Simultaneous pressure measurement and high-speed photography study of cavitation in a dynamically loaded journal bearing

NASA Technical Reports Server (NTRS)

Sun, D. C.; Brewe, D. E.; Abel, P. B.

1993-01-01

Cavitation of the oil film in a dynamically loaded journal bearing was studied using high-speed photography and pressure measurement simultaneously. Comparison of the visual and pressure data provided considerable insight into the occurence and non-occurrence of cavitation. It was found that (1), cavitation typically occurred in the form of one bubble with the pressure in the cavitation bubble close to the absolute zero; and (2), for cavitation-producing operating conditions, cavitation did not always occur; with the oil film then supporting a tensile stress.

Fluid mass and thermal loading effects on the modal characteristics of space shuttle main engine liquid oxygen inlet splitter vanes

NASA Technical Reports Server (NTRS)

Panossian, H. V.; Boehnlein, J. J.

1987-01-01

An analysis and evaluation of experimental modal survey test data on the variations of modal characteristics induced by pressure and thermal loading events are presented. Extensive modal survey tests were carried out on a Space Shuttle Main Engine (SSME) test article using liquid nitrogen under cryogenic temperatures and high pressures. The results suggest that an increase of pressure under constant cryogenic temperature or a decrease of temperature under high pressure induces an upward shift of frequencies of various modes of the structures.

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.

Plantar Pressure Anomalies After Open Reduction With Internal Fixation of High-Grade Calcaneal Fractures.

PubMed

Hetsroni, Iftach; Ben-Sira, David; Nyska, Meir; Ayalon, Moshe

2014-07-01

Plantar pressure abnormalities after open reduction with internal fixation (ORIF) of intra-articular calcaneal fractures have been observed previously, but high-grade fractures were not selectively investigated and follow-up times were shorter than 2 years. The purpose of this study was to characterize plantar pressure anomalies in patients with exclusively high-grade calcaneal fractures after ORIF with a minimum 2 years of follow-up, and to test the association between plantar pressure distribution and the clinical outcome. The orthopaedic registry was reviewed to identify patients with isolated high-grade calcaneal fractures (Sanders types III-IV) who were operated on and had a minimum 2 years of follow-up. Sixteen patients were evaluated. Mean age was 47 years and follow-up was between 2 and 6 years. The Pedar-Mobile system was used to measure 3 loading and 3 temporal variables and compare these between the operated and the uninjured limbs. Mean American Orthopaedic Foot and Ankle Society (AOFAS) score was 76 ± 7 at latest follow-up. Bohler's angle was 5 ± 8 degrees before surgery and 25 ± 7 degrees at latest follow-up. Stance was shorter in operated limbs (P = .001). Timing of the peak of pressure was delayed in operated limbs under the hallux and the second toe (P ≤ .03). Peak pressure, force time integral, and pressure time integral were increased under the lateral midfoot (P ≤ .03) and decreased under the second metatarsal (P ≤ .03). Force time integral was decreased under the first metatarsal (P = .02) and under the hallux and the lateral toes (P ≤ .05). Increased loading under the lateral midfoot and decreased loading under the lateral toes were correlated with poorer clinical outcome (r = -.53, P < .05, and r = .63, P < .01, respectively). Side-to-side plantar pressure mismatch persisted at more than 2 years after ORIF of high-grade calcaneal fractures performed via lateral approach, despite improvement of Bohler's angle. This was characterized by shortened stance phase, delayed timing of peak of pressure under the hallux and second toe, lateral load shift at the midfoot, and decreased toe pressures in operated limbs. Since loading abnormalities were correlated with the clinical outcome, modifications in treatment strategy that can improve foot loading may be desirable in these cases. Level III, case control. © The Author(s) 2014.

A Flexible and Highly Sensitive Pressure Sensor Based on a PDMS Foam Coated with Graphene Nanoplatelets

PubMed Central

Rinaldi, Andrea; Tamburrano, Alessio; Fortunato, Marco; Sarto, Maria Sabrina

2016-01-01

The demand for high performance multifunctional wearable devices is more and more pushing towards the development of novel low-cost, soft and flexible sensors with high sensitivity. In the present work, we describe the fabrication process and the properties of new polydimethylsiloxane (PDMS) foams loaded with multilayer graphene nanoplatelets (MLGs) for application as high sensitive piezoresistive pressure sensors. The effective DC conductivity of the produced foams is measured as a function of MLG loading. The piezoresistive response of the MLG-PDMS foam-based sensor at different strain rates is assessed through quasi-static pressure tests. The results of the experimental investigations demonstrated that sensor loaded with 0.96 wt.% of MLGs is characterized by a highly repeatable pressure-dependent conductance after a few stabilization cycles and it is suitable for detecting compressive stresses as low as 10 kPa, with a sensitivity of 0.23 kPa−1, corresponding to an applied pressure of 70 kPa. Moreover, it is estimated that the sensor is able to detect pressure variations of ~1 Pa. Therefore, the new graphene-PDMS composite foam is a lightweight cost-effective material, suitable for sensing applications in the subtle or low and medium pressure ranges. PMID:27999251

G-protection mechanisms afforded by the anti-G suit abdominal bladder with and without pressure breathing.

PubMed

Eiken, Ola; Bergsten, Eddie; Grönkvist, Mikael

2011-10-01

G protection afforded by the abdominal bladder of a pneumatic anti-G suit is usually attributed to counteraction of G-induced caudad displacement of the heart and pooling of blood in the abdominal veins. The study examined whether the abdominal bladder might provide G protection also via other mechanisms. Each subject was exposed to +Gz loads while sitting relaxed, wearing a full-coverage anti-G suit modified to permit separate pressurization of the abdominal and leg bladders. In two experimental series (N = 8, N = 14), subjects were breathing at positive airway pressure (PPB); in a third series, five subjects were breathing at atmospheric airway pressure. Intrathoracic pressures were estimated by use of esophageal catheters. During PPB at high G loads, intrathoracic pressure was higher with than without the pressurized abdominal bladder. In 7 of the 14 subjects, basilar intrathoracic pressure exceeded airway pressure during PPB when the abdominal bladder was pressurized. The mean arterial pressure response at high G loads was higher in this subset of subjects (55 +/- 23 mmHg) than in the subjects in whom airway pressure exceeded intrathoracic pressure (41 +/- 27 mmHg). Without PPB at increased G load, the intrathoracic pressure gradient was higher with than without the pressurized abdominal bladder. During PPB, the abdominal bladder acts as an airway counterpressure, thereby facilitating pressure transmission from the airways to the thorax and hence improving G protection. It also appears that in several individuals, pressure may be transmitted from the abdominal bladder to the thorax and heart.

An Ultrahigh CO2-Loaded Silicalite-1 Zeolite: Structural Stability and Physical Properties at High Pressures and Temperatures.

PubMed

Marqueño, Tomas; Santamaria-Perez, David; Ruiz-Fuertes, Javier; Chuliá-Jordán, Raquel; Jordá, Jose L; Rey, Fernando; McGuire, Chris; Kavner, Abby; MacLeod, Simon; Daisenberger, Dominik; Popescu, Catalin; Rodriguez-Hernandez, Placida; Muñoz, Alfonso

2018-06-04

We report the formation of an ultrahigh CO 2 -loaded pure-SiO 2 silicalite-1 structure at high pressure (0.7 GPa) from the interaction of empty zeolite and fluid CO 2 medium. The CO 2 -filled structure was characterized in situ by means of synchrotron powder X-ray diffraction. Rietveld refinements and Fourier recycling allowed the location of 16 guest carbon dioxide molecules per unit cell within the straight and sinusoidal channels of the porous framework to be analyzed. The complete filling of pores by CO 2 molecules favors structural stability under compression, avoiding pressure-induced amorphization below 20 GPa, and significantly reduces the compressibility of the system compared to that of the parental empty one. The structure of CO 2 -loaded silicalite-1 was also monitored at high pressures and temperatures, and its thermal expansivity was estimated.

Effects of winglets on a first-generation jet transport wing. 7: Sideslip effects on winglet loads and selected wing loads at subsonic speeds for a full-span model

NASA Technical Reports Server (NTRS)

Meyer, Robert R., Jr.; Covell, Peter F.

1986-01-01

The effect of sideslip on winglet loads and selected wing loads was investigated at high and low subsonic Mach numbers. The investigation was conducted in two separate wind tunnel facilities, using two slightly different 0.035-scale full-span models. Results are presented which indicate that, in general, winglet loads as a result of sideslip are analogous to wing loads caused by angle of attack. The center-of-pressure locations on the winglets are somewhat different than might be expected for an analogous wing. The spanwise center of pressure for a winglet tends to be more inboard than for a wing. The most notable chordwise location is a forward center-of-pressure location on the winglet at high sideslip angles. The noted differences between a winglet and an analogous wing are the result of the influence of the wing on the winglet.

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

NASA Technical Reports Server (NTRS)

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

2009-01-01

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

Load cell verification of the uprated high pressure oxygen turbopump for the Space Shuttle Main Engine

NASA Technical Reports Server (NTRS)

Beatty, R. F.; Hine, M. J.

1986-01-01

The high pressure turbomachinery of the Space Shuttle Main Engine has the highest power-to-weight ratio of any operational machine known. Subsynchronous rotor whirl of the high pressure oxygen turbopump occurred in development testing at full-power level (109 percent thrust). The means by which the turbopump was successfully uprated is presented herein. The subsynchronous motion was determined to be driven by impeller destabilizing forces in combination with low net damping and bearing degradation. The degradation resulted from ball wear due primarily to an excessive loading condition of operating too near the lightly damped rotor second critical speed while under a large static load and, secondarily, from reverse bearing loading or loss of internal clearance and coolant during simulated flight conditions. The rotor response was reduced by stiffening the shaft and supports, optimizing the stiffness and damping of annular seals, and increasing the bearing deadband. The uprated oxygen turbopump configuration was verified by converting the pump and bearing support into a load cell for the purpose of systematically quantifying the load reduction benefits relative to baseline turbopumps. The damped second critical speed margin and the load sharing have been substantially improved which has resulted in reduced bearing loads for improved service life of the machine at full-power level.

Evaluation of shuttle turbopump bearings

NASA Technical Reports Server (NTRS)

Dufrane, K. F.; Kannel, J. W.

1978-01-01

Because the high pressure turbopumps used on the space shuttle main engine (SSME) are high speed machines and rotor dynamics analysis of these units is very complicated, it was considered necessary to verify calculated turbomachinery shaft bearing loads by analysis of ball bearing load tracks. This report presents the methods used and the results of load track analysis on one set of bearings removed from a high pressure liquid oxygen turbopump which had been subjected to SSME static firing tests. This type of analysis was found useful in determining bearing operating conditions and for verifying rotor dynamics computer models.

Simultaneous pressure measurement and high-speed photography study of cavitation in a dynamically loaded journal bearing

NASA Technical Reports Server (NTRS)

Sun, D. C.; Brewe, David E.; Abel, Philip B.

1994-01-01

Cavitation of the oil film in a dynamically loaded journal bearing was studied using high-speed photography and pressure measurement simultaneously. Comparison of the visual and pressure data provided considerable insight into the occurrence and nonoccurrence of cavitation. It was found that (1) for the submerged journal bearing, cavitation typically occurred in the form of one bubble with the pressure in the cavitation bubble close to the absolute zero; and (2) for cavitation-producing operating conditions, cavitation did not always occur; with the oil film then supporting a tensile stress.

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.

Experimental investigation on a high head model Francis turbine during load rejection

NASA Astrophysics Data System (ADS)

Goyal, R.; Bergan, C.; Cervantes, M. J.; Gandhi, B. K.; Dahlhaug, O. G.

2016-11-01

Francis-99 is a set of workshop aiming to determine the state of the art of high head model Francis turbine simulations (flow and structure) under steady and transient operating conditions as well as to promote their development and knowledge dissemination openly. The first workshop (Trondheim, 2014) was concerned with steady state operation. The second workshop will focus on transient operations such as load variation and start-stop. In the present work, 2-D particle image velocimetry (PIV) with synchronized pressure measurements performed in the draft tube cone of the Francis-99 test case during load rejection is presented. Pressure sensors were mounted in the vaneless space and draft tube cone to estimate the instantaneous pressure fluctuations while operating the turbine from the best efficiency point (9.8°) to part load (6.7°) with the presence of a rotating vortex rope (RVR). The time-resolved velocity and pressure data are presented in this paper showing the transition in the turbine from one state to another.

Analysis of various descent trajectories for a hypersonic-cruise, cold-wall research airplane

NASA Technical Reports Server (NTRS)

Lawing, P. L.

1975-01-01

The probable descent operating conditions for a hypersonic air-breathing research airplane were examined. Descents selected were cruise angle of attack, high dynamic pressure, high lift coefficient, turns, and descents with drag brakes. The descents were parametrically exercised and compared from the standpoint of cold-wall (367 K) aircraft heat load. The descent parameters compared were total heat load, peak heating rate, time to landing, time to end of heat pulse, and range. Trends in total heat load as a function of cruise Mach number, cruise dynamic pressure, angle-of-attack limitation, pull-up g-load, heading angle, and drag-brake size are presented.

Modelling cavitation erosion using fluid–material interaction simulations

PubMed Central

Chahine, Georges L.; Hsiao, Chao-Tsung

2015-01-01

Material deformation and pitting from cavitation bubble collapse is investigated using fluid and material dynamics and their interaction. In the fluid, a novel hybrid approach, which links a boundary element method and a compressible finite difference method, is used to capture non-spherical bubble dynamics and resulting liquid pressures efficiently and accurately. The bubble dynamics is intimately coupled with a finite-element structure model to enable fluid/structure interaction simulations. Bubble collapse loads the material with high impulsive pressures, which result from shock waves and bubble re-entrant jet direct impact on the material surface. The shock wave loading can be from the re-entrant jet impact on the opposite side of the bubble, the fast primary collapse of the bubble, and/or the collapse of the remaining bubble ring. This produces high stress waves, which propagate inside the material, cause deformation, and eventually failure. A permanent deformation or pit is formed when the local equivalent stresses exceed the material yield stress. The pressure loading depends on bubble dynamics parameters such as the size of the bubble at its maximum volume, the bubble standoff distance from the material wall and the pressure driving the bubble collapse. The effects of standoff and material type on the pressure loading and resulting pit formation are highlighted and the effects of bubble interaction on pressure loading and material deformation are preliminarily discussed. PMID:26442140

Water Flow Testing and Unsteady Pressure Analysis of a Two-Bladed Liquid Oxidizer Pump Inducer

NASA Technical Reports Server (NTRS)

Schwarz, Jordan B.; Mulder, Andrew; Zoladz, Thomas

2011-01-01

The unsteady fluid dynamic performance of a cavitating two-bladed oxidizer turbopump inducer was characterized through sub-scale water flow testing. While testing a novel inlet duct design that included a cavitation suppression groove, unusual high-frequency pressure oscillations were observed. With potential implications for inducer blade loads, these high-frequency components were analyzed extensively in order to understand their origins and impacts to blade loading. Water flow testing provides a technique to determine pump performance without the costs and hazards associated with handling cryogenic propellants. Water has a similar density and Reynolds number to liquid oxygen. In a 70%-scale water flow test, the inducer-only pump performance was evaluated. Over a range of flow rates, the pump inlet pressure was gradually reduced, causing the flow to cavitate near the pump inducer. A nominal, smooth inducer inlet was tested, followed by an inlet duct with a circumferential groove designed to suppress cavitation. A subsequent 52%-scale water flow test in another facility evaluated the combined inducer-impeller pump performance. With the nominal inlet design, the inducer showed traditional cavitation and surge characteristics. Significant bearing loads were created by large side loads on the inducer during synchronous cavitation. The grooved inlet successfully mitigated these loads by greatly reducing synchronous cavitation, however high-frequency pressure oscillations were observed over a range of frequencies. Analytical signal processing techniques showed these oscillations to be created by a rotating, multi-celled train of pressure pulses, and subsequent CFD analysis suggested that such pulses could be created by the interaction of rotating inducer blades with fluid trapped in a cavitation suppression groove. Despite their relatively low amplitude, these high-frequency pressure oscillations posed a design concern due to their sensitivity to flow conditions and test scale. The amplitude and frequency of oscillations varied considerably over the pump s operating space, making it difficult to predict blade loads.

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.

Applications of pressure-sensitive dielectric elastomer sensors

NASA Astrophysics Data System (ADS)

Böse, Holger; Ocak, Deniz; Ehrlich, Johannes

2016-04-01

Dielectric elastomer sensors for the measurement of compression loads with high sensitivity are described. The basic design of the sensors exhibits two profiled surfaces between which an elastomer film is confined. All components of the sensor were prepared with silicone whose stiffness can be varied in a wide range. Depending on details of the sensor design, various effects contribute to the enhancement of the capacitance. The intermediate elastomer film is stretched upon compression and electrode layers on the elastomer profiles and in the elastomer film approach each other. Different designs of the pressure sensor give rise to very different sensor characteristics in terms of the dependence of electric capacitance on compression force. Due to their inherent flexibility, the pressure sensors can be used on compliant substrates such as seats or beds or on the human body. This gives rise to numerous possible applications. The contribution describes also some examples of possible sensor applications. A glove was equipped with various sensors positioned at the finger tips. When grabbing an object with the glove, the sensors can detect the gripping forces of the individual fingers with high sensitivity. In a demonstrator of the glove equipped with seven sensors, the capacitances representing the gripping forces are recorded on a display. In another application example, a lower limb prosthesis was equipped with a pressure sensor to detect the load on the remaining part of the leg and the load is displayed in terms of the measured capacitance. The benefit of such sensors is to detect an eventual overload in order to prevent possible pressure sores. A third example introduces a seat load sensor system based on four extended pressure sensor mats. The sensor system detects the load distribution of a person on the seat. The examples emphasize the high performance of the new pressure sensor technology.

Pulsed power accelerator for material physics experiments

DOE PAGES

Reisman, D.  B.; Stoltzfus, B.  S.; Stygar, W.  A.; ...

2015-09-01

We have developed the design of Thor: a pulsed power accelerator that delivers a precisely shaped current pulse with a peak value as high as 7 MA to a strip-line load. The peak magnetic pressure achieved within a 1-cm-wide load is as high as 100 GPa. Thor is powered by as many as 288 decoupled and transit-time isolated bricks. Each brick consists of a single switch and two capacitors connected electrically in series. The bricks can be individually triggered to achieve a high degree of current pulse tailoring. Because the accelerator is impedance matched throughout, capacitor energy is delivered tomore » the strip-line load with an efficiency as high as 50%. We used an iterative finite element method (FEM), circuit, and magnetohydrodynamic simulations to develop an optimized accelerator design. When powered by 96 bricks, Thor delivers as much as 4.1 MA to a load, and achieves peak magnetic pressures as high as 65 GPa. When powered by 288 bricks, Thor delivers as much as 6.9 MA to a load, and achieves magnetic pressures as high as 170 GPa. We have developed an algebraic calculational procedure that uses the single brick basis function to determine the brick-triggering sequence necessary to generate a highly tailored current pulse time history for shockless loading of samples. Thor will drive a wide variety of magnetically driven shockless ramp compression, shockless flyer plate, shock-ramp, equation of state, material strength, phase transition, and other advanced material physics experiments.« less

The effect of circumferential distortion on fan performance at two levels of blade loading

NASA Technical Reports Server (NTRS)

Hartmann, M. J.; Sanger, N. L.

1975-01-01

Single stage fans designed for two levels of pressure ratio or blade loading were subjected to screen-induced circumferential distortions of 90-degree extent. Both fan rotors were designed for a blade tip speed of 425 m/sec, blade solidity of 1.3 and a hub-to-tip radius ratio of 0.5. Circumferential measurements of total pressure, temperature, static pressure, and flow angle were obtained at the hub, mean and tip radii at five axial stations. Rotor loading level did not appear to have a significant influence on rotor response to distorted flow. Losses in overall pressure ratio due to distortion were most severe in the stator hub region of the more highly loaded stage. At the near stall operating condition tip and hub regions of (either) rotor demonstrated different response characteristics to the distorted flow. No effect of loading was apparent on interactions between rotor and upstream distorted flow fields.

Acoustical properties of individual liposome-loaded microbubbles.

PubMed

Luan, Ying; Faez, Telli; Gelderblom, Erik; Skachkov, Ilya; Geers, Bart; Lentacker, Ine; van der Steen, Ton; Versluis, Michel; de Jong, Nico

2012-12-01

A comparison between phospholipid-coated microbubbles with and without liposomes attached to the microbubble surface was performed using the ultra-high-speed imaging camera (Brandaris 128). We investigated 73 liposome-loaded microbubbles (loaded microbubbles) and 41 microbubbles without liposome loading (unloaded microbubbles) with a diameter ranging from 3-10 μm at frequencies ranging from 0.6-3.8 MHz and acoustic pressures ranging from 5-100 kPa. The experimental data showed nearly the same shell elasticity for the loaded and unloaded bubbles, but the shell viscosity was higher for loaded bubbles compared with unloaded bubbles. For loaded bubbles, a higher pressure threshold for the bubble vibrations was noticed. In addition, an "expansion-only" behavior was observed for up to 69% of the investigated loaded bubbles, which mostly occurred at low acoustic pressures (≤30 kPa). Finally, fluorescence imaging showed heterogeneity of liposome distributions of the loaded bubbles. Copyright © 2012 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Influence of particle size distribution on the blast pressure profile from explosives buried in saturated soils

NASA Astrophysics Data System (ADS)

Rigby, S. E.; Fay, S. D.; Tyas, A.; Clarke, S. D.; Reay, J. J.; Warren, J. A.; Gant, M.; Elgy, I.

2018-05-01

The spatial and temporal distribution of pressure and impulse from explosives buried in saturated cohesive and cohesionless soils has been measured experimentally for the first time. Ten experiments have been conducted at quarter-scale, where localised pressure loading was measured using an array of 17 Hopkinson pressure bars. The blast pressure measurements are used in conjunction with high-speed video filmed at 140,000 fps to investigate in detail the physical processes occurring at the loaded face. Two coarse cohesionless soils and one fine cohesive soil were tested: a relatively uniform sand, a well-graded sandy gravel, and a fine-grained clay. The results show that there is a single fundamental loading mechanism when explosives are detonated in saturated soil, invariant of particle size and soil cohesion. It is also shown that variability in localised loading is intrinsically linked to the particle size distribution of the surrounding soil.

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.

High density load bearing insulation peg

DOEpatents

Nowobilski, Jeffert J.; Owens, William J.

1985-01-01

A high density peg which can support a large load and exhibits excellent thermal resistance produced by a method wherein the peg is made in compliance with specified conditions of time, temperature and pressure.

High pressure generation using scaled-up Kawai-cell

NASA Astrophysics Data System (ADS)

Shatskiy, A.; Katsura, T.; Litasov, K. D.; Shcherbakova, A. V.; Borzdov, Y. M.; Yamazaki, D.; Yoneda, A.; Ohtani, E.; Ito, E.

2011-11-01

A scaled-up version of a 6-8 Kawai-type multianvil apparatus equipped with 47-mm WC anvils has been developed at the Institute for the Study of the Earth's Interior for operation over pressure ranging up to 19 and 24 GPa using the conventional system with larger compressional volumes between 1.2 and 0.4 cm 3, respectively. This system is used under uniaxial compression along cube diagonal of the Kawai-cell up to the press load of 19 MN. Experiments are performed using octahedral pressure media (PM) made of MgO- and ZrO 2-based semi-sintered ceramics and unfired pyrophyllite gaskets. In this study we used "Toshiba-F" grade WC anvils allowing pressure generation up to 24 GPa. We perform pressure calibrations at room and high temperatures, with octahedron/anvil truncation edge-length ratios ( a0/ b, mm) of 12.2/6, 14/6, 14/7, 16/7, 18/7, 18/9, and 18/10. Different configurations show that an increase in edge-length ratio of a0/b permits the achievement of higher pressure, which agrees with the results of Frost at al. (Frost, D.J., Poe, B.T., Tronnes, R.G., Liebske, C., Duba, A., Rubie, D.C., 2004. A new large-volume multianvil system. Phys. Earth Planet. Inter. 143, 507). However, it also shifts the pressure maximum to higher press loads, in some cases exceeding the capacity of a press. Our and Frost et al. (2004) data reveal that the 14/6, 18/8, and 18/10 assemblies are the most suitable in generating pressures of up to 19-24 GPa at 19 MN press load limits. The assemblies with a low a0/ b ratio have a lower upper pressure limit; however, they exhibit a systematically higher efficiency in pressure generation at low press loads. Consequently, assemblages with high and low a0/ b ratios should be used in high and low pressure experiments, respectively. For example, the 18/12 assembly is suitable for 5-11 GPa pressure range (Stoyanov, E., Haussermann, U., Leinenweber, K., 2010. Large-volume multianvil cells designed for chemical synthesis at high pressures. High Pressure Res., 30, 175), whereas the 14/6, 18/8 ( Frost et al., 2004), and 18/10 assemblies are suitable for 22-24, 19-23, and 11-19 GPa pressure ranges, respectively. The maximum pressure generation achieved in the present study is 24 GPa, using the 14/6 assembly. This appears to be the maximum pressure level attainable by using WC anvils.

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.

Force-velocity relation for actin-polymerization-driven motility from Brownian dynamics simulations.

PubMed

Lee, Kun-Chun; Liu, Andrea J

2009-09-02

We report numerical simulation results for the force-velocity relation for actin-polymerization-driven motility. We use Brownian dynamics to solve a physically consistent formulation of the dendritic nucleation model with semiflexible filaments that self-assemble and push a disk. We find that at small loads, the disk speed is independent of load, whereas at high loads, the speed decreases and vanishes at a characteristic stall pressure. Our results demonstrate that at small loads, the velocity is controlled by the reaction rates, whereas at high loads the stall pressure is determined by the mechanical properties of the branched actin network. The behavior is consistent with experiments and with our recently proposed self-diffusiophoretic mechanism for actin-polymerization-driven motility. New in vitro experiments to measure the force-velocity relation are proposed.

Apparatus and method for pressure testing closure disks

DOEpatents

Merten, Jr., Charles W.

1992-01-21

A method and device for testing the burst pressure of closure disks which provides high pressure to both sides of a disk and rapidly releases pressure from one side thereof causing a high rate of change of pressure. A hollow notched plug allows the rapid release of pressure upon rupturing. A tensile load is transmitted by a piston in combination with fluid pressure to the hollow notched plug.

Mechanical and histological characterization of trachea tissue subjected to blast-type pressures

NASA Astrophysics Data System (ADS)

Butler, B. J.; Bo, C.; Tucker, A. W.; Jardine, A. P.; Proud, W. G.; Williams, A.; Brown, K. A.

2014-05-01

Injuries to the respiratory system can be a component of polytrauma in blast-loading injuries. Tissues located at air-liquid interfaces, including such tissues in the respiratory system, are particularly vulnerable to damage by blast overpressures. There is a lack of information about the mechanical and cellular responses that contribute to the damage of this class of tissues subjected to the high strain rates associated with blast loading. Here, we describe the results of dynamic blast-like pressure loading tests at high strain rates on freshly harvested ex vivo trachea tissue specimens.

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.

High-Pressure Quasi-Isentropic Loading and Unloading of Interferometer Windows on the Veloce Pulsed Power Generator

NASA Astrophysics Data System (ADS)

Ao, Tommy; Asay, James; Knudson, Marcus; Davis, Jean-Paul

2007-06-01

The Isentropic Compression Experiment technique has proven to be a valuable complement to the well-established method of shock compression of condensed matter. However, whereas the high-pressure compression response of window materials has been studied extensively under shock loading, similar knowledge of these materials under ICE loading is limited. We present recent experimental results on the isentropic compression of the high-pressure windows sapphire and LiF. It has previously been observed that c-cut sapphire yields under shock loading at the HEL of ˜15-18GPa, and subsequently loses transparency at higher stresses. However, it will be shown that under isentropic ramp wave loading sapphire appears to remain elastic and transparent at stresses well above 20GPa [D.B. Hayes et al, JAP 94, 2331 (2003)]. LiF is another frequently used window material in isentropic loading and unloading experiments, yet the unloading response of LiF is usually neglected. Research is in progress to measure strength properties of LiF for ramp loading and unloading. It will be shown how the strength of LiF may influence wave profile analysis and thus inferred material strength. Sandia is a multiprogram laboratory operated by Sandia Corp., a Lockheed Martin Company, for the US DOE's NNSA under Contract No.DE-AC04-94AL85000.

PVDF Gauge Piezoelectric Response under Two-Stage Light Gas Gun Impact Loading

NASA Astrophysics Data System (ADS)

Bauer, Francois

2002-07-01

Stress gauges based on ferroelectric polymer (PVDF) studies under very high pressure shock compression have shown that the piezoelectric response exhibits a precise reproducible behavior up to 25 GPa. Shock pressure profiles obtained with "in situ" PVDF gauges in porous H.E. (Formex) in a detonation regime have been achieved. Observations of a fast superpressure of a few nanoseconds followed by a pressure release have raised the question of the loading path dependence of the piezoelectric response of PVDF at high shock pressure levels. Consequently, studies of the piezoelectric behavior of PVDF gauges under impact loading using a two-stage light gas gun have been conducted recently. Symmetric impact as well as non symmetric impact and reverse impact techniques have been achieved. Strong viscoplastic behavior of some materials is observed. In typical experiments, the piezoelectric response of PVDF at shock equilibrium could be determined. These results show that the PVDF response appears independent of the loading path up to 30 GPa. Accurate measurements in situ H.E. are also reported with very low inductance PVDF gauges.

Effects of Front-Loading and Stagger Angle on Endwall Losses of High Lift Low Pressure Turbine Vanes

DTIC Science & Technology

2012-09-01

TURBINE VANES DISSERTATION Presented to the Faculty Department of Aeronautical and Astronautical... Engineering and Management iv AFIT/DS/ENY/12-05 Abstract Past efforts to reduce the airfoil count in low pressure turbines have produced high lift...LOSSES OF HIGH LIFT LOW PRESSURE TURBINE VANES 1. Introduction The low pressure turbine (LPT) in modern high bypass ratio aero- engines is

The determination of equivalent bearing loading for the BSMT that simulate SSME high pressure oxidizer turbopump conditions using the SHABERTH/SINDA computer programs

NASA Technical Reports Server (NTRS)

Mcdonald, Gary H.

1987-01-01

The MSFC bearing seal material tester (BSMT) can be used to evaluate the SSME high pressure oxygen turbopump (HPOTP) bearing performance. The four HPOTP bearings have both an imposed radial and axial load. These radial and axial loads are caused by the HPOTP's shaft, main impeller, preburner impeller, turbine and by the LOX coolant flow through the bearings, respectively. These loads coupled with bearing geometry and operating speed can define bearing contact angle, contact Hertz stress, and heat generation rates. The BSMT has the capability of operating at HPOTP shaft speeds, provide proper coolant flowrates but can only apply an axial load. Due to the inability to operate the bearings in the BSMT with an applied radial load, it is important to develop an equivalency between the applied axial loads and the actual HPOTP loadings. A shaft-bearing-thermal computer code (SHABERTH/SINDA) is used to simulate the BSMT bearing-shaft geometry and thermal-fluid operating conditions.

Simulation of plasma loading of high-pressure RF cavities

NASA Astrophysics Data System (ADS)

Yu, K.; Samulyak, R.; Yonehara, K.; Freemire, B.

2018-01-01

Muon beam-induced plasma loading of radio-frequency (RF) cavities filled with high pressure hydrogen gas with 1% dry air dopant has been studied via numerical simulations. The electromagnetic code SPACE, that resolves relevant atomic physics processes, including ionization by the muon beam, electron attachment to dopant molecules, and electron-ion and ion-ion recombination, has been used. Simulations studies have been performed in the range of parameters typical for practical muon cooling channels.

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

Performance evaluation of high-strength steel pipelines for high-pressure gaseous hydrogen transportation.

DOT National Transportation Integrated Search

2009-01-01

Pipeline steels suffer significant degradation of their mechanical properties in high-pressure : gaseous hydrogen, including their fatigue cracking resistances to cyclic loading. The current : project work was conducted to produce fatigue crack growt...

High density load bearing insulation peg

DOEpatents

Nowobilski, J.J.; Owens, W.J.

1985-01-29

A high density peg is disclosed which can support a large load and exhibits excellent thermal resistance produced by a method wherein the peg is made in compliance with specified conditions of time, temperature and pressure. 4 figs.

Recent advances in high-pressure freezing: equipment- and specimen-loading methods.

PubMed

McDonald, Kent L; Morphew, Mary; Verkade, Paul; Müller-Reichert, Thomas

2007-01-01

This chapter is an update of material first published by McDonald in the first volume of this book. Here, we discuss the improvements in the technology and the methodology of high-pressure freezing (HPF) since that article was published. First, we cover the latest innovation in HPF, the Leica EM PACT2. This machine differs significantly from the BAL-TEC HPM 010 high-pressure freezer, which was the main subject of the former chapter. The EM PACT2 is a smaller, portable machine and has an optional attachment, the Rapid Transfer System (RTS). This RTS permits easy and reproducible loading of the sample and allows one to do correlative light and electron microscopy with high time resolution. We also place more emphasis in this article on the details of specimen loading for HPF, which is considered the most critical phase of the whole process. Detailed procedures are described for how to high-pressure freeze cells in suspension, cells attached to substrates, tissue samples, or whole organisms smaller than 300 microm, and tissues or organisms greater than 300 microm in size. We finish the article with a brief discussion of freeze substitution and recommend some sample protocols for this procedure.

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

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.

Effect of Winglets on a First-Generation Jet Transport Wing. 2: Pressure and Spanwise Load Distributions for a Semispan Model at High Subsonic Speeds. [in the Langley 8 ft transonic tunnel

NASA Technical Reports Server (NTRS)

Montoya, L. C.; Flechner, S. G.; Jacobs, P. F.

1977-01-01

Pressure and spanwise load distributions on a first-generation jet transport semispan model at high subsonic speeds are presented for the basic wing and for configurations with an upper winglet only, upper and lower winglets, and a simple wing-tip extension. Selected data are discussed to show the general trends and effects of the various configurations.

Energy efficient fluid powered linear actuator with variable area

DOEpatents

Lind, Randall F.; Love, Lonnie J.

2016-09-13

Hydraulic actuation systems having variable displacements and energy recovery capabilities include cylinders with pistons disposed inside of barrels. When operating in energy consuming modes, high speed valves pressurize extension chambers or retraction chambers to provide enough force to meet or counteract an opposite load force. When operating in energy recovery modes, high speed valves return a working fluid from extension chambers or retraction chambers, which are pressurized by a load, to an accumulator for later use.

Simulation of plasma loading of high-pressure RF cavities

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

Yu, K.; Samulyak, R.; Yonehara, K.

2018-01-11

Muon beam-induced plasma loading of radio-frequency (RF) cavities filled with high pressure hydrogen gas with 1% dry air dopant has been studied via numerical simulations. The electromagnetic code SPACE, that resolves relevant atomic physics processes, including ionization by the muon beam, electron attachment to dopant molecules, and electron-ion and ion-ion recombination, has been used. Simulations studies have also been performed in the range of parameters typical for practical muon cooling channels.

Analysis of a Hybrid Wing Body Center Section Test Article

NASA Technical Reports Server (NTRS)

Wu, Hsi-Yung T.; Shaw, Peter; Przekop, Adam

2013-01-01

The hybrid wing body center section test article is an all-composite structure made of crown, floor, keel, bulkhead, and rib panels utilizing the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) design concept. The primary goal of this test article is to prove that PRSEUS components are capable of carrying combined loads that are representative of a hybrid wing body pressure cabin design regime. This paper summarizes the analytical approach, analysis results, and failure predictions of the test article. A global finite element model of composite panels, metallic fittings, mechanical fasteners, and the Combined Loads Test System (COLTS) test fixture was used to conduct linear structural strength and stability analyses to validate the specimen under the most critical combination of bending and pressure loading conditions found in the hybrid wing body pressure cabin. Local detail analyses were also performed at locations with high stress concentrations, at Tee-cap noodle interfaces with surrounding laminates, and at fastener locations with high bearing/bypass loads. Failure predictions for different composite and metallic failure modes were made, and nonlinear analyses were also performed to study the structural response of the test article under combined bending and pressure loading. This large-scale specimen test will be conducted at the COLTS facility at the NASA Langley Research Center.

Inelastic compaction, dilation and hysteresis of sandstones under hydrostatic conditions

NASA Astrophysics Data System (ADS)

Shalev, Eyal; Lyakhovsky, Vladimir; Ougier-Simonin, Audrey; Hamiel, Yariv; Zhu, Wenlu

2014-05-01

Sandstones display non-linear and inelastic behaviour such as hysteresis when subjected to cyclic loading. We present three hydrostatic compaction experiments with multiple loading-unloading cycles on Berea and Darley Dale sandstones and explain their hysteretic behaviour using non-linear inelastic compaction and dilation. Each experiment included eight to nine loading-unloading cycles with increasing maximum pressure in each subsequent cycle. Different pressure-volumetric strain relations during loading and unloading were observed. During the first cycles, under relatively low pressures, not all of the volumetric strain is recovered at the end of each cycle whereas at the last cycles, under relatively high pressures, the strain is recovered and the pressure-volumetric strain hysteresis loops are closed. The observed pressure-volumetric strain relations are non-linear and the effective bulk modulus of the sandstones changes between cycles. Observations are modelled with two inelastic deformation processes: irreversible compaction caused by changes in grain packing and recoverable compaction associated with grain contact adhesion, frictional sliding on grains or frictional sliding on cracks. The irreversible compaction is suggested to reflect rearrangement of grains into a more compact mode as the maximum pressure increases. Our model describes the `inelastic compaction envelope' in which sandstone sample will follow during hydrostatic loading. Irreversible compaction occurs when pressure is greater than a threshold value defined by the `inelastic compaction envelope'.

Numerical Simulation and Validation of a High Head Model Francis Turbine at Part Load Operating Condition

NASA Astrophysics Data System (ADS)

Goyal, Rahul; Trivedi, Chirag; Kumar Gandhi, Bhupendra; Cervantes, Michel J.

2017-07-01

Hydraulic turbines are operated over an extended operating range to meet the real time electricity demand. Turbines operated at part load have flow parameters not matching the designed ones. This results in unstable flow conditions in the runner and draft tube developing low frequency and high amplitude pressure pulsations. The unsteady pressure pulsations affect the dynamic stability of the turbine and cause additional fatigue. The work presented in this paper discusses the flow field investigation of a high head model Francis turbine at part load: 50% of the rated load. Numerical simulation of the complete turbine has been performed. Unsteady pressure pulsations in the vaneless space, runner, and draft tube are investigated and validated with available experimental data. Detailed analysis of the rotor stator interaction and draft tube flow field are performed and discussed. The analysis shows the presence of a rotating vortex rope in the draft tube at the frequency of 0.3 times of the runner rotational frequency. The frequency of the vortex rope precession, which causes severe fluctuations and vibrations in the draft tube, is predicted within 3.9% of the experimental measured value. The vortex rope results pressure pulsations propagating in the system whose frequency is also perceive in the runner and upstream the runner.

Transient Pressure Measurements in the Vaneless Space of a Francis Turbine during Load Acceptances from Minimum Load

NASA Astrophysics Data System (ADS)

Goyal, R.; Gandhi, B. K.; Cervantes, M. J.

2018-06-01

Increased penetration of solar and the wind impels the designers of the hydroelectric power generation unit to provide more flexibility in operation for the stability of the grid. The power generating unit includes turbine which needs to sustain sudden change in its operating conditions. Thus, the hydraulic turbine experiences more transients per day which result in chronic problems such as fatigue to the runner, instrument malfunctioning, vibrations, wear and tear etc. This paper describes experiments performed on a high model (1.5:1) Francis turbine for load acceptances from the minimum load. The experiments presented in the paper are the part of Francis-99 workshop which aims to determine the performance of numerical models in simulations of model Francis turbine under steady and transient operating conditions. The aim of the paper is to present the transient pressure variation in the vaneless space of a Francis turbine where high-frequency pulsations are normally expected. For this, two pressure sensors, VL1 and VL2, are mounted at the vaneless space, one near the beginning of the spiral casing and the other before the end of the spiral casing. Both are used to capture the unsteady pressure field developed in the space between guide vanes and runner inlet. The time-resolved pressure signals are analyzed and presented during the transient to observe the pressure variation and dominant frequencies of pulsations.

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.

Composite load spectra for select space propulsion structural components

NASA Technical Reports Server (NTRS)

Newell, J. F.; Ho, H. W.; Kurth, R. E.

1991-01-01

The work performed to develop composite load spectra (CLS) for the Space Shuttle Main Engine (SSME) using probabilistic methods. The three methods were implemented to be the engine system influence model. RASCAL was chosen to be the principal method as most component load models were implemented with the method. Validation of RASCAL was performed. High accuracy comparable to the Monte Carlo method can be obtained if a large enough bin size is used. Generic probabilistic models were developed and implemented for load calculations using the probabilistic methods discussed above. Each engine mission, either a real fighter or a test, has three mission phases: the engine start transient phase, the steady state phase, and the engine cut off transient phase. Power level and engine operating inlet conditions change during a mission. The load calculation module provides the steady-state and quasi-steady state calculation procedures with duty-cycle-data option. The quasi-steady state procedure is for engine transient phase calculations. In addition, a few generic probabilistic load models were also developed for specific conditions. These include the fixed transient spike model, the poison arrival transient spike model, and the rare event model. These generic probabilistic load models provide sufficient latitude for simulating loads with specific conditions. For SSME components, turbine blades, transfer ducts, LOX post, and the high pressure oxidizer turbopump (HPOTP) discharge duct were selected for application of the CLS program. They include static pressure loads and dynamic pressure loads for all four components, centrifugal force for the turbine blade, temperatures of thermal loads for all four components, and structural vibration loads for the ducts and LOX posts.

Rotordynamic Characteristics of the HPOTP (High Pressure Oxygen Turbopump) of the SSME (Space Shuttle Main Engine)

NASA Technical Reports Server (NTRS)

Childs, D. W.

1984-01-01

Rotational stability of turbopump components in the space shuttle main engine was studied via analysis of component and structural dynamic models. Subsynchronous vibration caused unacceptable migration of the rotor/housing unit with unequal load sharing of the synchronous bearings that resulted in the failure of the High Pressure Oxygen Turbopump. Linear analysis shows that a shrouded inducer eliminates the second critical speed and the stability problem, a stiffened rotor improves the rotordynamic characteristics of the turbopump, and installing damper boost/impeller seals reduces bearing loads. Nonlinear analysis shows that by increasing the "dead band' clearances, a marked reduction in peak bearing loads occurs.

Combined pressure regulator and shutoff valve

NASA Technical Reports Server (NTRS)

Koch, E. F. (Inventor)

1974-01-01

A remotely operable pressure regulator and shutoff valve particularly suited for achieving high resolution and flow control, and positive shutoff is described. The valve is characterized by a spring-loaded ball coaxially aligned with a fluid port to be sealed, a spring-loaded pintle extended through the port into engagement with the ball, for controlling the position, a spring-loaded diaphragm for controlling the position of the pintle, and an axially displaceable spring supported by a movable stop which, in turn, is repositioned by a selectively operable stepper motor. Thus, the pressure-response characteristics for the valve can be varied through a selective repositioning of the stop.

Low-load resistance training with low relative pressure produces muscular changes similar to high-load resistance training.

PubMed

Kim, Daeyeol; Loenneke, Jeremy P; Ye, Xin; Bemben, Debra A; Beck, Travis W; Larson, Rebecca D; Bemben, Michael G

2017-12-01

This study compares the acute and chronic response of high-load resistance training (HL) to low-load resistance training with low blood flow restriction (LL-BFR) pressure. Participants completed elbow flexion with either HL or LL-BFR or nonexercise. In the chronic study, participants in the HL and LL-BFR groups were trained for 8 weeks to determine differences in muscle size and strength. The acute study examined the changes in pretesting/posttesting (Pre/Post) torque, muscle swelling, and blood lactate. In the chronic study, similar changes in muscle size and strength were observed for both HL and LL-BFR. In the acute study, Pre/Post changes in the torque, muscle swelling, and blood lactate were similar between HL and LL-BFR. Our findings indicate that pressure as low as 50% arterial occlusion can produce similar changes in muscle mass and strength compared with traditional HL. Muscle Nerve 56: E126-E133, 2017. © 2017 Wiley Periodicals, Inc.

Effects of Brass (Cu3Zn2) as High Thermal Expansion Material on Shrink Disc Performance During High Thermal Loading

NASA Astrophysics Data System (ADS)

Mazlan, MIS; Mohd, SA; Bahar, ND; Aziz, SAA

2018-03-01

This research work is focused on shrink disc operation at high temperature. Geometrical and material design selections have been done by taking into consideration the existing shrink disc operating at high temperature condition. The existing shrink disc confronted slip between shaft and shaft sleeve during thermal loading condition. The assessment has been obtained through virtual experiment by using Finite Element Analysis (FEA) -Thermal Transient Stress for 900 seconds with 300 °C of thermal loading. This investigation consists of the current and improved version of shrink disc, where identical geometries and material properties were utilized. High Thermal Expansion (HTE) material has been introduced to overcome the current design of the shrink disc. Brass (Cu3Zn2) has been selected as the HTE material in the improved shrink disc design due to its high thermal expansion properties. The HTE has shown a significant improvement on the total contact area and contact pressure on the shaft and the shaft sleeve. The improved shrink disc embedded with HTE during thermal loading exhibit a minimum of 1244.1 mm2 of the total area on shaft and shaft sleeve which uninfluenced the total contact area at normal condition which is 1254.3 mm2. Meanwhile, the total pressure of improved shrink disc had an increment of 108.1 MPa while existing shrink disc total pressure has lost 17.2 MPa during thermal loading.

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

NASA Technical Reports Server (NTRS)

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

1982-01-01

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

High pressure-assisted encapsulation of vitamin D2 in reassembled casein micelles

NASA Astrophysics Data System (ADS)

Menéndez-Aguirre, O.; Stuetz, W.; Grune, T.; Kessler, A.; Weiss, J.; Hinrichs, J.

2011-03-01

For the encapsulation of vitamin D2, native casein micelles and vitamin D2 with or without additional Ca2+-Pi were treated at 600 MPa and 37 °C for 60 min. The pressure release rate was set at 20 or 600 MPa/min. Vitamin D2 was quantified by reversed-phase high-performance liquid chromatography, and physical properties of the micelles were analysed by photon correlation spectroscopy. The results demonstrate that simultaneous application of Ca2+-Pi and high pressure treatment with a fast release rate significantly increased loading of vitamin D2 per casein by 6.9-fold. The addition of Ca2+-Pi enhanced micelle aggregation and the vitamin was entrapped within the formed aggregates. However, high pressure treatment without Ca2+-Pi with a slow pressure release rate revealed similar results, increasing vitamin D2 per casein by 6.7-fold. The vitamin D2 loading in reassembled casein micelles is supposed to be due to hydrophobic interactions between the hydrophobic domains of the micelles.

System Design of a Natural Gas PEM Fuel Cell Power Plant for Buildings

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

Joe Ferrall, Tim Rehg, Vesna Stanic

2000-09-30

The following conclusions are made based on this analysis effort: (1) High-temperature PEM data are not available; (2) Stack development effort for Phase II is required; (3) System results are by definition preliminary, mostly due to the immaturity of the high-temperature stack; other components of the system are relatively well defined; (4) The Grotthuss conduction mechanism yields the preferred system characteristics; the Grotthuss conduction mechanism is also much less technically mature than the vehicle mechanism; (5) Fuel processor technology is available today and can be procured for Phase II (steam or ATR); (6) The immaturity of high-temperature membrane technology requiresmore » that a robust system design be developed in Phase II that is capable of operating over a wide temperature and pressure range - (a) Unpressurized or Pressurized PEM (Grotthuss mechanism) at 140 C, Highest temperature most favorable, Lowest water requirement most favorable, Pressurized recommended for base loaded operation, Unpressurized may be preferred for load following; (b) Pressurized PEM (vehicle mechanism) at about 100 C, Pressure required for saturation, Fuel cell technology currently available, stack development required. The system analysis and screening evaluation resulted in the identification of the following components for the most promising system: (1) Steam reforming fuel processor; (2) Grotthuss mechanism fuel cell stack operating at 140 C; (3) Means to deliver system waste heat to a cogeneration unit; (4) Pressurized system utilizing a turbocompressor for a base-load power application. If duty cycling is anticipated, the benefits of compression may be offset due to complexity of control. In this case (and even in the base loaded case), the turbocompressor can be replaced with a blower for low-pressure operation.« less

Transient/structural analysis of a combustor under explosive loads

NASA Technical Reports Server (NTRS)

Gregory, Peyton B.; Holland, Anne D.

1992-01-01

The 8-Foot High Temperature Tunnel (HTT) at NASA Langley Research Center is a combustion-driven blow-down wind tunnel. A major potential failure mode that was considered during the combustor redesign was the possibility of a deflagration and/or detonation in the combustor. If a main burner flame-out were to occur, then unburned fuel gases could accumulate and, if reignited, an explosion could occur. An analysis has been performed to determine the safe operating limits of the combustor under transient explosive loads. The failure criteria was defined and the failure mechanisms were determined for both peak pressures and differential pressure loadings. An overview of the gas dynamics analysis was given. A finite element model was constructed to evaluate 13 transient load cases. The sensitivity of the structure to the frequency content of the transient loading was assessed. In addition, two closed form dynamic analyses were conducted to verify the finite element analysis. It was determined that the differential pressure load or thrust load was the critical load mechanism and that the nozzle is the weak link in the combustor system.

Further Development of Crack Growth Detection Techniques for US Test and Research Reactors

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

Kohse, Gordon; Carpenter, David M.; Ostrovsky, Yakov

One of the key issues facing Light Water Reactors (LWRs) in extending lifetimes beyond 60 years is characterizing the combined effect of irradiation and water chemistry on material degradation and failure. Irradiation Assisted Stress Corrosion Cracking (IASCC), in which a crack propagates in a susceptible material under stress in an aggressive environment, is a mechanism of particular concern. Full understanding of IASCC depends on real time crack growth data acquired under relevant irradiation conditions. Techniques to measure crack growth in actively loaded samples under irradiation have been developed outside the US - at the Halden Boiling Water Reactor, for example.more » Several types of IASCC tests have also been deployed at the MITR, including passively loaded crack growth measurements and actively loaded slow strain rate tests. However, there is not currently a facility available in the US to measure crack growth on actively loaded, pre-cracked specimens in LWR irradiation environments. A joint program between the Idaho National Laboratory (INL) and the Massachusetts Institute of Technology (MIT) Nuclear Reactor Laboratory (NRL) is currently underway to develop and demonstrate such a capability for US test and research reactors. Based on the Halden design, the samples will be loaded using miniature high pressure bellows and a compact loading mechanism, with crack length measured in real time using the switched Direct Current Potential Drop (DCPD) method. The basic design and initial mechanical testing of the load system and implementation of the DCPD method have been previously reported. This paper presents the results of initial autoclave testing at INL and the adaptation of the design for use in the high pressure, high temperature water loop at the MITR 6 MW research reactor, where an initial demonstration is planned in mid-2015. Materials considerations for the high pressure bellows are addressed. Design modifications to the loading mechanism required by the size constraints of the MITR water loop are described. The safety case for operation of the high pressure gas-driven bellows mechanism is also presented. Key issues are the design and response of systems to limit gas flow in the event of a high pressure gas leak in the in-core autoclave. Integrity of the autoclave must be maintained and reactivity effects due to voiding of the loop coolant must be shown to be within the reactor technical specifications. The technical development of the crack growth monitor for application in the INL Advanced Test Reactor or the MITR can act as a template for adaptation of this technology in other reactors. (authors)« less

The dynamics and control of fluctuating pressure loads in the reattachment region of a supersonic free shear layer

NASA Technical Reports Server (NTRS)

Smits, A. J.

1990-01-01

The primary aim is to investigate the mechanisms which cause the unsteady wall-pressure fluctuations in shock wave turbulent shear layer interactions. The secondary aim is to find means to reduce the magnitude of the fluctuating pressure loads by controlling the unsteady shock motion. The particular flow proposed for study is the unsteady shock wave interaction formed in the reattachment zone of a separated supersonic flow. Similar flows are encountered in many practical situations, and they are associated with high levels of fluctuating wall pressure. Wall pressure fluctuations were measured in the reattachment region of the supersonic free shear layer. The free shear layer was formed by the separation of a Mach 2.9 turbulent boundary layer from a backward facing step. Reattachment occurred on a 20 deg ramp. By adjusting the position of the ramp, the base pressure was set equal to the freestream pressure, and the free shear layer formed in the absence of a separation shock. An array of flush-mounted, miniature, high-frequency pressure transducers was used to make multichannel measurements of the fluctuating wall pressure in the vicinity of the reattachment region. Contrary to previous observations of this flow, the reattachment region was found to be highly unsteady, and the pressure fluctuations were found to be significant. The overall behavior of the wall pressure loading is similar in scale and magnitude to the unsteadiness of the wall pressure field in compression ramp flows at the same Mach number. Rayleigh scattering was used to visualize the instantaneous shock structure in the streamwise and spanwise direction. Spanwise wrinkles on the order of half the boundary layer thickness were observed.

Evaluation of load tracks and wear of two sets of bearings from space shuttle main engine high pressure oxygen turbopumps

NASA Technical Reports Server (NTRS)

Kannel, J. W.; Dufrane, K. F.

1985-01-01

Bearings supporting the rotor in the High Pressure Oxygen Turbopump (HPOTP) were examined. The No. 1 bearings from both units were in good condition and had successfully completed 5000 seconds of operation. The No. 2 bearings, which were in service the same length of time, were significantly degraded in the form of ball wear, race pitting, and damage from high axial loads. The No. 3 and 4 bearings were in generally acceptable condition. The general conclusion from the examinations was that improved cooling on the No. 2 bearings and further improvements in controlling axial and radial load would likely result in the HPOTP meeting the qualification test results.

The effective forces transmitted by high-speed, low-amplitude thoracic manipulation.

PubMed

Herzog, W; Kats, M; Symons, B

2001-10-01

Twenty asymptomatic volunteers each received three spinal manipulative treatments to the thoracic spine. The treatments consisted of a straight posterior-to-anterior high-speed, low-amplitude thrust to the transverse process of T3-T10 using a reinforced hypothenar contact. All treatments were given by a full-time practicing clinician with 3 years of experience. The primary objective of this study was to quantify local measures of loading applied by the clinician on the volunteers during spinal manipulative treatments and to compare these local measures of loading with previously described global measures. The sparse information on the mechanics of spinal manipulative treatments deals exclusively with global force or pressure measurements. On the basis of these global data, incorrect conclusions may be drawn about the beneficial effects of spinal manipulative therapy, the loading of internal structures, and the risks associated with these treatments. Twenty asymptomatic subjects each received three posterior-to-anterior, high-speed, low-amplitude spinal manipulative treatments to the transverse process of the thoracic spine. Total force, local force, contact area, peak pressure, and average pressure at the contact interface between clinician and subject were measured continuously by use of a thin, flexible pressure pad. Local and global measures of loading were compared and analyzed by use of nonparametric statistics (alpha = 0.01). The average peak total force was 238.2 N. The average peak local force over a target area of 25 mm2 was 5 N, indicating that global measures of loading vastly overestimate the local effective forces at the target site. The peak pressure point moved, on average, 9.8 mm during the course of the manipulation. To the authors' best knowledge, this is the first study to quantify local, effective measures of loading and compare them with the global measures typically used. The conclusions are limited because the study used a single clinician. The effective loading of specific target sites is much smaller than the global measures might suggest. This result occurs because as the forces during spinal manipulative treatment increase, so does the contact area; therefore, much of the total treatment force is taken up by non-target-specific tissues. Because of the vast discrepancy between the global and local measures of loading, it is suggested that risk-benefit assessments of high-speed, low-amplitude spinal manipulative treatments should be made, including local measures of loading. Finally, because theoretical approaches and the inverse dynamics approach can provide only global measures of loading, the results of such studies should be interpreted with caution.

The influence of exogenous cross-linking and compressive creep loading on intradiscal pressure.

PubMed

Chuang, Shih-Youeng; Lin, Leou-Chyr; Hedman, Thomas P

2010-10-01

This study involves a biomechanical evaluation of a prospective injectable treatment for degenerative discs. The high osmolarity of the non-degenerated nucleus pulposus attracts water contributing to the hydrostatic behavior of the tissue. This intradiscal pressure is known to drop as fluid is exuded from the matrix due to compressive loading. The objective of this study was to compare the changes in intradiscal pressure in control and genipin cross-linked intervertebral discs. Thirty bovine lumbar motion segments were randomly divided into a phosphate-buffered saline control group and a 0.33% genipin group and soaked at room temperature for 2 days. A needle pressure sensor was held in the center of the disc while short-term and static creep compressive loads were applied. The control group demonstrated a 25% higher average intradiscal pressure compared to genipin-treated discs under 750 N compressive load (p=0.029). Depressurization during static compressive creep was 56% higher in the control than in the genipin group (p=0.014). These results suggest cross-linking induced changes in the poroelastic properties of the involved tissues affected the mechanics of compressive load support in the disc with lower levels of nucleus pressure, a corresponding decrease in the elastic expansion of the annulus, and an increased axial compressive loading of the inner and outer annulus tissues. It is possible that concurrent changes in hydraulic permeability and proteoglycan retention known to be associated with genipin cross-linking were also contributors to poroelastic changes. Reduction of peak pressures and moderation of pressure fluctuations could be beneficial relative to discogenic pain.

Development of a novel test-setup for identifying the frictional characteristics of carbon fibre reinforced polymer composites at high surface pressure

NASA Astrophysics Data System (ADS)

Saxena, Prateek; Schinzel, Marie; Andrich, Manuela; Modler, Niels

2016-09-01

Carbon fibre reinforced polymer composites are extensively used in industrial applications. They are light in weight and have excellent load bearing properties. To understand this material's behaviour when carrying loads at high pressure, a tensile-friction test device was developed that can apply a contact surface pressure between composite and counterpart of 50-300 MPa. A tribological investigation of carbon fibre reinforced epoxy composites was carried out, in which the influence of the surface morphology was investigated by using grinding and sandblasting techniques. The friction coefficient of the polymer composite was measured at 100 MPa surface pressure against uncoated and Diamond-Like Carbon coated stainless steel counterparts.

Performance deterioration based on simulated aerodynamic loads test, JT9D jet engine diagnostics program

NASA Technical Reports Server (NTRS)

Stromberg, W. J.

1981-01-01

An engine was specially prepared with extensive instrumentation to monitor performance, case temperatures, and clearance changes. A special loading device was used to apply known loads on the engine by the use of cables placed around the flight inlet. These loads simulated the estimated aerodynamic pressure distributions that occur on the inlet in various segments of a typical airplane flight. Test results indicate that the engine lost 1.3 percent in take-off thrust specific fuel consumption (TSFC) during the course of the test effort. Permanent clearance changes due to the loads accounted for 1.1 percent; increase in low pressure compressor airfoil roughness and thermal distortion in the high pressure turbine accounted for 0.2 percent. Pretest predicted performance loss due to clearance changes was 0.9 percent in TSFC. Therefore, the agreement between measurement and prediction is considered to be excellent.

Helicopter rotor rotational noise predictions based on measured high-frequency blade loads

NASA Technical Reports Server (NTRS)

Hosier, R. N.; Ramakrishnan, R.

1974-01-01

In tests conducted at the Langley helicopter rotor test facility, simultaneous measurements of up to 200 harmonics of the fluctuating aerodynamic blade surface pressures and far-field radiated noise were made on a full-scale nontranslating rotor system. After their characteristics were determined, the measured blade surface pressures were converted to loading coefficients and used in an existing theory to predict the far-field rotational noise. A comparison of the calculated and measured noise shows generally good agreement up to 300 to 600 Hz, depending on the discreteness of the loading spectrum. Specific attention is given to the effects of the blade loading coefficients, chordwise loading distributions, blade loading phases, and observer azimuthal position on the calculations.

Energy efficient fluid powered linear actuator with variable area and concentric chambers

DOEpatents

Lind, Randall F.; Love, Lonnie J.

2016-11-15

Hydraulic actuation systems having concentric chambers, variable displacements and energy recovery capabilities include cylinders with pistons disposed inside of barrels. When operating in energy consuming modes, high speed valves pressurize extension chambers or retraction chambers to provide enough force to meet or counteract an opposite load force. When operating in energy recovery modes, high speed valves return a working fluid from extension chambers or retraction chambers, which are pressurized by a load, to an accumulator for later use.

High speed propeller performance and noise predictions at takeoff/landing conditions

NASA Technical Reports Server (NTRS)

Nallasamy, M.; Woodward, R. P.; Groeneweg, J. F.

1988-01-01

The performance and noise of a high speed SR-7A model propeller under takeoff/landing conditions are considered. The blade loading distributions are obtained by solving the three-dimensional Euler equations and the sound pressure levels are computed using a time domain approach. At the nominal takeoff operating point, the blade sections near the hub are lightly or negatively loaded. The chordwise loading distributions are distinctly different from those of cruise conditions. The noise of the SR-7A model propeller at takeoff is dominated by the loading noise, similar to that at cruise conditions. The waveforms of the acoustic pressure signature are nearly sinusoidal in the plane of the propeller. The computed directivity of the blade passing frequency tone agrees fairly well with the data at nominal takeoff blade angle.

High speed propeller performance and noise predictions at takeoff/landing conditions

NASA Technical Reports Server (NTRS)

Nallasamy, M.; Woodward, R. P.; Groeneweg, J. F.

1987-01-01

The performance and noise of a high speed SR-7A model propeller under takeoff/landing conditions are considered. The blade loading distributions are obtained by solving the three-dimensional Euler equations and the sound pressure levels are computed using a time domain approach. At the nominal takeoff operating point, the blade sections near the hub are lightly or negatively loaded. The chordwise loading distributions are distinctly different from those of cruise conditions. The noise of the SR-7A model propeller at takeoff is dominated by the loading noise, similar to that at cruise conditions. The waveforms of the acoustic pressure signature are nearly sinusoidal in the plane of the propeller. The computed directivity of the blade passing frequency tone agrees fairly well with the data at nominal takeoff blade angle.

Discontinuity stresses in metallic pressure vessels

NASA Technical Reports Server (NTRS)

1971-01-01

The state of the art, criteria, and recommended practices for the theoretical and experimental analyses of discontinuity stresses and their distribution in metallic pressure vessels for space vehicles are outlined. The applicable types of pressure vessels include propellant tanks ranging from main load-carrying integral tank structure to small auxiliary tanks, storage tanks, solid propellant motor cases, high pressure gas bottles, and pressurized cabins. The major sources of discontinuity stresses are discussed, including deviations in geometry, material properties, loads, and temperature. The advantages, limitations, and disadvantages of various theoretical and experimental discontinuity analysis methods are summarized. Guides are presented for evaluating discontinuity stresses so that pressure vessel performance will not fall below acceptable levels.

Time-dependent effects of intermittent hydrostatic pressure on articular chondrocyte type II collagen and aggrecan mRNA expression.

PubMed

Smith, R L; Lin, J; Trindade, M C; Shida, J; Kajiyama, G; Vu, T; Hoffman, A R; van der Meulen, M C; Goodman, S B; Schurman, D J; Carter, D R

2000-01-01

The normal loading of joints during daily activities causes the articular cartilage to be exposed to high levels of intermittent hydrostatic pressure. This study quantified effects of intermittent hydrostatic pressure on expression of mRNA for important extracellular matrix constituents. Normal adult bovine articular chondrocytes were isolated and tested in primary culture, either as high-density monolayers or formed aggregates. Loaded cells were exposed to 10 MPa of intermittent hydrostatic pressure at a frequency of 1 Hz for periods of 2, 4, 8, 12, and 24 hrs. Other cells were intermittently loaded for a period of 4 hrs per day for 4 days. Semiquantitative reverse transcription polymerase chain reaction assays were used to assess mRNA signal levels for collagen types II and I and aggrecan. The results showed that type II collagen mRNA signal levels exhibited a biphasic pattern, with an initial increase of approximately five-fold at 4 and 8 hrs that subsequently decreased by 24 hrs. In contrast, aggrecan mRNA signal increased progressively up to three-fold throughout the loading period. Changing the loading profile to 4 hrs per day for 4 days increased the mRNA signal levels for type II collagen nine-fold and for aggrecan twenty-fold when compared to unloaded cultures. These data suggest that specific mechanical loading protocols may be required to optimally promote repair and regeneration of diseased joints.

75 FR 81409 - Airworthiness Directives; The Boeing Company Model 737-200, -300, -400, and -500 Series Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-28

... cracking, caused by high flight cycle stresses from both pressurization and maneuver loads. We are issuing... sections, in addition to stub beam cracking, caused by high flight cycle stresses from both pressurization...

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.

Servo-controlled pneumatic pressure oscillator for respiratory impedance measurements and high-frequency ventilation.

PubMed

Kaczka, David W; Lutchen, Kenneth R

2004-04-01

The ability to provide forced oscillatory excitation of the respiratory system can be useful in mechanical impedance measurements as well as high frequency ventilation (HFV). Experimental systems currently used for generating forced oscillations are limited in their ability to provide high amplitude flows or maintain the respiratory system at a constant mean pressure during excitation. This paper presents the design and implementation of a pneumatic pressure oscillator based on a proportional solenoid valve. The device is capable of providing forced oscillatory excitations to the respiratory system over a bandwidth suitable for mechanical impedance measurements and HVF. It delivers high amplitude flows (> 1.4 l/s) and utilizes a servo-control mechanism to maintain a load at a fixed mean pressure during simultaneous oscillation. Under open-loop conditions, the device exhibited a static hysteresis of approximately 7%, while its dynamic magnitude and phase responses were flat out to 10 Hz. Broad-band measurement of total harmonic distortion was approximately 19%. Under closed-loop conditions, the oscillator was able to maintain a mechanical test load at both positive and negative mean pressures during oscillatory excitations from 0.1 to 10.0 Hz. Impedance of the test load agreed closely with theoretical predictions. We conclude that this servo-controlled oscillator can be a useful tool for respiratory impedance measurements as well as HFV.

Preliminary analytical study on the feasibility of using reinforced concrete pile foundations for renewable energy storage by compressed air energy storage technology

NASA Astrophysics Data System (ADS)

Tulebekova, S.; Saliyev, D.; Zhang, D.; Kim, J. R.; Karabay, A.; Turlybek, A.; Kazybayeva, L.

2017-11-01

Compressed air energy storage technology is one of the promising methods that have high reliability, economic feasibility and low environmental impact. Current applications of the technology are mainly limited to energy storage for power plants using large scale underground caverns. This paper explores the possibility of making use of reinforced concrete pile foundations to store renewable energy generated from solar panels or windmills attached to building structures. The energy will be stored inside the pile foundation with hollow sections via compressed air. Given the relatively small volume of storage provided by the foundation, the required storage pressure is expected to be higher than that in the large-scale underground cavern. The high air pressure typically associated with large temperature increase, combined with structural loads, will make the pile foundation in a complicated loading condition, which might cause issues in the structural and geotechnical safety. This paper presents a preliminary analytical study on the performance of the pile foundation subjected to high pressure, large temperature increase and structural loads. Finite element analyses on pile foundation models, which are built from selected prototype structures, have been conducted. The analytical study identifies maximum stresses in the concrete of the pile foundation under combined pressure, temperature change and structural loads. Recommendations have been made for the use of reinforced concrete pile foundations for renewable energy storage.

Neural control of vascular reactions: impact of emotion and attention.

PubMed

Okon-Singer, Hadas; Mehnert, Jan; Hoyer, Jana; Hellrung, Lydia; Schaare, Herma Lina; Dukart, Juergen; Villringer, Arno

2014-03-19

This study investigated the neural regions involved in blood pressure reactions to negative stimuli and their possible modulation by attention. Twenty-four healthy human subjects (11 females; age = 24.75 ± 2.49 years) participated in an affective perceptual load task that manipulated attention to negative/neutral distractor pictures. fMRI data were collected simultaneously with continuous recording of peripheral arterial blood pressure. A parametric modulation analysis examined the impact of attention and emotion on the relation between neural activation and blood pressure reactivity during the task. When attention was available for processing the distractor pictures, negative pictures resulted in behavioral interference, neural activation in brain regions previously related to emotion, a transient decrease of blood pressure, and a positive correlation between blood pressure response and activation in a network including prefrontal and parietal regions, the amygdala, caudate, and mid-brain. These effects were modulated by attention; behavioral and neural responses to highly negative distractor pictures (compared with neutral pictures) were smaller or diminished, as was the negative blood pressure response when the central task involved high perceptual load. Furthermore, comparing high and low load revealed enhanced activation in frontoparietal regions implicated in attention control. Our results fit theories emphasizing the role of attention in the control of behavioral and neural reactions to irrelevant emotional distracting information. Our findings furthermore extend the function of attention to the control of autonomous reactions associated with negative emotions by showing altered blood pressure reactions to emotional stimuli, the latter being of potential clinical relevance.

Focal cartilage defect compromises fluid-pressure dependent load support in the knee joint.

PubMed

Dabiri, Yaghoub; Li, LePing

2015-06-01

A focal cartilage defect involves tissue loss or rupture. Altered mechanics in the affected joint may play an essential role in the onset and progression of osteoarthritis. The objective of the present study was to determine the compromised load support in the human knee joint during defect progression from the cartilage surface to the cartilage-bone interface. Ten normal and defect cases were simulated with a previously tested 3D finite element model of the knee. The focal defects were considered in both condyles within high load-bearing regions. Fluid pressurization, anisotropic fibril-reinforcement, and depth-dependent mechanical properties were considered for the articular cartilages and menisci. The results showed that a small cartilage defect could cause 25% reduction in the load support of the knee joint due to a reduced capacity of fluid pressurization in the defect cartilage. A partial-thickness defect could cause a fluid pressure decrease or increase in the remaining underlying cartilage depending on the defect depth. A cartilage defect also increased the shear strain at the cartilage-bone interface, which was more significant with a full-thickness defect. The effect of cartilage defect on the fluid pressurization also depended on the defect sites and contact conditions. In conclusion, a focal cartilage defect causes a fluid-pressure dependent load reallocation and a compromised load support in the joint, which depend on the defect depth, site, and contact condition. Copyright © 2015 John Wiley & Sons, Ltd.

Load variation effects on the pressure fluctuations exerted on a Kaplan turbine runner

NASA Astrophysics Data System (ADS)

Amiri, K.; Mulu, B.; Raisee, M.; Cervantes, M. J.

2014-03-01

Introduction of intermittent electricity production systems like wind power and solar systems to electricity market together with the consumption-based electricity production resulted in numerous start/stops, load variations and off-design operation of water turbines. The hydropower systems suffer from the varying loads exerted on the stationary and rotating parts of the turbines during load variations which they are not designed for. On the other hand, investigations on part load operation of single regulated turbines, i.e., Francis and propeller, proved the formation of rotating vortex rope (RVR) in the draft tube. The RVR induces oscillating flow both in plunging and rotating modes which results in oscillating force with two different frequencies on the runner blades, bearings and other rotating parts of the turbine. The purpose of this study is to investigate the effect of transient operations on the pressure fluctuations on the runner and mechanism of the RVR formation/mitigation. Draft tube and runner blades of the Porjus U9 model, a Kaplan turbine, were equipped with pressure sensors. The model was run in off-cam mode during different load variation conditions to check the runner performance under unsteady condition. The results showed that the transients between the best efficiency point and the high load happens in a smooth way while transitions to/from the part load, where rotating vortex rope (RVR) forms in the draft tube induces high level of fluctuations with two frequencies on the runner; plunging and rotating mode of the RVR.

Some Effects of Horizontal-Tail Position on the Vertical-Tail Pressure Distributions of a Complete Model in Sideslip at High Subsonic Speeds

NASA Technical Reports Server (NTRS)

Alford, William J., Jr.

1958-01-01

An investigation has been made in the Langley high-speed 7- by 10-foot tunnel of some effects of horizontal-tail position on the vertical-tail pressure distributions of a complete model in sideslip at high subsonic speeds. The wing of the model was swept back 28.82 deg at the quarter-chord line and had an aspect ratio of 3.50, a taper ratio of 0.067, and NACA 65A004 airfoil sections parallel to the model plane of symmetry. Tests were made with the horizontal tail off, on the wing-chord plane extended, and in T-tail arrangements in forward and rearward locations. The test Mach numbers ranged from 0.60 to 0.92, which corresponds to a Reynolds number range from approximately 2.93 x 10(exp 6) to 3.69 x 10(exp 6), based on the wing mean aerodynamic chord. The sideslip angles varied from -3.9 deg to 12.7 deg at several selected angles of attack. The results indicated that, for a given angle of sideslip, increases in angle of attack caused reductions in the vertical-tail loads in the vicinity of the root chord and increases at the midspan and tip locations, with rearward movements in the local chordwise centers of pressure for the midspan locations and forward movements near the tip of the vertical tail. At the higher angles of attack all configurations investigated experienced outboard and rearward shifts in the center of pressure of the total vertical-tail load. Location of the horizontal tail on the wing- chord plane extended produced only small effects on the vertical-tail loads and centers of pressure. Locating the horizontal tail at the tip of the vertical tail in the forward position caused increases in the vertical-tail loads; this configuration, however, experienced considerable reduction in loads with increasing Mach number. Location of the horizontal tail at the tip of the vertical tail in the rearward position produced the largest increases in vertical-tail loads per degree sideslip angle; this configuration experienced the smallest variations of loads with Mach number of any of the configurations investigated.

A Experimental Study of Fluctuating Pressure Loads Beneath Swept Shock Wave/boundary Layer Interactions

NASA Astrophysics Data System (ADS)

Garg, Sanjay

An experimental research program providing basic knowledge and establishing a database on the fluctuating pressure loads produced on aerodynamic surfaces beneath three-dimensional shock wave/boundary layer interactions is described. Such loads constitute a fundamental problem of critical concern to future supersonic and hypersonic flight vehicles. A turbulent boundary layer on a flat plate is subjected to interactions with swept planar shock waves generated by sharp fins. Fin angles from 10 ^circ to 20^circ at freestream Mach numbers of 3 and 4 produce a variety of interaction strengths from weak to very strong. Miniature pressure transducers flush-mounted in the flat plate have been used to measure interaction-induced wall pressure fluctuations. The distributions of properties of the pressure fluctuations, such as their rms level, amplitude distribution and power spectra, are also determined. Measurements have been made for the first time in the aft regions of these interactions, revealing fluctuating pressure levels as high as 155 dB, which places them in the category of significant aeroacoustic load generators. The fluctuations near the foot of the fin are dominated by low frequency (0-5 kHz) components, and are caused by a previously unrecognized random motion of the primary attachment line. This phenomenon is probably intimately linked to the unsteadiness of the separation shock at the start of the interaction. The characteristics of the pressure fluctuations are explained in light of the features of the interaction flowfield. In particular, physical mechanisms responsible for the generation of high levels of surface pressure fluctuations are proposed based on the results of the study. The unsteadiness of the flowfield of the surface is also examined via a novel, non-intrusive optical technique. Results show that the entire shock structure generated by the interaction undergoes relatively low-frequency oscillations.

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

Space Shuttle Projects

NASA Image and Video Library

1987-07-01

A forward segment is being lowered into the Transient Pressure Test Article (TPTA) test stand at the Marshall Space Flight Center (MSFC) east test area. The TPTA test stand, 14-feet wide, 27-feet long, and 33-feet high, was built in 1987 to provide data to verify the sealing capability of the redesign solid rocket motor (SRM) field and nozzle joints. The test facility applies pressure, temperature, and external loads to a short stack of solid rocket motor hardware. The simulated SRM ignition pressure and temperature transients are achieved by firing a small amount of specially configured solid propellant. The pressure transient is synchronized with external programmable dynamic loads that simulate lift off loads at the external tank attach points. Approximately one million pounds of dead weight on top of the test article simulates the weight of the other Shuttle elements.

Space Shuttle Projects

NASA Image and Video Library

1987-07-01

A forward segment is being lowered into the Transient Pressure Test Article (TPTA) test stand at thw Marshall Space Flight Center (MSFC) east test area. The TPTA test stand, 14-feet wide, 27-feet long, and 33-feet high, was built in 1987 to provide data to verify the sealing capability of the redesign solid rocket motor (SRM) field and nozzle joints. The test facility applies pressure, temperature, and external loads to a short stack of solid rocket motor hardware. The simulated SRM ignition pressure and temperature transients are achieved by firing a small amount of specially configured solid propellant. The pressure transient is synchronized with external programmable dynamic loads that simulate lift off loads at the external tank attach points. Approximately one million pounds of dead weight on top of the test article simulates the weight of the other Shuttle elements.

An experimental study of fluctuating pressure loads beneath swept shock/boundary-layer interactions

NASA Technical Reports Server (NTRS)

Settles, Gary S.

1991-01-01

A database is established on the fluctuating pressure loads produced on aerodynamic surfaces beneath 3-D shock wave/boundary layer interactions. Such loads constitute a fundamental problem of critical concern to future supersonic and hypersonic flight vehicles. A turbulent boundary layer on a flat plate is subjected to interactions with swept planar shock waves generated by sharp fins. Fin angles from 5 to 25 deg at freestream Mach numbers between 2.5 and 4 produce a variety of interaction strengths from weak to very strong. Miniature Kulite pressure transducers mounted in the flat plate were used to measure interaction-induced wall pressure fluctuations. These data will be correlated with proposed new optical data on the fluctuations of the interaction structure, especially that of the lambda-shock system and its associated high-speed jet impingement.

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.

Strain measurements in a rotary engine housing

NASA Technical Reports Server (NTRS)

Lee, C. M.; Bond, T. H.; Addy, H. E.; Chun, K. S.; Lu, C. Y.

1989-01-01

The development of structural design tools for Rotary Combustion Engines (RCE) using Finite Element Modeling (FEM) requires knowledge about the response of engine materials to various service conditions. This paper describes experimental work that studied housing deformation as a result of thermal, pressure and mechanical loads. The measurement of thermal loads, clamping pressure, and deformation was accomplished by use of high-temperature strain gauges, thermocouples, and a high speed data acquisition system. FEM models for heat transfer stress analysis of the rotor housing will be verified and refined based on these experimental results.

Apparatus and methods for supplying auxiliary steam in a combined cycle system

DOEpatents

Gorman, William G.; Carberg, William George; Jones, Charles Michael

2002-01-01

To provide auxiliary steam, a low pressure valve is opened in a combined cycle system to divert low pressure steam from the heat recovery steam generator to a header for supplying steam to a second combined cycle's steam turbine seals, sparging devices and cooling steam for the steam turbine if the steam turbine and gas turbine lie on a common shaft with the generator. Cooling steam is supplied the gas turbine in the combined cycle system from the high pressure steam turbine. Spent gas turbine cooling steam may augment the low pressure steam supplied to the header by opening a high pressure valve whereby high and low pressure steam flows are combined. An attemperator is used to reduce the temperature of the combined steam in response to auxiliary steam flows above a predetermined flow and a steam header temperature above a predetermined temperature. The auxiliary steam may be used to start additional combined cycle units or to provide a host unit with steam turbine cooling and sealing steam during full-speed no-load operation after a load rejection.

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

SURVEY ON PREVACUUM HIGH-PRESSURE STEAM STERILIZERS.

PubMed

DARMADY, E M; DREWETT, S E; HUGHES, K E

1964-03-01

None of the 10 prevacuum high-pressure sterilizers of different makes tested was able to produce and maintain the conditions advocated by the Medical Research Council working party on high-pressure steam sterilizers (1959) or by Knox and Penikett (1958) with the result that steam did not penetrate adequately the single challenge load and it was not sterilized. The sterilization of ;group drums' of various sizes and contents was erratic and tended to give operators a false sense of security. An alarming number of minor engineering faults were present in seven out of 10 machines tested and they require very much more skilled maintenance than is being given at the moment. The possibility of centralizing sterilizers to central sterile supply departments and placing them under the care of a regional engineer cannot be too highly recommended. The presence of undetected ;leaks' and a failure to draw a prevacuum of 20 mm. even with a steam burst interferes with sterilization of a challenge load. A leak test should be performed twice daily and should not exceed more than 1 mm. in one minute at 20 mm. absolute. The centre of the load should be monitored by crossed tapes or Brownes tubes in each sterilizing cycle. Although the challenge load was sterilized when the chamber was filled to capacity, a more reliable cycle consisting of a double prevacuum of 20 mm. or more with intermediate steam burst to 10 lb. ensured the sterilizing of a single challenge load, which could be adequately controlled by the chamber drain temperature.

Design of a 4 1/2 stage turbine with a stage loading factor of 4.66 and high specific work output

NASA Technical Reports Server (NTRS)

Webster, P. F.

1976-01-01

The aerodynamic design of a highly loaded multistage fan drive turbine is discussed. Turbine flowpath and airfoil sections are presented along with respective pressure and velocity distributions. Vibrational modes are identified in the expected turbine operating range.

Spit-Hole Effects on the Ballistics of a 7.62-mm Cartridge

DTIC Science & Technology

2014-02-01

barrel retains 0.50 in (12.7 mm) of rifling. The midchamber pressure transducer, Kistler Model 6215 (8), is consistent with previous experiments...Nemours and Company. 2 Kistler Model 9031A Load Washer (9). Force transducer selection was driven by the anticipated load and the necessity of an...Development and Engineering Center, Picatinny Arsenal, NJ, January 1986. 8. Kistler Operating Instructions, Quartz High-Pressure Sensor Type 6215

Slot Antenna Integrated Re-Entrant Resonator Based Wireless Pressure Sensor for High-Temperature Applications.

PubMed

Su, Shujing; Lu, Fei; Wu, Guozhu; Wu, Dezhi; Tan, Qiulin; Dong, Helei; Xiong, Jijun

2017-08-25

The highly sensitive pressure sensor presented in this paper aims at wireless passive sensing in a high temperature environment by using microwave backscattering technology. The structure of the re-entrant resonator was analyzed and optimized using theoretical calculation, software simulation, and its equivalent lump circuit model was first modified by us. Micro-machining and high-temperature co-fired ceramic (HTCC) process technologies were applied to fabricate the sensor, solving the common problem of cavity sealing during the air pressure loading test. In addition, to prevent the response signal from being immersed in the strong background clutter of the hermetic metal chamber, which makes its detection difficult, we proposed two key techniques to improve the signal to noise ratio: the suppression of strong background clutter and the detection of the weak backscattered signal of the sensor. The pressure sensor demonstrated in this paper works well for gas pressure loading between 40 and 120 kPa in a temperature range of 24 °C to 800 °C. The experimental results show that the sensor resonant frequency lies at 2.1065 GHz, with a maximum pressure sensitivity of 73.125 kHz/kPa.

Mass loading in the solar wind interaction with Venus and Mars

NASA Astrophysics Data System (ADS)

Breus, T. K.; Bauer, S. J.; Krymskii, A. M.; Mitnitskii, V. Ya.

1989-03-01

An analysis of available experimental data and theoretical concepts indicates that the interaction of the solar wind (SW) on the subsolar side with Venus, which has no intrinsic magnetic field, and with Mars, which has a small intrinsic magnetic field, is determined by the solar wind dynamic pressure with a contribution from the neutral planetary atmosphere to this interaction. The pattern of the SW interaction with these planets is different in principle for high and low dynamic pressures of the SW and is related to the varying intensity of ion formation processes (the SW Mass loading effect) in the vicinity of the SW obstacle boundary, which moves for different SW dynamic pressures into regions of different neutral atmosphere density. For moderate or high SW dynamic pressures, the subsolar Martian magnetosphere is also affected by this process. Results of numerical simulations of the SW-Mars interaction for a magnetospheric obstacle boundary at an altitude of 300 km are presented. To estimate the relative role of photoionization and charge exchange processes and their effect on the shock front position, different versions of the mass loading effect were separately calculated.

CFD simulations of transient load change on a high head Francis turbine

NASA Astrophysics Data System (ADS)

Jakobsen, Ken-Robert G.; Aasved Holst, Martin

2017-01-01

Motivated by the importance of better understanding the structural integrity of high-head hydraulic turbines operating at intermittent conditions, complete 360º steady-state and transient simulations of a Francis turbine are presented in this paper. The main target of the work has been to investigate different numerical approaches such as mesh deformation for different operating conditions. Steady-state simulations were performed at the best efficiency point (BEP) and used as initial conditions for the transient simulations considering load rejection from BEP to part load (BEP2PL) and during load acceptance from BEP to high load (BEP2HL). Simulation results were compared with experimental data available for the Francis-99 project where close agreement was found for the mesh independent solution. The transient load analyses showed general trends in accordance with the measurement reports, especially for the pressure in vaneless space that is of high importance regarding RSI effects. Some deviations were identified for the net head at load rejection for which further investigations will be conducted. All CFD simulations were performed at model scale with ANSYS CFX v. 17 at either 96 or 120 cores (2.60 GHz). The immersed boundary technique was tested during the initial stages of the project, but had to be abandoned due to severe memory requirements. Pressure amplitudes and other instantaneous results were not considered.

Investigation of the design of a metal-lined fully wrapped composite vessel under high internal pressure

NASA Astrophysics Data System (ADS)

Kalaycıoğlu, Barış; Husnu Dirikolu, M.

2010-09-01

In this study, a Type III composite pressure vessel (ISO 11439:2000) loaded with high internal pressure is investigated in terms of the effect of the orientation of the element coordinate system while simulating the continuous variation of the fibre angle, the effect of symmetric and non-symmetric composite wall stacking sequences, and lastly, a stacking sequence evaluation for reducing the cylindrical section-end cap transition region stress concentration. The research was performed using an Ansys® model with 2.9 l volume, 6061 T6 aluminium liner/Kevlar® 49-Epoxy vessel material, and a service internal pressure loading of 22 MPa. The results show that symmetric stacking sequences give higher burst pressures by up to 15%. Stacking sequence evaluations provided a further 7% pressure-carrying capacity as well as reduced stress concentration in the transition region. Finally, the Type III vessel under consideration provides a 45% lighter construction as compared with an all metal (Type I) vessel.

Surface instabilities in shock loaded granular media

NASA Astrophysics Data System (ADS)

Kandan, K.; Khaderi, S. N.; Wadley, H. N. G.; Deshpande, V. S.

2017-12-01

The initiation and growth of instabilities in granular materials loaded by air shock waves are investigated via shock-tube experiments and numerical calculations. Three types of granular media, dry sand, water-saturated sand and a granular solid comprising PTFE spheres were experimentally investigated by air shock loading slugs of these materials in a transparent shock tube. Under all shock pressures considered here, the free-standing dry sand slugs remained stable while the shock loaded surface of the water-saturated sand slug became unstable resulting in mixing of the shocked air and the granular material. By contrast, the PTFE slugs were stable at low pressures but displayed instabilities similar to the water-saturated sand slugs at higher shock pressures. The distal surfaces of the slugs remained stable under all conditions considered here. Eulerian fluid/solid interaction calculations, with the granular material modelled as a Drucker-Prager solid, reproduced the onset of the instabilities as seen in the experiments to a high level of accuracy. These calculations showed that the shock pressures to initiate instabilities increased with increasing material friction and decreasing yield strain. Moreover, the high Atwood number for this problem implied that fluid/solid interaction effects were small, and the initiation of the instability is adequately captured by directly applying a pressure on the slug surface. Lagrangian calculations with the directly applied pressures demonstrated that the instability was caused by spatial pressure gradients created by initial surface perturbations. Surface instabilities are also shown to exist in shock loaded rear-supported granular slugs: these experiments and calculations are used to infer the velocity that free-standing slugs need to acquire to initiate instabilities on their front surfaces. The results presented here, while in an idealised one-dimensional setting, provide physical understanding of the conditions required to initiate instabilities in a range of situations involving the explosive dispersion of particles.

Investigation of instability, dynamic forces, and effect of dynamic loading on strength of cages for the bearings in the high pressure oxygen turbopumps for the space shuttle main engine

NASA Technical Reports Server (NTRS)

Dufrane, K. F.; Kannel, J. W.; Merriman, T. L.; Rosenfield, A. R.

1985-01-01

Experiments were performed to determine the effect of cyclic loading on bearing cage strength. A long term working tensile load of approximately 1300 N (300 lbs) was found to be the likely maximum. Higher loads caused a decrease in cage tensile strength after the 125,000 cycle testing period. Poisson's ratio in compression was found to be highly dependent upon the direction of the fiberglass plies. At room temperature the value was 0.15 with the plies and 0.68 across the plies. At -196 C (-321 F), the value with the plies was 0.20. The results of the analyses conducted have again demonstrated the critical need for improved lubrication in the high pressure oxygen turbopump bearings. Lubricant films with low shear strength and low friction coefficients promote cage stability and decrease ball/cage forces during marginal operating conditions. The analysis of the effect of combined bearing loads on ball/cage loads has identified a radial load of 3600 N (800 lbs) as the maximum for the current clearance of the balls and cage pockets. Liquid oxygen impinging on the cage in the direction of rotation was found to enhance cage stability.

Measuring refractive index and volume of liquid under high pressure with optical coherence tomography and light microscopy.

PubMed

Wang, Donglin; Yang, Kun; Zhou, Yin

2016-03-20

Measuring the refractive index and volume of liquid under high pressure simultaneously is a big challenge. This paper proposed an alternative solution by combing optical coherence tomography with microscopy. An experiment for a feasibility study was carried out on polydimethylsiloxane liquid in a diamond anvil cell. The refractive index of the sample increased dramatically with pressure loaded, and the curve of pressure volume was also obtained.

Loading Deformation Characteristic Simulation 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 paper constructed engineering vehicle refurbished tire computer geometry model, mechanics model, contact model, finite element analysis model, did simulation study on load-deformation property of engineering vehicle refurbished tire by comparing with that of the new and the same type tire, got load-deformation of engineering vehicle refurbished tire under the working condition of static state and ground contact. The analysis result shows that change rules of radial-direction deformation and side-direction deformation of engineering vehicle refurbished tire are close to that of the new tire, radial-direction and side-direction deformation value is a little less than that of the new tire. When air inflation pressure was certain, radial-direction deformation linear rule of engineer vehicle refurbished tire would increase with load adding, however, side-direction deformation showed linear change rule, when air inflation pressure was low; and it would show increase of non-linear change rule, when air inflation pressure was very high.

Rugged switch responds to minute pressure differentials

NASA Technical Reports Server (NTRS)

Friend, L. C.; Shaub, K. D.

1967-01-01

Pressure responsive switching device exhibits high sensitivity but is extremely rugged and resistant to large amplitude shock and velocity loading. This snap-action, single pole-double throw switch operates over a wide temperature range.

Psychometric evaluation of the Polish adaptation of the Hill-Bone Compliance to High Blood Pressure Therapy Scale.

PubMed

Uchmanowicz, Izabella; Jankowska-Polańska, Beata; Chudiak, Anna; Szymańska-Chabowska, Anna; Mazur, Grzegorz

2016-05-10

Development of simple instruments for the determination of the level of adherence in patients with high blood pressure is the subject of ongoing research. One such instrument, gaining growing popularity worldwide, is the Hill-Bone Compliance to High Blood Pressure Therapy. The aim of this study was to adapt and to test the reliability of the Polish version of Hill-Bone Compliance to High Blood Pressure Therapy Scale. A standard guideline was used for the translation and cultural adaptation of the English version of the Hill-Bone Compliance to High Blood Pressure Therapy Scale into Polish. The study included 117 Polish patients with hypertension aged between 27 and 90 years, among them 53 men and 64 women. Cronbach's alpha was used for analysing the internal consistency of the scale. The mean score in the reduced sodium intake subscale was M = 5.7 points (standard deviation SD = 1.6 points). The mean score in the appointment-keeping subscale was M = 3.4 points (standard deviation SD = 1.4 points). The mean score in the medication-taking subscale was M = 11.6 points (standard deviation SD = 3.3 points). In the principal component analysis, the three-factor system (1 - medication-taking, 2 - appointment-keeping, 3 - reduced sodium intake) accounted for 53 % of total variance. All questions had factor loadings > 0.4. The medication-taking subscale: most questions (6 out of 9) had the highest loadings with Factor 1. The appointment-keeping subscale: all questions (2 out of 2) had the highest loadings with Factor 2. The reduced sodium intake subscale: most questions (2 out of 3) had the highest loadings with Factor 3. Goodness of fit was tested at chi(2) = 248.87; p < 0.001. The Cronbach's alpha score for the entire questionnaire was 0.851. The Hill-Bone Compliance to High Blood Pressure Therapy Scale proved to be suitable for use in the Polish population. Use of this screening tool for the assessment of adherence to BP treatment is recommended.

Design integration and noise studies for jet STOL aircraft. Task 7C: Augmentor wing cruise blowing valveless system. Volume 2: Small-scale development testing of augmentor wing critical ducting components

NASA Technical Reports Server (NTRS)

Runnels, J. N.; Gupfa, A.

1973-01-01

Augmentor wing ducting system studies conducted on a valveless system configuration that provides cruise thrust from the augmentor nozzles have shown that most of the duct system pressure loss would occur in the strut-wing duct y-junction and the wing duct-augmentor lobe nozzles. These components were selected for development testing over a range of duct Mach numbers and pressure ratios to provide a technical basis for predicting installed wing thrust loading and for evaluating design wing loading of a particular wing aspect ratios. The flow characteristics of ducting components with relatively high pressure loss coefficients were investigated. The turbulent pressure fluctuations associated with flows at high Mach numbers were analyzed to evaluate potential duct fatigue problems.

Redifferentiation of chondrocytes and cartilage formation under intermittent hydrostatic pressure.

PubMed

Heyland, Jan; Wiegandt, Katharina; Goepfert, Christiane; Nagel-Heyer, Stefanie; Ilinich, Eduard; Schumacher, Udo; Pörtner, Ralf

2006-10-01

Since articular cartilage is subjected to varying loads in vivo and undergoes cyclic hydrostatic pressure during periods of loading, it is hypothesized that mimicking these in vivo conditions can enhance synthesis of important matrix components during cultivation in vitro. Thus, the influence of intermittent loading during redifferentiation of chondrocytes in alginate beads, and during cartilage formation was investigated. A statistically significant increased synthesis of glycosaminoglycan and collagen type II during redifferentiation of chondrocytes embedded in alginate beads, as well as an increase in glycosaminoglycan content of tissue-engineered cartilage, was found compared to control without load. Immunohistological staining indicated qualitatively a high expression of collagen type II for both cases.

A gas-loading system for LANL two-stage gas guns

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

Gibson, Lloyd Lee; Bartram, Brian Douglas; Dattelbaum, Dana Mcgraw

A novel gas loading system was designed for the specific application of remotely loading high purity gases into targets for gas-gun driven plate impact experiments. The high purity gases are loaded into well-defined target configurations to obtain Hugoniot states in the gas phase at greater than ambient pressures.The small volume of the gas samples is challenging, as slight changing in the ambient temperature result in measurable pressure changes. Therefore, the ability to load a gas gun target and continually monitor the sample pressure prior to firing provides the most stable and reliable target fielding approach. We present the design andmore » evaluation of a gas loading system built for the LANL 50 mm bore two-stage light gas gun. Targets for the gun are made of 6061 Al or OFHC Cu, and assembled to form a gas containment cell with a volume of approximately 1.38 cc. The compatibility of materials was a major consideration in the design of the system, particularly for its use with corrosive gases. Piping and valves are stainless steel with wetted seals made from Kalrez® and Teflon®. Preliminary testing was completed to ensure proper flow rate and that the proper safety controls were in place. The system has been used to successfully load Ar, Kr, Xe, and anhydrous ammonia with purities of up to 99.999 percent. The design of the system and example data from the plate impact experiments will be shown.« less

A gas-loading system for LANL two-stage gas guns

NASA Astrophysics Data System (ADS)

Gibson, L. L.; Bartram, B. D.; Dattelbaum, D. M.; Lang, J. M.; Morris, J. S.

2017-01-01

A novel gas loading system was designed for the specific application of remotely loading high purity gases into targets for gas-gun driven plate impact experiments. The high purity gases are loaded into well-defined target configurations to obtain Hugoniot states in the gas phase at greater than ambient pressures. The small volume of the gas samples is challenging, as slight changing in the ambient temperature result in measurable pressure changes. Therefore, the ability to load a gas gun target and continually monitor the sample pressure prior to firing provides the most stable and reliable target fielding approach. We present the design and evaluation of a gas loading system built for the LANL 50 mm bore two-stage light gas gun. Targets for the gun are made of 6061 Al or OFHC Cu, and assembled to form a gas containment cell with a volume of approximately 1.38 cc. The compatibility of materials was a major consideration in the design of the system, particularly for its use with corrosive gases. Piping and valves are stainless steel with wetted seals made from Kalrez® and Teflon®. Preliminary testing was completed to ensure proper flow rate and that the proper safety controls were in place. The system has been used to successfully load Ar, Kr, Xe, and anhydrous ammonia with purities of up to 99.999 percent. The design of the system and example data from the plate impact experiments will be shown.

The Effect of a Non-Gaussian Random Loading on High-Cycle Fatigue of a Thermally Post-Buckled Structure

NASA Technical Reports Server (NTRS)

Rizzi, Stephen A.; Behnke, marlana N.; Przekop, Adam

2010-01-01

High-cycle fatigue of an elastic-plastic beam structure under the combined action of thermal and high-intensity non-Gaussian acoustic loadings is considered. Such loadings can be highly damaging when snap-through motion occurs between thermally post-buckled equilibria. The simulated non-Gaussian loadings investigated have a range of skewness and kurtosis typical of turbulent boundary layer pressure fluctuations in the vicinity of forward facing steps. Further, the duration and steadiness of high excursion peaks is comparable to that found in such turbulent boundary layer data. Response and fatigue life estimates are found to be insensitive to the loading distribution, with the minor exception of cases involving plastic deformation. In contrast, the fatigue life estimate was found to be highly affected by a different type of non-Gaussian loading having bursts of high excursion peaks.

Ocean dynamics during the passage of Xynthia storm recorded by GPS

NASA Astrophysics Data System (ADS)

Nicolas, Joëlle; Ferenc, Marcell; Li, Zhao; van Dam, Tonie; Polidori, Laurent

2014-05-01

When computing the effect of atmospheric loading on geodetic coordinates, we must assign the response of the ocean to pressure loading. A pure inverted barometer and a solid Earth ocean response to pressure loading define the extremes of the response. At periods longer than a few days, the inverted barometer response is sufficient (Wunsch and Stammer, 1997). However, how does the ocean respond to fast moving storms? In this study we investigate the effect of a violent storm that progressed over Western Europe between the 27th of February and the 1st of March 2010 on sub-daily vertical GPS (Global Positioning System) position time series of the French GNSS permanent network (RGP). Xynthia was a huge low-pressure system (pressure drop of 40 mbar and a storm surge of 1.4 m (at La Rochelle tide gauge)) that crossed France from the southwest to the northeast over the course of about 20 hours. We study the different behaviour of the coastal and inland sites based on the comparison of the estimated 6-hourly stand-alone GPS position time series (GINS-PC software) with the local pressure and the predicted atmospheric pressure loading time series derived from the high resolution Modern-Era Retrospective Analysis for Research and Applications (NASA MERRA) and also the European Centre for Medium-Range Weather Forecasts (ECMWF) global dataset. We model the predicted displacements using the inverse barometer (IB) and the non-IB ocean response cases as endpoints. Predicted loading effects due to the atmospheric pressure and IB ocean reach up to 1.0, 1.3 and 13.7 mm for the east, north and up components, respectively. Then we attempt to use the GPS vertical surface displacements, the surface pressure, and tide gauge data (SONEL) to identify the true ocean dynamics on the continental shelf during the passage of this fast moving system. Keywords: GPS, GINS-PC, Xynthia, ocean dynamics, atmospheric pressure loading, deformation

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...

Nonlinear Reduced-Order Analysis with Time-Varying Spatial Loading Distributions

NASA Technical Reports Server (NTRS)

Prezekop, Adam

2008-01-01

Oscillating shocks acting in combination with high-intensity acoustic loadings present a challenge to the design of resilient hypersonic flight vehicle structures. This paper addresses some features of this loading condition and certain aspects of a nonlinear reduced-order analysis with emphasis on system identification leading to formation of a robust modal basis. The nonlinear dynamic response of a composite structure subject to the simultaneous action of locally strong oscillating pressure gradients and high-intensity acoustic loadings is considered. The reduced-order analysis used in this work has been previously demonstrated to be both computationally efficient and accurate for time-invariant spatial loading distributions, provided that an appropriate modal basis is used. The challenge of the present study is to identify a suitable basis for loadings with time-varying spatial distributions. Using a proper orthogonal decomposition and modal expansion, it is shown that such a basis can be developed. The basis is made more robust by incrementally expanding it to account for changes in the location, frequency and span of the oscillating pressure gradient.

Dynamics of the precessing vortex rope and its interaction with the system at Francis turbines part load operating conditions

NASA Astrophysics Data System (ADS)

Favrel, A.; Müller, A.; Landry, C.; Gomes, J.; Yamamoto, K.; Avellan, F.

2017-04-01

At part load conditions, Francis turbines experience the formation of a cavitation vortex rope at the runner outlet whose precession acts as a pressure excitation source for the hydraulic circuit. This can lead to hydro-acoustic resonances characterized by high pressure pulsations, as well as torque and output power fluctuations. This study highlights the influence of the discharge factor on both the vortex parameters and the pressure excitation source by performing Particle Image Velocimetry (PIV) and pressure measurements. Moreover, it is shown that the occurrence of hydro-acoustic resonances in cavitation conditions mainly depend on the swirl degree of the flow independently of the speed factor. Empirical laws linking both natural and precession frequencies with the operating parameters of the machine are, then, derived, enabling the prediction of resonance conditions on the complete part load operating range of the turbine.

Flow Control on Low-Pressure Turbine Airfoils Using Vortex Generator Jets

NASA Technical Reports Server (NTRS)

Volino, Ralph J.; Ibrahim, Mounir B.; Kartuzova, Olga

2010-01-01

Motivation - Higher loading on Low-Pressure Turbine (LPT) airfoils: Reduce airfoil count, weight, cost. Increase efficiency, and Limited by suction side separation. Growing understanding of transition, separation, wake effects: Improved models. Take advantage of wakes. Higher lift airfoils in use. Further loading increases may require flow control: Passive: trips, dimples, etc. Active: plasma actuators, vortex generator jets (VGJs). Can increased loading offset higher losses on high lift airfoils. Objectives: Advance knowledge of boundary layer separation and transition under LPT conditions. Demonstrate, improve understanding of separation control with pulsed VGJs. Produce detailed experimental data base. Test and develop computational models.

Architecture, component, and microbiome of biofilm involved in the fouling of membrane bioreactors.

PubMed

Inaba, Tomohiro; Hori, Tomoyuki; Aizawa, Hidenobu; Ogata, Atsushi; Habe, Hiroshi

2017-01-01

Biofilm formation on the filtration membrane and the subsequent clogging of membrane pores (called biofouling) is one of the most persistent problems in membrane bioreactors for wastewater treatment and reclamation. Here, we investigated the structure and microbiome of fouling-related biofilms in the membrane bioreactor using non-destructive confocal reflection microscopy and high-throughput Illumina sequencing of 16S rRNA genes. Direct confocal reflection microscopy indicated that the thin biofilms were formed and maintained regardless of the increasing transmembrane pressure, which is a common indicator of membrane fouling, at low organic-loading rates. Their solid components were primarily extracellular polysaccharides and microbial cells. In contrast, high organic-loading rates resulted in a rapid increase in the transmembrane pressure and the development of the thick biofilms mainly composed of extracellular lipids. High-throughput sequencing revealed that the biofilm microbiomes, including major and minor microorganisms, substantially changed in response to the organic-loading rates and biofilm development. These results demonstrated for the first time that the architectures, chemical components, and microbiomes of the biofilms on fouled membranes were tightly associated with one another and differed considerably depending on the organic-loading conditions in the membrane bioreactor, emphasizing the significance of alternative indicators other than the transmembrane pressure for membrane biofouling.

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

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

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

2015-10-15

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

Hydrogen storage container

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

Wang, Jy-An John; Feng, Zhili; Zhang, Wei

An apparatus and system is described for storing high-pressure fluids such as hydrogen. An inner tank and pre-stressed concrete pressure vessel share the structural and/or pressure load on the inner tank. The system and apparatus provide a high performance and low cost container while mitigating hydrogen embrittlement of the metal tank. System is useful for distributing hydrogen to a power grid or to a vehicle refueling station.

Static-stress analysis of dual-axis safety vessel

NASA Astrophysics Data System (ADS)

Bultman, D. H.

1992-11-01

An 8 ft diameter safety vessel, made of HSLA-100 steel, is evaluated to determine its ability to contain the quasi-static residual pressure from a high explosive (HE) blast. The safety vessel is designed for use with the Dual-Axis Radiographic Hydrotest (DARHT) facility being developed at Los Alamos National Laboratory. A smaller confinement vessel fits inside the safety vessel and contains the actual explosion, and the safety vessel functions as a second layer of containment in the unlikely case of a confinement vessel leak. The safety vessel is analyzed as a pressure vessel based on the ASME Boiler and Pressure Vessel Code, Section 8, Division 1, and the Welding Research Council Bulletin, WRC107. Combined stresses that result from internal pressure and external loads on nozzles are calculated and compared to the allowable stresses for HSLA-100 steel. Results confirm that the shell and nozzle components are adequately designed for a static pressure of 830 psi, plus the maximum expected external loads. Shell stresses at the 'shell to nozzle' interface, produced from external loads on the nozzles, were less than 700 psi. The maximum combined stress resulting from the internal pressure plus external loads was 17,384 psi, which is significantly less than the allowable stress of 42,375 psi for HSLA-100 steel.

High Pressure Oxidizer Turbopump (HPOTP) inducer dynamic design environment

NASA Technical Reports Server (NTRS)

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

1995-01-01

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

PATHFINDER ATOMIC POWER PLANT. FILTRATION OF ALUMINUM CORROSION PRODUCTS PRODUCED IN HIGH-TEMPERATURE, HIGH PURITY WATER SYSTEMS

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

Noble, J.H.; Davie, R.L.

1961-05-01

Filter tests were conducted to determine the most suitable filter for removing large quantities of aluminum corrosion product (boehmite) from reactor water. Filters tested included the following: wire-wound, sintered filter elements, sintered ceramic fllter elements, cotton stringwound filter elements, felted-cotton filter elements, cation resin, adsorption resin, diatomaceous earth precoat filter, and a wood-cellulose precoat filter. Parameters measured were flow rate, filter-influent and -effluent boehmite concentration, pressure drop, and final filter load. The pressure drop and efficiency of the filters was correlated with boehmite load. Boehmite deposits on filters as a nonporous gelatinous cake, and causes a rapidly increasing pressure drop.more » Tests indicate that the optimum load with filter elements and precoat filters is achieved at a pressure drop of 25 psi. Very little additional load can be obtained by operating to a higher pressure drop. Of the filters tested, the precoat filter snd 40 to 60 mesh cation resin were the more effective in removing boehmite. The efficiency of the precoat filter was in excess of 99%, and the efficiency of the cation resin was for the most part in excess of 95%. For various reasons, the other filters were eliminated from final consideration. The test program and available literature indicated that an element type precoat filter using wood cellulose as the precoat media would be most suitable for the proposed application. (auth)« less

Investigation of space shuttle vehicle 140C configuration orbiter (model 16-0) wheel well pressure loads in the Rockwell International 7.75 x 11 foot wind tunnel (OA143)

NASA Technical Reports Server (NTRS)

Mennell, R. C.

1975-01-01

Experimental aerodynamic investigations were conducted on a sting mounted .0405-scale representation of the 140C outer mold line space shuttle orbiter configuration in the Rockwell International 7.75 x 11.00 foot low speed wind tunnel. The primary test objectives were to define the orbiter wheel well pressure loading and its effects on landing gear thermal insulation and to investigate the pressure environment experienced by both the horizontal flight nose probe and air vent door probes. Steady state and dynamic pressure values were recorded in the orbiter nose gear well, left main landing gear well, horizontal flight nose probe, and both left and right air vent door probe. All steady state pressure levels were measured by Statham differential pressure transducers while dynamic pressure levels were recorded by Kulite high frequency response pressure sensors.

Nature of hydrothermal fluids at the shale-hosted Red Dog Zn-Pb-Ag deposits, Brooks Range, Alaska

USGS Publications Warehouse

Leach, David L.; Marsh, Erin E.; Emsbo, Poul; Rombach, Cameron; Kelley, Karen D.; Anthony, Michael W.

2004-01-01

The densities of the methane inclusions, together with the temperature of homogenization of coexisting aqueous fluid inclusions, show that these fluid inclusions were trapped between pressures of 800 and 3,400 bars and temperatures between 187° and 214°C. The pressures obtained provide unequivocal evidence that the quartz formed after ore deposition in the Carboniferous because such high fluid pressures could only have been produced from thrust loading during the Mesozoic Brookian orogeny. The observed large variation in pressure is best explained by transient fluid pressures from hydrostatic to lithostatic conditions during thrust loading. The 3,400 bars pressure corresponds with about 12 km of lithostatic burial, whereas the lower pressures (800 bars) correspond with about 8 km of hydrostatic pressure. Because of their low salinity (0-5 wt % NaCl equiv) the electrolyte compositions of the quartz fluid inclusions do not constrain their origin.

A reliable measure of footwear upper comfort enabled by an innovative sock equipped with textile pressure sensors.

PubMed

Herbaut, Alexis; Simoneau-Buessinger, Emilie; Barbier, Franck; Cannard, Francis; Guéguen, Nils

2016-10-01

Footwear comfort is essential and pressure distribution on the foot was shown as a relevant objective measurement to assess it. However, asperities on the foot sides, especially the metatarsals and the instep, make its evaluation difficult with available equipment. Thus, a sock equipped with textile pressure sensors was designed. Results from the mechanical tests showed a high linearity of the sensor response under incremental loadings and allowed to determine the regression equation to convert voltage values into pressure measurements. The sensor response was also highly repeatable and the creep under constant loading was low. Pressure measurements on human feet associated with a perception questionnaire exhibited that significant relationships existed between pressure and comfort perceived on the first, the third and the fifth metatarsals and top of the instep. Practitioner Summary: A sock equipped with textile sensors was validated for measuring the pressure on the foot top, medial and lateral sides to evaluate footwear comfort. This device may be relevant to help individuals with low sensitivity, such as children, elderly or neuropathic, to choose the shoes that fit the best.

On the upper part load vortex rope in Francis turbine: Experimental investigation

NASA Astrophysics Data System (ADS)

Nicolet, C.; Zobeiri, A.; Maruzewski, P.; Avellan, F.

2010-08-01

The swirling flow developing in Francis turbine draft tube under part load operation leads to pressure fluctuations usually in the range of 0.2 to 0.4 times the runner rotational frequency resulting from the so-called vortex breakdown. For low cavitation number, the flow features a cavitation vortex rope animated with precession motion. Under given conditions, these pressure fluctuations may lead to undesirable pressure fluctuations in the entire hydraulic system and also produce active power oscillations. For the upper part load range, between 0.7 and 0.85 times the best efficiency discharge, pressure fluctuations may appear in a higher frequency range of 2 to 4 times the runner rotational speed and feature modulations with vortex rope precession. It has been pointed out that for this particular operating point, the vortex rope features elliptical cross section and is animated of a self-rotation. This paper presents an experimental investigation focusing on this peculiar phenomenon, defined as the upper part load vortex rope. The experimental investigation is carried out on a high specific speed Francis turbine scale model installed on a test rig of the EPFL Laboratory for Hydraulic Machines. The selected operating point corresponds to a discharge of 0.83 times the best efficiency discharge. Observations of the cavitation vortex carried out with high speed camera have been recorded and synchronized with pressure fluctuations measurements at the draft tube cone. First, the vortex rope self rotation frequency is evidenced and the related frequency is deduced. Then, the influence of the sigma cavitation number on vortex rope shape and pressure fluctuations is presented. The waterfall diagram of the pressure fluctuations evidences resonance effects with the hydraulic circuit. The time evolution of the vortex rope volume is compared with pressure fluctuations time evolution using image processing. Finally, the influence of the Froude number on the vortex rope shape and the associated pressure fluctuations is analyzed by varying the rotational speed.

Stiffness and relaxation components of the exponential and logistic time constants may be used to derive a load-independent index of isovolumic pressure decay.

PubMed

Shmuylovich, Leonid; Kovács, Sándor J

2008-12-01

In current practice, empirical parameters such as the monoexponential time constant tau or the logistic model time constant tauL are used to quantitate isovolumic relaxation. Previous work indicates that tau and tauL are load dependent. A load-independent index of isovolumic pressure decline (LIIIVPD) does not exist. In this study, we derive and validate a LIIIVPD. Recently, we have derived and validated a kinematic model of isovolumic pressure decay (IVPD), where IVPD is accurately predicted by the solution to an equation of motion parameterized by stiffness (Ek), relaxation (tauc), and pressure asymptote (Pinfinity) parameters. In this study, we use this kinematic model to predict, derive, and validate the load-independent index MLIIIVPD. We predict that the plot of lumped recoil effects [Ek.(P*max-Pinfinity)] versus resistance effects [tauc.(dP/dtmin)], defined by a set of load-varying IVPD contours, where P*max is maximum pressure and dP/dtmin is the minimum first derivative of pressure, yields a linear relation with a constant (i.e., load independent) slope MLIIIVPD. To validate the load independence, we analyzed an average of 107 IVPD contours in 25 subjects (2,669 beats total) undergoing diagnostic catheterization. For the group as a whole, we found the Ek.(P*max-Pinfinity) versus tauc.(dP/dtmin) relation to be highly linear, with the average slope MLIIIVPD=1.107+/-0.044 and the average r2=0.993+/-0.006. For all subjects, MLIIIVPD was found to be linearly correlated to the subject averaged tau (r2=0.65), tauL(r2=0.50), and dP/dtmin (r2=0.63), as well as to ejection fraction (r2=0.52). We conclude that MLIIIVPD is a LIIIVPD because it is load independent and correlates with conventional IVPD parameters. Further validation of MLIIIVPD in selected pathophysiological settings is warranted.

Solubility of carbon dioxide in aqueous mixtures of alkanolamines

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

Dawodu, O.F.; Meisen, A.

1994-07-01

The solubility of CO[sub 2] in water + N-methyldiethanolamine + monoethanolamine (MDEA + MEA) and water + N-methyldiethanolamine + diethanolamine (MDEA + DEA) are reported at two compositions of 3.4 M MDEA + 0.8 M MEA or DEA and 2.1 M MDEA + 2.1 M MEA or DEA at temperatures from 70 to 180 C and CO[sub 2] partial pressures from 100 to 3,850 kPa. The solubility of CO[sub 2] in the blends decreased with an increase in temperature but increased with an increase in CO[sub 2] partial pressure. At low partial pressures of CO[sub 2] and the same totalmore » amine concentration, the equilibrium CO[sub 2] loadings were in the order MDEA + MEA > MDEA + DEA > MDEA. However, at high CO[sub 2] partial pressures, the equilibrium CO[sub 2] loadings in the MDEA solutions were higher than those of the MDEA + MEA and MDEA + DEA blends of equal molar strengths due to the stoichiometric loading limitations of MEA and DEA. The nonadditivity of the equilibrium loadings for single amine systems highlights the need for independent measurements on amine blends.« less

Survey on prevacuum high-pressure steam sterilizers

PubMed Central

Darmady, E. M.; Drewett, S. E.; Hughes, K. E. A.

1964-01-01

None of the 10 prevacuum high-pressure sterilizers of different makes tested was able to produce and maintain the conditions advocated by the Medical Research Council working party on high-pressure steam sterilizers (1959) or by Knox and Penikett (1958) with the result that steam did not penetrate adequately the single challenge load and it was not sterilized. The sterilization of `group drums' of various sizes and contents was erratic and tended to give operators a false sense of security. An alarming number of minor engineering faults were present in seven out of 10 machines tested and they require very much more skilled maintenance than is being given at the moment. The possibility of centralizing sterilizers to central sterile supply departments and placing them under the care of a regional engineer cannot be too highly recommended. The presence of undetected `leaks' and a failure to draw a prevacuum of 20 mm. even with a steam burst interferes with sterilization of a challenge load. A leak test should be performed twice daily and should not exceed more than 1 mm. in one minute at 20 mm. absolute. The centre of the load should be monitored by crossed tapes or Brownes tubes in each sterilizing cycle. Although the challenge load was sterilized when the chamber was filled to capacity, a more reliable cycle consisting of a double prevacuum of 20 mm. or more with intermediate steam burst to 10 lb. ensured the sterilizing of a single challenge load, which could be adequately controlled by the chamber drain temperature. PMID:14149935

Transient Pressure Test Article (TPTA) 1.1 and 1.1A, volume 1

NASA Technical Reports Server (NTRS)

Rebells, Clarence A.

1988-01-01

This final test report presents the results obtained during the static hot firing and cold-gas high Q tests of the first Transient Pressure Test Article (TPTA) 1.1. The TPTA consisted of field test joints A and B, which were the original RSRM J-insulation configuration, with a metal capture feature. It also consisted of a flight configuration nozzle-to-case test joint (Joint D) with shorter vent slots. Fluorocarbon O-rings were used in all the test joints. The purpose of the TPTA tests is to evaluate and characterize the RSMR field and nozzle-to-case joints under the influence of ignition and strut loads during liftoff anf high Q. All objectives of the cold-gas high Q (TPTA 1.1A) test were met and all measurements were close to predicted values. During the static hot-firing test (TPTA 1.1), the motor was inadvertently plugged by the quench injector plug, making it a more severe test, although no strut loads were applied. The motor was depressurized after approximately 11 min using an auxiliary system, and no anomalies were noted. In the static hot-firing test, pressure was incident on the insulation and the test joint gaps were within the predicted range. During the static hot-firing test, no strut loads were applied because the loading system malfunctioned. For this test, all measurements were within range of similar tests performed without strut loads.

Study of the strength of molybdenum under high pressure using electromagnetically applied compression-shear ramp loading

NASA Astrophysics Data System (ADS)

Ding, Jow; Alexander, C. Scott; Asay, James

2015-06-01

MAPS (Magnetically Applied Pressure Shear) is a new technique that has the potential to study material strength under mega-bar pressures. By applying a mixed-mode pressure-shear loading and measuring the resultant material responses, the technique provides explicit and direct information on material strength under high pressure. In order to apply sufficient shear traction to the test sample, the driver must have substantial strength. Molybdenum was selected for this reason along with its good electrical conductivity. In this work, the mechanical behavior of molybdenum under MAPS loading was studied. To understand the experimental data, a viscoplasticity model with tension-compression asymmetry was also developed. Through a combination of experimental characterization, model development, and numerical simulation, many unique insights were gained on the inelastic behavior of molybdenum such as the effects of strength on the interplay between longitudinal and shear stresses, potential interaction between the magnetic field and molybdenum strength, and the possible tension-compression asymmetry of the inelastic material response. Sandia National Labs is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corp., for the U.S. Dept. of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

Molecular dynamics simulation of shock-wave loading of copper and titanium

NASA Astrophysics Data System (ADS)

Bolesta, A. V.; Fomin, V. M.

2017-10-01

At extreme pressures and temperatures common materials form new dense phases with compacted atomic arrangements. By classical molecular dynamics simulation we observe that FCC copper undergo phase transformation to BCC structure. The transition occurs under shock wave loading at the pressures above 80 GPa and corresponding temperatures above 2000 K. We calculate phase diagram, show that at these pressures and low temperature FCC phase of copper is still stable and discuss the thermodynamic reason for phase transformation at high temperature shock wave regime. Titanium forms new hexagonal phase at high pressure as well. We calculate the structure of shock wave in titanium and observe that shock front splits in three parts: elastic, plastic and phase transformation. The possibility of using a phase transition behind a shock wave with further unloading for designing nanocrystalline materials with a reduced grain size is also shown.

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...

Special Considerations for Qualifying Thin Films for Supper Pressure Pumpkin Ultra Long Duration Balloon (ULDB) Missions

NASA Astrophysics Data System (ADS)

Said, M.

Pumpkin type super pressure balloons require much less stringent mechanical requirements on the envelope film material when compared to spherical super pressure type balloons. However, since suitable thin films are typically viscoelastic in nature, their creep characteristics must be fully characterized and must not exceed specific and predetermined design limits. Proper assessment of materials limits to meet these design limits requires creep-load-temperature data that characterizes the performance of the material over a time that exceeds the duration of the design service life by some specified margin. Contrary to the behavior of materials with purely elastic response, visco-elastic materials such as these considered for the ULDB design, change their geometry under sustained loading over time. This change is usually reflected by exhibiting a significant visco-elastic component over the service life of the mission. For that regime of large visco-elastic response, where the material is highly nonlinear, a certain load-temperature threshold can be reached where the creep is limited by an asymptote that depends on both the temperature and load level. Such creep is recoverable, although the recovery period may be much longer than the 100 day design service life of the ULDB structure plus the factor of safety required for the design. For a typical flight, the most significant creep occurs at the highest temperature, which also produces the highest internal pressure. At mid- latitudes a significant portion of the service life is spent at night, i.e. at low temperature and low load; for the ULDB film, this nighttime contribution to creep is insignificant in comparison to any daytime contribution. By contrast, flight exposure in an Antarctic summer is at an almost constant high temperature and corresponding high pressure. This response behavior must be sufficiently characterized to serve the needs of the structural design and performance predictions of the vehicle in service. In this work, a special emphasis will be given to the creep and dynamic characteristics of selected coextruded films and their dependence on the loading level and temperature. Preliminary testing has suggested t at the creep behavior of theh coextruded linear low density resin films is highly dependent on temperature and that the dynamic response depends on the make up of the composite film. In addition, the paper will, in general, highlight the process of qualify ing thin films for the pumpkin class of super pressure balloons.

Space Shuttle Main Engine structural analysis and data reduction/evaluation. Volume 7: High pressure fuel turbo-pump third stage impeller analysis

NASA Technical Reports Server (NTRS)

Pool, Kirby V.

1989-01-01

This volume summarizes the analysis used to assess the structural life of the Space Shuttle Main Engine (SSME) High Pressure Fuel Turbo-Pump (HPFTP) Third Stage Impeller. This analysis was performed in three phases, all using the DIAL finite element code. The first phase was a static stress analysis to determine the mean (non-varying) stress and static margin of safety for the part. The loads involved were steady state pressure and centrifugal force due to spinning. The second phase of the analysis was a modal survey to determine the vibrational modes and natural frequencies of the impeller. The third phase was a dynamic response analysis to determine the alternating component of the stress due to time varying pressure impulses at the outlet (diffuser) side of the impeller. The results of the three phases of the analysis show that the Third Stage Impeller operates very near the upper limits of its capability at full power level (FPL) loading. The static loading alone creates stresses in some areas of the shroud which exceed the yield point of the material. Additional cyclic loading due to the dynamic force could lead to a significant reduction in the life of this part. The cyclic stresses determined in the dynamic response phase of this study are based on an assumption regarding the magnitude of the forcing function.

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.

Transient Three-Dimensional Side Load Analysis of a Film Cooled Nozzle

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Guidos, Mike

2008-01-01

Transient three-dimensional numerical investigations on the side load physics for an engine encompassing a film cooled nozzle extension and a regeneratively cooled thrust chamber, were performed. The objectives of this study are to identify the three-dimensional side load physics and to compute the associated aerodynamic side load using an anchored computational methodology. The computational methodology is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, and a transient inlet history based on an engine system simulation. Ultimately, the computational results will be provided to the nozzle designers for estimating of effect of the peak side load on the nozzle structure. Computations simulating engine startup at ambient pressures corresponding to sea level and three high altitudes were performed. In addition, computations for both engine startup and shutdown transients were also performed for a stub nozzle, operating at sea level. For engine with the full nozzle extension, computational result shows starting up at sea level, the peak side load occurs when the lambda shock steps into the turbine exhaust flow, while the side load caused by the transition from free-shock separation to restricted-shock separation comes at second; and the side loads decreasing rapidly and progressively as the ambient pressure decreases. For the stub nozzle operating at sea level, the computed side loads during both startup and shutdown becomes very small due to the much reduced flow area.

Basketball lay-up - foot loading characteristics and the number of trials necessary to obtain stable plantar pressure variables.

PubMed

Chua, YaoHui K; Quek, Raymond K K; Kong, Pui W

2017-03-01

This study aimed (1) to profile the plantar loading characteristics when performing the basketball lay-up in a realistic setting and (2) to determine the number of trials necessary to establish a stable mean for plantar loading variables during the lay-up. Thirteen university male basketball players [age: 23.0 (1.4) years, height: 1.75 (0.05) m, mass: 68.4 (8.6) kg] performed ten successful basketball lay-ups from a stationary position. Plantar loading variables were recorded using the Novel Pedar-X in-shoe system. Loading variables including peak force, peak pressure, and pressure-time integral were extracted from eight foot regions. Performance stability of plantar loading variables during the take-off and landing steps were assessed using the sequential averaging technique and intra-class correlation coefficient (ICC). High plantar loadings were experienced at the heel during the take-off steps, and both the heel and forefoot regions upon landing. The sequential estimation technique revealed a five-eight trial range to achieve a stable mean across all plantar loading variables, whereas ICC analysis was insensitive to inter-trial differences of repeated lay-up performances. Future studies and performance evaluation protocols on plantar loading during basketball lay-ups should include at least eight trials to ensure that the measurements obtained are sufficiently stable.

Osmosis and viscoelasticity both contribute to time-dependent behaviour of the intervertebral disc under compressive load: A caprine in vitro study.

PubMed

Emanuel, Kaj S; van der Veen, Albert J; Rustenburg, Christine M E; Smit, Theodoor H; Kingma, Idsart

2018-03-21

The mechanical behaviour of the intervertebral disc highly depends on the content and transport of interstitial fluid. It is unknown, however, to what extent the time-dependent behaviour can be attributed to osmosis. Here we investigate the effect of both mechanical and osmotic loading on water content, nucleus pressure and disc height. Eight goat intervertebral discs, immersed in physiological saline, were subjected to a compressive force with a pressure needle inserted in the nucleus. The loading protocol was: 10 N (6 h); 150 N (42 h); 10 N (24 h). Half-way the 150 N-phase (24 h), we eliminated the osmotic gradient by adding 26% poly-ethylene glycol to the surrounding fluid. For 62 additional discs, we determined the water content of both nucleus and annulus after 6, 24, 48, or 72 h. The compressive load was initially counterbalanced by the hydrostatic pressure in the nucleus. The load forced 4.3% of the water out of the nucleus, which reduced nucleus pressure by 44(±6)%. Reduction of the osmotic gradient disturbed the equilibrium disc height, and a significant loss of annulus water content was found. Remarkably, pressure and water content of the nucleus pulposus remained unchanged. This shows that annulus water content is important in the response to axial loading. After unloading, in the absence of an osmotic gradient, there was substantial viscoelastic recovery of 53(±11)% of the disc height, without a change in water content. However, for restoration of the nucleus pressure and for full restoration of disc height, restoration of the osmotic gradient was needed. Copyright © 2017 Elsevier Ltd. All rights reserved.

The Reduced Effectiveness of EGR to Mitigate Knock at High Loads in Boosted SI Engines

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

Szybist, James P.; Wagnon, Scott W.; Splitter, Derek A.

Numerous studies have demonstrated that exhaust gas recirculation (EGR) can attenuate knock propensity in spark ignition (SI) engines at naturally aspirated or lightly boosted conditions. In this paper, we investigate the role of cooled EGR under higher load conditions with multiple fuel compositions, where highly retarded combustion phasing typical of modern SI engines was used. It was found that under these conditions, EGR attenuation of knock is greatly reduced, where EGR doesn’t allow significant combustion phasing advance as it does under lighter load conditions. Detailed combustion analysis shows that when EGR is added, the polytropic coefficient increases causing the compressivemore » pressure and temperature to increase. At sufficiently highly boosted conditions, the increase in polytropic coefficient and additional trapped mass from EGR can sufficiently reduce fuel ignition delay to overcome knock attenuation effects. Kinetic modeling demonstrates that the effectiveness of EGR to mitigate knock is highly dependent on the pressure-temperature condition. Experiments at 2000 rpm have confirmed reduced fuel ignition delay under highly boosted conditions relevant to modern downsized boosted SI engines, where in-cylinder pressure is higher and the temperature is cooler. Finally, at these conditions, charge reactivity increases compared to naturally aspirated conditions, and attenuation of knock by EGR is reduced.« less

The Reduced Effectiveness of EGR to Mitigate Knock at High Loads in Boosted SI Engines

DOE PAGES

Szybist, James P.; Wagnon, Scott W.; Splitter, Derek A.; ...

2017-09-04

Numerous studies have demonstrated that exhaust gas recirculation (EGR) can attenuate knock propensity in spark ignition (SI) engines at naturally aspirated or lightly boosted conditions. In this paper, we investigate the role of cooled EGR under higher load conditions with multiple fuel compositions, where highly retarded combustion phasing typical of modern SI engines was used. It was found that under these conditions, EGR attenuation of knock is greatly reduced, where EGR doesn’t allow significant combustion phasing advance as it does under lighter load conditions. Detailed combustion analysis shows that when EGR is added, the polytropic coefficient increases causing the compressivemore » pressure and temperature to increase. At sufficiently highly boosted conditions, the increase in polytropic coefficient and additional trapped mass from EGR can sufficiently reduce fuel ignition delay to overcome knock attenuation effects. Kinetic modeling demonstrates that the effectiveness of EGR to mitigate knock is highly dependent on the pressure-temperature condition. Experiments at 2000 rpm have confirmed reduced fuel ignition delay under highly boosted conditions relevant to modern downsized boosted SI engines, where in-cylinder pressure is higher and the temperature is cooler. Finally, at these conditions, charge reactivity increases compared to naturally aspirated conditions, and attenuation of knock by EGR is reduced.« less

Perceived parental food controlling practices are related to obesogenic or leptogenic child life style behaviors.

PubMed

Van Strien, Tatjana; van Niekerk, Rianne; Ouwens, Machteld A

2009-08-01

To better understand whether the parental food controlling practices pressure and restriction to eat are obesity preventing or obesity promoting, this study examined whether these parenting practices are related to other (food or non-food) areas that are generally regarded as obesogenic or leptogenic. Are these foods controlling practices more indicative of obesogenic or leptogenic child life style behaviors? In a sample of 7-12-year-old boys and girls (n = 943) the perceived parental food controlling practices were related to various measures for unhealthy life style. Using factor analysis we assessed whether there is a constellation of lifestyle behaviors that is potentially obesogenic or leptogenic. Remarkably, perceived parental restriction and pressure loaded on two different factors. Perceived parental restriction to eat had a negative loading on a factor that further comprised potential obesogenic child life style behaviors, such as snacking (positive loading), time spend with screen media (television or computer) (positive loadings) and frequency of fruit consumption (negative loading). Perceived parental pressure to eat had a positive loading on a factor that further comprised potential leptogenic life style behaviors such as frequency of eating a breakfast meal and sporting (positive loadings). It is concluded that low perceived parental restriction in regard to food may perhaps be a sign of more uninvolved 'neglecting' or indulgent parenting/obesogenic home environment, whereas high perceived parental pressure to eat may be sign of a more 'concerned' leptogenic parenting/home environment, though more research into style of parenting is needed.

Structural Benchmark Tests of Composite Combustion Chamber Support Completed

NASA Technical Reports Server (NTRS)

Krause, David L.; Thesken, John C.; Shin, E. Eugene; Sutter, James K.

2005-01-01

A series of mechanical load tests was completed on several novel design concepts for extremely lightweight combustion chamber support structures at the NASA Glenn Research Center (http://www.nasa.gov/glenn/). The tests included compliance evaluation, preliminary proof loadings, high-strain cyclic testing, and finally residual strength testing of each design (see the photograph on the left). Loads were applied with single rollers (see the photograph on the right) or pressure plates (not shown) located midspan on each side to minimize the influence of contact stresses on corner deformation measurements. Where rollers alone were used, a more severe structural loading was produced than the corresponding equal-force pressure loading: the maximum transverse shear force existed over the entire length of each side, and the corner bending moments were greater than for a distributed (pressure) loading. Failure modes initiating at the corner only provided a qualitative indication of the performance limitations since the stress state was not identical to internal pressure. Configurations were tested at both room and elevated temperatures. Experimental results were used to evaluate analytical prediction tools and finite-element methodologies for future work, and they were essential to provide insight into the deformation at the corners. The tests also were used to assess fabrication and bonding details for the complicated structures. They will be used to further optimize the design of the support structures for weight performance and the efficacy of corner reinforcement.

High pressure solubility of carbon dioxide (CO2) in aqueous solution of piperazine (PZ) activated N-methyldiethanolamine (MDEA) solvent for CO2 capture

NASA Astrophysics Data System (ADS)

Khan, Saleem Nawaz; Hailegiorgis, Sintayehu Mekuria; Man, Zakaria; Shariff, Azmi Mohd

2017-10-01

In this study, the solubility of carbon dioxide (CO2) in the aqueous solution of piperazine (PZ) activated N-methyldiethanolamine (MDEA) was investigated. In the aqueous solution the concentrations of the N-methyldiethanolamine (MDEA) and piperazine (PZ) were kept constant at 30 wt. % and 3 wt. %, respectively. The solubility experiments were carried out between the temperatures ranges of 303.15 to 333.15 K. The pressure range was selected as 2-50 bar for solubility of carbon dioxide in the aqueous solution. The solubility of the CO2 is reported in terms of CO2 loading capacity of the solvent. The loading capacity of the solvent is the ratio between the numbers of moles of CO2 absorbed to the numbers of moles of solvent used. The experimental data showed that the CO2 loading increased with increase in CO2 partial pressure, while it decreased with increase in system's temperature. It was also observed from the experimental data that the higher pressure favors the absorption process while the increased temperature hinders the absorption process of CO2 capture. The loading capacity of the investigated solvent was compared with the loading capacity of the solvents reported in the literature. The investigated solvent showed better solubility in terms of loading capacity.

Dynamic fracture of the surface of an aluminum alloy under conditions of high-speed erosion

NASA Astrophysics Data System (ADS)

Petrov, Yu. V.; Atroshenko, S. A.; Kazarinov, N. A.; Evstifeev, A. D.; Solov'ev, V. Yu.

2017-04-01

The kinetics of fracture and deformation of the standard aluminum alloy AD1 and a similar alloy subjected to severe plastic deformation by high-pressure torsion under conditions of high-speed erosion has been investigated. It has been shown that, with an increase in the loading rate, the fraction of the brittle component on the fracture surface of the standard material, as well as the thickness of the damaged layer, increases more significantly than that for the material after the severe plastic deformation by high-pressure torsion. A relationship of the surface roughness of the material after the erosion with the loading rate and the thickness of the erosion-damaged layer has been established.

Physics Simulation Software for Autonomous Propellant Loading and Gas House Autonomous System Monitoring

NASA Technical Reports Server (NTRS)

Regalado Reyes, Bjorn Constant

2015-01-01

1. Kennedy Space Center (KSC) is developing a mobile launching system with autonomous propellant loading capabilities for liquid-fueled rockets. An autonomous system will be responsible for monitoring and controlling the storage, loading and transferring of cryogenic propellants. The Physics Simulation Software will reproduce the sensor data seen during the delivery of cryogenic fluids including valve positions, pressures, temperatures and flow rates. The simulator will provide insight into the functionality of the propellant systems and demonstrate the effects of potential faults. This will provide verification of the communications protocols and the autonomous system control. 2. The High Pressure Gas Facility (HPGF) stores and distributes hydrogen, nitrogen, helium and high pressure air. The hydrogen and nitrogen are stored in cryogenic liquid state. The cryogenic fluids pose several hazards to operators and the storage and transfer equipment. Constant monitoring of pressures, temperatures and flow rates are required in order to maintain the safety of personnel and equipment during the handling and storage of these commodities. The Gas House Autonomous System Monitoring software will be responsible for constantly observing and recording sensor data, identifying and predicting faults and relaying hazard and operational information to the operators.

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.

Passive phloem loading and long-distance transport in a synthetic tree-on-a-chip.

PubMed

Comtet, Jean; Jensen, Kaare H; Turgeon, Robert; Stroock, Abraham D; Hosoi, A E

2017-03-20

Vascular plants rely on differences in osmotic pressure to export sugars from regions of synthesis (mature leaves) to sugar sinks (roots, fruits). In this process, known as Münch pressure flow, the loading of sugars from photosynthetic cells to the export conduit (the phloem) is crucial, as it sets the pressure head necessary to power long-distance transport. Whereas most herbaceous plants use active mechanisms to increase phloem sugar concentration above that of the photosynthetic cells, in most tree species, for which transport distances are largest, loading seems, counterintuitively, to occur by means of passive symplastic diffusion from the mesophyll to the phloem. Here, we use a synthetic microfluidic model of a passive loader to explore the non-linear dynamics that arise during export and determine the ability of passive loading to drive long-distance transport. We first demonstrate that in our device, the phloem concentration is set by the balance between the resistances to diffusive loading from the source and convective export through the phloem. Convection-limited export corresponds to classical models of Münch transport, where the phloem concentration is close to that of the source; in contrast, diffusion-limited export leads to small phloem concentrations and weak scaling of flow rates with hydraulic resistance. We then show that the effective regime of convection-limited export is predominant in plants with large transport resistances and low xylem pressures. Moreover, hydrostatic pressures developed in our synthetic passive loader can reach botanically relevant values as high as 10 bars. We conclude that passive loading is sufficient to drive long-distance transport in large plants, and that trees are well suited to take full advantage of passive phloem loading strategies.

Model Reduction of Computational Aerothermodynamics for Multi-Discipline Analysis in High Speed Flows

NASA Astrophysics Data System (ADS)

Crowell, Andrew Rippetoe

This dissertation describes model reduction techniques for the computation of aerodynamic heat flux and pressure loads for multi-disciplinary analysis of hypersonic vehicles. NASA and the Department of Defense have expressed renewed interest in the development of responsive, reusable hypersonic cruise vehicles capable of sustained high-speed flight and access to space. However, an extensive set of technical challenges have obstructed the development of such vehicles. These technical challenges are partially due to both the inability to accurately test scaled vehicles in wind tunnels and to the time intensive nature of high-fidelity computational modeling, particularly for the fluid using Computational Fluid Dynamics (CFD). The aim of this dissertation is to develop efficient and accurate models for the aerodynamic heat flux and pressure loads to replace the need for computationally expensive, high-fidelity CFD during coupled analysis. Furthermore, aerodynamic heating and pressure loads are systematically evaluated for a number of different operating conditions, including: simple two-dimensional flow over flat surfaces up to three-dimensional flows over deformed surfaces with shock-shock interaction and shock-boundary layer interaction. An additional focus of this dissertation is on the implementation and computation of results using the developed aerodynamic heating and pressure models in complex fluid-thermal-structural simulations. Model reduction is achieved using a two-pronged approach. One prong focuses on developing analytical corrections to isothermal, steady-state CFD flow solutions in order to capture flow effects associated with transient spatially-varying surface temperatures and surface pressures (e.g., surface deformation, surface vibration, shock impingements, etc.). The second prong is focused on minimizing the computational expense of computing the steady-state CFD solutions by developing an efficient surrogate CFD model. The developed two-pronged approach is found to exhibit balanced performance in terms of accuracy and computational expense, relative to several existing approaches. This approach enables CFD-based loads to be implemented into long duration fluid-thermal-structural simulations.

Fluctuating Pressure Environments and Hydrodynamic Radial Force Mitigation for a Two Blade Unshrouded Inducer

NASA Technical Reports Server (NTRS)

Mulder, Andrew; Skelley, Stephen

2011-01-01

Fluctuating pressure data from water flow testing of an unshrouded two blade inducer revealed a cavitation induced oscillation with the potential to induce a radial load on the turbopump shaft in addition to other more traditionally analyzed radial loads. Subsequent water flow testing of the inducer with a rotating force measurement system confirmed that the cavitation induced oscillation did impart a radial load to the inducer. After quantifying the load in a baseline configuration, two inducer shroud treatments were selected and tested to reduce the cavitation induced load. The first treatment was to increase the tip clearance, and the second was to introduce a circumferential groove near the inducer leading edge. Increasing the clearance resulted in a small load decrease along with some steady performance degradation. The groove greatly reduced the hydrodynamic load with little to no steady performance loss. The groove did however generate some new, relatively high frequency, spatially complex oscillations to the environment.

Fluctuating Pressure Environments and Hydrodynamic Radial Force Mitigation for a Two Blade Unshrouded Inducer

NASA Technical Reports Server (NTRS)

Mulder, Andrew; Skelley, Stephen

2011-01-01

Fluctuating pressure data from water flow testing of an unshrouded two blade inducer revealed a cavitation induced oscillation with the potential to induce a radial load on the turbopump shaft in addition to other more traditionally analyzed radial loads. Subsequent water flow testing of the inducer with a rotating force measurement system confirmed that the cavitation induced oscillation did impart a radial load to the inducer. After quantifying the load in a baseline configuration, two inducer shroud treatments were selected and tested to reduce the cavitation induced load. The first treatment was to increase the tip clearance, and the second was to introduce a circumferential groove near the inducer leading edge. Increasing the clearance resulted in a small decrease in radial load along with some steady performance degradation. The groove greatly reduced the hydrodynamic load with little to no steady performance loss. The groove did however generate some new, relatively high frequency, spatially complex oscillations to the flow environment.

Shock, release and Taylor impact of the semicrystalline thermoplastic polytetrafluoroethylene

NASA Astrophysics Data System (ADS)

Bourne, N. K.; Brown, E. N.; Millett, J. C. F.; Gray, G. T.

2008-04-01

The high strain-rate response of polymers is a subject that has gathered interest over recent years due to their increasing engineering importance, particularly in load bearing applications subject to extremes of pressure and strain rate. The current work presents two specific sets of experiments interrogating the effect of dynamic, high-pressure loading in the regime of the phase II to phase III pressure-induced crystalline phase transition in polytetrafluoroethylene (PTFE). These are gas-gun driven plate- and Taylor impact. Together these experiments highlight several effects associated with the dynamic, pressure-induced phase transitions in PTFE. An elevated release wave speed shows evidence of a pressure-induced phase change at a stress commensurate with that observed statically. It is shown that convergence between analytic derivations of release wave speed and the data requires the phase II to III transition to occur. Taylor impact is an integrated test that highlights continuum behavior that has origin in mesoscale response. There is a rapid transition from ductile to brittle behavior observed that occurs at a pressure consistent with this phase transition.

Role of load history in intervertebral disc mechanics and intradiscal pressure generation.

PubMed

Hwang, David; Gabai, Adam S; Yu, Miao; Yew, Alvin G; Hsieh, Adam H

2012-01-01

Solid-fluid interactions play an important role in mediating viscoelastic behaviour of biological tissues. In the intervertebral disc, water content is governed by a number of factors, including age, disease and mechanical loads, leading to changes in stiffness characteristics. We hypothesized that zonal stress distributions depend on load history, or the prior stresses experienced by the disc. To investigate these effects, rat caudal motion segments were subjected to compressive creep biomechanical testing in vitro using a protocol that consisted of two phases: a Prestress Phase (varied to represent different histories of load) followed immediately by an Exertion Phase, identical across all Prestress groups. Three analytical models were used to fit the experimental data in order to evaluate load history effects on gross and zonal disc mechanics. Model results indicated that while gross transient response was insensitive to load history, there may be changes in the internal mechanics of the disc. In particular, a fluid transport model suggested that the role of the nucleus pulposus in resisting creep during Exertion depended on Prestress conditions. Separate experiments using similarly defined load history regimens were performed to verify these predictions by measuring intradiscal pressure with a fibre optic sensor. We found that the ability for intradiscal pressure generation was load history-dependent and exhibited even greater sensitivity than predicted by analytical models. A 0.5 MPa Exertion load resulted in 537.2 kPa IDP for low magnitude Prestress compared with 373.7 kPa for high magnitude Prestress. Based on these measurements, we developed a simple model that may describe the pressure-shear environment in the nucleus pulposus. These findings may have important implications on our understanding of how mechanical stress contributes to disc health and disease etiology.

Nacelle Aerodynamic and Inertial Loads (NAIL) project

NASA Technical Reports Server (NTRS)

1982-01-01

A flight test survey of pressures measured on wing, pylon, and nacelle surfaces and of the operating loads on Boeing 747/Pratt & Whitney JT9D-7A nacelles was made to provide information on airflow patterns surrounding the propulsion system installations and to clarify processes responsible for inservice deterioration of fuel economy. Airloads at takeoff rotation were found to be larger than at any other normal service condition because of the combined effects of high angle of attack and high engine airflow. Inertial loads were smaller than previous estimates indicated. A procedure is given for estimating inlet airloads at low speeds and high angles of attack for any underwing high bypass ratio turbofan installation approximately resembling the one tested. Flight procedure modifications are suggested that may result in better fuel economy retention in service. Pressures were recorded on the core cowls and pylons of both engine installations and on adjacent wing surfaces for use in development of computer codes for analysis of installed propulsion system aerodynamic drag interference effects.

A pressure plate study on fore and hindlimb loading and the association with hoof contact area in sound ponies at the walk and trot.

PubMed

Oosterlinck, M; Pille, F; Back, W; Dewulf, J; Gasthuys, F

2011-10-01

The aim of this study was to evaluate the association between fore- and hind-hoof contact area and limb loading. Data from a previous study on forelimb loading and symmetry were compared with data on hindlimb kinetics, and the fore- and hind-hoof contact area at the walk and trot was evaluated. Five sound ponies, selected for symmetrical feet, were walked and trotted over a pressure plate embedded in a custom-made runway. The hindlimb peak vertical force (PVF) and vertical impulse (VI) were found to be significantly lower than in the forelimb, whereas their high symmetry ratios (>95%) did not show a significant difference from forelimb data. Hindlimb PVF in ponies was found to be slightly higher when compared to data reported for horses even though the ponies moved at a similar or lower relative velocity. The contact area had low intra-individual variability and was significantly smaller in the hind- than in the fore-hooves. A larger contact area was significantly associated with lower peak vertical pressure (PVP) but higher PVF and VI. No significant differences between left and right sides were found for contact area or loading variables. Pressure plate measurements demonstrated a significant association between hoof contact area and limb loading, in addition to intrinsic differences between fore and hindlimb locomotor function. The pressure plate provides the clinician with a tool to quantify simultaneously contralateral differences in hoof contact area and limb loading. Copyright © 2010 Elsevier Ltd. All rights reserved.

Treadmill walking with load carriage increases aortic pressure wave reflection.

PubMed

Ribeiro, Fernando; Oliveira, Nórton L; Pires, Joana; Alves, Alberto J; Oliveira, José

2014-01-01

The study examined the effects of treadmill walking with load carriage on derived measures of central pressure and augmentation index in young healthy subjects. Fourteen male subjects (age 31.0 ± 1.0 years) volunteered in this study. Subjects walked 10 minutes on a treadmill at a speed of 5 km/h carrying no load during one session and a load of 10% of their body weight on both upper limbs in two water carboys with handle during the other session. Pulse wave analysis was performed at rest and immediately after exercise in the radial artery of the right upper limb by applanation tonometry. The main result indicates that walking with load carriage sharply increased augmentation index at 75 bpm (-5.5 ± 2.2 to -1.4 ± 2.2% vs. -5.2 ± 2.8 to -5.5 ± 2.1%, p<0.05), and also induced twice as high increments in central pulse pressure (7.4 ± 1.5 vs. 3.1 ± 1.4 mmHg, p<0.05) and peripheral (20.5 ± 2.7 vs. 10.3 ± 2.5 mmHg, p<0.05) and central systolic pressure (14.7 ± 2.1 vs. 7.4 ± 2.0 mmHg, p<0.05). Walking with additional load of 10% of their body weight (aerobic exercise accompanied by upper limb isometric contraction) increases derived measures of central pressure and augmentation index, an index of wave reflection and arterial stiffness. Copyright © 2013 Sociedade Portuguesa de Cardiologia. Published by Elsevier España. All rights reserved.

Shock-activated reaction synthesis and high pressure response of titanium-based ternary carbide and nitride ceramics

NASA Astrophysics Data System (ADS)

Jordan, Jennifer Lynn

The objectives of this study were to (a) investigate the effect of shock activation of precursor powders for solid-state reaction synthesis of Ti-based ternary ceramics and (b) to determine the high pressure phase stability and Hugoniot properties of Ti3SiC2. Dynamically densified compacts of Ti, SiC, and graphite precursor powders and Ti and AlN precursor powders were used to study the shock-activated formation of Ti 3SiC2 and Ti2AlN ternary compounds, respectively, which are considered to be novel ceramics having high stiffness but low hardness. Gas gun and explosive loading techniques were used to obtain a range of loading conditions resulting in densification and activation. Measurements of fraction reacted as a function of time and temperature and activation energies obtained from DTA experiments were used to determine the degree of activation caused by shock compression and its subsequent effect on the reaction mechanisms and kinetics. In both systems, shock activation led to an accelerated rate of reaction at temperatures less than 1600°C and, above that temperature, it promoted the formation of almost 100% of the ternary compound. A kinetics-based mathematical model based on mass and thermal transport was developed to predict the effect of shock activation and reaction synthesis conditions that ensure formation of the ternary compounds. Model predictions revealed a transition temperature above which the reaction is taken over by the "run-away" combustion-type mode. The high pressure phase stability of pre-alloyed Ti 3SiC2 compound was investigated by performing Hugoniot shock and particle velocity measurements using the facilities at the National Institute for Materials Science (Tsukuba, Japan). Experiments performed at pressures of 95--120 GPa showed that the compressibility of Ti3SiC 2 at these pressures deviates from the previously reported compressibility of the material under static high pressure loading. The deviation in compressibility behavior is indicative of the transformation of the Ti3 SiC2 ceramic to a high pressure, high density phase.

Cardiopulmonary baroreceptors affect reflexive startle eye blink.

PubMed

Richter, S; Schulz, A; Port, J; Blumenthal, T D; Schächinger, H

2009-12-07

Baroafferent signals originating from the 'high pressure' arterial vascular system are known to impact reflexive startle eye blink responding. However, it is not known whether baroafferent feedback of the 'low pressure' cardiopulmonary system loading status exerts a similar effect. Lower Body Negative Pressure (LBNP) at gradients of 0, -10, -20, and -30mm Hg was applied to unload cardiopulmonary baroreceptors. Acoustic startle noise bursts were delivered 230 and 530ms after spontaneous R-waves, when arterial baroreceptors are either loaded or unloaded. Eye blink responses were measured by EMG, and psychomotor reaction time by button pushes to startle stimuli. The new finding of this study was that unloading of cardiopulmonary baroreceptors increases startle eye blink responsiveness. Furthermore, we replicated the effect of relative loading/unloading of arterial baroreceptors on startle eye blink responsiveness. Effects of either arterial or cardiopulmonary baroreceptor manipulations were not present for psychomotor reaction times. These results demonstrate that the loading status of cardiopulmonary baroreceptors has an impact on brainstem-based CNS processes.

Deep Tissue Injury in Development of Pressure Ulcers: A Decrease of Inflammasome Activation and Changes in Human Skin Morphology in Response to Aging and Mechanical Load

PubMed Central

Stojadinovic, Olivera; Minkiewicz, Julia; Sawaya, Andrew; Bourne, Jonathan W.; Torzilli, Peter; de Rivero Vaccari, Juan Pablo; Dietrich, W. Dalton; Keane, Robert W.; Tomic-Canic, Marjana

2013-01-01

Molecular mechanisms leading to pressure ulcer development are scarce in spite of high mortality of patients. Development of pressure ulcers that is initially observed as deep tissue injury is multifactorial. We postulate that biomechanical forces and inflammasome activation, together with ischemia and aging, may play a role in pressure ulcer development. To test this we used a newly-developed bio-mechanical model in which ischemic young and aged human skin was subjected to a constant physiological compressive stress (load) of 300 kPa (determined by pressure plate analyses of a person in a reclining position) for 0.5–4 hours. Collagen orientation was assessed using polarized light, whereas inflammasome proteins were quantified by immunoblotting. Loaded skin showed marked changes in morphology and NLRP3 inflammasome protein expression. Sub-epidermal separations and altered orientation of collagen fibers were observed in aged skin at earlier time points. Aged skin showed significant decreases in the levels of NLRP3 inflammasome proteins. Loading did not alter NLRP3 inflammasome proteins expression in aged skin, whereas it significantly increased their levels in young skin. We conclude that aging contributes to rapid morphological changes and decrease in inflammasome proteins in response to tissue damage, suggesting that a decline in the innate inflammatory response in elderly skin could contribute to pressure ulcer pathogenesis. Observed morphological changes suggest that tissue damage upon loading may not be entirely preventable. Furthermore, newly developed model described here may be very useful in understanding the mechanisms of deep tissue injury that may lead towards development of pressure ulcers. PMID:23967056

46 CFR 154.408 - Cargo tank external pressure load.

Code of Federal Regulations, 2010 CFR

2010-10-01

... minimum internal pressure (maximum vacuum), and the maximum external pressure to which any portion of the... 46 Shipping 5 2010-10-01 2010-10-01 false Cargo tank external pressure load. 154.408 Section 154... Equipment Cargo Containment Systems § 154.408 Cargo tank external pressure load. For the calculation...

Development and Assessment of Altitude Adjustable Convergent Divergent Nozzles Using Passive Flow Control

NASA Astrophysics Data System (ADS)

Mandour Eldeeb, Mohamed

The backward facing steps nozzle (BFSN) is a new developed flow adjustable exit area nozzle. It consists of two parts, the first is a base nozzle with small area ratio and the second part is a nozzle extension with surface consists of backward facing steps. The steps number and heights are carefully chosen to produce controlled flow separation at steps edges that adjust the nozzle exit area at all altitudes (pressure ratios). The BFSN performance parameters are assessed numerically in terms of thrust and side loads against the dual-bell nozzle with the same pressure ratios and cross sectional areas. Cold flow inside the planar BFSN and planar DBN are simulated using three-dimensional turbulent Navier-Stoke equations solver at different pressure ratios. The pressure distribution over the upper and the lower nozzles walls show symmetrical flow separation location inside the BFSN and an asymmetrical flow separation location inside the DBN at same vertical plane. The side loads are calculated by integrate the pressure over the nozzles walls at different pressure ratios for both nozzles. Time dependent solution for the DBN and the BFSN are obtained by solving two-dimensional turbulent flow. The side loads over the upper and lower nozzles walls are plotted against the flow time. The BFSN side loads history shows a small values of fluctuated side loads compared with the DBN which shows a high values with high fluctuations. Hot flow 3-D numerical solutions inside the axi-symmetric BFSN and DBN are obtained at different pressure ratios and compared to assess the BFSN performance against the DBN. Pressure distributions over the nozzles walls at different circumferential angels are plotted for both nozzles. The results show that the flow separation location is axi-symmetric inside the BFSN with symmetrical pressure distributions over the nozzle circumference at different pressure ratios. While the DBN results show an asymmetrical flow separation locations over the nozzle circumference at all pressure ratios.The results show that the side loads in the BFSN is 0.01%-0.6% of its value in the DBN for same pressure ratio. For further confirmation of the axi-symmetric nature of the flow in the BFSN, 2-D axi-symmetric solutions are obtained at same pressure ratios and boundary conditions. The flow parameters at the nozzle exit are calculated the 3-D and the 2-D solutions and compared to each other. The maximum difference between the 3-D and the 2-D solutions is less than 1%. Parametric studies are carried out with number of the backward facing steps varied from two to forty. The results show that as the number of backward facing steps increase, the nozzle performance in terms of thrust approach the DBN performance. The BFSN with two and six steps are simulated for pressure ratios range from 148 to 1500 and compared with the DBN and a conventional bell nozzle. Expandable BFSN study is carried out on the BFSN with two steps where the nozzle operation is divided into three modes related to the operating altitude (PR). Backward facing steps concept is applied to a full scale conventional bell nozzle by adding two backward facing steps at the end of the nozzle increasing its expansion area results in 1.8% increasing in its performance in terms of thrust coefficient at high altitudes.

Composite load spectra for select space propulsion structural components

NASA Technical Reports Server (NTRS)

Newell, J. F.; Kurth, R. E.; Ho, H.

1991-01-01

The objective of this program is to develop generic load models with multiple levels of progressive sophistication to simulate the composite (combined) load spectra that are induced in space propulsion system components, representative of Space Shuttle Main Engines (SSME), such as transfer ducts, turbine blades, and liquid oxygen posts and system ducting. The first approach will consist of using state of the art probabilistic methods to describe the individual loading conditions and combinations of these loading conditions to synthesize the composite load spectra simulation. The second approach will consist of developing coupled models for composite load spectra simulation which combine the deterministic models for composite load dynamic, acoustic, high pressure, and high rotational speed, etc., load simulation using statistically varying coefficients. These coefficients will then be determined using advanced probabilistic simulation methods with and without strategically selected experimental data.

Local plantar pressure relief in therapeutic footwear: design guidelines from finite element models.

PubMed

Erdemir, Ahmet; Saucerman, Jeffrey J; Lemmon, David; Loppnow, Bryan; Turso, Brie; Ulbrecht, Jan S; Cavanagh, Peter Re

2005-09-01

A major goal of therapeutic footwear in patients with pain or those at risk for skin injury is to relieve focal loading under prominent metatarsal heads. One frequent approach is to place plugs of compliant material into the midsole of the shoe. This study investigated 36 plug designs, a combination of three materials, six geometries, and two placements using a two-dimensional (2D) finite element model. Realistic loading conditions were obtained from plantar pressures (PP) recorded during walking in five subjects who wore control midsoles manufactured using Microcell Puff. Measured peak pressures underneath the second metatarsal head were similar to the results of the control model. PP obtained from simulations with the plugs built into a firm midsole were compared to the simulation results of the control midsole. Large plugs (e.g. 40 mm width), made out of Microcell Puff Lite or Plastazote Medium, placed at peak pressure sites, resulted in highest reductions in peak pressures (18-28%). Smaller plugs benefited from tapering when placed at high pressure areas. Case studies were completed on a healthy male subject and a diabetic female patient to address the efficacy of a plug design favored by our simulations (pressure based placement, 40 x 20 mm, Plastazote Medium). Successful reductions of second metatarsal head pressures were observed with a mediolateral load redistribution that was not represented by our model. 2D computer simulations allowed systematic investigation of plug properties without the need for high volume experimentation on human subjects and established basic guidelines for plug selection. In particular, plugs that are placed based on plantar pressure measurements were proven to be more effective when compared to those positioned according to the projection of the bony landmark on the foot-shoe plantar contact area.

High Stress Consolidation, Ultrasonic, and Permeability Measurements: Constraints on Physical Properties and In Situ Stress along the Costa Rica Subduction Plate Interface

NASA Astrophysics Data System (ADS)

Winner, A.; Saffer, D. M.; Valdez, R. D.

2014-12-01

Sediment permeability and consolidation behavior are key parameters in governing the drainage state and thus potential for excess pore fluid pressure in subduction zones. Elevated pore pressure, in turn, is one important control on the strength and sliding behavior of faults. Along many subduction margins, evidence of elevated, near-lithostatic, in situ pore pressure comes from high seismic reflectivity, low P-wave velocity (Vp), and high Vp/Vs ratios. This inference is broadly supported by numerical modeling studies that indicate elevated pore pressures are likely given high rates of burial and tectonic loading, combined with the low permeability of marine mudstones. Here, we report on a series of high-stress consolidation experiments on sediment core samples from the incoming Cocos plate obtained as part of Integrated Ocean Drilling Program (IODP) Expedition 344. Our experiments were designed to measure the consolidation behavior, permeability, and P-wave velocity of the incoming sediments over a range of confining stresses from .5 to 90 MPa. We explore a range of paths,including isostatic loading (σ1=σ2=σ3), K0 consolidation, in which the ratio of σ3/σ1 is maintained at ~0.6, and the trixial loading paths designed to maintain a near critical-state failure condition. In our tests, load is increased in a series of steps. After equilibration at each step, we conduct constant head permeability tests, and measure P-wave velocities in a "time of flight" mode. Initial results from isostatic loading tests on hemipelagic mudstone samples from 34 mbsf document consolidation and permeability-porosity trends, in which porosity decreases from 69% to 54% as stress in increased from .5 MPa to 15 MPa, and permeability decreases from 8.1 X 10-18 m2 at 1 MPa to 1.1 X 10-19 m2 at 15 MPa. P-wave velocity increases by 486-568 km/s over this effective stress range. Ultimately, data from our experiments will provide a robust basis for quantifying fluid content and pressure from seismic velocity and fault plane reflectivity at this margin, and provide data to parameterize forward models of fluid flow and consolidation.

75 FR 25124 - Airworthiness Directives; The Boeing Company Model 737-200, -300, -400, and -500 Series Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-07

... to stub beam cracking, caused by high flight cycle stresses from both pressurization and maneuver... high flight cycle stresses from both pressurization and maneuver loads. Reduced structural integrity of.... operators to comply with this proposed AD. Estimated Costs Number of U.S.- Action Work hours Average labor...

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.

Effect of propellant deformation on ignition and combustion processes in solid propellant cracks

NASA Technical Reports Server (NTRS)

Kumar, M.; Kuo, K. K.

1980-01-01

A comprehensive theoretical model was formulated to study the development of convective burning in a solid propellant crack which continually deforms due to burning and pressure loading. In the theoretical model, the effect of interrelated structural deformation and combustion processes was taken into account by considering (1) transient, one dimensional mass, momentum, and energy conservation equations in the gas phase; (2) a transient, one dimensional heat conduction equation in the solid phase; and (3) quasi-static deformation of the two dimensional, linear viscoelastic propellant crack caused by pressure loading. Partial closures may generate substantial local pressure peaks along the crack, implying a strong coupling between chamber pressurization, crack combustion, and propellant deformation, especially when the cracks are narrow and the chamber pressurization rates high. The maximum pressure in the crack cavity is generally higher than that in the chamber. The initial flame-spreading process is not affected by propellant deformation.

Preparation and evaluation of highly drug-loaded fine globular granules using a multi-functional rotor processor.

PubMed

Iwao, Yasunori; Kimura, Shin-Ichiro; Ishida, Masayuki; Mise, Ryohei; Yamada, Masaki; Namiki, Noriyuki; Noguchi, Shuji; Itai, Shigeru

2015-01-01

The manufacture of highly drug-loaded fine globular granules eventually applied for orally disintegrating tablets has been investigated using a unique multi-functional rotor processor with acetaminophen, which was used as a model drug substance. Experimental design and statistical analysis were used to evaluate potential relationships between three key operating parameters (i.e., the binder flow rate, atomization pressure and rotating speed) and a series of associated micromeritics (i.e., granule mean size, proportion of fine particles (106-212 µm), flowability, roundness and water content). The results of multiple linear regression analysis revealed several trends, including (1) the binder flow rate and atomization pressure had significant positive and negative effects on the granule mean size value, Carr's flowability index, granular roundness and water content, respectively; (2) the proportion of fine particles was positively affected by the product of interaction between the binder flow rate and atomization pressure; and (3) the granular roundness was negatively and positively affected by the product of interactions between the binder flow rate and the atomization pressure, and the binder flow rate and rotating speed, respectively. The results of this study led to the identification of optimal operating conditions for the preparation of granules, and could therefore be used to provide important information for the development of processes for the manufacture of highly drug-loaded fine globular granules.

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

PubMed

Liao, Fuyuan; Jan, Yih-Kuen

2012-06-01

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

Osteochondral microdamage from valgus bending of the human knee.

PubMed

Meyer, Eric G; Villwock, Mark R; Haut, Roger C

2009-08-01

Valgus bending of the knee is promoted as an anterior cruciate ligament injury mechanism and is associated with a characteristic "footprint" of bone bruising. The hypothesis of this study was that during ligamentous failure caused by valgus bending of the knee, high tibiofemoral contact pressures induce acute osteochondral microdamage. Four knee pairs were loaded in valgus bending until gross injury with or without a tibiofemoral compression pre-load. The peak valgus moment and resultant motions of the knee joint were recorded. Pressure sensitive film documented the magnitude and location of tibiofemoral contact. Cartilage fissures were documented on the tibial plateau, and microcracks in subchondral bone were documented from micro-computed tomography scans. Injuries were to the anterior cruciate ligament in three knees and the medial collateral ligament in seven knees. The mean (standard deviation) peak bending moment at failure was 107 (64)Nm. Valgus bending produced regions of contact on the lateral tibial plateau with average maximum pressures of approximately 30 (8)MPa. Cartilage fissures and subchondral bone microcracks were observed in these regions of high contact pressure. Combined valgus bending and tibiofemoral compression produce slightly higher contact pressures, but do not alter the gross injury pattern from isolated valgus bending experiments. Athletes who sustain a severe valgus knee bending moment, may be at risk of acute osteochondral damage especially if the loading mechanism occurs with a significant tibiofemoral compression component.

Advanced performance of small diaphragm vacuum pumps through the use of mechatronics

NASA Astrophysics Data System (ADS)

Lachenmann, R.; Dirscherl, J.

Oil-free diaphragm vacuum pumps have proven to be the best way in vacuum generation for the chemical laboratory and they also find increasing use as backing pumps for modern wide-range turbo molecular pumps. The majority of vacuum pumps in practical use pump only a rather small percentage of their lifetime at full gas load. A pump backing a turbo molecular pump does not have to pump a significant gas load when the high-vacuum pump is running at ultimate vacuum pressure. Also, for a vacuum distillation the vacuum pump has to operate at full speed only at the beginning to lower the pressure inside the system to a vacuum level where evaporation starts. In a rather leak-tight system the distillation process continues by evaporating from the hot liquid and condensing at the cold condenser without the need of a mechanical vacuum pump. Rotational speed controlled diaphragm pumps are now available through progress in mechatronics and offer high pumping speed capability for fast pump-down cycles and precise pressure control for distillations. At low gas load the rotational speed can be reduced, improving maintenance intervals, power consumption, noise, vibration and - surprisingly - also ultimate pressure. The different behaviour in pumping speed and ultimate pressure of rotational speed controlled diaphragm pumps in comparison to constant-speed pumps is related to the mechanical properties of the valves and gas dynamics .

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.

Brittle materials at high-loading rates: an open area of research

NASA Astrophysics Data System (ADS)

Forquin, Pascal

2017-01-01

Brittle materials are extensively used in many civil and military applications involving high-strain-rate loadings such as: blasting or percussive drilling of rocks, ballistic impact against ceramic armour or transparent windshields, plastic explosives used to damage or destroy concrete structures, soft or hard impacts against concrete structures and so on. With all of these applications, brittle materials are subjected to intense loadings characterized by medium to extremely high strain rates (few tens to several tens of thousands per second) leading to extreme and/or specific damage modes such as multiple fragmentation, dynamic cracking, pore collapse, shearing, mode II fracturing and/or microplasticity mechanisms in the material. Additionally, brittle materials exhibit complex features such as a strong strain-rate sensitivity and confining pressure sensitivity that justify expending greater research efforts to understand these complex features. Currently, the most popular dynamic testing techniques used for this are based on the use of split Hopkinson pressure bar methodologies and/or plate-impact testing methods. However, these methods do have some critical limitations and drawbacks when used to investigate the behaviour of brittle materials at high loading rates. The present theme issue of Philosophical Transactions A provides an overview of the latest experimental methods and numerical tools that are currently being developed to investigate the behaviour of brittle materials at high loading rates. This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'.

Brittle materials at high-loading rates: an open area of research

PubMed Central

2017-01-01

Brittle materials are extensively used in many civil and military applications involving high-strain-rate loadings such as: blasting or percussive drilling of rocks, ballistic impact against ceramic armour or transparent windshields, plastic explosives used to damage or destroy concrete structures, soft or hard impacts against concrete structures and so on. With all of these applications, brittle materials are subjected to intense loadings characterized by medium to extremely high strain rates (few tens to several tens of thousands per second) leading to extreme and/or specific damage modes such as multiple fragmentation, dynamic cracking, pore collapse, shearing, mode II fracturing and/or microplasticity mechanisms in the material. Additionally, brittle materials exhibit complex features such as a strong strain-rate sensitivity and confining pressure sensitivity that justify expending greater research efforts to understand these complex features. Currently, the most popular dynamic testing techniques used for this are based on the use of split Hopkinson pressure bar methodologies and/or plate-impact testing methods. However, these methods do have some critical limitations and drawbacks when used to investigate the behaviour of brittle materials at high loading rates. The present theme issue of Philosophical Transactions A provides an overview of the latest experimental methods and numerical tools that are currently being developed to investigate the behaviour of brittle materials at high loading rates. This article is part of the themed issue ‘Experimental testing and modelling of brittle materials at high strain rates’. PMID:27956517

Brittle materials at high-loading rates: an open area of research.

PubMed

Forquin, Pascal

2017-01-28

Brittle materials are extensively used in many civil and military applications involving high-strain-rate loadings such as: blasting or percussive drilling of rocks, ballistic impact against ceramic armour or transparent windshields, plastic explosives used to damage or destroy concrete structures, soft or hard impacts against concrete structures and so on. With all of these applications, brittle materials are subjected to intense loadings characterized by medium to extremely high strain rates (few tens to several tens of thousands per second) leading to extreme and/or specific damage modes such as multiple fragmentation, dynamic cracking, pore collapse, shearing, mode II fracturing and/or microplasticity mechanisms in the material. Additionally, brittle materials exhibit complex features such as a strong strain-rate sensitivity and confining pressure sensitivity that justify expending greater research efforts to understand these complex features. Currently, the most popular dynamic testing techniques used for this are based on the use of split Hopkinson pressure bar methodologies and/or plate-impact testing methods. However, these methods do have some critical limitations and drawbacks when used to investigate the behaviour of brittle materials at high loading rates. The present theme issue of Philosophical Transactions A provides an overview of the latest experimental methods and numerical tools that are currently being developed to investigate the behaviour of brittle materials at high loading rates.This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'. © 2016 The Author(s).

Jet Flap Stator Blade Test in the High Reaction Turbine Blade Cascade Tunnel

NASA Image and Video Library

1970-03-21

A researcher examines the setup of a jet flap blade in the High Reaction Turbine Blade Cascade Tunnel at the National Aeronautics and Space Administration (NASA) Lewis Research Center. Lewis researchers were seeking ways to increase turbine blade loading on aircraft engines in an effort to reduce the overall size and weight of engines. The ability of each blade to handle higher loads meant that fewer stages and fewer blades were required. This study analyzed the performance of a turbine blade using a jet flap and high loading. A jet of air was injected into the main stream from the pressure surface near the trailing edge. The jet formed an aerodynamic flap which deflected the flow and changed the circulation around the blade and thus increased the blade loading. The air jet also reduced boundary layer thickness. The jet-flap blade design was appealing because the cooling air may also be used for the jet. The performance was studied in a two-dimensional cascade including six blades. The researcher is checking the jet flat cascade with an exit survey probe. The probe measured the differential pressure that was proportional to the flow angle. The blades were tested over a range of velocity ratios and three jet flow conditions. Increased jet flow improved the turning and decreased both the weight flow and the blade loading. However, high blade loadings were obtained at all jet flow conditions.

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.

Design Considerations for Ceramic Matrix Composite Vanes for High Pressure Turbine Applications

NASA Technical Reports Server (NTRS)

Boyle, Robert J.; Parikh, Ankur H.; Nagpal, Vinod K.; Halbig, Michael C.

2013-01-01

Issues associated with replacing conventional metallic vanes with Ceramic Matrix Composite (CMC) vanes in the first stage of the High Pressure Turbine (HPT) are explored. CMC materials have higher temperature capability than conventional HPT vanes, and less vane cooling is required. The benefits of less vane coolant are less NOx production and improved vane efficiency. Comparisons between CMC and metal vanes are made at current rotor inlet temperatures and at an vane inlet pressure of 50 atm.. CMC materials have directionally dependent strength characteristics, and vane designs must accommodate these characteristics. The benefits of reduced NOx and improved cycle efficiency obtainable from using CMC vanes. are quantified Results are given for vane shapes made of a two dimensional CMC weave. Stress components due to thermal and pressure loads are shown for all configurations. The effects on stresses of: (1) a rib connecting vane pressure and suction surfaces; (2) variation in wall thickness; and (3) trailing edge region cooling options are discussed. The approach used to obtain vane temperature distributions is discussed. Film cooling and trailing edge ejection were required to avoid excessive vane material temperature gradients. Stresses due to temperature gradients are sometimes compressive in regions where pressure loads result in high tensile stresses.

Dynamic plasticity and failure of high-purity alumina under shock loading.

PubMed

Chen, M W; McCauley, J W; Dandekar, D P; Bourne, N K

2006-08-01

Most high-performance ceramics subjected to shock loading can withstand high failure strength and exhibit significant inelastic strain that cannot be achieved under conventional loading conditions. The transition point from elastic to inelastic response prior to failure during shock loading, known as the Hugoniot elastic limit (HEL), has been widely used as an important parameter in the characterization of the dynamic mechanical properties of ceramics. Nevertheless, the underlying micromechanisms that control HEL have been debated for many years. Here we show high-resolution electron microscopy of high-purity alumina, soft-recovered from shock-loading experiments. The change of deformation behaviour from dislocation activity in the vicinity of grain boundaries to deformation twinning has been observed as the impact pressures increase from below, to above HEL. The evolution of deformation modes leads to the conversion of material failure from an intergranular mode to transgranular cleavage, in which twinning interfaces serve as the preferred cleavage planes.

A novel tool for the prediction of tablet sticking during high speed compaction.

PubMed

Abdel-Hamid, Sameh; Betz, Gabriele

2012-01-01

During tableting, capping is a problem of cohesion while sticking is a problem of adhesion. Sticking is a multi-composite problem; causes are either material or machine related. Nowadays, detecting such a problem is a pre-requisite in the early stages of development. The aim of our study was to investigate sticking by radial die-wall pressure monitoring guided by compaction simulation. This was done by using the highly sticking drug; Mefenamic acid (MA) at different drug loadings with different fillers compacted at different pressures and speeds. By increasing MA loading, we found that viscoelastic fillers showed high residual radial pressure after compaction while plastic/brittle fillers showed high radial pressure during compaction, p < 0.05. Visually, plastic/brittle fillers showed greater tendencies for adhesion to punches than viscoelastic fillers while the later showed higher tendencies for adhesion to the die-wall. This was confirmed by higher values of axial stress transmission for plastic/brittle than viscoelastic fillers (higher punch surface/powder interaction), and higher residual die-wall and ejection forces for viscoelastic than plastic/brittle fillers, p < 0.05. Take-off force was not a useful tool to estimate sticking due to cohesive failure of the compacts. Radial die-wall pressure monitoring is suggested as a robust tool to predict sticking.

Effects of particle size, helium gas pressure and microparticle dose on the plasma concentration of indomethacin after bombardment of indomethacin-loaded poly-L-lactic acid microspheres using a Helios gun system.

PubMed

Uchida, Masaki; Natsume, Hideshi; Kobayashi, Daisuke; Sugibayashi, Kenji; Morimoto, Yasunori

2002-05-01

We investigated the effects of the particle size of indomethacin-loaded poly-L-lactic acid microspheres (IDM-loaded PLA MS), the helium pressure used to accelerate the particles, and the bombardment dose of PLA MS on the plasma concentration of IDM after bombarding with IDM-loaded PLA MS of different particle size ranges, 20-38, 44-53 and 75-100 microm, the abdomen of hairless rats using the Helios gene gun system (Helios gun system). Using larger particles and a higher helium pressure, produced an increase in the plasma IDM concentration and the area under the plasma concentration-time curve (AUC) and resultant F (relative bioavailability with respect to intracutaneous injection) of IDM increased by an amount depending on the particle size and helium pressure. Although a reduction in the bombardment dose led to a decrease in C(max) and AUC, F increased on decreasing the bombardment dose. In addition, a more efficient F was obtained after bombarding with IDM-loaded PLA MS of 75-100 microm in diameter at each low dose in different sites of the abdomen compared with that after bolus bombardment with a high dose (dose equivalent). These results suggest that the bombardment injection of drug-loaded microspheres by the Helios gun system is a very useful tool for delivering a variety of drugs in powder form into the skin and systemic circulation.

In-situ x-ray diffraction of a shock-induced phase transition in fluorite, CaF2

NASA Astrophysics Data System (ADS)

Glam, Benny; June Tracy, Sally; Turneaure, Stefan; Duffy, Thomas

2017-06-01

The difluorides are an important class of ionic compounds that show extensive polymorphism under both static and dynamic loading. In this study, the shock-induced phase transitions in CaF2 were investigated by in situ x-ray diffraction measurements in plate impact experiments carried out with the two-stage gas gun at the Dynamic Compression Sector of Argonne National Laboratory. Single-crystal samples in (100) and (111) orientations were shock loaded to pressures between 32 GPa to 70 GPa. The particle velocities at the interface between the sample and a LiF window were measured by VISAR and PDV. Synchrotron x-ray diffraction data were recorded at 153.4 ns intervals using a four-frame detector. The measured diffraction patterns show a high degree of sample texturing at all pressures. We observe evidence for a transition to a high-pressure phase followed by reverse transformation at late times during release. This study provides the first direct constraints on the high-pressure lattice structure of fluorite under shock compression.

High-tip-speed, low-loading transonic fan stage. Part 3: Final report

NASA Technical Reports Server (NTRS)

Ware, T. C.; Kobayashi, R. J.; Jackson, R. J.

1974-01-01

Tests were conducted on a high-tip-speed, low-loading transonic fan stage to determine the performance and inlet flow distortion tolerance of the design. The fan was designed for high efficiency at a moderate pressure ratio by designing the hub section to operate at minimum loss when the tip operates with an oblique shock. The design objective was an efficiency of 86 percent at a pressure ratio of 1.5, a specific flow (flow per unit annulus area) of 42 lb/sec-sq. ft (205.1 kgm/sec-m sq), and a tip speed of 1600 ft/sec (488.6 m/sec). During testing, a peak efficiency of 84 percent was achieved at design speed and design specific flow. At the design speed and pressure ratio, the flow was 4 percent greater than design, efficiency was 81 percent, and a stall margin of 24 percent was obtained. The stall line was improved with hub radial distortion but was reduced when the stage was tested with tip radial and circumferential flow distortions. Blade-to-blade values of static pressures were measured over the rotor blade tips.

Experimental and Analytical Determination of the Motion of Hydraulically Operated Valve Stems in Oil Engine Injection Systems

NASA Technical Reports Server (NTRS)

Gelalles, A G; Rothrock, A M

1930-01-01

This research on the pressure variations in the injection system of the N.A.C.A. Spray Photography Equipment and on the effects of these variations on the motion of the timing valve stem was undertaken in connection with the study of fuel injection systems for high-speed oil engines. The methods of analysis of the pressure variations and the general equation for the motion of the spring-loaded stem for the timing valve are applicable to a spring-loaded automatic injection valve, and in general to all hydraulically operated valves. A sample calculation for a spring-loaded automatic injection valve is included.

High pressure rotary piston coal feeder for coal gasification applications

DOEpatents

Gencsoy, Hasan T.

1977-05-24

The subject development is directed to an apparatus for feeding pulverized coal into a coal gasifier operating at relatively high pressures and elevated temperatures. This apparatus is a rotary piston feeder which comprises a circular casing having a coal loading opening therein diametrically opposed from a coal discharge and contains a rotatable discoid rotor having a cylinder in which a reciprocateable piston is disposed. The reciprocation of the piston within the cylinder is provided by a stationary conjugate cam arrangement whereby the pulverized coal from a coal hopper at atmospheric pressure can be introduced into the cylinder cavity and then discharged therefrom into the high-pressure gasifier without the loss of high pressure gases from within the latter.

Plantar pressure distribution of ostrich during locomotion on loose sand and solid ground

PubMed Central

Han, Dianlei; Ma, Songsong; Luo, Gang; Ji, Qiaoli; Xue, Shuliang; Yang, Mingming; Li, Jianqiao

2017-01-01

Background The ostrich is a cursorial bird with extraordinary speed and endurance, especially in the desert, and thus is an ideal large-scale animal model for mechanic study of locomotion on granular substrate. Methods The plantar pressure distributions of ostriches walking/running on loose sand/solid ground were recorded using a dynamic pressure plate. Results The center of pressure (COP) on loose sand mostly originated from the middle of the 3rd toe, which differed from the J-shaped COP trajectory on solid ground. At mid-stance, a high-pressure region was observed in the middle of the 3rd toe on loose sand, but three high-pressure regions were found on solid ground. The gait mode significantly affected the peak pressures of the 3rd and 4th toes (p = 1.5 × 10−6 and 2.39 × 10−8, respectively), but not that of the claw (p = 0.041). The effects of substrate were similar to those of the gait mode. Discussion Ground reaction force trials of each functional part showed the 3rd toe bore more body loads and the 4th toe undertook less loads. The pressure distributions suggest balance maintenance on loose sand was provided by the 3rd and 4th toes and the angle between their length axes. On loose sand, the middle of the 3rd toe was the first to touch the sand with a smaller attack angle to maximize the ground reaction force, but on solid ground, the lateral part was the first to touch the ground to minimize the transient loading. At push-off, the ostrich used solidification properties of granular sand under the compression of the 3rd toe to generate sufficient traction. PMID:28761792

Use of Adaptive Injection Strategies to Increase the Full Load Limit of RCCI Operation

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

Hanson, Reed; Ickes, Andrew; Wallner, Thomas

Dual-fuel combustion using port-injection of low reactivity fuel combined with direct injection (DI) of a higher reactivity fuel, otherwise known as reactivity controlled compression ignition (RCCI), has been shown as a method to achieve low-temperature combustion with moderate peak pressure rise rates, low engine-out soot and NOx emissions, and high indicated thermal efficiency. A key requirement for extending to high-load operation is moderating the reactivity of the premixed charge prior to the diesel injection. One way to accomplish this is to use a very low reactivity fuel such as natural gas. In this work, experimental testing was conducted on amore » 13 l multicylinder heavy-duty diesel engine modified to operate using RCCI combustion with port injection of natural gas and DI of diesel fuel. Engine testing was conducted at an engine speed of 1200 rpm over a wide variety of loads and injection conditions. The impact on dual-fuel engine performance and emissions with respect to varying the fuel injection parameters is quantified within this study. The injection strategies used in the work were found to affect the combustion process in similar ways to both conventional diesel combustion (CDC) and RCCI combustion for phasing control and emissions performance. As the load is increased, the port fuel injection (PFI) quantity was reduced to keep peak cylinder pressure (PCP) and maximum pressure rise rate (MPRR) under the imposed limits. Overall, the peak load using the new injection strategy was shown to reach 22 bar brake mean effective pressure (BMEP) with a peak brake thermal efficiency (BTE) of 47.6%.« less

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.

Limits on the prediction of helicopter rotor noise using thickness and loading sources: Validation of helicopter noise prediction techniques

NASA Technical Reports Server (NTRS)

Succi, G. P.

1983-01-01

The techniques of helicopter rotor noise prediction attempt to describe precisely the details of the noise field and remove the empiricisms and restrictions inherent in previous methods. These techniques require detailed inputs of the rotor geometry, operating conditions, and blade surface pressure distribution. The Farassat noise prediction techniques was studied, and high speed helicopter noise prediction using more detailed representations of the thickness and loading noise sources was investigated. These predictions were based on the measured blade surface pressures on an AH-1G rotor and compared to the measured sound field. Although refinements in the representation of the thickness and loading noise sources improve the calculation, there are still discrepancies between the measured and predicted sound field. Analysis of the blade surface pressure data indicates shocks on the blades, which are probably responsible for these discrepancies.

Structural and vibrational properties of solid nitromethane under high pressure by density functional theory.

PubMed

Liu, Hong; Zhao, Jijun; Wei, Dongqing; Gong, Zizheng

2006-03-28

The structural, vibrational, and electronic properties of solid nitromethane under hydrostatic pressure of up to 20 GPa have been studied using density functional theory. The changes of cell volume, the lattice constants, and the molecular geometry of solid nitromethane under hydrostatic loading are examined, and the bulk modulus B0 and its pressure derivative B0' are fitted from the volume-pressure relation. Our theoretical results are compared with available experiments. The change of electron band gap of nitromethane under high pressure is also discussed. Based on the optimized crystal structures, the vibrational frequencies for the internal and lattice modes of the nitromethane crystal at ambient and high pressures are computed, and the pressure-induced frequency shifts of these modes are discussed.

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.

Efficient and highly enantioselective construction of trifluoromethylated quaternary stereogenic centers via high-pressure mediated organocatalytic conjugate addition of nitromethane to β,β-disubstituted enones.

PubMed

Kwiatkowski, Piotr; Cholewiak, Agnieszka; Kasztelan, Adrian

2014-11-21

A very effective high-pressure-induced acceleration of asymmetric organocatalytic conjugate addition of nitromethane to sterically congested β,β-disubstituted β-CF3 enones has been developed. A combination of pressure (8-10 kbar) and noncovalent catalysis with low-loading of chiral tertiary amine-thioureas (0.5-3 mol %) is shown to provide very efficient access to a wide range of γ-nitroketones containing trifluoromethylated all-carbon quaternary stereogenic centers in the β-position (80-97%, 92-98% ee).

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.

Liner-less Tanks for Space Application - Design and Manufacturing Considerations

NASA Technical Reports Server (NTRS)

Jones, Brian H.; Li, Min-Chung

2003-01-01

Composite pressure vessels, used extensively for gas and fuel containment in space vehicles, are generally constructed with a metallic liner, while the fiber reinforcement carries the major portion of the pressure-induced load. The design is dominated by the liner s low strain at yield since the reinforcing fibers cannot operate at their potential load-bearing capability without resorting to pre-stressing (or autofrettaging). An ultra high-efficiency pressure vessel, which operates at the optimum strain capability of the fibers, can be potentially achieved with a liner-less construction. This paper discusses the design and manufacturing challenges to be overcome in the development of such a pressure vessel. These include: (1) gas/liquid containment and permeation, (2) design and structural analysis, and (3) manufacturing process development. The paper also presents the development and validation tests on a liner-less pressure vessel developed by Kaiser Compositek Inc. (KCI). It should be noted that KCI s liner-less tank exhibits a highly controlled leak-before-burst mode. This feature results in a structure having the highest level of safety.

DEVELOPMENT OF ASME SECTION X CODE RULES FOR HIGH PRESSURE COMPOSITE HYDROGEN PRESSURE VESSELS WITH NON-LOAD SHARING LINERS

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

Rawls, G.; Newhouse, N.; Rana, M.

2010-04-13

The Boiler and Pressure Vessel Project Team on Hydrogen Tanks was formed in 2004 to develop Code rules to address the various needs that had been identified for the design and construction of up to 15000 psi hydrogen storage vessel. One of these needs was the development of Code rules for high pressure composite vessels with non-load sharing liners for stationary applications. In 2009, ASME approved new Appendix 8, for Section X Code which contains the rules for these vessels. These vessels are designated as Class III vessels with design pressure ranging from 20.7 MPa (3,000 ps)i to 103.4 MPamore » (15,000 psi) and maximum allowable outside liner diameter of 2.54 m (100 inches). The maximum design life of these vessels is limited to 20 years. Design, fabrication, and examination requirements have been specified, included Acoustic Emission testing at time of manufacture. The Code rules include the design qualification testing of prototype vessels. Qualification includes proof, expansion, burst, cyclic fatigue, creep, flaw, permeability, torque, penetration, and environmental testing.« less

Development of a Filament-Overwrapped Cryoformed Metal Pressure Vessel

DTIC Science & Technology

1971-01-01

ABSTRACT High performance ARDEFORM cryoformed 301 stainless steel glass fiber reinforced (GFR) vessels were demonstrated by room temperature tests of 13 1...Appendix 6 - Vessel Testing ........... . A-54 7.7 Appendix 7 - Increased Ductility Liner High Performance Spherical GFR Vessel A-62 7.8 Appendix 8...vessel consisting of a load-bearing cryogenically stretched ARDEFORM 301 stainless steel liner overwrapped with fiber- glass for high pressure fluid

Time-varying wall stress: an index of ventricular vascular coupling.

PubMed

Dell'Italia, L J; Blackwell, G G; Thorn, B T; Pearce, D J; Bishop, S P; Pohost, G M

1992-08-01

Previous work in the isolated heart and intact circulation has suggested that the relationship between wall stress and time during left ventricular (LV) ejection is linear and that the slope, which will be referred to as time-varying wall stress, increases in response to augmentation in afterload. However, the etiology of the increase in slope has not been determined in an intact animal. Magnetic resonance imaging coupled with high-fidelity LV pressure measurement using a nonferrous catheter-tip manometer generates a detailed assessment of wall stress in an animal model where the thorax and pericardium have never been disturbed. Accordingly, six anesthetized dogs were studied during autonomic blockade with atropine and propranolol during angiotensin infusion, producing three widely disparate left ventricular systolic pressures (87 +/- 7 vs. 124 +/- 13 vs. 152 +/- 10 mmHg, P less than 0.001). Time-varying wall stress did not change from low to medium load (-42.4 +/- 9.5 to -27.3 +/- 22.3 g.cm-2.ms-1) but increased significantly at high load (-21.7 +/- 14.9 g.cm-2.ms-1, P less than 0.05). Analysis of the relative contribution of pressure, chamber radius, wall thickness, and long-axis dimension to the changes in time-varying wall stress demonstrated only the pressure component to change its relative contribution at medium (P less than 0.001) and high load (P less than 0.001). Therefore, we conclude that the increase in time-varying wall stress results from augmentation of pressure in the latter one-half of systole that is incompletely offset by shortening and wall thickening.(ABSTRACT TRUNCATED AT 250 WORDS)

Is the area under blood pressure curve the best parameter to evaluate 24-h ambulatory blood pressure monitoring data?

PubMed

Nobre, Fernando; Mion, Décio

2005-10-01

Ambulatory blood pressure monitoring (ABPM) provides relevant data about blood pressure over a 24-h period. The analysis of parameters to determine the blood pressure profile from these data is of great importance. To calculate areas under systolic and diastolic blood pressure curves (SBP-AUC/DBP-AUC) and compare with systolic and diastolic blood pressure load (SBPL/DBPL) and 24-h systolic and diastolic blood pressure (24-h SBP/24-h DBP) in order to determine which provides the best correlation with left ventricular mass index (LVMI). ABPM measurements (1143 individuals) were analyzed to obtain 24-h SBP/24-h DBP, SBPL/DBPL, and SBP-AUC/ DBP-AUC, using Spacelabs (90207) and CardioSistemas devices. Left ventricular mass was determined using an echocardiograph HP Sonos 5500 and LVMI was calculated. The correlations between all possible pairs within the group 24-h SBP/SBPL/SBP-AUC and 24-h DBP/DBPL/DBP-AUC were high and statistically significant. The correlations between 24-h SBP/24-h DBP and SBP-AUC/DBP-AUC with SBPL/DBPL close to 100%, were lower than those mentioned above. The correlations of the parameters obtained by ABPM with LVMI were also high and statistically significant, except for blood pressure load between 90 and 100%, and for 24-h SBP of 135 mmHg or less and SBPL higher than 50%. SBPL/DBPL and SBP-AUC/DBP-AUC can be used for the evaluation of ABPM data owing to the strong correlation with 24-h SBP/24-h DBP and with LVMI, except when SBPL is close to 100% or 24-h SBP is below 135 mmHg but SBPL is above 50%. SBP-AUC/DBP-AUC, however, are a better alternative because they do not have the limitations of blood pressure load or even of 24-h blood pressure present.

Growth and Characterization of In(1-x)Ga(x)As(y)P(1-y) and GaAs Using Molecular Beam Epitaxy.

DTIC Science & Technology

1980-03-01

incident beams of As and P, respectively. The high vapor pressure , group V elements have a very short lifetime on the heated substrate unless there is...oven loaded with a high vapor pressure , group V element such as arsenic and phosphorous. An error analysis of Equation 5 reveals that incremental

14 CFR 25.365 - Pressurized compartment loads.

Code of Federal Regulations, 2010 CFR

2010-01-01

... Pressurized compartment loads. For airplanes with one or more pressurized compartments the following apply: (a... differential loads from zero up to the maximum relief valve setting. (b) The external pressure distribution in... zero up to the maximum allowed during landing. (d) The airplane structure must be designed to be able...

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...

Development of the NTF-117S Semi-Span Balance

NASA Technical Reports Server (NTRS)

Lynn, Keith C.

2010-01-01

A new high-capacity semi-span force and moment balance has recently been developed for use at the National Transonic Facility at the NASA Langley Research Center. This new semi-span balance provides the NTF a new measurement capability that will support testing of semi-span test models at transonic high-lift testing regimes. Future testing utilizing this new balance capability will include active circulation control and propulsion simulation testing of semi-span transonic wing models. The NTF has recently implemented a new highpressure air delivery station that will provide both high and low mass flow pressure lines that are routed out to the semi-span models via a set high/low pressure bellows that are indirectly linked to the metric end of the NTF-117S balance. A new check-load stand is currently being developed to provide the NTF with an in-house capability that will allow for performing check-loads on the NTF-117S balance in order to determine the pressure tare affects on the overall performance of the balance. An experimental design is being developed that will allow for experimentally assessing the static pressure tare affects on the balance performance.

Role of the primary silicon particle on the dry sliding wear of hypereutectic aluminium-silicon alloy A390

NASA Astrophysics Data System (ADS)

Lee, Jung-Moo; Kang, Suk-Bong; Yoon, Sang-Chul

1999-07-01

The wear behavior of hypereutectic aluminium-silicon alloy A390 was investigated using a pin-on-disc wear machine under dry sliding conditions. The wear tests were performed within a load range of 10 to 300N at a constant sliding velocity of 0.5 m/sec. The microstructural and compositional changes that took place during wear were characterized by scanning electron microscopy (SEM) equipped with an energy dispersive X-ray analysis (EDXA) system. Based on the metallographic observations the role of the primary silicon particles was suggested. In a low pressure region, primary silicon particles supported the applied load and wear occurred mainly in the matrix. Thus the wear loss did not show much variation with the applied load. In the mid-load range, primary silicon particles did not yet fracture and thus supported the applied load in part. Transition from oxidative to metallic wear occurs mainly in the matrix and the increase of wear loss becomes sharper than that in a low pressure region. In the high pressure region, the fractures of primary silicon Particles occurred and wear loss increased sharply.

Startup analysis for a high temperature gas loaded heat pipe

NASA Technical Reports Server (NTRS)

Sockol, P. M.

1973-01-01

A model for the rapid startup of a high-temperature gas-loaded heat pipe is presented. A two-dimensional diffusion analysis is used to determine the rate of energy transport by the vapor between the hot and cold zones of the pipe. The vapor transport rate is then incorporated in a simple thermal model of the startup of a radiation-cooled heat pipe. Numerical results for an argon-lithium system show that radial diffusion to the cold wall can produce large vapor flow rates during a rapid startup. The results also show that startup is not initiated until the vapor pressure p sub v in the hot zone reaches a precise value proportional to the initial gas pressure p sub i. Through proper choice of p sub i, startup can be delayed until p sub v is large enough to support a heat-transfer rate sufficient to overcome a thermal load on the heat pipe.

Determination of performance of non-ideal aluminized explosives.

PubMed

Keshavarz, Mohammad Hossein; Mofrad, Reza Teimuri; Poor, Karim Esmail; Shokrollahi, Arash; Zali, Abbas; Yousefi, Mohammad Hassan

2006-09-01

Non-ideal explosives can have Chapman-Jouguet (C-J) detonation pressure significantly different from those expected from existing thermodynamic computer codes, which usually allows finding the parameters of ideal detonation of individual high explosives with good accuracy. A simple method is introduced by which detonation pressure of non-ideal aluminized explosives with general formula C(a)H(b)N(c)O(d)Al(e) can be predicted only from a, b, c, d and e at any loading density without using any assumed detonation products and experimental data. Calculated detonation pressures show good agreement with experimental values with respect to computed results obtained by complicated computer code. It is shown here how loading density and atomic composition can be integrated into an empirical formula for predicting detonation pressure of proposed aluminized explosives.

Functional assessment of the diaphragm by speckle tracking ultrasound during inspiratory loading.

PubMed

Oppersma, Eline; Hatam, Nima; Doorduin, Jonne; van der Hoeven, Johannes G; Marx, Gernot; Goetzenich, Andreas; Fritsch, Sebastian; Heunks, Leo M A; Bruells, Christian S

2017-11-01

Assessment of diaphragmatic effort is challenging, especially in critically ill patients in the phase of weaning. Fractional thickening during inspiration assessed by ultrasound has been used to estimate diaphragm effort. It is unknown whether more sophisticated ultrasound techniques such as speckle tracking are superior in the quantification of inspiratory effort. This study evaluates the validity of speckle tracking ultrasound to quantify diaphragm contractility. Thirteen healthy volunteers underwent a randomized stepwise threshold loading protocol of 0-50% of the maximal inspiratory pressure. Electric activity of the diaphragm and transdiaphragmatic pressures were recorded. Speckle tracking ultrasound was used to assess strain and strain rate as measures of diaphragm tissue deformation and deformation velocity, respectively. Fractional thickening was assessed by measurement of diaphragm thickness at end-inspiration and end-expiration. Strain and strain rate increased with progressive loading of the diaphragm. Both strain and strain rate were highly correlated to transdiaphragmatic pressure (strain r 2  = 0.72; strain rate r 2  = 0.80) and diaphragm electric activity (strain r 2  = 0.60; strain rate r 2  = 0.66). We conclude that speckle tracking ultrasound is superior to conventional ultrasound techniques to estimate diaphragm contractility under inspiratory threshold loading. NEW & NOTEWORTHY Transdiaphragmatic pressure using esophageal and gastric balloons is the gold standard to assess diaphragm effort. However, this technique is invasive and requires expertise, and the interpretation may be complex. We report that speckle tracking ultrasound can be used to detect stepwise increases in diaphragmatic effort. Strain and strain rate were highly correlated with transdiaphragmatic pressure, and therefore, diaphragm electric activity and speckle tracking might serve as reliable tools to quantify diaphragm effort in the future. Copyright © 2017 the American Physiological Society.

Buckling of Cracked Laminated Composite Cylindrical Shells Subjected to Combined Loading

NASA Astrophysics Data System (ADS)

Allahbakhsh, Hamidreza; Shariati, Mahmoud

2013-10-01

A series of finite element analysis on the cracked composite cylindrical shells under combined loading is carried out to study the effect of loading condition, crack size and orientation on the buckling behavior of laminated composite cylindrical shells. The interaction buckling curves of cracked laminated composite cylinders subject to different combinations of axial compression, bending, internal pressure and external pressure are obtained, using the finite element method. Results show that the internal pressure increases the critical buckling load of the CFRP cylindrical shells and bending and external pressure decrease it. Numerical analysis show that axial crack has the most detrimental effect on the buckling load of a cylindrical shell and results show that for lower values of the axial compressive load and higher values of the external pressure, the buckling is usually in the global mode and for higher values of axial compressive load and lower levels of external pressure the buckling mode is mostly in the local mode.

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.

High pressure and high temperature apparatus

DOEpatents

Voronov, Oleg A.

2005-09-13

A design for high pressure/high temperature apparatus and reaction cell to achieve .about.30 GPa pressure in .about.1 cm volume and .about.100 GPa pressure in .about.1 mm volumes and 20-5000.degree. C. temperatures in a static regime. The device includes profiled anvils (28) action on a reaction cell (14, 16) containing the material (26) to be processed. The reaction cell includes a heater (18) surrounded by insulating layers and screens. Surrounding the anvils are cylindrical inserts and supporting rings (30-48) whose hardness increases towards the reaction cell. These volumes may be increased considerably if applications require it, making use of presses that have larger loading force capability, larger frames and using larger anvils.

Francis-99: Transient CFD simulation of load changes and turbine shutdown in a model sized high-head Francis turbine

NASA Astrophysics Data System (ADS)

Mössinger, Peter; Jester-Zürker, Roland; Jung, Alexander

2017-01-01

With increasing requirements for hydropower plant operation due to intermittent renewable energy sources like wind and solar, numerical simulations of transient operations in hydraulic turbo machines become more important. As a continuation of the work performed for the first workshop which covered three steady operating conditions, in the present paper load changes and a shutdown procedure are investigated. The findings of previous studies are used to create a 360° model and compare measurements with simulation results for the operating points part load, high load and best efficiency. A mesh motion procedure is introduced, allowing to represent moving guide vanes for load changes from best efficiency to part load and high load. Additionally an automated re-mesh procedure is added for turbine shutdown to ensure reliable mesh quality during guide vane closing. All three transient operations are compared to PIV velocity measurements in the draft tube and pressure signals in the vaneless space. Simulation results of axial velocity distributions for all three steady operation points, during both load changes and for the shutdown correlated well with the measurement. An offset at vaneless space pressure is found to be a result of guide vane corrections for the simulation to ensure similar velocity fields. Short-time Fourier transformation indicating increasing amplitudes and frequencies at speed-no load conditions. Further studies will discuss the already measured start-up procedure and investigate the necessity to consider the hydraulic system dynamics upstream of the turbine by means of a 1D3D coupling between the 3D flow field and a 1D system model.

Aircraft tire behavior during high-speed operations in soil

NASA Technical Reports Server (NTRS)

Leland, T. J. W.; Smith, E. G.

1972-01-01

An investigation to determine aircraft tire behavior and operating problems in soil of different characteristics was conducted at the Langley landing-loads track with a 29 x 110.0-10, 8-ply-rating, type 3 tire. Four clay test beds of different moisture content and one sand test bed were used to explore the effects on axle drag loads developed during operation at different tire inflation pressures in free rolling, locked-wheel braking, and yawed (cornering) modes, all at forward speeds up to 95 knots. The test results indicated a complicated drag-load--velocity relationship, with a peak in the drag-load curve occurring near 40 knots for most test conditions. The magnitude of this peak was found to vary with tire inflation pressure and soil character and, in certain cases, might prove large enough to make take-off hazardous.

Prediction of Unsteady Blade Surface Pressures on an Advanced Propeller at an Angle of Attack

NASA Technical Reports Server (NTRS)

Nallasamy, M.; Groeneweg, J. F.

1989-01-01

The numerical solution of the unsteady, three-dimensional, Euler equations is considered in order to obtain the blade surface pressures of an advanced propeller at an angle of attack. The specific configuration considered is the SR7L propeller at cruise conditions with a 4.6 deg inflow angle corresponding to the plus 2 deg nacelle tilt of the Propeller Test Assessment (PTA) flight test condition. The results indicate nearly sinusoidal response of the blade loading, with angle of attack. For the first time, detailed variations of the chordwise loading as a function of azimuthal angle are presented. It is observed that the blade is lightly loaded for part of the revolution and shocks appear from hub to about 80 percent radial station for the highly loaded portion of the revolution.

Prediction of unsteady blade surface pressures on an advanced propeller at an angle of attack

NASA Technical Reports Server (NTRS)

Nallasamy, M.; Groeneweg, J. F.

1989-01-01

The paper considers the numerical solution of the unsteady, three-dimensional, Euler equations to obtain the blade surface pressures of an advanced propeller at an angle of attack. The specific configuration considered is the SR7L propeller at cruise conditions with a 4.6 deg inflow angle corresponding to the +2 deg nacelle tilt of the Propeller Test Assessment (PTA) flight test condition. The results indicate nearly sinusoidal response of the blade loading, with angle of attack. For the first time, detailed variations of the chordwise loading as a function of azimuthal angle are presented. It is observed that the blade is lightly loaded for part of the revolution and shocks appear from hub to about 80 percent radial station for the highly loaded portion of the revolution.

Fretting Fatigue Analysis of Additively Manufactured Blade Root Made of Intermetallic Ti-48Al-2Cr-2Nb Alloy at High Temperature.

PubMed

Lavella, Mario; Botto, Daniele

2018-06-21

Slots in the disk of aircraft turbines restrain the centrifugal load of blades. Contact surfaces between the blade root and the disk slot undergo high contact pressure and relative displacement that is the typical condition in which fretting occurs. The load level ranges from zero to the maximum during take-off. This cycle is repeated for each mission. In this paper, a fretting fatigue analysis of additively manufactured blades is presented. Blades are made of an intermetallic alloy γTiAl. Fretting fatigue experiments were performed at a frequency of 0.5 Hz and at a temperature of 640 °C to match the operating condition of real blades. The minimum load was fixed at 0.5 KN and three maximum loads were applied, namely 16, 18 and 20 kN. Both an analytical and a two-dimensional finite element model were used to evaluate the state of stress at the contact interfaces. The results of the analytical model showed good agreement with the numerical model. Experiments showed that cracks nucleate where the analytical model predicts the maximum contact pressure and the numerical model predicts the maximum equivalent stress. A parametric analysis performed with the analytical model indicates that there exists an optimum geometry to minimize the contact pressure. Tests showed that the component life changed dramatically with the maximum load variation. Optical topography and scanning electron microscopy (SEM) analysis reveals information about the damage mechanism.

Absorption of Carbon Dioxide in the aqueous solution of Diethanolamine (DEA) blended with 1-Butyl-1-Methylpyrrolidinium Trifluoromethanesulfonate [BmPyrr][OTf] at high pressure

NASA Astrophysics Data System (ADS)

Jamaludin, S. N.; Salleh, R. M.

2018-03-01

Solubility data of carbon dioxide (CO2) in aqueous Diethanolamine (DEA) blended with 1-Butyl-1-Methylpyrrolidinium Trifluoromethanesulfonate [Bmpyrr][OTf] were measured at temperature 313.15K, 323.15K, 333.15K and pressure from 500psi up to 700 psi. The experiments covered over the concentration range of 0-10wt% for [Bmpyrr][OTf] and 30-40wt% for DEA. The solubility of CO2 was evaluated by measuring the pressure drop in high pressure stirred absorption cell reactor. The experimental results showed that CO2 loading in all DEA-[BmPyrr][OTf] mixtures studied increases with increasing of CO2 partial pressure and temperature. It was also found that the CO2 loading capacity increase significantly as the concentration of [Bmpyrr][OTf] increases. Jou and Mather model was used to predict the solubility of CO2 in the mixtures where the experimental data were correlated as a function of temperature and CO2 partial pressure. It was found that the model was successful in predicting the solubility behavior of the aqueous DEA-[Bmpyrr][OTf] systems considered in this study.

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.

Investigation of fretting behaviour in pressure armour layers of flexible pipes

NASA Astrophysics Data System (ADS)

Don Rasika Perera, Solangarachchige

The incidence of fretting damage in the pressure armour wires of flexible pipes used in offshore oil explorations has been investigated. A novel experimental facility which is capable of simulating nub and valley contact conditions of interlocking wire winding with dynamic slip, representative of actual pipe loading, has been developed. The test set-up is equipped with a state of the art data acquisition system and a controller with transducers to measure and control the normal load, slip amplitude and friction force at the contact, in addition to the hoop stress in the wire. Tests were performed with selected loading and the fretted regions were examined using optical microscopy techniques. Results show that the magnitude of contact loading and the slip amplitude have a distinct influence on surface damage. Surface cracks originated from a fretting scar were observed at high contact loads in mixed slip sliding while surface damage predominantly due to wear was observed under gross slip. The position of surface cracks and the wear profile have been related to the contact pressure distribution. The evolution of friction force and surface damage under different slip and normal pressure conditions has been analysed. A fracture mechanics based numerical procedure has been developed to analyse the fretting damage behaviour. A severity parameter is proposed in order to ascertain whether the crack growth is in mode I or mode II cracking. The analysis show the influence of mode II cracking in the early stages of crack growth following which the crack deviates in the mode I direction making mode I the dominant crack propagation mechanism. The crack path determined by the numerical procedure correlates well with the experimental results. A numerical analysis was carried out for the fretting fatigue condition where a cyclic bulk stress superimposes with the friction force. The analysis correlates well with short crack growth behaviour. The analysis confirms that fretting is a significant factor that should be taken into account in design and operation of the pressure armour wires of flexible pipes at high contact pressure if the bulk cyclic load superimposes with the friction force. As predicted by the numerical procedure and further by experimental investigations, the surface cracks initiating on the wire in this condition are self arresting after propagating into a certain depth.

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

Dynamic analysis of slab track on multi-layered transversely isotropic saturated soils subjected to train loads

NASA Astrophysics Data System (ADS)

Zhan, Yongxiang; Yao, Hailin; Lu, Zheng; Yu, Dongming

2014-12-01

The dynamic responses of a slab track on transversely isotropic saturated soils subjected to moving train loads are investigated by a semi-analytical approach. The track model is described as an upper Euler beam to simulate the rails and a lower Euler beam to model the slab. Rail pads between the rails and slab are represented by a continuous layer of springs and dashpots. A series of point loads are formulated to describe the moving train loads. The governing equations of track-ground systems are solved using the double Fourier transform, and the dynamic responses in the time domain are obtained by the inverse Fourier transform. The results show that a train load with high velocity will generate a larger response in transversely isotropic saturated soil than the lower velocity load, and special attention should be paid on the pore pressure in the vicinity of the ground surface. The anisotropic parameters of a surface soil layer will have greater influence on the displacement and excess pore water pressure than those of the subsoil layer. The traditional design method taking ground soil as homogeneous isotropic soil is unsafe for the case of RE < 1 and RG < 1, so a transversely isotropic foundation model is of great significance to the design for high train velocities.

Injectable hydrogels with high fixed charge density and swelling pressure for nucleus pulposus repair: biomimetic glycosaminoglycan analogues.

PubMed

Sivan, S S; Roberts, S; Urban, J P G; Menage, J; Bramhill, J; Campbell, D; Franklin, V J; Lydon, F; Merkher, Y; Maroudas, A; Tighe, B J

2014-03-01

The load-bearing biomechanical role of the intervertebral disc is governed by the composition and organization of its major macromolecular components, collagen and aggrecan. The major function of aggrecan is to maintain tissue hydration, and hence disc height, under the high loads imposed by muscle activity and body weight. Key to this role is the high negative fixed charge of its glycosaminoglycan side chains, which impart a high osmotic pressure to the tissue, thus regulating and maintaining tissue hydration and hence disc height under load. In degenerate discs, aggrecan degrades and is lost from the disc, particularly centrally from the nucleus pulposus. This loss of fixed charge results in reduced hydration and loss of disc height; such changes are closely associated with low back pain. The present authors developed biomimetic glycosaminoglycan analogues based on sulphonate-containing polymers. These biomimetics are deliverable via injection into the disc where they polymerize in situ, forming a non-degradable, nuclear "implant" aimed at restoring disc height to degenerate discs, thereby relieving back pain. In vitro, these glycosaminoglycan analogues possess appropriate fixed charge density, hydration and osmotic responsiveness, thereby displaying the capacity to restore disc height and function. Preliminary biomechanical tests using a degenerate explant model showed that the implant adapts to the space into which it is injected and restores stiffness. These hydrogels mimic the role taken by glycosaminoglycans in vivo and, unlike other hydrogels, provide an intrinsic swelling pressure, which can maintain disc hydration and height under the high and variable compressive loads encountered in vivo. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Single Molecule Raman Spectroscopy Under High Pressure

NASA Astrophysics Data System (ADS)

Fu, Yuanxi; Dlott, Dana

2014-06-01

Pressure effects on surface-enhanced Raman scattering spectra of Rhdoamine 6G adsorbed on silver nanoparticle surfaces was studied using a confocal Raman microscope. Colloidal silver nanoparticles were treated with Rhodamine 6G (R6G) and its isotopically substituted partner, R6G-d4. Mixed isotopomers let us identify single-molecule spectra, since multiple-molecule spectra would show vibrational transitions from both species. The nanoparticles were embedded into a poly vinyl alcohol film, and loaded into a diamond anvil cell for the high-pressure Raman scattering measurement. Argon was the pressure medium. Ambient pressure Raman scattering spectra showed few single-molecule spectra. At moderately high pressure ( 1GPa), a surprising effect was observed. The number of sites with observable spectra decreased dramatically, and most of the spectra that could be observed were due to single molecules. The effects of high pressure suppressed the multiple-molecule Raman sites, leaving only the single-molecule sites to be observed.

Simulation of VSPT Experimental Cascade Under High and Low Free-Stream Turbulence Conditions

NASA Technical Reports Server (NTRS)

Ameri, Ali A.; Giel, Paul W.; Flegel, Ashlie B.

2014-01-01

Variable-Speed Power Turbines (VSPT) for rotorcraft applications operate at low Reynolds number and over a wide range in incidence associated with shaft speed change. A comprehensive linear cascade data set obtained includes the effects of Reynolds number, free-stream turbulence and incidence is available and this paper concerns itself with the presentation and numerical simulation of conditions resulting in a selected set of those data. As such, post-dictions of blade pressure loading, total-pressure loss and exit flow angles under conditions of high and low turbulence intensity for a single Reynolds number are presented. Analyses are performed with the three-equation turbulence models of Walters-Leylek and Walters and Cokljat. Transition, loading, total-pressure loss and exit angle variations are presented and comparisons are made with experimental data as available. It is concluded that at the low freestream turbulence conditions the Walters-Cokljat model is better suited to predictions while for high freestream conditions the two models generate similar predications that are generally satisfactory.

Simulation of VSPT Experimental Cascade Under High and Low Free-Stream Turbulence Conditions

NASA Technical Reports Server (NTRS)

Ameri, Ali A.; Giel, Paul W.; Flegel, Ashlie B.

2015-01-01

Variable-Speed Power Turbines (VSPT) for rotorcraft applications operate at low Reynolds number and over a wide range in incidence associated with shaft speed change. A comprehensive linear cascade data set obtained includes the effects of Reynolds number, free-stream turbulence and incidence is available and this paper concerns itself with the presentation and numerical simulation of conditions resulting in a selected set of those data. As such, post-dictions of blade pressure loading, total-pressure loss and exit flow angles under conditions of high and low turbulence intensity for a single Reynolds number are presented. Analyses are performed with the three-equation turbulence models of Walters- Leylek and Walters and Cokljat. Transition, loading, total-pressure loss and exit angle variations are presented and comparisons are made with experimental data as available. It is concluded that at the low freestream turbulence conditions the Walters-Cokljat model is better suited to predictions while for high freestream conditions the two models generate similar predications that are generally satisfactory.

Microstructure and Properties of Cobalt-and Zinc-Containing Magnetic Magnesium Alloys Processed by High-Pressure Die Casting

NASA Astrophysics Data System (ADS)

Klose, Christian; Demminger, Christian; Maier, Hans Jürgen

The inherent magnetic properties of lightweight alloys based on magnesium and cobalt offer a novel way in order to measure mechanical loads throughout the entire structural component using the magnetoelastic effect. Because the solubility of cobalt in the magnesium matrix is negligible, the magnetic properties mainly originate from Co-rich precipitates. Thus, the size and distribution of Co-containing phases within the alloy's microstructure wields a major influence on the amplitude of the load-sensitive properties which can be measured by employing the harmonic analysis of eddy-current signals. In this study, Mg-Co-based alloys are produced by several casting methods which allow the application of different cooling rates, e.g. gravity die casting and high-pressure die casting. The differences between the manufactured alloys' micro- and phase structures are compared depending on the applied cooling rate and the superior magnetic and mechanical properties of the high-pressure die cast material are demonstrated.

Time pressure and attention allocation effect on upper limb motion steadiness.

PubMed

Liu, Sicong; Eklund, Robert C; Tenenbaum, Gershon

2015-01-01

Following ironic process theory (IPT), the authors aimed at investigating how attentional allocation affects participants' upper limb motion steadiness under low and high levels of mental load. A secondary purpose was to examine the validity of skin conductance level in measuring perception of pressure. The study consisted of 1 within-participant factor (i.e., phase: baseline, test) and 4 between-participant factors (i.e., gender: male, female; mental load: fake time constraints, no time constraints; attention: positive, suppressive; order: baseline → → → test, test → → baseline). Eighty college students (40 men and 40 women, Mage = 20.20 years, SD(age) = 1.52 years) participated in the study. Gender-stratified random assignment was employed in a 2 × 2 × 2 × 2 × 2 mixed experimental design. The findings generally support IPT but its predictions on motor performance under mental load may not be entirely accurate. Unlike men, women's performance was not susceptible to manipulations of mental load and attention allocation. The validity of skin conductance readings as an index of pressure perception was called into question.

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

M Pravica; M Galley; E Kim

We report two separate synchrotron FTIR measurements of the high explosive HMX at ambient temperature and static high pressure in the far- (100-500 wavenumbers) and mid- (500-3200 wavenumbers) infrared (IR) regions up to 30 GPa. The sample for the far-IR experiment was loaded with no pressure-transmitting medium and the sample for the mid-IR study utilized a KBr pressurizing medium. Two possible phase transitions from beta-HMX at ambient conditions were observed near 5 and 12 GPa (likely into the epsilon phase). A phase transition was observed near 25 GPa probably into the delta phase. Pressure cycling in both experiments found nomore » irreversible damage within this pressure range.« less

Imitative modeling automatic system Control of steam pressure in the main steam collector with the influence on the main Servomotor steam turbine

NASA Astrophysics Data System (ADS)

Andriushin, A. V.; Zverkov, V. P.; Kuzishchin, V. F.; Ryzhkov, O. S.; Sabanin, V. R.

2017-11-01

The research and setting results of steam pressure in the main steam collector “Do itself” automatic control system (ACS) with high-speed feedback on steam pressure in the turbine regulating stage are presented. The ACS setup is performed on the simulation model of the controlled object developed for this purpose with load-dependent static and dynamic characteristics and a non-linear control algorithm with pulse control of the turbine main servomotor. A method for tuning nonlinear ACS with a numerical algorithm for multiparametric optimization and a procedure for separate dynamic adjustment of control devices in a two-loop ACS are proposed and implemented. It is shown that the nonlinear ACS adjusted with the proposed method with the regulators constant parameters ensures reliable and high-quality operation without the occurrence of oscillations in the transient processes the operating range of the turbine loads.

Flutter of High-Speed Civil Transport Flexible Semispan Model: Time-Frequency Analysis

NASA Technical Reports Server (NTRS)

Chabalko, Christopher C.; Hajj, Muhammad R.; Silva, Walter A.

2006-01-01

Time/frequency analysis of fluctuations measured by pressure taps and strain gauges in the experimental studies of the flexible semispan model of a high-speed civil transport wing configuration is performed. The interest is in determining the coupling between the aerodynamic loads and structural motions that led to the hard flutter conditions and loss of the model. The results show that, away from the hard flutter point, the aerodynamic loads at all pressure taps near the wing tip and the structural motions contained the same frequency components. On the other hand, in the flow conditions leading to the hard flutter, the frequency content of the pressure fluctuations near the leading and trailing edges varied significantly. This led to contribution to the structural motions over two frequency ranges. The ratio of these ranges was near 2:1, which suggests the possibility of nonlinear structural coupling.

Biomechanical evaluation of heel elevation on load transfer — experimental measurement and finite element analysis

NASA Astrophysics Data System (ADS)

Luximon, Yan; Luximon, Ameersing; Yu, Jia; Zhang, Ming

2012-02-01

In spite of ill-effects of high heel shoes, they are widely used for women. Hence, it is essential to understand the load transfer biomechanics in order to design better fit and comfortable shoes. In this study, both experimental measurement and finite element analysis were used to evaluate the biomechanical effects of heel height on foot load transfer. A controlled experiment was conducted using custom-designed platforms. Under different weight-bearing conditions, peak plantar pressure, contact area and center of pressure were analyzed. A three-dimensional finite element foot model was used to simulate the high-heel support and to predict the internal stress distributions and deformations for different heel heights. Results from both experiment and model indicated that heel elevations had significant effects on all variables. When heel elevation increased, the center of pressure shifted from the midfoot region to the forefoot region, the contact area was reduced by 26% from 0 to 10.2 cm heel and the internal stress of foot bones increased. Prediction results also showed that the strain and total tension force of plantar fascia was minimum at 5.1 cm heel condition. This study helps to better understand the biomechanical behavior of foot, and to provide better suggestions for design parameters of high heeled shoes.

Utilizing Photogrammetry and Strain Gage Measurement to Characterize Pressurization of Inflatable Modules

NASA Technical Reports Server (NTRS)

Mohammed, Anil

2011-01-01

This paper focuses on integrating a large hatch penetration into inflatable modules of various constructions. This paper also compares load predictions with test measurements. The strain was measured by utilizing photogrammetric methods and strain gages mounted to select clevises that interface with the structural webbings. Bench testing showed good correlation between strain data collected from an extensometer and photogrammetric measurements, even when the material transitioned from the low load to high load strain region of the curve. The full-scale torus design module showed mixed results as well in the lower load and high strain regions. After thorough analysis of photogrammetric measurements, strain gage measurements, and predicted load, the photogrammetric measurements seem to be off by a factor of two.

Static-stress analysis of dual-axis confinement vessel

NASA Astrophysics Data System (ADS)

Bultman, D. H.

1992-11-01

This study evaluates the static-pressure containment capability of a 6-ft-diameter, spherical vessel, made of HSLA-100 steel, to be used for high-explosive (HE) containment. The confinement vessel is designed for use with the Dual-Axis Radiographic Hydrotest Facility (DARHT) being developed at Los Alamos National Laboratory. Two sets of openings in the vessel are covered with x-ray transparent covers to allow radiographic imaging of an explosion as it occurs inside the vessel. The confinement vessel is analyzed as a pressure vessel based on the ASME Boiler and Pressure Vessel Code, Section 8, Division 1, and the Welding Research Council Bulletin, WRC-107. Combined stresses resulting from internal pressure and external loads on nozzles are calculated and compared with the allowable stresses for HSLA-100 steel. Results confirm that the shell and nozzles of the confinement vessel are adequately designed to safely contain the maximum residual pressure of 1675 psi that would result from an HE charge of 24.2 kg detonated in a vacuum. Shell stresses at the shell-to-nozzle interface, produced from external loads on the nozzles, were less than 400 psi. The maximum combined stress resulting from the internal pressure plus external loads was 16,070 psi, which is less than half the allowable stress of 42,375 psi for HSLA-100 steel.

Past Performance analysis of HPOTP bearings

NASA Technical Reports Server (NTRS)

Bhat, B. N.; Dolan, F. J.

1982-01-01

The past performance analysis conducted on three High Pressure Oxygen Turbopump (HPOTP) bearings from the Space Shuttle Main Engine is presented. Metallurgical analysis of failed bearing balls and races, and wear track and crack configuration analyses were carried out. In addition, one bearing was tested in laboratory at very high axial loads. The results showed that the cracks were surface initiated and propagated into subsurface locations at relatively small angles. Subsurface cracks were much more extensive than was appeared on the surface. The location of major cracks in the races corresponded to high radial loads rather than high axial loads. There was evidence to suggest that the inner races were heated to elevated temperatures. A failure scenario was developed based on the above findings. According to this scenario the HPOTP bearings are heated by a combination of high loads and high coefficient of friction (poor lubrication). Different methods of extending the HPOTP bearing life are also discussed. These include reduction of axial loads, improvements in bearing design, lubrication and cooling, and use of improved bearing materials.

Influence of critical closing pressure on systemic vascular resistance and total arterial compliance: A clinical invasive study.

PubMed

Chemla, Denis; Lau, Edmund M T; Hervé, Philippe; Millasseau, Sandrine; Brahimi, Mabrouk; Zhu, Kaixian; Sattler, Caroline; Garcia, Gilles; Attal, Pierre; Nitenberg, Alain

2017-12-01

Systemic vascular resistance (SVR) and total arterial compliance (TAC) modulate systemic arterial load, and their product is the time constant (Tau) of the Windkessel. Previous studies have assumed that aortic pressure decays towards a pressure asymptote (P∞) close to 0mmHg, as right atrial pressure is considered the outflow pressure. Using these assumptions, aortic Tau values of ∼1.5seconds have been documented. However, a zero P∞ may not be physiological because of the high critical closing pressure previously documented in vivo. To calculate precisely the Tau and P∞ of the Windkessel, and to determine the implications for the indices of systemic arterial load. Aortic pressure decay was analysed using high-fidelity recordings in 16 subjects. Tau was calculated assuming P∞=0mmHg, and by two methods that make no assumptions regarding P∞ (the derivative and best-fit methods). Assuming P∞=0mmHg, we documented a Tau value of 1372±308ms, with only 29% of Windkessel function manifested by end-diastole. In contrast, Tau values of 306±109 and 353±106ms were found from the derivative and best-fit methods, with P∞ values of 75±12 and 71±12mmHg, and with ∼80% completion of Windkessel function. The "effective" resistance and compliance were ∼70% and ∼40% less than SVR and TAC (area method), respectively. We did not challenge the Windkessel model, but rather the estimation technique of model variables (Tau, SVR, TAC) that assumes P∞=0. The study favoured a shorter Tau of the Windkessel and a higher P∞ compared with previous studies. This calls for a reappraisal of the quantification of systemic arterial load. Crown Copyright © 2017. Published by Elsevier Masson SAS. All rights reserved.

Fluidic assembly for an ultra-high-speed chromosome flow sorter

DOEpatents

Gray, J.W.; Alger, T.W.; Lord, D.E.

1978-11-26

A fluidic assembly for an ultra-high-speed chromosome flow sorter using a fluid drive system of high pressure in the range of 250 to 1000 psi for greater flow velocity, a nozzle with an orifice having a small ratio of length to diameter for laminar flow rates well above the critical Reynolds number for the high flow velocity, and means for vibrating the nozzle along its axis at high frequencies in a range of about 300 kHz to 800 kHz ae described. The orifice is provided with a sharp edge at its inlet, and a conical section at its outlet for a transition from a short cylindrical aperture of small length to diameter ratio to free space. Sample and sheath fluids in separte low pressure reservoirs are transferred into separate high pressure buffer reservoirs through valve means which first permit the fluids to be loaded into the buffer reservoirs under low pressure. Once loaded, the buffer reservoirs are subjected ato high pressure and valves are operated to permit the buffer reservoirs to be emptied through the nozzle under high pressure. A sensor and decision logic is positioned at the exit of the nozzle, and a charging pulse is applied to the jet when a particle reaches a position further downstream where the droplets are formed. In order to adjust the timing of charge pulses, the distance between the sensing station at the outlet of the nozzle and the droplet breakoff point is determined by stroboscopic illumination of the droplet breakoff region using a laser and a revolving lucite cylinder for breaking up the coherency of the laser, and a beam on/off modulator. The breakoff point in the region thus illuminated may then be viewed, using a television monitor.

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.

Fluidic assembly for an ultra-high-speed chromosome flow sorter

DOEpatents

Gray, Joe W.; Alger, Terry W.; Lord, David E.

1982-01-01

A fluidic assembly for an ultra-high-speed chromosome flow sorter using a fluid drive system, a nozzle with an orifice having a small ratio of length to diameter, and mechanism for vibrating the nozzle along its axis at high frequencies. The orifice is provided with a sharp edge at its inlet, and a conical section at its outlet for a transition from a short cylindrical aperture of small length to diameter ratio to free space. Sample and sheath fluids in separate low pressure reservoirs are transferred into separate high pressure buffer reservoirs through a valve arrangement which first permit the fluids to be loaded into the buffer reservoirs under low pressure. Once loaded, the buffer reservoirs are subjected to high pressure and valves are operated to permit the buffer reservoirs to be emptied through the nozzle under high pressure. A sensor and decision logic is positioned at the exit of the nozzle, and a charging pulse is applied to the jet when a particle reaches a position further downstream where the droplets are formed. In order to adjust the timing of charge pulses, the distance between the sensing station at the outlet of the nozzle and the droplet breakoff point is determined by stroboscopic illumination of the droplet breakoff region using a laser and a revolving lucite cylinder, and a beam on/off modulator. The breakoff point in the region thus illuminated may then be viewed, using a television monitor.

Peg supported thermal insulation panel

DOEpatents

Nowobilski, Jeffert J.; Owens, William J.

1985-01-01

A thermal insulation panel which is lightweight, load bearing, accommodates thermal stress, and has excellent high temperature insulation capability comprising high performance insulation between thin metal walls supported by high density, high strength glass pegs made in compliance with specified conditions of time, temperature and pressure.

Development and validation of a computational model of the knee joint for the evaluation of surgical treatments for osteoarthritis

PubMed Central

Mootanah, R.; Imhauser, C.W.; Reisse, F.; Carpanen, D.; Walker, R.W.; Koff, M.F.; Lenhoff, M.W.; Rozbruch, S.R.; Fragomen, A.T.; Dewan, Z.; Kirane, Y.M.; Cheah, Pamela A.; Dowell, J.K.; Hillstrom, H.J.

2014-01-01

A three-dimensional (3D) knee joint computational model was developed and validated to predict knee joint contact forces and pressures for different degrees of malalignment. A 3D computational knee model was created from high-resolution radiological images to emulate passive sagittal rotation (full-extension to 65°-flexion) and weight acceptance. A cadaveric knee mounted on a six-degree-of-freedom robot was subjected to matching boundary and loading conditions. A ligament-tuning process minimised kinematic differences between the robotically loaded cadaver specimen and the finite element (FE) model. The model was validated by measured intra-articular force and pressure measurements. Percent full scale error between EE-predicted and in vitro-measured values in the medial and lateral compartments were 6.67% and 5.94%, respectively, for normalised peak pressure values, and 7.56% and 4.48%, respectively, for normalised force values. The knee model can accurately predict normalised intra-articular pressure and forces for different loading conditions and could be further developed for subject-specific surgical planning. PMID:24786914

Development and validation of a computational model of the knee joint for the evaluation of surgical treatments for osteoarthritis.

PubMed

Mootanah, R; Imhauser, C W; Reisse, F; Carpanen, D; Walker, R W; Koff, M F; Lenhoff, M W; Rozbruch, S R; Fragomen, A T; Dewan, Z; Kirane, Y M; Cheah, K; Dowell, J K; Hillstrom, H J

2014-01-01

A three-dimensional (3D) knee joint computational model was developed and validated to predict knee joint contact forces and pressures for different degrees of malalignment. A 3D computational knee model was created from high-resolution radiological images to emulate passive sagittal rotation (full-extension to 65°-flexion) and weight acceptance. A cadaveric knee mounted on a six-degree-of-freedom robot was subjected to matching boundary and loading conditions. A ligament-tuning process minimised kinematic differences between the robotically loaded cadaver specimen and the finite element (FE) model. The model was validated by measured intra-articular force and pressure measurements. Percent full scale error between FE-predicted and in vitro-measured values in the medial and lateral compartments were 6.67% and 5.94%, respectively, for normalised peak pressure values, and 7.56% and 4.48%, respectively, for normalised force values. The knee model can accurately predict normalised intra-articular pressure and forces for different loading conditions and could be further developed for subject-specific surgical planning.

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.

High-pressure phase transitions of α-quartz under nonhydrostatic dynamic conditions: A reconnaissance study at PETRA III

NASA Astrophysics Data System (ADS)

Carl, Eva-Regine; Mansfeld, Ulrich; Liermann, Hanns-Peter; Danilewsky, Andreas; Langenhorst, Falko; Ehm, Lars; Trullenque, Ghislain; Kenkmann, Thomas

2017-07-01

Hypervelocity collisions of solid bodies occur frequently in the solar system and affect rocks by shock waves and dynamic loading. A range of shock metamorphic effects and high-pressure polymorphs in rock-forming minerals are known from meteorites and terrestrial impact craters. Here, we investigate the formation of high-pressure polymorphs of α-quartz under dynamic and nonhydrostatic conditions and compare these disequilibrium states with those predicted by phase diagrams derived from static experiments under equilibrium conditions. We create highly dynamic conditions utilizing a mDAC and study the phase transformations in α-quartz in situ by synchrotron powder X-ray diffraction. Phase transitions of α-quartz are studied at pressures up to 66.1 and different loading rates. At compression rates between 0.14 and 1.96 GPa s-1, experiments reveal that α-quartz is amorphized and partially converted to stishovite between 20.7 GPa and 28.0 GPa. Therefore, coesite is not formed as would be expected from equilibrium conditions. With the increasing compression rate, a slight increase in the transition pressure occurs. The experiments show that dynamic compression causes an instantaneous formation of structures consisting only of SiO6 octahedra rather than the rearrangement of the SiO4 tetrahedra to form a coesite. Although shock compression rates are orders of magnitude faster, a similar mechanism could operate in impact events.

Numerical analysis of rotating stall instabilities of a pump- turbine in pump mode

NASA Astrophysics Data System (ADS)

Xia, L. S.; Cheng, Y. G.; Zhang, X. X.; Yang, J. D.

2014-03-01

Rotating stall may occur at part load flow of a pump-turbine in pump mode. Unstable flow structures developing under stall condition can lead to a sudden drop of efficiency, high dynamic load and even cavitation. CFD simulations on a pump-turbine model in pump mode were carried out to reveal the onset and developed mechanisms of these unstable flow phenomena at part load. The simulation results of energy-discharge and efficiency characteristics are in good agreement with those obtained by experiments. The more deviate from design conditions with decreasing flow rate, the more flow separations within the vanes. Under specific conditions, four stationary separation zones begin to progress on the circumference, rotating at a fraction of the impeller rotation rate. Rotating stalls lead to the flow in the vane diffuser channels alternating between outward jet flow and blockage. Strong jets impact the spiral casing wall causing high pressure pulsations. Severe separations of the stall cells disturb the flow inducing periodical large amplitude pressure fluctuations, of which the intensity at different span wise of the guide vanes is different. The enforced rotating nonuniform pressure distributions on the circumference lead to dynamic uniform forces on the impeller and guide vanes. The results show that the CFD simulations are capable to gain the complicated flow structure information for analysing the unstable characteristics of the pump mode at part load.

Methodologies for Combined Loads Tests Using a Multi-Actuator Test Machine

NASA Technical Reports Server (NTRS)

Rouse, Marshall

2013-01-01

The NASA Langley COmbined Loads Test System (COLTS) Facility was designed to accommodate a range of fuselage structures and wing sections and subject them to both quasistatic and cyclic loading conditions. Structural tests have been conducted in COLTS that address structural integrity issues of metallic and fiber reinforced composite aerospace structures in support of NASA Programs (i.e. the Aircraft Structural Integrity (ASIP) Program, High-Speed-Research program and the Supersonic Project, NASA Engineering and Safety Center (NESC) Composite Crew Module Project, and the Environmentally Responsible Aviation Program),. This paper presents experimental results for curved panels subjected to mechanical and internal pressure loads using a D-box test fixture. Also, results are presented that describe use of a checkout beam for development of testing procedures for a combined mechanical and pressure loading test of a Multi-bay box. The Multi-bay box test will be used to experimentally verify the structural performance of the Multi-bay box in support of the Environmentally Responsible Aviation Project at NASA Langley.

Effects of cognitive appraisal and mental workload factors on performance in an arithmetic task.

PubMed

Galy, Edith; Mélan, Claudine

2015-12-01

We showed in a previous study an additive interaction between intrinsic and extraneous cognitive loads and of participants' alertness in an 1-back working memory task. The interaction between intrinsic and extraneous cognitive loads was only observed when participants' alertness was low (i.e. in the morning). As alertness is known to reflect an individual's general functional state, we suggested that the working memory capacity available for germane cognitive load depends on a participant's functional state, in addition to intrinsic and extraneous loads induced by the task and task conditions. The relationships between the different load types and their assessment by specific load measures gave rise to a modified cognitive load model. The aim of the present study was to complete the model by determining to what extent and at what processing level an individual's characteristics intervene in order to implement efficient strategies in a working memory task. Therefore, the study explored participants' cognitive appraisal of the situation in addition to the load factors considered previously-task difficulty, time pressure and alertness. Each participant performed a mental arithmetic task in four different cognitive load conditions (crossover of two task difficulty conditions and of two time pressure conditions), both while their alertness was low (9 a.m.) and high (4 p.m.). Results confirmed an additive effect of task difficulty and time pressure, previously reported in the 1-back memory task, thereby lending further support to the modified cognitive load model. Further, in the high intrinsic and extraneous load condition, performance was reduced on the morning session (i.e. when alertness was low) on one hand, and in those participants' having a threat appraisal of the situation on the other hand. When these factors were included into the analysis, a performance drop occurred in the morning irrespective of cognitive appraisal, and with threat appraisal in the afternoon (i.e. high alertness). Taken together, these findings indicate that mental overload can be the result of a combination of subject-related characteristics, including alertness and cognitive appraisal, in addition to well-documented task-related components (intrinsic and extraneous load). As the factors investigated in the study are known to be critically involved in a number of real job-activities, the findings suggest that solutions designed to reduce incidents and accidents at work should consider the situation from a global perspective, including individual characteristics, task parameters, and work organization, rather than dealing with each factor separately.

Short-period cyclic loading system for in situ X-ray observation of anelastic properties at high pressure.

PubMed

Yoshino, Takashi; Yamazaki, Daisuke; Tange, Yoshinori; Higo, Yuji

2016-10-01

To determine the anelastic properties of materials of the Earth's interior, a short-period cyclic loading system was installed for in situ X-ray radiographic observation under high pressure to the multi-anvil deformation DIA press at the bending magnet beam line BL04B1 at SPring-8. The hydraulic system equipped with a piston controlled by a solenoid was designed so as to enable producing smooth sinusoidal stress in a wide range of oscillation period from 0.2 to 100 s and generating variable amplitudes. Time resolved X-ray radiography imaging of the sample and reference material provides their strain as a function of time during cyclic loading. A synchrotron X-ray radiation source allows us to resolve their strain variation with time even at the short period (<1 s). The minimum resolved strain is as small as 10 -4 , and the shortest oscillation period to detect small strain is 0.5 s. Preliminary experimental results exhibited that the new system can resolve attenuation factor Q -1 at upper mantle conditions. These results are in quantitative agreement with previously reported data obtained at lower pressures.

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,...

Peg supported thermal insulation panel

DOEpatents

Nowobilski, J.J.; Owens, W.J.

1985-04-30

A thermal insulation panel which is lightweight, load bearing, accommodates thermal stress, and has excellent high temperature insulation capability comprises high performance insulation between thin metal walls supported by high density, high strength glass pegs made in compliance with specified conditions of time, temperature and pressure. 2 figs.

High speed turboprop aeroacoustic study (single rotation). Volume 1: Model development

NASA Technical Reports Server (NTRS)

Whitfield, C. E.; Gliebe, P. R.; Mani, R.; Mungur, P.

1989-01-01

A frequency-domain noncompact-source theory for the steady loading and volume-displacement (thickness) noise of high speed propellers has been developed and programmed. Both near field and far field effects have been considered. The code utilizes blade surface pressure distributions obtained from three-dimensional nonlinear aerodynamic flow field analysis programs as input for evaluating the steady loading noise. Simplified mathematical models of the velocity fields induced at the propeller disk by nearby wing and fuselage surfaces and by angle-of-attack operation have been developed to provide estimates of the unsteady loading imposed on the propeller by these potential field type interactions. These unsteady blade loadings have been coupled to a chordwise compact propeller unsteady loading noise model to provide predictions of unsteady loading noise caused by these installation effects. Finally, an analysis to estimate the corrections to be applied to the free-field noise predictions in order to arrive at the measurable fuselage sound pressure levels has been formulated and programmed. This analysis considers the effects of fuselage surface reflection and diffraction together with surface boundary layer refraction. The steady loading and thickness model and the unsteady loading model have been verified using NASA-supplied data for the SR-2 and SR-3 model propfans. In addition, the steady loading and thickness model has been compared with data from the SR-6 model propfan. These theoretical models have been employed in the evaluation of the SR-7 powered Gulfstream aircraft in terms of noise characteristics at representative takeoff, cruise, and approach operating conditions. In all cases, agreement between theory and experiment is encouraging.

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.

Composite Load Spectra for Select Space Propulsion Structural Components

NASA Technical Reports Server (NTRS)

Ho, Hing W.; Newell, James F.

1994-01-01

Generic load models are described with multiple levels of progressive sophistication to simulate the composite (combined) load spectra (CLS) that are induced in space propulsion system components, representative of Space Shuttle Main Engines (SSME), such as transfer ducts, turbine blades and liquid oxygen (LOX) posts. These generic (coupled) models combine the deterministic models for composite load dynamic, acoustic, high-pressure and high rotational speed, etc., load simulation using statistically varying coefficients. These coefficients are then determined using advanced probabilistic simulation methods with and without strategically selected experimental data. The entire simulation process is included in a CLS computer code. Applications of the computer code to various components in conjunction with the PSAM (Probabilistic Structural Analysis Method) to perform probabilistic load evaluation and life prediction evaluations are also described to illustrate the effectiveness of the coupled model approach.

Mechanics of advancing pin-loaded contacts with friction

NASA Astrophysics Data System (ADS)

Sundaram, Narayan; Farris, T. N.

2010-11-01

This paper considers finite friction contact problems involving an elastic pin and an infinite elastic plate with a circular hole. Using a suitable class of Green's functions, the singular integral equations governing a very general class of conforming contact problems are formulated. In particular, remote plate stresses, pin loads, moments and distributed loading of the pin by conservative body forces are considered. Numerical solutions are presented for different partial slip load cases. In monotonic loading, the dependence of the tractions on the coefficient of friction is strongest when the contact is highly conforming. For less conforming contacts, the tractions are insensitive to an increase in the value of the friction coefficient above a certain threshold. The contact size and peak pressure in monotonic loading are only weakly dependent on the pin load distribution, with center loads leading to slightly higher peak pressure and lower peak shear than distributed loads. In contrast to half-plane cylinder fretting contacts, fretting behavior is quite different depending on whether or not the pin is allowed to rotate freely. If pin rotation is disallowed, the fretting tractions resemble half-plane fretting tractions in the weakly conforming regime but the contact resists sliding in the strongly conforming regime. If pin rotation is allowed, the shear traction behavior resembles planar rolling contacts in that one slip zone is dominant and the peak shear occurs at its edge. In this case, the effects of material dissimilarity in the strongly conforming regime are only secondary and the contact never goes into sliding. Fretting tractions in the forward and reversed load states show shape asymmetry, which persists with continued load cycling. Finally, the governing integro-differential equation for full sliding is derived; in the limiting case of no friction, the same equation governs contacts with center loading and uniform body force loading, resulting in identical pressures when their resultants are equal.

The simulation of the alternate turbopump development high pressure oxygen and fuel turbopumps for the space shuttle main engine using the Shaberth computer program

NASA Technical Reports Server (NTRS)

Mcdonald, Gary H.

1988-01-01

The Space Shuttle Main Engine (SSME) is basically comprised of a combustion chamber and nozzle, high and low pressure oxygen turbopumps and high and low pressure fuel turbopumps. In the current configuration, the high pressure fuel (HPTFP) and high pressure oxygen turbopumps (HPOTP) have experienced a history of ball bearing wear. The wear problem can be attributed to numerous factors including the hydrodynamic axial and radial loads caused by the flow of liquid oxygen and liquid hydrogen through the turbopump impellers and turbine. Also, friction effects between the rolling elements, races, and cage can create thermally induced bearing geometry changes. To alleviate some of the current configuration problems, an alternate turbopump development (ATD) was proposed. However, the ATD HPOTP and HPTFP are constrained to operate interchangeably with the current turbopumps, thus, the operation conditions must be similar. The ATD configuration features a major change in bearings used to support the integrated shaft, impeller, and turbine system. A single ball and single roller will replace the pump-end and turbine and duplex ball bearings. The Shaft-Bearing-Thermal (SHABERTH) computer code was used to model the ATD HPOTP and ATD HPFTP configurations. A two bearing model was used to simulate the HPOTP and HPFTP bearings and shaft geometry. From SHABERTH, a comparison of bearing reaction loads, frictional heat generation rates, and Hertz contact stresses will be attempted with analysis at the 109 percent and 65 percent power levels.

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.

Hydromechanical drilling device

DOEpatents

Summers, David A.

1978-01-01

A hydromechanical drilling tool which combines a high pressure water jet drill with a conventional roller cone type of drilling bit. The high pressure jet serves as a tap drill for cutting a relatively small diameter hole in advance of the conventional bit. Auxiliary laterally projecting jets also serve to partially cut rock and to remove debris from in front of the bit teeth thereby reducing significantly the thrust loading for driving the bit.

Use of Adaptive Injection Strategies to Increase the Full Load Limit of RCCI Operation

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

Hanson, Reed; Ickes, Andrew; Wallner, Thomas

2015-01-01

Dual-fuel combustion using port-injection of low reactivity fuel combined with direct injection of a higher reactivity fuel, otherwise known as Reactivity Controlled Compression Ignition (RCCI), has been shown as a method to achieve low-temperature combustion with moderate peak pressure rise rates, low engine-out soot and NOx emissions, and high indicated thermal efficiency. A key requirement for extending to high-load operation is moderating the reactivity of the premixed charge prior to the diesel injection. One way to accomplish this is to use a very low reactivity fuel such as natural gas. In this work, experimental testing was conducted on a 13Lmore » multi-cylinder heavy-duty diesel engine modified to operate using RCCI combustion with port injection of natural gas and direct injection of diesel fuel. Engine testing was conducted at an engine speed of 1200 RPM over a wide variety of loads and injection conditions. The impact on dual-fuel engine performance and emissions with respect to varying the fuel injection parameters is quantified within this study. The injection strategies used in the work were found to affect the combustion process in similar ways to both conventional diesel combustion and RCCI combustion for phasing control and emissions performance. As the load is increased, the port fuel injection quantity was reduced to keep peak cylinder pressure and maximum pressure rise rate under the imposed limits. Overall, the peak load using the new injection strategy was shown to reach 22 bar BMEP with a peak brake thermal efficiency of 47.6%.« less

Control of Mechanical Stresses of High Pressure Container Walls by Magnetoelastic Method

NASA Astrophysics Data System (ADS)

Kulak, S. M.; Novikov, V. F.; Baranov, A. V.

2016-10-01

Deformations of the walls of pressure vessels arising in the process of testing and operation, as well as reduce their thickness due to corrosion, to create the prerequisites for the growth of mechanical stresses which accelerating the processes of strain aging, embrittlement of the material and reducing its fatigue properties. This article is devoted to researches of the magnetoelastic demagnetization in the wall of steel vessel of loading by internal pressure. It is established that the increasing pressure on the vessel wall is accompanied by a monotonic decrease in the intensity of the magnetic stray field of local magnetization of steel. It is shown that a magnetic stray field of local magnetization of the wall of steel vessel is non-uniform due to differences in structure and stresses. It is proposed to use the obtained results to control the stress state of vessels, experiencing multi-axial loads generated by internal pressure (pipelines, oil tanks, etc.) The method of magnetoelastic of the demagnetization of the steel has a high sensitivity to mechanical stress, the simplicity of implementation and expressiveness compared to the strain gauge and method of coercive force.

High-pressure resistivity technique for quasi-hydrostatic compression experiments.

PubMed

Rotundu, C R; Ćuk, T; Greene, R L; Shen, Z-X; Hemley, Russell J; Struzhkin, V V

2013-06-01

Diamond anvil cell techniques are now well established and powerful methods for measuring materials properties to very high pressure. However, high pressure resistivity measurements are challenging because the electrical contacts attached to the sample have to survive to extreme stress conditions. Until recently, experiments in a diamond anvil cell were mostly limited to non-hydrostatic or quasi-hydrostatic pressure media other than inert gases. We present here a solution to the problem by using focused ion beam ultrathin lithography for a diamond anvil cell loaded with inert gas (Ne) and show typical resistivity data. These ultrathin leads are deposited on the culet of the diamond and are attaching the sample to the anvil mechanically, therefore allowing for measurements in hydrostatic or nearly hydrostatic conditions of pressure using noble gases like Ne or He as pressure transmitting media.

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.

A Review of Fatigue Crack Growth of Pressure Vessel and Piping Steels in High-Temperature, Pressurized Reactor-Grade Water.

DTIC Science & Technology

1980-09-19

ratio, irradiation, materials Germany Kraftwerk Union Materials, temperature, Erlangen, Germany load ratio, frequency, electro- chemical potential Italy...H. Munster, "Frequenzeinfluss auf das Risswachstumsverhalten des Stahles 22NiMoCr37", KWU/R 413/8/80, Kraftwerk Union, Erlangen (1980). 76. D. F

Theoretical study of hull-rotor aerodynamic interference on semibuoyant vehicles

NASA Technical Reports Server (NTRS)

Spangler, S. B.; Smith, C. A.

1978-01-01

Analytical methods are developed to predict the pressure distribution and overall loads on the hulls of airships which have close coupled, relatively large and/or high disk loading propulsors for attitude control, station keeping, and partial support of total weight as well as provision of thrust in cruise. The methods comprise a surface-singularity, potential-flow model for the hull and lifting surfaces (such as tails) and a rotor model which calculates the velocity induced by the rotor and its wake at points adjacent to the wake. Use of these two models provides an inviscid pressure distribution on the hull with rotor interference. A boundary layer separation prediction method is used to locate separation on the hull, and a wake pressure is imposed on the separated region for purposes of calculating hull loads. Results of calculations are shown to illustrate various cases of rotor-hull interference and comparisons with small scale data are made to evaluate the method.

Comparison of microbiological loads and physicochemical properties of raw milk treated with single-/multiple-cycle high hydrostatic pressure and ultraviolet-C light

NASA Astrophysics Data System (ADS)

Hu, Guanglan; Zheng, Yuanrong; Wang, Danfeng; Zha, Baoping; Liu, Zhenmin; Deng, Yun

2015-07-01

The effects of ultraviolet-C radiation (UV-C, 11.8 W/m2), single-cycle and multiple-cycle high hydrostatic pressure (HHP at 200, 400 or 600 MPa) on microbial load and physicochemical quality of raw milk were evaluated. Reductions of aerobic plate count (APC) and coliform count (CC) by HHP were more than 99.9% and 98.7%, respectively. Inactivation efficiency of microorganisms increased with pressure level. At the same pressure level, two-cycle treatments caused lower APC, but did not show CC differences compared with single-cycle treatments. Reductions of APC and CC by UV-C were somewhere between 200 MPa and 400/600 MPa. Both HHP and UV-C significantly decreased lightness and increased pH, but did not change soluble solids content and thiobarbituric acid-reactive substances' values. Two 2.5 min cycles of HHP at 600 MPa caused minimum APC and CC, and maximum conductivity. Compared with HHP, UV-C markedly increased protein oxidation and reduced darkening.

Flexible Composite-Material Pressure Vessel

NASA Technical Reports Server (NTRS)

Brown, Glen; Haggard, Roy; Harris, Paul A.

2003-01-01

A proposed lightweight pressure vessel would be made of a composite of high-tenacity continuous fibers and a flexible matrix material. The flexibility of this pressure vessel would render it (1) compactly stowable for transport and (2) more able to withstand impacts, relative to lightweight pressure vessels made of rigid composite materials. The vessel would be designed as a structural shell wherein the fibers would be predominantly bias-oriented, the orientations being optimized to make the fibers bear the tensile loads in the structure. Such efficient use of tension-bearing fibers would minimize or eliminate the need for stitching and fill (weft) fibers for strength. The vessel could be fabricated by techniques adapted from filament winding of prior composite-material vessels, perhaps in conjunction with the use of dry film adhesives. In addition to the high-bias main-body substructure described above, the vessel would include a low-bias end substructure to complete coverage and react peak loads. Axial elements would be overlaid to contain damage and to control fiber orientation around side openings. Fiber ring structures would be used as interfaces for connection to ancillary hardware.

Transient Two-Dimensional Analysis of Side Load in Liquid Rocket Engine Nozzles

NASA Technical Reports Server (NTRS)

Wang, Ten-See

2004-01-01

Two-dimensional planar and axisymmetric numerical investigations on the nozzle start-up side load physics were performed. The objective of this study is to develop a computational methodology to identify nozzle side load physics using simplified two-dimensional geometries, in order to come up with a computational strategy to eventually predict the three-dimensional side loads. The computational methodology is based on a multidimensional, finite-volume, viscous, chemically reacting, unstructured-grid, and pressure-based computational fluid dynamics formulation, and a transient inlet condition based on an engine system modeling. The side load physics captured in the low aspect-ratio, two-dimensional planar nozzle include the Coanda effect, afterburning wave, and the associated lip free-shock oscillation. Results of parametric studies indicate that equivalence ratio, combustion and ramp rate affect the side load physics. The side load physics inferred in the high aspect-ratio, axisymmetric nozzle study include the afterburning wave; transition from free-shock to restricted-shock separation, reverting back to free-shock separation, and transforming to restricted-shock separation again; and lip restricted-shock oscillation. The Mach disk loci and wall pressure history studies reconfirm that combustion and the associated thermodynamic properties affect the formation and duration of the asymmetric flow.

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.

Wind tunnel tests for wind pressure distribution on gable roof buildings.

PubMed

Jing, Xiao-kun; Li, Yuan-qi

2013-01-01

Gable roof buildings are widely used in industrial buildings. Based on wind tunnel tests with rigid models, wind pressure distributions on gable roof buildings with different aspect ratios were measured simultaneously. Some characteristics of the measured wind pressure field on the surfaces of the models were analyzed, including mean wind pressure, fluctuating wind pressure, peak negative wind pressure, and characteristics of proper orthogonal decomposition results of the measured wind pressure field. The results show that extremely high local suctions often occur in the leading edges of longitudinal wall and windward roof, roof corner, and roof ridge which are the severe damaged locations under strong wind. The aspect ratio of building has a certain effect on the mean wind pressure coefficients, and the effect relates to wind attack angle. Compared with experimental results, the region division of roof corner and roof ridge from AIJ2004 is more reasonable than those from CECS102:2002 and MBMA2006.The contributions of the first several eigenvectors to the overall wind pressure distributions become much bigger. The investigation can offer some basic understanding for estimating wind load distribution on gable roof buildings and facilitate wind-resistant design of cladding components and their connections considering wind load path.

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

Crack identification and evolution law in the vibration failure process of loaded coal

NASA Astrophysics Data System (ADS)

Li, Chengwu; Ai, Dihao; Sun, Xiaoyuan; Xie, Beijing

2017-08-01

To study the characteristics of coal cracks produced in the vibration failure process, we set up a static load and static and dynamic combination load failure test simulation system, prepared with different particle size, formation pressure, and firmness coefficient coal samples. Through static load damage testing of coal samples and then dynamic load (vibration exciter) and static (jack) combination destructive testing, the crack images of coal samples under the load condition were obtained. Combined with digital image processing technology, an algorithm of crack identification with high precision and in real-time is proposed. With the crack features of the coal samples under different load conditions as the research object, we analyzed the distribution of cracks on the surface of the coal samples and the factors influencing crack evolution using the proposed algorithm and a high-resolution industrial camera. Experimental results showed that the major portion of the crack after excitation is located in the rear of the coal sample where the vibration exciter cannot act. Under the same disturbance conditions, crack size and particle size exhibit a positive correlation, while crack size and formation pressure exhibit a negative correlation. Soft coal is more likely to lead to crack evolution than hard coal, and more easily causes instability failure. The experimental results and crack identification algorithm provide a solid basis for the prevention and control of instability and failure of coal and rock mass, and they are helpful in improving the monitoring method of coal and rock dynamic disasters.

Special considerations for qualifying thin films for super pressure pumpkin ultra long duration balloon missions

NASA Astrophysics Data System (ADS)

Said, Magdi A.

2004-01-01

The assessment of creep and dynamic response behaviors on materials intended for ultra long duration balloon (ULDB) applications is essential. The first provides needed information for design and fabrication. The second ensures that the film is sufficiently tough to survive the dynamic events during launch and ascent. Characterization and assessment of these two important parameters are discussed in this paper. Visco-elastic behavior of materials in a loaded structure, such as the ULDB film change their geometry significantly over time under load causing possible changes in the load path and the stress distribution. These changes must be held in check to satisfy the functional requirements of the structure over its service life. Typically, the balloon experiences during its service life various environmental conditions each with a different creep response. These are characterized by a simplified load temperature history for the purpose of lifetime response assessment. At mid-latitudes a significant portion of the service life is spent at night, i.e., at low temperature and low load; for the ULDB film this night-time contribution to creep is negligible. By contrast, flight exposure in an Antarctic summer is at an almost constant high temperature and corresponding high pressure. This paper presents the creep behavior of the ULDB film as a function of load, temperature, and time along with an overview of its implementation in the design. In addition, it presents a quantitative assessment on the toughness of the material under dynamic "Snatch" loading.

[Evaluation of ergonomic load of clinical nursing procedures].

PubMed

Yan, P; Zhang, L; Li, F Y; Yang, Y; Wang, Y N; Huang, A M; Dai, Y L; Yao, H

2017-08-20

Objective: To evaluate the ergonomic load of clinical nursing procedures and to provide evidence for the prevention and management of work-related musculoskeletal disorders (WMSDs) in nurses. Methods: Based on the nursing unit characteristics and the common departments involving patient-turning procedures, 552 nurses were selected from 6 clinical departments from July to September, 2016. The ergonomic load of four types of patient-turning procedures, i.e., turning the patient's body, changing the bed linen of in-bed patients, moving patients, and chest physiotherapy, was evaluated by the on-site inspectors and self-evaluated by the operators using the Quick Exposure Check. The exposure value, exposure level, and exposure rate of WMSDs were assessed based on the procedure-related physical loads on the back, shoulders/arms, wrists/hands and neck, as well as the loads from work rhythm and work pressure. Results: All surveyed subjects were females who were aged mostly between 26-30 years (49.46%) , with a mean age of 29.66±5.28 years. These nurses were mainly from the Department of Infection (28.99%) and Spine Surgery (21.56%) . There were significant differences in the back, shoulders/arms, neck, work rhythm, and work pressure scores between different nursing procedures ( F =16.613, 5.884, 3.431, 3.222, and 5.085, respectively; P <0.05) . Patient-turning nursing procedures resulted in high to intermediate physical load in nurses. Procedures with high to low level of WMSDs exposure were patient turning (72.69%) , bed linen changing (67.15%) , patient transfer (65.82%) , and chest physiotherapy (58.34%) . In particular, patient turning was considered as very high-risk procedure, whereas others were considered as high-risk procedures. Conclusion: Patient-turning nursing procedures result in high ergonomic load in the operators. Therefore, more focus should be placed on the ergonomics of the caretakers and nurses.

The Grid Density Dependence of the Unsteady Pressures of the J-2X Turbines

NASA Technical Reports Server (NTRS)

Schmauch, Preston B.

2011-01-01

The J-2X engine was originally designed for the upper stage of the cancelled Crew Launch Vehicle. Although the Crew Launch Vehicle was cancelled the J-2X engine, which is currently undergoing hot-fire testing, may be used on future programs. The J-2X engine is a direct descendent of the J-2 engine which powered the upper stage during the Apollo program. Many changes including a thrust increase from 230K to 294K lbf have been implemented in this engine. As part of the design requirements, the turbine blades must meet minimum high cycle fatigue factors of safety for various vibrational modes that have resonant frequencies in the engine's operating range. The unsteady blade loading is calculated directly from CFD simulations. A grid density study was performed to understand the sensitivity of the spatial loading and the magnitude of the on blade loading due to changes in grid density. Given that the unsteady blade loading has a first order effect on the high cycle fatigue factors of safety, it is important to understand the level of convergence when applying the unsteady loads. The convergence of the unsteady pressures of several grid densities will be presented for various frequencies in the engine's operating range.

Laser drive development for the APS Dynamic Compression Sector

NASA Astrophysics Data System (ADS)

Lagrange, Thomas; Swift, Damian; Reed, Bryan; Bernier, Joel; Kumar, Mukul; Hawreliak, James; Eggert, Jon; Dixit, Sham; Collins, Gilbert

2013-06-01

The Dynamic Compression Sector (DCS) at the APS synchrotron offers unprecedented possibilities for x-ray diffraction and scattering measurements in-situ during dynamic loading, including single-shot data collection with x-ray energies high enough (tens of kV) to study high-Z samples in transmission as well as reflection. Dynamic loading induced by laser ablation is an important component of load generation, as the duration, strain rate, and pressure can be controlled via the energy, spot size, and pulse shape. Using radiation hydrodynamics simulations, validated by experiments at several laser facilities, we have investigated the relationship between irradiance history and pressure for ablative loads designed to induce shock and ramp loading in the nanosecond to microsecond range, and including free ablation and also ablation confined by a transparent substrate. We have investigated the effects of lateral release, which constrains the minimum diameter of the focal spot for a given drive duration. In this way, we are able to relate the desired drive conditions to the total laser energy needed, which dictates the laser technologies suitable for a given type of experiment. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Experimental Investigation and Fundamental Understanding of a Slowed UH-60A Rotor at High Advance Ratios

NASA Technical Reports Server (NTRS)

Datta, Anubhav; Yeo, Hyeonsoo; Norman, Thomas R.

2011-01-01

This paper describes and analyzes the measurements from a full-scale, slowed RPM, UH-60A rotor tested at the National Full-Scale Aerodynamics Complex 40- by 80- ft wind tunnel up to an advance ratio of 1.0. A comprehensive set of measurements, that includes performance, blade loads, hub loads and pressures/airloads makes this data set unique. The measurements reveal new and rich aeromechanical phenomena that are special to this exotic regime. These include reverse chord dynamic stall, retreating side impulse in pitch-link load, large inboard-outboard elastic twist differential, supersonic flow at low subsonic advancing tip Mach numbers, diminishing rotor forces yet dramatic build up of blade loads, and dramatic blade loads yet benign levels of vibratory hub loads. The objective of this research is the fundamental understanding of these unique aeromechanical phenomena. The intent is to provide useful knowledge for the design of high speed, high efficiency, slowed RPM rotors of the future and a challenging database for advanced analyses validation.

High-Intensity Running and Plantar-Flexor Fatigability and Plantar-Pressure Distribution in Adolescent Runners

PubMed Central

Fourchet, François; Kelly, Luke; Horobeanu, Cosmin; Loepelt, Heiko; Taiar, Redha; Millet, Grégoire

2015-01-01

Context: Fatigue-induced alterations in foot mechanics may lead to structural overload and injury. Objectives: To investigate how a high-intensity running exercise to exhaustion modifies ankle plantar-flexor and dorsiflexor strength and fatigability, as well as plantar-pressure distribution in adolescent runners. Design: Controlled laboratory study. Setting: Academy research laboratory. Patients or Other Participants: Eleven male adolescent distance runners (age = 16.9 ± 2.0 years, height = 170.6 ± 10.9 cm, mass = 54.6 ± 8.6 kg) were tested. Intervention(s): All participants performed an exhausting run on a treadmill. An isokinetic plantar-flexor and dorsiflexor maximal-strength test and a fatigue test were performed before and after the exhausting run. Plantar-pressure distribution was assessed at the beginning and end of the exhausting run. Main Outcome Measure(s): We recorded plantar-flexor and dorsiflexor peak torques and calculated the fatigue index. Plantar-pressure measurements were recorded 1 minute after the start of the run and before exhaustion. Plantar variables (ie, mean area, contact time, mean pressure, relative load) were determined for 9 selected regions. Results: Isokinetic peak torques were similar before and after the run in both muscle groups, whereas the fatigue index increased in plantar flexion (28.1%; P = .01) but not in dorsiflexion. For the whole foot, mean pressure decreased from 1 minute to the end (−3.4%; P = .003); however, mean area (9.5%; P = .005) and relative load (7.2%; P = .009) increased under the medial midfoot, and contact time increased under the central forefoot (8.3%; P = .01) and the lesser toes (8.9%; P = .008). Conclusions: Fatigue resistance in the plantar flexors declined after a high-intensity running bout performed by adolescent male distance runners. This phenomenon was associated with increased loading under the medial arch in the fatigued state but without any excessive pronation. PMID:25531143

Underexpanded Supersonic Plume Surface Interactions: Applications for Spacecraft Landings on Planetary Bodies

NASA Technical Reports Server (NTRS)

Mehta, M.; Sengupta, A.; Renno, N. O.; Norman, J. W.; Gulick, D. S.

2011-01-01

Numerical and experimental investigations of both far-field and near-field supersonic steady jet interactions with a flat surface at various atmospheric pressures are presented in this paper. These studies were done in assessing the landing hazards of both the NASA Mars Science Laboratory and Phoenix Mars spacecrafts. Temporal and spatial ground pressure measurements in conjunction with numerical solutions at altitudes of approx.35 nozzle exit diameters and jet expansion ratios (e) between 0.02 and 100 are used. Data from steady nitrogen jets are compared to both pulsed jets and rocket exhaust plumes at Mach approx.5. Due to engine cycling, overpressures and the plate shock dynamics are different between pulsed and steady supersonic impinging jets. In contrast to highly over-expanded (e <1) and underexpanded exhaust plumes, results show that there is a relative ground pressure load maximum for moderately underexpanded (e approx.2-5) jets which demonstrate a long collimated plume shock structure. For plumes with e much >5 (lunar atmospheric regime), the ground pressure is minimal due to the development of a highly expansive shock structure. We show this is dependent on the stability of the plate shock, the length of the supersonic core and plume decay due to shear layer instability which are all a function of the jet expansion ratio. Asymmetry and large gradients in the spatial ground pressure profile and large transient overpressures are predominantly linked to the dynamics of the plate shock. More importantly, this study shows that thruster plumes exhausting into martian environments possess the largest surface pressure loads and can occur at high spacecraft altitudes in contrast to the jet interactions at terrestrial and lunar atmospheres. Theoretical and analytical results also show that subscale supersonic cold gas jets adequately simulate the flow field and loads due to rocket plume impingement provided important scaling parameters are in agreement. These studies indicate the critical importance of testing and modeling plume-surface interactions for descent and ascent of spacecraft and launch vehicles.

Experimental investigation into the coupling effects of magnetic field, temperature and pressure on electrical resistivity of non-oriented silicon steel sheet

NASA Astrophysics Data System (ADS)

Xiao, Lijun; Yu, Guodong; Zou, Jibin; Xu, Yongxiang

2018-05-01

In order to analyze the performance of magnetic device which operate at high temperature and high pressure, such as submersible motor, oil well transformer, the electrical resistivity of non-oriented silicon steel sheets is necessary for precise analysis. But the reports of the examination of the measuring method suitable for high temperature up to 180 °C and high pressure up to 140 MPa are few. In this paper, a measurement system based on four-probe method and Archimedes spiral shape measurement specimens is proposed. The measurement system is suitable for measuring the electrical resistivity of unconventional specimens under high temperature and high pressure and can simultaneously consider the influence of the magnetic field on the electrical resistivity. It can be seen that the electrical resistivity of the non-oriented silicon steel sheets will fluctuate instantaneously when the magnetic field perpendicular to the conductive path of the specimens is loaded or removed. The amplitude and direction of the fluctuation are not constant. Without considering the effects of fluctuations, the electrical resistivity of the non-oriented silicon steel sheets is the same when the magnetic field is loaded or removed. And the influence of temperature on the electrical resistivity of the non-oriented silicon steel sheet is still the greatest even though the temperature and the pressure are coupled together. The measurement results also show that the electrical resistivity varies linearly with temperature, so the temperature coefficient of resistivity is given in the paper.

Face Sheet/Core Disbond Growth in Honeycomb Sandwich Panels Subjected to Ground-Air-Ground Pressurization and In-Plane Loading

NASA Technical Reports Server (NTRS)

Chen, Zhi M.; Krueger, Ronald; Rinker, Martin

2015-01-01

Typical damage modes in light honeycomb sandwich structures include face sheet/core disbonding and core fracture, both of which can pose a threat to the structural integrity of a component. These damage modes are of particular interest to aviation certification authorities since several in-service occurrences, such as rudder structural failure and other control surface malfunctions, have been attributed to face sheet/core disbonding. Extensive studies have shown that face sheet/core disbonding and core fracture can lead to damage propagation caused by internal pressure changes in the core. The increasing use of composite sandwich construction in aircraft applications makes it vitally important to understand the effect of ground-air-ground (GAG) cycles and conditions such as maneuver and gust loads on face sheet/core disbonding. The objective of the present study was to use a fracture mechanics based approach developed earlier to evaluate the loading at the disbond front caused by ground-air-ground pressurization and in-plane loading. A honeycomb sandwich panel containing a circular disbond at one face sheet/core interface was modeled with three-dimensional (3D) solid finite elements. The disbond was modeled as a discrete discontinuity and the strain energy release rate along the disbond front was computed using the Virtual Crack Closure Technique (VCCT). 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. The commercial finite element analysis software, Abaqus/Standard, was used for the analyses. The recursive pressure-deformation coupling problem was solved by representing the entrapped air in the honeycomb cells as filled cavities in Abaqus/Standard. The results show that disbond size, face sheet thickness and core thickness are important parameters that determine crack tip loading at the disbond front. Further, the pressure-deformation coupling was found to have an important load decreasing effect [6]. In this paper, a detailed problem description is provided first. Second, the analysis methodology is presented. The fracture mechanics approach used is described and the specifics of the finite element model, including the fluid-filled cavities, are introduced. Third, the initial model verification and validation are discussed. Fourth, the findings from a closely related earlier study [6] are summarized. These findings provided the basis for the current investigation. Fifth, an aircraft ascent scenario from 0 to 12192 m (0 to 40000 ft) is considered and the resulting crack tip loading at the disbond front is determined. In-plane loading to simulate maneuvers and gust conditions are also considered. Sixth, the results are shown for a curved panel, which was used to simulate potential fuselage applications. Finally, a brief summary of observations is presented and recommendations for improvement are provided.

High pressure rinsing system comparison

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

D. Sertore; M. Fusetti; P. Michelato

2007-06-01

High pressure rinsing (HPR) is a key process for the surface preparation of high field superconducting cavities. A portable apparatus for the water jet characterization, based on the transferred momentum between the water jet and a load cell, has been used in different laboratories. This apparatus allows to collected quantitative parameters that characterize the HPR water jet. In this paper, we present a quantitative comparison of the different water jet produced by various nozzles routinely used in different laboratories for the HPR process

Influence of shoe midsole hardness on plantar pressure distribution in four basketball-related movements.

PubMed

Lam, Wing-Kai; Ng, Wei Xuan; Kong, Pui Wah

2017-01-01

This study examined how shoe midsole hardness influenced plantar pressure in basketball-related movements. Twenty male university basketball players wore customized shoes with hard and soft midsoles (60 and 50 Shore C) to perform four movements: running, maximal forward sprinting, maximal 45° cutting and lay-up. Plantar loading was recorded using an in-shoe pressure measuring system, with peak pressure (PP) and pressure time integral (PTI) extracted from 10 plantar regions. Compared with hard shoes, subjects exhibited lower PP in one or more plantar regions when wearing the soft shoes across all tested movements (Ps < 0.05). Lower PTI was also observed in the hallux for 45° cutting, and the toes and forefoot regions during the first step of lay-up in the soft shoe condition (Ps < 0.05). In conclusion, using a softer midsole in the forefoot region may be a plausible remedy to reduce the high plantar loading experienced by basketball players.

Corrosion fatigue characterization of reactor pressure vessel steels. [PWR; BWR

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

Van Der Sluys, W.A.

1982-12-01

During routine operation, light water reactor (LWR) pressure vessels are subjected to a variety of transients that result in time-varying stresses. Consequently, fatigue and environmentally-assisted fatigue are mechanisms of growth relevant to flaws in these pressure vessels. To provide a better understanding of the resistance of nuclear pressure vessel steels to these flaw growth processes, fracture mechanics data were generated on the rates of fatigue crack growth for SA508-2 and SA533B-1 steels in both room temperature air and 288/sup 0/C water. Areas investigated were: the relationship of crack growth rate to prior loading history; the effects of loading frequency andmore » R ratio (K/sub min//K/sub max/) on crack growth rate as a function of the stress intensity factor range (..delta..K); transient aspects of the fatigue crack growth behavior; the effect of material chemistry (sulphur content) on fatigue crack; and growth rate; water chemistry effects (high-purity water versus simulated pressurized water reactotr (PWR) primary coolant).« less

Thermodynamic Equilibrium Solubility of Diethanolamine – N-Butyl-1-Methylpyrrolidinium Dicyanamide [DEABMPYRR DCA] Mixtures for Carbon Dioxide Capture

NASA Astrophysics Data System (ADS)

Salleh, R. M.; Jamaludin, S. N.

2018-05-01

Solubility data of carbon dioxide (CO2) in aqueous Diethanolamine (DEA) blended with pyrrolidinium-based ionic liquid: N-Butyl-1-Methylpyrrolidinium Dıcyanamıde [Bmpyrr][DCA] are presented at various temperatures (313.15K-333.15K) and pressure up to about 700 psi. The concentration of [Bmpyrr][DCA] ranges from 0-10wt% and 30-40wt% for DEA. The solubility of CO2 was evaluated by measuring the pressure drop in high pressure stirred absorption cell reactor. The CO2 loading in all studied mixtures increases with an increase in CO2 partial pressure and decreases with temperature. It was also found that the CO2 loading capacity decrease as the concentration of [Bmpyrr][DCA] increases. The experimental data were correlated as a function of temperature and CO2 partial pressure to predict the solubility of CO2 in the mixtures. It was found that the model predicted results in a good agreement with experimental value.

High pressure electrical insulated feed thru connector

DOEpatents

Oeschger, Joseph E.; Berkeland, James E.

1979-11-13

A feed-thru type hermetic electrical connector including at least one connector pin feeding through an insulator block within the metallic body of the connector shell. A compression stop arrangement coaxially disposed about the insulator body is brazed to the shell, and the shoulder on the insulator block bears against this top in a compression mode, the high pressure or internal connector being at the opposite end of the shell. Seals between the pin and an internal bore at the high pressure end of the insulator block and between the insulator block and the metallic shell at the high pressure end are hermetically brazed in place, the first of these also functioning to transfer the axial compressive load without permitting appreciable shear action between the pin and insulator block.

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.

Turboexpanders with pressurized magnetic bearings for off-shore applications

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

Agahi, R.R.; Ershaghi, B.; Baudelocque, L.

1995-12-31

There are two primary parameters that encourage the use of magnetic bearings in turbomachinery: oil-free process and space requirements. For cryogenic processes such as hydrogen purification and ethylene plants, oil free process is the primary objective. In the case of off-shore platforms for oil and gas production, the occupied space and weight are of prime concern. In off-shore operations, the process gas density is usually higher than in normal process plants because the gas is untreated and at high pressure. High density process gas generates more windage loss and may also cause excessive radial load to journal bearings. The bearingmore » assembly design should be suitable for sour gas environments as well. Furthermore, the thrust bearing system should withstand process fluctuations which are more severe due to high pressure. In this paper, the authors explain their experience of designing a turboexpander-compressor with magnetic bearings for an off-shore oil production platform. They will present side load analysis and their solutions for heat dissipation and coping with process fluctuations.« less

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.

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.

High-pressure, High-temperature Deformation Experiment Using the New Generation Griggs-type Apparatus

PubMed Central

Précigout, Jacques; Stünitz, Holger; Pinquier, Yves; Champallier, Rémi; Schubnel, Alexandre

2018-01-01

In order to address geological processes at great depths, rock deformation should ideally be tested at high pressure (> 0.5 GPa) and high temperature (> 300 °C). However, because of the low stress resolution of current solid-pressure-medium apparatuses, high-resolution measurements are today restricted to low-pressure deformation experiments in the gas-pressure-medium apparatus. A new generation of solid-medium piston-cylinder ("Griggs-type") apparatus is here described. Able to perform high-pressure deformation experiments up to 5 GPa and designed to adapt an internal load cell, such a new apparatus offers the potential to establish a technological basis for high-pressure rheology. This paper provides video-based detailed documentation of the procedure (using the "conventional" solid-salt assembly) to perform high-pressure, high-temperature experiments with the newly designed Griggs-type apparatus. A representative result of a Carrara marble sample deformed at 700 °C, 1.5 GPa and 10-5 s-1 with the new press is also given. The related stress-time curve illustrates all steps of a Griggs-type experiment, from increasing pressure and temperature to sample quenching when deformation is stopped. Together with future developments, the critical steps and limitations of the Griggs apparatus are then discussed. PMID:29683444

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.

High-speed propeller noise predictions - Effects of boundary conditions used in blade loading calculations

NASA Technical Reports Server (NTRS)

Nallasamy, M.; Clark, B. J.; Groeneweg, J. F.

1987-01-01

The acoustics of an advanced single rotation SR-3 propeller at cruise conditions are studied employing a time-domain approach. The study evaluates the acoustic significance of the differences in blade pressures computed using nonreflecting rather than hard wall boundary conditions in the three-dimensional Euler code solution. The directivities of the harmonics of the blade passing frequency tone and the effects of chordwise loading on tone directivity are examined. The results show that the maximum difference in the computed sound pressure levels due to the use of blade pressure distributions obtained with the nonreflecting rather than the hard wall boundary conditions is about 1.5 dB. The blade passing frequency tone directivity obtained in the present study shows good agreement with jetstar flight data.

High-speed propeller noise predictions: Effects of boundary conditions used in blade loading calculations

NASA Technical Reports Server (NTRS)

Nallasamy, M.; Clark, B. J.; Groeneweg, J. F.

1987-01-01

The acoustics of an advanced single rotation SR-3 propeller at cruise conditions are studied employing a time-domain approach. The study evaluates the acoustic significance of the differences in blade pressures computed using nonreflecting rather than hard wall boundary conditions in the three-dimensional Euler code solution. The directivities of the harmonics of the blade passing frequency tone and the effects of chordwise loading on tone directivity are examined. The results show that the maximum difference in the computed sound pressure levels due to the use of blade pressure distributions obtained with the nonreflecting rather than the hard wall boundary conditions is about 1.5 dB. The blade passing frequency tone directivity obtained in the present study shows good agreement with jetstar flight data.

Terminal area energy management regime investigations utilizing an 0.030-scale model (47-0) of the space shuttle vehicle orbiter configuration 140A/B/C/R in the Ames Research Center 11 x 11 foot transonic wind tunnel (OA148), volume 5

NASA Technical Reports Server (NTRS)

Hawthorne, P. J.

1976-01-01

Data obtained in wind tunnel test OA148 are presented. The objectives of the test series were to: (1) obtain pressure distributions, forces and moments over the vehicle 5 orbiter in the thermal area energy management (TAEM) and approach phases of flight; (2) obtain elevon and rudder hinge moments in the TAEM and approach phases of flight; (3) obtain body flap and elevon loads for verification of loads balancing with integrated pressure distributions; and (4) obtain pressure distributions near the short OMS pods in the high subsonic, transonic and low supersonic Mach number regimes.

Raman scattering from superhard rhenium diboride under high pressure

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

Xie, Miao; Winkler, Björn; Mao, Zhu

2014-01-06

Lattice vibrational properties of superhard rhenium diboride (ReB{sub 2}) were examined up to 8 GPa in a diamond anvil cell using Raman spectroscopy techniques. Linear pressure coefficients and mode Grüneisen parameters are obtained. Good agreement is found between the experimental and theoretical calculated Grüneisen parameters. Examination of the calculated mode Grüneisen parameters reveals that both B-B and Re-B covalent bonds play a dominant role in supporting the applied load under pressure. A comparison of vibrations parallel and perpendicular to the c-axis indicates that bonds along the c-axis tend to take greater loads. Our results agree with observations of elastic lattice anisotropymore » obtained from both in situ X-ray diffraction measurements and ultrasonic resonance spectra.« less

Compatibility of an Ultraselective Microcatheter and Epirubicin Loaded 300-500-μm DC Bead in Ex Vivo Study.

PubMed

Fukuoka, Yasushi; Tanaka, Toshihiro; Nishiofuku, Hideyuki; Sato, Takeshi; Kichikawa, Kimihiko

2015-10-01

The purpose of this study is to examine whether epirubicin loaded DC Bead 300-500 μm in size can pass through a 1.8-Fr ultraselective microcatheter in ex vivo study. Epirubicin (25 mg/1 mL) loaded 100-300 and 300-500 μm DC Bead were tested. Both sizes were diluted 5, 10, and 30 times using contrast material. Ultraselective microcatheter with the outer diameter of 1.8 Fr and the inner diameter of .017 inch (431.8 μm) was used. The diluted DC Bead was injected at a speed of 1 mL/min, and the pressure was continuously measured. The microspheres' shapes after ejection were observed by a stereomicroscope. The maximum pressure of contrast material alone was 8.40 ± 0.21 psi. The maximum pressure in 5, 10, and 30 times dilution groups of 100-300 μm were 9.67 ± 1.18, 9.25 ± 0.25, and 9.71 ± 0.28 psi, respectively, whereas 21.10 ± 10.2, 10.48 ± 2.14, 10.09 ± 0.37 psi, respectively in 300-500 μm groups. The maximum pressure in 5 times dilution group of 300-500 μm was significantly higher than the other groups (P < 0.05). In 300-500 μm, 4 of 10 measurements showed high pressure over 24 psi (the maximum value was 43.5 psi) in 5 times dilution group, whereas in 10 times and 30 times dilution groups, all measurements showed less than 12 psi. No damages of microspheres were found. Epirubicin loaded DC Bead 300-500 μm in size can pass through a 1.8-Fr ultraselective microcatheter. To avoid high resistance due to microspheres' aggregation, dilution more than 10 times is needed.

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.

Flexibility Considerations on the Hydrodynamic Loading on a Vertical Wedge Drop

NASA Astrophysics Data System (ADS)

Ren, Zhongshu; Wang, Zhaoyuan; Judge, Carolyn; Stern, Fred; Ikeda, Christine

2017-11-01

High-speed craft operating at in waves frequently become airborne and slam into the water surface. This fluid-structure interaction problem is important to understand in order to increase the operating envelope of these craft. The goals of the current work are to investigate both the hydrodynamic loads and the resulting structural response on a planing hull. A V-shaped wedge is dropped vertically into calm water. The hydrodynamic pressure is measured using pressure sensors at discrete points on the hull. Two hulls are studied: one is rigid and one is flexible. Predictions of the hydrodynamic loading are made using Wagner's theory, Vorus's theory, and simulations in CFDShip Iowa. These predictions assume the structure is completely rigid. These predictions of the pressure coefficient match well with the rigid hull, as expected. The spray root is tracked in the rigid experimental set and compared with the theoretical and computational models. The pressure coefficient measured on the flexible hull shows discrepancies with the predictions due to the fluid-structure interaction. These discrepancies are quantified and interpreted in light of the structural flexibility. Funding for this work is from the Office of Naval Research Grant Number N00014-16-1-3188.

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.

High-pressure phase transitions of α-quartz under nonhydrostatic dynamic conditions: A reconnaissance study at PETRA III

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

Carl, Eva-Regine; Mansfeld, Ulrich; Liermann, Hanns-Peter

Hypervelocity collisions of solid bodies occur frequently in the solar system and affect rocks by shock waves and dynamic loading. A range of shock metamorphic effects and high-pressure polymorphs in rock-forming minerals are known from meteorites and terrestrial impact craters. In this paper, we investigate the formation of high-pressure polymorphs of α-quartz under dynamic and nonhydrostatic conditions and compare these disequilibrium states with those predicted by phase diagrams derived from static experiments under equilibrium conditions. We create highly dynamic conditions utilizing a mDAC and study the phase transformations in α-quartz in situ by synchrotron powder X-ray diffraction. Phase transitions ofmore » α-quartz are studied at pressures up to 66.1 and different loading rates. At compression rates between 0.14 and 1.96 GPa s -1, experiments reveal that α-quartz is amorphized and partially converted to stishovite between 20.7 GPa and 28.0 GPa. Therefore, coesite is not formed as would be expected from equilibrium conditions. With the increasing compression rate, a slight increase in the transition pressure occurs. The experiments show that dynamic compression causes an instantaneous formation of structures consisting only of SiO 6 octahedra rather than the rearrangement of the SiO 4 tetrahedra to form a coesite. Although shock compression rates are orders of magnitude faster, a similar mechanism could operate in impact events.« less

High-pressure phase transitions of α-quartz under nonhydrostatic dynamic conditions: A reconnaissance study at PETRA III

DOE PAGES

Carl, Eva-Regine; Mansfeld, Ulrich; Liermann, Hanns-Peter; ...

2017-03-27

Hypervelocity collisions of solid bodies occur frequently in the solar system and affect rocks by shock waves and dynamic loading. A range of shock metamorphic effects and high-pressure polymorphs in rock-forming minerals are known from meteorites and terrestrial impact craters. In this paper, we investigate the formation of high-pressure polymorphs of α-quartz under dynamic and nonhydrostatic conditions and compare these disequilibrium states with those predicted by phase diagrams derived from static experiments under equilibrium conditions. We create highly dynamic conditions utilizing a mDAC and study the phase transformations in α-quartz in situ by synchrotron powder X-ray diffraction. Phase transitions ofmore » α-quartz are studied at pressures up to 66.1 and different loading rates. At compression rates between 0.14 and 1.96 GPa s -1, experiments reveal that α-quartz is amorphized and partially converted to stishovite between 20.7 GPa and 28.0 GPa. Therefore, coesite is not formed as would be expected from equilibrium conditions. With the increasing compression rate, a slight increase in the transition pressure occurs. The experiments show that dynamic compression causes an instantaneous formation of structures consisting only of SiO 6 octahedra rather than the rearrangement of the SiO 4 tetrahedra to form a coesite. Although shock compression rates are orders of magnitude faster, a similar mechanism could operate in impact events.« less

Finite-difference computations of rotor loads

NASA Technical Reports Server (NTRS)

Caradonna, F. X.; Tung, C.

1985-01-01

This paper demonstrates the current and future potential of finite-difference methods for solving real rotor problems which now rely largely on empiricism. The demonstration consists of a simple means of combining existing finite-difference, integral, and comprehensive loads codes to predict real transonic rotor flows. These computations are performed for hover and high-advance-ratio flight. Comparisons are made with experimental pressure data.

Finite-difference computations of rotor loads

NASA Technical Reports Server (NTRS)

Caradonna, F. X.; Tung, C.

1985-01-01

The current and future potential of finite difference methods for solving real rotor problems which now rely largely on empiricism are demonstrated. The demonstration consists of a simple means of combining existing finite-difference, integral, and comprehensive loads codes to predict real transonic rotor flows. These computations are performed for hover and high-advanced-ratio flight. Comparisons are made with experimental pressure data.

Effect of nutrient pollution on dinoflagellate cyst assemblages ...

EPA Pesticide Factsheets

We analyzed surface sediments from 23 northeast USA estuaries, from Maine to Delaware, and nine estuaries from Prince Edward Island (PEI, Canada), to determine how dinoflagellate cyst assemblages varied with nutrient loading. Overall the abundance of cysts of heterotrophic dinoflagellates correlates with modeled nitrogen loading, but there were also regional signals. On PEI cysts of Gymnodinium microreticulatum characterized estuaries with high nitrogen loading while the sediments of eutrophic Boston Harbor were characterized by high abundances of Spiniferites spp. In Delaware Bay and the Delaware Inland Bays Polysphaeridium zoharyi correlated with higher temperatures and nutrient loading. This is the first study to document the dinoflagellate cyst eutrophication signal at such a large geographic scale in estuaries, thus confirming their value as indicators of water quality change and anthropogenic impact. Estuarine and coastal waters are important resources for US and Canadian citizens. This paper summarizes the use of biological indicators that provide information on the eutrophication status and impacts for estuaries along the NW Atlantic coast. These relatively new biological indicators, dinoflagellate cysts, have the potential to provide environmental managers information on recent and historical environmental conditions in estuaries. Together with information on drivers and pressures, dinoflagellate cysts can be used to develop driver-pressure-state-imp

Strain measurements of the tibial insert of a knee prosthesis using a knee motion simulator.

PubMed

Sera, Toshihiro; Iwai, Yuya; Yamazaki, Takaharu; Tomita, Tetsuya; Yoshikawa, Hideki; Naito, Hisahi; Matsumoto, Takeshi; Tanaka, Masao

2017-12-01

The longevity of a knee prosthesis is influenced by the wear of the tibial insert due to its posture and movement. In this study, we assumed that the strain on the tibial insert is one of the main reasons for its wear and investigated the influence of the knee varus-valgus angles on the mechanical stress of the tibial insert. Knee prosthesis motion was simulated using a knee motion simulator based on a parallel-link six degrees-of-freedom actuator and the principal strain and pressure distribution of the tibial insert were measured. In particular, the early stance phase obtained from in vivo X-ray images was examined because the knee is applied to the largest load during extension/flexion movement. The knee varus-valgus angles were 0° (neutral alignment), 3°, and 5° malalignment. Under a neutral orientation, the pressure was higher at the middle and posterior condyles. The first and second principal strains were larger at the high and low pressure areas, respectively. Even for a 3° malalignment, the load was concentrated at one condyle and the positive first principal strain increased dramatically at the high pressure area. The negative second principal strain was large at the low pressure area on the other condyle. The maximum equivalent strain was 1.3-2.1 times larger at the high pressure area. For a 5° malalignment, the maximum equivalent strain increased slightly. These strain and pressure measurements can provide the mechanical stress of the tibial insert in detail for determining the longevity of an artificial knee joint.

24 CFR 3280.404 - Standard for egress windows and devices for use in manufactured homes.

Code of Federal Regulations, 2011 CFR

2011-04-01

... interior pressure tests for components and cladding must be conducted at the design wind loads required by... in high wind areas. For homes designed to be located in Wind Zones II and III, manufacturers shall... egress window openings. This method must be capable of resisting the design wind pressures specified in...

24 CFR 3280.404 - Standard for egress windows and devices for use in manufactured homes.

Code of Federal Regulations, 2012 CFR

2012-04-01

... interior pressure tests for components and cladding must be conducted at the design wind loads required by... in high wind areas. For homes designed to be located in Wind Zones II and III, manufacturers shall... egress window openings. This method must be capable of resisting the design wind pressures specified in...

24 CFR 3280.404 - Standard for egress windows and devices for use in manufactured homes.

Code of Federal Regulations, 2013 CFR

2013-04-01

... interior pressure tests for components and cladding must be conducted at the design wind loads required by... in high wind areas. For homes designed to be located in Wind Zones II and III, manufacturers shall... egress window openings. This method must be capable of resisting the design wind pressures specified in...

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.

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.

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.

Super-strengthening and stabilizing with carbon nanotube harnessed high density nanotwins in metals by shock loading

PubMed Central

Lin, Dong; Saei, Mojib; Suslov, Sergey; Jin, Shengyu; Cheng, Gary J.

2015-01-01

CNTs reinforced metal composites has great potential due to their superior properties, such as light weight, high strength, low thermal expansion and high thermal conductivity. The current strengthening mechanisms of CNT/metal composite mainly rely on CNTs’ interaction with dislocations and CNT’s intrinsic high strength. Here we demonstrated that laser shock loading the CNT/metal composite results in high density nanotwins, stacking fault, dislocation around the CNT/metal interface. The composites exhibit enhanced strength with excellent stability. The results are interpreted by both molecular dynamics simulation and experiments. It is found the shock wave interaction with CNTs induces a stress field, much higher than the applied shock pressure, surrounding the CNT/metal interface. As a result, nanotwins were nucleated under a shock pressure much lower than the critical values to generate twins in metals. This hybrid unique nanostructure not only enhances the strength, but also stabilize the strength, as the nanotwin boundaries around the CNTs help pin the dislocation movement. PMID:26493533

A novel liquid organic hydrogen carrier system based on catalytic peptide formation and hydrogenation

PubMed Central

Hu, Peng; Fogler, Eran; Diskin-Posner, Yael; Iron, Mark A.; Milstein, David

2015-01-01

Hydrogen is an efficient green fuel, but its low energy density when stored under high pressure or cryogenically, and safety issues, presents significant disadvantages; hence finding efficient and safe hydrogen carriers is a major challenge. Of special interest are liquid organic hydrogen carriers (LOHCs), which can be readily loaded and unloaded with considerable amounts of hydrogen. However, disadvantages include high hydrogen pressure requirements, high reaction temperatures for both hydrogenation and dehydrogenation steps, which require different catalysts, and high LOHC cost. Here we present a readily reversible LOHC system based on catalytic peptide formation and hydrogenation, using an inexpensive, safe and abundant organic compound with high potential capacity to store and release hydrogen, applying the same catalyst for loading and unloading hydrogen under relatively mild conditions. Mechanistic insight of the catalytic reaction is provided. We believe that these findings may lead to the development of an inexpensive, safe and clean liquid hydrogen carrier system. PMID:25882348

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.

Structural Evaluation of a Space Shuttle Main Engine (SSME) High Pressure Fuel Turbopump Turbine Blade

NASA Technical Reports Server (NTRS)

Abdul-Aziz, Ali

1996-01-01

Thermal and structural finite-element analyses were performed on the first high pressure fuel turbopump turbine blade of the space shuttle main engine (SSME). A two-dimensional (2-D) finite-element model of the blade and firtree disk attachment was analyzed using the general purpose MARC (finite-element) code. The loading history applied is a typical test stand engine cycle mission, which consists of a startup condition with two thermal spikes, a steady state and a shutdown transient. The blade material is a directionally solidified (DS) Mar-M 246 alloy, the blade rotor is forged with waspalloy material. Thermal responses under steady-state and transient conditions were calculated. The stresses and strains under the influence of mechanical and thermal loadings were also determined. The critical regions that exhibited high stresses and severe localized plastic deformation were the blade-rotor gaps.

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

DOE PAGES

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

2016-07-18

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

Hot forging of roll-cast high aluminum content magnesium alloys

NASA Astrophysics Data System (ADS)

Kishi, Tomohiro; Watari, Hisaki; Suzuki, Mayumi; Haga, Toshio

2017-10-01

This paper reports on hot forging of high aluminum content magnesium alloy sheets manufactured using horizontal twin-roll casting. AZ111 and AZ131 were applied for twin-roll casting, and a hot-forging test was performed to manufacture high-strength magnesium alloy components economically. For twin-roll casting, the casting conditions of a thick sheet for hot forging were investigated. It was found that twin-roll casting of a 10mm-thick magnesium alloy sheet was possible at a roll speed of 2.5m/min. The grain size of the cast strip was 50 to 70µm. In the hot-forging test, blank material was obtained from as-cast strip. A servo press machine with a servo die cushion was used to investigate appropriate forging conditions (e.g., temperature, forging load, and back pressure) for twin-roll casts (TRCs) AZ111 and AZ131. It was determined that high aluminum content magnesium alloy sheets manufactured using twin-roll casting could be forged with a forging load of 150t and a back pressure of 3t at 420 to 430°C. Applying back pressure during hot forging effectively forged a pin-shaped product.

Design and Analysis of Hydrostatic Transmission System

NASA Astrophysics Data System (ADS)

Mistry, Kayzad A.; Patel, Bhaumikkumar A.; Patel, Dhruvin J.; Parsana, Parth M.; Patel, Jitendra P.

2018-02-01

This study develops a hydraulic circuit to drive a conveying system dealing with heavy and delicate loads. Various safety circuits have been added in order to ensure stable working at high pressure and precise controlling. Here we have shown the calculation procedure based on an arbitrarily selected load. Also the circuit design and calculations of various components used is depicted along with the system simulation. The results show that the system is stable and efficient enough to transmit heavy loads by functioning of the circuit. By this information, one can be able to design their own hydrostatic circuits for various heavy loading conditions.

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

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

Could Nano-Structured Materials Enable the Improved Pressure Vessels for Deep Atmospheric Probes?

NASA Technical Reports Server (NTRS)

Srivastava, D.; Fuentes, A.; Bienstock, B.; Arnold, J. O.

2005-01-01

A viewgraph presentation on the use of Nano-Structured Materials to enable pressure vessel structures for deep atmospheric probes is shown. The topics include: 1) High Temperature/Pressure in Key X-Environments; 2) The Case for Use of Nano-Structured Materials Pressure Vessel Design; 3) Carbon based Nanomaterials; 4) Nanotube production & purification; 5) Nanomechanics of Carbon Nanotubes; 6) CNT-composites: Example (Polymer); 7) Effect of Loading sequence on Composite with 8% by volume; 8) Models for Particulate Reinforced Composites; 9) Fullerene/Ti Composite for High Strength-Insulating Layer; 10) Fullerene/Epoxy Composite for High Strength-Insulating Layer; 11) Models for Continuous Fiber Reinforced Composites; 12) Tensile Strength for Discontinuous Fiber Composite; 13) Ti + SWNT Composites: Thermal/Mechanical; 14) Ti + SWNT Composites: Tensile Strength; and 15) Nano-structured Shell for Pressure Vessels.

Thermocryogenic buckling and stress analyses of a partially filled cryogenic tank subjected to cylindrical strip heating

NASA Technical Reports Server (NTRS)

Ko, William L.

1994-01-01

Thermocryogenic buckling and stress analyses were conducted on a horizontally oriented cryogenic tank using the finite element method. The tank is a finite-length circular cylindrical shell with its two ends capped with hemispherical shells. The tank is subjected to cylindrical strip heating in the region above the liquid-cryogen fill level and to cryogenic cooling below the fill level (i.e., under thermocryogenic loading). The effects of cryogen fill level on the buckling temperature and thermocryogenic stress field were investigated in detail. Both the buckling temperature and stress magnitudes were relatively insensitive to the cryogen fill level. The buckling temperature, however, was quite sensitive to the radius-to-thickness ratio. A mechanical stress analysis of the tank also was conducted when the tank was under: (1) cryogen liquid pressure loading; (2) internal pressure loading; and (3) tank-wall inertia loading. Deformed shapes of the cryogenic tanks under different loading conditions were shown, and high-stress domains were mapped on the tank wall for the strain-gage installations. The accuracies of solutions from different finite element models were compared.

High Performance Auxiliary Power Unit Technology Demonstrator.

DTIC Science & Technology

1980-12-01

aft bearings 1.13 P3 - Power producer CDP 1.14 DPHE - Lube pressure drop at heat exchanger 1.15 POFP - Load airflow orifice pressure 1.16 DPOFP - Load...P𔃽I -PSI G PEBL -PSIG P2 -PS.IG DPHE -PID POFP -F Iu 0. 022±_ 77. 3478 6o5. 6 4±4 ±8L-. 4852 19. 51-17.4 DPOFP -PSID Ni -,. N2-i -RPM NSATM -FPM...28. 0250 83. 3505 29. 861 1:9. 7680 PGi -PSIG PEBL -PSIG P3 -PSIG DPHE -PSID POFP -PSIG 0. 0100 77. 9199 72.4862 17. 25 ±19. 4122 1= DPOFP -PSID NI

[Filtering facepieces: effect of oily aerosol load on penetration through the filtering material].

PubMed

Plebani, Carmela; Listrani, S; Di Luigi, M

2010-01-01

Electrostatic filters are widely used in applications requiring high filtration efficiency and low pressure drop. However various studies showed that the penetration through electrostatic filters increases during exposure to an aerosol flow. This study investigates the effects of prolonged exposure to an oily aerosol on the penetration through filtering facepieces available on the market. Some samples of FFP1, FFP2 and FFP3 filtering facepieces were exposed for 8 hours consecutively to a paraffin oil polydisperse aerosol. At the end of the exposure about 830 mg of paraffin oil were deposited in the facepiece. All the examined facepieces showed penetration values that increased with paraffin oil load while pressure drop values were substantially the same before and after exposure. The measured maximum penetration values did not exceed the maximum penetration values allowed by the European technical standards, except in one case. According to the literature, 830 mg of oil load in a facepiece is not feasible in workplaces over an eight- hour shift. However, the trend of the penetration versus exposure mass suggests that if the load increases, the penetration may exceed the maximum allowed values. For comparison a mechanical filter was also studied. This showed an initial pressure drop higher than FFP2 filtering facepieces characterized by comparable penetration values. During exposure the pressure drop virtually doubled while penetration did not change. The increase in penetration with no increase in pressure drop in the analyzed facepieces indicates that it is necessary to comply with the information supplied by the manufacturer that restricts their use to a single shift.

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.;

What is the relationship between mental workload factors and cognitive load types?

PubMed

Galy, Edith; Cariou, Magali; Mélan, Claudine

2012-03-01

The present study tested the hypothesis of an additive interaction between intrinsic, extraneous and germane cognitive load, by manipulating factors of mental workload assumed to have a specific effect on either type of cognitive load. The study of cognitive load factors and their interaction is essential if we are to improve workers' wellbeing and safety at work. High cognitive load requires the individual to allocate extra resources to entering information. It is thought that this demand for extra resources may reduce processing efficiency and performance. The present study tested the effects of three factors thought to act on either cognitive load type, i.e. task difficulty, time pressure and alertness in a working memory task. Results revealed additive effects of task difficulty and time pressure, and a modulation by alertness on behavioral, subjective and psychophysiological workload measures. Mental overload can be the result of a combination of task-related components, but its occurrence may also depend on subject-related characteristics, including alertness. Solutions designed to reduce incidents and accidents at work should consider work organization in addition to task constraints in so far that both these factors may interfere with mental workload. Copyright © 2011 Elsevier B.V. All rights reserved.

Characteristics of Plantar Loads During Walking in Patients with Knee Osteoarthritis.

PubMed

Zhang, Zhiwang; Wang, Lin; Hu, Kaijun; Liu, Yu

2017-12-01

BACKGROUND Knee osteoarthritis (KOA) is a common disease that can change the load on lower limbs during walking. Plantar loads in patients with KOA may provide a basis for clinical decisions regarding footwear and foot orthoses. This study aimed to compare plantar loads in females with and without KOA during gait. MATERIAL AND METHODS Plantar pressure during walking was recorded in 23 females with KOA and 23 females without KOA. Maximum force (MF), contact area (CA), and peak pressure (PP) were measured at 7 different regions underneath the foot, named heel (M1), midfoot (M2), first metatarsophalangeal joint (MPJ) (M3), second MPJ (M4), third to fifth MPJ (M5), hallux (M6), and lesser toes (M7). RESULTS PPs for M2 and (M3) in females with KOA were higher than those in females without KOA. High PPs were also found in females with KOA for M2, M3, and M4. CONCLUSIONS Increased plantar loading in females with KOA may lead to foot pronation and gait changes during walking. Plantar loading may be offered to patients with KOA when considering footwear and foot orthoses.

The flow field investigations of no load conditions in axial flow fixed-blade turbine

NASA Astrophysics Data System (ADS)

Yang, J.; Gao, L.; Wang, Z. W.; Zhou, X. Z.; Xu, H. X.

2014-03-01

During the start-up process, the strong instabilities happened at no load operation in a low head axial flow fixed-blade turbine, with strong pressure pulsation and vibration. The rated speed can not reach until guide vane opening to some extent, and stable operation could not be maintained under the rated speed at some head, which had a negative impact on the grid-connected operation of the unit. In order to find the reason of this phenomenon, the unsteady flow field of the whole flow passage at no load conditions was carried out to analyze the detailed fluid field characteristics including the pressure pulsation and force imposed on the runner under three typical heads. The main hydraulic cause of no load conditions instability was described. It is recommended that the power station should try to reduce the no-load running time and go into the high load operation as soon as possible when connected to grid at the rated head. Following the recommendations, the plant operation practice proved the unstable degree of the unit was reduced greatly during start up and connect to the power grid.

Wind-tunnel investigation of aerodynamic loading on a 0.237-scale model of a remotely piloted research vehicle with a thick, high-aspect-ratio supercritical wing

NASA Technical Reports Server (NTRS)

Byrdsong, T. A.; Brooks, C. W., Jr.

1983-01-01

Wind-tunnel measurements were made of the wing-surface static-pressure distributions on a 0.237 scale model of a remotely piloted research vehicle equipped with a thick, high-aspect-ratio supercritical wing. Data are presented for two model configurations (with and without a ventral pod) at Mach numbers from 0.70 to 0.92 at angles of attack from -4 deg to 8 deg. Large variations of wing-surface local pressure distributions were developed; however, the characteristic supercritical-wing pressure distribution occurred near the design condition of 0.80 Mach number and 2 deg angle of attack. The significant variations of the local pressure distributions indicated pronounced shock-wave movements that were highly sensitive to angle of attack and Mach number. The effect of the vertical pod varied with test conditions; however at the higher Mach numbers, the effects on wing flow characteristics were significant at semispan stations as far outboard as 0.815. There were large variations of the wing loading in the range of test conditions, both model configurations exhibited a well-defined peak value of normal-force coefficient at the cruise angle of attack (2 deg) and Mach number (0.80).

Speed control with end cushion for high speed air cylinder

DOEpatents

Stevens, Wayne W.; Solbrig, Charles W.

1991-01-01

A high speed air cylinder in which the longitudinal movement of the piston within the air cylinder tube is controlled by pressurizing the air cylinder tube on the accelerating side of the piston and releasing pressure at a controlled rate on the decelerating side of the piston. The invention also includes a method for determining the pressure required on both the accelerating and decelerating sides of the piston to move the piston with a given load through a predetermined distance at the desired velocity, bringing the piston to rest safely without piston bounce at the end of its complete stroke.

Erosion/corrosion of turbine airfoil materials in the high-velocity effluent of a pressurized fluidized coal combustor

NASA Technical Reports Server (NTRS)

Zellars, G. R.; Rowe, A. P.; Lowell, C. E.

1978-01-01

Four candidate turbine airfoil superalloys were exposed to the effluent of a pressurized fluidized bed with a solids loading of 2 to 4 g/scm for up to 100 hours at two gas velocities, 150 and 270 m/sec, and two temperatures, 730 deg and 795 C. Under these conditions, both erosion and corrosion occurred. The damaged specimens were examined by cross-section measurements, scanning electron and light microscopy, and X-ray analysis to evaluate the effects of temperature, velocity, particle loading, and alloy material. Results indicate that for a given solids loading the extent of erosion is primarily dependent on gas velocity. Corrosion occurred only at the higher temperature. There was little difference in the erosion/corrosion damage to the four alloys tested under these severe conditions.

Dynamic Pressure Distribution due to Horizontal Acceleration in Spherical LNG Tank with Cylindrical Central Part

NASA Astrophysics Data System (ADS)

Ko, Dae-Eun; Shin, Sang-Hoon

2017-11-01

Spherical LNG tanks having many advantages such as structural safety are used as a cargo containment system of LNG carriers. However, it is practically difficult to fabricate perfectly spherical tanks of different sizes in the yard. The most effective method of manufacturing LNG tanks of various capacities is to insert a cylindrical part at the center of existing spherical tanks. While a simplified high-precision analysis method for the initial design of the spherical tanks has been developed for both static and dynamic loads, in the case of spherical tanks with a cylindrical central part, the analysis method available only considers static loads. The purpose of the present study is to derive the dynamic pressure distribution due to horizontal acceleration, which is essential for developing an analysis method that considers dynamic loads as well.

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.

Performance of Maybach 300-horsepower airplane engine

NASA Technical Reports Server (NTRS)

Sparrow, S W

1923-01-01

This report contains the results of a test made upon a Maybach Engine in the altitude chamber of the Bureau of Standards, where controlled conditions of temperature and pressure can be made the same as those of the desired altitude. The results of this test lead to the following conclusions: from the standpoint of thermal efficiency the full-load performance of the engine is excellent at densities corresponding to altitudes up to and including 15,000 feet. The brake mean effective pressure is rather low even at wide-open throttle. This tends to give a high weight per horsepower, in as much as the weight of many engine parts is governed by the size rather than the power of the engine. At part load the thermal efficiency of the engine is low. Judged on a basis of performance the engine's chief claim to interest would appear to lie in the carburetor design, which is largely responsible excellent full-load efficiency and for its poor part-load efficiency.

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.

Biofilm architecture in a novel pressurized biofilm reactor.

PubMed

Jiang, Wei; Xia, Siqing; Duan, Liang; Hermanowicz, Slawomir W

2015-01-01

A novel pure-oxygen pressurized biofilm reactor was operated at different organic loading, mechanical shear and hydrodynamic conditions to understand the relationships between biofilm architecture and its operation. The ultimate goal was to improve the performance of the biofilm reactor. The biofilm was labeled with seven stains and observed with confocal laser scanning microscopy. Unusual biofilm architecture of a ribbon embedded between two surfaces with very few points of attachment was observed. As organic loading increased, the biofilm morphology changed from a moderately rough layer into a locally smoother biomass with significant bulging protuberances, although the chemical oxygen demand (COD) removal efficiency remained unchanged at about 75%. At higher organic loadings, biofilms contained a larger fraction of active cells distributed uniformly within a proteinaceous matrix with decreasing polysaccharide content. Higher hydrodynamic shear in combination with high organic loading resulted in the collapse of biofilm structure and a substantial decrease in reactor performance (a COD removal of 16%). Moreover, the important role of proteins for the spatial distribution of active cells was demonstrated quantitatively.

Studies of Halogen Bonding Using High-Pressure Diffractometry

DTIC Science & Technology

2007-11-08

mixed at room temperature. The 1:1 cocrystal was melted by heating it to and in the liquid form loaded to a DAC. Single-crystal of each compound or...upper edge. Figure 6. Isochoric growth of the 1,2-diiodoperfluoroethane:1,4-dioxane 1:1 cocrystal : (a) the melting process of the polycrystal...impurities in the mixture, which condensed at high pressure and grouped between the cocrystal upper face (001) and the upper culet. Figure 7. Isochoric

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.

The behavior of single-crystal silicon to dynamic loading using in-situ X-ray diffraction and phase contrast imaging

NASA Astrophysics Data System (ADS)

Lee, Hae Ja; Xing, Zhou; Galtier, Eric; Arnold, Brice; Granados, Eduardo; Brown, Shaughnessy B.; Tavella, Franz; McBride, Emma; Fry, Alan; Nagler, Bob; Schropp, Andreas; Seiboth, Frank; Samberg, Dirk; Schroer, Christian; Gleason, Arianna E.; Higginbotham, Andrew

Hydrostatic and uniaxial compression studies have revealed that crystalline silicon undergoes phase transitions from a cubic diamond structure to a variety of phases including orthorhombic Imma phase, body-centered tetragonal phase, and a hexagonal primitive phase. The dynamic response of silicon at high pressure, however, is not well understood. Phase contrast imaging has proven to be a powerful tool for probing density changes caused by the shock propagation into a material. In order to characterize the elastic and phase transitions, we image shock waves in Si with high spatial resolution using the LCLS X-ray free electron laser and Matter in Extreme Conditions instrument. In this study, the long pulse optical laser with pseudo-flat top shape creates high pressures up to 60 GPa. We measure the crystal structure by observing X-ray diffraction orthogonal to the shock propagation direction over a range of pressures. We describe the capability of simultaneously performing phase contrast imaging and in situ X-ray diffraction during shock loading and discuss the dynamic response of Si in high-pressure phases Use of the Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. The MEC instrument is supported by.

Transdiaphragmatic pressure and neural respiratory drive measured during inspiratory muscle training in stable patients with chronic obstructive pulmonary disease.

PubMed

Wu, Weiliang; Zhang, Xianming; Lin, Lin; Ou, Yonger; Li, Xiaoying; Guan, Lili; Guo, Bingpeng; Zhou, Luqian; Chen, Rongchang

2017-01-01

Inspiratory muscle training (IMT) is a rehabilitation therapy for stable patients with COPD. However, its therapeutic effect remains undefined due to the unclear nature of diaphragmatic mobilization during IMT. Diaphragmatic mobilization, represented by transdiaphragmatic pressure (Pdi), and neural respiratory drive, expressed as the corrected root mean square (RMS) of the diaphragmatic electromyogram (EMGdi), both provide vital information to select the proper IMT device and loads in COPD, therefore contributing to the curative effect of IMT. Pdi and RMS of EMGdi (RMSdi%) were measured and compared during inspiratory resistive training and threshold load training in stable patients with COPD. Pdi and neural respiratory drive were measured continuously during inspiratory resistive training and threshold load training in 12 stable patients with COPD (forced expiratory volume in 1 s ± SD was 26.1%±10.2% predicted). Pdi was significantly higher during high-intensity threshold load training (91.46±17.24 cmH 2 O) than during inspiratory resistive training (27.24±6.13 cmH 2 O) in stable patients with COPD, with P <0.01 for each. Significant difference was also found in RMSdi% between high-intensity threshold load training and inspiratory resistive training (69.98%±16.78% vs 17.26%±14.65%, P <0.01). We concluded that threshold load training shows greater mobilization of Pdi and neural respiratory drive than inspiratory resistive training in stable patients with COPD.

Wind Tunnel Tests for Wind Pressure Distribution on Gable Roof Buildings

PubMed Central

2013-01-01

Gable roof buildings are widely used in industrial buildings. Based on wind tunnel tests with rigid models, wind pressure distributions on gable roof buildings with different aspect ratios were measured simultaneously. Some characteristics of the measured wind pressure field on the surfaces of the models were analyzed, including mean wind pressure, fluctuating wind pressure, peak negative wind pressure, and characteristics of proper orthogonal decomposition results of the measured wind pressure field. The results show that extremely high local suctions often occur in the leading edges of longitudinal wall and windward roof, roof corner, and roof ridge which are the severe damaged locations under strong wind. The aspect ratio of building has a certain effect on the mean wind pressure coefficients, and the effect relates to wind attack angle. Compared with experimental results, the region division of roof corner and roof ridge from AIJ2004 is more reasonable than those from CECS102:2002 and MBMA2006.The contributions of the first several eigenvectors to the overall wind pressure distributions become much bigger. The investigation can offer some basic understanding for estimating wind load distribution on gable roof buildings and facilitate wind-resistant design of cladding components and their connections considering wind load path. PMID:24082851

Reduced Pressure Cabin Testing of the Orion Atmosphere Revitalization Technology

NASA Technical Reports Server (NTRS)

Button, Amy; Sweterlitsch, Jeffrey

2011-01-01

An amine-based carbon dioxide (CO2) and water vapor sorbent in pressure-swing regenerable beds has been developed by Hamilton Sundstrand and baselined for the Atmosphere Revitalization System for moderate duration missions of the Orion Multipurpose Crew Vehicle. In previous years at this conference, reports were presented on extensive Johnson Space Center testing of this technology in a sea-level pressure environment with simulated and actual human metabolic loads in both open and closed-loop configurations. In 2011, the technology was tested in an open cabin-loop configuration at ambient and two sub-ambient pressures to compare the performance of the system to the results of previous tests at ambient pressure. The testing used a human metabolic simulator with a different type of water vapor generation than previously used, which added some unique challenges in the data analysis. This paper summarizes the results of: baseline and some matrix testing at all three cabin pressures, increased vacuum regeneration line pressure with a high metabolic load, a set of tests studying CO2 and water vapor co-adsorption effects relative to model-predicted performance, and validation tests of flight program computer model predictions with specific operating conditions.

Reduced Pressure Cabin Testing of the Orion Atmosphere Revitalization Technology

NASA Technical Reports Server (NTRS)

Button, Amy; Sweterlisch, Jeffery J.

2013-01-01

An amine-based carbon dioxide (CO2) and water vapor sorbent in pressure-swing regenerable beds has been developed by Hamilton Sundstrand and baselined for the Atmosphere Revitalization System for moderate duration missions of the Orion Multipurpose Crew Vehicle. In previous years at this conference, reports were presented on extensive Johnson Space Center testing of this technology in a sea-level pressure environment with simulated and actual human metabolic loads in both open and closed-loop configurations. In 2011, the technology was tested in an open cabin-loop configuration at ambient and two sub-ambient pressures to compare the performance of the system to the results of previous tests at ambient pressure. The testing used a human metabolic simulator with a different type of water vapor generation than previously used, which added some unique challenges in the data analysis. This paper summarizes the results of: baseline and some matrix testing at all three cabin pressures, increased vacuum regeneration line pressure with a high metabolic load, a set of tests studying CO2 and water vapor co-adsorption effects relative to model-predicted performance, and validation tests of flight program computer model predictions with specific operating conditions.

Reduced Pressure Cabin Testing of the Orion Atmosphere Revitalization Technology

NASA Technical Reports Server (NTRS)

Button, Amy B.; Sweterlitsch, Jeffrey J.

2013-01-01

An amine-based carbon dioxide (CO2) and water vapor sorbent in pressure-swing regenerable beds has been developed by United Technologies Corp. Aerospace Systems (UTAS, formerly Hamilton Sundstrand) and baselined for the Atmosphere Revitalization System for moderate duration missions of the Orion Multipurpose Crew Vehicle (MPCV). In previous years at this conference, reports were presented on extensive Johnson Space Center testing of this technology in a sea-level pressure environment with simulated and actual human metabolic loads in both open and closed-loop configurations. In 2011, the technology was tested in an open cabin-loop configuration at ambient and two sub-ambient pressures to compare the performance of the system to the results of previous tests at ambient pressure. The testing used a human metabolic simulator with a different type of water vapor generation than previously used, which added some unique challenges in the data analysis. This paper summarizes the results of: baseline and some matrix testing at all three cabin pressures, increased vacuum regeneration line pressure testing with a high metabolic load, a set of tests studying CO2 and water vapor co-adsorption effects relative to model-predicted performance, and validation tests of flight project computer model predictions with specific operating conditions.

Recent advances in lightweight, filament-wound composite pressure vessel technology

NASA Technical Reports Server (NTRS)

Lark, R. F.

1977-01-01

A review of recent advances is presented for lightweight, high performance composite pressure vessel technology that covers the areas of design concepts, fabrication procedures, applications, and performance of vessels subjected to single cycle burst and cyclic fatigue loading. Filament wound fiber/epoxy composite vessels were made from S glass, graphite, and Kevlar 49 fibers and were equipped with both structural and nonstructural liners. Pressure vessels structural efficiencies were attained which represented weight savings, using different liners, of 40 to 60 percent over all titanium pressure vessels. Significant findings in each area are summarized.

Energy efficient solvent regeneration process for carbon dioxide capture

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

Zhou, Shaojun; Meyer, Howard S.; Li, Shiguang

A process for removing carbon dioxide from a carbon dioxide-loaded solvent uses two stages of flash apparatus. Carbon dioxide is flashed from the solvent at a higher temperature and pressure in the first stage, and a lower temperature and pressure in the second stage, and is fed to a multi-stage compression train for high pressure liquefaction. Because some of the carbon dioxide fed to the compression train is already under pressure, less energy is required to further compress the carbon dioxide to a liquid state, compared to conventional processes.

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.

Portable vibration exciter

NASA Technical Reports Server (NTRS)

Beecher, L. C.; Williams, F. T.

1970-01-01

Gas-driven vibration exciter produces a sinusoidal excitation function controllable in frequency and in amplitude. It allows direct vibration testing of components under normal loads, removing the possibility of component damage due to high static pressure.

Microstructural Design for Stress Wave Energy Management

DTIC Science & Technology

2013-04-01

Polyurea based foam 7 4) Controlling transmission and reflection of pressure and shear waves in a multilayered anisotropic structure 10 5... Polyurea based foam consists of several factors including high energy absorption, light weight, higher elastic modulus to density ratio (compared with... Polyurea ), and collapsible voids under extreme loading. Pure Polyurea offers unique properties such as increased shear stiffness under large pressure

ISSLS prize winner: microstructure and mechanical disruption of the lumbar disc annulus: part II: how the annulus fails under hydrostatic pressure.

PubMed

Veres, Samuel P; Robertson, Peter A; Broom, Neil D

2008-12-01

Mechanically induced annular disruption of lumbar intervertebral discs followed by microstructural investigation. To investigate the role that elevated nuclear pressures play in disrupting the lumbar intervertebral disc's annulus fibrosus. Compound mechanical loadings have been used to recreate clinically relevant annular disruptions in vitro. However, the role that individual loading parameters play in disrupting the lumbar disc's annulus remains unclear. The nuclei of ovine lumbar intervertebral discs were gradually pressurized by injecting a viscous radio-opaque gel via their inferior vertebrae. Pressurization was conducted until catastrophic failure of the disc occurred. Investigation of the resulting annular disruption was carried out using microcomputed tomography and differential interference contrast microscopy. Gel extrusion from the posterior annulus was the most common mode of disc failure. Unlike other aspects of the annular wall, the posterior region was unable to distribute hydrostatic pressures circumferentially. In each extrusion case, severe disruption of the posterior annulus occurred. Although intralamellar disruption occurred in the mid annulus, interlamellar disruption occurred in the outer posterior annulus. Radial ruptures between lamellae always occurred in the mid-axial plane. With respect to the annular wall, the posterior region is most susceptible to failure in the presence of high nuclear pressure, even when loaded in the neutral position. Weak interlamellar cohesion of the outer posterior lamellae may explain why the majority of herniations remain contained as protrusions within the outer annular wall.

Fatigue crack growth behavior of pressure vessel steels and submerged arc weldments in a high-temperature pressurized water environment

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

Liaw, P.K.; Logsdon, W.A.; Begley, J.A.

1989-10-01

The fatigue crack growth rate (FCGR) properties of SA508 Cl 2a and SA533 Gr A Cl 2 pressure vessel steels and the corresponding automatic submerged arc weldments were developed in a high-temperature pressurized water (HPW) environment at 288{degrees} C (550{degrees} F) and 7.2 MPa (1044 psi) at load ratios of 0.20 and 0.50. The properties were generally conservative compared to American Society of Mechanical Engineers Section XI water environment reference curve. The growth rate of fatigue cracks in the base materials, however, was faster in the HPW environment than in a 288{degrees} C (550{degrees} F) base line air environment. Themore » growth rate of fatigue cracks in the two submerged arc weldments was also accelerated in the HPW environment but to a lesser degree than that demonstrated by the base materials. In the air environment, fatigue striations were observed, independent of material and load ratio, while in the HPW environment, some intergranular facets were present. The greater environmental effect on crack growth rates displayed by the base materials compared the weldments attributed to a different sulfide composition and morphology.« less

Aerodynamic Analysis of a Hale Aircraft Joined-Wing Configuration

NASA Astrophysics Data System (ADS)

Sivaji, Rangarajan; Ghia, Urmila; Ghia, Karman; Thornburg, Hugh

2003-11-01

Aerodynamic analysis of a high-aspect ratio, joined wing of a High-Altitude Long Endurance (HALE) aircraft is performed. The requirement of high lift over extended flight periods for the HALE aircraft leads to high-aspect ratio wings experiencing significant deflections necessitating consideration of aeroelastic effects. The finite-volume solver COBALT, with Reynolds-averaged Navier-Stokes (RANS) and Detached Eddy Simulation (DES) capabilities, is used for the flow simulations. Calculations are performed at á = 0° and 12° for M = 0.6, at an altitude of 30,000 feet, at a Re per unit length of 5.6x106. The wing cross sections are NACA 4421 airfoils. Because of the high lift-to-drag ratio wings, an inviscid flow analysis is also performed. The inviscid surface pressure coefficient (Cp) is compared with the corresponding viscous Cp to examine the feasibility of the use of the inviscid pressure loads as an estimate of the total fluid loads on the structure. The viscous and inviscid Cp results compare reasonably only at á = 0°. The viscous flow is examined in detail via surface and field velocity vectors, vorticity, density and pressure contours. For á = 12°, the unsteady DES solutions show a weak shock at the aft-wing trailing edge. Also, the flow near the joint exhibits a region of mild separation.

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.

Stressors Among Latino Day Laborers A Pilot Study Examining Allostatic Load

PubMed Central

de Castro, A. B.; Voss, Joachim G.; Ruppin, Ayelet; Dominguez, Carlos F.; Seixas, Noah S.

2010-01-01

This pilot study evaluated the feasibility of conducting a research project focused on stressors and allostatic load (AL) among day laborers. A total of 30 Latino men were recruited from CASA Latina. a worker center in Seattle. Participants completed an interview and researchers measured six indicators of AL (body mass index, waist-to-hip ratio, systolic blood pressure, diastolic blood pressure, C-reactive protein, and cortisol). Percentages and mean scores were calculated for several self-reported stressors in work, economic, and social contexts and were compared between low and high AL groups. Overall, participants with high AL reported experiencing more stressors than those with low AL. Additionally, those with high AL generally reported being less healthy both physically and mentally. Findings suggest that Latino day laborers experience stressors that place them at risk for high AL. Also, a study of this nature is possible, but must be conducted with trust and collaboration between researchers and community partners. PMID:20507008

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

DTIC Science & Technology

2005-07-01

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

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

NASA Astrophysics Data System (ADS)

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

2012-10-01

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

High Strain Rate Deformation Mechanisms of Body Centered Cubic Material Subjected to Impact Loading

NASA Astrophysics Data System (ADS)

Visser, William

Low carbon steel is the most common grade of structural steel used; it has carbon content of 0.05% to 0.25% and very low content of alloying elements. It is produced in great quantities and provides material properties that are acceptable for many engineering applications, particularly in the construction industry in which low carbon steel is widely used as the strengthening phase in civil structures. The overall goal of this dissertation was to investigate the deformation response of A572 grade 50 steel when subjected to impact loading. This steel has a 0.23% by weight carbon content and has less than 2% additional alloying elements. The deformation mechanisms of this steel under shock loading conditions include both dislocation motion and twin formation. The goal of this work was achieved by performing experimental, analytical and numerical research in three integrated tasks. The first is to determine the relationship between the evolution of deformation twins and the impact pressure. Secondly, a stress criterion for twin nucleation during high strain rate loading was developed which can account for the strain history or initial dislocation density. Lastly, a method was applied for separating the effects of dislocations and twins generated by shock loading in order to determine their role in controlling the flow stress of the material. In this regard, the contents of this work have been categorically organized. First, the active mechanisms in body centered cubic (BCC) low carbon steel during shock loading have been determined as being a composed of the competing mechanisms of dislocations and deformation twins. This has been determined through a series of shock loading tests of the as-received steel. The shock loading tests were done by plate impact experiments at several impact pressures ranging from 2GPa up to 13GPa using a single stage light gas gun. A relationship between twin volume fraction and impact pressure was determined and an analytical model was utilized to simulate the shock loading and twin evolution for these loading conditions. The second part of this research ties into the modeling efforts. Within the model for predicting twin volume fraction is a twin growth equation and a constant describing the stress at which the twin nucleation will occur. By using a constant value for the twin nucleation stress modeling efforts fail to accurately predict the growth and final twin volume fraction. A second shock loading experimental study combined with high strain rate compression tests using a split Hopkinson pressure bar were completed to determine a twin nucleation stress equation as a function of dislocation density. Steel specimens were subjected to cold rolling to 3% strain and subsequently impacted using the gas gun at different pressures. The increase in dislocation density due to pre-straining substantially increased the twin nucleation stress indicating that twin nucleation stress in dependent upon prior strain history. This has been explained in terms of the velocity and generation rates of both perfect and partial dislocations. An explicit form of the critical twin nucleation stress was developed and parameters were determined through plate impact tests and low temperature (77K) SHPB compression tests. The final component in studying deformation twin mechanisms in BCC steel extends the research to the post-impact mechanical properties and how the twin volume fraction affects the dynamic flow stress. Compression tests between 293K and 923K at an average strain rate of 4700 s-1 were completed on the as-received and 3% pre-strained steels in both the initial condition and after being impacted at pressures of 6GPa and 11GPa. Results of the experimental testing were used in a thermal activation model in order to distinguish separate components in the microstructure contributing to the enhanced flow stress caused by the shock loading. It has been shown that the dislocations generated from shock loading are equivalent to those produced under lower rate straining and the addition of deformation twins in the microstructure contribute to the athermal stress by adding to the long range barriers.

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.

Endogenous ouabain and the renin-angiotensin-aldosterone system: distinct effects on Na handling and blood pressure in human hypertension.

PubMed

Manunta, Paolo; Hamlyn, John M; Simonini, Marco; Messaggio, Elisabetta; Lanzani, Chiara; Bracale, Maria; Argiolas, Giuseppe; Casamassima, Nunzia; Brioni, Elena; Glorioso, Nicola; Bianchi, Giuseppe

2011-02-01

To evaluate whether the renin-angiotensin-aldosterone system (RAAS) and endogenous ouabain system differently affect renal Na handling and blood pressure. Three hundred and one patients in whom we compared blood pressure, and renal Na tubular reabsorption in the basal condition and 2 h (T120) after saline infusion. Following multivariate-adjusted linear and quartiles analysis, baseline mean blood pressure (MBP) was significantly higher (113.7 ± 1.33 mmHg) in the fourth versus the first endogenous ouabain quartile (103.8 ± 1.04 mmHg) and the trend across the quartiles was highly significant (β = 0.23, P = 3.53e-04). In contrast, an inverse relationship was present in the renin activity (PRA) quartiles with MBP highest in the first (112.5 ± 1.26) and lowest in the fourth PRA quartile (107.6 ± 1.48, P = 0.039). Following an acute saline load, changes in MBP and the slope of the pressure-natriuresis relationship were inversely related across the PRA quartiles. The fractional excretion of sodium (FENa) showed a negative linear trend going from the first to the third endogenous ouabain quartiles (2.35 ± 0.17 and 1.90 ± 0.14%, P = 0.05). Patients in the fourth endogenous ouabain quartile (>323 pmol/l) showed increased FENa T120 (2.78 ± 0.18%, P < 0.01) and increased Na tubular rejection fraction (P = 0.007) after Na load. After the saline load, there was a biphasic relationship between plasma endogenous ouabain and FENa favoring Na retention at low endogenous ouabain and Na excretion at high endogenous ouabain levels. The RAAS and endogenous ouabain system are two independent and complementary systems having an inverse (RAAS) or a direct (endogenous ouabain system) relationship with hemodynamic parameters.

Fitness Level Modulates Intraocular Pressure Responses to Strength Exercises.

PubMed

Vera, Jesús; Jiménez, Raimundo; Redondo, Beatríz; Cárdenas, David; García-Ramos, Amador

2018-06-01

Purpose/Aim: The execution of strength exercises has demonstrated to increase the intraocular pressure (IOP) levels, and it may have a negative impact on the ocular health. We aimed to explore the influence of fitness level on the acute IOP response to strength exercises performed under different loading conditions, as well as to test whether the IOP responses differ between the bench press and jump squat when performed against the same relative loads. Forty military personnel males were divided in two subgroups (20 high-fit and 20 low-fit) based on their relative to body mass one-repetition maximum (1-RM). Participants performed an incremental loading test in the bench press and jump squat exercises, and IOP was assessed before and after each repetition by rebound tonometry. IOP increased immediately after executing both exercises (p < 0.01 in both cases), being the magnitude of the IOP increment positively and linearly associated with the increment of the load in both groups (i.e., high-fit and low-fit) and in both exercises (R 2 range: 0.81-1.00). Higher fitness level attenuated the IOP rise produced by both exercises (p < 0.01 in both cases). The bench press induced higher IOP increments than the jump squat for both groups at relative loads of ~50%1-RM and ~60%1-RM (p < 0.01 in all cases). These data indicate that IOP increases as a consequence of performing strength exercises, being the increment accentuated with the increase of the load and in the bench press compared to the jump squat exercise. Of special importance would be that the IOP responses were significantly reduced in high-fit individuals. These findings should be addressed in glaucoma patients.

Energy efficient engine high-pressure turbine component rig performance test report

NASA Technical Reports Server (NTRS)

Leach, K. P.

1983-01-01

A rig test of the cooled high-pressure turbine component for the Energy Efficient Engine was successfully completed. The principal objective of this test was to substantiate the turbine design point performance as well as determine off-design performance with the interaction of the secondary flow system. The measured efficiency of the cooled turbine component was 88.5 percent, which surpassed the rig design goal of 86.5 percent. The secondary flow system in the turbine performed according to the design intent. Characterization studies showed that secondary flow system performance is insensitive to flow and pressure variations. Overall, this test has demonstrated that a highly-loaded, transonic, single-stage turbine can achieve a high level of operating efficiency.

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

Low platinum loading for high temperature proton exchange membrane fuel cell developed by ultrasonic spray coating technique

NASA Astrophysics Data System (ADS)

Su, Huaneng; Jao, Ting-Chu; Barron, Olivia; Pollet, Bruno G.; Pasupathi, Sivakumar

2014-12-01

This paper reports use of an ultrasonic-spray for producing low Pt loadings membrane electrode assemblies (MEAs) with the catalyst coated substrate (CCS) fabrication technique. The main MEA sub-components (catalyst, membrane and gas diffusion layer (GDL)) are supplied from commercial manufacturers. In this study, high temperature (HT) MEAs with phosphoric acid (PA)-doped poly(2,5-benzimidazole) (AB-PBI) membrane are fabricated and tested under 160 °C, hydrogen and air feed 100 and 250 cc min-1 and ambient pressure conditions. Four different Pt loadings (from 0.138 to 1.208 mg cm-2) are investigated in this study. The experiment data are determined by in-situ electrochemical methods such as polarization curve, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The high Pt loading MEA exhibits higher performance at high voltage operating conditions but lower performances at peak power due to the poor mass transfer. The Pt loading 0.350 mg cm-2 GDE performs the peak power density and peak cathode mass power to 0.339 W cm-2 and 0.967 W mgPt-1, respectively. This work presents impressive cathode mass power and high fuel cell performance for high temperature proton exchange membrane fuel cells (HT-PEMFCs) with low Pt loadings.

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.

Effect of Loading Efficiency on the Process of Consolidation in Unsaturated Soils

NASA Astrophysics Data System (ADS)

Lo, W. C.; Lee, J. W.; Deng, J. H.; Liu, J. H.

2016-12-01

Loading efficiency is an undrained poroelastic coefficient that causes an increase in the pore pressure due to an increase in the compressive axial stress. In order to illustrate the importance of loading efficiency on the process of consolidation in unsaturated soils, we utilize two assumptions proposed by Biot (1941) and Terzaghi (1943) to formulate the initial conditions taking account of loading efficiency and without consideration of loading efficiency, respectively. In Biot's theory (1941), he suggested that water is not allowed to escape when the external loading is instantly applied on a porous medium. Accordingly, the soil texture sample is considered to be undrained, and the linearized increment of the fluid content is equal to zero. For this reason, water and air can sustain an external loading only partially at the moment it is imposed, leading to an immediate one-dimensional consolidation. On the contrary, Terzaghi (1943) posited that as the external loading is initially applied, it is entirely sustained by the pore fluid. Thus, the initial water and air pressures are equal to the stress of external loading. Numerical calculations of excess pore water pressure and total settlement were made for a soil with clay texture as an illustrative example. A comparative study shows that in the early stage of consolidation, the model of considering loading efficiency generates larger time-dependent total settlement and also has the highest value of excess pore water pressure initially. The physical cause behind this difference is that the initial conditions established from Biot's theory is much smaller, reflecting the soil skeleton to carry most of external load at the moment it is imposed. Our results indicate that, in terms of the initial conditions for water and air pressures, the loading efficiency must be taken into account in the early stage of consolidation.

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.

Enhancing tablet disintegration characteristics of a highly water-soluble high-drug-loading formulation by granulation process.

PubMed

Pandey, Preetanshu; Levins, Christopher; Pafiakis, Steve; Zacour, Brian; Bindra, Dilbir S; Trinh, Jade; Buckley, David; Gour, Shruti; Sharif, Shasad; Stamato, Howard

2018-07-01

The objective of this study was to improve the disintegration and dissolution characteristics of a highly water-soluble tablet matrix by altering the manufacturing process. A high disintegration time along with high dependence of the disintegration time on tablet hardness was observed for a high drug loading (70% w/w) API when formulated using a high-shear wet granulation (HSWG) process. Keeping the formulation composition mostly constant, a fluid-bed granulation (FBG) process was explored as an alternate granulation method using a 2 (4-1) fractional factorial design with two center points. FBG batches (10 batches) were manufactured using varying disingtegrant amount, spray rate, inlet temperature (T) and atomization air pressure. The resultant final blend particle size was affected significantly by spray rate (p = .0009), inlet T (p = .0062), atomization air pressure (p = .0134) and the interaction effect between inlet T*spray rate (p = .0241). The compactibility of the final blend was affected significantly by disintegrant amount (p < .0001), atomization air pressure (p = .0013) and spray rate (p = .05). It was observed that the fluid-bed batches gave significantly lower disintegration times than the HSWG batches, and mercury intrusion porosimetry data revealed that this was caused by the higher internal pore structure of tablets manufactured using the FBG batches.

Hydrogen Tank Project Q2 Report - FY 11

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

Johnson, Kenneth I.; Alvine, Kyle J.; Skorski, Daniel C.

2011-05-15

Quarterly report that represents PNNL's results of HDPE, LDPE, and industrial polymer materials testing. ASTM D638 type 3 samples were subjected to a high pressure hydrogen environment between 3000 and 4000 PSI. These samples were tested using an instron load frame and were analyzed using a proprietary set of excel macros to determine trends in data. The development of an in-situ high pressure hydrogen tensile testing apparatus is discussed as is the stress modeling of the carbon fiber tank exterior.

Structural integrated sensor and actuator systems for active flow control

NASA Astrophysics Data System (ADS)

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

2016-04-01

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

Measurement and interpretation of threshold stress intensity factors for steels in high-pressure hydrogen gas.

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

Dadfarnia, Mohsen; Nibur, Kevin A.; San Marchi, Christopher W.

2010-07-01

Threshold stress intensity factors were measured in high-pressure hydrogen gas for a variety of low alloy ferritic steels using both constant crack opening displacement and rising crack opening displacement procedures. The sustained load cracking procedures are generally consistent with those in ASME Article KD-10 of Section VIII Division 3 of the Boiler and Pressure Vessel Code, which was recently published to guide design of high-pressure hydrogen vessels. Three definitions of threshold were established for the two test methods: K{sub THi}* is the maximum applied stress intensity factor for which no crack extension was observed under constant displacement; K{sub THa} ismore » the stress intensity factor at the arrest position for a crack that extended under constant displacement; and K{sub JH} is the stress intensity factor at the onset of crack extension under rising displacement. The apparent crack initiation threshold under constant displacement, K{sub THi}*, and the crack arrest threshold, K{sub THa}, were both found to be non-conservative due to the hydrogen exposure and crack-tip deformation histories associated with typical procedures for sustained-load cracking tests under constant displacement. In contrast, K{sub JH}, which is measured under concurrent rising displacement and hydrogen gas exposure, provides a more conservative hydrogen-assisted fracture threshold that is relevant to structural components in which sub-critical crack extension is driven by internal hydrogen gas pressure.« less

Measurement and interpretation of threshold stress intensity factors for steels in high-pressure hydrogen gas.

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

Nibur, Kevin A.

2010-11-01

Threshold stress intensity factors were measured in high-pressure hydrogen gas for a variety of low alloy ferritic steels using both constant crack opening displacement and rising crack opening displacement procedures. The sustained load cracking procedures are generally consistent with those in ASME Article KD-10 of Section VIII Division 3 of the Boiler and Pressure Vessel Code, which was recently published to guide design of high-pressure hydrogen vessels. Three definitions of threshold were established for the two test methods: K{sub THi}* is the maximum applied stress intensity factor for which no crack extension was observed under constant displacement; K{sub THa} ismore » the stress intensity factor at the arrest position for a crack that extended under constant displacement; and K{sub JH} is the stress intensity factor at the onset of crack extension under rising displacement. The apparent crack initiation threshold under constant displacement, K{sub THi}*, and the crack arrest threshold, K{sub THa}, were both found to be non-conservative due to the hydrogen exposure and crack-tip deformation histories associated with typical procedures for sustained-load cracking tests under constant displacement. In contrast, K{sub JH}, which is measured under concurrent rising displacement and hydrogen gas exposure, provides a more conservative hydrogen-assisted fracture threshold that is relevant to structural components in which sub-critical crack extension is driven by internal hydrogen gas pressure.« less

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...

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.

Mimosa-inspired design of a flexible pressure sensor with touch sensitivity.

PubMed

Su, Bin; Gong, Shu; Ma, Zheng; Yap, Lim Wei; Cheng, Wenlong

2015-04-24

A bio-inspired flexible pressure sensor is generated with high sensitivity (50.17 kPa(-1)), quick responding time (<20 ms), and durable stability (negligible loading-unloading signal changes over 10 000 cycles). Notably, the key resource of surface microstructures upon sensor substrates results from the direct molding of natural mimosa leaves, presenting a simple, environment-friendly and easy scale-up fabrication process for these flexible pressure sensors. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Experimental measurement and thermodynamic modeling of the solubility of carbon dioxide in aqueous blends of monoethanolamine and diethanolamine

NASA Astrophysics Data System (ADS)

Suleman, Humbul; Maulud, Abdulhalim Shah; Man, Zakaria

2017-12-01

In this study, the solubilities of carbon dioxide in aqueous mixtures of monoethanolamine (MEA) and diethanolamine (DEA) were determined using a high pressure vapor-liquid equilibrium apparatus. The carbon dioxide loadings (mole of CO2/mole of amine mixture) were reported for a wide range of temperature (303.15, 323.15, 343.15 K) and pressure (100 - 4100 kPa). The carbon dioxide solubility shows an increase with increase in pressure and amine concentration and a decrease with increase in temperature in the aqueous blends of MEA and DEA. At carbon dioxide loadings above 1.0, the carbon dioxide solubility becomes a weak function of pressure and follows the general trend of carbon dioxide solubility in aqueous alkanolamines. The new experimental data points determined in this study were correlated by using a recently developed, enhanced Kent-Eisenberg model. An average absolute relative error of 9.4 % was observed between the model results and experimental data, indicating good correlative capability of the thermodynamic model.

Effects of microbial loading and sporulation temperature on atmospheric plasma inactivation of Bacillus subtilis spores

NASA Astrophysics Data System (ADS)

Deng, X. T.; Shi, J. J.; Shama, G.; Kong, M. G.

2005-10-01

Current inactivation studies of Bacillus subtilis spores using atmospheric-pressure glow discharges (APGD) do not consider two important factors, namely microbial loading at the surface of a substrate and sporulation temperature. Yet these are known to affect significantly microbial resistance to heat and hydrogen peroxide. This letter investigates effects of microbial loading and sporulation temperature on spore resistance to APGD. It is shown that microbial loading can lead to a stacking structure as a protective shield against APGD treatment and that high sporulation temperature increases spore resistance by altering core water content and cross-linked muramic acid content of B. subtilis spores.

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.

Compressive behavior of fine sand.

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

Martin, Bradley E.; Kabir, Md. E.; Song, Bo

2010-04-01

The compressive mechanical response of fine sand is experimentally investigated. The strain rate, initial density, stress state, and moisture level are systematically varied. A Kolsky bar was modified to obtain uniaxial and triaxial compressive response at high strain rates. A controlled loading pulse allows the specimen to acquire stress equilibrium and constant strain-rates. The results show that the compressive response of the fine sand is not sensitive to strain rate under the loading conditions in this study, but significantly dependent on the moisture content, initial density and lateral confinement. Partially saturated sand is more compliant than dry sand. Similar trendsmore » were reported in the quasi-static regime for experiments conducted at comparable specimen conditions. The sand becomes stiffer as initial density and/or confinement pressure increases. The sand particle size become smaller after hydrostatic pressure and further smaller after dynamic axial loading.« less

Load-Dependent Emission Factors and Chemical Characteristics of IVOCs from a Medium-Duty Diesel Engine.

PubMed

Cross, Eben S; Sappok, Alexander G; Wong, Victor W; Kroll, Jesse H

2015-11-17

A detailed understanding of the climate and air quality impacts of mobile-source emissions requires the characterization of intermediate-volatility organic compounds (IVOCs), relatively-low-vapor-pressure gas-phase species that may generate secondary organic aerosol with high yields. Due to challenges associated with IVOC detection and quantification, IVOC emissions remain poorly understood at present. Here, we describe measurements of the magnitude and composition of IVOC emissions from a medium-duty diesel engine. Measurements are made on an engine dynamometer and utilize a new mass-spectrometric instrument to characterize the load dependence of the emissions in near-real-time. Results from steady-state engine operation indicate that IVOC emissions are highly dependent on engine power, with highest emissions at engine idle and low-load operation (≤25% maximum rated power) with a chemical composition dominated by saturated hydrocarbon species. Results suggest that unburned fuel components are the dominant IVOCs emitted at low loads. As engine load increases, IVOC emissions decline rapidly and become increasingly characterized by unsaturated hydrocarbons and oxygenated organics, newly formed from incomplete combustion processes at elevated engine temperatures and pressures. Engine transients, including a cold-start ignition and engine acceleration, show IVOC emission profiles that are different in amount or composition compared to steady-state combustion, underscoring the utility of characterizing IVOC emissions with high time resolution across realistic engine operating conditions. We find possible evidence for IVOC losses on unheated dilution and sampling surfaces, which need to be carefully accounted for in IVOC emission studies.

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.

Tribological characteristics of perfluoropolyether liquid lubricants under sliding conditions in high vacuum

NASA Technical Reports Server (NTRS)

Masuko, Masabumi; Jones, William R., Jr.; Helmick, Larry S.

1993-01-01

Tribological characteristics of three PFPE's (Fomblin Z, Demnum, and Krytox) were studied under high vacuum using a four-ball apparatus with 440C steel specimens. Fomblin Z and Demnum exhibited initial scuffing-like high friction whereas Krytox did not. Steady state friction with Fomblin Z was the lowest among the three oils. Frictional values for Demnum and Krytox were almost the same. The lowest wear rate in air was provided by Krytox regardless of load, and low wear rates in vacuum at high load were achieved with Krytox and Demnum. Results are explained by reactivity and pressure-viscosity characteristics of the oils.

[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.

A case study of the fluid structure interaction of a Francis turbine

NASA Astrophysics Data System (ADS)

Müller, C.; Staubli, T.; Baumann, R.; Casartelli, E.

2014-03-01

The Francis turbine runners of the Grimsel 2 pump storage power plant showed repeatedly cracks during the last decade. It is assumed that these cracks were caused by flow induced forces acting on blades and eventual resonant runner vibrations lead to high stresses in the blade root areas. The eigenfrequencies of the runner were simulated in water using acoustic elements and compared to experimental data. Unsteady blades pressure distribution determined by a transient CFD simulation of the turbine were coupled to a FEM simulation. The FEM simulation enabled analyzing the stresses in the runner and the eigenmodes of the runner vibrations. For a part-load operating point, transient CFD simulations of the entire turbine, including the spiral case, the runner and the draft tube were carried out. The most significant loads on the turbine runner resulted from the centrifugal forces and the fluid forces. Such forces effect temporally invariant runner blades loads, in contrast rotor stator interaction or draft tube instabilities induce pressure fluctuations which cause the temporally variable forces. The blades pressure distribution resulting from the flow simulation was coupled by unidirectional-harmonic FEM simulation. The dominant transient blade pressure distribution of the CFD simulation were Fourier transformed, and the static and harmonic portion assigned to the blade surfaces in the FEM model. The evaluation of the FEM simulation showed that the simulated part load operating point do not cause critical stress peaks in the crack zones. The pressure amplitudes and frequencies are very small and interact only locally with the runner blades. As the frequencies are far below the modal frequencies of the turbine runner, resonant vibrations obviously are not excited.

High-pressure phase transition in silicon carbide under shock loading using ultrafast x-ray diffraction

NASA Astrophysics Data System (ADS)

Tracy, S. J.; Smith, R. F.; Wicks, J. K.; Fratanduono, D. E.; Gleason, A. E.; Bolme, C.; Speziale, S.; Appel, K.; Prakapenka, V. B.; Fernandez Panella, A.; Lee, H. J.; MacKinnon, A.; Eggert, J.; Duffy, T. S.

2017-12-01

The behavior of silicon carbide (SiC) under shock loading was investigated through a series of time-resolved pump-probe x-ray diffraction (XRD) measurements. SiC is found at impact sites and has been put forward as a possible constituent in the proposed class of extra-solar planets known as carbon planets. Previous studies have used wave profile measurements to identify a phase transition under shock loading near 1 Mbar, but crystal structure information was not obtained. We have carried out an in situ XRD study of shock-compressed SiC using the Matter in Extreme Conditions instrument of the Linac Coherent Light Source. The femtosecond time resolution of the x-ray free electron laser allows for the determination of time-dependent atomic arrangements during shock loading and release. Two high-powered lasers were used to generate ablation-driven compression waves in the samples. Time scans were performed using the same drive conditions and nominally identical targets. For each shot in a scan, XRD data was collected at a different probe time after the shock had entered the SiC. Probe times extended up to 40 ns after release. Scans were carried out for peak pressures of 120 and 185 GPa. Our results demonstrate that SiC transforms directly from the ambient tetrahedrally-coordinated phase to the octahedral B1 structure on the nanosecond timescale of laser-drive experiments and reverts to the tetrahedrally coordinated ambient phase within nanoseconds of release. The data collected at 120 GPa exhibit diffraction peaks from both compressed ambient phase and transformed B1 phase, while the data at 185 GPa show a complete transformation to the B1 phase. Densities determined from XRD peaks are in agreement with an extrapolation of previous continuum data as well as theoretical predictions. Additionally, a high degree of texture was retained in both the high-pressure phase as well as on back transformation. Two-dimensional fits to the XRD data reveal details of the orientational relationships between the low- and high-pressure phases that can be interpreted to provide information about transformation pathways between tetrahedral and octahedral coordination structures. We acknowledge support for this work from SLAC National Accelerator Laboratory, Lawrence Livermore National Laboratory, and Los Alamos National Laboratory.

AGARD Index of Publications 1983-1985

DTIC Science & Technology

1987-06-01

a high performance high speed General Aviation propeller the advent of the highly loaded program...distribution data at high speed and CLmax data at low speed are NS3-3036# Saab-.;cania, Linkoping (Sweden). described. A flight wing pressure survey which...also well with predictions based on wind tunnel data. flight at high speed and wind tunnel measurements on a half Reynolds Number and transition

46 CFR 54.01-30 - Loadings (modifies UG-22).

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 2 2013-10-01 2013-10-01 false Loadings (modifies UG-22). 54.01-30 Section 54.01-30 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PRESSURE VESSELS General Requirements § 54.01-30 Loadings (modifies UG-22). (a) The loadings for pressure vessels shall be as required by UG-22 of section VIII of the...

46 CFR 54.01-30 - Loadings (modifies UG-22).

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 2 2012-10-01 2012-10-01 false Loadings (modifies UG-22). 54.01-30 Section 54.01-30 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PRESSURE VESSELS General Requirements § 54.01-30 Loadings (modifies UG-22). (a) The loadings for pressure vessels shall be as required by UG-22 of section VIII of the...

46 CFR 54.01-30 - Loadings (modifies UG-22).

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 2 2010-10-01 2010-10-01 false Loadings (modifies UG-22). 54.01-30 Section 54.01-30 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PRESSURE VESSELS General Requirements § 54.01-30 Loadings (modifies UG-22). (a) The loadings for pressure vessels shall be as required by UG-22 of section VIII of the...

46 CFR 54.01-30 - Loadings (modifies UG-22).

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 2 2014-10-01 2014-10-01 false Loadings (modifies UG-22). 54.01-30 Section 54.01-30 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PRESSURE VESSELS General Requirements § 54.01-30 Loadings (modifies UG-22). (a) The loadings for pressure vessels shall be as required by UG-22 of section VIII of the...

46 CFR 54.01-30 - Loadings (modifies UG-22).

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 2 2011-10-01 2011-10-01 false Loadings (modifies UG-22). 54.01-30 Section 54.01-30 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PRESSURE VESSELS General Requirements § 54.01-30 Loadings (modifies UG-22). (a) The loadings for pressure vessels shall be as required by UG-22 of section VIII of the...

Worm Gear With Hydrostatic Engagement

NASA Technical Reports Server (NTRS)

Chaiko, Lev I.

1994-01-01

In proposed worm-gear transmission, oil pumped at high pressure through meshes between teeth of gear and worm coil. Pressure in oil separates meshing surfaces slightly, and oil reduces friction between surfaces. Conceived for use in drive train between gas-turbine engine and rotor of helicopter. Useful in other applications in which weight critical. Test apparatus simulates and measures some loading conditions of proposed worm gear with hydrostatic engagement.

The effect of unsteady blade loading on the aeroacoustics of a pusher propeller

NASA Astrophysics Data System (ADS)

Mauk, Clay S.; Farokhi, Saeed

1993-06-01

A theoretical/computational approach is developed to predict the change in near-field noise due to a momentum-deficit upstream of a propeller plane, specifically for a pylon wake in a pusher configuration. The acoustic pressure is computed using blade geometry and unsteady blade surface pressure history. The steady blade surface pressure is predicted using blade-momentum theory and two-dimensional airfoil characteristics. Unsteady blade pressures are derived from in-flight measurements. In-flight acoustic measurements are used for code validation purposes. Overall sound pressure levels (OSPL) are computed for an array of observer locations parallel to the propeller axis of rotation. In order to clearly realize the effect of the wake encounter on the radiated sound, the wake signature is eliminated from the unsteady blade pressures. By subtracting the OSPL computed with the smoothed data from that computed with the original unsteady data, the change in noise resulting from the wake encounter is deduced. In general, the noise was increased due to the propeller-wake chopping activity. For all flight conditions, the largest increase in radiated noise occurred for a highly loaded propeller. The results indicate that the propeller noise due to periodic wake encounter may possess a unique directivity pattern.

Physicomechanical characterization of the extrusion-spheronization process. I. Instrumentation of the extruder.

PubMed

Shah, R D; Kabadi, M; Pope, D G; Augsburger, L L

1994-03-01

Extrusion-spheronization is a popular means of producing spheres which can be coated to form a controlled-release system. In the extrusion process, stress is necessary to force a wet mass through small orifices, and as a result, frictional heat builds up at the screen. Therefore, the quantitative measurement of the screen pressure and screen temperature is described and shown to provide objective measures of extrudability. A strain gauge load cell was mounted tangentially to the screen of a Luwa EXDS-60 extruder with a specifically fabricated holder. The load cell output was calibrated in terms of pressure inside the screen with a special rubber plug system. A fast-response thermocouple was used to measure the screen temperature. Experiments with 50/50 lactose/Avicel PH101 revealed that a linear relationship exists between the amount of water used in the granulation and the screen pressure, that the percentage open area of the screen determines the rank order of the screen pressure, and that the maximal yield of 18/25-mesh cut pellets was uniquely related to the screen pressure. Also, a high degree of correlation was observed between the screen pressure and the screen temperature.

In vitro method for assessing the biomechanics of the patellofemoral joint following total knee arthroplasty.

PubMed

Coles, L G; Gheduzzi, S; Miles, A W

2014-12-01

The patellofemoral joint is a common site of pain and failure following total knee arthroplasty. A contributory factor may be adverse patellofemoral biomechanics. Cadaveric investigations are commonly used to assess the biomechanics of the joint, but are associated with high inter-specimen variability and often cannot be carried out at physiological levels of loading. This study aimed to evaluate the suitability of a novel knee simulator for investigating patellofemoral joint biomechanics. This simulator specifically facilitated the extended assessment of patellofemoral joint biomechanics under physiological levels of loading. The simulator allowed the knee to move in 6 degrees of freedom under quadriceps actuation and included a simulation of the action of the hamstrings. Prostheses were implanted on synthetic bones and key soft tissues were modelled with a synthetic analogue. In order to evaluate the physiological relevance and repeatability of the simulator, measurements were made of the quadriceps force and the force, contact area and pressure within the patellofemoral joint using load cells, pressure-sensitive film, and a flexible pressure sensor. The results were in agreement with those previously reported in the literature, confirming that the simulator is able to provide a realistic physiological loading situation. Under physiological loading, average standard deviations of force and area measurements were substantially lower and comparable to those reported in previous cadaveric studies, respectively. The simulator replicates the physiological environment and has been demonstrated to allow the initial investigation of factors affecting patellofemoral biomechanics following total knee arthroplasty. © IMechE 2014.

Seal Technology for Hypersonic Vehicle and Propulsion: An Overview

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M.

2008-01-01

Hypersonic vehicles and propulsion systems pose an extraordinary challenge for structures and materials. Airframes and engines require lightweight, high-temperature materials and structural configurations that can withstand the extreme environment of hypersonic flight. Some of the challenges posed include very high temperatures, heating of the whole vehicle, steady-state and transient localized heating from shock waves, high aerodynamic loads, high fluctuating pressure loads, potential for severe flutter, vibration, and acoustic loads and erosion. Correspondingly high temperature seals are required to meet these aggressive requirements. This presentation reviews relevant seal technology for both heritage (e.g. Space Shuttle, X-15, and X-38) vehicles and presents several seal case studies aimed at providing lessons learned for future hypersonic vehicle seal development. This presentation also reviews seal technology developed for the National Aerospace Plane propulsion systems and presents several seal case studies aimed at providing lessons learned for future hypersonic propulsion seal development.

Properties of immobile hydrogen confined in microporous carbon

DOE PAGES

Bahadur, Jitendra; Bhabha Atomic Research Centre; Contescu, Cristian I.; ...

2017-03-06

The mobility of H2 confined in microporous carbon was studied as a function of temperature and pressure using inelastic neutron scattering, and the translational and rotational motion of H2 molecules has been probed. At low loading, rotation of H2 molecules adsorbed in the smallest carbon pores (~6 ) is severely hindered, suggesting that the interaction between H2 and the host matrix is anisotropic. At higher loading, H2 molecules behave as nearly free rotor, implying lower anisotropic interactions with adsorption sites. At supercritical temperatures where bulk H2 is a gas, the inelastic spectrum of confined H2 provides evidence of a significantmore » fraction of immobile, solid-like hydrogen. The onset temperature for molecular mobility depends strongly on the loaded amount. The fraction of immobile molecules increases with pressure and attains a plateau at high pressures. Surprisingly, immobile H2 is present even at temperatures as high as ~110 K. This research at ORNL s Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U. S. Department of Energy. This research was supported in part by the ORNL Postdoctoral Research Associates Program, administered jointly by the ORNL and the Oak Ridge Institute for Science and Education. CIC and NCG acknowledge support from the Materials Science and Engineering Division, Office of Basic Energy Sciences, U.S. Department of Energy.« less

Structural Design and Analysis of the Upper Pressure Shell Section of a Composite Crew Module

NASA Technical Reports Server (NTRS)

Sleight, David W.; Paddock, David; Jeans, Jim W.; Hudeck, John D.

2008-01-01

This paper presents the results of the structural design and analysis of the upper pressure shell section of a carbon composite demonstration structure for the Composite Crew Module (CCM) Project. The project is managed by the NASA Engineering and Safety Center with participants from eight NASA Centers, the Air Force Research Laboratory, and multiple aerospace contractors including ATK/Swales, Northrop Grumman, Lockheed Martin, Collier Research Corporation, Genesis Engineering, and Janicki Industries. The paper discusses details of the upper pressure shell section design of the CCM and presents the structural analysis results using the HyperSizer structural sizing software and the MSC Nastran finite element analysis software. The HyperSizer results showed that the controlling load case driving most of the sizing in the upper pressure shell section was the internal pressure load case. The regions around the cutouts were controlled by internal pressure and the main parachute load cases. The global finite element analysis results showed that the majority of the elements of the CCM had a positive margin of safety with the exception of a few hot spots around the cutouts. These hot spots are currently being investigated with a more detailed analysis. Local finite element models of the Low Impact Docking System (LIDS) interface ring and the forward bay gussets with greater mesh fidelity were created for local sizing and analysis. The sizing of the LIDS interface ring was driven by the drogue parachute loads, Trans-Lunar Insertion (TLI) loads, and internal pressure. The drogue parachute loads controlled the sizing of the gusset cap on the drogue gusset and TLI loads controlled the sizing of the other five gusset caps. The main parachute loads controlled the sizing of the lower ends of the gusset caps on the main parachute fittings. The results showed that the gusset web/pressure shell and gusset web/gusset cap interfaces bonded using Pi-preform joints had local hot spots in the Pi-preform termination regions. These regions require a detailed three-dimensional analysis, which is currently being performed, to accurately address the load distribution near the Pi-preform termination in the upper and lower gusset caps.

Steady and unsteady blade stresses within the SSME ATD/HPOTP inducer

NASA Technical Reports Server (NTRS)

Gross, R. Steven

1994-01-01

There were two main goals of the ATD HPOTP (alternate turbopump development)(high pressure oxygen turbopump). First, determine the steady and unsteady inducer blade surface strains produced by hydrodynamic sources as a function of flow capacity (Q/N), suction specific speed (Nss), and Reynolds number (Re). Second, to identify the hydrodynamic source(s) of the unsteady blade strains. The reason the aforementioned goals are expressed in terms of blade strains as opposed to blade hydrodynamic pressures is because of the interest regarding the high cycle life of the inducer blades. This report focuses on the first goal of the test program which involves the determination of the steady and unsteady strain (stress) values at various points within the inducer blades. Strain gages were selected as the strain measuring devices. Concurrent with the experimental program, an analytical study was undertaken to produce a complete NASTRAN finite-element model of the inducer. Computational fluid dynamics analyses were utilized to provide the estimated steady-state blade surface pressure loading needed as load input to the NASTRAN inducer model.

In-flight investigation of shuttle tile pressure orifice installations

NASA Technical Reports Server (NTRS)

Moes, Timothy R.; Meyer, Robert R., Jr.

1990-01-01

To determine shuttle orbiter wing loads during ascent, wing load instrumentation was added to Columbia (OV-102). This instrumentation included strain gages and pressure orifices on the wing. The loads derived from wing pressure measurements taken during STS 61-C did not agree with those derived from strain gage measurements or with the loads predicted from the aerodynamic database. Anomalies in the surface immediately surrounding the pressure orifices in the thermal protection system (TPS) tiles were one possible cause of errors in the loads derived from wing pressure measurements. These surface anomalies were caused by a ceramic filler material which was installed around the pressure tubing. The filler material allowed slight movement of the TPS tile and pressure tube as the airframe flexed and bent under aerodynamic loads during ascent and descent. Postflight inspection revealed that this filler material had protruded from or receeded beneath the surface, causing the orifice to lose its flushness. Flight tests were conducted at NASA Ames Research Center Dryden Flight Research Facility to determine the effects of any anomaly in surface flushness of the orifice installation on the measured pressures at Mach numbers between 0.6 and 1.4. An F-104 aircraft with a flight test fixture mounted beneath the fuselage was used for these flights. Surface flushness anomalies typical of those on the orbiter after flight (STA 61-C) were tested. Also, cases with excessive protrusion and recession of the filler material were tested. This report shows that the anomalies in STS 61-C orifice installations adversely affected the pressure measurements. But the magnitude of the affect was not great enough to account for the discrepancies with the strain gage measurements and the aerodynamic predictions.

Infectious Causes of Cholesteatoma and Treatment of Infected Ossicles prior to Reimplantation by Hydrostatic High-Pressure Inactivation

PubMed Central

Hinz, Rebecca

2015-01-01

Chronic inflammation, which is caused by recurrent infections, is one of the factors contributing to the pathogenesis of cholesteatoma. If reimplantation of autologous ossicles after a surgical intervention is intended, inactivation of planktonic bacteria and biofilms is desirable. High hydrostatic pressure treatment is a procedure, which has been used to inactivate cholesteatoma cells on ossicles. Here we discuss the potential inactivating effect of high hydrostatic pressure on microbial pathogens including biofilms. Recent experimental data suggest an incomplete inactivation at a pressure level, which is tolerable for the bone substance of ossicles and results at least in a considerable reduction of pathogen load. Further studies are necessary to access how far this quantitative reduction of pathogens is sufficient to prevent ongoing chronic infections, for example, due to forming of biofilms. PMID:25705686

Experimental characterization and constitutive modeling of the mechanical behavior of molybdenum under electromagnetically applied compression-shear ramp loading

DOE PAGES

Alexander, C. Scott; Ding, Jow -Lian; Asay, James Russell

2016-03-09

Magnetically applied pressure-shear (MAPS) is a new experimental technique that provides a platform for direct measurement of material strength at extreme pressures. The technique employs an imposed quasi-static magnetic field and a pulsed power generator that produces an intense current on a planar driver panel, which in turn generates high amplitude magnetically induced longitudinal compression and transverse shear waves into a planar sample mounted on the drive panel. In order to apply sufficiently high shear traction to the test sample, a high strength material must be used for the drive panel. Molybdenum is a potential driver material for the MAPSmore » experiment because of its high yield strength and sufficient electrical conductivity. To properly interpret the results and gain useful information from the experiments, it is critical to have a good understanding and a predictive capability of the mechanical response of the driver. In this work, the inelastic behavior of molybdenum under uniaxial compression and biaxial compression-shear ramp loading conditions is experimentally characterized. It is observed that an imposed uniaxial magnetic field ramped to approximately 10 T through a period of approximately 2500 μs and held near the peak for about 250 μs before being tested appears to anneal the molybdenum panel. In order to provide a physical basis for model development, a general theoretical framework that incorporates electromagnetic loading and the coupling between the imposed field and the inelasticity of molybdenum was developed. Based on this framework, a multi-axial continuum model for molybdenum under electromagnetic loading is presented. The model reasonably captures all of the material characteristics displayed by the experimental data obtained from various experimental configurations. Additionally, data generated from shear loading provide invaluable information not only for validating but also for guiding the development of the material model for multiaxial loadings.« less

10 CFR 431.282 - Test Procedures [Reserved

Code of Federal Regulations, 2013 CFR

2013-01-01

... EQUIPMENT Mercury Vapor Lamp Ballasts § 431.282 Definitions concerning mercury vapor lamp ballasts. Ballast...) The arc tube wall loading is in excess of 3 Watts/cm2, including such lamps that are mercury vapor, metal halide, and high-pressure sodium lamps. Mercury vapor lamp means a high intensity discharge lamp...

10 CFR 431.282 - Test Procedures [Reserved

Code of Federal Regulations, 2011 CFR

2011-01-01

... EQUIPMENT Mercury Vapor Lamp Ballasts § 431.282 Definitions concerning mercury vapor lamp ballasts. Ballast...) The arc tube wall loading is in excess of 3 Watts/cm2, including such lamps that are mercury vapor, metal halide, and high-pressure sodium lamps. Mercury vapor lamp means a high intensity discharge lamp...

10 CFR 431.282 - Test Procedures [Reserved

Code of Federal Regulations, 2014 CFR

2014-01-01

... EQUIPMENT Mercury Vapor Lamp Ballasts § 431.282 Definitions concerning mercury vapor lamp ballasts. Ballast...) The arc tube wall loading is in excess of 3 Watts/cm2, including such lamps that are mercury vapor, metal halide, and high-pressure sodium lamps. Mercury vapor lamp means a high intensity discharge lamp...

10 CFR 431.282 - Test Procedures [Reserved

Code of Federal Regulations, 2012 CFR

2012-01-01

... EQUIPMENT Mercury Vapor Lamp Ballasts § 431.282 Definitions concerning mercury vapor lamp ballasts. Ballast...) The arc tube wall loading is in excess of 3 Watts/cm2, including such lamps that are mercury vapor, metal halide, and high-pressure sodium lamps. Mercury vapor lamp means a high intensity discharge lamp...

Dynamic hub load predicts cognitive decline after resective neurosurgery.

PubMed

Carbo, Ellen W S; Hillebrand, Arjan; van Dellen, Edwin; Tewarie, Prejaas; de Witt Hamer, Philip C; Baayen, Johannes C; Klein, Martin; Geurts, Jeroen J G; Reijneveld, Jaap C; Stam, Cornelis J; Douw, Linda

2017-02-07

Resective neurosurgery carries the risk of postoperative cognitive deterioration. The concept of 'hub (over)load', caused by (over)use of the most important brain regions, has been theoretically postulated in relation to symptomatology and neurological disease course, but lacks experimental confirmation. We investigated functional hub load and postsurgical cognitive deterioration in patients undergoing lesion resection. Patients (n = 28) underwent resting-state magnetoencephalography and neuropsychological assessments preoperatively and 1-year after lesion resection. We calculated stationary hub load score (SHub) indicating to what extent brain regions linked different subsystems; high SHub indicates larger processing pressure on hub regions. Dynamic hub load score (DHub) assessed its variability over time; low values, particularly in combination with high SHub values, indicate increased load, because of consistently high usage of hub regions. Hypothetically, increased SHub and decreased DHub relate to hub overload and thus poorer/deteriorating cognition. Between time points, deteriorating verbal memory performance correlated with decreasing upper alpha DHub. Moreover, preoperatively low DHub values accurately predicted declining verbal memory performance. In summary, dynamic hub load relates to cognitive functioning in patients undergoing lesion resection: postoperative cognitive decline can be tracked and even predicted using dynamic hub load, suggesting it may be used as a prognostic marker for tailored treatment planning.

Dynamic Response and Failure Mechanism of Brittle Rocks Under Combined Compression-Shear Loading Experiments

NASA Astrophysics Data System (ADS)

Xu, Yuan; Dai, Feng

2018-03-01

A novel method is developed for characterizing the mechanical response and failure mechanism of brittle rocks under dynamic compression-shear loading: an inclined cylinder specimen using a modified split Hopkinson pressure bar (SHPB) system. With the specimen axis inclining to the loading direction of SHPB, a shear component can be introduced into the specimen. Both static and dynamic experiments are conducted on sandstone specimens. Given carefully pulse shaping, the dynamic equilibrium of the inclined specimens can be satisfied, and thus the quasi-static data reduction is employed. The normal and shear stress-strain relationships of specimens are subsequently established. The progressive failure process of the specimen illustrated via high-speed photographs manifests a mixed failure mode accommodating both the shear-dominated failure and the localized tensile damage. The elastic and shear moduli exhibit certain loading-path dependence under quasi-static loading but loading-path insensitivity under high loading rates. Loading rate dependence is evidently demonstrated through the failure characteristics involving fragmentation, compression and shear strength and failure surfaces based on Drucker-Prager criterion. Our proposed method is convenient and reliable to study the dynamic response and failure mechanism of rocks under combined compression-shear loading.

The effects of backpack loads and spinal stabilization exercises on the dynamic foot pressure of elementary school children with idiopathic scoliosis

PubMed Central

Lee, Suemin; Shim, Jemyung

2015-01-01

[Purpose] The purpose of this study was to measure and observe the changes in dynamic plantar pressures when school children carried specific bag loads, and to determine whether improved physical balance after an eight-week spinal stabilization exercise program can influences plantar pressures. [Subjects] The subjects were 10 school students with Cobb angles of 10° or greater. [Methods] Gait View Pro 1.0 (Alfoots, Korea) was were based on to measure the pressure of the participants’ feet. Spinal stabilization exercises used TOGU Multi-roll Functional (TOGU, Germany) training. Dynamic plantar pressures were measured with bag loads of 0% no bag and 15% of subjects’ body weight. The independent t test was performed to analyze changes in plantar pressures. [Results] The plantar pressure measurements of bag load of 0% of subjects’ body weight before and after the spinal stabilization exercise program were not significantly different, but those of two foot areas with a 15% load were statistically significant (mt5, 67.32±24.25 and 51.77±25.52 kPa; lat heel, 126.00±20.46 and 102.08±23.87 kPa). [Conclusion] After performance of the spinal stabilization exercises subjects’ overall plantar pressures were reduced, which may suggest that physical balance improved. PMID:26311964

Effect of high pressure pasteurization on bacterial load and bioactivity of Echinacea purpurea.

PubMed

Chen, Xiu-Min; Hu, Chun; Raghubeer, Errol; Kitts, David D

2010-09-01

High hydrostatic pressure (HHP) technology was applied to organic Echinacea purpurea (E. purpurea) roots and flowers to determine the feasibility of using this technology for cold herb pasteurization, to produce microbiologically safe and shelf-stable products for the natural health products (NHPs) industry. HHP significantly (P < 0.01) reduced microbial contamination in both roots and flowers without affecting the phytochemical retention of chicoric and chlorogenic acids, and total alkamide contents. The antioxidant activity of E. purpurea methanol-derived extracts, evaluated in both chemical (2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) [ABTS] and oxygen radical absorption capacity [ORAC] assay) and in cell culture models (RAW264, 7 macrophage, H(2)O(2)-induced intracellular oxidation, and lipopolysaccharide [LPS]-induced nitric oxide production), was not adversely affected by the application of HHP at both 2 and 5 min at 600 mPa. Furthermore, HHP did not affect the capacity of E. purpurea extracts to suppress nitric oxide production in LPS-activated macrophage cells. Therefore, our results show that HHP is an effective pasteurization process treatment to reduce microbial-contamination load while not adversely altering chemical and bioactive function of active constituents present in organic E. purpurea. Our study reports for the first time, the effectiveness of using high hydrostatic pressure (HHP) technology pressure to pasteurize E. purpurea root and flower, and the comparative retention of bioactive phytochemicals. Therefore, this technique can be used in food and natural health product industries to produce high-quality, microbiologically safe, and shelf-stable products.

Fracture control method for composite tanks with load sharing liners

NASA Technical Reports Server (NTRS)

Bixler, W. D.

1975-01-01

The experimental program was based on the premise that the plastic sizing cycle, which each pressure vessel is subjected to prior to operation, acts as an effective proof test of the liner, screening out all flaws or cracks larger than a critical size. In doing so, flaw growth potential is available for cyclic operation at pressures less than the sizing pressure. Static fracture and cyclic life tests, involving laboratory type specimens and filament overwrapped tanks, were conducted on three liner materials: (1) 2219-T62 aluminum, (2) Inconel X750 STA, and (3) cryoformed 301 stainless steel. Variables included material condition, thickness, flaw size, flaw shape, temperature, sizing stress level, operating stress level and minimum-to-maximum operating stress ratio. From the empirical data base obtained, a procedure was established by which the service life of composite tanks with load sharing liners could be guaranteed with a high degree of confidence.

Thermodynamic performance testing of the orbiter flash evaporator system

NASA Technical Reports Server (NTRS)

Jaax, J. R.; Melgares, M. A.; Frahm, J. P.

1980-01-01

System level testing of the space shuttle orbiter's development flash evaporator system (FES) was performed in a thermal vacuum chamber capable of simulating ambient ascent, orbital, and entry temperature and pressure profiles. The test article included the evaporator assembly, high load and topping exhaust duct and nozzle assemblies, and feedwater supply assembly. Steady state and transient heat load, water pressure/temperature and ambient pressure/temperature profiles were imposed by especially designed supporting test hardware. Testing in 1978 verified evaporator and duct heater thermal design, determined FES performance boundaries, and assessed topping evaporator plume characteristics. Testing in 1979 combined the FES with the other systems in the orbiter active thermal control subsystem (ATCS). The FES met or exceeded all nominal and contingency performance requirements during operation with the integrated ATCS. During both tests stability problems were encountered during steady state operations which resulted in subsequent design changes to the water spray nozzle and valve plate assemblies.

Heat-transfer and pressure measurements on a simulated elevon deflected 30 deg near flight conditions at Mach 7

NASA Technical Reports Server (NTRS)

Johnson, C. B.; Taylor, A. H.; Weinstein, I.

1977-01-01

Heat transfer rates and pressures were obtained on an elevon plate (deflected 30 deg) and a flat plate upstream of the elevon in an 8 foot high-temperature structures tunnel. The flight Reynolds number and flight total enthalpy for altitudes of 26.8 km and 28.7 km at Mach seven were duplicated. The heat transfer and pressure data were used to establish heating and pressure loads. The measured heating was compared with several theoretical predictions, and the closest agreement obtained with a Schultz-Grunow reference enthalpy method of calculation.

Two-phase flows within systems with ambient pressure

NASA Technical Reports Server (NTRS)

Hendricks, R. C.; Braun, M. J.; Wheeler, R. L., III; Mullen, R. L.

1985-01-01

In systems where the design inlet and outlet pressures are maintained above the thermodynamic critical pressure, it is often assumed that two phase flows within the system cannot occur. Designers rely on this simple rule of thumb to circumvent problems associated with a highly compressible two phase flow occurring within the supercritical pressure system along with the uncertainties in rotordynamics, load capacity, heat transfer, fluid mechanics, and thermophysical property variations. The simple rule of thumb is adequate in many low power designs but is inadequate for high performance turbomachines and linear systems, where two phase regions can exist even though outlet pressure is greater than critical pressure. Rotordynamic-fluid-mechanic restoring forces depend on momentum differences, and those for a two phase zone can differ significantly from those for a single-phase zone. Using the Reynolds equation the angular velocity, eccentricity, geometry, and ambient conditions are varied to determine the point of two phase flow incipience.

Pressure signatures can influence tissue response for individuals supported on an alternating pressure mattress.

PubMed

Chai, C Y; Sadou, O; Worsley, P R; Bader, D L

2017-08-01

Prolonged mechanical loading can lead to the breakdown of skin and underlying tissues which can, in turn, develop into a pressure ulcer. The benefits of pressure relief and/or redistribution to minimise risk have been well documented. Manufacturers have developed alternating air pressure mattresses (APAMs) to provide periodic relief for individuals on prolonged bed-rest. The present study describes the development of a control system, termed Pneumatic Manager which can vary the signature of an APAM, namely its pressure amplitude, cell profile and cycle period. An experimental array was designed to investigate the effects of varying these parameters, particularly with respect to its ability to maintain skin viability in a group of five healthy volunteers lying in a supine position. Transcutaneous gas (T c PO 2 /T c PCO 2 ) tensions at the sacrum were monitored. In addition, pressures and microclimate parameters at the loaded support interface were also measured. In the majority of test conditions the alternating support produced sacral T c PO 2 values, which either remained relatively high or fluctuated in concert with cycle period providing adequate viability. However, in 46% of cases at the extreme pressure amplitude of 100/0 mmHg, there was compromise to the skin viability at the sacrum, as reflected in depressed T c PO 2 levels associated with an elevation of T c PCO 2 levels above the normal range. In all cases, both the humidity and temperature levels increased during the test period. It is interesting to note that interface pressures at the sacrum rarely exceeded 60 mmHg. Although such studies need to be extended to involve bed-bound individuals, the results provide a design template for the optimum pressure signatures of APAM systems to ensure maintenance of skin viability during pronged loading. Copyright © 2017 Tissue Viability Society. Published by Elsevier Ltd. All rights reserved.

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.

An experimental study of the sources of fluctuating pressure loads beneath swept shock/boundary-layer interactions

NASA Technical Reports Server (NTRS)

Settles, G. S.; Garg, S.

1993-01-01

An experimental research program providing basic knowledge and establishing a database on the fluctuating pressure loads produced on aerodynamic surfaces beneath three dimensional shock wave/boundary layer interactions is described. Such loads constitute a fundamental problem of critical concern to future supersonic and hypersonic flight vehicles. A turbulent boundary layer on a flat plate is subjected to interactions with swept planar shock waves generated by sharp fins at angle of attack. Fin angles from 10 to 20 deg at freestream Mach numbers of 3 and 4 produce a variety of interaction strengths from weak to very strong. Miniature Kulite pressure transducers flush-mounted in the flat plate are used to measure interaction-induced wall pressure fluctuations. The distributions of properties of the pressure fluctuations, such as their ring levels, amplitude distributions, and power spectra, are also determined. Measurements were made for the first time in the aft regions of these interactions, revealing fluctuating pressure levels as high as 160 dB. These fluctuations are dominated by low frequency (0-5 kHz) signals. The maximum ring levels in the interactions show an increasing trend with increasing interaction strength. On the other hand, the maximum ring levels in the forward portion of the interactions decrease linearly with increasing interaction sweep back. These ring pressure distributions and spectra are correlated with the features of the interaction flowfield. The unsteadiness of the off-surface flowfield is studied using a new, non-intrusive technique based on the shadow graph method. The results indicate that the entire lambda-shock structure generated by the interaction undergoes relatively low-frequency oscillations. Some regions where particularly strong fluctuations are generated were identified. Fluctuating pressure measurements are also made along the line of symmetry of an axisymmetric jet impinging upon a flat plate at an angle. This flow was chosen as a simple analog to the impinging jet region found in the rear portion of the shock wave/boundary layer interactions under study. It is found that a sharp peak in ring pressure level exists at or near the mean stagnation point. It is suggested that the phenomena responsible for this peak may be active in the swept interactions as well, and may cause the extremely high fluctuating pressures observed in the impinging jet region in the present experimental program.

Toward Understanding Tip Leakage Flows in Small Compressor Cores Including Stator Leakage Flow

NASA Technical Reports Server (NTRS)

Berdanier, Reid A.; Key, Nicole L.

2017-01-01

The focus of this work was to provide additional data to supplement the work reported in NASA/CR-2015-218868 (Berdanier and Key, 2015b). The aim of that project was to characterize the fundamental flow physics and the overall performance effects due to increased rotor tip clearance heights in axial compressors. Data have been collected in the three-stage axial research compressor at Purdue University with a specific focus on analyzing the multistage effects resulting from the tip leakage flow. Three separate rotor tip clearances were studied with nominal tip clearance gaps of 1.5 percent, 3.0 percent, and 4.0 percent based on a constant annulus height. Overall compressor performance was previously investigated at four corrected speedlines (100 percent, 90 percent, 80 percent, and 68 percent) for each of the three tip clearance configurations. This study extends the previously published results to include detailed steady and time-resolved pressure data at two loading conditions, nominal loading (NL) and high loading (HL), on the 100 percent corrected speedline for the intermediate clearance level (3.0 percent). Steady detailed radial traverses of total pressure at the exit of each stator row are supported by flow visualization techniques to identify regions of flow recirculation and separation. Furthermore, detailed radial traverses of time-resolved total pressures at the exit of each rotor row have been measured with a fast-response pressure probe. These data were combined with existing three-component velocity measurements to identify a novel technique for calculating blockage in a multistage compressor. Time-resolved static pressure measurements have been collected over the rotor tips for all rotors with each of the three tip clearance configurations for up to five loading conditions along the 100 percent corrected speedline using fast-response piezoresistive pressure sensors. These time-resolved static pressure measurements reveal new knowledge about the trajectory of the tip leakage flow through the rotor passage. Further, these data extend previous measurements identifying a modulation of the tip leakage flow due to upstream stator wake propagation. Finally, a novel instrumentation technique has been implemented to measure pressures in the shrouded stator cavities. These data provide boundary conditions relating to the flow across the shrouded stator knife seal teeth. Moreover, the utilization of fast-response pressure sensors provides a new look at the time-resolved pressure field, leading to instantaneous differential pressures across the seal teeth. Ultimately, the data collected for this project represent a unique data set which contributes to build a better understanding of the tip leakage flow field and its associated loss mechanisms. These data will facilitate future engine design goals leading to small blade heights in the rear stages of high pressure compressors and aid in the development of new blade designs which are desensitized to the performance penalties attributed to rotor tip leakage flows.

Fatigue crack growth behavior of pressure vessel steels and submerged arc weldments in a high-temperature pressurized water environment

NASA Astrophysics Data System (ADS)

Liaw, P. K.; Logsdon, W. A.; Begley, J. A.

1989-10-01

The fatigue crack growth rate (FCGR) properties of SA508 C1 2a and SA533 Gr A C1 2 pressure vessel steels and the corresponding automatic submerged are weldments were developed in a high-temperature pressurized water (HPW) environment at 288 °C (550°F) and 7.2 MPa (1044 psi) at load ratios of 0.02 and 0.50. The HPW enviromment FCGR properties of these pressure vessel steels and submerged arc weldments were generally conservative, compared with the approrpriate American Society of Mechanical Engineers (ASME) Section XI water environmental reference curve. The growth rate of fatigue cracks in the base materials, however, was considerably faster in the HPW environment than in a corresponding 288°C (550°F) base line air environment. The growth rate of fatigue cracks in the two submerged are weldments was also accelerated in the HPW environment but to a significantly lesser degree than that demonstrated by the corresponding base materials. In the air environment, fatigue striations were observed, independent of material and load ratio, while in the HPW environment, some intergranular facets were present. The greater environmental effect on crack growth rates displayed by the base materials, as compared with the weldments, was attributed to a different sulfide composition and morphology.

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

Hess, Mark Harry; Hutsel, Brian Thomas; Jennings, Christopher Ashley

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

Spatial Distribution of Amorphization Intensity in Boron Carbide During Rate-Dependent Indentation and Impact Processes

NASA Astrophysics Data System (ADS)

Parsard, Gregory G.

Boron carbide is a lightweight ceramic commonly used in applications requiring high hardness. At sufficiently high stresses, the material experiences a localized phase transformation (amorphization) which seemingly weakens its structure. Raman spectroscopy is used to distinguish these transformed regions from crystalline material based on the evolution of new peaks in collected Raman spectra. Vickers indentations of various loads were created at quasistatic and dynamic strain rates to trigger amorphization. The resulting imprints and subsurface regions were scanned with Raman spectroscopy to map amorphization intensity at several depths to generate three-dimensional representations of the amorphized zones, which were analyzed to determine the influence of load and strain rate upon amorphized zone characteristics. The square of amorphized zone depth beneath Vickers indentations increases linearly with load and shows little to no strain rate dependence. Sudden decreases in amorphization intensity at certain depths coincided with the presence of lateral cracks, suggesting that lateral cracks may lead to a loss of amorphized material during mechanical polishing. Experimental results were compared against finite element simulations to estimate critical values of stress and strain associated with amorphization. Raman spectra were also analyzed to determine the indentation-induced residual compressive pressure in crystalline boron carbide. In unstressed crystalline boron carbide, a peak exists near 1088 cm-1 which shifts to higher wavenumbers with the application of compressive pressure. The change in position of this crystalline peak was tracked across surfaces at various depths beneath the indentations and then converted into pressure using the piezospectroscopic coefficient of boron carbide. Residual compressive pressures on the order of gigapascals were found near the indentations, with stress relaxation near regions affected by radial cracks, spall, and graphitic inclusions. These measured residual compressive pressures were consistently higher than those predicted by finite element simulations at various loads, suggesting that amorphization, which was not accounted for by the simulations, may increase compressive residual stress in the crystalline material. Amorphization may cause affected regions to expand relative to their formerly crystalline state and exerting radial compressive forces upon the surrounding crystalline regions and circumferential tension along its boundary, thus promoting crack propagation within the amorphized region.

Slip measurement in a frictional connection by torsional LDV

NASA Astrophysics Data System (ADS)

Schäfer, Günter; Lohrengel, Armin; Hilgermann, Jan Lukas

2016-06-01

Frictional shaft-hub connections are often used in drive train applications. The classic version is fitted by a temperature difference between the cold shaft und the hot hub, or simply axial press-fitted at room temperature. The critical point in this type of connection is the contact pressure at the edge of the hub regarding the relative deformation between the shaft and the hub under dynamic operating loads. Another innovative version, the internal press-fit, leads to a tolerance insensitive lightweight design using a tube as shaft and a controlled plastic deformation by internal high pressure. The internal press-fit connection is a special research topic at the IMW, TU Clausthal. The use of internal high pressure allows to trigger the contact pressure at the edge of the hub on an optimum value. The product of contact pressure and slipway is the key value to determine the fatigue resistance and load capacity of this kind of connection. /1/ and /2/ defined a critical range of slipway amplitudes between 5 and 25 µm for fretting. The normal use and main function of a shaft-hub connection is the transmission of torque. Regarding the different torsional stiffness of the shaft and the hub, there will be a difference in deformation in the contact zone between the shaft and the hub, which is necessary to measure on a probe under oscillating torque load. The measurement on the test-rig in /3/ was done with a POLYTEC torsional LDV (controller OFV-4000, sensor head OFV-400). In general the continuously oscillating torque load allowed a serial measurement of the torsional movement of the shaft and the hub. The difference of the two maximum values is the expected slipway between the two parts in the critical zone at the edge of the hub. The main benefits of the Torsional LDV in this application are the very small measuring point (next to the contact), no influence on the probe, no special preparation of the probe and a really good resolution. The paper gives an overview to the technical background of the measured value, to the measuring setup, to the other used measuring techniques and to the measuring results.

Compatibility of an Ultraselective Microcatheter and Epirubicin Loaded 300–500-μm DC Bead in Ex Vivo Study

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

Fukuoka, Yasushi, E-mail: miyano.y.fukuoka@gmail.com; Tanaka, Toshihiro, E-mail: toshihir@bf6.so-net.ne.jp; Nishiofuku, Hideyuki, E-mail: nishiofukuhideyuki@yahoo.co.jp

PurposeThe purpose of this study is to examine whether epirubicin loaded DC Bead 300–500 μm in size can pass through a 1.8-Fr ultraselective microcatheter in ex vivo study.MethodsEpirubicin (25 mg/1 mL) loaded 100–300 and 300–500 μm DC Bead were tested. Both sizes were diluted 5, 10, and 30 times using contrast material. Ultraselective microcatheter with the outer diameter of 1.8 Fr and the inner diameter of .017 inch (431.8 μm) was used. The diluted DC Bead was injected at a speed of 1 mL/min, and the pressure was continuously measured. The microspheres’ shapes after ejection were observed by a stereomicroscope.ResultsThe maximum pressure of contrast material alone was 8.40 ± 0.21 psi.more » The maximum pressure in 5, 10, and 30 times dilution groups of 100–300 μm were 9.67 ± 1.18, 9.25 ± 0.25, and 9.71 ± 0.28 psi, respectively, whereas 21.10 ± 10.2, 10.48 ± 2.14, 10.09 ± 0.37 psi, respectively in 300–500 μm groups. The maximum pressure in 5 times dilution group of 300–500 μm was significantly higher than the other groups (P < 0.05). In 300–500 μm, 4 of 10 measurements showed high pressure over 24 psi (the maximum value was 43.5 psi) in 5 times dilution group, whereas in 10 times and 30 times dilution groups, all measurements showed less than 12 psi. No damages of microspheres were found.ConclusionsEpirubicin loaded DC Bead 300–500 μm in size can pass through a 1.8-Fr ultraselective microcatheter. To avoid high resistance due to microspheres’ aggregation, dilution more than 10 times is needed.« less

Algae separation from urban landscape water using a high density microbubble layer enhanced by micro-flocculation.

PubMed

Chen, Shuwen; Xu, Jingcheng; Liu, Jia; Wei, Qiaoling; Li, Guangming; Huang, Xiangfeng

2014-01-01

Eutrophication of raw water results in outbreaks of algae, which hinders conventional water treatment. In this study, high density microbubble layers combined with micro-flocculation was adopted to remove algae from urban landscape water, and the effects of pressure, hydraulic loading, microbubble layer height and flocculation dosage on the removal efficiency for algae were studied. The greatest removal efficiency for algae, chemical oxygen demand, nitrogen and phosphorus was obtained at 0.42 MPa with hydraulic loading at 5 m/h and a flocculation dosage of 4 mg/L using a microbubble layer with a height of 130 cm. Moreover, the size, clearance distance and concentration of microbubbles were found to be affected by pressure and the height of the microbubble layer. Based on the study, this method was an alternative for algae separation from urban landscape water and water purification.

Vibration characteristics of the HPOTP (High-Pressure Oxygen Turbopump) of the SSME (Space Shuttle Main Engine)

NASA Technical Reports Server (NTRS)

Childs, D. W.; Moyer, D. S.

1984-01-01

Attention is given to rotor dynamic problems that have been encountered and eliminated in the course of Space Shuttle Main Engine (SSME) development, as well as continuing, subsynchronous problems which are being encountered in the development of a 109-percent power level engine. The basic model for the SSME's High Pressure Oxygen Turbopump (HPOTP) encompasses a structural dynamic model for the rotor and housing, and component models for the liquid and gas seals, turbine clearance excitation forces, and impeller diffuser forces. Linear model results are used to examine the synchronous response and stability characteristics of the HPOTP, with attention to bearing load and stability problems associated with the second critical speed. Differences between linear and nonlinear model results are discussed and explained in terms of simple models. Simulation results indicate that while synchronous bearing loads can be reduced, subsynchronous motion is not eliminated by seal modifications.

Development of a three-dimensional multistage inverse design method for aerodynamic matching of axial compressor blading

NASA Astrophysics Data System (ADS)

van Rooij, Michael P. C.

Current turbomachinery design systems increasingly rely on multistage Computational Fluid Dynamics (CFD) as a means to assess performance of designs. However, design weaknesses attributed to improper stage matching are addressed using often ineffective strategies involving a costly iterative loop between blading modification, revision of design intent, and evaluation of aerodynamic performance. A design methodology is presented which greatly improves the process of achieving design-point aerodynamic matching. It is based on a three-dimensional viscous inverse design method which generates the blade camber surface based on prescribed pressure loading, thickness distribution and stacking line. This inverse design method has been extended to allow blading analysis and design in a multi-blade row environment. Blade row coupling was achieved through a mixing plane approximation. Parallel computing capability in the form of MPI has been implemented to reduce the computational time for multistage calculations. Improvements have been made to the flow solver to reach the level of accuracy required for multistage calculations. These include inclusion of heat flux, temperature-dependent treatment of viscosity, and improved calculation of stress components and artificial dissipation near solid walls. A validation study confirmed that the obtained accuracy is satisfactory at design point conditions. Improvements have also been made to the inverse method to increase robustness and design fidelity. These include the possibility to exclude spanwise sections of the blade near the endwalls from the design process, and a scheme that adjusts the specified loading area for changes resulting from the leading and trailing edge treatment. Furthermore, a pressure loading manager has been developed. Its function is to automatically adjust the pressure loading area distribution during the design calculation in order to achieve a specified design objective. Possible objectives are overall mass flow and compression ratio, and radial distribution of exit flow angle. To supplement the loading manager, mass flow inlet and exit boundary conditions have been implemented. Through appropriate combination of pressure or mass flow inflow/outflow boundary conditions and loading manager objectives, increased control over the design intent can be obtained. The three-dimensional multistage inverse design method with pressure loading manager was demonstrated to offer greatly enhanced blade row matching capabilities. Multistage design allows for simultaneous design of blade rows in a mutually interacting environment, which permits the redesigned blading to adapt to changing aerodynamic conditions resulting from the redesign. This ensures that the obtained blading geometry and performance implied by the prescribed pressure loading distribution are consistent with operation in the multi-blade row environment. The developed methodology offers high aerodynamic design quality and productivity, and constitutes a significant improvement over existing approaches used to address design-point aerodynamic matching.

Rocketdyne LOX bearing tester program

NASA Technical Reports Server (NTRS)

Keba, J. E.; Beatty, R. F.

1988-01-01

The cause, or causes, for the Space Shuttle Main Engine ball wear were unknown, however, several mechanisms were suspected. Two testers were designed and built for operation in liquid oxygen to empirically gain insight into the problems and iterate solutions in a timely and cost efficient manner independent of engine testing. Schedules and test plans were developed that defined a test matrix consisting of parametric variations of loading, cooling or vapor margin, cage lubrication, material, and geometry studies. Initial test results indicated that the low pressure pump thrust bearing surface distress is a function of high axial load. Initial high pressure turbopump bearing tests produced the wear phenomenon observed in the turbopump and identified an inadequate vapor margin problem and a coolant flowrate sensitivity issue. These tests provided calibration data of analytical model predictions to give high confidence in the positive impact of future turbopump design modification for flight. Various modifications will be evaluated in these testers, since similar turbopump conditions can be produced and the benefit of the modification will be quantified in measured wear life comparisons.

Cryogenic, high speed, turbopump bearing cooling requirements

NASA Technical Reports Server (NTRS)

Dolan, Fred J.; Gibson, Howard G.; Cannon, James L.; Cody, Joe C.

1988-01-01

Although the Space Shuttle Main Engine (SSME) has repeatedly demonstrated the capability to perform during launch, the High Pressure Oxidizer Turbopump (HPOTP) main shaft bearings have not met their 7.5 hour life requirement. A tester is being employed to provide the capability of subjecting full scale bearings and seals to speeds, loads, propellants, temperatures, and pressures which simulate engine operating conditions. The tester design permits much more elaborate instrumentation and diagnostics than could be accommodated in an SSME turbopump. Tests were made to demonstrate the facilities; and the devices' capabilities, to verify the instruments in its operating environment and to establish a performance baseline for the flight type SSME HPOTP Turbine Bearing design. Bearing performance data from tests are being utilized to generate: (1) a high speed, cryogenic turbopump bearing computer mechanical model, and (2) a much improved, very detailed thermal model to better understand bearing internal operating conditions. Parametric tests were also made to determine the effects of speed, axial loads, coolant flow rate, and surface finish degradation on bearing performance.

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.

Knee Cartilage Thickness, T1ρ and T2 Relaxation Time Are Related to Articular Cartilage Loading in Healthy Adults

PubMed Central

Van Rossom, Sam; Smith, Colin Robert; Zevenbergen, Lianne; Thelen, Darryl Gerard; Vanwanseele, Benedicte; Van Assche, Dieter; Jonkers, Ilse

2017-01-01

Cartilage is responsive to the loading imposed during cyclic routine activities. However, the local relation between cartilage in terms of thickness distribution and biochemical composition and the local contact pressure during walking has not been established. The objective of this study was to evaluate the relation between cartilage thickness, proteoglycan and collagen concentration in the knee joint and knee loading in terms of contact forces and pressure during walking. 3D gait analysis and MRI (3D-FSE, T1ρ relaxation time and T2 relaxation time sequence) of fifteen healthy subjects were acquired. Experimental gait data was processed using musculoskeletal modeling to calculate the contact forces, impulses and pressure distribution in the tibiofemoral joint. Correlates to local cartilage thickness and mean T1ρ and T2 relaxation times of the weight-bearing area of the femoral condyles were examined. Local thickness was significantly correlated with local pressure: medial thickness was correlated with medial condyle contact pressure and contact force, and lateral condyle thickness was correlated with lateral condyle contact pressure and contact force during stance. Furthermore, average T1ρ and T2 relaxation time correlated significantly with the peak contact forces and impulses. Increased T1ρ relaxation time correlated with increased shear loading, decreased T1ρ and T2 relaxation time correlated with increased compressive forces and pressures. Thicker cartilage was correlated with higher condylar loading during walking, suggesting that cartilage thickness is increased in those areas experiencing higher loading during a cyclic activity such as gait. Furthermore, the proteoglycan and collagen concentration and orientation derived from T1ρ and T2 relaxation measures were related to loading. PMID:28076431

Biomechanical effects of sitting with adjustable ischial and lumbar support on occupational low back pain: evaluation of sitting load and back muscle activity

PubMed Central

Makhsous, Mohsen; Lin, Fang; Bankard, James; Hendrix, Ronald W; Hepler, Matthew; Press, Joel

2009-01-01

Background Compared to standing posture, sitting decreases lumbar lordosis, increases low back muscle activity, disc pressure, and pressure on the ischium, which are associated with occupational LBP. A sitting device that reduces spinal load and low back muscle activities may help increase sitting comfort and reduce LBP risk. The objective of this study is to investigate the biomechanical effect of sitting with a reduced ischial support and an enhanced lumbar support (Off-Loading) on load, interface pressure and muscle activities. Methods A laboratory test in low back pain (LBP) and asymptomatic subjects was designed to test the biomechanical effect of using the Off-Loading sitting posture. The load and interface pressure on seat and the backrest, and back muscle activities associated with usual and this Off-Loading posture were recorded and compared between the two postures. Results Compared with Normal (sitting upright with full support of the seat and flat backrest) posture, sitting in Off-Loading posture significantly shifted the center of the force and the peak pressure on the seat anteriorly towards the thighs. It also significantly decreased the contact area on the seat and increased that on the backrest. It decreased the lumbar muscle activities significantly. These effects are similar in individuals with and without LBP. Conclusion Sitting with reduced ischial support and enhanced lumbar support resulted in reduced sitting load on the lumbar spine and reduced the lumbar muscular activity, which may potentially reduce sitting-related LBP. PMID:19193245

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

Pashkin, E. Y.; Pankov, A. M.; Kulnitskiy, B. A.

The behavior of multiwall carbon nanotubes under a high pressure (up to 55 GPa) combined with shear deformation was studied by experimental and theoretical methods. The unexpectedly high stability of the nanotubes' structure under high stresses was observed. After the pressure was released, we observed that the nanotubes had restored their shapes. Atomistic simulations show that the hydrostatic and shear stresses affect the nanotubes' structure in a different way. It was found that the shear stress load in the multiwall nanotubes' outer walls can induce their connection and formation of an amorphized sp{sup 3}-hybridized region but internal core keeps the tubularmore » structure.« less

Experimental investigation of dynamic fragmentation of laser shock-loaded by soft recovery and X-ray radiography

NASA Astrophysics Data System (ADS)

Xin, Jianting; He, Weihua; Chu, Genbai; Gu, Yuqiu

2017-06-01

Dynamic fragmentation of metal under shock pressure is an important issue for both fundamental science and practical applications. And in recent decades, laser provides a promising shock loading technique for investigating the process of dynamic fragmentation under extreme condition application of high strain rate. Our group has performed experimental investigation of dynamic fragmentation under laser shock loading by soft recovery and X-ray radiography at SGC / ó prototype laser facility. The fragments under different loading pressures were recovered by PMP foam and analyzed by X-ray micro-tomography and the improved watershed method. The experiment result showed that the bilinear exponential distribution is more appropriate for representing the fragment size distribution. We also developed X-ray radiography technique. Owing to its inherent advantage over shadowgraph technique, X-ray radiography can potentially determine quantitatively material densities by measuring the X-ray transmission. Our group investigated dynamic process of microjetting by X-ray radiography technique, the recorded radiographic images show clear microjetting from the triangular grooves in the free surface of tin sample.

Controllable load sharing for soft adhesive interfaces on three-dimensional surfaces.

PubMed

Song, Sukho; Drotlef, Dirk-Michael; Majidi, Carmel; Sitti, Metin

2017-05-30

For adhering to three-dimensional (3D) surfaces or objects, current adhesion systems are limited by a fundamental trade-off between 3D surface conformability and high adhesion strength. This limitation arises from the need for a soft, mechanically compliant interface, which enables conformability to nonflat and irregularly shaped surfaces but significantly reduces the interfacial fracture strength. In this work, we overcome this trade-off with an adhesion-based soft-gripping system that exhibits enhanced fracture strength without sacrificing conformability to nonplanar 3D surfaces. Composed of a gecko-inspired elastomeric microfibrillar adhesive membrane supported by a pressure-controlled deformable gripper body, the proposed soft-gripping system controls the bonding strength by changing its internal pressure and exploiting the mechanics of interfacial equal load sharing. The soft adhesion system can use up to ∼26% of the maximum adhesion of the fibrillar membrane, which is 14× higher than the adhering membrane without load sharing. Our proposed load-sharing method suggests a paradigm for soft adhesion-based gripping and transfer-printing systems that achieves area scaling similar to that of a natural gecko footpad.

Controllable load sharing for soft adhesive interfaces on three-dimensional surfaces

NASA Astrophysics Data System (ADS)

Song, Sukho; Drotlef, Dirk-Michael; Majidi, Carmel; Sitti, Metin

2017-05-01

For adhering to three-dimensional (3D) surfaces or objects, current adhesion systems are limited by a fundamental trade-off between 3D surface conformability and high adhesion strength. This limitation arises from the need for a soft, mechanically compliant interface, which enables conformability to nonflat and irregularly shaped surfaces but significantly reduces the interfacial fracture strength. In this work, we overcome this trade-off with an adhesion-based soft-gripping system that exhibits enhanced fracture strength without sacrificing conformability to nonplanar 3D surfaces. Composed of a gecko-inspired elastomeric microfibrillar adhesive membrane supported by a pressure-controlled deformable gripper body, the proposed soft-gripping system controls the bonding strength by changing its internal pressure and exploiting the mechanics of interfacial equal load sharing. The soft adhesion system can use up to ˜26% of the maximum adhesion of the fibrillar membrane, which is 14× higher than the adhering membrane without load sharing. Our proposed load-sharing method suggests a paradigm for soft adhesion-based gripping and transfer-printing systems that achieves area scaling similar to that of a natural gecko footpad.

Controllable load sharing for soft adhesive interfaces on three-dimensional surfaces

PubMed Central

Song, Sukho; Drotlef, Dirk-Michael; Majidi, Carmel; Sitti, Metin

2017-01-01

For adhering to three-dimensional (3D) surfaces or objects, current adhesion systems are limited by a fundamental trade-off between 3D surface conformability and high adhesion strength. This limitation arises from the need for a soft, mechanically compliant interface, which enables conformability to nonflat and irregularly shaped surfaces but significantly reduces the interfacial fracture strength. In this work, we overcome this trade-off with an adhesion-based soft-gripping system that exhibits enhanced fracture strength without sacrificing conformability to nonplanar 3D surfaces. Composed of a gecko-inspired elastomeric microfibrillar adhesive membrane supported by a pressure-controlled deformable gripper body, the proposed soft-gripping system controls the bonding strength by changing its internal pressure and exploiting the mechanics of interfacial equal load sharing. The soft adhesion system can use up to ∼26% of the maximum adhesion of the fibrillar membrane, which is 14× higher than the adhering membrane without load sharing. Our proposed load-sharing method suggests a paradigm for soft adhesion-based gripping and transfer-printing systems that achieves area scaling similar to that of a natural gecko footpad. PMID:28507143

MRI-based modeling for radiocarpal joint mechanics: validation criteria and results for four specimen-specific models.

PubMed

Fischer, Kenneth J; Johnson, Joshua E; Waller, Alexander J; McIff, Terence E; Toby, E Bruce; Bilgen, Mehmet

2011-10-01

The objective of this study was to validate the MRI-based joint contact modeling methodology in the radiocarpal joints by comparison of model results with invasive specimen-specific radiocarpal contact measurements from four cadaver experiments. We used a single validation criterion for multiple outcome measures to characterize the utility and overall validity of the modeling approach. For each experiment, a Pressurex film and a Tekscan sensor were sequentially placed into the radiocarpal joints during simulated grasp. Computer models were constructed based on MRI visualization of the cadaver specimens without load. Images were also acquired during the loaded configuration used with the direct experimental measurements. Geometric surface models of the radius, scaphoid and lunate (including cartilage) were constructed from the images acquired without the load. The carpal bone motions from the unloaded state to the loaded state were determined using a series of 3D image registrations. Cartilage thickness was assumed uniform at 1.0 mm with an effective compressive modulus of 4 MPa. Validation was based on experimental versus model contact area, contact force, average contact pressure and peak contact pressure for the radioscaphoid and radiolunate articulations. Contact area was also measured directly from images acquired under load and compared to the experimental and model data. Qualitatively, there was good correspondence between the MRI-based model data and experimental data, with consistent relative size, shape and location of radioscaphoid and radiolunate contact regions. Quantitative data from the model generally compared well with the experimental data for all specimens. Contact area from the MRI-based model was very similar to the contact area measured directly from the images. For all outcome measures except average and peak pressures, at least two specimen models met the validation criteria with respect to experimental measurements for both articulations. Only the model for one specimen met the validation criteria for average and peak pressure of both articulations; however the experimental measures for peak pressure also exhibited high variability. MRI-based modeling can reliably be used for evaluating the contact area and contact force with similar confidence as in currently available experimental techniques. Average contact pressure, and peak contact pressure were more variable from all measurement techniques, and these measures from MRI-based modeling should be used with some caution.

The Effect of a Bacteria- and Fungi- binding Mesh Dressing on the Bacterial Load of Pressure Ulcers Treated With Negative Pressure Wound Therapy: A Pilot Study.

PubMed

Ciliberti, Marino; De Lara, Francesco; Serra, Gianfranco; Tafuro, Felice; Iazzetta, Francesco Maria; Filosa, Alessia; Scognamiglio, Rosa; Ciliberti, Giorgia; Veneri, Maria Rosaria

2016-11-01

This study was designed to clinically evaluate the efficacy of a bacteria- and-fungi-binding mesh (BFBM) dressing to modify the bacterial load of pressure ulcers (PUs) of categories 3 and 4, when used as a wound contact layer (WCL) during negative pressure wound therapy (NPWT). This was an observational single-centre study in patients with PUs of categories 3 or 4, who were treated with NPWT. Patients were observed for 7 days and received NPWT at -80 mm Hg with the BFBM dressing as the WCL. Wound biopsies were performed at inclusion (B0), at 48 hours (B1), and at day 7 (B7). Bacteria- and fungi-binding mesh dressings were examined for bacterial load at 48 hours (D1) and at 7 days (D7). The primary endpoint was the changes in bacterial loads. Fifty patients were enrolled; 43 (86%) of their PUs were on the sacrum. At B0, 3 groups of wounds were identified by the bioburden level: group A had negative results (28%) to bacterial loads from 102 to 5 x 103 colony forming units (CFU) CFU/mL (18%); group B had 104 to 105 CFU/mL (18%); and group C with ≥ 106 CFU/mL (36%). The authors did not find any significant difference in bacterial loads in group A, but significant differences were found in group B at B1 and B7 (P = 0.04 and P = 0.0067) and in group C at B1 and B7 (P < 0.00001). There was no significant difference on the bacterial loads of the dressing at D1 and D7 (P = 0.823). No device-related adverse events were reported. The BFBM dressing seems to be at the origin of a statistically significant reduction of bacterial burden in wounds with moderate or high levels of colonization. The authors' findings suggest BFBM dressings may be a WCL of choice during the treatment of chronic wounds with NPWT.

Review of LOX Bearing and Seal Materials Tester (BSMT) radial load system

NASA Technical Reports Server (NTRS)

Dufrane, K. F.; Kannel, J. W.

1984-01-01

Problems concerning the bearings in the high pressure oxygen turbopumps (HPOTP) were investigated. The tasks involved: failure analyses, bearing dynamics calculations, lubrication studies, wear studies, and analyses of thermal transients. The radial load system on MSFC's bearing and seal tester used to study components for the HPOTP in liquid oxygen (LOX) is analyzed and the wear behavior of AISI 440C steel with polytetrafluoroethylene (PTFE) lubrication is studied.

Blast Load Simulator Experiments for Computational Model Validation: Report 1

DTIC Science & Technology

2016-08-01

involving the inclusion of non-responding box-type structures in a BLS simulated blast environment. The BLS is a highly tunable com- pressed-gas-driven...Blast Load Simulator (BLS) to evaluate its suitability for a future effort involving the inclusion of non-responding box-type structures located in...Recommendations Preliminary testing indicated that inclusion of the grill and diaphragm striker resulted in a decrease in peak pressure of about 12

Effects of high NaCl diet on arterial pressure in Sprague-Dawley rats with hepatic and sinoaortic denervation.

PubMed

Gao, Shuang; Tanaka, Kunihiko; Gotoh, Taro M; Morita, Hironobu

2005-08-01

The Na(+) receptor that exists in the hepatoportal region plays an important role in postprandial natriuresis and the regulation of Na(+) balance during NaCl load. Thus it would be considered that a dysfunction of the hepatic Na(+) receptor might result in the elevation of arterial pressure under a condition of high NaCl diet. To elucidate this hypothesis, arterial pressure was continuously measured during three weeks of high NaCl diet (8% NaCl) in four groups of rats: (i) intact rats, (ii) rats with hepatic denervation (HD), (iii) rats with sinoaortic denervation (SAD), and (iv) rats with SAD+HD. During a 1-week normal NaCl diet period, there was no difference in arterial pressure among the four groups. A high NaCl diet had no influence on arterial pressure in intact or HD rats; however, it significantly increased by 11 +/- 3 mmHg in SAD rats. The addition of HD to SAD had no synergistic effect on arterial pressure; i.e., in SAD+HD rats, mean arterial pressure increased by 13 +/- 1 mmHg. In conclusion, sinoaortic baroreceptor, but not hepatic Na(+) receptor, has a significant role in the long-term regulation of arterial pressure on a high NaCl diet.

Effect of skull flexural properties on brain response during dynamic head loading - biomed 2013.

PubMed

Harrigan, T P; Roberts, J C; Ward, E E; Carneal, C M; Merkle, A C

2013-01-01

The skull-brain complex is typically modeled as an integrated structure, similar to a fluid-filled shell. Under dynamic loads, the interaction of the skull and the underlying brain, cerebrospinal fluid, and other tissue produces the pressure and strain histories that are the basis for many theories meant to describe the genesis of traumatic brain injury. In addition, local bone strains are of interest for predicting skull fracture in blunt trauma. However, the role of skull flexure in the intracranial pressure response to blunt trauma is complex. Since the relative time scales for pressure and flexural wave transmission across the skull are not easily separated, it is difficult to separate out the relative roles of the mechanical components in this system. This study uses a finite element model of the head, which is validated for pressure transmission to the brain, to assess the influence of skull table flexural stiffness on pressure in the brain and on strain within the skull. In a Human Head Finite Element Model, the skull component was modified by attaching shell elements to the inner and outer surfaces of the existing solid elements that modeled the skull. The shell elements were given the properties of bone, and the existing solid elements were decreased so that the overall stiffness along the surface of the skull was unchanged, but the skull table bending stiffness increased by a factor of 2.4. Blunt impact loads were applied to the frontal bone centrally, using LS-Dyna. The intracranial pressure predictions and the strain predictions in the skull were compared for models with and without surface shell elements, showing that the pressures in the mid-anterior and mid-posterior of the brain were very similar, but the strains in the skull under the loads and adjacent to the loads were decreased 15% with stiffer flexural properties. Pressure equilibration to nearly hydrostatic distributions occurred, indicating that the important frequency components for typical impact loading are lower than frequencies based on pressure wave propagation across the skull. This indicates that skull flexure has a local effect on intracranial pressures but that the integrated effect of a dome-like structure under load is a significant part of load transfer in the skull in blunt trauma.

High-temperature, high-pressure bonding of nested tubular metallic components

DOEpatents

Quinby, T.C.

A tool is described for effecting high-temperature, high-compression bonding between the confronting faces of nested, tubular, metallic components. In a typical application, the tool is used to produce tubular target assemblies for irradiation in nuclear reactors or particle accelerators. The target assembly comprising a uranum foil and an aluninum-alloy substrate. The tool is composed of graphite. It comprises a tubular restraining member in which a mechanically expandable tubular core is mounted to form an annulus. The components to be bonded are mounted in nested relation in the annulus. The expandable core is formed of individually movable, axially elongated segments whose outer faces cooperatively define a cylindrical pressing surface and whose inner faces cooperatively define two opposed, inwardly tapered, axial bores. Tapered rams extend into the bores. The loaded tool is mounted in a conventional hot-press provided with evacuation means, heaters for maintaining its interior at bonding temperature, and hydraulic cylinders for maintaining a selected inwardly directed pressure on the tapered rams. With the hot-press evacuated and the loaded tool at the desired temperature, the cylinders are actuated to apply the selected pressure to the rams. The rams in turn expand the segmented core to maintain the nested components in compression against the restraining member. These conditions are maintained until the confronting faces of the nested components are joined in a continuous, uniform bond characterized by high thermal conductivity.

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.

Ambient and high pressure single crystal x-ray studies of pyrope and synthetic ferric majorite

NASA Astrophysics Data System (ADS)

Smith, Henrietta Mercer

The mineral garnet is widely accepted as a major constituent of Earth's upper mantle and transition zone. As such, understanding of the state of the material at high pressures and temperatures will increase our ability to correlate seismic data with the mineralogy in these regions of Earth's interior. Studies of varied compositions of garnet at ambient conditions may enhance our understanding of solid-solution energetics, and yield predictive power concerning element partitioning among various minerals at different depths within Earth. This study began with structure refinements at ambient conditions of eighteen natural and two synthetic garnets, nominally in the pyrope-grossular-almandine ternary system. The natural, nearly-pure pyrope sample of this group was then used in developing the techniques necessary for high-pressure structure refinements. For high pressure work, a diamond anvil pressure cell (DAC) was loaded with the sample and mounted on an 18 kW rotating anode four-circle diffractometer. Unit cells and oxygen positional parameters of the pyrope sample were refined at five pressures to 9.9 GPa. The data were in agreement with those of other studies, and extended by 40% the pressure range achieved previously. The zero-pressure bulk modulus, K = 176 GPa, with Ksp' = dK/dP = 4. Following the high pressure pyrope study, synthetic samples of Fe-bearing majoritic garnet became available. These samples are of particular interest because they were grown at transition zone conditions and coexisted with a hydrous wadsleyite phase. The hydration state of earth's mantle is a topic of much current research, and samples such as these will provide information necessary to the placement of constraints on the degree of hydration actually present. The structures of five majorite samples from three different synthesis runs were refined at ambient conditions, and two of these samples were analyzed using Mossbauer spectroscopy. Fesp{3+}/SigmaFe ranged from 85-95%. One sample, for which there were both X-ray and Mossbauer data, was loaded into a DAC. The structure was refined at ten pressures to 12.9 GPa. K = 172.5 GPa with Ksp{''} = 4. The bulk compression is nearly identical to that of pyrope, but the compressions of the coordination polyhedra are quite different.

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.

Work Status, Work Satisfaction, and Blood Pressure Among Married Black and White Women

ERIC Educational Resources Information Center

Hauenstein, Louise S.; And Others

1977-01-01

This study examined blood pressure levels of married women in relation to such work-related variables as work load, satisfaction with work, reported strain, and evaluated performance. Differences in work load were unrelated to blood pressure levels. However, currently unemployed working women had lower levels. (Author)

Rolling Maneuver Load Alleviation using active controls

NASA Technical Reports Server (NTRS)

Woods-Vedeler, Jessica A.; Pototzky, Anthony S.

1992-01-01

Rolling Maneuver Load Alleviation (RMLA) has been demonstrated on the Active Flexible Wing (AFW) wind tunnel model in the NASA Langley Transonic Dynamics Tunnel. The design objective was to develop a systematic approach for developing active control laws to alleviate wing incremental loads during roll maneuvers. Using linear load models for the AFW wind-tunnel model which were based on experimental measurements, two RMLA control laws were developed based on a single-degree-of-freedom roll model. The RMLA control laws utilized actuation of outboard control surface pairs to counteract incremental loads generated during rolling maneuvers and actuation of the trailing edge inboard control surface pairs to maintain roll performance. To evaluate the RMLA control laws, roll maneuvers were performed in the wind tunnel at dynamic pressures of 150, 200, and 250 psf and Mach numbers of 0.33, .38 and .44, respectively. Loads obtained during these maneuvers were compared to baseline maneuver loads. For both RMLA controllers, the incremental torsion moments were reduced by up to 60 percent at all dynamic pressures and performance times. Results for bending moment load reductions during roll maneuvers varied. In addition, in a multiple function test, RMLA and flutter suppression system control laws were operated simultaneously during roll maneuvers at dynamic pressures 11 percent above the open-loop flutter dynamic pressure.

Comparison of Water-Load Distributions Obtained during Seaplane Landings with Bureau of Aeronautics Specifications. TED No. NACA 2413

NASA Technical Reports Server (NTRS)

Smiley, Robert F.; Haines, Gilbert A.

1949-01-01

Bureau of Aeronautics Design Specifications SS-IC-2 for water loads in sheltered water are compared with experimental water loads obtained during a full--scale landing investigation. This investigation was conducted with a JRS-1 flying boat which has a 20 degrees dead-rise V-bottom with a partial chine flare. The range of landing conditions included airspeeds between 88 and 126 feet per second, sinking speeds between 1.6 and 9.1 feet per second, flight angles less than 6 degrees, and trims between 2 degrees and 12 degrees. Landings were moderate and were made in calm water. Measurements were obtained of maximum over-all loads, maximum pitching moments, and pressure distributions. Maximum experimental loads include over-all load factors of 2g, moments of 128,000 pound-feet, and maximum local pressures greater than 40 pounds per square inch. Experimental over-all loads are approximately one-half the design values, while local pressures are of the same order as or larger than pressures calculated from specifications for plating, stringer, floor, and frame design. The value of this comparison is limited, to some extent, by the moderate conditions of the test and by the necessary simplifying assumptions used in comparing the specifications with the experimental loads.

Investigation of the Leak Response of a Carbon-Fiber Laminate Loaded in Biaxial Tension

NASA Technical Reports Server (NTRS)

Jackson, Wade C.; Ratcliffe, James G.

2013-01-01

Designers of pressurized structures have been reluctant to use composite materials because of concerns over leakage. Biaxial stress states are expected to be the worst-case loading condition for allowing leakage to occur through microcracks. To investigate the leakage behavior under in-plane biaxial loading, a cruciform composite specimen was designed that would have a relatively large test section with a uniform 1:1 biaxial loading ratio. A 7.6-cm-square test section was desired for future investigations of the leakage response as a result of impact damage. Many iterations of the cruciform specimen were evaluated using finite element analysis to reduce stress concentrations and maximize the size of the uniform biaxial strain field. The final design allowed the specimen to go to relatively high biaxial strain levels without incurring damage away from the test section. The specimen was designed and manufactured using carbon/epoxy fabric with a four-ply-thick, quasi-isotropic, central test section. Initial validation and testing were performed on a specimen without impact damage. The specimen was tested to maximum biaxial strains of approximately 4500micro epsilon without apparent damage. A leak measurement system containing a pressurized cavity was clamped to the test section and used to measure the flow rate through the specimen. The leakage behavior of the specimen was investigated for pressure differences up to 172 kPa

Inducer Hydrodynamic Load Measurement Devices

NASA Technical Reports Server (NTRS)

Skelley, Stephen E.; Zoladz, Thomas F.

2002-01-01

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

Inducer Hydrodynamic Load Measurement Devices

NASA Technical Reports Server (NTRS)

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

2002-01-01

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

[Taurine as a regulator of fluid-electrolyte balance and arterial pressure].

PubMed

Ciechanowska, B

1997-01-01

Taurine is a sulfonic beta-amino acid which occurs in the highest concentration in the brain, the retina and in the myocardium. In cardiomyocytes it presents about 50% of free amino acids and plays a role as an osmoregulator, an inotropic factor and has an antiarrhythmic property. Moreover, taurine lowers arterial pressure by extension of diuresis and by vasodilatation. Similar effect on the vascular system and arterial pressure is exerted by atrial natriuretic peptide (ANP). Increase of both ANP secretion and myocardial taurine concentration is present in the same diseases as congestive cardiac failure, hypertension and hypernatremia. The aim of the study was the evaluation of general taurine depletion, caused by making the rats drink guanidinoethyl sulfonate (GES)--an inhibitor of taurine transport affecting fluid balance and arterial pressure as well as plasma ANP concentration under normal conditions and after increase of sodium load. The 103 male Wistar rats weighing 250-300 g were used. The animals were separated into 5 groups. Control group received tap water to drink. Group II was sodium-loaded by drinking 171 mmol/l NaCl. In group III depletion of taurine was obtained by the intake of 60 mmol/l GES. Rats in group IV were drinking 60 mmol/l GES in 171 mmol/l NaCl. Group V was made to drink 200 mmol/l taurine in 171 mmol/l NaCl. All animals had standard food and were able at any time to drink. Duration of the experiment was 20 days. At the onset and after 10 and 20 days the rats were weighed and their systolic blood pressure was measured by tail plethysmography. After 10 and 20 days of the study, plasma and myocardium taurine concentration, ANP, hematocrit, plasma osmolity, natremia, kalemia, urea and creatinine concentrations were determined. Taking GES for 20 days led to 43% decrease of plasma taurine and its myocardium content about 50% as compared to control group (Tab. 2). High, statistically significant correlation (r = 0.50, p < 0.001) between myocardium taurine and plasma ANP was found. The animals with taurine depletion had significantly lower (about 30%) plasma ANP concentration (Tab. 3), higher natremia (Tab. 4) and their arterial pressure increased due to sodium load. Systolic pressure was 11 mm Hg higher in that group in comparison to control and other groups (Tab. 1). However, the sodium-loading of the rats that drank taurine solution led to an increase of hematocrit, plasma osmolity, urea concentration and body mass gain as compared to control group, but without any arterial pressure increase. The sodium-loaded rats with normal plasma and myocardium taurine concentration were affected in a similar manner. The rats with higher myocardium taurine concentration had lower heart mass index. Results of this work lead to the following conclusions: 1. Depletion of taurine in hearts of examined rats leads to a decrease of plasma atrial natriuretic peptide (ANP) concentration in plasma. 2. ANP secretion caused by salt loading is lower in animals with taurine depletion than in normal animals. 3. Sodium-loading of animals with taurine depletion leads to hypernatremia and to an increase of arterial pressure. 4. Addition of taurine to animals loaded with sodium may lead to their dehydration.

Baroreflex sensitivity in acute hypoxia and carbohydrate loading.

PubMed

Klemenc, Matjaž; Golja, Petra

2011-10-01

Hypoxia decreases baroreflex sensitivity (BRS) and can be a sufficient cause for syncope in healthy individuals. Carbohydrate loading enhances efferent sympathetic activity, which affects cardiac contractility, heart rate and vascular resistance, the main determinants of blood pressure. Thus, in both normoxia and hypoxia, carbohydrate loading may be more than simply metabolically beneficial, as it may affect blood pressure regulation. We hypothesised that carbohydrate loading will, in both normoxia and hypoxia, alter the regulation of blood pressure, as reflected in a change in baroreflex sensitivity. Fourteen subjects participated in two experiments, composed of a 15-min normoxic period, after which the subjects ingested water or an equal amount of water with carbohydrates. A 30-min rest period was then followed by a 10-min second normoxic and a 30-min hypoxic period. Blood pressure and heart rate were monitored continuously during the experiment to determine BRS. Despite an increased sympathetic activation, reflected in increased heart rate (P < 0.001) BRS was lower (P < 0.01) after carbohydrate loading, as compared to the water experiment, in both normoxic [23.7 (12.4) versus 28.8 (13.8) ms/mmHg] and hypoxic [16.8 (11.0) versus 24.3 (12.3) ms/mmHg] phases of the present study. As BRS was decreased in acute hypoxic exposure, the results confirm that hypoxia interferes with blood pressure regulation. However, although oral carbohydrate loading induced sympathoexcitation, it did not improve blood pressure regulation in hypoxia, as evident from the BRS data. Baroreflex effects of other forms of carbohydrate loading, not causing postprandial blood shifts to digestive system, should therefore be investigated.

High pressure, energy, and impulse loading of the wall in a 1-GJ Laboratory Microfusion Facility

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

Harrach, R.J.

1989-07-24

A proposed Laboratory Microfusion Facility (LMF) must be able to withstand repeated, low-repetition-rate fusion explosions at the 1-GJ (one-quarter ton) yield level. The energy release will occur at the center of a chamber only a few meters in radius, subjecting the interior or first wall to severe levels of temperature, pressure, and impulse. We show by theory and computation that the wall loading can be ameliorated by interposing a spherical shell of low-Z material between the fuel and the wall. This sacrificial shield converts the source energy components that are most damaging to the wall (soft x-rays and fast ions)more » to more benign plasma kinetic energy from the vaporized shield, and stretches the time duration over which this energy is delivered to the wall from nanoseconds to microseconds. Numerical calculations emphasize thin, volleyball-sized plastic shields, and much thicker ones of frozen nitrogen. Wall shielding criteria of small (or no) amount of surface ablation, low impulse and pressure loading, minimal shrapnel danger, small expense, and convenience in handling all favor the thin plastic shields. 7 refs., 4 figs.« less

Tribological Behavior of Aqueous Copolymer Lubricant in Mixed Lubrication Regime.

PubMed

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

2016-03-02

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

Design of Large Stone Asphalt Mixes to Minimize Rutting

DOT National Transportation Integrated Search

1990-01-01

Rutting of heavy duty asphalt pavements has been increasingly experienced in recent years. This phenomenon is primarily resulting from high tire pressures and increased wheel loads. The design of Hot Mix Asphalt (HMA) which served reasonably well in ...

Effect of high pressure treatment on the characteristics of a model emulsion

NASA Astrophysics Data System (ADS)

Denavaut, Maxence; Verret, Catherine; El Moueffak, Abdelhamid; Largeteau, Alain; Quéveau, Delphine; de Lamballerie, Marie

2014-10-01

The aim of this study was to investigate the use of HP (high pressure) technology as a possible alternative method for decontamination of non-food medium. HP (500 MPa) did not modify significantly the physicochemical characteristics of a model non-food emulsion. A 10 min HP treatment inactivated totally Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Aspergillus niger and Candida albicans even if all the five microorganisms were inoculated together, regardless of the initial load. No recovery was observed until six months of storage at 25°C.

A seat cushion to provide realistic acceleration cues for aircraft simulators

NASA Technical Reports Server (NTRS)

Ashworth, B. R.

1976-01-01

A seat cushion to provide acceleration cues for aircraft simulator pilots was built, performance tested, and evaluated. The four cell seat, using a thin air cushion with highly responsive pressure control, attempts to reproduce the same events which occur in an aircraft seat under acceleration loading. The pressure controller provides seat cushion responses which are considered adequate for current high performance aircraft simulations. The initial tests of the seat cushions have resulted in excellent pilot opinion of the cushion's ability to provide realistic and useful cues to the simulator pilot.

[Stress in the nursing team of an emergency medical service].

PubMed

Panizzon, Cristiane; Luz, Anna Maria Hecker; Fensterseifer, Lísia Maria

2008-09-01

This exploratory study aimed at determining stress levels and stressors, verifying the association between stress and studied variables, and identifying the predictive stress factors in an emergency nursing team. Data were collected using a social-demographic questionnaire and a scale of labor pressure sources applied with 98 workers. Chi-square test and Spearman correlation test results showed a high stress level, and identified work load as the main stressor. All pressure sources at work had a positive significant correlation with stress leve, and the following predictors were identified: work load, problems related to the client, and organizational processes and structure. The results indicate the need of management changes in the emergency unit in order to reduce the stress of the nursing team.

Determination of the propellant combustion law under ballistic experiment conditions

NASA Astrophysics Data System (ADS)

Ishchenko, A. N.; Diachkovskii, A. S.; Zykova, A. I.; Kasimov, VZ; Samorokova, N. M.

2017-11-01

The main characteristics of ballistic experiment are the maximum pressure in the combustion chamber P max and the projectile velocity at the time of barrel leaving U M. During the work the burning law of the new high-energy fuel was determined in a ballistic experiment. This burning law was used for a parametric study of depending P max and U M from a powder charge mass and a traveling charge at initial temperature of + 20 °C was carried out. The optimal conditions for loading were obtained for improving the muzzle velocity by 14.9 %. Under optimal loading, there is defined the conditions, which is possible to get the greatest value muzzle velocity projectile at pressures up to 600 MPa.

Highly sensitive, self-powered and wearable electronic skin based on pressure-sensitive nanofiber woven fabric sensor.

PubMed

Zhou, Yuman; He, Jianxin; Wang, Hongbo; Qi, Kun; Nan, Nan; You, Xiaolu; Shao, Weili; Wang, Lidan; Ding, Bin; Cui, Shizhong

2017-10-11

The wearable electronic skin with high sensitivity and self-power has shown increasing prospects for applications such as human health monitoring, robotic skin, and intelligent electronic products. In this work, we introduced and demonstrated a design of highly sensitive, self-powered, and wearable electronic skin based on a pressure-sensitive nanofiber woven fabric sensor fabricated by weaving PVDF electrospun yarns of nanofibers coated with PEDOT. Particularly, the nanofiber woven fabric sensor with multi-leveled hierarchical structure, which significantly induced the change in contact area under ultra-low load, showed combined superiority of high sensitivity (18.376 kPa -1 , at ~100 Pa), wide pressure range (0.002-10 kPa), fast response time (15 ms) and better durability (7500 cycles). More importantly, an open-circuit voltage signal of the PPNWF pressure sensor was obtained through applying periodic pressure of 10 kPa, and the output open-circuit voltage exhibited a distinct switching behavior to the applied pressure, indicating the wearable nanofiber woven fabric sensor could be self-powered under an applied pressure. Furthermore, we demonstrated the potential application of this wearable nanofiber woven fabric sensor in electronic skin for health monitoring, human motion detection, and muscle tremor detection.

Structural Analysis of Pressurized Small Diameter Lines in a Random Vibration Environment

NASA Technical Reports Server (NTRS)

Davis, Mark; Ridnour, Andrew; Brethen, Mark

2011-01-01

The pressurization and propellant feed lines for the Ares 1 Upper Stage Reaction and Roll Control Systems (ReCS and RoCS) were required to be in a high g-load random vibration flight environment. The lines connected the system components and were filled with both liquid hydrazine and gaseous helium. They are considered small and varied between one fourth to one inch in diameter. The random vibration of the lines was considered to be base excitation through the mating components and mounting hardware. It was found that reducing the amount of support structure for the lines added flexibility to the system and improved the line stresses from random vibration, but caused higher stresses from the static g-loads. The locations and number of brackets were optimized by analyzing the mode shapes of the lines causing high stresses. The use of brackets that only constrain motion in the direction of concern further reduced the stresses in the lines. Finite element analysis was used to perform the analysis. The lines were pre-stressed by temperature and internal pressure with fluid and insulation included as non-structural mass. Base excitation was added to the model using Power Spectral Density (PSD) data for the expected flight loads. The random vibration and static g-load cases were combined to obtain the total stress in the lines. This approach advances the state of the art in line analysis by using FEA to predict the stresses in the lines and to optimize the entire system based on the expected flight environment. Adding flexibility to lines has been used in piping system for temperature loads, but in flight environments flexibility has been limited for the static stresses. Adding flexibility to the system in a flight environment by reducing brackets has the benefit of reducing stresses and weight

Hydrogen gas embrittlement and the disc pressure test

NASA Technical Reports Server (NTRS)

Bachelet, E. J.; Troiano, A. R.

1973-01-01

A disc pressure test has been used to study the influenced of a hydrogen gas environment on the mechanical properties of three high strength superalloys, Inconel 718, L-605 and A-286, in static and dynamic conditions. The influence of the hydrogen pressure, loading rate, temperature, mechanical and thermal fatigue has investigated. The permeation characteristics of Inconel 718 have been determined in collaboration with the French AEC. The results complemented by a fractographic study are consistent either with a stress-sorption or with an internal embrittlement type of mechanism.

Wearable woven supercapacitor fabrics with high energy density and load-bearing capability.

PubMed

Shen, Caiwei; Xie, Yingxi; Zhu, Bingquan; Sanghadasa, Mohan; Tang, Yong; Lin, Liwei

2017-10-30

Flexible power sources with load bearing capability are attractive for modern wearable electronics. Here, free-standing supercapacitor fabrics that can store high electrical energy and sustain large mechanical loads are directly woven to be compatible with flexible systems. The prototype with reduced package weight/volume provides an impressive energy density of 2.58 mWh g -1 or 3.6 mWh cm -3 , high tensile strength of over 1000 MPa, and bearable pressure of over 100 MPa. The nanoporous thread electrodes are prepared by the activation of commercial carbon fibers to have three-orders of magnitude increase in the specific surface area and 86% retention of the original strength. The novel device configuration woven by solid electrolyte-coated threads shows excellent flexibility and stability during repeated mechanical bending tests. A supercapacitor watchstrap is used to power a liquid crystal display as an example of load-bearing power sources with various form-factor designs for wearable electronics.

The effects of altered intrathoracic pressure on resting cerebral blood flow and its response to visual stimulation

PubMed Central

Hayen, Anja; Herigstad, Mari; Kelly, Michael; Okell, Thomas W.; Murphy, Kevin; Wise, Richard G.; Pattinson, Kyle T.S.

2013-01-01

Investigating how intrathoracic pressure changes affect cerebral blood flow (CBF) is important for a clear interpretation of neuroimaging data in patients with abnormal respiratory physiology, intensive care patients receiving mechanical ventilation and in research paradigms that manipulate intrathoracic pressure. Here, we investigated the effect of experimentally increased and decreased intrathoracic pressures upon CBF and the stimulus-evoked CBF response to visual stimulation. Twenty healthy volunteers received intermittent inspiratory and expiratory loads (plus or minus 9 cmH2O for 270 s) and viewed an intermittent 2 Hz flashing checkerboard, while maintaining stable end-tidal CO2. CBF was recorded with transcranial Doppler sonography (TCD) and whole-brain pseudo-continuous arterial spin labeling magnetic resonance imaging (PCASL MRI). Application of inspiratory loading (negative intrathoracic pressure) showed an increase in TCD-measured CBF of 4% and a PCASL-measured increase in grey matter CBF of 5%, but did not alter mean arterial pressure (MAP). Expiratory loading (positive intrathoracic pressure) did not alter CBF, while MAP increased by 3%. Neither loading condition altered the perfusion response to visual stimulation in the primary visual cortex. In both loading conditions localized CBF increases were observed in the somatosensory and motor cortices, and in the cerebellum. Altered intrathoracic pressures, whether induced experimentally, therapeutically or through a disease process, have possible significant effects on CBF and should be considered as a potential systematic confound in the interpretation of perfusion-based neuroimaging data. PMID:23108273

Performance of homeostasis model assessment and serum high-sensitivity C-reactive protein for prediction of isolated post-load hyperglycaemia.

PubMed

Lai, Y-C; Li, H-Y; Hung, C-S; Lin, M-S; Shih, S-R; Ma, W-Y; Hua, C-H; Chuang, L-M; Sung, F-C; Wei, J-N

2013-03-01

To evaluate whether homeostasis model assessment and high-sensitivity C-reactive protein improve the prediction of isolated post-load hyperglycaemia. The subjects were 1458 adults without self-reported diabetes recruited between 2006 and 2010. Isolated post-load hyperglycaemia was defined as fasting plasma glucose < 7 mmol/l and 2-h post-load plasma glucose ≥ 11.1 mmol/l. Risk scores of isolated post-load hyperglycaemia were constructed by multivariate logistic regression. An independent group (n = 154) was enrolled from 2010 to 2011 to validate the models' performance. One hundred and twenty-three subjects (8.28%) were newly diagnosed as having diabetes mellitus. Among those with undiagnosed diabetes, 64 subjects (52%) had isolated post-load hyperglycaemia. Subjects with isolated post-load hyperglycaemia were older, more centrally obese and had higher blood pressure, HbA(1c), fasting plasma glucose, triglycerides, LDL cholesterol, high-sensitivity C-reactive protein and homeostasis model assessment of insulin resistance and lower homeostasis model assessment of β-cell function than those without diabetes. The risk scores included age, gender, BMI, homeostasis model assessment, high-sensitivity C-reactive protein and HbA(1c). The full model had high sensitivity (84%) and specificity (87%) and area under the receiver operating characteristic curve (0.91), with a cut-off point of 23.81; validation in an independent data set showed 88% sensitivity, 77% specificity and an area under curve of 0.89. Over half of those with undiagnosed diabetes had isolated post-load hyperglycaemia. Homeostasis model assessment and high-sensitivity C-reactive protein are useful to identify subjects with isolated post-load hyperglycaemia, with improved performance over fasting plasma glucose or HbA(1c) alone. © 2012 The Authors. Diabetic Medicine © 2012 Diabetes UK.

Remotely Adjustable Hydraulic Pump

NASA Technical Reports Server (NTRS)

Kouns, H. H.; Gardner, L. D.

1987-01-01

Outlet pressure adjusted to match varying loads. Electrohydraulic servo has positioned sleeve in leftmost position, adjusting outlet pressure to maximum value. Sleeve in equilibrium position, with control land covering control port. For lowest pressure setting, sleeve shifted toward right by increased pressure on sleeve shoulder from servovalve. Pump used in aircraft and robots, where hydraulic actuators repeatedly turned on and off, changing pump load frequently and over wide range.

Overview of the 6 Meter HIAD Inflatable Structure and Flexible TPS Static Load Test Series

NASA Technical Reports Server (NTRS)

Swanson, Greg; Kazemba, Cole; Johnson, Keith; Calomino, Anthony; Hughes, Steve; Cassell, Alan; Cheatwood, Neil

2014-01-01

To support NASAs long term goal of landing humans on Mars, technologies which enable the landing of heavy payloads are being developed. Current entry, decent, and landing technologies are not practical for this class of payloads due to geometric constraints dictated by current launch vehicle fairing limitations. Therefore, past and present technologies are now being explored to provide a mass and volume efficient solution to atmospheric entry, including Hypersonic Inflatable Aerodynamic Decelerators (HIADs). At the beginning of 2014, a 6m HIAD inflatable structure with an integrated flexible thermal protection system (TPS) was subjected to a static load test series to verify the designs structural performance. The 6m HIAD structure was constructed in a stacked toroid configuration using nine inflatable torus segments composed of fiber reinforced thin films, which were joined together using adhesives and high strength textile woven structural straps to help distribute the loads throughout the inflatable structure. The 6m flexible TPS was constructed using multiple layers of high performance materials to protect the inflatable structure from heat loads that would be seen during atmospheric entry. To perform the static load test series, a custom test fixture was constructed. The fixture consisted of a structural tub rim with enough height to allow for displacement of the inflatable structure as loads were applied. The bottom of the tub rim had an airtight seal with the floor. The centerbody of the inflatable structure was attached to a pedestal mount as seen in Figure 1. Using an impermeable membrane seal draped over the test article, partial vacuum was pulled beneath the HIAD, resulting in a uniform static pressure load applied to the outer surface. During the test series an extensive amount of instrumentation was used to provide many data sets including: deformed shape, shoulder deflection, strap loads, cord loads, inflation pressures, and applied static load.In this overview, the 6m HIAD static load test series will be discussed in detail, including the 6m HIAD inflatable structure and flexible TPS design, test setup and execution, and finally initial results and conclusions from the test series.

High pressure and temperature equation of state and spectroscopic study of CeO 2

DOE PAGES

Jacobsen, Matthew K.; Velisavljevic, Nenad; Dattelbaum, Dana Mcgraw; ...

2016-03-17

One of the most widely used x-ray standards and a highly applied component of catalysis systems, CeO 2 has been studied for the purpose of better understanding its equation of state and electronic properties. Diamond anvil cells have been used to extend the equation of state for this material to 130 GPa and explore the electronic behavior with applied load. From the x-ray diffraction studies, it has been determined that the high pressure phase transition extends from approximately 35–75 GPa at ambient temperature. Elevation of temperature is found to decrease the initiation pressure for this transition, with multiple distinct temperaturemore » regions which indicate structural related anomalies. In addition, hydrostatic and non-hydrostatic effects are compared and exhibit a drastic difference in bulk moduli. Furthermore, the electronic results indicate a change in the scattering environment of the cerium atom, associated with the high pressure phase transition. Overall, these results present the first megabar pressure study and the first high pressure and temperature study of ceria. Additionally, this shows the first combined study of the K and L III edges of this material to 33 GPa.« less

The Pneumatic Actuators As Vertical Dynamic Load Simulators On Medium Weighted Wheel Suspension Mechanism

NASA Astrophysics Data System (ADS)

Ka'ka, Simon; Himran, Syukri; Renreng, Ilyas; Sutresman, Onny

2018-02-01

Almost all of road damage can be caused by dynamic loads of vehicles that fluctuate according to the type of vehicle that passes through. This study aims to calculate the vertical dynamic load of the vehicle actually occurs on road construction by the mechanism of vehicle wheel suspension. Pneumatic cylinders driven by pressurized air directly load the spring and shock absorber installed on the wheels of the vehicle. The load fluctuations of the medium weight categorized vehicles are determined by the regulation of the amount of pressurized air that enters into the pneumatic cylinder chamber, pushing the piston and connecting rods. The displacement that occurs during compression on the spring and shock absorber, is substituted into the equation of vehicle dynamic load while taking into account the spring stiffness constant, and the fluid or damper gas coefficient. The results show that the magnitude of the displacement when the compression force works has significant influences to the amount of vertical dynamic load of the vehicle that overlies the road construction. The presence of dynamic load of vehicles that fluctuates and repeats, also affects on the reduction of road ability to receive the load. Experimental results using pneumatic actuators instead of real dynamic vehicle loads illustrate the characteristics of the relationship between work pressure and dynamic load. If the working pressure of P2 (bar) is greater, the vertical dynamic load Ft (N) that overloads the road structure is also greater. The associate graphs show that the shock absorber has a greater ability to reduce dynamic load vertically that burden the road structure when compared with the ability of screw spring.