Development of a Pressure Box to Evaluate Reusable-Launch-Vehicle Cryogenic-Tank Panels

NASA Technical Reports Server (NTRS)

Ambur, Damodar R.; Sikora, Joseph; Maguire, James F.; Winn, Peter M.

1996-01-01

A cryogenic pressure-box test machine has been designed and is being developed to test full-scale reusable-launch-vehicle cryogenic-tank panels. This machine is equipped with an internal pressurization system, a cryogenic cooling system, and a heating system to simulate the mechanical and thermal loading conditions that are representative of a reusable-launch-vehicle mission profile. The cryogenic cooling system uses liquid helium and liquid nitrogen to simulate liquid hydrogen and liquid oxygen tank internal temperatures. A quartz lamp heating system is used for heating the external surface of the test panels to simulate cryogenic-tank external surface temperatures during re-entry of the launch vehicle. The pressurization system uses gaseous helium and is designed to be controlled independently of the cooling system. The tensile loads in the axial direction of the test panel are simulated by means of hydraulic actuators and a load control system. The hoop loads in the test panel are reacted by load-calibrated turnbuckles attached to the skin and frame elements of the test panel. The load distribution in the skin and frames can be adjusted to correspond to the tank structure by using these turnbuckles. The seal between the test panel and the cryogenic pressure box is made from a reinforced Teflon material which can withstand pressures greater than 52 psig at cryogenic temperatures. Analytical results and tests on prototype test components indicate that most of the cryogenic-tank loading conditions that occur in flight can be simulated in the cryogenic pressure-box test machine.

Handbook of structural stability part VI : strength of stiffened curved plates and shells

NASA Technical Reports Server (NTRS)

Becker, Herbert

1958-01-01

A comprehensive review of failure of stiffened curved plates and shells is presented. Panel instability in stiffened curved plates and general instability of stiffened cylinders are discussed. The loadings considered for the plates are axial, shear, and the combination of the two. For the cylinders, bending, external pressure, torsion, transverse shear, and combinations of these loads are considered. When possible, test data and theory were correlated. General instability in stiffened cylinders was investigated. For bending and torsion loads, test data and theory were correlated. For external pressure several existing theories were compared. As a result of this investigation a unified theoretical approach to analysis of general instability in stiffened cylinders was developed. (author)

Externally Pressurized Journal Gas Bearings

NASA Technical Reports Server (NTRS)

Laub, John H.

1959-01-01

Externally pressurized gas-lubricated bearings with multiple orifice feed are investigated. An analytical treatment is developed for a semi-cylindrical bearing with 9 orifices and for a cylindrical journal bearing with 192 radial and 24 axial orifices. Experiments are described on models of the two bearing configurations with specially designed fixtures which incorporate pneumatic loading and means for determining pressure profiles, gas flow and gap height. The correlation between theory and experiment is satisfactory.

Effects of external loads on balance control during upright stance: experimental results and model-based predictions.

PubMed

Qu, Xingda; Nussbaum, Maury A

2009-01-01

The purpose of this study was to identify the effects of external loads on balance control during upright stance, and to examine the ability of a new balance control model to predict these effects. External loads were applied to 12 young, healthy participants, and effects on balance control were characterized by center-of-pressure (COP) based measures. Several loading conditions were studied, involving combinations of load mass (10% and 20% of individual body mass) and height (at or 15% of stature above the whole-body COM). A balance control model based on an optimal control strategy was used to predict COP time series. It was assumed that a given individual would adopt the same neural optimal control mechanisms, identified in a no-load condition, under diverse external loading conditions. With the application of external loads, COP mean velocity in the anterior-posterior direction and RMS distance in the medial-lateral direction increased 8.1% and 10.4%, respectively. Predicted COP mean velocity and RMS distance in the anterior-posterior direction also increased with external loading, by 11.1% and 2.9%, respectively. Both experimental COP data and model-based predictions provided the same general conclusion, that application of larger external loads and loads more superior to the whole body center of mass lead to less effective postural control and perhaps a greater risk of loss of balance or falls. Thus, it can be concluded that the assumption about consistency in control mechanisms was partially supported, and it is the mechanical changes induced by external loads that primarily affect balance control.

Dynamic considerations for composite metal-rubber laminate acoustic power coupling bellows with application to thermoacoustic refrigeration

NASA Astrophysics Data System (ADS)

Smith, Robert William

Many electrically driven thermoacoustic refrigerators have employed corrugated metal bellows to couple work from an electro-mechanical transducer to the working fluid typically. An alternative bellows structure to mediate this power transfer is proposed: a laminated hollow cylinder comprised of alternating layers of rubber and metal 'hoop-stack'. Fatigue and visoelastic power dissipation in the rubber are critical considerations; strain energy density plays a role in both. Optimal aspect ratios for a rectangle corss-section in the rubber, for given values of bellows axial strain and oscillatory pressure loads are discussed. Comparisons of tearing energies estimated from known load cases and those obtained by finite element analysis for candidate dimensions are presented. The metal layers of bellows are subject to an out-of-plane buckling instability for the case of external pressure loading; failure of this type was experimentally observed. The proposed structure also exhibits column instability when subject to internal pressure, as do metal bellows. For hoop-stack bellows, shear deflection cannot be ignored and this leads to column instability for both internal and external pressures, the latter being analogous to the case of tension buckling of a beam. During prototype bellows testing, transverse modes of vibration are believed to have been excited parametrically as a consequence of the oscillatory pressures. Some operating frequencies of interest in this study lie above the cut-on frequency at which Timoshenko beam theory (TBT) predicts multiple phase speeds; it is shown that TBT fails to accurately predict both mode shapes and resonance frequencies in this regime. TBT is also shown to predict multiple phase speeds in the presence of axial tension, or external pressures, at magnitudes of interest in this study, over the entire frequency spectrum. For modes below cut-on absent a pressure differential (or equivalently, axial load) TBT predicts decreasing resonance frequencies for both internal external static pressure, and converges on known, valid static buckling solutions. Parametric stability in the presence of oscillatory pressure is discussed for such modes; periodic solutions to the Whittaker-Hill equation are pursued to illustrate the shape of the parametric instability regions, and contrasted with results of the more well-known Mathieu equation.

Intraocular pressure reduction and regulation system

NASA Technical Reports Server (NTRS)

Baehr, E. F.; Burnett, J. E.; Felder, S. F.; Mcgannon, W. J.

1979-01-01

An intraocular pressure reduction and regulation system is described and data are presented covering performance in: (1) reducing intraocular pressure to a preselected value, (2) maintaining a set minimum intraocular pressure, and (3) reducing the dynamic increases in intraocular pressure resulting from external loads applied to the eye.

Buckling tests of two 4.6-meter-diameter, magnesium ring-stiffened conical shells loaded under external pressure

NASA Technical Reports Server (NTRS)

Anderson, J. K.; DAVIS R. C.

1973-01-01

Two ring-stiffened magnesium conical shells with a 120 deg apex angle and a 4.6-meter diameter were loaded to failure by a uniform external pressure. The cones differed from one another only in the number of internal stiffening rings. Test specimen details, test procedure, and test results are discussed. Both buckling and prebuckling data are compared with appropriate theoretical predictions. Measured strains in skin and rings agreed well with theoretical predictions. Extensive imperfection measurements were made and reported on both cones in the as fabricated condition.

Investigation of the Loads on a Conventional Front and Rear Sliding Canopy

NASA Technical Reports Server (NTRS)

Dexter, Howard E.; Rickey, Edward A.

1947-01-01

As one phase of a comprehensive canopy load investigation, conventional front and rear sliding canopies which are typified by installation on the SB2C-4E airplane, were tested in the Langley full-scale tunnel to determine the pressure distributions and the aerodynamic loads on the canopies. A preliminary analysis of the results of these tests is presented in this report. Plots are presented that show the distribution of pressure at four longitudinal stations through each canopy for a range of conditions selected to determine the effects of varying canopy position, yaw, lift coefficient, and power. The results indicate that the maximum loads, based on the external-internal pressure differential, for the front and rear canopies were obtained with the airplane simulating the high speed flight condition. The highest loading on the front canopy was in the exploding direction for the configuration with the front and rear canopies closed. The highest loads on the rear canopy were in the crushing direction with the front canopy open and the rear canopy closed. For most of the simulated flight conditions, the highest loads on the front canopy, per unit area, were over twice as great as the highest loads on the rear canopy when the comparison was made for the most critical canopy configuration in each case. The external pressure distribution over the front and rear canopies, which were fairly symmetrical to 0 degree angle of yaw, were greatly distorted at other yaw attitudes, particularly for the propeller operating conditions. These distorted pressure distributions resulted in local exploding and crushing loads on both canopies which were often considerably higher than the average canopy loads.

Intradiscal pressure variation under spontaneous ventilation

NASA Astrophysics Data System (ADS)

Roriz, Paulo; Ferreira, J.; Potes, J. C.; Oliveira, M. T.; Santos, J. L.; Simões, J. A.; Frazão, O.

2014-05-01

The pressure measured in the intervertebral discs is a response to the loads acting on the spine. External loads, such as the reaction forces resulting from locomotion, manual handling and collisions are probably the most relevant in studying spine trauma. However, the physiological functions such as breathing and hearth rate also participate in subtle variations of intradiscal pressure that can be observed only in vivo at resting. Present work is an effort to measure the effect of breathing on intradiscal pressure of an anesthetized sheep.

A generalized force-modified potential energy surface (G-FMPES) for mechanochemical simulations

DOE PAGES

Subramanian, Gopinath; Mathew, Nithin; Leiding, Jeffery A.

2015-10-05

We describe the modifications that a spatially varying external load produces on a Born-Oppenheimer potential energy surface (PES) by calculating static quantities of interest. The effects of the external loads are exemplified using electronic structure calculations (at the HF/6-31G** level) of two different molecules: ethane and hexahydro-1,3,5-trinitro-s-triazine (RDX). The calculated transition states and The Hessian matrices of stationary points show that spatially varying external loads shift the stationary points and modify the curvature of the PES, thereby affecting the harmonic transition rates by altering both the energy barrier as well as the prefactor. The harmonic spectra of both molecules aremore » blue-shifted with increasing compressive “pressure.” Some stationary points on the RDX-PES disappear under application of the external load, indicating the merging of an energy minimum with a saddle point.« less

An analytical study of the effects of transverse shear deformation and anisotropy on buckling loads of laminated cylinders. M.S. Thesis - George Washington Univ.

NASA Technical Reports Server (NTRS)

Jegley, Dawn C.

1987-01-01

Buckling loads of thick-walled orthotropic and anisotropic simply supported circular cylinders are predicted using a higher-order transverse-shear deformation theory. A comparison of buckling loads predicted by the conventional first-order transverse-shear deformation theory and the higher-order theory show that the additional allowance for transverse shear deformation has a negligible effect on the predicted buckling loads of medium-thick metallic isotropic cylinders. However, the higher-order theory predicts buckling loads which are significantly lower than those predicted by the first-order transverse-shear deformation theory for certain short, thick-walled cylinders which have low through-the-thickness shear moduli. A parametric study of the effects of ply orientation on the buckling load of axially compressed cylinders indicates that laminates containing 45 degree plies are most sensitive to transverse-shear deformation effects. Interaction curves for buckling loads of cylinders subjected to axial compressive and external pressure loadings indicate that buckling loads due to external pressure loadings are as sensitive to transverse-shear deformation effects as buckling loads due to axial compressive loadings. The effects of anisotropy are important over a much wider range of cylinder geometries than the effects of transverse shear deformation.

An apparatus for altering the mechanical load of the respiratory system.

PubMed

Younes, M; Bilan, D; Jung, D; Kroker, H

1987-06-01

We describe an apparatus for altering the mechanical load against which the respiratory muscles operate in humans. A closed system incorporates a rolling seal spirometer. The spirometer piston shaft is coupled to a fast-responding linear actuator that develops force in proportion to desired command signals. The command signal may be flow (resistive loading or unloading), volume (elastic loading or unloading), constant voltage (continuous positive or negative pressure), or any external function. Combinations of loads can be applied. Logic circuits permit application of the load at specific times during the respiratory cycle, and the magnitude of the loads is continuously adjustable. Maximum pressure output is +/- 20 cmH2O. The apparatus permits loading or unloading over a range of ventilation extending from resting levels to those observed during high levels of exercise (over 100 l/min). In response to a square-wave input, pressure rises exponentially with a time constant of 20 ms.

14 CFR 23.365 - Pressurized cabin loads.

Code of Federal Regulations, 2010 CFR

2010-01-01

... stress concentrations, must be accounted for. (c) If landings may be made with the cabin pressurized... be designed for the effects of sudden release of pressure in any compartment with external doors or windows. This condition must be investigated for the effects of failure of the largest opening in the...

46 CFR 38.05-3 - Design and construction of pressure vessel type cargo tanks-TB/ALL.

Code of Federal Regulations, 2013 CFR

2013-10-01

... subjected to external loads. Consideration shall also be given to excessive loads that can be imposed on the tanks by their support due to static and dynamic forces under operating conditions or during testing...

46 CFR 38.05-3 - Design and construction of pressure vessel type cargo tanks-TB/ALL.

Code of Federal Regulations, 2011 CFR

2011-10-01

... subjected to external loads. Consideration shall also be given to excessive loads that can be imposed on the tanks by their support due to static and dynamic forces under operating conditions or during testing...

46 CFR 38.05-3 - Design and construction of pressure vessel type cargo tanks-TB/ALL.

Code of Federal Regulations, 2014 CFR

2014-10-01

... subjected to external loads. Consideration shall also be given to excessive loads that can be imposed on the tanks by their support due to static and dynamic forces under operating conditions or during testing...

46 CFR 38.05-3 - Design and construction of pressure vessel type cargo tanks-TB/ALL.

Code of Federal Regulations, 2012 CFR

2012-10-01

... subjected to external loads. Consideration shall also be given to excessive loads that can be imposed on the tanks by their support due to static and dynamic forces under operating conditions or during testing...

Energy Evolution Mechanism and Confining Pressure Effect of Granite under Triaxial Loading-Unloading Cycles

NASA Astrophysics Data System (ADS)

Wang, Hao; Miao, Sheng-jun

2018-05-01

Rock mass undergoes some deformational failure under the action of external loads, a process known to be associated with energy dissipation and release. A triaxial loading-unloading cycle test was conducted on granite in order to investigate the energy evolution pattern of rock mass under the action of external loads. The study results demonstrated: (1) The stress peaks increased by 50% and 22% respectively and the pre-peak weakening became more apparent in the ascending process of the confining pressure from 10MPa to 30MPa; the area enclosed by the hysteresis loop corresponding to 30MPa diminished by nearly 60% than that corresponding to 10MPa, indicating a higher confining pressure prohibits rock mass from plastic deformation and shifts strain toward elastic deformation. (2) In the vicinity of the strength limit, the slope of dissipation energy increased to 1.6 from the original 0.7 and the dissipation energy grew at an accelerating rate, demonstrating stronger propagation and convergence of internal cracks. (3) At a pressure of 70% of the stress peak, the elastic energy of the granite accounted for 88% of its peak value, suggesting the rock mechanical energy from the outside mostly changes into the elastic energy inside the rock, with little energy loss.(4) Prior to test specimen failure, the axial bearing capacity dropped with a decreasing confining pressure in an essentially linear way, and the existence of confirming pressure played a role in stabilizing the axial bearing capacity.

Modeling ARRM Xenon Tank Pressurization Using 1D Thermodynamic and Heat Transfer Equations

NASA Technical Reports Server (NTRS)

Gilligan, Patrick; Tomsik, Thomas

2016-01-01

As a first step in understanding what ground support equipment (GSE) is required to provide external cooling during the loading of 5,000 kg of xenon into 4 aluminum lined composite overwrapped pressure vessels (COPVs), a modeling analysis was performed using Microsoft Excel. The goals of the analysis were to predict xenon temperature and pressure throughout loading at the launch facility, estimate the time required to load one tank, and to get an early estimate of what provisions for cooling xenon might be needed while the tanks are being filled. The model uses the governing thermodynamic and heat transfer equations to achieve these goals. Results indicate that a single tank can be loaded in about 15 hours with reasonable external coolant requirements. The model developed in this study was successfully validated against flight and test data. The first data set is from the Dawn mission which also utilizes solar electric propulsion with xenon propellant, and the second is test data from the rapid loading of a hydrogen cylindrical COPV. The main benefit of this type of model is that the governing physical equations using bulk fluid solid temperatures can provide a quick and accurate estimate of the state of the propellant throughout loading which is much cheaper in terms of computational time and licensing costs than a Computation Fluid Dynamics (CFD) analysis while capturing the majority of the thermodynamics and heat transfer.

Modeling Xenon Tank Pressurization using One-Dimensional Thermodynamic and Heat Transfer Equations

NASA Technical Reports Server (NTRS)

Gilligan, Ryan P.; Tomsik, Thomas M.

2017-01-01

As a first step in understanding what ground support equipment (GSE) is required to provide external cooling during the loading of 5,000 kg of xenon into 4 aluminum lined composite overwrapped pressure vessels (COPVs), a modeling analysis was performed using Microsoft Excel. The goals of the analysis were to predict xenon temperature and pressure throughout loading at the launch facility, estimate the time required to load one tank, and to get an early estimate of what provisions for cooling xenon might be needed while the tanks are being filled. The model uses the governing thermodynamic and heat transfer equations to achieve these goals. Results indicate that a single tank can be loaded in about 15 hours with reasonable external coolant requirements. The model developed in this study was successfully validated against flight and test data. The first data set is from the Dawn mission which also utilizes solar electric propulsion with xenon propellant, and the second is test data from the rapid loading of a hydrogen cylindrical COPV. The main benefit of this type of model is that the governing physical equations using bulk fluid solid temperatures can provide a quick and accurate estimate of the state of the propellant throughout loading which is much cheaper in terms of computational time and licensing costs than a Computation Fluid Dynamics (CFD) analysis while capturing the majority of the thermodynamics and heat transfer.

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

NASA Astrophysics Data System (ADS)

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

2018-01-01

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

Characterization of Engine Control Authority on HCCI Combustion as the High Load Limit is Approached

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

Szybist, James P; Edwards, Kevin Dean; Foster, Matthew

2013-01-01

While the potential emissions and efficiency benefits of homogeneous charge compression ignition (HCCI) combustion are well known, realizing the potentials on a production intent engine presents numerous challenges. In this study we focus on characterizing the authority of the available engine controls as the high load limit of HCCI combustion is approached. The experimental work is performed on a boosted single-cylinder research engine equipped with direct injection (DI) fueling, cooled external exhaust gas recirculation (EGR), and a hydraulic valve actuation (HVA) valve train to enable the negative valve overlap (NVO) breathing strategy. Valve lift and duration are held constant whilemore » phasing is varied in an effort to make the results as relevant as possible to production intent cam-based variable valve actuation (VVA) systems on multi-cylinder engines. Results presented include engine loads from 350 to 650 kPa IMEPnet and manifold pressure from 98 to 190 kPaa at 2000 rpm. It is found that in order to increase engine load to 650 kPa IMEPnet, it is necessary to increase manifold pressure and external EGR while reducing the NVO duration. Both NVO duration and fuel injection timing are effective means of controlling combustion phasing, with NVO duration being a coarse control and fuel injection timing being a fine control. NOX emissions are low throughout the study, with emissions below 0.1 g/kW-h at all boosted HCCI conditions, while good combustion efficiency is maintained (>96.5%). Net indicated thermal efficiency increases with load up to 600 kPa IMEPnet, where a peak efficiency of 41% is achieved. Results of independent parametric investigations are presented on the effect of external EGR, intake effect of manifold pressure, and the effect of NVO duration. It is found that increasing EGR at a constant manifold pressure and increasing manifold pressure at a constant EGR rate both have the effect of retarding combustion phasing. It is also found that combustion phasing becomes increasingly sensitive to NVO duration as engine load increases. Finally, comparisons are made between three commonly used noise metrics (AVL noise meter, ringing intensity (RI), and maximum pressure rise rate (MPRR)). It is found that compared to the AVL noise meter, RI significantly underestimates combustion noise under boosted conditions.« less

Measurement of inspiratory muscle performance with incremental threshold loading: a comparison of two techniques.

PubMed Central

Bardsley, P A; Bentley, S; Hall, H S; Singh, S J; Evans, D H; Morgan, M D

1993-01-01

BACKGROUND--Incremental threshold loading (ITL) is a test of inspiratory muscle performance which is usually performed by breathing through a weighted inspiratory plunger, the load on the inspiratory muscles being increased by externally adding weights to the intake valve. This is not a true threshold device and may be inaccurate. This method was compared with a true threshold device consisting of a solenoid valve which only opens to supply air at a predetermined negative mouth pressure. METHODS--Six naive, normal subjects (three men and three women) aged 22-24 years underwent three tests using each system. The inspiratory loads were increased every minute by equivalent amounts, -10 cm H2O with the solenoid valve and by 50 g with the weighted plunger, until the subjects could not inspire or sustain inspiration for a full minute. Six experienced subjects (four men and two women) aged 23-41 years were subsequently randomised to perform ITL with the solenoid valve, twice with the breathing pattern fixed and twice free. RESULTS--The solenoid valve generated a more accurate mouth pressure response and was less variable at higher loads than the weighted plunger. The work performed (expressed as the pressure-time product) was less with the solenoid valve but was more reproducible. ITL with the solenoid valve was not influenced by controlling the breathing pattern of the subjects. CONCLUSIONS--The solenoid valve has several features that make it superior to the weighted plunger as a device for ITL. It generates a more accurate mouth pressure response which is less variable at higher loads. Increases in load are smoother and quicker to introduce. ITL with the solenoid valve is not influenced by varying breathing patterns and does not require any external regulation. PMID:8511732

Measurement of inspiratory muscle performance with incremental threshold loading: a comparison of two techniques.

PubMed

Bardsley, P A; Bentley, S; Hall, H S; Singh, S J; Evans, D H; Morgan, M D

1993-04-01

Incremental threshold loading (ITL) is a test of inspiratory muscle performance which is usually performed by breathing through a weighted inspiratory plunger, the load on the inspiratory muscles being increased by externally adding weights to the intake valve. This is not a true threshold device and may be inaccurate. This method was compared with a true threshold device consisting of a solenoid valve which only opens to supply air at a predetermined negative mouth pressure. Six naive, normal subjects (three men and three women) aged 22-24 years underwent three tests using each system. The inspiratory loads were increased every minute by equivalent amounts, -10 cm H2O with the solenoid valve and by 50 g with the weighted plunger, until the subjects could not inspire or sustain inspiration for a full minute. Six experienced subjects (four men and two women) aged 23-41 years were subsequently randomised to perform ITL with the solenoid valve, twice with the breathing pattern fixed and twice free. The solenoid valve generated a more accurate mouth pressure response and was less variable at higher loads than the weighted plunger. The work performed (expressed as the pressure-time product) was less with the solenoid valve but was more reproducible. ITL with the solenoid valve was not influenced by controlling the breathing pattern of the subjects. The solenoid valve has several features that make it superior to the weighted plunger as a device for ITL. It generates a more accurate mouth pressure response which is less variable at higher loads. Increases in load are smoother and quicker to introduce. ITL with the solenoid valve is not influenced by varying breathing patterns and does not require any external regulation.

Motor unit recruitment and firing rate in medial gastrocnemius muscles during external perturbations in standing in humans.

PubMed

Pollock, C L; Ivanova, T D; Hunt, M A; Garland, S J

2014-10-01

There is limited investigation of the interaction between motor unit recruitment and rate coding for modulating force during standing or responding to external perturbations. Fifty-seven motor units were recorded from the medial gastrocnemius muscle with intramuscular electrodes in response to external perturbations in standing. Anteriorly directed perturbations were generated by applying loads in 0.45-kg increments at the pelvis every 25-40 s until 2.25 kg was maintained. Motor unit firing rate was calculated for the initial recruitment load and all subsequent loads during two epochs: 1) dynamic response to perturbation directly following each load drop and 2) maintenance of steady state between perturbations. Joint kinematics and surface electromyography (EMG) from lower extremities and force platform measurements were assessed. Application of the external loads resulted in a significant forward progression of the anterior-posterior center of pressure (AP COP) that was accompanied by modest changes in joint angles (<3°). Surface EMG increased more in medial gastrocnemius than in the other recorded muscles. At initial recruitment, motor unit firing rate immediately after the load drop was significantly lower than during subsequent load drops or during the steady state at the same load. There was a modest increase in motor unit firing rate immediately after the load drop on subsequent load drops associated with regaining balance. There was no effect of maintaining balance with increased load and forward progression of the AP COP on steady-state motor unit firing rate. The medial gastrocnemius utilized primarily motor unit recruitment to achieve the increased levels of activation necessary to maintain standing in the presence of external loads. Copyright © 2014 the American Physiological Society.

A quantitative analysis of microcirculation in sore-prone pressure areas on conventional and pressure relief hospital mattresses using laser Doppler flowmetry and tissue spectrophotometry.

PubMed

Rothenberger, Jens; Krauss, Sabrina; Held, Manuel; Bender, Dominik; Schaller, Hans-Eberhard; Rahmanian-Schwarz, Afshin; Constantinescu, Mihai Adrian; Jaminet, Patrick

2014-11-01

Pressure ulcers are associated with severe impairment for the patients and high economic load. With this study we wanted to gain more insight to the skin perfusion dynamics due to external loading. Furthermore, we evaluated the effect of different types of pressure relief mattresses. A total of 25 healthy volunteers were enrolled in the study. Perfusion dynamics of the sacral and the heel area were assessed using the O2C-device, which combines a laser light, to determine blood flow, and white light to determine the relative amount of hemoglobin. Three mattresses were evaluated compared to a hard surface: a standard hospital foam mattress bed, a visco-elastic foam mattress, and an air-fluidized bed. In the heel area, only the air-fluidized bed was able to maintain the blood circulation (mean blood flow of 13.6 ± 6 versus 3.9 ± 3 AU and mean relative amount of hemoglobin of 44.0 ± 14 versus 32.7 ± 12 AU.) In the sacral area, all used mattresses revealed an improvement of blood circulation compared to the hard surface. The results of this study form a more precise pattern of perfusion changes due to external loading on various pressure relief mattresses. This knowledge may reduce the incidence of pressure ulcers and may be an influencing factor in pressure relief mattress selection. Copyright © 2014 Tissue Viability Society. Published by Elsevier Ltd. All rights reserved.

The effects of a dynamic tuberal support on ischial buttock load and pattern of blood supply.

PubMed

van Geffen, Paul; Reenalda, Jasper; Veltink, Peter H; Koopman, Bart F J M

2010-02-01

Sitting acquired pressure ulcers are places of tissue breakdown that mainly occur under the ischial tuberosities (ITs). Successive durations of pressure relief help the buttock tissue recover from sustained deformation and blood-flow stagnation. A computer-aided simulator chair was developed with two adjustable tuberal support elements (TSE) integrated in a force-sensing seating plane (FSP). This study investigated the redistribution of external buttock load in relation to the pattern (i.e., dynamics) of subtuberal blood supply in sitting with a dynamic tuberal support of 1/60 Hz (80 mm/min). Fifteen healthy male subjects were seated with their ITs on the TSE. The experiment involved periodic TSE adjustment in which buttock interface pressure was measured with the FSP and an external pressure mapping device (PMD). Light-guide tissue spectrophotometry was used for simultaneous noninvasive measurement of oxygenation and perfusion in the skin ( < 2 mm) and subcutaneous ( < 8 mm) tissue under the ITs. TSE adjustment seemed effective to regulate centre of buttock pressure and the forces under the ITs. Differences in measurement with the FSP and PMD have been found due to Hammocking at the seat interface and inaccurate peak pressure readings. Subtuberal blood supply was inversely related to the contact load under the ITs. A rapid inflow of blood in the initial stage of tuberal unloading, followed by a gradual outflow in the rest of the movement cycle indicates that the average blood supply increases when the adjustment frequency increases. Future studies must address the influence of a dynamic tuberal support on the ischial buttock load and pattern of blood supply in impaired individuals.

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

NASA Technical Reports Server (NTRS)

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

1987-01-01

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

Effects of osmotic pressure in the extracellular matrix on tissue deformation.

PubMed

Lu, Y; Parker, K H; Wang, W

2006-06-15

In soft tissues, large molecules such as proteoglycans trapped in the extracellular matrix (ECM) generate high levels of osmotic pressure to counter-balance external pressures. The semi-permeable matrix and fixed negative charges on these molecules serve to promote the swelling of tissues when there is an imbalance of molecular concentrations. Structural molecules, such as collagen fibres, form a network of stretch-resistant matrix, which prevents tissue from over-swelling and keeps tissue integrity. However, collagen makes little contribution to load bearing; the osmotic pressure in the ECM is the main contributor balancing external pressures. Although there have been a number of studies on tissue deformation, there is no rigorous analysis focusing on the contribution of the osmotic pressure in the ECM on the viscoelastic behaviour of soft tissues. Furthermore, most previous works were carried out based on the assumption of infinitesimal deformation, whereas tissue deformation is finite under physiological conditions. In the current study, a simplified mathematical model is proposed. Analytic solutions for solute distribution in the ECM and the free-moving boundary were derived by solving integro-differential equations under constant and dynamic loading conditions. Osmotic pressure in the ECM is found to contribute significantly to the viscoelastic characteristics of soft tissues during their deformation.

Smart Sensing and Dynamic Fitting for Enhanced Comfort and Performance of Prosthetics

DTIC Science & Technology

2015-10-01

developing the antenna pressure/shear sensors and the bubble actuators for pressure regulation. An antenna sensor that is capable of measuring shear and...liner materials. We have characterized the load bearing capability of bubble actuator arrays at different actuation pressures. A “limb-socket...laboratory test setup was developed for capturing the internal pressure change of bubble actuators when the “limb” was subjected to the external force. 15

Transient Reactivation of a Deep-Seated Landslide by Undrained Loading Captured With Repeat Airborne and Terrestrial Lidar

NASA Astrophysics Data System (ADS)

Booth, Adam M.; McCarley, Justin; Hinkle, Jason; Shaw, Susan; Ampuero, Jean-Paul; Lamb, Michael P.

2018-05-01

Landslides reactivate due to external environmental forcing or internal mass redistribution, but the process is rarely documented quantitatively. We capture the three-dimensional, 1-m resolution surface deformation field of a transiently reactivated landslide with image correlation of repeat airborne lidar. Undrained loading by two debris flows in the landslide's head, rather than external forcing, triggered reactivation. After that loading, the lower 2 km of the landslide advanced by up to 14 m in 2 years before completely stopping. The displacement field over those 2 years implies that the slip surface gained 1 kPa of shear strength, which was likely accomplished by a negative dilatancy-pore pressure feedback as material deformed around basal roughness elements. Thus, landslide motion can be decoupled from external environmental forcing in cases, motivating the need to better understand internal perturbations to the stress field to predict hazards and sediment fluxes as landscapes evolve.

A thermoelastic transversely isotropic thick walled cylinder/disk application: An analytical solution and study

NASA Technical Reports Server (NTRS)

Arnold, S. M.

1989-01-01

A continuum theory is utilized to represent the thermoelastic behavior of a thick walled composite cylinder that can be idealized as transversely isotropic. A multiaxial statement of the constitutive theory employed is presented, as well as the out of the plane of isotropy, plane stress, and plane strain reductions. The derived analytical solution presented is valid for a cylindrical tube or thin disk with a concentric hole, subjected to internal and/or external pressure and a general radial temperature distribution. A specific problem examined is that of a thick walled cylinder subjected to an internal and external pressure loading and a linear radial temperature distribution. The results are expressed in nondimensional form and the effects on the response behavior are examined for various material properties, fiber orientation and types of loadings.

Quantifying the effects of external shear loads on arterial and venous blood flow: implications for pressure ulcer development.

PubMed

Manorama, Abinand; Meyer, Ronald; Wiseman, Robert; Bush, Tamara Reid

2013-06-01

Forces applied to the skin cause a decrease in regional blood flow. This decrease in blood flow can cause tissue necrosis and lead to the formation of deep, penetrating wounds called pressure ulcers. These wounds are detrimental to individuals with compromised health, such as the elderly and spinal-cord injured. Although surface pressure is known to be a primary risk factor for developing a pressure ulcer, a seated individual rarely experiences pressure alone but rather combined loading which includes pressure as well as shear force on the skin. However, little research has been conducted to quantify the effects of shear forces on blood flow. Fifteen men were tested in a magnetic resonance imaging scanner under no load, a normal load, and a combination of normal and shear loads. Changes in arterial and venous blood flow in the forearm were measured using magnetic resonance angiography phase-contrast imaging. The blood flow in the anterior interosseous artery and basilic vein of the forearm decreased with the application of normal loads, and decreased further with the addition of shear loads. Marginal to significant differences at a 90% confidence level (P=0.08, 0.10) were observed, and medium to high effect sizes (0.3 to 0.5) were obtained. Based on these results, shear force is an important factor to consider in relation to pressure ulcer propagation and prevention, and hence, future prevention approaches should also focus on mitigating shear loads. Copyright © 2013 Elsevier Ltd. All rights reserved.

Force reduction induced by unidirectional transversal muscle loading is independent of local pressure.

PubMed

Siebert, Tobias; Rode, Christian; Till, Olaf; Stutzig, Norman; Blickhan, Reinhard

2016-05-03

Transversal unidirectional compression applied to muscles via external loading affects muscle contraction dynamics in the longitudinal direction. A recent study reported decreasing longitudinal muscle forces with increasing transversal load applied with a constant contact area (i.e., leading to a simultaneous increase in local pressure). To shed light on these results, we examine whether the decrease in longitudinal force depends on the load, the local pressure, or both. To this end, we perform isometric experiments on rat M. gastrocnemius medialis without and with transversal loading (i) changing the local pressure from 1.1-3.2Ncm(-2) (n=9) at a constant transversal load (1.62N) and (ii) increasing the transversal load (1.15-3.45N) at a constant local pressure of 2.3Ncm(-2) (n=7). While we did not note changes in the decrease in longitudinal muscle force in the first experiment, the second experiment resulted in an almost-linear reduction of longitudinal force between 7.5±0.6% and 14.1±1.7%. We conclude that the observed longitudinal force reduction is not induced by local effects such as malfunction of single muscle compartments, but that similar internal stress conditions and myofilament configurations occur when the local pressure changes given a constant load. The decreased longitudinal force may be explained by increased internal pressure and a deformed myofilament lattice that is likely associated with the decomposition of cross-bridge forces on the one hand and the inhibition of cross-bridges on the other hand. Copyright © 2016 Elsevier Ltd. All rights reserved.

Application of Newton's method to the postbuckling of rings under pressure loadings

NASA Technical Reports Server (NTRS)

Thurston, Gaylen A.

1989-01-01

The postbuckling response of circular rings (or long cylinders) is examined. The rings are subjected to four types of external pressure loadings; each type of pressure is defined by its magnitude and direction at points on the buckled ring. Newton's method is applied to the nonlinear differential equations of the exact inextensional theory for the ring problem. A zeroth approximation for the solution of the nonlinear equations, based on the mode shape corresponding to the first buckling pressure, is derived in closed form for each of the four types of pressure. The zeroth approximation is used to start the iteration cycle in Newton's method to compute numerical solutions of the nonlinear equations. The zeroth approximations for the postbuckling pressure-deflection curves are compared with the converged solutions from Newton's method and with similar results reported in the literature.

Bifurcation theory applied to buckling states of a cylindrical shell

NASA Astrophysics Data System (ADS)

Chaskalovic, J.; Naili, S.

1995-01-01

Veins, bronchii, and many other vessels in the human body are flexible enough to be capable of collapse if submitted to suitable applied external and internal loads. One way to describe this phenomenon is to consider an inextensible elastic and infinite tube, with a circular cross section in the reference configuration, subjected to a uniform external pressure. In this paper, we establish that the nonlinear equilibrium equation for this model has nontrivial solutions which appear for critical values of the pressure. To this end, the tools we use are the Liapunov-Schmidt decomposition and the bifurcation theorem for simple multiplicity. We conclude with the bifurcation diagram, showing the dependence between the cross-sectional area and the pressure.

Patterning of alloy precipitation through external pressure

NASA Astrophysics Data System (ADS)

Franklin, Jack A.

Due to the nature of their microstructure, alloyed components have the benefit of meeting specific design goals across a wide range of electrical, thermal, and mechanical properties. In general by selecting the correct alloy system and applying a proper heat treatment it is possible to create a metallic sample whose properties achieve a unique set of design requirements. This dissertation presents an innovative processing technique intended to control both the location of formation and the growth rates of precipitates within metallic alloys in order to create multiple patterned areas of unique microstructure within a single sample. Specific experimental results for the Al-Cu alloy system will be shown. The control over precipitation is achieved by altering the conventional heat treatment process with an external surface load applied to selected locations during the quench and anneal. It is shown that the applied pressures affect both the rate and directionality of the atomic diffusion in regions close to the loaded surfaces. The control over growth rates is achieved by altering the enthalpic energy required for successful diffusion between lattice sites. Changes in the local chemical free energy required to direct the diffusion of atoms are established by introducing a non-uniform elastic strain energy field within the samples created by the patterned surface pressures. Either diffusion rates or atomic mobility can be selected as the dominating control process by varying the quench rate; with slower quenches having greater control over the mobility of the alloying elements. Results have shown control of Al2Cu precipitation over 100 microns on mechanically polished surfaces. Further experimental considerations presented will address consistency across sample ensembles. This includes repeatable pressure loading conditions and the chemical interaction between any furnace environments and both the alloy sample and metallic pressure loading devices.

Features of lymphatic dysfunction in compressed skin tissues - Implications in pressure ulcer aetiology.

PubMed

Gray, Robert J; Voegeli, David; Bader, Dan L

2016-02-01

Impaired lymph formation and clearance has previously been proposed as a contributory factor in the development of pressure ulcers. The present study has been designed to trial fluorescence lymphangiography for establishing how lymphatic function is altered under a clinically relevant form of mechanical loading. Lymph formation and clearance was traced in both forearms by an intradermal injection of indocyanine green (ICG) (50 μl, 0.05%w/v), imaged using a commercial near-infrared fluorescence imaging unit (Fluobeam(®) 800). External uniaxial loading equivalent to a pressure of 60 mmHg was applied for 45 min in one arm using a custom-built indenter. Loading was associated with a decreased frequency of normal directional drainage (DD) of ICG within delineated vessels, both immediately after loading and 45 min thereafter. Loading was also associated with non-directional drainage (NDD) of ICG within the interstitium. Signal intensity within NDD was often greatest at areas of stress concentration, producing a 'halo pattern', corresponding to the rounded edges of the indenter. These results suggest that loading skin with a clinically relevant magnitude of pressure alters both lymph formation and clearance. Further work to quantify impaired clearance under mechanical loading could provide valuable insight into their involvement in the development of pressure ulcers. Copyright © 2016 Tissue Viability Society. Published by Elsevier Ltd. All rights reserved.

Investigation on the fiber based approach to estimate the axial load carrying capacity of the circular concrete filled steel tube (CFST)

NASA Astrophysics Data System (ADS)

Piscesa, B.; Attard, M. M.; Suprobo, P.; Samani, A. K.

2017-11-01

External confining devices are often used to enhance the strength and ductility of reinforced concrete columns. Among the available external confining devices, steel tube is one of the most widely used in construction. However, steel tube has some drawbacks such as local buckling which needs to be considered when estimating the axial load carrying capacity of the concrete-filled-steel-tube (CFST) column. To tackle this problem in design, Eurocode 4 provided guidelines to estimate the effective yield strength of the steel tube material. To study the behavior of CFST column, in this paper, a non-linear analysis using a fiber-based approach was conducted. The use of the fiber-based approach allows the engineers to predict not only the axial load carrying capacity but also the complete load-deformation curve of the CFST columns for a known confining pressure. In the proposed fiber-based approach, an inverse analysis is used to estimate the constant confining pressure similar to design-oriented models. This paper also presents comparisons between the fiber-based approach model with the experimental results and the 3D non-linear finite element analysis.

LOADING MACHINE FOR REACTORS

DOEpatents

Simon, S.L.

1959-07-01

An apparatus is described for loading or charging slugs of fissionable material into a nuclear reactor. The apparatus of the invention is a "muzzle loading" type comprising a delivery tube or muzzle designed to be brought into alignment with any one of a plurality of fuel channels. The delivery tube is located within the pressure shell and it is also disposed within shielding barriers while the fuel cantridges or slugs are forced through the delivery tube by an externally driven flexible ram.

Lateral Load Testing of the Advanced Stirling Convertor (ASC-E2) Heater Head

NASA Technical Reports Server (NTRS)

Cornell, Peggy A.; Krause, David L.; Davis, Glen; Robbie, Malcolm G.; Gubics, David A.

2010-01-01

Free-piston Stirling convertors are fundamental to the development of NASA s next generation of radioisotope power system, the Advanced Stirling Radioisotope Generator (ASRG). The ASRG will use General Purpose Heat Source (GPHS) modules as the energy source and Advanced Stirling Convertors (ASCs) to convert heat into electrical energy, and is being developed by Lockheed Martin under contract to the Department of Energy. Achieving flight status mandates that the ASCs satisfy design as well as flight requirements to ensure reliable operation during launch. To meet these launch requirements, GRC performed a series of quasi-static mechanical tests simulating the pressure, thermal, and external loading conditions that will be experienced by an ASC-E2 heater head assembly. These mechanical tests were collectively referred to as "lateral load tests" since a primary external load lateral to the heater head longitudinal axis was applied in combination with the other loading conditions. The heater head was subjected to the operational pressure, axial mounting force, thermal conditions, and axial and lateral launch vehicle acceleration loadings. To permit reliable prediction of the heater head s structural performance, GRC completed Finite Element Analysis (FEA) computer modeling for the stress, strain, and deformation that will result during launch. The heater head lateral load test directly supported evaluation of the analysis and validation of the design to meet launch requirements. This paper provides an overview of each element within the test and presents assessment of the modeling as well as experimental results of this task.

Lateral Load Testing of the Advanced Stirling Convertor (ASC-E2) Heater Head

NASA Technical Reports Server (NTRS)

Cornell, Peggy A.; Krause, David L.; Davis, Glen; Robbie, Malcolm G.; Gubics, David A.

2011-01-01

Free-piston Stirling convertors are fundamental to the development of NASA s next generation of radioisotope power system, the Advanced Stirling Radioisotope Generator (ASRG). The ASRG will use General Purpose Heat Source (GPHS) modules as the energy source and Advanced Stirling Convertors (ASCs) to convert heat into electrical energy, and is being developed by Lockheed Martin under contract to the Department of Energy. Achieving flight status mandates that the ASCs satisfy design as well as flight requirements to ensure reliable operation during launch. To meet these launch requirements, GRC performed a series of quasi-static mechanical tests simulating the pressure, thermal, and external loading conditions that will be experienced by an ASC-E2 heater head assembly. These mechanical tests were collectively referred to as "lateral load tests" since a primary external load lateral to the heater head longitudinal axis was applied in combination with the other loading conditions. The heater head was subjected to the operational pressure, axial mounting force, thermal conditions, and axial and lateral launch vehicle acceleration loadings. To permit reliable prediction of the heater head s structural performance, GRC completed Finite Element Analysis (FEA) computer modeling for the stress, strain, and deformation that will result during launch. The heater head lateral load test directly supported evaluation of the analysis and validation of the design to meet launch requirements. This paper provides an overview of each element within the test and presents assessment of the modeling as well as experimental results of this task.

Lateral Load Testing of the Advanced Stirling Convertor (ASC-E2) Heater Head

NASA Technical Reports Server (NTRS)

Cornell, Peggy A.; Krause, David L.; Davis, Glen; Robbie, Malcolm G.; Gubics, David A.

2010-01-01

Free-piston Stirling convertors are fundamental to the development of NASA s next generation of radioisotope power system, the Advanced Stirling Radioisotope Generator (ASRG). The ASRG will use General Purpose Heat Source (GPHS) modules as the energy source and Advanced Stirling Convertors (ASCs) to convert heat into electrical energy, and is being developed by Lockheed Martin under contract to the Department of Energy. Achieving flight status mandates that the ASCs satisfy design as well as flight requirements to ensure reliable operation during launch. To meet these launch requirements, GRC performed a series of quasi-static mechanical tests simulating the pressure, thermal, and external loading conditions that will be experienced by an ASC E2 heater head assembly. These mechanical tests were collectively referred to as lateral load tests since a primary external load lateral to the heater head longitudinal axis was applied in combination with the other loading conditions. The heater head was subjected to the operational pressure, axial mounting force, thermal conditions, and axial and lateral launch vehicle acceleration loadings. To permit reliable prediction of the heater head s structural performance, GRC completed Finite Element Analysis (FEA) computer modeling for the stress, strain, and deformation that will result during launch. The heater head lateral load test directly supported evaluation of the analysis and validation of the design to meet launch requirements. This paper provides an overview of each element within the test and presents assessment of the modeling as well as experimental results of this task.

Landing pressure loads of the 140A/B space shuttle orbiter (model 43-0) determined in the Rockwell International low speed wind tunnel (OA69), volume 1. [wind tunnel tests

NASA Technical Reports Server (NTRS)

Soard, T. L.

1975-01-01

Wind tunnel tests of a 0.0405 scale model of the -1404A/B configuration of the Space Shuttle Vehicle Orbiter are presented. Pressure loads data were obtained from the orbiter in the landing configuration in the presence of the ground for structural strength analysis. This was accomplished by locating as many as 30 static pressure bugs at various locations on external model surfaces as each configuration was tested. A complete pressure loads survey was generated for each configuration by combining data from all bug locations, and these loads are described for the fuselage, wing, vertical tail, and landing gear doors. Aerodynamic force data was measured by a six component internal strain gage balance. This data was recorded to correct model angles of attack and sideslip for sting and balance deflections and to determine the aerodynamic effects of landing gear extension. All testing was conducted at a Mach number of 0.165 and a Reynolds number of 1.2 million per foot. Photographs of test configurations are shown.

High-pressure endurable flexible tactile actuator based on microstructured dielectric elastomer

NASA Astrophysics Data System (ADS)

Pyo, Dongbum; Ryu, Semin; Kyung, Ki-Uk; Yun, Sungryul; Kwon, Dong-Soo

2018-02-01

We demonstrate a robust flexible tactile actuator that is capable of working under high external pressures. The tactile actuator is based on a pyramidal microstructured dielectric elastomer layer inducing variation in both mechanical and dielectric properties. The vibrational performance of the actuator can be modulated by changing the geometric parameter of the microstructures. We evaluated the performance of the actuator under high-pressure loads up to 25 kPa, which is over the typical range of pressure applied when humans touch or manipulate objects. Due to the benefit of nonlinearity of the pyramidal structure, the actuator could maintain high mechanical output under various external pressures in the frequency range of 100-200 Hz, which is the most sensitive to vibration acceleration for human finger pads. The responses are not only fast, reversible, and highly durable under consecutive cyclic operations, but also large enough to impart perceivable vibrations for haptic feedback on practical wearable device applications.

Beam Test of a Dielectric Loaded High Pressure RF Cavity for Use in Muon Cooling Channels

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

Freemire, Ben; Bowring, Daniel; Kochemirovskiy, Alexey

2016-06-01

Bright muon sources require six dimensional cooling to achieve acceptable luminosities. Ionization cooling is the only known method able to do so within the muon lifetime. One proposed cooling channel, the Helical Cooling Channel, utilizes gas filled radio frequency cavities to both mitigate RF breakdown in the presence of strong, external magnetic fields, and provide the cooling medium. Engineering constraints on the diameter of the magnets within which these cavities operate dictate the radius of the cavities be decreased at their nominal operating frequency. To accomplish this, one may load the cavities with a larger dielectric material. A 99.5% aluminamore » ring was inserted in a high pressure RF test cell and subjected to an intense proton beam at the MuCool Test Area at Fermilab. The results of the performance of this dielectric loaded high pressure RF cavity will be presented.« less

Elastic-plastic analysis of annular plate problems using NASTRAN

NASA Technical Reports Server (NTRS)

Chen, P. C. T.

1983-01-01

The plate elements of the NASTRAN code are used to analyze two annular plate problems loaded beyond the elastic limit. The first problem is an elastic-plastic annular plate loaded externally by two concentrated forces. The second problem is stressed radially by uniform internal pressure for which an exact analytical solution is available. A comparison of the two approaches together with an assessment of the NASTRAN code is given.

Analyzing Axial Stress and Deformation of Tubular for Steam Injection Process in Deviated Wells Based on the Varied (T, P) Fields

PubMed Central

Liu, Yunqiang; Xu, Jiuping; Wang, Shize; Qi, Bin

2013-01-01

The axial stress and deformation of high temperature high pressure deviated gas wells are studied. A new model is multiple nonlinear equation systems by comprehensive consideration of axial load of tubular string, internal and external fluid pressure, normal pressure between the tubular and well wall, and friction and viscous friction of fluid flowing. The varied temperature and pressure fields were researched by the coupled differential equations concerning mass, momentum, and energy equations instead of traditional methods. The axial load, the normal pressure, the friction, and four deformation lengths of tubular string are got ten by means of the dimensionless iterative interpolation algorithm. The basic data of the X Well, 1300 meters deep, are used for case history calculations. The results and some useful conclusions can provide technical reliability in the process of designing well testing in oil or gas wells. PMID:24163623

Subject-Specific Modeling of Muscle Force and Knee Contact in Total Knee Arthroplasty

PubMed Central

Navacchia, Alessandro; Rullkoetter, Paul J.; Schütz, Pascal; List, Renate B.; Fitzpatrick, Clare K.; Shelburne, Kevin B.

2017-01-01

Understanding the mechanical loading environment and resulting joint mechanics for activities of daily living in total knee arthroplasty is essential to continuous improvement in implant design. Although survivorship of these devices is good, a substantial number of patients report dissatisfaction with the outcome of their procedure. Knowledge of in vivo kinematics and joint loading will enable improvement in preclinical assessment and refinement of implant geometry. The purpose of this investigation was to describe the mechanics of total knee arthroplasty during a variety of activities of daily living (gait, walking down stairs, and chair rise/sit). Estimates of muscle forces, tibial contact load, location, and pressure distribution was performed through a combination of mobile fluoroscopy data collection, musculoskeletal modeling, and finite element simulation. For the activities evaluated, joint compressive load was greatest during walking down stairs; however, the highest contact pressure occurred during chair rise/sit. The joint contact moment in the frontal plane was mainly varus for gait and walking down stairs, while it was valgus during chair rise/sit. Excursion of the center of pressure on the tibial component was similar during each activity and between the medial and lateral sides. The main determinants of center of pressure location were internal–external rotation, joint load, and tibial insert conformity. PMID:26792665

Numerical Modelling and Analysis of Hydrostatic Thrust Air Bearings for High Loading Capacities and Low Air Consumption

NASA Astrophysics Data System (ADS)

Yu, Yunluo; Pu, Guang; Jiang, Kyle

2017-12-01

The paper presents a numerical simulation study on hydrostatic thrust air bearings to assess the load capacity, compressed air consumptions, and the dynamic response. Finite Difference Method (FDM) and Finite Volume Method (FVM) are combined to solve the non-linear Reynolds equation to find the pressure distribution of the air bearing gas film and the total loading capacity of the bearing. The influence of design parameters on air film gap characteristics, including the air film thickness, supplied pressure, depth of the groove and external load, are investigated based on the proposed FDM model. The simulation results show that the thrust air bearings with a groove have a higher load capacity and air consumption than without a groove, and the load capacity and air consumption both increase with the depth of the groove. Bearings without the groove are better damped than those with the grooves, and the stability of thrust bearing decreases when the groove depth increases. The stability of the thrust bearings is also affected by their loading.

Transient Pressure Test Article Test Program

NASA Technical Reports Server (NTRS)

Vibbart, Charles M.

1989-01-01

The Transient Pressure Test Article (TPTA) test program is being conducted at a new test facility located in the East Test Area at the National Aeronautics and Space Administration's (NASA's) Marshall Space Flight Center (MSFC) in Huntsville, Alabama. This facility, along with the special test equipment (STE) required for facility support, was constructed specifically to test and verify the sealing capability of the Redesigned Solid Rocket Motor (RSRM) field, igniter, and nozzle joints. The test article consists of full scale RSRM hardware loaded with inert propellant and assembled in a short stack configuration. The TPTA is pressurized by igniting a propellant cartridge capable of inducing a pressure rise rate which stimulates the ignition transient that occurs during launch. Dynamic loads are applied during the pressure cycle to simulate external tank attach (ETA) strut loads present on the ETA ring. Sealing ability of the redesigned joints is evaluated under joint movement conditions produced by these combined loads since joint sealing ability depends on seal resilience velocity being greater than gap opening velocity. Also, maximum flight dynamic loads are applied to the test article which is either pressurized to 600 psia using gaseous nitrogen (GN2) or applied to the test article as the pressure decays inside the test article on the down cycle after the ignition transient cycle. This new test facility is examined with respect to its capabilities. In addition, both the topic of test effectiveness versus space vehicle flight performance and new aerospace test techniques, as well as a comparison between the old SRM design and the RSRM are presented.

Preliminary 2-D shell analysis of the space shuttle solid rocket boosters

NASA Technical Reports Server (NTRS)

Knight, Norman F., Jr.; Gillian, Ronnie E.; Nemeth, Michael P.

1987-01-01

A two-dimensional shell model of an entire solid rocket booster (SRB) has been developed using the STAGSC-1 computer code and executed on the Ames CRAY computer. The purpose of these analyses is to calculate the overall deflection and stress distributions for the SRB when subjected to mechanical loads corresponding to critical times during the launch sequence. The mechanical loading conditions for the full SRB arise from the external tank (ET) attachment points, the solid rocket motor (SRM) pressure load, and the SRB hold down posts. The ET strut loads vary with time after the Space Shuttle main engine (SSME) ignition. The SRM internal pressure varies axially by approximately 100 psi. Static analyses of the full SRB are performed using a snapshot picture of the loads. The field and factory joints are modeled by using equivalent stiffness joints instead of detailed models of the joint. As such, local joint behavior cannot be obtained from this global model.

Thin film modeling of crystal dissolution and growth in confinement.

PubMed

Gagliardi, Luca; Pierre-Louis, Olivier

2018-01-01

We present a continuum model describing dissolution and growth of a crystal contact confined against a substrate. Diffusion and hydrodynamics in the liquid film separating the crystal and the substrate are modeled within the lubrication approximation. The model also accounts for the disjoining pressure and surface tension. Within this framework, we obtain evolution equations which govern the nonequilibrium dynamics of the crystal interface. Based on this model, we explore the problem of dissolution under an external load, known as pressure solution. We find that in steady state, diverging (power-law) crystal-surface repulsions lead to flat contacts with a monotonic increase of the dissolution rate as a function of the load. Forces induced by viscous dissipation then surpass those due to disjoining pressure at large enough loads. In contrast, finite repulsions (exponential) lead to sharp pointy contacts with a dissolution rate independent of the load and the liquid viscosity. Ultimately, in steady state, the crystal never touches the substrate when pressed against it. This result is independent from the nature of the crystal-surface interaction due to the combined effects of viscosity and surface tension.

Thin film modeling of crystal dissolution and growth in confinement

NASA Astrophysics Data System (ADS)

Gagliardi, Luca; Pierre-Louis, Olivier

2018-01-01

We present a continuum model describing dissolution and growth of a crystal contact confined against a substrate. Diffusion and hydrodynamics in the liquid film separating the crystal and the substrate are modeled within the lubrication approximation. The model also accounts for the disjoining pressure and surface tension. Within this framework, we obtain evolution equations which govern the nonequilibrium dynamics of the crystal interface. Based on this model, we explore the problem of dissolution under an external load, known as pressure solution. We find that in steady state, diverging (power-law) crystal-surface repulsions lead to flat contacts with a monotonic increase of the dissolution rate as a function of the load. Forces induced by viscous dissipation then surpass those due to disjoining pressure at large enough loads. In contrast, finite repulsions (exponential) lead to sharp pointy contacts with a dissolution rate independent of the load and the liquid viscosity. Ultimately, in steady state, the crystal never touches the substrate when pressed against it. This result is independent from the nature of the crystal-surface interaction due to the combined effects of viscosity and surface tension.

[Comparative evaluation of heat state in workers exposed to heating microclimate during cold and warm seasons].

PubMed

Afanas'eva, R F; Prokopenko, L V; Kiladze, N A; Konstantinov, E I

2009-01-01

The authors demonstrated differences in heat state among workers exposed to heating microclimate during cold and warm seasons. Same external thermal load in cold season induces more humidity loss, lower weighted average skin temperature, higher pulse rate, increased systolic and diastolic blood pressure. With that, heat discomfort was more in cold season, than in warm one, this necessitates decrease of thermal load in cold season vs. the warm one.

Behavior of medial gastrocnemius motor units during postural reactions to external perturbations after stroke.

PubMed

Pollock, C L; Ivanova, T D; Hunt, M A; Garland, S J

2015-10-01

This study investigated the behavior of medial gastrocnemius (GM) motor units (MU) during external perturbations in standing in people with chronic stroke. GM MUs were recorded in standing while anteriorly-directed perturbations were introduced by applying loads of 1% body mass (BM) at the pelvis every 25-40s until 5% BM was maintained. Joint kinematics, surface electromyography (EMG), and force platform measurements were assessed. Although external loads caused a forward progression of the anterior-posterior centre of pressure (APCOP), people with stroke decreased APCOP velocity and centre of mass (COM) velocity immediately following the highest perturbations, thereby limiting movement velocity in response to perturbations. MU firing rate did not increase with loading but the GM EMG magnitude increased, reflecting MU recruitment. MU inter spike interval (ISI) during the dynamic response was negatively correlated with COM velocity and hip angular velocity. The GM utilized primarily MU recruitment to maintain standing during external perturbations. The lack of MU firing rate modulation occurred with a change in postural central set. However, the relationship of MU firing rate with kinematic variables suggests underlying long-loop responses may be somewhat intact after stroke. People with stroke demonstrate alterations in postural control strategies which may explain MU behavior with external perturbations. Copyright © 2014 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

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

Guan, Jiwen; Song, Yang, E-mail: yang.song@uwo.ca; Department of Chemistry, University of Western Ontario, London, Ontario N6A 5B7

The polymerization process of condensed styrene to produce polystyrene as an industrially important polymeric material was investigated using a novel approach by combining external compression with ultraviolet radiation. The reaction evolution was monitored as a function of time and the reaction products were characterized by in situ Fourier transform infrared spectroscopy. By optimizing the loading pressures, we observed highly efficient and selective production of polystyrene of different tacticities. Specifically, at relatively low loading pressures, infrared spectra suggest that styrene monomers transform to amorphous atactic polystyrene (APS) with minor crystalline isotactic polystyrene. In contrast, APS was found to be the solemore » product when polymerization occurs at relatively higher loading pressures. The time-dependent reaction profiles allow the examination of the polymerization kinetics by analyzing the rate constant and activation volume as a function of pressure. As a result, an optimized pressure condition, which allows a barrierless reaction to proceed, was identified and attributed to the very desirable reaction yield and kinetics. Finally, the photoinitiated reaction mechanism and the growth geometry of the polymer chains were investigated from the energy diagram of styrene and by the topology analysis of the crystal styrene. This study shows strong promise to produce functional polymeric materials in a highly efficient and controlled manner.« less

Pressure-flow specificity of inspiratory muscle training.

PubMed

Tzelepis, G E; Vega, D L; Cohen, M E; Fulambarker, A M; Patel, K K; McCool, F D

1994-08-01

The inspiratory muscles (IM) can be trained by having a subject breathe through inspiratory resistive loads or by use of unloaded hyperpnea. These disparate training protocols are characterized by high inspiratory pressure (force) or high inspiratory flow (velocity), respectively. We tested the hypothesis that the posttraining improvements in IM pressure or flow performance are specific to training protocols in a way that is similar to force-velocity specificity of skeletal muscle training. IM training was accomplished in 15 normal subjects by use of three protocols: high inspiratory pressure-no flow (group A, n = 5), low inspiratory pressure-high flow (group B, n = 5), and intermediate inspiratory pressure and flow (group C, n = 5). A control group (n = 4) did no training. Before and after training, we measured esophageal pressure (Pes) and inspiratory flow (VI) during single maximal inspiratory efforts against a range of external resistances including an occluded airway. Efforts originated below relaxation volume (Vrel), and peak Pes and VI were measured at Vrel. Isovolume maximal Pes-VI plots were constructed to assess maximal inspiratory pressure-flow performance. Group A (pressure training) performed 30 maximal static inspiratory maneuvers at Vrel daily, group B (flow training) performed 30 sets of three maximal inspiratory maneuvers with no added external resistance daily, and group C (intermediate training) performed 30 maximal inspiratory efforts on a midrange external resistance (7 mm ID) daily. Subjects trained 5 days/wk for 6 wk. Data analysis included comparison of posttraining Pes-VI slopes among training groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Highly efficient and selective pressure-assisted photon-induced polymerization of styrene

NASA Astrophysics Data System (ADS)

Guan, Jiwen; Song, Yang

2016-06-01

The polymerization process of condensed styrene to produce polystyrene as an industrially important polymeric material was investigated using a novel approach by combining external compression with ultraviolet radiation. The reaction evolution was monitored as a function of time and the reaction products were characterized by in situ Fourier transform infrared spectroscopy. By optimizing the loading pressures, we observed highly efficient and selective production of polystyrene of different tacticities. Specifically, at relatively low loading pressures, infrared spectra suggest that styrene monomers transform to amorphous atactic polystyrene (APS) with minor crystalline isotactic polystyrene. In contrast, APS was found to be the sole product when polymerization occurs at relatively higher loading pressures. The time-dependent reaction profiles allow the examination of the polymerization kinetics by analyzing the rate constant and activation volume as a function of pressure. As a result, an optimized pressure condition, which allows a barrierless reaction to proceed, was identified and attributed to the very desirable reaction yield and kinetics. Finally, the photoinitiated reaction mechanism and the growth geometry of the polymer chains were investigated from the energy diagram of styrene and by the topology analysis of the crystal styrene. This study shows strong promise to produce functional polymeric materials in a highly efficient and controlled manner.

Topology optimization of pressure adaptive honeycomb for a morphing flap

NASA Astrophysics Data System (ADS)

Vos, Roelof; Scheepstra, Jan; Barrett, Ron

2011-03-01

The paper begins with a brief historical overview of pressure adaptive materials and structures. By examining avian anatomy, it is seen that pressure-adaptive structures have been used successfully in the Natural world to hold structural positions for extended periods of time and yet allow for dynamic shape changes from one flight state to the next. More modern pneumatic actuators, including FAA certified autopilot servoactuators are frequently used by aircraft around the world. Pneumatic artificial muscles (PAM) show good promise as aircraft actuators, but follow the traditional model of load concentration and distribution commonly found in aircraft. A new system is proposed which leaves distributed loads distributed and manipulates structures through a distributed actuator. By using Pressure Adaptive Honeycomb (PAH), it is shown that large structural deformations in excess of 50% strains can be achieved while maintaining full structural integrity and enabling secondary flight control mechanisms like flaps. The successful implementation of pressure-adaptive honeycomb in the trailing edge of a wing section sparked the motivation for subsequent research into the optimal topology of the pressure adaptive honeycomb within the trailing edge of a morphing flap. As an input for the optimization two known shapes are required: a desired shape in cruise configuration and a desired shape in landing configuration. In addition, the boundary conditions and load cases (including aerodynamic loads and internal pressure loads) should be specified for each condition. Finally, a set of six design variables is specified relating to the honeycomb and upper skin topology of the morphing flap. A finite-element model of the pressure-adaptive honeycomb structure is developed specifically tailored to generate fast but reliable results for a given combination of external loading, input variables, and boundary conditions. Based on two bench tests it is shown that this model correlates well to experimental results. The optimization process finds the skin and honeycomb topology that minimizes the error between the acquired shape and the desired shape in each configuration.

Mode I Fracture Toughness of Rock - Intrinsic Property or Pressure-Dependent?

NASA Astrophysics Data System (ADS)

Stoeckhert, F.; Brenne, S.; Molenda, M.; Alber, M.

2016-12-01

The mode I fracture toughness of rock is usually regarded as an intrinsic material parameter independent of pressure. However, most fracture toughness laboratory tests are conducted only at ambient pressure. To investigate fracture toughness of rock under elevated pressures, sleeve fracturing laboratory experiments were conducted with various rock types and a new numerical method was developed for the evaluation of these experiments. The sleeve fracturing experiments involve rock cores with central axial boreholes that are placed in a Hoek triaxial pressure cell to apply an isostatic confining pressure. A polymere tube is pressurized inside these hollow rock cylinders until they fail by tensile fracturing. Numerical simulations incorporating fracture mechanical models are used to obtain a relation between tensile fracture propagation and injection pressure. These simulations indicate that the magnitude of the injection pressure at specimen failure is only depending on the fracture toughness of the tested material, the specimen dimensions and the magnitude of external loading. The latter two are known parameters in the experiments. Thus, the fracture toughness can be calculated from the injection pressure recorded at specimen breakdown. All specimens had a borehole diameter to outer diameter ratio of about 1:10 with outer diameters of 40 and 62 mm. The length of the specimens was about two times the diameter. Maximum external loading was 7.5 MPa corresponding to maximum injection pressures at specimen breakdown of about 100 MPa. The sample set tested in this work includes Permian and Carboniferous sandstones, Jurassic limestones, Triassic marble, Permian volcanic rocks and Devonian slate from Central Europe. The fracture toughness values determined from the sleeve fracturing experiments without confinement using the new numerical method were found to be in good agreement with those from Chevron bend testing according to the ISRM suggested methods. At elevated confining pressures, the results indicate a significant positive correlation between fracture toughness and confining pressure for most tested rock types.

Axisymmetric inlet minimum weight design method

NASA Technical Reports Server (NTRS)

Nadell, Shari-Beth

1995-01-01

An analytical method for determining the minimum weight design of an axisymmetric supersonic inlet has been developed. The goal of this method development project was to improve the ability to predict the weight of high-speed inlets in conceptual and preliminary design. The initial model was developed using information that was available from inlet conceptual design tools (e.g., the inlet internal and external geometries and pressure distributions). Stiffened shell construction was assumed. Mass properties were computed by analyzing a parametric cubic curve representation of the inlet geometry. Design loads and stresses were developed at analysis stations along the length of the inlet. The equivalent minimum structural thicknesses for both shell and frame structures required to support the maximum loads produced by various load conditions were then determined. Preliminary results indicated that inlet hammershock pressures produced the critical design load condition for a significant portion of the inlet. By improving the accuracy of inlet weight predictions, the method will improve the fidelity of propulsion and vehicle design studies and increase the accuracy of weight versus cost studies.

Structures to Resist the Effects of Accidental Explosions

DTIC Science & Technology

1969-06-01

theorems, are generally used. il to Ce e same structure. reactions of the foundatio4 must also be equal to zero . e. For the analysis of structures...3. BASIS FOR STRUCTURAL D)ESIGN Section 1. Structural Response General ----------------------------------- -c--- -13- Pressure design ranges...4-11 4-.i9 V. External Blast Loads on Structures General

46 CFR 162.018-4 - Construction and workmanship.

Code of Federal Regulations, 2011 CFR

2011-10-01

... external spring-loaded type, suitable for the intended service. (b) Safety relief valve body, base, bonnet... with side or top outlet discharge connections. (f)(1) Springs shall not show a permanent set exceeding... the spring solid. (2) Springs may not be re-set for any pressure more than 10 percent above or 10...

46 CFR 162.018-4 - Construction and workmanship.

Code of Federal Regulations, 2012 CFR

2012-10-01

... external spring-loaded type, suitable for the intended service. (b) Safety relief valve body, base, bonnet... with side or top outlet discharge connections. (f)(1) Springs shall not show a permanent set exceeding... the spring solid. (2) Springs may not be re-set for any pressure more than 10 percent above or 10...

46 CFR 162.018-4 - Construction and workmanship.

Code of Federal Regulations, 2010 CFR

2010-10-01

... external spring-loaded type, suitable for the intended service. (b) Safety relief valve body, base, bonnet... with side or top outlet discharge connections. (f)(1) Springs shall not show a permanent set exceeding... the spring solid. (2) Springs may not be re-set for any pressure more than 10 percent above or 10...

46 CFR 162.018-4 - Construction and workmanship.

Code of Federal Regulations, 2013 CFR

2013-10-01

... external spring-loaded type, suitable for the intended service. (b) Safety relief valve body, base, bonnet... with side or top outlet discharge connections. (f)(1) Springs shall not show a permanent set exceeding... the spring solid. (2) Springs may not be re-set for any pressure more than 10 percent above or 10...

46 CFR 162.018-4 - Construction and workmanship.

Code of Federal Regulations, 2014 CFR

2014-10-01

... external spring-loaded type, suitable for the intended service. (b) Safety relief valve body, base, bonnet... with side or top outlet discharge connections. (f)(1) Springs shall not show a permanent set exceeding... the spring solid. (2) Springs may not be re-set for any pressure more than 10 percent above or 10...

Load responsive multilayer insulation performance testing

NASA Astrophysics Data System (ADS)

Dye, S.; Kopelove, A.; Mills, G. L.

2014-01-01

Cryogenic insulation designed to operate at various pressures from one atmosphere to vacuum, with high thermal performance and light weight, is needed for cryogenically fueled space launch vehicles and aircraft. Multilayer insulation (MLI) performs well in a high vacuum, but the required vacuum shell for use in the atmosphere is heavy. Spray-on foam insulation (SOFI) is often used in these systems because of its light weight, but can have a higher heat flux than desired. We report on the continued development of Load Responsive Multilayer Insulation (LRMLI), an advanced thermal insulation system that uses dynamic beam discrete spacers that provide high thermal performance both in atmosphere and vacuum. LRMLI consists of layers of thermal radiation barriers separated and supported by micromolded polymer spacers. The spacers have low thermal conductance, and self-support a thin, lightweight vacuum shell that provides internal high vacuum in the insulation. The dynamic load responsive spacers compress to support the external load of a vacuum shell in one atmosphere, and decompress under reduced atmospheric pressure for lower heat leak. Structural load testing was performed on the spacers with various configurations. LRMLI was installed on a 400 liter tank and boil off testing with liquid nitrogen performed at various chamber pressures from one atmosphere to high vacuum. Testing was also performed with an MLI blanket on the outside of the LRMLI.

Cellular pressure and volume regulation and implications for cell mechanics

NASA Astrophysics Data System (ADS)

Jiang, Hongyuan; Sun, Sean

2013-03-01

In eukaryotic cells, small changes in cell volume can serve as important signals for cell proliferation, death and migration. Volume and shape regulation also directly impacts the mechanics of the cell and multi-cellular tissues. Recent experiments found that during mitosis, eukaryotic cells establish a preferred steady volume and pressure, and the steady volume and pressure can robustly adapt to large osmotic shocks. Here we develop a mathematical model of cellular pressure and volume regulation, incorporating essential elements such as water permeation, mechano-sensitive channels, active ion pumps and active stresses in the actomyosin cortex. The model can fully explain the available experimental data, and predicts the cellular volume and pressure for several models of cell cortical mechanics. Furthermore, we show that when cells are subjected to an externally applied load, such as in an AFM indentation experiment, active regulation of volume and pressure leads to complex cellular response. We found the cell stiffness highly depends on the loading rate, which indicates the transport of water and ions might contribute to the observed viscoelasticity of cells.

Breakdown of Amontons' Law of Friction in Sheared-Elastomer with Local Amontons' Friction

NASA Astrophysics Data System (ADS)

Matsukawa, Hiroshi; Otsuki, Michio

2012-02-01

It is well known that Amontons' law of friction i.e. the frictional force against the sliding motion of solid object is proportional to the loading force and not dependent on the contact area, holds well for various systems. Here we show, however, the breakdown of the Amontons' law for the elastic object which have local friction obeying Amontons' law and is under uniform pressure by FEM calculation The external shearing force applied to the trailing edge of the sample induces local slip. The range of the slip increases with the increasing external force adiabatically at first. When the range reaches the critical magnitude, the slips moves rapidly and reaches the leading edge of the sample then the whole system slides. These behaviors are consistent with the experiment by Rubinstein et.al. (Phys. Rev. Lett. 98, 226103). The static frictional coefficient, the ratio between the static frictional force for the whole system and the loading force, decreases with the increasing pressure. This means the breakdown of Amontons' law. The pressure dependence of the frictional coefficient is caused by the change of the critical length of the local slip. The behaviors of the local slip and the frictional coefficient are well explained by the 1 dimensional model analytically.

Analysis, Design and Optimization of Non-Cylindrical Fuselage for Blended-Wing-Body (BWB) Vehicle

NASA Technical Reports Server (NTRS)

Mukhopadhyay, V.; Sobieszczanski-Sobieski, J.; Kosaka, I.; Quinn, G.; Charpentier, C.

2002-01-01

Initial results of an investigation towards finding an efficient non-cylindrical fuselage configuration for a conceptual blended-wing-body flight vehicle were presented. A simplified 2-D beam column analysis and optimization was performed first. Then a set of detailed finite element models of deep sandwich panel and ribbed shell construction concepts were analyzed and optimized. Generally these concepts with flat surfaces were found to be structurally inefficient to withstand internal pressure and resultant compressive loads simultaneously. Alternatively, a set of multi-bubble fuselage configuration concepts were developed for balancing internal cabin pressure load efficiently, through membrane stress in inner-stiffened shell and inter-cabin walls. An outer-ribbed shell was designed to prevent buckling due to external resultant compressive loads. Initial results from finite element analysis appear to be promising. These concepts should be developed further to exploit their inherent structurally efficiency.

Results of Experimental Investigations to Determine External Tank Protuberance Loads Using a 0.03-Scale Model of the Space Shuttle Launch Configuration (Model 47-OTS) in the NASA/ARC Unitary Plan Wind Tunnel, Volume 2

NASA Technical Reports Server (NTRS)

Houlihan, S. R.

1992-01-01

Data were obtained on a 3-percent model of the Space Shuttle launch vehicle in the NASA/Ames Research Center 11x11-foot and 9x7-foot Unitary Plan Wind Tunnels. This test series has been identified as IA19OA/B and was conducted from 7 Feb. 1980 to 19 Feb. 1980 (IA19OA) and from 17 March 1980 to 19 March 1980 and from 8 May 1980 to 30 May 1980 (IA19OB). The primary test objective was to obtain structural loads on the following external tank protuberances: (1) LO2 feedline; (2) GO2 pressure line; (3) LO2 antigeyser line; (4) GH2 pressure line; (5) LH2 tank cable tray; (6) LO2 tank cable tray; (7) Bipod; (8) ET/SRB cable tray; and (9) Crossbeam/Orbiter cable tray. To fulfill these objectives the following steps were taken: Eight 3-component balances were used to measure forces on various sections of 1 thru 6 above; 315 pressure orifices were distributed over all 9 above items. The LO2 feedline was instrumented with 96 pressure taps and was rotated to four positions to yield 384 pressure measurements. The LO2 antigeyser line was instrumented with 64 pressure taps and was rotated to two positions to yield 128 pressure measurements; Three Chrysler miniature flow direction probes were mounted on a traversing mechanism on the tank upper surface centerline to obtain flow field data between the forward and aft attach structures; and Schlieren photographs and ultraviolet flow photographs were taken at all test conditions. Data from each of the four test phases are presented.

Results of experimental investigations to determine external tank protuberance loads using a 0.03-scale model of the Space Shuttle launch configuration (model 47-OTS) in the NASA/ARC unitary plan wind tunnel, volume 1

NASA Technical Reports Server (NTRS)

Houlihan, S. R.

1992-01-01

Data were obtained on a 3-percent model of the Space Shuttle launch vehicle in the NASA/Ames Research Center 11x11-foot and 9x7-foot Unitary Plan Wind Tunnels. This test series has been identified as IA190A/B and was conducted from 7 Feb. 1980 to 19 Feb. 1980 (IA190A) and from 17 March 1980 to 19 March 1980 and from 8 May 1980 to 30 May 1980 (IA190B). The primary test objective was to obtain structural loads on the following external tank protuberances: (1) LO2 feedline, (2) GO2 pressure line, (3) LO2 antigeyser line, (4) GH2 pressure line, (5) LH2 tank cable tray, (6) LO2 tank cable tray, (7) Bipod, (8) ET/SRB cable tray, and (9) Crossbeam/Orbiter cable tray. To fulfill these objectives the following steps were taken: (1) Eight 3-component balances were used to measure forces on various sections of 1 thru 6 above. (2) 315 pressure orifices were distributed over all 9 above items. The LO2 feedline was instrumented with 96 pressure taps and was rotated to four positions to yield 384 pressure measurements. The LO2 antigeyser line was instrumented with 64 pressure taps and was rotated to two positions to yield 128 pressure measurements. (3) Three Chrysler miniature flow direction probes were mounted on a traversing mechanism on the tank upper surface centerline to obtain flow field data between the forward and aft attach structures. (4) Schlieren photographs and ultraviolet flow photographs were taken at all test conditions. Data from each of the four test phases are presented.

Effects of external pressure on the performance and ageing of single-layer lithium-ion pouch cells

NASA Astrophysics Data System (ADS)

Mussa, Abdilbari Shifa; Klett, Matilda; Lindbergh, Göran; Lindström, Rakel Wreland

2018-05-01

The effects of external compression on the performance and ageing of NMC(1/3)/Graphite single-layer Li-ion pouch cells are investigated using a spring-loaded fixture. The influence of pressure (0.66, 0.99, 1.32, and 1.98 MPa) on impedance is characterized in fresh cells that are subsequently cycled at the given pressure levels. The aged cells are analyzed for capacity fade and impedance rise at the cell and electrode level. The effect of pressure distribution that may occur in large-format cells or in a battery pack is simulated using parallel connected cells. The results show that the kinetic and mass transport resistance increases with pressure in a fresh cell. An optimum pressure around 1.3 MPa is shown to be beneficial to reduce cyclable-lithium loss during cycling. The minor active mass losses observed in the electrodes are independent of the ageing pressure, whereas ageing pressure affects the charge transfer resistance of both NMC and graphite electrodes and the ohmic resistance of the cell. Pressure distribution induces current distribution but the enhanced current throughput at lower pressures cell does not accelerate its ageing. Conclusions from this work can explain some of the discrepancies in non-uniform ageing reported in the literature and indicate coupling between electrochemistry and mechanics.

Bending strength model for internal spur gear teeth

NASA Technical Reports Server (NTRS)

Savage, Michael; Rubadeux, K. L.; Coe, H. H.

1995-01-01

Internal spur gear teeth are normally stronger than pinion teeth of the same pitch and face width since external teeth are smaller at the base. However, ring gears which are narrower have an unequal addendum or are made of a material with a lower strength than that of the meshing pinion may be loaded more critically in bending. In this study, a model for the bending strength of an internal gear tooth as a function of the applied load pressure angle is presented which is based on the inscribed Lewis constant strength parabolic beam. The bending model includes a stress concentration factor and an axial compression term which are extensions of the model for an external gear tooth. The geometry of the Lewis factor determination is presented, the iteration to determine the factor is described, and the bending strength J factor is compared to that of an external gear tooth. This strength model will assist optimal design efforts for unequal addendum gears and gears of mixed materials.

Evaluation of Load Analysis Methods for NASAs GIII Adaptive Compliant Trailing Edge Project

NASA Technical Reports Server (NTRS)

Cruz, Josue; Miller, Eric J.

2016-01-01

The Air Force Research Laboratory (AFRL), NASA Armstrong Flight Research Center (AFRC), and FlexSys Inc. (Ann Arbor, Michigan) have collaborated to flight test the Adaptive Compliant Trailing Edge (ACTE) flaps. These flaps were installed on a Gulfstream Aerospace Corporation (GAC) GIII aircraft and tested at AFRC at various deflection angles over a range of flight conditions. External aerodynamic and inertial load analyses were conducted with the intention to ensure that the change in wing loads due to the deployed ACTE flap did not overload the existing baseline GIII wing box structure. The objective of this paper was to substantiate the analysis tools used for predicting wing loads at AFRC. Computational fluid dynamics (CFD) models and distributed mass inertial models were developed for predicting the loads on the wing. The analysis tools included TRANAIR (full potential) and CMARC (panel) models. Aerodynamic pressure data from the analysis codes were validated against static pressure port data collected in-flight. Combined results from the CFD predictions and the inertial load analysis were used to predict the normal force, bending moment, and torque loads on the wing. Wing loads obtained from calibrated strain gages installed on the wing were used for substantiation of the load prediction tools. The load predictions exhibited good agreement compared to the flight load results obtained from calibrated strain gage measurements.

Test Report for MSFC Test No. 83-2: Pressure scaled water impact test of a 12.5 inch diameter model of the Space Shuttle solid rocket booster filament wound case and external TVC PCD

NASA Technical Reports Server (NTRS)

1983-01-01

Water impact tests using a 12.5 inch diameter model representing a 8.56 percent scale of the Space Shuttle Solid Rocket Booster configuration were conducted. The two primary objectives of this SRB scale model water impact test program were: 1. Obtain cavity collapse applied pressure distributions for the 8.56 percent rigid body scale model FWC pressure magnitudes as a function of full-scale initial impact conditions at vertical velocities from 65 to 85 ft/sec, horizontal velocities from 0 to 45 ft/sec, and angles from -10 to +10 degrees. 2. Obtain rigid body applied pressures on the TVC pod and aft skirt internal stiffener rings at initial impact and cavity collapse loading events. In addition, nozzle loads were measured. Full scale vertical velocities of 65 to 85 ft/sec, horizontal velocities of 0 to 45 ft/sec, and impact angles from -10 to +10 degrees simulated.

Predicting the conditions under which vibroacoustic resonances with external periodic loads occur in the primary coolant circuits of VVER-based NPPs

NASA Astrophysics Data System (ADS)

Proskuryakov, K. N.; Fedorov, A. I.; Zaporozhets, M. V.

2015-08-01

The accident at the Japanese Fukushima Daiichi nuclear power plant (NPP) caused by an earthquake showed the need of taking further efforts aimed at improving the design and engineering solutions for ensuring seismic resistance of NPPs with due regard to mutual influence of the dynamic processes occurring in the NPP building structures and process systems. Resonance interaction between the vibrations of NPP equipment and coolant pressure pulsations leads to an abnormal growth of dynamic stresses in structural materials, accelerated exhaustion of equipment service life, and increased number of sudden equipment failures. The article presents the results from a combined calculation-theoretical and experimental substantiation of mutual amplification of two kinds of external periodic loads caused by rotation of the reactor coolant pump (RCP) rotor and an earthquake. The data of vibration measurements at an NPP are presented, which confirm the predicted multiple amplification of vibrations in the steam generator and RCP at a certain combination of coolant thermal-hydraulic parameters. It is shown that the vibration frequencies of the main equipment may fall in the frequency band corresponding to the maximal values in the envelope response spectra constructed on the basis of floor accelerograms. The article presents the results from prediction of conditions under which vibroacoustic resonances with external periodic loads take place, which confirm the occurrence of additional earthquake-induced multiple growth of pressure pulsation intensity in the steam generator at the 8.3 Hz frequency and additional multiple growth of vibrations of the RCP and the steam generator cold header at the 16.6 Hz frequency. It is shown that at the elastic wave frequency equal to 8.3 Hz in the coolant, resonance occurs with the frequency of forced vibrations caused by the rotation of the RCP rotor. A conclusion is drawn about the possibility of exceeding the design level of equipment vibrations under the effect of external periodic loads caused by an earthquake when the vibration frequency of the reactor plant main equipment and the frequency of elastic waves fall in the frequency band corresponding to the maximal values of envelope response spectra.

Subject-specific modeling of muscle force and knee contact in total knee arthroplasty.

PubMed

Navacchia, Alessandro; Rullkoetter, Paul J; Schütz, Pascal; List, Renate B; Fitzpatrick, Clare K; Shelburne, Kevin B

2016-09-01

Understanding the mechanical loading environment and resulting joint mechanics for activities of daily living in total knee arthroplasty is essential to continuous improvement in implant design. Although survivorship of these devices is good, a substantial number of patients report dissatisfaction with the outcome of their procedure. Knowledge of in vivo kinematics and joint loading will enable improvement in preclinical assessment and refinement of implant geometry. The purpose of this investigation was to describe the mechanics of total knee arthroplasty during a variety of activities of daily living (gait, walking down stairs, and chair rise/sit). Estimates of muscle forces, tibial contact load, location, and pressure distribution was performed through a combination of mobile fluoroscopy data collection, musculoskeletal modeling, and finite element simulation. For the activities evaluated, joint compressive load was greatest during walking down stairs; however, the highest contact pressure occurred during chair rise/sit. The joint contact moment in the frontal plane was mainly varus for gait and walking down stairs, while it was valgus during chair rise/sit. Excursion of the center of pressure on the tibial component was similar during each activity and between the medial and lateral sides. The main determinants of center of pressure location were internal-external rotation, joint load, and tibial insert conformity. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1576-1587, 2016. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Hydromechanics in dentine: role of dentinal tubules and hydrostatic pressure on mechanical stress-strain distribution.

PubMed

Kishen, A; Vedantam, S

2007-10-01

This investigation is to understand the role of free water in the dentinal tubules on the mechanical integrity of bulk dentine. Three different experiments were conducted in this study. In experiment 1, three-dimensional models of dentine with gradient elastic modulus, homogenous elastic modulus, and with and without hydrostatic pressure were simulated using the finite element method. Static compressive loads of 15, 50 and 100 N were applied and the distribution of the principal stresses, von Mises stresses, and strains in loading direction were determined. In experiment 2, experimental compression testing of fully hydrated and partially dehydrated dentine (21 degrees C for 72 h) was conducted using a Universal testing machine. In experiment 3, Fourier transform infrared spectroscopic analysis of hydrated and partially dehydrated dentine was carried out. The finite element analysis revealed that the dentine model with simulated hydrostatic pressure displayed residual tensile stresses and strains in the inner region adjacent to the root canal. When external compressive loads were applied to the model, the residual stresses and strains counteracted the applied loads. Similarly the hydrated specimens subjected to experimental compression loads showed greater toughness when compared to the partially dehydrated specimens. The stress at fracture was significantly higher in partially dehydrated specimens (p=0.014), while the strain at fracture was significantly higher in hydrated dentine specimens (p=0.037). These experiments highlighted the distinct role of free water in the dentinal tubules and hydrostatic pressure on the stress-strain distribution within the bulk dentine.

[The effects of work in an air-conditioned cabin and stay in a resting chamber on blood pressure and heart rate of operators employed in deep copper mines].

PubMed

Borodulin-Nadzieja, L; Janocha, A; Pietraszkiewicz, T; Salomon, E; Stańda, M

2001-01-01

This paper is part of a wider comparative study of the heart rate, blood pressure, external and core temperature in operators of self-propelled mining machines with and without air-conditioning cabins. Two groups, each of ten operators, characterised by the similar age and duration of employment, stayed for 20 min a specially prepared resting chamber with much more advantageous microclimatic conditions. The results of our examinations (Holter heart rate and continuous blood pressure recordings, external and core temperature measurements) revealed that during the work (particularly during the increased work-load) all parameters recorded were significantly lower in air-conditioning cabins as compared with the group working without air-condition. In both groups, a complete restitution of the heart rate and blood pressure was observed after a 20-min stay in the resting chamber. During the work, a statistically significant increase in the external temperature was found in both groups of operators, whereas the increase in the core temperature was observed only in operators working without air-condition. After a 20-min stay in the resting chamber, a complete return to the normal temperature was noted only in operators working in air-conditioned cabins.

Frequency effects on the stability of a journal bearing for periodic loading

NASA Technical Reports Server (NTRS)

Vijayaraghavan, D.; Brewe, D. E.

1991-01-01

The stability of a journal bearing is numerically predicted when a unidirectional periodic external load is applied. The analysis is performed using a cavitation algorithm, which mimics the Jakobsson-Floberg and Olsson (JFO) theory by accounting for the mass balance through the complete bearing. Hence, the history of the film is taken into consideration. The loading pattern is taken to be sinusoidal and the frequency of the load cycle is varied. The results are compared with the predictions using Reynolds boundary conditions for both film rupture and reformation. With such comparisons, the need for accurately predicting the cavitation regions for complex loading patterns is clearly demonstrated. For a particular frequency of loading, the effects of mass, amplitude of load variation and frequency of journal speed are also investigated. The journal trajectories, transient variations in fluid film forces, net surface velocity and minimum film thickness, and pressure profiles are also presented.

Double-cross hydrostatic pressure sample injection for chip CE: variable sample plug volume and minimum number of electrodes.

PubMed

Luo, Yong; Wu, Dapeng; Zeng, Shaojiang; Gai, Hongwei; Long, Zhicheng; Shen, Zheng; Dai, Zhongpeng; Qin, Jianhua; Lin, Bingcheng

2006-09-01

A novel sample injection method for chip CE was presented. This injection method uses hydrostatic pressure, generated by emptying the sample waste reservoir, for sample loading and electrokinetic force for dispensing. The injection was performed on a double-cross microchip. One cross, created by the sample and separation channels, is used for formation of a sample plug. Another cross, formed by the sample and controlling channels, is used for plug control. By varying the electric field in the controlling channel, the sample plug volume can be linearly adjusted. Hydrostatic pressure takes advantage of its ease of generation on a microfluidic chip, without any electrode or external pressure pump, thus allowing a sample injection with a minimum number of electrodes. The potential of this injection method was demonstrated by a four-separation-channel chip CE system. In this system, parallel sample separation can be achieved with only two electrodes, which is otherwise impossible with conventional injection methods. Hydrostatic pressure maintains the sample composition during the sample loading, allowing the injection to be free of injection bias.

Load responsive multilayer insulation performance testing

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

Dye, S.; Kopelove, A.; Mills, G. L.

Cryogenic insulation designed to operate at various pressures from one atmosphere to vacuum, with high thermal performance and light weight, is needed for cryogenically fueled space launch vehicles and aircraft. Multilayer insulation (MLI) performs well in a high vacuum, but the required vacuum shell for use in the atmosphere is heavy. Spray-on foam insulation (SOFI) is often used in these systems because of its light weight, but can have a higher heat flux than desired. We report on the continued development of Load Responsive Multilayer Insulation (LRMLI), an advanced thermal insulation system that uses dynamic beam discrete spacers that providemore » high thermal performance both in atmosphere and vacuum. LRMLI consists of layers of thermal radiation barriers separated and supported by micromolded polymer spacers. The spacers have low thermal conductance, and self-support a thin, lightweight vacuum shell that provides internal high vacuum in the insulation. The dynamic load responsive spacers compress to support the external load of a vacuum shell in one atmosphere, and decompress under reduced atmospheric pressure for lower heat leak. Structural load testing was performed on the spacers with various configurations. LRMLI was installed on a 400 liter tank and boil off testing with liquid nitrogen performed at various chamber pressures from one atmosphere to high vacuum. Testing was also performed with an MLI blanket on the outside of the LRMLI.« less

The Effect of Muscle Direction on the Predictions of Finite Element Model of Human Lumbar Spine

PubMed Central

Wang, Zhi-peng; Pei, Xiao-long

2018-01-01

The normal physiological loads from muscles experienced by the spine are largely unknown due to a lack of data. The aim of this study is to investigate the effects of varying muscle directions on the outcomes predicted from finite element models of human lumbar spine. A nonlinear finite element model of L3–L5 was employed. The force of the erector spinae muscle, the force of the rectus abdominis muscle, follower loads, and upper body weight were applied. The model was fixed in a neural standing position and the direction of the force of the erector spinae muscle and rectus abdominis muscle was varied in three directions. The intradiscal pressure, reaction moments, and intervertebral rotations were calculated. The intradiscal pressure of L4-L5 was 0.56–0.57 MPa, which agrees with the in vivo pressure of 0.5 MPa from the literatures. The models with the erector spinae muscle loaded in anterior-oblique direction showed the smallest reaction moments (less than 0.6 Nm) and intervertebral rotations of L3-L4 and L4-L5 (less than 0.2 degrees). In comparison with loading in the vertical direction and posterior-oblique direction, the erector spinae muscle loaded in the anterior-oblique direction required lower external force or moment to keep the lumbar spine in the neutral position. PMID:29511680

The Effect of Muscle Direction on the Predictions of Finite Element Model of Human Lumbar Spine.

PubMed

Zhu, Rui; Niu, Wen-Xin; Wang, Zhi-Peng; Pei, Xiao-Long; He, Bin; Zeng, Zhi-Li; Cheng, Li-Ming

2018-01-01

The normal physiological loads from muscles experienced by the spine are largely unknown due to a lack of data. The aim of this study is to investigate the effects of varying muscle directions on the outcomes predicted from finite element models of human lumbar spine. A nonlinear finite element model of L3-L5 was employed. The force of the erector spinae muscle, the force of the rectus abdominis muscle, follower loads, and upper body weight were applied. The model was fixed in a neural standing position and the direction of the force of the erector spinae muscle and rectus abdominis muscle was varied in three directions. The intradiscal pressure, reaction moments, and intervertebral rotations were calculated. The intradiscal pressure of L4-L5 was 0.56-0.57 MPa, which agrees with the in vivo pressure of 0.5 MPa from the literatures. The models with the erector spinae muscle loaded in anterior-oblique direction showed the smallest reaction moments (less than 0.6 Nm) and intervertebral rotations of L3-L4 and L4-L5 (less than 0.2 degrees). In comparison with loading in the vertical direction and posterior-oblique direction, the erector spinae muscle loaded in the anterior-oblique direction required lower external force or moment to keep the lumbar spine in the neutral position.

ASTRYD: A new numerical tool for aircraft cabin and environmental noise prediction

NASA Astrophysics Data System (ADS)

Berhault, J.-P.; Venet, G.; Clerc, C.

ASTRYD is an analytical tool, developed originally for underwater applications, that computes acoustic pressure distribution around three-dimensional bodies in closed spaces like aircraft cabins. The program accepts data from measurements or other simulations, processes them in the time domain, and delivers temporal evolutions of the acoustic pressures and accelerations, as well as the radiated/diffracted pressure at arbitrary points located in the external/internal space. A typical aerospace application is prediction of acoustic load on satellites during the launching phase. An aeronautic application is engine noise distribution on a business jet body for prediction of environmental and cabin noise.

Aerodynamic and heat transfer analysis of the low aspect ratio turbine

NASA Astrophysics Data System (ADS)

Sharma, O. P.; Nguyen, P.; Ni, R. H.; Rhie, C. M.; White, J. A.

1987-06-01

The available two- and three-dimensional codes are used to estimate external heat loads and aerodynamic characteristics of a highly loaded turbine stage in order to demonstrate state-of-the-art methodologies in turbine design. By using data for a low aspect ratio turbine, it is found that a three-dimensional multistage Euler code gives good averall predictions for the turbine stage, yielding good estimates of the stage pressure ratio, mass flow, and exit gas angles. The nozzle vane loading distribution is well predicted by both the three-dimensional multistage Euler and three-dimensional Navier-Stokes codes. The vane airfoil surface Stanton number distributions, however, are underpredicted by both two- and three-dimensional boundary value analysis.

An optical method for measuring exhaust gas pressure from an internal combustion engine at high speed

NASA Astrophysics Data System (ADS)

Leach, Felix C. P.; Davy, Martin H.; Siskin, Dmitrij; Pechstedt, Ralf; Richardson, David

2017-12-01

Measurement of exhaust gas pressure at high speed in an engine is important for engine efficiency, computational fluid dynamics analysis, and turbocharger matching. Currently used piezoresistive sensors are bulky, require cooling, and have limited lifetimes. A new sensor system uses an interferometric technique to measure pressure by measuring the size of an optical cavity, which varies with pressure due to movement of a diaphragm. This pressure measurement system has been used in gas turbine engines where the temperatures and pressures have no significant transients but has never been applied to an internal combustion engine before, an environment where both temperature and pressure can change rapidly. This sensor has been compared with a piezoresistive sensor representing the current state-of-the-art at three engine operating points corresponding to both light load and full load. The results show that the new sensor can match the measurements from the piezoresistive sensor except when there are fast temperature swings, so the latter part of the pressure during exhaust blowdown is only tracked with an offset. A modified sensor designed to compensate for these temperature effects is also tested. The new sensor has shown significant potential as a compact, durable sensor, which does not require external cooling.

An optical method for measuring exhaust gas pressure from an internal combustion engine at high speed.

PubMed

Leach, Felix C P; Davy, Martin H; Siskin, Dmitrij; Pechstedt, Ralf; Richardson, David

2017-12-01

Measurement of exhaust gas pressure at high speed in an engine is important for engine efficiency, computational fluid dynamics analysis, and turbocharger matching. Currently used piezoresistive sensors are bulky, require cooling, and have limited lifetimes. A new sensor system uses an interferometric technique to measure pressure by measuring the size of an optical cavity, which varies with pressure due to movement of a diaphragm. This pressure measurement system has been used in gas turbine engines where the temperatures and pressures have no significant transients but has never been applied to an internal combustion engine before, an environment where both temperature and pressure can change rapidly. This sensor has been compared with a piezoresistive sensor representing the current state-of-the-art at three engine operating points corresponding to both light load and full load. The results show that the new sensor can match the measurements from the piezoresistive sensor except when there are fast temperature swings, so the latter part of the pressure during exhaust blowdown is only tracked with an offset. A modified sensor designed to compensate for these temperature effects is also tested. The new sensor has shown significant potential as a compact, durable sensor, which does not require external cooling.

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

PubMed

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

2005-07-01

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

Buckling analysis of Big Dee Vacuum Vessel

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

Lightner, S.; Gallix, R.

1983-12-01

A simplified three-dimensional shell buckling analysis of the GA Technologies Inc., Big Dee Vacuum Vessel (V/V) was performed using the finite element program TRICO. A coarse-mesh linear elastic model, which accommodated the support boundary conditions, was used to determine the buckling mode shape under a uniform external pressure. Using this buckling mode shape, refined models were used to calculate the linear buckling load (P/sub crit/) more accurately. Several different designs of the Big Dee V/V were considered in this analysis. The supports for the V/V were equally-spaced radial pins at the outer diameter of the mid-plane. For all the casesmore » considered, the buckling mode was axisymmetric in the toroidal direction. Therefore, it was possible to use only a small angular sector of a toric shell for the refined analysis. P/sub crit/ for the Big Dee is about 60 atm for a uniform external pressure. Also investigated in this analysis were the effects of geometrical imperfections and non-uniform pressure distributions.« less

Rambling and trembling in response to body loading.

PubMed

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

2012-04-01

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

Influence of abutment screw preload on stress distribution in marginal bone.

PubMed

Khraisat, Ameen

2012-01-01

Changes in an implant assembly after abutment connection might possibly cause deformation in the implant/abutment joint and even in the marginal bone. The aim of this study was to evaluate the influence of abutment screw preload through the implant collar on marginal bone stress without external load application. Models of three implant parts made of titanium (implant, abutment, and abutment screw) and cortical bone were built and positioned with computer-aided design software. Meshing and generation of boundary conditions, loads, and interactions were performed. Each part was meshed independently. The sole load applied to the model was a torque of 32 Ncm on the abutment screw about its axis of rotation. The implant collar was deformed axially after the screw was tightened (3 μm). This deformation resulted in 60 MPa of stress in the marginal bone. Moreover, pressure on the marginal bone in a radial direction was observed. It can be concluded that, without any external load application, abutment screw preload exerts stresses on the implant collar and the marginal bone. These findings should help guide the development of new implant/abutment joint designs that exert less stress on the marginal bone.

Effect of External Loading on Force and Power Production During Plyometric Push-ups.

PubMed

Hinshaw, Taylour J; Stephenson, Mitchell L; Sha, Zhanxin; Dai, Boyi

2018-04-01

Hinshaw, TJ, Stephenson, ML, Sha, Z, and Dai, B. Effect of external loading on force and power production during plyometric push-ups. J Strength Cond Res 32(4): 1099-1108, 2018-One common exercise to train upper-body strength and power is the push-up. Training at the loads that would produce the greatest power is an effective way to increase peak power. The purpose of the current study was to quantify the changes in peak force, peak power, and peak velocity among a modified plyometric push-up and plyometric push-ups with or without external loading in physically active young adults. Eighteen male and 17 female participants completed 4 push-ups: (a) modified plyometric push-up on the knees, (b) plyometric push-up without external loading, (c) plyometric push-up with an external load of 5% of body weight, and (d) plyometric push-up with an external load of 10% of body weight. Two force platforms were set up to collect vertical ground reaction forces at the hands and feet. The modified plyometric push-up demonstrated the lowest force, power, and velocity (5.4≥ Cohen's dz ≥1.2). Peak force and force at peak velocity increased (3.8≥ Cohen's dz ≥0.3) and peak velocity and velocity at peak power decreased (1.4≥ Cohen's dz ≥0.8) for the push-up without external loading compared with the 2 push-ups with external loading. No significant differences were observed for peak power among the push-ups with or without external loading (0.4≥ Cohen's dz ≥0.1). Although peak power is similar with or without external loading, push-ups without external loading may be more beneficial for a quick movement, and push-ups with external loading may be more beneficial for a greater force production.

Method to predict external store carriage characteristics at transonic speeds

NASA Technical Reports Server (NTRS)

Rosen, Bruce S.

1988-01-01

Development of a computational method for prediction of external store carriage characteristics at transonic speeds is described. The geometric flexibility required for treatment of pylon-mounted stores is achieved by computing finite difference solutions on a five-level embedded grid arrangement. A completely automated grid generation procedure facilitates applications. Store modeling capability consists of bodies of revolution with multiple fore and aft fins. A body-conforming grid improves the accuracy of the computed store body flow field. A nonlinear relaxation scheme developed specifically for modified transonic small disturbance flow equations enhances the method's numerical stability and accuracy. As a result, treatment of lower aspect ratio, more highly swept and tapered wings is possible. A limited supersonic freestream capability is also provided. Pressure, load distribution, and force/moment correlations show good agreement with experimental data for several test cases. A detailed computer program description for the Transonic Store Carriage Loads Prediction (TSCLP) Code is included.

The effect of gas and fluid flows on nonlinear lateral vibrations of rotating drill strings

NASA Astrophysics Data System (ADS)

Khajiyeva, Lelya; Kudaibergenov, Askar; Kudaibergenov, Askat

2018-06-01

In this work we develop nonlinear mathematical models describing coupled lateral vibrations of a rotating drill string under the effect of external supersonic gas and internal fluid flows. An axial compressive load and a torque also affect the drill string. The mathematical models are derived by the use of Novozhilov's nonlinear theory of elasticity with implementation of Hamilton's variation principle. Expressions for the gas flow pressure are determined according to the piston theory. The fluid flow is considered as added mass inside the curved tube of the drill string. Using an algorithm developed in the Mathematica computation program on the basis of the Galerkin approach and the stiffness switching method the numerical solution of the obtained approximate differential equations is found. Influences of the external loads, drill string angular speed of rotation, parameters of the gas and fluid flows on the drill string vibrations are shown.

14 CFR 133.17 - Requirements for issuance of a rotorcraft external-load operator certificate.

Code of Federal Regulations, 2010 CFR

2010-01-01

... external-load operator certificate. 133.17 Section 133.17 Aeronautics and Space FEDERAL AVIATION...: CERTIFICATION AND OPERATIONS ROTORCRAFT EXTERNAL-LOAD OPERATIONS Certification Rules § 133.17 Requirements for... §§ 133.19, 133.21, and 133.23, the Administrator issues a Rotorcraft External-Load Operator Certificate...

Simulation of Propellant Loading System Senior Design Implement in Computer Algorithm

NASA Technical Reports Server (NTRS)

Bandyopadhyay, Alak

2010-01-01

Propellant loading from the Storage Tank to the External Tank is one of the very important and time consuming pre-launch ground operations for the launch vehicle. The propellant loading system is a complex integrated system involving many physical components such as the storage tank filled with cryogenic fluid at a very low temperature, the long pipe line connecting the storage tank with the external tank, the external tank along with the flare stack, and vent systems for releasing the excess fuel. Some of the very important parameters useful for design purpose are the prediction of pre-chill time, loading time, amount of fuel lost, the maximum pressure rise etc. The physics involved for mathematical modeling is quite complex due to the fact the process is unsteady, there is phase change as some of the fuel changes from liquid to gas state, then conjugate heat transfer in the pipe walls as well as between solid-to-fluid region. The simulation is very tedious and time consuming too. So overall, this is a complex system and the objective of the work is student's involvement and work in the parametric study and optimization of numerical modeling towards the design of such system. The students have to first become familiar and understand the physical process, the related mathematics and the numerical algorithm. The work involves exploring (i) improved algorithm to make the transient simulation computationally effective (reduced CPU time) and (ii) Parametric study to evaluate design parameters by changing the operational conditions

Importance of the mitral apparatus for left ventricular function: an experimental approach.

PubMed

Gams, E; Hagl, S; Schad, H; Heimisch, W; Mendler, N; Sebening, F

1992-01-01

In an experimental study of 31 anesthetized dogs the importance of the mitral apparatus for the left ventricular function was investigated. During extracorporeal circulation bileaflet mitral valve prostheses were implanted preserving the mitral subvalvular apparatus. Flexible wires were slung around the chordae tendineae and exteriorized through the left ventricular wall to cut the chordae by electrocautery from the outside when the heart was beating again. External and internal left ventricular dimensions were measured by sonomicrometry, left ventricular stroke volume by electromagnetic flowmeters around the ascending aorta, left ventricular end-diastolic volume by dye dilution technique, and left ventricular pressure by catheter tip manometers. Different preload levels were achieved by volume loading with blood transfusion before and after cutting the chordae tendineae. When the chordae had been divided peak systolic left ventricular pressure did not change. Heart rate only increased at the lowest left ventricular end-diastolic pressures of 3-4 mmHg, but remained unchanged at higher preload levels. Cardiac output decreased significantly up to -9% at left ventricular end-diastolic pressures of 5-10 mmHg, while left ventricular dp/dtmax showed a consistent reduction of up to -15% at any preload level. Significant reductions were also seen in systolic shortening in the left ventricular major axis (by external measurements -27%, by internal recording -43%). Left ventricular end-diastolic dimensions increased in the major axis by +2% when recorded externally, by +10% when measured internally. Systolic and diastolic changes in the minor axis were not consistent and different in the external and internal recordings.(ABSTRACT TRUNCATED AT 250 WORDS)

Space shuttle solid rocket booster water entry cavity collapse loads

NASA Technical Reports Server (NTRS)

Keefe, R. T.; Rawls, E. A.; Kross, D. A.

1982-01-01

Solid rocket booster cavity collapse flight measurements included external pressures on the motor case and aft skirt, internal motor case pressures, accelerometers located in the forward skirt, mid-body area, and aft skirt, as well as strain gages located on the skin of the motor case. This flight data yielded applied pressure longitudinal and circumferential distributions which compare well with model test predictions. The internal motor case ullage pressure, which is below atmospheric due to the rapid cooling of the hot internal gas, was more severe (lower) than anticipated due to the ullage gas being hotter than predicted. The structural dynamic response characteristics were as expected. Structural ring and wall damage are detailed and are considered to be attributable to the direct application of cavity collapse pressure combined with the structurally destabilizing, low internal motor case pressure.

Pressure vessel bottle mount

NASA Technical Reports Server (NTRS)

Wingett, Paul (Inventor)

2001-01-01

A mounting assembly for mounting a composite pressure vessel to a vehicle includes a saddle having a curved surface extending between two pillars for receiving the vessel. The saddle also has flanged portions which can be bolted to the vehicle. Each of the pillars has hole in which is mounted the shaft portion of an attachment member. A resilient member is disposed between each of the shaft portions and the holes and loaded by a tightening nut. External to the holes, each of the attachment members has a head portion to which a steel band is attached. The steel band circumscribes the vessel and translates the load on the springs into a clamping force on the vessel. As the vessel expands and contracts, the resilient members expand and contract so that the clamping force applied by the band to the vessel remains constant.

An ex vivo porcine skin model to evaluate pressure-reducing devices of different mechanical properties used for pressure ulcer prevention.

PubMed

Yeung, Ching-Yan C; Holmes, David F; Thomason, Helen A; Stephenson, Christian; Derby, Brian; Hardman, Matthew J

2016-11-01

Pressure ulcers are complex wounds caused by pressure- and shear-induced trauma to skin and underlying tissues. Pressure-reducing devices, such as dressings, have been shown to successfully reduce pressure ulcer incidence, when used in adjunct to pressure ulcer preventative care. While pressure-reducing devices are available in a range of materials, with differing mechanical properties, understanding of how a material's mechanical properties will influence clinical efficacy remains limited. The aim of this study was to establish a standardized ex vivo model to allow comparison of the cell protection potential of two gel-like pressure-reducing devices with differing mechanical properties (elastic moduli of 77 vs. 35 kPa). The devices also displayed differing energy dissipation under compressive loading, and resisted strain differently under constant load in compressive creep tests. To evaluate biological efficacy we employed a new ex vivo porcine skin model, with a confirmed elastic moduli closely matching that of human skin (113 vs. 119 kPa, respectively). Static loads up to 20 kPa were applied to porcine skin ex vivo with subsequent evaluation of pressure-induced cell death and cytokine release. Pressure application alone increased the percentage of epidermal apoptotic cells from less than 2% to over 40%, and increased cellular secretion of the pro-inflammatory cytokine TNF-alpha. Co-application of a pressure-reducing device significantly reduced both cellular apoptosis and cytokine production, protecting against cellular damage. These data reveal new insight into the relationship between mechanical properties of pressure-reducing devices and their biological effects. After appropriate validation of these results in clinical pressure ulcer prevention with all tissue layers present between the bony prominence and external surface, this ex vivo porcine skin model could be widely employed to optimize design and evaluation of devices aimed at reducing pressure-induced skin damage. © 2016 The Authors Wound Repair and Regeneration published by Wiley Periodicals, Inc. on behalf of The Wound Healing Society.

Ocean Engineering Studies Compiled 1991. Volume 9. External Pressure Housing - Conrete

DTIC Science & Technology

1991-01-01

by inserts of different rigidities would thus be obtained. Table 1. Description of Concrete Sphere Models and Test...relationship between the insert’s rigidity and the strain increase in its vicinity. Planned investigation by NCEL employing photoelastic analysis of models of ... structural , in which only the load -carrying ability of the structure was checked. In the operational tests, the small-scale model habitat

Molecular dynamics study of silicon carbide properties under external dynamic loading

NASA Astrophysics Data System (ADS)

Utkin, A. V.; Fomin, V. M.

2017-10-01

In this study, molecular dynamic simulations of high-velocity impact of a spherical 3C-SiC cluster, with a wide range of velocities (from 100 to 2600 m/s) and with a rigid wall, were performed. The analysis of the final structure shows that no structural phase transformation occurred in the material, despite the high pressure during the collision process.

The Influence of External Load on Quadriceps Muscle and Tendon Dynamics during Jumping.

PubMed

Earp, Jacob E; Newton, Robert U; Cormie, Prue; Blazevich, Anthony J

2017-11-01

Tendons possess both viscous (rate-dependent) and elastic (rate-independent) properties that determine tendon function. During high-speed movements external loading increases both the magnitude (FT) and rate (RFDT) of tendon loading. The influence of external loading on muscle and tendon dynamics during maximal vertical jumping was explored. Ten resistance-trained men performed parallel-depth, countermovement vertical jumps with and without additional load (0%, 30%, 60%, and 90% of maximum squat lift strength), while joint kinetics and kinematics, quadriceps tendon length (LT) and patellar tendon FT and RFDT were estimated using integrated ultrasound, motion analysis and force platform data and muscle tendon modelling. Estimated FT and RFDT, but not peak LT, increased with external loading. Temporal comparisons between 0% and 90% loads revealed that FT was greater with 90% loading throughout the majority of the movement (11%-81% and 87%-95% movement duration). However, RFDT was greater with 90% load only during the early movement initiation phase (8%-15% movement duration) but was greater in the 0% load condition later in the eccentric phase (27%-38% movement duration). LT was longer during the early movement (12%-23% movement duration) but shorter in the late eccentric and early concentric phases (48%-55% movement duration) with 90% load. External loading positively influenced peak FT and RFDT but tendon strain appeared unaffected, suggesting no additive effect of external loading on patellar tendon lengthening during human jumping. Temporal analysis revealed that external loading resulted in a large initial RFDT that may have caused dynamic stiffening of the tendon and attenuated tendon strain throughout the movement. These results suggest that external loading influences tendon lengthening in both a load- and movement-dependent manner.

Effects of an external circuit on a MHD slider bearing with couplestress fluid between conducting plates

NASA Astrophysics Data System (ADS)

Tasneem Fathima, Syeda; Jamal, Salma; Hanumagowda, B. N.

2018-04-01

A MHD Slider bearing lubricated with conducting couplestress fluid (CCSF) between two electrical conducting plates under the influence of magnetic field in free space is theoretically investigated. A closed form solution for the film pressure and load carrying capacity is obtained analytically in terms of inlet-outlet (IO) film height ratio of slider bearings. The results are presented graphically for different values of operating parameters. The results suggest that the bearings with couplestress fluid as lubricant provide significant load carrying capacity than Newtonian lubricant case. Further, it is observed that the influence of applied magnetic field and induced magnetic field is to increase the load carrying capacity substantially while, the load decreases with increase in IO film ratio. Besides, the conductivity increases the load carrying capacity significantly. The results are compared with the Newtonian Fluid case.

Flexible Piezoelectric-Induced Pressure Sensors for Static Measurements Based on Nanowires/Graphene Heterostructures.

PubMed

Chen, Zefeng; Wang, Zhao; Li, Xinming; Lin, Yuxuan; Luo, Ningqi; Long, Mingzhu; Zhao, Ni; Xu, Jian-Bin

2017-05-23

The piezoelectric effect is widely applied in pressure sensors for the detection of dynamic signals. However, these piezoelectric-induced pressure sensors have challenges in measuring static signals that are based on the transient flow of electrons in an external load as driven by the piezopotential arisen from dynamic stress. Here, we present a pressure sensor with nanowires/graphene heterostructures for static measurements based on the synergistic mechanisms between strain-induced polarization charges in piezoelectric nanowires and the caused change of carrier scattering in graphene. Compared to the conventional piezoelectric nanowire or graphene pressure sensors, this sensor is capable of measuring static pressures with a sensitivity of up to 9.4 × 10 -3 kPa -1 and a fast response time down to 5-7 ms. This demonstration of pressure sensors shows great potential in the applications of electronic skin and wearable devices.

Buckling of thin walled composite cylindrical shell filled with solid propellant

NASA Astrophysics Data System (ADS)

Dash, A. P.; Velmurugan, R.; Prasad, M. S. R.

2017-12-01

This paper investigates the buckling of thin walled composite cylindrical tubes that are partially filled with solid propellant equivalent elastic filler. Experimental investigation is conducted on thin composite tubes made out of S2-glass epoxy, which is made by using filament winding technique. The composite tubes are filled with elastic filler having similar mechanical properties as that of a typical solid propellant used in rocket motors. The tubes are tested for their buckling strength against the external pressure in the presence of the filler. Experimental data confirms the enhancement of external pressure carrying capacity of the composite tubes by up to three times as that of empty tubes for a volumetric loading fraction (VLF) of 0.9. Furthermore, the finite element based geometric nonlinearity analysis predicts the buckling behaviour of the partially filled composite tubes close to the experimental results.

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

Kalaskar, Vickey B; Szybist, James P; Splitter, Derek A

In recent years a number of studies have demonstrated that boosted operation combined with external EGR is a path forward for expanding the high load limit of homogeneous charge compression ignition (HCCI) operation with the negative valve overlap (NVO) valve strategy. However, the effects of fuel composition with this strategy have not been fully explored. In this study boosted HCCI combustion is investigated in a single-cylinder research engine equipped with direct injection (DI) fueling, cooled external exhaust gas recirculation (EGR), laboratory pressurized intake air, and a fully-variable hydraulic valve actuation (HVA) valve train. Three fuels with significant compositional differences aremore » investigated: regular grade gasoline (RON = 90.2), 30% ethanol-gasoline blend (E30, RON = 100.3), and 24% iso-butanol-gasoline blend (IB24, RON = 96.6). Results include engine loads from 350 to 800 kPa IMEPg for all fuels at three engine speeds 1600, 2000, and 2500 rpm. All operating conditions achieved thermal efficiency (gross indicated efficiency) between 38 and 47%, low NOX emissions ( 0.1 g/kWh), and high combustion efficiency ( 96.5%). Detailed sweeps of intake manifold pressure (atmospheric to 250 kPaa), EGR (0 25% EGR), and injection timing are conducted to identify fuel-specific effects. The major finding of this study is that while significant fuel compositional differences exist, in boosted HCCI operation only minor changes in operational conditions are required to achieve comparable operation for all fuels. In boosted HCCI operation all fuels were able to achieve matched load-speed operation, whereas in conventional SI operation the fuel-specific knock differences resulted in significant differences in the operable load-speed space. Although all fuels were operable in boosted HCCI, the respective air handling requirements are also discussed, including an analysis of the demanded turbocharger efficiency.« less

Development of a thermal and structural analysis procedure for cooled radial turbines

NASA Technical Reports Server (NTRS)

Kumar, Ganesh N.; Deanna, Russell G.

1988-01-01

A procedure for computing the rotor temperature and stress distributions in a cooled radial turbine is considered. Existing codes for modeling the external mainstream flow and the internal cooling flow are used to compute boundary conditions for the heat transfer and stress analyses. An inviscid, quasi three-dimensional code computes the external free stream velocity. The external velocity is then used in a boundary layer analysis to compute the external heat transfer coefficients. Coolant temperatures are computed by a viscous one-dimensional internal flow code for the momentum and energy equation. These boundary conditions are input to a three-dimensional heat conduction code for calculation of rotor temperatures. The rotor stress distribution may be determined for the given thermal, pressure and centrifugal loading. The procedure is applied to a cooled radial turbine which will be tested at the NASA Lewis Research Center. Representative results from this case are included.

Development of a thermal and structural analysis procedure for cooled radial turbines

NASA Technical Reports Server (NTRS)

Kumar, Ganesh N.; Deanna, Russell G.

1988-01-01

A procedure for computing the rotor temperature and stress distributions in a cooled radial turbine are considered. Existing codes for modeling the external mainstream flow and the internal cooling flow are used to compute boundary conditions for the heat transfer and stress analysis. The inviscid, quasi three dimensional code computes the external free stream velocity. The external velocity is then used in a boundary layer analysis to compute the external heat transfer coefficients. Coolant temperatures are computed by a viscous three dimensional internal flow cade for the momentum and energy equation. These boundary conditions are input to a three dimensional heat conduction code for the calculation of rotor temperatures. The rotor stress distribution may be determined for the given thermal, pressure and centrifugal loading. The procedure is applied to a cooled radial turbine which will be tested at the NASA Lewis Research Center. Representative results are given.

Designing and Constructing an Optical Monitoring System of Blood Supply to Tissues under Pressure.

PubMed

Hadi, Akbari; Amin, Younessi Heravi Mohammad

2012-04-01

Reduced blood flow due to obstruction is in most cases a primary factor in pressure ulcer formation and creation of bedsores. The aim of this study is to design and manufacture a care system for tissue under pressure, based on variations in blood flow at different depths of tissue. In the manufacture of the system two infrared light transmitters and receivers were located between 5 and 10 mm depth to measure the flow of blood at different in the under- pressure heel tissue. In addition, blood flow was evaluated in an unloaded and loaded condition, with 30 mmHg and 60.0 mmHg. A total of 15 people participated with a mean age of 50. Of these 15; 9 (60%) were men and 6 (40%) were women. Primary measurement results showed different individual differences in variation of blood flow in the tissue. To study signal amplitude changes significantly influenced by external pressure the PPG, P-value was measured. It was noted that there were significant changes in PPG signal amplitude during loading both pressures of 30 and 60 mmHg. Further development of this system would be possible with the use of a more flexible probe and by using a stronger optical receiver and transmitter to access more depth.

29 CFR 1926.958 - External load helicopters.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 29 Labor 8 2010-07-01 2010-07-01 false External load helicopters. 1926.958 Section 1926.958 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR... External load helicopters. In all operations performed using a rotorcraft for moving or placing external...

29 CFR 1926.958 - External load helicopters.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 29 Labor 8 2014-07-01 2014-07-01 false External load helicopters. 1926.958 Section 1926.958 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR... External load helicopters. In all operations performed using a rotorcraft for moving or placing external...

29 CFR 1926.958 - External load helicopters.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 29 Labor 8 2011-07-01 2011-07-01 false External load helicopters. 1926.958 Section 1926.958 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR... External load helicopters. In all operations performed using a rotorcraft for moving or placing external...

29 CFR 1926.958 - External load helicopters.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 29 Labor 8 2012-07-01 2012-07-01 false External load helicopters. 1926.958 Section 1926.958 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR... External load helicopters. In all operations performed using a rotorcraft for moving or placing external...

29 CFR 1926.958 - External load helicopters.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 29 Labor 8 2013-07-01 2013-07-01 false External load helicopters. 1926.958 Section 1926.958 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR... External load helicopters. In all operations performed using a rotorcraft for moving or placing external...

Fluctuating pressures in flow fields of jets

NASA Technical Reports Server (NTRS)

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

1976-01-01

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

Effect of cyclic loading and retightening on reverse torque value in external and internal implants.

PubMed

Cho, Woong-Rae; Huh, Yoon-Hyuk; Park, Chan-Jin; Cho, Lee-Ra

2015-08-01

The aim of this study was to evaluate the effect of cyclic loading and screw retightening on reverse torque value (RTV) in external and internal type implants. Cement-retained abutments were connected with 30 Ncm torque to external and internal type implants. Experimental groups were classified according to implant connection type and retightening/loading protocol. In groups with no retightening, RTV was evaluated after cyclic loading for 100,000 cycles. In groups with retightening, RTV was measured after 3, 10, 100 cycles as well as every 20,000 cycles until 100,000 cycles of loading. Every group showed decreased RTV after cyclic loading. Before and after cyclic loading, external type implants had significantly higher RTVs than internal type implants. In external type implants, retightening did not affect the decrease in RTV. In contrast, retightening 5 times and retightening after 10 cycles of dynamic loading was effective for maintaining RTV in internal type implants. Retightening of screws is more effective in internal type implants than external type implants. Retightening of screws is recommended in the early stage of functional loading.

The relationships between internal and external training load models during basketball training.

PubMed

Scanlan, Aaron T; Wen, Neal; Tucker, Patrick S; Dalbo, Vincent J

2014-09-01

The present investigation described and compared the internal and external training loads during basketball training. Eight semiprofessional male basketball players (mean ± SD, age: 26.3 ± 6.7 years; stature: 188.1 ± 6.2 cm; body mass: 92.0 ± 13.8 kg) were monitored across a 7-week period during the preparatory phase of the annual training plan. A total of 44 total sessions were monitored. Player session ratings of perceived exertion (sRPE), heart rate, and accelerometer data were collected across each training session. Internal training load was determined using the sRPE, training impulse (TRIMP), and summated-heart-rate-zones (SHRZ) training load models. External training load was calculated using an established accelerometer algorithm. Pearson product-moment correlations with 95% confidence intervals (CIs) were used to determine the relationships between internal and external training load models. Significant moderate relationships were observed between external training load and the sRPE (r42 = 0.49, 95% CI = 0.23-0.69, p < 0.001) and TRIMP models (r42 = 0.38, 95% CI = 0.09-0.61, p = 0.011). A significant large correlation was evident between external training load and the SHRZ model (r42 = 0.61, 95% CI = 0.38-0.77, p < 0.001). Although significant relationships were found between internal and external training load models, the magnitude of the correlations and low commonality suggest that internal training load models measure different constructs of the training process than the accelerometer training load model in basketball settings. Basketball coaching and conditioning professionals should not assume a linear dose-response between accelerometer and internal training load models during training and are recommended to combine internal and external approaches when monitoring training load in players.

Plastic-bonded electrodes for nickel-cadmium accumulators. IV - Some specific problems of the positive active layer

NASA Astrophysics Data System (ADS)

Micka, K.; Mrha, J.; Klapste, B.

1980-06-01

The active layer of plastic-bonded nickel oxide electrodes undergoes expansion during discharging and contraction during charging; the latter however does not fully compensate for the expansion. These volume changes can be made reversible by the action of an external pressure. The electro-chemical behavior of the conductive components, carbon black and graphite, shows more or less severe corrosion during anodic current loading.

Distribution of internal pressure around bony prominences: implications to deep tissue injury and effectiveness of intermittent electrical stimulation.

PubMed

Solis, Leandro R; Liggins, Adrian; Uwiera, Richard R E; Poppe, Niek; Pehowich, Enid; Seres, Peter; Thompson, Richard B; Mushahwar, Vivian K

2012-08-01

The overall goal of this project is to develop interventions for the prevention of deep tissue injury (DTI), a form of pressure ulcers that originates in deep tissue around bony prominences. The present study focused on: (1) obtaining detailed measures of the distribution of pressure experienced by tissue around the ischial tuberosities, and (2) investigating the effectiveness of intermittent electrical stimulation (IES), a novel strategy for the prevention of DTI, in alleviating pressure in regions at risk of breakdown due to sustained loading. The experiments were conducted in adult pigs. Five animals had intact spinal cords and healthy muscles and one had a spinal cord injury that led to substantial muscle atrophy at the time of the experiment. A force-controlled servomotor was used to load the region of the buttocks to levels corresponding to 25%, 50% or 75% of each animal's body weight. A pressure transducer embedded in a catheter was advanced into the tissue to measure pressure along a three dimensional grid around the ischial tuberosity of one hind leg. For all levels of external loading in intact animals, average peak internal pressure was 2.01 ± 0.08 times larger than the maximal interfacial pressure measured at the level of the skin. In the animal with spinal cord injury, similar absolute values of internal pressure as that in intact animals were recorded, but the substantial muscle atrophy produced larger maximal interfacial pressures. Average peak internal pressure in this animal was 1.43 ± 0.055 times larger than the maximal interfacial pressure. Peak internal pressure was localized within a ±2 cm region medio-laterally and dorso-ventrally from the bone in intact animals and ±1 cm in the animal with spinal cord injury. IES significantly redistributed internal pressure, shifting the peak values away from the bone in spinally intact and injured animals. These findings provide critical information regarding the relationship between internal and interfacial pressure around the ischial tuberosities during loading levels equivalent to those experienced while sitting. The information could guide future computer models investigating the etiology of DTI, as well as inform the design and prescription of seating cushions for people with reduced mobility. The findings also suggest that IES may be an effective strategy for the prevention of DTI.

SRM attrition rate study of the aft motor case segments due to water impact cavity collapse loading

NASA Technical Reports Server (NTRS)

Crockett, C. D.

1976-01-01

The attrition assessment of the aft segments of Solid Rocket Motor due to water impact requires the establishment of a correlation between loading occurrences and structural capability. Each discrete load case, as identified by the water impact velocities and angle, varies longitudinally and radially in magnitude and distribution of the external pressure. The distributions are further required to be shifted forward or aft one-fourth the vehicle diameter to assure minimization of the effect of test instrumentation location for the load determinations. The asymmetrical load distributions result in large geometric nonlinearities in structural response. The critical structural response is progressive buckling of the case. Discrete stiffeners have been added to these aft segments to aid in gaining maximum structural capability for minimum weight addition for resisting these loads. This report presents the development of the attrition assessment of the aft segments and includes the rationale for eliminating all assessable conservatisms from this assessment.

Nonlinear effects in a plain journal bearing. I - Analytical study. II - Results

NASA Technical Reports Server (NTRS)

Choy, F. K.; Braun, M. J.; Hu, Y.

1991-01-01

In the first part of this work, a numerical model is presented which couples the variable-property Reynolds equation with a rotor-dynamics model for the calculation of a plain journal bearing's nonlinear characteristics when working with a cryogenic fluid, LOX. The effects of load on the linear/nonlinear plain journal bearing characteristics are analyzed and presented in a parametric form. The second part of this work presents numerical results obtained for specific parametric-study input variables (lubricant inlet temperature, external load, angular rotational speed, and axial misalignment). Attention is given to the interrelations between pressure profiles and bearing linear and nonlinear characteristics.

Nonlinear ultrasonic imaging method for closed cracks using subtraction of responses at different external loads.

PubMed

Ohara, Yoshikazu; Horinouchi, Satoshi; Hashimoto, Makoto; Shintaku, Yohei; Yamanaka, Kazushi

2011-08-01

To improve the selectivity of closed cracks for objects other than cracks in ultrasonic imaging, we propose an extension of a novel imaging method, namely, subharmonic phased array for crack evaluation (SPACE) as well as another approach using the subtraction of responses at different external loads. By applying external static or dynamic loads to closed cracks, the contact state in the cracks varies, resulting in an intensity change of responses at cracks. In contrast, objects other than cracks are independent of external load. Therefore, only cracks can be extracted by subtracting responses at different loads. In this study, we performed fundamental experiments on a closed fatigue crack formed in an aluminum alloy compact tension (CT) specimen using the proposed method. We examined the static load dependence of SPACE images and the dynamic load dependence of linear phased array (PA) images by simulating the external loads with a servohydraulic fatigue testing machine. By subtracting the images at different external loads, we show that this method is useful in extracting only the intensity change of responses related to closed cracks, while canceling the responses of objects other than cracks. Copyright © 2010 Elsevier B.V. All rights reserved.

Effect of cyclic loading and retightening on reverse torque value in external and internal implants

PubMed Central

Cho, Woong-Rae; Huh, Yoon-Hyuk; Park, Chan-Jin

2015-01-01

PURPOSE The aim of this study was to evaluate the effect of cyclic loading and screw retightening on reverse torque value (RTV) in external and internal type implants. MATERIALS AND METHODS Cement-retained abutments were connected with 30 Ncm torque to external and internal type implants. Experimental groups were classified according to implant connection type and retightening/loading protocol. In groups with no retightening, RTV was evaluated after cyclic loading for 100,000 cycles. In groups with retightening, RTV was measured after 3, 10, 100 cycles as well as every 20,000 cycles until 100,000 cycles of loading. RESULTS Every group showed decreased RTV after cyclic loading. Before and after cyclic loading, external type implants had significantly higher RTVs than internal type implants. In external type implants, retightening did not affect the decrease in RTV. In contrast, retightening 5 times and retightening after 10 cycles of dynamic loading was effective for maintaining RTV in internal type implants. CONCLUSION Retightening of screws is more effective in internal type implants than external type implants. Retightening of screws is recommended in the early stage of functional loading. PMID:26330975

Delamination of Composite Cylinders

NASA Astrophysics Data System (ADS)

Davies, Peter; Carlsson, Leif A.

The delamination resistance of filament wound glass/epoxy cylinders has been characterized for a range of winding angles and fracture mode ratios using beam fracture specimens. The results reveal that the delamination fracture resistance increases with increasing winding angle and mode II (shear) fraction (GΠ/G). It was also found that interlaced fiber bundles in the filament wound cylinder wall acted as effective crack arresters in mode I loading. To examine the sensitivity of delamina-tion damage on the strength of the cylinders, external pressure tests were performed on filament-wound glass/epoxy composite cylinders with artificial defects and impact damage. The results revealed that the cylinder strength was insensitive to the presence of single delaminations but impact damage caused reductions in failure pressure. The insensitivity of the failure pressure to a single delamination is attributed to the absence of buckling of the delaminated sublaminates before the cylinder wall collapsed. The impacted cylinders contained multiple delaminations, which caused local reduction in the compressive load capability and reduction in failure pressure. The response of glass/epoxy cylinders was compared to impacted carbon reinforced cylinders. Carbon/epoxy is more sensitive to damage but retains higher implosion resistance while carbon/PEEK shows the opposite trend.

14 CFR 27.865 - External loads.

Code of Federal Regulations, 2012 CFR

2012-01-01

... Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... must be shown by analysis, test, or both, that the rotorcraft external load attaching means for rotorcraft-load combinations to be used for nonhuman external cargo applications can withstand a limit static...

14 CFR 27.865 - External loads.

Code of Federal Regulations, 2014 CFR

2014-01-01

... Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... must be shown by analysis, test, or both, that the rotorcraft external load attaching means for rotorcraft-load combinations to be used for nonhuman external cargo applications can withstand a limit static...

14 CFR 27.865 - External loads.

Code of Federal Regulations, 2013 CFR

2013-01-01

... Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... must be shown by analysis, test, or both, that the rotorcraft external load attaching means for rotorcraft-load combinations to be used for nonhuman external cargo applications can withstand a limit static...

14 CFR 27.865 - External loads.

Code of Federal Regulations, 2010 CFR

2010-01-01

... Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... must be shown by analysis, test, or both, that the rotorcraft external load attaching means for rotorcraft-load combinations to be used for nonhuman external cargo applications can withstand a limit static...

14 CFR 27.865 - External loads.

Code of Federal Regulations, 2011 CFR

2011-01-01

... Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... must be shown by analysis, test, or both, that the rotorcraft external load attaching means for rotorcraft-load combinations to be used for nonhuman external cargo applications can withstand a limit static...

Numerical analysis for sea wave loading on the pile foundation of detached structures by using CADMAS-SURF

NASA Astrophysics Data System (ADS)

Matsuda, Tatsuya; Miura, Kinya; Sawada, Yayoi

2017-10-01

This study investigated the characteristics of wave forces loading on the detached structure that consisted of an upper structure and a pile foundation. In this study, structure stability was also considered on the results obtained from previous studies on the instability of seabed induced by wave force. When a wave force acted on the structure, an external force acted on the pile foundation as if pulling out the foundation on the outer harbor side and pushing it in on the inner harbor. The effective stress in seabed was increase so the pile foundation was considered to maintain sufficient bearing capacity. Subsequently, when the bearing capacity of the ground was decreased because the water pressure in the ground surface layer decreased, the pile foundation will be aggravated settled down. The external force acting on the pile foundation was not same on outer harbor and inner harbor with the form of the upper structure. As a result, we found that the strain will be generated on the structure.

Coupled BE/FE/BE approach for scattering from fluid-filled structures

NASA Technical Reports Server (NTRS)

Everstine, Gordon C.; Cheng, Raymond S.

1990-01-01

NASHUA is a coupled finite element/boundary element capability built around NASTRAN for calculating the low frequency far-field acoustic pressure field radiated or scattered by an arbitrary, submerged, three-dimensional, elastic structure subjected to either internal time-harmonic mechanical loads or external time-harmonic incident loadings. Described here are the formulation and use of NASHUA for solving such structural acoustics problems when the structure is fluid-filled. NASTRAN is used to generate the structural finite element model and to perform most of the required matrix operations. Both fluid domains are modeled using the boundary element capability in NASHUA, whose matrix formulation (and the associated NASTRAN DMAP) for evacuated structures can be used with suitable interpretation of the matrix definitions. After computing surface pressures and normal velocities, far-field pressures are evaluated using an asymptotic form of the Helmholtz exterior integral equation. The proposed numerical approach is validated by comparing the acoustic field scattered from a submerged fluid-filled spherical thin shell to that obtained with a series solution, which is also derived here.

An experimental investigation of wind flow over tall towers in staggered form

NASA Astrophysics Data System (ADS)

Anwar, Proma; Islam, Md. Quamrul; Ali, Mohammad

2016-07-01

In this research work an experiment is conducted to see the effect of wind loading on square, pentagonal and Hexagonal shape cylinders in staggered form. The experiment is done in an open circuit wind tunnel at a Reynolds number of 4.23×104 based on the face width of the cylinder across the flow direction. The flow velocity has been kept uniform throughout the experiment at 14.3 m/s. The test has been conducted for single cylinders first and then in staggered form. Angle of attack is chosen at a definite interval. The static pressure at different locations of the cylinder is measured by inclined multi-manometer. From the surface static pressure readings pressure coefficients are calculated first, then drag and lift coefficients are calculated using numerical Integration Method. These results will surely help engineers to design buildings with such shapes more efficiently. All the results are expressed in non-dimensional form, so they can be applied for prototype buildings and determine the wind loading at any wind speed on structures of similar external shapes.

Minimum distraction gap: how much ankle joint space is enough in ankle distraction arthroplasty?

PubMed

Fragomen, Austin T; McCoy, Thomas H; Meyers, Kathleen N; Rozbruch, S Robert

2014-02-01

The success of ankle distraction arthroplasty relies on the separation of the tibiotalar articular surfaces. The purpose of this study was to find the minimum distraction gap needed to ensure that the tibiotalar joint surfaces would not contact each other with full weight-bearing while under distraction. Circular external fixators were mounted to nine cadaver ankle specimens. Each specimen was then placed into a custom-designed load chamber. Loads of 0, 350, and 700N were applied to the specimen. Radiographic joint space was measured and joint contact pressure was monitored under each load. The external fixator was then sequentially distracted, and the radiographic joint space was measured under the three different loads. The experiment was stopped when there was no joint contact under 700N of load. The radiographic joint space was measured and the initial (undistracted) radiographic joint space was subtracted from it yielding the distraction gap. The minimum distraction gap (mDG) that would provide total unloading was calculated. The average mDG was 2.4 mm (range, 1.6 to 4.0 mm) at 700N of load, 4.4 mm (range, 3.7 to 5.8 mm) at 350N of load, and 4.9 mm (range, 3.7 to 7.0 mm) at 0N of load. These results suggest that if the radiographic joint space of on a standing X-ray of an ankle undergoing distraction arthroplasty shows a minimum of 5.8 mm of DG, then there will be no contact between joint surfaces during full weight-bearing. Therefore, 5 mm of radiographic joint space, as recommended historically, may not be adequate to prevent contact of the articular surfaces during weight-bearing.

14 CFR 29.865 - External loads.

Code of Federal Regulations, 2014 CFR

2014-01-01

... Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS...) It must be shown by analysis, test, or both, that the rotorcraft external load attaching means for rotorcraft-load combinations to be used for nonhuman external cargo applications can withstand a limit static...

14 CFR 29.865 - External loads.

Code of Federal Regulations, 2010 CFR

2010-01-01

... Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS...) It must be shown by analysis, test, or both, that the rotorcraft external load attaching means for rotorcraft-load combinations to be used for nonhuman external cargo applications can withstand a limit static...

14 CFR 29.865 - External loads.

Code of Federal Regulations, 2012 CFR

2012-01-01

... Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS...) It must be shown by analysis, test, or both, that the rotorcraft external load attaching means for rotorcraft-load combinations to be used for nonhuman external cargo applications can withstand a limit static...

14 CFR 29.865 - External loads.

Code of Federal Regulations, 2013 CFR

2013-01-01

... Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS...) It must be shown by analysis, test, or both, that the rotorcraft external load attaching means for rotorcraft-load combinations to be used for nonhuman external cargo applications can withstand a limit static...

14 CFR 29.865 - External loads.

Code of Federal Regulations, 2011 CFR

2011-01-01

... Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS...) It must be shown by analysis, test, or both, that the rotorcraft external load attaching means for rotorcraft-load combinations to be used for nonhuman external cargo applications can withstand a limit static...

The optimum tension for bridging sutures in transosseous-equivalent rotator cuff repair: a cadaveric biomechanical study.

PubMed

Park, Ji Soon; McGarry, Michelle H; Campbell, Sean T; Seo, Hyuk Jun; Lee, Yeon Soo; Kim, Sae Hoon; Lee, Thay Q; Oh, Joo Han

2015-09-01

Transosseous-equivalent (TOE) rotator cuff repair can increase contact area and contact pressure between the repaired cuff tendon and bony footprint and can show higher ultimate loads to failure and smaller gap formation compared with other repair techniques. However, it has been suggested that medial rotator cuff failure after TOE repair may result from increased bridging suture tension. To determine optimum bridging suture tension in TOE repair by evaluating footprint contact and construct failure characteristics at different tensions. Controlled laboratory study. A total of 18 fresh-frozen cadaveric shoulders, randomly divided into 3 groups, were constructed with a TOE configuration using the same medial suture anchor and placing a Tekscan sensing pad between the repaired rotator cuff tendon and footprint. Nine of the 18 shoulders were used to measure footprint contact characteristics. With use of the Tekscan measurement system, the contact pressure and area between the rotator cuff tendon and greater tuberosity were quantified for bridging suture tensions of 60, 90, and 120 N with glenohumeral abduction angles of 0° and 30° and humeral rotation angles of 30° (internal), 0°, and 30° (external). TOE constructs of all 18 shoulders then underwent construct failure testing (cyclic loading and load to failure) to determine the yield load, ultimate load, stiffness, hysteresis, strain, and failure mode at 60 and 120 N of tension. As bridging suture tension increased, contact force, contact pressure, and peak pressure increased significantly at all positions (P < .05 for all). Regarding contact area, no significant differences were found between 90 and 120 N at all positions, although there were significant differences between 60 and 90 N. The construct failure test demonstrated no significant differences in any parameters according to various tensions (P > .05 for all). Increasing bridging suture tension to over 90 N did not improve contact area but did increase contact force and pressure. Bridging suture tension did not significantly affect ultimate failure loads. Considering the risks of overtensioning bridging sutures, it may be clinically more beneficial to keep bridging suture tension below 90 N. © 2015 The Author(s).

Vertebral end-plate fractures as a result of high rate pressure loading in the nucleus of the young adult porcine spine.

PubMed

Brown, Stephen H M; Gregory, Diane E; McGill, Stuart M

2008-01-01

In a healthy spine, end-plate fractures occur from excessive pressurization of the intervening nucleus. Younger spines are most susceptible to such type of injury due to the highly hydraulic nature of their intervertebral discs. The purpose of this paper was to confirm this fracture mechanism of the healthy spine through the pressurization of the nucleus in the absence of external compressive loading. Sixteen functional porcine spine units were dissected and both injection and pressure transducer needles were inserted into the nucleus of the intervertebral disc. Hydraulic fluid was rapidly injected into the nucleus until failure occurred. Peak pressure and rate of pressure development were monitored. Spine units were dissected to determine the type and location of fracture. Fifteen of the 16 spine units fractured (the remaining unit had a degenerated disc). Of the 15 fractures, 13 occurred at the posterior margin of the end-plate along the lines of the growth plates. A slightly exponential relationship was found between peak pressure and its rate of development (R(2) = 0.544). Also, in each of the growth-plate fractured specimens, nuclear material was forcefully emitted, during fracture, from the intervertebral disc into the vertebral foramen. The posterior end-plate fractures produced here are similar to those often seen in young adult humans. This provides insight into a mechanism of fracture development through pressurization of the nucleus that might be seen in older adolescents and younger adults during athletic events or mild trauma.

Computer simulation of the effects of shoe cushioning on internal and external loading during running impacts.

PubMed

Miller, Ross H; Hamill, Joseph

2009-08-01

Biomechanical aspects of running injuries are often inferred from external loading measurements. However, previous research has suggested that relationships between external loading and potential injury-inducing internal loads can be complex and nonintuitive. Further, the loading response to training interventions can vary widely between subjects. In this study, we use a subject-specific computer simulation approach to estimate internal and external loading of the distal tibia during the impact phase for two runners when running in shoes with different midsole cushioning parameters. The results suggest that: (1) changes in tibial loading induced by footwear are not reflected by changes in ground reaction force (GRF) magnitudes; (2) the GRF loading rate is a better surrogate measure of tibial loading and stress fracture risk than the GRF magnitude; and (3) averaging results across groups may potentially mask differential responses to training interventions between individuals.

DEVICE FOR CHARGING OR DISCHARGING

DOEpatents

Untemeyer, S.; Hutter, E.

1959-01-13

A loading and unloading device is presented for loading objects into and unloading them from an apparatus in which fluid under pressure is employed, such as a heterogeneous rcactor wherein the fuel elements are in the form of slugs. This device is comprised essentially of a cylindrical member disposed coaxially with and as an accessible extension of an internal tube member of the apparatus in which the objects, or fuel elements, are normally disposed in use. The outermost end of the cylindrical extension is closed by a removable seal plug. The lower end of the cylindrical extension is separated from the intennal tube by a disk valve which is operated externally. A source of pressure fluid and a drain line are provided in communication with the interior of the cylindrical extension. To load an object into the internal tube, the disk valve is closed, the seal plug is renmoved, an object is placed in the cylindrical extension, and the seal plug is replaced. The disk valve is then opened and ihe pressure of the fluid within the cylindrical extension is increased until it is greater than the pressure within the internal tube and forces the object out of the cylindrical extension into the internal tube. To remove an object from the tube the disk valve is opened and the intenior of thc cylindnical extension is connected to the drain line whereby the operating pressure within the intennal tube forces the object out of the internal tube and up into the cylindrical extension. The disk valve is then closed and the seal plug is removed to permit removal of the object.

Internalizing and externalizing problems in adolescence: general and dimension-specific effects of familial loadings and preadolescent temperament traits.

PubMed

Ormel, J; Oldehinkel, A J; Ferdinand, R F; Hartman, C A; De Winter, A F; Veenstra, R; Vollebergh, W; Minderaa, R B; Buitelaar, J K; Verhulst, F C

2005-12-01

We investigated the links between familial loading, preadolescent temperament, and internalizing and externalizing problems in adolescence, hereby distinguishing effects on maladjustment in general versus dimension-specific effects on either internalizing or externalizing problems. In a population-based sample of 2230 preadolescents (10-11 years) familial loading (parental lifetime psychopathology) and offspring temperament were assessed at baseline by parent report, and offspring psychopathology at 2.5-years follow-up by self-report, teacher report and parent report. We used purified measures of temperament and psychopathology and partialled out shared variance between internalizing and externalizing problems. Familial loading of internalizing psychopathology predicted offspring internalizing but not externalizing problems, whereas familial loading of externalizing psychopathology predicted offspring externalizing but not internalizing problems. Both familial loadings were associated with Frustration, low Effortful Control, and Fear. Frustration acted as a general risk factor predicting severity of maladjustment; low Effortful Control and Fear acted as dimension-specific risk factors that predicted a particular type of psychopathology; whereas Shyness, High-Intensity Pleasure, and Affiliation acted as direction markers that steered the conditional probability of internalizing versus externalizing problems, in the event of maladjustment. Temperament traits mediated one-third of the association between familial loading and psychopathology. Findings were robust across different composite measures of psychopathology, and applied to girls as well as boys. With regard to familial loading and temperament, it is important to distinguish general risk factors (Frustration) from dimension-specific risk factors (familial loadings, Effortful Control, Fear), and direction markers that act as pathoplastic factors (Shyness, High-Intensity Pleasure, Affiliation) from both types of risk factors. About one-third of familial loading effects on psychopathology in early adolescence are mediated by temperament.

Seal Joint Analysis and Design for the Ares-I Upper Stage LOX Tank

NASA Technical Reports Server (NTRS)

Phillips, Dawn R.; Wingate, Robert J.

2011-01-01

The sealing capability of the Ares-I Upper Stage liquid oxygen tank-to-sump joint is assessed by analyzing the deflections of the joint components. Analyses are performed using three-dimensional symmetric wedge finite element models and the ABAQUS commercial finite element software. For the pressure loads and feedline interface loads, the analyses employ a mixed factor of safety approach to comply with the Constellation Program factor of safety requirements. Naflex pressure-assisted seals are considered first because they have been used successfully in similar seal joints in the Space Shuttle External Tank. For the baseline sump seal joint configuration with a Naflex seal, the predicted joint opening greatly exceeds the seal design specification. Three redesign options of the joint that maintain the use of a Naflex seal are studied. The joint openings for the redesigned seal joints show improvement over the baseline configuration; however, these joint openings still exceed the seal design specification. RACO pressure-assisted seals are considered next because they are known to also be used on the Space Shuttle External Tank, and the joint opening allowable is much larger than the specification for the Naflex seals. The finite element models for the RACO seal analyses are created by modifying the models that were used for the Naflex seal analyses. The analyses show that the RACO seal may provide sufficient sealing capability for the sump seal joint. The results provide reasonable data to recommend the design change and plan a testing program to determine the capability of RACO seals in the Ares-I Upper Stage liquid oxygen tank sump seal joint.

Regulation of gene expression in intervertebral disc cells by low and high hydrostatic pressure.

PubMed

Neidlinger-Wilke, Cornelia; Würtz, Karin; Urban, Jill P G; Börm, Wolfgang; Arand, Markus; Ignatius, Anita; Wilke, Hans-Joachim; Claes, Lutz E

2006-08-01

Intervertebral disc structures are exposed to wide ranges of intradiscal hydrostatic pressure during different loading exercises and are at their minimum during lying or relaxed sitting and at maximum during lifting weights with a round back. We hypothesize that these different loading magnitudes influence the intervertebral disc (IVD) by alteration of disc matrix turnover depending on their magnitudes. Therefore the aim of this study was to assess changes in gene expression of human nucleus cells after the application of low hydrostatic pressure (0.25 MPa) and high hydrostatic pressure (2.5 MPa). IVD cells isolated from the nucleus of human (n = 18) and bovine (n = 24 from four animals) disc biopsies were seeded into three-dimensional collagen type-I matrices and exposed to the different loading magnitudes by specially developed pressure chambers. The lower pressure range (0.25 MPa, 30 min, 0.1 Hz) was applied with a recently published device by using an external compression cylinder. For the application of higher loads (2.5 MPa, 30 min, 0.1 Hz) the cell-loaded collagen gels were sealed into sterile bags with culture medium and stimulated in a newly developed water-filled compression cylinder by using a loading frame. These methods allowed the comparison of loading regimes in a wide physiological range under an equal three-dimensional culture conditions. Cells were harvested 24 h after the end of stimulation and changes in the expression of genes known to influence IVD matrix turnover (collagen-I, collagen-II, aggrecan, MMP1, MMP2, MMP3, MMP13) were analyzed by real-time RT-PCR. A Wilcoxon signed-rank test(1) and a Wilcoxon 2-sample test(2) were performed to detect differences between the stimulated and control samples(1) and differences between low and high hydrostatic pressure(2). Multiple testing was considered by adjusting the p value appropriately. Both regimes of hydrostatic pressure influenced gene expression in nucleus cells with opposite tendencies for the matrix forming proteins aggrecan and collagen type-I in response to the two different pressure magnitudes: Low hydrostatic-pressure (0.25 MPa) tended to increase collagen-I and aggrecan expression of human nucleus cells (P < 0.05) but only to a small degree. High hydrostatic pressure (2.5 MPa) tended to decrease gene expression of all anabolic proteins with significant effects on aggrecan expression of nucleus cells (P = 0.004). Low hydrostatic pressure had no influence on the expression of matrix metalloproteinases (MMP1, MMP2, MMP3 and MMP13). In contrast, high hydrostatic pressure tended to increase the expression of MMP1, MMP3 and MMP13 of human nucleus cells with high individual-individual variations. The decreased expression of aggrecan (P = 0.008) and collagen type II (P = 0.023) and the increased MMP3 expression (P = 0.008) in response to high hydrostatic pressure could be confirmed in additional experiments with bovine nucleus cells. These results suggest that hydrostatic pressure as one of the physiological stimuli of the IVD may influence matrix turnover in a magnitude dependent way. Low hydrostatic pressure (0.25 MPa) has quite small influences with a tendency to anabolic effects, whereas high hydrostatic pressure (2.5 MPa) tends to decrease the matrix protein expression with a tendency to increase some matrix-turnover enzymes. Therefore, hydrostatic pressure may regulate disc matrix turnover in a dose-dependent way.

Axisymmetric deformations and stresses of unsymmetrically laminated composite cylinders in axial compression with thermally-induced preloading effects

NASA Technical Reports Server (NTRS)

Paraska, Peter J.

1993-01-01

This report documents an analytical study of the response of unsymmetrically laminated cylinders subjected to thermally-induced preloading effects and compressive axial load. Closed-form solutions are obtained for the displacements and intralaminar stresses and recursive relations for the interlaminar shear stress were obtained using the closed-form intralaminar stress solutions. For the cylinder geometries and stacking sequence examples analyzed, several important and as yet undocumented effects of including thermally-induced preloading in the analysis are observed. It should be noted that this work is easily extended to include uniform internal and/or external pressure loadings and the application of strain and stress failure theories.

A miniature fiber optic pressure sensor for intradiscal pressure measurements of rodents

NASA Astrophysics Data System (ADS)

Nesson, Silas; Yu, Miao; Hsieh, Adam H.

2007-04-01

Lower back pain continues to be a leading cause of disability in people of all ages, and has been associated with degenerative disc disease. It is well accepted that mechanical stress, among other factors, can play a role in the development of disc degeneration. Pressures generated in the intervertebral disc have been measured both in vivo and in vitro for humans and animals. However, thus far it has been difficult to measure pressure experimentally in rodent discs due to their small size. With the prevalent use of rodent tail disc models in mechanobiology, it is important to characterize the intradiscal pressures generated with externally applied stresses. In this paper, a miniature fiber optic Fabry-Perot interferometric pressure sensor with an outer diameter of 360 μm was developed to measure intradiscal pressures in rat caudal discs. A low coherence interferometer based optical system was used, which includes a broadband light source, a high-speed spectrometer, and a Fabry-Perot sensor. The sensor employs a capillary tube, a flexible, polymer diaphragm coated with titanium as a partial mirror, and a fiber tip as another mirror. The pressure induced deformation of the diaphragm results in a cavity length change of the Fabry-Perot interferometer which can be calculated from the wavelength shift of interference fringes. The sensor exhibited good linearity with small applied pressures. Our validation experiments show that owing to the small size, inserting the sensor does not disrupt the annulus fibrosus and will not alter intradiscal pressures generated. Measurements also demonstrate the feasibility of using this sensor to quantify external load intradiscal pressure relationships in small animal discs.

Biomechanics of pressure ulcer in body tissues interacting with external forces during locomotion.

PubMed

Mak, Arthur F T; Zhang, Ming; Tam, Eric W C

2010-08-15

Forces acting on the body via various external surfaces during locomotion are needed to support the body under gravity, control posture, and overcome inertia. Examples include the forces acting on the body via the seating surfaces during wheelchair propulsion, the forces acting on the plantar foot tissues via the insole during gait, and the forces acting on the residual-limb tissues via the prosthetic socket during various movement activities. Excessive exposure to unwarranted stresses at the body-support interfaces could lead to tissue breakdowns commonly known as pressure ulcers, often presented as deep-tissue injuries around bony prominences or as surface damage on the skin. In this article, we review the literature that describes how the involved tissues respond to epidermal loading, taking into account both experimental and computational findings from in vivo and in vitro studies. In particular, we discuss related literature about internal tissue deformation and stresses, microcirculatory responses, and histological, cellular, and molecular observations.

Are external knee load and EMG measures accurate indicators of internal knee contact forces during gait?

PubMed

Meyer, Andrew J; D'Lima, Darryl D; Besier, Thor F; Lloyd, David G; Colwell, Clifford W; Fregly, Benjamin J

2013-06-01

Mechanical loading is believed to be a critical factor in the development and treatment of knee osteoarthritis. However, the contact forces to which the knee articular surfaces are subjected during daily activities cannot be measured clinically. Thus, the ability to predict internal knee contact forces accurately using external measures (i.e., external knee loads and muscle electromyographic [EMG] signals) would be clinically valuable. We quantified how well external knee load and EMG measures predict internal knee contact forces during gait. A single subject with a force-measuring tibial prosthesis and post-operative valgus alignment performed four gait patterns (normal, medial thrust, walking pole, and trunk sway) to induce a wide range of external and internal knee joint loads. Linear regression analyses were performed to assess how much of the variability in internal contact forces was accounted for by variability in the external measures. Though the different gait patterns successfully induced significant changes in the external and internal quantities, changes in external measures were generally weak indicators of changes in total, medial, and lateral contact force. Our results suggest that when total contact force may be changing, caution should be exercised when inferring changes in knee contact forces based on observed changes in external knee load and EMG measures. Advances in musculoskeletal modeling methods may be needed for accurate estimation of in vivo knee contact forces. Copyright © 2012 Orthopaedic Research Society.

Estimation of the Unsteady Aerodynamic Load on Space Shuttle External Tank Protuberances from a Component Wind Tunnel Test

NASA Technical Reports Server (NTRS)

Panda, Jayatana; Martin, Fred W.; Sutliff, Daniel L.

2008-01-01

At the wake of the Columbia (STS-107) accident it was decided to remove the Protuberance Aerodynamic Load (PAL) Ramp that was originally intended to protect various protuberances outside of the Space Shuttle External Tank from high buffet load induced by cross-flows at transonic speed. In order to establish the buffet load without the PAL ramp, a wind tunnel test was conducted where segments of the protuberances were instrumented with dynamic pressure transducers; and power-spectra of sectional lift and drag forces at various span-wise locations between two adjacent support brackets were measured under different cross flow angles, Mach number and other conditions. Additionally, frequency-dependent spatial correlations between the sectional forces were also established. The sectional forces were then adjusted by the correlation length to establish span-averaged spectra of normal and lateral forces that can be suitably "added" to various other unsteady forces encountered by the protuberance. This paper describes the methodology used for calculating the correlation-adjusted power spectrum of the buffet load. A second part of the paper describes wind-tunnel results on the difference in the buffet load on the protuberances with and without the PAL ramp. In general when the ramp height is the same as that of the protuberance height, such as that found on the liquid Oxygen part of the tank, the ramp is found to cause significant reduction of the unsteady aerodynamic load. However, on the liquid Hydrogen part of the tank, where the Oxygen feed-line is far larger in diameter than the height of the PAL ramp, little protection is found to be available to all but the Cable Tray.

Demolition of a hospital building by controlled explosion: the impact on filamentous fungal load in internal and external air.

PubMed

Bouza, E; Peláez, T; Pérez-Molina, J; Marín, M; Alcalá, L; Padilla, B; Muñoz, P; Adán, P; Bové, B; Bueno, M J; Grande, F; Puente, D; Rodríguez, M P; Rodríguez-Créixems, M; Vigil, D; Cuevas, O

2002-12-01

The demolition of a maternity building at our institution provided us with the opportunity to study the load of filamentous fungi in the air. External (nearby streets) and internal (within the hospital buildings) air was sampled with an automatic volumetric machine (MAS-100 Air Samplair) at least daily during the week before the demolition, at 10, 30, 60, 90,120, 180, 240, 420, 540 and 660 min post-demolition, daily during the week after the demolition and weekly during weeks 2, 3 and 4 after demolition. Samples were duplicated to analyse reproducibility. Three hundred and forty samples were obtained: 115 external air, 69 'non-protected' internal air and 156 protected internal air [high efficiency particulate air (HEPA) filtered air under positive pressure]. A significant increase in the colony count of filamentous fungi occurred after the demolition. Median colony counts of external air on demolition day were significantly higher than from internal air (70.2 cfu/m(3) vs 35.8 cfu/m(3)) (P < 0.001). Mechanical demolition on day +4 also produced a significant difference between external and internal air (74.5 cfu/m(3) vs 41.7 cfu/m(3)). The counts returned to baseline levels on day +11. Most areas with a protected air supply yielded no colonies before demolition day and remained negative on demolition day. The reproducibility of the count method was good (intra-assay variance: 2.4 cfu/m(3)). No episodes of invasive filamentous mycosis were detected during the three months following the demolition. Demolition work was associated with a significant increase in the fungal colony counts of hospital external and non-protected internal air. Effective protective measures may be taken to avoid the emergence of clinical infections. Copyright 2002 The Hospital Infection Society

Airworthiness Qualification Criteria for Rotorcraft with External Sling Loads

NASA Technical Reports Server (NTRS)

Key, David L.

2002-01-01

This report presents the results of a study to develop airworthiness requirements for rotorcraft with external sling loads. The report starts with a review of the various phenomena that limit external sling load operations. Specifically discussed are the rotorcraft-load aeroservoelastic stability, load-on handling qualities, effects of automatic flight control system failure, load suspension system failure, and load stability at speed. Based on past experience and treatment of these phenomena, criteria are proposed to form a package for airworthiness qualification. The desired end objective is a set of operational flight envelopes for the rotorcraft with intended loads that can be provided to the user to guide operations in the field. The specific criteria proposed are parts of ADS-33E-PRF; MIL-F-9490D, and MIL-STD-913A all applied in the context of external sling loads. The study was performed for the Directorate of Engineering, U.S. Army Aviation and Missile Command (AMCOM), as part of the contract monitored by the Aerothermodynamics Directorate, U.S. Army AMCOM.

Four dimensional X-ray imaging of deformation modes in organic-rich Green River Shale retorted under uniaxial compression

NASA Astrophysics Data System (ADS)

Kobchenko, M.; Pluymakers, A.; Cordonnier, B.; Tairova, A.; Renard, F.

2017-12-01

Time-lapse imaging of fracture network development in organic-rich shales at elevated temperatures while kerogen is retorted allows characterizing the development of microfractures and the onset of primary migration. When the solid organic matter is transformed to hydrocarbons with lower molecular weight, the local pore-pressure increases and drives the propagation of hydro-fractures sub-parallel to the shale lamination. On the scale of samples of several mm size, these fractures can be described as mode I opening, where fracture walls dilate in the direction of minimal compression. However, so far experiments coupled to microtomography in situ imaging have been performed on samples where no load was imposed. Here, an external load was applied perpendicular to the sample laminations and we show that this stress state slows down, but does not stop, the propagation of fracture along bedding. Conversely, microfractures also propagate sub-perpendicular to the shale lamination, creating a percolating network in three dimensions. To monitor this process we have used a uniaxial compaction rig combined with in-situ heating from 50 to 500 deg C, while capturing three-dimensional X-ray microtomography scans at a voxel resolution of 2.2 μm; Data were acquired at beamline ID19 at the European Synchrotron Radiation Facility. In total ten time-resolved experiments were performed at different vertical loading conditions, with and without lateral passive confinement and different heating rates. At high external load the sample fails by symmetric bulging, while at lower external load the reaction-induced fracture network develops with the presence of microfractures both sub-parallel and sub-perpendicular to the bedding direction. In addition, the variation of experimental conditions allows the decoupling of the effects of the hydrocarbon decomposition reaction on the deformation process from the influence of thermal stress heating on the weakening and failure mode of immature shale.

Structural analysis of the space shuttle solid rocket booster/external tank attach ring

NASA Technical Reports Server (NTRS)

Dorsey, John T.

1988-01-01

An External Tank (ET) attach ring is used in the Space Shuttle System to transfer lateral loads between the ET and the Solid Rocket Booster (SRB). Following the Challenger (51-L) accident, the flight performance of the ET attach ring was reviewed, and negative margins of safety and failed bolts in the attach ring were subsequently identified. The analyses described in this report were performed in order to understand the existing ET attach ring structural response to motor case internal pressurization as well as to aid in an ET attach ring redesign effort undertaken by NASA LaRC. The finite element model as well as the results from linear and nonlinear static structural analyses are described.

Aeroelastic analysis of circular cylindrical and truncated conical shells subjected to a supersonic flow

NASA Astrophysics Data System (ADS)

Sabri, Farhad

Shells of revolution, particularly cylindrical and conical shells, are one of the basic structural elements in the aerospace structures. With the advent of high speed aircrafts, these shells can show dynamic instabilities when they are exposed to a supersonic flow. Therefore, aeroelastic analysis of these elements is one of the primary design criteria which aeronautical engineers are dealing with. This analysis can be done with the help of finite element method (FEM) coupled with the computational fluid dynamic (CFD) or by experimental methods but it is time consuming and very expensive. The purpose of this dissertation is to develop such a numerical tool to do aeroelastic analysis in a fast and precise way. Meanwhile during the design stage, where the different configurations, loading and boundary conditions may need to be analyzed, this numerical method can be used very easily with the high order of reliability. In this study structural modeling is a combination of linear Sanders thin shell theory and classical finite element method. Based on this hybrid finite element method, the shell displacements are found from the exact solutions of shell theory rather than approximating by polynomial function done in traditional finite element method. This leads to a precise and fast convergence. Supersonic aerodynamic modeling is done based on the piston theory and modified piston theory with the shell curvature term. The stress stiffening due to lateral pressure and axial compression are also taken into accounts. Fluid-structure interaction in the presence of inside quiescent fluid is modeled based on the potential theory. In this method, fluid is considered as a velocity potential variable at each node of the shell element where its motion is expressed in terms of nodal elastic displacements at the fluid-structure interface. This proposed hybrid finite element has capabilities to do following analysis: (i) Buckling and vibration of an empty or partially fluid filled circular cylindrical shell or truncated conical shell subjected to internal/external pressure and axial compression loading. This is a typical example of external liquid propellant tanks of space shuttles and re-entry vehicles where they may experience this kind of loading during the flight. In the current work, different end boundary conditions of a circular cylindrical shell with different filling ratios were analyzed. To the best author' knowledge this is the first study where this kind of complex loading and boundary conditions are treated together during such an analysis. Only static instability, divergence, was observed where it showed that the fluid filling ratio does not have any effect on the critical buckling pressure and axial compression. It only reduces the vibration frequencies. It also revealed that the pressurized shell loses its stability at a higher critical axial load. (ii) Aeroelastic analysis of empty or partially liquid filled circular cylindrical and conical shells. Different boundary conditions with different geometries of shells subjected to supersonic air flow are studied here. In all of cases shell loses its stability though the coupled mode flutter. The results showed that internal pressure has a stabilizing effect and increases the critical flutter speed. It is seen that the value of critical dynamic pressure changes rapidly and widely as the filling ratio increases from a low value. In addition, by increasing the length ratio the decrement of flutter speed is decreased and vanishes. This rapid change in critical dynamic pressure at low filling ratios and its almost steady behaviour at large filling ratios indicate that the fluid near the bottom of the shell is largely influenced by elastic deformation when a shell is subjected to external subsonic flow. Based on comparison with the existing numerical, analytical and experimental data and the power of capabilities of this hybrid finite element method to model different boundary conditions and complex loadings, this FEM package can be used effectively for the design of advanced aerospace structures. It provides the results at less computational cost compare to the commercial FEM software, which imposes some restrictions when such an analysis is done.

Cellular characterization of compression induced-damage in live biological samples

NASA Astrophysics Data System (ADS)

Bo, Chiara; Balzer, Jens; Hahnel, Mark; Rankin, Sara M.; Brown, Katherine A.; Proud, William G.

2011-06-01

Understanding the dysfunctions that high-intensity compression waves induce in human tissues is critical to impact on acute-phase treatments and requires the development of experimental models of traumatic damage in biological samples. In this study we have developed an experimental system to directly assess the impact of dynamic loading conditions on cellular function at the molecular level. Here we present a confinement chamber designed to subject live cell cultures in liquid environment to compression waves in the range of tens of MPa using a split Hopkinson pressure bars system. Recording the loading history and collecting the samples post-impact without external contamination allow the definition of parameters such as pressure and duration of the stimulus that can be related to the cellular damage. The compression experiments are conducted on Mesenchymal Stem Cells from BALB/c mice and the damage analysis are compared to two control groups. Changes in Stem cell viability, phenotype and function are assessed flow cytometry and with in vitro bioassays at two different time points. Identifying the cellular and molecular mechanisms underlying the damage caused by dynamic loading in live biological samples could enable the development of new treatments for traumatic injuries.

High-Reynolds Number Active Blowing Semi-Span Force Measurement System Development

NASA Technical Reports Server (NTRS)

Lynn, Keith C.; Rhew, Ray D.; Acheson, Michael J.; Jones, Gregory S.; Milholen, William E.; Goodliff, Scott L.

2012-01-01

Recent wind-tunnel tests at the NASA Langley Research Center National Transonic Facility utilized high-pressure bellows to route air to the model for evaluating aircraft circulation control. The introduction of these bellows within the Sidewall Model Support System significantly impacted the performance of the external sidewall mounted semi-span balance. As a result of this impact on the semi-span balance measurement performance, it became apparent that a new capability needed to be built into the National Transonic Facility s infrastructure to allow for performing pressure tare calibrations on the balance in order to properly characterize its performance under the influence of static bellows pressure tare loads and bellows thermal effects. The objective of this study was to design both mechanical calibration hardware and an experimental calibration design that can be employed at the facility in order to efficiently and precisely perform the necessary loadings in order to characterize the semi-span balance under the influence of multiple calibration factors (balance forces/moments and bellows pressure/temperature). Using statistical design of experiments, an experimental design was developed allowing for strategically characterizing the behavior of the semi-span balance for use in circulation control and propulsion-type flow control testing at the National Transonic Facility.

14 CFR 133.17 - Requirements for issuance of a rotorcraft external-load operator certificate.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 14 Aeronautics and Space 3 2014-01-01 2014-01-01 false Requirements for issuance of a rotorcraft external-load operator certificate. 133.17 Section 133.17 Aeronautics and Space FEDERAL AVIATION... §§ 133.19, 133.21, and 133.23, the Administrator issues a Rotorcraft External-Load Operator Certificate...

14 CFR 133.17 - Requirements for issuance of a rotorcraft external-load operator certificate.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 14 Aeronautics and Space 3 2013-01-01 2013-01-01 false Requirements for issuance of a rotorcraft external-load operator certificate. 133.17 Section 133.17 Aeronautics and Space FEDERAL AVIATION... §§ 133.19, 133.21, and 133.23, the Administrator issues a Rotorcraft External-Load Operator Certificate...

Load control system. [for space shuttle external tank ground tests

NASA Technical Reports Server (NTRS)

Grosse, J. C.

1977-01-01

The load control system developed for the shuttle external structural tests is described. The system consists of a load programming/display module, and a load control module along with the following hydraulic system components: servo valves, dump valves, hydraulic system components, and servo valve manifold blocks. One load programming/display subsystem can support multiple load control subsystem modules.

49 CFR 195.108 - External pressure.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 3 2012-10-01 2012-10-01 false External pressure. 195.108 Section 195.108... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PIPELINE SAFETY TRANSPORTATION OF HAZARDOUS LIQUIDS BY PIPELINE Design Requirements § 195.108 External pressure. Any external pressure that will be exerted on the...

49 CFR 195.108 - External pressure.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 3 2011-10-01 2011-10-01 false External pressure. 195.108 Section 195.108... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PIPELINE SAFETY TRANSPORTATION OF HAZARDOUS LIQUIDS BY PIPELINE Design Requirements § 195.108 External pressure. Any external pressure that will be exerted on the...

49 CFR 195.108 - External pressure.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 3 2013-10-01 2013-10-01 false External pressure. 195.108 Section 195.108... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PIPELINE SAFETY TRANSPORTATION OF HAZARDOUS LIQUIDS BY PIPELINE Design Requirements § 195.108 External pressure. Any external pressure that will be exerted on the...

49 CFR 195.108 - External pressure.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 3 2010-10-01 2010-10-01 false External pressure. 195.108 Section 195.108... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PIPELINE SAFETY TRANSPORTATION OF HAZARDOUS LIQUIDS BY PIPELINE Design Requirements § 195.108 External pressure. Any external pressure that will be exerted on the...

49 CFR 195.108 - External pressure.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 3 2014-10-01 2014-10-01 false External pressure. 195.108 Section 195.108... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PIPELINE SAFETY TRANSPORTATION OF HAZARDOUS LIQUIDS BY PIPELINE Design Requirements § 195.108 External pressure. Any external pressure that will be exerted on the...

Improvement of fatigue resistance for multilayer lead zirconate titanate (PZT)-based ceramic actuators by external mechanical loads

NASA Astrophysics Data System (ADS)

Yang, Gang; Yue, Zhenxing; Ji, Ye; Chu, Xiangcheng; Li, Longtu

2008-12-01

The influence of external compressive loads, applied along a direction perpendicular to polarization, on fatigue behaviors of multilayer lead zirconate titanate (PZT)-based ceramic actuators was investigated. Under no external mechanical load, a normal fatigue behavior was observed, demonstrating that both switching polarization (Pswitching) and remnant polarization (Pr) progressively decreased with increasing switching cycles due to domain pinning by charge point defects. However, an anomalous enhancement in both switching and remnant polarizations was observed upon application of the external compressive loads. After 5×106 cycles of polarization switching, Pswitching and Pr increase by about 13% and 6% at 40 MPa, respectively, while Pswitching and Pr increase by about 11% and 21% at 60 MPa, respectively. The improvement of fatigue resistance can be attributed to non-180° domain switching and suppression of microcracking, triggered by external mechanical loads.

Medial knee loading is altered in subjects with early osteoarthritis during gait but not during step-up-and-over task

PubMed Central

Wesseling, Mariska; Smith, Colin R.; Thelen, Darryl G.; Verschueren, Sabine; Jonkers, Ilse

2017-01-01

This study evaluates knee joint loading during gait and step-up-and-over tasks in control subjects, subjects with early knee OA and those with established knee OA. Thirty-seven subjects with varying degrees of medial compartment knee OA severity (eighteen with early OA and sixteen with established OA), and nineteen healthy controls performed gait and step-up-and-over tasks. Knee joint moments, contact forces (KCF), the magnitude of contact pressures and center of pressure (CoP) location were analyzed for the three groups for both activities using a multi-body knee model with articular cartilage contact, 14 ligaments, and six degrees of freedom tibiofemoral and patellofemoral joints. During gait, the first peak of the medial KCF was significantly higher for patients with early knee OA (p = 0.048) and established knee OA (p = 0.001) compared to control subjects. Furthermore, the medial contact pressure magnitudes and CoP location were significantly different in both groups of patients compared to controls. Knee rotation moments (KRMs) and external rotation angles were significantly higher during early stance in both patient groups (p < 0.0001) compared to controls. During step-up-and-over, there was a high variability between the participants and no significant differences in KCF were observed between the groups. Knee joint loading and kinematics were found to be altered in patients with early knee OA only during gait. This is an indication that an excessive medial KCF and altered loading location, observed in these patients, is a contributor to early progression of knee OA. PMID:29117248

[The physiology of the isolated dog pancreas--the influence of the actual blood glucose level on the blood circulation in the pancreas].

PubMed

Hempfling, H; Husemann, B

1975-06-01

1. Glucose loading tests were undertaken on isolated pancreas or pancreas-duodenal preparations. 2. In 75% of cases a vasodilatation can be observed which leads to enhanced blood circulation under constant pressure in the isolated organ. 3. This vasodilatation persists until the level of blood sugar has normalized. 4. The experiment being carried out on an isolated organ, external factors such as the vagus nerve, do not become active.

Small, high-speed bearing technology for cryogenic turbo-pumps

NASA Technical Reports Server (NTRS)

Winn, L. W.; Eusepi, M. W.; Smalley, A. J.

1974-01-01

The design of 20-mm bore ball bearings is described for cryogenic turbo-machinery applications, operating up to speeds of 120,000 rpm. A special section is included on the design of hybrid bearings. Each hybrid bearing is composed of a ball bearing in series with a conventional pressurized fluid-film journal bearing. Full details are presented on the design of a test vehicle which possesses the capability of testing the above named bearings within the given speed range under externally applied radial and axial loads.

Flight loads measurements obtained from calibrated strain-gage bridges mounted externally on the skin of a low-aspect-ratio wing

NASA Technical Reports Server (NTRS)

Eckstrom, C. V.

1976-01-01

Flight-test measurements of wingloads (shear, bending moment, and torque) were obtained by means of strain-gage bridges mounted on the exterior surface of a low-aspect-ratio, thin, swept wing which had a structural skin, full-depth honeycomb core, sandwich construction. Details concerning the strain-gage bridges, the calibration procedures used, and the flight-test results are presented along with some pressure measurements and theoretical calculations for comparison purposes.

Dorzolamide Loaded Niosomal Vesicles: Comparison of Passive and Remote Loading Methods.

PubMed

Hashemi Dehaghi, Mohadeseh; Haeri, Azadeh; Keshvari, Hamid; Abbasian, Zahra; Dadashzadeh, Simin

2017-01-01

Glaucoma is a common progressive eye disorder and the treatment strategies will benefit from nanoparticulate delivery systems with high drug loading and sustained delivery of intraocular pressure lowering agents. Niosomes have been reported as a novel approach to improve drug low corneal penetration and bioavailability characteristics. Along with this, poor entrapment efficiency of hydrophilic drug in niosomal formulation remains as a major formulation challenge. Taking this perspective into consideration, dorzolamide niosomes were prepared employing two different loading methodologies (passive and remote loading methods) and the effects of various formulation variables (lipid to drug ratio, cholesterol percentage, drug concentration, freeze/thaw cycles, TPGS content, and external and internal buffer molarity and pH) on encapsulation efficiency were assessed. Encapsulation of dorzolamide within niosomes increased remarkably by the incorporation of higher cholesterol percentage as well as increasing the total lipid concentration. Remote loading method showed higher efficacy for drug entrapment compared to passive loading technique. Incorporation of TPGS in bilayer led to decrease in EE; however, retarded drug release rate. Scanning electron microscopy (SEM) studies confirmed homogeneous particle distribution, and spherical shape with smooth surface. In conclusion, the highest encapsulation can be obtained using phosphate gradient method and 50% cholesterol in Span 60 niosomal formulation.

Transformation-Induced Diffraction Peak Broadening During Bainitic and Martensitic Transformations Under Small External Loads in a Quenched and Tempered High Strength Steel

NASA Astrophysics Data System (ADS)

Dutta, R. K.; Huizenga, R. M.; Amirthalingam, M.; Hermans, M. J. M.; King, A.; Richardson, I. M.

2013-09-01

In situ phase transformation behavior of a high strength S690QL1 steel during continuous cooling under different mechanical loading conditions has been used to investigate the effect of small external loads on the transformation-induced plasticity during bainitic and martensitic transformations. The results show that during phase transformations, the untransformed austenite undergoes plastic deformation, thereby retarding further transformation to bainite/martensite. This occurs independent of external load.

Assessing the Impact of Agricultural Pressures on N and P Loads and Potential Eutrophication Risk at Regional Scales

NASA Astrophysics Data System (ADS)

Dupas, R.; Gascuel-odoux, C.; Delmas, M.; Moatar, F.

2014-12-01

Excessive nutrient loading of freshwater bodies results in increased eutrophication risk worldwide. The processes controlling N/P transfer in agricultural landscapes are well documented through scientific studies conducted in intensively monitored catchments. However, managers need tools to assess water quality and evaluate the contribution of agriculture to eutrophication at regional scales, including unmonitored or poorly monitored areas. To this end, we present an assessment framework which includes: i) a mass-balance model to estimate diffuse N/P transfer and retention and ii) indicators based on N:P:Si molar ratios to assess potential eutrophication risk from external loads. The model, called Nutting (Dupas et al., 2013), integrates variables for both detailed description of agricultural pressures (N surplus, soil P content) and characterisation of physical attributes of catchments (including spatial attributes). It was calibrated on 160 catchments, and applied to 2210 unmonitored headwater bodies in France (Dupas et al., under review). N and P retention represented 53% and 95% of soil N and P surplus, respectively, and was mainly controlled by runoff and an index characterising infiltration/runoff properties. According to our estimates, diffuse agricultural sources represented a mean of 97% of N loads and N exceeded Si in 93% of the catchments, whilst they represented 46% of P loads and P exceeded Si in 26-65% of the catchments. Estimated eutrophication risk was highly sensitive to assumptions about P bioavailability, hence the range of headwaters potentially at risk spanned 26-63% of the catchments, depending on assumptions. To reduce this uncertainty, we recommend introducing P bioavailability tests in water monitoring programs, especially in sensitive areas. Dupas R et al. Assessing N emissions in surface water at the national level: comparison of country-wide vs. regionalized models. Sci Total Environ 2013; 443: 152-62. Dupas R et al. Assessing the impact of agricultural pressures on N and P loads and eutrophication risk (under review).

Dynamic hydraulic fluid stimulation regulated intramedullary pressure.

PubMed

Hu, Minyi; Serra-Hsu, Frederick; Bethel, Neville; Lin, Liangjun; Ferreri, Suzanne; Cheng, Jiqi; Qin, Yi-Xian

2013-11-01

Physical signals within the bone, i.e. generated from mechanical loading, have the potential to initiate skeletal adaptation. Strong evidence has pointed to bone fluid flow (BFF) as a media between an external load and the bone cells, in which altered velocity and pressure can ultimately initiate the mechanotransduction and the remodeling process within the bone. Load-induced BFF can be altered by factors such as intramedullary pressure (ImP) and/or bone matrix strain, mediating bone adaptation. Previous studies have shown that BFF induced by ImP alone, with minimum bone strain, can initiate bone remodeling. However, identifying induced ImP dynamics and bone strain factor in vivo using a non-invasive method still remains challenging. To apply ImP as a means for alteration of BFF, it was hypothesized that non-invasive dynamic hydraulic stimulation (DHS) can induce local ImP with minimal bone strain to potentially elicit osteogenic adaptive responses via bone-muscle coupling. The goal of this study was to evaluate the immediate effects on local and distant ImP and strain in response to a range of loading frequencies using DHS. Simultaneous femoral and tibial ImP and bone strain values were measured in three 15-month-old female Sprague Dawley rats during DHS loading on the tibia with frequencies of 1Hz to 10Hz. DHS showed noticeable effects on ImP induction in the stimulated tibia in a nonlinear fashion in response to DHS over the range of loading frequencies, where they peaked at 2Hz. DHS at various loading frequencies generated minimal bone strain in the tibiae. Maximal bone strain measured at all loading frequencies was less than 8με. No detectable induction of ImP or bone strain was observed in the femur. This study suggested that oscillatory DHS may regulate the local fluid dynamics with minimal mechanical strain in the bone, which serves critically in bone adaptation. These results clearly implied DHS's potential as an effective, non-invasive intervention for osteopenia and osteoporosis treatments. © 2013. Published by Elsevier Inc. All rights reserved.

Does Maximal External Tibial Component Rotation Influence Tibiofemoral Load Distribution in the Primary Knee Arthroplasty Setting: A Comparison of Neutral vs Maximal Anatomical External Rotatory States.

PubMed

Manning, William A; Ghosh, Kanishka M; Blain, Alasdair P; Longstaff, Lee M; Rushton, Steven P; Deehan, David J

2017-06-01

Tibial component rotation at time of knee arthroplasty can influence conformity, load transmission across the polyethylene surface, and perhaps ultimately determined survivorship. Optimal tibial component rotation on the cut surface is reliant on standard per operative manual stressing. This subjective assessment aims to balance constraint and stability of the articulation through a full arc of movement. Using a cadaveric model, computer navigation and under defined, previously validated loaded conditions mimicking the in vivo setting, the influence of maximal tibial component external rotation compared with the neutral state was examined for changes in laxity and tibiofemoral continuous load using 3D displacement measurement and an orthosensor continuous load sensor implanted within the polyethylene spacer in a simulated single radius total knee arthroplasty. No significant difference was found throughout arc of motion (0-115 degrees of flexion) for maximal varus and/or valgus or rotatory laxity between the 2 states. The neutral state achieved equivalence for mediolateral load distribution at each point of flexion. We have found that external rotation of the tibial component increased medial compartment load in comparison with the neutral position. Compared with the neutral state, external rotation consistently effected a marginal, but not significant reduction in lateral load under similar loading conditions. The effects were most pronounced in midflexion. On the basis of these findings, we would advocate for the midtibial tubercle point to determine tibial component rotation and caution against component external rotation. Copyright © 2017 Elsevier Inc. All rights reserved.

CFD Assessment of Forward Booster Separation Motor Ignition Overpressure on ET XT 718 Ice/Frost Ramp

NASA Technical Reports Server (NTRS)

Tejnil, Edward; Rogers, Stuart E.

2012-01-01

Computational fluid dynamics assessment of the forward booster separation motor ignition over-pressure was performed on the space shuttle external tank X(sub T) 718 ice/frost ramp using the flow solver OVERFLOW. The main objective of this study was the investigation of the over-pressure during solid rocket booster separation and its affect on the local pressure and air-load environments. Delta pressure and plume impingement were investigated as a possible contributing factor to the cause of the debris loss on shuttle missions STS-125 and STS-127. A simplified computational model of the Space Shuttle Launch Vehicle was developed consisting of just the external tank and the solid rocket boosters with separation motor nozzles and plumes. The simplified model was validated by comparison to full fidelity computational model of the Space Shuttle without the separation motors. Quasi steady-state plume solutions were used to calibrate the thrust of the separation motors. Time-accurate simulations of the firing of the booster-separation motors were performed. Parametric studies of the time-step size and the number of sub-iterations were used to find the best converged solution. The computed solutions were compared to previous OVERFLOW steady-state runs of the separation motors with reaction control system jets and to ground test data. The results indicated that delta pressure from the overpressure was small and within design limits, and thus was unlikely to have contributed to the foam losses.

Breathing efficiency during inspiratory threshold loading in patients with chronic obstructive pulmonary disease.

PubMed

Baarends, E M; Schols, A M; Nusmeier, C M; van der Grinten, C P; Wouters, E F

1998-05-01

Patients with chronic obstructive pulmonary disease (COPD) demonstrate an increased oxygen cost of breathing. It is as yet unclear whether this is related to a decreased breathing efficiency. The aim of the present study was to compare breathing efficiency in 16 patients with COPD (11 men, five women) and 16 healthy elderly subjects (seven men, nine women), and to investigate a possible relationship between breathing efficiency and resting energy expenditure (REE). REE was measured using a ventilated hood system. Breathing efficiency was assessed by measuring oxygen consumption (V'O2), mean inspiratory mouth pressure (MIP) and flow during breathing at rest and subsequently during breathing against an inspiratory threshold (40% of maximal inspiratory pressure). During loaded breathing there was a significant increase in V'O2, MIP, and external work of breathing compared with unloaded breathing in both groups. As intended, ventilation did not increase significantly during the breathing efficiency test in the patients with COPD. The breathing efficiency (median, range) of the patients with COPD was similar (3.7%, 1.4-8.7%) to that of the healthy elderly subjects (3.2%, 1.7-8.3%). Breathing efficiency was not correlated with REE in either group. In the present study, in which dynamic hyperinflation was probably prevented, no difference in breathing efficiency was found between healthy elderly subjects and COPD patients when breathing against an external inspiratory threshold. Furthermore, breathing efficiency was not related to REE in both groups.

Postural Stability Assessment of University Marching Musicians Using Force Platform Measures.

PubMed

Magnotti, Trevor D; McElhiney, Danielle; Russell, Jeffrey A

2016-09-01

Lower extremity injury is prevalent in marching musicians, and poor postural stability is a possible risk factor for this. The external load of an instrument may predispose these performers to injury by decreasing postural stability. The purpose of this study was to determine the relationship between instrument load and static and dynamic postural stability in this population. Fourteen university marching musicians were recruited and completed a balance assessment protocol on a force platform with and without their instrument. Mean center of pressure (CoP) displacement was then calculated for each exercise in the anterior/posterior and medial/lateral planes. Mean anterior/posterior CoP displacement significantly increased in the instrument condition for the static surface, eyes closed, 2 feet condition (p≤0.005; d=0.89). No significant differences were found in the medial/lateral plane between non-instrument and instrument conditions. Significant differences were not found between test stance conditions independent of group. Comparisons between the non-instrument-loaded and instrument-loaded conditions revealed possible significance of instrument load on postural stability in the anterior/posterior plane. Mean differences indicated that an unstable surface created a greater destabilizing effect on postural stability than instrument load.

Turbomachine Sealing and Secondary Flows - Part 3. Part 3; Review of Power-Stream Support, Unsteady Flow Systems, Seal and Disk Cavity Flows, Engine Externals, and Life and Reliability Issues

NASA Technical Reports Server (NTRS)

Hendricks, R. C.; Steinetz, B. M.; Zaretsky, E. V.; Athavale, M. M.; Przekwas, A. J.

2004-01-01

The issues and components supporting the engine power stream are reviewed. It is essential that companies pay close attention to engine sealing issues, particularly on the high-pressure spool or high-pressure pumps. Small changes in these systems are reflected throughout the entire engine. Although cavity, platform, and tip sealing are complex and have a significant effect on component and engine performance, computational tools (e.g., NASA-developed INDSEAL, SCISEAL, and ADPAC) are available to help guide the designer and the experimenter. Gas turbine engine and rocket engine externals must all function efficiently with a high degree of reliability in order for the engine to run but often receive little attention until they malfunction. Within the open literature statistically significant data for critical engine components are virtually nonexistent; the classic approach is deterministic. Studies show that variations with loading can have a significant effect on component performance and life. Without validation data they are just studies. These variations and deficits in statistical databases require immediate attention.

Aerodynamic Heat-Power Engine Operating on a Closed Cycle

NASA Technical Reports Server (NTRS)

Ackeret, J.; Keller, D. C.

1942-01-01

Hot-air engines with dynamic compressors and turbines offer new prospects of success through utilization of units of high efficiencies and through the employment of modern materials of great strength at high temperature. Particular consideration is given to an aerodynamic prime mover operating on a closed circuit and heated externally. Increase of the pressure level of the circulating air permits a great increase of limit load of the unit. This also affords a possibility of regulation for which the internal efficiency of the unit changes but slightly. The effect of pressure and temperature losses is investigated. A general discussion is given of the experimental installation operating at the Escher Wyss plant in Zurich for a considerable time at high temperatures.

Induced charge electroosmosis micropumps using arrays of Janus micropillars.

PubMed

Paustian, Joel S; Pascall, Andrew J; Wilson, Neil M; Squires, Todd M

2014-09-07

We report on a microfluidic AC-driven electrokinetic pump that uses Induced Charge Electro-Osmosis (ICEO) to generate on-chip pressures. ICEO flows occur when a bulk electric field polarizes a metal object to induce double layer formation, then drives electroosmotic flow. A microfabricated array of metal-dielectric Janus micropillars breaks the symmetry of ICEO flow, so that an AC electric field applied across the array drives ICEO flow along the length of the pump. When pumping against an external load, a pressure gradient forms along the pump length. The design was analyzed theoretically with the reciprocal theorem. The analysis reveals a maximum pressure and flow rate that depend on the ICEO slip velocity and micropillar geometry. We then fabricate and test the pump, validating our design concept by demonstrating non-local pressure driven flow using local ICEO slip flows. We varied the voltage, frequency, and electrolyte composition, measuring pump pressures of 15-150 Pa. We use the pump to drive flows through a high-resistance microfluidic channel. We conclude by discussing optimization routes suggested by our theoretical analysis to enhance the pump pressure.

Effects of load on ground reaction force and lower limb kinematics during concentric squats.

PubMed

Kellis, Eleftherios; Arambatzi, Fotini; Papadopoulos, Christos

2005-10-01

The purpose of this study was to examine the effects of external load on vertical ground reaction force, and linear and angular kinematics, during squats. Eight males aged 22.1 +/- 0.8 years performed maximal concentric squats using loads ranging from 7 to 70% of one-repetition maximum on a force plate while linear barbell velocity and the angular kinematics of the hip, knee and ankle were recorded. Maximum, average and angle-specific values were recorded. The ground reaction force ranged from 1.67 +/- 0.20 to 3.21 +/- 0.29 times body weight and increased significantly as external load increased (P < 0.05). Bar linear velocity ranged from 0.54 +/- 0.11 to 2.50 +/- 0.50 m x s(-1) and decreased significantly with increasing external load (P < 0.05). Hip, knee and ankle angles at maximum ground reaction force were affected by external load (P < 0.05). The force-barbell velocity curves were fitted using linear models with coefficients (r2) ranging from 0.59 to 0.96. The results suggest that maximal force exertion during squat exercises is not achieved at the same position of the lower body as external load is increased. In contrast, joint velocity coordination does not change as load is increased. The force-velocity relationship was linear and independent from the set of data used for its determination.

Identification of Individual Efficiency for Barometric Pressure and Ocean Tide Load Simultaneously Acted on Deep Aquifers Adjacent to the West Pacific Ocean

NASA Astrophysics Data System (ADS)

Shih, David Ching-Fang

2018-06-01

Groundwater fluctuation usually reflects the property of aquifer in nature. Actually, water level change can be caused not only by barometric pressure changes resulted from atmospheric motion, but also by the tidal effect from nearby marine system or water body. In confined aquifer, an increase in barometric pressure usually will cause a decrease in water level in well to an amount described by the barometric efficiency. The barometric efficiency can be also used as a correction factor to remove barometric effects on water levels in wells during an aquifer test. With the rise of the tidal sea on the coastal aquifer, it indicates that there will be compensating increases of water pressure and stress in the skeleton of aquifer. External forcing on groundwater level in the coastal aquifer, such as barometric effect and tidal sea, usually affect the water level to fluctuate with different phases to some extent. An adaptive adjustment to remove the combination of barometric and oceanic tidal efficiency is presented in this study. This research suggests that the presented formula can simultaneously identify the individual efficiency for barometric effect and load of tidal sea considering their combined observation of groundwater level in aquifer system. An innovative application has been demonstrated for the deep aquifers adjacent to the West Pacific Ocean.

The analysis of the transient pressure response of the shuttle EPS-ECS cryogenic tanks with external pressurization systems

NASA Technical Reports Server (NTRS)

Barton, J. E.; Patterson, H. W.

1973-01-01

An analysis of transient pressures in externally pressurized cryogenic hydrogen and oxygen tanks was conducted and the effects of design variables on pressure response determined. The analysis was conducted with a computer program which solves the compressible viscous flow equations in two-dimensional regions representing the tank and external loop. The external loop volume, thermal mass, and heat leak were the dominant design variables affecting the system pressure response. No significant temperature stratification occurred in the fluid contained in the tank.

A test apparatus and facility to identify the rotordynamic coefficients of high-speed hydrostatic bearings

NASA Technical Reports Server (NTRS)

Childs, Dara; Hale, Keith

1994-01-01

A facility and apparatus are described which determine stiffness, damping, and added-mass rotordynamic coefficients plus steady-state operating characteristics of high speed hydrostatic journal bearings. The apparatus has a current top speed of 29,800 rpm with a bearing diameter of 7.62 cm (3 in.). Purified warm water, 55 C (130 F), is used as a test fluid to achieve elevated Reynolds numbers during operation. The test-fluid pump yields a bearing maximum inlet pressure of 6.9 Mpa (1000 psi). Static load on the bearing is independently controlled and measured. Orthogonally mounted external shakers are used to excite the test stator in the direction of, and perpendicular to, the static load. The apparatus can independently calculate all rotordynamic coefficients at a given operating condition.

A predictive model of human performance.

NASA Technical Reports Server (NTRS)

Walters, R. F.; Carlson, L. D.

1971-01-01

An attempt is made to develop a model describing the overall responses of humans to exercise and environmental stresses for prediction of exhaustion vs an individual's physical characteristics. The principal components of the model are a steady state description of circulation and a dynamic description of thermal regulation. The circulatory portion of the system accepts changes in work load and oxygen pressure, while the thermal portion is influenced by external factors of ambient temperature, humidity and air movement, affecting skin blood flow. The operation of the model is discussed and its structural details are given.

Intersecting vane machines

DOEpatents

Bailey, H. Sterling; Chomyszak, Stephen M.

2007-01-16

The invention provides a toroidal intersecting vane machine incorporating intersecting rotors to form primary and secondary chambers whose porting configurations minimize friction and maximize efficiency. Specifically, it is an object of the invention to provide a toroidal intersecting vane machine that greatly reduces the frictional losses through meshing surfaces without the need for external gearing by modifying the function of one or the other of the rotors from that of "fluid moving" to that of "valving" thereby reducing the pressure loads and associated inefficiencies at the interface of the meshing surfaces. The inventions described herein relate to these improvements.

Transient analysis using conical shell elements

NASA Technical Reports Server (NTRS)

Yang, J. C. S.; Goeller, J. E.; Messick, W. T.

1973-01-01

The use of the NASTRAN conical shell element in static, eigenvalue, and direct transient analyses is demonstrated. The results of a NASTRAN static solution of an externally pressurized ring-stiffened cylinder agree well with a theoretical discontinuity analysis. Good agreement is also obtained between the NASTRAN direct transient response of a uniform cylinder to a dynamic end load and one-dimensional solutions obtained using a method of characteristics stress wave code and a standing wave solution. Finally, a NASTRAN eigenvalue analysis is performed on a hydroballistic model idealized with conical shell elements.

Study of Nox Emission Characteristics of a 1025t/h Coal-Fired Circulating Fluidized Bed Boiler

NASA Astrophysics Data System (ADS)

Li, Q. Y.; Mi, Z. D.; Zhang, Q. F.

Measurements of emission are carried out in a 1025t/h CFB boiler. The effect of some factors including coal properties, bed temperature, unit load, excess air on the emission of NOx are investigated. The measurement results show that the N concentration in the coal is dominant parameter to predict the NOx emission from a large-scale CFB boiler. NOx emission from the 1025t/h CFB boiler increases with cyclone temperature and upper pressure drop due to post combustion and external cycle.

Proof of Concept of Integrated Load Measurement in 3D Printed Structures

PubMed Central

Hinderdael, Michaël; Jardon, Zoé; Lison, Margot; De Baere, Dieter; Devesse, Wim; Strantza, Maria; Guillaume, Patrick

2017-01-01

Currently, research on structural health monitoring systems is focused on direct integration of the system into a component or structure. The latter results in a so-called smart structure. One example of a smart structure is a component with integrated strain sensing for continuous load monitoring. Additive manufacturing, or 3D printing, now also enables such integration of functions inside components. As a proof-of-concept, the Fused Deposition Modeling (FDM) technique was used to integrate a strain sensing element inside polymer (ABS) tensile test samples. The strain sensing element consisted of a closed capillary filled with a fluid and connected to an externally mounted pressure sensor. The volumetric deformation of the integrated capillary resulted in pressure changes in the fluid. The obtained pressure measurements during tensile testing are reported in this paper and compared to state-of-the-art extensometer measurements. The sensitivity of the 3D printed pressure-based strain sensor is primarily a function of the compressibility of the capillary fluid. Air- and watertightness are of critical importance for the proper functioning of the 3D printed pressure-based strain sensor. Therefore, the best after-treatment procedure was selected on basis of a comparative analysis. The obtained pressure measurements are linear with respect to the extensometer readings, and the uncertainty on the strain measurement of a capillary filled with water (incompressible fluid) is ±3.1 µstrain, which is approximately three times less sensitive than conventional strain gauges (±1 µstrain), but 32 times more sensitive than the same sensor based on air (compressible fluid) (±101 µstrain). PMID:28208779

Hydrology and water quality of Delavan Lake in southeastern Wisconsin

USGS Publications Warehouse

Field, S.J.; Duerk, M.D.

1988-01-01

External loading of phosphorus and nitrogen were sufficient to cause eutrophic conditions. Internal loading of phosphorus was more than two times the external phosphorus supply. Most of the internal loading occurred when the hypolimnion was anoxic during summer. Internal loading of phosphorus during the 1985 water year was significantly reduced from that of 1984 because of a shorter anoxic period.

Residual strength of thin panels with cracks

NASA Technical Reports Server (NTRS)

Madenci, Erdogan

1994-01-01

The previous design philosophies involving safe life, fail-safe and damage tolerance concepts become inadequate for assuring the safety of aging aircraft structures. For example, the failure mechanism for the Aloha Airline accident involved the coalescence of undetected small cracks at the rivet holes causing a section of the fuselage to peel open during flight. Therefore, the fuselage structure should be designed to have sufficient residual strength under worst case crack configurations and in-flight load conditions. Residual strength is interpreted as the maximum load carrying capacity prior to unstable crack growth. Internal pressure and bending moment constitute the two major components of the external loads on the fuselage section during flight. Although the stiffeners in the form of stringers, frames and tear straps sustain part of the external loads, the significant portion of the load is taken up by the skin. In the presence of a large crack in the skin, the crack lips bulge out with considerable yielding; thus, the geometric and material nonlinearities must be included in the analysis for predicting residual strength. Also, these nonlinearities do not permit the decoupling of in-plane and out-of-plane bending deformations. The failure criterion combining the concepts of absorbed specific energy and strain energy density addresses the aforementioned concerns. The critical absorbed specific energy (local toughness) for the material is determined from the global specimen response and deformation geometry based on the uniaxial tensile test data and detailed finite element modeling of the specimen response. The use of the local toughness and stress-strain response at the continuum level eliminates the size effect. With this critical parameter and stress-strain response, the finite element analysis of the component by using STAGS along with the application of this failure criterion provides the stable crack growth calculations for residual strength predictions.

Biomechanical effect of latissimus dorsi tendon transfer for irreparable massive cuff tear.

PubMed

Oh, Joo Han; Tilan, Justin; Chen, Yu-Jen; Chung, Kyung Chil; McGarry, Michelle H; Lee, Thay Q

2013-02-01

The purpose of this study was to determine the biomechanical effects of latissimus dorsi transfer in a cadaveric model of massive posterosuperior rotator cuff tear. Eight cadaveric shoulders were tested at 0°, 30°, and 60° of abduction in the scapular plane with anatomically based muscle loading. Humeral rotational range of motion and the amount of humeral rotation due to muscle loading were measured. Glenohumeral kinematics and contact characteristics were measured throughout the range of motion. After testing in the intact condition, the supraspinatus and infraspinatus were resected. The cuff tear was then repaired by latissimus dorsi transfer. Two muscle loading conditions were applied after latissimus transfer to simulate increased tension that may occur due to limited muscle excursion. A repeated-measures analysis of variance was used for statistical analysis. The amount of internal rotation due to muscle loading and maximum internal rotation increased with massive cuff tear and was restored with latissimus transfer (P < .05). At maximum internal rotation, the humeral head apex shifted anteriorly, superiorly, and laterally at 0° of abduction after massive cuff tear (P < .05); this abnormal shift was corrected with latissimus transfer (P < .05). However, at 30° and 60° of abduction, latissimus transfer significantly altered kinematics (P < .05) and latissimus transfer with increased muscle loading increased contact pressure, especially at 60° of abduction. Latissimus dorsi transfer is beneficial in restoring humeral internal/external rotational range of motion, the internal/external rotational balance of the humerus, and glenohumeral kinematics at 0° of abduction. However, latissimus dorsi transfer with simulated limited excursion may lead to an overcompensation that can further deteriorate normal biomechanics, especially at higher abduction angles. Published by Mosby, Inc.

Dorzolamide Loaded Niosomal Vesicles: Comparison of Passive and Remote Loading Methods

PubMed Central

Hashemi Dehaghi, Mohadeseh; Haeri, Azadeh; Keshvari, Hamid; Abbasian, Zahra; Dadashzadeh, Simin

2017-01-01

Glaucoma is a common progressive eye disorder and the treatment strategies will benefit from nanoparticulate delivery systems with high drug loading and sustained delivery of intraocular pressure lowering agents. Niosomes have been reported as a novel approach to improve drug low corneal penetration and bioavailability characteristics. Along with this, poor entrapment efficiency of hydrophilic drug in niosomal formulation remains as a major formulation challenge. Taking this perspective into consideration, dorzolamide niosomes were prepared employing two different loading methodologies (passive and remote loading methods) and the effects of various formulation variables (lipid to drug ratio, cholesterol percentage, drug concentration, freeze/thaw cycles, TPGS content, and external and internal buffer molarity and pH) on encapsulation efficiency were assessed. Encapsulation of dorzolamide within niosomes increased remarkably by the incorporation of higher cholesterol percentage as well as increasing the total lipid concentration. Remote loading method showed higher efficacy for drug entrapment compared to passive loading technique. Incorporation of TPGS in bilayer led to decrease in EE; however, retarded drug release rate. Scanning electron microscopy (SEM) studies confirmed homogeneous particle distribution, and spherical shape with smooth surface. In conclusion, the highest encapsulation can be obtained using phosphate gradient method and 50% cholesterol in Span 60 niosomal formulation. PMID:28979296

CRYogenic Orbital TEstbed Ground Test Article Thermal Analysis

NASA Technical Reports Server (NTRS)

Piryk, David; Schallhorn, Paul; Walls, Laurie; Stopnitzky, Benny; Rhys, Noah; Wollen, Mark

2012-01-01

The purpose of this study was to anchor thermal and fluid system models to CRYOTE ground test data. The CRYOTE ground test artide was jointly developed by Innovative Engineering Solutions, United Launch Alliance and NASA KSC. The test article was constructed out of a titanium alloy tank, Sapphire 77 composite skin (similar to G10), an external secondary payload adapter ring, thermal vent system, multi layer insulation and various data acquisition instrumentation. In efforts to understand heat loads throughout this system, the GTA (filled with liquid nitrogen for safety purposes) was subjected to a series of tests in a vacuum chamber at Marshall Space Flight Center. By anchoring analytical models against test data, higher fidelity thermal environment predictions can be made for future flight articles which would eventually demonstrate critical cryogenic fluid management technologies such as system chilldown, transfer, pressure control and long term storage. Significant factors that influenced heat loads included radiative environments, multi-layer insulation performance, tank fill levels and pressures and even contact conductance coefficients. This report demonstrates how analytical thermal/fluid networks were established and includes supporting rationale for specific thermal responses.

Calculation methods for externally pressurised (hydrostatic) journal bearings with capillary restrictor control

NASA Astrophysics Data System (ADS)

1992-09-01

ESDU 92026 provides a procedure for the design and performance analysis of the bearings with five or more identical equally-spaced rectangular recesses (or pockets) fed by identical capillary restrictors from a constant pressure supply. The method takes account of stiffness and overload capacity requirements and determines the bearing overall size and proportions from the required load, speed and shaft diameter, recommends the clearance and supply pressure, and defines the recess dimensions and capillary restrictor size from the properties of the chosen lubricant. Equations and charts allow prediction of the journal displacement under load, the power loss, the lubricant flow rate, and the bearing and lubricant temperatures. The method applies to laminar flow and guidance is given for assessing the onset of non-laminar flow in the bearing and restrictors. Guidance is also given on the likelihood of bearing-induced instability. The user is assisted by flowcharts in applying the method, and two practical worked examples illustrate the procedure. ESDU 92037 introduces a FORTRAN program that implements the method, and magnetic media are available in ESDUpac A9237.

The Bulging Behavior of Thick-Walled 6063 Aluminum Alloy Tubes Under Double-Sided Pressures

NASA Astrophysics Data System (ADS)

Cui, Xiao-Lei; Wang, Xiao-Song; Yuan, Shi-Jian

2015-05-01

To make further exploration on the deformation behavior of tube under double-sided pressures, the thick-walled 6063 aluminum alloy tubes with an outer diameter of 65 mm and an average thickness of 7.86 mm have been used to be bulged under the combined action of internal and external pressures. In the experiment, two ends of the thick-walled tubes were fixed using the tooth and groove match. Three levels of external pressure (0 MPa, 40 MPa, and 80 MPa), in conjunction with the internal pressure, were applied on the tube outside and inside simultaneously. The effect of external pressure on the bulging behavior of the thick-walled tubes, such as the limiting expansion ratio, the bulging zone profile, and the thickness distribution, has been investigated. It is shown that the limiting expansion ratio, the bulging zone profile, and the thickness distribution in the homogeneous bulging area are all insensitive to the external pressure. However, the external pressure can make the thick-walled tube achieve a thinner wall at the fracture area. It reveals that the external pressure can only improve the fracture limit of the thick-walled 6063 tubes, but it has very little effect on their homogeneous bulging behavior. It might be because the external pressure can only increase the magnitude of the hydrostatic pressure for the tube but has no effect on the Lode parameter.

Tensiomyographical responses to accelerometer loads in female collegiate basketball players.

PubMed

Peterson, Kyle D; Quiggle, Gabriela T

2017-12-01

The purpose of the present study was to characterise the relationship between relative versus absolute internal and external loads in collegiate basketball players throughout the course of a season. Five Division I basketball players wore triaxial accelerometers throughout the 2015-2016 season and were tensiomyographically assessed weekly. One-way repeated-measure analysis of variance (RM ANOVA) with least-significant-difference (LSD) pairwise comparisons was used to determine which absolute weekly loads were different across the season. Cohen's d was used to supplement the determination of meaningful relative load changes. Overall RM ANOVA models suggest absolute external load differences occurred (PlayerLoad™ F = 17.63; IMA™ F = 31.63). Two-way RM ANOVA models revealed main effect differences were revealed between muscle groups for Tc (F = 9.11) and Dm (F = 3.25). Meaningful relative load changes between weeks were observed for both external and internal. The present study observed that tensiomyography utilised as a tool to monitor internal load may be more suitable for detecting fatigue from relative external load changes versus absolute load attained. Limiting weekly training volume changes to ≤10% may maintain appropriate adaptation. Mediolateral plane IMA™ and adductor longus muscle group may be pertinent metrics when monitoring female collegiate basketball athletes.

14 CFR 29.471 - General.

Code of Federal Regulations, 2011 CFR

2011-01-01

... equilibrium. For limit ground loads— (1) The limit ground loads obtained in the landing conditions in this part must be considered to be external loads that would occur in the rotorcraft structure if it were acting as a rigid body; and (2) In each specified landing condition, the external loads must be placed in...

46 CFR 64.19 - External pressure.

Code of Federal Regulations, 2012 CFR

2012-10-01

... HANDLING SYSTEMS Standards for an MPT § 64.19 External pressure. (a) A tank without a vacuum breaker must be designed to withstand an external pressure of 71/2 psig or more. (b) A tank with a vacuum breaker...

46 CFR 64.19 - External pressure.

Code of Federal Regulations, 2013 CFR

2013-10-01

... HANDLING SYSTEMS Standards for an MPT § 64.19 External pressure. (a) A tank without a vacuum breaker must be designed to withstand an external pressure of 71/2 psig or more. (b) A tank with a vacuum breaker...

46 CFR 64.19 - External pressure.

Code of Federal Regulations, 2014 CFR

2014-10-01

... HANDLING SYSTEMS Standards for an MPT § 64.19 External pressure. (a) A tank without a vacuum breaker must be designed to withstand an external pressure of 71/2 psig or more. (b) A tank with a vacuum breaker...

46 CFR 64.19 - External pressure.

Code of Federal Regulations, 2011 CFR

2011-10-01

... HANDLING SYSTEMS Standards for an MPT § 64.19 External pressure. (a) A tank without a vacuum breaker must be designed to withstand an external pressure of 71/2 psig or more. (b) A tank with a vacuum breaker...

46 CFR 64.19 - External pressure.

Code of Federal Regulations, 2010 CFR

2010-10-01

... HANDLING SYSTEMS Standards for an MPT § 64.19 External pressure. (a) A tank without a vacuum breaker must be designed to withstand an external pressure of 71/2 psig or more. (b) A tank with a vacuum breaker...

Relationships Between Results Of An Internal And External Match Load Determining Method In Male, Singles Badminton Players.

PubMed

Abdullahi, Yahaya; Coetzee, Ben; Van den Berg, Linda

2017-07-03

The study purpose was to determine relationships between results of internal and external match load determining methods. Twenty-one players, who participated in selected badminton championships during the 2014/2015 season served as subjects. The heart rate (HR) values and GPS data of each player were obtained via a fix Polar HR Transmitter Belt and MinimaxX GPS device. Moderate significant Spearman's rank correlations were found between HR and absolute duration (r = 0.43 at a low intensity (LI) and 0.44 at a high intensity (HI)), distance covered (r = 0.42 at a HI) and player load (PL) (r = 0.44 at a HI). Results also revealed an opposite trend for external and internal measures of load as the average relative HR value was found to be the highest for the HI zone (54.1%) compared to the relative measures of external load where average values (1.29-9.89%) were the lowest for the HI zone. In conclusion, our findings show that results of an internal and external badminton match load determining method are more related to each other in the HI zone than other zones and that the strength of relationships depend on the duration of activities that are performed in especially LI and HI zones. Overall, trivial to moderate relationships between results of an internal and external match load determining method in male, singles badminton players reaffirm the conclusions of others that these constructs measure distinctly different demands and should therefore be measured concurrently to fully understand the true requirements of badminton match play.

Method for the measurement of susceptibility to decubitus ulcer formation.

PubMed

Meijer, J H; Schut, G L; Ribbe, M W; Goovaerts, H G; Nieuwenhuys, R; Reulen, J P; Schneider, H

1989-09-01

A method for measuring the susceptibility of a patient to develop decubitus ulcers is described and initially evaluated. It is based on an indirect, noninvasive measurement of the transient regional blood flow response after a test pressure load which simulates the external stimulus for pressure-sore formation. This method was developed to determine the individual risk of a patient and to study the subfactors which contribute to the susceptibility. This would also offer the possibility of evaluating the effect of preventive treatment aimed at reducing the susceptibility. The method was found to discriminate between preselected elderly patients at risk on the one hand, and non-risk patients and healthy young adults on the other hand. No differences in blood flow responses were found between the non-risk elderly patients and the healthy young adults. This suggests that age per se is not a factor in the formation of pressure sores. In the risk group the recovery time after pressure relief was found to be three times as long as the duration of the pressure exercise. This indicates that the recovery time after pressure exercise may be as important as the period of pressure exercise in deducing the risk of developing decubitus ulcers.

3D multiphysics modeling of superconducting cavities with a massively parallel simulation suite

NASA Astrophysics Data System (ADS)

Kononenko, Oleksiy; Adolphsen, Chris; Li, Zenghai; Ng, Cho-Kuen; Rivetta, Claudio

2017-10-01

Radiofrequency cavities based on superconducting technology are widely used in particle accelerators for various applications. The cavities usually have high quality factors and hence narrow bandwidths, so the field stability is sensitive to detuning from the Lorentz force and external loads, including vibrations and helium pressure variations. If not properly controlled, the detuning can result in a serious performance degradation of a superconducting accelerator, so an understanding of the underlying detuning mechanisms can be very helpful. Recent advances in the simulation suite ace3p have enabled realistic multiphysics characterization of such complex accelerator systems on supercomputers. In this paper, we present the new capabilities in ace3p for large-scale 3D multiphysics modeling of superconducting cavities, in particular, a parallel eigensolver for determining mechanical resonances, a parallel harmonic response solver to calculate the response of a cavity to external vibrations, and a numerical procedure to decompose mechanical loads, such as from the Lorentz force or piezoactuators, into the corresponding mechanical modes. These capabilities have been used to do an extensive rf-mechanical analysis of dressed TESLA-type superconducting cavities. The simulation results and their implications for the operational stability of the Linac Coherent Light Source-II are discussed.

Non-equilibrium phase behavior and friction of confined molecular films under shear: A non-equilibrium molecular dynamics study.

PubMed

Maćkowiak, Sz; Heyes, D M; Dini, D; Brańka, A C

2016-10-28

The phase behavior of a confined liquid at high pressure and shear rate, such as is found in elastohydrodynamic lubrication, can influence the traction characteristics in machine operation. Generic aspects of this behavior are investigated here using Non-equilibrium Molecular Dynamics (NEMD) simulations of confined Lennard-Jones (LJ) films under load with a recently proposed wall-driven shearing method without wall atom tethering [C. Gattinoni et al., Phys. Rev. E 90, 043302 (2014)]. The focus is on thick films in which the nonequilibrium phases formed in the confined region impact on the traction properties. The nonequilibrium phase and tribological diagrams are mapped out in detail as a function of load, wall sliding speed, and atomic scale surface roughness, which is shown can have a significant effect. The transition between these phases is typically not sharp as the external conditions are varied. The magnitude of the friction coefficient depends strongly on the nonequilibrium phase adopted by the confined region of molecules, and in general does not follow the classical friction relations between macroscopic bodies, e.g., the frictional force can decrease with increasing load in the Plug-Slip (PS) region of the phase diagram owing to structural changes induced in the confined film. The friction coefficient can be extremely low (∼0.01) in the PS region as a result of incommensurate alignment between a (100) face-centered cubic wall plane and reconstructed (111) layers of the confined region near the wall. It is possible to exploit hysteresis to retain low friction PS states well into the central localization high wall speed region of the phase diagram. Stick-slip behavior due to periodic in-plane melting of layers in the confined region and subsequent annealing is observed at low wall speeds and moderate external loads. At intermediate wall speeds and pressure values (at least) the friction coefficient decreases with increasing well depth of the LJ potential between the wall atoms, but increases when the attractive part of the potential between wall atoms and confined molecules is made larger.

Monitoring external and internal loads of brazilian soccer referees during official matches.

PubMed

Costa, Eduardo C; Vieira, Caio M A; Moreira, Alexandre; Ugrinowitsch, Carlos; Castagna, Carlo; Aoki, Marcelo S

2013-01-01

This study aimed to assess the external and internal loads of Brazilian soccer referees during official matches. A total of 11 field referees (aged 36.2 ± 7.5 years) were monitored during 35 matches. The external (distance covered, mean and maximal speed) and internal load parameters (session ratings of perceived exertion [RPE] training load [TL], Edwards' TL, and time spent in different heart rate [HR] zones) were assessed in 3-4 matches per referee. External load parameters were measured using a wrist Global Positioning System (GPS) receiver. No differences in distance covered (5.219 ± 205 vs. 5.230 ± 237 m) and maximal speed (19.3 ± 1.0 vs. 19.4 ± 1.4 km·h(-1)) were observed between the halves of the matches (p > 0.05). However, the mean speed was higher in the first half of the matches (6.6 ± 0.4 vs. 6.4 ± 0.3 km·h(-1)) (p < 0.05) than in the second half. The mean HR during the matches was ~89% of HRmax. In ~95% of the matches, the referees demonstrated a HR ≥ 80% of HRmax. Nonetheless, the time spent at 90-100% of HRmax was higher in the first half (59.9 vs. 52.3%) (p < 0.05). Significant correlations between session RPE TL and distance covered at 90-100% of HRmax (r = 0.62) and session RPE TL and maximal speed (r = 0.54) (p < 0.05) were noted. Furthermore, there was a positive correlation between session RPE TL and Edwards' TL (r = 0.61) (p < 0.05). Brazilian soccer referees demonstrated high external and internal load demands during official matches. The portable GPS/HR monitors and session RPE method can provide relevant information regarding the magnitude of the physiological strain during official matches. Key PointsHigh external and internal loads were imposed on Brazilian soccer referees during official matches.There was a high positive correlation between a subjective marker of internal load (session RPE) and parameters of external load (distance covered between 90-100% of HRmax and maximal speed).There was a high positive correlation between session RPE method and Edwards' method.Session RPE seems to be a reliable marker of internal load.The portable GPS/HR monitors and the session RPE method can provide relevant information regarding the magnitude of external and internal loads of soccer referees during official matches.

Simulated decadal modes of the NH atmospheric circulation arising from intra-decadal variability, external forcing and slow-decadal climate processes

NASA Astrophysics Data System (ADS)

Lou, Jiale; Zheng, Xiaogu; Frederiksen, Carsten S.; Liu, Haibo; Grainger, Simon; Ying, Kairan

2017-04-01

A decadal variance decomposition method is applied to the Northern Hemisphere (NH) 500-hPa geopotential height (GPH) and the sea level pressure (SLP) taken from the last millennium (850-1850 AD) experiment with the coupled climate model CCSM4, to estimate the contribution of the intra-decadal variability to the inter-decadal variability. By removing the intra-decadal variability from the total inter-decadal variability, the residual variability is more likely to be associated with slowly varying external forcings and slow-decadal climate processes, and therefore is referred to as slow-decadal variability. The results show that the (multi-)decadal changes of the NH 500-hPa GPH are primarily dominated by slow-decadal variability, whereas the NH SLP field is primarily dominated by the intra-decadal variability. At both pressure levels, the leading intra-decadal modes each have features related to the El Niño-southern oscillation, the intra-decadal variability of the Pacific decadal oscillation (PDO) and the Arctic oscillation (AO); while the leading slow-decadal modes are associated with external radiative forcing (mostly with volcanic aerosol loadings), the Atlantic multi-decadal oscillation and the slow-decadal variability of AO and PDO. Moreover, the radiative forcing has much weaker effect to the SLP than that to the 500-hPa GPH.

Passive and active response of bacteria under mechanical compression

NASA Astrophysics Data System (ADS)

Garces, Renata; Miller, Samantha; Schmidt, Christoph F.; Byophysics Team; Institute of Medical Sciences Collaboration

Bacteria display simple but fascinating cellular structures and geometries. Their shapes are the result of the interplay between osmotic pressure and cell wall construction. Typically, bacteria maintain a high difference of osmotic pressure (on the order of 1 atm) to the environment. This pressure difference (turgor pressure) is supported by the cell envelope, a composite of lipid membranes and a rigid cell wall. The response of the cell envelope to mechanical perturbations such as geometrical confinements is important for the cells survival. Another key property of bacteria is the ability to regulate turgor pressure after abrupt changes of external osmotic conditions. This response relies on the activity of mechanosensitive (MS) channels: membrane proteins that release solutes in response to excessive stress in the cell envelope. We here present experimental data on the mechanical response of the cell envelope and on turgor regulation of bacteria subjected to compressive forces. We indent living cells with micron-sized beads attached to the cantilever of an atomic force microscope (AFM). This approach ensures global deformation of the cell. We show that such mechanical loading is sufficient to gate mechanosensitive channels in isosmotic conditions.

Quantifying the Influence of Lightning Strike Pressure Loading on Composite Specimen Damage

NASA Astrophysics Data System (ADS)

Foster, P.; Abdelal, G.; Murphy, A.

2018-04-01

Experimental work has shown that a component of lightning strike damage is caused by a mechanical loading. As the profile of the pressure loading is unknown a number of authors propose different pressure loads, varying in form, application area and magnitude. The objective of this paper is to investigate the potential contribution of pressure loading to composite specimen damage. This is achieved through a simulation study using an established modelling approach for composite damage prediction. The study examines the proposed shockwave loads from the literature. The simulation results are compared with measured test specimen damage examining the form and scale of damage. The results for the first time quantify the significance of pressure loading, demonstrating that although a pressure load can cause damage consistent with that measured experimentally, it has a negligible contribution to the overall scale of damage. Moreover the requirements for a pressure to create the damage behaviours typically witnessed in testing requires that the pressure load be within a very precise window of magnitude and loading area.

Results of investigations conducted in the LaRC 8-foot transonic pressure tunnel using the 0.010-scale 72-OTS model of the space shuttle integrated vehicle (IA93)

NASA Technical Reports Server (NTRS)

Nichols, M. E.

1976-01-01

Test procedures, history, and data from the wind tunnel test are presented. Aero-loads were investigated on the updated configuration-5 space shuttle launch vehicle at Mach numbers from 0.600 to 1.205. Six-component vehicle forces and moments, base and sting-cavity pressures, elevon hinge moments, wing-root bending and torsion moments, and normal shear force data were obtained. Full simulation of updated vehicle protuberances and attach hardware was employed. Various elevon deflection angles were tested with two different forward orbiter-to-external-tank attach-strut configurations. The entire model was supported by means of a balance mounted in the orbiter through its base and suspended from a sting.

Requirements of Inconel 718 alloy for aeronautical applications

NASA Astrophysics Data System (ADS)

Ghiban, Brandusa; Elefterie, Cornelia Florina; Guragata, Constantin; Bran, Dragos

2018-02-01

The main requirements imposed by aviation components made from super alloys based on Nickel are presented in present paper. A significant portion of fasteners, locking lugs, blade retainers and inserts are manufactured from Inconel 718 alloy. The thesis describes environmental factors (corrosion), conditions of external aggression (salt air, intense heat, heavy industrial pollution, high condensation, high pressure), mechanical characteristics (tensile strength, creep, density, yield strength, fracture toughness, fatigue resistance) and loadings (tensions, compression loads) that must be satisfied simultaneously by Ni-based super alloy, compared to other classes of aviation alloys (as egg. Titanium alloys, Aluminum alloys). For this alloy the requirements are strength, durability, damage tolerance, fail safety and so on. The corrosion can be an issue, but the fatigue under high-magnitude cyclic tensile loading it what limits the lifetime of the airframe. The excellent malleability and weldability characteristics of the 718 system make the material physical properties tolerant of manufacturing processes. These characteristics additionally continue to provide new opportunities for advanced manufacturing methods.

Results of tests OA12 and IA9 in the Ames Research Center unitary plan wind tunnels on an 0.030-scale model of the space shuttle vehicle 2A to determine aerodynamic loads, volume 14

NASA Technical Reports Server (NTRS)

Spangler, R. H.

1974-01-01

Tests were conducted in wind tunnels during April and May 1973, on a 0.030-scale replica of the Space Shuttle Vehicle Configuration 2A. Aerodynamic loads data were obtained at Mach numbers from 0.6 to 3.5. The investigation included tests on the integrated (launch) configuration and the isolated orbiter (entry configuration). The integrated vehicle was tested at angles of attack and sideslip from -8 degrees to +8 degrees. The isolated orbiter was tested at angles of attack from -15 degrees to +40 degrees and angles of sideslip from -10 degrees to +10 degrees as dictated by trajectory considerations. The effects of orbiter/external tank incidence angle and deflected control surfaces on aerodynamic loads were also investigated. Tabulated pressure data were obtained for upper and lower wing surfaces and left and right vertical tail surfaces.

Aeronautical requirements for Inconel 718 alloy

NASA Astrophysics Data System (ADS)

Elefterie, C. F.; Guragata, C.; Bran, D.; Ghiban, B.

2017-06-01

The project goal is to present the requirements imposed by aviation components made from super alloys based on Nickel. A significant portion of fasteners, locking lugs, blade retainers and inserts are manufactured from Alloy 718. The thesis describes environmental factors (corrosion), conditions of external aggression (salt air, intense heat, heavy industrial pollution, high condensation, high pressure), mechanical characteristics (tensile strength, yield strength and fatigue resistance) and loadings (tensions, compression loads) that must be satisfied simultaneously by Ni-based super alloy, compared to other classes of aviation alloys (as egg. Titanium alloys, Aluminum alloys). For this alloy the requirements are strength durability, damage tolerance, fail safety and so on. The corrosion can be an issue, but the fatigue under high-magnitude cyclic tensile loading it’s what limits the lifetime of the airframe. Also, the excellent malleability and weldability characteristics of the 718 system make the material physical properties tolerant of manufacturing processes. These characteristics additionally continue to provide new opportunities for advanced manufacturing methods.

Development of Handling Qualities Criteria for Rotorcraft with Externally Slung Loads

NASA Technical Reports Server (NTRS)

Hoh, Roger H.; Heffley, Robert K.; Mitchell, David G.

2006-01-01

Piloted simulations were performed on the NASA-Ames Vertical Motion Simulator (VMS) to explore handling qualities issues for large cargo helicopters, particularly focusing on external slung load operations. The purpose of this work was based upon the need to include handling qualities criteria for cargo helicopters in an upgrade to the U.S. Army's rotorcraft handling qualities specification, Aeronautical Design Standard-33 (ADS-33E-PRF). From the VMS results, handling qualities criteria were developed fro cargo helicopters carrying external slung loads in the degraded visual environment (DVE). If satisfied, these criteria provide assurance that the handling quality rating (HQR) will be 4 or better for operations in the DVE, and with a load mass ratio of 0.33 or less. For lighter loads, flying qualities were found to be less dependent on the load geometry and therefore the significance of the criteria is less. For heavier loads, meeting the criteria ensures the best possible handling qualities, albeit Level 2 for load mass ratios greater than 0.33.

Upper limb load as a function of repetitive task parameters: part 1--a model of upper limb load.

PubMed

Roman-Liu, Danuta

2005-01-01

The aim of the study was to develop a theoretical indicator of upper limb musculoskeletal load based on repetitive task parameters. As such the dimensionless parameter, Integrated Cycle Load (ICL) was accepted. It expresses upper limb load which occurs during 1 cycle. The indicator is based on a model of a repetitive task, which consists of a model of the upper limb, a model of basic types of upper limb forces and a model of parameters of a repetitive task such as length of the cycle, length of periods of the cycle and external force exerted during each of the periods of the cycle. Calculations of the ICL parameter were performed for 12 different variants of external load characterised by different values of repetitive task parameters. A comparison of ICL, which expresses external load with a physiological indicator of upper limb load, is presented in Part 2 of the paper.

The use of 3d scanner for testing changes in shape of human limbs under the influence of external mechanical load

NASA Astrophysics Data System (ADS)

Kasperska, Kamila; Wieczorowski, Michał; Krolczyk, Jolanta B.

2017-10-01

Three-dimensional scanning is used in many fields: medicine, architecture, industry, reverse engineering. The aim of the article was to analyze the changes in the shape of the limbs under the influence of a mechanical external load using the method of three-dimensional scanner uses white light technology. The paper presents a system of human movement, passive part - skeleton and active part - the muscles, and principles of their interaction, which results in a change of the position of the body. Furthermore, by using the 3D scan, the differences in appearance of the arm and leg depending on the size of the external load in different positions have been presented. The paper shows that with increasing load, which muscles must prevent, increases the volume of certain parts of the legs, while another parts of them will be reduced. Results of the research using three-dimensional scanner allow determining what impact on changing the legs shape has an external mechanical load.

The impact of cognitive control, incentives, and working memory load on the P3 responses of externalizing prisoners.

PubMed

Baskin-Sommers, Arielle R; Krusemark, Elizabeth A; Curtin, John J; Lee, Christopher; Vujnovich, Aleice; Newman, Joseph P

2014-02-01

The P3 amplitude reduction is one of the most common correlates of externalizing. However, few studies have used experimental manipulations designed to challenge different cognitive functions in order to clarify the processes that impact this reduction. To examine factors moderating P3 amplitude in trait externalizing, we administered an n-back task that manipulated cognitive control demands, working memory load, and incentives to a sample of male offenders. Offenders with high trait externalizing scores did not display a global reduction in P3 amplitude. Rather, the negative association between trait externalizing and P3 amplitude was specific to trials involving inhibition of a dominant response during infrequent stimuli, in the context of low working memory load, and incentives for performance. In addition, we discuss the potential implications of these findings for externalizing-related psychopathologies. The results complement and expand previous work on the process-level dysfunction contributing to externalizing-related deficits in P3. Copyright © 2013 Elsevier B.V. All rights reserved.

Highly Sensitive and Patchable Pressure Sensors Mimicking Ion-Channel-Engaged Sensory Organs.

PubMed

Chun, Kyoung-Yong; Son, Young Jun; Han, Chang-Soo

2016-04-26

Biological ion channels have led to much inspiration because of their unique and exquisite operational functions in living cells. Specifically, their extreme and dynamic sensing abilities can be realized by the combination of receptors and nanopores coupled together to construct an ion channel system. In the current study, we demonstrated that artificial ion channel pressure sensors inspired by nature for detecting pressure are highly sensitive and patchable. Our ion channel pressure sensors basically consisted of receptors and nanopore membranes, enabling dynamic current responses to external forces for multiple applications. The ion channel pressure sensors had a sensitivity of ∼5.6 kPa(-1) and a response time of ∼12 ms at a frequency of 1 Hz. The power consumption was recorded as less than a few μW. Moreover, a reliability test showed stability over 10 000 loading-unloading cycles. Additionally, linear regression was performed in terms of temperature, which showed no significant variations, and there were no significant current variations with humidity. The patchable ion channel pressure sensors were then used to detect blood pressure/pulse in humans, and different signals were clearly observed for each person. Additionally, modified ion channel pressure sensors detected complex motions including pressing and folding in a high-pressure range (10-20 kPa).

A comparison of low-pressure and supercharged operation of polymer electrolyte membrane fuel cell systems for aircraft applications

NASA Astrophysics Data System (ADS)

Werner, C.; Preiß, G.; Gores, F.; Griebenow, M.; Heitmann, S.

2016-08-01

Multifunctional fuel cell systems are competitive solutions aboard future generations of civil aircraft concerning energy consumption, environmental issues, and safety reasons. The present study compares low-pressure and supercharged operation of polymer electrolyte membrane fuel cells with respect to performance and efficiency criteria. This is motivated by the challenge of pressure-dependent fuel cell operation aboard aircraft with cabin pressure varying with operating altitude. Experimental investigations of low-pressure fuel cell operation use model-based design of experiments and are complemented by numerical investigations concerning supercharged fuel cell operation. It is demonstrated that a low-pressure operation is feasible with the fuel cell device under test, but that its range of stable operation changes between both operating modes. Including an external compressor, it can be shown that the power demand for supercharging the fuel cell is about the same as the loss in power output of the fuel cell due to low-pressure operation. Furthermore, the supercharged fuel cell operation appears to be more sensitive with respect to variations in the considered independent operating parameters load requirement, cathode stoichiometric ratio, and cooling temperature. The results indicate that a pressure-dependent self-humidification control might be able to exploit the potential of low-pressure fuel cell operation for aircraft applications to the best advantage.

Influences of load characteristics on impaired control of grip forces in patients with cerebellar damage.

PubMed

Brandauer, B; Timmann, D; Häusler, A; Hermsdörfer, J

2010-02-01

Various studies showed a clear impairment of cerebellar patients to modulate grip force in anticipation of the loads resulting from movements with a grasped object. This failure corroborated the theory of internal feedforward models in the cerebellum. Cerebellar damage also impairs the coordination of multiple-joint movements and this has been related to deficient prediction and compensation of movement-induced torques. To study the effects of disturbed torque control on feedforward grip-force control, two self-generated load conditions with different demands on torque control-one with movement-induced and the other with isometrically generated load changes-were directly compared in patients with cerebellar degeneration. Furthermore the cerebellum is thought to be more involved in grip-force adjustment to self-generated loads than to externally generated loads. Consequently, an additional condition with externally generated loads was introduced to further test this hypothesis. Analysis of 23 patients with degenerative cerebellar damage revealed clear impairments in predictive feedforward mechanisms in the control of both self-generated load types. Besides feedforward control, the cerebellar damage also affected more reactive responses when the externally generated load destabilized the grip, although this impairment may vary with the type of load as suggested by control experiments. The present findings provide further support that the cerebellum plays a major role in predictive control mechanisms. However, this impact of the cerebellum does not strongly depend on the nature of the load and the specific internal forward model. Contributions to reactive (grip force) control are not negligible, but seem to be dependent on the physical characteristics of an externally generated load.

Generic aerocapture atmospheric entry study, volume 1

NASA Technical Reports Server (NTRS)

1980-01-01

An atmospheric entry study to fine a generic aerocapture vehicle capable of missions to Mars, Saturn, and Uranus is reported. A single external geometry was developed through atmospheric entry simulations. Aerocapture is a system design concept which uses an aerodynamically controlled atmospheric entry to provide the necessary velocity depletion to capture payloads into planetary orbit. Design concepts are presented which provide the control accuracy required while giving thermal protection for the mission payload. The system design concepts consist of the following elements: (1) an extendable biconic aerodynamic configuration with lift to drag ratio between 1.0 and 2.0; (2) roll control system concepts to control aerodynamic lift and disturbance torques; (3) aeroshell design concepts capable of meeting dynamic pressure loads during aerocapture; and (4) entry thermal protection system design concepts to meet thermodynamic loads during aerocapture.

Investigation of solid nitrogen for cryogenic thermal storage in superconducting cable terminations for enhanced resiliency

NASA Astrophysics Data System (ADS)

Suttell, N.; Zhang, Z.; Kweon, J.; Nes, T.; Kim, C. H.; Pamidi, S.; Ordonez, J. C.

2017-12-01

Low heat capacity of helium makes the helium gas cooled high temperature superconducting (HTS) power devices susceptible to large temperature rises during unexpected heat loads such as electrical faults or cryogenic system failures. Cryogenic thermal storage in the form of solid nitrogen designed in the terminations is explored as a means to increase the thermal stability and operational time of HTS power cables in the event of unexpected heat loads. An external tank containing activated charcoal is used as an adsorption buffer tank for nitrogen gas. The use of activated charcoal minimizes the volume of the buffer tank and prevents pressure rises during melting and boiling of the solid nitrogen. Calculations of the cryogenic thermal storage needed and a description of the experimental setup used to understand the design constraints are discussed.

Dynamic loads on twin jet exhaust nozzles due to shock noise

NASA Technical Reports Server (NTRS)

Norum, T. D.; Shearin, J. G.

1986-01-01

Acoustic near field data were collected with model single and twin jet nozzles to determine if closely spaced nozzles produce higher acoustic loading than do single nozzles. The tests were spurred by structural failure of the B-1 exhaust nozzle external flaps and similar damage on the F-15. The test was performed using two 5/8 in. ID pipes machined and placed side-by-side to mimic B-1 nozzles. A microphone mounted on the internozzle fairing measured acoustic levels near the nozzle exit plane. The nozzles oscillated significantly more than did a single nozzle over a wide range of nozzle pressure ratios. Acoustic levels in the dual jets exceeded single jet noise by as much as 20 dB, making acoustic resonance a definite candidate for structural damage in the twin jet configuration.

Load-dependent assembly of the bacterial flagellar motor.

PubMed

Tipping, Murray J; Delalez, Nicolas J; Lim, Ren; Berry, Richard M; Armitage, Judith P

2013-08-20

It is becoming clear that the bacterial flagellar motor output is important not only for bacterial locomotion but also for mediating the transition from liquid to surface living. The output of the flagellar motor changes with the mechanical load placed on it by the external environment: at a higher load, the motor runs more slowly and produces higher torque. Here we show that the number of torque-generating units bound to the flagellar motor also depends on the external mechanical load, with fewer stators at lower loads. Stalled motors contained at least as many stators as rotating motors at high load, indicating that rotation is unnecessary for stator binding. Mutant stators incapable of generating torque could not be detected around the motor. We speculate that a component of the bacterial flagellar motor senses external load and mediates the strength of stator binding to the rest of the motor. The transition between liquid living and surface living is important in the life cycles of many bacteria. In this paper, we describe how the flagellar motor, used by bacteria for locomotion through liquid media and across solid surfaces, is capable of adjusting the number of bound stator units to better suit the external load conditions. By stalling motors using external magnetic fields, we also show that rotation is not required for maintenance of stators around the motor; instead, torque production is the essential factor for motor stability. These new results, in addition to previous data, lead us to hypothesize that the motor stators function as mechanosensors as well as functioning as torque-generating units.

Fifteen-year study of environmental dredging effect on variation of nitrogen and phosphorus exchange across the sediment-water interface of an urban lake.

PubMed

Liu, Cheng; Zhong, Jicheng; Wang, Jianjun; Zhang, Lu; Fan, Chengxin

2016-12-01

Environmental dredging has been applied widely in Chinese lakes to reduce their internal nutrient loads. However, the efficacy of dredging to reduce internal loading of nitrogen (N) and phosphorus (P) and to improve water quality has been questioned by some researchers. In this study, the long-term (∼15 years) effects of dredging to reduce internal N and P loading in a closed, polluted urban lake were investigated. The results showed that the release of soluble reactive phosphorus (SRP) could be suppressed quickly after dredging, and that the dredging effect was sustained for about 18 months. A significant release of NH 4 + -N was discovered during the first 2-8 months after dredging, followed by maintenance of low-level release rates for about 21-32 months. The continuous inflowing of external pollution loading led to the increase in the release rates of SRP and NH 4 + -N. The external pollution loading was therefore reduced three years after dredging to strengthen the remediation effect. After that, high diffusive flux from the sediment was observed for both NH 4 + -N and SRP during summer seasons for about six years, followed by a decreasing trend. The NH 4 + -N concentration in the overlying water was reduced after the reduction of external loading, while a high concentration of SRP in the overlying water was still observed during summer seasons. In conclusion, the mid-term (<3 years) reduction of internal N and P loading could be achieved by dredging if the external pollution loading were not reduced. Achieving long-term control would require modification of external loading. Copyright © 2016 Elsevier Ltd. All rights reserved.

14 CFR 23.301 - Loads.

Code of Federal Regulations, 2010 CFR

2010-01-01

... load would significantly change the distribution of external or internal loads, this redistribution...) and ultimate loads (limit loads multiplied by prescribed factors of safety). Unless otherwise provided...

46 CFR 64.59 - Spring loaded pressure relief valve.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 2 2012-10-01 2012-10-01 false Spring loaded pressure relief valve. 64.59 Section 64.59... AND CARGO HANDLING SYSTEMS Pressure Relief Devices and Vacuum Relief Devices for MPTs § 64.59 Spring loaded pressure relief valve. A spring loaded pressure relief valve must— (a) Be set at a nominal...

46 CFR 64.59 - Spring loaded pressure relief valve.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 2 2014-10-01 2014-10-01 false Spring loaded pressure relief valve. 64.59 Section 64.59... AND CARGO HANDLING SYSTEMS Pressure Relief Devices and Vacuum Relief Devices for MPTs § 64.59 Spring loaded pressure relief valve. A spring loaded pressure relief valve must— (a) Be set at a nominal...

46 CFR 64.59 - Spring loaded pressure relief valve.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 2 2011-10-01 2011-10-01 false Spring loaded pressure relief valve. 64.59 Section 64.59... AND CARGO HANDLING SYSTEMS Pressure Relief Devices and Vacuum Relief Devices for MPTs § 64.59 Spring loaded pressure relief valve. A spring loaded pressure relief valve must— (a) Be set at a nominal...

46 CFR 64.59 - Spring loaded pressure relief valve.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 2 2013-10-01 2013-10-01 false Spring loaded pressure relief valve. 64.59 Section 64.59... AND CARGO HANDLING SYSTEMS Pressure Relief Devices and Vacuum Relief Devices for MPTs § 64.59 Spring loaded pressure relief valve. A spring loaded pressure relief valve must— (a) Be set at a nominal...

46 CFR 64.59 - Spring loaded pressure relief valve.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 2 2010-10-01 2010-10-01 false Spring loaded pressure relief valve. 64.59 Section 64.59... AND CARGO HANDLING SYSTEMS Pressure Relief Devices and Vacuum Relief Devices for MPTs § 64.59 Spring loaded pressure relief valve. A spring loaded pressure relief valve must— (a) Be set at a nominal...

21 CFR 868.5935 - External negative pressure ventilator.

Code of Federal Regulations, 2010 CFR

2010-04-01

... ventilator. (a) Identification. An external negative pressure ventilator (e.g., iron lung, cuirass) is a device chamber that is intended to support a patient's ventilation by alternately applying and releasing external negative pressure over the diaphragm and upper trunk of the patient. (b) Classification. Class II...

On the modeling and characterization of an interlocked flexible electronic skin

NASA Astrophysics Data System (ADS)

Khalili, Nazanin; Shen, Xuechen; Naguib, Hani E.

2017-04-01

Development of an electronic skin with ultra-high pressure sensitivity is now of critical importance due its broad range of applications including prosthetic skins and biomimetic robotics. Microstructured conductive composite elastomers can acquire mechanical and electrical properties analogous to those of natural skin. One of the most prominent features of human skin is its tactile sensing property which can be mimicked in an electronic skin. Herein, an electrically conductive composite comprising polydimethylsiloxane and conductive fillers is used as a flexible and stretchable piezoresistive sensor. The electrical conductivity is induced within the elastomer matrix via carbon nanotubes whereas the piezoresistivity is obtained by means of microstructuring the surface of the substrate. An interlocked array of pyramids in micro-scale allows the change in the contact resistance between two thin layers of the composite upon application of an external load. Deformation of the interlocked arrays endows the sensor with an ultra-high sensitivity to the external pressures within the range of human skin perception. Moreover, using finite element analysis, the change in the contact are between the two layers was captured for different geometries. The structure of the sensor can be optimized through an optimization model in order to acquire maximum sensitivity.

ARCADE-R2 experiment on board BEXUS 17 stratospheric balloon

NASA Astrophysics Data System (ADS)

Barbetta, Marco; Boesso, Alessandro; Branz, Francesco; Carron, Andrea; Olivieri, Lorenzo; Prendin, Jacopo; Rodeghiero, Gabriele; Sansone, Francesco; Savioli, Livia; Spinello, Fabio; Francesconi, Alessandro

2015-09-01

This paper provides an overview of the ARCADE-R2 experiment, a technology demonstrator that aimed to prove the feasibility of small-scale satellite and/or aircraft systems with automatic (a) attitude determination, (b) control and (c) docking capabilities. The experiment embodies a simplified scenario in which an unmanned vehicle mock-up performs rendezvous and docking operations with a fixed complementary unit. The experiment is composed by a supporting structure, which holds a small vehicle with one translational and one rotational degree of freedom, and its fixed target. The dual system features three main custom subsystems: a relative infrared navigation sensor, an attitude control system based on a reaction wheel and a small-scale docking mechanism. The experiment bus is equipped with pressure and temperature sensors, and wind probes to monitor the external environmental conditions. The experiment flew on board the BEXUS 17 stratospheric balloon on October 10, 2013, where several navigation-control-docking sequences were executed and data on the external pressure, temperature, wind speed and direction were collected, characterizing the atmospheric loads applied to the vehicle. This paper describes the critical components of ARCADE-R2 as well as the main results obtained from the balloon flight.

Relationships of cognitive load on eating and weight-related behaviors of young adults.

PubMed

Byrd-Bredbenner, Carol; Quick, Virginia; Koenings, Mallory; Martin-Biggers, Jennifer; Kattelmann, Kendra K

2016-04-01

Little is known about the relationship between weight-related behaviors and cognitive load (working memory available to complete mental activities like those required for planning meals, selecting foods, and other health-related decisions). Thus, the purpose of this study was to explore associations between cognitive load and eating behaviors, physical activity, body mass index (BMI), and waist circumference of college students. College students (n=1018) from 13 institutions completed an online survey assessing eating behaviors (e.g., routine and compensatory restraint, emotional eating, and fruit/vegetable intake), stress level, and physical activity level. BMI and waist circumference were measured by trained researchers. A cognitive load score was derived from stress level, time pressure/income needs, race and nationality. High cognitive load participants (n=425) were significantly (P<0.05) more likely to be female, older, and further along in school than those with low cognitive loads (n=593). Compared to low cognitive load participants, high cognitive load participants were significantly more likely to eat <5 cups of fruits/vegetables/day, have greater routine and compensatory restraint, and greater susceptibility to eating in response to external cues and emotional eating. Both males and females with high cognitive load scores had a non-significant trend toward higher BMIs, waist circumferences, and drinking more alcohol than low cognitive load counterparts. In conclusion, cognitive load may be an important contributor to health behaviors. Understanding how cognitive load may affect eating and other weight-related behaviors could potentially lead to improvements in the effectiveness of obesity prevention and intervention programs. Copyright © 2015 Elsevier Ltd. All rights reserved.

A Si/Glass Bulk-Micromachined Cryogenic Heat Exchanger for High Heat Loads: Fabrication, Test, and Application Results.

PubMed

Zhu, Weibin; White, Michael J; Nellis, Gregory F; Klein, Sanford A; Gianchandani, Yogesh B

2010-02-01

This paper reports on a micromachined Si/glass stack recuperative heat exchanger with in situ temperature sensors. Numerous high-conductivity silicon plates with integrated platinum resistance temperature detectors (Pt RTDs) are stacked, alternating with low-conductivity Pyrex spacers. The device has a 1 x 1-cm(2) footprint and a length of up to 3.5 cm. It is intended for use in Joule-Thomson (J-T) coolers and can sustain pressure exceeding 1 MPa. Tests at cold-end inlet temperatures of 237 K-252 K show that the heat exchanger effectiveness is 0.9 with 0.039-g/s helium mass flow rate. The integrated Pt RTDs present a linear response of 0.26%-0.30%/K over an operational range of 205 K-296 K but remain usable at lower temperatures. In self-cooling tests with ethane as the working fluid, a J-T system with the heat exchanger drops 76.1 K below the inlet temperature, achieving 218.7 K for a pressure of 835.8 kPa. The system reaches 200 K in transient state; further cooling is limited by impurities that freeze within the flow stream. In J-T self-cooling tests with an external heat load, the system reaches 239 K while providing 1 W of cooling. In all cases, there is an additional parasitic heat load estimated at 300-500 mW.

Load distribution of articular cartilage from MR-images by neural nets.

PubMed

Seidel, Peter; Hanke, Göran; Gründer, Wilfried

2005-01-01

Artificial neural nets were used to determine the Young's modulus and spatial load distribution in articular cartilage by means of T2-weighted MR imaging. MR images were obtained in vitro (ex vivo?) from the joints of sheep of different ages (3 months, 9 months, 15 months, 1.5 years, 5 years, 5.5 years) and pigs (4 and 6 months) with a Bruker AMX 300 (7 T) spectrometer equipped with a micro-imaging unit. The knee of a 29-year-old male volunteer was studied in vivo under mechanical load using a clinical Siemens Vision MRT (1.5 T). The load of the cartilage is understood as a non-linear image transformation of loaded versus unloaded images. The artificial neural net was used to recognize given reference pixels of the unloaded cartilage within the image of the loaded cartilage. The Young's modulus was calculated from the local strain and the external pressure using the Hooke's law. With this method, the average Young's modulus was obtained in relationship to the biological age of the cartilage. The investigated age interval showed a progressive increase of 0.5 +/- 0.3 MPa per year. These results are consistent with published results. As shown in this pilot study, the method of neural nets allows the visualization of the spatial load distribution within the articular cartilage.

Internal ecosystem feedbacks enhance nitrogen-fixing cyanobacteria blooms and complicate management in the Baltic Sea.

PubMed

Vahtera, Emil; Conley, Daniel J; Gustafsson, Bo G; Kuosa, Harri; Pitkänen, Heikki; Savchuk, Oleg P; Tamminen, Timo; Viitasalo, Markku; Voss, Maren; Wasmund, Norbert; Wulff, Fredrik

2007-04-01

Eutrophication of the Baltic Sea has potentially increased the frequency and magnitude of cyanobacteria blooms. Eutrophication leads to increased sedimentation of organic material, increasing the extent of anoxic bottoms and subsequently increasing the internal phosphorus loading. In addition, the hypoxic water volume displays a negative relationship with the total dissolved inorganic nitrogen pool, suggesting greater overall nitrogen removal with increased hypoxia. Enhanced internal loading of phosphorus and the removal of dissolved inorganic nitrogen leads to lower nitrogen to phosphorus ratios, which are one of the main factors promoting nitrogenfixing cyanobacteria blooms. Because cyanobacteria blooms in the open waters of the Baltic Sea seem to be strongly regulated by internal processes, the effects of external nutrient reductions are scale-dependent. During longer time scales, reductions in external phosphorus load may reduce cyanobacteria blooms; however, on shorter time scales the internal phosphorus loading can counteract external phosphorus reductions. The coupled processes inducing internal loading, nitrogen removal, and the prevalence of nitrogen-fixing cyanobacteria can qualitatively be described as a potentially self-sustaining "vicious circle." To effectively reduce cyanobacteria blooms and overall signs of eutrophication, reductions in both nitrogen and phosphorus external loads appear essential.

Slide Release Device. Shuttle Orbiter/External Tank Forward Attachment

NASA Technical Reports Server (NTRS)

1981-01-01

A prototype release mechanism is discussed which is interchangeable with the existing orbiter/external tank separation bolt and offers reduced weight, shock, and cost. The components are reuseable. The unit takes maximum advantage of the shank diameter and installs in the monoball just as does the shear bolt, by threading in the completely assembled condition. Actuation is different, in that instead of axially breaking the shank by very high pressure (on the order of 60,000 psi) using a very large force (over 235, 000 pounds), this mechanism releases the shank by cross-axis movement against a lubricated surface. Once free, the shank is driven out of the monoball by an axially precompressed spring. Final weight can be as low as 30 pounds, and the cartridge contains less than one gram of powder. The components show no significant wear after eleven actuations under load.

ROCOPT: A user friendly interactive code to optimize rocket structural components

NASA Technical Reports Server (NTRS)

Rule, William K.

1989-01-01

ROCOPT is a user-friendly, graphically-interfaced, microcomputer-based computer program (IBM compatible) that optimizes rocket components by minimizing the structural weight. The rocket components considered are ring stiffened truncated cones and cylinders. The applied loading is static, and can consist of any combination of internal or external pressure, axial force, bending moment, and torque. Stress margins are calculated by means of simple closed form strength of material type equations. Stability margins are determined by approximate, orthotropic-shell, closed-form equations. A modified form of Powell's method, in conjunction with a modified form of the external penalty method, is used to determine the minimum weight of the structure subject to stress and stability margin constraints, as well as user input constraints on the structural dimensions. The graphical interface guides the user through the required data prompts, explains program options and graphically displays results for easy interpretation.

Biomechanical Evaluation of Glenoid Reconstruction With an Implant-Free J-Bone Graft for Anterior Glenoid Bone Loss.

PubMed

Pauzenberger, Leo; Dyrna, Felix; Obopilwe, Elifho; Heuberer, Philipp R; Arciero, Robert A; Anderl, Werner; Mazzocca, Augustus D

2017-10-01

The anatomic restoration of glenoid morphology with an implant-free J-shaped iliac crest bone graft offers an alternative to currently widely used glenoid reconstruction techniques. No biomechanical data on the J-bone grafting technique are currently available. To evaluate (1) glenohumeral contact patterns, (2) graft fixation under cyclic loading, and (3) the initial stabilizing effect of anatomic glenoid reconstruction with the implant-free J-bone grafting technique. Controlled laboratory study. Eight fresh-frozen cadaveric shoulders and J-shaped iliac crest bone grafts were used for this study. J-bone grafts were harvested, prepared, and implanted according to a previously described, clinically used technique. Glenohumeral contact patterns were measured using dynamic pressure-sensitive sensors under a compressive load of 440 N with the humerus in (a) 30° of abduction, (b) 30° of abduction and 60° of external rotation, (c) 60° of abduction, and (d) 60° of abduction and 60° of external rotation. Using a custom shoulder-testing system allowing positioning with 6 degrees of freedom, a compressive load of 50 N was applied, and the peak force needed to translate the humeral head 10 mm anteriorly at a rate of 2.0 mm/s was recorded. All tests were performed (1) for the intact glenoid, (2) after the creation of a 30% anterior osseous glenoid defect parallel to the longitudinal axis of the glenoid, and (3) after anatomic glenoid reconstruction with an implant-free J-bone graft. Furthermore, after glenoid reconstruction, each specimen was translated anteriorly for 5 mm at a rate of 4.0 mm/s for a total of 3000 cycles while logging graft protrusion and mediolateral bending motions. Graft micromovements were recorded using 2 high-resolution, linear differential variable reluctance transducer strain gauges placed in line with the long leg of the graft and the mediolateral direction, respectively. The creation of a 30% glenoid defect significantly decreased glenohumeral contact areas ( P < .05) but significantly increased contact pressures at all abduction and rotation positions ( P < .05). Glenoid reconstruction restored the contact area and contact pressure back to levels of the native glenohumeral joint in all tested positions. The mean (±SD) force to translate the humeral head anteriorly for 10 mm (60° of abduction: 31.7 ± 12.6 N; 60° of abduction and 60° of external rotation: 28.6 ± 7.6 N) was significantly reduced after the creation of a 30% anterior bone glenoid defect (60° of abduction: 12.2 ± 6.8 N; 60° of abduction and 60° of external rotation: 11.4 ± 5.4 N; P < .001). After glenoid reconstruction with a J-bone graft, the mean peak translational force significantly increased (60° of abduction: 85.0 ± 8.2 N; 60° of abduction and 60° of external rotation: 73.6 ± 4.5 N; P < .001) compared with the defect state and baseline. The mean total graft protrusion under cyclical translation of the humeral head over 3000 cycles was 138.3 ± 169.8 µm, whereas the mean maximal mediolateral graft deflection was 320.1 ± 475.7 µm. Implant-free anatomic glenoid reconstruction with the J-bone grafting technique restored near-native glenohumeral contact areas and pressures, provided secure initial graft fixation, and demonstrated excellent osseous glenohumeral stability at time zero. The implant-free J-bone graft is a viable alternative to commonly used glenoid reconstruction techniques, providing excellent graft fixation and glenohumeral stability immediately postoperatively. The normalization of glenohumeral contact patterns after reconstruction could potentially avoid the progression of dislocation arthropathy.

Biomechanical evaluation of an innovative spring-loaded axillary crutch design.

PubMed

Zhang, Yanxin; Liu, Guangyu; Xie, Shengquan; Liger, Aurélien

2011-01-01

We evaluated an innovative spring-loaded crutch design by comparing its performance with standard crutches through a biomechanical approach. Gait analysis was conducted for 7 male subjects under two conditions: walking with standard crutches and with spring-loaded crutches. Three-dimensional kinematic data and ground reaction force were recorded. Spatiotemporal variables, external mechanical work, and elastic energy (for spring crutches) were calculated based on recorded data. The trajectories of vertical ground reaction forces with standard crutches had two main peaks before and after mid-stance, and those with optimized spring-loaded crutches had only one main peak. The magnitude of external mechanical work was significantly higher with spring-loaded crutches than with standard crutches for all subjects, and the transferred elastic energy made an important contribution to the total external work for spring-loaded crutches. No significant differences in the spatiotemporal parameters were observed. Optimized spring-loaded crutches can efficiently propel crutch walkers and could reduce the total energy expenditure in crutch walking. Further research using optimized spring-loaded crutches with respect to energy efficiency is recommended.

Effects of External Loads on Human Head Movement Control Systems

NASA Technical Reports Server (NTRS)

Nam, M. H.; Choi, O. M.

1984-01-01

The central and reflexive control strategies underlying movements were elucidated by studying the effects of external loads on human head movement control systems. Some experimental results are presented on dynamic changes weigh the addition of aviation helmet (SPH4) and lead weights (6 kg). Intended time-optimal movements, their dynamics and electromyographic activity of neck muscles in normal movements, and also in movements made with external weights applied to the head were measured. It was observed that, when the external loads were added, the subject went through complex adapting processes and the head movement trajectory and its derivatives reached steady conditions only after transient adapting period. The steady adapted state was reached after 15 to 20 seconds (i.e., 5 to 6 movements).

In vitro modeling of human tibial strains during exercise in micro-gravity

NASA Technical Reports Server (NTRS)

Peterman, M. M.; Hamel, A. J.; Cavanagh, P. R.; Piazza, S. J.; Sharkey, N. A.

2001-01-01

Prolonged exposure to micro-gravity causes substantial bone loss (Leblanc et al., Journal of Bone Mineral Research 11 (1996) S323) and treadmill exercise under gravity replacement loads (GRLs) has been advocated as a countermeasure. To date, the magnitudes of GRLs employed for locomotion in space have been substantially less than the loads imposed in the earthbound 1G environment, which may account for the poor performance of locomotion as an intervention. The success of future treadmill interventions will likely require GRLs of greater magnitude. It is widely held that mechanical tissue strain is an important intermediary signal in the transduction pathway linking the external loading environment to bone maintenance and functional adaptation; yet, to our knowledge, no data exist linking alterations in external skeletal loading to alterations in bone strain. In this preliminary study, we used unique cadaver simulations of micro-gravity locomotion to determine relationships between localized tibial bone strains and external loading as a means to better predict the efficacy of future exercise interventions proposed for bone maintenance on orbit. Bone strain magnitudes in the distal tibia were found to be linearly related to ground reaction force magnitude (R(2)>0.7). Strain distributions indicated that the primary mode of tibial loading was in bending, with little variation in the neutral axis over the stance phase of gait. The greatest strains, as well as the greatest strain sensitivity to altered external loading, occurred within the anterior crest and posterior aspect of the tibia, the sites furthest removed from the neutral axis of bending. We established a technique for estimating local strain magnitudes from external loads, and equations for predicting strain during simulated micro-gravity walking are presented.

Flight Testing and Real-Time System Identification Analysis of a UH-60A Black Hawk Helicopter with an Instrumented External Sling Load

NASA Technical Reports Server (NTRS)

McCoy, Allen H.

1998-01-01

Helicopter external air transportation plays an important role in today's world. For both military and civilian helicopters, external sling load operations offer an efficient and expedient method of handling heavy, oversized cargo. With the ability to reach areas otherwise inaccessible by ground transportation, helicopter external load operations are conducted in industries such as logging, construction, and fire fighting, as well as in support of military tactical transport missions. Historically, helicopter and load combinations have been qualified through flight testing, requiring considerable time and cost. With advancements in simulation and flight test techniques there is potential to substantially reduce costs and increase the safety of helicopter sling load certification. Validated simulation tools make possible accurate prediction of operational flight characteristics before initial flight tests. Real time analysis of test data improves the safety and efficiency of the testing programs. To advance these concepts, the U.S. Army and NASA, in cooperation with the Israeli Air Force and Technion, under a Memorandum of Agreement, seek to develop and validate a numerical model of the UH-60 with sling load and demonstrate a method of near real time flight test analysis. This thesis presents results from flight tests of a U.S. Army Black Hawk helicopter with various external loads. Tests were conducted as the U.S. first phase of this MOA task. The primary load was a container express box (CONEX) which contained a compact instrumentation package. The flights covered the airspeed range from hover to 70 knots. Primary maneuvers were pitch and roll frequency sweeps, steps, and doublets. Results of the test determined the effect of the suspended load on both the aircraft's handling qualities and its control system's stability margins. Included were calculations of the stability characteristics of the load's pendular motion. Utilizing CIFER(R) software, a method for near-real time system identification was also demonstrated during the flight test program.

14 CFR 23.365 - Pressurized cabin loads.

Code of Federal Regulations, 2011 CFR

2011-01-01

... landing. (d) The airplane structure must be strong enough to withstand the pressure differential loads... AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Structure Flight Loads § 23... structure must be strong enough to withstand the flight loads combined with pressure differential loads from...

Noninvasive 3D Visualization of Defects and Crack Propagation in Layered Foam Structures by Phase Contrast Microimaging

NASA Technical Reports Server (NTRS)

Hu, Z. W.; DeCarlo, F.

2006-01-01

Applications of polymeric foams in our modern society continue to grow because of their light weight, high strength, excellent thermal and mechanical insulation, and the ease of engineering. Among others, closed-cell foam has been structurally used for thermally insulating the shuttle external tank. However, internal defects of the foams were difficult to observe non-invasively due to limited sensitivity to the low-density structures possessed by traditional imaging tools such as computed X-ray tomography By combining phase contrast X-ray imaging with pressure loading, we succeeded in precisely mapping intact cellular structure and defects inside the bulk of layered foam and visualizing its subsequent response to the pressure in three-dimensional space. The work demonstrated a powerfir1 approach for yielding insight into underlying problems in lightweight cellular materials otherwise unobtainable.

Space shuttle solid rocket booster recovery system definition. Volume 3: SRB water impact loads computer program, user's manual

NASA Technical Reports Server (NTRS)

1973-01-01

This user's manual describes the FORTRAN IV computer program developed to compute the total vertical load, normal concentrated pressure loads, and the center of pressure of typical SRB water impact slapdown pressure distributions specified in the baseline configuration. The program prepares the concentrated pressure load information in punched card format suitable for input to the STAGS computer program. In addition, the program prepares for STAGS input the inertia reacting loads to the slapdown pressure distributions.

Facesheet Delamination of Composite Sandwich Materials at Cryogenic Temperatures

NASA Technical Reports Server (NTRS)

Gates, Thomas S.; Odegard, Gregory M.; Herring, Helen M.

2003-01-01

The next generation of space transportation vehicles will require advances in lightweight structural materials and related design concepts to meet the increased demands on performance. One potential source for significant structural weight reduction is the replacement of traditional metallic cryogenic fuel tanks with new designs for polymeric matrix composite tanks. These new tank designs may take the form of thin-walled sandwich constructed with lightweight core and composite facesheets. Life-time durability requirements imply the materials must safely carry pressure loads, external structural loads, resist leakage and operate over an extremely wide temperature range. Aside from catastrophic events like tank wall penetration, one of the most likely scenarios for failure of a tank wall of sandwich construction is the permeation of cryogenic fluid into the sandwich core and the subsequent delamination of the sandwich facesheet due to the build-up of excessive internal pressure. The research presented in this paper was undertaken to help understand this specific problem of core to facesheet delamination in cryogenic environments and relate this data to basic mechanical properties. The experimental results presented herein provide data on the strain energy release rate (toughness) of the interface between the facesheet and the core of a composite sandwich subjected to simulated internal pressure. A unique test apparatus and associated test methods are described and the results are presented to highlight the effects of cryogenic temperature on the measured material properties.

Accelerated crack growth, residual stress, and a cracked zinc coated pressure shell

NASA Technical Reports Server (NTRS)

Dittman, Daniel L.; Hampton, Roy W.; Nelson, Howard G.

1987-01-01

During a partial inspection of a 42 year old, operating, pressurized wind tunnel at NASA-Ames Research Center, a surface connected defect 114 in. long having an indicated depth of a 0.7 in. was detected. The pressure shell, constructed of a medium carbon steel, contains approximately 10 miles of welds and is cooled by flowing water over its zinc coated external surface. Metallurgical and fractographic analysis showed that the actual detect was 1.7 in. deep, and originated from an area of lack of weld penetration. Crack growth studies were performed on the shell material in the laboratory under various loading rates, hold times, and R-ratios with a simulated shell environment. The combination of zinc, water with electrolyte, and steel formed an electrolytic cell which resulted in an increase in cyclic crack growth rate by as much as 500 times over that observed in air. It was concluded that slow crack growth occurred in the pressure shell by a combination of stress corrosion cracking due to the welding residual stress and corrosion fatigue due to the cyclic operating stress.

Static and dynamic pressure prediction for prosthetic socket fitting assessment utilising an inverse problem approach.

PubMed

Sewell, Philip; Noroozi, Siamak; Vinney, John; Amali, Ramin; Andrews, Stephen

2012-01-01

It has been recognised in a review of the developments of lower-limb prosthetic socket fitting processes that the future demands new tools to aid in socket fitting. This paper presents the results of research to design and clinically test an artificial intelligence approach, specifically inverse problem analysis, for the determination of the pressures at the limb/prosthetic socket interface during stance and ambulation. Inverse problem analysis is based on accurately calculating the external loads or boundary conditions that can generate a known amount of strain, stresses or displacements at pre-determined locations on a structure. In this study a backpropagation artificial neural network (ANN) is designed and validated to predict the interfacial pressures at the residual limb/socket interface from strain data collected from the socket surface. The subject of this investigation was a 45-year-old male unilateral trans-tibial (below-knee) traumatic amputee who had been using a prosthesis for 22 years. When comparing the ANN predicted interfacial pressure on 16 patches within the socket with actual pressures applied to the socket there is shown to be 8.7% difference, validating the methodology. Investigation of varying axial load through the subject's prosthesis, alignment of the subject's prosthesis, and pressure at the limb/socket interface during walking demonstrates that the validated ANN is able to give an accurate full-field study of the static and dynamic interfacial pressure distribution. To conclude, a methodology has been developed that enables a prosthetist to quantitatively analyse the distribution of pressures within the prosthetic socket in a clinical environment. This will aid in facilitating the "right first time" approach to socket fitting which will benefit both the patient in terms of comfort and the prosthetist, by reducing the time and associated costs of providing a high level of socket fit. Copyright © 2011 Elsevier B.V. All rights reserved.

Computational techniques for design optimization of thermal protection systems for the space shuttle vehicle. Volume 1: Final report

NASA Technical Reports Server (NTRS)

1971-01-01

Computational techniques were developed and assimilated for the design optimization. The resulting computer program was then used to perform initial optimization and sensitivity studies on a typical thermal protection system (TPS) to demonstrate its application to the space shuttle TPS design. The program was developed in Fortran IV for the CDC 6400 but was subsequently converted to the Fortran V language to be used on the Univac 1108. The program allows for improvement and update of the performance prediction techniques. The program logic involves subroutines which handle the following basic functions: (1) a driver which calls for input, output, and communication between program and user and between the subroutines themselves; (2) thermodynamic analysis; (3) thermal stress analysis; (4) acoustic fatigue analysis; and (5) weights/cost analysis. In addition, a system total cost is predicted based on system weight and historical cost data of similar systems. Two basic types of input are provided, both of which are based on trajectory data. These are vehicle attitude (altitude, velocity, and angles of attack and sideslip), for external heat and pressure loads calculation, and heating rates and pressure loads as a function of time.

Euler Strut: A Mechanical Analogy for Dynamics in the Vicinity of a Critical Point

ERIC Educational Resources Information Center

Bobnar, Jaka; Susman, Katarina; Parsegian, V. Adrian; Rand, Peter R.; Cepic, Mojca; Podgornik, Rudolf

2011-01-01

An anchored elastic filament (Euler strut) under an external point load applied to its free end is a simple model for a second-order phase transition. In the static case, a load greater than the critical load causes a Euler buckling instability, leading to a change in the filament's shape. The analysis of filament dynamics with an external point…

How graphene slides: measurement and theory of strain-dependent frictional forces between graphene and SiO2.

PubMed

Kitt, Alexander L; Qi, Zenan; Rémi, Sebastian; Park, Harold S; Swan, Anna K; Goldberg, Bennett B

2013-06-12

Strain, bending rigidity, and adhesion are interwoven in determining how graphene responds when pulled across a substrate. Using Raman spectroscopy of circular, graphene-sealed microchambers under variable external pressure, we demonstrate that graphene is not firmly anchored to the substrate when pulled. Instead, as the suspended graphene is pushed into the chamber under pressure, the supported graphene outside the microchamber is stretched and slides, pulling in an annulus. Analyzing Raman G band line scans with a continuum model extended to include sliding, we extract the pressure dependent sliding friction between the SiO2 substrate and mono-, bi-, and trilayer graphene. The sliding friction for trilayer graphene is directly proportional to the applied load, but the friction for monolayer and bilayer graphene is inversely proportional to the strain in the graphene, which is in violation of Amontons' law. We attribute this behavior to the high surface conformation enabled by the low bending rigidity and strong adhesion of few layer graphene.

The Relationships Between Internal and External Measures of Training Load and Intensity in Team Sports: A Meta-Analysis.

PubMed

McLaren, Shaun J; Macpherson, Tom W; Coutts, Aaron J; Hurst, Christopher; Spears, Iain R; Weston, Matthew

2018-03-01

The associations between internal and external measures of training load and intensity are important in understanding the training process and the validity of specific internal measures. We aimed to provide meta-analytic estimates of the relationships, as determined by a correlation coefficient, between internal and external measures of load and intensity during team-sport training and competition. A further aim was to examine the moderating effects of training mode on these relationships. We searched six electronic databases (Scopus, Web of Science, PubMed, MEDLINE, SPORTDiscus, CINAHL) for original research articles published up to September 2017. A Boolean search phrase was created to include search terms relevant to team-sport athletes (population; 37 keywords), internal load (dependent variable; 35 keywords), and external load (independent variable; 81 keywords). Articles were considered for meta-analysis when a correlation coefficient describing the association between at least one internal and one external measure of session load or intensity, measured in the time or frequency domain, was obtained from team-sport athletes during normal training or match-play (i.e., unstructured observational study). The final data sample included 122 estimates from 13 independent studies describing 15 unique relationships between three internal and nine external measures of load and intensity. This sample included 295 athletes and 10,418 individual session observations. Internal measures were session ratings of perceived exertion (sRPE), sRPE training load (sRPE-TL), and heart-rate-derived training impulse (TRIMP). External measures were total distance (TD), the distance covered at high and very high speeds (HSRD ≥ 13.1-15.0 km h -1 and VHSRD ≥ 16.9-19.8 km h -1 , respectively), accelerometer load (AL), and the number of sustained impacts (Impacts > 2-5 G). Distinct training modes were identified as either mixed (reference condition), skills, metabolic, or neuromuscular. Separate random effects meta-analyses were conducted for each dataset (n = 15) to determine the pooled relationships between internal and external measures of load and intensity. The moderating effects of training mode were examined using random-effects meta-regression for datasets with at least ten estimates (n = 4). Magnitude-based inferences were used to interpret analyses outcomes. During all training modes combined, the external load relationships for sRPE-TL were possibly very large with TD [r = 0.79; 90% confidence interval (CI) 0.74 to 0.83], possibly large with AL (r = 0.63; 90% CI 0.54 to 0.70) and Impacts (r = 0.57; 90% CI 0.47 to 0.64), and likely moderate with HSRD (r = 0.47; 90% CI 0.32 to 0.59). The relationship between TRIMP and AL was possibly large (r = 0.54; 90% CI 0.40 to 0.66). All other relationships were unclear or not possible to infer (r range 0.17-0.74, n = 10 datasets). Between-estimate heterogeneity [standard deviations (SDs) representing unexplained variation; τ] in the pooled internal-external relationships were trivial to extremely large for sRPE (τ range = 0.00-0.47), small to large for sRPE-TL (τ range = 0.07-0.31), and trivial to moderate for TRIMP (τ range= 0.00-0.17). The internal-external load relationships during mixed training were possibly very large for sRPE-TL with TD (r = 0.82; 90% CI 0.75 to 0.87) and AL (r = 0.81; 90% CI 0.74 to 0.86), and TRIMP with AL (r = 0.72; 90% CI 0.55 to 0.84), and possibly large for sRPE-TL with HSRD (r = 0.65; 90% CI 0.44 to 0.80). A reduction in these correlation magnitudes was evident for all other training modes (range of the change in r when compared with mixed training - 0.08 to - 0.58), with these differences being unclear to possibly large. Training mode explained 24-100% of the between-estimate variance in the internal-external load relationships. Measures of internal load derived from perceived exertion and heart rate show consistently positive associations with running- and accelerometer-derived external loads and intensity during team-sport training and competition, but the magnitude and uncertainty of these relationships are measure and training mode dependent.

Helium process cycle

DOEpatents

Ganni, Venkatarao

2008-08-12

A unique process cycle and apparatus design separates the consumer (cryogenic) load return flow from most of the recycle return flow of a refrigerator and/or liquefier process cycle. The refrigerator and/or liquefier process recycle return flow is recompressed by a multi-stage compressor set and the consumer load return flow is recompressed by an independent consumer load compressor set that maintains a desirable constant suction pressure using a consumer load bypass control valve and the consumer load return pressure control valve that controls the consumer load compressor's suction pressure. The discharge pressure of this consumer load compressor is thereby allowed to float at the intermediate pressure in between the first and second stage recycle compressor sets. Utilizing the unique gas management valve regulation, the unique process cycle and apparatus design in which the consumer load return flow is separate from the recycle return flow, the pressure ratios of each recycle compressor stage and all main pressures associated with the recycle return flow are allowed to vary naturally, thus providing a naturally regulated and balanced floating pressure process cycle that maintains optimal efficiency at design and off-design process cycle capacity and conditions automatically.

Helium process cycle

DOEpatents

Ganni, Venkatarao

2007-10-09

A unique process cycle and apparatus design separates the consumer (cryogenic) load return flow from most of the recycle return flow of a refrigerator and/or liquefier process cycle. The refrigerator and/or liquefier process recycle return flow is recompressed by a multi-stage compressor set and the consumer load return flow is recompressed by an independent consumer load compressor set that maintains a desirable constant suction pressure using a consumer load bypass control valve and the consumer load return pressure control valve that controls the consumer load compressor's suction pressure. The discharge pressure of this consumer load compressor is thereby allowed to float at the intermediate pressure in between the first and second stage recycle compressor sets. Utilizing the unique gas management valve regulation, the unique process cycle and apparatus design in which the consumer load return flow is separate from the recycle return flow, the pressure ratios of each recycle compressor stage and all main pressures associated with the recycle return flow are allowed to vary naturally, thus providing a naturally regulated and balanced floating pressure process cycle that maintains optimal efficiency at design and off-design process cycle capacity and conditions automatically.

[Measurement of periapical pressure created by occlusal loading].

PubMed

Dobó, Nagy Csaba; Fejérdy, Pál; Angyal, János; Harasztosi, Lajos; Daróczi, Lajos; Beke, Dezsó; Wesselink, Paul R

2004-04-01

The aim of this study was to develop an in vitro model in which the pressure in the periapical tissues can be measured during loading. Extracted human maxillary central incisors were embedded into resin blocks that had physical characteristics similar to bone and periodontal ligament. Each tooth was loaded with 20, 40, 50, 60, 75, 85, 100, 200, 300 and 450 N vertical forces from the incisal edge of the crown; this procedure was carried out three consecutive times. A minute resistor embedded in the periapical space was used to detect apical pressure changes during occlusal loading. The ratio of apical pressure changes (delta P) to the loading force changes (delta F) was calculated. The periapical pressure detected was in direct proportion to the loading force. The mean value of delta P/delta F was 5.994 kPa/N (SD = 2.04). Direct proportionality was found between the coronal loading and the apical hydrostatic pressure. The (delta P)/(delta F) ratio determined in this study makes it easier to estimate the apical hydrostatic pressure values during occlusal loading of single rooted teeth. In this study the apical pressure generated under occlusal loading was of the same magnitude as that estimated with the finite element method.

Measurement of periapical pressure created by occlusal loading.

PubMed

Dobó-Nagy, C; Fejérdy, P; Angyal, J; Harasztosi, L; Daróczi, L; Beke, D; Wesselink, P R

2003-10-01

To develop an in vitro model in which the pressure in the periapical tissues can be measured during loading. Extracted human maxillary central incisors were embedded in resin blocks that had physical characteristics similar to those of bone and periodontal ligament. Each tooth was loaded with 20, 40, 50, 60, 75, 85, 100, 200, 300 and 450 N vertical forces from the incisal edge of the crown on three consecutive occasions. A minute resistor embedded in the periapical space was used to detect apical pressure changes during occlusal loading. The ratio of apical pressure changes (DeltaP) to the loading force changes (DeltaF) was calculated. The periapical pressure detected was in direct proportion to the loading force. The mean value of DeltaP/DeltaF was 5.994 kPa N-1 (SD = 2.04). Direct proportionality was found between the coronal loading and the apical hydrostatic pressure. The DeltaP/DeltaF ratio determined in this study makes it easier to estimate the apical hydrostatic pressure values during occlusal loading of single-rooted teeth. In this study, the apical pressure generated under occlusal loading was the same magnitude as that estimated with the finite element method.

Oscillating load-induced acoustic emission in laboratory experiment

USGS Publications Warehouse

Ponomarev, Alexander; Lockner, David A.; Stroganova, S.; Stanchits, S.; Smirnov, Vladmir

2010-01-01

Spatial and temporal patterns of acoustic emission (AE) were studied. A pre-fractured cylinder of granite was loaded in a triaxial machine at 160 MPa confining pressure until stick-slip events occurred. The experiments were conducted at a constant strain rate of 10−7 s−1 that was modulated by small-amplitude sinusoidal oscillations with periods of 175 and 570 seconds. Amplitude of the oscillations was a few percent of the total load and was intended to simulate periodic loading observed in nature (e.g., earth tides or other sources). An ultrasonic acquisition system with 13 piezosensors recorded acoustic emissions that were generated during deformation of the sample. We observed a correlation between AE response and sinusoidal loading. The effect was more pronounced for higher frequency of the modulating force. A time-space spectral analysis for a “point” process was used to investigate details of the periodic AE components. The main result of the study was the correlation of oscillations of acoustic activity synchronized with the applied oscillating load. The intensity of the correlated AE activity was most pronounced in the “aftershock” sequences that followed large-amplitude AE events. We suggest that this is due to the higher strain-sensitivity of the failure area when the sample is in a transient, unstable mode. We also found that the synchronization of AE activity with the oscillating external load nearly disappeared in the period immediately after the stick-slip events and gradually recovered with further loading.

External nutrient loading from land, sea and atmosphere to all 656 Swedish coastal water bodies.

PubMed

Bryhn, Andreas C; Dimberg, Peter H; Bergström, Lena; Fredriksson, Ronny E; Mattila, Johanna; Bergström, Ulf

2017-01-30

Identifying the main sources of nutrient loading is a key factor for efficient mitigation of eutrophication. This study has investigated the pathways of external nutrient loading to 656 coastal water bodies along the entire Swedish coastline. The studied water bodies have been delineated to meet requirements in the European Union's Water Framework Directive, and recent status assessments have shown that 57% of them fail to attain good or high ecological status with respect to nutrients. The analysis in the study was performed on data from mass-balance based nutrient budgets computed using the modelling framework Vattenwebb. The external nutrient contribution from the sea to the water bodies was highly variable, ranging from about 1% to nearly 100%, but the median contribution was >99% of the total external loading regarding both nitrogen and phosphorus. External loading from the atmosphere and local catchment area played a minor role in general. However, 45 coastal water bodies received >25% of the external nitrogen and phosphorus from their catchments. Loading from land typically peaked in April following ice-break and snow melting and was comparatively low during summer. The results indicate that for many eutrophicated Swedish coastal water bodies, nutrient abatement is likely to be optimally effective when potential measures in all of the catchment area of the concerned sea basin are considered. Local-scale mitigation in single water bodies will likely be locally effective only in the small proportion of areas where water and thereby also nutrient input from the catchment is high compared to the influx from the sea. Future studies should include nutrient reduction scenarios in order to refine these conclusions and to identify relevant spatial scales for coastal eutrophication mitigation measures from a water body perspective. Copyright © 2017 Elsevier Ltd. All rights reserved.

Merging Hyperspectural Imagery and Multi Scale Modeling for Laser Lethality

DTIC Science & Technology

2016-02-24

standing aluminum films, (2) the effect of the external gas pressure on the flow structures and the mechanisms of the alumina and oxygen transport to...expansion from Al target irradiated by a continuous wave laser into a supersonic external air flow is investigated in kinetic simulations performed for...a broad range of pressure in the external flow. The results of the simulations reveal a significant effect of the external gas pressure on the flow

On the Health Risk of the Lumbar Spine due to Whole-Body VIBRATION—THEORETICAL Approach, Experimental Data and Evaluation of Whole-Body Vibration

NASA Astrophysics Data System (ADS)

Seidel, H.; Blüthner, R.; Hinz, B.; Schust, M.

1998-08-01

The guidance on the effects of vibration on health in standards for whole-body vibration (WBV) does not provide quantitative relationships between WBV and health risk. The paper aims at the elucidation of exposure-response relationships. An analysis of published data on the static and dynamic strength of vertebrae and bone, loaded with various frequencies under different conditions, provided the basis for a theoretical approach to evaluate repetitive loads on the lumbar spine (“internal loads”). The approach enabled the calculation of “equivalent”—with respect to cumulative fatigue failure—combinations of amplitudes and numbers of internal cyclic stress. In order to discover the relation between external peak accelerations at the seat and internal peak loads, biodynamic data of experiments (36 subjects, three somatotypes, two different postures—relaxed and bent forward; random WBV,aw, r.m.s. 1·4 ms-2, containing high transients) were used as input to a biomechanical model. Internal pressure changes were calculated using individual areas of vertebral endplates. The assessment of WBV was based on the quantitative relations between peak accelerations at the seat and pressures predicted for the disk L5/S1. For identical exposures clearly higher rates of pressure rise in the bent forward compared to the relaxed posture were predicted. The risk assessment for internal forces considered the combined internal static and dynamic loads, in relation to the predicted individual strength, and Miner's hypothesis. For exposure durations between 1 min and 8 h, energy equivalent vibration magnitudes (formula B.1, ISO 2631-1, 1997) and equivalent vibration magnitudes according to formula B.2 (time dependence over-energetic) were compared with equivalent combinations of upward peak accelerations and exposure durations according to predicted cumulative fatigue failures of lumbar vertebrae. Formula B.1 seems to underestimate the health risk caused by high magnitudes, formula B.2 is recommended for the evaluation of such conditions.

Laboratory evaluation of compressor blades considered for use in CIP/CUP compressors. [GAT2, 214X, X224, and D-15Al alloys

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

Ritchie, K.L.

1976-04-30

Four die-casting alloys, the external-pressure-pin and conventional casting methods, an accelerated aging heat treatment, and an airfoil fillet modification were evaluated for 33F-S1 compressor blades considered for use in axial flow compressors installed during the Cascade Improvement and Uprating Programs at the three gaseous diffusion plants. Based on castability, resonant frequency, resistance to fatigue cracking, and shank breaking load, the ranking of the four alloys from highest to lowest is GAT2, 214X, X224, and D-15. The GAT2 alloy ranked highest in all categories except impact value; the impact values of both X224 and 214X alloys exceeded that of the GAT2more » alloy, thus indicating the latter is relatively more brittle. However, in view of its other excellent properties, including fatigue cracking resistance, GAT2 alloy is worthy of consideration for use in blades for CIP/CUP or Add-on Plant compressors, particularly if castability becomes a problem with the presently used 214X alloy. Use of the external-pressure-pin casting method is not recommended because the resulting casting difficulties cannot be justified by the small increases in shank breaking loads. The airfoil fillet modification, which is a change from the conventional circular fillet to an elliptical fillet, resulted in increases (1.5 to 4.0 percent) in the average resonant frequency and in resistance to fatigue cracking (15 to 100 percent). The results of giving the blades an accelerated aging heat treatment, designed to simulate in excess of 10,000 hours of cascade exposure, showed that overaging had no significant effect on average resonant frequency but that overaging improved blade quality by reducing residual casting stress. (auth)« less

3D multiphysics modeling of superconducting cavities with a massively parallel simulation suite

DOE PAGES

Kononenko, Oleksiy; Adolphsen, Chris; Li, Zenghai; ...

2017-10-10

Radiofrequency cavities based on superconducting technology are widely used in particle accelerators for various applications. The cavities usually have high quality factors and hence narrow bandwidths, so the field stability is sensitive to detuning from the Lorentz force and external loads, including vibrations and helium pressure variations. If not properly controlled, the detuning can result in a serious performance degradation of a superconducting accelerator, so an understanding of the underlying detuning mechanisms can be very helpful. Recent advances in the simulation suite ace3p have enabled realistic multiphysics characterization of such complex accelerator systems on supercomputers. In this paper, we presentmore » the new capabilities in ace3p for large-scale 3D multiphysics modeling of superconducting cavities, in particular, a parallel eigensolver for determining mechanical resonances, a parallel harmonic response solver to calculate the response of a cavity to external vibrations, and a numerical procedure to decompose mechanical loads, such as from the Lorentz force or piezoactuators, into the corresponding mechanical modes. These capabilities have been used to do an extensive rf-mechanical analysis of dressed TESLA-type superconducting cavities. Furthermore, the simulation results and their implications for the operational stability of the Linac Coherent Light Source-II are discussed.« less

3D multiphysics modeling of superconducting cavities with a massively parallel simulation suite

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

Kononenko, Oleksiy; Adolphsen, Chris; Li, Zenghai

Radiofrequency cavities based on superconducting technology are widely used in particle accelerators for various applications. The cavities usually have high quality factors and hence narrow bandwidths, so the field stability is sensitive to detuning from the Lorentz force and external loads, including vibrations and helium pressure variations. If not properly controlled, the detuning can result in a serious performance degradation of a superconducting accelerator, so an understanding of the underlying detuning mechanisms can be very helpful. Recent advances in the simulation suite ace3p have enabled realistic multiphysics characterization of such complex accelerator systems on supercomputers. In this paper, we presentmore » the new capabilities in ace3p for large-scale 3D multiphysics modeling of superconducting cavities, in particular, a parallel eigensolver for determining mechanical resonances, a parallel harmonic response solver to calculate the response of a cavity to external vibrations, and a numerical procedure to decompose mechanical loads, such as from the Lorentz force or piezoactuators, into the corresponding mechanical modes. These capabilities have been used to do an extensive rf-mechanical analysis of dressed TESLA-type superconducting cavities. Furthermore, the simulation results and their implications for the operational stability of the Linac Coherent Light Source-II are discussed.« less

14 CFR 25.301 - Loads.

Code of Federal Regulations, 2010 CFR

2010-01-01

... significantly change the distribution of external or internal loads, this redistribution must be taken into... loads multiplied by prescribed factors of safety). Unless otherwise provided, prescribed loads are limit...

Bubble fusion: Preliminary estimates

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

Krakowski, R.A.

1995-02-01

The collapse of a gas-filled bubble in disequilibrium (i.e., internal pressure {much_lt} external pressure) can occur with a significant focusing of energy onto the entrapped gas in the form of pressure-volume work and/or acoustical shocks; the resulting heating can be sufficient to cause ionization and the emission of atomic radiations. The suggestion that extreme conditions necessary for thermonuclear fusion to occur may be possible has been examined parametrically in terms of the ratio of initial bubble pressure relative to that required for equilibrium. In this sense, the disequilibrium bubble is viewed as a three-dimensional ``sling shot`` that is ``loaded`` tomore » an extent allowed by the maximum level of disequilibrium that can stably be achieved. Values of this disequilibrium ratio in the range 10{sup {minus}5}--10{sup {minus}6} are predicted by an idealized bubble-dynamics model as necessary to achieve conditions where nuclear fusion of deuterium-tritium might be observed. Harmonic and aharmonic pressurizations/decompressions are examined as means to achieve the required levels of disequilibrium required to create fusion conditions. A number of phenomena not included in the analysis reported herein could enhance or reduce the small levels of nuclear fusions predicted.« less

Biomechanics Analysis of Pressure Ulcer Using Damaged Interface Model between Bone and Muscle in the Human Buttock

NASA Astrophysics Data System (ADS)

Slamet, Samuel Susanto; Takano, Naoki; Tanabe, Yoshiyuki; Hatano, Asako; Nagasao, Tomohisa

This paper aims at building up a computational procedure to study the bio-mechanism of pressure ulcer using the finite element method. Pressure ulcer is a disease that occurs in the human body after 2 hours of continuous external force. In the very early stage of pressure ulcer, it is found that the tissues inside the body are damaged, even though skin surface looks normal. This study assumes that tension and/or shear strain will cause damage to loose fibril tissue between the bone and muscle and that propagation of damaged area will lead to fatal stage. Analysis was performed using the finite element method by modeling the damaged fibril tissue as a cutout. By varying the loading directions and watching both tensile and shear strains, the risk of fibril tissue damage and propagation of the damaged area is discussed, which may give new insight for the careful nursing for patients, particularly after surgical treatment. It was found that the pressure ulcer could reoccur for a surgical flap treatment. The bone cut and surgical flap surgery is not perfect to prevent the bone-muscle interfacial damage.

Calibration and Data Analysis of the MC-130 Air Balance

NASA Technical Reports Server (NTRS)

Booth, Dennis; Ulbrich, N.

2012-01-01

Design, calibration, calibration analysis, and intended use of the MC-130 air balance are discussed. The MC-130 balance is an 8.0 inch diameter force balance that has two separate internal air flow systems and one external bellows system. The manual calibration of the balance consisted of a total of 1854 data points with both unpressurized and pressurized air flowing through the balance. A subset of 1160 data points was chosen for the calibration data analysis. The regression analysis of the subset was performed using two fundamentally different analysis approaches. First, the data analysis was performed using a recently developed extension of the Iterative Method. This approach fits gage outputs as a function of both applied balance loads and bellows pressures while still allowing the application of the iteration scheme that is used with the Iterative Method. Then, for comparison, the axial force was also analyzed using the Non-Iterative Method. This alternate approach directly fits loads as a function of measured gage outputs and bellows pressures and does not require a load iteration. The regression models used by both the extended Iterative and Non-Iterative Method were constructed such that they met a set of widely accepted statistical quality requirements. These requirements lead to reliable regression models and prevent overfitting of data because they ensure that no hidden near-linear dependencies between regression model terms exist and that only statistically significant terms are included. Finally, a comparison of the axial force residuals was performed. Overall, axial force estimates obtained from both methods show excellent agreement as the differences of the standard deviation of the axial force residuals are on the order of 0.001 % of the axial force capacity.

The influence of operational and environmental loads on the process of assessing damages in beams

NASA Astrophysics Data System (ADS)

Furdui, H.; Muntean, F.; Minda, A. A.; Praisach, Z. I.; Gillich, N.

2015-07-01

Damage detection methods based on vibration analysis make use of the modal parameter changes. Natural frequencies are the features that can be acquired most simply and inexpensively. But this parameter is influenced by environmental conditions, e.g. temperature and operational loads as additional masses or axial loads induced by restraint displacements. The effect of these factors is not completely known, but in the numerous actual research it is considered that they affect negatively the damage assessment process. This is justified by the small frequency changes occurring due to damage, which can be masked by the frequency shifts due to external loads. The paper intends to clarify the effect of external loads on the natural frequencies of beams and truss elements, and to show in which manner the damage detection process is affected by these loads. The finite element analysis, performed on diverse structures for a large range of temperature values, has shown that the temperature itself has a very limited effect on the frequency changes. Thus, axial forces resulted due to obstructed displacements can influence more substantially the frequency changes. These facts are demonstrated by experimental and theoretical studies. Finally, we succeed to adapt a prior contrived relation providing the frequency changes due to damage in order to fit the case of known external loads. Whereas a new baseline for damage detection was found, considering the effect of temperature and external loads, this process can be performed without other complication.

Brachial blood flow under relative levels of blood flow restriction is decreased in a nonlinear fashion.

PubMed

Mouser, J Grant; Ade, Carl J; Black, Christopher D; Bemben, Debra A; Bemben, Michael G

2018-05-01

Blood flow restriction (BFR), the application of external pressure to occlude venous return and restrict arterial inflow, has been shown to increase muscular size and strength when combined with low-load resistance exercise. BFR in the research setting uses a wide range of pressures, applying a pressure based upon an individual's systolic pressure or a percentage of occlusion pressure; not a directly determined reduction in blood flow. The relationship between relative pressure and blood flow has not been established. To measure blood flow in the arm under relative levels of BFR. Forty-five people (18-40 years old) participated. Arterial occlusion pressure in the right arm was measured using a 5-cm pneumatic cuff. Blood flow in the brachial artery was measured at rest and at pressures between 10% and 90% of occlusion using ultrasound. Blood flow decreased in a nonlinear, stepped fashion. Blood flow decreased at 10% of occlusion and remained constant until decreasing again at 40%, where it remained until 90% of occlusion. The decrease in brachial blood flow is not proportional to the applied relative pressure. The prescription of blood flow restriction should take into account the stimulus provided at each relative level of blood flow. © 2017 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

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

PubMed

Liu, Yong; Lin, Zhongguo

2014-04-01

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

Hydrodynamic interactions induce movement against an external load in a ratchet dimer Brownian motor.

PubMed

Fornés, José A

2010-01-15

We use the Brownian dynamics with hydrodynamic interactions simulation in order to describe the movement of a elastically coupled dimer Brownian motor in a ratchet potential. The only external forces considered in our system were the load, the random thermal noise and an unbiased thermal fluctuation. For a given set of parameters we observe direct movement against the load force if hydrodynamic interactions were considered.

Micromechanics of Spray-On Foam Insulation

NASA Technical Reports Server (NTRS)

Bednarcyk, Brett A.; Aboudi, Jacob; Arnold, Steven M.; Sullivan, Roy M.

2007-01-01

Understanding the thermo-mechanical response of the Space Shuttle External Tank spray-on foam insulation (SOFI) material is critical, to NASA's Return to Flight effort. This closed-cell rigid polymeric foam is used to insulate the metallic Space Shuttle External Tank, which is at cryogenic temperatures immediately prior to and during lift off. The shedding of the SOFI during ascent led to the loss of the Columbia, and eliminating/minimizing foam lass from the tank has become a priority for NASA as it seeks to resume scheduled space shuttle missions. Determining the nature of the SOFI material behavior in response to both thermal and mechanical loading plays an important role as any structural modeling of the shedding phenomenon k predicated on knowledge of the constitutive behavior of the foam. In this paper, the SOFI material has been analyzed using the High-Fidelity Generalized Method of Cells (HFGMC) micromechanics model, which has recently been extended to admit a triply-periodic 3-D repeating unit cell (RUC). Additional theoretical extensions that mere made in order to enable modeling of the closed-cell-foam material include the ability to represent internal boundaries within the RUC (to simulated internal pores) and the ability to impose an internal pressure within the simulated pores. This latter extension is crucial as two sources contribute to significant internal pressure changes within the SOFI pores. First, gas trapped in the pores during the spray process will expand or contract due to temperature changes. Second, the pore pressure will increase due to outgassing of water and other species present in the foam skeleton polymer material. With HFGMC's new pore pressure modeling capabilities, a nonlinear pressure change within the simulated pore can be imposed that accounts for both of these sources, in addition to stmdar&-thermal and mechanical loading; The triply-periodic HFGMC micromechanics model described above was implemented within NASA GRC's MAC/GMC software package, giving the model access to a range of nonlinear constitutive models for the polymeric foam skeleton material. A repeating unit cell architecture was constructed that, while relatively simple, still accounts for the geometric anisotropy of the porous foam microstructure and its thin walls and thicker edges. With the lack of reliable polymeric foam skeleton materia1 properties, many simulations were executed aimed at backing out these material properties. Then, using these properties, predictions of the thermo-mechanical behavior of the foam, including calculated internal applied pressure profiles, were performed and compared with appropriate experimental data.

Effects of external mechanical loading on phase diagrams and dielectric properties in epitaxial ferroelectric thin films with anisotropic in-plane misfit strains

NASA Astrophysics Data System (ADS)

Qiu, J. H.; Jiang, Q.

2007-02-01

A phenomenological Landau-Devonshine theory is used to describe the effects of external mechanical loading on equilibrium polarization states and dielectric properties in epitaxial ferroelectric thin films grown on dissimilar orthorhombic substrates which induce anisotropic misfit strains in the film plane. The calculation focuses on single-domain perovskite BaTiO3 and PbTiO3 thin films on the assumption that um1=-um2. Compared with the phase diagrams without external loading, the characteristic features of "misfit strain-misfit strain" phase diagrams at room temperature are the presence of paraelectric phase and the strain-induced ferroelectric to paraelectric phase transition. Due to the external loading, the "misfit strain-stress" and "stress-temperature" phase diagrams also have drastic changes, especially for the vanishing of paraelectric phase in "misfit strain-stress" phase map and the appearance of possible ferroelectric phases. We also investigate the dielectric properties and the tunability of both BaTiO3 and PbTiO3 thin films. We find that the external stress dependence of phase diagrams and dielectric properties largely depends on strain anisotropy as well.

Phase sensitivity of fundamental mode to external atmospheric pressure for hollow-core photonic bandgap fiber

NASA Astrophysics Data System (ADS)

Xu, Xiaobin; Liu, Yangqian; Gao, Fuyu; Song, Ningfang

2018-07-01

Hollow-core photonic bandgap fibers (HC-PBFs) are suitable for spaceborne fiber optical gyroscopes owing to their excellent environmental adaptability. However, hundreds of small holes full of air at one atmosphere of pressure can make the HC-PBF sensitive to external atmospheric pressure. In this study, we investigated the phase sensitivity of the fundamental mode to external atmospheric pressure for the HC-PBF, and the experimental result indicates that the phase sensitivity is approximately 1.6 × 10-5 ppm/Pa, which is mostly contributed by the change in the pressure-induced length. Through the choice of coating, the phase sensitivity to external atmospheric pressure can be reduced by about a factor of five compared to current HC-PBFs, and the excellent temperature performance can be maintained at the same time.

From "Publish or Perish" to "Grant or Perish": Examining Grantsmanship in Communication and the Pressures on Communication Faculty to Procure External Funding for Research

ERIC Educational Resources Information Center

Musambira, George; Collins, Steven; Brown, Tim; Voss, Kimberly

2012-01-01

Although communication program faculty have traditionally not enjoyed large grants for research, administrators are pressuring them to garner external funding. This article examines the success rate of securing external funding that communication administrators reported for their units. Results show that while the pressure has increased on most…

Finite element analysis of electroactive polymer and magnetoactive elastomer based actuation for origami folding

NASA Astrophysics Data System (ADS)

Zhang, Wei; Ahmed, Saad; Masters, Sarah; Ounaies, Zoubeida; Frecker, Mary

2017-10-01

The incorporation of smart materials such as electroactive polymers and magnetoactive elastomers in origami structures can result in active folding using external electric and magnetic stimuli, showing promise in many origami-inspired engineering applications. In this study, 3D finite element analysis (FEA) models are developed using COMSOL Multiphysics software for three configurations that incorporate a combination of active and passive material layers, namely: (1) a single-notch unimorph folding configuration actuated using only external electric field, (2) a double-notch unimorph folding configuration actuated using only external electric field, and (3) a bifold configuration which is actuated using multi-field (electric and magnetic) stimuli. The objectives of the study are to verify the effectiveness of the FEA models to simulate folding behavior and to investigate the influence of geometric parameters on folding quality. Equivalent mechanical pressure and surface stress are used as external loads in the FEA to simulate electric and magnetic fields, respectively. Compared quantitatively with experimental data, FEA captured the folding performance of electric actuation well for notched configurations and magnetic actuation for a bifold structure, but underestimated electric actuation for the bifold structure. By investigating the impact of geometric parameters and locations to place smart materials, FEA can be used in design, avoiding trial-and-error iterations of experiments.

Pneumatic load compensating or controlling system

NASA Technical Reports Server (NTRS)

Rogers, J. R. (Inventor)

1975-01-01

A pneumatic load compensating or controlling system for restraining a load with a predetermined force or applying a predetermined force to the load is described; it includes a source of pressurized air, a one-way pneumatic actuator operatively connected to a load, and a fluid conduit fluidically connecting the actuator with the source of pressurized air. The actuator is of the piston and cylinder type, and the end of the fluid conduit is connected to the upper or lower portion of the cylinder whereby the actuator alternatively and selectively restrains the load with a predetermined force or apply a predetermined force to the load. Pressure regulators are included within the system for variably selectively adjusting the pressurized fluid to predetermined values as desired or required; a pressure amplifier is included within the system for multiplying the pressurized values so as to achieve greater load forces. An accumulator is incorporated within the system as a failsafe operating mechanism, and visual and aural alarm devices, operatively associated with pressure detecting apparatus, readily indicate the proper or improper functioning of the system.

Variable stiffness corrugated composite structure with shape memory polymer for morphing skin applications

NASA Astrophysics Data System (ADS)

Gong, Xiaobo; Liu, Liwu; Scarpa, Fabrizio; Leng, Jinsong; Liu, Yanju

2017-03-01

This work presents a variable stiffness corrugated structure based on a shape memory polymer (SMP) composite with corrugated laminates as reinforcement that shows smooth aerodynamic surface, extreme mechanical anisotropy and variable stiffness for potential morphing skin applications. The smart composite corrugated structure shows a low in-plane stiffness to minimize the actuation energy, but also possess high out-of-plane stiffness to transfer the aerodynamic pressure load. The skin provides an external smooth aerodynamic surface because of the one-sided filling with the SMP. Due to variable stiffness of the shape memory polymer the morphing skin exhibits a variable stiffness with a change of temperature, which can help the skin adjust its stiffness according different service environments and also lock the temporary shape without external force. Analytical models related to the transverse and bending stiffness are derived and validated using finite element techniques. The stiffness of the morphing skin is further investigated by performing a parametric analysis against the geometry of the corrugation and various sets of SMP fillers. The theoretical and numerical models show a good agreement and demonstrate the potential of this morphing skin concept for morphing aircraft applications. We also perform a feasibility study of the use of this morphing skin in a variable camber morphing wing baseline. The results show that the morphing skin concept exhibits sufficient bending stiffness to withstand the aerodynamic load at low speed (less than 0.3 Ma), while demonstrating a large transverse stiffness variation (up to 191 times) that helps to create a maximum mechanical efficiency of the structure under varying external conditions.

Ontogenetic changes in the internal and external morphology of the ilium in modern humans

PubMed Central

Abel, Richard; Macho, Gabriele A

2011-01-01

Trabecular architecture forms an important structural component of bone and, depending on the loading conditions encountered during life, is organised in a systematic, bone- and species-specific manner. However, recent studies suggested that gross trabecular arrangement (e.g. density distribution), like overall bone shape, is predetermined and/or affected by factors other than loading and perhaps less plastic than commonly assumed. To explore this issue further, the present cross-sectional ontogenetic study investigated morphological changes in external bone shape in relation to changes in trabecular bundle orientation and anisotropy. Radiographs of 73 modern human ilia were assessed using radiographic and Geometric Morphometric techniques. The study confirmed the apparently strong predetermination of trabecular bundle development, i.e. prior to external loading, although loading clearly also had an effect on overall morphology. For example, the sacro-pubic bundle, which follows the path of load transmission from the auricular surface to the acetabulum, is well defined and shows relatively high levels of anisotropy from early stages of development; the situation for the ischio-iliac strut is similar. However, while the sacro-pubic strut retains a constant relationship with the external landmarks defining the joint surfaces, the ischio-iliac bundle changes its relationship with the external landmarks and becomes aligned with the iliac tubercle only during late adolescence/early adulthood. It is tentatively proposed that the rearrangement of the ischio-iliac strut may reflect a change in locomotor pattern and/or a shift in positional behavior with increasing mass after growth of external bone dimensions has slowed/ceased. PMID:21323915

Preparation for Testing a Multi-Bay Box Subjected to Combined Loads

NASA Technical Reports Server (NTRS)

Rouse, Marshall; Jegley, Dawn

2015-01-01

The COmbined Loads Test System (COLTS) facility at NASA Langley Research Center provides a test capability to help develop validated structures technologies. The test machine was design to accommodate a range of fuselage structures and wing sections and subject them to both quasistatic and cyclic loading conditions. The COLTS facility is capable of testing fuselage barrels up to 4.6 m in diameter and 13.7 m long with combined mechanical, internal pressure, and thermal loads. The COLTS facility is currently being prepared to conduct a combined mechanical and pressure loading for a multi-bay pressure box to experimentally verify the structural performance of a composite structure which is 9.1 meters long and representative of a section of a hybrid wing body fuselage section in support of the Environmentally Responsible Aviation Project at NASA. This paper describes development of the multi-bay pressure box test using the COLTS facility. The multi-bay test article will be subjected to mechanical loads and internal pressure loads up to design ultimate load. Mechanical and pressure loads will be applied independently in some tests and simultaneously in others.

Compliant Foil Journal Bearing Performance at Alternate Pressures and Temperatures

NASA Technical Reports Server (NTRS)

Bruckner, Robert J.; Puleo, Bernadette J.

2008-01-01

An experimental test program has been conducted to determine the highly loaded performance of current generation gas foil bearings at alternate pressures and temperatures. Typically foil bearing performance has been reported at temperatures relevant to turbomachinery applications but only at an ambient pressure of one atmosphere. This dearth of data at alternate pressures has motivated the current test program. Two facilities were used in the test program, the ambient pressure rig and the high pressure rig. The test program utilized a 35 mm diameter by 27 mm long foil journal bearing having an uncoated Inconel X-750 top foil running against a shaft with a PS304 coated journal. Load capacity tests were conducted at 3, 6, 9, 12, 15, 18, and 21 krpm at temperatures from 25 to 500 C and at pressures from 0.1 to 2.5 atmospheres. Results show an increase in load capacity with increased ambient pressure and a reduction in load capacity with increased ambient temperature. Below one-half atmosphere of ambient pressure a dramatic loss of load capacity is experienced. Additional lightly loaded foil bearing performance in nitrogen at 25 C and up to 48 atmospheres of ambient pressure has also been reported. In the lightly loaded region of operation the power loss increases for increasing pressure at a fixed load. Knowledge of foil bearing performance at operating conditions found within potential machine applications will reduce program development risk of future foil bearing supported turbomachines.

A physical interpretation of softening of pressure-sensitive and anisotropic materials

NASA Astrophysics Data System (ADS)

Hu, W.; Wang, Z. R.

2010-07-01

Several new dynamic models are proposed to explain the mechanical behaviour of softening of pressure-sensitive and anisotropic materials at a macroscopic level. If a pressure-sensitive material is loaded by a force and a variable pressure or an anisotropic material is subjected to a load with a changeable loading direction relative to the material frame, their stress-strain relationships become more complicated. Mechanical behaviours of these stress-strain relationships have to cover the feature concerning the change of pressure or loading direction, i.e. mechanical properties of pressure-sensitive material corresponding to different pressure state or anisotropic material relating to different loading direction will play an important role in deciding their stress-strain relationships. Such shift of material properties due to the variable pressure or loading history may significantly expand the traditional concept of the stability of material deformation, and the second order of plastic work being negative may be a response of stable plastic deformation, which is commonly called softening.

Preventing Seal Leak During Negative Pressure Wound Therapy Near External Fixators: A Technical Tip.

PubMed

Mannino, Brian J; Pullen, Michael W; Gaines, Robert

2017-03-01

Negative pressure wound therapy is an effective tool for the treatment of open wounds. Occasionally these wounds are associated with injuries or procedures that require treatment with an external fixator. This article shows how a simple, inexpensive, and commercially available product can be used to prevent loss of suction around external fixator pins within the negative pressure wound treatment area.

A Si/Glass Bulk-Micromachined Cryogenic Heat Exchanger for High Heat Loads: Fabrication, Test, and Application Results

PubMed Central

Zhu, Weibin; White, Michael J.; Nellis, Gregory F.; Klein, Sanford A.; Gianchandani, Yogesh B.

2010-01-01

This paper reports on a micromachined Si/glass stack recuperative heat exchanger with in situ temperature sensors. Numerous high-conductivity silicon plates with integrated platinum resistance temperature detectors (Pt RTDs) are stacked, alternating with low-conductivity Pyrex spacers. The device has a 1 × 1-cm2 footprint and a length of up to 3.5 cm. It is intended for use in Joule–Thomson (J–T) coolers and can sustain pressure exceeding 1 MPa. Tests at cold-end inlet temperatures of 237 K–252 K show that the heat exchanger effectiveness is 0.9 with 0.039-g/s helium mass flow rate. The integrated Pt RTDs present a linear response of 0.26%–0.30%/K over an operational range of 205 K–296 K but remain usable at lower temperatures. In self-cooling tests with ethane as the working fluid, a J–T system with the heat exchanger drops 76.1 K below the inlet temperature, achieving 218.7 K for a pressure of 835.8 kPa. The system reaches 200 K in transient state; further cooling is limited by impurities that freeze within the flow stream. In J–T self-cooling tests with an external heat load, the system reaches 239 K while providing 1 W of cooling. In all cases, there is an additional parasitic heat load estimated at 300–500 mW. PMID:20490284

Space Shuttle Projects

NASA Image and Video Library

1988-03-21

The Marshall Space Flight Center (MSFC) successfully test fired the third in a series of Transient Pressure Test Articles (TPTA) in its east test area. The test article was a short-stack solid rocket motor 52-feet long and 12-feet in diameter. The TPTA tests were designed to evaluate the effects of temperature, pressure and external loads encountered by the SRM, primarily during ignition transients. Instrumentation on the motor recorded approximately 1,000 charnels of data to verify the structural performance, thermal response, sealing capability of the redesign field, and case-to-nozzle joints. The TPTA test stand, 14-feet wide by 26-feet long by 33-feet high, was built in 1987. The TPTA series was a joint effort among Morton Thiokol, Inc., United Space Boosters, Inc., Wyle Laboratories, and MSFC. Wyle Laboratories conducted the tests for the MSFC, which manages the redesigned SRM program for NASA.

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

Lu, Dingjie; Xie, Yi Min; Huang, Xiaodong

Analytical studies on the size effects of a simply-shaped beam fixed at both ends have successfully explained the sudden changes of effective Young's modulus as its diameter decreases below 100 nm. Yet they are invalid for complex nanostructures ubiquitously existing in nature. In accordance with a generalized Young-Laplace equation, one of the representative size effects is transferred to non-uniformly distributed pressure against an external surface due to the imbalance of inward and outward loads. Because the magnitude of pressure depends on the principal curvatures, iterative steps have to be adopted to gradually stabilize the structure in finite element analysis. Computational resultsmore » are in good agreement with both experiment data and theoretical prediction. Furthermore, the investigation on strengthened and softened Young's modulus for two complex nanostructures demonstrates that the proposed computational method provides a general and effective approach to analyze the size effects for nanostructures in arbitrary shape.« less

Variable camber wing based on pneumatic artificial muscles

NASA Astrophysics Data System (ADS)

Yin, Weilong; Liu, Libo; Chen, Yijin; Leng, Jinsong

2009-07-01

As a novel bionic actuator, pneumatic artificial muscle has high power to weight ratio. In this paper, a variable camber wing with the pneumatic artificial muscle is developed. Firstly, the experimental setup to measure the static output force of pneumatic artificial muscle is designed. The relationship between the static output force and the air pressure is investigated. Experimental result shows the static output force of pneumatic artificial muscle decreases nonlinearly with increasing contraction ratio. Secondly, the finite element model of the variable camber wing is developed. Numerical results show that the tip displacement of the trailing-edge increases linearly with increasing external load and limited with the maximum static output force of pneumatic artificial muscles. Finally, the variable camber wing model is manufactured to validate the variable camber concept. Experimental result shows that the wing camber increases with increasing air pressure and that it compare very well with the FEM result.

20 plus Years of Computational Fluid Dynamics for the Space Shuttle

NASA Technical Reports Server (NTRS)

Gomez, Reynaldo J., III

2011-01-01

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

Load apparatus and method for bolt-loaded compact tension test specimen

DOEpatents

Buescher, B.J. Jr.; Lloyd, W.R.; Ward, M.B.; Epstein, J.S.

1997-02-04

A bolt-loaded compact tension test specimen load apparatus includes: (a) a body having first and second opposing longitudinal ends, the first end comprising an externally threaded portion sized to be threadedly received within the test specimen threaded opening; (b) a longitudinal loading rod having first and second opposing longitudinal ends, the loading rod being slidably received in a longitudinal direction within the body internally through the externally threaded portion and slidably extending longitudinally outward of the body first longitudinal end; (c) a force sensitive transducer slidably received within the body and positioned to engage relative to the loading rod second longitudinal end; and (d) a loading bolt threadedly received relative to the body, the loading bolt having a bearing end surface and being positioned to bear against the transducer to forcibly sandwich the transducer between the loading bolt and loading rod. Also disclosed is a method of in situ determining applied force during crack propagation in a bolt-loaded compact tension test specimen. 6 figs.

Load apparatus and method for bolt-loaded compact tension test specimen

DOEpatents

Buescher, Jr., Brent J.; Lloyd, W. Randolph; Ward, Michael B.; Epstein, Jonathan S.

1997-01-01

A bolt-loaded compact tension test specimen load apparatus includes: a) a body having first and second opposing longitudinal ends, the first end comprising an externally threaded portion sized to be threadedly received within the test specimen threaded opening; b) a longitudinal loading rod having first and second opposing longitudinal ends, the loading rod being slidably received in a longitudinal direction within the body internally through the externally threaded portion and slidably extending longitudinally outward of the body first longitudinal end; c) a force sensitive transducer slidably received within the body and positioned to engage relative to the loading rod second longitudinal end; and d) a loading bolt threadedly received relative to the body, the loading bolt having a bearing end surface and being positioned to bear against the transducer to forcibly sandwich the transducer between the loading bolt and loading rod. Also disclosed is a method of in situ determining applied force during crack propagation in a bolt-loaded compact tension test specimen.

Crystal Thermoelasticity at Extreme Loading Rates and Pressures: Analysis of Higher-Order Energy Potentials

DTIC Science & Technology

2015-07-01

ARL-RP-0526 ● JULY 2015 US Army Research Laboratory Crystal Thermoelasticity at Extreme Loading Rates and Pressures : Analysis of...ARL-RP-0526 ● JULY 2015 US Army Research Laboratory Crystal Thermoelasticity at Extreme Loading Rates and Pressures : Analysis of...2015 4. TITLE AND SUBTITLE Crystal Thermoelasticity at Extreme Loading Rates and Pressures : Analysis of Higher-Order Energy Potentials 5a. CONTRACT

Effects of static fingertip loading on carpal tunnel pressure

NASA Technical Reports Server (NTRS)

Rempel, D.; Keir, P. J.; Smutz, W. P.; Hargens, A.

1997-01-01

The purpose of this study was to explore the relationship between carpal tunnel pressure and fingertip force during a simple pressing task. Carpal tunnel pressure was measured in 15 healthy volunteers by means of a saline-filled catheter inserted percutaneously into the carpal tunnel of the nondominant hand. The subjects pressed on a load cell with the tip of the index finger and with 0, 6, 9, and 12 N of force. The task was repeated in 10 wrist postures: neutral; 10 and 20 degrees of ulnar deviation; 10 degrees of radial deviation; and 15, 30, and 45 degrees of both flexion and extension. Fingertip loading significantly increased carpal tunnel pressure for all wrist angles (p = 0.0001). Post hoc analyses identified significant increase (p < 0.05) in carpal tunnel pressure between unloaded (0 N) and all loaded conditions, as well as between the 6 and 12 N load conditions. This study demonstrates that the process whereby fingertip loading elevates carpal tunnel pressure is independent of wrist posture and that relatively small fingertip loads have a large effect on carpal tunnel pressure. It also reveals the response characteristics of carpal tunnel pressure to fingertip loading, which is one step in understanding the relationship between sustained grip and pinch activities and the aggravation or development of median neuropathy at the wrist.

Ground reaction forces and plantar pressure distribution during occasional loaded gait.

PubMed

Castro, Marcelo; Abreu, Sofia; Sousa, Helena; Machado, Leandro; Santos, Rubim; Vilas-Boas, João Paulo

2013-05-01

This study compared the ground reaction forces (GRF) and plantar pressures between unloaded and occasional loaded gait. The GRF and plantar pressures of 60 participants were recorded during unloaded gait and occasional loaded gait (wearing a backpack that raised their body mass index to 30); this load criterion was adopted because is considered potentially harmful in permanent loaded gait (obese people). The results indicate an overall increase (absolute values) of GRF and plantar pressures during occasional loaded gait (p < 0.05); also, higher normalized (by total weight) values in the medial midfoot and toes, and lower values in the lateral rearfoot region were observed. During loaded gait the magnitude of the vertical GRF (impact and thrust maximum) decreased and the shear forces increased more than did the proportion of the load (normalized values). These data suggest a different pattern of GRF and plantar pressure distribution during occasional loaded compared to unloaded gait. Copyright © 2012 Elsevier Ltd and The Ergonomics Society. All rights reserved.

Water Quality, Hydrology, and Simulated Response to Changes in Phosphorus Loading of Butternut Lake, Price and Ashland Counties, Wisconsin, with Special Emphasis on the Effects of Internal Phosphorus Loading in a Polymictic Lake

USGS Publications Warehouse

Robertson, Dale M.; Rose, William J.

2008-01-01

Butternut Lake is a 393-hectare, eutrophic to hypereutrophic lake in northcentral Wisconsin. After only minor improvements in water quality were observed following several actions taken to reduce the nutrient inputs to the lake, a detailed study was conducted from 2002 to 2007 by the U.S. Geological Survey to better understand how the lake functions. The goals of this study were to describe the water quality and hydrology of the lake, quantify external and internal sources of phosphorus, and determine the effects of past and future changes in phosphorus inputs on the water quality of the lake. Since the early 1970s, the water quality of Butternut Lake has changed little in response to nutrient reductions from the watershed. The largest changes were in near-surface total phosphorus concentrations: August concentrations decreased from about 0.09 milligrams per liter (mg/L) to about 0.05 mg/L, but average summer concentrations decreased only from about 0.055-0.060 mg/L to about 0.045 mg/L. Since the early 1970s, only small changes were observed in chlorophyll a concentrations and water clarity (Secchi depths). All major water and phosphorus sources, including the internal release of phosphorus from the sediments (internal loading), were measured directly, and minor sources were estimated to construct detailed water and phosphorus budgets for the lake during monitoring years (MY) 2003 and 2004. During these years, Butternut Creek, Spiller Creek, direct precipitation, small tributaries and near-lake drainage area, and ground water contributed about 62, 20, 8, 7, and 3 percent of the inflow, respectively. The average annual load of phosphorus to the lake was 2,540 kilograms (kg), of which 1,590 kg came from external sources (63 percent) and 945 kg came from the sediments in the lake (37 percent). Of the total external sources, Butternut Creek, Spiller Creek, small tributaries and near-lake drainage area, septic systems, precipitation, and ground water contributed about 63, 23, 9, 3, 1, and 1 percent, respectively. Because of the high internal phosphorus loading, the eutrophication models used in this study were unable to simulate the observed water-quality characteristics in the lake without incorporating this source of phosphorus. However, when internal loading of phosphorus was added to the BATHTUB model, it accurately simulated the average water-quality characteristics measured in MY 2003 and 2004. Model simulations demonstrated a relatively linear response between in-lake total phosphorus concentrations and external phosphorus loading; however, the changes in concentrations were smaller than the changes in external phosphorus loadings (about 25-40 percent of the change in phosphorus loading). Changes in chlorophyll a concentrations, the percentage of days with algal blooms, and Secchi depths were nonlinear and had a greater response to reductions in phosphorus loading than to increases in phosphorus loading. A 50-percent reduction in external phosphorus loading caused an 18-percent decrease in chlorophyll a concentrations, a 41-percent decrease in the percentage of days with algal blooms, and a 12-percent increase in Secchi depth. When the additional internal phosphorus loading was removed from model simulations, all of these constituents showed a much greater response to changes in external phosphorus loading. Because of Butternut Lake's morphometry, it is polymictic, which means it mixes frequently and does not develop stable thermal stratification throughout the summer. This characteristic makes it more vulnerable than dimictic lakes, which mix in spring and fall and develop stable thermal stratification during summer, to the high internal phosphorus loading that has resulted from historically high, nonnatural, external phosphorus loading. In polymictic lakes, the phosphorus released from the sediments is mixed into the upper part of the lake throughout summer. Once Butternut Lake became hypereutrophic (very p

Nonlinear vibration of a hemispherical dome under external water pressure

NASA Astrophysics Data System (ADS)

Ross, C. T. F.; McLennan, A.; Little, A. P. F.

2011-07-01

The aim of this study was to analyse the behaviour of a hemi-spherical dome when vibrated under external water pressure, using the commercial computer package ANSYS 11.0. In order to achieve this aim, the dome was modelled and vibrated in air and then in water, before finally being vibrated under external water pressure. The results collected during each of the analyses were compared to the previous studies, and this demonstrated that ANSYS was a suitable program and produced accurate results for this type of analysis, together with excellent graphical displays. The analysis under external water pressure, clearly demonstrated that as external water pressure was increased, the resonant frequencies decreased and a type of dynamic buckling became likely; because the static buckling eigenmode was similar to the vibration eigenmode. ANSYS compared favourably with the in-house software, but had the advantage that it produced graphical displays. This also led to the identification of previously undetected meridional modes of vibration; which were not detected with the in-house software.

46 CFR 64.5 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-10-01

..., excluding the allowance for corrosion and the thickness for loadings other than pressure, as provided for in the ASME Code. (e) Test pressure means a hydrostatic pressure of at least one and one-half times the maximum allowable working pressure. (f) Dynamic loading conditions means the following: (1) A loading in...

46 CFR 64.5 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-10-01

..., excluding the allowance for corrosion and the thickness for loadings other than pressure, as provided for in the ASME Code. (e) Test pressure means a hydrostatic pressure of at least one and one-half times the maximum allowable working pressure. (f) Dynamic loading conditions means the following: (1) A loading in...

46 CFR 64.5 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-10-01

..., excluding the allowance for corrosion and the thickness for loadings other than pressure, as provided for in the ASME Code. (e) Test pressure means a hydrostatic pressure of at least one and one-half times the maximum allowable working pressure. (f) Dynamic loading conditions means the following: (1) A loading in...

46 CFR 64.5 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-10-01

..., excluding the allowance for corrosion and the thickness for loadings other than pressure, as provided for in the ASME Code. (e) Test pressure means a hydrostatic pressure of at least one and one-half times the maximum allowable working pressure. (f) Dynamic loading conditions means the following: (1) A loading in...

Analysis and Design of the NASA Langley Cryogenic Pressure Box

NASA Technical Reports Server (NTRS)

Glass, David E.; Stevens, Jonathan C.; Vause, R. Frank; Winn, Peter M.; Maguire, James F.; Driscoll, Glenn C.; Blackburn, Charles L.; Mason, Brian H.

1999-01-01

A cryogenic pressure box was designed and fabricated for use at NASA Langley Research Center (LaRC) to subject 72 in. x 60 in. curved panels to cryogenic temperatures and biaxial tensile loads. The cryogenic pressure box is capable of testing curved panels down to -423 F (20K) with 54 psig maximum pressure on the concave side, and elevated temperatures and atmospheric pressure on the convex surface. The internal surface of the panel is cooled by high pressure helium as that is cooled to -423 F by liquid helium heat exchangers. An array of twelve independently controlled fans circulate the high pressure gaseous helium to provide uniform cooling on the panel surface. The load introduction structure, consisting of four stainless steel load plates and numerous fingers attaching the load plates to the test panel, is designed to introduce loads into the test panel that represent stresses that will he observed in the actual tank structure. The load plates are trace cooled with liquid nitrogen to reduce thermal gradients that may result in bending the load plates, and thus additional stresses in the test panel. The design of the cryogenic systems, load introduction structure, and control system are discussed in this report.

Counterrotating-Shoulder Mechanism for Friction Stir Welding

NASA Technical Reports Server (NTRS)

Nunes, Arthur C., Jr.

2007-01-01

A counterrotating-shoulder mechanism has been proposed as an alternative to the mechanism and fixtures used in conventional friction stir welding. The mechanism would internally react most or all of the forces and torques exerted on the workpiece, making it unnecessary to react the forces and torques through massive external fixtures. In conventional friction stir welding, a rotating pin tool is inserted into, and moved along, a weld seam. As the pin tool moves, it stirs together material from the opposite sides of the seam to form the weld. A large axial plunge force must be exerted upon the workpiece through and by the pin tool and a shoulder attached above the pin tool in order to maintain the pressure necessary for the process. The workpiece is secured on top of an anvil, which supports the workpiece against the axial plunge force and against the torque exerted by the pin tool and shoulder. The anvil and associated fixtures must be made heavy (and, therefore, are expensive) to keep the workpiece stationary. In addition, workpiece geometries must be limited to those that can be accommodated by the fixtures. The predecessor of the proposed counterrotating-shoulder mechanism is a second-generation, self-reacting tool, resembling a bobbin, that makes it possible to dispense with the heavy anvil. This tool consists essentially of a rotating pin tool with opposing shoulders. Although the opposing shoulders maintain the necessary pressure without need to externally apply or react a large plunge force, the torque exerted on the workpiece remains unreacted in the absence of a substantial external fixture. Depending on the RPM and the thickness of the workpiece, the torque can be large. The proposed mechanism (see figure) would include a spindle attached to a pin tool with a lower shoulder. The spindle would be coupled via splines to the upper one of three bevel gears in a differential drive. The middle bevel gear would be the power-input gear and would be coupled to the upper and lower bevel gears. The lower bevel gear would be attached to the upper shoulder and would slide and rotate freely over the spindle. The spindle would be fastened by its threaded upper end to an external submechanism that would exert axial tension on the spindle to load the workpiece in compression between the shoulders. By reducing or eliminating (relative to the use of a self reacting tool) the torque that must be reacted externally, the use of the proposed tool would reduce the tendency toward distortion or slippage of the workpiece. To begin a weld, the spindle would be inserted through a hole in the workpiece or run-on tab at the beginning of the seam and fastened to the loading submechanism. Rotation and axial loading would be increased gradually from zero and, after a time to be determined by trial and error, translation along the weld seam would be increased gradually from zero to a steady weld speed. The weld would be ended by running the mechanism off the workpiece or, if the lower shoulder were detachable, by detaching the lower shoulder from the spindle and pulling the pin tool out.

Characterization and measurement of hybrid gas journal bearings

NASA Astrophysics Data System (ADS)

Lawrence, Tom Marquis

This thesis concentrates on the study of hybrid gas journal bearings (bearings with externally pressurized mass addition). It differs from most work in that it goes back to "basics" to explore the hydrodynamic phenomena in the bearing gap. The thesis compares geometrically identical bearings with 2 configurations of external pressurization, porous liners where mass-addition compensation is varied by varying the liner's permeability, and bushings with 2 rows of 6 feedholes where the mass-addition compensation is varied by the feedhole diameter. Experimentally, prototype bearings with mass-addition compensation that spans 2 orders of magnitude with differing clearances are built and their aerostatic properties and mass addition characteristics are thoroughly tested. The fundamental equations for compressible, laminar, Poiseuille flow are used to suggest how the mass flow "compensation" should be mathematically modeled. This is back-checked against the experimental mass flow measurements and is used to determine a mass-addition compensation parameter (called Kmeas) for each prototype bushing. In so doing, the methodology of modeling and measuring the mass addition in a hybrid gas bearing is re-examined and an innovative, practical, and simple method is found that makes it possible to make an "apples-to-apples" comparison between different configurations of external pressurization. This mass addition model is used in conjunction with the Reynolds equation to perform theory-based numerical analysis of virtual hybrid gas journal bearings (CFD experiments). The first CFD experiments performed use virtual bearings modeled to be identical to the experimental prototypes and replicate the experimental work. The results are compared and the CFD model is validated. The ontological significance of appropriate dimensionless similitude parameters is re-examined and a, previously lacking, complete set of similitude factors is found for hybrid bearings. A new practical method is developed to study in unprecedented detail the aerostatic component of the hybrid bearings. It is used to definitively compare the feedhole bearings to the porous liner bearings. The hydrostatic bearing efficiency (HBE) is defined and it is determined that the maximum achievable hydrostatic bearing efficiency (MAHBE) is determined solely by the bearing's mass addition configuration. The MAHBE of the porous liner bearings is determined to be over 5 times that of the feedhole bearings. The method also presents a means to tune the Kmeas to the clearance to achieve the MAHBE as well as giving a complete mapping of the hitherto misunderstood complex shapes of aerostatic load versus radial deflection curves. This method also rediscovers the obscure phenomenon of static instability which is called in this thesis the "near surface effect" and appears to be the first work to present a practical method to predict the range of static instability and quantify its resultant stiffness fall-off. It determines that porous liner type bearings are not subject to the phenomenon which appears for feedhole type bearings when the clearance exceeds a critical value relative to its mass-addition compensation. The standing pressure waves of hydrostatic and hybrid bearings with the 2 configurations of external pressurization as well as a geometrically identical hydrodynamic bearing are studied in detail under the methodology of the "CFD microscope". This method is used to characterize and identify the development, growth, and movement of the pressure wave extrema with increased hydrodynamic action (either increasing speed or increasing eccentricity). This method is also used to determine the "cause" of the "near surface effect". A gedanken experiment is performed based on these results which indicates that a bearing with a "stronger aerostatic strength" component should be more stable than one with a low aerostatic strength component. Numerical instability "speed limits" are found that are also related to the hydrostatic strength of the bearing. The local conditions in the standing waves are characterized in terms of their local Mach number, Knudsen number, Reynolds number, and Taylor Number. It is concluded that low eccentricity bearing whirl can be attributed to the off load-line orientation of the bearing load force caused by the overlay of the hydrodynamic bearing standing wave onto the hydrostatic bearing wave of the hybrid bearing, whereas it is hypothesized that aperiodic and random self-excited vibration which occurs at high eccentricity, as reported in the literature, is probably due to shock waves, turbulence, near surface effect, and slip at local areas of the standing wave.

7 CFR 1710.206 - Approval requirements for load forecasts prepared pursuant to approved load forecast work plans.

Code of Federal Regulations, 2010 CFR

2010-01-01

... narrative shall address the overall approach, time periods, and expected internal and external uses of the forecast. Examples of internal uses include providing information for developing or monitoring demand side... suppliers. Examples of external uses include meeting state and Federal regulatory requirements, obtaining...

Gas-liquid two-phase flow behaviors and performance characteristics of proton exchange membrane fuel cells in a short-term microgravity environment

NASA Astrophysics Data System (ADS)

Guo, Hang; Liu, Xuan; Zhao, Jian Fu; Ye, Fang; Ma, Chong Fang

2017-06-01

In this work, proton exchange membrane fuel cells (PEMFCs) with transparent windows are designed to study the gas-liquid two-phase flow behaviors inside flow channels and the performance of a PEMFC with vertical channels and a PEMFC with horizontal channels in a normal gravity environment and a 3.6 s short-term microgravity environment. Experiments are conducted under high external circuit load and low external circuit load at low temperature where is 35 °C. The results of the present experimental work demonstrate that the performance and the gas-liquid two-phase flow behaviors of the PEMFC with vertical channels exhibits obvious changes when the PEMFCs enter the 3.6 s short-term microgravity environment from the normal gravity environment. Meanwhile, the performance of the PEMFC with vertical channels increases after the PEMFC enters the 3.6 s short-term microgravity environment under high external circuit load, while under low external circuit load, the PEMFC with horizontal channels exhibits better performance in both the normal gravity environment and the 3.6 s short-term microgravity environment.

Comparisons of wing pressure distribution from flight tests of flush and external orifices for Mach numbers from 0.50 to 0.97

NASA Technical Reports Server (NTRS)

Montoya, L. C.; Lux, D. P.

1975-01-01

Wing pressure distributions obtained in flight with flush orifice and external tubing orifice installations for Mach numbers from 0.50 to 0.97 are compared. The procedure used to install the external tubing orifice is discussed. The results indicate that external tubing orifice installations can give useful results.

Comparative effect of the sites of anterior cervical pressure on the geometry of the upper esophageal sphincter high-pressure zone.

PubMed

Mei, Ling; Jiao, Hongmei; Sharma, Tarun; Dua, Arshish; Sanvanson, Patrick; Jadcherla, Sudarshan R; Shaker, Reza

2017-11-01

External cricoid pressure is increasingly used to augment the upper esophageal sphincter (UES). Our objective was to determine the effect of 1) pressures applied to cricoid, supracricoid, and subcricoid regions on the length and amplitude of the UES high-pressure zone (UESHPZ), and 2) the external cricoid pressure on lower esophageal sphincter (LES) tone. Case-control study. We studied 11 patients with supraesophageal reflux (mean age 58 ± 12 years) and 10 healthy volunteers (mean age 47 ± 19 years). We tested 20, 30, and 40 mm Hg pressures to cricoid, 1 cm proximal and 1 cm distal to the cricoid. In an additional 15 healthy volunteers (mean age 46 ± 23 years), we studied the effect of external cricoid pressure on LES tone. UES and LES pressures were determined using high-resolution manometry. There was significant increase of UESHPZ length with application of pressure at all sites. The increase of UESHPZ length was relatively symmetric, more orad, and more caudad when the pressure was applied at the cricoid, supracricoid, and subcricoid levels, respectively. The magnitude of pressure increase was greatest at the middle and orad part of the UESHPZ when the pressure was applied at the cricoid and supracricoid levels, respectively. The corresponding magnitude of increase in the caudad part of the UESHPZ was not observed with pressure at the subcricoid level. There was no change of the LES pressure with application of cricoid pressure. The effect of external pressure on the UESHPZ is site dependent. Subcricoid pressure has the least effect on UESHPZ. External cricoid pressure at 20 to 40 mm Hg has no effect on the LES pressure. 3b. Laryngoscope, 127:2466-2474, 2017. © 2017 The American Laryngological, Rhinological and Otological Society, Inc.

Alternate Methods in Refining the SLS Nozzle Plug Loads

NASA Technical Reports Server (NTRS)

Burbank, Scott; Allen, Andrew

2013-01-01

Numerical analysis has shown that the SLS nozzle environmental barrier (nozzle plug) design is inadequate for the prelaunch condition, which consists of two dominant loads: 1) the main engines startup pressure and 2) an environmentally induced pressure. Efforts to reduce load conservatisms included a dynamic analysis which showed a 31% higher safety factor compared to the standard static analysis. The environmental load is typically approached with a deterministic method using the worst possible combinations of pressures and temperatures. An alternate probabilistic approach, utilizing the distributions of pressures and temperatures, resulted in a 54% reduction in the environmental pressure load. A Monte Carlo simulation of environmental load that used five years of historical pressure and temperature data supported the results of the probabilistic analysis, indicating the probabilistic load is reflective of a 3-sigma condition (1 in 370 probability). Utilizing the probabilistic load analysis eliminated excessive conservatisms and will prevent a future overdesign of the nozzle plug. Employing a similar probabilistic approach to other design and analysis activities can result in realistic yet adequately conservative solutions.

A human model of restricted upper esophageal sphincter opening and its pharyngeal and UES deglutitive pressure phenomena

PubMed Central

Jiao, Hongmei; Mei, Ling; Sharma, Tarun; Kern, Mark; Sanvanson, Patrick

2016-01-01

Oropharyngeal dysphagia due to upper esophageal sphincter (UES) dysfunction is commonly encountered in the clinical setting. Selective experimental perturbation of various components of the deglutitive apparatus can provide an opportunity to improve our understanding of the swallowing physiology and pathophysiology. The aim is to characterize the pharyngeal and UES deglutitive pressure phenomena in an experimentally induced restriction of UES opening in humans. We studied 14 volunteers without any dysphagic symptoms (7 men, 66 ± 11 yr) but with various supraesophageal reflux symptoms. To induce UES restriction, we used a handmade device that with adjustment could selectively apply 0, 20, 30, or 40 mmHg pressure perpendicularly to the cricoid cartilage. Deglutitive pharyngeal and UES pressure phenomena were determined during dry and 5- and 10-ml water swallows × 3 for each of the UES perturbations. External cricoid pressure against the UES resulted in a significant increase in hypopharyngeal intrabolus pressure and UES nadir deglutitive relaxation pressure for all tested swallowed volumes (P < 0.05). Application of external cricoid pressure increased the length of the UES high pressure zone from 2.5 ± 0.2 to 3.1 ± 0.2, 3.5 ± 0.1, and 3.7 ± 0.1 cm for 20, 30, and 40 mmHg cricoid pressure, respectively (P < 0.05). External cricoid pressure had no significant effect on pharyngeal peristalsis. On the other hand, irrespective of external cricoid pressure deglutitive velopharyngeal contractile integral progressively increased with increased swallowed volumes (P < 0.05). In conclusion, acute experimental restriction of UES opening by external cricoid pressure manifests the pressure characteristics of increased resistance to UES transsphincteric flow observed clinically without affecting the pharyngeal peristaltic contractile function. PMID:27198193

The effect of pressure and shear on tissue viability of human skin in relation to the development of pressure ulcers: a systematic review.

PubMed

Hoogendoorn, Iris; Reenalda, Jasper; Koopman, Bart F J M; Rietman, Johan S

2017-08-01

Pressure ulcers are a significant problem in health care, due to high costs and large impact on patients' life. In general, pressure ulcers develop as tissue viability decreases due to prolonged mechanical loading. The relation between load and tissue viability is highly influenced by individual characteristics. It is proposed that measurements of skin blood flow regulation could provide good assessment of the risk for pressure ulcer development, as skin blood flow is essential for tissue viability. . Therefore, the aim of this systematic review is to gain insight in the relation between mechanical load and the response of the skin and underlying tissue to this loading measured in-vivo with non-invasive techniques. A systematic literature search was performed to identify articles analysing the relation between mechanical load (pressure and/or shear) and tissue viability measured in-vivo. Two independent reviewers scored the methodological quality of the 22 included studies. Methodological information as well as tissue viability parameters during load application and after load removal were extracted from the included articles and used in a meta-analysis. Pressure results in a decrease in skin blood flow parameters, compared to baseline; showing a larger decrease with higher magnitudes of load. The steepness of the decrease is mostly dependent on the anatomical location. After load removal the magnitude of the post-reactive hyperaemic peak is related to the magnitude of pressure. Lastly, shear in addition to pressure, shows an additional negative effect, but the effect is less apparent than pressure on skin viability. Copyright © 2017 Tissue Viability Society. Published by Elsevier Ltd. All rights reserved.

Harnessing the wandering mind: the role of perceptual load.

PubMed

Forster, Sophie; Lavie, Nilli

2009-06-01

Perceptual load is a key determinant of distraction by task-irrelevant stimuli (e.g., Lavie, N. (2005). Distracted and confused?: Selective attention under load. Trends in Cognitive Sciences, 9, 75-82). Here we establish the role of perceptual load in determining an internal form of distraction by task-unrelated thoughts (TUTs or "mind-wandering"). Four experiments demonstrated reduced frequency of TUTs with high compared to low perceptual load in a visual-search task. Alternative accounts in terms of increased demands on responses, verbal working memory or motivation were ruled out and clear effects of load were found for unintentional TUTs. Individual differences in load effects on internal (TUTs) and external (response-competition) distractors were correlated. These results suggest that exhausting attentional capacity in task-relevant processing under high perceptual load can reduce processing of task-irrelevant information from external and internal sources alike.

Unusual properties of high-compliance porosity extracted from measurements of pressure-dependent wave velocities in rocks

NASA Astrophysics Data System (ADS)

Zaitsev, Vladimir Y.; Radostin, Andrey V.; Pasternak, Elena; Dyskin, Arcady

2016-04-01

Conventionally the interpretation of wave velocities and their variations under load is conducted assuming that closable cracks have simple planar shapes, like the popular model of penny-shape cracks. For such cracks, the proportion between complementary variations in different elastic parameters of rocks (such as S- and P-wave velocities) is strictly pre-determined, in particular, it is independent of the crack aspect ratio and rather weakly dependent on the Poisson's ratio of the intact rock. Real rocks, however, contain multitude of cracks of different geometry. Faces of such cracks can exhibit complex modes of interaction when closed by external load, which may result in very different ratios between normal- and shear compliances of such defects. In order to describe the reduction of different elastic moduli, we propose a model in which the compliances of crack-like defects are explicitly decoupled and are not predetermined, so that the ratio q between total normal- and shear- compliances imparted to the rock mass (as well as individual values of these compliances) can be estimated from experimental data on reduction of different elastic moduli (e.g., pressure dependences of P- and S-wave velocities). Physically, the so-extracted ratio q can be interpreted as intrinsic property of individual crack-like defects similar to each other, or as a characteristic of proportion between concentrations of pure normal cracks with very large q and pure shear cracks with q→0. The latter case can correspond, e.g., to saturated cracks in which weakly-compressible liquid prevents crack closing under normal loading. It can be shown that for conventional dry planar cracks, the compliance ratio is q ˜2. The developed model applied to the data on wave-velocity variations with external pressure indicates that elastic properties of the real crack-like defects in rocks can differ considerably from the usually assumed ones. Comparison with experimental data on variations P- and S-wave velocities with hydrostatic compression of different dry and saturated rocks (sandstones, Westerly granite and Webatuck dolomite, etc.) shows that our model is accurate in a wide range of pressures with constant (i.e., pressure-independent) values of parameter q. Furthermore, the determined values of the latter are considerably different from those of conventional cracks. In particular, although all saturated samples have values q <1, the simplified approximation q=0 (i.e., the absence of normal compressibility that is often assumed for wet cracks) leads to large errors in the prediction of complementary variations in the shear- and bulk elastic moduli. Among dry sandstones, the majority have q >2 and many sandstones exhibit unusually high q»1 suggesting quite rough and tortoise nature of real cracks in those rocks. We demonstrate that in such cases, the use of the conventional assumption q ˜2 typical of penny-shape cracks leads to striking inconsistency between the predicted and experimentally observed crack-induced complementary variations in different elastic moduli. Furthermore, among samples with q»1, we revealed numerous examples that demonstrate negative Poisson's ratio at low pressures. VYZ and AVR acknowledge the financial support by RFBR grant No 15-05-05143.

Acoustics Research of Propulsion Systems

NASA Technical Reports Server (NTRS)

Gao, Ximing; Houston, Janice

2014-01-01

The liftoff phase induces high acoustic loading over a broad frequency range for a launch vehicle. These external acoustic environments are used in the prediction of the internal vibration responses of the vehicle and components. Present liftoff vehicle acoustic environment prediction methods utilize stationary data from previously conducted hold-down tests to generate 1/3 octave band Sound Pressure Level (SPL) spectra. In an effort to update the accuracy and quality of liftoff acoustic loading predictions, non-stationary flight data from the Ares I-X were processed in PC-Signal in two flight phases: simulated hold-down and liftoff. In conjunction, the Prediction of Acoustic Vehicle Environments (PAVE) program was developed in MATLAB to allow for efficient predictions of sound pressure levels (SPLs) as a function of station number along the vehicle using semi-empirical methods. This consisted of generating the Dimensionless Spectrum Function (DSF) and Dimensionless Source Location (DSL) curves from the Ares I-X flight data. These are then used in the MATLAB program to generate the 1/3 octave band SPL spectra. Concluding results show major differences in SPLs between the hold-down test data and the processed Ares I-X flight data making the Ares I-X flight data more practical for future vehicle acoustic environment predictions.

Effect of abutment screw length and cyclic loading on removal torque in external and internal hex implants.

PubMed

Mohammed, Hnd Hadi; Lee, Jin-Han; Bae, Ji-Myung; Cho, Hye-Won

2016-02-01

The purpose of this study was to evaluate the effects of abutment screw length and cyclic loading on the removal torque (RTV) in external hex (EH) and internal hex (IH) implants. Forty screw-retained single crowns were connected to external and internal hex implants. The prepared titanium abutment screws were classified into 8 groups based on the number of threads (n = 5 per group): EH 12.5, 6.5, 3.5, 2.5 and IH 6.5, 5, 3.5, 2.5 threads. The abutment screws were tightened with 20 Ncm torque twice with 10-minute intervals. After 5 minutes, the initial RTVs of the abutment screws were measured with a digital torque gauge (MGT12). A customized jig was constructed to apply a load along the implant long axis at the central fossa of the maxillary first molar. The post-loading RTVs were measured after 16,000 cycles of mechanical loading with 50 N at a 1-Hz frequency. Statistical analysis included one-way analysis of variance and paired t-tests. The post-loading RTVs were significantly lower than the initial RTVs in the EH 2.5 thread and IH 2.5 thread groups (P<.05). The initial RTVs exhibited no significant differences among the 8 groups, whereas the post-loading RTVs of the EH 6.5 and EH 3.5 thread groups were higher than those of the IH 3.5 thread group (P<.05). Within the limitations of this study, the external hex implants with short screw lengths were more advantageous than internal hex implants with short screw lengths in torque maintenance after cyclic loading.

Effect of abutment screw length and cyclic loading on removal torque in external and internal hex implants

PubMed Central

Mohammed, Hnd Hadi; Lee, Jin-Han; Bae, Ji-Myung

2016-01-01

PURPOSE The purpose of this study was to evaluate the effects of abutment screw length and cyclic loading on the removal torque (RTV) in external hex (EH) and internal hex (IH) implants. MATERIALS AND METHODS Forty screw-retained single crowns were connected to external and internal hex implants. The prepared titanium abutment screws were classified into 8 groups based on the number of threads (n = 5 per group): EH 12.5, 6.5, 3.5, 2.5 and IH 6.5, 5, 3.5, 2.5 threads. The abutment screws were tightened with 20 Ncm torque twice with 10-minute intervals. After 5 minutes, the initial RTVs of the abutment screws were measured with a digital torque gauge (MGT12). A customized jig was constructed to apply a load along the implant long axis at the central fossa of the maxillary first molar. The post-loading RTVs were measured after 16,000 cycles of mechanical loading with 50 N at a 1-Hz frequency. Statistical analysis included one-way analysis of variance and paired t-tests. RESULTS The post-loading RTVs were significantly lower than the initial RTVs in the EH 2.5 thread and IH 2.5 thread groups (P<.05). The initial RTVs exhibited no significant differences among the 8 groups, whereas the post-loading RTVs of the EH 6.5 and EH 3.5 thread groups were higher than those of the IH 3.5 thread group (P<.05). CONCLUSION Within the limitations of this study, the external hex implants with short screw lengths were more advantageous than internal hex implants with short screw lengths in torque maintenance after cyclic loading. PMID:26949489

Thermodynamic aspects of an LNG tank in fire and experimental validation

NASA Astrophysics Data System (ADS)

Hulsbosch-Dam, Corina; Atli-Veltin, Bilim; Kamperveen, Jerry; Velthuis, Han; Reinders, Johan; Spruijt, Mark; Vredeveldt, Lex

Mechanical behaviour of a Liquefied Natural Gas (LNG) tank and the thermodynamic behaviour of its containment under extreme heat load - for instance when subjected to external fire source as might occur during an accident - are extremely important when addressing safety concerns. In a scenario where external fire is present and consequent release of LNG from pressure relief valves (PRV) has occurred, escalation of the fire might occur causing difficulty for the fire response teams to approach the tank or to secure the perimeter. If the duration of the tank exposure to fire is known, the PRV opening time can be estimated based on the thermodynamic calculations. In this paper, such an accidental scenario is considered, relevant thermodynamic equations are derived and presented. Moreover, an experiment is performed with liquid nitrogen and the results are compared to the analytical ones. The analytical results match very well with the experimental observations. The resulting analytical models are suitable to be applied to other cryogenic liquids.

Numerical Estimation of Sound Transmission Loss in Launch Vehicle Payload Fairing

NASA Astrophysics Data System (ADS)

Chandana, Pawan Kumar; Tiwari, Shashi Bhushan; Vukkadala, Kishore Nath

2017-08-01

Coupled acoustic-structural analysis of a typical launch vehicle composite payload faring is carried out, and results are validated with experimental data. Depending on the frequency range of interest, prediction of vibro-acoustic behavior of a structure is usually done using the finite element method, boundary element method or through statistical energy analysis. The present study focuses on low frequency dynamic behavior of a composite payload fairing structure using both coupled and uncoupled vibro-acoustic finite element models up to 710 Hz. A vibro-acoustic model, characterizing the interaction between the fairing structure, air cavity, and satellite, is developed. The external sound pressure levels specified for the payload fairing's acoustic test are considered as external loads for the analysis. Analysis methodology is validated by comparing the interior noise levels with those obtained from full scale Acoustic tests conducted in a reverberation chamber. The present approach has application in the design and optimization of acoustic control mechanisms at lower frequencies.

Phase Synchronization and Desynchronization of Structural Response Induced by Turbulent and External Sound

NASA Technical Reports Server (NTRS)

Maestrello, Lucio

2002-01-01

Acoustic and turbulent boundary layer flow loadings over a flexible structure are used to study the spatial-temporal dynamics of the response of the structure. The stability of the spatial synchronization and desynchronization by an active external force is investigated with an array of coupled transducers on the structure. In the synchronous state, the structural phase is locked, which leads to the formation of spatial patterns while the amplitude peaks exhibit chaotic behaviors. Large amplitude, spatially symmetric loading is superimposed on broadband, but in the desynchronized state, the spectrum broadens and the phase space is lost. The resulting pattern bears a striking resemblance to phase turbulence. The transition is achieved by using a low power external actuator to trigger broadband behaviors from the knowledge of the external acoustic load inducing synchronization. The changes are made favorably and efficiently to alter the frequency distribution of power, not the total power level. Before synchronization effects are seen, the panel response to the turbulent boundary layer loading is discontinuously spatio-temporally correlated. The stability develops from different competing wavelengths; the spatial scale is significantly shorter than when forced with the superimposed external sound. When the external sound level decreases and the synchronized phases are lost, changes in the character of the spectra can be linked to the occurrence of spatial phase transition. These changes can develop broadband response. Synchronized responses of fuselage structure panels have been observed in subsonic and supersonic aircraft; results from two flights tests are discussed.

Measurement of Intrasound from the Marine Environment

DTIC Science & Technology

2015-09-01

external inertial measurement unit (IMU) was used to estimate the heave, and was highly correlated with the pressure interference signal...moves up and down. An external inertial measurement unit (IMU) was used to estimate the heave, and was highly correlated with the pressure...10 EXTERNAL INTEGRATED MEASUREMENT UNIT ..................................................... 13 ADAPTIVE NOISE CANCELATION

Aerodynamic Improvements of an Empty Timber Truck can Have the Potential of Significantly Reducing Fuel Consumption

NASA Astrophysics Data System (ADS)

Andersson, Magnus; Marashi, Seyedeh Sepideh; Karlsson, Matts

2012-11-01

In the present study, aerodynamic drag (AD) has been estimated for an empty and a fully loaded conceptual timber truck (TT) using Computational Fluid Dynamics (CFD). The increasing fuel prices have challenged heavy duty vehicle (HDV) manufactures to strive for better fuel economy, by e.g. utilizing drag reducing external devices. Despite this knowledge, the TT fleets seem to be left in the dark. Like HDV aerodynamics, similarities can be observed as a large low pressure wake is formed behind the tractor (unloaded) and downstream of the trailer (full load) thus generating AD. As TTs travel half the time without any cargo, focus on drag reduction is important. The full scaled TTs where simulated using the realizable k-epsilon model with grid adaption techniques for mesh independence. Our results indicate that a loaded TT reduces the AD significantly as both wake size and turbulence kinetic energy are lowered. In contrast to HDV the unloaded TTs have a much larger design space available for possible drag reducing devices, e.g. plastic wrapping and/or flaps. This conceptual CFD study has given an indication of the large AD difference between the unloaded and fully loaded TT, showing the potential for significant AD improvements.

Advanced Metallic Thermal Protection System Development

NASA Technical Reports Server (NTRS)

Blosser, M. L.; Chen, R. R.; Schmidt, I. H.; Dorsey, J. T.; Poteet, C. C.; Bird, R. K.

2002-01-01

A new Adaptable, Robust, Metallic, Operable, Reusable (ARMOR) thermal protection system (TPS) concept has been designed, analyzed, and fabricated. In addition to the inherent tailorable robustness of metallic TPS, ARMOR TPS offers improved features based on lessons learned from previous metallic TPS development efforts. A specific location on a single-stage-to-orbit reusable launch vehicle was selected to develop loads and requirements needed to design prototype ARMOR TPS panels. The design loads include ascent and entry heating rate histories, pressures, acoustics, and accelerations. Additional TPS design issues were identified and discussed. An iterative sizing procedure was used to size the ARMOR TPS panels for thermal and structural loads as part of an integrated TPS/cryogenic tank structural wall. The TPS panels were sized to maintain acceptable temperatures on the underlying structure and to operate under the design structural loading. Detailed creep analyses were also performed on critical components of the ARMOR TPS panels. A lightweight, thermally compliant TPS support system (TPSS) was designed to connect the TPS to the cryogenic tank structure. Four 18-inch-square ARMOR TPS panels were fabricated. Details of the fabrication process are presented. Details of the TPSS for connecting the ARMOR TPS panels to the externally stiffened cryogenic tank structure are also described. Test plans for the fabricated hardware are presented.

Loading direction regulates the affinity of ADP for kinesin.

PubMed

Uemura, Sotaro; Ishiwata, Shin'ichi

2003-04-01

Kinesin is an ATP-driven molecular motor that moves processively along a microtubule. Processivity has been explained as a mechanism that involves alternating single- and double-headed binding of kinesin to microtubules coupled to the ATPase cycle of the motor. The internal load imposed between the two bound heads has been proposed to be a key factor regulating the ATPase cycle in each head. Here we show that external load imposed along the direction of motility on a single kinesin molecule enhances the binding affinity of ADP for kinesin, whereas an external load imposed against the direction of motility decreases it. This coupling between loading direction and enzymatic activity is in accord with the idea that the internal load plays a key role in the unidirectional and cooperative movement of processive motors.

Relationships Between the External and Internal Training Load in Professional Soccer: What Can We Learn From Machine Learning?

PubMed

Jaspers, Arne; De Beéck, Tim Op; Brink, Michel S; Frencken, Wouter G P; Staes, Filip; Davis, Jesse J; Helsen, Werner F

2018-05-01

Machine learning may contribute to understanding the relationship between the external load and internal load in professional soccer. Therefore, the relationship between external load indicators (ELIs) and the rating of perceived exertion (RPE) was examined using machine learning techniques on a group and individual level. Training data were collected from 38 professional soccer players over 2 seasons. The external load was measured using global positioning system technology and accelerometry. The internal load was obtained using the RPE. Predictive models were constructed using 2 machine learning techniques, artificial neural networks and least absolute shrinkage and selection operator (LASSO) models, and 1 naive baseline method. The predictions were based on a large set of ELIs. Using each technique, 1 group model involving all players and 1 individual model for each player were constructed. These models' performance on predicting the reported RPE values for future training sessions was compared with the naive baseline's performance. Both the artificial neural network and LASSO models outperformed the baseline. In addition, the LASSO model made more accurate predictions for the RPE than did the artificial neural network model. Furthermore, decelerations were identified as important ELIs. Regardless of the applied machine learning technique, the group models resulted in equivalent or better predictions for the reported RPE values than the individual models. Machine learning techniques may have added value in predicting RPE for future sessions to optimize training design and evaluation. These techniques may also be used in conjunction with expert knowledge to select key ELIs for load monitoring.

Redifferentiation of dedifferentiated bovine articular chondrocytes enhanced by cyclic hydrostatic pressure under a gas-controlled system.

PubMed

Kawanishi, Makoto; Oura, Atsuhiro; Furukawa, Katsuko; Fukubayashi, Toru; Nakamura, Kozo; Tateishi, Tetsuya; Ushida, Takashi

2007-05-01

Hydrostatic pressure is one of the most frequently used mechanical stimuli in chondrocyte experiments. A variety of hydrostatic pressure loading devices have been used in cartilage cell experiments. However, no gas-controlled system with other than a low pressure load was used up to this time. Hence we used a polyolefin bag from which gas penetration was confirmed. Chondrocytes were extracted from bovine normal knee joint cartilage. After 3 passages, dedifferentiated chondrocytes were applied to form a pellet. These pellets were cultured in chemically defined serum-free medium with ITS+Premix for 3 days. Then 5 MPa of cyclic hydrostatic pressure was applied at 0.5 Hz for 4 h per day for 4 days. Semiquantitative reverse transcriptase-polymerase chain reaction showed a 5-fold increase in the levels of aggrecan mRNA due to cyclic hydrostatic pressure load (p<0.01). Type II collagen mRNA levels were also upregulated 4-fold by a cyclic hydrostatic pressure load (p<0.01). Type I collagen mRNA levels were similarly reduced in the cyclic hydrostatic pressure load group and in the control group. The partial oxygen pressure (PO2) and partial carbon dioxide pressure (PCO2) of the medium in the bag reached equilibrium in 24 h, and no significant change was observed for 3 days afterwards. PO2 and PCO2 were very well controlled. The loaded pellet showed better safranin O/fast green staining than did the control pellet. Metachromatic staining by Alcian blue staining was found to be stronger in the loaded than in the control pellets. The extracellular matrices excretion of loaded pellets was higher than that of control pellets. These results suggest that gas-controlled cyclic hydrostatic pressure enhanced the cartilaginous matrix formation of dedifferentiated cells differentiated in vitro.

External Pressure, Motivation, and Treatment Outcome among Pregnant Substance-Using Women

PubMed Central

Ondersma, Steven J.; Winhusen, Theresa; Lewis, Daniel F.

2009-01-01

The weight of evidence suggests that legal pressure to enter treatment facilitates retention. However, the extent to which such mandates (a) influence actual levels of substance use, or (b) also facilitate retention among pregnant women, is unclear. Associations between external pressure—defined as self-reported pressure to attend treatment under threat of incarceration, loss of child custody, and/or loss of subsidized housing—and the key outcomes of retention and substance use were therefore examined in a sample of 200 pregnant women receiving community-based substance abuse treatment. The role of external pressure was examined in a series of Cox and GEE regressions, which suggested that external pressure as measured at baseline was associated with decreased risk of dropout (Hazard Ratio = .47, p = .001) and fewer drug-positive urine tests throughout treatment and 12-week follow-up (OR = 0.48, p = .03). These differences did not appear to be the result of baseline differences between coerced and non-coerced participants in education, legal history, presence or absence of a substance use disorder, employment, or motivation. The present findings extend the larger literature on external pressure by demonstrating effects on drug use as well as on retention, and among pregnant women. PMID:19926408

Influence of parafunctional loading and prosthetic connection on stress distribution: a 3D finite element analysis.

PubMed

Torcato, Leonardo Bueno; Pellizzer, Eduardo Piza; Verri, Fellippo Ramos; Falcón-Antenucci, Rosse Mary; Santiago Júnior, Joel Ferreira; de Faria Almeida, Daniel Augusto

2015-11-01

Clinicians should consider parafunctional occlusal load when planning treatment. Prosthetic connections can reduce the stress distribution on an implant-supported prosthesis. The purpose of this 3-dimensional finite element study was to assess the influence of parafunctional loading and prosthetic connections on stress distribution. Computer-aided design software was used to construct 3 models. Each model was composed of a bone and an implant (external hexagon, internal hexagon, or Morse taper) with a crown. Finite element analysis software was used to generate the finite element mesh and establish the loading and boundary conditions. A normal force (200-N axial load and 100-N oblique load) and parafunctional force (1000-N axial and 500-N oblique load) were applied. Results were visualized as the maximum principal stress. Three-way analysis of variance and Tukey test were performed, and the percentage of contribution of each variable to the stress concentration was calculated from sum-of squares-analysis. Stress was concentrated around the implant at the cortical bone, and models with the external hexagonal implant showed the highest stresses (P<.001). Oblique loads produced high tensile stress concentrations on the site opposite the load direction. Internal connection implants presented the most favorable biomechanical situation, whereas the least favorable situation was the biomechanical behavior of external connection implants. Parafunctional loading increased the magnitude of stress by 3 to 4 times. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Evaluation of muscle activity for loaded and unloaded dynamic squats during vertical whole-body vibration.

PubMed

Hazell, Tom J; Kenno, Kenji A; Jakobi, Jennifer M

2010-07-01

The purpose of this investigation was to examine if the addition of a light external load would enhance whole-body vibration (WBV)-induced increases in muscle activity during dynamic squatting in 4 leg muscles. Thirteen recreationally active male university students performed a series of dynamic squats (unloaded with no WBV, unloaded with WBV, loaded with no WBV, and loaded with WBV). The load was set to 30% of body mass and WBV included 25-, 35-, and 45-Hz frequencies with 4-mm amplitude. Muscle activity was recorded with surface electromyography (EMG) on the vastus lateralis (VL), biceps femoris (BF), tibialis anterior (TA), and gastrocnemius (GC) and is reported as EMGrms (root mean square) normalized to %maximal voluntary exertion. During unloaded dynamic squats, exposure to WBV (45 Hz) significantly (p < 0.05) increased baseline muscle activity in all muscles, except the TA compared with no WBV. Adding a light external load without WBV increased baseline muscle activity of the squat exercise in all muscles but decreased the TA. This loaded level of muscle activity was further increased with WBV (45 Hz) in all muscles. The WBV-induced increases in muscle activity in the loaded condition (approximately 3.5%) were of a similar magnitude to the WBV-induced increases during the unloaded condition (approximately 2.5%) demonstrating the addition of WBV to unloaded or loaded dynamic squatting results in an increase in muscle activity. These results demonstrate the potential effectiveness of using external loads with exposure to WBV.

Sterilization by Cooling in Isochoric Conditions: The Case of Escherichia coli

PubMed Central

Salinas-Almaguer, Samuel; Angulo-Sherman, Abril; Sierra-Valdez, Francisco Javier; Mercado-Uribe, Hilda

2015-01-01

High hydrostatic pressure (HHP) affects the structure, metabolism and survival of micro-organisms including bacteria. For this reason HHP is a promising treatment in the food industry. The aim of this work is to evaluate the effect of high pressure, under isochoric cooling conditions, on Escherichia coli, where such high pressure develops due to the fact water cannot expand. We combine survival curves obtained by spectrophotometry and images of atomic force microscopy in this study. Our results show that cooling at -20 and -30°C leads to a partial destruction of a Escherichia coli population. However, cooling at -15°C causes a total extermination of bacteria. This intriguing result is explained by the phase diagram of water. In the first case, the simultaneous formation of ice III and ice Ih crystals provides a safe environment for bacteria. In the second case (-15°C) Escherichia coli remains in a metastable and amorphous free-of-crystals liquid subjected to high pressure. Our work is the first experimental study carried out to inactivate Escherichia coli under isochoric cooling conditions. Unlike HHP, which is based on the application of an external load to augment the pressure, this technique only requires cooling. The method could be used for annihilation of other Escherichia coli strains and perhaps other micro-organisms. PMID:26480032

Calculated Condenser Performance for a Mercury-Turbine Power Plant for Aircraft

NASA Technical Reports Server (NTRS)

Doyle, Ronald B.

1948-01-01

As part of an investigation af the application of nuclear energy to various types of power plants for aircraft, calculations have been made to determine the effect of several operating conditions on the performance of condensers for mercury-turbine power plants. The analysis covered 8 range of turbine-outlet pressures from 1 to 200 pounds per square inch absolute, turbine-inlet pressures from 300 to 700 pounds per square inch absolute,and a range of condenser cooling-air pressure drops, airplane flight speeds, and altitudes. The maximum load-carrying capacity (available for the nuclear reactor, working fluid, and cargo) of a mercury-turbine powered aircraft would be about half the gross weight of the airplane at a flight speed of 509 miles per hour and an altitude of 30,000 feet. This maximum is obtained with specific condenser frontal areas of 0.0063 square foot per net thrust horsepower with the condenser in a nacelle and 0.0060 square foot per net thrust horsepower with the condenser submerged in the wings (no external condenser drag) for a turbine-inlet pressure of 500 pounds per square inch absolute, a turbine-outlet pressure of 10 pounds per square inch absolute, and 8 turbine-inlet temperature of 1600 F.

High-pressure high-temperature phase diagram of gadolinium studied using a boron-doped heater anvil

NASA Astrophysics Data System (ADS)

Montgomery, J. M.; Samudrala, G. K.; Velisavljevic, N.; Vohra, Y. K.

2016-04-01

A boron-doped designer heater anvil is used in conjunction with powder x-ray diffraction to collect structural information on a sample of quasi-hydrostatically loaded gadolinium metal up to pressures above 8 GPa and 600 K. The heater anvil consists of a natural diamond anvil that has been surface modified with a homoepitaxially grown chemical-vapor-deposited layer of conducting boron-doped diamond, and is used as a DC heating element. Internally insulating both diamond anvils with sapphire support seats allows for heating and cooling of the high-pressure area on the order of a few tens of seconds. This device is then used to scan the phase diagram of the sample by oscillating the temperature while continuously increasing the externally applied pressure and collecting in situ time-resolved powder diffraction images. In the pressure-temperature range covered in this experiment, the gadolinium sample is observed in its hcp, αSm, and dhcp phases. Under this temperature cycling, the hcp → αSm transition proceeds in discontinuous steps at points along the expected phase boundary. From these measurements (representing only one hour of synchrotron x-ray collection time), a single-experiment equation of state and phase diagram of each phase of gadolinium is presented for the range of 0-10 GPa and 300-650 K.

Feasibility study of an active soft catheter actuated by SMA wires

NASA Astrophysics Data System (ADS)

Konh, Bardia; Karimi, Saeed; Miller, Scott

2018-03-01

This study aims to assess the feasibility of using a combination of thin elastomer tubes and SMA wires to develop an active catheter. Cardiac catheters have been widely used in investigational and interventional procedures such as angiography, angioplasty, electro- physiology, and endocardial ablation. The commercial models manually steer inside the patient's body via internally installed pull wires. Active catheters, on the other hand, have the potential to revolutionize surgical procedures because of their computer-controlled and enhanced motion. Shape memory alloys have been used for almost a decade as a trustworthy actuator for biomedical applications. In this work, SMA wires were attached to a small pressurized elastomer tube to realize deflection. The tube was pressurized to maintain a constant stress on the SMA wires. The tip motion via actuation of SMA wires was then measured and reported. The results of this study showed that by adopting an appropriate training process for the SMA wires prior to performing the experiments and adopting an appropriate internal pressure for the elastomer tube, less external loads on SMA wires would be needed for a consistent actuation.

Stress-strain analysis of porous scaffolds made from titanium alloys synthesized via SLS method

NASA Astrophysics Data System (ADS)

Shishkovsky, I.

2009-09-01

A layer-by-layer selective laser sintering (SLS) technology seems to be greatly promising for solving the plastic surgery problems, particularly those pertaining to the facial reconstruction. Made from titanium-based alloys (titanium or nitinol, i.e. NiTi-intermetallic phase), the porous scaffolds for cranioplasty are an efficient tool for rectifying the face defects and for the dental orthopedic surgery. The progress in the oral surgery and teeth implantation is caused by the problem of an osteointegration on the one hand, and by achievements of the implant synthesis techniques, on the other hand. An important problem thereby is a profound study of the stress-strain behavior of porous implants under the masticatory load or pressure. In the present study the ways for the optimization of the porous implant structural and strength properties as the function of the laser synthesis parameters are described. The finite element approach (ANSYS) was used here for a complex dowel description and numerical simulations. In order to evaluate the processes in the porous implant under the external loading, a CAD 3D model was built for different internal and external configurations of the implant and/or initial shape of powdered particles. The stress-strain dependences were calculated that displayed the irregularity of the stress distribution by the implant volume in the bone tissue. Most of the values are concentrated in places of object contact.

Effects of mucosal loading on vocal fold vibration.

PubMed

Tao, Chao; Jiang, Jack J

2009-06-01

A chain model was proposed in this study to examine the effects of mucosal loading on vocal fold vibration. Mucosal loading was defined as the loading caused by the interaction between the vocal folds and the surrounding tissue. In the proposed model, the vocal folds and the surrounding tissue were represented by a series of oscillators connected by a coupling spring. The lumped masses, springs, and dampers of the oscillators modeled the tissue properties of mass, stiffness, and viscosity, respectively. The coupling spring exemplified the tissue interactions. By numerically solving this chain model, the effects of mucosal loading on the phonation threshold pressure, phonation instability pressure, and energy distribution in a voice production system were studied. It was found that when mucosal loading is small, phonation threshold pressure increases with the damping constant R(r), the mass constant R(m), and the coupling constant R(mu) of mucosal loading but decreases with the stiffness constant R(k). Phonation instability pressure is also related to mucosal loading. It was found that phonation instability pressure increases with the coupling constant R(mu) but decreases with the stiffness constant R(k) of mucosal loading. Therefore, it was concluded that mucosal loading directly affects voice production.

Effects of mucosal loading on vocal fold vibration

NASA Astrophysics Data System (ADS)

Tao, Chao; Jiang, Jack J.

2009-06-01

A chain model was proposed in this study to examine the effects of mucosal loading on vocal fold vibration. Mucosal loading was defined as the loading caused by the interaction between the vocal folds and the surrounding tissue. In the proposed model, the vocal folds and the surrounding tissue were represented by a series of oscillators connected by a coupling spring. The lumped masses, springs, and dampers of the oscillators modeled the tissue properties of mass, stiffness, and viscosity, respectively. The coupling spring exemplified the tissue interactions. By numerically solving this chain model, the effects of mucosal loading on the phonation threshold pressure, phonation instability pressure, and energy distribution in a voice production system were studied. It was found that when mucosal loading is small, phonation threshold pressure increases with the damping constant Rr, the mass constant Rm, and the coupling constant Rμ of mucosal loading but decreases with the stiffness constant Rk. Phonation instability pressure is also related to mucosal loading. It was found that phonation instability pressure increases with the coupling constant Rμ but decreases with the stiffness constant Rk of mucosal loading. Therefore, it was concluded that mucosal loading directly affects voice production.

Load identification approach based on basis pursuit denoising algorithm

NASA Astrophysics Data System (ADS)

Ginsberg, D.; Ruby, M.; Fritzen, C. P.

2015-07-01

The information of the external loads is of great interest in many fields of structural analysis, such as structural health monitoring (SHM) systems or assessment of damage after extreme events. However, in most cases it is not possible to measure the external forces directly, so they need to be reconstructed. Load reconstruction refers to the problem of estimating an input to a dynamic system when the system output and the impulse response functions are usually the knowns. Generally, this leads to a so called ill-posed inverse problem, which involves solving an underdetermined linear system of equations. For most practical applications it can be assumed that the applied loads are not arbitrarily distributed in time and space, at least some specific characteristics about the external excitation are known a priori. In this contribution this knowledge was used to develop a more suitable force reconstruction method, which allows identifying the time history and the force location simultaneously by employing significantly fewer sensors compared to other reconstruction approaches. The properties of the external force are used to transform the ill-posed problem into a sparse recovery task. The sparse solution is acquired by solving a minimization problem known as basis pursuit denoising (BPDN). The possibility of reconstructing loads based on noisy structural measurement signals will be demonstrated by considering two frequently occurring loading conditions: harmonic excitation and impact events, separately and combined. First a simulation study of a simple plate structure is carried out and thereafter an experimental investigation of a real beam is performed.

Modeling attitude towards drug treament: the role of internal motivation, external pressure, and dramatic relief.

PubMed

Conner, Bradley T; Longshore, Douglas; Anglin, M Douglas

2009-04-01

Motivation for change has historically been viewed as the crucial element affecting responsiveness to drug treatment. Various external pressures, such as legal coercion, may engender motivation in an individual previously resistant to change. Dramatic relief may be the change process that is most salient as individuals internalize such external pressures. Results of structural equation modeling on data from 465 drug users (58.9% male; 21.3% Black, 34.2% Hispanic/Latino, and 35.1% White) entering drug treatment indicated that internal motivation and external pressure significantly and positively predicted dramatic relief and that dramatic relief significantly predicted attitudes towards drug treatment: chi (2) = 142.20, df = 100, p < 0.01; Robust Comparative Fit Index = 0.97, Root Mean Squared Error of Approximation = 0.03. These results indicate that when external pressure and internal motivation are high, dramatic relief is also likely to be high. When dramatic relief is high, attitudes towards drug treatment are likely to be positive. The findings indicate that interventions to get individuals into drug treatment should include processes that promote Dramatic Relief. Implications for addictions health services are discussed.

Coupled loads analysis for Space Shuttle payloads

NASA Technical Reports Server (NTRS)

Eldridge, J.

1992-01-01

Described here is a method for determining the transient response of, and the resultant loads in, a system exposed to predicted external forces. In this case, the system consists of four racks mounted on the inside of a space station resource node module (SSRNMO) which is mounted in the payload bay of the space shuttle. The predicted external forces are forcing functions which envelope worst case forces applied to the shuttle during liftoff and landing. This analysis, called a coupled loads analysis, is used to couple the payload and shuttle models together, determine the transient response of the system, and then recover payload loads, payload accelerations, and payload to shuttle interface forces.

Experimental and numerical investigation on laser-assisted bending of pre-loaded metal plate

NASA Astrophysics Data System (ADS)

Nowak, Zdzisław; Nowak, Marcin; Widłaszewski, Jacek; Kurp, Piotr

2018-01-01

The laser forming technique has an important disadvantage, which is the limitation of plastic deformation generated by a single laser beam pass. To increase the plastic deformation it is possible to apply external forces in the laser forming process. In this paper, we investigate the influence of external pre-loads on the laser bending of steel plate. The pre-loads investigated generate bending towards the laser beam. The thermal, elastic-plastic analysis is performed using the commercial nonlinear finite element analysis package ABAQUS. The focus of the paper is to identify how this pattern of the pre-load influence the final bend angle of the plate.

Heat of adsorption, adsorption stress, and optimal storage of methane in slit and cylindrical carbon pores predicted by classical density functional theory.

PubMed

Hlushak, Stepan

2018-01-03

Temperature, pressure and pore-size dependences of the heat of adsorption, adsorption stress, and adsorption capacity of methane in simple models of slit and cylindrical carbon pores are studied using classical density functional theory (CDFT) and grand-canonical Monte-Carlo (MC) simulation. Studied properties depend nontrivially on the bulk pressure and the size of the pores. Heat of adsorption increases with loading, but only for sufficiently narrow pores. While the increase is advantageous for gas storage applications, it is less significant for cylindrical pores than for slits. Adsorption stress and the average adsorbed fluid density show oscillatory dependence on the pore size and increase with bulk pressure. Slit pores exhibit larger amplitude of oscillations of the normal adsorption stress with pore size increase than cylindrical pores. However, the increase of the magnitude of the adsorption stress with bulk pressure increase is more significant for cylindrical than for slit pores. Adsorption stress appears to be negative for a wide range of pore sizes and external conditions. The pore size dependence of the average delivered density of the gas is analyzed and the optimal pore sizes for storage applications are estimated. The optimal width of slit pore appears to be almost independent of storage pressure at room temperature and pressures above 10 bar. Similarly to the case of slit pores, the optimal radius of cylindrical pores does not exhibit much dependence on the storage pressure above 15 bar. Both optimal width and optimal radii of slit and cylindrical pores increase as the temperature decreases. A comparison of the results of CDFT theory and MC simulations reveals subtle but important differences in the underlying fluid models employed by the approaches. The differences in the high-pressure behaviour between the hard-sphere 2-Yukawa and Lennard-Jones models of methane, employed by the CDFT and MC approaches, respectively, result in an overestimation of the heat of adsorption by the CDFT theory at higher loadings. However, both adsorption stress and adsorption capacity appear to be much less sensitive to the differences between the models and demonstrate excellent agreement between the theory and the computer experiment.

The molecular dynamics simulation on the mechanical properties of Ni glass with external pressure

NASA Astrophysics Data System (ADS)

Zhang, Chuan-Hui; Wang, Ying; Sun, Dong-Bai

2017-08-01

In this paper, rapid quenching of Ni from crystal to metallic glass (MG) at different external pressures is simulated by molecular dynamics. The pair distribution functions (PDFs), mean-square displacement, glass transition temperature (Tg) and elastic property are calculated and compared with each other. The split of the second PDF peak means the liquid’s transition to glass state starts as previously reported for other MGs. And the Ri/R1 ratio rule is found to hold very well in Ni MG and reveals the SPO structural feature in the configurations. Moreover, with high external pressure, Tg values are more approximated by density-temperature and enthalpy-temperature curves. At last, the elastic modulus and mechanics modulus of quenching models produced a monotonous effect with increasing external pressure and temperature.

Load and inflation pressure effects on soil compaction of forwarder tires

Treesearch

Tim McDonald; Tom Way; Bjorn Lofgren; Fernando Seixas; Mats Landstrom

1996-01-01

A standard forwarder tire (600/55-26.5) was tested to determine its range of soil compaction with various inflation pressures and dynamic loads. Past research has shown that compaction of heavier equipment can be somewhat mitigated by operating with lower inflation pressures. Results indicated a significant effect of both load and inflation pressure on bulk density,...

Influence of loading and unloading velocity of confining pressure on strength and permeability characteristics of crystalline sandstone

NASA Astrophysics Data System (ADS)

Zhang, Dong-ming; Yang, Yu-shun; Chu, Ya-pei; Zhang, Xiang; Xue, Yan-guang

2018-06-01

The triaxial compression test of crystalline sandstone under different loading and unloading velocity of confining pressure is carried out by using the self-made "THM coupled with servo-controlled seepage apparatus for containing-gas coal", analyzed the strength, deformation and permeability characteristics of the sample, the results show that: with the increase of confining pressures loading-unloading velocity, Mohr's stress circle center of the specimen shift to the right, and the ultimate intensity, peak strain and residual stress of the specimens increase gradually. With the decrease of unloading velocity of confining pressure, the axial strain, the radial strain and the volumetric strain of the sample decrease first and then increases, but the radial strain decreases more greatly. The loading and unloading of confining pressure has greater influence on axial strain of specimens. The deformation modulus decreases rapidly with the increase of axial strain and the Poisson's ratio decreases gradually at the initial stage of loading. When the confining pressure is loaded, the deformation modulus decrease gradually, and the Poisson's ratio increases gradually. When the confining pressure is unloaded, the deformation modulus increase gradually, and the Poisson's ratio decreases gradually. When the specimen reaches the ultimate intensity, the deformation modulus decreases rapidly, while the Poisson's ratio increases rapidly. The fitting curve of the confining pressure and the deformation modulus and the Poisson's ratio in accordance with the distribution of quadratic polynomial function in the loading-unloading confining pressure. There is a corresponding relationship between the evolution of rock permeability and damage deformation during the process of loading and unloading. In the late stage of yielding, the permeability increases slowly, and the permeability increases sharply after the rock sample is destroyed. Fitting the permeability and confining pressure conform to the variation law of the exponential function.

Quantification of Training and Competition Loads in Endurance Sports: Methods and Applications.

PubMed

Mujika, Iñigo

2017-04-01

Training quantification is basic to evaluate an endurance athlete's responses to training loads, ensure adequate stress/recovery balance, and determine the relationship between training and performance. Quantifying both external and internal workload is important, because external workload does not measure the biological stress imposed by the exercise sessions. Generally used quantification methods include retrospective questionnaires, diaries, direct observation, and physiological monitoring, often based on the measurement of oxygen uptake, heart rate, and blood lactate concentration. Other methods in use in endurance sports include speed measurement and the measurement of power output, made possible by recent technological advances such as power meters in cycling and triathlon. Among subjective methods of quantification, rating of perceived exertion stands out because of its wide use. Concurrent assessments of the various quantification methods allow researchers and practitioners to evaluate stress/recovery balance, adjust individual training programs, and determine the relationships between external load, internal load, and athletes' performance. This brief review summarizes the most relevant external- and internal-workload-quantification methods in endurance sports and provides practical examples of their implementation to adjust the training programs of elite athletes in accordance with their individualized stress/recovery balance.

Stress distribution and mechanical properties of free and assembled Ni3Al nanoclusters

NASA Astrophysics Data System (ADS)

Zhurkin, E. E.; Hautier, G.; Hou, M.

2006-03-01

Classical molecular dynamics with a semiempirical N -body potential is used to study the distribution of local stress in bimetallic Ni3Al nanoparticles and in cluster-assembled materials. The materials considered are synthesized with these particles by low-energy deposition at 0.5eV per atom and by compaction with an external pressure of 2GPa , thus featuring different nanostructures. Both are nanoporous, the lowest density being obtained by deposition. Their mechanical response to a uniaxial external load is then studied and deformation mechanisms are identified and are found to be similar in both nanostructures. In the core of isolated clusters, the partial pressures on the nickel and aluminium subsystems are found to differ by several GPa and, as a balance to surface tension, the hydrostatic core pressure is positive and depends on the cluster size. The surface stress is tensile and, because of structural disorder, the partial pressures distributions on Ni and Al at the surface are scattered. When nanostructured systems are formed, strong and highly inhomogeneous shear stress appears, the cluster cores may become tensile, and the interfacial areas remain mainly tensile as well. The partial pressure difference between Ni and Al is somewhat reduced. It is shown that the effect of temperature is to reduce this difference still further and to homogenize the spatial stress distribution. When subjected to a uniaxial stress, both materials display an elastic and a plastic regime. The elastic limit is the lowest for the most porous material and decreases with increasing temperature. Plastic deformation is dominated by both grain boundary sliding and by the enlargement of the open volumes, without evidence for the nucleation of cracks. These open volumes are found to facilitate dislocation activity which is evidenced in grains with sizes as small as two nanometers. This dislocation activity is found to result in the production of stacking faults as well as to the recovery of defects induced by the deposition or by the compaction.

78 FR 64417 - Airworthiness Directives; Twin Commander Aircraft LLC Airplanes; Initial Regulatory Flexibility...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-10-29

... window channels, aft cabin pressure web, external wing to fuselage fillets, and fasteners; repair or..., the vertical channels, the upper picture window channels, aft cabin pressure web, external wing to... lower wing main spar, the vertical channels, the upper picture window channels, aft cabin pressure web...

A 3 kbar hydrogen-compatible gas loader for Paris-Edinburgh presses

NASA Astrophysics Data System (ADS)

Klotz, S.; Philippe, J.; Bull, C. L.; Loveday, J. S.; Nelmes, R. J.

2013-03-01

We present a device which allows compressed gases to be loaded into large volume opposed anvils used for high pressure neutron scattering in the multi-10 GPa range. The gases are initially loaded into clamps which can then be inserted into VX-Paris-Edinburgh load frames. The system is compatible with all inert gases as well as hydrogen and permits loading pressures of up to 3 kbar for which most gases have densities close to that of the liquid at ambient pressure. The device should have applications for the study of simple molecular solids as well as for loading gases as pressure-transmitting media.

Pulsatile plasma filtration and cell-free DNA amplification using a water-head-driven point-of-care testing chip.

PubMed

Lee, Yonghun; Kim, Dong-Min; Li, Zhenglin; Kim, Dong-Eun; Kim, Sung-Jin

2018-03-13

We demonstrate a microfiltration chip that separates blood plasma by using water-head-driven pulsatile pressures rather than any external equipment and use it for on-chip amplification of nucleic acids. The chip generates pulsatile pressures to significantly reduce filter clogging without hemolysis, and consists of an oscillator, a plasma-extraction pump, and filter units. The oscillator autonomously converts constant water-head pressure to pulsatile pressure, and the pump uses the pulsatile pressure to extract plasma through the filter. Because the pulsatile pressure can periodically clear blood cells from the filter surface, filter clogging can be effectively reduced. In this way, we achieve plasma extraction with 100% purity and 90% plasma recovery at 15% hematocrit. During a 10 min period, the volume of plasma extracted was 43 μL out of a 243 μL extraction volume at 15% hematocrit. We also studied the influence of the pore size and diameter of the filter, blood loading volume, oscillation period, and hematocrit level on the filtration performance. To demonstrate the utility of our chip for point-of-care testing (POCT) applications, we successfully implemented on-chip amplification of a nucleic acid (miDNA21) in plasma filtered from blood. We expect our chip to be useful not only for POCT applications but also for other bench-top analysis tools using blood plasma.

Static Footprint Local Forces, Areas, and Aspect Ratios for Three Type 7 Aircraft Tires

NASA Technical Reports Server (NTRS)

Howell, William E.; Perez, Sharon E.; Vogler, William A.

1991-01-01

The National Tire Modeling Program (NTMP) is a joint NASA/industry effort to improve the understanding of tire mechanics and develop accurate analytical design tools. This effort includes fundamental analytical and experimental research on the structural mechanics of tires. Footprint local forces, areas, and aspect ratios were measured. Local footprint forces in the vertical, lateral, and drag directions were measured with a special footprint force transducer. Measurements of the local forces in the footprint were obtained by positioning the transducer at specified locations within the footprint and externally loading the tires. Three tires were tested: (1) one representative of those used on the main landing gear of B-737 and DC-9 commercial transport airplanes, (2) a nose landing gear tire for the Space Shuttle Orbiter, and (3) a main landing gear tire for the Space Shuttle Orbiter. Data obtained for various inflation pressures and vertical loads are presented for two aircraft tires. The results are presented in graphical and tabulated forms.

Dynamics of bubble collapse under vessel confinement in 2D hydrodynamic experiments

NASA Astrophysics Data System (ADS)

Shpuntova, Galina; Austin, Joanna

2013-11-01

One trauma mechanism in biomedical treatment techniques based on the application of cumulative pressure pulses generated either externally (as in shock-wave lithotripsy) or internally (by laser-induced plasma) is the collapse of voids. However, prediction of void-collapse driven tissue damage is a challenging problem, involving complex and dynamic thermomechanical processes in a heterogeneous material. We carry out a series of model experiments to investigate the hydrodynamic processes of voids collapsing under dynamic loading in configurations designed to model cavitation with vessel confinement. The baseline case of void collapse near a single interface is also examined. Thin sheets of tissue-surrogate polymer materials with varying acoustic impedance are used to create one or two parallel material interfaces near the void. Shadowgraph photography and two-color, single-frame particle image velocimetry quantify bubble collapse dynamics including jetting, interface dynamics and penetration, and the response of the surrounding material. Research supported by NSF Award #0954769, ``CAREER: Dynamics and damage of void collapse in biological materials under stress wave loading.''

Gas loading apparatus for the Paris-Edinburgh press

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

Bocian, A.; Kamenev, K. V.; Bull, C. L.

2010-09-15

We describe the design and operation of an apparatus for loading gases into the sample volume of the Paris-Edinburgh press at room temperature and high pressure. The system can be used for studies of samples loaded as pure or mixed gases as well as for loading gases as pressure-transmitting media in neutron-scattering experiments. The apparatus consists of a high-pressure vessel and an anvil holder with a clamp mechanism. The vessel, designed to operate at gas pressures of up to 150 MPa, is used for applying the load onto the anvils located inside the clamp. This initial load is sufficient formore » sealing the pressurized gas inside the sample containing gasket. The clamp containing the anvils and the sample is then transferred into the Paris-Edinburgh press by which further load can be applied to the sample. The clamp has apertures for scattered neutron beams and remains in the press for the duration of the experiment. The performance of the gas loading system is illustrated with the results of neutron-diffraction experiments on compressed nitrogen.« less

Parasitic load control system for exhaust temperature control

DOEpatents

Strauser, Aaron D.; Coleman, Gerald N.; Coldren, Dana R.

2009-04-28

A parasitic load control system is provided. The system may include an exhaust producing engine and a fuel pumping mechanism configured to pressurize fuel in a pressure chamber. The system may also include an injection valve configured to cause fuel pressure to build within the pressure chamber when in a first position and allow injection of fuel from the pressure chamber into one or more combustion chambers of the engine when in a second position. The system may further include a controller configured to independently regulate the pressure in the pressure chamber and the injection of fuel into the one or more combustion chambers, to increase a load on the fuel pumping mechanism, increasing parasitic load on the engine, thereby increasing a temperature of the exhaust produced by the engine.

Preparation of hemoglobin-loaded nano-sized particles with porous structure as oxygen carriers.

PubMed

Zhao, Jian; Liu, Chang-Sheng; Yuan, Yuan; Tao, Xin-Yi; Shan, Xiao-Qian; Sheng, Yan; Wu, Fan

2007-03-01

Hb (hemoglobin)-loaded particles (HbP) encapsulated by a biodegradable polymer used as oxygen carrier were prepared. A modified double emulsion and solvent diffusion/evaporation method was adopted. All experiments were performed based on two types of biodegradable polymers, poly(epsilon-caprolactone) (PCL) and poly(epsilon-caprolactone-ethylene glycol) (PCL-PEG). The biodistribution and the survival time in blood of the particles were investigated in a mouse model. Encapsulation efficiency and pore-connecting efficiency were evaluated by a novel sulfocyanate potassium method. The influence of process parameters on the particle size and pore-connecting efficiency (PCE%) of nanoparticles have been discussed. The prepared conditions: solvent, external aqueous phase, pressure were discussed. The system utilizing dichloromethane (DCM)/ethyl acetate (EA) as a solvent with an unsaturated external aqueous phase yielded the highest encapsulation efficiency (87.35%) with a small mean particle size (153 nm). The formation of porous channels was attributed to the diffusion of solvent. The PCE% was more sensitive to the rate of solvent diffusion that was obviously affected by the preparation temperature. The PCE% reached 87.47% when PCL-PEG was employed at 25 degrees C. P(50) of HbP was 27 mmHg, which does not seem to be greatly affected by the encapsulation procedure. In vivo, following intravenous injection of 6-coumarin labeled HbP, the major organ accumulating Hb-loaded particles was the liver. The half-life of nano-sized PCL HbP was 3.1 times as long as the micro-sized PCL HbP. Also, Nano-sized as well as a PEGylated surface on HbP is beneficial for prolonged blood residence (7.2 fold increase).

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

DTIC Science & Technology

2007-06-01

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

Sliding enhances fluid and solute transport into buried articular cartilage contacts.

PubMed

Graham, B T; Moore, A C; Burris, D L; Price, C

2017-12-01

Solutes and interstitial water are naturally transported from cartilage by load-induced interstitial fluid pressures. Fluid and solute recovery during joint articulation have been primarily attributed to passive diffusion and mechanical 'pumping' from dynamic loading. This paper tests if the sliding action of articulation is a significant and independent driver of fluid and solute transport in cartilage. The large osteochondral samples utilized in the present study preserve the convergent wedges necessary for physiological hydrodynamics. Following static load-induced fluid exudation and prior to sliding, a fluorescent solute (AlexaFluor 633) was added to the lubricant bath. In situ confocal microscopy was used to quantify the transport of solute from the bath into the buried stationary contact area (SCA) during sliding. Following static exudation, significant reductions in friction and strain during sliding at 60 mm/s were accompanied by significant solute transport into the inaccessible center of the buried contact; no such transport was detected for the 0- or 1 mm/s sliding conditions. The results suggest that external hydrodynamic pressures from sliding induced advective flows that carried solutes from the bath toward the center of contact. These results provide the first direct evidence that the action of sliding is a significant contributor to fluid and solute recovery by cartilage. Furthermore, they indicate that the sliding-induced transport of solutes into the buried interface was orders of magnitude greater than that attributable to diffusion alone, a result with critical implications for disease prevention and tissue engineering. Copyright © 2017 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

Stability of the electroosmotic flow of a two-layer electrolyte-dielectric system with external pressure gradient⋆.

PubMed

Gorbacheva, E V; Ganchenko, G S; Demekhin, E A

2018-03-27

The stability of the electroosmotic flow of electrolyte-dielectric viscous liquids under the influence of the DC and AC electric fields along with the external pressure gradient is studied theoretically. Liquids are bounded by two infinite parallel plates. The lower wall bordering the electrolyte is assumed to be a charged surface, and the upper wall is electrically isolated. The charge at the lower boundary is assumed to be immobile, while the surface charge at the free surface is assumed to be mobile. In this paper, we study the micro- and nanosized liquid layers. The mathematical model is described by a nonlinear system of the Nernst-Planck-Poisson-Stokes partial differential equations with the appropriate boundary conditions on the solid surface, the electrolyte/dielectric interface, and on the upper wall. The pressure gradient is highly important for the stability of the flow. For the DC case, the external pressure could either stabilize and destabilize the flow depending on the relative directions of the electroosmotic flow and the pressure-driven flow. For the AC case, the dependence on the value of the external pressure is not monotonous for different wave numbers of perturbations, but, as a rule, the external pressure destabilizes the flow. As the frequency of the electric field increases, the one-dimensional solution of the problem becomes stable.

Experimental and numerical study of Bondura® 6.6 PIN joints

NASA Astrophysics Data System (ADS)

Berkani, I.; Karlsen, Ø.; Lemu, H. G.

2017-12-01

Pin joints are widely used in heavy-duty machinery such as aircrafts, cranes and offshore drilling equipment to transfer multi-dimensional shear forces. Their strength and service life depend on the clamping force in the contact region that is provided by interference fits. Though the interference fits provide full contact at the pin-hole interface under pretension loads, the contact interface reduces when the pin is subjected to an external load and hence a smaller contact surface leads to dramatic increase of the contact stress. The PIN joint of Bondura® Technology, investigated in this study, is an innovative solution intended to reduce the slack at the contact surface of the pin joint of heavy-duty machinery by using tapered sleeves on each end of the PIN. The study is aimed to better understand the contact pressure build-up and stress distribution in the supporting contact surface under pre-loading of the joint and the influence of temperature difference between part assembly and operation conditions. Numerical simulation using finite element method and diverse experimental tests were conducted. The numerical simulation and the test results, particularly the tests conducted with lubricated joints, show good conformance.

Atmospheric pressure loading effects on Global Positioning System coordinate determinations

NASA Technical Reports Server (NTRS)

Vandam, Tonie M.; Blewitt, Geoffrey; Heflin, Michael B.

1994-01-01

Earth deformation signals caused by atmospheric pressure loading are detected in vertical position estimates at Global Positioning System (GPS) stations. Surface displacements due to changes in atmospheric pressure account for up to 24% of the total variance in the GPS height estimates. The detected loading signals are larger at higher latitudes where pressure variations are greatest; the largest effect is observed at Fairbanks, Alaska (latitude 65 deg), with a signal root mean square (RMS) of 5 mm. Out of 19 continuously operating GPS sites (with a mean of 281 daily solutions per site), 18 show a positive correlation between the GPS vertical estimates and the modeled loading displacements. Accounting for loading reduces the variance of the vertical station positions on 12 of the 19 sites investigated. Removing the modeled pressure loading from GPS determinations of baseline length for baselines longer than 6000 km reduces the variance on 73 of the 117 baselines investigated. The slight increase in variance for some of the sites and baselines is consistent with expected statistical fluctuations. The results from most stations are consistent with approximately 65% of the modeled pressure load being found in the GPS vertical position measurements. Removing an annual signal from both the measured heights and the modeled load time series leaves this value unchanged. The source of the remaining discrepancy between the modeled and observed loading signal may be the result of (1) anisotropic effects in the Earth's loading response, (2) errors in GPS estimates of tropospheric delay, (3) errors in the surface pressure data, or (4) annual signals in the time series of loading and station heights. In addition, we find that using site dependent coefficients, determined by fitting local pressure to the modeled radial displacements, reduces the variance of the measured station heights as well as or better than using the global convolution sum.

Wellbeing perception and the impact on external training output among elite soccer players.

PubMed

Malone, Shane; Owen, Adam; Newton, Matt; Mendes, Bruno; Tiernan, Leo; Hughes, Brian; Collins, Kieran

2018-01-01

The objective of the investigation was to observe the impact of player wellbeing on the training output of elite soccer players. Prospective cohort design. Forty-eight soccer players (age: 25.3±3.1years; height: 183±7cm; mass: 72±7kg) were involved in this single season observational study across two teams. Each morning, pre-training, players completed customised perceived wellbeing questionnaires. Global positioning technology devices were used to measure external load (total distance, total high-speed running distance, high speed running, player load, player load slow, maximal velocity, maximal velocity exposures). Players reported ratings of perceived exertion using the modified Borg CR-10 scale. Integrated training load ratios were also analysed for total distance:RPE, total high speed distance:RPE player load:RPE and player load slow:RPE respectively. Mixed-effect linear models revealed significant effects of wellbeing Z-score on external and integrated training load measures. A wellbeing Z-score of -1 corresponded to a -18±2m (-3.5±1.1%), 4±1m (-4.9±2.1%,) 0.9±0.1kmh -1 (-3.1±2.1%), 1±1 (-4.6±2.9%), 25±3AU (-4.9±3.1%) and 11±0.5AU (-8.9±2.9%) reduction in total high speed distance, high speed distance, maximal velocity, maximal velocity exposures, player load and player load slow respectively. A reduction in wellbeing impacted external:internal training load ratios and resulted in -0.49±0.12mmin -1 , -1.20±0.08mmin -1 ,-0.02±0.01AUmin -1 in total distance:RPE, total high speed distance:RPE and player load slow:RPE respectively. The results suggest that systematic monitoring of player wellbeing within soccer cohorts can provide coaches with information about the training output that can be expected from individual players during a training session. Copyright © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

75 FR 16655 - Airworthiness Directives; Rolls-Royce plc RB211-Trent 700 Series Turbofan Engines

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-02

... pressure (HP-IP) turbine internal and external oil vent tubes for coking and carbon buildup, and cleaning... borescope inspections of the HP-IP turbine internal and external oil vent tubes for coking and carbon...-intermediate pressure (HP-IP) turbine internal oil vent tubes, external oil vent tubes, and bearing chamber...

Sensate Scaffolds Can Reliably Detect Joint Loading

PubMed Central

Bliss, C. L.; Szivek, J. A.; Tellis, B. C.; Margolis, D. S.; Schnepp, A. B.; Ruth, J. T.

2008-01-01

Treatment of cartilage defects is essential to the prevention of osteoarthritis. Scaffold-based cartilage tissue engineering shows promise as a viable technique to treat focal defects. Added functionality can be achieved by incorporating strain gauges into scaffolds, thereby providing a real-time diagnostic measurement of joint loading. Strain-gauged scaffolds were placed into the medial femoral condyles of 14 adult canine knees and benchtop tested. Loads between 75 and 130 N were applied to the stifle joints at 30°, 50°, and 70° of flexion. Strain-gauged scaffolds were able to reliably assess joint loading at all applied flexion angles and loads. Pressure sensitive films were used to determine joint surface pressures during loading and to assess the effect of scaffold placement on joint pressures. A comparison of peak pressures in control knees and joints with implanted scaffolds, as well as a comparison of pressures before and after scaffold placement, showed that strain-gauged scaffold implantation did not significantly alter joint pressures. Future studies could possibly use strain-gauged scaffolds to clinically establish normal joint loads and to determine loads that are damaging to both healthy and tissue-engineered cartilage. Strain-gauged scaffolds may significantly aid the development of a functional engineered cartilage tissue substitute as well as provide insight into the native environment of cartilage. PMID:16941586

Internal phosphorus loading across a cascade of three eutrophic basins: A synthesis of short- and long-term studies.

PubMed

Tammeorg, Olga; Horppila, Jukka; Tammeorg, Priit; Haldna, Marina; Niemistö, Juha

2016-12-01

Ascertaining the phosphorus (P) release processes in polymictic lakes is one of the methodologically most complex questions in limnology. In the current study, we combined short- and long-term investigations to elucidate the role of sediments in the P budget in a chain of eutrophic lake basins. We quantified the internal loading of P in three basins of Lake Peipsi (Estonia/Russia) for two periods characterized by different external P loadings using radiometrically dated sediment cores (long-term studies). The relationships between different water quality variables and the internal P loading, and the external P loading were studied. Our short-term studies aimed at elucidating the possible mechanisms behind variations in internal P loading included examination of the surficial sediments, i.e., seasonal measurements of redox potential, sediment pore water P concentrations and diffusive fluxes. Our results provided evidence for a potentially high importance of internal P loading in regulating water quality. The sediment core analyses revealed an increase in the internal P loading during the period of lower external P loading coinciding with the general deterioration in the lake water quality (i.e, higher concentrations of soluble reactive phosphorus, total phosphorus and biomass of cyanobacteria). Increase in wave action between the two studied periods appeared to cause more frequent sediment resuspension, and thus be the most likely reason for the variations in internal P loading. Our short-term measurements indicated that resuspension events can be followed by a considerable increase in the diffusive fluxes. Copyright © 2016 Elsevier B.V. All rights reserved.

Watershed Modeling to Assess the Sensitivity of Streamflow, Nutrient, and Sediment Loads to Potential Climate Change and Urban Development in 20 U.S. Watersheds (External Review Draft)

EPA Science Inventory

EPA has released for independent external peer review and public comment a draft report titled, Watershed Modeling to Assess the Sensitivity of Streamflow, Nutrient, and Sediment Loads to Potential Climate Change and Urban Development in 20 U.S. Watersheds. This is a draft...

A loose bolt delays loading of Endeavour's external tank

NASA Technical Reports Server (NTRS)

2000-01-01

This loose bracket, observed hanging down from the side of the White Room at Launch Pad 39B, delayed loading of Endeavour's external tank by several hours to allow technicians to remove it. A 'U' bolt connects the bracket to a fire suppression water line attached to the exterior of the White Room. The loose bolt could have possibly created a debris hazard.

Evaluative pressure overcomes perceptual load effects.

PubMed

Normand, Alice; Autin, Frédérique; Croizet, Jean-Claude

2015-06-01

Perceptual load has been found to be a powerful bottom-up determinant of distractibility, with high perceptual load preventing distraction by any irrelevant information. However, when under evaluative pressure, individuals exert top-down attentional control by giving greater weight to task-relevant features, making them more distractible from task-relevant distractors. One study tested whether the top-down modulation of attention under evaluative pressure overcomes the beneficial bottom-up effect of high perceptual load on distraction. Using a response-competition task, we replicated previous findings that high levels of perceptual load suppress task-relevant distractor response interference, but only for participants in a control condition. Participants under evaluative pressure (i.e., who believed their intelligence was assessed) showed interference from task-relevant distractor at all levels of perceptual load. This research challenges the assumptions of the perceptual load theory and sheds light on a neglected determinant of distractibility: the self-relevance of the performance situation in which attentional control is solicited.

Modeling Attitude towards Drug Treament: The Role of Internal Motivation, External Pressure, and Dramatic Relief

PubMed Central

Longshore, Douglas; Anglin, M. Douglas

2009-01-01

Motivation for change has historically been viewed as the crucial element affecting responsiveness to drug treatment. Various external pressures, such as legal coercion, may engender motivation in an individual previously resistant to change. Dramatic relief may be the change process that is most salient as individuals internalize such external pressures. Results of structural equation modeling on data from 465 drug users (58.9% male; 21.3% Black, 34.2% Hispanic/Latino, and 35.1% White) entering drug treatment indicated that internal motivation and external pressure significantly and positively predicted dramatic relief and that dramatic relief significantly predicted attitudes towards drug treatment: χ2=142.20, df=100, p<0.01; Robust Comparative Fit Index=0.97, Root Mean Squared Error of Approximation=0.03. These results indicate that when external pressure and internal motivation are high, dramatic relief is also likely to be high. When dramatic relief is high, attitudes towards drug treatment are likely to be positive. The findings indicate that interventions to get individuals into drug treatment should include processes that promote Dramatic Relief. Implications for addictions health services are discussed. PMID:18535908

The Manufacturing Process for the NASA Composite Crew Module Demonstration Structure

NASA Technical Reports Server (NTRS)

Pelham, Larry; Higgins, John E.

2008-01-01

This paper will describe the approaches and methods selected in fabrication of a carbon composite demonstration structure for the Composite Crew Module (CCM) Program. The program is managed by the NASA Safety and Engineering Center with participants from ten NASA Centers and AFRL. Multiple aerospace contractors are participating in the design development, tooling and fabrication effort as well. The goal of the program is to develop an agency wide design team for composite habitable spacecraft. The specific goals for this development project are: a).To gain hands on experience in design, building and testing a composite crew module. b) To validate key assumptions by resolving composite spacecraft design details through fabrication and testing of hardware. This abstract is based on Preliminary Design data..The final design will continue to evolve through the fall of 2007 with fabrication mostly completed by conference date. From a structures perspective, the.CCM can be viewed as a pressure module with variable pressure time histories and a series of both impact and quasi-static, high intensity point, line, and area distributed loads. The portion of the overall space vehicle being designed and. fabricated by the CCM team is just the pressure module and primary loading points. The heaviest point loads are applied and distributed to the pressure module at.an aluminum Service Module/Alternate Launch Abort System (SM/ALAS) fittings and at Main and Drogue Chute fittings. Significant line loads with metal to metal impact is applied at.the Lids ring. These major external point and line loads as well as pressure impact loads (blast and water landing) are applied to the lobed floor though the reentry shield and crushable materials. The pressure module is divided into upper and lower. shells that mate together with a bonded belly band splice joint to create the completed structural assembly. The benefits of a split CCM far outweigh the risks of a joint. These benefits include lower tooling cost and less manufacturing risk. Assembly of the top and bottom halves of the pressure shell will allow access to the interior of the shell throughout remaining fabrication sequence and can also potentially permit extensive installation of equipment and .crew facilities prior to final assembly of the two shell halves. A Pi pre-form is a woven carbon composite material which is provided in pre-impregnated form and frozen for long term storage. The cross-section shape allows the top of the pi to be bonded to a flat or curved surface with a second flat plate composite section bonded between two upstanding legs of the Pi. One of the regions relying on the merits of the Pi pre-form is the backbone. All connections among plates of the backbone structure, including the upper flanges, and to the lobe base of the pressure shell are currently joined by Pi pre-forms. The intersection of backbone composite plates is formed by application of two Pi pre-forms, top flanges and lobed surfaces are bonded with one Pi pre-form. The process of applying the pre-impregnated pi-preform will be demonstrated to include important steps like surface preparation, forming, application of pressure dams, vacuum bagging for consolidation, and curing techniques. Chopped carbon fiber tooling was selected over other traditional metallic and carbon fiber tooling. The requirement of schedule and cost economy for a moderate reuse cure tool warranted composite tooling options. Composite tooling schedule duration of 18 weeks compared favorably against other metallic tooling including invar tooling. Composite tooling also shows significant cost savings over low CTE metallic options. The composite tooling options were divided into two groups and the final decision was based on the cost, schedule, tolerance, temperature, and reuse requirements.

Influence of the height of the external hexagon and surface treatment on fatigue life of commercially pure titanium dental implants.

PubMed

Gil, Francisco Javier; Aparicio, Conrado; Manero, Jose M; Padros, Alejandro

2009-01-01

This study evaluated the effect of external hexagon height and commonly applied surface treatments on the fatigue life of titanium dental implants. Electropolished commercially pure titanium dental implants (seven implants per group) with three different external hexagon heights (0.6, 1.2, and 1.8 mm) and implants with the highest external hexagon height (1.8 mm) and different surface treatments (electropolishing, grit blasting with aluminium oxide, and acid etching with sulfuric acid) were tested to evaluate their mechanical fatigue life. To do so, 10-Hz triangular flexural load cycles were applied at 37 degrees C in artificial saliva, and the number of load cycles until implant fracture was determined. Tolerances of the hexagon/abutment fit and implant surface roughness were analyzed by scanning electron microscopy and light interferometry. Transmission electron microscopy and electron diffraction analyses of titanium hydrides were performed. First, the fatigue life of implants with the highest hexagon (8,683 +/- 978 load cycles) was more than double that of the implants with the shortest hexagons (3,654 +/- 789 load cycles) (P < .02). Second, the grit-blasted implants had the longest fatigue life of the tested materials (21,393 +/- 2,356 load cycles), which was significantly greater than that of the other surfaces (P < .001). The compressive surface residual stresses induced when blasting titanium are responsible for this superior mechanical response. Third, precipitation of titanium hydrides in grain boundaries of titanium caused by hydrogen adsorption from the acid solution deteriorates the fatigue life of acid-etched titanium dental implants. These implants had the shortest fatigue life (P < .05). The fatigue life of threaded root-form dental implants varies with the height of the external hexagon and/or the surface treatment of the implant. An external hexagon height of 1.8 mm and/or a blasting treatment appear to significantly increase fatigue life of dental implants.

Damage tolerance and arrest characteristics of pressurized graphite/epoxy tape cylinders

NASA Technical Reports Server (NTRS)

Ranniger, Claudia U.; Lagace, Paul A.; Graves, Michael J.

1993-01-01

An investigation of the damage tolerance and damage arrest characteristics of internally-pressurized graphite/epoxy tape cylinders with axial notches was conducted. An existing failure prediction methodology, developed and verified for quasi-isotropic graphite/epoxy fabric cylinders, was investigated for applicability to general tape layups. In addition, the effect of external circumferential stiffening bands on the direction of fracture path propagation and possible damage arrest was examined. Quasi-isotropic (90/0/plus or minus 45)s and structurally anisotropic (plus or minus 45/0)s and (plus or minus 45/90)s coupons and cylinders were constructed from AS4/3501-6 graphite/epoxy tape. Notched and unnotched coupons were tested in tension and the data correlated using the equation of Mar and Lin. Cylinders with through-thickness axial slits were pressurized to failure achieving a far-field two-to-one biaxial stress state. Experimental failure pressures of the (90/0/plus or minus 45)s cylinders agreed with predicted values for all cases but the specimen with the smallest slit. However, the failure pressures of the structurally anisotropic cylinders, (plus or minus 45/0)s and (plus or minus 45/90)s, were above the values predicted utilizing the predictive methodology in all cases. Possible factors neglected by the predictive methodology include structural coupling in the laminates and axial loading of the cylindrical specimens. Furthermore, applicability of the predictive methodology depends on the similarity of initial fracture modes in the coupon specimens and the cylinder specimens of the same laminate type. The existence of splitting which may be exacerbated by the axial loading in the cylinders, shows that this condition is not always met. The circumferential stiffeners were generally able to redirect fracture propagation from longitudinal to circumferential. A quantitative assessment for stiffener effectiveness in containing the fracture, based on cylinder radius, slit size, and bending stiffnesses of the laminates, is proposed.

Calibration of aero-structural reduced order models using full-field experimental measurements

NASA Astrophysics Data System (ADS)

Perez, R.; Bartram, G.; Beberniss, T.; Wiebe, R.; Spottswood, S. M.

2017-03-01

The structural response of hypersonic aircraft panels is a multi-disciplinary problem, where the nonlinear structural dynamics, aerodynamics, and heat transfer models are coupled. A clear understanding of the impact of high-speed flow effects on the structural response, and the potential influence of the structure on the local environment, is needed in order to prevent the design of overly-conservative structures, a common problem in past hypersonic programs. The current work investigates these challenges from a structures perspective. To this end, the first part of this investigation looks at the modeling of the response of a rectangular panel to an external heating source (thermo-structural coupling) where the temperature effect on the structure is obtained from forward looking infrared (FLIR) measurements and the displacement via 3D-digital image correlation (DIC). The second part of the study uses data from a previous series of wind-tunnel experiments, performed to investigate the response of a compliant panel to the effects of high-speed flow, to train a pressure surrogate model. In this case, the panel aero-loading is obtained from fast-response pressure sensitive paint (PSP) measurements, both directly and from the pressure surrogate model. The result of this investigation is the use of full-field experimental measurements to update the structural model and train a computational efficient model of the loading environment. The use of reduced order models, informed by these full-field physical measurements, is a significant step toward the development of accurate simulation models of complex structures that are computationally tractable.

Internal cycling, not external loading, decides the nutrient limitation in eutrophic lake: A dynamic model with temporal Bayesian hierarchical inference.

PubMed

Wu, Zhen; Liu, Yong; Liang, Zhongyao; Wu, Sifeng; Guo, Huaicheng

2017-06-01

Lake eutrophication is associated with excessive anthropogenic nutrients (mainly nitrogen (N) and phosphorus (P)) and unobserved internal nutrient cycling. Despite the advances in understanding the role of external loadings, the contribution of internal nutrient cycling is still an open question. A dynamic mass-balance model was developed to simulate and measure the contributions of internal cycling and external loading. It was based on the temporal Bayesian Hierarchical Framework (BHM), where we explored the seasonal patterns in the dynamics of nutrient cycling processes and the limitation of N and P on phytoplankton growth in hyper-eutrophic Lake Dianchi, China. The dynamic patterns of the five state variables (Chla, TP, ammonia, nitrate and organic N) were simulated based on the model. Five parameters (algae growth rate, sediment exchange rate of N and P, nitrification rate and denitrification rate) were estimated based on BHM. The model provided a good fit to observations. Our model results highlighted the role of internal cycling of N and P in Lake Dianchi. The internal cycling processes contributed more than external loading to the N and P changes in the water column. Further insights into the nutrient limitation analysis indicated that the sediment exchange of P determined the P limitation. Allowing for the contribution of denitrification to N removal, N was the more limiting nutrient in most of the time, however, P was the more important nutrient for eutrophication management. For Lake Dianchi, it would not be possible to recover solely by reducing the external watershed nutrient load; the mechanisms of internal cycling should also be considered as an approach to inhibit the release of sediments and to enhance denitrification. Copyright © 2017 Elsevier Ltd. All rights reserved.

Force and displacement measurements of the distal fibula during simulated ankle loading tests for high ankle sprains.

PubMed

Markolf, Keith L; Jackson, Steven; McAllister, David R

2012-09-01

Syndesmosis (high ankle) sprains produce disruption of the distal tibiofibular ligaments. Forces on the distal fibula that produce these injuries are unknown. Twenty-seven fresh-frozen lower extremities were used for this study. A load cell recorded forces acting on the distal fibula from forced ankle dorsiflexion and applied external foot torque; medial-lateral and anterior-posterior displacements of the distal fibula were recorded. Fibular forces and axial displacements were also recorded with applied axial force. During forced ankle dorsiflexion and external foot torque tests, the distal fibula always displaced posteriorly with respect to the tibia with no measurable medial-lateral displacement. With 10 Nm dorsiflexion moment, cutting the tibiofibular ligaments approximately doubled fibular force and displacement values. Cutting the tibiofibular ligaments significantly increased fibular displacement from applied external foot torque. Fibular forces and axial displacements from applied axial weight-bearing force were highest with the foot dorsiflexed. The highest mean fibular force in the study (271.9 N) occurred with 10 Nm external foot torque applied to a dorsiflexed foot under 1000 N axial force. Two important modes of loading that could produce high ankle sprains were identified: forced ankle dorsiflexion and external foot torque applied to a dorsiflexed ankle loaded with axial force. The distal tibiofibular ligaments restrained fibular displacement during these tests. Residual mortise widening observed at surgery may be the result of tibiofibular ligament injuries caused by posterior displacement of the fibula. Therefore, a syndesmosis screw used to fix the fibula would be subjected to posterior bending forces from these loading modes. Ankle bracing to prevent extreme ankle dorsiflexion during rehabilitation may be advisable to prevent excessive fibular motions that could affect syndesmosis healing.

Job strain, blood pressure and response to uncontrollable stress.

PubMed

Steptoe, A; Cropley, M; Joekes, K

1999-02-01

The association between cardiovascular disease risk and job strain (high-demand, low-control work) may be mediated by heightened physiological stress responsivity. We hypothesized that high levels of job strain lead to increased cardiovascular responses to uncontrollable but not controllable stressors. Associations between job strain and blood pressure reductions after the working day (unwinding) were also assessed. Assessment of cardiovascular responses to standardized behavioral tasks, and ambulatory monitoring of blood pressure and heart rate during a working day and evening. We studied 162 school teachers (60 men, 102 women) selected from a larger survey as experiencing high or low job strain. Blood pressure, heart rate and electrodermal responses to an externally paced (uncontrollable) task and a self-paced (controllable) task were assessed. Blood pressure was monitored using ambulatory apparatus from 0900 to 2230 h on a working day. The groups of subjects with high and low job strain did not differ in demographic factors, body mass or resting cardiovascular activity. Blood pressure reactions to the uncontrollable task were greater in high than low job-strain groups, but responses to the controllable task were not significantly different between groups. Systolic and diastolic blood pressure did not differ between groups over the working day, but decreased to a greater extent in the evening in subjects with low job strain. Job strain is associated with a heightened blood pressure response to uncontrollable but not controllable tasks. The failure of subjects with high job strain to show reduced blood pressure in the evening may be a manifestation of chronic allostatic load.

Identification of a Very High Cuff Pressure by Manual Palpation of the External Cuff Balloon on an Endotracheal Tube.

PubMed

Hedberg, Pia; Eklund, Carolina; Högqvist, Sandra

2015-06-01

The most common complication due to intubation is a high cuff pressure. A high cuff pressure can cause postanesthetic tracheal mucosal injuries in patients undergoing surgery. The aim of this cross-sectional study was to describe whether anesthetic nurses and anesthesiologists identified a very high cuff pressure by manual palpation of the external cuff balloon on an endotracheal tube. An airway device was intubated with an endotracheal tube cuffed to 95 cm H2O. Each participant palpated the external cuff balloon and then filled out a questionnaire, including estimation of the cuff pressure and user frequency of the cuff pressure manometer. The results showed that 89.1% estimated that the cuff pressure was high. Among the participants who rated the cuff pressure as high, 44.8% rated the pressure as quite high and 60.6% rated the pressure as very high. There was no significant relationship between profession and skill in identifying a very high cuff pressure (P = .843) or between work experience and skill in terms of identifying a very high cuff pressure (P = .816). These findings indicate that 10% of patients are at risk of tracheal erosion because of a high cuff pressure.

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

NASA Technical Reports Server (NTRS)

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

1994-01-01

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

External jugular venous pressure as an alternative to conventional central venous pressure in right lobe donor hepatectomies.

PubMed

Abdullah, Mohamed Hussein; Soliman, Hossam El Deen; Morad, Wessam Saber

2011-12-01

Many centers have adopted central vein cannulation both for central venous pressure monitoring and fluid administration for right hepatectomy in living-liver donors. However, use of central venous catheters is associated with adverse events that are hazardous to patients and expensive to treat. This study sought to examine the use of external jugular venous pressure as an alternative to conventional central venous pressure in right lobe donor hepatectomies Forty ASA grade I adult living liver-donors without a known history of significant cardiac or pulmonary diseases were enrolled in this prospective observational study. Paired measurement of venous pressures (external jugular venous pressure and internal jugular venous pressure) were taken at the following times: after induction of anesthesia, 30 minutes after skin incision, during right lobe mobilization (every 15 minutes), during hepatic transaction (every 15 minutes), after right lobe resection (every 15 minutes), and after abdominal closure. Paired measurements were equal in 47.5%, 53.5%, 61.5%, 46.3%, and 52.5% for after induction, after skin incision, right lobe mobilization, right lobe transection, after resection, and before abdominal closure periods. However, all measurements were within acceptable limits of bias measurements (± 2 mm Hg). Central venous pressure catheter placement can be avoided and replaced by a less-invasive method such as external jugular venous pressure (which gave an acceptable estimate of central venous pressure in all phases of right lobe resection) in living-donor liver transplant and allowed equivalent monitor even during fluid restriction phases.

In situ forces and length patterns of the fibular collateral ligament under controlled loading: an in vitro biomechanical study using a robotic system.

PubMed

Liu, Ping; Wang, Jianquan; Xu, Yan; Ao, Yingfang

2015-04-01

The aim of this study was to determine the in situ forces and length patterns of the fibular collateral ligament (FCL) and kinematics of the knee under various loading conditions. Six fresh-frozen cadaveric knees were used (mean age 46 ± 14.4 years; range 20-58). In situ forces and length patterns of FCL and kinematics of the knee were determined under the following loading conditions using a robotic/universal force-moment sensor testing system: no rotation, varus (10 Nm), external rotation (5 Nm), and internal rotation (5 Nm) at 0°, 15°, 30°, 60º, 90°, and 120° of flexion, respectively. Under no rotation loading, the distances between the centres of the FCL attachments decreased as the knee flexed. Under varus loading, the force in FCL peaked at 15° of flexion and decreased with further knee flexion, while distances remained nearly constant and the varus rotation increased with knee flexion. Using external rotation, the force in the FCL also peaked at 15° flexion and decreased with further knee flexion, the distances decreased with flexion, and external rotation increased with knee flexion. Using internal rotation load, the force in the FCL was relatively small across all knee flexion angles, and the distances decreased with flexion; the amount of internal rotation was fairly constant. FCL has a primary role in preventing varus and external rotation at 15° of flexion. The FCL does not perform isometrically following knee flexion during neutral rotation, and tibia rotation has significant effects on the kinematics of the FCL. Varus and external rotation laxity increased following knee flexion. By providing more realistic data about the function and length patterns of the FCL and the kinematics of the intact knee, improved reconstruction and rehabilitation protocols can be developed.

An improved sample loading technique for cellular metabolic response monitoring under pressure

NASA Astrophysics Data System (ADS)

Gikunda, Millicent Nkirote

To monitor cellular metabolism under pressure, a pressure chamber designed around a simple-to-construct capillary-based spectroscopic chamber coupled to a microliter-flow perfusion system is used in the laboratory. Although cyanide-induced metabolic responses from Saccharomyces cerevisiae (baker's yeast) could be controllably induced and monitored under pressure, previously used sample loading technique was not well controlled. An improved cell-loading technique which is based on use of a secondary inner capillary into which the sample is loaded then inserted into the capillary pressure chamber, has been developed. As validation, we demonstrate the ability to measure the chemically-induced metabolic responses at pressures of up to 500 bars. This technique is shown to be less prone to sample loss due to perfusive flow than the previous techniques used.

Evolution of ferromagnetism in charge ordered manganite: An effect of external pressure

NASA Astrophysics Data System (ADS)

Dash, S.; Pradhan, M. K.; Rao, T. Lakshmana

2018-05-01

Detailed magnetic measurements of the Pr0.75Na0.25MnO3 polycrystalline sample have been carried out under external hydrostatic pressure upto 10kbar. Pressure strongly suppresses the first order magnetic transition, while thermal hysteresis narrows down progressively and then disappears with increase in pressure. The significant enhancement of the field cooled magnetization value at different pressures is due to the antiferromagnetic to ferromagnetic transformation, while ruling out any contribution from the domain alignment within the ferromagnetic phase.

Effect of amplitude and duration of impulsive pressure on endothelial permeability in in vitro fluid percussion trauma.

PubMed

Nakadate, Hiromichi; Inuzuka, Koji; Akanuma, Suguru; Kakuta, Akira; Aomura, Shigeru

2014-04-16

Intracranial pressure changes during head impact cause brain injuries such as vasogenic edema and cerebral contusion. However, the influence of impulsive pressure on endothelial function has not yet been fully studied in vitro. In this study, we developed a pressure loading device that produced positive and negative pressures by modifying an in vitro fluid percussion model and examined the effects of the amplitude and duration of the pressures on endothelial permeability. Human umbilical vein endothelial cells were subjected to three types of positive pressure (average amplitude/average duration of 352 kPa/23 ms, 73 kPa/27 ms, and 70 kPa/44 ms) and three types of negative pressure (-72 kPa/41 ms, -67 kPa/104 ms, and -91 kPa/108 ms), and the transendothelial electrical resistance (TEER) was measured between 15 min and 24 h after pressure loading for quantifying the formation of an integral monolayer of endothelial cells. After loading, vascular endothelial- (VE-) cadherin, an endothelium-specific cell-cell adhesion molecule involved in endothelial barrier function, was stained and observed using fluorescence microscopy. The pressure loading device could produce positive pressure pulses with amplitudes of 53-1348 kPa and durations of 9-29.1 ms and negative pressure pulses with amplitudes of -52 - -93 kPa and durations of 42.9-179.5 ms. The impulsive pressure reduced the TEER associated with the change in VE-cadherin localization. Additionally, TEER decreased considerably at 15 min and 6 h post-loading, with these changes being significant in positive pressure with larger amplitude and shorter duration and in all types of negative pressures compared to pre-loading. The changes in intracranial pressure during head impact impair endothelial barrier function by the disruption of the integrity of endothelial cell-cell junctions, and the degree of increase in endothelial permeability depends on the amplitude, duration, and direction (compressive and tensile) of the impulsive pressure.

External pressure measurement system

NASA Astrophysics Data System (ADS)

Chandler, Jon K.; Fowler, Don P.

Hydraulic systems comprise an important part of jet aircraft and their pressure needs must be checked constantly. Tests of the prototype external pressure measurement system show that it is possible to accurately convert the small expansion of tubing with pressure into a direct pressure reading without inserting a pressure gage into the piping system. The tool described in the paper is a clamp-on displacement transducer that can read pressure directly in PSI from 0 to 5000. Some limitations concerning temperature and accuracy should be remedied by additional design work. The system promises to streamline troubleshooting of all types of piping systems.

Environmental And Quality Management System In The Context Of Sustainable Development

NASA Astrophysics Data System (ADS)

Rusko, Miroslav

2015-06-01

Growing load and deterioration of the environment can be interpreted as a result of some external effects interventions. While the positive externalities influence the positive productional and utilizational functions of other subjects, the negative externalities influence the negative ones. Both types of external effects can act as parcial or global externalities. Linking of environmental issues to economy and finance is an important sphere.

National Launch System cycle 1 loads and models data book

NASA Technical Reports Server (NTRS)

Bugg, F.; Brunty, J.; Ernsberger, G.; Mcghee, D.; Gagliano, L.; Harrington, F.; Meyer, D.; Blades, E.

1992-01-01

This document contains preliminary cycle 1 loads for the National Launch System (NLS) 1 and 2 vehicles. The loads provided and recommended as design loads represent the maximum load expected during prelaunch and flight regimes, i.e., limit loads, except that propellant tank ullage pressure has not been included. Ullage pressure should be added to the loads book values for cases where the addition results in higher loads. The loads must be multiplied by the appropriate factors of safety to determine the ultimate loads for which the structure must be capable.

3-D Analysis of Flanged Joints Through Various Preload Methods Using ANSYS

NASA Astrophysics Data System (ADS)

Murugan, Jeyaraj Paul; Kurian, Thomas; Jayaprakash, Janardhan; Sreedharapanickar, Somanath

2015-10-01

Flanged joints are being employed in aerospace solid rocket motor hardware for the integration of various systems or subsystems. Hence, the design of flanged joints is very important in ensuring the integrity of motor while functioning. As these joints are subjected to higher loads due to internal pressure acting inside the motor chamber, an appropriate preload is required to be applied in this joint before subjecting it to the external load. Preload, also known as clamp load, is applied on the fastener and helps to hold the mating flanges together. Generally preload is simulated as a thermal load and the exact preload is obtained through number of iterations. Infact, more iterations are required when considering the material nonlinearity of the bolt. This way of simulation will take more computational time for generating the required preload. Now a days most commercial software packages use pretension elements for simulating the preload. This element does not require iterations for inducing the preload and it can be solved with single iteration. This approach takes less computational time and thus one can study the characteristics of the joint easily by varying the preload. When the structure contains more number of joints with different sizes of fasteners, pretension elements can be used compared to thermal load approach for simulating each size of fastener. This paper covers the details of analyses carried out simulating the preload through various options viz., preload through thermal, initial state command and pretension element etc. using ANSYS finite element package.

Structural Stability of a Stiffened Aluminum Fuselage Panel Subjected to Combined Mechanical and Internal Pressure Loads

NASA Technical Reports Server (NTRS)

Rouse, Marshall; Young, Richard D.; Gehrki, Ralph R.

2003-01-01

Results from an experimental and analytical study of a curved stiffened aluminum panel subjected to combined mechanical and internal pressure loads are presented. The panel loading conditions were simulated using a D-box test fixture. Analytical buckling load results calculated from a finite element analysis are presented and compared to experimental results. Buckling results presented indicate that the buckling load of the fuselage panel is significantly influenced by internal pressure loading. The experimental results suggest that the stress distribution is uniform in the panel prior to buckling. Nonlinear finite element analysis results correlates well with experimental results up to buckling.

Expansion Work without the External Pressure and Thermodynamics in Terms of Quasistatic Irreversible Processes

ERIC Educational Resources Information Center

Schmidt-Rohr, Klaus

2014-01-01

We demonstrate that the formula for irreversible expansion work in most chemical thermodynamics textbooks does not apply during the expansion process. Instead of the "external pressure" P[subscript ext], the pressure P[subscript sys,mb] on the piston or other moving boundary (hence the subscript mb), which is nearly equal to the system…

Inducing Peer Pressure to Promote Cooperation

PubMed Central

Mani, Ankur; Rahwan, Iyad; Pentland, Alex

2013-01-01

Cooperation in a large society of self-interested individuals is notoriously difficult to achieve when the externality of one individual's action is spread thin and wide on the whole society. This leads to the ‘tragedy of the commons’ in which rational action will ultimately make everyone worse-off. Traditional policies to promote cooperation involve Pigouvian taxation or subsidies that make individuals internalize the externality they incur. We introduce a new approach to achieving global cooperation by localizing externalities to one's peers in a social network, thus leveraging the power of peer-pressure to regulate behavior. The mechanism relies on a joint model of externalities and peer-pressure. Surprisingly, this mechanism can require a lower budget to operate than the Pigouvian mechanism, even when accounting for the social cost of peer pressure. Even when the available budget is very low, the social mechanisms achieve greater improvement in the outcome. PMID:23619166

Inducing peer pressure to promote cooperation.

PubMed

Mani, Ankur; Rahwan, Iyad; Pentland, Alex

2013-01-01

Cooperation in a large society of self-interested individuals is notoriously difficult to achieve when the externality of one individual's action is spread thin and wide on the whole society. This leads to the 'tragedy of the commons' in which rational action will ultimately make everyone worse-off. Traditional policies to promote cooperation involve Pigouvian taxation or subsidies that make individuals internalize the externality they incur. We introduce a new approach to achieving global cooperation by localizing externalities to one's peers in a social network, thus leveraging the power of peer-pressure to regulate behavior. The mechanism relies on a joint model of externalities and peer-pressure. Surprisingly, this mechanism can require a lower budget to operate than the Pigouvian mechanism, even when accounting for the social cost of peer pressure. Even when the available budget is very low, the social mechanisms achieve greater improvement in the outcome.

Inducing Peer Pressure to Promote Cooperation

NASA Astrophysics Data System (ADS)

Mani, Ankur; Rahwan, Iyad; Pentland, Alex

2013-04-01

Cooperation in a large society of self-interested individuals is notoriously difficult to achieve when the externality of one individual's action is spread thin and wide on the whole society. This leads to the `tragedy of the commons' in which rational action will ultimately make everyone worse-off. Traditional policies to promote cooperation involve Pigouvian taxation or subsidies that make individuals internalize the externality they incur. We introduce a new approach to achieving global cooperation by localizing externalities to one's peers in a social network, thus leveraging the power of peer-pressure to regulate behavior. The mechanism relies on a joint model of externalities and peer-pressure. Surprisingly, this mechanism can require a lower budget to operate than the Pigouvian mechanism, even when accounting for the social cost of peer pressure. Even when the available budget is very low, the social mechanisms achieve greater improvement in the outcome.

Self-healing of low-velocity impact damage in glass fabric/epoxy composites using an epoxy-mercaptan healing agent

NASA Astrophysics Data System (ADS)

Chao Yuan, Yan; Ye, Yueping; Zhi Rong, Min; Chen, Haibin; Wu, Jingshen; Qiu Zhang, Ming; Qin, Shi Xiang; Yang, Gui Cheng

2011-01-01

Self-healing woven glass fabric-reinforced epoxy composite laminates were made by embedding epoxy- and mercaptan-loaded microcapsules. After being subjected to low-velocity impact, the laminates were able to heal the damage in an autonomic way at room temperature. The healing-induced reduction in the damaged areas was visualized using a scanning acoustic microscope. The rate of damage area reduction, which is closely related to the effect of crack rehabilitation and mechanical recovery, is a function of impact energy, content and size of the healing microcapsules. Minor damage, such as microcracks in the matrix, can be completely repaired by the healing system without manual intervention, including external pressure. Microcapsules with larger size and/or higher concentration are propitious for delivering more healing agent to cracked portions, while imposition of lateral pressure on damaged specimens forces the separated faces to approach each other. Both can improve the rate of damage area reduction in the case of severe damage.

Aortic Wave Dynamics and Its Influence on Left Ventricular Workload

PubMed Central

Pahlevan, Niema M.; Gharib, Morteza

2011-01-01

The pumping mechanism of the heart is pulsatile, so the heart generates pulsatile flow that enters into the compliant aorta in the form of pressure and flow waves. We hypothesized that there exists a specific heart rate at which the external left ventricular (LV) power is minimized. To test this hypothesis, we used a computational model to explore the effects of heart rate (HR) and aortic rigidity on left ventricular (LV) power requirement. While both mean and pulsatile parts of the pressure play an important role in LV power requirement elevation, at higher rigidities the effect of pulsatility becomes more dominant. For any given aortic rigidity, there exists an optimum HR that minimizes the LV power requirement at a given cardiac output. The optimum HR shifts to higher values as the aorta becomes more rigid. To conclude, there is an optimum condition for aortic waves that minimizes the LV pulsatile load and consequently the total LV workload. PMID:21853075

A Hydrostatic Bearing Test System for Measuring Bearing Load Using Magnetic-Fluid Lubricants.

PubMed

Weng, Huei Chu; Chen, Lu-Yu

2016-05-01

This paper conducts a study on the design of a hydrostatic bearing test system. It involves the determination of viscous properties of magnetic-fluid lubricants. The load of a hydrostatic thrust bearing using a water-based magnetite nanofluid of varying volume flow rate is measured under an applied external induction field via the test system. Results reveal that the presence of nanoparticles in a carrier liquid would cause an enhanced bearing load. Such an effect could be further magnified by increasing the lubricant volume flow rate or the external induction field strength.

Analysis of an Aircraft Honeycomb Sandwich Panel with Circular Face Sheet/Core Disbond Subjected to Ground-Air Pressurization

NASA Technical Reports Server (NTRS)

Rinker, Martin; Krueger, Ronald; Ratcliffe, James

2013-01-01

The ground-air pressurization of lightweight honeycomb sandwich structures caused by alternating pressure differences between the enclosed air within the honeycomb core and the ambient environment is a well-known and controllable loading condition of aerospace structures. However, initial face sheet/core disbonds intensify the face sheet peeling effect of the internal pressure load significantly and can decrease the reliability of the sandwich structure drastically. Within this paper, a numerical parameter study was carried out to investigate the criticality of initial disbonds in honeycomb sandwich structures under ground-air pressurization. A fracture mechanics approach was used to evaluate the loading at the disbond front. In this case, the strain energy release rate was computed via the Virtual Crack Closure Technique. Special attention was paid to the pressure-deformation coupling which can decrease the pressure load within the disbonded sandwich section significantly when the structure is highly deformed.

A loose bolt delays loading of Endeavour's external tank

NASA Technical Reports Server (NTRS)

2000-01-01

A closeup reveals the loose bracket, observed hanging down from the side of the White Room at Launch Pad 39B, that delayed loading of Endeavour's external tank by several hours to allow technicians to remove it. A 'U' bolt connects the bracket to a fire suppression water line attached to the exterior of the White Room. The loose bolt could have possibly created a debris hazard.

Relative importance of expertise, lifting height and weight lifted on posture and lumbar external loading during a transfer task in manual material handling.

PubMed

Plamondon, André; Larivière, Christian; Delisle, Alain; Denis, Denys; Gagnon, Denis

2012-01-01

The objective of this study was to measure the effect size of three important factors in manual material handling, namely expertise, lifting height and weight lifted. The effect of expertise was evaluated by contrasting 15 expert and 15 novice handlers, the effect of the weight lifted with a 15-kg box and a 23-kg box and the effect of lifting height with two different box heights: ground level and a 32 cm height. The task consisted of transferring a series of boxes from a conveyor to a hand trolley. Lifting height and weight lifted had more effect size than expertise on external back loading variables (moments) while expertise had low impact. On the other hand, expertise showed a significant effect of posture variables on the lumbar spine and knees. All three factors are important, but for a reduction of external back loading, the focus should be on the lifting height and weight lifted. The objective was to measure the effect size of three important factors in a transfer of boxes from a conveyor to a hand trolley. Lifting height and weight lifted had more effect size than expertise on external back loading variables but expertise was a major determinant in back posture.

External fixation using locking plate in distal tibial fracture: a finite element analysis.

PubMed

Zhang, Jingwei; Ebraheim, Nabil; Li, Ming; He, Xianfeng; Schwind, Joshua; Liu, Jiayong; Zhu, Limei

2015-08-01

External fixation of tibial fractures using a locking plate has been reported with favorable results in some selected patients. However, the stability of external plate fixation in this fracture pattern has not been previously demonstrated. We investigated the stability of external plate fixation with different plate-bone distances. In this study, the computational processing model of external fixation of a distal tibial metaphyseal fracture utilizing the contralateral femoral less invasive stabilization system plate was analyzed. The plate was placed on the anteromedial aspect of tibia with different plate-bone distances: 1, 10, 20, and 30 mm. Under axial load, the stiffness of construct in all groups was higher than intact tibia. Under axial load with an internal rotational force, the stiffness of construct with 1 and 10 mm plate-bone distances was similar to that of an intact tibia and the stiffness of the construct with 20 and 30 mm distances was lower than that of an intact tibia. Under axial load with an external rotational force, the stiffness of the construct in all groups was lower than that of an intact tibia. The maximum plate stresses were concentrated at the two most distal screws and were highest in the construct with the 10 mm plate-bone distance, and least in the construct with a 1 mm plate-bone distance. To guarantee a stable external plate fixation in distal tibial fracture, the plate-bone distance should be less than 30 mm.

Orbiter Gap Filler Bending Model for Re-entry

NASA Technical Reports Server (NTRS)

Campbell, Charles H.

2007-01-01

Pressure loads on a protruding gap filler during an Orbiter reentry are investigated to evaluate the likelihood of extraction due to pressure loads, and to ascertain how much bending will be induced by re-entry pressure loads. Oblique shock wave theory is utilized to develop a representation of the pressure loads induced on a gap filler for the ISSHVFW trajectory, representative of a heavy weight ISS return. A free body diagram is utilized to react the forces induced by the pressure forces. Preliminary results developed using these methods demonstrate that pressure loads, alone, are not likely causes of gap filler extraction during reentry. Assessment of the amount a gap filler will bend over is presented. Implications of gap filler bending during re-entry include possible mitigation of early boundary layer transition concerns, uncertainty in ground based measurement of protruding gap fillers from historical Orbiter flight history, and uncertainty in the use of Orbiter gap fillers for boundary layer prediction calibration. Authors will be added to the author list as appropriate.

Inspiratory muscle training in patients with chronic obstructive pulmonary disease: structural adaptation and physiologic outcomes.

PubMed

Ramirez-Sarmiento, Alba; Orozco-Levi, Mauricio; Guell, Rosa; Barreiro, Esther; Hernandez, Nuria; Mota, Susana; Sangenis, Merce; Broquetas, Joan M; Casan, Pere; Gea, Joaquim

2002-12-01

The present study was aimed at evaluating the effects of a specific inspiratory muscle training protocol on the structure of inspiratory muscles in patients with chronic obstructive pulmonary disease. Fourteen patients (males, FEV1, 24 +/- 7% predicted) were randomized to either inspiratory muscle or sham training groups. Supervised breathing using a threshold inspiratory device was performed 30 minutes per day, five times a week, for 5 consecutive weeks. The inspiratory training group was subjected to inspiratory loading equivalent to 40 to 50% of their maximal inspiratory pressure. Biopsies from external intercostal muscles and vastus lateralis (control muscle) were taken before and after the training period. Muscle samples were processed for morphometric analyses using monoclonal antibodies against myosin heavy chain isoforms I and II. Increases in both the strength and endurance of the inspiratory muscles were observed in the inspiratory training group. This improvement was associated with increases in the proportion of type I fibers (by approximately 38%, p < 0.05) and in the size of type II fibers (by approximately 21%, p < 0.05) in the external intercostal muscles. No changes were observed in the control muscle. The study demonstrates that inspiratory training induces a specific functional improvement of the inspiratory muscles and adaptive changes in the structure of external intercostal muscles.

Preconditioning of mesenchymal stromal cells toward nucleus pulposus-like cells by microcryogels-based 3D cell culture and syringe-based pressure loading system.

PubMed

Zeng, Yang; Feng, Siyu; Liu, Wei; Fu, Qinyouen; Li, Yaqian; Li, Xiaokang; Chen, Chun; Huang, Chenyu; Ge, Zigang; Du, Yanan

2017-04-01

To precondition mesenchymal stromal/stem cells (MSCs) with mechanical stimulation may enhance cell survival and functions following implantation in load bearing environment such as nucleus pulposus (NP) in intervertebral disc (IVD). In this study, preconditioning of MSCs toward NP-like cells was achieved in previously developed poly (ethylene glycol) diacrylate (PEGDA) microcryogels (PMs) within a syringe-based three-dimensional (3D) culture system which provided a facile and cost-effective pressure loading approach. PMs loaded with alginate and MSCs could be incubated in a sealable syringe which could be air-compressed to apply pressure loading through a programmable syringe pump. Expression levels of chondrogenic marker genes SOX9, COL II, and ACAN were significantly upregulated in MSCs when pressure loading of 0.2 MPa or 0.8 MPa was implemented. Expression levels of COL I and COL X were downregulated when pressure loading was applied. In a nude mouse model, MSCs loaded in PMs mechanically stimulated for three days were subcutaneously injected using the same culture syringe. Three weeks postinjection, more proteoglycans (PGs) were deposited and more SOX9 and COL II but less COL I and COL X were stained in 0.2 MPa group. Furthermore, injectable MSCs-loaded PMs were utilized in an ex vivo rabbit IVD organ culture model that demonstrated the leak-proof function and enhanced cell retention of PMs assisted cell delivery to a load bearing environment for potential NP regeneration. This microcryogels-based 3D cell culture and syringe-based pressure loading system represents a novel method for 3D cell culture with mechanical stimulation for better function. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 507-520, 2017. © 2015 Wiley Periodicals, Inc.

Identifying interactive effects of task demands in lifting on estimates of in vivo low back joint loads.

PubMed

Gooyers, Chad E; Beach, Tyson A C; Frost, David M; Howarth, Samuel J; Callaghan, Jack P

2018-02-01

This investigation examined interactions between the magnitude of external load, movement speed and (a)symmetry of load placement on estimates of in vivo joint loading in the lumbar spine during simulated occupational lifting. Thirty-two participants with manual materials handling experience were included in the study. Three-dimensional motion data, ground reaction forces, and activation of six bilateral trunk muscle groups were captured while participants performed lifts with two loads at two movement speeds and using two load locations. L4-L5 joint compression and shear force-time histories were estimated using an EMG-assisted musculoskeletal model of the lumbar spine. Results from this investigation provide strong evidence that known mechanical low back injury risk factors should not be viewed in isolation. Rather, injury prevention efforts need to consider the complex interactions that exist between external task demands and their combined influence on internal joint loading. Copyright © 2017 Elsevier Ltd. All rights reserved.

Detection of an anomalous pressure on a magneto-inertial-fusion load current diagnostic

DOE PAGES

Hess, Mark Harry; Hutsel, Brian Thomas; Jennings, Christopher Ashley; ...

2017-01-30

Recent Magnetized Liner Inertial Fusion experiments at the Sandia National Laboratories Z pulsed power facility have featured a PDV (Photonic Doppler Velocimetry) diagnostic in the final power feed section for measuring load current. In this paper, we report on an anomalous pressure that is detected on this PDV diagnostic very early in time during the current ramp. Early time load currents that are greater than both B-dot upstream current measurements and existing Z machine circuit models by at least 1 MA would be necessary to describe the measured early time velocity of the PDV flyer. This leads us to infermore » that the pressure producing the early time PDV flyer motion cannot be attributed to the magnetic pressure of the load current but rather to an anomalous pressure. Using the MHD code ALEGRA, we are able to compute a time-dependent anomalous pressure function, which when added to the magnetic pressure of the load current, yields simulated flyer velocities that are in excellent agreement with the PDV measurement. As a result, we also provide plausible explanations for what could be the origin of the anomalous pressure.« less

Effect of beta-adrenergic blockade with timolol on myocardial blood flow during exercise after myocardial infarction in the dog.

PubMed

Herzog, C A; Aeppli, D P; Bache, R J

1984-12-01

The effect of beta-adrenergic blockade with timolol (40 micrograms/kg) on myocardial blood flow during rest and graded treadmill exercise was assessed in 12 chronically instrumented dogs 10 to 14 days after myocardial infarction was produced by acute left circumflex coronary artery occlusion. During exercise at comparable external work loads, the heart rate-systolic blood pressure product was significantly decreased after timilol, with concomitant reductions of myocardial blood flow in normal, border and central ischemic areas (p less than 0.001) and increases in subendocardial/subepicardial blood flow ratios (p less than 0.05). In addition to the blunted chronotropic response to exercise, timolol exerted an effect on myocardial blood flow that was not explained by changes in heart rate or blood pressure. At comparable rate-pressure products during exercise, total myocardial blood flow was 24% lower after timolol (p less than 0.02) and flow was redistributed from subepicardium to subendocardium in all myocardial regions. Thus, timolol altered myocardial blood flow during exercise by two separate mechanisms: a negative chronotropic effect, and a significant selective reduction of subepicardial perfusion independent of changes in heart rate or blood pressure with transmural redistribution of flow toward the subendocardium.

Skull flexure as a contributing factor in the mechanism of injury in the rat when exposed to a shock wave.

PubMed

Bolander, Richard; Mathie, Blake; Bir, Cynthia; Ritzel, David; VandeVord, Pamela

2011-10-01

The manner in which energy from an explosion is transmitted into the brain is currently a highly debated topic within the blast injury community. This study was conducted to investigate the injury biomechanics causing blast-related neurotrauma in the rat. Biomechanical responses of the rat head under shock wave loading were measured using strain gauges on the skull surface and a fiber optic pressure sensor placed within the cortex. MicroCT imaging techniques were applied to quantify skull bone thickness. The strain gauge results indicated that the response of the rat skull is dependent on the intensity of the incident shock wave; greater intensity shock waves cause greater deflections of the skull. The intracranial pressure (ICP) sensors indicated that the peak pressure developed within the brain was greater than the peak side-on external pressure and correlated with surface strain. The bone plates between the lambda, bregma, and midline sutures are probable regions for the greatest flexure to occur. The data provides evidence that skull flexure is a likely candidate for the development of ICP gradients within the rat brain. This dependency of transmitted stress on particular skull dynamics for a given species should be considered by those investigating blast-related neurotrauma using animal models.

Space Shuttle with rail system and aft thrust structure securing solid rocket boosters to external tank

NASA Technical Reports Server (NTRS)

Vonpragenau, G. L. (Inventor)

1984-01-01

The configuration and relationship of the external propellant tank and solid rocket boosters of space transportation systems such as the space shuttle are described. The space shuttle system with the improved propellant tank is shown. The external tank has a forward pressure vessel for liquid hydrogen and an aft pressure vessel for liquid oxygen. The solid rocket boosters are joined together by a thrust frame which extends across and behind the external tank. The thrust of the orbiter's main rocket engines are transmitted to the aft portion of the external tank and the thrust of the solid rocket boosters are transmitted to the aft end of the external tank.

Marrow fat may distribute the energy of impact loading throughout subchondral bone

PubMed Central

Simkin, Peter A

2018-01-01

Abstract Most students of articular mechanics consider impact loads to be compressive forces that are borne by an intraosseous, trabecular scaffold. The possible role of marrow fat, which comprises about 75% of the structure, is generally ignored, and the potential contribution of type 1 collagen, the prototypic tensile protein, is not considered. Here, I question the evidence underlying these omissions and reject the conclusion of exclusive trabecular compression. Instead, I suggest that impact loading pressurizes the fat in subchondral compartments, and those pressures stretch the elastic trabecular walls, which are thereby subjected to tensile loading. The load-driven pressure pulses then diminish as they pass from each compartment to its adjoining neighbours. The resulting pressure gradient distributes the burden throughout the subchondrium, stores energy for ensuing recovery and subjects individual trabeculae only to the net pressure differences between adjacent compartments. PMID:28977578

Evaluation of spinal internal loads and lumbar curvature under holding static load at different trunk and knee positions.

PubMed

Kahrizi, Sedighe; Parnianpour, Mohammad; Firoozabadi, Seyyed Mohammad; Kasemnejad, Anoshirvan; Karimi, Elham

2007-04-01

A study was performed to investigate how different trunk and knee positions while holding static loads affect the lumbar curvature and internal loads on the lumbar spine at L4-L5. Ten healthy male subjects participated in this study. Two inclinometers were used to evaluate the curvature of lumbar spine, lordosis, while a 3D static biomechanical model was used to predict the spinal compression and shear forces at L4-L5. Eighteen static tasks while holding three level of load (0, 10 and 20 kg), two levels of knee position (45 and 180 degrees of flexion) and three levels of trunk position (neutral, 15 and 30 degree of flexion) were simulated for 10 healthy male subjects. The results of this study revealed that the lordosis of lumbar spine changed to kyphosis with increasing weight of load from 0 to 20 kg in trunk flexion position (p<0.05), but in squatting position (45 degrees knee full flexion) the higher load did not affect the curvature. The results of this study suggested, at a more flexed trunk and standing position with higher loads both external moment and internal loads increased significantly at L4-L5 level but with 45 knee flexion external moment and compression force increased and shear force decreased significantly (p < 0.05). Subjects made more effort to maintain stability of the body in squat position. The highest external moment and compression force were computed at flexed knee and trunk position with highest loads. Hence holding weight in this position must be avoided by implementing ergonomic change to the workplace.

Analysing the mechanical performance and growth adaptation of Norway spruce using a non-linear finite-element model and experimental data.

PubMed

Lundström, T; Jonas, T; Volkwein, A

2008-01-01

Thirteen Norway spruce [Picea abies (L.) Karst.] trees of different size, age, and social status, and grown under varying conditions, were investigated to see how they react to complex natural static loading under summer and winter conditions, and how they have adapted their growth to such combinations of load and tree state. For this purpose a non-linear finite-element model and an extensive experimental data set were used, as well as a new formulation describing the degree to which the exploitation of the bending stress capacity is uniform. The three main findings were: material and geometric non-linearities play important roles when analysing tree deflections and critical loads; the strengths of the stem and the anchorage mutually adapt to the local wind acting on the tree crown in the forest canopy; and the radial stem growth follows a mechanically high-performance path because it adapts to prevailing as well as acute seasonal combinations of the tree state (e.g. frozen or unfrozen stem and anchorage) and load (e.g. wind and vertical and lateral snow pressure). Young trees appeared to adapt to such combinations in a more differentiated way than older trees. In conclusion, the mechanical performance of the Norway spruce studied was mostly very high, indicating that their overall growth had been clearly influenced by the external site- and tree-specific mechanical stress.

Efficient vibration mode analysis of aircraft with multiple external store configurations

NASA Technical Reports Server (NTRS)

Karpel, M.

1988-01-01

A coupling method for efficient vibration mode analysis of aircraft with multiple external store configurations is presented. A set of low-frequency vibration modes, including rigid-body modes, represent the aircraft. Each external store is represented by its vibration modes with clamped boundary conditions, and by its rigid-body inertial properties. The aircraft modes are obtained from a finite-element model loaded by dummy rigid external stores with fictitious masses. The coupling procedure unloads the dummy stores and loads the actual stores instead. The analytical development is presented, the effects of the fictitious mass magnitudes are discussed, and a numerical example is given for a combat aircraft with external wing stores. Comparison with vibration modes obtained by a direct (full-size) eigensolution shows very accurate coupling results. Once the aircraft and stores data bases are constructed, the computer time for analyzing any external store configuration is two to three orders of magnitude less than that of a direct solution.

Trunk response and stability in standing under sagittal-symmetric pull-push forces at different orientations, elevations and magnitudes.

PubMed

El Ouaaid, Z; Shirazi-Adl, A; Plamondon, A

2018-03-21

To reduce lifting and associated low back injuries, manual material handling operations often involve pulling-pushing of carts at different weights, orientations, and heights. The loads on spine and risk of injury however need to be investigated. The aim of this study was to evaluate muscle forces, spinal loads and trunk stability in pull-push tasks in sagittal-symmetric, static upright standing posture. Three hand-held load magnitudes (80, 120 and 160 N) at four elevations (0, 20, 40 and 60 cm to the L5-S1) and 24 force directions covering all pull/push orientations were considered. For this purpose, a musculoskeletal finite element model with kinematics measured earlier were used. Results demonstrated that peak spinal forces occur under inclined pull (lift) at upper elevations but inclined push at the lowermost one. Minimal spinal loads, on the other hand, occurred at and around vertical pull directions. Overall, spinal forces closely followed variations in the net external moment of pull-push forces at the L5-S1. Local lumbar muscles were most active in pulls while global extensor muscles in lifts. The trunk stability margin decreased with load elevation except at and around horizontal push; it peaked under pulls and reached minimum at vertical lifts. It also increased with antagonist activity in muscles and intra-abdominal pressure. Results provide insight into the marked effects of variation in the load orientation and elevation on muscle forces, spinal loads and trunk stability and hence offer help in rehabilitation, performance enhancement training and design of safer workplaces. Copyright © 2017 Elsevier Ltd. All rights reserved.

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.;

High-pressure high-temperature phase diagram of gadolinium studied using a boron-doped heater anvil

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

Montgomery, J. M.; Samudrala, G. K.; Vohra, Y. K.

A boron-doped designer heater anvil is used in conjunction with powder x-ray diffraction to collect structural information on a sample of quasi-hydrostatically loaded gadolinium metal up to pressures above 8 GPa and 600 K. The heater anvil consists of a natural diamond anvil that has been surface modified with a homoepitaxially grown chemical-vapor-deposited layer of conducting boron-doped diamond, and is used as a DC heating element. Internally insulating both diamond anvils with sapphire support seats allows for heating and cooling of the high-pressure area on the order of a few tens of seconds. This device is then used to scan the phasemore » diagram of the sample by oscillating the temperature while continuously increasing the externally applied pressure and collecting in situ time-resolved powder diffraction images. In the pressure-temperature range covered in this experiment, the gadolinium sample is observed in its hcp, αSm, and dhcp phases. Under this temperature cycling, the hcp → αSm transition proceeds in discontinuous steps at points along the expected phase boundary. From these measurements (representing only one hour of synchrotron x-ray collection time), a single-experiment equation of state and phase diagram of each phase of gadolinium is presented for the range of 0–10 GPa and 300–650 K.« less

Susceptibility of experimental faults to pore pressure increase: insights from load-controlled experiments on calcite-bearing rocks

NASA Astrophysics Data System (ADS)

Spagnuolo, Elena; Violay, Marie; Nielsen, Stefan; Cornelio, Chiara; Di Toro, Giulio

2017-04-01

Fluid pressure has been indicated as a major factor controlling natural (e.g., L'Aquila, Italy, 2009 Mw 6.3) and induced seismicity (e.g., Wilzetta, Oklahoma, 2011 Mw 5.7). Terzaghi's principle states that the effective normal stress is linearly reduced by a pore pressure (Pf) increase σeff=σn(1 - αPf), where the effective stress parameter α, may be related to the fraction of the fault area that is flooded. A value of α =1 is often used by default, with Pf shifting the Mohr circle towards lower normal effective stresses and anticipating failure on pre-existing faults. However, within a complex fault core of inhomogeneous permeability, α may vary in a yet poorly understood way. To shed light on this problem, we conducted experiments on calcite-bearing rock samples (Carrara marble) at room humidity conditions and in the presence of pore fluids (drained conditions) using a rotary apparatus (SHIVA). A pre-cut fault is loaded by constant shear stress τ under constant normal stress σn=15 MPa until a target value corresponding roughly to the 80 % of the frictional fault strength. The pore pressure Pf is then raised with regular pressure and time steps to induce fault instability. Assuming α=1 and a threshold for instability τp_eff=μp σeff, the experiments reveal that an increase of Pf does not necessarily induce an instability even when the effective strength threshold is largely surpassed (e.g., τp_eff=1.3 μpσeff). This result may indicate that the Pf increase did not instantly diffuse throughout the slip zone, but took a finite time to equilibrate with the external imposed pressure increase due to finite permeability. Under our experimental conditions, a significant departure from α=1 is observed provided that the Pf step is shorter than about < 20s. We interpret this delay as indicative of the diffusion time (td), which is related to fluid penetration length l by l = √ κtd-, where κ is the hydraulic diffusivity on the fault plane. We show that a simple cubic law relates td to hydraulic aperture, pore pressure gradient and injection rate. We redefine α as the ratio between the fluid penetration length and sample dimension L resulting in α = min(√ktd,L) L. Under several pore pressure loading rates this relation yields an approximate hydraulic diffusivity κ ˜10-8 m2 s-1 which is compatible, for example, with a low porosity shale. Our results highlight that a high injection flow rate in fault plane do not necessarily induce seismogenic fault slip: a critical pore penetration length or fluid patch size is necessary to trigger fault instability.

Salinity Gradient Energy from Expansion and Contraction of Poly(allylamine hydrochloride) Hydrogels.

PubMed

Bui, Tri Quang; Cao, Vinh Duy; Do, Nu Bich Duyen; Christoffersen, Trine Eker; Wang, Wei; Kjøniksen, Anna-Lena

2018-06-22

Salinity gradients exhibit a great potential for production of renewable energy. Several techniques such as pressure-retarded osmosis and reverse electrodialysis have been employed to extract this energy. Unfortunately, these techniques are restricted by the high costs of membranes and problems with membrane fouling. However, the expansion and contraction of hydrogels can be a new and cheaper way to harvest energy from salinity gradients since the hydrogels swell in freshwater and shrink in saltwater. We have examined the effect of cross-linker concentration and different external loads on the energy recovered for this type of energy-producing systems. Poly(allylamine hydrochloride) hydrogels were cross-linked with glutaraldehyde to produce hydrogels with excellent expansion and contraction properties. Increasing the cross-linker concentration markedly improved the energy that could be recovered from the hydrogels, especially at high external loads. A swollen hydrogel of 60 g could recover more than 1800 mJ when utilizing a high cross-linker concentration, and the maximum amount of energy produced per gram of polymer was 3.4 J/g. Although more energy is recovered at high cross-linking densities, the maximum amount of energy produced per gram of polymer is highest at an intermediate cross-linking concentration. Energy recovery was reduced when the salt concentration was increased for the low-concentration saline solution. The results illustrate that hydrogels are promising for salinity gradient energy recovery, and that optimizing the systems significantly increases the amount of energy that can be recovered.

Aeroelastic Response of Swept Aircraft Wings in a Compressible Flow Field

NASA Technical Reports Server (NTRS)

Marzocca, Piergiovanni; Librescu, Liviu; Silva, Walter A.

2000-01-01

The present study addresses the subcritical aeroelastic response of swept wings, in various flight speed regimes, to arbitrary time-dependent external excitations. The methodology based on the concept of indicial functions is carried out in time and frequency domains. As a result of this approach, the proper unsteady aerodynamic loads necessary to study the subcritical aeroelastic response of the open/closed loop aeroelastic systems, and of flutter instability, respectively are obtained. Validation of the aeroelastic model is provided, and applications to subcritical aeroelastic response to blast pressure signatures are illustrated. In this context, an original representation of the aeroelastic response in the phase-space is displayed, and pertinent conclusions on the implications of a number of selected parameters of the system are outlined.

The Use of a Block Diagram Simulation Language for Rapid Model Prototyping

NASA Technical Reports Server (NTRS)

Whitlow, Johnathan E.; Engrand, Peter

1996-01-01

The research performed this summer was a continuation of work performed during the 1995 NASA/ASEE Summer Fellowship. The focus of the work was to expand previously generated predictive models for liquid oxygen (LOX) loading into the external fuel tank of the shuttle. The models which were developed using a block diagram simulation language known as VisSim, were evaluated on numerous shuttle flights and found to well in most cases. Once the models were refined and validated, the predictive methods were integrated into the existing Rockwell software propulsion advisory tool (PAT). Although time was not sufficient to completely integrate the models developed into PAT, the ability to predict flows and pressures in the orbiter section and graphically display the results was accomplished.

Effect of an alternate winglet on the pressure and spanwise load distributions of a first generation jet transport wing

NASA Technical Reports Server (NTRS)

Montoya, L. C.; Flechner, S. G.; Jacobs, P. F.

1978-01-01

Pressure and spanwise load distributions on a first-generation jet transport semispan model at subsonic speeds are presented. The wind tunnel data were measured for the wing with and without an alternate winglet. The results show that the winglet affected outboard wing pressure distributions and increased the spanwise loads near the tip.

Effect of boundary conditions and panel geometry on the response of laminated panels subjected to transverse pressure loads

NASA Technical Reports Server (NTRS)

Jegley, Dawn C.

1993-01-01

The behavior of thin laminated flat and curved panels subjected to transverse pressure and inplane loads is considered. The effects of panel geometry, boundary conditions and laminate stacking sequence on the response of panels subjected to transverse pressure loads up to 12.4 N/sq cm is presented. The response of thin laminated panels is evaluated analytically and selected results are compared with test data. A parametric study of the deformation and strain responses of panels with radius of curvature ranging from 20 to 305 cm is presented. The combination of inplane tensile and pressure loads is also considered.

Clinical assessment of auto-positive end-expiratory pressure by diaphragmatic electrical activity during pressure support and neurally adjusted ventilatory assist.

PubMed

Bellani, Giacomo; Coppadoro, Andrea; Patroniti, Nicolò; Turella, Marta; Arrigoni Marocco, Stefano; Grasselli, Giacomo; Mauri, Tommaso; Pesenti, Antonio

2014-09-01

Auto-positive end-expiratory pressure (auto-PEEP) may substantially increase the inspiratory effort during assisted mechanical ventilation. Purpose of this study was to assess whether the electrical activity of the diaphragm (EAdi) signal can be reliably used to estimate auto-PEEP in patients undergoing pressure support ventilation and neurally adjusted ventilatory assist (NAVA) and whether NAVA was beneficial in comparison with pressure support ventilation in patients affected by auto-PEEP. In 10 patients with a clinical suspicion of auto-PEEP, the authors simultaneously recorded EAdi, airway, esophageal pressure, and flow during pressure support and NAVA, whereas external PEEP was increased from 2 to 14 cm H2O. Tracings were analyzed to measure apparent "dynamic" auto-PEEP (decrease in esophageal pressure to generate inspiratory flow), auto-EAdi (EAdi value at the onset of inspiratory flow), and IDEAdi (inspiratory delay between the onset of EAdi and the inspiratory flow). The pressure necessary to overcome auto-PEEP, auto-EAdi, and IDEAdi was significantly lower in NAVA as compared with pressure support ventilation, decreased with increase in external PEEP, although the effect of external PEEP was less pronounced in NAVA. Both auto-EAdi and IDEAdi were tightly correlated with auto-PEEP (r = 0.94 and r = 0.75, respectively). In the presence of auto-PEEP at lower external PEEP levels, NAVA was characterized by a characteristic shape of the airway pressure. In patients with auto-PEEP, NAVA, compared with pressure support ventilation, led to a decrease in the pressure necessary to overcome auto-PEEP, which could be reliably monitored by the electrical activity of the diaphragm before inspiratory flow onset (auto-EAdi).

Synchronization of distributed power grids with the external loading system

NASA Astrophysics Data System (ADS)

Wei, Duqu; Mei, Chuncao

2018-06-01

In this paper, the synchronization between spatially distributed power plants and their supported consumers is studied, where the case of Kuramoto-like model power grids connected to an external permanent magnet synchronous motor (PMSM) is taken as an example. We focus on the dependence of the synchronization on the coupling coefficient. To quantitatively study the synchronization degree, we introduce the order parameter and the frequency deviation to measure the synchronization of the coupled system. It is found that as the external coupling coefficient is increased, the distributed power grids and the loading system become more and more synchronized in space, and the complete synchronization appears at a particular value of external coupling coefficient. Our results may provide a useful tip for analyzing the synchronous ability of distributed power grids.

Momentum Management Tool for Low-Thrust Missions

NASA Technical Reports Server (NTRS)

Swenka, Edward R.; Smith, Brett A.; Vanelli, Charles A.

2010-01-01

A momentum management tool was designed for the Dawn low-thrust interplanetary spacecraft en route to the asteroids Vesta and Ceres, in an effort to better understand the early creation of the solar system. Momentum must be managed to ensure the spacecraft has enough control authority to perform necessary turns and hold a fixed inertial attitude against external torques. Along with torques from solar pressure and gravity-gradients, ion-propulsion engines produce a torque about the thrust axis that must be countered by the four reaction wheel assemblies (RWA). MomProf is a ground operations tool built to address these concerns. The momentum management tool was developed during initial checkout and early cruise, and has been refined to accommodate a wide range of momentum-management issues. With every activity or sequence, wheel speeds and momentum state must be checked to avoid undesirable conditions and use of consumables. MomProf was developed to operate in the MATLAB environment. All data are loaded into MATLAB as a structure to provide consistent access to all inputs by individual functions within the tool. Used in its most basic application, the Dawn momentum tool uses the basic principle of angular momentum conservation, computing momentum in the body frame, and RWA wheel speeds, for all given orientations in the input file. MomProf was designed specifically to be able to handle the changing external torques and frequent de - saturations. Incorporating significant external torques adds complexity since there are various external torques that act under different operational modes.

Thermal Insulation Performance of Textile Structures for Spacesuit Applications at Martian Pressure and Temperature

NASA Technical Reports Server (NTRS)

Orndoff, Evelyne; Trevino, Luis A.

2000-01-01

Protection of astronauts from the extreme temperatures in the space environment has been provided in the past using multi-layer insulation in ultra-high vacuum environments of low earth orbit and the lunar surface. For planetary environments with residual gas atmospheres such as Mars with ambient pressures between 8 to 14 hPa (8 to 14 mbar), new protection techniques are required because of the dominating effect of the ambient gas on heat loss through the insulation. At Mars ambient pressure levels, the heat loss can be excessive at expected suit external temperatures of 172 K with state-of-the-art suit insulation, requiring an active heat source and its accompanying weight and volume penalties. Micro-fibers have been identified as one potential structure to reduce the heat losses, but existing fundamental data on fiber heat transfer at low pressure is lacking for integrated fabric structures. This baseline study presents insulation performance test data at different pressures and fabric loads for selected polyesters and aramids as a function of fiber density, fiber diameter, fabric density, and fabric construction. A set of trend data of thermal conductivity versus ambient pressure is presented for each fiber and fabric construction design to identify the design effects on thermal conductivity at various ambient pressures, and to select a fiber and fabric design for further development as a suit insulation. The trend data also shows the pressure level at which thermal conductivity approaches a minimum, below which no further improvement is possible for a given fiber and fabric design. The pressure levels and resulting thermal conductivities from the trend data can then be compared to the ambient pressure at a planetary surface, Mars for example, to determine if a particular fiber and fabric design has potential as a suit insulation.

Design and implementation of an external quality assessment program for HIV viral load measurements using dried blood spots.

PubMed

Prach, Lisa M; Puren, Adrian; Lippman, Sheri A; Carmona, Sergio; Stephenson, Sophie; Cutler, Ewalde; Barnhart, Scott; Liegler, Teri

2015-03-01

An external quality assurance program was developed for HIV-1 RNA viral load measurements taken from dried blood spots using a reference panel and field-collected specimens. The program demonstrated that accurate and reproducible quantitation can be obtained from field-collected specimens. Residual proviral DNA may confound interpretation in virologically suppressed subjects. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

A theoretical derivation of the dilatancy equation for brittle rocks based on Maxwell model

NASA Astrophysics Data System (ADS)

Li, Jie; Huang, Houxu; Wang, Mingyang

2017-03-01

In this paper, the micro-cracks in the brittle rocks are assumed to be penny shaped and evenly distributed; the damage and dilatancy of the brittle rocks is attributed to the growth and expansion of numerous micro-cracks under the local tensile stress. A single crack's behaviour under the local tensile stress is generalized to all cracks based on the distributed damage mechanics. The relationship between the local tensile stress and the external loading is derived based on the Maxwell model. The damage factor corresponding to the external loading is represented using the p-alpha ( p- α) model. A dilatancy equation that can build up a link between the external loading and the rock dilatancy is established. A test of dilatancy of a brittle rock under triaxial compression is conducted; the comparison between experimental results and our theoretical results shows good consistency.

Mechanical Properties Experimental Study of Engineering Vehicle Refurbished Tire

NASA Astrophysics Data System (ADS)

Qiang, Wang; Xiaojie, Qi; Zhao, Yang; Yunlong, Wang; Guotian, Wang; Degang, Lv

2018-05-01

The vehicle refurbished tire test system was constructed, got load-deformation, load-stiffness, and load-compression ratio property laws of engineering vehicle refurbished tire under the working condition of static state and ground contact, and built radial direction loading deformation mathematics model of 26.5R25 engineering vehicle refurbished tire. The test results show that radial-direction and side-direction deformation value is a little less than that of the new tire. The radial-direction stiffness and compression ratio of engineering vehicle refurbished tire were greatly influenced by radial-direction load and air inflation pressure. When load was certain, radial-direction stiffness would increase with air inflation pressure increasing. When air inflation pressure was certain, compression ratio of engineering vehicle refurbished tire would enlarge with radial-direction load increasing, which was a little less than that of the new and the same type tire. Aging degree of old car-case would exert a great influence on deformation property of engineering vehicle refurbished tire, thus engineering vehicle refurbished tires are suitable to the working condition of low tire pressure and less load.

A facility for long-term Mars simulation experiments: the Mars Environmental Simulation Chamber (MESCH).

PubMed

Jensen, Lars Liengaard; Merrison, Jonathan; Hansen, Aviaja Anna; Mikkelsen, Karina Aarup; Kristoffersen, Tommy; Nørnberg, Per; Lomstein, Bente Aagaard; Finster, Kai

2008-06-01

We describe the design, construction, and pilot operation of a Mars simulation facility comprised of a cryogenic environmental chamber, an atmospheric gas analyzer, and a xenon/mercury discharge source for UV generation. The Mars Environmental Simulation Chamber (MESCH) consists of a double-walled cylindrical chamber. The double wall provides a cooling mantle through which liquid N(2) can be circulated. A load-lock system that consists of a small pressure-exchange chamber, which can be evacuated, allows for the exchange of samples without changing the chamber environment. Fitted within the MESCH is a carousel, which holds up to 10 steel sample tubes. Rotation of the carousel is controlled by an external motor. Each sample in the carousel can be placed at any desired position. Environmental data, such as temperature, pressure, and UV exposure time, are computer logged and used in automated feedback mechanisms, enabling a wide variety of experiments that include time series. Tests of the simulation facility have successfully demonstrated its ability to produce temperature cycles and maintain low temperature (down to -140 degrees C), low atmospheric pressure (5-10 mbar), and a gas composition like that of Mars during long-term experiments.

A Facility for Long-Term Mars Simulation Experiments: The Mars Environmental Simulation Chamber (MESCH)

NASA Astrophysics Data System (ADS)

Jensen, Lars Liengaard; Merrison, Jonathan; Hansen, Aviaja Anna; Mikkelsen, Karina Aarup; Kristoffersen, Tommy; Nørnberg, Per; Lomstein, Bente Aagaard; Finster, Kai

2008-06-01

We describe the design, construction, and pilot operation of a Mars simulation facility comprised of a cryogenic environmental chamber, an atmospheric gas analyzer, and a xenon/mercury discharge source for UV generation. The Mars Environmental Simulation Chamber (MESCH) consists of a double-walled cylindrical chamber. The double wall provides a cooling mantle through which liquid N2 can be circulated. A load-lock system that consists of a small pressure-exchange chamber, which can be evacuated, allows for the exchange of samples without changing the chamber environment. Fitted within the MESCH is a carousel, which holds up to 10 steel sample tubes. Rotation of the carousel is controlled by an external motor. Each sample in the carousel can be placed at any desired position. Environmental data, such as temperature, pressure, and UV exposure time, are computer logged and used in automated feedback mechanisms, enabling a wide variety of experiments that include time series. Tests of the simulation facility have successfully demonstrated its ability to produce temperature cycles and maintain low temperature (down to -140°C), low atmospheric pressure (5 10 mbar), and a gas composition like that of Mars during long-term experiments.

Characterization of size-dependent mechanical properties of tip-growing cells using a lab-on-chip device.

PubMed

Hu, Chengzhi; Munglani, Gautam; Vogler, Hannes; Ndinyanka Fabrice, Tohnyui; Shamsudhin, Naveen; Wittel, Falk K; Ringli, Christoph; Grossniklaus, Ueli; Herrmann, Hans J; Nelson, Bradley J

2016-12-20

Quantification of mechanical properties of tissues, living cells, and cellular components is crucial for the modeling of plant developmental processes such as mechanotransduction. Pollen tubes are tip-growing cells that provide an ideal system to study the mechanical properties at the single cell level. In this article, a lab-on-a-chip (LOC) device is developed to quantitatively measure the biomechanical properties of lily (Lilium longiflorum) pollen tubes. A single pollen tube is fixed inside the microfluidic chip at a specific orientation and subjected to compression by a soft membrane. By comparing the deformation of the pollen tube at a given external load (compressibility) and the effect of turgor pressure on the tube diameter (stretch ratio) with finite element modeling, its mechanical properties are determined. The turgor pressure and wall stiffness of the pollen tubes are found to decrease considerably with increasing initial diameter of the pollen tubes. This observation supports the hypothesis that tip-growth is regulated by a delicate balance between turgor pressure and wall stiffness. The LOC device is modular and adaptable to a variety of cells that exhibit tip-growth, allowing for the straightforward measurement of mechanical properties.

The analysis of metabolites in human sweat: analytical methods and potential application to investigation of pressure ischaemia of soft tissues.

PubMed

Taylor, R P; Polliack, A A; Bader, D L

1994-01-01

A straightforward technique was developed for sweat collection applicable to tissues subjected to external load without introducing distortion of underlying tissues, and for analysis of six metabolites in the collected sweat. Chloride was measured colorimetrically and lactate, urea and urate by enzymatic methods on a centrifugal analyser. Sodium and potassium were measured by flame photometry. The methods showed good precision, recovery and linearity. To assess the technique sweat was collected: (i) from the sacrum, ischium, forearm and calf in healthy individuals at 32 degrees C for 1 h; (ii) from the sacrum of healthy subjects at ambient temperature for 9 h; (iii) at ambient temperature from the sacrum of a patient with a history of pressure sores. Sweat rates were greater at the sacrum and ischium than the calf or forearm. There were differences in the concentrations of lactate and urea between sites but these were smaller when expressed as amount secreted. Sweat rates were significantly lower in groups (ii) and (iii), but sweat could be collected reliably. This technique has potential clinical application to the investigation of susceptibility to pressure sores.

Modeling of Propagation of Interacting Cracks Under Hydraulic Pressure Gradient

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

Huang, Hai; Mattson, Earl Douglas; Podgorney, Robert Karl

A robust and reliable numerical model for fracture initiation and propagation, which includes the interactions among propagating fractures and the coupling between deformation, fracturing and fluid flow in fracture apertures and in the permeable rock matrix, would be an important tool for developing a better understanding of fracturing behaviors of crystalline brittle rocks driven by thermal and (or) hydraulic pressure gradients. In this paper, we present a physics-based hydraulic fracturing simulator based on coupling a quasi-static discrete element model (DEM) for deformation and fracturing with conjugate lattice network flow model for fluid flow in both fractures and porous matrix. Fracturingmore » is represented explicitly by removing broken bonds from the network to represent microcracks. Initiation of new microfractures and growth and coalescence of the microcracks leads to the formation of macroscopic fractures when external and/or internal loads are applied. The coupled DEM-network flow model reproduces realistic growth pattern of hydraulic fractures. In particular, simulation results of perforated horizontal wellbore clearly demonstrate that elastic interactions among multiple propagating fractures, fluid viscosity, strong coupling between fluid pressure fluctuations within fractures and fracturing, and lower length scale heterogeneities, collectively lead to complicated fracturing patterns.« less

Macro- and meiofaunal community features in the critical environmental system of a tourist harbour (Rapallo, Ligurian Sea, NW Mediterranean).

PubMed

Harriague, Anabella Covazzi; Albertelli, Giancarlo; Misic, Cristina

2012-03-01

Two samplings were carried out in a tourist harbour, during low and high touristic activity periods, to study the macro- and meiofaunal communities in relation to the environmental features. A multivariate analysis showed close relationships: the maritime traffic disturbance and the food quality and availability drive the spatial differences of the assemblages, dividing the area into three sub-areas: the area near the Boate torrent that empties into the harbour, the harbour proper, and the external area (just outside the harbour). Macro- and meiofauna showed notably different temporal trends, indicating competition for the resources and the higher sensitivity of the macrofauna to environmental pressures. The macrofauna strongly decreased as a response to heavier harbour activities, with increasing turbidity also affecting the external station outside the harbour. Finally, comparing the macrofaunal communities to those sampled in the same area 10 years before, we found that their abundance, richness and biomass had notably decreased, highlighting the worsening of the harbour environment due to the increased organic load and turbidity. Copyright © 2011 Elsevier Ltd. All rights reserved.

Kinematic evaluation of patients with total and reverse shoulder arthroplasty during rehabilitation exercises with different loads.

PubMed

de Toledo, Joelly Mahnic; Loss, Jefferson Fagundes; Janssen, Thomas W; van der Scheer, Jan W; Alta, Tjarco D; Willems, W Jaap; Veeger, DirkJan H E J

2012-10-01

Following shoulder arthroplasty, any well-planned rehabilitation program should include muscle strengthening. However, it is not always clear how different external loads influence shoulder kinematics in patients with shoulder prostheses. The objective of this study was to describe shoulder kinematics and determine the contribution of the scapulothoracic joint to total shoulder motion of patients with total and reverse shoulder arthroplasties and of healthy individuals during rehabilitation exercises (anteflexion and elevation in the scapular plane) using different loading conditions (without external load, 1 kg and elastic resistance). Shoulder motions were measured using an electromagnetic tracking device. A force transducer was used to record force signals during loaded conditions using elastic resistance. Statistical comparisons were made using a three-way repeated-measures analysis of variance with a Bonferroni post hoc testing. The scapula contributed more to movement of the arm in subjects with prostheses compared to healthy subjects. The same applies for loaded conditions (1 kg and elastic resistance) relative to unloaded tasks. For scapular internal rotation, upward rotation and posterior tilt no significant differences among groups were found during both exercises. Glenohumeral elevation angles during anteflexion were significantly higher in the total shoulder arthroplasty group compared to the reverse shoulder arthroplasty group. Differences in contribution of the scapula to total shoulder motion between patients with different types of arthroplasties were not significant. However, compared to healthy subjects, they were. Furthermore, scapular kinematics of patients with shoulder arthroplasty was influenced by implementation of external loads, but not by the type of load. Copyright © 2012 Elsevier Ltd. All rights reserved.

Foot loading characteristics during three fencing-specific movements.

PubMed

Trautmann, Caroline; Martinelli, Nicolo; Rosenbaum, Dieter

2011-12-01

Plantar pressure characteristics during fencing movements may provide more specific information about the influence of foot loading on overload injury patterns. Twenty-nine experienced fencers participated in the study. Three fencing-specific movements (lunge, advance, retreat) and normal running were performed with three different shoe models: Ballestra (Nike, USA), Adistar Fencing Lo (Adidas, Germany), and the fencers' own shoes. The Pedar system (Novel, Munich, Germany) was used to collect plantar pressures at 50 Hz. Peak pressures, force-time integrals and contact times for five foot regions were compared between four athletic tasks in the lunge leg and supporting leg. Plantar pressure analysis revealed characteristic pressure distribution patterns for the fencing movements. For the lunge leg, during the lunge and advance movements the heel is predominantly loaded; during retreat, it is the hallux. For the supporting leg, during the lunge and advance movements the forefoot is predominantly loaded; during retreat, it is the hallux. Fencing-specific movements load the plantar surface in a distinct way compared with running. An effective cushioning in the heel and hallux region would help to minimize foot loading during fencing-specific movements.

Fiber pressure sensors based on periodical mode coupling effects

NASA Astrophysics Data System (ADS)

Lotem, Haim; Wang, Wen C.; Wang, Michael; Schaafsma, David; Skolnick, Bob; Grebel, Haim

2005-05-01

Fiber optic sensor technology offers the possibility of implementing low weight, high performance and cost effective health and damage assessment for infrastructure elements. Common fiber sensors are based on the effect of external action on the spectral response of a Fabry-Perot or a Bragg grating section, or on the modal dynamics in multimode (MM) fiber. In the latter case, the fiber itself acts as the sensor, giving it the potential for large range coverage. We were interested in this type of sensor because of its cost advantage in monitoring structural health. In the course of the research, a new type of a rugged modal filter device, based on off-center splicing, was developed. This device, in combination with a MM fiber, was found to be a potential single point-pressure sensing device. Additionally, by translating the pressing point along a MM sensing fiber with a constant load and speed, a sinusoidal intensity modulation was observed. This harmonic behavior, during load translation, is explained by the theory of mode coupling and dispersion. The oscillation period, L~0.43. mm, obtained at 980 nm in a Corning SMF-28 fiber, corresponds to the wavevector difference, Db, between the two-coupled modes, by L = 2p/Db. An additional outcome of the present research is the observation that the response of the loaded MM fiber is strongly dependent on the polarization state of the light traveling along the MM fiber due to different response of the modes to polarization active elements. Our main conclusions are that in MM fiber optic sensor design, special cautions need to be taken in order to stabilize the system, and that the sensitivity along a MM fiber sensor is periodic with a period of ~ 0.4 - 0.5 mm, depending on various fiber parameters and excited modes.

The effect of ignition location on explosion venting of hydrogen-air mixtures

NASA Astrophysics Data System (ADS)

Cao, Y.; Guo, J.; Hu, K.; Xie, L.; Li, B.

2017-07-01

The effect of ignition location and vent burst pressure on the internal pressure-time history and external flame propagation was investigated for vented explosions of hydrogen-air mixtures in a small cylindrical vessel. A high-speed camera was used to record videos of the external flame while pressure transducers were used to record pressure-time histories. It was found that central ignition always leads to the maximum internal peak overpressure, and front ignition resulted in the lowest value of internal peak overpressure. The internal peak overpressures are increased corresponding to the increase in the vent burst pressure in the cases of central and rear ignition. Because of the effect of acoustic oscillations, the phenomenon of oscillations is observed in the internal pressure profile for the case of front ignition. The pressure oscillations for the cases of rear and central ignition are triggered by external explosions. The behavior of flames outside the chamber is significantly associated with the internal pressure of the chamber so that the velocity of the jet flame is closely related to the internal overpressure peak.

Tensile testing grips ensure uniform loading of bimetal tubing specimens

NASA Technical Reports Server (NTRS)

Driscol, S. D.; Hunt, V.

1968-01-01

Tensile testing grip uniformly distributes stresses to the internal and external tube of bimetal tubing specimens. The grip is comprised of a slotted external tube grip, a slotted internal tube grip, a machine bolt and nut, an internal grip expansion cone, and an external grip compression nut.

Nontidal Loading Applied in VLBI Geodetic Analysis

NASA Astrophysics Data System (ADS)

MacMillan, D. S.

2015-12-01

We investigate the application of nontidal atmosphere pressure, hydrology, and ocean loading series in the analysis of VLBI data. The annual amplitude of VLBI scale variation is reduced to less than 0.1 ppb, a result of the annual components of the vertical loading series. VLBI site vertical scatter and baseline length scatter is reduced when these loading models are applied. We operate nontidal loading services for hydrology loading (GLDAS model), atmospheric pressure loading (NCEP), and nontidal ocean loading (JPL ECCO model). As an alternative validation, we compare these loading series with corresponding series generated by other analysis centers.

Effect of amplitude and duration of impulsive pressure on endothelial permeability in in vitro fluid percussion trauma

PubMed Central

2014-01-01

Background Intracranial pressure changes during head impact cause brain injuries such as vasogenic edema and cerebral contusion. However, the influence of impulsive pressure on endothelial function has not yet been fully studied in vitro. In this study, we developed a pressure loading device that produced positive and negative pressures by modifying an in vitro fluid percussion model and examined the effects of the amplitude and duration of the pressures on endothelial permeability. Methods Human umbilical vein endothelial cells were subjected to three types of positive pressure (average amplitude/average duration of 352 kPa/23 ms, 73 kPa/27 ms, and 70 kPa/44 ms) and three types of negative pressure (−72 kPa/41 ms, −67 kPa/104 ms, and −91 kPa/108 ms), and the transendothelial electrical resistance (TEER) was measured between 15 min and 24 h after pressure loading for quantifying the formation of an integral monolayer of endothelial cells. After loading, vascular endothelial- (VE-) cadherin, an endothelium-specific cell-cell adhesion molecule involved in endothelial barrier function, was stained and observed using fluorescence microscopy. Results The pressure loading device could produce positive pressure pulses with amplitudes of 53–1348 kPa and durations of 9–29.1 ms and negative pressure pulses with amplitudes of −52–−93 kPa and durations of 42.9–179.5 ms. The impulsive pressure reduced the TEER associated with the change in VE-cadherin localization. Additionally, TEER decreased considerably at 15 min and 6 h post-loading, with these changes being significant in positive pressure with larger amplitude and shorter duration and in all types of negative pressures compared to pre-loading. Conclusions The changes in intracranial pressure during head impact impair endothelial barrier function by the disruption of the integrity of endothelial cell-cell junctions, and the degree of increase in endothelial permeability depends on the amplitude, duration, and direction (compressive and tensile) of the impulsive pressure. PMID:24739360

Elastic-Plastic Nonlinear Response of a Space Shuttle External Tank Stringer. Part 2; Thermal and Mechanical Loadings

NASA Technical Reports Server (NTRS)

Knight, Norman F., Jr.; Warren, Jerry E.; Elliott, Kenny B.; Song, Kyongchan; Raju, Ivatury S.

2012-01-01

Elastic-plastic, large-deflection nonlinear thermo-mechanical stress analyses are performed for the Space Shuttle external tank s intertank stringers. Detailed threedimensional finite element models are developed and used to investigate the stringer s elastic-plastic response for different thermal and mechanical loading events from assembly through flight. Assembly strains caused by initial installation on an intertank panel are accounted for in the analyses. Thermal loading due to tanking was determined to be the bounding loading event. The cryogenic shrinkage caused by tanking resulted in a rotation of the intertank chord flange towards the center of the intertank, which in turn loaded the intertank stringer feet. The analyses suggest that the strain levels near the first three fasteners remain sufficiently high that a failure may occur. The analyses also confirmed that the installation of radius blocks on the stringer feet ends results in an increase in the stringer capability.

Validation of a dynamic linked segment model to calculate joint moments in lifting.

PubMed

de Looze, M P; Kingma, I; Bussmann, J B; Toussaint, H M

1992-08-01

A two-dimensional dynamic linked segment model was constructed and applied to a lifting activity. Reactive forces and moments were calculated by an instantaneous approach involving the application of Newtonian mechanics to individual adjacent rigid segments in succession. The analysis started once at the feet and once at a hands/load segment. The model was validated by comparing predicted external forces and moments at the feet or at a hands/load segment to actual values, which were simultaneously measured (ground reaction force at the feet) or assumed to be zero (external moments at feet and hands/load and external forces, beside gravitation, at hands/load). In addition, results of both procedures, in terms of joint moments, including the moment at the intervertebral disc between the fifth lumbar and first sacral vertebra (L5-S1), were compared. A correlation of r = 0.88 between calculated and measured vertical ground reaction forces was found. The calculated external forces and moments at the hands showed only minor deviations from the expected zero level. The moments at L5-S1, calculated starting from feet compared to starting from hands/load, yielded a coefficient of correlation of r = 0.99. However, moments calculated from hands/load were 3.6% (averaged values) and 10.9% (peak values) higher. This difference is assumed to be due mainly to erroneous estimations of the positions of centres of gravity and joint rotation centres. The estimation of the location of L5-S1 rotation axis can affect the results significantly. Despite the numerous studies estimating the load on the low back during lifting on the basis of linked segment models, only a few attempts to validate these models have been made. This study is concerned with the validity of the presented linked segment model. The results support the model's validity. Effects of several sources of error threatening the validity are discussed. Copyright © 1992. Published by Elsevier Ltd.

The effects of loaded and unloaded high-velocity resistance training on functional fitness among community-dwelling older adults.

PubMed

Glenn, Jordan M; Gray, Michelle; Binns, Ashley

2015-11-01

Physical function declines up to 4% per year after the age of 65. High-velocity training is important for maintaining muscular power and ultimately, physical function; however, whether performing high-velocity training without external resistance increases functional fitness among older adults remains unclear. The purpose of this investigation was to evaluate loaded and unloaded high-velocity training on lower body muscular power and functional fitness in older adults. Fifty-seven community-dwelling older adults (n = 16 males, n = 41 females) participated in this study. Inclusion criteria comprised ≥65 years of age, ≥24 on the Mini-mental state examination and no falls within past year. Two groups completed a 20-week high-velocity training intervention. The non-weighted group (UNLOAD, n = 27) performed the protocol without external load while the intervention group (LOAD, n = 30) used external loads via exercise machines. Functional fitness was assessed using the Short Physical Performance Battery (SPPB), Senior Fitness Test (SFT), hand-grip and lower body power measures. Multivariate ANOVA revealed that both groups had significant improvements for average (17.21%) and peak (9.26%) lower body power, along with the SFT arm curl (16.94%), chair stand (20.10%) and 8 ft. up-and-go (15.67%). Improvements were also noticed for SPPB 8 ft. walk (25.21%). However, improvements for all functional fitness measures were independent of training group. Unloaded high-velocity training increased functional fitness and power the same as loaded training. The ability of high-velocity movements to elicit gains in functional fitness without external loads may help health professionals develop fitness programs when time/space is limiting factor. © The Author 2015. Published by Oxford University Press on behalf of the British Geriatrics Society. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Tolerance of Artemia to static and shock pressure loading

NASA Astrophysics Data System (ADS)

Fitzmaurice, B. C.; Appleby-Thomas, G. J.; Painter, J. D.; Ono, F.; McMillan, P. F.; Hazael, R.; Meersman, F.

2017-10-01

Hydrostatic and hydrodynamic pressure loading has been applied to unicellular organisms for a number of years due to interest from food technology and extremophile communities. There is also an emerging interest in the response of multicellular organisms to high pressure conditions. Artemia salina is one such organism. Previous experiments have shown a marked difference in the hatching rate of these organisms after exposure to different magnitudes of pressure, with hydrostatic tests showing hatching rates at pressures up to several GPa, compared to dynamic loading that resulted in comparatively low survival rates at lower pressure magnitudes. In order to begin to investigate the origin of this difference, the work presented here has focussed on the response of Artemia salina to (quasi) one-dimensional shock loading. Such experiments were carried out using the plate-impact technique in order to create a planar shock front. Artemia cysts were investigated in this manner along with freshly hatched larvae (nauplii). The nauplii and cysts were observed post-shock using optical microscopy to detect motility or hatching, respectively. Hatching rates of 18% were recorded at pressures reaching 1.5 GPa, as determined with the aid of numerical models. Subjecting Artemia to quasi-one-dimensional shock loading offers a way to more thoroughly explore the shock pressure ranges these organisms can survive.

The effect of external coaptation on plate deformation in an ex vivo model of canine pancarpal arthrodesis.

PubMed

Woods, S; Wallace, R J; Mosley, J R

2012-01-01

Since external coaptation is applied clinically to prevent plate failure during healing in canine pancarpal arthrodesis (PCA), we tested the hypothesis that external coaptation does not significantly reduce plate strain in an experimental ex vivo model of canine PCA. Ten thoracic limbs from healthy Greyhounds euthanatized for reasons un- related to the study were harvested and the carpus was stabilised with a dorsally applied 2.7/3.5 mm hybrid PCA plate. The strain in the plate adjacent to the most distal radial screw hole (R4) and the radial carpal bone (RCB) screw hole was measured as the limbs were loaded axially to a load that approximated that of controlled walking. Each limb was tested with and without external coaptation in place. Mean strain amplitude at the RCB was -177.2 με (± 20.78) without external coaptation. Following cast application, strain reduced significantly to -34.7 με (± 9.84) (p <0.002). Mean strain at R4 was -89.4 με (± 22.10) without external support and -66.9 με (± 10.74) following application of a cast. This reduction in recorded strain was not statistically significant. The application of a cast to the distal portion of the limb significantly reduced strain in the 2.7/3.5 mm hybrid PCA plate, but the magnitude of the measured strain was low, suggesting that fatigue damage is unlikely to accumulate as a result of this type of loading and that external coaptation may not be necessary to prevent fatigue failure of the plate.

Finite element modelling of sound transmission from outer to inner ear.

PubMed

Areias, Bruno; Santos, Carla; Natal Jorge, Renato M; Gentil, Fernanda; Parente, Marco Pl

2016-11-01

The ear is one of the most complex organs in the human body. Sound is a sequence of pressure waves, which propagates through a compressible media such as air. The pinna concentrates the sound waves into the external auditory meatus. In this canal, the sound is conducted to the tympanic membrane. The tympanic membrane transforms the pressure variations into mechanical displacements, which are then transmitted to the ossicles. The vibration of the stapes footplate creates pressure waves in the fluid inside the cochlea; these pressure waves stimulate the hair cells, generating electrical signals which are sent to the brain through the cochlear nerve, where they are decoded. In this work, a three-dimensional finite element model of the human ear is developed. The model incorporates the tympanic membrane, ossicular bones, part of temporal bone (external auditory meatus and tympanic cavity), middle ear ligaments and tendons, cochlear fluid, skin, ear cartilage, jaw and the air in external auditory meatus and tympanic cavity. Using the finite element method, the magnitude and the phase angle of the umbo and stapes footplate displacement are calculated. Two slightly different models are used: one model takes into consideration the presence of air in the external auditory meatus while the other does not. The middle ear sound transfer function is determined for a stimulus of 60 dB SPL, applied to the outer surface of the air in the external auditory meatus. The obtained results are compared with previously published data in the literature. This study highlights the importance of external auditory meatus in the sound transmission. The pressure gain is calculated for the external auditory meatus.

Integrating a hip belt with body armour reduces the magnitude and changes the location of shoulder pressure and perceived discomfort in soldiers.

PubMed

Lenton, Gavin K; Doyle, Tim L A; Saxby, David J; Billing, Dan; Higgs, Jeremy; Lloyd, David G

2018-04-01

Soldiers carry heavy loads that may cause general discomfort, shoulder pain and injury. This study assessed if new body armour designs that incorporated a hip belt reduced shoulder pressures and improved comfort. Twenty-one Australian soldiers completed treadmill walking trials wearing six different body armours with two different loads (15 and 30 kg). Contact pressures applied to the shoulders were measured using pressure pads, and qualitative assessment of comfort and usability were acquired from questionnaires administered after walking trials. Walking with hip belt compared to no hip belt armour resulted in decreased mean and maximum shoulder pressures (p < 0.005), and 30% fewer participants experiencing shoulder discomfort (p < 0.005) in best designs, although hip discomfort did increase. Laterally concentrated shoulder pressures were associated with 1.34-times greater likelihood of discomfort (p = 0.026). Results indicate body armour and backpack designs should integrate a hip belt and distribute load closer to shoulder midline to reduce load carriage discomfort and, potentially, injury risk. Practitioner Summary: Soldiers carry heavy loads that increase their risk of discomfort and injury. New body armour designs are thought to ease this burden by transferring the load to the hips. This study demonstrated that designs incorporating a hip belt reduced shoulder pressure and shoulder discomfort compared to the current armour design.

Salt loading produces severe renal hemodynamic dysfunction independent of arterial pressure in spontaneously hypertensive rats.

PubMed

Matavelli, Luis C; Zhou, Xiaoyan; Varagic, Jasmina; Susic, Dinko; Frohlich, Edward D

2007-02-01

We have previously shown that salt excess has adverse cardiac effects in spontaneously hypertensive rats (SHR), independent of its increased arterial pressure; however, the renal effects have not been reported. In the present study we evaluated the role of three levels of salt loading in SHR on renal function, systemic and renal hemodynamics, and glomerular dynamics. At 8 wk of age, rats were given a 4% (n = 11), 6% (n = 9), or 8% (n = 11) salt-load diet for the ensuing 8 wk; control rats (n = 11) received standard chow (0.6% NaCl). Rats had weekly 24-h proteinuria and albuminuria quantified. At the end of salt loading, all rats had systemic and renal hemodynamics measured; glomerular dynamics were specially studied by renal micropuncture in the control, 4% and 6% salt-loaded rats. Proteinuria and albuminuria progressively increased by the second week of salt loading in the 6% and 8% salt-loaded rats. Mean arterial pressure increased minimally, and glomerular filtration rate decreased in all salt-loaded rats. The 6% and 8% salt-loaded rats demonstrated decreased renal plasma flow and increased renal vascular resistance and serum creatinine concentration. Furthermore, 4% and 6% salt-loaded rats had diminished single-nephron plasma flow and increased afferent and efferent arteriolar resistances; glomerular hydrostatic pressure also increased in the 6% salt-loaded rats. In conclusion, dietary salt loading as low as 4% dramatically deteriorated renal function, renal hemodynamics, and glomerular dynamics in SHR independent of a minimal further increase in arterial pressure. These findings support the concept of a strong independent causal relationship between salt excess and cardiovascular and renal injury.

The proprioceptive reflex control of the intercostal muscles during their voluntary activation

PubMed Central

Davis, J. Newsom; Sears, T. A.

1970-01-01

1. A quantitative study has been made of the reflex effects of sudden changes in mechanical load on contracting human intercostal muscles during willed breathing movements involving the chest wall. Averaging techniques were applied to recordings of electromyogram (EMG) and lung volume, and to other parameters of breathing. 2. Load changes were effected for brief periods (10-150 msec) at any predetermined lung volume by sudden connexion of the airway to a pressure source variable between ± 80 cm H2O so that respiratory movement could be either assisted or opposed. In some experiments airway resistance was suddenly reduced by porting from a high to a low resistance external airway. 3. Contracting inspiratory and expiratory intercostal muscles showed a `silent period' with unloading which is attributed to the sudden withdrawal from intercostal motoneurones of monosynaptic excitation of muscle spindle origin. 4. For both inspiratory and expiratory intercostal muscles the typical immediate effect of an increase in load was an inhibitory response (IR) with a latency of about 22 msec followed by an excitatory response (ER) with a latency of 50-60 msec. 5. It was established using brief duration stimuli (< 40 msec) that the IR depended on mechanical events associated with the onset of stimulation, whereas stimuli greater than 40 msec in duration were required to evoke the ER. 6. For constant expiratory flow rate and a constant load, the ER of expiratory intercostal muscles increased as lung volume decreased within the limits set by maximal activation of the motoneurone pool as residual volume was approached. 7. The ER to a constant load increased directly with the expiratory flow rate at which the load applied, also within limits set by maximal activation of the motoneurone pool. 8. For a given load, the ER during phonation was greater than that occurring at a similar expiratory flow rate without phonation when the resistance of the phonating larynx was mimicked by an external airway resistance. 9. It is argued that the IR is due to autogenetic inhibition arising from tendon organs and that the ER is due to autogenetic excitation arising from intercostal muscle spindles. 10. The initial dominance of inhibition in this dual proprioceptive reflex control was not predicted by the servo theory. It is proposed that the reflex pathways subserving autogenetic inhibition are under a centrifugal control which determines in relation to previous experience (learning) the conditions under which autogenetic facilitation is allowed. PMID:5499805

Quantitative Structure – Property Relationship Modeling of Remote Liposome Loading Of Drugs

PubMed Central

Cern, Ahuva; Golbraikh, Alexander; Sedykh, Aleck; Tropsha, Alexander; Barenholz, Yechezkel; Goldblum, Amiram

2012-01-01

Remote loading of liposomes by trans-membrane gradients is used to achieve therapeutically efficacious intra-liposome concentrations of drugs. We have developed Quantitative Structure Property Relationship (QSPR) models of remote liposome loading for a dataset including 60 drugs studied in 366 loading experiments internally or elsewhere. Both experimental conditions and computed chemical descriptors were employed as independent variables to predict the initial drug/lipid ratio (D/L) required to achieve high loading efficiency. Both binary (to distinguish high vs. low initial D/L) and continuous (to predict real D/L values) models were generated using advanced machine learning approaches and five-fold external validation. The external prediction accuracy for binary models was as high as 91–96%; for continuous models the mean coefficient R2 for regression between predicted versus observed values was 0.76–0.79. We conclude that QSPR models can be used to identify candidate drugs expected to have high remote loading capacity while simultaneously optimizing the design of formulation experiments. PMID:22154932

Biomechanical consequences of a tear of the posterior root of the medial meniscus. Surgical technique.

PubMed

Harner, Christopher D; Mauro, Craig S; Lesniak, Bryson P; Romanowski, James R

2009-10-01

Tears of the posterior root of the medial meniscus are becoming increasingly recognized. They can cause rapidly progressive arthritis, yet their biomechanical effects are not understood. The goal of this study was to determine the effects of posterior root tears of the medial meniscus and their repairs on tibiofemoral joint contact pressure and kinematics. Nine fresh-frozen cadaver knees were used. An axial load of 1000 N was applied with a custom testing jig at each of four knee-flexion angles: 0 degrees , 30 degrees , 60 degrees , and 90 degrees . The knees were otherwise unconstrained. Four conditions were tested: (1) intact, (2) a posterior root tear of the medial meniscus, (3) a repaired posterior root tear, and (4) a total medial meniscectomy. Fuji pressure-sensitive film was used to record the contact pressure and area for each testing condition. Kinematic data were obtained by using a robotic arm to record the position of the knees for each loading condition. Three-dimensional knee kinematics were analyzed with custom programs with use of previously described transformations. The measured variables were axial rotation, varus angulation, lateral translation, and anterior translation. In the medial compartment, a posterior root tear of the medial meniscus caused a 25% increase in peak contact pressure compared with that found in the intact condition (p < 0.001). Repair restored the peak contact pressure to normal. No difference was detected between the peak contact pressure after the total medial meniscectomy and that associated with the root tear. The peak contact pressure in the lateral compartment after the total medial meniscectomy was up to 13% greater than that for all other conditions (p = 0.026). Significant increases in external rotation and lateral tibial translation, compared with the values in the intact knee, were observed in association with the posterior root tear (2.98 degrees and 0.84 mm, respectively) and the meniscectomy (4.45 degrees and 0.80 mm, respectively), and these increases were corrected by the repair. This study demonstrated significant changes in contact pressure and knee joint kinematics due to a posterior root tear of the medial meniscus. Root repair was successful in restoring joint biomechanics to within normal conditions.

Biomechanical consequences of a tear of the posterior root of the medial meniscus. Similar to total meniscectomy.

PubMed

Allaire, Robert; Muriuki, Muturi; Gilbertson, Lars; Harner, Christopher D

2008-09-01

Tears of the posterior root of the medial meniscus are becoming increasingly recognized. They can cause rapidly progressive arthritis, yet their biomechanical effects are not understood. The goal of this study was to determine the effects of posterior root tears of the medial meniscus and their repairs on tibiofemoral joint contact pressure and kinematics. Nine fresh-frozen cadaver knees were used. An axial load of 1000 N was applied with a custom testing jig at each of four knee-flexion angles: 0 degrees, 30 degrees, 60 degrees, and 90 degrees. The knees were otherwise unconstrained. Four conditions were tested: (1) intact, (2) a posterior root tear of the medial meniscus, (3) a repaired posterior root tear, and (4) a total medial meniscectomy. Fuji pressure-sensitive film was used to record the contact pressure and area for each testing condition. Kinematic data were obtained by using a robotic arm to record the position of the knees for each loading condition. Three-dimensional knee kinematics were analyzed with custom programs with use of previously described transformations. The measured variables were axial rotation, varus angulation, lateral translation, and anterior translation. In the medial compartment, a posterior root tear of the medial meniscus caused a 25% increase in peak contact pressure compared with that found in the intact condition (p < 0.001). Repair restored the peak contact pressure to normal. No difference was detected between the peak contact pressure after the total medial meniscectomy and that associated with the root tear. The peak contact pressure in the lateral compartment after the total medial meniscectomy was up to 13% greater than that for all other conditions (p = 0.026). Significant increases in external rotation and lateral tibial translation, compared with the values in the intact knee, were observed in association with the posterior root tear (2.98 degrees and 0.84 mm, respectively) and the meniscectomy (4.45 degrees and 0.80 mm, respectively), and these increases were corrected by the repair. This study demonstrated significant changes in contact pressure and knee joint kinematics due to a posterior root tear of the medial meniscus. Root repair was successful in restoring joint biomechanics to within normal conditions.

Internal and External Match Loads of University-Level Soccer Players: A Comparison Between Methods.

PubMed

Sparks, Martinique; Coetzee, Ben; Gabbett, Tim J

2017-04-01

Sparks, M, Coetzee, B, and Gabbett, TJ. Internal and external match loads of university-level soccer players: a comparison between methods. J Strength Cond Res 31(4): 1072-7077, 2017-The aim of this study was to use individualized intensity zones to compare the external (velocity and player load, PL) and internal loads (heart rate, HR) of a cohort of university-level soccer players. Thirteen soccer players completed a 40-m maximum speed test and the Yo-Yo intermittent recovery test 1 (Yo-Yo IR1) to determine individualized velocity and HR thresholds. Heart rate values and global positioning system (GPS) data of each player were recorded during 5 league matches. A large (r = 0.46; p ≤ 0.01) correlation was found between time spent in the low-intensity (LI) velocity zone (LIVZ) and the LI HR zone. Similarly, there were moderate (r = 0.25; p ≤ 0.01) to large (r = 0.57; p ≤ 0.01) correlations between the relative and absolute time spent in the moderate-intensity (MI) velocity zone (MIVZ) and the MI HR zone. No significant correlations (p ≤ 0.01) existed between the high-intensity (HI) velocity zones (HIVZ) and the HI HR zone. On the other hand, PL showed significant correlations with all velocity and HR (absolute and relative) variables, with the exception of a nonsignificant correlation between the HI HR variables and PL. To conclude, PL showed good correlations with both velocity and HR zones and therefore may have the potential to serve as a good indicator of both external and internal soccer match loads.

Pressure and shear stress in trabecular bone marrow during whole bone loading.

PubMed

Metzger, Thomas A; Schwaner, Stephen A; LaNeve, Anthony J; Kreipke, Tyler C; Niebur, Glen L

2015-09-18

Skeletal adaptation to mechanical loading is controlled by mechanobiological signaling. Osteocytes are highly responsive to applied strains, and are the key mechanosensory cells in bone. However, many cells residing in the marrow also respond to mechanical cues such as hydrostatic pressure and shear stress, and hence could play a role in skeletal adaptation. Trabecular bone encapsulates marrow, forming a poroelastic solid. According to the mechanical theory, deformation of the pores induces motion in the fluid-like marrow, resulting in pressure and velocity gradients. The latter results in shear stress acting between the components of the marrow. To characterize the mechanical environment of trabecular bone marrow in situ, pore pressure within the trabecular compartment of whole porcine femurs was measured with miniature pressure transducers during stress-relaxation and cyclic loading. Pressure gradients ranging from 0.013 to 0.46 kPa/mm were measured during loading. This range was consistent with calculated pressure gradients from continuum scale poroelastic models with the same permeability. Micro-scale computational fluid dynamics models created from computed tomography images were used to calculate the micromechanical stress in the marrow using the measured pressure differentials as boundary conditions. The volume averaged shear stress in the marrow ranged from 1.67 to 24.55 Pa during cyclic loading, which exceeds the mechanostimulatory threshold for mesenchymal lineage cells. Thus, the loading of bone through activities of daily living may be an essential component of bone marrow health and mechanobiology. Additional studies of cell-level interactions during loading in healthy and disease conditions will provide further incite into marrow mechanobiology. Copyright © 2015 Elsevier Ltd. All rights reserved.

Global Response of the Space Shuttle External Tank with the Presence of Intertank Stringer Cracks and Radius Blocks

NASA Technical Reports Server (NTRS)

Lovejoy, Andrew E.; Rankin, Charles C.

2013-01-01

After propellant was loaded into the external tank (ET), the November 5, 2010 launch of Space Shuttle mission STS-133 was scrubbed due to a gaseous hydrogen leak located in a vent line near the ground umbilical and ET connection. Subsequent visual inspections identified cracks in the sprayed-on foam insulation in the forward end of the ET intertank segment, adjacent to the liquid oxygen (LOX) tank, as shown in Figure 1. These cracks necessitated repair of the foam due to debris concerns that violated launch constraints. As part of the repair process, the affected foam was removed to reveal cracks in the underlying external hat stiffeners on the intertank, as shown in Figure 2. Ultimately, five stiffeners were discovered to be cracked adjacent to the LOX tank. As the managing center for the ET Project, NASA Marshall Space Flight Center (MSFC) coordinated failure investigation and repair activities among multiple organizations, which included the ET prime contractor (Lockheed Martin Space Systems Michoud Operations), the Space Shuttle Program Office at the NASA Johnson Space Center (JSC), the NASA Kennedy Space Center (KSC), and the NASA Engineering and Safety Center (NESC). STS-133 utilized the external tank designated as ET-137. Many aspects of the investigation have been reported previously in Refs. 1-7, which focus on the root cause of the failures, the flight readiness rationale and the local analyses of the stringer failures and repair. This paper summarizes the global analyses that were conducted on ET-137 as part of the NESC effort during the investigation, which was conducted primarily to determine if the repairs that were introduced to the stringers would alter the global response of the ET. In the process of the investigation, a new STAGS tabular input capability was developed to more easily introduce the aerodynamic pressure loads using a method that could easily be extended to incorporate finite element property data such as skin and stiffener thicknesses and beam cross-sectional properties.

A loose bolt delays loading of Endeavour's external tank

NASA Technical Reports Server (NTRS)

2000-01-01

This view shows the pipe (center top) leading toward Endeavour from the side of the White Room at Launch Pad 39B. A loose bracket observed hanging down from the pipe delayed loading of Endeavour's external tank by several hours to allow technicians to remove it. A 'U' bolt connects the bracket to a fire suppression water line attached to the exterior of the White Room. The loose bolt could have possibly created a debris hazard.

Effect of fuel injection pressure on a heavy-duty diesel engine nonvolatile particle emission.

PubMed

Lähde, Tero; Rönkkö, Topi; Happonen, Matti; Söderström, Christer; Virtanen, Annele; Solla, Anu; Kytö, Matti; Rothe, Dieter; Keskinen, Jorma

2011-03-15

The effects of the fuel injection pressure on a heavy-duty diesel engine exhaust particle emissions were studied. Nonvolatile particle size distributions and gaseous emissions were measured at steady-state engine conditions while the fuel injection pressure was changed. An increase in the injection pressure resulted in an increase in the nonvolatile nucleation mode (core) emission at medium and at high loads. At low loads, the core was not detected. Simultaneously, a decrease in soot mode number concentration and size and an increase in the soot mode distribution width were detected at all loads. Interestingly, the emission of the core was independent of the soot mode concentration at load conditions below 50%. Depending on engine load conditions, growth of the geometric mean diameter of the core mode was also detected with increasing injection pressure. The core mode emission and also the size of the mode increased with increasing NOx emission while the soot mode size and emission decreased simultaneously.

The effect of long and short head biceps loading on glenohumeral joint rotational range of motion and humeral head position.

PubMed

McGarry, Michelle H; Nguyen, Michael L; Quigley, Ryan J; Hanypsiak, Bryan; Gupta, Ranjan; Lee, Thay Q

2016-06-01

To evaluate the effect of loading the long and short heads of the biceps on glenohumeral range of motion and humeral head position. Eight cadaveric shoulders were tested in 60° abduction in the scapula and coronal plane. Muscle loading was applied based on cross-sectional area ratios. The short and long head of the biceps were loaded individually followed by combined loading. Range of motion was measured with 2.2 Nm torque, and the humeral head apex position was measured using a MicroScribe. A paired t test with Bonferroni correction was used for statistics. Long head loading decreased internal rotation in both the scapular (17.9 %) and coronal planes (5.7 %) and external rotation in the scapular plane (2.6 %) (P < 0.04). With only short head loading, maximum internal rotation was significantly increased in the scapular and coronal plane. Long head and short head loading shifted the humeral head apex posteriorly in maximum internal rotation in both planes with the long head shift being significantly greater than the short head. Long head loading also shifted the humeral apex inferiorly in internal rotation and inferiorly posteriorly in neutral rotation in the scapular plane. With the long head unloaded, there was a significant superior shift with short head loading in both planes. Loading the long head of the biceps had a much greater effect on glenohumeral range of motion and humeral head shift than the short head of the biceps; however, in the absence of long head loading, with the short head loaded, maximum internal rotation increases and the humeral head shifts superiorly, which may contribute to impingement following tenodesis of the long head of the biceps. These small changes in rotational range of motion and humeral head position with biceps tenodesis may not lead to pathologic conditions in low-demand patients; however, in throwers, biceps tenodesis may lead to increased contact pressures in late-cocking and deceleration that will likely translate to decreased performance therefore every effort should be made to preserve the biceps-labral complex.

46 CFR 154.517 - Piping: Liquid pressure relief.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 5 2014-10-01 2014-10-01 false Piping: Liquid pressure relief. 154.517 Section 154.517... and Process Piping Systems § 154.517 Piping: Liquid pressure relief. The cargo loading and discharge crossover headers, cargo hoses, and cargo loading arms must have means to relieve cargo pressure and to...

46 CFR 154.517 - Piping: Liquid pressure relief.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 5 2013-10-01 2013-10-01 false Piping: Liquid pressure relief. 154.517 Section 154.517... and Process Piping Systems § 154.517 Piping: Liquid pressure relief. The cargo loading and discharge crossover headers, cargo hoses, and cargo loading arms must have means to relieve cargo pressure and to...

46 CFR 154.517 - Piping: Liquid pressure relief.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 5 2012-10-01 2012-10-01 false Piping: Liquid pressure relief. 154.517 Section 154.517... and Process Piping Systems § 154.517 Piping: Liquid pressure relief. The cargo loading and discharge crossover headers, cargo hoses, and cargo loading arms must have means to relieve cargo pressure and to...

46 CFR 154.517 - Piping: Liquid pressure relief.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 5 2010-10-01 2010-10-01 false Piping: Liquid pressure relief. 154.517 Section 154.517... and Process Piping Systems § 154.517 Piping: Liquid pressure relief. The cargo loading and discharge crossover headers, cargo hoses, and cargo loading arms must have means to relieve cargo pressure and to...

46 CFR 154.517 - Piping: Liquid pressure relief.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 5 2011-10-01 2011-10-01 false Piping: Liquid pressure relief. 154.517 Section 154.517... and Process Piping Systems § 154.517 Piping: Liquid pressure relief. The cargo loading and discharge crossover headers, cargo hoses, and cargo loading arms must have means to relieve cargo pressure and to...

Model-Based Diagnostics for Propellant Loading Systems

NASA Technical Reports Server (NTRS)

Daigle, Matthew John; Foygel, Michael; Smelyanskiy, Vadim N.

2011-01-01

The loading of spacecraft propellants is a complex, risky operation. Therefore, diagnostic solutions are necessary to quickly identify when a fault occurs, so that recovery actions can be taken or an abort procedure can be initiated. Model-based diagnosis solutions, established using an in-depth analysis and understanding of the underlying physical processes, offer the advanced capability to quickly detect and isolate faults, identify their severity, and predict their effects on system performance. We develop a physics-based model of a cryogenic propellant loading system, which describes the complex dynamics of liquid hydrogen filling from a storage tank to an external vehicle tank, as well as the influence of different faults on this process. The model takes into account the main physical processes such as highly nonequilibrium condensation and evaporation of the hydrogen vapor, pressurization, and also the dynamics of liquid hydrogen and vapor flows inside the system in the presence of helium gas. Since the model incorporates multiple faults in the system, it provides a suitable framework for model-based diagnostics and prognostics algorithms. Using this model, we analyze the effects of faults on the system, derive symbolic fault signatures for the purposes of fault isolation, and perform fault identification using a particle filter approach. We demonstrate the detection, isolation, and identification of a number of faults using simulation-based experiments.

A computer program to calculate the longitudinal aerodynamic characteristics of wing-flap configurations with externally blown flaps

NASA Technical Reports Server (NTRS)

Mendenhall, M. R.; Goodwin, F. K.; Spangler, S. B.

1976-01-01

A vortex lattice lifting-surface method is used to model the wing and multiple flaps. Each lifting surface may be of arbitrary planform having camber and twist, and the multiple-slotted trailing-edge flap system may consist of up to ten flaps with different spans and deflection angles. The engine wakes model consists of a series of closely spaced vortex rings with circular or elliptic cross sections. The rings are normal to a wake centerline which is free to move vertically and laterally to accommodate the local flow field beneath the wing and flaps. The two potential flow models are used in an iterative fashion to calculate the wing-flap loading distribution including the influence of the waves from up to two turbofan engines on the semispan. The method is limited to the condition where the flow and geometry of the configurations are symmetric about the vertical plane containing the wing root chord. The calculation procedure starts with arbitrarily positioned wake centerlines and the iterative calculation continues until the total configuration loading converges within a prescribed tolerance. Program results include total configuration forces and moments, individual lifting-surface load distributions, including pressure distributions, individual flap hinge moments, and flow field calculation at arbitrary field points.

Computational study of single-expansion-ramp nozzles with external burning

NASA Astrophysics Data System (ADS)

Yungster, Shaye; Trefny, Charles J.

1992-04-01

A computational investigation of the effects of external burning on the performance of single expansion ramp nozzles (SERN) operating at transonic speeds is presented. The study focuses on the effects of external heat addition and introduces a simplified injection and mixing model based on a control volume analysis. This simplified model permits parametric and scaling studies that would have been impossible to conduct with a detailed CFD analysis. The CFD model is validated by comparing the computed pressure distribution and thrust forces, for several nozzle configurations, with experimental data. Specific impulse calculations are also presented which indicate that external burning performance can be superior to other methods of thrust augmentation at transonic speeds. The effects of injection fuel pressure and nozzle pressure ratio on the performance of SERN nozzles with external burning are described. The results show trends similar to those reported in the experimental study, and provide additional information that complements the experimental data, improving our understanding of external burning flowfields. A study of the effect of scale is also presented. The results indicate that combustion kinetics do not make the flowfield sensitive to scale.

Computational study of single-expansion-ramp nozzles with external burning

NASA Technical Reports Server (NTRS)

Yungster, Shaye; Trefny, Charles J.

1992-01-01

A computational investigation of the effects of external burning on the performance of single expansion ramp nozzles (SERN) operating at transonic speeds is presented. The study focuses on the effects of external heat addition and introduces a simplified injection and mixing model based on a control volume analysis. This simplified model permits parametric and scaling studies that would have been impossible to conduct with a detailed CFD analysis. The CFD model is validated by comparing the computed pressure distribution and thrust forces, for several nozzle configurations, with experimental data. Specific impulse calculations are also presented which indicate that external burning performance can be superior to other methods of thrust augmentation at transonic speeds. The effects of injection fuel pressure and nozzle pressure ratio on the performance of SERN nozzles with external burning are described. The results show trends similar to those reported in the experimental study, and provide additional information that complements the experimental data, improving our understanding of external burning flowfields. A study of the effect of scale is also presented. The results indicate that combustion kinetics do not make the flowfield sensitive to scale.

The role of water management on the oxygen transport resistance in polymer electrolyte fuel cell with ultra-low precious metal loading

NASA Astrophysics Data System (ADS)

Srouji, A. K.; Zheng, L. J.; Dross, R.; Aaron, D.; Mench, M. M.

2017-10-01

Limiting current measurements are used to evaluate oxygen transport resistance in the catalyst layer of a polymer electrolyte fuel cell (PEFC). The pressure independent oxygen transport resistance in the electrode is quantified for two cell architectures and two cathode Pt loadings (0.4 and 0.07 mgPt.cm-2). The compounded effect of the flow field and Pt loading is used to shed light on the nature of the observed transport resistance, especially its response to fundamentally different flow fields, which is shown to directly or indirectly scale with Pt loading in the open literature. By varying gas pressure and using low oxygen concentrations, the total oxygen transport resistance is divided into intermolecular gas diffusion (a pressure-dependent component) and a pressure independent component, which can be attributed to Knudsen diffusion or dissolution film resistance. The pressure-independent oxygen transport resistance in the catalyst layer varies between 13.3 and 34.4 s/m. It is shown that the pressure independent oxygen transport resistance increases with reduced Pt loading, but that effect is greatly exacerbated by using conventional channel/lands. The results indicate that open metallic element architecture improves the oxygen transport resistance in ultra-low Pt loading electrodes, likely due to enhanced water management at the catalyst layer.

Stretchable Dual-Capacitor Multi-Sensor for Touch-Curvature-Pressure-Strain Sensing.

PubMed

Jin, Hanbyul; Jung, Sungchul; Kim, Junhyung; Heo, Sanghyun; Lim, Jaeik; Park, Wonsang; Chu, Hye Yong; Bien, Franklin; Park, Kibog

2017-09-07

We introduce a new type of multi-functional capacitive sensor that can sense several different external stimuli. It is fabricated only with polydimethylsiloxane (PDMS) films and silver nanowire electrodes by using selective oxygen plasma treatment method without photolithography and etching processes. Differently from the conventional single-capacitor multi-functional sensors, our new multi-functional sensor is composed of two vertically-stacked capacitors (dual-capacitor). The unique dual-capacitor structure can detect the type and strength of external stimuli including curvature, pressure, strain, and touch with clear distinction, and it can also detect the surface-normal directionality of curvature, pressure, and touch. Meanwhile, the conventional single-capacitor sensor has ambiguity in distinguishing curvature and pressure and it can detect only the strength of external stimulus. The type, directionality, and strength of external stimulus can be determined based on the relative capacitance changes of the two stacked capacitors. Additionally, the logical flow reflected on a tree structure with its branches reaching the direction and strength of the corresponding external stimulus unambiguously is devised. This logical flow can be readily implemented in the sensor driving circuit if the dual-capacitor sensor is commercialized actually in the future.

Blood Pressure and Arterial Load After Transcatheter Aortic Valve Replacement for Aortic Stenosis.

PubMed

Lindman, Brian R; Otto, Catherine M; Douglas, Pamela S; Hahn, Rebecca T; Elmariah, Sammy; Weissman, Neil J; Stewart, William J; Ayele, Girma M; Zhang, Feifan; Zajarias, Alan; Maniar, Hersh S; Jilaihawi, Hasan; Blackstone, Eugene; Chinnakondepalli, Khaja M; Tuzcu, E Murat; Leon, Martin B; Pibarot, Philippe

2017-07-01

After aortic valve replacement, left ventricular afterload is often characterized by the residual valve obstruction. Our objective was to determine whether higher systemic arterial afterload-as reflected in blood pressure, pulsatile and resistive load-is associated with adverse clinical outcomes after transcatheter aortic valve replacement (TAVR). Total, pulsatile, and resistive arterial load were measured in 2141 patients with severe aortic stenosis treated with TAVR in the PARTNER I trial (Placement of Aortic Transcatheter Valve) who had systolic blood pressure (SBP) and an echocardiogram obtained 30 days after TAVR. The primary end point was 30-day to 1-year all-cause mortality. Lower SBP at 30 days after TAVR was associated with higher mortality (20.0% for SBP 100-129 mm Hg versus 12.0% for SBP 130-170 mm Hg; P <0.001). This association remained significant after adjustment, was consistent across subgroups, and confirmed in sensitivity analyses. In adjusted models that included SBP, higher total and pulsatile arterial load were associated with increased mortality ( P <0.001 for all), but resistive load was not. Patients with low 30-day SBP and high pulsatile load had a 3-fold higher mortality than those with high 30-day SBP and low pulsatile load (26.1% versus 8.1%; hazard ratio, 3.62; 95% confidence interval, 2.36-5.55). Even after relief of valve obstruction in patients with aortic stenosis, there is an independent association between post-TAVR blood pressure, systemic arterial load, and mortality. Blood pressure goals in patients with a history of aortic stenosis may need to be redefined. Increased pulsatile arterial load, rather than blood pressure, may be a target for adjunctive medical therapy to improve outcomes after TAVR. URL: http://www.clinicaltrials.gov. Unique identifier: NCT00530894. © 2017 American Heart Association, Inc.

[Effect of different backpack loads on physiological parame ters in walking].

PubMed

Zhao, Meiya; Tian, Shan; Tang, Qiaohong; Ni, Yikun; Wang, Lizhen; Fan, Yubo

2014-10-01

This study investigated the effect of prolonged walking with load carriage on body posture, muscle fatigue, heart rate and blood pressure of the tested subjects. Ten healthy volunteers performed 30 min walking trials on treadmill (speed = 1.1 m/s) with different backpack loads [0% body weight (BW), 10% BW, 15% BW and 20% BW]. The change of body posture, muscle fatigue, heart rate and blood pressure before and after walking and the recovery of muscle fatigue during the rest time (0, 5, 10 and 15 min) were collected using the Bortec AMT-8 and the NDI Optotrak Certus. Results showed that the forward trunk and head angle, muscle fatigue, heart rate and blood pressure increased with the increasing backpack loads and bearing time. With the 20% BW load, the forward angle, muscle fatigue and systolic pressure were significantly higher than with lighter weights. No significantly increased heart rate and diastolic pressure were found. Decreased muscle fatigue was found after removing the backpack in each load trial. But the recovery of the person with 20% BW load was slower than that of 0% BW, 10% BW and 15% BW. These findings indicated that the upper limit of backpack loads for college-aged students should be between 15% BW and 20% BW according to muscle fatigue and forward angle. It is suggested that backpack loads should be restricted to no more than 15% BW for walks of up to 30 min duration to avoid irreversible muscle fatigue.

The Financial Sector and Sustainable Development

NASA Astrophysics Data System (ADS)

Rusko, Miroslav; Korauš, Anton

2010-01-01

Growing load and deterioration of the environment can be interpreted as a result of some external effects interventions. While the positive externalities influence the positive productional and utilizational functions of other subjects, the negative externalities influence the negative ones. Both types of external effects can act as parcial or global externalities. Linking the environmental issues to economy and finance is an important sphere. Coimplementation of both marketing and environmental audits is an important element of this sphere too.

Enhanced Performance of Streamline-Traced External-Compression Supersonic Inlets

NASA Technical Reports Server (NTRS)

Slater, John W.

2015-01-01

A computational design study was conducted to enhance the aerodynamic performance of streamline-traced, external-compression inlets for Mach 1.6. Compared to traditional external-compression, two-dimensional and axisymmetric inlets, streamline-traced inlets promise reduced cowl wave drag and sonic boom, but at the expense of reduced total pressure recovery and increased total pressure distortion. The current study explored a new parent flowfield for the streamline tracing and several variations of inlet design factors, including the axial displacement and angle of the subsonic cowl lip, the vertical placement of the engine axis, and the use of porous bleed in the subsonic diffuser. The performance was enhanced over that of an earlier streamline-traced inlet such as to increase the total pressure recovery and reduce total pressure distortion.

14 CFR 133.47 - Rotorcraft-load combination flight manual.

Code of Federal Regulations, 2010 CFR

2010-01-01

.... 133.47 Section 133.47 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF... ROTORCRAFT EXTERNAL-LOAD OPERATIONS Airworthiness Requirements § 133.47 Rotorcraft-load combination flight... been demonstrated in accordance with §§ 133.41 and 133.43; and (c) In the information section of the...