttica, Michael J.; Collins, Jeremy D.; Selvaraj, Senthil; Chatterjee, Neil R.; Guetter, Christoph; Carr, James C.; Carroll, Timothy J.

2015-01-01

Purpose We propose a method for non-invasive quantification of hemodynamic changes in the pulmonary arteries resulting from pulmonary hypertension (PH). Methods Using a two-element windkessel model, and input parameters derived from standard MRI evaluation of flow, cardiac function and valvular motion, we derive: pulmonary artery compliance (C), mean pulmonary artery pressure (mPAP), pulmonary vascular resistance (PVR), pulmonary capillary wedge pressure (PCWP), time-averaged intra-pulmonary pressure waveforms and pulmonary artery pressures (systolic (sPAP) and diastolic (dPAP)). MRI results were compared directly to reference standard values from right heart catheterization (RHC) obtained in a series of patients with suspected pulmonary hypertension (PH). Results In 7 patients with suspected PH undergoing RHC, MRI and echocardiography, there was no statistically significant difference (p<0.05) between parameters measured by MRI and RHC. Using standard clinical cutoffs to define PH (mPAP ≥ 25 mmHg), MRI was able to correctly identify all patients as having pulmonary hypertension, and to correctly distinguish between pulmonary arterial (mPAP≥ 25 mmHg, PCWP<15 mmHg) and venous hypertension (mPAP ≥ 25 mmHg, PCWP ≥ 15 mmHg) in 5 of 7 cases. Conclusions We have developed a mathematical model capable of quantifying physiological parameters that reflect the severity of PH. PMID:26283577

Development of a Pressure Sensitive Paint System with Correction for Temperature Variation

NASA Technical Reports Server (NTRS)

Simmons, Kantis A.

1995-01-01

Pressure Sensitive Paint (PSP) is known to provide a global image of pressure over a model surface. However, improvements in its accuracy and reliability are needed. Several factors contribute to the inaccuracy of PSP. One major factor is that luminescence is temperature dependent. To correct the luminescence of the pressure sensing component for changes in temperature, a temperature sensitive luminophore incorporated in the paint allows the user to measure both pressure and temperature simultaneously on the surface of a model. Magnesium Octaethylporphine (MgOEP) was used as a temperature sensing luminophore, with the pressure sensing luminophore, Platinum Octaethylporphine (PtOEP), to correct for temperature variations in model surface pressure measurements.

Passive tire pressure sensor and method

DOEpatents

Pfeifer, Kent Bryant; Williams, Robert Leslie; Waldschmidt, Robert Lee; Morgan, Catherine Hook

2006-08-29

A surface acoustic wave device includes a micro-machined pressure transducer for monitoring tire pressure. The device is configured having a micro-machined cavity that is sealed with a flexible conductive membrane. When an external tire pressure equivalent to the cavity pressure is detected, the membrane makes contact with ridges on the backside of the surface acoustic wave device. The ridges are electrically connected to conductive fingers of the device. When the detected pressure is correct, selected fingers on the device will be grounded producing patterned acoustic reflections to an impulse RF signal. When the external tire pressure is less than the cavity reference pressure, a reduced reflected signal to the receiver results. The sensor may further be constructed so as to identify itself by a unique reflected identification pulse series.

Passive tire pressure sensor and method

DOEpatents

Pfeifer, Kent Bryant; Williams, Robert Leslie; Waldschmidt, Robert Lee; Morgan, Catherine Hook

2007-09-04

A surface acoustic wave device includes a micro-machined pressure transducer for monitoring tire pressure. The device is configured having a micro-machined cavity that is sealed with a flexible conductive membrane. When an external tire pressure equivalent to the cavity pressure is detected, the membrane makes contact with ridges on the backside of the surface acoustic wave device. The ridges are electrically connected to conductive fingers of the device. When the detected pressure is correct, selected fingers on the device will be grounded producing patterned acoustic reflections to an impulse RF signal. When the external tire pressure is less than the cavity reference pressure, a reduced reflected signal to the receiver results. The sensor may further be constructed so as to identify itself by a unique reflected identification pulse series.

Jet-boundary and Plan-form Corrections for Partial-Span Models with Reflection-Plane, End-Plate, or No End-Plate in a Closed Circular Wind Tunnel

NASA Technical Reports Server (NTRS)

Sivells, James C; Deters, Owen J

1946-01-01

A method is presented for determining the jet-boundary and plan-form corrections necessary for application to test data for a partial-span model with a reflection plane, an end plate, or no end plate in a closed circular wind tunnel. Examples are worked out for a partial-span model with each of the three end conditions in the Langley 19-foot pressure tunnel and the corrections are applied to measured values of lift, drag, pitching-moment, rolling-moment, and yawing-moment coefficients.

A Full-Core Resonance Self-Shielding Method Using a Continuous-Energy Quasi–One-Dimensional Slowing-Down Solution that Accounts for Temperature-Dependent Fuel Subregions and Resonance Interference

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

Liu, Yuxuan; Martin, William; Williams, Mark

In this paper, a correction-based resonance self-shielding method is developed that allows annular subdivision of the fuel rod. The method performs the conventional iteration of the embedded self-shielding method (ESSM) without subdivision of the fuel to capture the interpin shielding effect. The resultant self-shielded cross sections are modified by correction factors incorporating the intrapin effects of radial variation of the shielded cross section, radial temperature distribution, and resonance interference. A quasi–one-dimensional slowing-down equation is developed to calculate such correction factors. The method is implemented in the DeCART code and compared with the conventional ESSM and subgroup method with benchmark MCNPmore » results. The new method yields substantially improved results for both spatially dependent reaction rates and eigenvalues for typical pressurized water reactor pin cell cases with uniform and nonuniform fuel temperature profiles. Finally, the new method is also proved effective in treating assembly heterogeneity and complex material composition such as mixed oxide fuel, where resonance interference is much more intense.« less

A wall interference assessment/correction system

NASA Technical Reports Server (NTRS)

Lo, Ching F.; Overby, Glenn; Qian, Cathy X.; Sickles, W. L.; Ulbrich, N.

1992-01-01

A Wall Signature method originally developed by Hackett has been selected to be adapted for the Ames 12-ft Wind Tunnel WIAC system in the project. This method uses limited measurements of the static pressure at the wall, in conjunction with the solid wall boundary condition, to determine the strength and distribution of singularities representing the test article. The singularities are used in turn for estimating blockage wall interference. The lifting interference will be treated separately by representing in a horseshoe vortex system for the model's lifting effects. The development and implementation of a working prototype will be completed, delivered and documented with a software manual. The WIAC code will be validated by conducting numerically simulated experiments rather than actual wind tunnel experiments. The simulations will be used to generate both free-air and confined wind-tunnel flow fields for each of the test articles over a range of test configurations. Specifically, the pressure signature at the test section wall will be computed for the tunnel case to provide the simulated 'measured' data. These data will serve as the input for the WIAC method--Wall Signature method. The performance of the WIAC method then may be evaluated by comparing the corrected data with those of the free-air simulation.

75 FR 10410 - Alternate Fracture Toughness Requirements for Protection Against Pressurized Thermal Shock Events...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-08

... Toughness Requirements for Protection Against Pressurized Thermal Shock Events; Correcting Amendment AGENCY... Commission (NRC) is revising its regulations to add a table that was inadvertently omitted in a correction... toughness requirements for protection against pressurized thermal shock (PTS) events for pressurized water...

Investigation of Convection and Pressure Treatment with Splitting Techniques

NASA Technical Reports Server (NTRS)

Thakur, Siddharth; Shyy, Wei; Liou, Meng-Sing

1995-01-01

Treatment of convective and pressure fluxes in the Euler and Navier-Stokes equations using splitting formulas for convective velocity and pressure is investigated. Two schemes - controlled variation scheme (CVS) and advection upstream splitting method (AUSM) - are explored for their accuracy in resolving sharp gradients in flows involving moving or reflecting shock waves as well as a one-dimensional combusting flow with a strong heat release source term. For two-dimensional compressible flow computations, these two schemes are implemented in one of the pressure-based algorithms, whose very basis is the separate treatment of convective and pressure fluxes. For the convective fluxes in the momentum equations as well as the estimation of mass fluxes in the pressure correction equation (which is derived from the momentum and continuity equations) of the present algorithm, both first- and second-order (with minmod limiter) flux estimations are employed. Some issues resulting from the conventional use in pressure-based methods of a staggered grid, for the location of velocity components and pressure, are also addressed. Using the second-order fluxes, both CVS and AUSM type schemes exhibit sharp resolution. Overall, the combination of upwinding and splitting for the convective and pressure fluxes separately exhibits robust performance for a variety of flows and is particularly amenable for adoption in pressure-based methods.

Some ideas and opportunities concerning three-dimensional wind-tunnel wall corrections

NASA Technical Reports Server (NTRS)

Rubbert, P. E.

1982-01-01

Opportunities for improving the accuracy and reliability of wall corrections in conventional ventilated test sections are presented. The approach encompasses state-of-the-art technology in transonic computational methods combined with the measurement of tunnel-wall pressures. The objective is to arrive at correction procedures of known, verifiable accuracy that are practical within a production testing environment. It is concluded that: accurate and reliable correction procedures can be developed for cruise-type aerodynamic testing for any wall configuration; passive walls can be optimized for minimal interference for cruise-type aerodynamic testing (tailored slots, variable open area ratio, etc.); monitoring and assessment of noncorrectable interference (buoyancy and curvature in a transonic stream) can be an integral part of a correction procedure; and reasonably good correction procedures can probably be developd for complex flows involving extensive separation and other unpredictable phenomena.

Analysis of Cricoid Pressure Force and Technique Among Anesthesiologists, Nurse Anesthetists, and Registered Nurses.

PubMed

Lefave, Melissa; Harrell, Brad; Wright, Molly

2016-06-01

The purpose of this project was to assess the ability of anesthesiologists, nurse anesthetists, and registered nurses to correctly identify anatomic landmarks of cricoid pressure and apply the correct amount of force. The project included an educational intervention with one group pretest-post-test design. Participants demonstrated cricoid pressure on a laryngotracheal model. After an educational intervention video, participants were asked to repeat cricoid pressure on the model. Participants with a nurse anesthesia background applied more appropriate force pretest than other participants; however, post-test results, while improved, showed no significant difference among providers. Participant identification of the correct anatomy of the cricoid cartilage and application of correct force were significantly improved after education. This study revealed that participants lacked prior knowledge of correct cricoid anatomy and pressure as well as the ability to apply correct force to the laryngotracheal model before an educational intervention. The intervention used in this study proved successful in educating health care providers. Copyright © 2016 American Society of PeriAnesthesia Nurses. Published by Elsevier Inc. All rights reserved.

An improved method for predicting brittleness of rocks via well logs in tight oil reservoirs

NASA Astrophysics Data System (ADS)

Wang, Zhenlin; Sun, Ting; Feng, Cheng; Wang, Wei; Han, Chuang

2018-06-01

There can be no industrial oil production in tight oil reservoirs until fracturing is undertaken. Under such conditions, the brittleness of the rocks is a very important factor. However, it has so far been difficult to predict. In this paper, the selected study area is the tight oil reservoirs in Lucaogou formation, Permian, Jimusaer sag, Junggar basin. According to the transformation of dynamic and static rock mechanics parameters and the correction of confining pressure, an improved method is proposed for quantitatively predicting the brittleness of rocks via well logs in tight oil reservoirs. First, 19 typical tight oil core samples are selected in the study area. Their static Young’s modulus, static Poisson’s ratio and petrophysical parameters are measured. In addition, the static brittleness indices of four other tight oil cores are measured under different confining pressure conditions. Second, the dynamic Young’s modulus, Poisson’s ratio and brittleness index are calculated using the compressional and shear wave velocity. With combination of the measured and calculated results, the transformation model of dynamic and static brittleness index is built based on the influence of porosity and clay content. The comparison of the predicted brittleness indices and measured results shows that the model has high accuracy. Third, on the basis of the experimental data under different confining pressure conditions, the amplifying factor of brittleness index is proposed to correct for the influence of confining pressure on the brittleness index. Finally, the above improved models are applied to formation evaluation via well logs. Compared with the results before correction, the results of the improved models agree better with the experimental data, which indicates that the improved models have better application effects. The brittleness index prediction method of tight oil reservoirs is improved in this research. It is of great importance in the optimization of fracturing layer and fracturing construction schemes and the improvement of oil recovery.

An efficient mass-preserving interface-correction level set/ghost fluid method for droplet suspensions under depletion forces

NASA Astrophysics Data System (ADS)

Ge, Zhouyang; Loiseau, Jean-Christophe; Tammisola, Outi; Brandt, Luca

2018-01-01

Aiming for the simulation of colloidal droplets in microfluidic devices, we present here a numerical method for two-fluid systems subject to surface tension and depletion forces among the suspended droplets. The algorithm is based on an efficient solver for the incompressible two-phase Navier-Stokes equations, and uses a mass-conserving level set method to capture the fluid interface. The four novel ingredients proposed here are, firstly, an interface-correction level set (ICLS) method; global mass conservation is achieved by performing an additional advection near the interface, with a correction velocity obtained by locally solving an algebraic equation, which is easy to implement in both 2D and 3D. Secondly, we report a second-order accurate geometric estimation of the curvature at the interface and, thirdly, the combination of the ghost fluid method with the fast pressure-correction approach enabling an accurate and fast computation even for large density contrasts. Finally, we derive a hydrodynamic model for the interaction forces induced by depletion of surfactant micelles and combine it with a multiple level set approach to study short-range interactions among droplets in the presence of attracting forces.

Correction of static pressure on a research aircraft in accelerated flight using differential pressure measurements

NASA Astrophysics Data System (ADS)

Rodi, A. R.; Leon, D. C.

2012-11-01

A method is described that estimates the error in the static pressure measurement on an aircraft from differential pressure measurements on the hemispherical surface of a Rosemount model 858AJ air velocity probe mounted on a boom ahead of the aircraft. The theoretical predictions for how the pressure should vary over the surface of the hemisphere, involving an unknown sensitivity parameter, leads to a set of equations that can be solved for the unknowns - angle of attack, angle of sideslip, dynamic pressure and the error in static pressure - if the sensitivity factor can be determined. The sensitivity factor was determined on the University of Wyoming King Air research aircraft by comparisons with the error measured with a carefully designed sonde towed on connecting tubing behind the aircraft - a trailing cone - and the result was shown to have a precision of about ±10 Pa over a wide range of conditions, including various altitudes, power settings, and gear and flap extensions. Under accelerated flight conditions, geometric altitude data from a combined Global Navigation Satellite System (GNSS) and inertial measurement unit (IMU) system are used to estimate acceleration effects on the error, and the algorithm is shown to predict corrections to a precision of better than ±20 Pa under those conditions. Some limiting factors affecting the precision of static pressure measurement on a research aircraft are discussed.

Error correction in multi-fidelity molecular dynamics simulations using functional uncertainty quantification

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

Reeve, Samuel Temple; Strachan, Alejandro, E-mail: strachan@purdue.edu

We use functional, Fréchet, derivatives to quantify how thermodynamic outputs of a molecular dynamics (MD) simulation depend on the potential used to compute atomic interactions. Our approach quantifies the sensitivity of the quantities of interest with respect to the input functions as opposed to its parameters as is done in typical uncertainty quantification methods. We show that the functional sensitivity of the average potential energy and pressure in isothermal, isochoric MD simulations using Lennard–Jones two-body interactions can be used to accurately predict those properties for other interatomic potentials (with different functional forms) without re-running the simulations. This is demonstrated undermore » three different thermodynamic conditions, namely a crystal at room temperature, a liquid at ambient pressure, and a high pressure liquid. The method provides accurate predictions as long as the change in potential can be reasonably described to first order and does not significantly affect the region in phase space explored by the simulation. The functional uncertainty quantification approach can be used to estimate the uncertainties associated with constitutive models used in the simulation and to correct predictions if a more accurate representation becomes available.« less

Isolating Curvature Effects in Computing Wall-Bounded Turbulent Flows

NASA Technical Reports Server (NTRS)

Rumsey, Christopher L.; Gatski, Thomas B.

2001-01-01

The flow over the zero-pressure-gradient So-Mellor convex curved wall is simulated using the Navier-Stokes equations. An inviscid effective outer wall shape, undocumented in the experiment, is obtained by using an adjoint optimization method with the desired pressure distribution on the inner wall as the cost function. Using this wall shape with a Navier-Stokes method, the abilities of various turbulence models to simulate the effects of curvature without the complicating factor of streamwise pressure gradient can be evaluated. The one-equation Spalart-Allmaras turbulence model overpredicts eddy viscosity, and its boundary layer profiles are too full. A curvature-corrected version of this model improves results, which are sensitive to the choice of a particular constant. An explicit algebraic stress model does a reasonable job predicting this flow field. However, results can be slightly improved by modifying the assumption on anisotropy equilibrium in the model's derivation. The resulting curvature-corrected explicit algebraic stress model possesses no heuristic functions or additional constants. It lowers slightly the computed skin friction coefficient and the turbulent stress levels for this case (in better agreement with experiment), but the effect on computed velocity profiles is very small.

Incompressible material point method for free surface flow

NASA Astrophysics Data System (ADS)

Zhang, Fan; Zhang, Xiong; Sze, Kam Yim; Lian, Yanping; Liu, Yan

2017-02-01

To overcome the shortcomings of the weakly compressible material point method (WCMPM) for modeling the free surface flow problems, an incompressible material point method (iMPM) is proposed based on operator splitting technique which splits the solution of momentum equation into two steps. An intermediate velocity field is first obtained by solving the momentum equations ignoring the pressure gradient term, and then the intermediate velocity field is corrected by the pressure term to obtain a divergence-free velocity field. A level set function which represents the signed distance to free surface is used to track the free surface and apply the pressure boundary conditions. Moreover, an hourglass damping is introduced to suppress the spurious velocity modes which are caused by the discretization of the cell center velocity divergence from the grid vertexes velocities when solving pressure Poisson equations. Numerical examples including dam break, oscillation of a cubic liquid drop and a droplet impact into deep pool show that the proposed incompressible material point method is much more accurate and efficient than the weakly compressible material point method in solving free surface flow problems.

An Experimental Investigation of the Flow Physics Associated With End Wall Losses and Large Rotor Tip Clearances as Found in the Rear Stages of a High Pressure Compressor

NASA Technical Reports Server (NTRS)

Berdanier, Reid A.; Key, Nicole L.

2015-01-01

The focus of this work was to characterize the fundamental flow physics and the overall performance effects due to increased rotor tip clearance heights in axial compressors. Data have been collected in the three-stage axial research compressor at Purdue University with a specific focus on analyzing the multistage effects resulting from the tip leakage flow. Three separate rotor tip clearance heights were studied with nominal tip clearance heights of 1.5%, 3.0%, and 4.0% based on a constant annulus height. Overall compressor performance was investigated at four corrected speedlines (100%, 90%, 80%, and 68%) for each of the three tip clearance configurations using total pressure and total temperature rakes distributed throughout the compressor. The results have confirmed results from previous authors showing a decrease of total pressure rise, isentropic efficiency, and stall margin which is approximately linear with increasing tip clearance height. The stall inception mechanisms have also been evaluated at the same corrected speeds for each of the tip clearance configurations. Detailed flow field measurements have been collected at two loading conditions, nominal loading (NL) and high loading (HL), on the 100% corrected speedline for the smallest and largest tip clearance heights (1.5% and 4.0%). Steady detailed radial traverses of total pressure at the exit of each stator row have been supported by flow visualization techniques to identify regions of flow recirculation and separation. Furthermore, detailed radial traverses of time-resolved total pressures at the exit of each rotor row have been measured with a fast-response pressure probe. These data have helped to quantify the size of the leakage flow at the exit of each rotor. Thermal anemometry has also been implemented to evaluate the time-resolved three-dimensional components of velocity throughout the compressor and calculate blockage due to the rotor tip leakage flow throughout the compressor. These measurements have also been used to calculate streamwise vorticity. Time-resolved static pressure measurements have been collected over the rotor tips for all rotors with each of the three tip clearance configurations for up to five loading conditions along the 100% corrected speedline using fast-response piezoresistive pressure sensors. These time-resolved static pressure measurements, as well as the time-resolved total pressures and velocities have helped to reveal a profound influence of the upstream stator vane on the size and shape of the rotor tip leakage flow. Finally, a novel particle image velocimetry (PIV) technique has been developed as a proof-of- concept. In contrast to PIV methods that have been typically been utilized for turbomachinery applications in the past, the method used for this study introduced the laser light through the same access window that was also used to image the flow. This new method addresses potential concerns related to the intrusive laser-introducing techniques that have typically been utilized by other authors in the past. Ultimately, the data collected for this project represent a unique data set which contributes to build a better understanding of the tip leakage flow field and its associated loss mechanisms. These data will facilitate future engine design goals leading to small blade heights in the rear stages of high pressure compressors and aid in the development of new blade designs which are desensitized to the performance penalties attributed to rotor tip leakage flows.

Study of the integration of wind tunnel and computational methods for aerodynamic configurations

NASA Technical Reports Server (NTRS)

Browne, Lindsey E.; Ashby, Dale L.

1989-01-01

A study was conducted to determine the effectiveness of using a low-order panel code to estimate wind tunnel wall corrections. The corrections were found by two computations. The first computation included the test model and the surrounding wind tunnel walls, while in the second computation the wind tunnel walls were removed. The difference between the force and moment coefficients obtained by comparing these two cases allowed the determination of the wall corrections. The technique was verified by matching the test-section, wall-pressure signature from a wind tunnel test with the signature predicted by the panel code. To prove the viability of the technique, two cases were considered. The first was a two-dimensional high-lift wing with a flap that was tested in the 7- by 10-foot wind tunnel at NASA Ames Research Center. The second was a 1/32-scale model of the F/A-18 aircraft which was tested in the low-speed wind tunnel at San Diego State University. The panel code used was PMARC (Panel Method Ames Research Center). Results of this study indicate that the proposed wind tunnel wall correction method is comparable to other methods and that it also inherently includes the corrections due to model blockage and wing lift.

Method and system for turbomachinery surge detection

DOEpatents

Faymon, David K.; Mays, Darrell C.; Xiong, Yufei

2004-11-23

A method and system for surge detection within a gas turbine engine, comprises: measuring the compressor discharge pressure (CDP) of the gas turbine over a period of time; determining a time derivative (CDP.sub.D ) of the measured (CDP) correcting the CDP.sub.D for altitude, (CDP.sub.DCOR); estimating a short-term average of CDP.sub.DCOR.sup.2 ; estimating a short-term average of CDP.sub.DCOR ; and determining a short-term variance of corrected CDP rate of change (CDP.sub.roc) based upon the short-term average of CDP.sub.DCOR and the short-term average of CDP.sub.DCOR.sup.2. The method and system then compares the short-term variance of corrected CDP rate of change with a pre-determined threshold (CDP.sub.proc) and signals an output when CDP.sub.roc >CDP.sub.proc. The method and system provides a signal of a surge within the gas turbine engine when CDP.sub.roc remains>CDP.sub.proc for pre-determined period of time.

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

Martínez-Ruiz, F. J.; Blas, F. J., E-mail: felipe@uhu.es; Centro de Investigación de Física Teórica y Matemática, Universidad de Huelva, 21071 Huelva

We propose an extension of the improved version of the inhomogeneous long-range corrections of Janeček [J. Phys. Chem. B 110, 6264–6269 (2006)], presented recently by MacDowell and Blas [J. Chem. Phys. 131, 074705 (2009)] to account for the intermolecular potential energy of spherical, rigid, and flexible molecular systems, to deal with the contributions to the microscopic components of the pressure tensor due to the dispersive long-range corrections. We have performed Monte Carlo simulations in the canonical ensemble to obtain the interfacial properties of spherical Lennard-Jones molecules with different cutoff distances, r{sub c} = 2.5, 3, 4, and 5σ. In addition,more » we have also considered cutoff distances r{sub c} = 2.5 and 3σ in combination with the inhomogeneous long-range corrections proposed in this work. The normal and tangential microscopic components of the pressure tensor are obtained using the mechanical or virial route in combination with the recipe of Irving and Kirkwood, while the macroscopic components are calculated using the Volume Perturbation thermodynamic route proposed by de Miguel and Jackson [J. Chem. Phys. 125, 164109 (2006)]. The vapour-liquid interfacial tension is evaluated using three different procedures, the Irving-Kirkwood method, the difference between the macroscopic components of the pressure tensor, and the Test-Area methodology. In addition to the pressure tensor and the surface tension, we also obtain density profiles, coexistence densities, vapour pressure, critical temperature and density, and interfacial thickness as functions of temperature, paying particular attention to the effect of the cutoff distance and the long-range corrections on these properties. According to our results, the main effect of increasing the cutoff distance (at fixed temperature) is to sharpen the vapour-liquid interface, to decrease the vapour pressure, and to increase the width of the biphasic coexistence region. As a result, the interfacial thickness decreases, the width of the tangential microscopic component of the pressure tensor profile increases, and the surface tension increases as the cutoff distance is larger. We have also checked the effect of the impulsive contribution to the pressure due to the discontinuity of the intermolecular interaction potential when it is cut. If this contribution is not accounted for in the calculation of the microscopic components of the pressure tensor, incorrect values of both components as well as a wrong structure along the vapour-liquid interface are obtained.« less

Air-braked cycle ergometers: validity of the correction factor for barometric pressure.

PubMed

Finn, J P; Maxwell, B F; Withers, R T

2000-10-01

Barometric pressure exerts by far the greatest influence of the three environmental factors (barometric pressure, temperature and humidity) on power outputs from air-braked ergometers. The barometric pressure correction factor for power outputs from air-braked ergometers is in widespread use but apparently has never been empirically validated. Our experiment validated this correction factor by calibrating two air-braked cycle ergometers in a hypobaric chamber using a dynamic calibration rig. The results showed that if the power output correction for changes in air resistance at barometric pressures corresponding to altitudes of 38, 600, 1,200 and 1,800 m above mean sea level were applied, then the coefficients of variation were 0.8-1.9% over the range of 160-1,597 W. The overall mean error was 3.0 % but this included up to 0.73 % for the propagated error that was associated with errors in the measurement of: a) temperature b) relative humidity c) barometric pressure d) force, distance and angular velocity by the dynamic calibration rig. The overall mean error therefore approximated the +/- 2.0% of true load that was specified by the Laboratory Standards Assistance Scheme of the Australian Sports Commission. The validity of the correction factor for barometric pressure on power output was therefore demonstrated over the altitude range of 38-1,800 m.

Experimental demonstration of passive acoustic imaging in the human skull cavity using CT-based aberration corrections.

PubMed

Jones, Ryan M; O'Reilly, Meaghan A; Hynynen, Kullervo

2015-07-01

Experimentally verify a previously described technique for performing passive acoustic imaging through an intact human skull using noninvasive, computed tomography (CT)-based aberration corrections Jones et al. [Phys. Med. Biol. 58, 4981-5005 (2013)]. A sparse hemispherical receiver array (30 cm diameter) consisting of 128 piezoceramic discs (2.5 mm diameter, 612 kHz center frequency) was used to passively listen through ex vivo human skullcaps (n = 4) to acoustic emissions from a narrow-band fixed source (1 mm diameter, 516 kHz center frequency) and from ultrasound-stimulated (5 cycle bursts, 1 Hz pulse repetition frequency, estimated in situ peak negative pressure 0.11-0.33 MPa, 306 kHz driving frequency) Definity™ microbubbles flowing through a thin-walled tube phantom. Initial in vivo feasibility testing of the method was performed. The performance of the method was assessed through comparisons to images generated without skull corrections, with invasive source-based corrections, and with water-path control images. For source locations at least 25 mm from the inner skull surface, the modified reconstruction algorithm successfully restored a single focus within the skull cavity at a location within 1.25 mm from the true position of the narrow-band source. The results obtained from imaging single bubbles are in good agreement with numerical simulations of point source emitters and the authors' previous experimental measurements using source-based skull corrections O'Reilly et al. [IEEE Trans. Biomed. Eng. 61, 1285-1294 (2014)]. In a rat model, microbubble activity was mapped through an intact human skull at pressure levels below and above the threshold for focused ultrasound-induced blood-brain barrier opening. During bursts that led to coherent bubble activity, the location of maximum intensity in images generated with CT-based skull corrections was found to deviate by less than 1 mm, on average, from the position obtained using source-based corrections. Taken together, these results demonstrate the feasibility of using the method to guide bubble-mediated ultrasound therapies in the brain. The technique may also have application in ultrasound-based cerebral angiography.

Direct means of obtaining CAVI0-a corrected cardio-ankle vascular stiffness index (CAVI)-from conventional CAVI measurements or their underlying variables.

PubMed

Spronck, Bart; Mestanik, Michal; Tonhajzerova, Ingrid; Jurko, Alexander; Jurko, Tomas; Avolio, Alberto P; Butlin, Mark

2017-09-21

Cardio-ankle vascular index (CAVI) as measured using the VaSera device (CAVI VS , Fukuda Denshi), has been proposed as a stiffness index that does not depend on blood pressure. We have recently shown theoretically that CAVI VS still exhibits blood pressure dependence, and proposed the corrected index CAVI 0 . The present study aims to establish a method of calculating [Formula: see text] either (i) from VaSera-reported values of cardiac-brachial and brachial-ankle pulse transit times (tb and tba, respectively) and blood pressure, or (ii) directly from CAVI VS . To derive this method, the relationship among CAVI VS and its scale constants a and b, tb, tba, and blood pressure has to be established. From data of 497 subjects, eight candidate CAVI parameters were defined and calculated, containing all combinations of left or right tb/tba/blood pressure. Candidates were evaluated through correlation with measured left and right CAVI VS . Correlations were compared statistically. Once the correct candidates were determined, two constants (a and b) required for converting CAVI VS to CAVI 0 were estimated through linear regression. Left and right CAVI VS are calculated using left and right tba; however, both left and right CAVI VS are calculated using right brachial blood pressures and right tb. Constants a and b for conversion of CAVI VS to CAVI 0 were estimated to be 0.842 [0.836 0.848] and 0.753 [0.721 0.786] (mean [95%CI]), respectively. Equations to estimate CAVI 0 from CAVI VS , and to directly calculate CAVI 0 from the VaSera output are provided in this paper, as well as in a directly usable spreadsheet supplement. Our results permit straightforward calculation of [Formula: see text] during a study, as well as retrospective estimation of [Formula: see text] from CAVI VS in already published studies or where the original transit time values are not available, paving the way for thorough comparison of CAVI 0 to CAVI VS in clinical and research settings. Novelty and significance Cardio-ankle vascular index (CAVI) as measured using the VaSera device (CAVI VS , Fukuda Denshi), has been proposed as a blood pressure-independent arterial stiffness index. We have recently shown theoretically that CAVI VS still exhibits pressure dependence, and proposed a corrected index, CAVI 0 . In the present study, we derived equations to directly obtain CAVI 0 using data from the VaSera device. Our results permit straightforward calculation of [Formula: see text] during a study, as well as retrospective estimation of [Formula: see text] from CAVI VS in already published studies, paving the way for thorough comparison of CAVI 0 to CAVI VS in clinical and research settings.

40 CFR 144.55 - Corrective action.

Code of Federal Regulations, 2012 CFR

2012-07-01

... the case of Class II wells operating over the fracture pressure of the injection formation, all known wells within the area of review penetrating formations affected by the increase in pressure. For such... injection until all required corrective action has been taken. (3) Injection pressure limitation. The...

40 CFR 144.55 - Corrective action.

Code of Federal Regulations, 2011 CFR

2011-07-01

... the case of Class II wells operating over the fracture pressure of the injection formation, all known wells within the area of review penetrating formations affected by the increase in pressure. For such... injection until all required corrective action has been taken. (3) Injection pressure limitation. The...

40 CFR 144.55 - Corrective action.

Code of Federal Regulations, 2013 CFR

2013-07-01

... the case of Class II wells operating over the fracture pressure of the injection formation, all known wells within the area of review penetrating formations affected by the increase in pressure. For such... injection until all required corrective action has been taken. (3) Injection pressure limitation. The...

40 CFR 144.55 - Corrective action.

Code of Federal Regulations, 2014 CFR

2014-07-01

... the case of Class II wells operating over the fracture pressure of the injection formation, all known wells within the area of review penetrating formations affected by the increase in pressure. For such... injection until all required corrective action has been taken. (3) Injection pressure limitation. The...

77 FR 2928 - Airworthiness Directives; Airbus Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-01-20

... pressure hose and electrical wiring of the green electrical motor pump (EMP). This proposed AD would... for correct condition and installation of hydraulic pressure hoses, electrical conduits, feeder cables... detect and correct chafing of hydraulic pressure hoses and electrical wiring of the green EMPs, which in...

Capillary pressure-saturation relationships for porous granular materials: Pore morphology method vs. pore unit assembly method

NASA Astrophysics Data System (ADS)

Sweijen, Thomas; Aslannejad, Hamed; Hassanizadeh, S. Majid

2017-09-01

In studies of two-phase flow in complex porous media it is often desirable to have an estimation of the capillary pressure-saturation curve prior to measurements. Therefore, we compare in this research the capability of three pore-scale approaches in reproducing experimentally measured capillary pressure-saturation curves. To do so, we have generated 12 packings of spheres that are representative of four different glass-bead packings and eight different sand packings, for which we have found experimental data on the capillary pressure-saturation curve in the literature. In generating the packings, we matched the particle size distributions and porosity values of the granular materials. We have used three different pore-scale approaches for generating the capillary pressure-saturation curves of each packing: i) the Pore Unit Assembly (PUA) method in combination with the Mayer and Stowe-Princen (MS-P) approximation for estimating the entry pressures of pore throats, ii) the PUA method in combination with the hemisphere approximation, and iii) the Pore Morphology Method (PMM) in combination with the hemisphere approximation. The three approaches were also used to produce capillary pressure-saturation curves for the coating layer of paper, used in inkjet printing. Curves for such layers are extremely difficult to determine experimentally, due to their very small thickness and the presence of extremely small pores (less than one micrometer in size). Results indicate that the PMM and PUA-hemisphere method give similar capillary pressure-saturation curves, because both methods rely on a hemisphere to represent the air-water interface. The ability of the hemisphere approximation and the MS-P approximation to reproduce correct capillary pressure seems to depend on the type of particle size distribution, with the hemisphere approximation working well for narrowly distributed granular materials.

STC-SAB program users manual for the turbulent boundary layer and turbulent separation prediction methods employed in the NASA Langley streamtube curvature computer program

NASA Technical Reports Server (NTRS)

Ferguson, D. R.

1972-01-01

The streamtube curvature program (STC) has been developed to predict the inviscid flow field and the pressure distribution about nacelles at transonic speeds. The effects of boundary layer are to displace the inviscid flow and effectively change the body shape. Thus, the body shape must be corrected by the displacement thickness in order to calculate the correct pressure distribution. This report describes the coupling of the Stratford and Beavers boundary layer solution with the inviscid STC analysis so that all nacelle pressure forces, friction drag, and incipient separation may be predicted. The usage of the coupled STC-SAB computer program is outlined and the program input and output are defined. Included in this manual are descriptions of the principal boundary layer tables and other revisions to the STC program. The use of the viscous option is controlled by the engineer during program input definition.

Stable and Spectrally Accurate Schemes for the Navier-Stokes Equations

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

Jia, Jun; Liu, Jie

2011-01-01

In this paper, we present an accurate, efficient and stable numerical method for the incompressible Navier-Stokes equations (NSEs). The method is based on (1) an equivalent pressure Poisson equation formulation of the NSE with proper pressure boundary conditions, which facilitates the design of high-order and stable numerical methods, and (2) the Krylov deferred correction (KDC) accelerated method of lines transpose (mbox MoL{sup T}), which is very stable, efficient, and of arbitrary order in time. Numerical tests with known exact solutions in three dimensions show that the new method is spectrally accurate in time, and a numerical order of convergence 9more » was observed. Two-dimensional computational results of flow past a cylinder and flow in a bifurcated tube are also reported.« less

An approximate method for calculating three-dimensional inviscid hypersonic flow fields

NASA Technical Reports Server (NTRS)

Riley, Christopher J.; Dejarnette, Fred R.

1990-01-01

An approximate solution technique was developed for 3-D inviscid, hypersonic flows. The method employs Maslen's explicit pressure equation in addition to the assumption of approximate stream surfaces in the shock layer. This approximation represents a simplification to Maslen's asymmetric method. The present method presents a tractable procedure for computing the inviscid flow over 3-D surfaces at angle of attack. The solution procedure involves iteratively changing the shock shape in the subsonic-transonic region until the correct body shape is obtained. Beyond this region, the shock surface is determined using a marching procedure. Results are presented for a spherically blunted cone, paraboloid, and elliptic cone at angle of attack. The calculated surface pressures are compared with experimental data and finite difference solutions of the Euler equations. Shock shapes and profiles of pressure are also examined. Comparisons indicate the method adequately predicts shock layer properties on blunt bodies in hypersonic flow. The speed of the calculations makes the procedure attractive for engineering design applications.

Cerebral responses to innocuous somatic pressure stimulation following aerobic exercise rehabilitation in chronic pain patients: a functional magnetic resonance imaging study

PubMed Central

Micalos, Peter S; Korgaonkar, Mayuresh S; Drinkwater, Eric J; Cannon, Jack; Marino, Frank E

2014-01-01

Objective The purpose of this research was to assess the functional brain activity and perceptual rating of innocuous somatic pressure stimulation before and after exercise rehabilitation in patients with chronic pain. Materials and methods Eleven chronic pain patients and eight healthy pain-free controls completed 12 weeks of supervised aerobic exercise intervention. Perceptual rating of standardized somatic pressure stimulation (2 kg) on the right anterior mid-thigh and brain responses during functional magnetic resonance imaging (fMRI) were assessed at pre- and postexercise rehabilitation. Results There was a significant difference in the perceptual rating of innocuous somatic pressure stimulation between the chronic pain and control groups (P=0.02) but no difference following exercise rehabilitation. Whole brain voxel-wise analysis with correction for multiple comparisons revealed trends for differences in fMRI responses between the chronic pain and control groups in the superior temporal gyrus (chronic pain > control, corrected P=0.30), thalamus, and caudate (control > chronic, corrected P=0.23). Repeated measures of the regions of interest (5 mm radius) for blood oxygen level-dependent signal response revealed trend differences for superior temporal gyrus (P=0.06), thalamus (P=0.04), and caudate (P=0.21). Group-by-time interactions revealed trend differences in the caudate (P=0.10) and superior temporal gyrus (P=0.29). Conclusion Augmented perceptual and brain responses to innocuous somatic pressure stimulation were shown in the chronic pain group compared to the control group; however, 12-weeks of exercise rehabilitation did not significantly attenuate these responses. PMID:25210471

Fracture Sustainability Pressure, Temperature, Differential Pressure, and Aperture Closure Data

DOE Data Explorer

Tim Kneafsey

2016-09-30

In these data sets, the experiment time, actual date and time, room temperature, sample temperature, upstream and downstream pressures (measured independently), corrected differential pressure (measured independently and corrected for offset and room temperature) indication of aperture closure by linear variable differential transformer are presented. An indication of the sample is in the file name and in the first line of data.

Elevation correction factor for absolute pressure measurements

NASA Technical Reports Server (NTRS)

Panek, Joseph W.; Sorrells, Mark R.

1996-01-01

With the arrival of highly accurate multi-port pressure measurement systems, conditions that previously did not affect overall system accuracy must now be scrutinized closely. Errors caused by elevation differences between pressure sensing elements and model pressure taps can be quantified and corrected. With multi-port pressure measurement systems, the sensing elements are connected to pressure taps that may be many feet away. The measurement system may be at a different elevation than the pressure taps due to laboratory space or test article constraints. This difference produces a pressure gradient that is inversely proportional to height within the interface tube. The pressure at the bottom of the tube will be higher than the pressure at the top due to the weight of the tube's column of air. Tubes with higher pressures will exhibit larger absolute errors due to the higher air density. The above effect is well documented but has generally been taken into account with large elevations only. With error analysis techniques, the loss in accuracy from elevation can be easily quantified. Correction factors can be applied to maintain the high accuracies of new pressure measurement systems.

Scalability and performance of data-parallel pressure-based multigrid methods for viscous flows

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

Blosch, E.L.; Shyy, W.

1996-05-01

A full-approximation storage multigrid method for solving the steady-state 2-d incompressible Navier-Stokes equations on staggered grids has been implemented in Fortran on the CM-5, using the array aliasing feature in CM-Fortran to avoid declaring fine-grid-sized arrays on all levels while still allowing a variable number of grid levels. Thus, the storage cost scales with the number of unknowns, allowing us to consider significantly larger problems than would otherwise be possible. Timings over a range of problem sizes and numbers of processors, up to 4096 x 4096 on 512 nodes, show that the smoothing procedure, a pressure-correction technique, is scalable andmore » that the restriction and prolongation steps are nearly so. The performance obtained for the multigrid method is 333 Mflops out of the theoretical peak 4 Gflops on a 32-node CM-5. In comparison, a single-grid computation obtained 420 Mflops. The decrease is due to the inefficiency of the smoothing iterations on the coarse grid levels. W cycles cost much more and are much less efficient than V cycles, due to the increased contribution from the coarse grids. The convergence rate characteristics of the pressure-correction multigrid method are investigated in a Re = 5000 lid-driven cavity flow and a Re = 300 symmetric backward-facing step flow, using either a defect-correction scheme or a second-order upwind scheme. A heuristic technique relating the convergence tolerances for the course grids to the truncation error of the discretization has been found effective and robust. With second-order upwinding on all grid levels, a 5-level 320 x 80 step flow solution was obtained in 20 V cycles, which corresponds to a smoothing rate of 0.7, and required 25 s on a 32-node CM-5. Overall, the convergence rates obtained in the present work are comparable to the most competitive findings reported in the literature. 62 refs., 13 figs.« less

Scalability and Performance of Data-Parallel Pressure-Based Multigrid Methods for Viscous Flows

NASA Astrophysics Data System (ADS)

Blosch, Edwin L.; Shyy, Wei

1996-05-01

A full-approximation storage multigrid method for solving the steady-state 2-dincompressible Navier-Stokes equations on staggered grids has been implemented in Fortran on the CM-5,using the array aliasing feature in CM-Fortran to avoid declaring fine-grid-sized arrays on all levels while still allowing a variable number of grid levels. Thus, the storage cost scales with the number of unknowns,allowing us to consider significantly larger problems than would otherwise be possible. Timings over a range of problem sizes and numbers of processors, up to 4096 × 4096 on 512 nodes, show that the smoothing procedure, a pressure-correction technique, is scalable and that the restriction and prolongation steps are nearly so. The performance obtained for the multigrid method is 333 Mflops out of the theoretical peak 4 Gflops on a 32-node CM-5. In comparison, a single-grid computation obtained 420 Mflops. The decrease is due to the inefficiency of the smoothing iterations on the coarse grid levels. W cycles cost much more and are much less efficient than V cycles, due to the increased contribution from the coarse grids. The convergence rate characteristics of the pressure-correction multigrid method are investigated in a Re = 5000 lid-driven cavity flow and a Re = 300 symmetric backward-facing step flow, using either a defect-correction scheme or a second-order upwind scheme. A heuristic technique relating the convergence tolerances for the coarse grids to the truncation error of the discretization has been found effective and robust. With second-order upwinding on all grid levels, a 5-level 320× 80 step flow solution was obtained in 20 V cycles, which corresponds to a smoothing rate of 0.7, and required 25 s on a 32-node CM-5. Overall, the convergence rates obtained in the present work are comparable to the most competitive findings reported in the literature.

Molecular-dynamics evaluation of fluid-phase equilibrium properties by a novel free-energy perturbation approach: Application to gas solubility and vapor pressure of liquid hexane

NASA Astrophysics Data System (ADS)

Kuwajima, Satoru; Kikuchi, Hiroaki; Fukuda, Mitsuhiro

2006-03-01

A novel free-energy perturbation method is developed for the computation of the free energy of transferring a molecule between fluid phases. The methodology consists in drawing a free-energy profile of the target molecule moving across a binary-phase structure built in the computer. The novelty of the method lies in the difference of the definition of the free-energy profile from the common definition. As an important element of the method, the process of making a correction to the transfer free energy with respect to the cutoff of intermolecular forces is elucidated. In order to examine the performance of the method in the application to fluid-phase equilibrium properties, molecular-dynamics computations are carried out for the evaluation of gas solubility and vapor pressure of liquid n-hexane at 298.15K. The gas species treated are methane, ethane, propane, and n-butane, with the gas solubility expressed as Henry's constant. It is shown that the method works fine and calculated results are generally in good agreement with experiments. It is found that the cutoff correction is strikingly large, constituting a dominant part of the calculated transfer free energy at the cutoff of 8Å.

Method of controlling a variable geometry type turbocharger

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

Hirabayashi, Y.

1988-08-23

This patent describes a method of controlling the supercharging pressure of a variable geometry type turbocharger having a bypass, comprising the following steps which are carried out successively: receiving signals from an engine speed sensor and from an engine knocking sensor; receiving a signal from a throttle valve sensor; judging whether or not an engine is being accelerated, and proceeding to step below if the engine is being accelerated and to step below if the engine is not being accelerated, i.e., if the engine is in a constant speed operation; determining a first correction value and proceeding to step below;more » judging whether or not the engine is knocking, and proceeding to step (d) if knocking is occurring and to step (f) below if no knocking is occurring; determining a second correction value and proceeding to step; receiving signals from the engine speed sensor and from an airflow meter which measures the quantity of airflow to be supplied to the engine; calculating an airflow rate per engine revolution; determining a duty valve according to the calculated airflow rate; transmitting the corrected duty value to control means for controlling the geometry of the variable geometry type turbocharger and the opening of bypass of the turbocharger, thereby controlling the supercharging pressure of the turbocharger.« less

Investigation of Unsteady Pressure-Sensitive Paint (uPSP) and a Dynamic Loads Balance to Predict Launch Vehicle Buffet Environments

NASA Technical Reports Server (NTRS)

Schuster, David M.; Panda, Jayanta; Ross, James C.; Roozeboom, Nettie H.; Burnside, Nathan J.; Ngo, Christina L.; Kumagai, Hiro; Sellers, Marvin; Powell, Jessica M.; Sekula, Martin K.;

Monitoring of intracranial compliance: correction for a change in body position.

PubMed

Raabe, A; Czosnyka, M; Piper, I; Seifert, V

1999-01-01

The objectives of our study were 1. to investigate whether the intracranial compliance changes with body position; 2. to test if the pressure-volume index (PVI) calculation is affected by different body positions; 3. to define the optimal parameter to correct PVI for changes in body position and 4. to investigate the physiological meaning of the constant term (P0) in the model of the intracranial volume-pressure relationship. Thirteen patients were included in this study. All patients were subjected to 2 to 3 different body positions. In each position, either classic bolus injection was performed for measurement of intracranial compliance and calculation of PVI or the new Spiegelberg compliance monitor was used to calculate PVI continuously. Four different models were used for calculating the constant pressure term P0 and the P0 corrected PVI values. Pressure volume index not corrected for the constant term P0 significantly decreased with elevating the patients head (r = 0.70, p < 0.0001). In contrast, volume-pressure response and ICP pulse amplitude did not change with position. Using the constant term P0 to correct the PVI we found no changes between the different body positions. Our results suggest that during the variation in body position there is no change in intracranial compliance but a change in hydrostatic offset pressure which causes a shifting of the volume-pressure curve along the pressure axis without its shape being affected. PVI measurements should either be performed only with the patient in the 0 degree recumbent position or that the PVI calculation should be corrected for the hydrostatic difference between the level of the ICP transducer and the hydrostatic indifference point of the craniospinal system close to the third thoracic vertebra.

Self-Correcting Electronically-Scanned Pressure Sensor

NASA Technical Reports Server (NTRS)

Gross, C.; Basta, T.

1982-01-01

High-data-rate sensor automatically corrects for temperature variations. Multichannel, self-correcting pressure sensor can be used in wind tunnels, aircraft, process controllers and automobiles. Offers data rates approaching 100,000 measurements per second with inaccuracies due to temperature shifts held below 0.25 percent (nominal) of full scale over a temperature span of 55 degrees C.

Direct calculation of wall interferences and wall adaptation for two-dimensional flow in wind tunnels with closed walls

NASA Technical Reports Server (NTRS)

Amecke, Juergen

1986-01-01

A method for the direct calculation of the wall induced interference velocity in two dimensional flow based on Cauchy's integral formula was derived. This one-step method allows the calculation of the residual corrections and the required wall adaptation for interference-free flow starting from the wall pressure distribution without any model representation. Demonstrated applications are given.

Increasing Accuracy in Computed Inviscid Boundary Conditions

NASA Technical Reports Server (NTRS)

Dyson, Roger

2004-01-01

A technique has been devised to increase the accuracy of computational simulations of flows of inviscid fluids by increasing the accuracy with which surface boundary conditions are represented. This technique is expected to be especially beneficial for computational aeroacoustics, wherein it enables proper accounting, not only for acoustic waves, but also for vorticity and entropy waves, at surfaces. Heretofore, inviscid nonlinear surface boundary conditions have been limited to third-order accuracy in time for stationary surfaces and to first-order accuracy in time for moving surfaces. For steady-state calculations, it may be possible to achieve higher accuracy in space, but high accuracy in time is needed for efficient simulation of multiscale unsteady flow phenomena. The present technique is the first surface treatment that provides the needed high accuracy through proper accounting of higher-order time derivatives. The present technique is founded on a method known in art as the Hermitian modified solution approximation (MESA) scheme. This is because high time accuracy at a surface depends upon, among other things, correction of the spatial cross-derivatives of flow variables, and many of these cross-derivatives are included explicitly on the computational grid in the MESA scheme. (Alternatively, a related method other than the MESA scheme could be used, as long as the method involves consistent application of the effects of the cross-derivatives.) While the mathematical derivation of the present technique is too lengthy and complex to fit within the space available for this article, the technique itself can be characterized in relatively simple terms: The technique involves correction of surface-normal spatial pressure derivatives at a boundary surface to satisfy the governing equations and the boundary conditions and thereby achieve arbitrarily high orders of time accuracy in special cases. The boundary conditions can now include a potentially infinite number of time derivatives of surface-normal velocity (consistent with no flow through the boundary) up to arbitrarily high order. The corrections for the first-order spatial derivatives of pressure are calculated by use of the first-order time derivative velocity. The corrected first-order spatial derivatives are used to calculate the second- order time derivatives of velocity, which, in turn, are used to calculate the corrections for the second-order pressure derivatives. The process as described is repeated, progressing through increasing orders of derivatives, until the desired accuracy is attained.

A fluid-structure interaction model of the internal carotid and ophthalmic arteries for the noninvasive intracranial pressure measurement method.

PubMed

Misiulis, Edgaras; Džiugys, Algis; Navakas, Robertas; Striūgas, Nerijus

2017-05-01

Accurate and clinically safe measurements of intracranial pressure (ICP) are crucial for secondary brain damage prevention. There are two methods of ICP measurement: invasive and noninvasive. Invasive methods are clinically unsafe; therefore, safer noninvasive methods are being developed. One of the noninvasive ICP measurement methods implements the balance principle, which assumes that if the velocity of blood flow in both ophthalmic artery segments - the intracranial (IOA) and extracranial (EOA) - is equal, then the acting ICP on the IOA and the external pressure (Pe) on the EOA are also equal. To investigate the assumption of the balance principle, a generalized computational model incorporating a fluid-structure interaction (FSI) module was created and used to simulate noninvasive ICP measurement by accounting for the time-dependent behavior of the elastic internal carotid (ICA) and ophthalmic (OA) arteries and their interaction with pulsatile blood flow. It was found that the extra balance pressure term, which incorporates the hydrodynamic pressure drop between measurement points, must be added into the balance equation, and the corrections on a difference between the velocity of blood flow in the IOA and EOA must be made, due to a difference in the blood flow rate. Copyright © 2017 Elsevier Ltd. All rights reserved.

Open-path FTIR data reduction algorithm with atmospheric absorption corrections: the NONLIN code

NASA Astrophysics Data System (ADS)

Phillips, William; Russwurm, George M.

1999-02-01

This paper describes the progress made to date in developing, testing, and refining a data reduction computer code, NONLIN, that alleviates many of the difficulties experienced in the analysis of open path FTIR data. Among the problems that currently effect FTIR open path data quality are: the inability to obtain a true I degree or background, spectral interferences of atmospheric gases such as water vapor and carbon dioxide, and matching the spectral resolution and shift of the reference spectra to a particular field instrument. This algorithm is based on a non-linear fitting scheme and is therefore not constrained by many of the assumptions required for the application of linear methods such as classical least squares (CLS). As a result, a more realistic mathematical model of the spectral absorption measurement process can be employed in the curve fitting process. Applications of the algorithm have proven successful in circumventing open path data reduction problems. However, recent studies, by one of the authors, of the temperature and pressure effects on atmospheric absorption indicate there exist temperature and water partial pressure effects that should be incorporated into the NONLIN algorithm for accurate quantification of gas concentrations. This paper investigates the sources of these phenomena. As a result of this study a partial pressure correction has been employed in NONLIN computer code. Two typical field spectra are examined to determine what effect the partial pressure correction has on gas quantification.

Measurement of attenuation coefficients of the fundamental and second harmonic waves in water

NASA Astrophysics Data System (ADS)

Zhang, Shuzeng; Jeong, Hyunjo; Cho, Sungjong; Li, Xiongbing

2016-02-01

Attenuation corrections in nonlinear acoustics play an important role in the study of nonlinear fluids, biomedical imaging, or solid material characterization. The measurement of attenuation coefficients in a nonlinear regime is not easy because they depend on the source pressure and requires accurate diffraction corrections. In this work, the attenuation coefficients of the fundamental and second harmonic waves which come from the absorption of water are measured in nonlinear ultrasonic experiments. Based on the quasilinear theory of the KZK equation, the nonlinear sound field equations are derived and the diffraction correction terms are extracted. The measured sound pressure amplitudes are adjusted first for diffraction corrections in order to reduce the impact on the measurement of attenuation coefficients from diffractions. The attenuation coefficients of the fundamental and second harmonics are calculated precisely from a nonlinear least squares curve-fitting process of the experiment data. The results show that attenuation coefficients in a nonlinear condition depend on both frequency and source pressure, which are much different from a linear regime. In a relatively lower drive pressure, the attenuation coefficients increase linearly with frequency. However, they present the characteristic of nonlinear growth in a high drive pressure. As the diffraction corrections are obtained based on the quasilinear theory, it is important to use an appropriate source pressure for accurate attenuation measurements.

Correlated environmental corrections in TOPEX/POSEIDON, with a note on ionospheric accuracy

NASA Technical Reports Server (NTRS)

Zlotnicki, V.

1994-01-01

Estimates of the effectiveness of an altimetric correction, and interpretation of sea level variability as a response to atmospheric forcing, both depend upon assuming that residual errors in altimetric corrections are uncorrelated among themselves and with residual sea level, or knowing the correlations. Not surprisingly, many corrections are highly correlated since they involve atmospheric properties and the ocean surface's response to them. The full corrections (including their geographically varying time mean values), show correlations between electromagnetic bias (mostly the height of wind waves) and either atmospheric pressure or water vapor of -40%, and between atmospheric pressure and water vapor of 28%. In the more commonly used collinear differences (after removal of the geographically varying time mean), atmospheric pressure and wave height show a -30% correlation, atmospheric pressure and water vapor a -10% correlation, both pressure and water vapor a 7% correlation with residual sea level, and a bit surprisingly, ionospheric electron content and wave height a 15% correlation. Only the ocean tide is totally uncorrelated with other corrections or residual sea level. The effectiveness of three ionospheric corrections (TOPEX dual-frequency, a smoothed version of the TOPEX dual-frequency, and Doppler orbitography and radiopositioning integrated by satellite (DORIS) is also evaluated in terms of their reduction in variance of residual sea level. Smooth (90-200 km along-track) versions of the dual-frequency altimeter ionosphere perform best both globally and within 20 deg in latitude from the equator. The noise variance in the 1/s TOPEX inospheric samples is approximately (11 mm) squared, about the same as noise in the DORIS-based correction; however, the latter has its error over scales of order 10(exp 3) km. Within 20 deg of the equator, the DORIS-based correction adds (14 mm) squared to the residual sea level variance.

Nanowire growth kinetics in aberration corrected environmental transmission electron microscopy

DOE PAGES

Chou, Yi -Chia; Panciera, Federico; Reuter, Mark C.; ...

2016-03-15

Here, we visualize atomic level dynamics during Si nanowire growth using aberration corrected environmental transmission electron microscopy, and compare with lower pressure results from ultra-high vacuum microscopy. We discuss the importance of higher pressure observations for understanding growth mechanisms and describe protocols to minimize effects of the higher pressure background gas.

Matrix effect and correction by standard addition in quantitative liquid chromatographic-mass spectrometric analysis of diarrhetic shellfish poisoning toxins.

PubMed

Ito, Shinya; Tsukada, Katsuo

2002-01-11

An evaluation of the feasibility of liquid chromatography-mass spectrometry (LC-MS) with atmospheric pressure ionization was made for quantitation of four diarrhetic shellfish poisoning toxins, okadaic acid, dinophysistoxin-1, pectenotoxin-6 and yessotoxin in scallops. When LC-MS was applied to the analysis of scallop extracts, large signal suppressions were observed due to coeluting substances from the column. To compensate for these matrix signal suppressions, the standard addition method was applied. First, the sample was analyzed and then the sample involving the addition of calibration standards is analyzed. Although this method requires two LC-MS runs per analysis, effective correction of quantitative errors was found.

Absorption of infrared radiation by carbon monoxide at elevated temperatures and pressures: Part B. Total emissivity charts and correlations

NASA Astrophysics Data System (ADS)

Alberti, Michael; Weber, Roman; Mancini, Marco

2017-10-01

The line-by-line procedure developed in the associated paper (Part A ) has been used to generate the total emissivity chart for pure CO and CO -N2 /air mixtures at 1 bar total pressure, in the 300 to 3000 K temperature and 0.01 to 3000 bar cm pressure path length range. Methods of scaling the emissivity to pressures different to 1 bar, in the range 0.1 to 40 bar, are provided through pressure correction graphs and EXCEL interpolator (Supplementary Material). The interpolated emissivities are within ± 2% margin from the line-by-line calculated values. The newly developed emissivity graphs are substantially more accurate than the existing Ulrich (1936) & Hottel (1954) and Abu-Romia & Tien (1966) charts.

Uncertainty evaluation of mass values determined by electronic balances in analytical chemistry: a new method to correct for air buoyancy.

PubMed

Wunderli, S; Fortunato, G; Reichmuth, A; Richard, Ph

2003-06-01

A new method to correct for the largest systematic influence in mass determination-air buoyancy-is outlined. A full description of the most relevant influence parameters is given and the combined measurement uncertainty is evaluated according to the ISO-GUM approach [1]. A new correction method for air buoyancy using an artefact is presented. This method has the advantage that only a mass artefact is used to correct for air buoyancy. The classical approach demands the determination of the air density and therefore suitable equipment to measure at least the air temperature, the air pressure and the relative air humidity within the demanded uncertainties (i.e. three independent measurement tasks have to be performed simultaneously). The calculated uncertainty is lower for the classical method. However a field laboratory may not always be in possession of fully traceable measurement systems for these room climatic parameters.A comparison of three approaches applied to the calculation of the combined uncertainty of mass values is presented. Namely the classical determination of air buoyancy, the artefact method, and the neglecting of this systematic effect as proposed in the new EURACHEM/CITAC guide [2]. The artefact method is suitable for high-precision measurement in analytical chemistry and especially for the production of certified reference materials, reference values and analytical chemical reference materials. The method could also be used either for volume determination of solids or for air density measurement by an independent method.

Accurate Projection Methods for the Incompressible Navier–Stokes Equations

DOE PAGES

Brown, David L.; Cortez, Ricardo; Minion, Michael L.

2001-04-10

This paper considers the accuracy of projection method approximations to the initial–boundary-value problem for the incompressible Navier–Stokes equations. The issue of how to correctly specify numerical boundary conditions for these methods has been outstanding since the birth of the second-order methodology a decade and a half ago. It has been observed that while the velocity can be reliably computed to second-order accuracy in time and space, the pressure is typically only first-order accurate in the L ∞-norm. Here, we identify the source of this problem in the interplay of the global pressure-update formula with the numerical boundary conditions and presentsmore » an improved projection algorithm which is fully second-order accurate, as demonstrated by a normal mode analysis and numerical experiments. In addition, a numerical method based on a gauge variable formulation of the incompressible Navier–Stokes equations, which provides another option for obtaining fully second-order convergence in both velocity and pressure, is discussed. The connection between the boundary conditions for projection methods and the gauge method is explained in detail.« less

Laboratory simulation of cratering on small bodies

NASA Technical Reports Server (NTRS)

Schmidt, Robert M.

1991-01-01

A new technique using external pressure was developed to simulate the lithostatic pressure due to self-gravity of small bodies. A 13-in. diameter cylindrical test chamber with L/D of 1 was fabricated to accommodate firing explosive charges with gas overpressures of up to 6000 psi. The chamber was hydrotested to 9000 psi. The method allows much larger scale factors that can be obtained with existing centrifuges and has the correct spherical geometry of self gravity. A simulant for jointed rock to be used in this fixture was developed using weakly cemented basalt. Various strength/pressure scaling theories can now be examined and tested.

Statistical Calibration and Validation of a Homogeneous Ventilated Wall-Interference Correction Method for the National Transonic Facility

NASA Technical Reports Server (NTRS)

Walker, Eric L.

2005-01-01

Wind tunnel experiments will continue to be a primary source of validation data for many types of mathematical and computational models in the aerospace industry. The increased emphasis on accuracy of data acquired from these facilities requires understanding of the uncertainty of not only the measurement data but also any correction applied to the data. One of the largest and most critical corrections made to these data is due to wall interference. In an effort to understand the accuracy and suitability of these corrections, a statistical validation process for wall interference correction methods has been developed. This process is based on the use of independent cases which, after correction, are expected to produce the same result. Comparison of these independent cases with respect to the uncertainty in the correction process establishes a domain of applicability based on the capability of the method to provide reasonable corrections with respect to customer accuracy requirements. The statistical validation method was applied to the version of the Transonic Wall Interference Correction System (TWICS) recently implemented in the National Transonic Facility at NASA Langley Research Center. The TWICS code generates corrections for solid and slotted wall interference in the model pitch plane based on boundary pressure measurements. Before validation could be performed on this method, it was necessary to calibrate the ventilated wall boundary condition parameters. Discrimination comparisons are used to determine the most representative of three linear boundary condition models which have historically been used to represent longitudinally slotted test section walls. Of the three linear boundary condition models implemented for ventilated walls, the general slotted wall model was the most representative of the data. The TWICS code using the calibrated general slotted wall model was found to be valid to within the process uncertainty for test section Mach numbers less than or equal to 0.60. The scatter among the mean corrected results of the bodies of revolution validation cases was within one count of drag on a typical transport aircraft configuration for Mach numbers at or below 0.80 and two counts of drag for Mach numbers at or below 0.90.

Feasibility study of patient motion monitoring by using tactile array sensors

NASA Astrophysics Data System (ADS)

Kim, Tae-Ho; Kang, Seong-Hee; Kim, Dong-Su; Cho, Min-Seok; Kim, Kyeong-Hyeon; Suh, Tae-Suk; Kim, Siyong

2015-07-01

An ideal alignment method based on the external anatomical surface of the patient should consider the entire region of interest. However, optical-camera-based systems cannot blindly monitor such areas as the patient's back, for example. Furthermore, collecting enough information to correct the associated deformation error is impossible. The study aim is to propose a new patient alignment method using tactile array sensors that can measure the distributed pressure profiles along the contact surface. The TactArray system includes one sensor, a signal-conditioning device (USB drive/interface electronics, power supply, and cables), and a PC. The tactile array sensor was placed between the patient's back and the treatment couch, and the deformations at different location on the patient's back were evaluated. Three healthy male volunteers were enrolled in this study, and pressure profile distributions (PPDs) were obtained with and without immobilization. After the initial pretreatment setup using the laser alignment system, the PPD of the patient's back was acquired. The results were obtained at four different times and included a reference PPD dataset. The contact area and the center-of-pressure value were also acquired based on the PPD data for a more elaborate quantitative data analysis. To evaluate the clinical feasibility of using the proposed alignment method for reducing the deformation error, we implemented a real-time self-correction procedure. Despite the initial alignment, we confirmed that PPD variations existed in both cases of the volunteer studies (with and without the use of the immobilization tool). Additionally, we confirmed that the contact area and the center of pressure varied in both cases, and those variations were observed in all three volunteers. With the proposed alignment method and the real-time selfcorrection procedure, the deformation error was significantly reduced. The proposed alignment method can be used to account for the limitation of the camera-based system and to improve the accuracy of the external surface-based patient setup.

Wavelet filter analysis of local atmospheric pressure effects in the long-period tidal bands

NASA Astrophysics Data System (ADS)

Hu, X.-G.; Liu, L. T.; Ducarme, B.; Hsu, H. T.; Sun, H.-P.

2006-11-01

It is well known that local atmospheric pressure variations obviously affect the observation of short-period Earth tides, such as diurnal tides, semi-diurnal tides and ter-diurnal tides, but local atmospheric pressure effects on the long-period Earth tides have not been studied in detail. This is because the local atmospheric pressure is believed not to be sufficient for an effective pressure correction in long-period tidal bands, and there are no efficient methods to investigate local atmospheric effects in these bands. The usual tidal analysis software package, such as ETERNA, Baytap-G and VAV, cannot provide detailed pressure admittances for long-period tidal bands. We propose a wavelet method to investigate local atmospheric effects on gravity variations in long-period tidal bands. This method constructs efficient orthogonal filter bank with Daubechies wavelets of high vanishing moments. The main advantage of the wavelet filter bank is that it has excellent low frequency response and efficiently suppresses instrumental drift of superconducting gravimeters (SGs) without using any mathematical model. Applying the wavelet method to the 13-year continuous gravity observations from SG T003 in Brussels, Belgium, we filtered 12 long-period tidal groups into eight narrow frequency bands. Wavelet method demonstrates that local atmospheric pressure fluctuations are highly correlated with the noise of SG measurements in the period band 4-40 days with correlation coefficients higher than 0.95 and local atmospheric pressure variations are the main error source for the determination of the tidal parameters in these bands. We show the significant improvement of long-period tidal parameters provided by wavelet method in term of precision.

Thermal properties of nuclear matter in a variational framework with relativistic corrections

NASA Astrophysics Data System (ADS)

Zaryouni, S.; Hassani, M.; Moshfegh, H. R.

2014-01-01

The properties of hot symmetric nuclear matter for a wide range of densities and temperatures are investigated by employing the AV14 potential within the lowest order constrained variational (LOCV) method with the inclusion of a phenomenological three-body force as well as relativistic corrections. The relativistic corrections of many-body kinetic energies as well as the boot interaction corrections are presented for a wide range of densities and temperatures. The free energy, pressure, incompressibility, and other thermodynamic quantities of symmetric nuclear matter are obtained and discussed. The critical temperature is found, and the liquid-gas phase transition is analyzed both with and without the inclusion of three-body forces and relativistic corrections in the LOCV approach. It is shown that the critical temperature is strongly affected by the three-body forces but does not depend on the relativistic corrections. Finally, the results obtained in the present study are compared with other many-body calculations and experimental predictions.

Leak Location and Classification in the Space Shuttle Main Engine Nozzle by Infrared Testing

NASA Technical Reports Server (NTRS)

Russell, Samuel S.; Walker, James L.; Lansing, Mathew

2003-01-01

The Space Shuttle Main Engine (SSME) is composed of cooling tubes brazed to the inside of a conical structural jacket. Because of the geometry there are regions that can't be inspected for leaks using the bubble solution and low-pressure method. The temperature change due escaping gas is detectable on the surface of the nozzle under the correct conditions. The methods and results presented in this summary address the thermographic identification of leaks in the Space Shuttle Main Engine nozzles. A highly sensitive digital infrared camera is used to record the minute temperature change associated with a leak source, such as a crack or pinhole, hidden within the nozzle wall by observing the inner "hot wall" surface as the nozzle is pressurized. These images are enhanced by digitally subtracting a thermal reference image taken before pressurization, greatly diminishing background noise. The method provides a nonintrusive way of localizing the tube that is leaking and the exact leak source position to within a very small axial distance. Many of the factors that influence the inspectability of the nozzle are addressed; including pressure rate, peak pressure, gas type, ambient temperature and surface preparation.

Are you overloading you skidder tires?

Treesearch

Cleveland J. Biller; Cleveland J. Biller

1972-01-01

The undersize and underinflated tire is one of the costliest problems in Appalachian logging. Overloaded and underinflated tires cause excessive wear and expensive early replacement. In seeking a solution to this problem, we have developed a method that can be used for choosing the correct tire size and inflation pressure for a particular skidder.

Thermodynamic evaluation of transonic compressor rotors using the finite volume approach

NASA Technical Reports Server (NTRS)

Moore, J.; Nicholson, S.; Moore, J. G.

1985-01-01

Research at NASA Lewis Research Center gave the opportunity to incorporate new control volumes in the Denton 3-D finite-volume time marching code. For duct flows, the new control volumes require no transverse smoothing and this allows calculations with large transverse gradients in properties without significant numerical total pressure losses. Possibilities for improving the Denton code to obtain better distributions of properties through shocks were demonstrated. Much better total pressure distributions through shocks are obtained when the interpolated effective pressure, needed to stabilize the solution procedure, is used to calculate the total pressure. This simple change largely eliminates the undershoot in total pressure down-stream of a shock. Overshoots and undershoots in total pressure can then be further reduced by a factor of 10 by adopting the effective density method, rather than the effective pressure method. Use of a Mach number dependent interpolation scheme for pressure then removes the overshoot in static pressure downstream of a shock. The stability of interpolation schemes used for the calculation of effective density is analyzed and a Mach number dependent scheme is developed, combining the advantages of the correct perfect gas equation for subsonic flow with the stability of 2-point and 3-point interpolation schemes for supersonic flow.

Near-infrared spectroscopy determined cerebral oxygenation with eliminated skin blood flow in young males.

PubMed

Hirasawa, Ai; Kaneko, Takahito; Tanaka, Naoki; Funane, Tsukasa; Kiguchi, Masashi; Sørensen, Henrik; Secher, Niels H; Ogoh, Shigehiko

2016-04-01

We estimated cerebral oxygenation during handgrip exercise and a cognitive task using an algorithm that eliminates the influence of skin blood flow (SkBF) on the near-infrared spectroscopy (NIRS) signal. The algorithm involves a subtraction method to develop a correction factor for each subject. For twelve male volunteers (age 21 ± 1 yrs) +80 mmHg pressure was applied over the left temporal artery for 30 s by a custom-made headband cuff to calculate an individual correction factor. From the NIRS-determined ipsilateral cerebral oxyhemoglobin concentration (O2Hb) at two source-detector distances (15 and 30 mm) with the algorithm using the individual correction factor, we expressed cerebral oxygenation without influence from scalp and scull blood flow. Validity of the estimated cerebral oxygenation was verified during cerebral neural activation (handgrip exercise and cognitive task). With the use of both source-detector distances, handgrip exercise and a cognitive task increased O2Hb (P < 0.01) but O2Hb was reduced when SkBF became eliminated by pressure on the temporal artery for 5 s. However, when the estimation of cerebral oxygenation was based on the algorithm developed when pressure was applied to the temporal artery, estimated O2Hb was not affected by elimination of SkBF during handgrip exercise (P = 0.666) or the cognitive task (P = 0.105). These findings suggest that the algorithm with the individual correction factor allows for evaluation of changes in an accurate cerebral oxygenation without influence of extracranial blood flow by NIRS applied to the forehead.

[Hemodynamic changes in hypoglycemic shock].

PubMed

Gutiérrez, C; Piza, R; Chousleb, A; Hidalgo, M A; Ortigosa, J L

1977-01-01

Severe hypoglycemia may be present in seriously ill patients; if it is not corrected opportunely a series of neuroendocrinal mechanisms take place aimed at correcting metabolic alterations. These mechanisms can produce hemodynamic alterations as well. Nine mongrel dogs were studied with continuous registration of: blood pressure, central venous pressure, cardiac frequency, respiratory frequency, electrocardiogram and first derivative (Dp/Dt). Six dogs received crystalline (fast acting) insuline intravenously (group 1). After hemodynamic changes were registered hypoglycemia was corrected with 50 per cent glucose solution. Complementary insuline doses were administered to three dogs (group 2); in this group hypoglycemia was not corrected. In group 1 during hypoglycemia there was an increase in blood pressure, central venous pressure, cardiac frequency, respiratory frequency and Dp/Dt, and changes in QT and T wave on the EKG; these changes were partially reversible after hypoglycemia was corrected. The above mentioned alterations persisted in group 2, breathing became irregular irregular and respiratory arrest supervened. It can be inferred that the hemodynamic response to hypoglycemia is predominantly adrenergic. The role of catecolamines, glucocorticoides, glucagon, insuline, cyclic AMP in metabolic and hemodynamic alterations consecutive to hypoglycemia are discussed.

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

New method of calculating the power at altitude of aircraft engines equipped with superchargers on the basis of tests made under sea-level conditions

NASA Technical Reports Server (NTRS)

Sarracino, Marcello

1941-01-01

The present article deals with what is considered to be a simpler and more accurate method of determining, from the results of bench tests under approved rating conditions, the power at altitude of a supercharged aircraft engine, without application of correction formulas. The method of calculating the characteristics at altitude, of supercharged engines, based on the consumption of air, is a more satisfactory and accurate procedure, especially at low boost pressures.

Index of Refraction of Shock Loaded Soda-Lime Glass

NASA Astrophysics Data System (ADS)

Alexander, C. S.

2009-12-01

Soda-lime glass (SLG) is a potential low-cost VISAR window for use at moderate shock pressures (up to 2430 GPa) where the material remains transparent. In order for SLG to be practical as a VISAR window, the correction factor, which describes the frequency correction related to the strain dependence of the refractive index, and hence the index of refraction itself, must be characterized as a function of pressure. Characterization data are reported in this paper and compared to previous results. The present data show good agreement with those of Dandekar [J. Appl. Phys. 84, 6614 (1998)] and separate study results by Gibbons and Ahrens [J. Geophys. Res. 76, 5489 (1971)] up to 7 GPa. However, at stresses over 7 GPa, marked discrepancies are evident between the present data and that of Gibbons and Ahrens. Differences in test methods may explain these discrepancies.

Index of Refraction of Shock Loaded Soda-Lime Glass

NASA Astrophysics Data System (ADS)

Alexander, Scott

2009-06-01

Soda-lime glass (SLG) is a potential low-cost VISAR window for use at moderate shock pressures (up to approximately 25 GPa) where the material remains transparent. In order for SLG to be practical as a VISAR window, the correction factor, which describes the frequency correction related to the strain dependence of the refractive index, and hence the index of refraction itself, must be characterized as a function of pressure. Characterization data are reported in this paper and compared to previous results. The present data show good agreement with those of Dandekar [J. App. Physics, 84, 6614 (1998)] and separate study results by Gibbons and Ahrens [J. Geophys. Res., 76, 5489 (1971)] up to 7 GPa. However, at stresses over 7 GPa, marked discrepancies are evident between the present data and that of Gibbons and Ahrens. Differences in test methods may explain these discrepancies.

INDEX OF REFRACTION OF SHOCK LOADED SODA-LIME GLASS

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

Alexander, C. S.

2009-12-28

Soda-lime glass (SLG) is a potential low-cost VISAR window for use at moderate shock pressures (up to 2430 GPa) where the material remains transparent. In order for SLG to be practical as a VISAR window, the correction factor, which describes the frequency correction related to the strain dependence of the refractive index, and hence the index of refraction itself, must be characterized as a function of pressure. Characterization data are reported in this paper and compared to previous results. The present data show good agreement with those of Dandekar [J. Appl. Phys. 84, 6614 (1998)] and separate study results bymore » Gibbons and Ahrens [J. Geophys. Res. 76, 5489 (1971)] up to 7 GPa. However, at stresses over 7 GPa, marked discrepancies are evident between the present data and that of Gibbons and Ahrens. Differences in test methods may explain these discrepancies.« less

Methods of measuring water levels in deep wells

USGS Publications Warehouse

Garber, M.S.; Koopman, F. C.

1968-01-01

Accurate measurement of water levels deeper than 1,000 feet in wells requires specialized equipment. Corrections for stretch and thermal expansion of measuring tapes must be considered, and other measuring devices must be calibrated periodically. Bore-hole deviation corrections also must be made. Devices for recording fluctuation of fluid level usually require mechanical modification for use at these depths. A multichannel recording device utilizing pressure transducers has been constructed. This device was originally designed to record aquifer response to nearby underground nuclear explosions but can also be used for recording data from multi-well pumping tests. Bottom-hole recording devices designed for oil-field use have been utilized in a limited manner. These devices were generally found to lack the precision required, in ground-water investigations at the Nevada Test Site but may be applicable in other areas. A newly developed bottom-hole recording pressure gauge of improved accuracy has been used with satisfactory results.

Effects of Discrete Charge Clustering in Simulations of Charged Interfaces.

PubMed

Grime, John M A; Khan, Malek O

2010-10-12

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

Clinical characterization of 2D pressure field in human left ventricles

NASA Astrophysics Data System (ADS)

Borja, Maria; Rossini, Lorenzo; Martinez-Legazpi, Pablo; Benito, Yolanda; Alhama, Marta; Yotti, Raquel; Perez Del Villar, Candelas; Gonzalez-Mansilla, Ana; Barrio, Alicia; Fernandez-Aviles, Francisco; Bermejo, Javier; Khan, Andrew; Del Alamo, Juan Carlos

2014-11-01

The evaluation of left ventricle (LV) function in the clinical setting remains a challenge. Pressure gradient is a reliable and reproducible indicator of the LV function. We obtain 2D relative pressure field in the LV using in-vivo measurements obtained by processing Doppler-echocardiography images of healthy and dilated hearts. Exploiting mass conservation, we solve the Poisson pressure equation (PPE) dropping the time derivatives and viscous terms. The flow acceleration appears only in the boundary conditions, making our method weakly sensible to the time resolution of in-vivo acquisitions. To ensure continuity with respect to the discrete operator and grid used, a potential flow correction is applied beforehand, which gives another Poisson equation. The new incompressible velocity field ensures that the compatibility equation for the PPE is satisfied. Both Poisson equations are efficiently solved on a Cartesian grid using a multi-grid method and immersed boundary for the LV wall. The whole process is computationally inexpensive and could play a diagnostic role in the clinical assessment of LV function.

Acoustic propagation operators for pressure waves on an arbitrarily curved surface in a homogeneous medium

NASA Astrophysics Data System (ADS)

Sun, Yimin; Verschuur, Eric; van Borselen, Roald

2018-03-01

The Rayleigh integral solution of the acoustic Helmholtz equation in a homogeneous medium can only be applied when the integral surface is a planar surface, while in reality almost all surfaces where pressure waves are measured exhibit some curvature. In this paper we derive a theoretically rigorous way of building propagation operators for pressure waves on an arbitrarily curved surface. Our theory is still based upon the Rayleigh integral, but it resorts to matrix inversion to overcome the limitations faced by the Rayleigh integral. Three examples are used to demonstrate the correctness of our theory - propagation of pressure waves acquired on an arbitrarily curved surface to a planar surface, on an arbitrarily curved surface to another arbitrarily curved surface, and on a spherical cap to a planar surface, and results agree well with the analytical solutions. The generalization of our method for particle velocities and the calculation cost of our method are also discussed.

Curvature controlled wetting in two dimensions

NASA Astrophysics Data System (ADS)

Gil, Tamir; Mikheev, Lev V.

1995-07-01

A complete wetting transition at vanishing curvature of the substrate in two-dimensional circular geometry is studied by the transfer matrix method. We find an exact formal mapping of the partition function of the problem onto that of a (1+1)-dimensional wetting problem in planar geometry. As the radius of the substrate r0-->∞, the leading effect of the curvature is adding the Laplace pressure ΠL~r-10 to the pressure balance in the film. At temperatures and pressures under which the wetting is complete in planar geometry, Laplace pressure suppresses divergence of the mean thickness of the wetting layer lW, leading to a power law lW~r1/30. At a critical wetting transition of a planar substrate, curvature adds a relevant field; the corresponding multiscaling forms are readily available. The method allows for the systematic evaluation of corrections to the leading behavior; the next to the leading term reduces the thickness by the amount proportional to r-1/30

Description and evaluation of an interference assessment for a slotted-wall wind tunnel

NASA Technical Reports Server (NTRS)

Kemp, William B., Jr.

1991-01-01

A wind-tunnel interference assessment method applicable to test sections with discrete finite-length wall slots is described. The method is based on high order panel method technology and uses mixed boundary conditions to satisfy both the tunnel geometry and wall pressure distributions measured in the slotted-wall region. Both the test model and its sting support system are represented by distributed singularities. The method yields interference corrections to the model test data as well as surveys through the interference field at arbitrary locations. These results include the equivalent of tunnel Mach calibration, longitudinal pressure gradient, tunnel flow angularity, wall interference, and an inviscid form of sting interference. Alternative results which omit the direct contribution of the sting are also produced. The method was applied to the National Transonic Facility at NASA Langley Research Center for both tunnel calibration tests and tests of two models of subsonic transport configurations.

Slip Correction Measurements of Certified PSL Nanoparticles Using a Nanometer Differential Mobility Analyzer (Nano-DMA) for Knudsen Number From 0.5 to 83

PubMed Central

Kim, Jung Hyeun; Mulholland, George W.; Kukuck, Scott R.; Pui, David Y. H.

2005-01-01

The slip correction factor has been investigated at reduced pressures and high Knudsen number using polystyrene latex (PSL) particles. Nano-differential mobility analyzers (NDMA) were used in determining the slip correction factor by measuring the electrical mobility of 100.7 nm, 269 nm, and 19.90 nm particles as a function of pressure. The aerosol was generated via electrospray to avoid multiplets for the 19.90 nm particles and to reduce the contaminant residue on the particle surface. System pressure was varied down to 8.27 kPa, enabling slip correction measurements for Knudsen numbers as large as 83. A condensation particle counter was modified for low pressure application. The slip correction factor obtained for the three particle sizes is fitted well by the equation: C = 1 + Kn (α + β exp(−γ/Kn)), with α = 1.165, β = 0.483, and γ = 0.997. The first quantitative uncertainty analysis for slip correction measurements was carried out. The expanded relative uncertainty (95 % confidence interval) in measuring slip correction factor was about 2 % for the 100.7 nm SRM particles, about 3 % for the 19.90 nm PSL particles, and about 2.5 % for the 269 nm SRM particles. The major sources of uncertainty are the diameter of particles, the geometric constant associated with NDMA, and the voltage. PMID:27308102

A coupled Eulerian/Lagrangian method for the solution of three-dimensional vortical flows

NASA Technical Reports Server (NTRS)

Felici, Helene Marie

1992-01-01

A coupled Eulerian/Lagrangian method is presented for the reduction of numerical diffusion observed in solutions of three-dimensional rotational flows using standard Eulerian finite-volume time-marching procedures. A Lagrangian particle tracking method using particle markers is added to the Eulerian time-marching procedure and provides a correction of the Eulerian solution. In turn, the Eulerian solutions is used to integrate the Lagrangian state-vector along the particles trajectories. The Lagrangian correction technique does not require any a-priori information on the structure or position of the vortical regions. While the Eulerian solution ensures the conservation of mass and sets the pressure field, the particle markers, used as 'accuracy boosters,' take advantage of the accurate convection description of the Lagrangian solution and enhance the vorticity and entropy capturing capabilities of standard Eulerian finite-volume methods. The combined solution procedures is tested in several applications. The convection of a Lamb vortex in a straight channel is used as an unsteady compressible flow preservation test case. The other test cases concern steady incompressible flow calculations and include the preservation of turbulent inlet velocity profile, the swirling flow in a pipe, and the constant stagnation pressure flow and secondary flow calculations in bends. The last application deals with the external flow past a wing with emphasis on the trailing vortex solution. The improvement due to the addition of the Lagrangian correction technique is measured by comparison with analytical solutions when available or with Eulerian solutions on finer grids. The use of the combined Eulerian/Lagrangian scheme results in substantially lower grid resolution requirements than the standard Eulerian scheme for a given solution accuracy.

Direct numerical simulation of droplet-laden isotropic turbulence

NASA Astrophysics Data System (ADS)

Dodd, Michael S.

Interaction of liquid droplets with turbulence is important in numerous applications ranging from rain formation to oil spills to spray combustion. The physical mechanisms of droplet-turbulence interaction are largely unknown, especially when compared to that of solid particles. Compared to solid particles, droplets can deform, break up, coalesce and have internal fluid circulation. The main goal of this work is to investigate using direct numerical simulation (DNS) the physical mechanisms of droplet-turbulence interaction, both for non-evaporating and evaporating droplets. To achieve this objective, we develop and couple a new pressure-correction method with the volume-of-fluid (VoF) method for simulating incompressible two-fluid flows. The method's main advantage is that the variable coefficient Poisson equation that arises in solving the incompressible Navier-Stokes equations for two-fluid flows is reduced to a constant coefficient equation. This equation can then be solved directly using, e.g., the FFT-based parallel Poisson solver. For a 10243 mesh, our new pressure-correction method using a fast Poisson solver is ten to forty times faster than the standard pressure-correction method using multigrid. Using the coupled pressure-correction and VoF method, we perform direct numerical simulations (DNS) of 3130 finite-size, non-evaporating droplets of diameter approximately equal to the Taylor lengthscale and with 5% droplet volume fraction in decaying isotropic turbulence at initial Taylor-scale Reynolds number Relambda = 83. In the droplet-laden cases, we vary one of the following three parameters: the droplet Weber number based on the r.m.s. velocity of turbulence (0.1 ≤ Werms ≤ 5), the droplet- to carrier-fluid density ratio (1 ≤ rhod/rho c ≤ 100) or the droplet- to carrier-fluid viscosity ratio (1 ≤ mud/muc ≤ 100). We derive the turbulence kinetic energy (TKE) equations for the two-fluid, carrier-fluid and droplet-fluid flow. These equations allow us to explain the pathways for TKE exchange between the carrier turbulent flow and the flow inside the droplet. We also explain the role of the interfacial surface energy in the two-fluid TKE equation through work performed by surface tension. Furthermore, we derive the relationship between the power of surface tension and the rate of change of total droplet surface area. This link allows us to explain how droplet deformation, breakup and coalescence play roles in the temporal evolution of TKE. We then extend the code for non-evaporating droplets and develop a combined VoF method and low-Mach-number approach to simulate evaporating and condensing droplets. The two main novelties of the method are: (i) the VOF algorithm captures the motion of the liquid gas interface in the presence of mass transfer due to evaporation and condensation without requiring a projection step for the liquid velocity, and (ii) the low-Mach-number approach allows for local volume changes caused by phase change while the total volume of the liquid-gas system is constant. The method is verified against an analytical solution for a Stefan flow problem, and the D2 law is verified for a single droplet in quiescent gas. Finally, we perform DNS of an evaporating liquid droplet in forced isotropic turbulence. We show that the method accurately captures the temperature and vapor fields in the turbulent regime, and that the local evaporation rate can vary along the droplet surface depending on the structure of the surrounding vapor cloud. We also report the time evolution of the mean Sherwood number, which indicates that turbulence enhances the vaporization rate of liquid droplets.

Extracting biomolecule collision cross sections from the high-resolution FT-ICR mass spectral linewidths.

PubMed

Jiang, Ting; Chen, Yu; Mao, Lu; Marshall, Alan G; Xu, Wei

2016-01-14

It is known that the ion collision cross section (CCS) may be calculated from the linewidth of a Fourier transform ion cyclotron resonance (FT-ICR) mass spectral peak at elevated pressure (e.g., ∼10(-6) Torr). However, the high mass resolution of FT-ICR is sacrificed in those experiments due to high buffer gas pressure. In this study, we describe a linewidth correction method to eliminate the windowing-induced peak broadening effect. Together with the energetic ion-neutral collision model previously developed by our group, this method enables the extraction of CCSs of biomolecules from high-resolution FT-ICR mass spectral linewidths, obtained at a typical operating buffer gas pressure of modern FT-ICR instruments (∼10(-10) Torr). CCS values of peptides including MRFA, angiotensin I, and bradykinin measured by the proposed method agree well with ion mobility measurements, and the unfolding of protein ions (ubiquitin) at higher charge states is also observed.

Experimental aspects of buoyancy correction in measuring reliable highpressure excess adsorption isotherms using the gravimetric method.

PubMed

Nguyen, Huong Giang T; Horn, Jarod C; Thommes, Matthias; van Zee, Roger D; Espinal, Laura

2017-12-01

Addressing reproducibility issues in adsorption measurements is critical to accelerating the path to discovery of new industrial adsorbents and to understanding adsorption processes. A National Institute of Standards and Technology Reference Material, RM 8852 (ammonium ZSM-5 zeolite), and two gravimetric instruments with asymmetric two-beam balances were used to measure high-pressure adsorption isotherms. This work demonstrates how common approaches to buoyancy correction, a key factor in obtaining the mass change due to surface excess gas uptake from the apparent mass change, can impact the adsorption isotherm data. Three different approaches to buoyancy correction were investigated and applied to the subcritical CO 2 and supercritical N 2 adsorption isotherms at 293 K. It was observed that measuring a collective volume for all balance components for the buoyancy correction (helium method) introduces an inherent bias in temperature partition when there is a temperature gradient (i.e. analysis temperature is not equal to instrument air bath temperature). We demonstrate that a blank subtraction is effective in mitigating the biases associated with temperature partitioning, instrument calibration, and the determined volumes of the balance components. In general, the manual and subtraction methods allow for better treatment of the temperature gradient during buoyancy correction. From the study, best practices specific to asymmetric two-beam balances and more general recommendations for measuring isotherms far from critical temperatures using gravimetric instruments are offered.

Evaluation of Agency Non-Code Layered Pressure Vessels (LPVs). Corrected Copy, Aug. 25, 2014

NASA Technical Reports Server (NTRS)

Prosser, William H.

2014-01-01

In coordination with the Office of Safety and Mission Assurance and the respective Center Pressure System Managers (PSMs), the NASA Engineering and Safety Center (NESC) was requested to formulate a consensus draft proposal for the development of additional testing and analysis methods to establish the technical validity, and any limitation thereof, for the continued safe operation of facility non-code layered pressure vessels. The PSMs from each NASA Center were asked to participate as part of the assessment team by providing, collecting, and reviewing data regarding current operations of these vessels. This report contains the outcome of the assessment and the findings, observations, and NESC recommendations to the Agency and individual NASA Centers.

Evaporation rate and vapor pressure of selected polymeric lubricating oils.

NASA Technical Reports Server (NTRS)

Gardos, M. N.

1973-01-01

A recently developed ultrahigh-vacuum quartz spring mass sorption microbalance has been utilized to measure the evaporation rates of several low-volatility polymeric lubricating oils at various temperatures. The evaporation rates are used to calculate the vapor pressures by the Langmuir equation. A method is presented to accurately estimate extended temperature range evaporation rate and vapor pressure data for polymeric oils, incorporating appropriate corrections for the increases in molecular weight and the change in volatility of the progressively evaporating polymer fractions. The logarithms of the calculated data appear to follow linear relationships within the test temperature ranges, when plotted versus 1000/T. These functions and the observed effusion characteristics of the fluids on progressive volatilization are useful in estimating evaporation rate and vapor pressure changes on evaporative depletion.

Precise predictions of H2O line shapes over a wide pressure range using simulations corrected by a single measurement

NASA Astrophysics Data System (ADS)

Ngo, N. H.; Nguyen, H. T.; Tran, H.

2018-03-01

In this work, we show that precise predictions of the shapes of H2O rovibrational lines broadened by N2, over a wide pressure range, can be made using simulations corrected by a single measurement. For that, we use the partially-correlated speed-dependent Keilson-Storer (pcsdKS) model whose parameters are deduced from molecular dynamics simulations and semi-classical calculations. This model takes into account the collision-induced velocity-changes effects, the speed dependences of the collisional line width and shift as well as the correlation between velocity and internal-state changes. For each considered transition, the model is corrected by using a parameter deduced from its broadening coefficient measured for a single pressure. The corrected-pcsdKS model is then used to simulate spectra for a wide pressure range. Direct comparisons of the corrected-pcsdKS calculated and measured spectra of 5 rovibrational lines of H2O for various pressures, from 0.1 to 1.2 atm, show very good agreements. Their maximum differences are in most cases well below 1%, much smaller than residuals obtained when fitting the measurements with the Voigt line shape. This shows that the present procedure can be used to predict H2O line shapes for various pressure conditions and thus the simulated spectra can be used to deduce the refined line-shape parameters to complete spectroscopic databases, in the absence of relevant experimental values.

Influence of surface rectangular defect winding layer on burst pressure of CNG-II composite cylinder

NASA Astrophysics Data System (ADS)

You, H. X.; Peng, L.; Zhao, C.; Ma, K.; Zhang, S.

2018-01-01

To study the influence of composite materials’ surface defect on the burst pressure of CNG-II composite cylinder, the surface defect was simplified as a rectangular slot of certain size on the basis of actually investigating the shape of cylinder’s surface defect. A CNG-II composite cylinder with a rectangular slot defect (2mm in depth) was used for burst test, and the numerical simulation software ANSYS was used to calculate its burst pressure. Through comparison between the burst pressure in the test and the numerical analysis result, the correctness of the numerical analysis method was verified. On this basis, the numerical analysis method was conducted for composite cylinders with surface defect in other depth. The result showed that surface defect in the form of rectangular slot had no significant effect on the liner stress of composite cylinder. Instead, it had a great influence on the stress of fiber-wrapped layer. The burst pressure of the composite cylinder decreased as the defect depth increasing. The hoop stress at the bottom of the defect in the shape of rectangular slot exceeded the maximum of the composite materials’ tensile strength, which could result in the burst pressure of composite cylinders decreasing.

Viscous pressure correction in the irrotational flow outside Prandtl's boundary layer

NASA Astrophysics Data System (ADS)

Joseph, Daniel; Wang, Jing

2004-11-01

We argue that boundary layers on solid with irrotational motion outside are like a gas bubble because the shear stress vanishes at the edge of the boundary layer but the irrotational shear stress does not. This discrepancy induces a pressure correction and an additional drag which can be advertised as due to the viscous dissipation of the irrotational flow. Typically, this extra correction to the drag would be relatively small. A much more interesting implication of the extra pressure theory arises from the consideration of the effects of viscosity on the normal stress on a solid boundary which are entirely neglected in Prandtl's theory. It is very well known and easily demonstrated that as a consequence of the continuity equation the viscous normal stress must vanish on a rigid solid. It follows that all the greatly important effects of viscosity on the normal stress are buried in the pressure and the leading order effects of viscosity on the normal stress can be obtained from the viscous correction of viscous potential flow.

Pressure-Sensitive Paint Measurements on Surfaces with Non-Uniform Temperature

NASA Technical Reports Server (NTRS)

Bencic, Timothy J.

1999-01-01

Pressure-sensitive paint (PSP) has become a useful tool to augment conventional pressure taps in measuring the surface pressure distribution of aerodynamic components in wind tunnel testing. While the PSP offers the advantage of a non-intrusive global mapping of the surface pressure, one prominent drawback to the accuracy of this technique is the inherent temperature sensitivity of the coating's luminescent intensity. A typical aerodynamic surface PSP test has relied on the coated surface to be both spatially and temporally isothermal, along with conventional instrumentation for an in situ calibration to generate the highest accuracy pressure mappings. In some tests however, spatial and temporal thermal gradients are generated by the nature of the test as in a blowing jet impinging on a surface. In these cases, the temperature variations on the painted surface must be accounted for in order to yield high accuracy and reliable data. A new temperature correction technique was developed at NASA Lewis to collapse a "family" of PSP calibration curves to a single intensity ratio versus pressure curve. This correction allows a streamlined procedure to be followed whether or not temperature information is used in the data reduction of the PSP. This paper explores the use of conventional instrumentation such as thermocouples and pressure taps along with temperature-sensitive paint (TSP) to correct for the thermal gradients that exist in aeropropulsion PSP tests. Temperature corrected PSP measurements for both a supersonic mixer ejector and jet cavity interaction tests are presented.

Constant pressure and temperature discrete-time Langevin molecular dynamics

NASA Astrophysics Data System (ADS)

Grønbech-Jensen, Niels; Farago, Oded

2014-11-01

We present a new and improved method for simultaneous control of temperature and pressure in molecular dynamics simulations with periodic boundary conditions. The thermostat-barostat equations are built on our previously developed stochastic thermostat, which has been shown to provide correct statistical configurational sampling for any time step that yields stable trajectories. Here, we extend the method and develop a set of discrete-time equations of motion for both particle dynamics and system volume in order to seek pressure control that is insensitive to the choice of the numerical time step. The resulting method is simple, practical, and efficient. The method is demonstrated through direct numerical simulations of two characteristic model systems—a one-dimensional particle chain for which exact statistical results can be obtained and used as benchmarks, and a three-dimensional system of Lennard-Jones interacting particles simulated in both solid and liquid phases. The results, which are compared against the method of Kolb and Dünweg [J. Chem. Phys. 111, 4453 (1999)], show that the new method behaves according to the objective, namely that acquired statistical averages and fluctuations of configurational measures are accurate and robust against the chosen time step applied to the simulation.

Correction of Altitude-Induced Changes in Performance of the Volumetric Diffusive Respirator

DTIC Science & Technology

2017-04-05

to a plateau pressure. The positive pressure delivery of each percussive pulse is followed by a passive fall in pressure as the spring moves the ...AFRL-SA-WP-SR-2017-0007 Correction of Altitude- Induced Changes in Performance of the Volumetric Diffusive Respirator Thomas...Blakeman, MSc RRT April 2017 Air Force Research Laboratory 711th Human Performance Wing U.S. Air Force School of Aerospace

A Method for Large Eddy Simulation of Acoustic Combustion Instabilities

NASA Astrophysics Data System (ADS)

Wall, Clifton; Pierce, Charles; Moin, Parviz

2002-11-01

A method for performing Large Eddy Simulation of acoustic combustion instabilities is presented. By extending the low Mach number pressure correction method to the case of compressible flow, a numerical method is developed in which the Poisson equation for pressure is replaced by a Helmholtz equation. The method avoids the acoustic CFL condition by using implicit time advancement, leading to large efficiency gains at low Mach number. The method also avoids artificial damping of acoustic waves. The numerical method is attractive for the simulation of acoustic combustion instabilities, since these flows are typically at low Mach number, and the acoustic frequencies of interest are usually low. Both of these characteristics suggest the use of larger time steps than those allowed by an acoustic CFL condition. The turbulent combustion model used is the Combined Conserved Scalar/Level Set Flamelet model of Duchamp de Lageneste and Pitsch for partially premixed combustion. Comparison of LES results to the experiments of Besson et al will be presented.

Airframe noise prediction evaluation

NASA Technical Reports Server (NTRS)

Yamamoto, Kingo J.; Donelson, Michael J.; Huang, Shumei C.; Joshi, Mahendra C.

1995-01-01

The objective of this study is to evaluate the accuracy and adequacy of current airframe noise prediction methods using available airframe noise measurements from tests of a narrow body transport (DC-9) and a wide body transport (DC-10) in addition to scale model test data. General features of the airframe noise from these aircraft and models are outlined. The results of the assessment of two airframe prediction methods, Fink's and Munson's methods, against flight test data of these aircraft and scale model wind tunnel test data are presented. These methods were extensively evaluated against measured data from several configurations including clean, slat deployed, landing gear-deployed, flap deployed, and landing configurations of both DC-9 and DC-10. They were also assessed against a limited number of configurations of scale models. The evaluation was conducted in terms of overall sound pressure level (OASPL), tone corrected perceived noise level (PNLT), and one-third-octave band sound pressure level (SPL).

Storage, transmission and distribution of hydrogen

NASA Technical Reports Server (NTRS)

Kelley, J. H.; Hagler, R., Jr.

1979-01-01

Current practices and future requirements for the storage, transmission and distribution of hydrogen are reviewed in order to identify inadequacies to be corrected before hydrogen can achieve its full potential as a substitute for fossil fuels. Consideration is given to the storage of hydrogen in underground solution-mined salt caverns, portable high-pressure containers and dewars, pressure vessels and aquifers and as metal hydrides, hydrogen transmission in evacuated double-walled insulated containers and by pipeline, and distribution by truck and internal distribution networks. Areas for the improvement of these techniques are indicated, and these technological deficiencies, including materials development, low-cost storage and transmission methods, low-cost, long-life metal hydrides and novel methods for hydrogen storage, are presented as challenges for research and development.

Electronic structure and properties of lanthanum

NASA Astrophysics Data System (ADS)

Nixon, Lane; Papaconstantopoulos, Dimitrios

2008-03-01

The total energy and electronic structure of lanthanum have been calculated in the bcc, fcc, hcp and dhcp structures for pressures up to 50 GPa. The full potential linearized-augmented-planewave method was used with both the local-density and general-gradient approximations. The correct phase ordering has been found, with lattice parameters and bulk moduli in good agreement with experimental data. The GGA method shows excellent agreement overall while the LDA results show larger discrepancies. The calculated strain energies for the fcc and bcc structures demonstrate the respective stable and unstable configurations at ambient conditions. The calculated superconductivity properties under pressure for the fcc structure are also found to agree well with measurements. Both LDA and GGA, with minor differences, reproduce well the experimental results for Tc.

The structure of MgO-SiO2 glasses at elevated pressure.

PubMed

Wilding, Martin; Guthrie, Malcolm; Kohara, Shinji; Bull, Craig L; Akola, Jaakko; Tucker, Matt G

2012-06-06

The magnesium silicate system is an important geophysical analogue and neutron diffraction data from glasses formed in this system may also provide an initial framework for understanding the structure-dependent properties of related liquids that are important during planetary formation. Neutron diffraction data collected in situ for a single composition (38 mol% SiO(2)) magnesium silicate glass sample shows local changes in structure as pressure is increased from ambient conditions to 8.6 GPa at ambient temperature. A method for obtaining the fully corrected, total structure factor, S(Q), has been developed that allows accurate structural characterization as this weakly scattering glass sample is compressed. The measured S(Q) data indicate changes in chemical ordering with pressure and the real-space transforms show an increase in Mg-O coordination number and a distortion of the local environment around magnesium ions. We have used reverse Monte Carlo methods to compare the high pressure and ambient pressure structures and also compare the high pressure form with a more silica-poor glass (Mg(2)SiO(4)) that represents the approach to a more dense, void-free and topologically ordered structure. The Mg-O coordination number increases with pressure and we also find that the degree of continuous connectivity of Si-O bonds increases via a collapse of interstices.

Self-correcting electronically scanned pressure sensor

NASA Technical Reports Server (NTRS)

Gross, C. (Inventor)

1983-01-01

A multiple channel high data rate pressure sensing device is disclosed for use in wind tunnels, spacecraft, airborne, process control, automotive, etc., pressure measurements. Data rates in excess of 100,000 measurements per second are offered with inaccuracies from temperature shifts less than 0.25% (nominal) of full scale over a temperature span of 55 C. The device consists of thirty-two solid state sensors, signal multiplexing electronics to electronically address each sensor, and digital electronic circuitry to automatically correct the inherent thermal shift errors of the pressure sensors and their associated electronics.

First principles study of pressure induced polymorphic phase transition in KNO3

NASA Astrophysics Data System (ADS)

Yedukondalu, N.; Vaitheeswaran, G.

2015-06-01

We report the structural, elastic, electronic, and vibrational properties of polymorphic phases II and III of KNO3 based on density functional theory (DFT). Using semi-empirical dispersion correction (DFT-D2) method, we predicted the correct thermodynamic ground state of KNO3 and the obtained ground state properties of the polymorphs are in good agreement with the experiments. We further used this method to calculate the elastic constants, IR and Raman spectra, vibrational frequencies and their assignment of these polymorphs. The calculated Tran Blaha-modified Becke Johnson (TB-mBJ) electronic structure shows that both the polymorphic phases are direct band gap insulators with mixed ionic and covalent bonding. Also the TB-mBJ band gaps are improved over standard DFT functionals which are comparable with the available experiments.

A coarse-grid-projection acceleration method for finite-element incompressible flow computations

NASA Astrophysics Data System (ADS)

Kashefi, Ali; Staples, Anne; FiN Lab Team

2015-11-01

Coarse grid projection (CGP) methodology provides a framework for accelerating computations by performing some part of the computation on a coarsened grid. We apply the CGP to pressure projection methods for finite element-based incompressible flow simulations. Based on it, the predicted velocity field data is restricted to a coarsened grid, the pressure is determined by solving the Poisson equation on the coarse grid, and the resulting data are prolonged to the preset fine grid. The contributions of the CGP method to the pressure correction technique are twofold: first, it substantially lessens the computational cost devoted to the Poisson equation, which is the most time-consuming part of the simulation process. Second, it preserves the accuracy of the velocity field. The velocity and pressure spaces are approximated by Galerkin spectral element using piecewise linear basis functions. A restriction operator is designed so that fine data are directly injected into the coarse grid. The Laplacian and divergence matrices are driven by taking inner products of coarse grid shape functions. Linear interpolation is implemented to construct a prolongation operator. A study of the data accuracy and the CPU time for the CGP-based versus non-CGP computations is presented. Laboratory for Fluid Dynamics in Nature.

Reducing Bolt Preload Variation with Angle-of-Twist Bolt Loading

NASA Technical Reports Server (NTRS)

Thompson, Bryce; Nayate, Pramod; Smith, Doug; McCool, Alex (Technical Monitor)

2001-01-01

Critical high-pressure sealing joints on the Space Shuttle reusable solid rocket motor require precise control of bolt preload to ensure proper joint function. As the reusable solid rocket motor experiences rapid internal pressurization, correct bolt preloads maintain the sealing capability and structural integrity of the hardware. The angle-of-twist process provides the right combination of preload accuracy, reliability, process control, and assembly-friendly design. It improves significantly over previous methods. The sophisticated angle-of-twist process controls have yielded answers to all discrepancies encountered while the simplicity of the root process has assured joint preload reliability.

Automatic Calculation of Hydrostatic Pressure Gradient in Patients with Head Injury: A Pilot Study.

PubMed

Moss, Laura; Shaw, Martin; Piper, Ian; Arvind, D K; Hawthorne, Christopher

2016-01-01

The non-surgical management of patients with traumatic brain injury is the treatment and prevention of secondary insults, such as low cerebral perfusion pressure (CPP). Most clinical pressure monitoring systems measure pressure relative to atmospheric pressure. If a patient is managed with their head tilted up, relative to their arterial pressure transducer, then a hydrostatic pressure gradient (HPG) can act against arterial pressure and cause significant errors in calculated CPP.To correct for HPG, the arterial pressure transducer should be placed level with the intracranial pressure transducer. However, this is not always achieved. In this chapter, we describe a pilot study investigating the application of speckled computing (or "specks") for the automatic monitoring of the patient's head tilt and subsequent automatic calculation of HPG. In future applications this will allow us to automatically correct CPP to take into account any HPG.

Thrust performance of a variable-geometry, divergent exhaust nozzle on a turbojet engine at altitude

NASA Technical Reports Server (NTRS)

Straight, D. M.; Collom, R. R.

1983-01-01

A variable geometry, low aspect ratio, nonaxisymmetric, two dimensional, convergent-divergent exhaust nozzle was tested at simulated altitude on a turbojet engine to obtain baseline axial, dry thrust performance over wide ranges of operating nozzle pressure ratios, throat areas, and internal expansion area ratios. The thrust data showed good agreement with theory and scale model test results after the data were corrected for seal leakage and coolant losses. Wall static pressure profile data were also obtained and compared with one dimensional theory and scale model data. The pressure data indicate greater three dimensional flow effects in the full scale tests than with models. The leakage and coolant penalties were substantial, and the method to determine them is included.

Turbofan forced mixer-nozzle internal flowfield. Volume 3: A computer code for 3-D mixing in axisymmetric nozzles

NASA Technical Reports Server (NTRS)

Kreskovsky, J. P.; Briley, W. R.; Mcdonald, H.

1982-01-01

A finite difference method is developed for making detailed predictions of three dimensional subsonic turbulent flow in turbofan lobe mixers. The governing equations are solved by a forward-marching solution procedure which corrects an inviscid potential flow solution for viscous and thermal effects, secondary flows, total pressure distortion and losses, internal flow blockage and pressure drop. Test calculations for a turbulent coaxial jet flow verify that the turbulence model performs satisfactorily for this relatively simple flow. Lobe mixer flows are presented for two geometries typical of current mixer design. These calculations included both hot and cold flow conditions, and both matched and mismatched Mach number and total pressure in the fan and turbine streams.

The manufacture of moulded supportive seating for the handicapped.

PubMed

Nelham, R L

1975-10-01

The wheelchair-bound population often have difficulty in obtaining a correct or comfortable posture in their chairs and sometimes develop pressure sores from long-duration sitting. This problem is being solved by manufacturing personalised, contoured seats which support the patient over the maximum area possible thereby reducing the pressure on the body and the incidence of pressure sores. A cast is obtained of the patient in a comfortable, medically correct posture and from this cast the seat is vacuum formed in thermoplastic materials or hand layed up in glass fibre reinforced resin. Some correction of deformity may be achieved. It is also possible to use the moulded seat in a vehicle.

Effect of Medial Patellofemoral Ligament Reconstruction Method on Patellofemoral Contact Pressures and Kinematics.

PubMed

Stephen, Joanna M; Kittl, Christoph; Williams, Andy; Zaffagnini, Stefano; Marcheggiani Muccioli, Giulio Maria; Fink, Christian; Amis, Andrew A

2016-05-01

There remains a lack of evidence regarding the optimal method when reconstructing the medial patellofemoral ligament (MPFL) and whether some graft constructs can be more forgiving to surgical errors, such as overtensioning or tunnel malpositioning, than others. The null hypothesis was that there would not be a significant difference between reconstruction methods (eg, graft type and fixation) in the adverse biomechanical effects (eg, patellar maltracking or elevated articular contact pressure) resulting from surgical errors such as tunnel malpositioning or graft overtensioning. Controlled laboratory study. Nine fresh-frozen cadaveric knees were placed on a customized testing rig, where the femur was fixed but the tibia could be moved freely from 0° to 90° of flexion. Individual quadriceps heads and the iliotibial tract were separated and loaded to 205 N of tension using a weighted pulley system. Patellofemoral contact pressures and patellar tracking were measured at 0°, 10°, 20°, 30°, 60°, and 90° of flexion using pressure-sensitive film inserted between the patella and trochlea, in conjunction with an optical tracking system. The MPFL was transected and then reconstructed in a randomized order using a (1) double-strand gracilis tendon, (2) quadriceps tendon, and (3) tensor fasciae latae allograft. Pressure maps and tracking measurements were recorded for each reconstruction method in 2 N and 10 N of tension and with the graft positioned in the anatomic, proximal, and distal femoral tunnel positions. Statistical analysis was undertaken using repeated-measures analyses of variance, Bonferroni post hoc analyses, and paired t tests. Anatomically placed grafts during MPFL reconstruction tensioned to 2 N resulted in the restoration of intact medial joint contact pressures and patellar tracking for all 3 graft types investigated (P > .050). However, femoral tunnels positioned proximal or distal to the anatomic origin resulted in significant increases in the mean medial joint contact pressure, medial patellar tilt, and medial patellar translation during knee flexion or extension, respectively (P < .050), regardless of graft type, as did tensioning to 10 N. The importance of the surgical technique, specifically correct femoral tunnel positioning and graft tensioning, in restoring normal patellofemoral joint (PFJ) kinematics and articular cartilage contact stresses is evident, and the type of MPFL graft appeared less important. The correct femoral tunnel position and graft tension for restoring normal PFJ kinematics and articular cartilage contact stresses appear to be more important than graft selection during MPFL reconstruction. These findings emphasize the importance of the surgical technique when undertaking this procedure. © 2016 The Author(s).

Analysis of three-phase equilibrium conditions for methane hydrate by isometric-isothermal molecular dynamics simulations.

PubMed

Yuhara, Daisuke; Brumby, Paul E; Wu, David T; Sum, Amadeu K; Yasuoka, Kenji

2018-05-14

To develop prediction methods of three-phase equilibrium (coexistence) conditions of methane hydrate by molecular simulations, we examined the use of NVT (isometric-isothermal) molecular dynamics (MD) simulations. NVT MD simulations of coexisting solid hydrate, liquid water, and vapor methane phases were performed at four different temperatures, namely, 285, 290, 295, and 300 K. NVT simulations do not require complex pressure control schemes in multi-phase systems, and the growth or dissociation of the hydrate phase can lead to significant pressure changes in the approach toward equilibrium conditions. We found that the calculated equilibrium pressures tended to be higher than those reported by previous NPT (isobaric-isothermal) simulation studies using the same water model. The deviations of equilibrium conditions from previous simulation studies are mainly attributable to the employed calculation methods of pressure and Lennard-Jones interactions. We monitored the pressure in the methane phase, far from the interfaces with other phases, and confirmed that it was higher than the total pressure of the system calculated by previous studies. This fact clearly highlights the difficulties associated with the pressure calculation and control for multi-phase systems. The treatment of Lennard-Jones interactions without tail corrections in MD simulations also contributes to the overestimation of equilibrium pressure. Although improvements are still required to obtain accurate equilibrium conditions, NVT MD simulations exhibit potential for the prediction of equilibrium conditions of multi-phase systems.

Analysis of three-phase equilibrium conditions for methane hydrate by isometric-isothermal molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Yuhara, Daisuke; Brumby, Paul E.; Wu, David T.; Sum, Amadeu K.; Yasuoka, Kenji

2018-05-01

To develop prediction methods of three-phase equilibrium (coexistence) conditions of methane hydrate by molecular simulations, we examined the use of NVT (isometric-isothermal) molecular dynamics (MD) simulations. NVT MD simulations of coexisting solid hydrate, liquid water, and vapor methane phases were performed at four different temperatures, namely, 285, 290, 295, and 300 K. NVT simulations do not require complex pressure control schemes in multi-phase systems, and the growth or dissociation of the hydrate phase can lead to significant pressure changes in the approach toward equilibrium conditions. We found that the calculated equilibrium pressures tended to be higher than those reported by previous NPT (isobaric-isothermal) simulation studies using the same water model. The deviations of equilibrium conditions from previous simulation studies are mainly attributable to the employed calculation methods of pressure and Lennard-Jones interactions. We monitored the pressure in the methane phase, far from the interfaces with other phases, and confirmed that it was higher than the total pressure of the system calculated by previous studies. This fact clearly highlights the difficulties associated with the pressure calculation and control for multi-phase systems. The treatment of Lennard-Jones interactions without tail corrections in MD simulations also contributes to the overestimation of equilibrium pressure. Although improvements are still required to obtain accurate equilibrium conditions, NVT MD simulations exhibit potential for the prediction of equilibrium conditions of multi-phase systems.

Reactions of Fe+ and FeO+ with C2H2, C2H4, and C2H6: Temperature-Dependent Kinetics

DTIC Science & Technology

2013-09-12

studies to lead to the development of efficient quantum chemical calculation methods by offering benchmarks for testing and refinement. Due to the...EXPERIMENTAL METHODS All measurements were performed on the Air Force Research Laboratory’s variable temperature selected ion flow tube (VT- SIFT) instrument...correct within error, indicating that they are in the low-pressure limit,52,53 and the termolecular rate constant is obtained from the slope. In contrast

Optimal guidance law development for an advanced launch system

NASA Technical Reports Server (NTRS)

Calise, Anthony J.; Hodges, Dewey H.

1990-01-01

A regular perturbation analysis is presented. Closed-loop simulations were performed with a first order correction including all of the atmospheric terms. In addition, a method was developed for independently checking the accuracy of the analysis and the rather extensive programming required to implement the complete first order correction with all of the aerodynamic effects included. This amounted to developing an equivalent Hamiltonian computed from the first order analysis. A second order correction was also completed for the neglected spherical Earth and back-pressure effects. Finally, an analysis was begun on a method for dealing with control inequality constraints. The results on including higher order corrections do show some improvement for this application; however, it is not known at this stage if significant improvement will result when the aerodynamic forces are included. The weak formulation for solving optimal problems was extended in order to account for state inequality constraints. The formulation was tested on three example problems and numerical results were compared to the exact solutions. Development of a general purpose computational environment for the solution of a large class of optimal control problems is under way. An example, along with the necessary input and the output, is given.

Viscosity-adjusted estimation of pressure head and pump flow with quasi-pulsatile modulation of rotary blood pump for a total artificial heart.

PubMed

Yurimoto, Terumi; Hara, Shintaro; Isoyama, Takashi; Saito, Itsuro; Ono, Toshiya; Abe, Yusuke

2016-09-01

Estimation of pressure and flow has been an important subject for developing implantable artificial hearts. To realize real-time viscosity-adjusted estimation of pressure head and pump flow for a total artificial heart, we propose the table estimation method with quasi-pulsatile modulation of rotary blood pump in which systolic high flow and diastolic low flow phased are generated. The table estimation method utilizes three kinds of tables: viscosity, pressure and flow tables. Viscosity is estimated from the characteristic that differential value in motor speed between systolic and diastolic phases varies depending on viscosity. Potential of this estimation method was investigated using mock circulation system. Glycerin solution diluted with salty water was used to adjust viscosity of fluid. In verification of this method using continuous flow data, fairly good estimation could be possible when differential pulse width modulation (PWM) value of the motor between systolic and diastolic phases was high. In estimation under quasi-pulsatile condition, inertia correction was provided and fairly good estimation was possible when the differential PWM value was high, which was not different from the verification results using continuous flow data. In the experiment of real-time estimation applying moving average method to the estimated viscosity, fair estimation could be possible when the differential PWM value was high, showing that real-time viscosity-adjusted estimation of pressure head and pump flow would be possible with this novel estimation method when the differential PWM value would be set high.

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.

Distributed Relaxation Multigrid and Defect Correction Applied to the Compressible Navier-Stokes Equations

NASA Technical Reports Server (NTRS)

Thomas, J. L.; Diskin, B.; Brandt, A.

1999-01-01

The distributed-relaxation multigrid and defect- correction methods are applied to the two- dimensional compressible Navier-Stokes equations. The formulation is intended for high Reynolds number applications and several applications are made at a laminar Reynolds number of 10,000. A staggered- grid arrangement of variables is used; the coupled pressure and internal energy equations are solved together with multigrid, requiring a block 2x2 matrix solution. Textbook multigrid efficiencies are attained for incompressible and slightly compressible simulations of the boundary layer on a flat plate. Textbook efficiencies are obtained for compressible simulations up to Mach numbers of 0.7 for a viscous wake simulation.

A Gaussian method to improve work-of-breathing calculations.

PubMed

Petrini, M F; Evans, J N; Wall, M A; Norman, J R

1995-01-01

The work of breathing is a calculated index of pulmonary function in ventilated patients that may be useful in deciding when to wean and when to extubate. However, the accuracy of the calculated work of breathing of the patient (WOBp) can suffer from artifacts introduced by coughing, swallowing, and other non-breathing maneuvers. The WOBp in this case will include not only the usual work of inspiration, but also the work of performing these non-breathing maneuvers. The authors developed a method to objectively eliminate the calculated work of these movements from the work of breathing, based on fitting to a Gaussian curve the variable P, which is obtained from the difference between the esophageal pressure change and the airway pressure change during each breath. In spontaneously breathing adults the normal breaths fit the Gaussian curve, while breaths that contain non-breathing maneuvers do not. In this Gaussian breath-elimination method (GM), breaths that are two standard deviations from that mean obtained by the fit are eliminated. For normally breathing control adult subjects, GM had little effect on WOBp, reducing it from 0.49 to 0.47 J/L (n = 8), while there was a 40% reduction in the coefficient of variation. Non-breathing maneuvers were simulated by coughing, which increased WOBp to 0.88 (n = 6); with the GM correction, WOBp was 0.50 J/L, a value not significantly different from that of normal breathing. Occlusion also increased WOBp to 0.60 J/L, but GM-corrected WOBp was 0.51 J/L, a normal value. As predicted, doubling the respiratory rate did not change the WOBp before or after the GM correction.(ABSTRACT TRUNCATED AT 250 WORDS)

Fracture resistance of welded thick-walled high-pressure vessels in power plants. Report No. 2. Approach to evaluating static strength

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

Gorynin, I.V.; Filatov, V.M.; Ignatov, V.A.

1986-07-01

The authors examine data on the effect of defects on the fracture resistance of high-pressure vessels and their models obtained within the framework of the HSST program. Results of internal-pressure tests of two types of vessels with a wall thickness of 152 mm made from forgings of steels SA508 and SA533, as well as small vessels with a wall thickness of 11.5 and 23mm made of steel SA533 are shown. The authors state that testing thick-walled welded high-pressure vessels and thin-walled vessels with surface defects of different sizes has demonstrated that there are substantial static-strength reserves in structures designed bymore » existing domestic and foreign standards on the strength of power-plant equipment. A correction was proposed for the presently used method of calculating the resistance of highpressure vessels to brittle fracture that allows for the dimensions of the defects in relation to the type of vessel, the manufacturing technology, and the method of inspection.« less

Validation of Test Methods for Air Leak Rate Verification of Spaceflight Hardware

NASA Technical Reports Server (NTRS)

Oravec, Heather Ann; Daniels, Christopher C.; Mather, Janice L.

2017-01-01

As deep space exploration continues to be the goal of NASAs human spaceflight program, verification of the performance of spaceflight hardware becomes increasingly critical. Suitable test methods for verifying the leak rate of sealing systems are identified in program qualification testing requirements. One acceptable method for verifying the air leak rate of gas pressure seals is the tracer gas leak detector method. In this method, a tracer gas (commonly helium) leaks past the test seal and is transported to the leak detector where the leak rate is quantified. To predict the air leak rate, a conversion factor of helium-to-air is applied depending on the magnitude of the helium flow rate. The conversion factor is based on either the molecular mass ratio or the ratio of the dynamic viscosities. The current work was aimed at validating this approach for permeation-level leak rates using a series of tests with a silicone elastomer O-ring. An established pressure decay method with constant differential pressure was used to evaluate both the air and helium leak rates of the O-ring under similar temperature and pressure conditions. The results from the pressure decay tests showed, for the elastomer O-ring, that neither the molecular flow nor the viscous flow helium-to-air conversion factors were applicable. Leak rate tests were also performed using nitrogen and argon as the test gas. Molecular mass and viscosity based helium-to-test gas conversion factors were applied, but did not correctly predict the measured leak rates of either gas. To further this study, the effect of pressure boundary conditions was investigated. Often, pressure decay leak rate tests are performed at a differential pressure of 101.3 kPa with atmospheric pressure on the downstream side of the test seal. In space applications, the differential pressure is similar, but with vacuum as the downstream pressure. The same O-ring was tested at four unique differential pressures ranging from 34.5 to 137.9 kPa. Up to six combinations of upstream and downstream pressures for each differential pressure were compared. For a given differential pressure, the various combinations of upstream and downstream dry air pressures did not significantly affect the leak rate. As expected, the leak rate of the O-ring increased with increasing differential pressure. The results suggested that the current leak test pressure conditions, used to verify spacecraft sealing systems with elastomer seals, produce accurate values even though the boundary conditions do not model the space application.

Formulation, Implementation and Validation of a Two-Fluid model in a Fuel Cell CFD Code

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

Jain, Kunal; Cole, J. Vernon; Kumar, Sanjiv

2008-12-01

Water management is one of the main challenges in PEM Fuel Cells. While water is essential for membrane electrical conductivity, excess liquid water leads to flooding of catalyst layers. Despite the fact that accurate prediction of two-phase transport is key for optimal water management, understanding of the two-phase transport in fuel cells is relatively poor. Wang et. al. have studied the two-phase transport in the channel and diffusion layer separately using a multiphase mixture model. The model fails to accurately predict saturation values for high humidity inlet streams. Nguyen et. al. developed a two-dimensional, two-phase, isothermal, isobaric, steady state modelmore » of the catalyst and gas diffusion layers. The model neglects any liquid in the channel. Djilali et. al. developed a three-dimensional two-phase multicomponent model. The model is an improvement over previous models, but neglects drag between the liquid and the gas phases in the channel. In this work, we present a comprehensive two-fluid model relevant to fuel cells. Models for two-phase transport through Channel, Gas Diffusion Layer (GDL) and Channel-GDL interface, are discussed. In the channel, the gas and liquid pressures are assumed to be same. The surface tension effects in the channel are incorporated using the continuum surface force (CSF) model. The force at the surface is expressed as a volumetric body force and added as a source to the momentum equation. In the GDL, the gas and liquid are assumed to be at different pressures. The difference in the pressures (capillary pressure) is calculated using an empirical correlations. At the Channel-GDL interface, the wall adhesion affects need to be taken into account. SIMPLE-type methods recast the continuity equation into a pressure-correction equation, the solution of which then provides corrections for velocities and pressures. However, in the two-fluid model, the presence of two phasic continuity equations gives more freedom and more complications. A general approach would be to form a mixture continuity equation by linearly combining the phasic continuity equations using appropriate weighting factors. Analogous to mixture equation for pressure correction, a difference equation is used for the volume/phase fraction by taking the difference between the phasic continuity equations. The relative advantages of the above mentioned algorithmic variants for computing pressure correction and volume fractions are discussed and quantitatively assessed. Preliminary model validation is done for each component of the fuel cell. The two-phase transport in the channel is validated using empirical correlations. Transport in the GDL is validated against results obtained from LBM and VOF simulation techniques. The Channel-GDL interface transport will be validated against experiment and empirical correlation of droplet detachment at the interface.« less

The effect of ambient pressure on well chamber response: Monte Carlo calculated results for the HDR 1000 plus.

PubMed

Bohm, Tim D; Griffin, Sheridan L; DeLuca, Paul M; DeWerd, Larry A

2005-04-01

The determination of the air kerma strength of a brachytherapy seed is necessary for effective treatment planning. Well ionization chambers are used on site at therapy clinics to determine the air kerma strength of seeds. In this work, the response of the Standard Imaging HDR 1000 Plus well chamber to ambient pressure is examined using Monte Carlo calculations. The experimental work examining the response of this chamber as well as other chambers is presented in a companion paper. The Monte Carlo results show that for low-energy photon sources, the application of the standard temperature pressure PTP correction factor produces an over-response at the reduced air densities/pressures corresponding to high elevations. With photon sources of 20 to 40 keV, the normalized PTP corrected chamber response is as much as 10% to 20% over unity for air densities/pressures corresponding to an elevation of 3048 m (10000 ft) above sea level. At air densities corresponding to an elevation of 1524 m (5000 ft), the normalized PTP-corrected chamber response is 5% to 10% over unity for these photon sources. With higher-energy photon sources (>100 keV), the normalized PTP corrected chamber response is near unity. For low-energy beta sources of 0.25 to 0.50 MeV, the normalized PTP-corrected chamber response is as much as 4% to 12% over unity for air densities/pressures corresponding to an elevation of 3048 m (10000 ft) above sea level. Higher-energy beta sources (>0.75 MeV) have a normalized PTP corrected chamber response near unity. Comparing calculated and measured chamber responses for common 103Pd- and 125I-based brachytherapy seeds show agreement to within 2.7% and 1.9%, respectively. Comparing MCNP calculated chamber responses with EGSnrc calculated chamber responses show agreement to within 3.1% at photon energies of 20 to 40 keV. We conclude that Monte Carlo transport calculations accurately model the response of this well chamber. Further, applying the standard PTP correction factor for this well chamber is insufficient in accounting for the change in chamber response with air pressure for low-energy (<100 keV) photon and low-energy (<0.75 MeV)beta sources.

Computational wave dynamics for innovative design of coastal structures

PubMed Central

GOTOH, Hitoshi; OKAYASU, Akio

2017-01-01

For innovative designs of coastal structures, Numerical Wave Flumes (NWFs), which are solvers of Navier-Stokes equation for free-surface flows, are key tools. In this article, various methods and techniques for NWFs are overviewed. In the former half, key techniques of NWFs, namely the interface capturing (MAC, VOF, C-CUP) and significance of NWFs in comparison with the conventional wave models are described. In the latter part of this article, recent improvements of the particle method are shown as one of cores of NWFs. Methods for attenuating unphysical pressure fluctuation and improving accuracy, such as CMPS method for momentum conservation, Higher-order Source of Poisson Pressure Equation (PPE), Higher-order Laplacian, Error-Compensating Source in PPE, and Gradient Correction for ensuring Taylor-series consistency, are reviewed briefly. Finally, the latest new frontier of the accurate particle method, including Dynamic Stabilization for providing minimum-required artificial repulsive force to improve stability of computation, and Space Potential Particle for describing the exact free-surface boundary condition, is described. PMID:29021506

Molecular dynamics simulations of the melting curve of NiAl alloy under pressure

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

Zhang, Wenjin; Peng, Yufeng; Liu, Zhongli, E-mail: zhongliliu@yeah.net

2014-05-15

The melting curve of B2-NiAl alloy under pressure has been investigated using molecular dynamics technique and the embedded atom method (EAM) potential. The melting temperatures were determined with two approaches, the one-phase and the two-phase methods. The first one simulates a homogeneous melting, while the second one involves a heterogeneous melting of materials. Both approaches reduce the superheating effectively and their results are close to each other at the applied pressures. By fitting the well-known Simon equation to our melting data, we yielded the melting curves for NiAl: 1783(1 + P/9.801){sup 0.298} (one-phase approach), 1850(1 + P/12.806){sup 0.357} (two-phase approach).more » The good agreement of the resulting equation of states and the zero-pressure melting point (calc., 1850 ± 25 K, exp., 1911 K) with experiment proved the correctness of these results. These melting data complemented the absence of experimental high-pressure melting of NiAl. To check the transferability of this EAM potential, we have also predicted the melting curves of pure nickel and pure aluminum. Results show the calculated melting point of Nickel agrees well with experiment at zero pressure, while the melting point of aluminum is slightly higher than experiment.« less

Dependence with air density of the response of the PTW SourceCheck ionization chamber for low energy brachytherapy sources.

PubMed

Tornero-López, Ana M; Guirado, Damián; Perez-Calatayud, Jose; Ruiz-Arrebola, Samuel; Simancas, Fernando; Gazdic-Santic, Maja; Lallena, Antonio M

2013-12-01

Air-communicating well ionization chambers are commonly used to assess air kerma strength of sources used in brachytherapy. The signal produced is supposed to be proportional to the air density within the chamber and, therefore, a density-independent air kerma strength is obtained when the measurement is corrected to standard atmospheric conditions using the usual temperature and pressure correction factor. Nevertheless, when assessing low energy sources, the ionization chambers may not fulfill that condition and a residual density dependence still remains after correction. In this work, the authors examined the behavior of the PTW 34051 SourceCheck ionization chamber when measuring the air kerma strength of (125)I seeds. Four different SourceCheck chambers were analyzed. With each one of them, two series of measurements of the air kerma strength for (125)I selectSeed(TM) brachytherapy sources were performed inside a pressure chamber and varying the pressure in a range from 747 to 1040 hPa (560 to 780 mm Hg). The temperature and relative humidity were kept basically constant. An analogous experiment was performed by taking measurements at different altitudes above sea level. Contrary to other well-known ionization chambers, like the HDR1000 PLUS, in which the temperature-pressure correction factor overcorrects the measurements, in the SourceCheck ionization chamber they are undercorrected. At a typical atmospheric situation of 933 hPa (700 mm Hg) and 20 °C, this undercorrection turns out to be 1.5%. Corrected measurements show a residual linear dependence on the density and, as a consequence, an additional density dependent correction must be applied. The slope of this residual linear density dependence is different for each SourceCheck chamber investigated. The results obtained by taking measurements at different altitudes are compatible with those obtained with the pressure chamber. Variations of the altitude and changes in the weather conditions may produce significant density corrections, and that effect should be taken into account. This effect is chamber-dependent, indicating that a specific calibration is necessary for each particular chamber. To our knowledge, this correction has not been considered so far for SourceCheck ionization chambers, but its magnitude cannot be neglected in clinical practice. The atmospheric pressure and temperature at which the chamber was calibrated need to be taken into account, and they should be reported in the calibration certificate. In addition, each institution should analyze the particular response of its SourceCheck ionization chamber and compute the adequate correction factors. In the absence of a suitable pressure chamber, a possibility for this assessment is to take measurements at different altitudes, spanning a wide enough air density range.

Author Correction: Reliability and feasibility of gait initiation centre-of-pressure excursions using a Wii® Balance Board in older adults at risk of falling.

PubMed

Lee, James; Webb, Graham; Shortland, Adam P; Edwards, Rebecca; Wilce, Charlotte; Jones, Gareth D

2018-05-12

In the original publication, the article title was incorrectly published as 'Reliability and feasibility of gait initiation centre-of-pressure excursions using a Wii® Balance Board in older adults at risk of failing'. The correct title should read as 'Reliability and feasibility of gait initiation centre-of-pressure excursions using a Wii® Balance Board in older adults at risk of falling'.

The Effects of Local Anaesthetics on QT Parameters during Thoracic Epidural Anaesthesia Combined with General Anaesthesia: Ropivacaine versus Bupivacaine

PubMed Central

Güven, Özlem; Sazak, Hilal; Alagöz, Ali; Şavkılıoğlu, Eser; Demirbaş, Çilsem Sevgen; Yıldız, Ali; Karabulut, Erdem

2013-01-01

Background: Many studies focusing on the effects of local anaesthetics on QT intervals have been performed, but the articles evaluating the relationship between thoracic epidural anaesthesia combined with general anaesthesia and QT parameters are very limited. Aims: We aimed to compare the effects of bupivacaine and ropivacaine on QT interval, corrected QT, dispersion of QT, and corrected dispersion of QT in patients undergoing lung resection under thoracic epidural anaesthesia combined with general anaesthesia. Study Design: Prospective clinical study. Methods: Thirty ASA physical status 1–3 patients requiring thoracic epidural anaesthesia combined with general anaesthesia for thoracic surgery. Patients were randomly assigned to two groups, which were allocated to receive either bupivacaine (Group B) or ropivacaine (Group R) during thoracic epidural anaesthesia. Following haemodynamic monitoring, a thoracic epidural catheter was inserted. Local anaesthetic at an average dose of 1.5 mL/ segment was given through an epidural catheter. The same general anaesthesia protocol was administered in both groups. Records and measurements were performed on 10 phases that were between the thoracic epidural catheter insertion to the 5th min of endobronchial intubation. In all phases, systolic arterial pressure, diastolic arterial pressure, mean arterial pressure, heart rate, peripheral O2 saturation, and electrocardiogram monitoring were performed in patients. All QT parameters were recorded by 12-lead electrocardiogram and analysed manually by a cardiologist. Results: QT intervals were similar between two groups. In Group R, corrected QT values at the 20th min of local anaesthetic injection and the 5th min of endobronchial intubation were shorter than those in Group B (p<0.05). The basal dispersion of QT and dispersion of QT values at the 1st min of propofol injection were shorter than those in Group R (p<0.05). The corrected dispersion of QT value at the 1st min of propofol injection was shorter in Group R (p<0.05). In Group R, the decrease in mean arterial pressure at the 1st min of fentanyl injection was significant compared with Group B (p<0.05). There was no significant difference between the groups with respect to heart rate and complications. Conclusion: The corrected QT, dispersion of QT, and corrected dispersion of QT intervals were slightly longer in the patients receiving bupivacaine compared with those receiving ropivacaine in various phases of the present study. PMID:25207150

Mott Transition of MnO under Pressure: A Comparison of Correlated Band Theories

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

Kasinathan, Deepa; Kunes, Jan; Koepernik, K

The electronic structure, magnetic moment, and volume collapse of MnO under pressure are obtained from four different correlated band theory methods; local density approximation+Hubbard U (LDA+U), pseudopotential self-interaction correction (pseudo-SIC), the hybrid functional (combined local exchange plus Hartree-Fock exchange), and the local spin density SIC (SIC-LSD) method. Each method treats correlation among the five Mn 3d orbitals (per spin), including their hybridization with three O 2p orbitals in the valence bands and their changes with pressure. The focus is on comparison of the methods for rock salt MnO (neglecting the observed transition to the NiAs structure in the 90-100 GPamore » range). Each method predicts a first-order volume collapse, but with variation in the predicted volume and critical pressure. Accompanying the volume collapse is a moment collapse, which for all methods is from high-spin to low-spin ((5/2){yields}(1/2)), not to nonmagnetic as the simplest scenario would have. The specific manner in which the transition occurs varies considerably among the methods: pseudo-SIC and SIC-LSD give insulator-to-metal, while LDA+U gives insulator-to-insulator and the hybrid method gives an insulator-to-semimetal transition. Projected densities of states above and below the transition are presented for each of the methods and used to analyze the character of each transition. In some cases the rhombohedral symmetry of the antiferromagnetically ordered phase clearly influences the character of the transition.« less

Study of the vortex conditions of wings with large sweepback by extrapolation of the Jones method

NASA Technical Reports Server (NTRS)

Hirsch, P.

1980-01-01

The pockets of separation originating on the leading edges are surrounded by vortex sheets. Their configuration and intensity were determined by four conditions with the JONES approximation, which is itself corrected by a simple logic. Field pressures and stresses were computed for different cases and are compared with test results (pure deltas, swallow tails, truncations, strakes, ducks, fuselage).

A study on flow development in an APU-style inlet and its effect on centrifugal compressor performance

NASA Astrophysics Data System (ADS)

Lou, Fangyuan

The objectives of this research were to investigate the flow development inside an APU-style inlet and its effect on centrifugal compressor performance. The motivation arises from the increased applications of gas turbine engines installed with APU-style inlets such as unmanned aerial vehicles, auxiliary power units, and helicopters. The inlet swirl distortion created from these complicated inlet systems has become a major performance and operability concern. To improve the integration between the APU-style inlet and gas turbine engines, better understanding of the flow field in the APU-style inlet and its effect on gas turbine is necessary. A research facility for the purpose of performing an experimental investigation of the flow field inside an APU-style inlet was developed. A subcritical air ejector is used to continuously flow the inlet at desired corrected mass flow rates. The facility is capable of flowing the APU inlet over a wide range of corrected mass flow rate that matches the same Mach numbers as engine operating conditions. Additionally, improvement in the system operational steadiness was achieved by tuning the pressure controller using a PID control method and utilizing multi-layer screens downstream of the APU inlet. Less than 1% relative unsteadiness was achieved for full range operation. The flow field inside the rectangular-sectioned 90? bend of the APU-style inlet was measured using a 3-Component LDV system. The structures for both primary flow and the secondary flow inside the bend were resolved. Additionally, the effect of upstream geometry on the flow development in the downstream bend was also investigated. Furthermore, a Single Stage Centrifugal Compressor research facility was developed at Purdue University in collaboration with Honeywell to operate the APU-style inlet at engine conditions with a compressor. To operate the facility, extensive infrastructure for facility health monitoring and performance control (including lubrication systems, secondary air systems, a throttle system, and different inlet configurations) were built. Additionally, three Labview programs were developed for acquiring the compressor health monitoring, steady and unsteady pressure and strain data. The baseline, steady aerodynamic performance map was established. Additionally, the unsteady pressure field in the compressor was investigated. Steady performance data have been acquired from choke to near surge at three different corrected speeds from 90% to 100% corrected speed in 5% increments. The performance of the compressor stage was characterized using total pressure ratio (TPR), total temperature ratio (TTR), and isentropic efficiency. The impeller alone and diffuser along performance were also investigated, and the high loss regions in the compressor were identified. At last, the compressor unsteady shroud pressure was investigated at 100% corrected speed in both the time domain and frequency domain. Results show strong pressure components in relation to the shaft frequency (SF). The impeller has 17 main blades and 17 splitter blades, and introduces pressure fluctuations at 17SF and its harmonics. Additionally, the diffuser has a vane count of 25 and results in pressure spectra of 59SF (17+17+25) due to the interactions between the impeller and diffuser.

Development of an Analysis and Design Optimization Framework for Marine Propellers

NASA Astrophysics Data System (ADS)

Tamhane, Ashish C.

In this thesis, a framework for the analysis and design optimization of ship propellers is developed. This framework can be utilized as an efficient synthesis tool in order to determine the main geometric characteristics of the propeller but also to provide the designer with the capability to optimize the shape of the blade sections based on their specific criteria. A hybrid lifting-line method with lifting-surface corrections to account for the three-dimensional flow effects has been developed. The prediction of the correction factors is achieved using Artificial Neural Networks and Support Vector Regression. This approach results in increased approximation accuracy compared to existing methods and allows for extrapolation of the correction factor values. The effect of viscosity is implemented in the framework via the coupling of the lifting line method with the open-source RANSE solver OpenFOAM for the calculation of lift, drag and pressure distribution on the blade sections using a transition kappa-o SST turbulence model. Case studies of benchmark high-speed propulsors are utilized in order to validate the proposed framework for propeller operation in open-water conditions but also in a ship's wake.

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

Martínez-Ruiz, F. J.; Blas, F. J., E-mail: felipe@uhu.es; Moreno-Ventas Bravo, A. I.

We determine the interfacial properties of a symmetrical binary mixture of equal-sized spherical Lennard-Jones molecules, σ{sub 11} = σ{sub 22}, with the same dispersive energy between like species, ϵ{sub 11} = ϵ{sub 22}, but different dispersive energies between unlike species low enough to induce phase separation. We use the extensions of the improved version of the inhomogeneous long-range corrections of Janecek [J. Phys. Chem. B 110, 6264 (2006)], presented recently by MacDowell and Blas [J. Chem. Phys. 131, 074705 (2009)] and Martínez-Ruiz et al. [J. Chem. Phys. 141, 184701 (2014)], to deal with the interaction energy and microscopic components ofmore » the pressure tensor. We perform Monte Carlo simulations in the canonical ensemble to obtain the interfacial properties of the symmetrical mixture with different cut-off distances r{sub c} and in combination with the inhomogeneous long-range corrections. The pressure tensor is obtained using the mechanical (virial) and thermodynamic route. The liquid-liquid interfacial tension is also evaluated using three different procedures, the Irving-Kirkwood method, the difference between the macroscopic components of the pressure tensor, and the test-area methodology. This allows to check the validity of the recent extensions presented to deal with the contributions due to long-range corrections for intermolecular energy and pressure tensor in the case of binary mixtures that exhibit liquid-liquid immiscibility. In addition to the pressure tensor and the surface tension, we also obtain density profiles and coexistence densities and compositions as functions of pressure, at a given temperature. According to our results, the main effect of increasing the cut-off distance r{sub c} is to sharpen the liquid-liquid interface and to increase the width of the biphasic coexistence region. Particularly interesting is the presence of a relative minimum in the total density profiles of the symmetrical mixture. This minimum is related with a desorption of the molecules at the interface, a direct consequence of a combination of the weak dispersive interactions between unlike species of the symmetrical binary mixture, and the presence of an interfacial region separating the two immiscible liquid phases in coexistence.« less

Residual interference assessment in adaptive wall wind tunnels

NASA Technical Reports Server (NTRS)

Murthy, A. V.

1989-01-01

A two-variable method is presented which is suitable for on-line calculation of residual interference in airfoil testing in the Langley 0.3-Meter Transonic Cryogenic Tunnel (0.3-M TCT). The method applies the Cauchy's integral formula to the closed contour formed by the contoured top and bottom walls, and the upstream and downstream ends. The measured top and bottom wall pressures and position are used to calculate the correction to the test Mach number and the airfoil angle of attack. Application to specific data obtained in the 0.3-M TCT adaptive wall test section demonstrates the need to assess residual interference to ensure that the desired level of wall streamlining is achieved. A FORTRAN computer program was developed for on-line calculation of the residual corrections during airfoil tests in the 0.3-M TCT.

[SIMULTANEOUS MEASUREMENT OF INTRAVENTRICULAR AND PARENCHYMAL INTRACRANIAL PRESSURE IN PATIENTS WITH SEVERE TRAUMA BRAIN INJURY].

PubMed

Oshorov, A V; Popugaev, K A; Savin, I A; Potapov, A A

2016-01-01

"Standard" assessment of ICP by measuring liquor ventricular pressure recently questioned. THE OBJECTIVE OF THE STUDY: Compare the values of ventricular and parenchymal ICP against the closure of open liquor drainage and during active CSF drainage. Examined 7 patients with TBI and intracranial hypertension syndrome, GCS 5.6 ± 1.2 points, 4.2 ± age 33 years. Compared parenchymal and ventricular ICP in three time periods: 1--during closure of ventricular drainage, 2--during of the open drains and drainage at the level of 14-15 mmHg, 3--during the period of active drainage. When comparing two methods of measurement used Bland-Altman method. 1. During time period of the closed drainage correlation coefficient was r = 0.83, p < 0.001. Bland-Altman method: the difference of the two measurements is equal to the minimum and 0.7 mm Hg, the standard deviation of 2.02 mm Hg 2. During time period of the open drainage was reduction of the correlation coefficient to r = 0.46, p < 0.01. Bland-Altman method: an increase in the difference of the two measurements to -0.84 mmHg, standard deviation 2.8 mm Hg 3. During time period of the active drainage of cerebrospinal fluid was marked difference between methods of measurement. Bland-Altman method: the difference was 8.64 mm Hg, and a standard deviation of 2.6 mm Hg. 1. During the closure of the ventricular drainage were good correlation between ventricular and parenchymal ICR 2. During open the liquor drainage correlation between the two methods of measuring the intracranial pressure is reduced. 3. During the active CSF drainage correlation between the two methods of measuring intracranial pressure can be completely lost. Under these conditions, CSF pressure is not correctly reflect the ICP 4. For an accurate and continuous measurement of intracranial pressure on the background of the active CSF drainage should be carried out simultaneous parenchymal ICP measurement.

Calibration of 3-D wind measurements on a single engine research aircraft

NASA Astrophysics Data System (ADS)

Mallaun, C.; Giez, A.; Baumann, R.

2015-02-01

An innovative calibration method for the wind speed measurement using a boom mounted Rosemount model 858 AJ air velocity probe is introduced. The method is demonstrated for a sensor system installed on a medium size research aircraft which is used for measurements in the atmospheric boundary layer. The method encounters a series of coordinated flight manoeuvres to directly estimate the aerodynamic influences on the probe and to calculate the measurement uncertainties. The introduction of a differential Global Positioning System (DGPS) combined with a high accuracy Inertial Reference System (IRS) has brought major advances to airborne measurement techniques. The exact determination of geometrical height allows the use of the pressure signal as an independent parameter. Furthermore, the exact height information and the stepwise calibration process lead to maximum accuracy. The results show a measurement uncertainty for the aerodynamic influence of the dynamic and static pressures of 0.1 hPa. The applied parametrisation does not require any height dependencies or time shifts. After extensive flight tests a correction for the flow angles (attack and sideslip angles) was found, which is necessary for a successful wind calculation. A new method is demonstrated to correct for the aerodynamic influence on the sideslip angle. For the 3-D wind vector (with 100 Hz resolution) a novel error propagation scheme is tested, which determines the measurement uncertainties to be 0.3 m s-1 for the horizontal and 0.2 m s-1 for the vertical wind components.

Calibration of 3-D wind measurements on a single-engine research aircraft

NASA Astrophysics Data System (ADS)

Mallaun, C.; Giez, A.; Baumann, R.

2015-08-01

An innovative calibration method for the wind speed measurement using a boom-mounted Rosemount model 858 AJ air velocity probe is introduced. The method is demonstrated for a sensor system installed on a medium-size research aircraft which is used for measurements in the atmospheric boundary layer. The method encounters a series of coordinated flight manoeuvres to directly estimate the aerodynamic influences on the probe and to calculate the measurement uncertainties. The introduction of a differential Global Positioning System (DGPS) combined with a high-accuracy inertial reference system (IRS) has brought major advances to airborne measurement techniques. The exact determination of geometrical height allows the use of the pressure signal as an independent parameter. Furthermore, the exact height information and the stepwise calibration process lead to maximum accuracy. The results show a measurement uncertainty for the aerodynamic influence of the dynamic and static pressures of 0.1 hPa. The applied parametrisation does not require any height dependencies or time shifts. After extensive flight tests a correction for the flow angles (attack and sideslip angles) was found, which is necessary for a successful wind calculation. A new method is demonstrated to correct for the aerodynamic influence on the sideslip angle. For the three-dimensional (3-D) wind vector (with 100 Hz resolution) a novel error propagation scheme is tested, which determines the measurement uncertainties to be 0.3 m s-1 for the horizontal and 0.2 m s-1 for the vertical wind components.

Revisiting the blind tests in crystal structure prediction: accurate energy ranking of molecular crystals.

PubMed

Asmadi, Aldi; Neumann, Marcus A; Kendrick, John; Girard, Pascale; Perrin, Marc-Antoine; Leusen, Frank J J

2009-12-24

In the 2007 blind test of crystal structure prediction hosted by the Cambridge Crystallographic Data Centre (CCDC), a hybrid DFT/MM method correctly ranked each of the four experimental structures as having the lowest lattice energy of all the crystal structures predicted for each molecule. The work presented here further validates this hybrid method by optimizing the crystal structures (experimental and submitted) of the first three CCDC blind tests held in 1999, 2001, and 2004. Except for the crystal structures of compound IX, all structures were reminimized and ranked according to their lattice energies. The hybrid method computes the lattice energy of a crystal structure as the sum of the DFT total energy and a van der Waals (dispersion) energy correction. Considering all four blind tests, the crystal structure with the lowest lattice energy corresponds to the experimentally observed structure for 12 out of 14 molecules. Moreover, good geometrical agreement is observed between the structures determined by the hybrid method and those measured experimentally. In comparison with the correct submissions made by the blind test participants, all hybrid optimized crystal structures (apart from compound II) have the smallest calculated root mean squared deviations from the experimentally observed structures. It is predicted that a new polymorph of compound V exists under pressure.

Above-Cloud Precipitable Water Retrievals using the MODIS 0.94 micron Band with Applications for Multi-Layer Cloud Detection

NASA Technical Reports Server (NTRS)

Platnick, S.; Wind, G.

2004-01-01

In order to perform satellite retrievals of cloud properties, it is important to account for the effect of the above-cloud atmosphere on the observations. The solar bands used in the operational MODIS Terra and Aqua cloud optical and microphysical algorithms (visible, NIR, and SWIR spectral windows) are primarily affected by water vapor, and to a lesser extent by well-mixed gases. For water vapor, the above-cloud column amount, or precipitable water, provides adequate information for an atmospheric correction; details of the vertical vapor distribution are not typically necessary for the level of correction required. Cloud-top pressure has a secondary effect due to pressure broadening influences. For well- mixed gases, cloud-top pressure is also required for estimates of above-cloud abundances. We present a method for obtaining above-cloud precipitable water over dark Ocean surfaces using the MODIS 0.94 pm vapor absorption band. The retrieval includes an iterative procedure for establishing cloud-top temperature and pressure, and is useful for both single layer water and ice clouds. Knowledge of cloud thermodynamic phase is fundamental in retrieving cloud optical and microphysical properties. However, in cases of optically thin cirrus overlapping lower water clouds, the concept of a single unique phase is ill- defined and depends, at least, on the spectral region of interest. We will present a method for multi-layer and multi-phase cloud detection which uses above-cloud precipitable water retrievals along with several existing MODIS operational cloud products (cloud-top pressure derived from a C02 slicing algorithm, IR and SWIR phase retrievals). Results are catagorized by whether the radiative signature in the MODIS solar bands is primarily that of a water cloud with ice cloud contamination, or visa-versa. Examples in polar and mid-latitude regions will be shown.

Performance of high area ratio nozzles for a small rocket thruster

NASA Technical Reports Server (NTRS)

Kushida, R. O.; Hermel, J.; Apfel, S.; Zydowicz, M.

1986-01-01

Theoretical estimates of supersonic nozzle performance have been compared to experimental test data for nozzles with an area ratio of 100:1 conical and 300:1 optimum contour, and 300:1 nozzles cut off at 200:1 and 100:1. These tests were done on a Hughes Aircraft Company 5 lbf monopropellant hydrazine thruster with chamber pressures ranging from 25 to 135 psia. The analytic method used is the conventional inviscid method of characteristic with correction for laminar boundary layer displacement and drag. Replacing the 100:1 conical nozzle with the 300:1 contoured nozzle resulted in an improvement in thrust performance of 0.74 percent at chamber pressure of 25 psia to 2.14 percent at chamber pressure of 135 psia. The data is significant because it is experimental verification that conventional nozzle design techniques are applicable even where the boundary layer is laminar and displaces as much as 35 percent of the flow at the nozzle exit plane.

SU-E-T-87: A TG-100 Approach for Quality Improvement of Associated Dosimetry Equipment

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

Manger, R; Pawlicki, T; Kim, G

2015-06-15

Purpose: Dosimetry protocols devote so much time to the discussion of ionization chamber choice, use and performance that is easy to forget about the importance of the associated dosimetry equipment (ADE) in radiation dosimetry - barometer, thermometer, electrometer, phantoms, triaxial cables, etc. Improper use and inaccuracy of these devices may significantly affect the accuracy of radiation dosimetry. The purpose of this study is to evaluate the risk factors in the monthly output dosimetry procedure and recommend corrective actions using a TG-100 approach. Methods: A failure mode and effects analysis (FMEA) of the monthly linac output check procedure was performed tomore » determine which steps and failure modes carried the greatest risk. In addition, a fault tree analysis (FTA) was performed to expand the initial list of failure modes making sure that none were overlooked. After determining the failure modes with the highest risk priority numbers (RPNs), 11 physicists were asked to score corrective actions based on their ease of implementation and potential impact. The results were aggregated into an impact map to determine the implementable corrective actions. Results: Three of the top five failure modes were related to the thermometer and barometer. The two highest RPN-ranked failure modes were related to barometric pressure inaccuracy due to their high lack-of-detectability scores. Six corrective actions were proposed to address barometric pressure inaccuracy, and the survey results found the following two corrective actions to be implementable: 1) send the barometer for recalibration at a calibration laboratory and 2) check the barometer accuracy against the local airport and correct for elevation. Conclusion: An FMEA on monthly output measurements displayed the importance of ADE for accurate radiation dosimetry. When brainstorming for corrective actions, an impact map is helpful for visualizing the overall impact versus the ease of implementation.« less

A toolkit for measurement error correction, with a focus on nutritional epidemiology

PubMed Central

Keogh, Ruth H; White, Ian R

2014-01-01

Exposure measurement error is a problem in many epidemiological studies, including those using biomarkers and measures of dietary intake. Measurement error typically results in biased estimates of exposure-disease associations, the severity and nature of the bias depending on the form of the error. To correct for the effects of measurement error, information additional to the main study data is required. Ideally, this is a validation sample in which the true exposure is observed. However, in many situations, it is not feasible to observe the true exposure, but there may be available one or more repeated exposure measurements, for example, blood pressure or dietary intake recorded at two time points. The aim of this paper is to provide a toolkit for measurement error correction using repeated measurements. We bring together methods covering classical measurement error and several departures from classical error: systematic, heteroscedastic and differential error. The correction methods considered are regression calibration, which is already widely used in the classical error setting, and moment reconstruction and multiple imputation, which are newer approaches with the ability to handle differential error. We emphasize practical application of the methods in nutritional epidemiology and other fields. We primarily consider continuous exposures in the exposure-outcome model, but we also outline methods for use when continuous exposures are categorized. The methods are illustrated using the data from a study of the association between fibre intake and colorectal cancer, where fibre intake is measured using a diet diary and repeated measures are available for a subset. © 2014 The Authors. PMID:24497385

Extension of the Haseman-Elston regression model to longitudinal data.

PubMed

Won, Sungho; Elston, Robert C; Park, Taesung

2006-01-01

We propose an extension to longitudinal data of the Haseman and Elston regression method for linkage analysis. The proposed model is a mixed model having several random effects. As response variable, we investigate the sibship sample mean corrected cross-product (smHE) and the BLUP-mean corrected cross product (pmHE), comparing them with the original squared difference (oHE), the overall mean corrected cross-product (rHE), and the weighted average of the squared difference and the squared mean-corrected sum (wHE). The proposed model allows for the correlation structure of longitudinal data. Also, the model can test for gene x time interaction to discover genetic variation over time. The model was applied in an analysis of the Genetic Analysis Workshop 13 (GAW13) simulated dataset for a quantitative trait simulating systolic blood pressure. Independence models did not preserve the test sizes, while the mixed models with both family and sibpair random effects tended to preserve size well. Copyright 2006 S. Karger AG, Basel.

Recovering Aerodynamic Side Loads on Rocket Nozzles using Quasi-Static Strain-Gage Measurements

NASA Technical Reports Server (NTRS)

Brown, Andrew; Ruf, Joseph H.; McDaniels, David M.

2009-01-01

During over-expanded operation of rocket nozzles, which is defined to be when the exit pressure is greater than internal pressure over some part of the nozzle, the nozzle will experience a transverse forcing function due to the pressure differential across the nozzle wall. Over-expansion occurs during the nozzle start-up and shutdown transient, even in high-altitude engines, because most test facilities cannot completely reproduce the near-vacuum pressures at those altitudes. During this transient, the pressure differential moves axially down the nozzle as it becomes pressurized, but this differential is never perfectly symmetric circumferentially. The character of the forcing function is highly complex and defined by a series of restricted and free shock separations. The subject of this paper is the determination of the magnitude of this loading during sub-scale testing via measurement of the structural dynamic response of the nozzle and its support structure. An initial attempt at back-calculating this load using the inverse of the transfer function was performed, but this attempt was shown to be highly susceptible to numerical error. The final method chosen was to use statically calibrated strain data and to filter out the system fundamental frequency such that the measured response yields close to the correct dynamic loading function. This method was shown to capture 93% of the pressure spectral energy using controlled load shaker testing. This method is one of the only practical ways for the inverse determination of the forcing function for non-stationary excitations, and, to the authors' knowledge, has not been described in the literature to date.

Third-order elastic constants of diamond determined from experimental data

DOE PAGES

Winey, J. M.; Hmiel, A.; Gupta, Y. M.

2016-06-01

The pressure derivatives of the second-order elastic constants (SOECs) of diamond were determined by analyzing previous sound velocity measurements under hydrostatic stress [McSkimin and Andreatch, J. Appl. Phys. 43, 294 (1972)]. Furthermore, our analysis corrects an error in the previously reported results.We present a complete and corrected set of third-order elastic constants (TOECs) using the corrected pressure derivatives, together with published data for the nonlinear elastic response of shock compressed diamond [Lang and Gupta, Phys. Rev. Lett. 106, 125502 (2011)] and it differs significantly from TOECs published previously.

A Method for Large Eddy Simulation of Acoustic Combustion Instabilities

NASA Astrophysics Data System (ADS)

Wall, Clifton; Moin, Parviz

2003-11-01

A method for performing Large Eddy Simulation of acoustic combustion instabilities is presented. By extending the low Mach number pressure correction method to the case of compressible flow, a numerical method is developed in which the Poisson equation for pressure is replaced by a Helmholtz equation. The method avoids the acoustic CFL condition by using implicit time advancement, leading to large efficiency gains at low Mach number. The method also avoids artificial damping of acoustic waves. The numerical method is attractive for the simulation of acoustics combustion instabilities, since these flows are typically at low Mach number, and the acoustic frequencies of interest are usually low. Additionally, new boundary conditions based on the work of Poinsot and Lele have been developed to model the acoustic effect of a long channel upstream of the computational inlet, thus avoiding the need to include such a channel in the computational domain. The turbulent combustion model used is the Level Set model of Duchamp de Lageneste and Pitsch for premixed combustion. Comparison of LES results to the reacting experiments of Besson et al. will be presented.

Microscopic Approach to the Nonlinear Elasticity of Compressed Emulsions

NASA Astrophysics Data System (ADS)

Jorjadze, Ivane; Pontani, Lea-Laetitia; Brujic, Jasna

2013-01-01

Using confocal microscopy, we measure the packing geometry and interdroplet forces as a function of the osmotic pressure in a 3D emulsion system. We assume a harmonic interaction potential over a wide range of volume fractions and attribute the observed nonlinear elastic response of the pressure with density to the first corrections to the scaling laws of the microstructure away from the critical point. The bulk modulus depends on the excess contacts created under compression, which leads to the correction exponent α=1.5. Microscopically, the nonlinearities manifest themselves as a narrowing of the distribution of the pressure per particle as a function of the global pressure.

Structural, electronic and optical properties of well-known primary explosive: Mercury fulminate

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

Yedukondalu, N.; Vaitheeswaran, G., E-mail: gvsp@uohyd.ernet.in

2015-11-28

Mercury Fulminate (MF) is one of the well-known primary explosives since 17th century and it has rendered invaluable service over many years. However, the correct molecular and crystal structures are determined recently after 300 years of its discovery. In the present study, we report pressure dependent structural, elastic, electronic and optical properties of MF. Non-local correction methods have been employed to capture the weak van der Waals interactions in layered and molecular energetic MF. Among the non-local correction methods tested, optB88-vdW method works well for the investigated compound. The obtained equilibrium bulk modulus reveals that MF is softer than themore » well known primary explosives Silver Fulminate (SF), silver azide and lead azide. MF exhibits anisotropic compressibility (b > a > c) under pressure, consequently the corresponding elastic moduli decrease in the following order: C{sub 22} > C{sub 11} > C{sub 33}. The structural and mechanical properties suggest that MF is more sensitive to detonate along c-axis (similar to RDX) due to high compressibility of Hg⋯O non-bonded interactions along that axis. Electronic structure and optical properties were calculated including spin-orbit (SO) interactions using full potential linearized augmented plane wave method within recently developed Tran-Blaha modified Becke-Johnson (TB-mBJ) potential. The calculated TB-mBJ electronic structures of SF and MF show that these compounds are indirect bandgap insulators. Also, SO coupling is found to be more pronounced for 4d and 5d-states of Ag and Hg atoms of SF and MF, respectively. Partial density of states and electron charge density maps were used to describe the nature of chemical bonding. Ag—C bond is more directional than Hg—C bond which makes SF to be more unstable than MF. The effect of SO coupling on optical properties has also been studied and found to be significant for both (SF and MF) of the compounds.« less

Efficient use of mobile devices for quantification of pressure injury images.

PubMed

Garcia-Zapirain, Begonya; Sierra-Sosa, Daniel; Ortiz, David; Isaza-Monsalve, Mariano; Elmaghraby, Adel

2018-01-01

Pressure Injuries are chronic wounds that are formed due to the constriction of the soft tissues against bone prominences. In order to assess these injuries, the medical personnel carry out the evaluation and diagnosis using visual methods and manual measurements, which can be inaccurate and may generate discomfort in the patients. By using segmentation techniques, the Pressure Injuries can be extracted from an image and accurately parameterized, leading to a correct diagnosis. In general, these techniques are based on the solution of differential equations and the involved numerical methods are demanding in terms of computational resources. In previous work, we proposed a technique developed using toroidal parametric equations for image decomposition and segmentation without solving differential equations. In this paper, we present the development of a mobile application useful for the non-contact assessment of Pressure Injuries based on the toroidal decomposition from images. The usage of this technique allows us to achieve an accurate segmentation almost 8 times faster than Active Contours without Edges (ACWE) and Dynamic Contours methods. We describe the techniques and the implementation for Android devices using Python and Kivy. This application allows for the segmentation and parameterization of injuries, obtain relevant information for the diagnosis and tracking the evolution of patient's injuries.

A new plastic surgical technique for adult congenital webbed penis

PubMed Central

Chen, Yue-bing; Ding, Xian-fan; Luo, Chong; Yu, Shi-cheng; Yu, Yan-lan; Chen, Bi-de; Zhang, Zhi-gen; Li, Gong-hui

2012-01-01

Objective: To introduce a novel surgical technique for correction of adult congenital webbed penis. Methods: From March 2010 to December 2011, 12 patients (age range: 14–23 years old) were diagnosed as having a webbed penis and underwent a new surgical procedure designed by us. Results: All cases were treated successfully without severe complication. The operation time ranged from 20 min to 1 h. The average bleeding volume was less than 50 ml. All patients achieved satisfactory cosmetic results after surgery. The penile curvature disappeared in all cases and all patients remained well after 1 to 3 months of follow-up. Conclusions: Adult webbed penis with complaints of discomfort or psychological pressure due to a poor profile should be indicators for surgery. Good corrective surgery should expose the glans and coronal sulcus, match the penile skin length to the penile shaft length dorsally and ventrally, and provide a normal penoscrotal junction. Our new technique is a safe and effective method for the correction of adult webbed penis, which produces satisfactory results. PMID:22949367

Efficient Multi-Atlas Registration using an Intermediate Template Image

PubMed Central

Dewey, Blake E.; Carass, Aaron; Blitz, Ari M.; Prince, Jerry L.

2017-01-01

Multi-atlas label fusion is an accurate but time-consuming method of labeling the human brain. Using an intermediate image as a registration target can allow researchers to reduce time constraints by storing the deformations required of the atlas images. In this paper, we investigate the effect of registration through an intermediate template image on multi-atlas label fusion and propose a novel registration technique to counteract the negative effects of through-template registration. We show that overall computation time can be decreased dramatically with minimal impact on final label accuracy and time can be exchanged for improved results in a predictable manner. We see almost complete recovery of Dice similarity over a simple through-template registration using the corrected method and still maintain a 3–4 times speed increase. Further, we evaluate the effectiveness of this method on brains of patients with normal-pressure hydrocephalus, where abnormal brain shape presents labeling difficulties, specifically the ventricular labels. Our correction method creates substantially better ventricular labeling than traditional methods and maintains the speed increase seen in healthy subjects. PMID:28943702

Efficient multi-atlas registration using an intermediate template image

NASA Astrophysics Data System (ADS)

Dewey, Blake E.; Carass, Aaron; Blitz, Ari M.; Prince, Jerry L.

2017-03-01

Multi-atlas label fusion is an accurate but time-consuming method of labeling the human brain. Using an intermediate image as a registration target can allow researchers to reduce time constraints by storing the deformations required of the atlas images. In this paper, we investigate the effect of registration through an intermediate template image on multi-atlas label fusion and propose a novel registration technique to counteract the negative effects of through-template registration. We show that overall computation time can be decreased dramatically with minimal impact on final label accuracy and time can be exchanged for improved results in a predictable manner. We see almost complete recovery of Dice similarity over a simple through-template registration using the corrected method and still maintain a 3-4 times speed increase. Further, we evaluate the effectiveness of this method on brains of patients with normal-pressure hydrocephalus, where abnormal brain shape presents labeling difficulties, specifically the ventricular labels. Our correction method creates substantially better ventricular labeling than traditional methods and maintains the speed increase seen in healthy subjects.

Composite Overwrap Pressure Vessels: Mechanics and Stress Rupture Lifting Philosophy

NASA Technical Reports Server (NTRS)

Thesken, John C.; Murthy, Pappu L. N.; Phoenix, S. L.

2009-01-01

The NASA Engineering and Safety Center (NESC) has been conducting an independent technical assessment to address safety concerns related to the known stress rupture failure mode of filament wound pressure vessels in use on Shuttle and the International Space Station. The Shuttle s Kevlar-49 (DuPont) fiber overwrapped tanks are of particular concern due to their long usage and the poorly understood stress rupture process in Kevlar-49 filaments. Existing long term data show that the rupture process is a function of stress, temperature and time. However due to the presence of load sharing liners and the complex manufacturing procedures, the state of actual fiber stress in flight hardware and test articles is not clearly known. Indeed nonconservative life predictions have been made where stress rupture data and lifing procedures have ignored the contribution of the liner in favor of applied pressure as the controlling load parameter. With the aid of analytical and finite element results, this paper examines the fundamental mechanical response of composite overwrapped pressure vessels including the influence of elastic plastic liners and degraded/creeping overwrap properties. Graphical methods are presented describing the non-linear relationship of applied pressure to Kevlar-49 fiber stress/strain during manufacturing, operations and burst loadings. These are applied to experimental measurements made on a variety of vessel systems to demonstrate the correct calibration of fiber stress as a function of pressure. Applying this analysis to the actual qualification burst data for Shuttle flight hardware revealed that the nominal fiber stress at burst was in some cases 23 percent lower than what had previously been used to predict stress rupture life. These results motivate a detailed discussion of the appropriate stress rupture lifing philosophy for COPVs including the correct transference of stress rupture life data between dissimilar vessels and test articles.

Composite Overwrap Pressure Vessels: Mechanics and Stress Rupture Lifing Philosophy

NASA Technical Reports Server (NTRS)

Thesken, John C.; Murthy, Pappu L. N.; Phoenix, Leigh

2007-01-01

The NASA Engineering and Safety Center (NESC) has been conducting an independent technical assessment to address safety concerns related to the known stress rupture failure mode of filament wound pressure vessels in use on Shuttle and the International Space Station. The Shuttle's Kevlar-49 fiber overwrapped tanks are of particular concern due to their long usage and the poorly understood stress rupture process in Kevlar-49 filaments. Existing long term data show that the rupture process is a function of stress, temperature and time. However due to the presence of load sharing liners and the complex manufacturing procedures, the state of actual fiber stress in flight hardware and test articles is not clearly known. Indeed non-conservative life predictions have been made where stress rupture data and lifing procedures have ignored the contribution of the liner in favor of applied pressure as the controlling load parameter. With the aid of analytical and finite element results, this paper examines the fundamental mechanical response of composite overwrapped pressure vessels including the influence of elastic-plastic liners and degraded/creeping overwrap properties. Graphical methods are presented describing the non-linear relationship of applied pressure to Kevlar-49 fiber stress/strain during manufacturing, operations and burst loadings. These are applied to experimental measurements made on a variety of vessel systems to demonstrate the correct calibration of fiber stress as a function of pressure. Applying this analysis to the actual qualification burst data for Shuttle flight hardware revealed that the nominal fiber stress at burst was in some cases 23% lower than what had previously been used to predict stress rupture life. These results motivate a detailed discussion of the appropriate stress rupture lifing philosophy for COPVs including the correct transference of stress rupture life data between dissimilar vessels and test articles.

Experimental evaluation of a mathematical model for predicting transfer efficiency of a high volume-low pressure air spray gun.

PubMed

Tan, Y M; Flynn, M R

2000-10-01

The transfer efficiency of a spray-painting gun is defined as the amount of coating applied to the workpiece divided by the amount sprayed. Characterizing this transfer process allows for accurate estimation of the overspray generation rate, which is important for determining a spray painter's exposure to airborne contaminants. This study presents an experimental evaluation of a mathematical model for predicting the transfer efficiency of a high volume-low pressure spray gun. The effects of gun-to-surface distance and nozzle pressure on the agreement between the transfer efficiency measurement and prediction were examined. Wind tunnel studies and non-volatile vacuum pump oil in place of commercial paint were used to determine transfer efficiency at nine gun-to-surface distances and four nozzle pressure levels. The mathematical model successfully predicts transfer efficiency within the uncertainty limits. The least squares regression between measured and predicted transfer efficiency has a slope of 0.83 and an intercept of 0.12 (R2 = 0.98). Two correction factors were determined to improve the mathematical model. At higher nozzle pressure settings, 6.5 psig and 5.5 psig, the correction factor is a function of both gun-to-surface distance and nozzle pressure level. At lower nozzle pressures, 4 psig and 2.75 psig, gun-to-surface distance slightly influences the correction factor, while nozzle pressure has no discernible effect.

Correction of complex foot deformities using the Ilizarov external fixator.

PubMed

Kocaoğlu, Mehmet; Eralp, Levent; Atalar, Ata Can; Bilen, F Erkal

2002-01-01

There are many drawbacks to using conventional approaches to the treatment of complex foot deformities, like the increased risk of neurovascular injury, soft-tissue injury, and the shortening of the foot. An alternative approach that can eliminate these problems is the Ilizarov method. In the current study, a total of 23 deformed feet in 22 patients were treated using the Ilizarov method. The etiologic factors were burn contracture, poliomyelitis, neglected and relapsed clubfoot, trauma, gun shot injury, meningitis, and leg-length discrepancy (LLD). The average age of the patients was 18.2 (5-50) years. The mean duration of fixator application was 5.1 (2-14) months. We performed corrections without an osteotomy in nine feet and with an osteotomy in 14 feet. Additional bony corrective procedures included three tibial and one femoral osteotomies for lengthening and deformity correction, and one tibiotalar arthrodesis in five separate extremities. At the time of fixator removal, a plantigrade foot was achieved in 21 of the 23 feet by pressure mat analysis. Compared to preoperative status, gait was subjectively improved in all patients. Follow-up time from surgery averaged 25 months (13-38). Pin-tract problems were observed in all cases. Other complications were toe contractures in two feet, metatarsophalangeal subluxation from flexor tendon contractures in one foot, incomplete osteotomy in one foot, residual deformity in two feet, and recurrence of deformity in one foot. Our results indicate that the Ilizarov method is an effective alternative means of correcting complex foot deformities, especially in feet that previously have undergone surgery.

Correction of Rayleigh Scattering Effects in Cloud Optical Thickness Retrievals

NASA Technical Reports Server (NTRS)

Wang, Meng-Hua; King, Michael D.

1997-01-01

We present results that demonstrate the effects of Rayleigh scattering on the 9 retrieval of cloud optical thickness at a visible wavelength (0.66 Am). The sensor-measured radiance at a visible wavelength (0.66 Am) is usually used to infer remotely the cloud optical thickness from aircraft or satellite instruments. For example, we find that without removing Rayleigh scattering effects, errors in the retrieved cloud optical thickness for a thin water cloud layer (T = 2.0) range from 15 to 60%, depending on solar zenith angle and viewing geometry. For an optically thick cloud (T = 10), on the other hand, errors can range from 10 to 60% for large solar zenith angles (0-60 deg) because of enhanced Rayleigh scattering. It is therefore particularly important to correct for Rayleigh scattering contributions to the reflected signal from a cloud layer both (1) for the case of thin clouds and (2) for large solar zenith angles and all clouds. On the basis of the single scattering approximation, we propose an iterative method for effectively removing Rayleigh scattering contributions from the measured radiance signal in cloud optical thickness retrievals. The proposed correction algorithm works very well and can easily be incorporated into any cloud retrieval algorithm. The Rayleigh correction method is applicable to cloud at any pressure, providing that the cloud top pressure is known to within +/- 100 bPa. With the Rayleigh correction the errors in retrieved cloud optical thickness are usually reduced to within 3%. In cases of both thin cloud layers and thick ,clouds with large solar zenith angles, the errors are usually reduced by a factor of about 2 to over 10. The Rayleigh correction algorithm has been tested with simulations for realistic cloud optical and microphysical properties with different solar and viewing geometries. We apply the Rayleigh correction algorithm to the cloud optical thickness retrievals from experimental data obtained during the Atlantic Stratocumulus Transition Experiment (ASTEX) conducted near the Azores in June 1992 and compare these results to corresponding retrievals obtained using 0.88 Am. These results provide an example of the Rayleigh scattering effects on thin clouds and further test the Rayleigh correction scheme. Using a nonabsorbing near-infrared wavelength lambda (0.88 Am) in retrieving cloud optical thickness is only applicable over oceans, however, since most land surfaces are highly reflective at 0.88 Am. Hence successful global retrievals of cloud optical thickness should remove Rayleigh scattering effects when using reflectance measurements at 0.66 Am.

An underwater blood pressure measuring device.

PubMed

Sieber, Arne; Kuch, Benjamin; L'abbate, Antonio; Wagner, Matthias; Dario, Paolo; Bedini, Remo

2008-09-01

Measurement of arterial blood pressure is an important vital sign for monitoring the circulation. However, up to now no instrument has been available that enables the measurement of blood pressure underwater. The present paper details a novel, oscillometric, automatic digital blood pressure (BP) measurement device especially designed for this purpose. It consists mainly of analogue and digital electronics in a lexan housing that is rated to a depth of up to 200 metres' sea water, a cuff and a solenoid for inflation of the cuff with air supplied from a scuba tank. An integrated differential pressure sensor, exposed to the same ambient pressure as the cuff, allows accurate BP measurement. Calculation of systolic and diastolic pressures is based on the analysis of pressure oscillations recorded during the deflation. In hyperbaric chamber tests to pressures up to 405 kPa, BP measurements taken with the prototype were comparable to those obtained with established manual and automated methods. Swimming pool tests confirmed the correct functioning of the system underwater. The quality of the recorded pressure oscillations was very good even at 10 metres' fresh water, and allowed determination of diastolic and systolic pressure values. Based on these results we envisage that this device will lead to a better understanding of human cardiovascular physiology in underwater and hyperbaric environments.

A Wind Tunnel Study on the Mars Pathfinder (MPF) Lander Descent Pressure Sensor

NASA Technical Reports Server (NTRS)

Soriano, J. Francisco; Coquilla, Rachael V.; Wilson, Gregory R.; Seiff, Alvin; Rivell, Tomas

2001-01-01

The primary focus of this study was to determine the accuracy of the Mars Pathfinder lander local pressure readings in accordance with the actual ambient atmospheric pressures of Mars during parachute descent. In order to obtain good measurements, the plane of the lander pressure sensor opening should ideally be situated so that it is parallel to the freestream. However, due to two unfavorable conditions, the sensor was positioned in locations where correction factors are required. One of these disadvantages is due to the fact that the parachute attachment point rotated the lander's center of gravity forcing the location of the pressure sensor opening to be off tangent to the freestream. The second and most troublesome factor was that the lander descends with slight oscillations that could vary the amplitude of the sensor readings. In order to accurately map the correction factors required at each sensor position, an experiment simulating the lander descent was conducted in the Martian Surface Wind Tunnel at NASA Ames Research Center. Using a 115 scale model at Earth ambient pressures, the test settings provided the necessary Reynolds number conditions in which the actual lander was possibly subjected to during the descent. In the analysis and results of this experiment, the readings from the lander sensor were converted to the form of pressure coefficients. With a contour map of pressure coefficients at each lander oscillatory position, this report will provide a guideline to determine the correction factors required for the Mars Pathfinder lander descent pressure sensor readings.

Complex admixtures of clathrate hydrates in a water desalination method

DOEpatents

Simmons, Blake A [San Francisco, CA; Bradshaw, Robert W [Livermore, CA; Dedrick, Daniel E [Berkeley, CA; Anderson, David W [Riverbank, CA

2009-07-14

Disclosed is a method that achieves water desalination by utilizing and optimizing clathrate hydrate phenomena. Clathrate hydrates are crystalline compounds of gas and water that desalinate water by excluding salt molecules during crystallization. Contacting a hydrate forming gaseous species with water will spontaneously form hydrates at specific temperatures and pressures through the extraction of water molecules from the bulk phase followed by crystallite nucleation. Subsequent dissociation of pure hydrates yields fresh water and, if operated correctly, allows the hydrate-forming gas to be efficiently recycled into the process stream.

Ab Initio Reaction Kinetics of CH 3 O$$\\dot{C}$$(=O) and $$\\dot{C}$$H 2 OC(=O)H Radicals

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

Tan, Ting; Yang, Xueliang; Ju, Yiguang

The dissociation and isomerization kinetics of the methyl ester combustion intermediates methoxycarbonyl radical (CH3Omore » $$\\dot{C}$$(=O)) and (formyloxy)methyl radical ($$\\dot{C}$$H2OC(=O)H) are investigated theoretically using high-level ab initio methods and Rice–Ramsperger–Kassel–Marcus (RRKM)/master equation (ME) theory. Geometries obtained at the hybrid density functional theory (DFT) and coupled cluster singles and doubles with perturbative triples correction (CCSD(T)) levels of theory are found to be similar. We employ high-level ab initio wave function methods to refine the potential energy surface: CCSD(T), multireference singles and doubles configuration interaction (MRSDCI) with the Davidson–Silver (DS) correction, and multireference averaged coupled-pair functional (MRACPF2) theory. MRSDCI+DS and MRACPF2 capture the multiconfigurational character of transition states (TSs) and predict lower barrier heights than CCSD(T). The temperature- and pressure-dependent rate coefficients are computed using RRKM/ME theory in the temperature range 300–2500 K and a pressure range of 0.01 atm to the high-pressure limit, which are then fitted to modified Arrhenius expressions. Dissociation of CH3O$$\\dot{C}$$(=O) to $$\\dot{C}$$H3 and CO2 is predicted to be much faster than dissociating to CH3$$\\dot{O}$$ and CO, consistent with its greater exothermicity. Isomerization between CH3O$$\\dot{C}$$(=O) and $$\\dot{C}$$H2OC(=O)H is predicted to be the slowest among the studied reactions and rarely happens even at high temperature and high pressure, suggesting the decomposition pathways of the two radicals are not strongly coupled. The predicted rate coefficients and branching fractions at finite pressures differ significantly from the corresponding high-pressure-limit results, especially at relatively high temperatures. Finally, because it is one of the most important CH3$$\\dot{O}$$ removal mechanisms under atmospheric conditions, the reaction kinetics of CH3$$\\dot{O}$$ + CO was also studied along the PES of CH3O$$\\dot{C}$$(=O); the resulting kinetics predictions are in remarkable agreement with experiments.« less

Dynamics in entangled polyethylene melts using coarse-grained models

NASA Astrophysics Data System (ADS)

Peters, Brandon L.; Grest, Gary S.; Salerno, K. Michael; Agrawal, Anupriya; Perahia, Dvora

Polymer dynamics creates distinctive viscoelastic behavior as a result of a coupled interplay of motion on multiple length scales. Capturing the broad time and length scales of polymeric motion however, remains a challenge. Using polyethylene (PE) as a model system, we probe the effects of the degree of coarse graining on polymer dynamics. Coarse-grained (CG) potentials are derived using iterative Boltzmann inversion (iBi) with 2-6 methyl groups per CG bead from all fully atomistic melt simulations for short chains. While the iBi methods produces non-bonded potentials which give excellent agreement for the atomistic and CG pair correlation functions, the pressure P = 100-500MPa for the CG model. Correcting for potential so P 0 leads to non-bonded models with slightly smaller effective diameter and much deeper minimum. However, both the pressure and non-pressure corrected CG models give similar results for mean squared displacement (MSD) and the stress auto correlation function G(t) for PE melts above the melting point. The time rescaling factor between CG and atomistic models is found to be nearly the same for both CG models. Transferability of potential for different temperatures was tested by comparing the MSD and G(t) for potentials generated at different temperatures.

Simulations of Dissipative Circular Restricted Three-body Problems Using the Velocity-scaling Correction Method

NASA Astrophysics Data System (ADS)

Wang, Shoucheng; Huang, Guoqing; Wu, Xin

2018-02-01

In this paper, we survey the effect of dissipative forces including radiation pressure, Poynting–Robertson drag, and solar wind drag on the motion of dust grains with negligible mass, which are subjected to the gravities of the Sun and Jupiter moving in circular orbits. The effect of the dissipative parameter on the locations of five Lagrangian equilibrium points is estimated analytically. The instability of the triangular equilibrium point L4 caused by the drag forces is also shown analytically. In this case, the Jacobi constant varies with time, whereas its integral invariant relation still provides a probability for the applicability of the conventional fourth-order Runge–Kutta algorithm combined with the velocity scaling manifold correction scheme. Consequently, the velocity-only correction method significantly suppresses the effects of artificial dissipation and a rapid increase in trajectory errors caused by the uncorrected one. The stability time of an orbit, regardless of whether it is chaotic or not in the conservative problem, is apparently longer in the corrected case than in the uncorrected case when the dissipative forces are included. Although the artificial dissipation is ruled out, the drag dissipation leads to an escape of grains. Numerical evidence also demonstrates that more orbits near the triangular equilibrium point L4 escape as the integration time increases.

Study of thermal properties of the metastable supersaturated vapor with the integral equation method

NASA Astrophysics Data System (ADS)

Nie, Chu; Geng, Jun; Marlow, W. H.

2008-02-01

Pressure, excess chemical potential, and excess free energy data for different densities of the supersaturated argon vapor at reduced temperatures from 0.7 to 1.2 are obtained by solving the integral equation with perturbation correction to the radial distribution function [F. Lado, Phys. Rev. 135, A1013 (1964)]. For those state points where there is no solution, the integral equation is solved with the interaction between argon atoms modeled by Lennard-Jones potential plus a repulsive potential with one controlling parameter, αexp(-r /σ) and in the end, all the thermal properties are mapped back to the α =0 case. Our pressure data and the spinodal obtained from the current method are compared with a molecular dynamics simulation study [A. Linhart et al., J. Chem. Phys. 122, 144506 (2005)] of the same system.

An experimental study of an adaptive-wall wind tunnel

NASA Technical Reports Server (NTRS)

Celik, Zeki; Roberts, Leonard

1988-01-01

A series of adaptive wall ventilated wind tunnel experiments was carried out to demonstrate the feasibility of using the side wall pressure distribution as the flow variable for the assessment of compatibility with free air conditions. Iterative and one step convergence methods were applied using the streamwise velocity component, the side wall pressure distribution and the normal velocity component in order to investigate their relative merits. The advantage of using the side wall pressure as the flow variable is to reduce the data taking time which is one the major contributors to the total testing time. In ventilated adaptive wall wind tunnel testing, side wall pressure measurements require simple instrumentation as opposed to the Laser Doppler Velocimetry used to measure the velocity components. In ventilated adaptive wall tunnel testing, influence coefficients are required to determine the pressure corrections in the plenum compartment. Experiments were carried out to evaluate the influence coefficients from side wall pressure distributions, and from streamwise and normal velocity distributions at two control levels. Velocity measurements were made using a two component Laser Doppler Velocimeter system.

Signal processing of aircraft flyover noise

NASA Technical Reports Server (NTRS)

Kelly, Jeffrey J.

1991-01-01

A detailed analysis of signal processing concerns for measuring aircraft flyover noise is presented. Development of a de-Dopplerization scheme for both corrected time history and spectral data is discussed along with an analysis of motion effects on measured spectra. A computer code was written to implement the de-Dopplerization scheme. Input to the code is the aircraft position data and the pressure time histories. To facilitate ensemble averaging, a uniform level flyover is considered but the code can accept more general flight profiles. The effects of spectral smearing and its removal is discussed. Using data acquired from XV-15 tilt rotor flyover test comparisons are made showing the measured and corrected spectra. Frequency shifts are accurately accounted for by the method. It is shown that correcting for spherical spreading, Doppler amplitude, and frequency can give some idea about source directivity. The analysis indicated that smearing increases with frequency and is more severe on approach than recession.

Accurate critical pressures for structural phase transitions of group IV, III-V, and II-VI compounds from the SCAN density functional

NASA Astrophysics Data System (ADS)

Shahi, Chandra; Sun, Jianwei; Perdew, John P.

2018-03-01

Most of the group IV, III-V, and II-VI compounds crystallize in semiconductor structures under ambient conditions. Upon application of pressure, they undergo structural phase transitions to more closely packed structures, sometimes metallic phases. We have performed density functional calculations using projector augmented wave (PAW) pseudopotentials to determine the transition pressures for these transitions within the local density approximation (LDA), the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA), and the strongly constrained and appropriately normed (SCAN) meta-GGA. LDA underestimates the transition pressure for most of the studied materials. PBE under- or overestimates in many cases. SCAN typically corrects the errors of LDA and PBE for the transition pressure. The accuracy of SCAN is comparable to that of computationally expensive methods like the hybrid functional HSE06, the random phase approximation (RPA), and quantum Monte Carlo (QMC), in cases where calculations with these methods have been reported, but at a more modest computational cost. The improvement from LDA to PBE to SCAN is especially clearcut and dramatic for covalent semiconductor-metal transitions, as for Si and Ge, where it reflects the increasing relative stabilization of the covalent semiconducting phases under increasing functional sophistication.

Rowan Gorilla I rigged up, heads for eastern Canada

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

Not Available

1984-03-01

Designed to operate in very hostile offshore environments, the first of the Rowan Gorilla class of self-elevating drilling rigs has been towed to its drilling assignment offshore Nova Scotia. About 40% larger than other jackups, these rigs can operate in 300 ft of water, drilling holes as deep as 30,000 ft. They also feature unique high-pressure and solids control systems that are expected to improve drilling procedures and efficiencies. A quantitative formation pressure evaluation program for the Hewlett-Packard HP-41 handheld calculator computes formation pressures by three independent methods - the corrected d exponent, Bourgoyne and Young, and normalized penetration ratemore » techniques for abnormal pressure detection and computation. Based on empirically derived drilling rate equations, each of the methods can be calculated separately, without being dependent on or influenced by the results or stored data from the other two subprograms. The quantitative interpretation procedure involves establishing a normal drilling rate trend and calculating the pore pressure from the magnitude of the drilling rate trend or plotting parameter increases above the trend line. Mobil's quick, accurate program could aid drilling operators in selecting the casing point, minimizing differential sticking, maintaining the proper mud weights to avoid kicks and lost circulation, and maximizing penetration rates.« less

Nurses' knowledge of prevention and management of pressure ulcer at a health insurance hospital in Alexandria.

PubMed

El Enein, Nagwa Younes Abou; Zaghloul, Ashraf Ahmad

2011-06-01

Nurses' knowledge of pressure ulcer prediction, prevention and management plays a very important role in the incidence and prevalence of pressure ulcers in health-care systems. The aim of the current study was to assess the nurse's knowledge about prevention and management of pressure ulcer at one of the largest health insurance hospitals in Alexandria. A descriptive cross-sectional study using an interview questionnaire format to assess the nurses' knowledge (n = 122) regarding prevention of pressure ulcers. The overall mean per cent score for nurses was below the minimum acceptable level. The mean per cent score for nurses was below 70% for nine measures of the 15 correct measures, which accounted for 60% of the measures of pressure ulcer prevention. Correct answers for non-useful measures for preventing pressure ulcers accounted for 66% of the non-useful measures on the questionnaire. It had been concluded that the nurses' knowledge regarding pressure ulcer prevention is below the acceptable levels. © 2011 Blackwell Publishing Asia Pty Ltd.

An experimental study of high-pressure droplet combustion

NASA Technical Reports Server (NTRS)

Norton, Chris M.; Litchford, Ron J.; Jeng, San-Mou

1990-01-01

The results are presented of an experimental study on suspended n-heptane droplet combustion in air for reduced pressures up to P(r) = 2.305. Transition to fully transient heat-up through the critical state is demonstrated above a threshold pressure corresponding to P(r) of roughly 1.4. A silhouette imaging technique resolves the droplet surface for reduced pressures up to about P(r) roughly 0.63, but soot formation conceals the surface at higher pressures. Images of the soot plumes do not show any sudden change in behavior indicative of critical transition. Mean burning rate constants are computed from the d-squared variation law using measured effective droplet diameters at ignition and measured burn times, and corrected burning times are computed for an effective initial droplet diameter. The results show that the burning rates increase as the fuel critical pressure is approached and decrease as the pressure exceeds the fuel critical pressure. Corrected burning times show inverse behavior.

Molecfit: A general tool for telluric absorption correction. II. Quantitative evaluation on ESO-VLT/X-Shooterspectra

NASA Astrophysics Data System (ADS)

Kausch, W.; Noll, S.; Smette, A.; Kimeswenger, S.; Barden, M.; Szyszka, C.; Jones, A. M.; Sana, H.; Horst, H.; Kerber, F.

2015-04-01

Context. Absorption by molecules in the Earth's atmosphere strongly affects ground-based astronomical observations. The resulting absorption line strength and shape depend on the highly variable physical state of the atmosphere, i.e. pressure, temperature, and mixing ratio of the different molecules involved. Usually, supplementary observations of so-called telluric standard stars (TSS) are needed to correct for this effect, which is expensive in terms of telescope time. We have developed the software package molecfit to provide synthetic transmission spectra based on parameters obtained by fitting narrow ranges of the observed spectra of scientific objects. These spectra are calculated by means of the radiative transfer code LBLRTM and an atmospheric model. In this way, the telluric absorption correction for suitable objects can be performed without any additional calibration observations of TSS. Aims: We evaluate the quality of the telluric absorption correction using molecfit with a set of archival ESO-VLT/X-Shooter visible and near-infrared spectra. Methods: Thanks to the wavelength coverage from the U to the K band, X-Shooter is well suited to investigate the quality of the telluric absorption correction with respect to the observing conditions, the instrumental set-up, input parameters of the code, the signal-to-noise of the input spectrum, and the atmospheric profiles. These investigations are based on two figures of merit, Ioff and Ires, that describe the systematic offsets and the remaining small-scale residuals of the corrections. We also compare the quality of the telluric absorption correction achieved with molecfit to the classical method based on a telluric standard star. Results: The evaluation of the telluric correction with molecfit shows a convincing removal of atmospheric absorption features. The comparison with the classical method reveals that molecfit performs better because it is not prone to the bad continuum reconstruction, noise, and intrinsic spectral features introduced by the telluric standard star. Conclusions: Fitted synthetic transmission spectra are an excellent alternative to the correction based on telluric standard stars. Moreover, molecfit offers wide flexibility for adaption to various instruments and observing sites. http://www.eso.org/sci/software/pipelines/skytools/

Effect of graft shape in lateral column lengthening on tarsal bone position and subtalar and talonavicular contact pressure in a cadaveric flatfoot model.

PubMed

Campbell, Sean T; Reese, Keri A; Ross, Steven D; McGarry, Michelle H; Leba, Thu-Ba; Lee, Thay Q

2014-11-01

Lateral column lengthening (LCL) has been used for correction of flatfoot deformity. The purpose of this study was to determine the effect of LCL graft shape on tarsal bone position and talonavicular and subtalar joint pressure. A flatfoot model was created in 6 cadaveric specimens. Corrective LCL was performed using a rectangular graft or a trapezoidal graft with the broad surface oriented dorsally, laterally, or plantarly. Bony surface markers were digitized to calculate angular parameters used in the evaluation of flatfoot deformity. Contact pressure and area in the subtalar and talonavicular joints were also recorded. All measurements were carried out under multiple axial loads in the intact and flatfoot conditions, and following LCL with each graft shape. Flatfoot creation resulted in significant changes in arch collapse and forefoot abduction. LCL with a rectangular graft best corrected these parameters, while a laterally oriented trapezoidal graft provided some correction. Talonavicular contact pressure was unchanged after flatfoot creation, and was significantly less than intact after LCL. Subtalar contact pressure decreased in some conditions after flatfoot creation, and decreased further after LCL. LCL with a rectangular graft best restored tarsal bone orientation in a cadaveric flatfoot model. The decreases in talonavicular pressure likely represent redistribution of force from the medial to lateral foot. When performing LCL for flatfoot deformity, increased bone graft volume medially better restores tarsal bone position. One way of achieving this is through the use of a rectangular graft as opposed to a trapezoidal graft. © The Author(s) 2014.

Electron band structure of the high pressure cubic phase of AlH3

NASA Astrophysics Data System (ADS)

Shi, Hongliang; Zarifi, Niliffar; Yim, Wai-Leung; Tse, J. S.

2012-07-01

The electronic band structure of the cubic Pm3n phase of AlH3 stable above 100 GPa is examined with semi-local, Tran-Blaha modified Becke-Johnson local density approximation (TB-mBJLDA), screened hybrid density functionals and GW methods. The shift of the conduction band to higher energy with increasing pressure is predicted by all methods. However, there are significant differences in detail band structure. In the pressure range from 90 to160 GPa, semi-local, hybrid functional and TB-mBJLDA calculations predicted that AlH3 is a poor metal. In comparison, GW calculations show a gap opening at 160 GPa and AlH3 becomes a small gap semi-conductor. From the trends of the calculated band shifts, it can be concluded that the favourable conditions leading to the nesting of Fermi surfaces predicted by semi-local calculation have disappeared if the exchange term is included. The results highlight the importance of the correction to the exchange energy on the band structure of hydrogen dominant dense metal hydrides at high pressure hydrides and may help to rationalize the absence of superconductivity in AlH3 from experimental measurements.

Optimization of the freeze-drying cycle: adaptation of the pressure rise analysis model to non-instantaneous isolation valves.

PubMed

Chouvenc, P; Vessot, S; Andrieu, J; Vacus, P

2005-01-01

The principal aim of this study is to extend to a pilot freeze-dryer equipped with a non-instantaneous isolation valve the previously presented pressure rise analysis (PRA) model for monitoring the product temperature and the resistance to mass transfer of the dried layer during primary drying. This method, derived from the original MTM method previously published, consists of interrupting rapidly (a few seconds) the water vapour flow from the sublimation chamber to the condenser and analysing the resulting dynamics of the total chamber pressure increase. The valve effect on the pressure rise profile observed during the isolation valve closing period was corrected by introducing in the initial PRA model a valve characteristic function factor which turned out to be independent of the operating conditions. This new extended PRA model was validated by implementing successively the two types of valves and by analysing the pressure rise kinetics data with the corresponding PRA models in the same operating conditions. The coherence and consistency shown on the identified parameter values (sublimation front temperature, dried layer mass transfer resistance) allowed validation of this extended PRA model with a non-instantaneous isolation valve. These results confirm that the PRA method, with or without an instantaneous isolation valve, is appropriate for on-line monitoring of product characteristics during freeze-drying. The advantages of PRA are that the method is rapid, non-invasive, and global. Consequently, PRA might become a powerful and promising tool not only for the control of pilot freeze-dryers but also for industrial freeze-dryers equipped with external condensers.

Pneumoperitoneum risk prognosis and correction of venous circulation disturbances in laparoscopic surgery. A pilot study.

PubMed

Emeljanov, S I; Fedenko, V V; Levite, E M; Panfilov, S A; Bobrinskaya, I G; Fedorov, A V; Matveev, N L; Evdoshenko, V V; Luosev, S V; Bokarev, V V; Musaeva, S R

1998-10-01

This study was initiated to find a method of determining the prognosis for possible changes in hemodynamic and respiratory parameters in patients with pneumoperitoneum (PP). We devised a model for a pseudopneumoperitoneum (PPP), which is created by encircling the wide pneumochamber on the entire abdomen and inflating it to a preset pressure. To verify the prognostic possibilities of the proposed model, we studied the pneumotachygraphy parameters, noninvasive and invasive monitoring parameters of PPP after induction of anaesthesia, and venous circulation disturbances, as well as the medical effect of the intermittent sequential compression device. In healthy patients, the restrictive lung syndrome did not approach the risky limit. In patients >/=60 years old, this syndrome was very close to the limit. In a number of patients with serious cardiovascular and pulmonary pathology, the pressure of >10 mmHg was considered to be intolerable. Lung compliance, which was the parameter most sensitive to the increased intraabdominal pressure, was 47 +/- 10 at baseline, and 29 +/- 4 (p > 0.05) at both PPP and real PP (14 mmHg). The PPP model is quite similar to the real PP and can be used for preoperative prognosis in laparoscopic surgery. The elevated intraabdominal pressure results in a significant disturbance of venous blood flow in the lower extremities. The use of the device for peristaltic pneumomassage of the lower limbs is effective in correcting negative changes in venous hemodynamics in laparoscopic surgery.

Numerical Simulation of Hydro-mechanical Deep Drawing — A Study on the Effect of Process Parameters on Drawability and Thickness Variation

NASA Astrophysics Data System (ADS)

Singh, Swadesh Kumar; Kumar, D. Ravi

2005-08-01

Hydro-mechanical deep drawing is a process for producing cup shaped parts with the assistance of a pressurized fluid. In the present work, numerical simulation of the conventional and counter pressure deep drawing processes has been done with the help of a finite element method based software. Simulation results were analyzed to study the improvement in drawability by using hydro-mechanical processes. The thickness variations in the drawn cups were analyzed and also the effect of counter pressure and oil gap on the thickness distribution was studied. Numerical simulations were also used for the die design, which combines both drawing and ironing processes in a single operation. This modification in the die provides high drawability, facilitates smooth material flow, gives more uniform thickness distribution and corrects the shape distortion.

Cross-validation of the osmotic pressure based on Pitzer model with air humidity osmometry at high concentration of ammonium sulfate solutions.

PubMed

Wang, Xiao-Lan; Zhan, Ting-Ting; Zhan, Xian-Cheng; Tan, Xiao-Ying; Qu, Xiao-You; Wang, Xin-Yue; Li, Cheng-Rong

2014-01-01

The osmotic pressure of ammonium sulfate solutions has been measured by the well-established freezing point osmometry in dilute solutions and we recently reported air humidity osmometry in a much wider range of concentration. Air humidity osmometry cross-validated the theoretical calculations of osmotic pressure based on the Pitzer model at high concentrations by two one-sided test (TOST) of equivalence with multiple testing corrections, where no other experimental method could serve as a reference for comparison. Although more strict equivalence criteria were established between the measurements of freezing point osmometry and the calculations based on the Pitzer model at low concentration, air humidity osmometry is the only currently available osmometry applicable to high concentration, serves as an economic addition to standard osmometry.

[Dynamic plantar pressure distribution after percutaneous hallux valgus correction using the Reverdin-Isham osteotomy].

PubMed

Rodríguez-Reyes, Gerardo; López-Gavito, Eduardo; Pérez-Sanpablo, Alberto Isaac; Galván Duque-Gastélum, Carlos; Alvarez-Camacho, Michelín; Mendoza-Cruz, Felipe; Parra-Téllez, Patricia; Vázquez-Escamilla, Jesús; Quiñones-Urióstegui, Ivett

2014-07-01

Percutaneous surgical techniques are suitable for the correction of the hallux valgus deformity. Satisfactory aesthetic and functional results obtained with the Reverdin- Isham osteotomy have been reported. The aim of this study was to describe dynamic plantar pressure redistribution after the correction of the deformity using this technique. A sample of 20 feet with mild or moderate hallux valgus was conformed and surgically treated using the Reverdin-Isham osteotomy. Clinical, radiological, surface and pressure assessments were performed pre and postoperatively. Postoperative mean (± SD) values of the American Orthopaedic Foot and Ankle Society (AOFAS) score, metatarsophalangeal, first intermetatarsal and proximal articular sect angles were 95.7 (3.3), 15.5° (5.4), 9.5° (1.5) y 5.3° (3.0), respectively. A significant decrease was observed in surface values of both lateral (P = 0.003) and medial (P = 0.001) masks of the forefoot. Mean pressure values of the lateral forefoot region denoted a significant increase (P < 0.001) while the medial forefoot region showed no change (P = 0.137). There is evidence that this particular surgical technique promotes a new plantar pressure pattern in the foot that might significantly favour the increase of the pressure observed under the lesser metatarsal heads and might not induce meaningful changes in the mean pressure registered under the first metatarsal head and hallux.

An efficient user-oriented method for calculating compressible flow in an about three-dimensional inlets. [panel method

NASA Technical Reports Server (NTRS)

Hess, J. L.; Mack, D. P.; Stockman, N. O.

1979-01-01

A panel method is used to calculate incompressible flow about arbitrary three-dimensional inlets with or without centerbodies for four fundamental flow conditions: unit onset flows parallel to each of the coordinate axes plus static operation. The computing time is scarcely longer than for a single solution. A linear superposition of these solutions quite rigorously gives incompressible flow about the inlet for any angle of attack, angle of yaw, and mass flow rate. Compressibility is accounted for by applying a well-proven correction to the incompressible flow. Since the computing times for the combination and the compressibility correction are small, flows at a large number of inlet operating conditions are obtained rather cheaply. Geometric input is aided by an automatic generating program. A number of graphical output features are provided to aid the user, including surface streamline tracing and automatic generation of curves of curves of constant pressure, Mach number, and flow inclination at selected inlet cross sections. The inlet method and use of the program are described. Illustrative results are presented.

Estimates of crystalline LiF thermal conductivity at high temperature and pressure by a Green-Kubo method

DOE PAGES

Jones, R. E.; Ward, D. K.

2016-07-18

Here, given the unique optical properties of LiF, it is often used as an observation window in high-temperature and -pressure experiments; hence, estimates of its transmission properties are necessary to interpret observations. Since direct measurements of the thermal conductivity of LiF at the appropriate conditions are difficult, we resort to molecular simulation methods. Using an empirical potential validated against ab initio phonon density of states, we estimate the thermal conductivity of LiF at high temperatures (1000–4000 K) and pressures (100–400 GPa) with the Green-Kubo method. We also compare these estimates to those derived directly from ab initio data. To ascertainmore » the correct phase of LiF at these extreme conditions, we calculate the (relative) phase stability of the B1 and B2 structures using a quasiharmonic ab initio model of the free energy. We also estimate the thermal conductivity of LiF in an uniaxial loading state that emulates initial stages of compression in high-stress ramp loading experiments and show the degree of anisotropy induced in the conductivity due to deformation.« less

Analyzing the errors of DFT approximations for compressed water systems

NASA Astrophysics Data System (ADS)

Alfè, D.; Bartók, A. P.; Csányi, G.; Gillan, M. J.

2014-07-01

We report an extensive study of the errors of density functional theory (DFT) approximations for compressed water systems. The approximations studied are based on the widely used PBE and BLYP exchange-correlation functionals, and we characterize their errors before and after correction for 1- and 2-body errors, the corrections being performed using the methods of Gaussian approximation potentials. The errors of the uncorrected and corrected approximations are investigated for two related types of water system: first, the compressed liquid at temperature 420 K and density 1.245 g/cm3 where the experimental pressure is 15 kilobars; second, thermal samples of compressed water clusters from the trimer to the 27-mer. For the liquid, we report four first-principles molecular dynamics simulations, two generated with the uncorrected PBE and BLYP approximations and a further two with their 1- and 2-body corrected counterparts. The errors of the simulations are characterized by comparing with experimental data for the pressure, with neutron-diffraction data for the three radial distribution functions, and with quantum Monte Carlo (QMC) benchmarks for the energies of sets of configurations of the liquid in periodic boundary conditions. The DFT errors of the configuration samples of compressed water clusters are computed using QMC benchmarks. We find that the 2-body and beyond-2-body errors in the liquid are closely related to similar errors exhibited by the clusters. For both the liquid and the clusters, beyond-2-body errors of DFT make a substantial contribution to the overall errors, so that correction for 1- and 2-body errors does not suffice to give a satisfactory description. For BLYP, a recent representation of 3-body energies due to Medders, Babin, and Paesani [J. Chem. Theory Comput. 9, 1103 (2013)] gives a reasonably good way of correcting for beyond-2-body errors, after which the remaining errors are typically 0.5 mEh ≃ 15 meV/monomer for the liquid and the clusters.

Analyzing the errors of DFT approximations for compressed water systems

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

Alfè, D.; London Centre for Nanotechnology, UCL, London WC1H 0AH; Thomas Young Centre, UCL, London WC1H 0AH

We report an extensive study of the errors of density functional theory (DFT) approximations for compressed water systems. The approximations studied are based on the widely used PBE and BLYP exchange-correlation functionals, and we characterize their errors before and after correction for 1- and 2-body errors, the corrections being performed using the methods of Gaussian approximation potentials. The errors of the uncorrected and corrected approximations are investigated for two related types of water system: first, the compressed liquid at temperature 420 K and density 1.245 g/cm{sup 3} where the experimental pressure is 15 kilobars; second, thermal samples of compressed watermore » clusters from the trimer to the 27-mer. For the liquid, we report four first-principles molecular dynamics simulations, two generated with the uncorrected PBE and BLYP approximations and a further two with their 1- and 2-body corrected counterparts. The errors of the simulations are characterized by comparing with experimental data for the pressure, with neutron-diffraction data for the three radial distribution functions, and with quantum Monte Carlo (QMC) benchmarks for the energies of sets of configurations of the liquid in periodic boundary conditions. The DFT errors of the configuration samples of compressed water clusters are computed using QMC benchmarks. We find that the 2-body and beyond-2-body errors in the liquid are closely related to similar errors exhibited by the clusters. For both the liquid and the clusters, beyond-2-body errors of DFT make a substantial contribution to the overall errors, so that correction for 1- and 2-body errors does not suffice to give a satisfactory description. For BLYP, a recent representation of 3-body energies due to Medders, Babin, and Paesani [J. Chem. Theory Comput. 9, 1103 (2013)] gives a reasonably good way of correcting for beyond-2-body errors, after which the remaining errors are typically 0.5 mE{sub h} ≃ 15 meV/monomer for the liquid and the clusters.« less

High-temperature calibration of a multi-anvil high pressure apparatus

NASA Astrophysics Data System (ADS)

Sokol, Alexander G.; Borzdov, Yury M.; Palyanov, Yury N.; Khokhryakov, Alexander F.

2015-04-01

Fusion and solidification of Al and Ag samples, as well as Fe93-Al3-C4, Fe56-Co37-Al3-C4, and Fe57.5-Co38-Al1-Pb0.5-C3 alloys (in wt%), have been investigated at 6.3 GPa. Heater power jumps due to heat consumption and release on metal fusion and solidification, respectively, were used to calibrate the thermal electromotive force of the thermocouple against the melting points (mp) for Ag and Al. Thus, obtained corrections are +100°C (for sample periphery) and +65°C (center) within the 1070-1320°C range. For small samples positioned randomly in the low-gradient zone of a high pressure cell, the corrections should be +80°C and +84°C at the temperatures 1070°C and 1320°C, respectively. The temperature contrast recorded in the low-gradient cell zone gives an error about ±17°C. The method has been applied to identify the mp of the systems, which is especially important for temperature-gradient growth of large type IIa synthetic diamonds.

Tropical cyclone warm core analyses with FY-3 microwave temperature sounder data

NASA Astrophysics Data System (ADS)

Liu, Zhe; Bai, Jie; Zhang, Wenjun; Yan, Jun; Zhou, Zhuhua

2014-05-01

Space-borne microwave instruments are well suited to analyze Tropical Cyclone (TC) warm core structure, because certain wavelengths of microwave energy are able to penetrate the cirrus above TC. With the vector discrete-ordinate microwave radiative transfer model, the basic atmospheric parameters of Hurricane BOB are used to simulate the upwelling brightness temperatures on each channel of the Microwave Temperature Sounder (MWTS) onboard FY-3A/3B observation. Based on the simulation, the characteristic of 1109 super typhoon "Muifa" warm core structure is analyzed with the MWTS channel 3. Through the radiative and hydrostatic equation, TC warm core brightness temperature anomalies are related to surface pressure anomalies. In order to correct the radiation attenuation caused by MWTS scan geometric features, and improve the capability in capturing the relatively complete warm core radiation, a proposed algorithm is devised to correct the bias from receiving warm core microwave radiation, shows similar time-variant tendency with "Muifa" minimal sea level pressure as described by TC best track data. As the next generation of FY-3 satellite will be launched in 2012, this method will be further verified

Investigation of high-speed free shear flows using improved pressure-strain correlated Reynolds stress turbulence model

NASA Technical Reports Server (NTRS)

Tiwari, S. N.; Lakshmanan, B.

1993-01-01

A high-speed shear layer is studied using compressibility corrected Reynolds stress turbulence model which employs newly developed model for pressure-strain correlation. MacCormack explicit prediction-corrector method is used for solving the governing equations and the turbulence transport equations. The stiffness arising due to source terms in the turbulence equations is handled by a semi-implicit numerical technique. Results obtained using the new model show a sharper reduction in growth rate with increasing convective Mach number. Some improvements were also noted in the prediction of the normalized streamwise stress and Reynolds shear stress. The computed results are in good agreement with the experimental data.

USGS Coal Desorption Equipment and a Spreadsheet for Analysis of Lost and Total Gas from Canister Desorption Measurements

USGS Publications Warehouse

Barker, Charles E.; Dallegge, Todd A.; Clark, Arthur C.

2002-01-01

We have updated a simple polyvinyl chloride plastic canister design by adding internal headspace temperature measurement, and redesigned it so it is made with mostly off-the-shelf components for ease of construction. Using self-closing quick connects, this basic canister is mated to a zero-head manometer to make a simple coalbed methane desorption system that is easily transported in small aircraft to remote localities. This equipment is used to gather timed measurements of pressure, volume and temperature data that are corrected to standard pressure and temperature (STP) and graphically analyzed using an Excel(tm)-based spreadsheet. Used together these elements form an effective, practical canister desorption method.

A new approximation for pore pressure accumulation in marine sediment due to water waves

NASA Astrophysics Data System (ADS)

Jeng, D.-S.; Seymour, B. R.; Li, J.

2007-01-01

The residual mechanism of wave-induced pore water pressure accumulation in marine sediments is re-examined. An analytical approximation is derived using a linear relation for pore pressure generation in cyclic loading, and mistakes in previous solutions (Int. J. Numer. Anal. Methods Geomech. 2001; 25:885-907; J. Offshore Mech. Arctic Eng. (ASME) 1989; 111(1):1-11) are corrected. A numerical scheme is then employed to solve the case with a non-linear relation for pore pressure generation. Both analytical and numerical solutions are verified with experimental data (Laboratory and field investigation of wave-sediment interaction. Joseph H. Defrees Hydraulics Laboratory, School of Civil and Environmental Engineering, Cornell University, Ithaca, NY, 1983), and provide a better prediction of pore pressure accumulation than the previous solution (J. Offshore Mech. Arctic Eng. (ASME) 1989; 111(1):1-11). The parametric study concludes that the pore pressure accumulation and use of full non-linear relation of pore pressure become more important under the following conditions: (1) large wave amplitude, (2) longer wave period, (3) shallow water, (4) shallow soil and (5) softer soils with a low consolidation coefficient. Copyright

A Semi-implicit Method for Resolution of Acoustic Waves in Low Mach Number Flows

NASA Astrophysics Data System (ADS)

Wall, Clifton; Pierce, Charles D.; Moin, Parviz

2002-09-01

A semi-implicit numerical method for time accurate simulation of compressible flow is presented. By extending the low Mach number pressure correction method, a Helmholtz equation for pressure is obtained in the case of compressible flow. The method avoids the acoustic CFL limitation, allowing a time step restricted only by the convective velocity, resulting in significant efficiency gains. Use of a discretization that is centered in both time and space results in zero artificial damping of acoustic waves. The method is attractive for problems in which Mach numbers are low, and the acoustic waves of most interest are those having low frequency, such as acoustic combustion instabilities. Both of these characteristics suggest the use of time steps larger than those allowable by an acoustic CFL limitation. In some cases it may be desirable to include a small amount of numerical dissipation to eliminate oscillations due to small-wavelength, high-frequency, acoustic modes, which are not of interest; therefore, a provision for doing this in a controlled manner is included in the method. Results of the method for several model problems are presented, and the performance of the method in a large eddy simulation is examined.

Estimation of wing nonlinear aerodynamic characteristics at supersonic speeds

NASA Technical Reports Server (NTRS)

Carlson, H. W.; Mack, R. J.

1980-01-01

A computational system for estimation of nonlinear aerodynamic characteristics of wings at supersonic speeds was developed and was incorporated in a computer program. This corrected linearized theory method accounts for nonlinearities in the variation of basic pressure loadings with local surface slopes, predicts the degree of attainment of theoretical leading edge thrust, and provides an estimate of detached leading edge vortex loadings that result when the theoretical thrust forces are not fully realized.

Improving the numerical integration solution of satellite orbits in the presence of solar radiation pressure using modified back differences

NASA Technical Reports Server (NTRS)

Lundberg, J. B.; Feulner, M. R.; Abusali, P. A. M.; Ho, C. S.

1991-01-01

The method of modified back differences, a technique that significantly reduces the numerical integration errors associated with crossing shadow boundaries using a fixed-mesh multistep integrator without a significant increase in computer run time, is presented. While Hubbard's integral approach can produce significant improvements to the trajectory solution, the interpolation method provides the best overall results. It is demonstrated that iterating on the point mass term correction is also important for achieving the best overall results. It is also shown that the method of modified back differences can be implemented with only a small increase in execution time.

A revised and unified pressure-clamp/relaxation theory for studying plant cell water relations with pressure probes: in-situ determination of cell volume for calculation of volumetric elastic modulus and hydraulic conductivity.

PubMed

Knipfer, T; Fei, J; Gambetta, G A; Shackel, K A; Matthews, M A

2014-10-21

The cell-pressure-probe is a unique tool to study plant water relations in-situ. Inaccuracy in the estimation of cell volume (νo) is the major source of error in the calculation of both cell volumetric elastic modulus (ε) and cell hydraulic conductivity (Lp). Estimates of νo and Lp can be obtained with the pressure-clamp (PC) and pressure-relaxation (PR) methods. In theory, both methods should result in comparable νo and Lp estimates, but this has not been the case. In this study, the existing νo-theories for PC and PR methods were reviewed and clarified. A revised νo-theory was developed that is equally valid for the PC and PR methods. The revised theory was used to determine νo for two extreme scenarios of solute mixing between the experimental cell and sap in the pressure probe microcapillary. Using a fully automated cell-pressure-probe (ACPP) on leaf epidermal cells of Tradescantia virginiana, the validity of the revised theory was tested with experimental data. Calculated νo values from both methods were in the range of optically determined νo (=1.1-5.0nL) for T. virginiana. However, the PC method produced a systematically lower (21%) calculated νo compared to the PR method. Effects of solute mixing could only explain a potential error in calculated νo of <3%. For both methods, this discrepancy in νo was almost identical to the discrepancy in the measured ratio of ΔV/ΔP (total change in microcapillary sap volume versus corresponding change in cell turgor) of 19%, which is a fundamental parameter in calculating νo. It followed from the revised theory that the ratio of ΔV/ΔP was inversely related to the solute reflection coefficient. This highlighted that treating the experimental cell as an ideal osmometer in both methods is potentially not correct. Effects of non-ideal osmotic behavior by transmembrane solute movement may be minimized in the PR as compared to the PC method. Copyright © 2014 Elsevier Ltd. All rights reserved.

40 CFR 53.56 - Test for effect of variations in ambient pressure.

Code of Federal Regulations, 2010 CFR

2010-07-01

... measurement accuracy. (iv) Coefficient of variability measurement accuracy. (v) Ambient pressure measurement... through the sample filter, measured in actual volume units at the temperature and pressure of the air as... volumetric flow rate corrections are made based on measurements of actual ambient temperature and pressure...

Kinetically reduced local Navier-Stokes equations for simulation of incompressible viscous flows.

PubMed

Borok, S; Ansumali, S; Karlin, I V

2007-12-01

Recently, another approach to study incompressible fluid flow was suggested [S. Ansumali, I. Karlin, and H. Ottinger, Phys. Rev. Lett. 94, 080602 (2005)]-the kinetically reduced local Navier-Stokes (KRLNS) equations. We consider a simplified two-dimensional KRLNS system and compare it with Chorin's artificial compressibility method. A comparison of the two methods for steady state computation of the flow in a lid-driven cavity at various Reynolds numbers shows that the results from both methods are in good agreement with each other. However, in the transient flow, it is demonstrated that the KRLNS equations correctly describe the time evolution of the velocity and of the pressure, unlike the artificial compressibility method.

Surgical correction of an aberrant right subclavian artery in a dog.

PubMed

Yoon, Hun-Young; Jeong, Soon-wuk

2011-10-01

A diagnosis of an aberrant right subclavian artery was made in a 3-month-old Boston terrier. Surgical correction was performed after confirming adequate collateral circulation. Reports of surgical correction and evaluation of the perioperative thoracic limb blood pressure are rare in dogs.

40 CFR 1066.605 - Mass-based and molar-based exhaust emission calculations.

Code of Federal Regulations, 2014 CFR

2014-07-01

... the test interval, corrected to standard temperature and pressure. m PMfil = mass of particulate... = stabilized, ht = hot transient), corrected to standard reference conditions. m PMfil = mass of particulate... stabilized), corrected to standard reference conditions. m PMfil = mass of particulate matter emissions on...

Hypertension and blood pressure awareness among American Indians of the northern plains.

PubMed

Sharlin, K S; Heath, G W; Ford, E S; Welty, T K

1993-01-01

This study compared self-reported and measured blood pressure among American Indians of the northern plains. In 1986, a group of American Indians from the northern plains was administered the Centers for Disease Control Behavioral Risk Factor Survey (which included a question about previous blood pressure measurements) and a health risk appraisal (which included blood pressure measurement). Approximately 18% of the respondents reported being told by a doctor, nurse, or other health professional that they had high blood pressure, and 11% actually had measured blood pressures of at least 140/90 mm Hg. Overall, only 50% of hypertensive participants correctly identified themselves as hypertensive (sensitivity); specificity was 92%, predictive value positive was 43%, predictive value negative was 94%, and efficiency (the proportion of individuals who correctly classified their blood pressure status as high or normal) was 87%. These findings agree with similar studies of hypertension awareness, and they indicate that lack of this awareness remains a significant problem in the fight against cardiovascular diseases and premature death among American Indians.

Vibrational and thermal properties of β-HMX and TATB from dispersion corrected density functional theory

NASA Astrophysics Data System (ADS)

Landerville, Aaron C.; Oleynik, Ivan I.

2017-01-01

Dispersion Corrected Density Functional Theory (DFT+vdW) calculations are performed to predict vibrational and thermal properties of the bulk energetic materials (EMs) β-octahydrocyclotetramethylene-tetranitramine (β-HMX) and triaminotrinitrobenzene (TATB). DFT+vdW calculations of pressure-dependent crystal structure and the hydrostatic equation of state are followed by frozen-phonon calculations of their respective vibration spectra at each pressure. These are then used under the quasi-harmonic approximation to obtain zero-point and thermal free energy contributions to the pressure, resulting in pressure-volume-temperature (PVT) EOS for each material that are in excellent agreement with experiment. Heat capacities, and coefficients of thermal expansion as functions of temperature are also calculated and compared with experiment.

Disturbance torque rejection properties of the NASA/JPL 70-meter antenna axis servos

NASA Technical Reports Server (NTRS)

Hill, R. E.

1989-01-01

Analytic methods for evaluating pointing errors caused by external disturbance torques are developed and applied to determine the effects of representative values of wind and friction torque. The expressions relating pointing errors to disturbance torques are shown to be strongly dependent upon the state estimator parameters, as well as upon the state feedback gain and the flow versus pressure characteristics of the hydraulic system. Under certain conditions, when control is derived from an uncorrected estimate of integral position error, the desired type 2 servo properties are not realized and finite steady-state position errors result. Methods for reducing these errors to negligible proportions through the proper selection of control gain and estimator correction parameters are demonstrated. The steady-state error produced by a disturbance torque is found to be directly proportional to the hydraulic internal leakage. This property can be exploited to provide a convenient method of determining system leakage from field measurements of estimator error, axis rate, and hydraulic differential pressure.

Autonomous Correction of Sensor Data Applied to Building Technologies Using Filtering Methods

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

Castello, Charles C; New, Joshua Ryan; Smith, Matt K

2013-01-01

Sensor data validity is extremely important in a number of applications, particularly building technologies where collected data are used to determine performance. An example of this is Oak Ridge National Laboratory s ZEBRAlliance research project, which consists of four single-family homes located in Oak Ridge, TN. The homes are outfitted with a total of 1,218 sensors to determine the performance of a variety of different technologies integrated within each home. Issues arise with such a large amount of sensors, such as missing or corrupt data. This paper aims to eliminate these problems using: (1) Kalman filtering and (2) linear predictionmore » filtering techniques. Five types of data are the focus of this paper: (1) temperature; (2) humidity; (3) energy consumption; (4) pressure; and (5) airflow. Simulations show the Kalman filtering method performed best in predicting temperature, humidity, pressure, and airflow data, while the linear prediction filtering method performed best with energy consumption data.« less

Prospective assessment of the frequency of low gradient severe aortic stenosis with preserved left ventricular ejection fraction: Critical impact of aortic flow misalignment and pressure recovery phenomenon.

PubMed

Ringle, Anne; Castel, Anne-Laure; Le Goffic, Caroline; Delelis, François; Binda, Camille; Bohbot, Yohan; Ennezat, Pierre Vladimir; Guerbaai, Raphaëlle A; Levy, Franck; Vincentelli, André; Graux, Pierre; Tribouilloy, Christophe; Maréchaux, Sylvestre

2018-02-10

The frequency of paradoxical low-gradient severe aortic stenosis (AS) varies widely across studies. The impact of misalignment of aortic flow and pressure recovery phenomenon on the frequency of low-gradient severe AS with preserved left ventricular ejection fraction (LVEF) has not been evaluated in prospective studies. To investigate prospectively the impact of aortic flow misalignment by Doppler and lack of pressure recovery phenomenon correction on the frequency of low-gradient (LG) severe aortic stenosis (AS) with preserved LVEF. Aortic jet velocities and mean pressure gradient (MPG) were obtained by interrogating all windows in 68 consecutive patients with normal LVEF and severe AS (aortic valve area [AVA] ≤1cm 2 ) on the basis of the apical imaging window alone (two-dimensional [2D] apical approach). Patients were classified as having LG or high-gradient (HG) AS according to MPG <40mmHg or ≥40mmHg, and normal flow (NF) or low flow (LF) according to stroke volume index >35mL/m 2 or ≤35mL/m 2 , on the basis of the 2D apical approach, the multiview approach (multiple windows evaluation) and AVA corrected for pressure recovery. The proportion of LG severe AS was 57% using the 2D apical approach alone. After the multiview approach and correction for pressure recovery, the proportion of LG severe AS decreased from 57% to 13% (LF-LG severe AS decreased from 23% to 3%; NF-LG severe AS decreased from 34% to 10%). As a result, 25% of patients were reclassified as having HG severe AS (AVA ≤1cm 2 and MPG ≥40mmHg) and 19% as having moderate AS. Hence, 77% of patients initially diagnosed with LG severe AS did not have "true" LG severe AS when the multiview approach and the pressure recovery phenomenon correction were used. Aortic flow misevaluation, resulting from lack of use of multiple windows evaluation and pressure recovery phenomenon correction, accounts for a large proportion of incorrectly graded AS and considerable overestimation of the frequency of LG severe AS with preserved LVEF. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Signal Analysis and Waveform Reconstruction of Shock Waves Generated by Underwater Electrical Wire Explosions with Piezoelectric Pressure Probes.

PubMed

Zhou, Haibin; Zhang, Yongmin; Han, Ruoyu; Jing, Yan; Wu, Jiawei; Liu, Qiaojue; Ding, Weidong; Qiu, Aici

2016-04-22

Underwater shock waves (SWs) generated by underwater electrical wire explosions (UEWEs) have been widely studied and applied. Precise measurement of this kind of SWs is important, but very difficult to accomplish due to their high peak pressure, steep rising edge and very short pulse width (on the order of tens of μs). This paper aims to analyze the signals obtained by two kinds of commercial piezoelectric pressure probes, and reconstruct the correct pressure waveform from the distorted one measured by the pressure probes. It is found that both PCB138 and Müller-plate probes can be used to measure the relative SW pressure value because of their good uniformities and linearities, but none of them can obtain precise SW waveforms. In order to approach to the real SW signal better, we propose a new multi-exponential pressure waveform model, which has considered the faster pressure decay at the early stage and the slower pressure decay in longer times. Based on this model and the energy conservation law, the pressure waveform obtained by the PCB138 probe has been reconstructed, and the reconstruction accuracy has been verified by the signals obtained by the Müller-plate probe. Reconstruction results show that the measured SW peak pressures are smaller than the real signal. The waveform reconstruction method is both reasonable and reliable.

Signal Analysis and Waveform Reconstruction of Shock Waves Generated by Underwater Electrical Wire Explosions with Piezoelectric Pressure Probes

PubMed Central

Zhou, Haibin; Zhang, Yongmin; Han, Ruoyu; Jing, Yan; Wu, Jiawei; Liu, Qiaojue; Ding, Weidong; Qiu, Aici

2016-01-01

Underwater shock waves (SWs) generated by underwater electrical wire explosions (UEWEs) have been widely studied and applied. Precise measurement of this kind of SWs is important, but very difficult to accomplish due to their high peak pressure, steep rising edge and very short pulse width (on the order of tens of μs). This paper aims to analyze the signals obtained by two kinds of commercial piezoelectric pressure probes, and reconstruct the correct pressure waveform from the distorted one measured by the pressure probes. It is found that both PCB138 and Müller-plate probes can be used to measure the relative SW pressure value because of their good uniformities and linearities, but none of them can obtain precise SW waveforms. In order to approach to the real SW signal better, we propose a new multi-exponential pressure waveform model, which has considered the faster pressure decay at the early stage and the slower pressure decay in longer times. Based on this model and the energy conservation law, the pressure waveform obtained by the PCB138 probe has been reconstructed, and the reconstruction accuracy has been verified by the signals obtained by the Müller-plate probe. Reconstruction results show that the measured SW peak pressures are smaller than the real signal. The waveform reconstruction method is both reasonable and reliable. PMID:27110789

Experimental Results of the First Two Stages of an Advanced Transonic Core Compressor Under Isolated and Multi-Stage Conditions

NASA Technical Reports Server (NTRS)

Prahst, Patricia S.; Kulkarni, Sameer; Sohn, Ki H.

2015-01-01

NASA's Environmentally Responsible Aviation (ERA) Program calls for investigation of the technology barriers associated with improved fuel efficiency of large gas turbine engines. Under ERA the task for a High Pressure Ratio Core Technology program calls for a higher overall pressure ratio of 60 to 70. This mean that the HPC would have to almost double in pressure ratio and keep its high level of efficiency. The challenge is how to match the corrected mass flow rate of the front two supersonic high reaction and high corrected tip speed stages with a total pressure ratio of 3.5. NASA and GE teamed to address this challenge by using the initial geometry of an advanced GE compressor design to meet the requirements of the first 2 stages of the very high pressure ratio core compressor. The rig was configured to run as a 2 stage machine, with Strut and IGV, Rotor 1 and Stator 1 run as independent tests which were then followed by adding the second stage. The goal is to fully understand the stage performances under isolated and multi-stage conditions and fully understand any differences and provide a detailed aerodynamic data set for CFD validation. Full use was made of steady and unsteady measurement methods to isolate fluid dynamics loss source mechanisms due to interaction and endwalls. The paper will present the description of the compressor test article, its predicted performance and operability, and the experimental results for both the single stage and two stage configurations. We focus the detailed measurements on 97 and 100 of design speed at 3 vane setting angles.

A flamelet model for transcritical LOx/GCH4 flames

NASA Astrophysics Data System (ADS)

Müller, Hagen; Pfitzner, Michael

2017-03-01

This work presents a numerical framework to efficiently simulate methane combustion at supercritical pressures. A LES flamelet approach is adapted to account for real-gas thermodynamics effects which are a prominent feature of flames at near-critical injection conditions. The thermodynamics model is based on the Peng-Robinson equation of state (PR-EoS) in conjunction with a novel volume-translation method to correct deficiencies in the transcritical regime. The resulting formulation is more accurate than standard cubic EoSs without deteriorating their good computational performance. To consistently account for pressure and strain fluctuations in the flamelet model, an additional enthalpy equation is solved along with the transport equations for mixture fraction and mixture fraction variance. The method is validated against available experimental data for a laboratory scale LOx/GCH4 flame at conditions that resemble those in liquid-propellant rocket engines. The LES result is in good agreement with the measured OH* radiation.

75 FR 72653 - Alternate Fracture Toughness Requirements for Protection Against Pressurized Thermal Shock Events...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-11-26

..., Criminal penalties, Fire protection, Intergovernmental relations, Nuclear power plants and reactors... Requirements for Protection Against Pressurized Thermal Shock Events; Correction AGENCY: Nuclear Regulatory... fracture toughness requirements for protection against pressurized thermal shock (PTS) events for...

COMPARISON OF HIGH-DEFINITION OSCILLOMETRIC AND DIRECT ARTERIAL BLOOD PRESSURE MEASUREMENT IN ANESTHETIZED CHEETAHS (ACINONYX JUBATUS).

PubMed

Sant Cassia, Emma V; Boswood, Adrian; Tordiffe, Adrian S W

2015-09-01

Blood pressure measurement reveals important insights into the health of conscious and anesthetized individuals. This is of particular interest in cheetahs (Acinonyx jubatus), which in captivity are known to suffer from chronic diseases that may be associated with hypertension and which often require immobilization for transport or veterinary treatment. Invasive testing methods are considered the gold standard but are not practical in many settings. Consequently, it is important to evaluate the use of noninvasive methods in this species. Measurements for systolic, diastolic, and mean arterial pressure obtained using high-definition oscillometry (HDO) at the coccygeal artery were compared to simultaneous direct measurements obtained via catheterization of the femoral or dorsal pedal artery in eight anesthetized captive cheetahs during nine anesthetic events. Overall, HDO and direct measurements agreed most closely for mean arterial pressure, and the poorest agreement was observed for systolic pressure. There was a tendency for low diastolic pressures to be underestimated and for high diastolic pressures to be overestimated. Across all three parameters, HDO measurements from the tail overestimated directly measured pressures in the femoral artery and underestimated those in the dorsal pedal artery. HDO agreed most closely with directly measured dorsal pedal pressures. Mean arterial pressure showed the greatest precision (standard deviation of 10.2 mm Hg) and lowest bias (-1.2 mm Hg), with 75.9% of readings within 10 mm Hg of the direct dorsal pedal pressure. Agreement with systolic pressure was hindered by a high bias (-10.4 mm Hg), but if a correction factor of +10 mm Hg was applied to all systolic measurements, agreement was improved and 65.7% of readings were within 10 mm Hg of the direct pressure. When compared to criteria defined by the American College of Veterinary Internal Medicine for validation of blood pressure devices, results were favorable, but a limited sample size prevented formal validation.

Phase aberration simulation study of MRgFUS breast treatments

PubMed Central

Farrer, Alexis I.; Almquist, Scott; Dillon, Christopher R.; Neumayer, Leigh A.; Parker, Dennis L.; Christensen, Douglas A.; Payne, Allison

2016-01-01

Purpose: This simulation study evaluates the effects of phase aberration in breast MR-guided focused ultrasound (MRgFUS) ablation treatments performed with a phased-array transducer positioned laterally to the breast. A quantification of these effects in terms of thermal dose delivery and the potential benefits of phase correction is demonstrated in four heterogeneous breast numerical models. Methods: To evaluate the effects of varying breast tissue properties on the quality of the focus, four female volunteers with confirmed benign fibroadenomas were imaged using 3T MRI. These images were segmented into numerical models with six tissue types, with each tissue type assigned standard acoustic properties from the literature. Simulations for a single-plane 16-point raster-scan treatment trajectory centered in a fibroadenoma in each modeled breast were performed for a breast-specific MRgFUS system. At each of the 16 points, pressure patterns both with and without applying a phase correction technique were determined with the hybrid-angular spectrum method. Corrected phase patterns were obtained using a simulation-based phase aberration correction technique to adjust each element’s transmit phase to obtain maximized constructive interference at the desired focus. Thermal simulations were performed for both the corrected and uncorrected pressure patterns using a finite-difference implementation of the Pennes bioheat equation. The effect of phase correction was evaluated through comparison of thermal dose accumulation both within and outside a defined treatment volume. Treatment results using corrected and uncorrected phase aberration simulations were compared by evaluating the power required to achieve a 20 °C temperature rise at the first treatment location. The extent of the volumes that received a minimum thermal dose of 240 CEM at 43 °C inside the intended treatment volume as well as the volume in the remaining breast tissues was also evaluated in the form of a dose volume ratio (DVR), a DVR percent change between corrected and uncorrected phases, and an additional metric that measured phase spread. Results: With phase aberration correction applied, there was an improvement in the focus for all breast anatomies as quantified by a reduction in power required (13%–102%) to reach 20 °C when compared to uncorrected simulations. Also, the DVR percent change increased by 5%–77% in seven out of eight cases, indicating an improvement to the treatment as measured by a reduction in thermal dose deposited to the nontreatment tissues. Breast compositions with a higher degree of heterogeneity along the ultrasound beam path showed greater reductions in thermal dose delivered outside of the treatment volume with correction applied than beam trajectories that propagated through more homogeneous breast compositions. An increasing linear trend was observed between the DVR percent change and the phase-spread metric (R2 = 0.68). Conclusions: These results indicate that performing phase aberration correction for breast MRgFUS treatments is beneficial for the small-aperture transducer (14.4 × 9.8 cm) evaluated in this work. While all breast anatomies could benefit from phase aberration correction, greater benefits are observed in more heterogeneous anatomies. PMID:26936722

Comparison between results of solution of Burgers' equation and Laplace's equation by Galerkin and least-square finite element methods

NASA Astrophysics Data System (ADS)

Adib, Arash; Poorveis, Davood; Mehraban, Farid

2018-03-01

In this research, two equations are considered as examples of hyperbolic and elliptic equations. In addition, two finite element methods are applied for solving of these equations. The purpose of this research is the selection of suitable method for solving each of two equations. Burgers' equation is a hyperbolic equation. This equation is a pure advection (without diffusion) equation. This equation is one-dimensional and unsteady. A sudden shock wave is introduced to the model. This wave moves without deformation. In addition, Laplace's equation is an elliptical equation. This equation is steady and two-dimensional. The solution of Laplace's equation in an earth dam is considered. By solution of Laplace's equation, head pressure and the value of seepage in the directions X and Y are calculated in different points of earth dam. At the end, water table is shown in the earth dam. For Burgers' equation, least-square method can show movement of wave with oscillation but Galerkin method can not show it correctly (the best method for solving of the Burgers' equation is discrete space by least-square finite element method and discrete time by forward difference.). For Laplace's equation, Galerkin and least square methods can show water table correctly in earth dam.

MEMS Reaction Control and Maneuvering for Picosat Beyond LEO

NASA Technical Reports Server (NTRS)

Alexeenko, Alina

2016-01-01

The MEMS Reaction Control and Maneuvering for Picosat Beyond LEO project will further develop a multi-functional small satellite technology for low-power attitude control, or orientation, of picosatellites beyond low Earth orbit (LEO). The Film-Evaporation MEMS Tunable Array (FEMTA) concept initially developed in 2013, is a thermal valving system which utilizes capillary forces in a microchannel to offset internal pressures in a bulk fluid. The local vapor pressure is increased by resistive film heating until it exceeds meniscus strength in a nozzle which induces vacuum boiling and provides a stagnation pressure equal to vapor pressure at that point which is used for propulsion. Interplanetary CubeSats can utilize FEMTA for high slew rate attitude corrections in addition to desaturating reaction wheels. The FEMTA in cooling mode can be used for thermal control during high-power communication events, which are likely to accompany the attitude correction. Current small satellite propulsion options are limited to orbit correction whereas picosatellites are lacking attitude control thrusters. The available attitude control systems are either quickly saturated reaction wheels or movable high drag surfaces with long response times.

Effects of Transducer Installation on Unsteady Pressure Measurements on Oscillating Blades

NASA Technical Reports Server (NTRS)

Lepicovsky, Jan

2006-01-01

Unsteady pressures were measured above the suction side of a blade that was oscillated to simulate blade stall flutter. Measurements were made at blade oscillation frequencies up to 500 Hz. Two types of miniature pressure transducers were used: surface-mounted flat custom-made, and conventional miniature, body-mounted transducers. The signals of the surface-mounted transducers are significantly affected by blade acceleration, whereas the signals of body-mounted transducers are practically free of this distortion. A procedure was introduced to correct the signals of surface-mounted transducers to rectify the signal distortion due to blade acceleration. The signals from body-mounted transducers, and corrected signals from surface-mounted transducers represent true unsteady pressure signals on the surface of a blade subjected to forced oscillations. However, the use of body-mounted conventional transducers is preferred for the following reasons: no signal corrections are needed for blade acceleration, the conventional transducers are noticeably less expensive than custom-made flat transducers, the survival rate of body-mounted transducers is much higher, and finally installation of body-mounted transducers does not disturb the blade surface of interest.

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.

Correction to: The effectiveness of a life style modification and peer support home blood pressure monitoring in control of hypertension: protocol for a cluster randomized controlled trial.

PubMed

Su, Tin Tin; Majid, Hazreen Abdul; Nahar, Azmi Mohamed; Azizan, Nurul Ain; Hairi, Farizah Mohd; Thangiah, Nithiah; Dahlui, Maznah; Bulgiba, Awang; Murray, Liam J

2017-11-06

After publication of the article [1], it has been brought to our attention that the methodology outlined in the original article was not able to be fully carried out. The article planned a two armed randomized control trial. However, due to a lower response than expected and one housing complex dropping out from the study, the method was changed to pre- and post-intervention with no control group. All other methods were conducted as outlined in the original article.

USSAERO computer program development, versions B and C

NASA Technical Reports Server (NTRS)

Woodward, F. A.

1980-01-01

Versions B and C of the unified subsonic and supersonic aerodynamic analysis program, USSAERO, are described. Version B incorporates a new symmetrical singularity method to provide improved surface pressure distributions on wings in subsonic flow. Version C extends the range of application of the program to include the analysis of multiple engine nacelles or finned external stores. In addition, nonlinear compressibility effects in high subsonic and supersonic flows are approximated using a correction based on the local Mach number at panel control points. Several examples are presented comparing the results of these programs with other panel methods and experimental data.

One-Component Pressure-Temperature Phase Diagrams in the Presence of Air

ERIC Educational Resources Information Center

Andrade-Gamboa, Julio; Martire, Daniel O.; Donati, Edgardo R.

2010-01-01

One-component phase diagrams are good approximations to predict pressure-temperature ("P-T") behavior of a substance in the presence of air, provided air pressure is not much higher than the vapor pressure. However, at any air pressure, and from the conceptual point of view, the use of a traditional "P-T" phase diagram is not strictly correct. In…

Characterizing bias correction uncertainty in wheat yield predictions

NASA Astrophysics Data System (ADS)

Ortiz, Andrea Monica; Jones, Julie; Freckleton, Robert; Scaife, Adam

2017-04-01

Farming systems are under increased pressure due to current and future climate change, variability and extremes. Research on the impacts of climate change on crop production typically rely on the output of complex Global and Regional Climate Models, which are used as input to crop impact models. Yield predictions from these top-down approaches can have high uncertainty for several reasons, including diverse model construction and parameterization, future emissions scenarios, and inherent or response uncertainty. These uncertainties propagate down each step of the 'cascade of uncertainty' that flows from climate input to impact predictions, leading to yield predictions that may be too complex for their intended use in practical adaptation options. In addition to uncertainty from impact models, uncertainty can also stem from the intermediate steps that are used in impact studies to adjust climate model simulations to become more realistic when compared to observations, or to correct the spatial or temporal resolution of climate simulations, which are often not directly applicable as input into impact models. These important steps of bias correction or calibration also add uncertainty to final yield predictions, given the various approaches that exist to correct climate model simulations. In order to address how much uncertainty the choice of bias correction method can add to yield predictions, we use several evaluation runs from Regional Climate Models from the Coordinated Regional Downscaling Experiment over Europe (EURO-CORDEX) at different resolutions together with different bias correction methods (linear and variance scaling, power transformation, quantile-quantile mapping) as input to a statistical crop model for wheat, a staple European food crop. The objective of our work is to compare the resulting simulation-driven hindcasted wheat yields to climate observation-driven wheat yield hindcasts from the UK and Germany in order to determine ranges of yield uncertainty that result from different climate model simulation input and bias correction methods. We simulate wheat yields using a General Linear Model that includes the effects of seasonal maximum temperatures and precipitation, since wheat is sensitive to heat stress during important developmental stages. We use the same statistical model to predict future wheat yields using the recently available bias-corrected simulations of EURO-CORDEX-Adjust. While statistical models are often criticized for their lack of complexity, an advantage is that we are here able to consider only the effect of the choice of climate model, resolution or bias correction method on yield. Initial results using both past and future bias-corrected climate simulations with a process-based model will also be presented. Through these methods, we make recommendations in preparing climate model output for crop models.

A modified elastance model to control mock ventricles in real-time: numerical and experimental validation.

PubMed

Colacino, Francesco Maria; Moscato, Francesco; Piedimonte, Fabio; Danieli, Guido; Nicosia, Salvatore; Arabia, Maurizio

2008-01-01

This article describes an elastance-based mock ventricle able to reproduce the correct ventricular pressure-volume relationship and its correct interaction with the hydraulic circuit connected to it. A real-time control of the mock ventricle was obtained by a new left ventricular mathematical model including resistive and inductive terms added to the classical Suga-Sagawa elastance model throughout the whole cardiac cycle. A valved piston pump was used to mimic the left ventricle. The pressure measured into the pump chamber was fed back into the mathematical model and the calculated reference left ventricular volume was used to drive the piston. Results show that the classical model is very sensitive to pressure disturbances, especially during the filling phase, while the modified model is able to filter out the oscillations thus eliminating their detrimental effects. The presented model is thus suitable to control mock ventricles in real-time, where sudden pressure disturbances represent a key issue and are not negligible. This real-time controlled mock ventricle is able to reproduce the elastance mechanism of a natural ventricle by mimicking its preload (mean atrial pressure) and afterload (mean aortic pressure) sensitivity, i.e., the Starling law. Therefore, it can be used for designing and testing cardiovascular prostheses due to its capability to reproduce the correct ventricle-vascular system interaction.

Bottom Pressure Tides Along a Line in the Southeast Atlantic Ocean and Comparisons with Satellite Altimetry

NASA Technical Reports Server (NTRS)

Ray, Richard D.; Byrne, Deidre A.

2010-01-01

Seafloor pressure records, collected at 11 stations aligned along a single ground track of the Topex/Poseidon and Jason satellites, are analyzed for their tidal content. With very low background noise levels and approximately 27 months of high-quality records, tidal constituents can be estimated with unusually high precision. This includes many high-frequency lines up through the seventh-diurnal band. The station deployment provides a unique opportunity to compare with tides estimated from satellite altimetry, point by point along the satellite track, in a region of moderately high mesoscale variability. That variability can significantly corrupt altimeter-based tide estimates, even with 17 years of data. A method to improve the along-track altimeter estimates by correcting the data for nontidal variability is found to yield much better agreement with the bottom-pressure data. The technique should prove useful in certain demanding applications, such as altimetric studies of internal tides.

[Non-pharmacologic treatment of arterial hypertension in hemodialysis patients].

PubMed

Chazot, C; Charra, B

2007-10-01

High blood pressure in dialysis patients is related to extracellular volume excess and the related increase of systemic vascular resistances. Scribner has early described the treatment of hypertension with ultrafiltration and low salt diet, without any drugs. The dry weight method relies on the progressive reduction of the postdialysis body weight until blood pressure is normalized. Additional measures are needed such as low salt diet, neutral sodium balance during dialysis treatment, stop of antihypertensive drugs, adequate length of the dialysis session, and patient education. It may exist a lag time between the normalization of the extracellular volume and blood pressure. It is related to the correction of the hemodynamic consequences of the extracellular volume overload. Moreover, the dry weight may potentially vary in patients undergoing catabolic intercurrent events. The complications of these changes (severe hypertension, pulmonary oedema) must be anticipated by the nephrologist and the staff to avoid additional morbidity to the patient.

New laser technologies in ophthalmology for normalisation of intraocular pressure and correction of refraction

NASA Astrophysics Data System (ADS)

Baum, O. I.; Yuzhakov, A. V.; Bolshunov, A. V.; Siplivyi, V. I.; Khomchik, O. V.; Zheltov, G. I.; Sobol, E. N.

2017-09-01

We present the results of recent studies that develop principally new approaches to solving the problem of visual impairment and provide the basis for new laser technologies in ophthalmology for the treatment of glaucoma, myopia and hypermetropia. The considered theoretical models and optical methods for detecting laser-induced structural changes in eye tissues pave the way to the invention of control systems with feedback, providing efficient and safe laser treatment.

Development of a pressure based multigrid solution method for complex fluid flows

NASA Technical Reports Server (NTRS)

Shyy, Wei

1991-01-01

In order to reduce the computational difficulty associated with a single grid (SG) solution procedure, the multigrid (MG) technique was identified as a useful means for improving the convergence rate of iterative methods. A full MG full approximation storage (FMG/FAS) algorithm is used to solve the incompressible recirculating flow problems in complex geometries. The algorithm is implemented in conjunction with a pressure correction staggered grid type of technique using the curvilinear coordinates. In order to show the performance of the method, two flow configurations, one a square cavity and the other a channel, are used as test problems. Comparisons are made between the iterations, equivalent work units, and CPU time. Besides showing that the MG method can yield substantial speed-up with wide variations in Reynolds number, grid distributions, and geometry, issues such as the convergence characteristics of different grid levels, the choice of convection schemes, and the effectiveness of the basic iteration smoothers are studied. An adaptive grid scheme is also combined with the MG procedure to explore the effects of grid resolution on the MG convergence rate as well as the numerical accuracy.

Comparison of the characteristics of small commercial NDIR CO2 sensor models and development of a portable CO2 measurement device.

PubMed

Yasuda, Tomomi; Yonemura, Seiichiro; Tani, Akira

2012-01-01

Many sensors have to be used simultaneously for multipoint carbon dioxide (CO(2)) observation. All the sensors should be calibrated in advance, but this is a time-consuming process. To seek a simplified calibration method, we used four commercial CO(2) sensor models and characterized their output tendencies against ambient temperature and length of use, in addition to offset characteristics. We used four samples of standard gas with different CO(2) concentrations (0, 407, 1,110, and 1,810 ppm). The outputs of K30 and AN100 models showed linear relationships with temperature and length of use. Calibration coefficients for sensor models were determined using the data from three individual sensors of the same model to minimize the relative RMS error. When the correction was applied to the sensors, the accuracy of measurements improved significantly in the case of the K30 and AN100 units. In particular, in the case of K30 the relative RMS error decreased from 24% to 4%. Hence, we have chosen K30 for developing a portable CO(2) measurement device (10 × 10 × 15 cm, 900 g). Data of CO(2) concentration, measurement time and location, temperature, humidity, and atmospheric pressure can be recorded onto a Secure Digital (SD) memory card. The CO(2) concentration in a high-school lecture room was monitored with this device. The CO(2) data, when corrected for simultaneously measured temperature, water vapor partial pressure, and atmospheric pressure, showed a good agreement with the data measured by a highly accurate CO(2) analyzer, LI-6262. This indicates that acceptable accuracy can be realized using the calibration method developed in this study.

Comparison of the Characteristics of Small Commercial NDIR CO2 Sensor Models and Development of a Portable CO2 Measurement Device

PubMed Central

Yasuda, Tomomi; Yonemura, Seiichiro; Tani, Akira

2012-01-01

Many sensors have to be used simultaneously for multipoint carbon dioxide (CO2) observation. All the sensors should be calibrated in advance, but this is a time-consuming process. To seek a simplified calibration method, we used four commercial CO2 sensor models and characterized their output tendencies against ambient temperature and length of use, in addition to offset characteristics. We used four samples of standard gas with different CO2 concentrations (0, 407, 1,110, and 1,810 ppm). The outputs of K30 and AN100 models showed linear relationships with temperature and length of use. Calibration coefficients for sensor models were determined using the data from three individual sensors of the same model to minimize the relative RMS error. When the correction was applied to the sensors, the accuracy of measurements improved significantly in the case of the K30 and AN100 units. In particular, in the case of K30 the relative RMS error decreased from 24% to 4%. Hence, we have chosen K30 for developing a portable CO2 measurement device (10 × 10 × 15 cm, 900 g). Data of CO2 concentration, measurement time and location, temperature, humidity, and atmospheric pressure can be recorded onto a Secure Digital (SD) memory card. The CO2 concentration in a high-school lecture room was monitored with this device. The CO2 data, when corrected for simultaneously measured temperature, water vapor partial pressure, and atmospheric pressure, showed a good agreement with the data measured by a highly accurate CO2 analyzer, LI-6262. This indicates that acceptable accuracy can be realized using the calibration method developed in this study. PMID:22737029

3D Numerical Simulation on the Rockslide Generated Tsunamis

NASA Astrophysics Data System (ADS)

Chuang, M.; Wu, T.; Wang, C.; Chu, C.

2013-12-01

The rockslide generated tsunami is one of the most devastating nature hazards. However, the involvement of the moving obstacle and dynamic free-surface movement makes the numerical simulation a difficult task. To describe both the fluid motion and solid movement at the same time, we newly developed a two-way fully-coupled moving solid algorithm with 3D LES turbulent model. The free-surface movement is tracked by volume of fluid (VOF) method. The two-step projection method is adopted to solve the Navier-Stokes type government equations. In the new moving solid algorithm, a fictitious body force is implicitly prescribed in MAC correction step to make the cell-center velocity satisfied with the obstacle velocity. We called this method the implicit velocity method (IVM). Because no extra terms are added to the pressure Poission correction, the pressure field of the fluid part is stable, which is the key of the two-way fluid-solid coupling. Because no real solid material is presented in the IVM, the time marching step is not restricted to the smallest effective grid size. Also, because the fictitious force is implicitly added to the correction step, the resulting velocity is accurate and fully coupled with the resulting pressure field. We validated the IVM by simulating a floating box moving up and down on the free-surface. We presented the time-history obstacle trajectory and compared it with the experimental data. Very accurate result can be seen in terms of the oscillating amplitude and the period (Fig. 1). We also presented the free-surface comparison with the high-speed snapshots. At the end, the IVM was used to study the rock-slide generated tsunamis (Liu et al., 2005). Good validations on the slide trajectory and the free-surface movement will be presented in the full paper. From the simulation results (Fig. 2), we observed that the rockslide generated waves are manly caused by the rebounding waves from two sides of the sliding rock after the water is dragging down by the solid downward motion. We also found that the turbulence has minor effect to the main flow field. The rock size, rock density, and the steepness of the slope were analyzed to understand their effects to the maximum runup height. The detailed algorithm of IVM, the validation, the simulation and analysis of rockslide tsunami will be presented in the full paper. Figure 1. Time-history trajectory of obstacle for the floating obstacle simulation. Figure 2. Snapshots of the free-surface elevation with streamlines for the rockslide tsunami simulation.

A DFT-D Study on Structural, Electronic, Thermodynamic, and Mechanical Properties of HMX/MPNO Cocrystal under High Pressure

NASA Astrophysics Data System (ADS)

Lin, He; Chen, Jian-Fu; Cui, Yu-Ming; Zhang, Zhen-Jiang; Yang, Dong-Dong; Zhu, Shun-Guan; Li, Hong-Zhen

2017-04-01

An investigation on the structural, electronic, thermodynamic, and mechanical properties of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)/2-methylpyridine-N-oxide (MPNO) cocrystal was carried out from 0 to 100 GPa by using a dispersion-corrected density functional theory (DFT-D) method. Our calculated crystal structure is in excellent agreement with experimental results at ambient pressure. Based on the analysis of lattice parameters, lattice angles, bond lengths, bond angles, and dihedral angles under high pressure, we observe that HMX molecules in the cocrystal bulk are seriously distorted but MPNO molecules remain relatively unchanged. Hydrogen bond lengths are greatly shortened under high pressure. In addition, with the increase in pressure, the bandgap decreases gradually. However, it increases suddenly at 70 GPa. Some important hydrogen bonds between HMX and MPNO are also observed in the density of states spectrum. According to the thermodynamic analysis, this cocrystal is more easily prepared under low pressure. Finally, we characterized its mechanical properties and the results show that this cocrystal is malleable in nature. We expect that this research can provide a fundamental basis for further HMX cocrystal design and preparation.

Environmental Technology Verification Coatings and Coating Equipment Program (ETV CCEP). High Transfer Efficiency Spray Equipment - Generic Verification Protocol (Revision 0)

DTIC Science & Technology

2006-09-30

High-Pressure Waterjet • CO2 Pellet/Turbine Wheel • Ultrahigh-Pressure Waterjet 5 Process Water Reuse/Recycle • Cross-Flow Microfiltration ...documented on a process or laboratory form. Corrective action will involve taking all necessary steps to restore a measuring system to proper working order...In all cases, a nonconformance will be rectified before sample processing and analysis continues. If corrective action does not restore the

Pressure-relieving equipment: promoting its correct use amongst nurses via differing modes of educational delivery.

PubMed

Wedge, Claire; Gosney, Margot

2005-04-01

To examine the impact of written and verbal education on bed-making practices, in an attempt to reduce the prevalence of pressure ulcers. The Department of Health has set targets for a 5% reduction per annum in the incidence of pressure ulcers. Electric profiling beds with a visco-elastic polymer mattress are a new innovation in pressure ulcer prevention; however, mattress efficacy is reduced by tightly tucking sheets around the mattress. A prospective randomized pre/post-test experimental design. Ward managers at a teaching hospital were approached to participate in the study. Two researchers independently examined the tightness of the sheets around the mattresses. Wards were randomized to one of two groups. Groups A and B received written education. In addition, group B received verbal education on alternate days for one week. Beds were re-examined one month later. One researcher was blinded to the educational delivery received by the wards. Twelve wards agreed to participate in the study and 245 beds were examined. Before education, 113 beds (46%) had sheets tucked correctly around the mattresses. Following education, this increased to 215 beds (87.8%) (chi2 = 68.03, P < 0.001). There was no significant difference in the number of correctly made beds between the two different education groups: 100 (87.72%) beds correctly made in group A vs. 115 (87.79%) beds in group B (chi2 = 0, P = 0.987). Clear, concise written instruction improved practice but verbal education was not additionally beneficial. Nurses are receptive to clear, concise written evidence regarding pressure ulcer prevention and incorporate this into clinical practice.

Mass-induced sea level variations in the Red Sea from GRACE, steric-corrected altimetry, in situ bottom pressure records, and hydrographic observations

NASA Astrophysics Data System (ADS)

Feng, W.; Lemoine, J.-M.; Zhong, M.; Hsu, H. T.

2014-08-01

An annual amplitude of ∼18 cm mass-induced sea level variations (SLV) in the Red Sea is detected from the Gravity Recovery and Climate Experiment (GRACE) satellites and steric-corrected altimetry from 2003 to 2011. The annual mass variations in the region dominate the mean SLV, and generally reach maximum in late January/early February. The annual steric component of the mean SLV is relatively small (<3 cm) and out of phase of the mass-induced SLV. In situ bottom pressure records at the eastern coast of the Red Sea validate the high mass variability observed by steric-corrected altimetry and GRACE. In addition, the horizontal water mass flux of the Red Sea estimated from GRACE and steric-corrected altimetry is validated by hydrographic observations.

Dynamic compression system for the correction of pectus carinatum.

PubMed

Martinez-Ferro, Marcelo; Fraire, Carlos; Bernard, Silvia

2008-08-01

Between April 2001 and 2007, we treated 208 patients with pectus carinatum by using a specially designed dynamic compression system (DCS) that uses a custom-made aluminum brace. Recently, an electronic pressure measuring device was added to the brace. Results were evaluated by using a double-blinded subjective scale (1 to 10). A total of 208 patients were treated over 6 years; 154 were males (74%) and the mean age was 12.5 years (range 3 to 18 years). Mean utilization time was 7.2 hours daily for 7 months (range 3 to 20 months). A total of 28 (13.4%) patients abandoned treatment and were not evaluated for final results. Of the 180 remaining patients, 112 completed treatment. A total of 99 of 112 (88.4%) had good to excellent results scoring between 7 and 10 points, and 13 (11.6%) patients scored 1 to 6 points and were judged as poor or failed results. The "Pressure for Initial Correction" (PIC) in pounds per square inch (PSI) proved that starting treatment with less than 2.5 PSI avoids skin lesions. Patients who require pressures higher than 7.5 PSI should not be treated with this method. We found a good correlation between PIC versus treatment duration and outcome. DCS is an effective treatment for pectus carinatum with minimal morbidity. We suggest that patients with pectus carinatum have a trial of compression therapy before recommending surgical resection. The use of pressure measurement avoids complications such as skin lesions, partial or poor results, and patient noncompliance.

Evaluation of the Vienna APL corrections using reprocessed GNSS series

NASA Astrophysics Data System (ADS)

Steigenberger, P.; Dach, R.

2011-12-01

The Institute of Geodesy and Geophysics of the Vienna University of Technology recently started an operational service to provide non-tidal atmospheric pressure loading (APL) corrections. As the series is based on European Centre for Medium-Range Weather Forecasts (ECMWF) pressure data, it is fully consistent with the Vienna Mapping Function 1 (VMF1) atmospheric delay correction model for microwave measurements. Whereas VMF1 is widely used for, e.g., observations of Global Navigation Satellite Systems (GNSS), applying APL corrections is not yet a standard nowadays. The Center for Orbit Determination in Europe (CODE) - a joint venture between the Astronomical Institute of the University of Bern (AIUB, Bern, Switzerland), the Federal Office of Topography (swisstopo, Wabern, Switzerland), the Federal Office for Cartography and Geodesy (BKG, Frankfurt am Main, Germany), and the Insitute for Astronomical and Physical Geodesy, TU Muenchen (IAPG, Munich, Germany) - uses a recently generated series of reprocessed multi-GNSS data (considering GPS and GLONASS) to evaluate the APL corrections provided by the Vienna group. The results are also used to investigate the propagation of the APL effect in GNSS-derived results if no corrections are applied.

A wall interference assessment/correction interface measurement system for the NASA/ARC 12-ft PWT

NASA Technical Reports Server (NTRS)

1989-01-01

Development of complex air vehicle configurations is placing increasing demands on wind tunnel testing capabilities. A major area of concern is wall induced interference. Recent developments in wall interference technology provide a means for assessing and correcting for the wall induced interference using information contained in the distribution of flow variables measured at, or near, the wall. The restoration of the NASA-ARC 12-ft pressure wind tunnel (PWT) provides an opportunity to incorporate a measurement system with which wall interference assessment/correction (WIAC) technology can be applied. In this first phase of the development of a WIAC system for the PWT, the design criteria for the placement and the geometry of wall static pressure orifices were determined with a three step approach. First, the operational environment of the PWT was analyzed as to the requirements for the WIAC system. Second, appropriate wall interference theories were evaluated against the requirements determined from the operational environment. Third, the flow about representative models in the PWT was calculated and, specifically, the pressure signatures at the location of the test section wall were obtained. The number of discrete pressure measurements and their locations were determined by curve fitting the pressure distribution through the discrete measurements and evaluating the resulting error.

A comparative study of several compressibility corrections to turbulence models applied to high-speed shear layers

NASA Technical Reports Server (NTRS)

Viegas, John R.; Rubesin, Morris W.

1991-01-01

Several recently published compressibility corrections to the standard k-epsilon turbulence model are used with the Navier-Stokes equations to compute the mixing region of a large variety of high speed flows. These corrections, specifically developed to address the weakness of higher order turbulence models to accurately predict the spread rate of compressible free shear flows, are applied to two stream flows of the same gas mixing under a large variety of free stream conditions. Results are presented for two types of flows: unconfined streams with either (1) matched total temperatures and static pressures, or (2) matched static temperatures and pressures, and a confined stream.

Basic tasks for improving spectral-acoustic forecasting of dynamic phenomena in coal mines

NASA Astrophysics Data System (ADS)

Shadrin, A. V.; Kontrimas, A. A.

2017-09-01

A number of tasks for improving the spectral-acoustic method for forecasting dynamic phenomena and controlling stress condition in coalmines is considered. They are: considering the influence of a gas factor on the danger indicator, dependence of a relative pressure coefficient on the distance between the source and the receiver of the probing acoustic signal, correct selection of operating frequencies, the importance of developing the techniques for defining the critical value of the outburst danger index The influence of the rock mass stress condition ahead of the preliminary opening face on the relative pressure coefficient defined for installing the sound receiver in the wall of the opening behind the opening face is also justified in the article.

Improving and assessing vapour pressure estimation methods for organic compounds of atmospheric relevance using a Knudsen Effusion Mass Spectrometer (KEMS)

NASA Astrophysics Data System (ADS)

Booth, A. M.; Topping, D. O.; McFiggans, G. B.; Garforth, A.; Percival, C. J.

2009-12-01

Aerosol particles influence climate directly through the scattering and absorbing radiation and indirectly through their role as cloud condensation nuclei (CCN). Traditionally, models aiming to capture the behaviour of aerosols in the atmosphere have concentrated on the role of inorganic compounds. However, organic components, covering a huge range of chemical and physical properties (Jacobson et.al., 2000), may constitute a significant fraction depending on location (Houghton et.al., 2001). Knowledge of pure component vapour pressures is essential for calculations of gas/particle partitioning. There are many methods of estimating vapour pressures but most of the experimental data collected to date has been for intermediate or high pressure compounds (and often measured at temperatures considerably above ambient) and the proportion of experimental data for low (less than 100Pa) vapour pressure compounds has been very small. Hence the datasets used for developing the estimation methods have reflected this bias in addition to the fact that components studied tend to have one or two functional groups at the most. Thus it is unsurprising that some of the estimation methods can give errors in vapour pressure of several orders of magnitude for multifunctional compounds at ambient temperatures. Knudsen Effusion Mass Spectrometer (KEMS) has been used to measure solid state vapour pressures for multifunctional organic compounds based on dicarboxylic acids (Booth et al 2009). In the atmosphere these compounds are likely to exist in the sub-cooled state so Differential Scanning Calorimetry (DSC) was used to obtain thermochemical data to effect a correction between solid and sub-cooled vapour pressures. The group contribution method of Nanoolal and co-workers (Nanoolal et al., 2008) is one of the best predictive methods in terms of reproducing available low volatility vapour pressure data (barley et al., 2009). The Nanoolal method relies on the use of primary and secondary functional groups and interaction parameters, derived from experimental data, to reliably predict boiling points and vapour pressures. A sensitivity study was undertaken to establish the impact of the new experimentally determined vapour pressures on partitioning models. Jacobson, M.C., et al. Rev Geophys, 38 (2), 267-294, 2000. Houghton et al. Climate Change 2001: The Scientific Basis. Contribution of Working Group 1 to the Third Assessment Report of the IPCC., 881 pp., Cambridge University Press, 2001. Johnson, D. , et al. Atmo. Chem. Phys., Vol. 6, 419-431, 2006 Yu, J. Z., et al. J Atmos Chem. 34, 207-258, 1999 Booth, A.M. et al Atmos. Meas. Tech.,2,355-361, 2009 Nanoolal, Y. et al Fluid Phase Equilibria, 269,117-133., 2008. Barley, M. et al Atmos. Chem. Phys., -,to be submitted.

Fast, rugged and sensitive ultra high pressure liquid chromatography tandem mass spectrometry method for analysis of cyanotoxins in raw water and drinking water--First findings of anatoxins, cylindrospermopsins and microcystin variants in Swedish source waters and infiltration ponds.

PubMed

Pekar, Heidi; Westerberg, Erik; Bruno, Oscar; Lääne, Ants; Persson, Kenneth M; Sundström, L Fredrik; Thim, Anna-Maria

2016-01-15

Freshwater blooms of cyanobacteria (blue-green algae) in source waters are generally composed of several different strains with the capability to produce a variety of toxins. The major exposure routes for humans are direct contact with recreational waters and ingestion of drinking water not efficiently treated. The ultra high pressure liquid chromatography tandem mass spectrometry based analytical method presented here allows simultaneous analysis of 22 cyanotoxins from different toxin groups, including anatoxins, cylindrospermopsins, nodularin and microcystins in raw water and drinking water. The use of reference standards enables correct identification of toxins as well as precision of the quantification and due to matrix effects, recovery correction is required. The multi-toxin group method presented here, does not compromise sensitivity, despite the large number of analytes. The limit of quantification was set to 0.1 μg/L for 75% of the cyanotoxins in drinking water and 0.5 μg/L for all cyanotoxins in raw water, which is compliant with the WHO guidance value for microcystin-LR. The matrix effects experienced during analysis were reasonable for most analytes, considering the large volume injected into the mass spectrometer. The time of analysis, including lysing of cell bound toxins, is less than three hours. Furthermore, the method was tested in Swedish source waters and infiltration ponds resulting in evidence of presence of anatoxin, homo-anatoxin, cylindrospermopsin and several variants of microcystins for the first time in Sweden, proving its usefulness. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

The Krylov accelerated SIMPLE(R) method for flow problems in industrial furnaces

NASA Astrophysics Data System (ADS)

Vuik, C.; Saghir, A.; Boerstoel, G. P.

2000-08-01

Numerical modeling of the melting and combustion process is an important tool in gaining understanding of the physical and chemical phenomena that occur in a gas- or oil-fired glass-melting furnace. The incompressible Navier-Stokes equations are used to model the gas flow in the furnace. The discrete Navier-Stokes equations are solved by the SIMPLE(R) pressure-correction method. In these applications, many SIMPLE(R) iterations are necessary to obtain an accurate solution. In this paper, Krylov accelerated versions are proposed: GCR-SIMPLE(R). The properties of these methods are investigated for a simple two-dimensional flow. Thereafter, the efficiencies of the methods are compared for three-dimensional flows in industrial glass-melting furnaces. Copyright

40 CFR 144.55 - Corrective action.

Code of Federal Regulations, 2010 CFR

2010-07-01

... injection zone does not exceed hydrostatic pressure at the site of any improperly completed or abandoned... the case of Class II wells operating over the fracture pressure of the injection formation, all known wells within the area of review penetrating formations affected by the increase in pressure. For such...

Modeling and Real-Time Process Monitoring of Organometallic Chemical Vapor Deposition of III-V Phosphides and Nitrides at Low and High Pressure

NASA Technical Reports Server (NTRS)

Bachmann, K. J.; Cardelino, B. H.; Moore, C. E.; Cardelino, C. A.; Sukidi, N.; McCall, S.

1999-01-01

The purpose of this paper is to review modeling and real-time monitoring by robust methods of reflectance spectroscopy of organometallic chemical vapor deposition (OMCVD) processes in extreme regimes of pressure. The merits of p-polarized reflectance spectroscopy under the conditions of chemical beam epitaxy (CBE) and of internal transmission spectroscopy and principal angle spectroscopy at high pressure are assessed. In order to extend OMCVD to materials that exhibit large thermal decomposition pressure at their optimum growth temperature we have designed and built a differentially-pressure-controlled (DCP) OMCVD reactor for use at pressures greater than or equal to 6 atm. We also describe a compact hard-shell (CHS) reactor for extending the pressure range to 100 atm. At such very high pressure the decomposition of source vapors occurs in the vapor phase, and is coupled to flow dynamics and transport. Rate constants for homogeneous gas phase reactions can be predicted based on a combination of first principles and semi-empirical calculations. The pressure dependence of unimolecular rate constants is described by RRKM theory, but requires variational and anharmonicity corrections not included in presently available calculations with the exception of ammonia decomposition. Commercial codes that include chemical reactions and transport exist, but do not adequately cover at present the kinetics of heteroepitaxial crystal growth.

New correction procedures for the fast field program which extend its range

NASA Technical Reports Server (NTRS)

West, M.; Sack, R. A.

1990-01-01

A fast field program (FFP) algorithm was developed based on the method of Lee et al., for the prediction of sound pressure level from low frequency, high intensity sources. In order to permit accurate predictions at distances greater than 2 km, new correction procedures have had to be included in the algorithm. Certain functions, whose Hankel transforms can be determined analytically, are subtracted from the depth dependent Green's function. The distance response is then obtained as the sum of these transforms and the Fast Fourier Transformation (FFT) of the residual k dependent function. One procedure, which permits the elimination of most complex exponentials, has allowed significant changes in the structure of the FFP algorithm, which has resulted in a substantial reduction in computation time.

Computer program to predict aircraft noise levels

NASA Technical Reports Server (NTRS)

Clark, B. J.

1981-01-01

Methods developed at the NASA Lewis Research Center for predicting the noise contributions from various aircraft noise sources were programmed to predict aircraft noise levels either in flight or in ground tests. The noise sources include fan inlet and exhaust, jet, flap (for powered lift), core (combustor), turbine, and airframe. Noise propagation corrections are available for atmospheric attenuation, ground reflections, extra ground attenuation, and shielding. Outputs can include spectra, overall sound pressure level, perceived noise level, tone-weighted perceived noise level, and effective perceived noise level at locations specified by the user. Footprint contour coordinates and approximate footprint areas can also be calculated. Inputs and outputs can be in either System International or U.S. customary units. The subroutines for each noise source and propagation correction are described. A complete listing is given.

A method of reconstruction of clinical gas-analyzer signals corrupted by positive-pressure ventilation.

PubMed

Farmery, A D; Hahn, C E

2001-04-01

The use of sidestream infrared and paramagnetic clinical gas analyzers is widespread in anesthesiology and respiratory medicine. For most clinical applications, these instruments are entirely satisfactory. However, their ability to measure breath-by-breath volumetric gas fluxes, as required for measurement of airway dead space, oxygen uptake, and so on, is usually inferior to that of the mass spectrometer, and this is thought to be due, in part, to their slower response times. We describe how volumetric gas analysis with the Datex Ultima analyzer, although reasonably accurate for spontaneous ventilation, gives very inaccurate results in conditions of positive-pressure ventilation. We show that this problem is a property of the gas sampling system rather than the technique of gas analysis itself. We examine the source of this error and describe how cyclic changes in airway pressure result in variations in the flow rate of the gas within the sampling catheter. This results in the phenomenon of "time distortion," and the resultant gas concentration signal becomes a nonlinear time series. This corrupted signal cannot be aligned or integrated with the measured flow signal. We describe a method to correct for this effect. With the use of this method, measurements required for breath-by-breath gas-exchange models can be made easily and reliably in the clinical setting.

A fractional Fourier transform analysis of a bubble excited by an ultrasonic chirp.

PubMed

Barlow, Euan; Mulholland, Anthony J

2011-11-01

The fractional Fourier transform is proposed here as a model based, signal processing technique for determining the size of a bubble in a fluid. The bubble is insonified with an ultrasonic chirp and the radiated pressure field is recorded. This experimental bubble response is then compared with a series of theoretical model responses to identify the most accurate match between experiment and theory which allows the correct bubble size to be identified. The fractional Fourier transform is used to produce a more detailed description of each response, and two-dimensional cross correlation is then employed to identify the similarities between the experimental response and each theoretical response. In this paper the experimental bubble response is simulated by adding various levels of noise to the theoretical model output. The method is compared to the standard technique of using time-domain cross correlation. The proposed method is shown to be far more robust at correctly sizing the bubble and can cope with much lower signal to noise ratios.

Sequential limiting in continuous and discontinuous Galerkin methods for the Euler equations

NASA Astrophysics Data System (ADS)

Dobrev, V.; Kolev, Tz.; Kuzmin, D.; Rieben, R.; Tomov, V.

2018-03-01

We present a new predictor-corrector approach to enforcing local maximum principles in piecewise-linear finite element schemes for the compressible Euler equations. The new element-based limiting strategy is suitable for continuous and discontinuous Galerkin methods alike. In contrast to synchronized limiting techniques for systems of conservation laws, we constrain the density, momentum, and total energy in a sequential manner which guarantees positivity preservation for the pressure and internal energy. After the density limiting step, the total energy and momentum gradients are adjusted to incorporate the irreversible effect of density changes. Antidiffusive corrections to bounds-compatible low-order approximations are limited to satisfy inequality constraints for the specific total and kinetic energy. An accuracy-preserving smoothness indicator is introduced to gradually adjust lower bounds for the element-based correction factors. The employed smoothness criterion is based on a Hessian determinant test for the density. A numerical study is performed for test problems with smooth and discontinuous solutions.

Calculation of wall effects of flow on a perforated wall with a code of surface singularities

NASA Astrophysics Data System (ADS)

Piat, J. F.

1994-07-01

Simplifying assumptions are inherent in the analytic method previously used for the determination of wall interferences on a model in a wind tunnel. To eliminate these assumptions, a new code based on the vortex lattice method was developed. It is suitable for processing any shape of test sections with limited areas of porous wall, the characteristic of which can be nonlinear. Calculation of wall effects in S3MA wind tunnel, whose test section is rectangular 0.78 m x 0.56 m, and fitted with two or four perforated walls, have been performed. Wall porosity factors have been adjusted to obtain the best fit between measured and computed pressure distributions on the test section walls. The code was checked by measuring nearly equal drag coefficients for a model tested in S3MA wind tunnel (after wall corrections) and in S2MA wind tunnel whose test section is seven times larger (negligible wall corrections).

Grading of direct laryngoscopy. A survey of current practice.

PubMed

Cohen, A M; Fleming, B G; Wace, J R

1994-06-01

One hundred and twenty anaesthetists (30 of each grade), from three separate regions, were interviewed as to how they recorded the appearance of laryngeal structures at direct laryngoscopy and about their knowledge of the commonly used numerical grading system. About two-thirds of anaesthetists surveyed (69.2%) used the numerical grading system, but of these, over half could not identify a 'grade 2' laryngoscopic appearance correctly. Of anaesthetists who did not use the numerical method, over half could not correctly state the difference between a 'grade 2' and a 'grade 3' laryngoscopic appearance. Over 40% of anaesthetists stated incorrectly that the grading should be made on the initial view, even when laryngeal pressure had been needed. Junior anaesthetists were more likely to use the numerical method of recording. The results show that there is unacceptable uncertainty and inaccuracy in the use of the numerical grading system by users as well as non-users, which makes the current routine clinical use of the numerical grading system unsatisfactory.

Pressure standards and sensors up to 3 GPa, actual state and development trends

NASA Astrophysics Data System (ADS)

Wisniewski, Roland; Molinar, Gianfranco

1999-04-01

Metrological problems connected with pressure standards and sensors up to 3 GPa as an introduction to the pressure measurements in the so-called “GIGAPASCAL REGION”, 1-100 GPa, are discussed. Re-examination of Bi I-Bi II phase transition pressure as a fixed point of the International Practical Pressure Scale and correction of the NaCl Pressure Scale is proposed. Well-established sensors as candidates for secondary pressure standards up to 3 GPa are briefly presented.

The impact of xylem cavitation on water potential isotherms measured by the pressure chamber technique in Metasequoia glyptostroboides Hu & W.C. Cheng.

PubMed

Yang, Dongmei; Pan, Shaoan; Tyree, Melvin T

2016-08-01

Pressure-volume (PV) curve analysis is the most common and accurate way of estimating all components of the water relationships in leaves (water potential isotherms) as summarized in the Höfler diagram. PV curve analysis yields values of osmotic pressure, turgor pressure, and elastic modulus of cell walls as a function of relative water content. It allows the computation of symplasmic/apoplastic water content partitioning. For about 20 years, cavitation in xylem has been postulated as a possible source of error when estimating the above parameters, but, to the best of the authors' knowledge, no one has ever previously quantified its influence. Results in this paper provide independent estimates of osmotic pressure by PV curve analysis and by thermocouple psychrometer measurement. An anatomical evaluation was also used for the first time to compare apoplastic water fraction estimates from PV analysis with anatomical values. Conclusions include: (i) PV curve values of osmotic pressure are underestimated prior to correcting osmotic pressure for water loss by cavitation in Metasequoia glyptostroboides; (ii) psychrometer estimates of osmotic pressure obtained in tissues killed by freezing or heating agreed with PV values before correction for apoplastic water dilution; (iii) after correction for dilution effects, a solute concentration enhancement (0.27MPa or 0.11 osmolal) was revealed. The possible sources of solute enhancement were starch hydrolysis and release of ions from the Donnan free space of needle cell walls. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Determinants and clinical impact of pressure drift in manoscan anorectal high resolution manometry system.

PubMed

Parthasarathy, G; McMaster, J; Feuerhak, K; Zinsmeister, A R; Bharucha, A E

2016-09-01

Pressure drift (PD), resulting from differences between room and body temperature, reduces the accuracy of pressure measurements with the Manoscan high resolution manometry (HRM) system. Our aims were to assess PD during anorectal HRM. Defined as the residual pressure measured immediately after the catheter was removed, PD was calculated for each sensor and averaged across all 12 sensors in 454 anorectal consecutive studies recorded with 3 HRM catheters. The relationship between PD and study duration, number of prior uses of a catheter, and peak and average pressure exposure during a study were evaluated. The correction of PD with a software algorithm (thermal compensation) was evaluated in 76 studies where the most distal sensor was outside the body. The PD varied among sensors and across catheters. The average PD (7.3 ± 0.2 mmHg) was significantly greater for newer catheters, during longer studies, or when sensors were exposed to higher pressures. Together, these factors explained 81% of the variance in overall PD. After thermal compensation, the uncorrected median PD for the most distal sensor was 2.5-5 mmHg over the study duration. Correcting this changed the interpretation (e.g., as abnormal instead of normal) of at least 1 anorectal parameter in eight of 76 studies. During anorectal HRM, PD declines with catheter use and is greater for newer catheters, when sensors are exposed to higher pressures, and for studies of longer duration. While PD is partially corrected with thermal compensation algorithms, the impact on interpretation is modest. © 2016 John Wiley & Sons Ltd.

Computational fluid dynamics combustion analysis evaluation

NASA Technical Reports Server (NTRS)

Kim, Y. M.; Shang, H. M.; Chen, C. P.; Ziebarth, J. P.

1992-01-01

This study involves the development of numerical modelling in spray combustion. These modelling efforts are mainly motivated to improve the computational efficiency in the stochastic particle tracking method as well as to incorporate the physical submodels of turbulence, combustion, vaporization, and dense spray effects. The present mathematical formulation and numerical methodologies can be casted in any time-marching pressure correction methodologies (PCM) such as FDNS code and MAST code. A sequence of validation cases involving steady burning sprays and transient evaporating sprays will be included.

A material-sparing method for assessment of powder deformation characteristics using data collected during a single compression-decompression cycle.

PubMed

Katz, Jeffrey M; Roopwani, Rahul; Buckner, Ira S

2013-10-01

Compressibility profiles, or functions of solid fraction versus applied pressure, are used to provide insight into the fundamental mechanical behavior of powders during compaction. These functions, collected during compression (in-die) or post ejection (out-of-die), indicate the amount of pressure that a given powder formulation requires to be compressed to a given density or thickness. To take advantage of the benefits offered by both methods, the data collected in-die during a single compression-decompression cycle will be used to generate the equivalent of a complete out-of-die compressibility profile that has been corrected for both elastic and viscoelastic recovery of the powder. This method has been found to be both a precise and accurate means of evaluating out-of-die compressibility for four common tableting excipients. Using this method, a comprehensive characterization of powder compaction behavior, specifically in relation to plastic/brittle, elastic and viscoelastic deformation, can be obtained. Not only is the method computationally simple, but it is also material-sparing. The ability to characterize powder compressibility using this approach can improve productivity and streamline tablet development studies. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association.

Written Corrective Feedback in IELTS Writing Task 2: Teachers' Priorities, Practices, and Beliefs

ERIC Educational Resources Information Center

Pearson, William S.

2018-01-01

Teacher corrective feedback is widely recognised as integral in supporting developing L2 writers. The potentially high pressure IELTS test preparation classroom presents a context where feedback has not yet been extensively studied. Consequently, teachers' approaches to corrective feedback on Writing Task 2, the essay component of IELTS Writing,…

Theoretical and experimental study on the magnetic fluid seal of reciprocating shaft

NASA Astrophysics Data System (ADS)

Li, Decai; Xu, Haiping; He, Xinzhi; Lan, Huiqing

2005-03-01

The authors obtain anti-pressure formula of reciprocating shaft magnetic fluid seal from general Navier-Stokes equation. In order to verify the correctness of the anti-pressure formula, the authors set up a magnetic fluid anti-pressure experiment rig for a reciprocating seal. Finally, the authors have verified influence of speed and stroke on the seal anti-pressure.

Direct measurements of local bed shear stress in the presence of pressure gradients

NASA Astrophysics Data System (ADS)

Pujara, Nimish; Liu, Philip L.-F.

2014-07-01

This paper describes the development of a shear plate sensor capable of directly measuring the local mean bed shear stress in small-scale and large-scale laboratory flumes. The sensor is capable of measuring bed shear stress in the range 200 Pa with an accuracy up to 1 %. Its size, 43 mm in the flow direction, is designed to be small enough to give spatially local measurements, and its bandwidth, 75 Hz, is high enough to resolve time-varying forcing. Typically, shear plate sensors are restricted to use in zero pressure gradient flows because secondary forces on the edge of the shear plate caused by pressure gradients can introduce large errors. However, by analysis of the pressure distribution at the edges of the shear plate in mild pressure gradients, we introduce a new methodology for correcting for the pressure gradient force. The developed sensor includes pressure tappings to measure the pressure gradient in the flow, and the methodology for correction is applied to obtain accurate measurements of bed shear stress under solitary waves in a small-scale wave flume. The sensor is also validated by measurements in a turbulent flat plate boundary layer in open channel flow.

Apoplastic water fraction and rehydration techniques introduce significant errors in measurements of relative water content and osmotic potential in plant leaves.

PubMed

Arndt, Stefan K; Irawan, Andi; Sanders, Gregor J

2015-12-01

Relative water content (RWC) and the osmotic potential (π) of plant leaves are important plant traits that can be used to assess drought tolerance or adaptation of plants. We estimated the magnitude of errors that are introduced by dilution of π from apoplastic water in osmometry methods and the errors that occur during rehydration of leaves for RWC and π in 14 different plant species from trees, grasses and herbs. Our data indicate that rehydration technique and length of rehydration can introduce significant errors in both RWC and π. Leaves from all species were fully turgid after 1-3 h of rehydration and increasing the rehydration time resulted in a significant underprediction of RWC. Standing rehydration via the petiole introduced the least errors while rehydration via floating disks and submerging leaves for rehydration led to a greater underprediction of RWC. The same effect was also observed for π. The π values following standing rehydration could be corrected by applying a dilution factor from apoplastic water dilution using an osmometric method but not by using apoplastic water fraction (AWF) from pressure volume (PV) curves. The apoplastic water dilution error was between 5 and 18%, while the two other rehydration methods introduced much greater errors. We recommend the use of the standing rehydration method because (1) the correct rehydration time can be evaluated by measuring water potential, (2) overhydration effects were smallest, and (3) π can be accurately corrected by using osmometric methods to estimate apoplastic water dilution. © 2015 Scandinavian Plant Physiology Society.

Protocols for pressure ulcer prevention: are they evidence-based?

PubMed

Chaves, Lidice M; Grypdonck, Mieke H F; Defloor, Tom

2010-03-01

This study is a report of a study to determine the quality of protocols for pressure ulcer prevention in home care in the Netherlands. If pressure ulcer prevention protocols are evidence-based and practitioners use them correctly in practice, this will result a reduction in pressure ulcers. Very little is known about the evidence-based content and quality of the pressure ulcer prevention protocols. In 2008, current pressure ulcer prevention protocols from 24 home-care agencies in the Netherlands were evaluated. A checklist developed and validated by two pressure ulcer prevention experts was used to assess the quality of the protocols, and weighted and unweighted quality scores were computed and analysed using descriptive statistics. The 24 pressure ulcer prevention protocols had a mean weighted quality score of 63.38 points out of a maximum of 100 (sd 5). The importance of observing the skin at the pressure points at least once a day was emphasized in 75% of the protocols. Only 42% correctly warned against the use of materials that were 'less effective or that could potentially cause harm'. Pressure ulcer prevention commands a reasonable amount of attention in home care, but the incidence of pressure ulcers and lack of a consistent, standardized document for use in actual practice indicate a need for systematic implementation of national pressure ulcer prevention standards in the Netherlands to ensure adherence to the established protocols.

Compression-ignition Engine Performance at Altitudes and at Various Air Pressures and Temperatures

NASA Technical Reports Server (NTRS)

Moore, Charles S; Collins, John H

1937-01-01

Engine test results are presented for simulated altitude conditions. A displaced-piston combustion chamber on a 5- by 7-inch single cylinder compression-ignition engine operating at 2,000 r.p.m. was used. Inlet air temperature equivalent to standard altitudes up to 14,000 feet were obtained. Comparison between performance at altitude of the unsupercharged compression-ignition engine compared favorably with the carburetor engine. Analysis of the results for which the inlet air temperature, inlet air pressure, and inlet and exhaust pressure were varied indicates that engine performance cannot be reliably corrected on the basis of inlet air density or weight of air charge. Engine power increases with inlet air pressure and decreases with inlet air temperatures very nearly as straight line relations over a wide range of air-fuel ratios. Correction factors are given.

Gay-Lussac Did Better Than He Knew

NASA Astrophysics Data System (ADS)

Holbrow, Charles H.; Amato, Joseph C.

2011-04-01

In his 1802 paper Joseph Louis Gay-Lussac reported the first definitive experimental evidence that many different gases exhibit the same fractional expansion of volume when heated. This property is known as Charles Law, Amontons Law, Dalton's Law, or the law of volumes. Gay-Lussac concluded from his experiments that many gases expand by 37.5% when heated from 0 ,oC to 100,oC. Although his result is within 2.5% of the modern value of 36.6% = 100/273.15, the discrepancy is surprising because his direct and simple experimental method allowed him to measure changes in volume with a precision of a few tenths of a percent. An examination of his original paper suggests, however, that he did not take into account that his measurements of the initial and final volumes of gas were made at slightly different pressures. With reasonable assumptions about the diagrams in his paper, one can use Pascal's law and the ideal gas law to correct the measured volumes so that they correspond to the same initial and final pressure. With this correction the results imply δV/V = .366. Gay-Lussac did better than he knew.

An analysis method for multi-component airfoils in separated flow

NASA Technical Reports Server (NTRS)

Rao, B. M.; Duorak, F. A.; Maskew, B.

1980-01-01

The multi-component airfoil program (Langley-MCARF) for attached flow is modified to accept the free vortex sheet separation-flow model program (Analytical Methods, Inc.-CLMAX). The viscous effects are incorporated into the calculation by representing the boundary layer displacement thickness with an appropriate source distribution. The separation flow model incorporated into MCARF was applied to single component airfoils. Calculated pressure distributions for angles of attack up to the stall are in close agreement with experimental measurements. Even at higher angles of attack beyond the stall, correct trends of separation, decrease in lift coefficients, and increase in pitching moment coefficients are predicted.

The predictive value of the sacral base pressure test in detecting specific types of sacroiliac dysfunction

PubMed Central

Mitchell, Travis D.; Urli, Kristina E.; Breitenbach, Jacques; Yelverton, Chris

2007-01-01

Abstract Objective This study aimed to evaluate the validity of the sacral base pressure test in diagnosing sacroiliac joint dysfunction. It also determined the predictive powers of the test in determining which type of sacroiliac joint dysfunction was present. Methods This was a double-blind experimental study with 62 participants. The results from the sacral base pressure test were compared against a cluster of previously validated tests of sacroiliac joint dysfunction to determine its validity and predictive powers. The external rotation of the feet, occurring during the sacral base pressure test, was measured using a digital inclinometer. Results There was no statistically significant difference in the results of the sacral base pressure test between the types of sacroiliac joint dysfunction. In terms of the results of validity, the sacral base pressure test was useful in identifying positive values of sacroiliac joint dysfunction. It was fairly helpful in correctly diagnosing patients with negative test results; however, it had only a “slight” agreement with the diagnosis for κ interpretation. Conclusions In this study, the sacral base pressure test was not a valid test for determining the presence of sacroiliac joint dysfunction or the type of dysfunction present. Further research comparing the agreement of the sacral base pressure test or other sacroiliac joint dysfunction tests with a criterion standard of diagnosis is necessary. PMID:19674694

77 FR 64755 - Medicare and Medicaid Programs; Electronic Health Record Incentive Program-Stage 2; Corrections

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-23

... EHR PQRS, ACO, Group Clinical Process/ Blood Pressure. Contact Information: Reporting PQRS, UDS... of hypertension and whose blood pressure was adequately controlled ( www.asco.org ;. cancer who are...

Reconstructing functional near-infrared spectroscopy (fNIRS) signals impaired by extra-cranial confounds: an easy-to-use filter method.

PubMed

Haeussinger, F B; Dresler, T; Heinzel, S; Schecklmann, M; Fallgatter, A J; Ehlis, A-C

2014-07-15

Functional near-infrared spectroscopy (fNIRS) is an optical neuroimaging method that detects temporal concentration changes of oxygenated and deoxygenated hemoglobin within the cortex, so that neural activation can be inferred. However, even though fNIRS is a very practical and well-tolerated method with several advantages particularly in methodically challenging measurement situations (e.g., during tasks involving movement or open speech), it has been shown to be confounded by systemic compounds of non-cerebral, extra-cranial origin (e.g. changes in blood pressure, heart rate). Especially event-related signal patterns induced by dilation or constriction of superficial forehead and temple veins impair the detection of frontal brain activation elicited by cognitive tasks. To further investigate this phenomenon, we conducted a simultaneous fNIRS-fMRI study applying a working memory paradigm (n-back). Extra-cranial signals were obtained by extracting the BOLD signal from fMRI voxels within the skin. To develop a filter method that corrects for extra-cranial skin blood flow, particularly intended for fNIRS data sets recorded by widely used continuous wave systems with fixed optode distances, we identified channels over the forehead with probable major extra-cranial signal contributions. The averaged signal from these channels was then subtracted from all fNIRS channels of the probe set. Additionally, the data were corrected for motion and non-evoked systemic artifacts. Applying these filters, we can show that measuring brain activation in frontal brain areas with fNIRS was substantially improved. The resulting signal resembled the fMRI parameters more closely than before the correction. Future fNIRS studies measuring functional brain activation in the forehead region need to consider the use of different filter options to correct for interfering extra-cranial signals. Copyright © 2014 Elsevier Inc. All rights reserved.

Modeling the melting of multicomponent systems: the case of MgSiO3 perovskite under lower mantle conditions

PubMed Central

Di Paola, Cono; P. Brodholt, John

2016-01-01

Knowledge of the melting properties of materials, especially at extreme pressure conditions, represents a long-standing scientific challenge. For instance, there is currently considerable uncertainty over the melting temperatures of the high-pressure mantle mineral, bridgmanite (MgSiO3-perovskite), with current estimates of the melting T at the base of the mantle ranging from 4800 K to 8000 K. The difficulty with experimentally measuring high pressure melting temperatures has motivated the use of ab initio methods, however, melting is a complex multi-scale phenomenon and the timescale for melting can be prohibitively long. Here we show that a combination of empirical and ab-initio molecular dynamics calculations can be used to successfully predict the melting point of multicomponent systems, such as MgSiO3 perovskite. We predict the correct low-pressure melting T, and at high-pressure we show that the melting temperature is only 5000 K at 120 GPa, a value lower than nearly all previous estimates. In addition, we believe that this strategy is of general applicability and therefore suitable for any system under physical conditions where simpler models fail. PMID:27444854

Mathematical Modelling of the Infusion Test

NASA Astrophysics Data System (ADS)

Cieslicki, Krzysztof

2007-01-01

The objective of this paper was to improve the well established in clinical practice Marmarou model for intracranial volume-pressure compensation by adding the pulsatile components. It was demonstrated that complicated pulsation and growth in intracranial pressure during infusion test could be successfully modeled by the relatively simple analytical expression derived in this paper. The CSF dynamics were tested in 25 patients with clinical symptoms of hydrocephalus. Basing on the frequency spectrum of the patient's baseline pressure and identified parameters of CSF dynamic, for each patient an "ideal" infusion test curve free from artefacts and slow waves was simulated. The degree of correlation between simulated and real curves obtained from clinical observations gave insight into the adequacy of assumptions of Marmarou model. The proposed method of infusion tests analysis designates more exactly the value of the reference pressure, which is usually treated as a secondary and of uncertain significance. The properly identified value of the reference pressure decides on the degree of pulsation amplitude growth during IT, as well as on the value of elastance coefficient. The artificially generated tests with various pulsation components were also applied to examine the correctness of the used algorithm of identification of the original Marmarou model parameters.

Coarse-grained modeling of crystal growth and polymorphism of a model pharmaceutical molecule.

PubMed

Mandal, Taraknath; Marson, Ryan L; Larson, Ronald G

2016-10-04

We describe a systematic coarse-graining method to study crystallization and predict possible polymorphs of small organic molecules. In this method, a coarse-grained (CG) force field is obtained by inverse-Boltzmann iteration from the radial distribution function of atomistic simulations of the known crystal. With the force field obtained by this method, we show that CG simulations of the drug phenytoin predict growth of a crystalline slab from a melt of phenytoin, allowing determination of the fastest-growing surface, as well as giving the correct lattice parameters and crystal morphology. By applying meta-dynamics to the coarse-grained model, a new crystalline form of phenytoin (monoclinic, space group P2 1 ) was predicted which is different from the experimentally known crystal structure (orthorhombic, space group Pna2 1 ). Atomistic simulations and quantum calculations then showed the polymorph to be meta-stable at ambient temperature and pressure, and thermodynamically more stable than the conventional orthorhombic crystal at high pressure. The results suggest an efficient route to study crystal growth of small organic molecules that could also be useful for identification of possible polymorphs as well.

Observation of the pressure effect in simulations of droplets splashing on a dry surface

NASA Astrophysics Data System (ADS)

Boelens, A. M. P.; Latka, A.; de Pablo, J. J.

2018-06-01

At atmospheric pressure, a drop of ethanol impacting on a solid surface produces a splash. Reducing the ambient pressure below its atmospheric value suppresses this splash. The origin of this so-called pressure effect is not well understood, and this study presents an in-depth comparison between various theoretical models that aim to predict splashing and simulations. In this paper, the pressure effect is explored numerically by resolving the Navier-Stokes equations at a 3-nm resolution. In addition to reproducing numerous experimental observations, it is found that different models all provide elements of what is observed in the simulations. The skating droplet model correctly predicts the existence and scaling of a gas film under the droplet, the lamella formation theory is able to correctly predict the scaling of the lamella ejection velocity as a function of the impact velocity for liquids with different viscosity, and lastly, the dewetting theory's hypothesis of a lift force acting on the liquid sheet after ejection is consistent with our results.

78 FR 42895 - Airworthiness Directives; The Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-07-18

... for cracking of the pressure floor of both main wheel wells, and related investigative and corrective actions if necessary; and would require modifying the pressure floor of both main wheel wells. We are proposing this AD to prevent fatigue cracking in the pressure floor of the main wheel wells, which could...

77 FR 2658 - Airworthiness Directives; Bombardier, Inc. Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-01-19

... high pressure fuel lines due to improper installation of an expandable pin on the lower cowl assembly... chafing of the high pressure fuel lines, which if not corrected, could cause fuel leakage in a fire zone... on a high pressure (HP) fuel line. The source of chafing was related to the improper installation of...

Low Power Shoe Integrated Intelligent Wireless Gait Measurement System

NASA Astrophysics Data System (ADS)

Wahab, Y.; Mazalan, M.; Bakar, N. A.; Anuar, A. F.; Zainol, M. Z.; Hamzah, F.

2014-04-01

Gait analysis measurement is a method to assess and identify gait events and the measurements of dynamic, motion and pressure parameters involving the lowest part of the body. This significant analysis is widely used in sports, rehabilitation as well as other health diagnostic towards improving the quality of life. This paper presents a new system empowered by Inertia Measurement Unit (IMU), ultrasonic sensors, piezoceramic sensors array, XBee wireless modules and Arduino processing unit. This research focuses on the design and development of a low power ultra-portable shoe integrated wireless intelligent gait measurement using MEMS and recent microelectronic devices for foot clearance, orientation, error correction, gait events and pressure measurement system. It is developed to be cheap, low power, wireless, real time and suitable for real life in-door and out-door environment.

Corrigendum to “Atom probe tomography characterization of neutron irradiated surveillance samples from the R.E. Ginna reactor pressure vessel”

DOE PAGES

Edmondson, Philip D.; Miller, Michael K.; Powers, K. A.; ...

2017-03-24

In our recent paper entitled “Atom probe tomography characterization of neutron irradiated surveillance samples from the R. E. Ginna reactor pressure vessel”, we make reference to a table within the article as providing the average compositions of the precipitates, when in fact the bulk compositions were given. In this correction, we present the average precipitate compositions for the data presented in Ref. [1]. These correct compositions are provided for information and do not alter the conclusions of the original manuscript.

The Effect of Fuel Composition, Compression Pressure, and Fuel-Air Ratio on the Compression-Ignition Characteristics of Several Fuels

DTIC Science & Technology

1948-03-01

to this arbitrary value as ntandard. The compression time was maintained unifcum by uElng a ccnstent . driving ~ essure of 500 pounds per squ=e inch...ir ratio,0.066 (chemlo~ correct); initial~ essure , 14.7 lb/sq in. abs.; intt Ml temperature, 609° F abs~ Ignitiondelay Compres- Compres- sion...chemically correct); initial ~ essure , 14.7 lb/sq in. abso; fimal pressures 379 lb/sq in. abs.; initial temperatume~ 6090 F abs.; final temperature, 1340° F abs

Real-Gas Correction Factors for Hypersonic Flow Parameters in Helium

NASA Technical Reports Server (NTRS)

Erickson, Wayne D.

1960-01-01

The real-gas hypersonic flow parameters for helium have been calculated for stagnation temperatures from 0 F to 600 F and stagnation pressures up to 6,000 pounds per square inch absolute. The results of these calculations are presented in the form of simple correction factors which must be applied to the tabulated ideal-gas parameters. It has been shown that the deviations from the ideal-gas law which exist at high pressures may cause a corresponding significant error in the hypersonic flow parameters when calculated as an ideal gas. For example the ratio of the free-stream static to stagnation pressure as calculated from the thermodynamic properties of helium for a stagnation temperature of 80 F and pressure of 4,000 pounds per square inch absolute was found to be approximately 13 percent greater than that determined from the ideal-gas tabulation with a specific heat ratio of 5/3.

Revised calibration of the Sm:SrB{sub 4}O{sub 7} pressure sensor using the Sm-doped yttrium-aluminum garnet primary pressure scale

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

Rashchenko, Sergey V., E-mail: rashchenko@igm.nsc.ru; Litasov, Konstantin D.; Novosibirsk State University, 630090 Novosibirsk

2015-04-14

The pressure-induced shift of Sm:SrB{sub 4}O{sub 7} fluorescence was calibrated in a quasi-hydrostatic helium medium up to 60 GPa using the recent Sm-doped yttrium-aluminum garnet primary pressure scale as a reference. The resulting calibration can be written as P = −2836/14.3 [(1 + Δλ/685.51){sup −14.3 }− 1]. Previous calibrations based on the internally inconsistent primary scales are revised, and, after appropriate correction, found to agree with the proposed one. The calibration extended to 120 GPa was also performed using corrected previous data and can be written as P = 4.20 Δλ (1 + 0.020 Δλ)/(1 + 0.036 Δλ)

Adaptive support ventilation may deliver unwanted respiratory rate-tidal volume combinations in patients with acute lung injury ventilated according to an open lung concept.

PubMed

Dongelmans, Dave A; Paulus, Frederique; Veelo, Denise P; Binnekade, Jan M; Vroom, Margreeth B; Schultz, Marcus J

2011-05-01

With adaptive support ventilation, respiratory rate and tidal volume (V(T)) are a function of the Otis least work of breathing formula. We hypothesized that adaptive support ventilation in an open lung ventilator strategy would deliver higher V(T)s to patients with acute lung injury. Patients with acute lung injury were ventilated according to a local guideline advising the use of lower V(T) (6-8 ml/kg predicted body weight), high concentrations of positive end-expiratory pressure, and recruitment maneuvers. Ventilation parameters were recorded when the ventilator was switched to adaptive support ventilation, and after recruitment maneuvers. If V(T) increased more than 8 ml/kg predicted body weight, airway pressure was limited to correct for the rise of V(T). Ten patients with a mean (±SD) Pao(2)/Fio(2) of 171 ± 86 mmHg were included. After a switch from pressure-controlled ventilation to adaptive support ventilation, respiratory rate declined (from 31 ± 5 to 21 ± 6 breaths/min; difference = 10 breaths/min, 95% CI 3-17 breaths/min, P = 0.008) and V(T) increased (from 6.5 ± 0.8 to 9.0 ± 1.6 ml/kg predicted body weight; difference = 2.5 ml, 95% CI 0.4-4.6 ml/kg predicted body weight, P = 0.02). Pressure limitation corrected for the rise of V(T), but minute ventilation declined, forcing the user to switch back to pressure-controlled ventilation. Adaptive support ventilation, compared with pressure-controlled ventilation in an open lung strategy setting, delivers a lower respiratory rate-higher V(T) combination. Pressure limitation does correct for the rise of V(T), but leads to a decline in minute ventilation.

Calibration of International Space Station (ISS) Node 1 Vibro-Acoustic Model-Report 2

NASA Technical Reports Server (NTRS)

Zhang, Weiguo; Raveendra, Ravi

2014-01-01

Reported here is the capability of the Energy Finite Element Method (E-FEM) to predict the vibro-acoustic sound fields within the International Space Station (ISS) Node 1 and to compare the results with simulated leak sounds. A series of electronically generated structural ultrasonic noise sources were created in the pressure wall to emulate leak signals at different locations of the Node 1 STA module during its period of storage at Stennis Space Center (SSC). The exact sound source profiles created within the pressure wall at the source were unknown, but were estimated from the closest sensor measurement. The E-FEM method represents a reverberant sound field calculation, and of importance to this application is the requirement to correctly handle the direct field effect of the sound generation. It was also important to be able to compute the sound energy fields in the ultrasonic frequency range. This report demonstrates the capability of this technology as applied to this type of application.

Explicit accounting of electronic effects on the Hugoniot of porous materials

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

Nayak, Bishnupriya; Menon, S. V. G., E-mail: menon.svg98@gmail.com

2016-03-28

A generalized enthalpy based equation of state, which includes thermal electron excitations explicitly, is formulated from simple considerations. Its application to obtain Hugoniot of materials needs simultaneous evaluation of pressure-volume curve and temperature, the latter requiring solution of a differential equation. The errors involved in two recent papers [Huayun et al., J. Appl. Phys. 92, 5917 (2002); 92, 5924 (2002)], which employed this approach, are brought out and discussed. In addition to developing the correct set of equations, the present work also provides a numerical method to implement this approach. Constant pressure specific heat of ions and electrons and ionicmore » enthalpy parameter, needed for applications, are calculated using a three component equation of state. The method is applied to porous Cu with different initial porosities. Comparison of results with experimental data shows good agreement. It is found that temperatures along the Hugoniot of porous materials are significantly modified due to electronic effects.« less

Incompressible SPH method for simulating Newtonian and non-Newtonian flows with a free surface

NASA Astrophysics Data System (ADS)

Shao, Songdong; Lo, Edmond Y. M.

An incompressible smoothed particle hydrodynamics (SPH) method is presented to simulate Newtonian and non-Newtonian flows with free surfaces. The basic equations solved are the incompressible mass conservation and Navier-Stokes equations. The method uses prediction-correction fractional steps with the temporal velocity field integrated forward in time without enforcing incompressibility in the prediction step. The resulting deviation of particle density is then implicitly projected onto a divergence-free space to satisfy incompressibility through a pressure Poisson equation derived from an approximate pressure projection. Various SPH formulations are employed in the discretization of the relevant gradient, divergence and Laplacian terms. Free surfaces are identified by the particles whose density is below a set point. Wall boundaries are represented by particles whose positions are fixed. The SPH formulation is also extended to non-Newtonian flows and demonstrated using the Cross rheological model. The incompressible SPH method is tested by typical 2-D dam-break problems in which both water and fluid mud are considered. The computations are in good agreement with available experimental data. The different flow features between Newtonian and non-Newtonian flows after the dam-break are discussed.

Selection of neural network structure for system error correction of electro-optical tracker system with horizontal gimbal

NASA Astrophysics Data System (ADS)

Liu, Xing-fa; Cen, Ming

2007-12-01

Neural Network system error correction method is more precise than lest square system error correction method and spheric harmonics function system error correction method. The accuracy of neural network system error correction method is mainly related to the frame of Neural Network. Analysis and simulation prove that both BP neural network system error correction method and RBF neural network system error correction method have high correction accuracy; it is better to use RBF Network system error correction method than BP Network system error correction method for little studying stylebook considering training rate and neural network scale.

A Novel Quasi-3D Method for Cascade Flow Considering Axial Velocity Density Ratio

NASA Astrophysics Data System (ADS)

Chen, Zhiqiang; Zhou, Ming; Xu, Quanyong; Huang, Xudong

2018-03-01

A novel quasi-3D Computational Fluid Dynamics (CFD) method of mid-span flow simulation for compressor cascades is proposed. Two dimension (2D) Reynolds-Averaged Navier-Stokes (RANS) method is shown facing challenge in predicting mid-span flow with a unity Axial Velocity Density Ratio (AVDR). Three dimension (3D) RANS solution also shows distinct discrepancies if the AVDR is not predicted correctly. In this paper, 2D and 3D CFD results discrepancies are analyzed and a novel quasi-3D CFD method is proposed. The new quasi-3D model is derived by reducing 3D RANS Finite Volume Method (FVM) discretization over a one-spanwise-layer structured mesh cell. The sidewall effect is considered by two parts. The first part is explicit interface fluxes of mass, momentum and energy as well as turbulence. The second part is a cell boundary scaling factor representing sidewall boundary layer contraction. The performance of the novel quasi-3D method is validated on mid-span pressure distribution, pressure loss and shock prediction of two typical cascades. The results show good agreement with the experiment data on cascade SJ301-20 and cascade AC6-10 at all test condition. The proposed quasi-3D method shows superior accuracy over traditional 2D RANS method and 3D RANS method in performance prediction of compressor cascade.

Sea level static calibration of a compact multimission aircraft propulsion simulator with inlet flow distortion

NASA Technical Reports Server (NTRS)

Won, Mark J.

1990-01-01

Wind tunnel tests of propulsion-integrated aircraft models have identified inlet flow distortion as a major source of compressor airflow measurement error in turbine-powered propulsion simulators. Consequently, two Compact Multimission Aircraft Propulsion Simulator (CMAPS) units were statically tested at sea level ambient conditions to establish simulator operating performance characteristics and to calibrate the compressor airflow against an accurate bellmouth flowmeter in the presence of inlet flow distortions. The distortions were generated using various-shaped wire mesh screens placed upstream of the compressor. CMAPS operating maps and performance envelopes were obtained for inlet total pressure distortions (ratio of the difference between the maximum and minimum total pressures to the average total pressure) up to 35 percent, and were compared to baseline simulator operating characteristics for a uniform inlet. Deviations from CMAPS baseline performance were attributed to the coupled variation of both compressor inlet-flow distortion and Reynolds number index throughout the simulator operating envelope for each screen configuration. Four independent methods were used to determine CMAPS compressor airflow; direct compressor inlet and discharge measurements, an entering/exiting flow-balance relationships, and a correlation between the mixer pressure and the corrected compressor airflow. Of the four methods, the last yielded the least scatter in the compressor flow coefficient, approximately + or - 3 percent over the range of flow distortions.

Volume of reaction by the Archibald ultracentrifuge method (lobster hemocyanin).

PubMed

Saxena, V P; Kegeles, G; Kikas, R

1976-07-01

Samples of lobster hemocyanin (Homarus americanus) under conditions of reversible reaction between whole (25 S) and half (17 S) molecules have been subjected to accurately known nitrogen pressures in analytical ultracentrifuge cells. A modified pressurization chamber of the type developed by Schumaker and colleagues has been constructed for this purpose. The molecular weight was then determined at the top (liquid-gas) meniscus, by means of the Archibald method. The logarithmic dependence upon pressure of the derived equilibrium constant then gave directly the volume of reaction. Experiments were performed in veronal-citrate buffers at pH 8, where the molar volume of formation of whole (dodecameric) molecules from half molecules appears to be negative, and at pH 8.46 in veronal-citrate buffer in the presence of 0.003 molar free calcium ion, where the molar volume of formation was estimated to be + 390 cm3/mole. In glycine-sodium hydroxide buffer at pH 9.6 containing 0.0047 molar free calcium, the molar volume of formation of whole molecules was estimated to be +120 +/- 70 cm3, corresponding to an estimated difference in partial specific volume between whole molecules and half molecules of only 1.3 (10)-4cm3/gram. The correctness of the sign of this value in glycine buffer has been verified by pressure-jump light-scattering experiments.

A Posteriori Study of a DNS Database Describing Super critical Binary-Species Mixing

NASA Technical Reports Server (NTRS)

Bellan, Josette; Taskinoglu, Ezgi

2012-01-01

Currently, the modeling of supercritical-pressure flows through Large Eddy Simulation (LES) uses models derived for atmospheric-pressure flows. Those atmospheric-pressure flows do not exhibit the particularities of high densitygradient magnitude features observed both in experiments and simulations of supercritical-pressure flows in the case of two species mixing. To assess whether the current LES modeling is appropriate and if found not appropriate to propose higher-fidelity models, a LES a posteriori study has been conducted for a mixing layer that initially contains different species in the lower and upper streams, and where the initial pressure is larger than the critical pressure of either species. An initially-imposed vorticity perturbation promotes roll-up and a double pairing of four initial span-wise vortices into an ultimate vortex that reaches a transitional state. The LES equations consist of the differential conservation equations coupled with a real-gas equation of state, and the equation set uses transport properties depending on the thermodynamic variables. Unlike all LES models to date, the differential equations contain, additional to the subgrid scale (SGS) fluxes, a new SGS term that is a pressure correction in the momentum equation. This additional term results from filtering of Direct Numerical Simulation (DNS) equations, and represents the gradient of the difference between the filtered pressure and the pressure computed from the filtered flow field. A previous a priori analysis, using a DNS database for the same configuration, found this term to be of leading order in the momentum equation, a fact traced to the existence of high-densitygradient magnitude regions that populated the entire flow; in the study, models were proposed for the SGS fluxes as well as this new term. In the present study, the previously proposed constantcoefficient SGS-flux models of the a priori investigation are tested a posteriori in LES, devoid of or including, the SGS pressure correction term. The present pressure-correction model is different from, and more accurate as well as less computationally intensive than that of the a priori study. The constant-coefficient SGS-flux models encompass the Smagorinsky (SMC), in conjunction with the Yoshizawa (YO) model for the trace, the Gradient (GRC) and the Scale Similarity (SSC) models, all exercised with the a priori study constant coefficients calibrated at the transitional state. The LES comparison is performed with the filtered- and-coarsened (FC) DNS, which represents an ideal LES solution. Expectably, an LES model devoid of SGS terms is shown to be considerably inferior to models containing SGS effects. Among models containing SGS effects, those including the pressure-correction term are substantially superior to those devoid of it. The sensitivity of the predictions to the initial conditions and grid size are also investigated. Thus, it has been discovered that, additional to the atmospheric-pressure models currently used, a new model is necessary to simulate supercritical-pressure flows. This model depends on the thermodynamic characteristics of the chemical species involved.

Theoretical study of band gap in CuAlO2: Pressure dependence and self-interaction correction

NASA Astrophysics Data System (ADS)

Nakanishi, Akitaka; Katayama-Yoshida, Hiroshi

2012-08-01

By using first-principles calculations, we studied the energy gaps of delafossite CuAlO2: (1) pressure dependence and (2) self-interaction correction (SIC). Our simulation shows that CuAlO2 transforms from a delafossite structure to a leaning delafossite structure at 60 GPa. The energy gap of CuAlO2 increases through the structural transition due to the enhanced covalency of Cu 3d and O 2p states. We implemented a self-interaction correction (SIC) into first-principles calculation code to go beyond local density approximation and applied it to CuAlO2. The energy gap calculated within the SIC is close to experimental data while one calculated without the SIC is about 1 eV smaller than the experimental data.

40 CFR 98.323 - Calculating GHG emissions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... the meter automatically corrects for temperature and pressure, replace “520 °R/Ti × Pi/1 atm” with “1... at which flow is measured (°R). Pi = Daily pressure at which flow is measured (atm). 1,440...

Strain Rate Behavior of HTPB-Based Magnetorheological Materials

NASA Astrophysics Data System (ADS)

Stoltz, Chad; Seminuk, Kenneth; Joshi, Vasant

2013-06-01

It is of particular interest to determine whether the mechanical properties of binder systems can be manipulated by adding ferrous or Magnetostrictive particulates. Strain rate response of two HTPB/Fe (Hydroxyl-terminated Polybutadiene/Iron) compositions under electromagnetic fields has been investigated using a Split Hopkinson Pressure bar arrangement equipped with aluminum bars. Two HTPB/Fe compositions were developed, the first without plasticizer and the second containing plasticizer. Samples were tested with and without the application of a 0.01 Tesla magnetic field coil. Strain gauge data taken from the Split Hopkinson Pressure bar has been used to determine what mechanical properties were changed by inducing a mild electromagnetic field onto each sample. The data reduction method to obtain stress-strain plots included dispersion corrections for deciphering minute changes due to compositional alterations. Data collected from the Split Hopkinson Pressure bar indicate changes in the Mechanical Stress-Strain curves and suggest that the impedance of a binder system can be altered by means of a magnetic field. We acknowledge the Defense Threat Reduction Agency for funding.

Development of an expert system for analysis of Shuttle atmospheric revitalization and pressure control subsystem anomalies

NASA Technical Reports Server (NTRS)

Lafuse, Sharon A.

1991-01-01

The paper describes the Shuttle Leak Management Expert System (SLMES), a preprototype expert system developed to enable the ECLSS subsystem manager to analyze subsystem anomalies and to formulate flight procedures based on flight data. The SLMES combines the rule-based expert system technology with the traditional FORTRAN-based software into an integrated system. SLMES analyzes the data using rules, and, when it detects a problem that requires simulation, it sets up the input for the FORTRAN-based simulation program ARPCS2AT2, which predicts the cabin total pressure and composition as a function of time. The program simulates the pressure control system, the crew oxygen masks, the airlock repress/depress valves, and the leakage. When the simulation has completed, other SLMES rules are triggered to examine the results of simulation contrary to flight data and to suggest methods for correcting the problem. Results are then presented in form of graphs and tables.

Beyond Bernoulli

PubMed Central

Donati, Fabrizio; Myerson, Saul; Bissell, Malenka M.; Smith, Nicolas P.; Neubauer, Stefan; Monaghan, Mark J.; Nordsletten, David A.

2017-01-01

Background— Transvalvular peak pressure drops are routinely assessed noninvasively by echocardiography using the Bernoulli principle. However, the Bernoulli principle relies on several approximations that may not be appropriate, including that the majority of the pressure drop is because of the spatial acceleration of the blood flow, and the ejection jet is a single streamline (single peak velocity value). Methods and Results— We assessed the accuracy of the Bernoulli principle to estimate the peak pressure drop at the aortic valve using 3-dimensional cardiovascular magnetic resonance flow data in 32 subjects. Reference pressure drops were computed from the flow field, accounting for the principles of physics (ie, the Navier–Stokes equations). Analysis of the pressure components confirmed that the spatial acceleration of the blood jet through the valve is most significant (accounting for 99% of the total drop in stenotic subjects). However, the Bernoulli formulation demonstrated a consistent overestimation of the transvalvular pressure (average of 54%, range 5%–136%) resulting from the use of a single peak velocity value, which neglects the velocity distribution across the aortic valve plane. This assumption was a source of uncontrolled variability. Conclusions— The application of the Bernoulli formulation results in a clinically significant overestimation of peak pressure drops because of approximation of blood flow as a single streamline. A corrected formulation that accounts for the cross-sectional profile of the blood flow is proposed and adapted to both cardiovascular magnetic resonance and echocardiographic data. PMID:28093412

Unsteady Newton-Busemann flow theory. I - Airfoils

NASA Technical Reports Server (NTRS)

Hui, W. H.; Tobak, M.

1981-01-01

Newtonian flow theory for unsteady flow at very high Mach numbers is completed by the addition of a centrifugal force correction to the impact pressures. The correction term is the unsteady counterpart of Busemann's centrifugal force correction to impact pressures in steady flow. For airfoils of arbitary shape, exact formulas for the unsteady pressure and stiffness and damping-in-pitch derivatives are obtained in closed form, which require only numerical quadratures of terms involving the airfoil shape. They are applicable to airfoils of arbitrary thickness having sharp or blunt leading edges. For wedges and thin airfoils these formulas are greatly simplified, and it is proved that the pitching motions of thin airfoils of convex shape and of wedges of arbitrary thickness are always dynamically stable according to Newton-Busemann theory. Leading-edge bluntness is shown to have a favorable effect on the dynamic stability; on the other hand, airfoils of concave shape tend toward dynamic instability over a range of axis positions if the surface curvature exceeds a certain limit. As a byproduct, it is also shown that a pressure formula recently given by Barron and Mandl for unsteady Newtonian flow over a pitching power-law shaped airfoil is erroneous and that their conclusion regarding the effect of pivot position on the dynamic stability is misleading.

Correction of Temperatures of Air-Cooled Engine Cylinders for Variation in Engine and Cooling Conditions

NASA Technical Reports Server (NTRS)

Schey, Oscar W; Pinkel, Benjamin; Ellerbrock, Herman H , Jr

1939-01-01

Factors are obtained from semiempirical equations for correcting engine-cylinder temperatures for variation in important engine and cooling conditions. The variation of engine temperatures with atmospheric temperature is treated in detail, and correction factors are obtained for various flight and test conditions, such as climb at constant indicated air speed, level flight, ground running, take-off, constant speed of cooling air, and constant mass flow of cooling air. Seven conventional air-cooled engine cylinders enclosed in jackets and cooled by a blower were tested to determine the effect of cooling-air temperature and carburetor-air temperature on cylinder temperatures. The cooling air temperature was varied from approximately 80 degrees F. to 230 degrees F. and the carburetor-air temperature from approximately 40 degrees F. to 160 degrees F. Tests were made over a large range of engine speeds, brake mean effective pressures, and pressure drops across the cylinder. The correction factors obtained experimentally are compared with those obtained from the semiempirical equations and a fair agreement is noted.

Simultaneous measurement of brain tissue oxygen partial pressure, temperature, and global oxygen consumption during hibernation, arousal, and euthermy in non-sedated and non-anesthetized Arctic ground squirrels.

PubMed

Ma, Yilong; Wu, Shufen

2008-09-30

This study reports an online temperature correction method for determining tissue oxygen partial pressure P(tO2) in the striatum and a novel simultaneous measurement of brain P(tO2) and temperature (T(brain)) in conjunction with global oxygen consumption V(O2) in non-sedated and non-anesthetized freely moving Arctic ground squirrels (AGS, Spermophilus parryii). This method fills an important research gap-the lack of a suitable method for physiologic studies of tissue P(O2) in hibernating or other cool-blooded species. P(tO2) in AGS brain during euthermy (21.22+/-2.06 mmHg) is significantly higher (P=0.016) than during hibernation (13.21+/-0.46 mmHg) suggests brain oxygenation in the striatum is normoxic during euthermy and hypoxic during hibernation. These results in P(tO2) are different from blood oxygen partial pressure P(aO2) in AGS, which are significantly lower during euthermy than during hibernation and are actually hypoxic during euthermy and normoxic during hibernation in our previous study. This intriguing difference between the P(O2) of brain tissue and blood during these two physiological states suggests that regional mechanisms in the brain play a role in maintaining tissue oxygenation and protect against hypoxia during hibernation.

Effects of the lapidus arthrodesis and chevron bunionectomy on plantar forefoot pressures.

PubMed

King, Christy M; Hamilton, Graham A; Ford, Lawrence A

2014-01-01

Hallux valgus with or without first ray insufficiency has been strongly implicated as a contributing factor in lesser metatarsal overload. The principle goals of a bunionectomy are to relieve the pain, correct the deformity, and restore first metatarsophalangeal joint congruity. Until now, little evidence has been available to assess the effects of bunionectomy procedures on forefoot pressure. The primary aim of the present prospective study was to evaluate the preoperative and postoperative plantar pressures after 2 specific bunionectomies: the chevron bunionectomy and Lapidus arthrodesis. A total of 68 subjects, 34 in each group, were included for radiographic and pedographic evaluation. Both procedures demonstrated radiographic improvements in the mean intermetatarsal and hallux abductus angles. The mean hallux plantar pressure decreased significantly in both procedure groups (p < .001). However, Lapidus group exhibited an increase in the mean fifth metatarsal head plantar pressure (p = .008) and pressure under the fifth metatarsal as a percentage of the total forefoot pressure (p = .01). Furthermore, the pressure under the second metatarsal as a percentage of the total forefoot pressure decreased significantly (p = .01). This study suggests that the Lapidus arthrodesis and chevron bunionectomy both provide correction for hallux valgus deformity, but when comparing forefoot load sharing pressures, the Lapidus arthrodesis appeared to have greater influence on the load sharing distribution of forefoot pressure than did the bunionectomy employing the chevron osteotomy. Copyright © 2014 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

Proposal and Evaluation of Subordinate Standard Solar Irradiance Spectra: Preprint

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

Habte, Aron M; Wilbert, Stefan; Jessen, Wilko

This paper introduces a concept for global tilted irradiance (GTI) subordinate standard spectra to supplement the current standard spectra used in solar photovoltaic applications as defined in ASTM G173 and IEC60904. The proposed subordinate standard spectra correspond to atmospheric conditions and tilt angles that depart significantly from the main standard spectrum, and they can be used to more accurately represent various local conditions. For the definition of subordinate standard spectra cases with an elevation 1.5 km above sea level, the question arises whether the air mass should be calculated including a pressure correction or not. This study focuses on themore » impact of air mass used in standard spectra, and it uses data from 29 locations to examine which air mass is most appropriate for GTI and direct normal irradiance (DNI) spectra. Overall, it is found that the pressure-corrected air mass of 1.5 is most appropriate for DNI spectra. For GTI, a non-pressure-corrected air mass of 1.5 was found to be more appropriate.« less

Accurate thermodynamics for short-ranged truncations of Coulomb interactions in site-site molecular models

NASA Astrophysics Data System (ADS)

Rodgers, Jocelyn M.; Weeks, John D.

2009-12-01

Coulomb interactions are present in a wide variety of all-atom force fields. Spherical truncations of these interactions permit fast simulations but are problematic due to their incorrect thermodynamics. Herein we demonstrate that simple analytical corrections for the thermodynamics of uniform truncated systems are possible. In particular, results for the simple point charge/extended (SPC/E) water model treated with spherically truncated Coulomb interactions suggested by local molecular field theory [J. M. Rodgers and J. D. Weeks, Proc. Natl. Acad. Sci. U.S.A. 105, 19136 (2008)] are presented. We extend the results developed by Chandler [J. Chem. Phys. 65, 2925 (1976)] so that we may treat the thermodynamics of mixtures of flexible charged and uncharged molecules simulated with spherical truncations. We show that the energy and pressure of spherically truncated bulk SPC/E water are easily corrected using exact second-moment-like conditions on long-ranged structure. Furthermore, applying the pressure correction as an external pressure removes the density errors observed by other research groups in NPT simulations of spherically truncated bulk species.

Multipollutant measurement error in air pollution epidemiology studies arising from predicting exposures with penalized regression splines

PubMed Central

Bergen, Silas; Sheppard, Lianne; Kaufman, Joel D.; Szpiro, Adam A.

2016-01-01

Summary Air pollution epidemiology studies are trending towards a multi-pollutant approach. In these studies, exposures at subject locations are unobserved and must be predicted using observed exposures at misaligned monitoring locations. This induces measurement error, which can bias the estimated health effects and affect standard error estimates. We characterize this measurement error and develop an analytic bias correction when using penalized regression splines to predict exposure. Our simulations show bias from multi-pollutant measurement error can be severe, and in opposite directions or simultaneously positive or negative. Our analytic bias correction combined with a non-parametric bootstrap yields accurate coverage of 95% confidence intervals. We apply our methodology to analyze the association of systolic blood pressure with PM2.5 and NO2 in the NIEHS Sister Study. We find that NO2 confounds the association of systolic blood pressure with PM2.5 and vice versa. Elevated systolic blood pressure was significantly associated with increased PM2.5 and decreased NO2. Correcting for measurement error bias strengthened these associations and widened 95% confidence intervals. PMID:27789915

Pressure Variations in Metamorphic Rocks: Implications for the Interpretation of Petrographic Observations

NASA Astrophysics Data System (ADS)

Tajčmanová, Lucie

2014-05-01

Metamorphic petrologists and structural geologists, using direct measurements, bring the only direct observational constrains for validating geodynamic models. Therefore, petrological and structural geological observations are essential for the quality and reproducibility of geodynamic reconstructions and models. One of the important assumptions for geodynamic reconstructions arises from the pressure and temperature estimates in the petrology analysis. Pressure is commonly converted to depth through the equation for lithostatic pressure and so the original position of the rock sample within the Earth's interior can be constrained. The current assumption that the studied sample corresponds to uniform pressure may not be correct, and if so, it has serious implications. Increasing evidence from analytical data shows that pressure is not constant even on a grain scale, posing new challenges because, if ignored, it leads to an incorrect use of petrology data in constraining geodynamic models. Well known examples of the preservation of coesite and diamond in a host mineral like garnet show that high pressure inclusions are preserved during decompression. Tajčmanová et al. (2014) has shown that grain-scale pressure variations can develop and that these pressure variations allow compositional zoning in minerals preserved over geological time scales. A new unconventional barometric method based on equilibrium under pressure variations has been developed . Such pressure variations are also connected with differences in fluid pressure in open systems and can be thus observed at all scales. Tajčmanová L., Podladchikov Y., Powell R., Moulas E., Vrijmoed J. and Connolly J. (2014). Grain scale pressure variations and chemical equilibrium in high-grade metamorphic rocks.Journal of Metamorphic Geology, doi:10.1111/jmg.12066 This work was supported by ERC starting grant 335577 to Lucie Tajcmanova

Experimental study of quartz inclusions in garnet at pressures up to 3.0 GPa: evaluating validity of the quartz-in-garnet inclusion elastic thermobarometer

NASA Astrophysics Data System (ADS)

Thomas, Jay B.; Spear, Frank S.

2018-05-01

Garnet crystals with quartz inclusions were hydrothermally crystallized from oxide starting materials in piston-cylinder apparatuses at pressures from 0.5 to 3 GPa and temperatures ranging from 700 to 800 °C to study how entrapment conditions affect remnant pressures of quartz inclusions used for quartz-in-garnet (QuiG) elastic thermobarometry. Systematic changes of the 128, 206 and 464 cm-1 Raman band frequencies of quartz were used to determine pressures of quartz inclusions in garnet using Raman spectroscopy calibrations that describe the P-T dependencies of Raman band shifts for quartz under hydrostatic pressure. Within analytical uncertainties, inclusion pressures calculated for each of the three Raman band frequencies are equivalent, which suggests that non-hydrostatic stress effects caused by elastic anisotropy in quartz are smaller than measurement errors. The experimental quartz inclusions have pressures ranging from - 0.351 to 1.247 GPa that span the range of values observed for quartz inclusions in garnets from natural rocks. Quartz inclusion pressures were used to model P-T conditions at which the inclusions could have been trapped. The accuracy of QuiG thermobarometry was evaluated by considering the differences between pressures measured during experiments and pressures calculated using published equation of state parameters for quartz and garnet. Our experimental results demonstrate that Raman measurements performed at room temperature can be used without corrections to estimate garnet crystallization pressures. Calculated entrapment pressures for quartz inclusions in garnet are less than 10% different from pressures measured during the experiments. Because the method is simple to apply with reasonable accuracy, we expect widespread usage of QuiG thermobarometry to estimate crystallization conditions for garnet-bearing silicic rocks.

Prediction of friction pressure drop for low pressure two-phase flows on the basis of approximate analytical models

NASA Astrophysics Data System (ADS)

Zubov, N. O.; Kaban'kov, O. N.; Yagov, V. V.; Sukomel, L. A.

2017-12-01

Wide use of natural circulation loops operating at low redused pressures generates the real need to develop reliable methods for predicting flow regimes and friction pressure drop for two-phase flows in this region of parameters. Although water-air flows at close-to-atmospheric pressures are the most widely studied subject in the field of two-phase hydrodynamics, the problem of reliably calculating friction pressure drop can hardly be regarded to have been fully solved. The specific volumes of liquid differ very much from those of steam (gas) under such conditions, due to which even a small change in flow quality may cause the flow pattern to alter very significantly. Frequently made attempts to use some or another universal approach to calculating friction pressure drop in a wide range of steam quality values do not seem to be justified and yield predicted values that are poorly consistent with experimentally measured data. The article analyzes the existing methods used to calculate friction pressure drop for two-phase flows at low pressures by comparing their results with the experimentally obtained data. The advisability of elaborating calculation procedures for determining the friction pressure drop and void fraction for two-phase flows taking their pattern (flow regime) into account is demonstrated. It is shown that, for flows characterized by low reduced pressures, satisfactory results are obtained from using a homogeneous model for quasi-homogeneous flows, whereas satisfactory results are obtained from using an annular flow model for flows characterized by high values of void fraction. Recommendations for making a shift from one model to another in carrying out engineering calculations are formulated and tested. By using the modified annular flow model, it is possible to obtain reliable predictions for not only the pressure gradient but also for the liquid film thickness; the consideration of droplet entrainment and deposition phenomena allows reasonable corrections to be introduced into calculations. To the best of the authors' knowledge, it is for the first time that the entrainment of droplets from the film surface is taken into consideration in the dispersed-annular flow model.

Knowledge, attitudes and barriers towards prevention of pressure ulcers in intensive care units: a descriptive cross-sectional study.

PubMed

Strand, Tillan; Lindgren, Margareta

2010-12-01

Pressure ulcer incidence varies between 1 and 56% in intensive care and prevention is an important quest for nursing staff. Critically ill patients that develop pressure ulcers suffer from increased morbidity and mortality and also requires prolonged intensive care. The aim of this study was to investigate registered nurses' and enrolled nurses' (1) attitudes, (2) knowledge and (3) perceived barriers and opportunities towards pressure ulcer prevention, in an ICU setting. These are important aspects in the Theory of Planned Behaviour, a conceptual framework when trying to predict, understand and change specific behaviours. The study is descriptive. Questionnaires were distributed to registered nurses and enrolled nurses in four ICUs in a Swedish hospital. The mean score regarding attitude was 34 ± 4. Correct categorisation of pressure ulcers was made by 46.8% of nursing staff with enrolled nurses having significantly less correct categorisation (p=0.019). Pressure relief (97.3%) and nutritional support (36.1%) were the most frequently reported preventive measures. Reported barriers were lack of time (57.8%) and severely ill patients (28.9%); opportunities were knowledge (38%) and access to pressure relieving equipment (35.5%). This study highlights areas where measures can be made to facilitate pressure ulcer prevention in intensive care units, such as raising knowledge and making pressure ulcer prevention a part of daily care. Copyright © 2010 Elsevier Ltd. All rights reserved.

A collection of sub-daily pressure and temperature observations for the early instrumental period with a focus on the "year without a summer" 1816

NASA Astrophysics Data System (ADS)

Brugnara, Y.; Auchmann, R.; Brönnimann, S.; Allan, R. J.; Auer, I.; Barriendos, M.; Bergström, H.; Bhend, J.; Brázdil, R.; Compo, G. P.; Cornes, R. C.; Dominguez-Castro, F.; van Engelen, A. F. V.; Filipiak, J.; Holopainen, J.; Jourdain, S.; Kunz, M.; Luterbacher, J.; Maugeri, M.; Mercalli, L.; Moberg, A.; Mock, C. J.; Pichard, G.; Řezníčková, L.; van der Schrier, G.; Slonosky, V.; Ustrnul, Z.; Valente, M. A.; Wypych, A.; Yin, X.

2015-08-01

The eruption of Mount Tambora (Indonesia) in April 1815 is the largest documented volcanic eruption in history. It is associated with a large global cooling during the following year, felt particularly in parts of Europe and North America, where the year 1816 became known as the "year without a summer". This paper describes an effort made to collect surface meteorological observations from the early instrumental period, with a focus on the years of and immediately following the eruption (1815-1817). Although the collection aimed in particular at pressure observations, correspondent temperature observations were also recovered. Some of the series had already been described in the literature, but a large part of the data, recently digitised from original weather diaries and contemporary magazines and newspapers, is presented here for the first time. The collection puts together more than 50 sub-daily series from land observatories in Europe and North America and from ships in the tropics. The pressure observations have been corrected for temperature and gravity and reduced to mean sea level. Moreover, an additional statistical correction was applied to take into account common error sources in mercury barometers. To assess the reliability of the corrected data set, the variance in the pressure observations is compared with modern climatologies, and single observations are used for synoptic analyses of three case studies in Europe. All raw observations will be made available to the scientific community in the International Surface Pressure Databank.

Full-wave acoustic and thermal modeling of transcranial ultrasound propagation and investigation of skull-induced aberration correction techniques: a feasibility study.

PubMed

Kyriakou, Adamos; Neufeld, Esra; Werner, Beat; Székely, Gábor; Kuster, Niels

2015-01-01

Transcranial focused ultrasound (tcFUS) is an attractive noninvasive modality for neurosurgical interventions. The presence of the skull, however, compromises the efficiency of tcFUS therapy, as its heterogeneous nature and acoustic characteristics induce significant distortion of the acoustic energy deposition, focal shifts, and thermal gain decrease. Phased-array transducers allow for partial compensation of skull-induced aberrations by application of precalculated phase and amplitude corrections. An integrated numerical framework allowing for 3D full-wave, nonlinear acoustic and thermal simulations has been developed and applied to tcFUS. Simulations were performed to investigate the impact of skull aberrations, the possibility of extending the treatment envelope, and adverse secondary effects. The simulated setup comprised an idealized model of the ExAblate Neuro and a detailed MR-based anatomical head model. Four different approaches were employed to calculate aberration corrections (analytical calculation of the aberration corrections disregarding tissue heterogeneities; a semi-analytical ray-tracing approach compensating for the presence of the skull; two simulation-based time-reversal approaches with and without pressure amplitude corrections which account for the entire anatomy). These impact of these approaches on the pressure and temperature distributions were evaluated for 22 brain-targets. While (semi-)analytical approaches failed to induced high pressure or ablative temperatures in any but the targets in the close vicinity of the geometric focus, simulation-based approaches indicate the possibility of considerably extending the treatment envelope (including targets below the transducer level and locations several centimeters off the geometric focus), generation of sharper foci, and increased targeting accuracy. While the prediction of achievable aberration correction appears to be unaffected by the detailed bone-structure, proper consideration of inhomogeneity is required to predict the pressure distribution for given steering parameters. Simulation-based approaches to calculate aberration corrections may aid in the extension of the tcFUS treatment envelope as well as predict and avoid secondary effects (standing waves, skull heating). Due to their superior performance, simulationbased techniques may prove invaluable in the amelioration of skull-induced aberration effects in tcFUS therapy. The next steps are to investigate shear-wave-induced effects in order to reliably exclude secondary hot-spots, and to develop comprehensive uncertainty assessment and validation procedures.

Blade resonance parameter identification based on tip-timing method without the once-per revolution sensor

NASA Astrophysics Data System (ADS)

Guo, Haotian; Duan, Fajie; Zhang, Jilong

2016-01-01

Blade tip-timing is the most effective method for blade vibration online measurement of turbomachinery. In this article a synchronous resonance vibration measurement method of blade based on tip-timing is presented. This method requires no once-per revolution sensor which makes it more generally applicable in the condition where this sensor is difficult to install, especially for the high-pressure rotors of dual-rotor engines. Only three casing mounted probes are required to identify the engine order, amplitude, natural frequency and the damping coefficient of the blade. A method is developed to identify the blade which a tip-timing data belongs to without once-per revolution sensor. Theoretical analyses of resonance parameter measurement are presented. Theoretic error of the method is investigated and corrected. Experiments are conducted and the results indicate that blade resonance parameter identification is achieved without once-per revolution sensor.

A temperature and pressure controlled calibration system for pressure sensors

NASA Technical Reports Server (NTRS)

Chapman, John J.; Kahng, Seun K.

1989-01-01

A data acquisition and experiment control system capable of simulating temperatures from -184 to +220 C and pressures either absolute or differential from 0 to 344.74 kPa is developed to characterize silicon pressure sensor response to temperature and pressure. System software is described that includes sensor data acquisition, algorithms for numerically derived thermal offset and sensitivity correction, and operation of the environmental chamber and pressure standard. This system is shown to be capable of computer interfaced cryogenic testing to within 1 C and 34.47 Pa of single channel or multiplexed arrays of silicon pressure sensors.

Simulation of ultrasonic focus aberration and correction through human tissue.

PubMed

Tabei, Makoto; Mast, T Douglas; Waag, Robert C

2003-02-01

Ultrasonic focusing in two dimensions has been investigated by calculating the propagation of ultrasonic pulses through cross-sectional models of human abdominal wall and breast. Propagation calculations used a full-wave k-space method that accounts for spatial variations in density, sound speed, and frequency-dependent absorption and includes perfectly matched layer absorbing boundary conditions. To obtain a distorted receive wavefront, propagation from a point source through the tissue path was computed. Receive focusing used an angular spectrum method. Transmit focusing was accomplished by propagating a pressure wavefront from a virtual array through the tissue path. As well as uncompensated focusing, focusing that employed time-shift compensation and time-shift compensation after backpropagation was investigated in both transmit and receive and time reversal was investigated for transmit focusing in addition. The results indicate, consistent with measurements, that breast causes greater focus degradation than abdominal wall. The investigated compensation methods corrected the receive focus better than the transmit focus. Time-shift compensation after backpropagation improved the focus from that obtained using time-shift compensation alone but the improvement was less in transmit focusing than in receive focusing. Transmit focusing by time reversal resulted in lower sidelobes but larger mainlobes than the other investigated transmit focus compensation methods.

Measuring Thermodynamic Properties of Metals and Alloys With Knudsen Effusion Mass Spectrometry

NASA Technical Reports Server (NTRS)

Copland, Evan H.; Jacobson, Nathan S.

2010-01-01

This report reviews Knudsen effusion mass spectrometry (KEMS) as it relates to thermodynamic measurements of metals and alloys. First, general aspects are reviewed, with emphasis on the Knudsen-cell vapor source and molecular beam formation, and mass spectrometry issues germane to this type of instrument are discussed briefly. The relationship between the vapor pressure inside the effusion cell and the measured ion intensity is the key to KEMS and is derived in detail. Then common methods used to determine thermodynamic quantities with KEMS are discussed. Enthalpies of vaporization, the fundamental measurement, are determined from the variation of relative partial pressure with temperature using the second-law method or by calculating a free energy of formation and subtracting the entropy contribution using the third-law method. For single-cell KEMS instruments, measurements can be used to determine the partial Gibbs free energy if the sensitivity factor remains constant over multiple experiments. The ion-current ratio method and dimer-monomer method are also viable in some systems. For a multiple-cell KEMS instrument, activities are obtained by direct comparison with a suitable component reference state or a secondary standard. Internal checks for correct instrument operation and general procedural guidelines also are discussed. Finally, general comments are made about future directions in measuring alloy thermodynamics with KEMS.

Prognostic value of cardiovascular magnetic resonance imaging measurements corrected for age and sex in idiopathic pulmonary arterial hypertension.

PubMed

Swift, Andrew J; Rajaram, Smitha; Campbell, Michael J; Hurdman, Judith; Thomas, Steve; Capener, Dave; Elliot, Charlie; Condliffe, Robin; Wild, Jim M; Kiely, David G

2014-01-01

There are limited data on the prognostic value of cardiovascular magnetic resonance measurements in idiopathic pulmonary arterial hypertension, with no studies investigating the impact of correction of cardiovascular magnetic resonance indices for age and sex on prognostic value. Consecutive patients with idiopathic pulmonary arterial hypertension underwent cardiovascular magnetic resonance imaging at 1.5T. Steady-state free precession cardiac volumes and mass measurements were corrected for age, sex, and body surface area according to reference data and prognostic significance assessed. A total of 80 patients with idiopathic pulmonary arterial hypertension were identified, and 23 patients died during the mean follow-up of 32±14 months. Corrected for age, sex, and body surface area, right ventricular end-systolic volume (P=0.004) strongly predicted mortality, independent of World Health Organization functional class, mean right atrial pressure, cardiac index, and mixed venous oxygen saturations. Consideration should be given to correcting cardiovascular magnetic resonance measures for age, sex, and body surface area, particularly given the changing demographics of patients with idiopathic pulmonary arterial hypertension. Corrected right ventricular end-systolic volume is a strong prognostic marker in idiopathic pulmonary arterial hypertension, independent of invasively derived measurements, mean right atrial pressure cardiac index, and mixed venous oxygen saturations.

Control Strategy of Active Power Filter Based on Modular Multilevel Converter

NASA Astrophysics Data System (ADS)

Xie, Xifeng

2018-03-01

To improve the capacity, pressure resistance and the equivalent switching frequency of active power filter (APF), a control strategy of APF based on Modular Multilevel Converter (MMC) is presented. In this Control Strategy, the indirect current control method is used to achieve active current and reactive current decoupling control; Voltage Balance Control Strategy is to stabilize sub-module capacitor voltage, the predictive current control method is used to Track and control of harmonic currents. As a result, the harmonic current is restrained, and power quality is improved. Finally, the simulation model of active power filter controller based on MMC is established in Matlab/Simulink, the simulation proves that the proposed strategy is feasible and correct.

The method of the gas-dynamic centrifugal compressor stage characteristics recalculation for variable rotor rotational speeds and the rotation angle of inlet guide vanes blades if the kinematic and dynamic similitude conditions are not met

NASA Astrophysics Data System (ADS)

Vanyashov, A. D.; Karabanova, V. V.

2017-08-01

A mathematical description of the method for obtaining gas-dynamic characteristics of a centrifugal compressor stage is proposed, taking into account the control action by varying the rotor speed and the angle of rotation of the guide vanes relative to the "basic" characteristic, if the kinematic and dynamic similitude conditions are not met. The formulas of the correction terms for the non-dimensional coefficients of specific work, consumption and efficiency are obtained. A comparative analysis of the calculated gas-dynamic characteristics of a high-pressure centrifugal stage with experimental data is performed.

Examining public knowledge and preferences for adult preventive services coverage

PubMed Central

Ortiz, Selena E.

2017-01-01

Introduction To examine (1) what individuals know about the existing adult preventive service coverage provisions of the Affordable Care Act (ACA), and (2) which preventive services individuals think should be covered without cost sharing. Methods An online panel from Survey Monkey was used to obtain a sample of 2,990 adults age 18 and older in March 2015, analyzed 2015–2017. A 17-item survey instrument was designed and used to evaluate respondents’ knowledge of the adult preventive services provision of the ACA. Additionally, we asked whether various preventive services should be covered. The data include age, sex, race/ethnicity, and educational attainment as well as measures of political ideology, previous insurance status, the number of chronic conditions, and usual source of care. Results Respondents correctly answered 38.6% of the questions about existing coverage under the ACA, while on average respondents thought 12.1 of 15 preventive services should be covered (SD 3.5). Respondents were more knowledgeable about coverage for routine screenings, such as blood pressure (63.4% correct) than potentially stigmatizing screenings, such as for alcohol misuse (28.8% correct). Blood pressure screening received the highest support of coverage (89.8%) while coverage of gym memberships received the lowest support (59.4%). Individuals with conservative ideologies thought fewer services on average should be covered, but the difference was small—around one service less than those with liberal ideologies. Conclusions Overwhelmingly, individuals think that most preventive services should be covered without cost sharing. Despite several years of coverage for preventive services, there is still confusion and lack of knowledge about which services are covered. PMID:29261757

Esophageal Manometry and Regional Transpulmonary Pressure in Lung Injury.

PubMed

Yoshida, Takeshi; Amato, Marcelo B P; Grieco, Domenico Luca; Chen, Lu; Lima, Cristhiano A S; Roldan, Rollin; Morais, Caio C A; Gomes, Susimeire; Costa, Eduardo L V; Cardoso, Paulo F G; Charbonney, Emmanuel; Richard, Jean-Christophe M; Brochard, Laurent; Kavanagh, Brian P

2018-04-15

Esophageal manometry is the clinically available method to estimate pleural pressure, thus enabling calculation of transpulmonary pressure (Pl). However, many concerns make it uncertain in which lung region esophageal manometry reflects local Pl. To determine the accuracy of esophageal pressure (Pes) and in which regions esophageal manometry reflects pleural pressure (Ppl) and Pl; to assess whether lung stress in nondependent regions can be estimated at end-inspiration from Pl. In lung-injured pigs (n = 6) and human cadavers (n = 3), Pes was measured across a range of positive end-expiratory pressure, together with directly measured Ppl in nondependent and dependent pleural regions. All measurements were obtained with minimal nonstressed volumes in the pleural sensors and esophageal balloons. Expiratory and inspiratory Pl was calculated by subtracting local Ppl or Pes from airway pressure; inspiratory Pl was also estimated by subtracting Ppl (calculated from chest wall and respiratory system elastance) from the airway plateau pressure. In pigs and human cadavers, expiratory and inspiratory Pl using Pes closely reflected values in dependent to middle lung (adjacent to the esophagus). Inspiratory Pl estimated from elastance ratio reflected the directly measured nondependent values. These data support the use of esophageal manometry in acute respiratory distress syndrome. Assuming correct calibration, expiratory Pl derived from Pes reflects Pl in dependent to middle lung, where atelectasis usually predominates; inspiratory Pl estimated from elastance ratio may indicate the highest level of lung stress in nondependent "baby" lung, where it is vulnerable to ventilator-induced lung injury.

SU-F-P-18: Development of the Technical Training System for Patient Set-Up Considering Rotational Correction in the Virtual Environment Using Three-Dimensional Computer Graphic Engine

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

Imura, K; Fujibuchi, T; Hirata, H

Purpose: Patient set-up skills in radiotherapy treatment room have a great influence on treatment effect for image guided radiotherapy. In this study, we have developed the training system for improving practical set-up skills considering rotational correction in the virtual environment away from the pressure of actual treatment room by using three-dimensional computer graphic (3DCG) engine. Methods: The treatment room for external beam radiotherapy was reproduced in the virtual environment by using 3DCG engine (Unity). The viewpoints to perform patient set-up in the virtual treatment room were arranged in both sides of the virtual operable treatment couch to assume actual performancemore » by two clinical staffs. The position errors to mechanical isocenter considering alignment between skin marker and laser on the virtual patient model were displayed by utilizing numerical values expressed in SI units and the directions of arrow marks. The rotational errors calculated with a point on the virtual body axis as the center of each rotation axis for the virtual environment were corrected by adjusting rotational position of the body phantom wound the belt with gyroscope preparing on table in a real space. These rotational errors were evaluated by describing vector outer product operations and trigonometric functions in the script for patient set-up technique. Results: The viewpoints in the virtual environment allowed individual user to visually recognize the position discrepancy to mechanical isocenter until eliminating the positional errors of several millimeters. The rotational errors between the two points calculated with the center point could be efficiently corrected to display the minimum technique mathematically by utilizing the script. Conclusion: By utilizing the script to correct the rotational errors as well as accurate positional recognition for patient set-up technique, the training system developed for improving patient set-up skills enabled individual user to indicate efficient positional correction methods easily.« less

Wavelength references for interferometry in air

NASA Astrophysics Data System (ADS)

Fox, Richard W.; Washburn, Brian R.; Newbury, Nathan R.; Hollberg, Leo

2005-12-01

Cavity-mode wavelengths in air are determined by measuring a laser's frequency while it is locked to the mode in vacuum during a calibration step and subsequently correcting the mode wavelength for atmospheric pressure compression, temperature difference, and material aging. Using a Zerodur ring cavity, we demonstrate a repeatability of ±2×10-8 (3σ), with the wavelength accuracy limited to ±4×10-8 by knowledge of the absolute helium gas temperature during the pressure calibration. Mirror cleaning perturbed the mode frequency by less than Δ ν/ν˜3×10-9, limited by temperature correction residuals.

Bilateral acute angle closure glaucoma after hyperopic LASIK correction

PubMed Central

Osman, Essam A.; Alsaleh, Ahmed A.; Al Turki, Turki; AL Obeidan, Saleh A.

2009-01-01

Acute angle closure glaucoma is unexpected complication following laser in situ keratomileusis (LASIK). We are reporting a 49-years-old lady that was presented to the emergency department with acute glaucoma in both eyes soon after LASIK correction. Diagnosis was made on detailed clinical history and examination, slit lamp examination, intraocular pressure measurement and gonioscopy. Laser iridotomy in both eyes succeeded in controlling the attack and normalizing the intraocular pressure (IOP) more than 6 months of follow-up. Prophylactic laser iridotomy is essential for narrow angle patients before LASIK surgery if refractive laser surgery is indicated. PMID:23960863

Wavelength references for interferometry in air

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

Fox, Richard W.; Washburn, Brian R.; Newbury, Nathan R.

2005-12-20

Cavity-mode wavelengths in air are determined by measuring a laser's frequency while it is locked to the mode in vacuum during a calibration step and subsequently correcting the mode wavelength for atmospheric pressure compression, temperature difference, and material aging. Using a Zerodur ring cavity, we demonstrate a repeatability of {+-}2x10-8(3{sigma}), with the wavelength accuracy limited to {+-}4x10-8by knowledge of the absolute helium gas temperature during the pressure calibration. Mirror cleaning perturbed the mode frequency by less than {delta} {nu}/{nu}{approx}3x10-9, limited by temperature correction residuals.

Wavelength references for interferometry in air.

PubMed

Fox, Richard W; Washburn, Brian R; Newbury, Nathan R; Hollberg, Leo

2005-12-20

Cavity-mode wavelengths in air are determined by measuring a laser's frequency while it is locked to the mode in vacuum during a calibration step and subsequently correcting the mode wavelength for atmospheric pressure compression, temperature difference, and material aging. Using a Zerodur ring cavity, we demonstrate a repeatability of +/- 2 x 10(-8) (3sigma), with the wavelength accuracy limited to +/- 4 x 10(-8) by knowledge of the absolute helium gas temperature during the pressure calibration. Mirror cleaning perturbed the mode frequency by less than deltav/v approximately 3 x 10(-9), limited by temperature correction residuals.

Assessment of coronary artery stenosis pressure gradient by quantitative coronary arteriography in patients with coronary artery disease.

PubMed

Atar, D; Ramanujam, P S; Saunamäki, K; Haunsø, S

1994-01-01

The aim of the study described here was to correlate coronary artery (CA) stenosis pressure gradients calculated by quantitative coronary arteriography (QCA) to invasively measured transstenotic pressure drops in patients with anginal symptoms and with known or suspected coronary artery disease. Furthermore, the known mathematical models are improved by introducing (1) pressure catheter-corrected minimal stenosis area, (2) modification of flow assumptions, and (3) stenosis exit angle. Included in the study were 45 patients with 61 stenoses. The visually estimated CA lesion severity in these non-complex stenoses was in the equivocal range of 40-70%. All measurements were performed after intracoronary administration of nifedipine and nitroglycerin. Stenosis dimensions were assessed from magnified cinefilms, using hand-held calipers. Highly significant overall correlation was found between measured and calculated pressure gradients with correction for the impact of the intracoronary catheter (P < 0.00001, r = 0.84). In particular, a substantial number of stenoses with haemodynamically-insignificant pressure gradients were identified by hydrodynamic calculations. In conclusion, the great majority of the coronary artery stenoses could be classified reliably by QCA as being haemodynamically insignificant or significant, respectively.

Processing Raman Spectra of High-Pressure Hydrogen Flames

NASA Technical Reports Server (NTRS)

Nguyen, Quang-Viet; Kojima, Jun

2006-01-01

The Raman Code automates the analysis of laser-Raman-spectroscopy data for diagnosis of combustion at high pressure. On the basis of the theory of molecular spectroscopy, the software calculates the rovibrational and pure rotational Raman spectra of H2, O2, N2, and H2O in hydrogen/air flames at given temperatures and pressures. Given a set of Raman spectral data from measurements on a given flame and results from the aforementioned calculations, the software calculates the thermodynamic temperature and number densities of the aforementioned species. The software accounts for collisional spectral-line-broadening effects at pressures up to 60 bar (6 MPa). The line-broadening effects increase with pressure and thereby complicate the analysis. The software also corrects for spectral interference ("cross-talk") among the various chemical species. In the absence of such correction, the cross-talk is a significant source of error in temperatures and number densities. This is the first known comprehensive computer code that, when used in conjunction with a spectral calibration database, can process Raman-scattering spectral data from high-pressure hydrogen/air flames to obtain temperatures accurate to within 10 K and chemical-species number densities accurate to within 2 percent.

[Urodynamic studies prior to urinary incontinence surgery : What is useful?

PubMed

Kaufmann, A

2017-12-01

Surgery is often necessary after failure of conservative therapy for urinary incontinence. Guidelines recommend urodynamic studies before surgery. A distinction is made between non-invasive (uroflowmetry) and invasive methods (cystometry and pressure-flow study, if necessary as combined videourodynamics, as well as urethral pressure profile). All examinations serve to objectify and quantify the symptoms, to correctly assign symptoms to the pathophysiology and anatomy as well as to identify risk factors, which often have a significant influence on the success of surgical therapy. Given appropriate experience, complications and often significant sequelae of bladder dysfunction affecting the patient's quality of life and life expectancy can be recognized. Urodynamic studies are performed to help narrow down potential diagnoses, to develop therapeutic strategies, and to obtain prognostic parameters. The following article is intended to provide some support.

Sensitive determination of RDX, nitroso-RDX metabolites, and other munitions in ground water by solid-phase extraction and isotope dilution liquid chromatography-atmospheric pressure electro-spray [correction of chemical] ionization mass spectrometry.

PubMed

Cassada, D A; Monson, S J; Snow, D D; Spalding, R F

1999-06-04

Recent improvements in the LC-MS interface have increased the sensitivity and selectivity of this instrument in the analysis of polar and thermally-labile aqueous constituents. Determination of RDX, nitroso-RDX metabolites, and other munitions was enhanced using LC-MS with solid-phase extraction, 15N3-RDX internal standard, and electrospray ionization (ESI) in negative ion mode. ESI produced a five-fold increase in detector response over atmospheric pressure chemical ionization (APCI) for the nitramine compounds, while the more energetic APCI produced more than twenty times the ESI response for nitroaromatics. Method detection limits in ESI for nitramines varied from 0.03 microgram l-1 for MNX to 0.05 microgram l-1 for RDX.

[Changes of twenty-four-hour profile blood pressure and its correction of patients with arterial hypertension on the background of combined antihypertensive therapy application].

PubMed

Solomennchuk, T M; Slaba, N A; Prots'ko, V V; Bedzaĭ, A O

2014-01-01

The aim of this research was the study of efficiency and endurance antihypertensive therapy on the basis of fixed combination of enalapril and hydrochlorothiazide (HCTZ) and enalapril and HCTZ in combination with amlodipine according to the twenty-four-hour (? day-and-night) monitoring of blood pressure (? 24H BPM) of patients with arterial hypertension (AH) 2-3 severity. The study included 33 patients with 2-3 grade of hypertension (average age--54,40 ± 3.45 years). All patients performed ? 24H BPM before treatment and after 12 weeks of therapy. The combination of enalapril and HCTZ allowed to achieve target levels of blood pressure in 79% of patients, amlodipine additional purpose--in 86% of patients. We found that this therapy has a corrective effect on daily blood pressure profile, significantly reducing the load pressure and blood pressure variability. During treatment with the combination of enalapril and HCTZ combination of enalapril, HCTZ with amlodipine optimal daily profile of blood pressure after 12 weeks of reaching respectively 63.1% and 71.4% of patients. The treatment with combination of enalapril and HCTZ and adding of amlodipine is characterized by good endurance and high adherence to treatment.

Table and Charts of Equilibrium Normal-shock Properties for Pure Hydrogen with Velocities to 70 km/sec. Revised.

NASA Technical Reports Server (NTRS)

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

1976-01-01

Errors found in the original edition are corrected. Refinement was made in procedures for solving the conservation relations for an incident (moving), standing, and reflected normal shock, as well as in computational methods for determining thermochemical-equilibrium hydrogen properties. A six-species hydrogen model replaces the original four-species model, and the heat of formation and spectroscopic constants used in this six-species model are listed in appendix A. In appendix B, comparisons are made between a number of methods for determining equilibrium thermodynamic properties for hydrogen for several values of pressure and temperatures to 50000 K. A comparison is also performed between the present method and a second method for determining thermodynamic properties and flow velocity behind an incident shock into pure hydrogen and behind a reflected shock.

Reduction of atmospheric disturbances in PSInSAR measure technique based on ENVISAT ASAR data for Erta Ale Ridge

NASA Astrophysics Data System (ADS)

Kopeć, Anna

2018-01-01

The interferometric synthetic aperture radar (InSAR) is becoming more and more popular to investigate surface deformation, associated with volcanism, earthquakes, landslides, and post-mining surface subsidence. The measuring accuracy depends on many factors: surface, time and geometric decorrelation, orbit errors, however the largest challenges are the tropospheric delays. The spatial and temporal variations in temperature, pressure, and relative humidity are responsible for tropospheric delays. So far, many methods have been developed, but researchers are still searching for the one, that will allow to correct interferograms consistently in different regions and times. The article focuses on examining the methods based on empirical phase-based methods, spectrometer measurements and weather model. These methods were applied to the ENVISAT ASAR data for the Erta Ale Ridge in the Afar Depression, East Africa

ALTIMETER ERRORS,

DTIC Science & Technology

CIVIL AVIATION, *ALTIMETERS, FLIGHT INSTRUMENTS, RELIABILITY, ERRORS , PERFORMANCE(ENGINEERING), BAROMETERS, BAROMETRIC PRESSURE, ATMOSPHERIC TEMPERATURE, ALTITUDE, CORRECTIONS, AVIATION SAFETY, USSR.

Air density dependence of the soft X-ray PTW 34013 ionization chamber.

PubMed

Torres Del Río, Julia; Forastero, Cristina; Tornero-López, Ana M; López, Jesús J; Guirado, Damián; Perez-Calatayud, José; Lallena, Antonio M

2018-02-01

We studied the dependence on air density of the response of the PTW 34013 ionization chamber, recently upgraded for dosimetry control of low energy X-ray beams. Measurements were performed by changing the pressure conditions inside a pressure chamber. The behavior of the measurements against the air density inside this chamber was analyzed. X-ray beams generated with 50, 70, 100, 150 and 200 kVp and the two electrometer polarities were considered. For all beams studied, measurements corrected with the conventional temperature and pressure factor showed a residual dependence on the air density that was described with a linear function of the air density. For the 50 and 70 kVp beams, corrected measurements remained ∼1% smaller than the value found at standard pressure/temperature conditions, for both electrometer polarities and for the air density range typical in clinical conditions. For air densities smaller than the standard one, measurements found for 100, 150 and 200 kVp beams were below or above the value found at standard pressure and temperature when the negative or positive electrometer polarities were used, respectively. The differences with the measurements at standard conditions were less than 1% for the 100 kVp beam and below 4% for the other two beams. The PTW 34013 ionization chamber showed a dependence on the air density that is not properly described with the usual temperature and pressure correction factor. This residual dependence is negligible for low energy beams, for which this chamber is recommended, but is more substantial for beams with energy above 80 kVp. Copyright © 2018 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Quality Controlled Radiosonde Profile from MC3E

DOE Data Explorer

Toto, Tami; Jensen, Michael

2014-11-13

The sonde-adjust VAP produces data that corrects documented biases in radiosonde humidity measurements. Unique fields contained within this datastream include smoothed original relative humidity, dry bias corrected relative humidity, and final corrected relative humidity. The smoothed RH field refines the relative humidity from integers - the resolution of the instrument - to fractions of a percent. This profile is then used to calculate the dry bias corrected field. The final correction fixes a time-lag problem and uses the dry-bias field as input into the algorithm. In addition to dry bias, solar heating is another correction that is encompassed in the final corrected relative humidity field. Additional corrections were made to soundings at the extended facility sites (S0*) as necessary: Corrected erroneous surface elevation (and up through rest of height of sounding), for S03, S04 and S05. Corrected erroneous surface pressure at Chanute (S02).

On the flow of a compressible fluid by the hodograph method I : unification and extension of present-day results

NASA Technical Reports Server (NTRS)

Garrick, I E; Kaplan, Carl

1944-01-01

Elementary basic solutions of the equations of motion of a compressible fluid in the hodograph variables are developed and used to provide a basis for comparison, in the form of velocity correction formulas, of corresponding compressible and incompressible flows. The known approximate results of Chaplygin, Von Karman and Tsien, Temple and Yarwood, and Prandtl and Glauert are unified by means of the analysis of the present paper. Two new types of approximations, obtained from the basic solutions, are introduced; they possess certain desirable features of the other approximations and appear preferable as a basis for extrapolation into the range of high stream Mach numbers and large disturbances to the main stream. Tables and figures giving velocity and pressure-coefficient correction factors are included in order to facilitate the practical application of the results.

Elastic electron differential cross sections for argon atom in the intermediate energy range from 40 eV to 300 eV

NASA Astrophysics Data System (ADS)

Ranković, Miloš Lj.; Maljković, Jelena B.; Tökési, Károly; Marinković, Bratislav P.

2018-02-01

Measurements and calculations for electron elastic differential cross sections (DCS) of argon atom in the energy range from 40 to 300 eV are presented. DCS have been measured in the crossed beam arrangement of the electron spectrometer with an energy resolution of 0.5 eV and angular resolution of 1.5∘ in the range of scattering angles from 20∘ to 126∘. Both angular behaviour and energy dependence of DCS are obtained in a separate sets of experiments, while the absolute scale is achieved via relative flow method, using helium as a reference gas. All data is corrected for the energy transmission function, changes of primary electron beam current and target pressure, and effective path length (volume correction). DCSs are calculated in relativistic framework by expressing the Mott's cross sections in partial wave expansion. Our results are compared with other available data.

Water hammer effect in the spiral case and penstock of Francis turbines

NASA Astrophysics Data System (ADS)

Pepa, D.; Ursoniu, C.; Gillich, R. N.; Campian, C. V.

2017-01-01

Sudden pressure increases in the penstock or spiral case of a hydraulic turbine are the effect of sudden flow variation that occur during transient processes of type opening / closing or load rejection of the hydro unit. The consequence of the pressure rise in the spiral case and penstock is the water hammer phenomenon, whose effects can be devastating in some cases, up to breaking pipes and calamities produced in the area. This paper aims to analyze the method of calculation of the maximum pressure values that might occur in load rejection situations to a hydraulic turbine, in spiral case and in penstock, conditioned by the limiting of the values of the over speed and measures of limiting the increase in pressure in conjunction with limiting the increase in speed in these specific processes. As an example, we studied and analyzed the situation of a hydroelectric power plant equipped with a 7.8 MW Francis turbine without pressure regulator and the inflow surge. The results of analytical calculation overlaid on the experimental measurements performed during the performance tests of the hydro unit lead to the conclusion that the calculation algorithm proposed has been chosen correctly and the 2-stage closing law of the wicket gate promoted in this case is effective in such situations.

Structure and interactions of fully hydrated dioleoylphosphatidylcholine bilayers.

PubMed Central

Tristram-Nagle, S; Petrache, H I; Nagle, J F

1998-01-01

This study focuses on dioleoylphosphatidylcholine (DOPC) bilayers near full hydration. Volumetric data and high-resolution synchrotron x-ray data are used in a method that compares DOPC with well determined gel phase dipalmitoylphosphatidylcholine (DPPC). The key structural quantity obtained is fully hydrated area/lipid A0 = 72.2 +/- 1.1 A2 at 30 degrees C, from which other quantities such as thickness of the bilayer are obtained. Data for samples over osmotic pressures from 0 to 56 atmospheres give an estimate for the area compressibility of KA = 188 dyn/cm. Obtaining the continuous scattering transform and electron density profiles requires correction for liquid crystal fluctuations. Quantitation of these fluctuations opens an experimental window on the fluctuation pressure, the primary repulsive interaction near full hydration. The fluctuation pressure decays exponentially with water spacing, in agreement with analytical results for soft confinement. However, the ratio of decay length lambda(fl) = 5.8 A to hydration pressure decay length lambda = 2.2 A is significantly larger than the value of 2 predicted by analytical theory and close to the ratio obtained in recent simulations. We also obtain the traditional osmotic pressure versus water spacing data. Our analysis of these data shows that estimates of the Hamaker parameter H and the bending modulus Kc are strongly coupled. PMID:9675192

Kendall Analysis of Cannon Pressure Vessels

DTIC Science & Technology

2012-04-11

corrections in the expressions to account for the reduction in compressive yield strength near the bore of an autofrettaged vessel; [iii] Fatigue life...see Table 1. Pressure vessel results are shown in Table 1 for breech sections of four ASTM A723 steel cannon tubes that were pressurized in small...ID ratio of 1.87 and degree of autofrettage (c-a)/(b-a) = 0.51. For A723 steel pressure vessels near this configuration and degree of autofrettage

A Guide for Estimation of Aeroacoustic Loads on Flight Vehicle Surfaces

DTIC Science & Technology

1977-02-01

Nozzle aspect ratio correction of one-third octave band sound pressure levels of USB noise . 122 31. Impingement angle correction of one-third octave...breech weapons ....................... 175 IX •: •-•,..i .•,z. •... LIST OF FIGURES (Cont.) page Figure 61. Rectangular cavity ...and a nozzle aspect ratio of 4.0, and without a deflector. Obtain the corrected one-third octave band level SPL from the baseline level, from " b

Gait Phase Recognition for Lower-Limb Exoskeleton with Only Joint Angular Sensors

PubMed Central

Liu, Du-Xin; Wu, Xinyu; Du, Wenbin; Wang, Can; Xu, Tiantian

2016-01-01

Gait phase is widely used for gait trajectory generation, gait control and gait evaluation on lower-limb exoskeletons. So far, a variety of methods have been developed to identify the gait phase for lower-limb exoskeletons. Angular sensors on lower-limb exoskeletons are essential for joint closed-loop controlling; however, other types of sensors, such as plantar pressure, attitude or inertial measurement unit, are not indispensable.Therefore, to make full use of existing sensors, we propose a novel gait phase recognition method for lower-limb exoskeletons using only joint angular sensors. The method consists of two procedures. Firstly, the gait deviation distances during walking are calculated and classified by Fisher’s linear discriminant method, and one gait cycle is divided into eight gait phases. The validity of the classification results is also verified based on large gait samples. Secondly, we build a gait phase recognition model based on multilayer perceptron and train it with the phase-labeled gait data. The experimental result of cross-validation shows that the model has a 94.45% average correct rate of set (CRS) and an 87.22% average correct rate of phase (CRP) on the testing set, and it can predict the gait phase accurately. The novel method avoids installing additional sensors on the exoskeleton or human body and simplifies the sensory system of the lower-limb exoskeleton. PMID:27690023

Note: Additionally refined new possibilities of plasma probe diagnostics.

PubMed

Riaby, V A; Savinov, V P; Masherov, P E; Yakunin, V G

2018-03-01

In two previous Notes published in this journal, a method of measuring probe sheath thickness and ion mass was described using Langmuir probe diagnostics in low pressure xenon plasma close to Maxwellian substance. According to the first Note, this method includes two stages: (i) in a special experiment with known ion mass, the Bohm and Child-Langmuir-Boguslavsky (CLB) equations for cylindrical Langmuir probes used in this xenon plasma were solved jointly to determine the probe sheath thicknesses and Bohm coefficient C BCyl ≈ 1.13; and (ii) in a general experiment, with known C BCyl , the same equations could be solved to obtain the probe sheath thicknesses and the mean ion mass. In the second Note, the (i) stage of this method was refined: the results of the CLB probe sheath model application, which were termed "evaluations," were corrected using the step-front probe sheath model, which was closer to reality in the special experiment with the xenon plasma. This process resulted in a Bohm coefficient of C BCyl ≈ 1.23 for the cylindrical probe. In the present Note, corrected xenon plasma parameters without the influence of the bare probe protective shield were used for the (i) stage of this diagnostic method. This action also refined the Bohm coefficient, lowering it to C BCyl ≈ 0.745 for cylindrical probes. This advance makes the new diagnostics method more objective and reliable.

Note: Additionally refined new possibilities of plasma probe diagnostics

NASA Astrophysics Data System (ADS)

Riaby, V. A.; Savinov, V. P.; Masherov, P. E.; Yakunin, V. G.

2018-03-01

In two previous Notes published in this journal, a method of measuring probe sheath thickness and ion mass was described using Langmuir probe diagnostics in low pressure xenon plasma close to Maxwellian substance. According to the first Note, this method includes two stages: (i) in a special experiment with known ion mass, the Bohm and Child-Langmuir-Boguslavsky (CLB) equations for cylindrical Langmuir probes used in this xenon plasma were solved jointly to determine the probe sheath thicknesses and Bohm coefficient CBCyl ≈ 1.13; and (ii) in a general experiment, with known CBCyl, the same equations could be solved to obtain the probe sheath thicknesses and the mean ion mass. In the second Note, the (i) stage of this method was refined: the results of the CLB probe sheath model application, which were termed "evaluations," were corrected using the step-front probe sheath model, which was closer to reality in the special experiment with the xenon plasma. This process resulted in a Bohm coefficient of CBCyl ≈ 1.23 for the cylindrical probe. In the present Note, corrected xenon plasma parameters without the influence of the bare probe protective shield were used for the (i) stage of this diagnostic method. This action also refined the Bohm coefficient, lowering it to CBCyl ≈ 0.745 for cylindrical probes. This advance makes the new diagnostics method more objective and reliable.

A projection hybrid high order finite volume/finite element method for incompressible turbulent flows

NASA Astrophysics Data System (ADS)

Busto, S.; Ferrín, J. L.; Toro, E. F.; Vázquez-Cendón, M. E.

2018-01-01

In this paper the projection hybrid FV/FE method presented in [1] is extended to account for species transport equations. Furthermore, turbulent regimes are also considered thanks to the k-ε model. Regarding the transport diffusion stage new schemes of high order of accuracy are developed. The CVC Kolgan-type scheme and ADER methodology are extended to 3D. The latter is modified in order to profit from the dual mesh employed by the projection algorithm and the derivatives involved in the diffusion term are discretized using a Galerkin approach. The accuracy and stability analysis of the new method are carried out for the advection-diffusion-reaction equation. Within the projection stage the pressure correction is computed by a piecewise linear finite element method. Numerical results are presented, aimed at verifying the formal order of accuracy of the scheme and to assess the performance of the method on several realistic test problems.

Moho depth variations over the Maldive Ridge and adjoining Arabian and Central Indian Basins, Western Indian Ocean, from three dimensional inversion of gravity anomalies

NASA Astrophysics Data System (ADS)

Kunnummal, Priyesh; Anand, S. P.; Haritha, C.; Rama Rao, P.

2018-05-01

Analysis of high resolution satellite derived free air gravity data has been undertaken in the Greater Maldive Ridge (GMR) (Maldive Ridge, Deep Sea Channel, northern limit of Chagos Bank) segment of the Chagos Laccadive Ridge and the adjoining Arabian and Central Indian Basins. A Complete Bouguer Anomaly (CBA) map was generated from the Indian Ocean Geoidal Low removed Free Air Gravity (hereinafter referred to as "FAG-IOGL") data by incorporating Bullard A, B and C corrections. Using the Parker method, Moho topography was initially computed by inverting the CBA data. From the CBA the Mantle Residual Gravity Anomalies (MRGA) were computed by incorporating gravity effects of sediments and lithospheric temperature and pressure induced anomalies. Further, the MRGA was inverted to get Moho undulations from which the crustal thickness was also estimated. It was found that incorporating the lithospheric thermal and pressure anomaly correction has provided substantial improvement in the computed Moho depths especially in the oceanic areas. But along the GMR, there was not much variation in the Moho thickness computed with and without the thermal and pressure gravity correction implying that the crustal thickness of the ridge does not depend on the oceanic isochrones used for the thermal corrections. The estimated Moho depths in the study area ranges from 7 km to 28 km and the crustal thickness from 2 km to 27 km. The Moho depths are shallower in regions closer to Central Indian Ridge in the Arabian Basin i.e., the region to the west of the GMR is thinner compared to the region in the east (Central Indian Basin). The thickest crust and the deepest Moho are found below the N-S trending GMR segment of the Chagos-Laccadive Ridge. Along the GMR the crustal thickness decreases from north to south with thickness of 27 km below the Maldives Ridge reducing to ∼9 km at 3°S and further increasing towards Chagos Bank. Even though there are similarities in crustal thickness between Maldive Ridge and other regions like Mascarene Plateau which was recently interpreted as underlain by continental crust, much more geoscientific work including drilling has to be undertaken to finally confirm the exact nature of the ridge.

Effects of sound level fluctuations on annoyance caused by aircraft-flyover noise

NASA Technical Reports Server (NTRS)

Mccurdy, D. A.

1979-01-01

A laboratory experiment was conducted to determine the effects of variations in the rate and magnitude of sound level fluctuations on the annoyance caused by aircraft-flyover noise. The effects of tonal content, noise duration, and sound pressure level on annoyance were also studied. An aircraft-noise synthesis system was used to synthesize 32 aircraft-flyover noise stimuli representing the factorial combinations of 2 tone conditions, 2 noise durations, 2 sound pressure levels, 2 level fluctuation rates, and 2 level fluctuation magnitudes. Thirty-two test subjects made annoyance judgements on a total of 64 stimuli in a subjective listening test facility simulating an outdoor acoustic environment. Variations in the rate and magnitude of level fluctuations were found to have little, if any, effect on annoyance. Tonal content, noise duration, sound pressure level, and the interaction of tonal content with sound pressure level were found to affect the judged annoyance significantly. The addition of tone corrections and/or duration corrections significantly improved the annoyance prediction ability of noise rating scales.

FLUID: A numerical interpolation procedure for obtaining thermodynamic and transport properties of fluids

NASA Technical Reports Server (NTRS)

Fessler, T. E.

1977-01-01

A computer program subroutine, FLUID, was developed to calculate thermodynamic and transport properties of pure fluid substances. It provides for determining the thermodynamic state from assigned values for temperature-density, pressure-density, temperature-pressure, pressure-entropy, or pressure-enthalpy. Liquid or two-phase (liquid-gas) conditions are considered as well as the gas phase. A van der Waals model is used to obtain approximate state values; these values are then corrected for real gas effects by model-correction factors obtained from tables based on experimental data. Saturation conditions, specific heat, entropy, and enthalpy data are included in the tables for each gas. Since these tables are external to the FLUID subroutine itself, FLUID can implement any gas for which a set of tables has been generated. (A setup phase is used to establish pointers dynamically to the tables for a specific gas.) Data-table preparation is described. FLUID is available in both SFTRAN and FORTRAN

[A practical procedure to improve the accuracy of radiochromic film dosimetry: a integration with a correction method of uniformity correction and a red/blue correction method].

PubMed

Uehara, Ryuzo; Tachibana, Hidenobu; Ito, Yasushi; Yoshino, Shinichi; Matsubayashi, Fumiyasu; Sato, Tomoharu

2013-06-01

It has been reported that the light scattering could worsen the accuracy of dose distribution measurement using a radiochromic film. The purpose of this study was to investigate the accuracy of two different films, EDR2 and EBT2, as film dosimetry tools. The effectiveness of a correction method for the non-uniformity caused from EBT2 film and the light scattering was also evaluated. In addition the efficacy of this correction method integrated with the red/blue correction method was assessed. EDR2 and EBT2 films were read using a flatbed charge-coupled device scanner (EPSON 10000G). Dose differences on the axis perpendicular to the scanner lamp movement axis were within 1% with EDR2, but exceeded 3% (Maximum: +8%) with EBT2. The non-uniformity correction method, after a single film exposure, was applied to the readout of the films. A corrected dose distribution data was subsequently created. The correction method showed more than 10%-better pass ratios in dose difference evaluation than when the correction method was not applied. The red/blue correction method resulted in 5%-improvement compared with the standard procedure that employed red color only. The correction method with EBT2 proved to be able to rapidly correct non-uniformity, and has potential for routine clinical IMRT dose verification if the accuracy of EBT2 is required to be similar to that of EDR2. The use of red/blue correction method may improve the accuracy, but we recommend we should use the red/blue correction method carefully and understand the characteristics of EBT2 for red color only and the red/blue correction method.

The Use of a Pressure-Indicating Sensor Film to Provide Feedback upon Hydrogel-Forming Microneedle Array Self-Application In Vivo.

PubMed

Vicente-Pérez, Eva M; Quinn, Helen L; McAlister, Emma; O'Neill, Shannon; Hanna, Lezley-Anne; Barry, Johanne G; Donnelly, Ryan F

2016-12-01

To evaluate the combination of a pressure-indicating sensor film with hydrogel-forming microneedle arrays, as a method of feedback to confirm MN insertion in vivo. Pilot in vitro insertion studies were conducted using a Texture Analyser to insert MN arrays, coupled with a pressure-indicating sensor film, at varying forces into excised neonatal porcine skin. In vivo studies involved twenty human volunteers, who self-applied two hydrogel-forming MN arrays, one with a pressure-indicating sensor film incorporated and one without. Optical coherence tomography was employed to measure the resulting penetration depth and colorimetric analysis to investigate the associated colour change of the pressure-indicating sensor film. Microneedle insertion was achieved in vitro at three different forces, demonstrating the colour change of the pressure-indicating sensor film upon application of increasing pressure. When self-applied in vivo, there was no significant difference in the microneedle penetration depth resulting from each type of array, with a mean depth of 237 μm recorded. When the pressure-indicating sensor film was present, a colour change occurred upon each application, providing evidence of insertion. For the first time, this study shows how the incorporation of a simple, low-cost pressure-indicating sensor film can indicate microneedle insertion in vitro and in vivo, providing visual feedback to assure the user of correct application. Such a strategy may enhance usability of a microneedle device and, hence, assist in the future translation of the technology to widespread clinical use.

Cerebral autoregulation and flow/metabolism coupling during cardiopulmonary bypass: the influence of PaCO/sub 2/

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

Murkin, J.M.; Farrar, J.K.; Tweed, W.A.

Measurement of /sup 133/Xe clearance and effluent cerebral venous blood sampling were used in 38 patients to determine the effects of cardiopulmonary bypass, and of maintaining temperature corrected or noncorrected PaCO/sub 2/ at 40 mm Hg on regulation of cerebral blood flow (CBF) and flow/metabolism coupling. After induction of anesthesia with diazepam and fentanyl, mean CBF was 25 ml X 100 g-1 X min-1 and cerebral oxygen consumption, 1.67 ml X 100 g-1 X min-1. Cerebral oxygen consumption during nonpulsatile cardiopulmonary bypass at 26 degrees C was reduced to 0.42 ml X 100 g-1 X min-1 in both groups. CBFmore » was reduced to 14-15 ml X 100 g-1 X min-1 in the non-temperature-corrected group (n = 21), was independent of cerebral perfusion pressure over the range of 20-100 mm Hg, but correlated with cerebral oxygen consumption. In the temperature-corrected group (n = 17), CBF varied from 22 to 32 ml X 100 g-1 X min-1, and flow/metabolism coupling was not maintained (i.e., CBF and cerebral oxygen consumption varied independently). However, variation in CBF correlated significantly with cerebral perfusion pressure over the pressure range of 15-95 mm Hg. This study demonstrates a profound reduction in cerebral oxygen consumption during hypothermic nonpulsatile cardiopulmonary bypass. When a non-temperature-corrected PaCO/sub 2/ of approximately 40 mm Hg was maintained, CBF was lower, and analysis of pooled data suggested that CBF regulation was better preserved, i.e., CBF was independent of pressure changes and dependent upon cerebral oxygen consumption.« less

Use of Telemedicine for Management of Diabetes in Correctional Facilities.

PubMed

Kassar, Kinan; Roe, Cheryl; Desimone, Marisa

2017-01-01

Prisoners can have difficulty obtaining subspecialty consultations. Telemedicine is used to provide diabetes consultations for residents of correctional facilities from our diabetes center. Telemedicine helps improve access to endocrinologists at reduced cost, but little outcome data are available. A retrospective chart review of prisoners from 15 correctional facilities who received televisits for diabetes from 2011 to 2014 was performed. Demographic information, complications, medications, blood pressure, and laboratory results were collected. At baseline (n = 106), mean age was 44 years, duration of diabetes was 15 years, 44% had type 1 diabetes, and all were male. Only 64 of the participants had ≥2 video consultations; 58/64 had follow-up HbA1c results; and 53/58 were insulin requiring. Mean initial HbA1c was 9.3% with an average decrease of 0.5% from initial to final visit (a mean of 3.6 televisits). Patients with an initial HbA1c >9% (n = 28) had an average drop of 1.3%. Twenty-two subjects had initial elevated blood pressure; 20/22 (91%) were prescribed angiotensin-converting-enzyme-inhibitors (ACE-I)/angiotensin II receptor blockers (ARB); and 15 of these 20 (75%) had a final blood pressure <140/90 mm Hg over a mean of 3.3 televisits. 17/20 with high low-density lipoprotein (LDL) were treated with statin drugs; 15/17 (88%) had improved LDL on follow-up. Follow-up was limited by prisoner availability or visit cancellation by prison facility. Improvements in glycemic, blood pressure, and lipid control for prisoners with diabetes can be achieved with teleconsultations to correctional institutions. Given the high costs of transporting prisoners to healthcare facilities, telemedicine should be considered to help improve diabetes care for this vulnerable population.

Single-shot pressure-sensitive paint lifetime measurements on fast rotating blades using an optimized double-shutter technique

NASA Astrophysics Data System (ADS)

Weiss, Armin; Geisler, Reinhard; Schwermer, Till; Yorita, Daisuke; Henne, Ulrich; Klein, Christian; Raffel, Markus

2017-09-01

A pressure-sensitive paint (PSP) system is presented to measure global surface pressures on fast rotating blades. It is dedicated to solve the problem of blurred image data employing the single-shot lifetime method. The efficient blur reduction capability of an optimized double-shutter imaging technique is demonstrated omitting error-prone post-processing or laborious de-rotation setups. The system is applied on Mach-scaled DSA-9A helicopter blades in climb at various collective pitch settings and blade tip Mach and chord Reynolds numbers (M_{ {tip}} = 0.29-0.57; Re_{ {tip}} = 4.63-9.26 × 10^5). Temperature effects in the PSP are corrected by a theoretical approximation validated against measured temperatures using temperature-sensitive paint (TSP) on a separate blade. Ensemble-averaged PSP results are comparable to pressure-tap data on the same blade to within 250 Pa. Resulting pressure maps on the blade suction side reveal spatially high resolved flow features such as the leading edge suction peak, footprints of blade-tip vortices and evidence of laminar-turbulent boundary-layer (BL) transition. The findings are validated by a separately conducted BL transition measurement by means of TSP and numerical simulations using a 2D coupled Euler/boundary-layer code. Moreover, the principal ability of the single-shot technique to capture unsteady flow phenomena is stressed revealing three-dimensional pressure fluctuations at stall.

The effect of spinal curvature on the photogrammetric assessment on static balance in elderly women.

PubMed

Drzał-Grabiec, Justyna; Rachwał, Maciej; Podgórska-Bednarz, Justyna; Rykała, Justyna; Snela, Sławomir; Truszczyńska, Aleksandra; Trzaskoma, Zbigniew

2014-05-29

Involutional changes to the body in elderly patients affect the shape of the spine and the activity of postural muscles. The purpose of this study was to assess the influence of age-related changes in spinal curvature on postural balance in elderly women. The study population consisted of 90 women, with a mean age of 70 ± 8.01 years. Static balance assessments were conducted on a tensometric platform, and posturographic assessments of body posture were performed using a photogrammetric method based on the Projection Moiré method. The results obtained were analysed using the Spearman's rank correlation coefficient test. We found a statistically significant correlation between body posture and the quality of the balance system response based on the corrective function of the visual system. The shape of the spinal curvature influenced postural stability, as measured by static posturography. Improvement in the quality of the balance system response depended on corrective information from the visual system and proprioceptive information from the paraspinal muscles. The sensitivity of the balance system to the change of centre of pressure location was influenced by the direction of the change in rotation of the shoulder girdle and spine. Development of spinal curvature in the sagittal plane and maintenance of symmetry in the coronal and transverse planes are essential for correct balance control, which in turn is essential for the development of a properly proportioned locomotor system.

An estimation of tropospheric corrections using GPS and synoptic data: Improving Urmia Lake water level time series from Jason-2 and SARAL/AltiKa satellite altimetry

NASA Astrophysics Data System (ADS)

Arabsahebi, Reza; Voosoghi, Behzad; Tourian, Mohammad J.

2018-05-01

Tropospheric correction is one of the most important corrections in satellite altimetry measurements. Tropospheric wet and dry path delays have strong dependence on temperature, pressure and humidity. Tropospheric layer has particularly high variability over coastal regions due to humidity, wind and temperature gradients. Depending on the extent of water body and wind conditions over an inland water, Wet Tropospheric Correction (WTC) is within the ranges from a few centimeters to tens of centimeters. Therefore, an extra care is needed to estimate tropospheric corrections on the altimetric measurements over inland waters. This study assesses the role of tropospheric correction on the altimetric measurements over the Urmia Lake in Iran. For this purpose, four types of tropospheric corrections have been used: (i) microwave radiometer (MWR) observations, (ii) tropospheric corrections computed from meteorological models, (iii) GPS observations and (iv) synoptic station data. They have been applied to Jason-2 track no. 133 and SARAL/AltiKa track no. 741 and 356 corresponding to 117-153 and the 23-34 cycles, respectively. In addition, the corresponding measurements of PISTACH and PEACHI, include new retracking method and an innovative wet tropospheric correction, have also been used. Our results show that GPS observation leads to the most accurate tropospheric correction. The results obtained from the PISTACH and PEACHI projects confirm those obtained with the standard SGDR, i.e., the role of GPS in improving the tropospheric corrections. It is inferred that the MWR data from Jason-2 mission is appropriate for the tropospheric corrections, however the SARAL/AltiKa one is not proper because Jason-2 possesses an enhanced WTC near the coast. Furthermore, virtual stations are defined for assessment of the results in terms of time series of Water Level Height (WLH). The results show that GPS tropospheric corrections lead to the most accurate WLH estimation for the selected virtual stations, which improves the accuracy of the obtained WLH time series by about 5%.

a Cell Vertex Algorithm for the Incompressible Navier-Stokes Equations on Non-Orthogonal Grids

NASA Astrophysics Data System (ADS)

Jessee, J. P.; Fiveland, W. A.

1996-08-01

The steady, incompressible Navier-Stokes (N-S) equations are discretized using a cell vertex, finite volume method. Quadrilateral and hexahedral meshes are used to represent two- and three-dimensional geometries respectively. The dependent variables include the Cartesian components of velocity and pressure. Advective fluxes are calculated using bounded, high-resolution schemes with a deferred correction procedure to maintain a compact stencil. This treatment insures bounded, non-oscillatory solutions while maintaining low numerical diffusion. The mass and momentum equations are solved with the projection method on a non-staggered grid. The coupling of the pressure and velocity fields is achieved using the Rhie and Chow interpolation scheme modified to provide solutions independent of time steps or relaxation factors. An algebraic multigrid solver is used for the solution of the implicit, linearized equations.A number of test cases are anlaysed and presented. The standard benchmark cases include a lid-driven cavity, flow through a gradual expansion and laminar flow in a three-dimensional curved duct. Predictions are compared with data, results of other workers and with predictions from a structured, cell-centred, control volume algorithm whenever applicable. Sensitivity of results to the advection differencing scheme is investigated by applying a number of higher-order flux limiters: the MINMOD, MUSCL, OSHER, CLAM and SMART schemes. As expected, studies indicate that higher-order schemes largely mitigate the diffusion effects of first-order schemes but also shown no clear preference among the higher-order schemes themselves with respect to accuracy. The effect of the deferred correction procedure on global convergence is discussed.

On the anomaly of velocity-pressure decoupling in collocated mesh solutions

NASA Technical Reports Server (NTRS)

Kim, Sang-Wook; Vanoverbeke, Thomas

1991-01-01

The use of various pressure correction algorithms originally developed for fully staggered meshes can yield a velocity-pressure decoupled solution for collocated meshes. The mechanism that causes velocity-pressure decoupling is identified. It is shown that the use of a partial differential equation for the incremental pressure eliminates such a mechanism and yields a velocity-pressure coupled solution. Example flows considered are a three dimensional lid-driven cavity flow and a laminar flow through a 90 deg bend square duct. Numerical results obtained using the collocated mesh are in good agreement with the measured data and other numerical results.

Atomistic properties of γ uranium.

PubMed

Beeler, Benjamin; Deo, Chaitanya; Baskes, Michael; Okuniewski, Maria

2012-02-22

The properties of the body-centered cubic γ phase of uranium (U) are calculated using atomistic simulations. First, a modified embedded-atom method interatomic potential is developed for the high temperature body-centered cubic (γ) phase of U. This phase is stable only at high temperatures and is thus relatively inaccessible to first principles calculations and room temperature experiments. Using this potential, equilibrium volume and elastic constants are calculated at 0 K and found to be in close agreement with previous first principles calculations. Further, the melting point, heat capacity, enthalpy of fusion, thermal expansion and volume change upon melting are calculated and found to be in reasonable agreement with experiment. The low temperature mechanical instability of γ U is correctly predicted and investigated as a function of pressure. The mechanical instability is suppressed at pressures greater than 17.2 GPa. The vacancy formation energy is analyzed as a function of pressure and shows a linear trend, allowing for the calculation of the extrapolated zero pressure vacancy formation energy. Finally, the self-defect formation energy is analyzed as a function of temperature. This is the first atomistic calculation of γ U properties above 0 K with interatomic potentials.

Atomistic properties of γ uranium

NASA Astrophysics Data System (ADS)

Beeler, Benjamin; Deo, Chaitanya; Baskes, Michael; Okuniewski, Maria

2012-02-01

The properties of the body-centered cubic γ phase of uranium (U) are calculated using atomistic simulations. First, a modified embedded-atom method interatomic potential is developed for the high temperature body-centered cubic (γ) phase of U. This phase is stable only at high temperatures and is thus relatively inaccessible to first principles calculations and room temperature experiments. Using this potential, equilibrium volume and elastic constants are calculated at 0 K and found to be in close agreement with previous first principles calculations. Further, the melting point, heat capacity, enthalpy of fusion, thermal expansion and volume change upon melting are calculated and found to be in reasonable agreement with experiment. The low temperature mechanical instability of γ U is correctly predicted and investigated as a function of pressure. The mechanical instability is suppressed at pressures greater than 17.2 GPa. The vacancy formation energy is analyzed as a function of pressure and shows a linear trend, allowing for the calculation of the extrapolated zero pressure vacancy formation energy. Finally, the self-defect formation energy is analyzed as a function of temperature. This is the first atomistic calculation of γ U properties above 0 K with interatomic potentials.

Calibrating the Grigg's' Apparatus using Experiments performed at the Quartz-Coesite Transition

NASA Astrophysics Data System (ADS)

Heilbronner, R.; Stunitz, H.; Richter, B.

2015-12-01

The Griggs deformation apparatus is increasingly used for shear experiments. The tested material is placed on a 45° pre-cut between two forcing blocks. During the experiment, the axial displacement, load, temperature, and confining pressure are recorded as a function of time. From these records, stress, strain, and other mechanical data can be calculated - provided the machine is calibrated. Experimentalists are well aware that calibrating a Griggs apparatus is not easy. The stiffness correction accounts for the elastic extension of the rig as load is applied to the sample. An 'area correction' accounts for the decreasing overlap of the forcing blocks as slip along the pre-cut progresses. Other corrections are sometimes used to account for machine specific behaviour. While the rig stiffness can be measured very accurately, the area correction involves model assumptions. Depending on the choice of the model, the calculated stresses may vary by as much as 100 MPa. Also, while the assumptions appear to be theoretically valid, in practice they tend to over-correct the data, yielding strain hardening curves even in cases where constant flow stress or weakening is expected. Using the results of experiments on quartz gouge at the quartz-coesite transition (see Richter et al. this conference), we are now able to improve and constrain our corrections. We introduce an elastic salt correction based on the assumption that the confining pressure is increased as the piston advances and reduces the volume in the confining medium. As the compressibility of salt is low, the correction is significant and increases with strain. Applying this correction, the strain hardening artefact introduced by the area correction can be counter-balanced. Using a combination of area correction and salt correction we can now reproduce strain weakening, for which there is evidence in samples where coesite transforms back to quartz.

Validation of two case definitions to identify pressure ulcers using hospital administrative data

PubMed Central

Ho, Chester; Jiang, Jason; Eastwood, Cathy A; Wong, Holly; Weaver, Brittany; Quan, Hude

2017-01-01

Objective Pressure ulcer development is a quality of care indicator, as pressure ulcers are potentially preventable. Yet pressure ulcer is a leading cause of morbidity, discomfort and additional healthcare costs for inpatients. Methods are lacking for accurate surveillance of pressure ulcer in hospitals to track occurrences and evaluate care improvement strategies. The main study aim was to validate hospital discharge abstract database (DAD) in recording pressure ulcers against nursing consult reports, and to calculate prevalence of pressure ulcers in Alberta, Canada in DAD. We hypothesised that a more inclusive case definition for pressure ulcers would enhance validity of cases identified in administrative data for research and quality improvement purposes. Setting A cohort of patients with pressure ulcers were identified from enterostomal (ET) nursing consult documents at a large university hospital in 2011. Participants There were 1217 patients with pressure ulcers in ET nursing documentation that were linked to a corresponding record in DAD to validate DAD for correct and accurate identification of pressure ulcer occurrence, using two case definitions for pressure ulcer. Results Using pressure ulcer definition 1 (7 codes), prevalence was 1.4%, and using definition 2 (29 codes), prevalence was 4.2% after adjusting for misclassifications. The results were lower than expected. Definition 1 sensitivity was 27.7% and specificity was 98.8%, while definition 2 sensitivity was 32.8% and specificity was 95.9%. Pressure ulcer in both DAD and ET consultation increased with age, number of comorbidities and length of stay. Conclusion DAD underestimate pressure ulcer prevalence. Since various codes are used to record pressure ulcers in DAD, the case definition with more codes captures more pressure ulcer cases, and may be useful for monitoring facility trends. However, low sensitivity suggests that this data source may not be accurate for determining overall prevalence, and should be cautiously compared with other prevalence studies. PMID:28851785

Flight evaluation of an engine static pressure noseprobe in an F-15 airplane

NASA Technical Reports Server (NTRS)

Foote, C. H.; Jaekel, R. F.

1981-01-01

The flight testing of an inlet static pressure probe and instrumented inlet case produced results consistent with sea-level and altitude stand testing. The F-15 flight test verified the basic relationship of total to static pressure ratio versus corrected airflow and automatic distortion downmatch with the engine pressure ratio control mode. Additionally, the backup control inlet case statics demonstrated sufficient accuracy for backup control fuel flow scheduling, and the station 6 manifolded production probe was in agreement with the flight test station 6 tota pressure probes.

Models of brachial to finger pulse wave distortion and pressure decrement.

PubMed

Gizdulich, P; Prentza, A; Wesseling, K H

1997-03-01

To model the pulse wave distortion and pressure decrement occurring between brachial and finger arteries. Distortion reversion and decrement correction were also our aims. Brachial artery pressure was recorded intra-arterially and finger pressure was recorded non-invasively by the Finapres technique in 53 adult human subjects. Mean pressure was subtracted from each pressure waveform and Fourier analysis applied to the pulsations. A distortion model was estimated for each subject and averaged over the group. The average inverse model was applied to the full finger pressure waveform. The pressure decrement was modelled by multiple regression on finger systolic and diastolic levels. Waveform distortion could be described by a general, frequency dependent model having a resonance at 7.3 Hz. The general inverse model has an anti-resonance at this frequency. It converts finger to brachial pulsations thereby reducing average waveform distortion from 9.7 (s.d. 3.2) mmHg per sample for the finger pulse to 3.7 (1.7) mmHg for the converted pulse. Systolic and diastolic level differences between finger and brachial arterial pressures changed from -4 (15) and -8 (11) to +8 (14) and +8 (12) mmHg, respectively, after inverse modelling, with pulse pressures correct on average. The pressure decrement model reduced both the mean and the standard deviation of systolic and diastolic level differences to 0 (13) and 0 (8) mmHg. Diastolic differences were thus reduced most. Brachial to finger pulse wave distortion due to wave reflection in arteries is almost identical in all subjects and can be modelled by a single resonance. The pressure decrement due to flow in arteries is greatest for high pulse pressures superimposed on low means.

A level set method for determining critical curvatures for drainage and imbibition.

PubMed

Prodanović, Masa; Bryant, Steven L

2006-12-15

An accurate description of the mechanics of pore level displacement of immiscible fluids could significantly improve the predictions from pore network models of capillary pressure-saturation curves, interfacial areas and relative permeability in real porous media. If we assume quasi-static displacement, at constant pressure and surface tension, pore scale interfaces are modeled as constant mean curvature surfaces, which are not easy to calculate. Moreover, the extremely irregular geometry of natural porous media makes it difficult to evaluate surface curvature values and corresponding geometric configurations of two fluids. Finally, accounting for the topological changes of the interface, such as splitting or merging, is nontrivial. We apply the level set method for tracking and propagating interfaces in order to robustly handle topological changes and to obtain geometrically correct interfaces. We describe a simple but robust model for determining critical curvatures for throat drainage and pore imbibition. The model is set up for quasi-static displacements but it nevertheless captures both reversible and irreversible behavior (Haines jump, pore body imbibition). The pore scale grain boundary conditions are extracted from model porous media and from imaged geometries in real rocks. The method gives quantitative agreement with measurements and with other theories and computational approaches.

Cavitation guide for control valves

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

Tullis, J.P.

1993-04-01

This guide teaches the basic fundamentals of cavitation to provide the reader with an understanding of what causes cavitation, when it occurs, and the potential problems cavitation can cause to a valve and piping system. The document provides guidelines for understanding how to reduce the cavitation and/or select control valves for a cavitating system. The guide provides a method for predicting the cavitation intensity of control valves, and how the effect of cavitation on a system will vary with valve type, valve function, valve size, operating pressure, duration of operation and details of the piping installation. The guide defines sixmore » cavitation limits identifying cavitation intensities ranging from inception to the maximum intensity possible. The intensity of the cavitation at each limit Is described, including a brief discussion of how each level of cavitation influences the valve and system. Examples are included to demonstrate how to apply the method, including making both size and pressure scale effects corrections. Methods of controlling cavitation are discussed providing information on various techniques which can be used to design a new system or modify an existing one so it can operate at a desired level of cavitation.« less

An improved weakly compressible SPH method for simulating free surface flows of viscous and viscoelastic fluids

NASA Astrophysics Data System (ADS)

Xu, Xiaoyang; Deng, Xiao-Long

2016-04-01

In this paper, an improved weakly compressible smoothed particle hydrodynamics (SPH) method is proposed to simulate transient free surface flows of viscous and viscoelastic fluids. The improved SPH algorithm includes the implementation of (i) the mixed symmetric correction of kernel gradient to improve the accuracy and stability of traditional SPH method and (ii) the Rusanov flux in the continuity equation for improving the computation of pressure distributions in the dynamics of liquids. To assess the effectiveness of the improved SPH algorithm, a number of numerical examples including the stretching of an initially circular water drop, dam breaking flow against a vertical wall, the impact of viscous and viscoelastic fluid drop with a rigid wall, and the extrudate swell of viscoelastic fluid have been presented and compared with available numerical and experimental data in literature. The convergent behavior of the improved SPH algorithm has also been studied by using different number of particles. All numerical results demonstrate that the improved SPH algorithm proposed here is capable of modeling free surface flows of viscous and viscoelastic fluids accurately and stably, and even more important, also computing an accurate and little oscillatory pressure field.

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

PubMed

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

2016-12-20

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

Experimental Investigation of Composite Pressure Vessel Performance and Joint Stiffness for Pyramid and Inverted Pyramid Joints

NASA Technical Reports Server (NTRS)

Verhage, Joseph M.; Bower, Mark V.; Gilbert, Paul A. (Technical Monitor)

2001-01-01

The focus of this study is on the suitability in the application of classical laminate theory analysis tools for filament wound pressure vessels with adhesive laminated joints in particular: pressure vessel wall performance, joint stiffness and failure prediction. Two 18-inch diameter 12-ply filament wound pressure vessels were fabricated. One vessel was fabricated with a 24-ply pyramid laminated adhesive double strap butt joint. The second vessel was fabricated with the same number of plies in an inverted pyramid joint. Results from hydrostatic tests are presented. Experimental results were used as input to the computer programs GENLAM and Laminate, and the output compared to test. By using the axial stress resultant, the classical laminate theory results show a correlation within 1% to the experimental results in predicting the pressure vessel wall pressure performance. The prediction of joint stiffness for the two adhesive joints in the axial direction is within 1% of the experimental results. The calculated hoop direction joint stress resultant is 25% less than the measured resultant for both joint configurations. A correction factor is derived and used in the joint analysis. The correction factor is derived from the hoop stress resultant from the tank wall performance investigation. The vessel with the pyramid joint is determined to have failed in the joint area at a hydrostatic pressure 33% value below predicted failure. The vessel with the inverted pyramid joint failed in the wall acreage at a hydrostatic pressure within 10% of the actual failure pressure.

New method for estimating arterial pulse wave velocity at single site.

PubMed

Abdessalem, Khaled Ben; Flaud, Patrice; Zobaidi, Samir

2018-01-01

The clinical importance of measuring local pulse wave velocity (PWV), has encouraged researchers to develop several local methods to estimate it. In this work, we proposed a new method, the sum-of-squares method [Formula: see text], that allows the estimations of PWV by using simultaneous measurements of blood pressure (P) and arterial diameter (D) at single-location. Pulse waveforms generated by: (1) two-dimensional (2D) fluid-structure interaction simulation (FSI) in a compliant tube, (2) one-dimensional (1D) model of 55 larger human systemic arteries and (3) experimental data were used to validate the new formula and evaluate several classical methods. The performance of the proposed method was assessed by comparing its results to theoretical PWV calculated from the parameters of the model and/or to PWV estimated by several classical methods. It was found that values of PWV obtained by the developed method [Formula: see text] are in good agreement with theoretical ones and with those calculated by PA-loop and D 2 P-loop. The difference between the PWV calculated by [Formula: see text] and PA-loop does not exceed 1% when data from simulations are used, 3% when in vitro data are used and 5% when in vivo data are used. In addition, this study suggests that estimated PWV from arterial pressure and diameter waveforms provide correct values while methods that require flow rate (Q) and velocity (U) overestimate or underestimate PWV.

Wave Change of Intraoperative Transcranial Motor-Evoked Potentials During Corrective Fusion for Syndromic and Neuromuscular Scoliosis.

PubMed

Ando, Kei; Kobayashi, Kazuyoshi; Ito, Kenyu; Tsushima, Mikito; Morozumi, Masayoshi; Tanaka, Satoshi; Machino, Masaaki; Ota, Kyotaro; Nishida, Yoshihiro; Ishiguro, Naoki; Imagama, Shiro

2018-03-29

There is little information on intraoperative neuromonitoring during correction fusion surgery for syndromic scoliosis. To investigate intraoperative TcMEPs and conditions (body temperature and blood pressure) for syndromic scoliosis. The subjects were 23 patients who underwent 25 surgeries for corrective fusion using TcMEP. Patients were divided into groups based on a decrease (DA+) or no decrease (DA-) of the amplitude of the TcMEP waveform of ≥70%. The groups were compared for age, sex, disease, type of surgery, fusion area, operation time, estimated blood loss, body temperature, blood pressure, Cobb angle, angular curve (Cobb angle/number of vertebra), bending flexibility, correction rate, and recovery. The mean Cobb angles before and after surgery were 85.2° and 29.1°, giving a correction rate of 68.2%. There were 16 surgeries (64.0%) with intraoperative TcMEP wave changes. The DA+ and DA- groups had similar intraoperative conditions, but the short angular curve differed significantly between these groups. Amplitude deterioration occurred in 4 cases during first rod placement, in 8 during rotation, and in 3 during second rod placement after rotation. Seven patients had complete loss of TcMEP. However, most TcMEP changes recovered after pediclectomy or decreased correction. The preoperative angular curve differed significantly between patients with and without TcMEP changes (P < .05). Intraoperative TcMEP wave changes occurred in 64.0% of surgeries for corrective fusion, and all but one of these changes occurred during the correction procedure. The angular curve was a risk factor for intraoperative motor deficit.

Promoting sustainability in quality improvement: an evaluation of a web-based continuing education program in blood pressure measurement.

PubMed

Block, Lauren; Flynn, Sarah J; Cooper, Lisa A; Lentz, Caroline; Hull, Tammie; Dietz, Katherine B; Boonyasai, Romsai T

2018-01-10

The accuracy of blood pressure measurement is variable in office-based settings. Even when staff training programs are effective, knowledge and skills decay over time, supporting the need for ongoing staff training. We evaluated whether a web-based continuing education program in blood pressure measurement reinforced knowledge and skills among clinical staff and promoted sustainability of an existing quality improvement program. Medical assistants and nurses at six primary care clinics within a health system enrolled in a 30-min online educational program designed to refresh their knowledge of blood pressure measurement. A 20-question pre- and post-intervention survey addressed learners' knowledge and attitudes. Direct observation of blood pressure measurement technique before and after the intervention was performed. Differences in responses to pre- and post-module knowledge and attitudes questions and in observation data were analyzed using chi-square tests and simple logistic regression. All 88 clinical staff members participated in the program and completed the evaluation survey. Participants answered 80.6% of questions correctly before the module and 93.4% afterwards (p < 0.01). Scores improved significantly among staff from all job types. Licensed practical nurses and staff who had been in their current job at least a year were more likely to answer questions correctly than registered nurses and those in their current job less than a year. Attitudes toward correct blood pressure measurement were high at baseline and did not improve significantly. Prior to the intervention, staff adhered to 9 of 18 elements of the recommended technique during at least 90% of observations. Following the program, staff was more likely to explain the protocol, provide a rest period, measure an average blood pressure, and record the average blood pressure, but less likely to measure blood pressure with the arm at heart level and use the right arm. We designed, implemented, and evaluated a web-based educational program to improve knowledge, skills, and attitudes in blood pressure measurement and use of an automated device among nurses and medical assistants in ambulatory care. The program reinforced knowledge related to recommended blood pressure measurement technique. Retrospectively registered with ClincalTrials.gov on March 22, 2012; registration number NCT01566864 .

Non-thermal pressure in the outskirts of Abell 2142

NASA Astrophysics Data System (ADS)

Fusco-Femiano, Roberto; Lapi, Andrea

2018-03-01

Clumping and turbulence are expected to affect the matter accreted on to the outskirts of galaxy clusters. To determine their impact on the thermodynamic properties of Abell 2142, we perform an analysis of the X-ray temperature data from XMM-Newton via our SuperModel, a state-of-the-art tool for investigating the astrophysics of the intracluster medium already tested on many individual clusters (since Cavaliere, Lapi & Fusco-Femiano 2009). Using the gas density profile corrected for clumpiness derived by Tchernin et al. (2016), we find evidence for the presence of a non-thermal pressure component required to sustain gravity in the cluster outskirts of Abell 2142, that amounts to about 30 per cent of the total pressure at the virial radius. The presence of the non-thermal component implies the gas fraction to be consistent with the universal value at the virial radius and the electron thermal pressure profile to be in good agreement with that inferred from the SZ data. Our results indicate that the presence of gas clumping and of a non-thermal pressure component are both necessary to recover the observed physical properties in the cluster outskirts. Moreover, we stress that an alternative method often exploited in the literature (included Abell 2142) to determine the temperature profile kBT = Pe/ne basing on a combination of the Sunyaev-Zel'dovich (SZ) pressure Pe and of the X-ray electron density ne does not allow us to highlight the presence of non-thermal pressure support in the cluster outskirts.

40 CFR 63.1659 - Reporting requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... followed and the corrective actions taken. (2) Venturi scrubbers. In addition to the information required... identify the periods when the average hourly pressure drop of venturi scrubbers used to control particulate... of the scrubber pressure drop limit per paragraph (b)(2) of this section. These reports are to be...

DSS 13 antenna monitor system. [Deep Space Network

NASA Technical Reports Server (NTRS)

Siev, B.; Bayergo, D.

1979-01-01

The development of a monitor system for the DSS 13 antenna is presented. The system checks for accumulator pressures, differential pressures, wind velocity, power supplies, fluid temperatures, and fluid levels. It was concluded that the system performed properly in high winds and correctly reported all malfunctions.

An empirical method to estimate shear wave velocity of soils in the New Madrid seismic zone

USGS Publications Warehouse

Wei, B.-Z.; Pezeshk, S.; Chang, T.-S.; Hall, K.H.; Liu, Huaibao P.

1996-01-01

In this study, a set of charts are developed to estimate shear wave velocity of soils in the New Madrid seismic zone (NMSZ), using the standard penetration test (SPT) N values and soil depths. Laboratory dynamic test results of soil samples collected from the NMSZ showed that the shear wave velocity of soils is related to the void ratio and the effective confining pressure applied to the soils. The void ratio of soils can be estimated from the SPT N values and the effective confining pressure depends on the depth of soils. Therefore, the shear wave velocity of soils can be estimated from the SPT N value and the soil depth. To make the methodology practical, two corrections should be made. One is that field SPT N values of soils must be adjusted to an unified SPT N??? value to account the effects of overburden pressure and equipment. The second is that the effect of water table to effective overburden pressure of soils must be considered. To verify the methodology, shear wave velocities of five sites in the NMSZ are estimated and compared with those obtained from field measurements. The comparison shows that our approach and the field tests are consistent with an error of less than of 15%. Thus, the method developed in this study is useful for dynamic study and practical designs in the NMSZ region. Copyright ?? 1996 Elsevier Science Limited.

Screening tests for assessing the anaerobic biodegradation of pollutant chemicals in subsurface environments

USGS Publications Warehouse

Suflita, Joseph M.; Concannon, Frank

1995-01-01

Screening methods were developed to assess the susceptibility of ground water contaminants to anaerobic biodegradation. One method was an extrapolation of a procedure previously used to measure biodegradation activity in dilute sewage sludge. Aquifer solids and ground water with no additional nutritive media were incubated anaerobically in 160-ml serum bottles containing 250 mg·l−1 carbon of the substrate of interest. This method relied on the detection of gas pressure or methane production in substrateamended microcosms relative to background controls. Other screening procedures involved the consumption of stoichiometrically required amounts of sulfate or nitrate from the same type of incubations. Close agreement was obtained between the measured and calculated amounts of substrate bioconversion based on the measured biogas pressure in methanogenic microcosms. Storage of the microcosms for up to 6 months did not adversely influence the onset or rate of benzoic acid mineralization. The lower detection limits of the methanogenic assay were found to be a function of the size of the microcosm headspace, the mean oxidation state of the substrate carbon, and the method used to correct for background temperature fluctuations. Using these simple screening procedures, biodegradation information of regulatory interest could be generated, including, (i) the length of the adaptation period, (ii) the rate of substrate decay and (iii) the completeness of the bioconversion.

A database for the static dielectric constant of water and steam

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

Fernandez, D.P.; Mulev, Y.; Goodwin, A.R.H.

All reliable sources of data for the static dielectric constant or relative permittivity of water and steam, many of them unpublished or inaccessible, have been collected, evaluated, corrected when required, and converted to the ITS-90 temperature scale. The data extend over a temperature range from 238 to 873 K and over a pressure range from 0.1 MPa up to 1189 MPa. The evaluative part of this work includes a review of the different types of measurement techniques, and the corrections for frequency dependence due to the impedance of circuit components, and to electrode polarization. It also includes a detailed assessmentmore » of the uncertainty of each particular data source, as compared to other sources in the same range of pressure and temperature. Both the raw and the corrected data have been tabulated, and are also available on diskette. A comprehensive list of references to the literature is included.« less

Computation of the properties of liquid neon, methane, and gas helium at low temperature by the Feynman-Hibbs approach.

PubMed

Tchouar, N; Ould-Kaddour, F; Levesque, D

2004-10-15

The properties of liquid methane, liquid neon, and gas helium are calculated at low temperatures over a large range of pressure from the classical molecular-dynamics simulations. The molecular interactions are represented by the Lennard-Jones pair potentials supplemented by quantum corrections following the Feynman-Hibbs approach. The equations of state, diffusion, and shear viscosity coefficients are determined for neon at 45 K, helium at 80 K, and methane at 110 K. A comparison is made with the existing experimental data and for thermodynamical quantities, with results computed from quantum numerical simulations when they are available. The theoretical variation of the viscosity coefficient with pressure is in good agreement with the experimental data when the quantum corrections are taken into account, thus reducing considerably the 60% discrepancy between the simulations and experiments in the absence of these corrections.

Unsteady Newton-Busemann flow theory. Part 2: Bodies of revolution

NASA Technical Reports Server (NTRS)

Hui, W. H.; Tobak, M.

1981-01-01

Newtonian flow theory for unsteady flow past oscillating bodies of revolution at very high Mach numbers is completed by adding a centrifugal force correction to the impact pressures. Exact formulas for the unsteady pressure and the stability derivatives are obtained in closed form and are applicable to bodies of revolution that have arbitrary shapes, arbitrary thicknesses, and either sharp or blunt noses. The centrifugal force correction arising from the curved trajectories followed by the fluid particles in unsteady flow cannot be neglected even for the case of a circular cone. With this correction, the present theory is in excellent agreement with experimental results for sharp cones and for cones with small nose bluntness; gives poor agreement with the results of experiments in air for bodies with moderate or large nose bluntness. The pitching motions of slender power-law bodies of revulution are shown to be always dynamically stable according to Newton-Busemann theory.

[A comparison of degree of precision of auscultation, partial pressure of carbon dioxide in end-expiration, and transillumination technique in verifying accurate position of endotracheal tube].

PubMed

Qi, Le; Liu, Rong; Tang, Enhui; Li, Shouchun; Jin, Jun; He, Xihuan; Lyu, Shaojun; Weng, Hao

2015-10-01

To evaluate the effect of auscultation, partial pressure of carbon dioxide in end-expiration (P(ET)CO2), transillumination technique to judge whether the endotracheal tube is misplaced into the esophagus. A blinded randomized controlled trial was conducted. Sixty patients with American Society of Anesthesiology (ASA) grade I - II undergoing endotracheal intubation in Fengxian Central Hospital admitted from September 2014 to February 2015 were enrolled. Two endotracheal tubes with the same size were respectively inserted into the trachea and esophagus for the same depth after general anesthesia by the same person. Two blinded anesthetists with different experience checked the tube position using three methods including auscultation, P(ET)CO2, and transillumination technique, respectively. The order of the tubes tested (trachea or esophagus) and the method used were randomized according to randomise numbers table. The experienced anesthetists conducted the test first, followed by an inexperienced anesthetist conducting the same methods. The numbers of right and wrong determinations with different methods by different anesthetists were recorded. Sixty patients underwent the procedures for 180 times, with intratracheal intubation for 90 times, and esophageal intubation for 90 times. It was shown that the results were not different in two groups [96.7% (174/180) vs. 92.2% (166/180), χ2 = 3.500, P = 0.057]. By using auscultation, the correct rate of experienced anesthetist was higher than that of inexperienced (95.0% vs. 78.3%, χ2 = 5.786, P = 0.013). Using P(ET)CO2, both anesthetists were correct in all cases, and the accuracy was 100%. Using transillumination, the experienced anesthetist was mistaken in 3 cases (accuracy was 95.0%), while the inexperienced mistook in 1 case (accuracy was 98.3%), and no significant difference was found between two groups χ2 = 0.500, P = 0.250). The correct rate of using transillumination was significantly higher than that of using auscultation χ2 = 7.563, P = 0.004). The sensitivity and specificity of the auscultation was 70.0% and 80.0%, that of transillumination technique was 96.7% and 93.3%, and P(ET)CO2 was 100%, respectively, for two groups. P(ET)CO2 is the most reliable method for determining tube position, and it is superior to auscultation and transillumination. Transillumination technique is superior to auscultation, irrespective of anesthetists' experience, while the accuracy of auscultation showed an obvious relationship with the anesthetists' experience.

A new technique for monitoring the water vapor in the atmosphere

NASA Technical Reports Server (NTRS)

Black, H. D.; Eisner, A.

1984-01-01

In the correction of satellite Doppler data for tropospheric effects the precipitable water vapor (PWV) is inferred at the tracking site. The technique depends on: (1) an ephemeris for the satellite; (2) an analytic model for the refraction range effect that is good to a few centimeters; (3) Doppler data with noise level below 10 centimeters; and (4) a surface pressure/temperature measurement at the tracking site. The PWV is a by product of the computation necessary to correct the Doppler data for tropospheric effects. A formulation of the refraction integral minimizes the necessity for explicit water vapor, temperature and pressure profiles.

Investigation of supersonic jet plumes using an improved two-equation turbulence model

NASA Technical Reports Server (NTRS)

Lakshmanan, B.; Abdol-Hamid, Khaled S.

1994-01-01

Supersonic jet plumes were studied using a two-equation turbulence model employing corrections for compressible dissipation and pressure-dilatation. A space-marching procedure based on an upwind numerical scheme was used to solve the governing equations and turbulence transport equations. The computed results indicate that two-equation models employing corrections for compressible dissipation and pressure-dilatation yield improved agreement with the experimental data. In addition, the numerical study demonstrates that the computed results are sensitive to the effect of grid refinement and insensitive to the type of velocity profiles used at the inflow boundary for the cases considered in the present study.

Achieving Political Trans-Correctness: Integrating Sensitivity and Authenticity in Diversity Management Education

ERIC Educational Resources Information Center

Avery, Derek R.; Steingard, David S.

2008-01-01

Due to mounting pressures to avoid offending individuals on the basis of demographic group membership, political correctness has begun to restrict student participation in our diversity courses. This restriction diminishes what can be learned from class dialogue, an important component of diversity instruction. This article offers a model of…

Laser-driven shock compression of gold foam in the terapascal pressure range

NASA Astrophysics Data System (ADS)

Liu, Wei; Duan, Xiaoxi; Jiang, Shaoen; Wang, Zhebin; Sun, Liang; Liu, Hao; Yang, Weiming; Zhang, Huan; Ye, Qing; Wang, Peng; Li, Yulong; Yi, Lin; Dong, Suo

2018-06-01

Shock compression experiments are carried out on gold foam with an initial density of 3.2 g/cm3 through indirectly laser-driven shock waves at the SG-III prototype laser facility. The impedance-matching technique is applied to determine the equation-of-state (EOS) data of the shocked gold foam. A passive shock breakout diagnostic system is employed to obtain the shock velocities in both the standard material and gold foam. The gold foams are compressed to a maximum density of 20 g/cm3 under a shock pressure of about 2 TPa. The effects of the unsteadiness of shock waves on the EOS measurement are quantitatively analyzed and corrected. The correction of unsteady waves, as well as the good planarity of the shock waves and the low preheating of the gold foam, contributes high-confidence EOS data for the gold foam. The corrected experimental data are compared with the Hugoniot states from the SESAME library. The comparison suggests that the database is suitable for describing the states of gold foam with an initial density of 3.2 g/cm3 under a pressure of about 2 TPa.

Mass-induced sea level variations in the Red Sea from steric-corrected altimetry, GRACE, in-situ bottom pressure records, and hydrographic observations

NASA Astrophysics Data System (ADS)

Feng, Wei; Lemoine, Jean-Michel; Zhong, Min; Xu, Houze

2014-05-01

An annual amplitude of ~18 cm mass-induced sea level variations (SLV) in the Red Sea is detected from steric-corrected altimetry and the Gravity Recovery and Climate Experiment (GRACE) satellites from 2003 to 2011, which dominates the mean sea level in the region. Seawater mass variations here generally reach maximum in late January/early February. The steric component of SLV calculated from oceanographic temperature and salinity data is relatively small and peaks about seven months later than mass variations. The phase difference between the steric SLV and the mass-induced SLV indicates that when the Red Sea gains the mass from inflow water in winter, the steric SLV fall, and vice versa in summer. In-situ bottom pressure records in the eastern coast of the Red Sea validate the high mass variability observed by steric-corrected altimetry and GRACE. Furthermore, we compare the horizontal water mass flux in the Red Sea from steric-corrected altimetry and GRACE with that estimated from hydrographic observations.

Preliminary Results of an Altitude-Wind-Tunnel Investigation of an Axial-Flow Gas Turbine-Propeller Engine. 4; Compressor and Turbine Performance Characteristics

NASA Technical Reports Server (NTRS)

Wallner, Lewis E.; Saari, Martin J.

1948-01-01

As part of an investigation of the performance and operational characteristics of the axial-flow gas turbine-propeller engine, conducted in the Cleveland altitude wind tunnel, the performance characteristics of the compressor and the turbine were obtained. The data presented were obtained at a compressor-inlet ram-pressure ratio of 1.00 for altitudes from 5000 to 35,000 feet, engine speeds from 8000 to 13,000 rpm, and turbine-inlet temperatures from 1400 to 2100 R. The highest compressor pressure ratio obtained was 6.15 at a corrected air flow of 23.7 pounds per second and a corrected turbine-inlet temperature of 2475 R. Peak adiabatic compressor efficiencies of about 77 percent were obtained near the value of corrected air flow corresponding to a corrected engine speed of 13,000 rpm. This maximum efficiency may be somewhat low, however, because of dirt accumulations on the compressor blades. A maximum adiabatic turbine efficiency of 81.5 percent was obtained at rated engine speed for all altitudes and turbine-inlet temperatures investigated.

Preliminary Results of an Altitude-Wind-Tunnel Investigation of a TG-100A Gas Turbine-Propeller Engine. 4; Compressor and Turbine Performance Characteristics

NASA Technical Reports Server (NTRS)

Wallner, Lewis E.; Saari, Martin J.

1947-01-01

As part of an investigation of the performance and operational characteristics of the TG-100A gas turbine-propeller engine, conducted in the Cleveland altitude wind tunnel, the performance characteristics of the compressor and the turbine were obtained. The data presented were obtained at a compressor-inlet ram-pressure ratio of 1.00 for altitudes from 5000 to 35,000 feet, engine speeds from 8000 to 13,000 rpm, and turbine-inlet temperatures from 1400 to 2100R. The highest compressor pressure ratio was 6.15 at a corrected air flow of 23.7 pounds per second and a corrected turbine-inlet temperature of 2475R. Peak adiabatic compressor efficiencies of about 77 percent were obtained near the value of corrected air flow corresponding to a corrected engine speed of 13,000 rpm. This maximum efficiency may be somewhat low, however, because of dirt accumulations on the compressor blades. A maximum adiabatic turbine efficiency of 81.5 percent was obtained at rated engine speed for all altitudes and turbine-inlet temperatures investigated.

Estimation Of Rheological Law By Inverse Method From Flow And Temperature Measurements With An Extrusion Die

NASA Astrophysics Data System (ADS)

Pujos, Cyril; Regnier, Nicolas; Mousseau, Pierre; Defaye, Guy; Jarny, Yvon

2007-05-01

Simulation quality is determined by the knowledge of the parameters of the model. Yet the rheological models for polymer are often not very accurate, since the viscosity measurements are made under approximations as homogeneous temperature and empirical corrections as Bagley one. Furthermore rheological behaviors are often traduced by mathematical laws as the Cross or the Carreau-Yasuda ones, whose parameters are fitted from viscosity values, obtained with corrected experimental data, and not appropriate for each polymer. To correct these defaults, a table-like rheological model is proposed. This choice makes easier the estimation of model parameters, since each parameter has the same order of magnitude. As the mathematical shape of the model is not imposed, the estimation process is appropriate for each polymer. The proposed method consists in minimizing the quadratic norm of the difference between calculated variables and measured data. In this study an extrusion die is simulated, in order to provide us temperature along the extrusion channel, pressure and flow references. These data allow to characterize thermal transfers and flow phenomena, in which the viscosity is implied. Furthermore the different natures of data allow to estimate viscosity for a large range of shear rates. The estimated rheological model improves the agreement between measurements and simulation: for numerical cases, the error on the flow becomes less than 0.1% for non-Newtonian rheology. This method couples measurements and simulation, constitutes a very accurate mean of rheology determination, and allows to improve the prediction abilities of the model.

Flash Lamp Integrating Sphere Technique for Measuring the Dynamic Reflectance of Shocked Materials

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

Stevens, Gerald; La Lone, Brandon; Veeser, Lynn

2013-07-08

Accurate reflectance (R) measurements of metals undergoing shock wave compression can benefit high pressure research in several ways. For example, pressure dependent reflectance measurements can be used to deduce electronic band structure, and discrete changes with pressure or temperature may indicate the occurrence of a phase boundary. Additionally, knowledge of the wavelength dependent emissivity (1 -R, for opaque samples) of the metal surface is essential for accurate pyrometric temperature measurement because the radiance is a function of both the temperature and emissivity. We have developed a method for measuring dynamic reflectance in the visible and near IR spectral regions withmore » nanosecond response time and less than 1.5% uncertainty. The method utilizes an integrating sphere fitted with a xenon flash-lamp illumination source. Because of the integrating sphere, the measurements are insensitive to changes in surface curvature or tilt. The in-situ high brightness of the flash-lamp exceeds the sample’s thermal radiance and also enables the use of solid state detectors for recording the reflectance signals with minimal noise. Using the method, we have examined the dynamic reflectance of gallium and tin subjected to shock compression from high explosives. The results suggest significant reflectance changes across phase boundaries for both metals. We have also used the method to determine the spectral emissivity of shock compressed tin at the interface between tin and a LiF window. The results were used to perform emissivity corrections to previous pyrometry data and obtain shock temperatures of the tin/LiF interface with uncertainties of less than 2%.« less

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.

[Differentiation between moisture lesions and pressure ulcers using photographs in a critical area].

PubMed

Valls-Matarín, Josefa; Del Cotillo-Fuente, Mercedes; Pujol-Vila, María; Ribal-Prior, Rosa; Sandalinas-Mulero, Inmaculada

2016-01-01

To identify difficulties for nurses in differentiating between moisture lesions and pressure ulcers, proper classification of pressure ulcers to assess the adequate classification of the Grupo Nacional para el Estudio y Asesoramiento de Úlceras por Presión y Heridas Crónicas (GNEAUPP) and the degree of agreement in the correct assessment by type and category of injury. Cross-sectional study in a critical area during 2014. All nurses who agreed to participate were included. They performed a questionnaire with 14 photographs validated by experts of moisture lesions or pressure ulcers in the sacral area and buttocks, with 6 possible answers: Pressure ulcer category I, II, III, IV, moisture lesions and unknown. Demographics and knowledge of the classification system of the pressure ulcers were collected according to GNEAUPP. It involved 98% of the population (n=56); 98.2% knew the classification system of the GNEAUPP; 35.2% of moisture lesions were considered as pressure ulcers, most of them as a category II (18.9%). The 14.8% of the pressure ulcers photographs were identified as moisture lesions and 16.1% were classified in another category. The agreement between nurses earned a global Kappa index of .38 (95% CI: .29-.57). There are difficulties differentiating between pressure ulcers and moisture lesions, especially within initial categories. Nurses have the perception they know the pressure ulcers classification, but they do not classify them correctly. The degree of concordance in the diagnosis of skin lesions was low. Copyright © 2016 Elsevier España, S.L.U. All rights reserved.

Application of finite element analysis in pre-operative planning for deformity correction of abnormal hip joints--a case series.

PubMed

Rhyu, K H; Kim, Y H; Park, W M; Kim, K; Cho, T-J; Choi, I H

2011-09-01

In experimental and clinical research, it is difficult to directly measure responses in the human body, such as contact pressure and stress in a joint, but finite element analysis (FEA) enables the examination of in vivo responses by contact analysis. Hence, FEA is useful for pre-operative planning prior to orthopaedic surgeries, in order to gain insight into which surgical options will result in the best outcome. The present study develops a numerical simulation technique based on FEA to predict the surgical outcomes of osteotomy methods for the treatment of slipped capital femoral epiphyses. The correlation of biomechanical parameters including contact pressure and stress, for moderate and severe cases, is investigated. For severe slips, a base-of-neck osteotomy is thought to be the most reliable and effective surgical treatment, while any osteotomy may produce dramatic improvement for moderate slips. This technology of pre-operative planning using FEA can provide information regarding biomechanical parameters that might facilitate the selection of optimal osteotomy methods and corresponding surgical options.

Method for analyzing E x B probe spectra from Hall thruster plumes.

PubMed

Shastry, Rohit; Hofer, Richard R; Reid, Bryan M; Gallimore, Alec D

2009-06-01

Various methods for accurately determining ion species' current fractions using E x B probes in Hall thruster plumes are investigated. The effects of peak broadening and charge exchange on the calculated values of current fractions are quantified in order to determine the importance of accounting for them in the analysis. It is shown that both peak broadening and charge exchange have a significant effect on the calculated current fractions over a variety of operating conditions, especially at operating pressures exceeding 10(-5) torr. However, these effects can be accounted for using a simple approximation for the velocity distribution function and a one-dimensional charge exchange correction model. In order to keep plume attenuation from charge exchange below 30%, it is recommended that pz < or = 2, where p is the measured facility pressure in units of 10(-5) torr and z is the distance from the thruster exit plane to the probe inlet in meters. The spatial variation of the current fractions in the plume of a Hall thruster and the error induced from taking a single-point measurement are also briefly discussed.

[PERCUTANEOUS CORRECTION OF FOREFOOT DEFORMITIES IN DIABETIC PATIENTS IN ORDER TO PREVENT PRESSURE SORES - TECHNIQUE AND RESULTS IN 20 CONSECUTIVE PATIENTS].

PubMed

Yassin, Mustafa; Garti, Avraham; Heller, Eyal; Weissbrot, Moshe; Robinson, Dror

2017-04-01

Diabetes mellitus is a 21st century pandemic. Due to life-span prolongation combined with the increased rate of diabetes, a growing population of patients is afflicted with neuropathic foot deformities. Traditional operative repair of these deformities is associated with a high complication rate and relatively common infection incidence. In recent years, in order to prevent these complications, percutaneous deformity correction methods were developed. Description of experience accumulated in treating 20 consecutive patients with diabetic neuropathic foot deformities treated in a percutaneous fashion. A consecutive series of patients treated at our institute for neuropathic foot deformity was assessed according to a standard protocol using the AOFAS forefoot score and the LUMT score performed at baseline as well as at 6 months and 12 months. Treatment related complications were monitored. All procedures were performed in an ambulatory setting using local anesthesia. A total of 12 patients had soft tissue corrections, and 8 had a combined soft tissue and bone correction. Baseline AOFAS score was 48±7 and improved to 73±9 at six months and 75±7 at one year. LUMT score in 11 patients with a chronic wound decreased from 22±4 to 2±1 at one year post-op. One patient required hospitalization due to post-op bleeding. Percutaneous techniques allow deformity correction of diabetic feet, including those with open wounds in an ambulatory setting with a low complication rate.

40 CFR 1065.659 - Removed water correction.

Code of Federal Regulations, 2011 CFR

2011-07-01

... know that saturated water vapor conditions exist. Use good engineering judgment to measure the... absolute pressure based on an alarm set point, a pressure regulator set point, or good engineering judgment... from raw exhaust, you may determine the amount of water based on intake-air humidity, plus a chemical...

40 CFR 1065.659 - Removed water correction.

Code of Federal Regulations, 2010 CFR

2010-07-01

... know that saturated water vapor conditions exist. Use good engineering judgment to measure the... absolute pressure based on an alarm set point, a pressure regulator set point, or good engineering judgment... from raw exhaust, you may determine the amount of water based on intake-air humidity, plus a chemical...

Assessment of noise exposure for basketball sports referees.

PubMed

Masullo, Massimiliano; Lenzuni, Paolo; Maffei, Luigi; Nataletti, Pietro; Ciaburro, Giuseppe; Annesi, Diego; Moschetto, Antonio

2016-01-01

Dosimetric measurements carried out on basketball referees have shown that whistles not only generate very high peak sound pressure levels, but also play a relevant role in determining the overall exposure to noise of the exposed subjects. Because of the peculiar geometry determined by the mutual positions of the whistle, the microphone, and the ear, experimental data cannot be directly compared with existing occupational noise exposure and/or action limits. In this article, an original methodology, which allows experimental results to be reliably compared with the aforementioned limits, is presented. The methodology is based on the use of two correction factors to compensate the effects of the position of the dosimeter microphone (fR) and of the sound source (fS). Correction factors were calculated by means of laboratory measurements for two models of whistles (Fox 40 Classic and Fox 40 Sonik) and for two head orientations (frontal and oblique).Results sho w that for peak sound pressure levels the values of fR and fS, are in the range -8.3 to -4.6 dB and -6.0 to -1.7 dB, respectively. If one considers the Sound Exposure Levels (SEL) of whistle events, the same correction factors are in the range of -8.9 to -5.3 dB and -5.4 to -1.5 dB, respectively. The application of these correction factors shows that the corrected weekly noise exposure level for referees is 80.6 dB(A), which is slightly in excess of the lower action limit of the 2003/10/EC directive, and a few dB below the Recommended Exposure Limit (REL) proposed by the National Institute for Occupational Safety and Health (NIOSH). The corrected largest peak sound pressure level is 134.7 dB(C) which is comparable to the lower action limit of the 2003/10/EC directive, but again substantially lower than the ceiling limit of 140 dB(A) set by NIOSH.

Airframe noise of the DC-9

NASA Technical Reports Server (NTRS)

Bauer, A. B.; Munson, A. G.

1977-01-01

Airframe noise measurements are reported for the DC-9-31 aircraft flown at several speeds and with a number of flap, landing gear, and slat extension configurations. The data are corrected for atmospheric attenuation and spherical divergence, and are presented for an overhead position normalized to a 1-meter height. The sound pressure levels are found to vary approximately as the fifth power of flight velocity. Both lift and drag dipoles exist as a significant part of the airframe noise. The data are compared with airframe noise predictions using the drag element and the data analysis methods. Although some of the predictions are very good, further work is needed to refine these methods, particularly for the gear-down and flaps-down configurations.

A Method for Computing Leading-Edge Loads

NASA Technical Reports Server (NTRS)

Rhode, Richard V; Pearson, Henry A

1933-01-01

In this report a formula is developed that enables the determination of the proper design load for the portion of the wing forward of the front spar. The formula is inherently rational in concept, as it takes into account the most important variables that affect the leading-edge load, although theoretical rigor has been sacrificed for simplicity and ease of application. Some empirical corrections, based on pressure distribution measurements on the PW-9 and M-3 airplanes have been introduced to provide properly for biplanes. Results from the formula check experimental values in a variety of cases with good accuracy in the critical loading conditions. The use of the method for design purposes is therefore felt to be justified and is recommended.

A Navier-Stokes Solution of Hull-Ring Wing-Thruster Interaction

NASA Technical Reports Server (NTRS)

Yang, C.-I.; Hartwich, P.; Sundaram, P.

1991-01-01

Navier-Stokes simulations of high Reynolds number flow around an axisymmetric body supported in a water tunnel were made. The numerical method is based on a finite-differencing high resolution second-order accurate implicit upwind scheme. Four different configurations were investigated, these are: (1) barebody; (2) body with an operating propeller; (3) body with a ring wing; and (4) body with a ring wing and an operating propeller. Pressure and velocity components near the stern region were obtained computationally and are shown to compare favorably with the experimental data. The method correctly predicts the existence and extent of stern flow separation for the barebody and the absence of flow separation for the three other configurations with ring wing and/or propeller.

A predictor-corrector scheme for vortex identification

NASA Technical Reports Server (NTRS)

Singer, Bart A.; Banks, David C.

1994-01-01

A new algorithm for identifying and characterizing vortices in complex flows is presented. The scheme uses both the vorticity and pressure fields. A skeleton line along the center of a vortex is produced by a two-step predictor-corrector scheme. The technique uses the vector field to move in the direction of the skeleton line and the scalar field to correct the location in the plane perpendicular to the skeleton line. A general vortex cross section can be concisely defined with five parameters at each point along the skeleton line. The details of the method and examples of its use are discussed.

Resolving the nanostructure of plasma-enhanced chemical vapor deposited nanocrystalline SiOx layers for application in solar cells

NASA Astrophysics Data System (ADS)

Klingsporn, M.; Kirner, S.; Villringer, C.; Abou-Ras, D.; Costina, I.; Lehmann, M.; Stannowski, B.

2016-06-01

Nanocrystalline silicon suboxides (nc-SiOx) have attracted attention during the past years for the use in thin-film silicon solar cells. We investigated the relationships between the nanostructure as well as the chemical, electrical, and optical properties of phosphorous, doped, nc-SiO0.8:H fabricated by plasma-enhanced chemical vapor deposition. The nanostructure was varied through the sample series by changing the deposition pressure from 533 to 1067 Pa. The samples were then characterized by X-ray photoelectron spectroscopy, spectroscopic ellipsometry, Raman spectroscopy, aberration-corrected high-resolution transmission electron microscopy, selected-area electron diffraction, and a specialized plasmon imaging method. We found that the material changed with increasing pressure from predominantly amorphous silicon monoxide to silicon dioxide containing nanocrystalline silicon. The nanostructure changed from amorphous silicon filaments to nanocrystalline silicon filaments, which were found to cause anisotropic electron transport.

Space Satellite Dynamics with Applications to Sunlight Pressure Attitude Control. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Stuck, B. W.

1972-01-01

A research program into three aspects of space satellite dynamics was carried out. First, a four-dimensional space-time formulation of Newtonian mechanics is developed. This theory allows a new physical interpretation of the conservation theorems of mechanics first derived rigorously by Noether. Second, a new concept for estimating the three angles which specify the orientation in space of a rigid body is presented. Two separate methods for implementing this concept are discussed, one based on direction cosines, the other on quaternions. Two examples are discussed: constant orientation in space, and constant rate of change of the three angles with time. Third, two synchronous equatorial orbit communication satellite designs which use sunlight pressure to control their attitude are analyzed. Each design is equipped with large reflecting surfaces, called solar sails, which can be canted in different directions to generate torques to correct pointing errors.

A new flux splitting scheme

NASA Technical Reports Server (NTRS)

Liou, Meng-Sing; Steffen, Christopher J., Jr.

1993-01-01

A new flux splitting scheme is proposed. The scheme is remarkably simple and yet its accuracy rivals and in some cases surpasses that of Roe's solver in the Euler and Navier-Stokes solutions performed in this study. The scheme is robust and converges as fast as the Roe splitting. An approximately defined cell-face advection Mach number is proposed using values from the two straddling cells via associated characteristic speeds. This interface Mach number is then used to determine the upwind extrapolation for the convective quantities. Accordingly, the name of the scheme is coined as Advection Upstream Splitting Method (AUSM). A new pressure splitting is introduced which is shown to behave successfully, yielding much smoother results than other existing pressure splittings. Of particular interest is the supersonic blunt body problem in which the Roe scheme gives anomalous solutions. The AUSM produces correct solutions without difficulty for a wide range of flow conditions as well as grids.

A new flux splitting scheme

NASA Technical Reports Server (NTRS)

Liou, Meng-Sing; Steffen, Christopher J., Jr.

1991-01-01

A new flux splitting scheme is proposed. The scheme is remarkably simple and yet its accuracy rivals and in some cases surpasses that of Roe's solver in the Euler and Navier-Stokes solutions performed in this study. The scheme is robust and converges as fast as the Roe splitting. An approximately defined cell-face advection Mach number is proposed using values from the two straddling cells via associated characteristic speeds. This interface Mach number is then used to determine the upwind extrapolation for the convective quantities. Accordingly, the name of the scheme is coined as Advection Upstream Splitting Method (AUSM). A new pressure splitting is introduced which is shown to behave successfully, yielding much smoother results than other existing pressure splittings. Of particular interest is the supersonic blunt body problem in which the Roe scheme gives anomalous solutions. The AUSM produces correct solutions without difficulty for a wide range of flow conditions as well as grids.

Hemodynamic monitoring in the critically ill.

PubMed

Voga, G

1995-06-01

Monitoring of vital functions is one of the most important and essential tools in the management of critically ill patients in the ICU. Today it is possible to detect and analyze a great variety of physiological signals by various noninvasive and invasive techniques. An intensivist should be able to select and perform the most appropriate monitoring method for the individual patient considering risk-benefit ratio of the particular monitoring technique and the need for immediate therapy, specific diagnosis, continuous monitoring and evaluation of morphology should be included. Despite rapid development of noninvasive monitoring techniques, invasive hemodynamic monitoring in still one of the most basic ICU procedures. It enables monitoring of pressures, flow and saturation, pressures in the systemic and pulmonary circulation, estimation of cardiac performance and judgment of the adequacy of the cardiocirculatory system. Carefully and correctly obtained information are basis for proper hemodynamic assessment which usually effects the therapeutic decisions.

Modified Finite Particle Methods for Stokes problems

NASA Astrophysics Data System (ADS)

Montanino, A.; Asprone, D.; Reali, A.; Auricchio, F.

2018-04-01

The Modified Finite Particle Method (MFPM) is a numerical method belonging to the class of meshless methods, nowadays widely investigated due to their characteristic of being capable to easily model large deformation and fluid-dynamic problems. Here we use the MFPM to approximate the Stokes problem. Since the classical formulation of the Stokes problem may lead to pressure spurious oscillations, we investigate alternative formulations and focus on how MFPM discretization behaves in those situations. Some of the investigated formulations, in fact, do not enforce strongly the incompressibility constraint, and therefore an important issue of the present work is to verify if the MFPM is able to correctly reproduce the incompressibility in those cases. The numerical results show that for the formulations in which the incompressibility constraint is properly satisfied from a numerical point of view, the expected second-order is achieved, both in static and in dynamic problems.

Improved Convergence and Robustness of USM3D Solutions on Mixed-Element Grids

NASA Technical Reports Server (NTRS)

Pandya, Mohagna J.; Diskin, Boris; Thomas, James L.; Frink, Neal T.

2016-01-01

Several improvements to the mixed-element USM3D discretization and defect-correction schemes have been made. A new methodology for nonlinear iterations, called the Hierarchical Adaptive Nonlinear Iteration Method, has been developed and implemented. The Hierarchical Adaptive Nonlinear Iteration Method provides two additional hierarchies around a simple and approximate preconditioner of USM3D. The hierarchies are a matrix-free linear solver for the exact linearization of Reynolds-averaged Navier-Stokes equations and a nonlinear control of the solution update. Two variants of the Hierarchical Adaptive Nonlinear Iteration Method are assessed on four benchmark cases, namely, a zero-pressure-gradient flat plate, a bump-in-channel configuration, the NACA 0012 airfoil, and a NASA Common Research Model configuration. The new methodology provides a convergence acceleration factor of 1.4 to 13 over the preconditioner-alone method representing the baseline solver technology.

Improved Convergence and Robustness of USM3D Solutions on Mixed-Element Grids

NASA Technical Reports Server (NTRS)

Pandya, Mohagna J.; Diskin, Boris; Thomas, James L.; Frinks, Neal T.

2016-01-01

Several improvements to the mixed-elementUSM3Ddiscretization and defect-correction schemes have been made. A new methodology for nonlinear iterations, called the Hierarchical Adaptive Nonlinear Iteration Method, has been developed and implemented. The Hierarchical Adaptive Nonlinear Iteration Method provides two additional hierarchies around a simple and approximate preconditioner of USM3D. The hierarchies are a matrix-free linear solver for the exact linearization of Reynolds-averaged Navier-Stokes equations and a nonlinear control of the solution update. Two variants of the Hierarchical Adaptive Nonlinear Iteration Method are assessed on four benchmark cases, namely, a zero-pressure-gradient flat plate, a bump-in-channel configuration, the NACA 0012 airfoil, and a NASA Common Research Model configuration. The new methodology provides a convergence acceleration factor of 1.4 to 13 over the preconditioner-alone method representing the baseline solver technology.

Dynamical generation of a repulsive vector contribution to the quark pressure

NASA Astrophysics Data System (ADS)

Restrepo, Tulio E.; Macias, Juan Camilo; Pinto, Marcus Benghi; Ferrari, Gabriel N.

2015-03-01

Lattice QCD results for the coefficient c2 appearing in the Taylor expansion of the pressure show that this quantity increases with the temperature towards the Stefan-Boltzmann limit. On the other hand, model approximations predict that when a vector repulsion, parametrized by GV, is present this coefficient reaches a maximum just after Tc and then deviates from the lattice predictions. Recently, this discrepancy has been used as a guide to constrain the (presently unknown) value of GV within the framework of effective models at large Nc (LN). In the present investigation we show that, due to finite Nc effects, c2 may also develop a maximum even when GV=0 since a vector repulsive term can be dynamically generated by exchange-type radiative corrections. Here we apply the optimized perturbation theory (OPT) method to the two-flavor Polyakov-Nambu-Jona-Lasinio model (at GV=0 ) and compare the results with those furnished by lattice simulations and by the LN approximation at GV=0 and also at GV≠0 . The OPT numerical results for c2 are impressively accurate for T ≲1.2 Tc but, as expected, they predict that this quantity develops a maximum at high T . After identifying the mathematical origin of this extremum we argue that such a discrepant behavior may naturally arise within this type of effective quark theories (at GV=0 ) whenever the first 1 /Nc corrections are taken into account. We then interpret this hypothesis as an indication that beyond the large-Nc limit the correct high-temperature (perturbative) behavior of c2 will be faithfully described by effective models only if they also mimic the asymptotic freedom phenomenon.

Pressure activated interconnection of micro transfer printed components

NASA Astrophysics Data System (ADS)

Prevatte, Carl; Guven, Ibrahim; Ghosal, Kanchan; Gomez, David; Moore, Tanya; Bonafede, Salvatore; Raymond, Brook; Trindade, António Jose; Fecioru, Alin; Kneeburg, David; Meitl, Matthew A.; Bower, Christopher A.

2016-05-01

Micro transfer printing and other forms of micro assembly deterministically produce heterogeneously integrated systems of miniaturized components on non-native substrates. Most micro assembled systems include electrical interconnections to the miniaturized components, typically accomplished by metal wires formed on the non-native substrate after the assembly operation. An alternative scheme establishing interconnections during the assembly operation is a cost-effective manufacturing method for producing heterogeneous microsystems, and facilitates the repair of integrated microsystems, such as displays, by ex post facto addition of components to correct defects after system-level tests. This letter describes pressure-concentrating conductor structures formed on silicon (1 0 0) wafers to establish connections to preexisting conductive traces on glass and plastic substrates during micro transfer printing with an elastomer stamp. The pressure concentrators penetrate a polymer layer to form the connection, and reflow of the polymer layer bonds the components securely to the target substrate. The experimental yield of series-connected test systems with >1000 electrical connections demonstrates the suitability of the process for manufacturing, and robustness of the test systems against exposure to thermal shock, damp heat, and mechanical flexure shows reliability of the resulting bonds.

Cost-Effectiveness Analysis of Plasma Versus Recombinant Factor VIIa for Placing Intracranial Pressure Monitors in Pretransplant Patients With Acute Liver Failure.

PubMed

Pham, Huy P; Sireci, Anthony N; Kim, Chong H; Schwartz, Joseph

2014-09-01

Both plasma- and recombinant activated factor VII (rFVIIa)-based algorithms can be used to correct coagulopathy in preliver transplant patients with acute liver failure requiring intracranial pressure monitor (ICPM) placement. A decision model was created to compare the cost-effectiveness of these methods. A 70-kg patient could receive either 1 round of plasma followed by coagulation testing or 2 units of plasma and 40 μg/kg rFVIIa. Intracranial pressure monitor is placed without coagulation testing after rFVIIa administration. In the plasma algorithm, the probability of ICPM placement was estimated based on expected international normalized ratio (INR) after plasma administration. Risks of rFVIIa thrombosis and transfusion reactions were also included. The model was run for patients with INRs ranging from 2 to 6 with concomitant adjustments to model parameters. The model supported the initial use of rFVIIa for ICPM placement as a cost-effective treatment when INR ≥2 (with incremental cost-effectiveness ratio of at most US$7088.02). © The Author(s) 2014.

[New concepts for pressure-controlled glaucoma implants].

PubMed

Allemann, R; Stachs, O; Falke, K; Schmidt, W; Siewert, S; Sternberg, K; Chichkov, B; Wree, A; Schmitz, K-P; Guthoff, R F

2013-08-01

In industrialized countries glaucoma is one of the most common causes that leads to blindness. It is also the most common cause of irreversible blindness worldwide. In addition to local treatment of intraocular pressure and filtering glaucoma surgery, alloplastic implants are increasingly being used in glaucoma therapy. As long-term results published in the literature of commonly used implants are unsatisfactory, it seems useful to search for new concepts. In order to avoid the well-known short-term and long-term postoperative complications a pressure-controlled microstent with antiproliferative surface modifications was developed. Additionally, the functionality of such a microstent should be investigated using an animal glaucoma model. This paper describes the concept of a microstent which drains aquous humour from the anterior chamber into the suprachoroidal space. In addition, the glaucoma models described in the literature are discussed. Unfortunately, none of the methods could be reproduced permanently. First results show a correct implantation of a coated microstent with valve where the anti-proliferative effect could be demonstrated histologically. The promising results should lead to further investigations and the final goal will be the testing of the stent in the human eye.

Three-Dimensional Numerical Simulation of Airflow in Nasopharynx.

NASA Astrophysics Data System (ADS)

Shome, Biswadip; Wang, Lian-Ping; Santare, Michael H.; Szeri, Andras Z.; Prasad, Ajay K.; Roberts, David

1996-11-01

A three-dimensional numerical simulation of airflow in nasopharynx (from the soft palate to the epiglottis) was conducted, using anatomically accurate model and finite element method, to study the influence of flow characteristics on obstructive sleep apnea (OSA). The results showed that the pressure drop in the nasopharynx is in the range 200-500 Pa. Ten different nasopharynx geometries resulting from three OSA treatment therapies (CPAP, mandibular repositioning devices, and surgery) were compared. The results confirmed that the airflow in the nasopharynx lies in the transitional flow regime and thus, a subtle change in the morphology caused by these treatment therapies has a large effect on the airflow. The onset of turbulence can cause as much as 40% of increase in pressure drop. For the transitional flow regime, the k-ɛ turbulence model was found to be the most appropriate model, when compared to the mixing length and the k-ω model, as it correctly reproduces the limiting laminar behavior. In addition, the pressure drop increased approximately as the square of the volumetric flow rate. Supported by NIH.

Tuneable diode laser spectroscopy correction factor investigation on ammonia measurement

NASA Astrophysics Data System (ADS)

Li, Nilton; El-Hamalawi, Ashraf; Baxter, Jim; Barrett, Richard; Wheatley, Andrew

2018-01-01

Current diesel engine aftertreatment systems, such as Selective Catalyst Reduction (SCR) use ammonia (NH3) to reduce Nitrogen Oxides (NOx) into Nitrogen (N2) and water (H2O). However, if the reaction between NH3 and NOx is unbalanced, it can lead either NH3 or NOx being released into the environment. As NH3 is classified as a dangerous compound in the environment, its accurate measurement is essential. Tuneable Diode Laser (TDL) spectroscopy is one of the methods used to measure raw emissions inside engine exhaust pipes, especially NH3. This instrument requires a real-time exhaust temperature, pressure and other interference compounds in order to adjust itself to reduce the error in NH3 readings. Most researchers believed that exhaust temperature and pressure were the most influential factors in TDL when measuring NH3 inside exhaust pipes. The aim of this paper was to quantify these interference effects on TDL when undertaking NH3 measurement. Surprisingly, the results show that pressure was the least influential factor when compared to temperature, H2O, CO2 and O2 when undertaking NH3 measurement using TDL.

A high-resolution Godunov method for compressible multi-material flow on overlapping grids

NASA Astrophysics Data System (ADS)

Banks, J. W.; Schwendeman, D. W.; Kapila, A. K.; Henshaw, W. D.

2007-04-01

A numerical method is described for inviscid, compressible, multi-material flow in two space dimensions. The flow is governed by the multi-material Euler equations with a general mixture equation of state. Composite overlapping grids are used to handle complex flow geometry and block-structured adaptive mesh refinement (AMR) is used to locally increase grid resolution near shocks and material interfaces. The discretization of the governing equations is based on a high-resolution Godunov method, but includes an energy correction designed to suppress numerical errors that develop near a material interface for standard, conservative shock-capturing schemes. The energy correction is constructed based on a uniform-pressure-velocity flow and is significant only near the captured interface. A variety of two-material flows are presented to verify the accuracy of the numerical approach and to illustrate its use. These flows assume an equation of state for the mixture based on the Jones-Wilkins-Lee (JWL) forms for the components. This equation of state includes a mixture of ideal gases as a special case. Flow problems considered include unsteady one-dimensional shock-interface collision, steady interaction of a planar interface and an oblique shock, planar shock interaction with a collection of gas-filled cylindrical inhomogeneities, and the impulsive motion of the two-component mixture in a rigid cylindrical vessel.

Final report on supplementary comparison APMP.M.P-S6 in gas gauge pressure from 10 MPa to 100 MPa

NASA Astrophysics Data System (ADS)

Kajikawa, Hiroaki; Olson, Douglas A.; Iizumi, Hideaki; Driver, Robert Greg; Kojima, Momoko

2016-01-01

A supplementary comparison of gas high-pressure standards was conducted between the National Metrology Institute of Japan (NMIJ/AIST) and the National Institute of Standards and Technology (NIST), within the framework of the Asia-Pacific Metrology Programme (APMP), in order to determine their degrees of equivalence in the pressure range from 10 MPa to 100 MPa in gauge mode. The pilot institute was NMIJ/AIST. The measurements were carried out from July 2014 to October 2014. Both participating institutes used pressure balances as their pressure standards. Different gases were used for the pressure medium: NMIJ/AIST used Nitrogen, while NIST used Helium. A set of two pressure monitors was used as the transfer standard. The pressure monitors were found sufficiently stable during the measurements. Characteristics of the pressure monitors were evaluated at the pilot institute, and then used for data corrections and uncertainty estimations. In particular, the effect of the gas medium on the pressure monitors was found to be significant, and then all the measurement data were corrected to those with Nitrogen. The degrees of equivalence between the two institutes were evaluated by the relative differences of the participant's results and their associated expanded (k = 2) uncertainties. The gas pressure standards in the range 10 MPa to 100 MPa for gauge mode of the two participating institutes were found to be equivalent within their claimed uncertainties. 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).

Empirical source strength correlations for rans-based acoustic analogy methods

NASA Astrophysics Data System (ADS)

Kube-McDowell, Matthew Tyndall

JeNo is a jet noise prediction code based on an acoustic analogy method developed by Mani, Gliebe, Balsa, and Khavaran. Using the flow predictions from a standard Reynolds-averaged Navier-Stokes computational fluid dynamics solver, JeNo predicts the overall sound pressure level and angular spectra for high-speed hot jets over a range of observer angles, with a processing time suitable for rapid design purposes. JeNo models the noise from hot jets as a combination of two types of noise sources; quadrupole sources dependent on velocity fluctuations, which represent the major noise of turbulent mixing, and dipole sources dependent on enthalpy fluctuations, which represent the effects of thermal variation. These two sources are modeled by JeNo as propagating independently into the far-field, with no cross-correlation at the observer location. However, high-fidelity computational fluid dynamics solutions demonstrate that this assumption is false. In this thesis, the theory, assumptions, and limitations of the JeNo code are briefly discussed, and a modification to the acoustic analogy method is proposed in which the cross-correlation of the two primary noise sources is allowed to vary with the speed of the jet and the observer location. As a proof-of-concept implementation, an empirical correlation correction function is derived from comparisons between JeNo's noise predictions and a set of experimental measurements taken for the Air Force Aero-Propulsion Laboratory. The empirical correlation correction is then applied to JeNo's predictions of a separate data set of hot jets tested at NASA's Glenn Research Center. Metrics are derived to measure the qualitative and quantitative performance of JeNo's acoustic predictions, and the empirical correction is shown to provide a quantitative improvement in the noise prediction at low observer angles with no freestream flow, and a qualitative improvement in the presence of freestream flow. However, the results also demonstrate that there are underlying flaws in JeNo's ability to predict the behavior of a hot jet's acoustic signature at certain rear observer angles, and that this correlation correction is not able to correct these flaws.

Sociology: a view from the diaspora.

PubMed

Rosenfeld, Richard

2010-12-01

From the vantage point of criminology, one of sociology's main export subject areas, the present and future of sociology appear a good deal more promising than John Holmwood's essay on the discipline's misfortune would suggest. Sociology remains in high demand by students and faculty hiring remains strong, even in its more critical sub-fields, such as race and ethnicity, sex and gender, and social inequality. Holmwood is correct that sociology is vulnerable to external pressures to demonstrate its relevance to social practice, but those pressures come from left-wing social movements as well as from centres of power. He is also correct that external pressures contribute to internal disagreement, but sociology has been at war with itself since the 1960s, with little evident decline in its academic standing or intellectual vitality. Those of us on the discipline's diaspora, who depend on sociology for both support and light, must remain hopeful about sociology's continued good fortune.

Analysis of fatigue reliability for high temperature and high pressure multi-stage decompression control valve

NASA Astrophysics Data System (ADS)

Yu, Long; Xu, Juanjuan; Zhang, Lifang; Xu, Xiaogang

2018-03-01

Based on stress-strength interference theory to establish the reliability mathematical model for high temperature and high pressure multi-stage decompression control valve (HMDCV), and introduced to the temperature correction coefficient for revising material fatigue limit at high temperature. Reliability of key dangerous components and fatigue sensitivity curve of each component are calculated and analyzed by the means, which are analyzed the fatigue life of control valve and combined with reliability theory of control valve model. The impact proportion of each component on the control valve system fatigue failure was obtained. The results is shown that temperature correction factor makes the theoretical calculations of reliability more accurate, prediction life expectancy of main pressure parts accords with the technical requirements, and valve body and the sleeve have obvious influence on control system reliability, the stress concentration in key part of control valve can be reduced in the design process by improving structure.