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1

Model Of Bearing With Hydrostatic Damper  

NASA Technical Reports Server (NTRS)

Improved mathematical model of rotational and vibrational dynamics of bearing package in turbopump incorporates effects of hydrostatic damper. Part of larger finite-element model representing rotational and vibrational dynamics of rotor and housing of pump. Includes representations of deadband and nonlinear stiffness and damping of ball bearings, nonlinear stiffness and damping of hydrostatic film, and stiffness of bearing support. Enables incorporation of effects of hydrostatic damper into overall rotor-dynamic mathematical model without addition of mathematical submodel of major substructure.

Goggin, David G.

1991-01-01

2

Hydrostatic liquid-bearing for precision gyro  

NASA Technical Reports Server (NTRS)

Unit with 2W power increase and slightly larger overall dimensions performs as well as or better than its gas-bearing counterpart. Liquid-bearings are built by reworking serviceable gas-bearing components /sleeves, endplates, and cylinders/. Hydrostatic bearing is self-centered, requiring no magnetic suspension or centering jewel.

Sgambati, R. J.

1971-01-01

3

Rubber supported hydrostatic thrust bearings with rigid bearing surfaces  

Microsoft Academic Search

The film pressure of tilted hydrostatic thrust bearings results in a tilt opposing moment. This self-aligning action of the tilt opposing moment can be used effectively to reduce the deflection of the film contour. For this reduction some adjustment (elasticity) of the bearing system is necessary. Such elasticity is realized by means of a rubber support.

A. van Beek; A. Segal

1997-01-01

4

Hydrostatic bearings for a turbine fluid flow metering device  

Microsoft Academic Search

A rotor assembly fluid metering device has been improved by development of a hydrostatic bearing fluid system which provides bearing fluid at a common pressure to rotor assembly bearing surfaces. The bearing fluid distribution system produces a uniform film of fluid between bearing surfaces and allows rapid replacement of bearing fluid between bearing surfaces, thereby minimizing bearing wear and corrosion.

Fincke

1982-01-01

5

Hydrostatic bearings for a turbine fluid flow metering device  

DOEpatents

A rotor assembly fluid metering device has been improved by development of a hydrostatic bearing fluid system which provides bearing fluid at a common pressure to rotor assembly bearing surfaces. The bearing fluid distribution system produces a uniform film of fluid between bearing surfaces and allows rapid replacement of bearing fluid between bearing surfaces, thereby minimizing bearing wear and corrosion. 3 figs.

Fincke, J.R.

1982-05-04

6

Hydrostatic shoe bearing system for the TIM  

NASA Astrophysics Data System (ADS)

We present an active, low cost hydrostatic shoe bearing system for the Mexican Infrared Telescope which solves the suspension and motion of a 100 ton, 7.8 m telescope. Different geometries are analyzed to optimize the shoe's pressure print. These designs offer a self-adjusting action between the shoe's sliding path and the girth track. Different parameters such as pressure, temperature and proximity are measured and implemented into a control system in order to stabilize the bearing from the fluid's thermal viscosity effects. A simple method for fluid injection is discussed.

Ruiz Schneider, Elfego; Sohn, Erika; Quiros-Pacheco, Fernando; Godoy, Javier; Farah Simon, Alejandro; Quintanilla, R.; Soto, P.; Salas, Luis; Cruz-Gonzales, Irene

2000-08-01

7

Hydrostatic bearings for a turbine fluid flow metering device  

Microsoft Academic Search

A rotor assembly fluid metering device has been improved by development of a hydrostatic bearing fluid system which provides bearing fluid at a common pressure to rotor assembly bearing surfaces. The bearing fluid distribution system produces a uniform film of fluid distribution system produces a uniform film of fluid between bearing surfaces and allows rapid replacement of bearing fluid between

Fincke

1980-01-01

8

Three-D CFD analysis of hydrostatic bearings  

NASA Astrophysics Data System (ADS)

The hydrostatic bearing promises life and speed characteristics currently unachievable with rolling element bearings alone. In order to achieve the speed and life requirements of the next generation of rocket engines, turbopump manufacturers are proposing hydrostatic bearings to be used in place of, or in series with, rolling element bearings. The design of a hydrostatic bearing is dependent on accurate pressure in the bearing. The stiffness and damping of the hydrostatic bearing is very sensitive to the bearing recess pressure ratio. In the conventional approach, usually ad hoc assumptions were made in determining the bearing pressure of this approach is inherently incorrect. In the present paper, a more elaborate approach to obtain bearing pressure is used. The bearing pressure and complete flow features of the bearing are directly computed by solving the complete 3-D Navier Stokes equation. The code used in the present calculation is a modified version of REACT3D code. Several calculations have been performed for the hydrostatic bearing designed and tested at Texas A&M. Good agreement has been obtained between computed and test results. Detailed flow features in the bearing will also be described and discussed.

Lin, Shyi-Jang; Hibbs, Robert I., Jr.

1993-07-01

9

Coating Hydrostatic Bearings To Resist Ignition In Oxygen  

NASA Technical Reports Server (NTRS)

Coats of superalloy MA754 plasma-sprayed onto occasionally rubbing surfaces of hydrostatic journal bearings operating in liquid and/or gaseous oxygen, according to proposal. Prevents ignition and combustion occurring when components made of stainless steels or other conventional bearing alloys rub against each other in oxygen. Eliminates need for runner and enhances control over critical bearing clearance.

Funkhouser, Merle E.

1993-01-01

10

Evaluation of a hybrid hydrostatic bearing for cryogenic turbopump application  

NASA Technical Reports Server (NTRS)

A hybrid hydrostatic bearing was designed to operate in liquid hydrogen at speeds to 80,000 rpm and radial loads to 440 n (100 lbf). The bearing assembly consisted of a pair of 20-mm angular-contact ball bearings encased in a journal, which was in turn supported by a fluid film of liquid hydrogen. The size and operating conditions of the bearing were selected to be compatible with the operating requirements of an advanced technology turbopump. Several test parameters were varied to characterize the bearing's steady-state operation. The rotation of the tester shaft was varied between 0 and 80,000 rpm. Bearing inlet fluid pressure was varied between 2.07 and 4.48 MPa (300 and 650 psia), while the fluid sump pressure was independently varied between 0.34 and 2.07 MPa (50 and 300 psia). The maximum radial load applied to the bearing was 440 N (110 lbf). Measured hybrid-hydrostatic-bearing stiffness was 1.5 times greater than predicted, while the fluid flow rate through the bearing was 35 to 65 percent less than predicted. Under two-phase fluid conditions, the stiffness was even greater and the flow rate was less. The optimal pressure ratio for the bearing should be between 0.2 and 0.55 depending on the balance desired between bearing efficiency and stiffness. Startup and shutdown cyclic tests were conducted to demonstrate the ability of the hybrid-hydrostatic-bearing assembly to survive at least a 300-firing-duty cycle. For a typical cycle, the shaft was accelerated to 50,000 rpm in 1.8 sec. The bearing operated for 337 start-stop cycles without failure.

Spica, P. W.; Hannum, N. P.; Meyer, S. D.

1986-01-01

11

Hybrid Hydrostatic/Ball Bearings in High-Speed Turbomachinery.  

National Technical Information Service (NTIS)

A high speed, high pressure liquid hydrogen turbopump was designed, fabricated, and tested under a previous contract. This design was then modified to incorporate hybrid hydrostatic/ball bearings on both the pump end and turbine end to replace the origina...

C. E. Nielson

1983-01-01

12

An analysis of the 70-meter antenna hydrostatic bearing by means of computer simulation  

NASA Technical Reports Server (NTRS)

Recently, the computer program 'A Computer Solution for Hydrostatic Bearings with Variable Film Thickness,' used to design the hydrostatic bearing of the 70-meter antennas, was modified to improve the accuracy with which the program predicts the film height profile and oil pressure distribution between the hydrostatic bearing pad and the runner. This article presents a description of the modified computer program, the theory upon which the computer program computations are based, computer simulation results, and a discussion of the computer simulation results.

Bartos, R. D.

1993-01-01

13

Performance of membrane compensated multirecess hydrostatic\\/hybrid flexible journal bearing system considering various recess shapes  

Microsoft Academic Search

The paper describes a theoretical study concerning the performance of an externally pressurized multirecess hydrostatic\\/hybrid flexible journal bearing system by varying the geometric shape of recess and using the membrane flow valve restrictor as a compensating element. The four different recess geometries of the bearing studied in the present study are a square recessed bearing, a circular recessed bearing, an

Narendra Singh; Satish C. Sharma; S. C. Jain; S. Sanjeeva Reddy

2004-01-01

14

Fluid compressibility effects on the dynamic response of hydrostatic journal bearings  

NASA Technical Reports Server (NTRS)

A theoretical analysis for the dynamic performance characteristics of laminar flow, capillar/orifice compensated hydrostatic journal bearings is presented. The analysis considers in detail the effect of fluid compressibility in the bearing recesses. At high frequency excitations beyond a break frequency, the bearing hydrostatic stiffness increases sharply and it is accompanied by a rapid decrease in direct damping. Also, the potential of pneumatic hammer instability (negative damping) at low frequencies is likely to occur in hydrostatic bearing applications handling highly compressible fluids. Useful design criteria to avoid undesirable dynamic operating conditions at low and high frequencies are determined. The effect of fluid recess compressibility is brought into perspective, and found to be of utmost importance on the entire frequency spectrum response and stability characteristics of hydrostatic/hybrid journal bearings.

Sanandres, Luis A.

1991-01-01

15

On the Analytical and Experimental Investigation of a Hydrostatic Axisymmetric Compliant-Surface Thrust Bearing.  

National Technical Information Service (NTIS)

The paper presents experimental and theoretical data on the axisymmetric hydrostatic thrust bearing with one bonded compliant surface. The theoretical results are exact and are based on linear elasticity theory. The effects of compliance on the behavior o...

V. Castelli G. K. Rightmire D. D. Fuller

1966-01-01

16

Research on performance of slide-valve in water hydraulic servo-valve with hydrostatic bearing  

Microsoft Academic Search

In order to optimize the motion characteristics of slide-valve in water hydraulic servo-valve. Hydrostatic bearing technology has been used between valve core and sleeve. The research on performance about the static characteristics of slide-valve in water hydraulic servo-valve with hydrostatic bearing structure and traditional throttle with fixed orifice has been carried. The mathematical model of the pressure-flow characteristics, the pressure

Wang Xinhua; Zheng Jian; Sun Shuwen; Li Wei; Chang Jiaqing

2010-01-01

17

Hydrostatic bearing arrangement for high stiffness support of the Large Synoptic Survey Telescope  

NASA Astrophysics Data System (ADS)

Meeting the stringent slew and settling requirements of the Large Synoptic Survey Telescope (LSST) will require an exceptionally stiff mount. The unique three mirror design and large, 64 cm diameter, focal plane preclude the use of a fast steering mirror or active focal plane. Consequently, a smooth (low vibrations) drive and bearing system is also required. This combination of smooth motion and high stiffness is best achieved with hydrostatic bearings. Hydrostatic bearings have historically proven use for the support of azimuth and elevation axes of telescopes due to these performance advantages. In addition to the known benefit of mount stiffness and tracking accuracy from exceedingly low friction, the hydrostatic bearing provides a wide range of geometric possibilities for large telescopes, reference 1. This paper analyzes various bearing arrangements for the azimuth and elevation axes of the Large Synoptic Survey Telescope to conceptualize the greatest stiffness for the mount and provide data to determine system performance.

Neill, Douglas R.; Krabbendam, Victor L.; Romero, Mario; Olsson, Karl-Olof; Benigni, Thomas G.

2008-07-01

18

The effect of journal misalignment on the operation of a turbulent flow hydrostatic bearing  

SciTech Connect

An analysis for calculation of the dynamic force and moment response in turbulent flow, orifice compensated hydrostatic journal bearings is presented. The fully developed flow of a barotropic liquid is described by variable properties, bulk-flow equations and local turbulent friction factors based on bearing surface condition. Bearing load and moments and, dynamic force and moment coefficients are calculated for perturbations in journal center displacements and misaligned journal axis rotations. Numerical results for the effect of static misalignment angles in the plane of the eccentricity vector are presented for a water lubricated hydrostatic bearing. The predictions show that journal axis misalignment causes a reduction in load capacity due to loss in film thickness, increases the flow rate and produces significant restoring moments (couples). Force and moment coefficients due to dynamic journal axis rotations are also discussed. 37 refs.

San Andres, L. (Texas A M Univ., College Station (United States))

1993-07-01

19

Research on hydrostatic bearing technology applied in water hydraulic servo valve  

Microsoft Academic Search

Water hydraulic technology has been developing rapidly over the past decades due to its outstanding advantages, including cleanliness, security, environmental protection and cost-effectiveness and so on. At present, the research and development of water hydraulic servo valve with the performance of high precision, frequency response and high reliability become an important direction of water hydraulic technology. Hydrostatic bearing technology has

Xinhua Wang; Jian Zheng; Shuwen Sun; Jiaqing Chang

2009-01-01

20

Mixed Lubrication Simulation of Hydrostatic Spherical Bearings for Hydraulic Piston Pumps and Motors  

NASA Astrophysics Data System (ADS)

Mixed and fluid film lubrication characteristics of hydrostatic spherical bearings for swash-plate-type axial piston pumps and motors are studied theoretically under non-steady-state conditions. The basic equations incorporating interference and contact of surface roughness are derived fundamentally through combination of the GW and PC models. Furthermore, a programming code that is applicable to the caulked-socket-type and open-socket-type bearings is developed. Effects of caulking, operating conditions, and the bearing dimension on the motion of the sphere and tribological performance of the bearings are examined. Salient conclusions are the following: The sphere's eccentricity increases in the low supply pressure period. The time-lag of the load change engenders greater motion of the sphere. Caulking of the bearing socket suppresses the sphere's motion. The bearing stiffness increases and power loss decreases for smaller recess angles. Minimum power loss is given under the condition that the bearing socket radius nearly equals the equivalent load radius.

Kazama, Toshiharu

21

Investigation of a hydrostatic azimuth thrust bearing for a large steerable antenna  

NASA Technical Reports Server (NTRS)

The problems inherent in the design and construction of a hydrostatic azimuth thrust bearing for a tracking antenna of very large size were studied. For a load of 48,000,000 lbs., it is concluded that the hydrostatic bearing concept is feasible, provided that a particular multiple pad arrangement, high oil viscosity, and a particular load spreading arrangement are used. Presently available computer programs and techniques are deemed to be adequate for a good portion of the design job but new integrated programs will have to be developed in the area of the computation of the deflections of the supporting bearing structure. Experimental studies might also be indicated to ascertain the life characteristics of grouting under cyclic loading, and the optimization of hydraulic circuits and pipe sizes to insure the long life operation of pumps with high viscosity oil while avoiding cavitation.

Rumbarger, J.; Castelli, V.; Rippel, H.

1972-01-01

22

Dynamic force response of spherical hydrostatic journal bearing for cryogenic applications  

NASA Technical Reports Server (NTRS)

Hydrostatic Journal Bearings (HJB's) are reliable and resilient fluid film rotor support elements ideal to replace roller bearings in cryogenic turbomachinery. HJB' will be used for primary space-power applications due to their long lifetime, low friction and wear, large load capacity, large direct stiffness, and damping force coefficients. An analysis for the performance characteristics of turbulent flow, orifice compensated, spherical hydrostatic journal bearings (HJB's) is presented. Spherical bearings allow tolerance for shaft misalignment without force performance degradation and have also the ability to support axial loads. The spherical HJB combines these advantages to provide a bearing design which could be used efficiently on high performance turbomachinery. The motion of a barotropic liquid on the thin film bearing lands is described by bulk-flow mass and momentum equations. These equations are solved numerically using an efficient CFD method. Numerical predictions of load capacity and force coefficients for a 6 recess, spherical HJB in a LO2 environment are presented. Fluid film axial forces and force coefficients of a magnitude about 20% of the radial load capacity are predicted for the case analyzed. Fluid inertia effects, advective and centrifugal, are found to affect greatly the static and dynamic force performance of the bearing studied.

Sanandres, Luis

1994-01-01

23

Numerical modelling of the flow in the annular multi-recess hydrostatic thrust bearing using CFD methods  

NASA Astrophysics Data System (ADS)

The current research of hydrostatic bearings and hydrostatic slide-ways is far from being over. The topic is constantly evolving, creating new geometries of the sliding bearings, developing new types of friction materials and lubricants. The control elements of hydraulic mechanisms that serve to regulation of the hydrostatic bearings tipping are still in progress. Almost every application has different requirements for the bearings, whether in terms of loading capacity, speed rotation, and also the price. All these aspects should be included in the design of hydrostatic thrust bearings. Thanks to great advances in the development of computer technology and software for numerical modelling, we can simulate real movement of viscous fluids. To create a numerical model of hydrostatic thrust bearing, Ansys Fluent 14.0 software package has been applied. The article describes the basic methods of numerical modelling of the given problem and evaluates the pressure field and the loading capacity of annular multi-recess hydrostatic thrust bearing and its dependence on the change in static pressure.

Kozdera, M.; Drbáková, S.

2013-04-01

24

Dynamic characteristics of a hydrostatic gas bearing driven by oscillating exhaust pressure  

SciTech Connect

Vibration of a statically loaded, inherently compensated hydrostatic journal bearing due to oscillating exhaust pressure is investigated. Both angular and radial vibration modes are analyzed. The time-dependent Reynolds equation governing the pressure distribution between the oscillating journal and sleeve is solved together with the journal equation of motion to obtain the response characteristics of the bearing. The Reynolds equation and the equation of motion are simplified by applying regular perturbation theory for small displacements. The numerical solutions of the perturbation equations are obtained by discretizing the pressure field using finite-difference aproximations with a discrete, nonuniform line-source model which excludes effects due to feeding hole volume. An iterative scheme is used to simultaneously satisfy the equations of motion for the journal. The results presented include Bode plots of bearing-oscillation gain and phase for a particular bearing configuration for various combinations of parameters over a range of frequencies, including the resonant frequency. 17 references.

Watkins, C.B.; Eronini, I.E.

1984-10-01

25

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

NASA Technical Reports Server (NTRS)

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

Childs, Dara; Hale, Keith

1994-01-01

26

Three Dimensional Flow and Pressure Patterns in a Hydrostatic Journal Bearing  

NASA Technical Reports Server (NTRS)

The flow in a hydrostatic journal bearing (HJB) is described by a mathematical model that uses the three dimensional non-orthogonal form of the Navier-Stokes equations. Using the u, v, w, and p, as primary variables, a conservative formulation, finite volume multi-block method is applied through a collocated, body fitted grid. The HJB has four shallow pockets with a depth/length ratio of 0.067. This paper represents a natural extension to the two and three dimensional studies undertaken prior to this project.

Braun, M. Jack; Dzodzo, Milorad B.

1996-01-01

27

The Experimental Analyses of the Effects of the Geometric and Working Parameters on the Circular Hydrostatic Thrust Bearings  

NASA Astrophysics Data System (ADS)

In this paper, the characteristics of disk-type hydrostatic thrust bearings supporting concentric loads; simulating the major bearing/seal parts of axial piston pumps and motors were investigated. An experimental setup was designed to determine the performance of slippers, which are capable of increasing the efficiency of axial piston pumps and motors, for different conditions. The working parameters and the slipper geometry causing the minimum frictional power loss and leakage oil loss were determined. Since slippers affect the performance of the system considerably, the effects of surface roughnesses on lubrication were studied in slippers with varying hydrostatic bearing areas and surface roughness. The results of the study suggest that the frictional power loss and leakage oil loss were caused by the surface roughness, the relative velocity, the size of the hydrostatic bearing area, supply pressure and capillary tube diameter.

Canbulut, Fazıl

28

Comparison of Code Predictions to Test Measurements for Two Orifice Compensated Hydrostatic Bearings at High Reynolds Numbers  

NASA Technical Reports Server (NTRS)

Rotordynamic coefficients obtained from testing two different hydrostatic bearings are compared to values predicted by two different computer programs. The first set of test data is from a relatively long (L/D=1) orifice compensated hydrostatic bearing tested in water by Texas A&M University (TAMU Bearing No.9). The second bearing is a shorter (L/D=.37) bearing and was tested in a lower viscosity fluid by Rocketdyne Division of Rockwell (Rocketdyne 'Generic' Bearing) at similar rotating speeds and pressures. Computed predictions of bearing rotordynamic coefficients were obtained from the cylindrical seal code 'ICYL', one of the industrial seal codes developed for NASA-LeRC by Mechanical Technology Inc., and from the hydrodynamic bearing code 'HYDROPAD'. The comparison highlights the difference the bearing has on the accuracy of the predictions. The TAMU Bearing No. 9 test data is closely matched by the predictions obtained for the HYDROPAD code (except for added mass terms) whereas significant differences exist between the data from the Rocketdyne 'Generic' bearing the code predictions. The results suggest that some aspects of the fluid behavior in the shorter, higher Reynolds Number 'Generic' bearing may not be modeled accurately in the codes. The ICYL code predictions for flowrate and direct stiffness approximately equal those of HYDROPAD. Significant differences in cross-coupled stiffness and the damping terms were obtained relative to HYDROPAD and both sets of test data. Several observations are included concerning application of the ICYL code.

Keba, John E.

1996-01-01

29

High Speed, High Temperature, Fault Tolerant Operation of a Combination Magnetic-Hydrostatic Bearing Rotor Support System for Turbomachinery  

NASA Technical Reports Server (NTRS)

Closed loop operation of a single, high temperature magnetic radial bearing to 30,000 RPM (2.25 million DN) and 540 C (1000 F) is discussed. Also, high temperature, fault tolerant operation for the three axis system is examined. A novel, hydrostatic backup bearing system was employed to attain high speed, high temperature, lubrication free support of the entire rotor system. The hydrostatic bearings were made of a high lubricity material and acted as journal-type backup bearings. New, high temperature displacement sensors were successfully employed to monitor shaft position throughout the entire temperature range and are described in this paper. Control of the system was accomplished through a stand alone, high speed computer controller and it was used to run both the fault-tolerant PID and active vibration control algorithms.

Jansen, Mark; Montague, Gerald; Provenza, Andrew; Palazzolo, Alan

2004-01-01

30

Hotfire testing of a SSME HPOTP with an annular hydrostatic bearing  

NASA Technical Reports Server (NTRS)

A new fluid film bearing package has been tested in the SSME High Pressure Oxygen Turbopump (HPOTP). This fluid film element functions as both the pump end bearing and the preburner pump rear wear ring seal. Most important, it replaces a duplex ball bearing package which has been the primary life limiting component in the turbopump. The design and predicted performance of the turbopump are reviewed. Results are presented for measured pump and bearing performance. The most significant results were obtained from proximity probes located in the bearing bore which revealed large subsynchronous precession at 10 percent of shaft speed during engine start which subsided prior to mainstage power levels and reappeared during engine shutdown at equivalent power levels below 65 percent of nominal. This phenomenon has been attributed to rotating stall in the diffuser. The proximity probes also revealed the location of the bearing in the bore for different operating speeds. Pump vibration characteristics were improved as compared to pumps tested with ball bearings. After seven starts and more than 700 seconds of testing, the pump showed no signs of performance degradation.

Nolan, Steven A.; Hibbs, Robert I.; Genge, Gary G.

1993-01-01

31

Hotfire testing of a SSME HPOTP with an annular hydrostatic bearing  

NASA Astrophysics Data System (ADS)

A new fluid film bearing package has been tested in the Space Shuttle Main Engine (SSME) High Pressure Oxygen Turbopump (HPOTP). This fluid film element functions as both the pump end bearing and the preburner pump rear wear ring seal. Most importantly, it replaces a duplex ball bearing package which has been the primary life limiting component in the turbopump. The design and predicted performance of the turbopump are reviewed. Results are presented for measured pump and bearing performance during testing on the NASA Technology Test Bed (TTB) Engine located at MSFC. The most significant results were obtained from proximity probes located in the bearing bore which revealed large subsynchronous precession at ten percent of shaft speed during engine start which subsided prior to mainstage power levels and reappeared during engine shutdown at equivalent power levels below 65% of nominal. This phenomenon has been attributed to rotating stall in the diffuser. The proximity probes also revealed the location of the bearing in the bore for different operating speeds. Pump vibration characteristics were improved as compared to pumps tested with ball bearings. After seven starts and more than 700 seconds of testing, the pump showed no signs of performance degradation.

Nolan, Steven A.; Hibbs, Robert I.; Genge, Gary G.

1994-01-01

32

Hotfire testing of a SSME HPOTP with an annular hydrostatic bearing  

NASA Astrophysics Data System (ADS)

A new fluid film bearing package has been tested in the SSME High Pressure Oxygen Turbopump (HPOTP). This fluid film element functions as both the pump end bearing and the preburner pump rear wear ring seal. Most important, it replaces a duplex ball bearing package which has been the primary life limiting component in the turbopump. The design and predicted performance of the turbopump are reviewed. Results are presented for measured pump and bearing performance. The most significant results were obtained from proximity probes located in the bearing bore which revealed large subsynchronous precession at 10 percent of shaft speed during engine start which subsided prior to mainstage power levels and reappeared during engine shutdown at equivalent power levels below 65 percent of nominal. This phenomenon has been attributed to rotating stall in the diffuser. The proximity probes also revealed the location of the bearing in the bore for different operating speeds. Pump vibration characteristics were improved as compared to pumps tested with ball bearings. After seven starts and more than 700 seconds of testing, the pump showed no signs of performance degradation.

Nolan, Steven A.; Hibbs, Robert I.; Genge, Gary G.

1993-06-01

33

Three Dimensional Flow and Pressure Patterns in a Single Pocket of a Hydrostatic Journal Bearing  

NASA Technical Reports Server (NTRS)

The flow in a hydrostatic pocket is described by a mathematical model that uses the three dimensional Navier-Stokes equations written in terms of the primary variables, u, v, w, and p. Using a conservative formulation, a finite volume multi-block method is applied through a collocated, body fitted grid. The flow is simulated in a shallow pocket with a depth/length ratio of 0.02. The flow structures obtained and described by the authors in their previous two dimensional models are made visible in their three dimensional aspect for the Couette flow. It has been found that the flow regimes formed central and secondary vortical cells with three dimensional corkscrew-like structures that lead the fluid on an outward bound path in the axial direction of the pocket. The position of the central vortical cell center is at the exit region of the capillary restrictor feedline. It has also been determined that a fluid turn around zone occupies all the upstream space between the floor of the pocket and the runner, thus preventing any flow exit through the upstream port. The corresponding pressure distribution under the shaft presented as well. It was clearly established that for the Couette dominated case the pressure varies significantly in the pocket in the circumferential direction, while its variation is less pronounced axially.

Braun, M. Jack; Dzodzo, Milorad B.

1996-01-01

34

Hydrostatic lubrication with cryogenic fluids  

Microsoft Academic Search

The paper presents a computational procedure that can be useful in assessing the main performance parameters (load, flow rate, attitude angle) of hydrostatic journal bearings, without resorting to full numerical computing. The procedure is based on the ‘lumped resistance method’, which has been extended to take into account turbulence and inertia effects. Comparison with available experimental data shows a pretty

Roberto Bassani; Enrico Ciulli; Bruno Piccigallo; Maurizio Pirozzi; Ubaldo Staffilano

2006-01-01

35

Tribology in liquid oxygen of SiC/SiC ceramic matrix composites in connection with the design of hydrostatic bearing  

NASA Astrophysics Data System (ADS)

This paper aims with the characterization of ceramic matrix composites for bearing applications in LOX. First, compatibility tests have been performed to assume the safety and feasibility of further research operations. Then tribology tests were made on a pin-on-disc apparatus using LOX as working environment. The measurement of friction and wear allowed a comparison between different kinds of CMC and steel 440C materials. As a logical approach, a real geometry test rig is now being built up. The design of a hybrid journal bearing has been finished and the manufacturing of the rig components started.

Bozet, J. L.; Nelis, M.; Leuchs, M.; Bickel, M.

2001-09-01

36

The Hydrostatic Paradox.  

ERIC Educational Resources Information Center

Presents an example demonstrating the quantitative resolution of the hydrostatic paradox which is the realization that the force due to fluid pressure on the bottom of a vessel can be considerably greater or considerably less than the weight of the fluid in the vessel. (JRH)

Wilson, Alpha E.

1995-01-01

37

A Hydrostatic Paradox Revisited  

ERIC Educational Resources Information Center

This paper revisits a well-known hydrostatic paradox, observed when turning upside down a glass partially filled with water and covered with a sheet of light material. The phenomenon is studied in its most general form by including the mass of the cover. A historical survey of this experiment shows that a common misunderstanding of the phenomenon…

Ganci, Salvatore

2012-01-01

38

Hydrostatic Pressure Equilibrated Tensiometer.  

National Technical Information Service (NTIS)

A tensiometer has been developed that can measure long-term wire system performance at any depth, immune to hydrostatic pressure effects. Line tension is sensed and displayed on a Bourdon-type pressure gauge which is photographed at preselected intervals ...

S. Niskin

1975-01-01

39

Controls for hydrostatic systems  

SciTech Connect

In a control for a hydrostatic drive system with a primary energy source and with an adjustable pump and at least one adjustable consumer of hydrostatic energy and with a pump adjusting piston connected with the adjusting element of the pump and capable of sliding in a pump adjustment cylinder, where the load on the pump adjustment cylinder is regulated by means of a servo control valve, also with a constant pump connected to the drive shaft of the pump, the delivery line of which leads to a restrictor and to which a signal-pressure line is connected in front of the restrictor, where the pressure-signal present in it regulates a relief valve jet, which in turn is located in a control-signal line, the improvement characterized in that an additional restrictor is located in the control-signal line and means are provided for switching the pressure gradient in it to the servo control valve.

Krusche, A.

1985-01-29

40

Hydrostatic drive arrangement  

SciTech Connect

A hydrostatic drive arrangement is described for a vehicle which consists of: a pair of variable speed hydrostatic transmissions each having a hydraulic pump, a hydraulic motor and a closed loop hydraulic circuit interconnecting the pump and the motor for communicating fluid therebetween; synchronizing valve means interconnected between the hydraulic circuits of the transmissions normally permitting interflow of fluid through first passage means between the hydraulic circuits for synchronizing the output speeds of the transmissions when the fluid pressure in the hydraulic circuits is below a predetermined value, the synchronizing valve means being responsive to fluid pressures in the hydraulic circuits to restrict interflow therebetween through restricted second passage means when the fluid pressure in one of the hydraulic circuits exceeds the predetermined value; a hydraulic charge pump connected with the closed loop hydraulic circuits for replenishing fluid lost from the hydraulic circuits; and selector valve means disposed between the hydraulic charge pump and the synchronizing valve means for selectively communicating the synchronizing valve means normally blocking communication between the synchronizing valve means and the hydraulic charge pump and establishing communication between the synchronizing valve means and the drain thereby permitting interflow of fluid between the hydraulic circuits, and means responsive to a steering operation of the vehicle to establish communication between the synchronizing valve means and the hydraulic charge pump thereby blocking interflow of fluid between the hydraulic circuits.

Hoashi, K.; Morita, K.; Matsuda, K.

1986-04-22

41

Hybrid bearings for turbopumps and the like  

NASA Technical Reports Server (NTRS)

In rocket engines power is usually obtained by burning fuel and oxidizer which are mixed, pressurized, and directed to a combustion chamber by means of turbopumps. Roller bearings are generally used in these turbopumps, but because of bearing demands hydrostatic bearings were proposed. The use of such bearings is quite feasible because during flight hydrostatic lubrication can reduce roller bearing wear. A disadvantage of such proposals is that during startup, acceleration, and shutdown high pressure fluids are not available for hydrostatic bearings. The fluid lubrication film is not always present in bearings of turbopumps. During these periods a second bearing is required to carry the load. This requirement suggests the use of hybrid bearings in rocket engine turbopumps. Such duplex bearings were provided, but when their inner races are keyed to the shaft or journal two of them are required. And such duplex bearings do not wear evenly. A hybrid hydrostatic-rolling element bearing was provided wherein the rolling element bearing is locked on the stationary housing rather than on the rotating journal.

Justak, John F. (inventor); Owens, Gregg R. (inventor)

1994-01-01

42

Performance of Gas-Lubricated Nonconforming Pivoted-Pad Journal Bearings and a Flexibly Mounted Spiral-Groove Thrust Bearing.  

National Technical Information Service (NTIS)

A test program was conducted to determine the performance characteristics of gas-lubricated nonconforming pivoted-pad journal bearings and a spiral-groove thrust bearing designed for the Brayton cycle rotating unit (BRU). Hydrostatic, hybrid (simultaneous...

L. W. Ream

1973-01-01

43

Hydrostatic continuously variable transmission  

SciTech Connect

A hydrostatic continuously variable transmission is described, comprising: a swashplate type hydraulic pump having a pump swashplate and annularly arranged pump plungers whose suction and discharge strokes are provided by the pump swashplate; a swashplate type hydraulic motor having a motor swashplate and annularly arranged motor plungers whose expansion and shrinkage strokes are provided by the motor swashplate; and a hydraulic closed circuit formed between the hydraulic pump and the hydraulic motor. The transmission has at least one of a relationship that a middle point of a discharge region of the hydraulic pump is angularly delayed at a given angle in a direction of rotation of the hydraulic pump relative to a tilting axis of the pump swashplate and a relationship that a middle point of an expansion region of the hydraulic motor is angularly advanced at a given angle in a direction of rotation of the hydraulic motor relative to a tilting axis of the motor swashplate, wherein the transmission has at least one of a relationship that a suction region of the hydraulic pump is set at an angle larger than that of the discharge region thereof and a relationship that a shrinkage region of the hydraulic motor is set at an angle larger than that of the expansion region of the motor.

Hayashi, T.; Saito, M.; Matsuto, T.; Nakajima, Y.; Sakakibara, K.; Yakigaya, N.; Nakamura, K.

1989-05-09

44

Orbit transfer vehicle engine technology program. Task B-6 high speed turbopump bearings  

NASA Technical Reports Server (NTRS)

Bearing types were evaluated for use on the Orbit Transfer Vehicle (OTV) high pressure fuel pump. The high speed, high load, and long bearing life requirements dictated selection of hydrostatic bearings as the logical candidate for this engine. Design and fabrication of a bearing tester to evaluate these cryogenic hydrostatic bearings was then conducted. Detailed analysis, evaluation of bearing materials, and design of the hydrostatic bearings were completed resulting in fabrication of Carbon P5N and Kentanium hydrostatic bearings. Rotordynamic analyses determined the exact bearing geometry chosen. Instrumentation was evaluated and data acquisition methods were determined for monitoring shaft motion up to speeds in excess of 200,000 RPM in a cryogenic atmosphere. Fabrication of all hardware was completed, but assembly and testing was conducted outside of this contract.

1992-01-01

45

Computing Flows In Turbine End Bearings  

NASA Technical Reports Server (NTRS)

Computer program implements mathematical model of flow through turbine and bearings of high-pressure-oxygen turbopump of Space Shuttle main engine. Intended to determine rate of flow and margin before vaporization in these bearings for various types of geometries. Effects of hydrostatic damper and/or back-pressure seal included. Modified for application to other turbomachines and fluids other than oxygen.

Smith, Tyn S.

1990-01-01

46

Worm Gear With Hydrostatic Engagement  

NASA Technical Reports Server (NTRS)

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.

Chaiko, Lev I.

1994-01-01

47

Hydrostatic extrusion of UFG aluminium  

Microsoft Academic Search

The feasibility of hydrostatic extrusion (HE) of ultrafine grained (UFG) AA1070 has been investigated. The UFG material was\\u000a produced by equal channel angular pressing (ECAP) using a scaled-up, two-turn, S-shape channel. Four passes of ECAP were followed\\u000a by three passes of HE, which reduced the billet cross-section from a 26?×?26 mm2 square to 5 mm diameter round section. The average grain size

L. Olejnik; M. Kulczyk; W. Pachla; A. Rosochowski

2009-01-01

48

ANSYS Modeling of Hydrostatic Stress Effects  

NASA Technical Reports Server (NTRS)

Classical metal plasticity theory assumes that hydrostatic pressure has no effect on the yield and postyield behavior of metals. Plasticity textbooks, from the earliest to the most modem, infer that there is no hydrostatic effect on the yielding of metals, and even modem finite element programs direct the user to assume the same. The object of this study is to use the von Mises and Drucker-Prager failure theory constitutive models in the finite element program ANSYS to see how well they model conditions of varying hydrostatic pressure. Data is presented for notched round bar (NRB) and "L" shaped tensile specimens. Similar results from finite element models in ABAQUS are shown for comparison. It is shown that when dealing with geometries having a high hydrostatic stress influence, constitutive models that have a functional dependence on hydrostatic stress are more accurate in predicting material behavior than those that are independent of hydrostatic stress.

Allen, Phillip A.

1999-01-01

49

Switching skeletons: hydrostatic support in molting crabs  

NASA Technical Reports Server (NTRS)

Skeletal support systems are essential for support, movement, muscular antagonism, and locomotion. Crustaceans shed their rigid exoskeleton at each molt yet are still capable of forceful movement. We hypothesize that the soft water-inflated body of newly molted crabs may rely on a hydrostatic skeleton, similar to that of worms and polyps. We measured internal hydrostatic pressure and the force exerted during claw adduction and observed a strong correlation between force and hydrostatic pressure, consistent with hydrostatic skeletal support. This alternation between the two basic skeletal types may be widespread among arthropods.

Taylor, Jennifer R A.; Kier, William M.; Walker, I. D. (Principal Investigator)

2003-01-01

50

Hydrostatic compaction of Microtherm HT.  

SciTech Connect

Two samples of jacketed Microtherm{reg_sign}HT were hydrostatically pressurized to maximum pressures of 29,000 psi to evaluate both pressure-volume response and change in bulk modulus as a function of density. During testing, each of the two samples exhibited large irreversible compactive volumetric strains with only small increases in pressure; however at volumetric strains of approximately 50%, the Microtherm{reg_sign}HT stiffened noticeably at ever increasing rates. At the maximum pressure of 29,000 psi, the volumetric strains for both samples were approximately 70%. Bulk modulus, as determined from hydrostatic unload/reload loops, increased by more than two-orders of magnitude (from about 4500 psi to over 500,000 psi) from an initial material density of {approx}0.3 g/cc to a final density of {approx}1.1 g/cc. An empirical fit to the density vs. bulk modulus data is K = 492769{rho}{sup 4.6548}, where K is the bulk modulus in psi, and {rho} is the material density in g/cm{sup 3}. The porosity decreased from 88% to {approx}20% indicating that much higher pressures would be required to compact the material fully.

Broome, Scott Thomas; Bauer, Stephen J.

2010-09-01

51

Hydrostatic Hyperbaric Chamber Ventilation System  

NASA Technical Reports Server (NTRS)

The hydrostatic hyperbaric chamber (HHC) represents the merger of several technologies in development for NASA aerospace applications, harnessed to directly benefit global health. NASA has significant experience developing composite hyperbaric chambers for a variety of applications. NASA also has researched the application of water-filled vessels to increase tolerance of acceleration forces. The combination of these two applications has resulted in the hydrostatic chamber, which has been conceived as a safe, affordable means of making hyperbaric oxygen therapy (HBOT) available in the developing world for the treatment of a variety of medical conditions. Specifically, HBOT is highly-desired as a possibly curative treatment for Buruli Ulcer, an infectious condition that afflicts children in sub-Saharan Africa. HBOT is simply too expensive and too dangerous to implement in the developing world using standard equipment. The HHC technology changes the paradigm. The HHC differs from standard hyperbaric chambers in that the majority of its volume is filled with water which is pressurized by oxygen being supplied in the portion of the chamber containing the patient s head. This greatly reduces the amount of oxygen required to sustain a hyperbaric atmosphere, thereby making the system more safe and economical to operate. An effort was taken to develop an HHC system to apply HBOT to children that is simple and robust enough to support transport, assembly, maintenance and operation in developing countries. This paper details the concept for an HHC ventilation and pressurization system to provide controlled pressurization and adequate washout of carbon dioxide while the subject is enclosed in the confined space during the administration of the medical treatment. The concept took into consideration operational complexity, safety to the patient and operating personnel, and physiological considerations. The simple schematic, comprised of easily acquired commercial hardware, supports sustainability.

Sarguisingh, Miriam J.

2012-01-01

52

Marshall Space Flight Center High Speed Turbopump Bearing Test Rig  

NASA Technical Reports Server (NTRS)

The Marshall Space Flight Center has a unique test rig that is used to test and develop rolling element bearings used in high-speed cryogenic turbopumps. The tester is unique in that it uses liquid hydrogen as the coolant for the bearings. This test rig can simulate speeds and loads experienced in the Space Shuttle Main Engine turbopumps. With internal modifications, the tester can be used for evaluating fluid film, hydrostatic, and foil bearing designs. At the present time, the test rig is configured to run two ball bearings or a ball and roller bearing, both with a hydrostatic bearing. The rig is being used to evaluate the lifetimes of hybrid bearings with silicon nitride rolling elements and steel races.

Gibson, Howard; Moore, Chip; Thom, Robert

2000-01-01

53

Polar Bears  

NSDL National Science Digital Library

Use the following websites to answer questions about the rapid disappearance of polar bears in the Arctic region. Polar Bear picture Polar Bear Tracker 1: What region in the world has the fewest polar bears? 2: Using the internet as a resource, provide some reasons as to why this region is suffering from the most polar bear differences? Polar Bears Change Diet 1: Why are polar bears having to change their diets? 2: List some other factors (besides diet) in the ...

Thomas, Mr.

2010-09-27

54

Analytical analysis and optimisation of the Rayleigh step slider bearing  

Microsoft Academic Search

In tribology, the Rayleigh step is known as a bearing with the highest load capacity amongst all other possible bearing geometries. In classical resources on tribology, it is also shown that there is an optimum geometry for the Rayleigh step providing the highest load capacity. However, the analyses are confined to a special case where the effect of hydrostatic pressure

R. Rahmani; A. Shirvani; H. Shirvani

2009-01-01

55

Vertical Breakout Behavior of the Hydrostatic Anchor.  

National Technical Information Service (NTIS)

The vertical breakout behavior of the hydrostatic anchor depends greatly upon the anchor geometry including anchor diameter and skirt length, the soil strength properties, and the pressure difference between the ambient pressure and that underneath the po...

M. C. Wang V. A. Nacci K. R. Demars

1974-01-01

56

Hydrostatic Stress Effects in Metal Plasticity  

NASA Technical Reports Server (NTRS)

Since the 1940s, the theory of plasticity has assumed that hydrostatic stress does not affect the yield or postyield behavior of metals. This assumption is based on the early work of Bridgman. Bridgman found that hydrostatic pressure (compressive stress) does not affect yield behavior until a substantial amount of pressure (greater than 100 ksi) is present. The objective of this study was to determine the effect of hydrostatic tension on yield behavior. Two different specimen geometries were examined: an equal-arm bend specimen and a double edge notch specimen. The presence of a notch is sufficient to develop high enough hydrostatic tensile stresses to affect yield. The von Mises yield function, which does not have a hydrostatic component, and the Drucker-Prager yield function, which includes a hydrostatic component, were used in finite element analyses of the two specimen geometries. The analyses were compared to test data from IN 100 specimens. For both geometries, the analyses using the Drucker-Prager yield function more closely simulated the test data. The von Mises yield function lead to 5-10% overprediction of the force-displacement or force-strain response of the test specimens.

Wilson, Christopher D.

1999-01-01

57

Fault Tolerant Magnetic Bearing Testing and Conical Magnetic Bearing Development for Extreme Temperature Environments  

NASA Technical Reports Server (NTRS)

During the six month tenure of the grant, activities included continued research of hydrostatic bearings as a viable backup-bearing solution for a magnetically levitated shaft system in extreme temperature environments (1000 F), developmental upgrades of the fault-tolerant magnetic bearing rig at the NASA Glenn Research Center, and assisting in the development of a conical magnetic bearing for extreme temperature environments, particularly turbomachinery. It leveraged work from the ongoing Smart Efficient Components (SEC) and the Turbine-Based Combined Cycle (TBCC) program at NASA Glenn Research Center. The effort was useful in providing technology for more efficient and powerful gas turbine engines.

Keith, Theo G., Jr.; Clark, Daniel

2004-01-01

58

A computationally efficient finite volume hydrostatic/non-hydrostatic hybrid model with a vertical Lagrangian coordinate  

NASA Astrophysics Data System (ADS)

Resolving interactions between clouds and aerosols in the atmosphere, which have both direct and indirect effects on climate change, requires accurate and stable numerical discretization of the equations for the non-hydrostatic atmosphere. On the other hand, the use of the hydrostatic approximation allows one to achieve high computational efficiency in simulations of large scale atmospheric motions. Here we demonstrate a computational approach for the representation of small scale motions within a GCM by utilizing adaptive grid techniques that work to couple hydrostatic and non-hydrostatic flows for future climate model predictions. We have developed consistent equations for treating the change in physics associated with smooth solutions across the interface between hydrostatic and non-hydrostatic regions. We demonstrate the use of our grid adaptation technique (the ABLCarT library) over a portion of the global grid to test its capability to treat efficiently and accurately horizontal and vertical advection. We use a test suite to examine the behavior of the adaptive coupled hydrostatic-nonhydrostatic model using 2D and 3D configurations.

Chen, X.; Andronova, N. G.; Penner, J. E.; Stout, Q. F.; Vandenberg, D.

2011-12-01

59

Polar Bear  

NSDL National Science Digital Library

This site from the World Wildlife Fund (WWF) International provides general information about polar bears as well as data on the movements of two radio-collared bears, along with the ice status, through a series of online maps.

2007-01-01

60

Gear bearings  

NASA Technical Reports Server (NTRS)

A gear bearing having a first gear and a second gear, each having a plurality of teeth. Each gear operates on two non-parallel surfaces of the opposing gear teeth to perform both gear and bearing functions simultaneously. The gears are moving at substantially the same speed at their contact points. The gears may be roller gear bearings or phase-shifted gear bearings, and may be arranged in a planet/sun system or used as a transmission.

Vranish, John M. (Inventor)

2003-01-01

61

Develop a Fan Drive Hydro-Static Transmission.  

National Technical Information Service (NTIS)

This report details the development and endurance testing of a hydrostatic transmission consisting of a temperature controlled pressure compensated pump and a fixed-stroke inline piston hydraulic motor. The hydrostatic transmission was developed for appli...

W. F. Wesmann

1974-01-01

62

49 CFR 230.36 - Hydrostatic testing of boilers.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false Hydrostatic testing of boilers. 230.36 Section 230.36 Transportation...LOCOMOTIVE INSPECTION AND MAINTENANCE STANDARDS Boilers and Appurtenances Pressure Testing of Boilers § 230.36 Hydrostatic testing of...

2013-10-01

63

Hydrostatic Stress Effect On the Yield Behavior of Inconel 100.  

National Technical Information Service (NTIS)

Classical metal plasticity theory assumes that hydrostatic stress has no effect on the yield and postyield behavior of metals. Recent reexaminations of classical theory have revealed a significant effect of hydrostatic stress on the yield behavior of notc...

P. A. Allen C. D. Wilson

2002-01-01

64

Railcar waste transfer system hydrostatic test  

SciTech Connect

Recent modifications have been performed on the T-Plant Railcar Waste Transfer System, This Acceptance Test Procedure (ATP) has been prepared to demonstrate that identified piping welds and mechanical connections incorporated during the modification are of high integrity and are acceptable for service. This will be achieved by implementation of a hydrostatic leak test.

Ellingson, S.D.

1997-03-31

65

Methods of resisting hydrostatic uplift in substructures  

Microsoft Academic Search

Many underground structures are constructed for use as car parks and shops in basements of buildings and as mass rapid transit stations, depressed roadways and civil defense shelters in cities located in coastal areas where the ground is level and the elevations are low, with an attendant high groundwater table. This paper discusses the various methods of resisting hydrostatic uplift.

I. H Wong

2001-01-01

66

Studies of Deformation under Hydrostatic Pressure.  

National Technical Information Service (NTIS)

Single crystals of NaCl were deformed by fluid-to-fluid extrusion and uniaxial compression under hydrostatic pressure at ambient temperature. The effect of pressure on the deformation and fracture was studied. Wavy slip was observed in crystals extruded a...

R. J. Murphy W. B. Nowak F. M. Glock

1971-01-01

67

Hydrostatic tidal model for lunar asymmetry  

Microsoft Academic Search

A hydrostatic tidal model is presented which can successfully account for the two major features of lunar asymmetry. These are the observed offset between the center of figure and the center of mass, and the preferential distribution of lunar maria on the earthward side of the moon. The model requires that the following three processes occurred at the Roche stability

Susan Friedlander

1980-01-01

68

Non-hydrostatic pressure in ?-coordinate ocean models  

Microsoft Academic Search

Numerical ocean modelling is computationally very demanding. Traditionally, the hydrostatic approximation has been applied to reduce the computational burden. This approximation is valid in large scale studies with coarse grid resolution. With faster computers and gradually smaller grid sizes, we may expect that more studies will be performed with non-hydrostatic ocean models. In recent papers several methods for including non-hydrostatic

Eirik Keilegavlen; Jarle Berntsen

2009-01-01

69

Thrust bearing  

NASA Technical Reports Server (NTRS)

A gas lubricated thrust bearing is described which employs relatively rigid inwardly cantilevered spokes carrying a relatively resilient annular member or annulus. This annulus acts as a beam on which are mounted bearing pads. The resilience of the beam mount causes the pads to accept the load and, with proper design, responds to a rotating thrust-transmitting collar by creating a gas film between the pads and the thrust collar. The bearing may be arranged for load equalization thereby avoiding the necessity of gimbal mounts or the like for the bearing. It may also be arranged to respond to rotation in one or both directions.

Anderson, W. J. (inventor)

1976-01-01

70

High hydrostatic pressure processing of tropical fruits.  

PubMed

Interest in the nonthermal method of high hydrostatic pressure (HHP) for food preservation has increased recently due to the possibility of inactivating microorganisms and enzymes while maintaining product sensorial and nutritional properties. This work deals with HHP use for the preservation of tropical fruit products. HHP is shown to be a practical approach to obtaining high-quality tropical fruit products that are both nutritive and safe. PMID:20233363

Lopes, Maria Lúcia M; Valente Mesquita, Vera L; Chiaradia, Ana Cristina N; Fernandes, Antônio Alberto R; Fernandes, Patricia M B

2010-02-01

71

Fracture of notched polycarbonate under hydrostatic pressure  

Microsoft Academic Search

The brittle fracture behaviour and plastic deformation of round-notched polycarbonate bars subjected to three-point bending under hydrostatic pressure have been studied. Below a certain critical pressure, the brittle fracture initiated from an internal craze nucleated at the tip of the local plastic zone ahead of the notch rooT. The position of the nucleation of the craze receded from the tip

M. Ishikawa; I. Narisawa

1983-01-01

72

A Multipurpose Device for Some Hydrostatics Questions  

ERIC Educational Resources Information Center

A number of well-known hydrostatics problems dealing with Archimedes' principle concern a loaded boat floating in a pool. Examples of this sort of problem include: 1. (a) If a stone is thrown overboard from a boat floating in a pool, does the water level in the pool rise, fall, or remain unchanged? (b) If a hole is made in the bottom of the boat…

Ganci, Salvatore

2008-01-01

73

Dry Friction Bearings.  

National Technical Information Service (NTIS)

Contents: Porous metal ceramic bearings; Mineral ceramic bearings; Self-lubricating pressed wood bearings; Metal materials for special bearings; Operation of rolling surface bearings under dry friction conditions; Rolling surface bearings with solid lubri...

B. D. Voronkov

1970-01-01

74

Magnetic Bearing  

NASA Technical Reports Server (NTRS)

AVCON, Inc. produces advanced magnetic bearing systems for industrial use, offering a unique technological approach based on contract work done at Marshall Space Flight Center and Lewis Research Center. Designed for the turbopump of the Space Shuttle main engine, they are now used in applications such as electric power generation, petroleum refining, machine tool operation and natural gas pipelines. Magnetic bearings support moving machinery without physical contact; AVCON's homopolar approach is a hybrid of permanent and electromagnets which are one-third the weight, smaller and more power- efficient than previous magnetic bearings.

1996-01-01

75

Bobbie Bear  

NSDL National Science Digital Library

Using a virtual manipulative, children construct combinations of different colored shirts and pants to help Bobbie Bear, who is planning a vacation and wants to know how many different outfits he will be able to make from these combinations.

Mathematics, Illuminations N.

2009-03-06

76

The performance and application of high speed long life LH2 hybrid bearings for reusable rocket engine turbomachinery  

NASA Technical Reports Server (NTRS)

Data are presented for two different experimental programs which were conducted to investigate the characteristics of a hybrid (hydrostatic/ball) bearing operating in liquid hydrogen. The same bearing design was used in both programs. Analytical predictions were made of the bearing characteristics and are compared with the experimental results when possible. The first program used a bearing tester to determine the steady state, transient, and cyclic life characteristics of the bearing over a wide range of operating conditions. The second program demonstrated the feasibility of applying hybrid bearings to an actual high speed turbopump by retrofitting and then testing an existing liquid hydrogen turbopump with the bearings.

Hannum, N. P.; Nielson, C. E.

1983-01-01

77

Parameter identification of a rotor supported in a pressurized bearing lubricated with water  

NASA Technical Reports Server (NTRS)

A rig for testing an externally pressurized (hydrostatic), water-lubricated bearing was developed. Applying a nonsynchronous sweep frequency, rotating perturbation force with a constant amplitude as an input, rotor vibration response data was acquired in Bode and Dynamic Stiffness formats. Using this data, the parameters of the rotor/bearing system were identified. The rotor/bearing model was represented by the generalized (modal) parameters of the first lateral mode, with the rotational character of the fluid force taken into account.

Grant, John W.; Muszynska, Agnes; Bently, Donald E.

1994-01-01

78

Power control for a hydrostatic transmission  

SciTech Connect

A power control for a hydrostatic transmission is described having a pair of hydraulic units at least one of which being of variable displacement. The variable displacement hydraulic unit has hydraulic servo means for varying the displacement. The hydrostatic transmission furthermore has a fixed displacement speed signal pump driven at a speed proportional to the input speed of the transmission and providing a hydraulic input speed signal. The power control comprises first and second valves in series flow relationship between the speed signal pump and the servo means. The first valve is a variable orifice valve spring biased toward a cloeed position and biased by the input speed signal toward an open position to establish a pressure drop having a generally linear relationship to the input speed signal. The second valve is spring biased toward a closed position relative to communicating the output of the first valve to the servo means and having first and second opposed pilots connected across the first valve so that the input speed signal induced pressure drop biases the second valve toward an open position. The second valve also has an output feedback proportional to pressure in the servo means and connected to a third pilot biasing the second valve towards the closed position.

Geringer, K.G.

1988-05-24

79

A hydrostatic pressure approach to cuffless blood pressure monitoring  

Microsoft Academic Search

This paper presents the underlying principle and accompanying initial validation results towards the development of an optically-based, cuffless blood pressure monitoring method. As opposed to traditional oscillometric techniques, the optical sensor is calibrated with a known patient-controlled hydrostatic perturbation. In particular, the hydrostatic pressure challenge is utilized to parameterize the characteristic sigmoidal vascular compliance curve that links transmural pressure to

P. Shaltis; A. Reisner; H. Asada

2004-01-01

80

Factors influencing the system efficiency of hydrostatic transmission hybrid vehicles  

Microsoft Academic Search

Series hydrostatic transmission hybrid vehicle (SHHV) is an application of hydrostatic transmission technology to improve vehicle fuel economy and emissions. To make good use of the on-board energy sources in the SHHV design and application, several influencing factors on the SnHHV system efficiency are studied and evaluated. Then, the improved measures are proposed to enhance the efficiency of SHHV. Simulation

Sun Hui; Jiang Ji-hai; Wang Xin

2008-01-01

81

75 FR 48728 - The Hydrostatic Testing Provision of the Portable Fire Extinguishers Standard; Extension of the...  

Federal Register 2010, 2011, 2012, 2013

...Hydrostatic Testing Provision of the Portable Fire Extinguishers Standard; Extension of the...Hydrostatic Testing provision of the Portable Fire Extinguishers Standard for General Industry...Hydrostatic Testing provision of the Portable Fire Extinguishers Standard are necessary...

2010-08-11

82

78 FR 70324 - Thy Hydrostatic Testing Provision of the Portable Fire Extinguishers Standard; Extension of the...  

Federal Register 2010, 2011, 2012, 2013

...Hydrostatic Testing Provision of the Portable Fire Extinguishers Standard; Extension of the...Hydrostatic Testing provision of the Portable Fire Extinguishers Standard for General Industry...Hydrostatic Testing Provision of the Portable Fire Extinguishers Standard are necessary...

2013-11-25

83

Bear Bones  

NSDL National Science Digital Library

An estimated ten million Americans have osteoporosis, an age-related disease in which the bones gradually become brittle and weak. Now, scientists are looking to animals for clues on how to combat this condition. This resource describes the study of sustaining bone strength of hibernating bears.

Science Update;

2004-03-08

84

Hydrostatic Stress Effect On the Yield Behavior of Inconel 100  

NASA Technical Reports Server (NTRS)

Classical metal plasticity theory assumes that hydrostatic stress has no effect on the yield and postyield behavior of metals. Recent reexaminations of classical theory have revealed a significant effect of hydrostatic stress on the yield behavior of notched geometries. New experiments and nonlinear finite element analyses (FEA) of Inconel 100 (IN 100) equal-arm bend and double-edge notch tension (DENT) test specimens have revealed the effect of internal hydrostatic tensile stresses on yielding. Nonlinear FEA using the von Mises (yielding is independent of hydrostatic stress) and the Drucker-Prager (yielding is linearly dependent on hydrostatic stress) yield functions was performed. In all test cases, the von Mises constitutive model, which is independent of hydrostatic pressure, overestimated the load for a given displacement or strain. Considering the failure displacements or strains, the Drucker-Prager FEMs predicted loads that were 3% to 5% lower than the von Mises values. For the failure loads, the Drucker Prager FEMs predicted strains that were 20% to 35% greater than the von Mises values. The Drucker-Prager yield function seems to more accurately predict the overall specimen response of geometries with significant internal hydrostatic stress influence.

Allen, Phillip A.; Wilson, Christopher D.

2002-01-01

85

Highly birefringent microstructured fibers with enhanced sensitivity to hydrostatic pressure.  

PubMed

We designed, manufactured and characterized two birefringent microstructured fibers that feature a 5-fold increase in polarimetric sensitivity to hydrostatic pressure compared to the earlier reported values for microstructured fibers. We demonstrate a good agreement between the finite element simulations and the experimental values for the polarimetric sensitivity to pressure and to temperature. The sensitivity to hydrostatic pressure has a negative sign and exceeds -43 rad/MPa x m at 1.55 microm for both fibers. In combination with the very low sensitivity to temperature, this makes our fibers the candidates of choice for the development of microstructured fiber based hydrostatic pressure measurement systems. PMID:20639996

Martynkien, Tadeusz; Statkiewicz-Barabach, Gabriela; Olszewski, Jacek; Wojcik, Jan; Mergo, Pawe?; Geernaert, Thomas; Sonnenfeld, Camille; Anuszkiewicz, Alicja; Szczurowski, Marcin K; Tarnowski, Karol; Makara, Mariusz; Skorupski, Krzysztof; Klimek, Jacek; Poturaj, Krzysztof; Urbanczyk, Waclaw; Nasilowski, Tomasz; Berghmans, Francis; Thienpont, Hugo

2010-07-01

86

Biomechanics: a pneumo-hydrostatic skeleton in land crabs.  

PubMed

Like their aquatic counterparts, terrestrial crabs repeatedly shed their rigid exoskeleton during moulting. But in the case of land crabs, little water is available to provide a temporary hydrostatic skeleton before the new skeleton hardens, and air does not provide the buoyancy necessary to support the animal. Here we show that whenever its exoskeleton is shed, the blackback land crab Gecarcinus lateralis relies on an unconventional type of hydrostatic skeleton that uses both gas and liquid (a 'pneumo-hydrostat'). To our knowledge, this is the first experimental evidence for a locomotor skeleton that depends on a gas. It establishes a new category of hydrostatic skeletal support and possibly a critical adaptation to life on land for the Crustacea. PMID:16625186

Taylor, Jennifer R A; Kier, William M

2006-04-20

87

Production of Inconel 718 Mortar Tubes by Hydrostatic Extrusion.  

National Technical Information Service (NTIS)

Using subscale tubes, extrusion parameters were developed and then applied to full size 60mm tubes. It was shown that tubes can be satisfactorily produced at a reduced cost. Estimates were developed to mass produce hydrostatically extruded tubes. The proc...

J. R. Douglas W. R. Landis G. E. Meyer T. G. Byrer R. J. Fiorentino

1974-01-01

88

Fabrication and characterization of a micro turbine\\/bearing rig  

Microsoft Academic Search

This paper reports on a process to build, package, and instrument a 5-level wafer-bonded micromachined turbine\\/bearing rig. The process flow involves the use of 5 wafers, 16 masks, and 9 deep silicon etching steps, as well as utilizing aligned wafer bonding, double-sided deep reactive ion etching and laser-assisted-etching. This paper also shows experimental results on flow characteristics of the hydrostatic

Chuang-Chia Lin; Reza Ghodssi; Arturo A. Ayon; Dye-Zone Chen; Stuart Jacobson; Kenneth Breuer; Alan H. Epstein; Martin A. Schmidt

1999-01-01

89

Influence of boundary conditions and turntable speeds on the stability of hydrostatic oil cavity  

NASA Astrophysics Data System (ADS)

The flow, bearing, and carrying capacity of the cycloidal hydrostatic oil cavity in hydrostatic turntable systems are numerically simulated, considering the rotation speeds of a turntable from 0 to 5 m/s and different boundary conditions. The vortex effect is weakened, and the stability of the oil cavity is enhanced with the increase in lubricant viscosity. However, the increase in inlet speed, depth, and inlet radius of the oil cavity causes the vortex effect to increase and the stability of oil cavity to reduce. With the increase in the oil film thickness, the carrying capacity of the oil cavity diminishes. The oil cavity pressure increases along the direction of the motion of the turntable; it is distributed unevenly because of the rotation of the turntable. With the increase in turntable speed, the location and size of the vortex scope in the oil cavity flow field and the strength of the vortex near the entrance gradually weaken and move away from the entry. The distribution of pressure is determined by the locations of the vortex. When the vortex is close to the wall, the wall pressure increases at its location. Otherwise, the wall pressure decreases first and then increases after the center of the vortex.

Liu, Zhaomiao; Zhang, Chengyin; Shen, Feng

2011-09-01

90

Hydrostatic and boundary lubrication of joints--nature of boundary lubricant.  

PubMed

A very low coefficient of friction in joints makes it difficult to define clearly the mechanism of cartilage lubrication. The present paper describes the two currently predominant and mutually complementary views aiming to elucidate this mechanism. The first mechanism, referred to as hydrostatic lubrication, involves interstitial fluid pressurization from the cartilage and its importance for the formation of a layer separating the weight-bearing surfaces. The second mechanism, called boundary lubrication, assumes the existence of a substance that binds to the cartilage surface, permanently separating the friction elements. It has not been clearly determined which substances occurring in the synovial fluid function as boundary lubricants. The authors briefly describe the physicochemical properties of lubricin, surface-active phospholipids and hyaluronic acid, including their role in boundary lubrication. PMID:22402631

Moskalewski, Stanis?aw; Jankowska-Steifer, Ewa

2012-01-01

91

Cryogenic turbopump bearing materials  

NASA Technical Reports Server (NTRS)

Materials used for modern cryogenic turbopump bearings must withstand extreme conditions of loads and speeds under marginal lubrication. Naturally, these extreme conditions tend to limit the bearing life. It is possible to significantly improve the life of these bearings, however, by improving the fatigue and wear resistance of bearing alloys, and improving the strength, liquid oxygen compatibility and lubricating ability of the bearing cage materials. Improved cooling will also help to keep the bearing temperatures low and hence prolong the bearing life.

Bhat, Biliyar N.

1989-01-01

92

A Twist-Roller Friction Drive for Nanometer Positioning – Simplified Design Using Ball Bearings  

Microsoft Academic Search

The authors have reported in a previous paper that the twist-roller friction drive can realize sub-nanometer positioning resolution. However, a structural difficulty of the device is that hydrostatic bearings are used to support the twist-rollers. The present paper describes how the structure of the twist-roller friction drive can be simplified by using ball bearings to support the twist-rollers. Even with

H. Mizumoto; S. Arii; A. Yoshimoto; T. Shimizu; N. Ikawa

1996-01-01

93

Magnetic bearings for free-piston Stirling engines  

NASA Technical Reports Server (NTRS)

The feasibility and efficiency of applying magnetic bearings to free-piston Stirling-cycle power conversion machinery currently being developed for long-term space missions are assessed. The study was performed for a 50-kWe Reference Stirling Space Power Converter (RSSPC) which currently uses hydrostatic gas bearings to support the reciprocating displacer and power piston assemblies. Active magnetic bearings of the attractive electromagnetic type are feasible for the RSSPC power piston. Magnetic support of the displacer assembly would require unacceptable changes to the design of the current RSSPC. However, magnetic suspension of both displacer and power piston is feasible for a relative-displacer version of the RSSPC. Magnetic suspension of the RSSPC power piston can potentially increase overall efficiency by 0.5 to 1 percent (0.1 to 0.3 efficieny points). Magnetic bearings will also overcome several operational concerns associated with hydrostatic gas bearing systems. These advantages, however, are accompanied by a 5 percent increase in specific mass of the RSSPC.

Curwen, P. W.; Flemig, D. P.; Rao, D. K.; Wilson, D. S.

1992-01-01

94

Static and dynamic characteristics of externally pressurized circular step thrust bearings lubricated with couple stress fluids  

Microsoft Academic Search

The combined effects of couple stresses, fluid inertia and recess volume fluid compressibility on the steady-state performance and the dynamic stiffness and damping characteristics of hydrostatic circular step thrust bearings are presented theoretically. Based on the micro-continuum theory, the modified Reynolds equation and the recess flow continuity equation are derived by using the Stokes constitutive equations to account for the

Jaw-Ren Lin

1999-01-01

95

An In-Vitro Traumatic Model To Evaluate the Response of Myelinated Cultures to Sustained Hydrostatic Compression Injury  

PubMed Central

Abstract While a variety of in-vitro models have been employed to investigate the response of load-bearing tissues to hydrostatic pressure, long-term studies are limited by the need to provide for adequate gas exchange during pressurization. Applying compression in vitro may alter the equilibrium of the system and thereby disrupt the gas exchange kinetics. To address this, several sophisticated compression chamber designs have been developed. However, these systems are limited in the magnitude of pressure that can be applied and may require frequent media changes, thereby eliminating critical autocrine and paracrine signaling factors. To better isolate the cellular response to long-term compression, we created a model that features continuous gas flow through the chamber during pressurization, and a negative feedback control system to rigorously control dissolved oxygen levels. Monitoring dissolved oxygen continuously during pressurization, we find that the ensuing response exhibits characteristics of a second- or higher-order system which can be mathematically modeled using a second-order differential equation. Finally, we use the system to model chronic nerve compression injuries, such as carpal tunnel syndrome and spinal nerve root stenosis, with myelinated neuron-Schwann cell co-cultures. Cell membrane integrity assay results show that co-cultures respond differently to hydrostatic pressure, depending on the magnitude and duration of stimulation. In addition, we find that myelinated Schwann cells proliferate in response to applied hydrostatic compression.

Frieboes, Laura R.

2009-01-01

96

Hydrostatic Microextrusion of Steel and Copper  

NASA Astrophysics Data System (ADS)

The paper presents an experimental investigation based on hydrostatic micro extrusion of billets in low carbon steel and commercially pure copper, and the relevant results. The starting billets have a diameter of 0.3 mm and are 5 mm long; a high pressure generator consisting of a manually operated piston screw pump is used to pressurize the fluid up to 4200 bar, the screw pump is connected through a 3-way distribution block to the extrusion die and to a strain gauge high pressure sensor. The sensor has a full scale of 5000 bar and the extrusion pressure is acquired at a sampling rate of 2 kHz by means of an acquisition program written in the LabVIEW environment. Tests have been conducted at room temperature and a lubricant for wire drawing (Chemetall Gardolube DO 338) acts both as the pressurizing fluid and lubricant too. In addition, billets were graphite coated. Different fluid pressures and process durations have been adopted, resulting in different extrusion lengths. The required extrusion pressure is much higher than in non-micro forming operations (this effect is more evident for steel). On the cross section of the extruded parts, hardness and grain size distribution have been measured, the former through Vickers micro hardness (10 g load) tests. In the case of the extrusion of copper, the material behaves as in microdrawing process. In the case of the extrusion of steel, the hardness increases from the core to the surface as in the drawing process, but with lower values. The analysis evidenced the presence of the external layer, but its thickness is about 1/3 of the external layer in the drawn wire and the grains appear smaller than in the layer of the drawn wire. The extruding force required along the extruding direction is higher (22-24 N) than the drawing force along the same direction (12 N): being the material, the reduction ratio, the die sliding length the same in both cases, the higher extrusion force should be caused by a higher tangential friction force and/or a higher redundant work of deformation and/or a different material behaviour. Which is the real mechanism is not clear at present, but surface layer grains in extrusion are more deformed than in wire drawing. For this reason the deformation inhomogeneity increases in extrusion and the material under the highly deformed surface layer should be subjected to lower strains, strain hardening and finally resulting in lower hardness.

Berti, Guido; Monti, Manuel; D'Angelo, Luciano

2011-05-01

97

Hydrostatic pressure mimics gravitational pressure in characean cells  

NASA Technical Reports Server (NTRS)

Hydrostatic pressure applied to one end of a horizontal Chara cell induces a polarity of cytoplasmic streaming, thus mimicking the effect of gravity. A positive hydrostatic pressure induces a more rapid streaming away from the applied pressure and a slower streaming toward the applied pressure. In contrast, a negative pressure induces a more rapid streaming toward and a slower streaming away from the applied pressure. Both the hydrostatic pressure-induced and gravity-induced polarity of cytoplasmic streaming respond identically to cell ligation, UV microbeam irradiation, external Ca2+ concentrations, osmotic pressure, neutral red, TEA Cl-, and the Ca2+ channel blockers nifedipine and LaCl3. In addition, hydrostatic pressure applied to the bottom of a vertically-oriented cell can abolish and even reverse the gravity-induced polarity of cytoplasmic streaming. These data indicate that both gravity and hydrostatic pressure act at the same point of the signal transduction chain leading to the induction of a polarity of cytoplasmic streaming and support the hypothesis that characean cells respond to gravity by sensing a gravity-induced pressure differential between the cell ends.

Staves, M. P.; Wayne, R.; Leopold, A. C.

1992-01-01

98

Hydrostatic Stress Effect on the Yield Behavior of Inconel 100  

NASA Technical Reports Server (NTRS)

Classical metal plasticity theory assumes that hydrostatic stress has negligible effect on the yield and postyield behavior of metals. Recent reexaminations of classical theory have revealed a significant effect of hydrostatic stress on the yield behavior of various geometries. Fatigue tests and nonlinear finite element analyses (FEA) of Inconel 100 (IN100) equal-arm bend specimens and new monotonic tests and nonlinear finite element analyses of IN100 smooth tension, smooth compression, and double-edge notch tension (DENT) test specimens have revealed the effect of internal hydrostatic tensile stresses on yielding. Nonlinear FEA using the von Mises (yielding is independent of hydrostatic stress) and the Drucker-Prager (yielding is linearly dependent on hydrostatic stress) yield functions were performed. A new FEA constitutive model was developed that incorporates a pressure-dependent yield function with combined multilinear kinematic and multilinear isotropic hardening using the ABAQUS user subroutine (UMAT) utility. In all monotonic tensile test cases, the von Mises constitutive model, overestimated the load for a given displacement or strain. Considering the failure displacements or strains for the DENT specimen, the Drucker-Prager FEM s predicted loads that were approximately 3% lower than the von Mises values. For the failure loads, the Drucker Prager FEM s predicted strains that were up to 35% greater than the von Mises values. Both the Drucker-Prager model and the von Mises model performed equally-well in simulating the equal-arm bend fatigue test.

Allen, Phillip A.; Wilson, Christopher D.

2003-01-01

99

Bearings for Extreme Environments.  

National Technical Information Service (NTIS)

Dry lubricated bearings for applications under extreme environmental conditions were developed. Results with ball bearings assembled from bearing rings coated with hard carbide layers, steel balls, and cages of various materials with self-lubricating prop...

H. Gass H. E. Hintermann G. Stehle H. M. Briscoe

1975-01-01

100

Hydro-Support: An Elasto-Hydrostatic Thrust Bearing with Mixed Lubrication.  

National Technical Information Service (NTIS)

The 'classic' solution for the support of a translating, lock-gate, the wheel-on-rail support, has relatively high construction as well as inspection and maintenance costs. An alternative support which has previously been developed for use in the Prins Wi...

R. van Ostayen

2003-01-01

101

A model for hydrostatic consolidation of Pierre shale  

USGS Publications Warehouse

This paper presents closed-form solutions for consolidation of transversely isotropic porous media under hydrostatic stress. The solutions are applied to model the time variation of pore pressure, volume strain and strains parallel and normal to bedding, and to obtain coefficients of consolidation and permeability, as well as other properties, and the bulk modulus resulting from hydrostatic consolidation of Pierre shale. It is found that the coefficients consolidation and permeability decrease and the bulk moduli increase with increasing confining pressure, reflecting the closure of voids in the rock. ?? 1991.

Savage, W. Z.; Braddock, W. A.

1991-01-01

102

Angled Injection: Turbulent Flow Hybrid Bearings Comparison to Test Results  

NASA Technical Reports Server (NTRS)

Hydrostatic/hydrodynamic (hybrid) journal bearings handling process liquids have limited dynamic stability characteristics and their application as support elements to high speed flexible rotating systems is severely restricted. Measurements on water hybrid bearings with angled orifice injection have demonstrated improved rotordynamic performance with virtual elimination of cross-coupled stiffness coefficients and null or negative whirl frequency ratios. A bulk-flow model for prediction of the static performance and force coefficients of hybrid bearings with angled orifice injection is advanced. The analysis reveals that the fluid momentum exchange at the orifice discharge produces a pressure rise in the hydrostatic recess retards the shear flow induced by journal rotation, and thus, reduces cross-coupling forces. The predictions from the model are compared with experimental measurements for a 45 deg. angled orifice injection, 5 recess water hybrid bearing operating at 10.2, 17.4, and 24.6 krpm and with supply pressures of 4, 5.5, and 7 MPa. The correlations include recess pressures, flow rates, and rotordynamic force coefficients at the journal centered position.

SanAndres, Luis; Childs, Dara

1997-01-01

103

Thrust bearing for turbocharger  

Microsoft Academic Search

A thrust bearing is described for sustaining the thrust load of the rotor shaft of a turbocharger, the thrust bearing having a first and second opposed side surface, comprising: A first groove formed in the first side surface of the thrust bearing for holding lubricating oil supplied to the bearing; at least one first oil passage extending from the groove

T. Tamura; N. Shibata; T. Kawakami

1987-01-01

104

Passive magnetic bearing configurations  

DOEpatents

A journal bearing provides vertical and radial stability to a rotor of a passive magnetic bearing system when the rotor is not rotating and when it is rotating. In the passive magnetic bearing system, the rotor has a vertical axis of rotation. Without the journal bearing, the rotor is vertically and radially unstable when stationary, and is vertically stable and radially unstable when rotating.

Post, Richard F. (Walnut Creek, CA) [Walnut Creek, CA

2011-01-25

105

Getting Your Bearings  

NSDL National Science Digital Library

In this activity, learners explore the concept of friction and how ball bearings reduce friction. Learners investigate different uses for ball bearings, how the design has changed over time to incorporate roller bearings, test friction using marbles, and identify the use of ball bearings in everyday items.

Ieee

2013-08-30

106

Punching Tests on Disks of Rock Under Hydrostatic Pressure  

Microsoft Academic Search

A simple apparatus for making punching tests on disks of rock subjected to an additional hydrostatic pressure is described. Experiments have been made on marble, slate, and sandstone. They give an approximate value for the variation of shear strength with con- fining pressure. For marble and slate, confining pressure has a considerable strengthening effect, but for sandstone this effect is

J. C. Jaeger

1962-01-01

107

Some fuzzy controllers for electro-hydrostatic servo-actuator  

Microsoft Academic Search

The aims of this paper, are to obtain for an electro-hydrostatic servo-actuator, good performances, (time response and frequency characteristics), making it usable on aircraft, and a more simple configuration of the regulator, with a short computing time and a more simple program, in order to obtain a cheaper and more simple implementation. The strategy is to reduce the membership functions

D. Liviu; C. Adrian; C. J. Ileana; G. Teodor-Lucian

2010-01-01

108

Calculation of PETN molecular crystal vibrational frequencies under hydrostatic pressure  

NASA Astrophysics Data System (ADS)

First-principles calculations of the effects of hydrostatic pressure on pentaerythritol tetranitrate (PETN) are performed using the all-electron CRYSTAL03 program. The procedure for applying hydrostatic pressure by performing a series of volumetric changes coincident with lattice constant and internal coordinate optimization using various scripts and support programs is described. Once the optimized internal coordinates and lattice constants have been obtained for a given hydrostatic pressure, a separate algorithm consisting of additional scripts and programs is employed for performing a complete normal-mode analysis, with analytic first derivatives and numeric second derivatives of the total energy. The eigenvalues obtained provide the vibrational frequencies and the eigenvectors are used for mode identification. The role of the Gaussian basis sets chosen and the exchange-correlation potential used is discussed. The vibrational frequencies obtained at ambient pressure are shown to compare well with experiment and gas-phase calculations. The shift of the vibrational frequencies under hydrostatic pressure is compared with experiment.

Perger, Warren; Zhao, Jijun

2005-03-01

109

Biomechanics: A pneumo-hydrostatic skeleton in land crabs  

Microsoft Academic Search

Like their aquatic counterparts, terrestrial crabs repeatedly shed their rigid exoskeleton during moulting. But in the case of land crabs, little water is available to provide a temporary hydrostatic skeleton before the new skeleton hardens, and air does not provide the buoyancy necessary to support the animal. Here we show that whenever its exoskeleton is shed, the blackback land crab

Jennifer R. A. Taylor; William M. Kier

2006-01-01

110

Piercing of Steel Sheet by using Hydrostatic Pressure  

Microsoft Academic Search

In order to improve the dimensional accuracy of the hole made by piercing a sheet\\/tube in hydroforming, some piercing methods using hydrostatic pressure are examined. In piercing by pushing a steel sheet into the pressurised liquid with a punch, the sheet is warped and the edge of the hole sinks (edge drop). In piercing by pushing the sheet outwards with

M. Shiomi; Y. Ueda; K. Osakada

2006-01-01

111

Correcting Laboratory Retention Curves for Hydrostatic Fluid Distributions  

Microsoft Academic Search

a mathematical formula that accounts for nonuniform fluid distributions due to hydrostatic fluid pressures, and Many experimental methods for obtaining capillary pressure- thus enables the correction of experimentally obtained volumetric fluid content relations in porous media are affected by odeling the flowof immiscible fluids in a porousnonwetting fluid, whose pressure is gradually stepwise in- medium requires knowledge of the capillary

Marc Jalbert; Jacob H. Dane

2001-01-01

112

Hydrostatic Pressure Dependence of Elastic Constants for Lead Fluoride Crystal.  

National Technical Information Service (NTIS)

The variations of the second order elastic constants (SOEC) and longitudinal and shear moduli with hydrostatic pressure for the lead fluoride have been investigated theoretically, for the first time, by means of a three-body force potential (TBP) model. T...

R. K. Singh C. N. Rao

1988-01-01

113

The compressive failure of polymeric composites under hydrostatic confinement  

Microsoft Academic Search

In order to better establish the fundamental mechanisms responsible for the onset of microstructural instability during compressive loading, several fibre-reinforced polymeric matrix composites were tested under conditions involving hydrostatic confinement. It was found that the dependence of strength upon pressure was mild, indicating that the overwhelming factor in the compressive failure of these materials, irrespective of fibre type, matrix, composition

J. Lankford

1997-01-01

114

Enhancements to the Pellissier H5 Hydrostatic Level  

Microsoft Academic Search

The Pellissier H5 Hydrostatic Level is used for applications requiring an order of magnitude improvement in accuracy over conventional optical leveling. The H5 has been used on such applications as the 32-meter radius track for the National Radio Astronomy Observatory (NRAO) Green Bank Telescope (GBT) alidade, the Final Focus Test Beam (FFTB) project at Stanford Linear Accelerator Center (SLAC), the

David H. Parker; John W. Shelton; Bill Radcliff

2000-01-01

115

High Hydrostatic Pressure Processing of Fruit and Vegetable Products  

Microsoft Academic Search

High hydrostatic pressure (HHP) as a minimal thermal technology is a valuable tool for microbiologically safe and shelf-stable fruit and vegetable production. Microorganisms and deteriorative enzymes can be inhibited or inactivated depending on the amount of pressure and time applied to the product. The resistance of microorganisms and enzymes to pressure in fruit and vegetable products also is dependent on

José A. Guerrero-Beltrán; Gustavo V. Barbosa-Cánovas; Barry G. Swanson

2005-01-01

116

Development And Application Of Non-Hydrostatic Model To The Coastal Engineering Problems  

Microsoft Academic Search

The 3D non-hydrostatic free surface model developed by Kanarska and Maderich (2003) for stratified flows was further improved and has been used to simulate coastal processes. In the model the surface elevation, hydrostatic and non-hydrostatic components of pressure and velocity are calculated at sequential stages. Unlike most non-hydrostatic models, the 2-D depth-averaged momentum and continuity equations were integrated explicitly, whereas

V. Maderych; I. Brovchenko; S. Fenical; V. Nikishov; K. Terletska

2007-01-01

117

Rolling-Element Bearings  

NASA Technical Reports Server (NTRS)

Rolling element bearings are a precision, yet simple, machine element of great utility. A brief history of rolling element bearings is reviewed and the type of rolling element bearings, their geometry and kinematics, as well as the materials they are made from and the manufacturing processes they involve are described. Unloaded and unlubricated rolling element bearings, loaded but unlubricated rolling element bearings and loaded and lubricated rolling element bearings are considered. The recognition and understanding of elastohydrodynamic lubrication covered, represents one of the major development in rolling element bearings.

Hamrock, B. J.; Anderson, W. J.

1983-01-01

118

Design and fabrication of gas bearings for Brayton cycle rotating unit  

NASA Technical Reports Server (NTRS)

Analysis, design, and testing of two types of pivoted pad journal bearings and a spiral-grooved thrust bearing suitable for direct installation into the NASA 2 to 15 KW Brayton Cycle Rotating Unit (BRU) have been accomplished. Both types of tilting pad bearing assemblies are of the preloaded type, consisting of three pads with one pad flexibly mounted. One type utilizes a non-conforming pivot, while the other replaces the conventional spherical pivot with a cruciform flexible member. The thrust bearing is flexure mounted to accommodate static machine mislinement. Test results indicate that both types of journal bearings should satisfy the requirements imposed by the BRU. Hydrostatic tests of the spiral-grooved thrust bearing showed it to be free of pneumatic hammer with as many as 24 orifices over the BRU pressure and load range.

Frost, A.; Tessarzik, J. M.; Arwas, E. B.; Waldron, W. D. (editor)

1973-01-01

119

Introduction to ball bearings  

NASA Technical Reports Server (NTRS)

The purpose of a ball bearing is to provide a relative positioning and rotational freedom while transmitting a load between two structures, usually a shaft and a housing. For high rotational speeds (e.g., in gyroscope ball bearings) the purpose can be expanded to include rotational freedom with practically no wear in the bearing. This condition can be achieved by separating the bearing parts with a coherent film of fluid known as an elastohydrodynamic film. This film can be maintained not only when the bearing carries the load on a shaft, but also when the bearing is preloaded to position the shaft to within micro- or nano-inch accuracy and stability. Background information on ball bearings is provided, different types of ball bearings and their geometry and kinematics are defined, bearing materials, manufacturing processes, and separators are discussed. It is assumed, for the purposes of analysis, that the bearing carries no load.

Hamrock, B. J.; Dowson, D.

1981-01-01

120

High efficiency magnetic bearings  

NASA Technical Reports Server (NTRS)

Research activities concerning high efficiency permanent magnet plus electromagnet (PM/EM) pancake magnetic bearings at the University of Maryland are reported. A description of the construction and working of the magnetic bearing is provided. Next, parameters needed to describe the bearing are explained. Then, methods developed for the design and testing of magnetic bearings are summarized. Finally, a new magnetic bearing which allows active torque control in the off axes directions is discussed.

Studer, Philip A.; Jayaraman, Chaitanya P.; Anand, Davinder K.; Kirk, James A.

1993-01-01

121

Post-thaw survival of cryopreserved biological material by hydrostatic pressure challenge  

US Patent & Trademark Office Database

The present invention relates to a method for improving post-thaw survival of cryopreserved biological material comprising applying hydrostatic pressure to said biological material; keeping the said biological material at the hydrostatic pressure for a predetermined time period; releasing the hydrostatic pressure; and freezing the said biological material using any protocol applicable thereto.

2013-04-09

122

Transcriptional activation in chondrocytes submitted to hydrostatic pressure.  

PubMed

At present, only a little is known about the transcriptional regulation in chondrocytes submitted to various physicomechanical factors known to exist in articular cartilage. Recently, we have investigated the effects of hydrostatic pressure on transcriptional control in chondrocytes using human chondrosarcoma and immortalized chondrocyte cell lines for the experiments. Hydrostatic pressure was applied on the cells in a special computer-controlled, water-filled pressure chamber, where cyclic and static pressures up to 32 MPa can be created. Differential display RT-PCR and probing of cDNA arrays are the methods we have used to study differential gene expression due to hydrostatic pressure. By differential display RT-PCR experiments, we have observed several differentially expressed cDNA bands under continuous 30 MPa hydrostatic pressure, while 30 MPa cyclic pressure at 1 Hz produced much fewer changes. In the first phase of our studies, we have focused on the effects of 30 MPa hydrostatic pressure because it causes a unique hsp70-mediated stress response in immortalized chondrocytes. Differential display RT-PCR screening provided us with several clones that derive from low-abundance mRNAs, such as death-associated protein 3 (DAP3), a nucleotide-binding protein which increases due to interferon-gamma induced cell death; PTZ-17 (or p311), a seizure-related protein; H-NUC, a nuclear DNA binding protein; and one new gene of unknown function. In Northern blots, an induction was confirmed for the new gene, DAP3 and PTZ-17 were down-regulated in some but not in all parallel experiments; however, basal level of H-NUC mRNA was too low to be detected in Northern blots. We then chose to widen our screening to a number of known genes arrayed as cDNA blots. Under 30 MPa continuous hydrostatic pressure, four different time points were chosen (0, 3, 6 and 24 h) for the experiments. The screening of 588 cDNAs showed 15 up-regulated and 6 down-regulated genes. Consistently with our previous results hsp70 was highly induced, as well as hsp40, a chaperone protein functioning together with hsp70. Gadd45 and to a lesser extent Gadd153 (stress genes induced by, e.g., ionizing radiation and ischaemia) were up-regulated, as well as p21waf1,cip1, a protein participating in cell cycle regulation that can interact with Gadd45. Northern blots confirmed Gadd45 induction. Down-regulated transcripts included, e.g., DAD-1, glutathione S-transferase pI, DNA-binding inhibitor ID-1H, and cytoplasmic dynein light chain. PMID:10912181

Sironen, R; Elo, M; Kaarniranta, K; Helminen, H J; Lammi, M J

2000-01-01

123

Hydrostatics and steady dynamics of spatially varying electromechanical flow structures  

NASA Technical Reports Server (NTRS)

The hydrostatic and steady laminar hydrodynamic equilibria of spatially varying electromechanical flow structures are investigated. Under certain conditions the relationship between the dielectric height of rise and the applied voltage is found to be double valued. It is found that one of the two equilibrium values is always unstable. This gives rise to the experimentally observed spontaneous rise of the fluid to the top of the structure, once a certain critical voltage is reached. Starting above this critical voltage with the structure completely filled and decreasing the applied voltage toward the critical value results in pinch-in failure at an intermediate point along the structure and trapping of dielectric fluid at the top. The simple mathematical model developed predicts all these phenomena, without recourse to tedious point-by-point surface force equilibrium determination. Experiments are reported which verify the results for the hydrostatic case.

Jones, T. B.

1974-01-01

124

Hydrostatic compression of Fe(1-x)O wuestite  

NASA Technical Reports Server (NTRS)

Hydrostatic compression measurements on Fe(0.95)O wuestite up to 12 GPa yield a room temperature value for the isothermal bulk modulus of K(ot) = 157 (+ or - 10) GPa at zero pressure. This result is in accord with previous hydrostatic and nonhydrostatic measurements of K(ot) for wuestites of composition: 0.89 = Fe/O 0.95. Dynamic measurements of the bulk modulus by ultrasonic, shock-wave and neutron-scattering experiments tend to yield a larger value: K(ot) approximately 180 GPa. The discrepancy between static and dynamic values cannot be explained by the variation of K(ot) with composition, as has been proposed. This conclusion is based on high-precision compression data and on theoretical models of the effects of defects on elastic constants. Barring serious errors in the published measurements, the available data suggest that wuestite exhibits a volume relaxation under pressure.

Jeanloz, R.; Sato-Sorensen, Y.

1986-01-01

125

Active Magnetic Bearings.  

National Technical Information Service (NTIS)

The paper deals with a nonconventional type of bearing that is active magnetic bearing (AMB). Rotor suspension in AMB is achieved by attractive forces of electromagnetic poles. To stabilize the rotor position, the automatic control system is introduced. T...

Y. N. Zhuravlyov

1992-01-01

126

High Efficiency Magnetic Bearings.  

National Technical Information Service (NTIS)

Research activities concerning high efficiency permanent magnet plus electromagnet (PM/EM) pancake magnetic bearings at the University of Maryland are reported. A description of the construction and working of the magnetic bearing is provided. Next, param...

P. A. Studer C. P. Jayaraman D. K. Anand J. A. Kirk

1993-01-01

127

Shielded Bearing Lubrication.  

National Technical Information Service (NTIS)

Precise quantities of lubricant under automatic control are injected through chambers of housings into shielded rolling element bearings. Separate feed line conduits directly deliver the lubricant to the shielded critical surfaces of such bearings and ins...

J. A. Wong T. L. Daugherty G. D. Huntzberry

1996-01-01

128

Mechanical spin bearings  

NASA Technical Reports Server (NTRS)

A spin bearing assembly including, a pair of mutually opposing complementary bearing support members having mutually spaced apart bearing support surfaces which may be, for example, bearing races and a set of spin bearings located therebetween. Each spin bearing includes a pair of end faces, a central rotational axis passing through the end faces, a waist region substantially mid-way between the end faces and having a first thickness dimension, and discrete side surface regions located between the waist region and the end faces and having a second thickness dimension different from the first thickness dimension of the waist region and wherein the side surface regions further have respective curvilinear contact surfaces adapted to provide a plurality of bearing contact points on the bearing support members.

Vranish, John M. (Inventor)

1998-01-01

129

High hydrostatic pressure inactivation kinetics of Salmonella typhimurium  

Microsoft Academic Search

The inactivation kinetics of high hydrostatic pressure for Salmonella typhimurium (KUEN 137) inoculated in tryptone soy broth (TSB) and foods (raw milk and orange juice) were studied from 250 to 400 MPa, 15–45 °C and pH adjusted from 5.0 to 7.0. The rate of inactivation of S. typhimurium during the initial 10 min was far greater than during the remaining treatment time. The

Osman Erkmen

2009-01-01

130

A free-standing hydrostatic bioreactor for neural tissue culture  

Microsoft Academic Search

A hydrostatic bioreactor for the study of cells and tissue is described. The system, which was developed to determine the effects of increased pressure on neural tissue, is capable of applying pressures of up to 100 mmHg with an error of ±2 mmHg in an enclosed chamber. On-line pH, pressure and temperature control enables the system to be monitored continuously

A. Previti; G. Vozzi; C. Scarpa; E. Novelli; V. Resta; L. Galli-Resta; F. Vivaldi; A. Ahluwalia

2002-01-01

131

Necessary and sufficient condition for hydrostatic equilibrium in general relativity  

Microsoft Academic Search

We present explicit examples to show that the `compatibility criterion' is\\u000acapable of providing a {\\\\em necessary} and {\\\\em sufficient} condition for any\\u000aregular configuration to be compatible with the state of hydrostatic\\u000aequilibrium. This conclusion is drawn on the basis of the finding that the\\u000a$M-R$ relation gives the necessary and sufficient condition for dynamical\\u000astability of equilibrium configurations

2006-01-01

132

Effect of high hydrostatic pressure on lycopene stability  

Microsoft Academic Search

The stability and isomerization of lycopene by high hydrostatic pressure (HHP) were evaluated. Lycopene standard in hexane and tomato puree were pressurized at 100, 200, 300, 400, 500 and 600MPa for 12min at controlled temperature (20±1°C). After application of pressure, samples were stored at refrigerator temperature (4±1°C) and ambient laboratory temperature (24±1°C) under lightproof conditions. HPLC and spectral analysis were

Weifen Qiu; Hanhu Jiang; Haifeng Wang; Yulong Gao

2006-01-01

133

Cold hydrostatic extrusion of powder metallurgy processed superconducting materials  

SciTech Connect

Hydrostatically extruded multifilamentary composites of Cu-Nb, Cu-Nb with a central tin core and Nb-Al were directly drawn to fine wires without intermediate annealing. Uniform deformation was observed throughout the process. Cu-Nb composite wires were Sn plated for external diffusion. Overall critical current densities of better than 10/sup 4/ A/cm/sup 2/ at 16 T were achieved for Nb/sub 3/Sn-Cu composite wires with nominal areal reductions of 2000.

Pourrahimi, S.; Thieme, C.L.H.; Foner, S.; Murphy, R.J.

1983-12-01

134

Testing Hydrostatic Equilibrium in Galaxy Cluster MS 2137  

NASA Astrophysics Data System (ADS)

We test the assumption of strict hydrostatic equilibrium in galaxy cluster MS2137.3-2353 (MS 2137) using the latest Chandra X-ray observations and results from a combined strong and weak lensing analysis based on optical observations. We deproject the two-dimensional X-ray surface brightness and mass surface density maps assuming spherical and spheroidal dark matter distributions. We find a significant, 40%-50%, contribution from non-thermal pressure in the core assuming a spherical model. This non-thermal pressure support is similar to what was found by Molnar et al. using a sample of massive relaxed clusters drawn from high-resolution cosmological simulations. We have studied hydrostatic equilibrium in MS 2137 under the assumption of elliptical cluster geometry adopting prolate models for the dark matter density distribution with different axis ratios. Our results suggest that the main effect of ellipticity (compared to spherical models) is to decrease the non-thermal pressure support required for equilibrium at all radii without changing the distribution qualitatively. We find that a prolate model with an axis ratio of 1.25 (axis in the line of sight over perpendicular to it) provides a physically acceptable model implying that MS 2137 is close to hydrostatic equilibrium at about 0.04-0.15 R vir and has an about 25% contribution from non-thermal pressure at the center. Our results provide further evidence that there is a significant contribution from non-thermal pressure in the core region of even relaxed clusters, i.e., the assumption of hydrostatic equilibrium is not valid in this region, independently of the assumed shape of the cluster.

Chiu, I.-Non Tim; Molnar, Sandor M.

2012-09-01

135

Axial Halbach Magnetic Bearings  

NASA Technical Reports Server (NTRS)

Axial Halbach magnetic bearings have been investigated as part of an effort to develop increasingly reliable noncontact bearings for future high-speed rotary machines that may be used in such applications as aircraft, industrial, and land-vehicle power systems and in some medical and scientific instrumentation systems. Axial Halbach magnetic bearings are passive in the sense that unlike most other magnetic bearings that have been developed in recent years, they effect stable magnetic levitation without need for complex active control.

Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

2008-01-01

136

Polar Bears Change Diet  

NSDL National Science Digital Library

This radio broadcast from 2001 explains how polar bears have adjusted their diet due to the climate warming around Hudson Bay, Canada. The ringed seals that polar bears normally eat have been harder for polar bears to get to, due to disappearing ice. This has forced polar bears to begin eating harbor seals and bearded seals. The clip is 4 minutes and 15 seconds in length.

Schneider, Doug

2007-12-12

137

Tracking Polar Bears  

USGS Multimedia Gallery

Movements of 9 satellite-collared adult female polar bears were tracked in February, 2010 by satellite telemetry. Bears were collared in 2007, 2008, and 2009 on the spring-time sea ice of the southern Beaufort Sea or on the autumn pack ice in 2009. Polar bear satellite telemetry data are shown with ...

2010-04-13

138

Cryogenic Hybrid Magnetic Bearing  

NASA Technical Reports Server (NTRS)

Cryogenic hybrid magnetic bearing is example of class of magnetic bearings in which permanent magnets and electromagnets used to suspend shafts. Electromagnets provide active control of position of shaft. Bearing operates at temperatures from -320 degrees F (-196 degrees C) to 650 degrees F (343 degrees C); designed for possible use in rocket-engine turbopumps, where effects of cryogenic environment and fluid severely limit lubrication of conventional ball bearings. This and similar bearings also suitable for terrestrial rotating machinery; for example, gas-turbine engines, high-vacuum pumps, canned pumps, precise gimbals that suspend sensors, and pumps that handle corrosive or gritty fluids.

Meeks, Crawford R.; Dirusso, Eliseo; Brown, Gerald V.

1994-01-01

139

Bulk-Flow Analysis of Hybrid Thrust Bearings for Advanced Cryogenic Turbopumps  

NASA Technical Reports Server (NTRS)

A bulk-flow analysis and computer program for prediction of the static load performance and dynamic force coefficients of angled injection, orifice-compensated hydrostatic/hydrodynamic thrust bearings have been completed. The product of the research is an efficient computational tool for the design of high-speed thrust bearings for cryogenic fluid turbopumps. The study addresses the needs of a growing technology that requires of reliable fluid film bearings to provide the maximum operating life with optimum controllable rotordynamic characteristics at the lowest cost. The motion of a cryogenic fluid on the thin film lands of a thrust bearing is governed by a set of bulk-flow mass and momentum conservation and energy transport equations. Mass flow conservation and a simple model for momentum transport within the hydrostatic bearing recesses are also accounted for. The bulk-flow model includes flow turbulence with fluid inertia advection, Coriolis and centrifugal acceleration effects on the bearing recesses and film lands. The cryogenic fluid properties are obtained from realistic thermophysical equations of state. Turbulent bulk-flow shear parameters are based on Hirs' model with Moody's friction factor equations allowing a simple simulation for machined bearing surface roughness. A perturbation analysis leads to zeroth-order nonlinear equations governing the fluid flow for the thrust bearing operating at a static equilibrium position, and first-order linear equations describing the perturbed fluid flow for small amplitude shaft motions in the axial direction. Numerical solution to the zeroth-order flow field equations renders the bearing flow rate, thrust load, drag torque and power dissipation. Solution to the first-order equations determines the axial stiffness, damping and inertia force coefficients. The computational method uses well established algorithms and generic subprograms available from prior developments. The Fortran9O computer program hydrothrust runs on a Windows 95/NT personal computer. The program, help files and examples are licensed by Texas A&M University Technology License Office. The study of the static and dynamic performance of two hydrostatic/hydrodynamic bearings demonstrates the importance of centrifugal and advection fluid inertia effects for operation at high rotational speeds. The first example considers a conceptual hydrostatic thrust bearing for an advanced liquid hydrogen turbopump operating at 170,000 rpm. The large axial stiffness and damping coefficients of the bearing should provide accurate control and axial positioning of the turbopump and also allow for unshrouded impellers, therefore increasing the overall pump efficiency. The second bearing uses a refrigerant R134a, and its application in oil-free air conditioning compressors is of great technological importance and commercial value. The computed predictions reveal that the LH2 bearing load capacity and flow rate increase with the recess pressure (i.e. increasing orifice diameters). The bearing axial stiffness has a maximum for a recess pressure rati of approx. 0.55. while the axial damping coefficient decreases as the recess pressure ratio increases. The computer results from three flow models are compared. These models are a) inertialess, b) fluid inertia at recess edges only, and c) full fluid inertia at both recess edges and film lands. The full inertia model shows the lowest flow rates, axial load capacity and stiffness coefficient but on the other hand renders the largest damping coefficients and inertia coefficients. The most important findings are related to the reduction of the outflow through the inner radius and the appearance of subambient pressures. The performance of the refrigerant hybrid thrust bearing is evaluated at two operating speeds and pressure drops. The computed results are presented in dimensionless form to evidence consistent trends in the bearing performance characteristics. As the applied axial load increases, the bearing film thickness and flow rate decrease while the recess pressure increases. The a

SanAndres, Luis

1998-01-01

140

The effect of hydrostatic pressure on S-layer-supported lipid membranes  

Microsoft Academic Search

We report on the behavior of unsupported and surface layer (S-layer)-supported lipid membranes at the application of a uniform hydrostatic pressure. At a hydrostatic pressure gradient higher than 6 N\\/m2, unsupported lipid membranes, independent from which side pressurized and S-layer-supported lipid membranes pressurized from the lipid-faced side revealed a pronounced increase in capacitance. A maximal hydrostatic pressure gradient of 11.0

Bernhard Schuster; Uwe B. Sleytr

2002-01-01

141

Thermal conductivity and compressive strain of foam neoprene insulation under hydrostatic pressure  

Microsoft Academic Search

The purpose of this study was to show that the thermal properties of foam neoprene under hydrostatic pressure cannot be predicted by theoretical means, and that uni-axial pressure cannot simulate hydrostatic compression. The thermal conductivity and compressive strain of foam neoprene were measured under hydrostatic pressure. In parallel, uni-axial compressive strain data were collected. The experimental set-up and data were

Erik Bardy; Joseph Mollendorf; David Pendergast

2005-01-01

142

Nonlinear study of a misaligned hydrodynamic journal bearing  

SciTech Connect

Hydrodynamic/hydrostatic journal bearings have been widely used in various types of high speed rotating machinery. For space applications, the issue of using cryogenic fluids as working lubricants has steadily gained in significance. The main objective of this paper is to study the nonlinear effects in a hydrodynamic journal bearing with special attention to the effects of journal axial misalignment. The numerical model that couples the Reynolds equation with the dynamics of the rotor is solved by means of a finite difference solution technique. Fluid film pressures that resulted from an iterative scheme are integrated to generate bearing supporting forces. A two-dimensional Newton-Raphson iteration method is used to locate the journal equilibrium position from which both linear and nonlinear bearing stiffness are evaluated by means of the small perturbation technique. The effects of axial misalignment on bearing equilibrium position, lubricant fluid film thickness, pressure distribution, and stiffness characteristics are examined. General conclusions are drawn from the parametric studies in load, speed, inlet temperature, and axial misalignment. 24 refs.

Choy, F.K.; Braun, M.J.; Hu, Y. (Akron Univ., OH (United States))

1993-07-01

143

Bearings: Technology and needs  

NASA Technical Reports Server (NTRS)

A brief status report on bearing technology and present and near-term future problems that warrant research support is presented. For rolling element bearings a material with improved fracture toughness, life data in the low Lambda region, a comprehensive failure theory verified by life data and incorporated into dynamic analyses, and an improved corrosion resistant alloy are perceived as important needs. For hydrodynamic bearings better definition of cavitation boundaries and pressure distributions for squeeze film dampers, and geometry optimization for minimum power loss in turbulent film bearings are needed. For gas film bearings, foil bearing geometries that form more nearly optimum film shapes for maximum load capacity, and more effective surface protective coatings for high temperature operation are needed.

Anderson, W. J.

1982-01-01

144

Hydrostatic extrusion of Cu-Ag melt spun ribbon  

DOEpatents

The present invention provides a method of producing high-strength and high-conductance copper and silver materials comprising the steps of combining a predetermined ratio of the copper with the silver to produce a composite material, and melt spinning the composite material to produce a ribbon of copper and silver. The ribbon of copper and silver is heated in a hydrogen atmosphere, and thereafter die pressed into a slug. The slug then is placed into a high-purity copper vessel and the vessel is sealed with an electron beam. The vessel and slug then are extruded into wire form using a cold hydrostatic extrusion process.

Hill, Mary Ann (Los Alamos, NM); Bingert, John F. (Jemez Springs, NM); Bingert, Sherri A. (Jemez Springs, NM); Thoma, Dan J. (Los Alamos, NM)

1998-01-01

145

Hydrostatic extrusion of Cu-Ag melt spun ribbon  

DOEpatents

The present invention provides a method of producing high-strength and high-conductance copper and silver materials comprising the steps of combining a predetermined ratio of the copper with the silver to produce a composite material, and melt spinning the composite material to produce a ribbon of copper and silver. The ribbon of copper and silver is heated in a hydrogen atmosphere, and thereafter die pressed into a slug. The slug then is placed into a high-purity copper vessel and the vessel is sealed with an electron beam. The vessel and slug then are extruded into wire form using a cold hydrostatic extrusion process. 5 figs.

Hill, M.A.; Bingert, J.F.; Bingert, S.A.; Thoma, D.J.

1998-09-08

146

An application of an efficient non-hydrostatic mesoscale model  

NASA Astrophysics Data System (ADS)

This paper deals with a non-hydrostatic mesoscale model that achieves full vectorization on computers like the CYBER 205. The model formulation ensures the conservation of all fluxes and takes into account the terrain inhomogeneities by the aid of suitable transformations. The diagnostic equation for the pressure change is solved using a very efficient vectorized elliptic solver. By imposing appropriate boundary conditions no additional precautions at the boundaries are necessary to achieve meaningful results. As an application, the steady-state inviscid flow over a single mountain is simulated.

Flassak, Th.; Moussiopoulos, N.

1987-12-01

147

Bear Spray Safety Program  

USGS Publications Warehouse

A bear spray safety program for the U.S. Geological Survey (USGS) was officially initiated by the Firearms Safety Committee to address accident prevention and to promote personnel training in bear spray and its transportation, storage, and use for defense against wild animals. Used as part of a system including firearms, or used alone for those who choose not to carry a firearm, bear spray is recognized as an effective tool that can prevent injury in a wild animal attack.

Blome, C. D.; Kuzniar, R. L.

2009-01-01

148

The Incredible Water Bear  

NSDL National Science Digital Library

This image-rich Micscape Magazine article explores how water bears can be found almost everywhere yet are still unknown to almost everybody, why there are relatively few light microscope photographs of water bears in the literature and on the Web, and how light microscopy can outperform scanning electron microscopy when viewing these animals. It includes a list of historical references, early sketches, and colorful images of water bears, also known as tardigrades.

Mach, Martin; Magazine, Micscape

149

Bearing restoration by grinding  

NASA Technical Reports Server (NTRS)

A joint program was undertaken by the NASA Lewis Research Center and the Army Aviation Systems Command to restore by grinding those rolling-element bearings which are currently being discarded at aircraft engine and transmission overhaul. Three bearing types were selected from the UH-1 helicopter engine (T-53) and transmission for the pilot program. No bearing failures occurred related to the restoration by grinding process. The risk and cost of a bearing restoration by grinding programs was analyzed. A microeconomic impact analysis was performed.

Hanau, H.; Parker, R. J.; Zaretsky, E. V.; Chen, S. M.; Bull, H. L.

1976-01-01

150

The Effect of Bearing Deformation in Slider-bearing Lubrication  

Microsoft Academic Search

The slider-bearing with the bearing elastic is analyzed for its load carrying characteristics. The deflection of the bearing under load acts to reduce the load capacity by an amount which can be significant as is illustrated by a numerical example. Contributed by the ASLE Technical Committee on Bearings and Bearing Lubrication and presented at the Annual Meeting of the American

F. Osterle; Edward Saibel

1958-01-01

151

Power transmission arrangement for a hydrostatically driven vehicle  

SciTech Connect

A power transmission arrangement is described for a hydrostatically driven vehicle having a vehicle body and a pair of endless tracks each mounted on each side of the vehicle body. The arrangement consists of: a prime mover mounted at the rear of the vehicle; a power transmission shaft connected to the prime mover; power distributor means mounted on a front section of the vehicle body, the power distributor means having a power input connectible to the power transmission shaft and at least two power outputs; a pair of pump and motor units each unit being mounted on either side of the vehicle body relative to the power transmission shaft, intermediate the prime mover and the power distributor means, and forming a hydrostatic transmission, each unit having a power input connectible to the power output of the power distributor means and a power output; and a pair of final drive means for driving the endless tracks, each of the final drive means being connectible to a power output of the pump and motor unit.

Tokunga, N.

1986-03-25

152

Microbial Growth Modification by Compressed Gases and Hydrostatic Pressure  

PubMed Central

Studies of the growth-modifying actions for Escherichia coli, Saccharomyces cerevisiae, and Tetrahymena thermophila of helium, nitrogen, argon, krypton, xenon, and nitrous oxide led to the conclusion that there are two definable classes of gases. Class 1 gases, including He, N2, and Ar, are not growth inhibitors; in fact, they can reverse the growth inhibitory action of hydrostatic pressures. Class 2 gases, including Kr, Xe, and N2O, are potent growth inhibitors at low pressures. For example, at 24°C, 50% growth-inhibitory pressures of N2O were found to be ca. 1.7 MPa for E. coli, 1.0 MPa for S. cerevisiae, and 0.5 MPa for T. thermophila. Class 1 gases could act as potentiators for growth inhibition by N2O, O2, Kr, or Xe. Hydrostatic pressure alone is known to reverse N2O inhibition of growth, but we found that it did not greatly alter oxygen toxicity. Therefore, potentiation by class 1 gases appeared to be a gas effect rather than a pressure effect. The temperature profile for growth inhibition of S. cerevisiae by N2O revealed an optimal temperature for cell resistance of ca. 24°C, with lower resistance at higher and lower temperatures. Overall, it appeared that microbial growth modification by hyperbaric gases could not be related to their narcotic actions but reflected definably different physiological actions.

Thom, Stephen R.; Marquis, Robert E.

1984-01-01

153

Inelastic compaction, dilation and hysteresis of sandstones under hydrostatic conditions  

NASA Astrophysics Data System (ADS)

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'.

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

2014-05-01

154

DX centers in III-V semiconductors under hydrostatic pressure  

SciTech Connect

DX centers are deep level defects found in some III-V semiconductors. They have persistent photoconductivity and large difference between thermal and optical ionization energies. Hydrostatic pressure was used to study microstructure of these defects. A new local vibrational mode (LVM) was observed in hydrostatically stressed, Si-doped GaAs. Corresponding infrared absorption peak is distinct from the Si{sub Ga} shallow donor LVM peak, which is the only other LVM peak observed in our samples, and is assigned to the Si DX center. Analysis of the relative intensities of the Si DX LVM and the Si shallow donor LVM peaks, combined with Hall effect and resistivity indicate that the Si DX center is negatively charged. Frequency of this new mode provides clues to the structure of this defect. A pressure induced deep donor level in S-doped InP was also discovered which has the properties of a DX center. Pressure at which the new defect becomes more stable than the shallow donor is 82 kbar. Optical ionization energy and energy dependence of the optical absorption cross section was measured for this new effect. Capture barrier from the conduction band into the DX state were also determined. That DX centers can be formed in InP by pressure suggests that DX states should be common in n-type III-V semiconductors. A method is suggested for predicting under what conditions these defects will be the most stable form of the donor impurity.

Wolk, J.A.

1992-11-01

155

Non-hydrostatic sound-proof equations of motion for gravity-dominated compressible flows  

NASA Astrophysics Data System (ADS)

Non-hydrostatic sound-proof equations of motion for gravity-dominated compressible flows Compressible non-hydrostatic equations of motion with density diagnosed from potential temperature through hydrostatic balance are derived from Hamilton's principle of least action. The corresponding local budgets of energy, potential vorticity and momentum are obtained. Slaving density to potential temperature suppresses the degrees of freedom supporting the propagation of acoustic waves and results in a sound-proof system. The linear normal modes and dispersion relationship for infinitesimal departures from an isothermal state of rest on f- and ?- planes are studied and found to be very accurate from hydrostatic to non-hydrostatic scales. Especially the Lamb wave and long Rossby waves are not distorted, unlike with anelastic or pseudo-incompressible systems. Compared to similar equations derived by Arakawa and Konor (2009), the unified system derived here possesses an additional term in the horizontal momentum budget. This apparent force is crucial for the derivation of a well-defined linear elliptic problem. Unlike with anelastic/pseudo-incompressible systems or the equations obtained by Arakawa and Konor (2009), the elliptic problem is vertically fourth-order, reflecting the fact that the hydrostatic constraint satisfied by density involves a vertical derivative. As with hydrostatic equations, vertical velocity is diagnosed through Richardson's equation. Our unified system has therefore precisely the same degrees of freedom as the hydrostatic primitive equations, while retaing accuracy from hydrostatic to non-hydrostatic scales. These equations may be useful as the basis of global non-hydrostatic numerical models. They also provide an accurate way to filter out the acoustic component from a given flow. Variational data assimilation systems may benefit from such a filter, restricting the optimization space to physically relevant motion. Similarly, filtering may be useful to prevent the transient emission of acoustic waves in a fully-compressible model at initialization or after physics parameterizations have acted.

Dubos, Thomas; Voitus, Fabrice

2014-05-01

156

Bearing fatigue investigation 3  

NASA Technical Reports Server (NTRS)

The operating characteristics of large diameter rolling-element bearings in the ultra high speed regimes expected in advanced turbine engines for high performance aircraft were investigated. A high temperature lubricant, DuPont Krytox 143 AC, was evaluated at bearing speeds to 3 million DN. Compared to the results of earlier, similar tests using a MIL-L-23699 (Type II) lubricant, bearings lubricated with the high density Krytox fluid showed significantly higher power requirements. Additionally, short bearing lives were observed when this fluid was used with AISI M50 bearings in an air atmosphere. The primary mode of failure was corrosion initiated surface distress (fatigue) on the raceways. The potential of a case-carburized bearing to sustain a combination of high-tangential and hertzian stresses without experiencing race fracture was also investigated. Limited full scale bearing tests of a 120 mm bore ball bearing at a speed of 25,000 rpm (3 million DN) indicated that a carburized material could sustain spalling fatigue without subsequent propagation to fracture. Planned life tests of the carburized material had to be aborted, however, because of apparent processing-induced material defects.

Nahm, A. H.; Bamberger, E. N.; Signer, H. R.

1982-01-01

157

Grizzly bears and forestry  

Microsoft Academic Search

Timber harvesting and oil and gas extraction create ecological change beyond just the footprint of the resource extraction. These activities also create a permanent network of roads that can have lasting effects on forest ecology. Grizzly bears (Ursus arctos) suffer higher mortality when in close proximity to roads, yet bears in the foothills of west-central Alberta, continue to use these

C. L. Roever; M. S. Boyce; G. B. Stenhouse

2008-01-01

158

Bearing Lubrication Apparatus.  

National Technical Information Service (NTIS)

The patent described apparatus for lubrication of anti-friction bearings which uses the oil bleeding characteristics of grease. The apparatus consists of a housing for attachment to a bearing and a grease reservoir wherein the grease is retained in a slop...

K. H. Warren

1970-01-01

159

Antident Bearing-Ball Retainer  

NASA Technical Reports Server (NTRS)

Jig prevents indentation of bearing balls by hard contact with edges of inner bearing rings during assembly. Jig is retaining ring which includes fingers that separates balls and pushes them against outer bearing and out of contact with inner bearing rings. Eliminates need for ball-retaining tabs on bearing cage.

Thomas, Larry L., Jr.

1995-01-01

160

Thermohydrodynamic analysis of cryogenic liquid turbulent flow fluid film bearings, phase 2  

NASA Technical Reports Server (NTRS)

The Phase 2 (1994) Annual Progress Report presents two major report sections describing the thermal analysis of tilting- and flexure-pad hybrid bearings, and the unsteady flow and transient response of a point mass rotor supported on fluid film bearings. A literature review on the subject of two-phase flow in fluid film bearings and part of the proposed work for 1995 are also included. The programs delivered at the end of 1994 are named hydroflext and hydrotran. Both codes are fully compatible with the hydrosealt (1993) program. The new programs retain the same calculating options of hydrosealt plus the added bearing geometries, and unsteady flow and transient forced response. Refer to the hydroflext & hydrotran User's Manual and Tutorial for basic information on the analysis and instructions to run the programs. The Examples Handbook contains the test bearing cases along with comparisons with experimental data or published analytical values. The following major tasks were completed in 1994 (Phase 2): (1) extension of the thermohydrodynamic analysis and development of computer program hydroflext to model various bearing geometries, namely, tilting-pad hydrodynamic journal bearings, flexure-pad cylindrical bearings (hydrostatic and hydrodynamic), and cylindrical pad bearings with a simple elastic matrix (ideal foil bearings); (2) improved thermal model including radial heat transfer through the bearing stator; (3) calculation of the unsteady bulk-flow field in fluid film bearings and the transient response of a point mass rotor supported on bearings; and (4) a literature review on the subject of two-phase flows and homogeneous-mixture flows in thin-film geometries.

Sanandres, Luis

1994-01-01

161

Birefringence and dispersion properties of elliptical hollow core optical fiber under hydrostatic pressure  

Microsoft Academic Search

Highly birefringent elliptical hollow core optical fiber under hydrostatic pressure is analyzed in this work using finite element method. The combined effects of thermal stress generated during fabrication and external applied stress have been considered. Birefringence increases while group velocity dispersion decreases when the fiber is under hydrostatic pressure. Higher birefringence, lower material dispersion and moderate effective area can make

Ahmad Zubair; Saima Afroz Siddiqui; M. Shah Alam

2009-01-01

162

Intermittent sub-ambient interstitial hydrostatic pressure as a potential mechanical stimulator for chondrocyte metabolism  

Microsoft Academic Search

Objective: Experimental findings have suggested that the metabolic activities of articular cartilage can be influenced by mechanical stimuli. Our mathematical analysis predicted that cyclic compressive loading may create periods of intermittent sub-ambient hydrostatic pressure within the cartilage extracellular matrix. Based on this mathematical analysis, the present study was aimed to investigate whether the intermittent sub-ambient hydrostatic pressure, created in the

Jun-Kyo Suh; Goo H. Baek; Asbjørn Arøen; Christina M. Malin; Christopher Niyibizi; Christopher H. Evans; Andrea Westerhausen-Larson

1999-01-01

163

Tensile Plastic Stress-Strain Relations of 2017T4 Aluminum Alloy under Hydrostatic Pressure.  

National Technical Information Service (NTIS)

For the aluminum alloy 2017-T4 tested in tension under hydrostatic pressures up to 50,000 psi, the following conclusions can be made: (1) The presence of hydrostatic pressure has no apparent effect on the strain-hardening coefficient n and the strength co...

L. W. Hu H. E. Shull

1964-01-01

164

Dynamic Culturing of Cartilage Tissue: The Significance of Hydrostatic Pressure  

PubMed Central

Human articular cartilage functions under a wide range of mechanical loads in synovial joints, where hydrostatic pressure (HP) is the prevalent actuating force. We hypothesized that the formation of engineered cartilage can be augmented by applying such physiologic stimuli to chondrogenic cells or stem cells, cultured in hydrogels, using custom-designed HP bioreactors. To test this hypothesis, we investigated the effects of distinct HP regimens on cartilage formation in vitro by either human nasal chondrocytes (HNCs) or human adipose stem cells (hASCs) encapsulated in gellan gum (GG) hydrogels. To this end, we varied the frequency of low HP, by applying pulsatile hydrostatic pressure or a steady hydrostatic pressure load to HNC-GG constructs over a period of 3 weeks, and evaluated their effects on cartilage tissue-engineering outcomes. HNCs (10×106 cells/mL) were encapsulated in GG hydrogels (1.5%) and cultured in a chondrogenic medium under three regimens for 3 weeks: (1) 0.4?MPa Pulsatile HP; (2) 0.4?MPa Steady HP; and (3) Static. Subsequently, we applied the pulsatile regimen to hASC-GG constructs and varied the amplitude of loading, by generating both low (0.4?MPa) and physiologic (5?MPa) HP levels. hASCs (10×106 cells/mL) were encapsulated in GG hydrogels (1.5%) and cultured in a chondrogenic medium under three regimens for 4 weeks: (1) 0.4?MPa Pulsatile HP; (2) 5?MPa Pulsatile HP; and (3) Static. In the HNC study, the best tissue development was achieved by the pulsatile HP regimen, whereas in the hASC study, greater chondrogenic differentiation and matrix deposition were obtained for physiologic loading, as evidenced by gene expression of aggrecan, collagen type II, and sox-9; metachromatic staining of cartilage extracellular matrix; and immunolocalization of collagens. We thus propose that both HNCs and hASCs detect and respond to physical forces, thus resembling joint loading, by enhancing cartilage tissue development in a frequency- and amplitude-dependant manner.

Pereira, Ana L.; Duarte, Ana R.C.; Frias, Ana M.; Pedro, Adriano J.; Oliveira, Joao T.; Sousa, Rui A.; Reis, Rui L.

2012-01-01

165

HTS magnetic bearings  

NASA Astrophysics Data System (ADS)

Radial HTS magnetic bearings (SMB) up to 200 mm size are developed and tested in prototype fast rotating machines to demonstrate the potential to replace conventional bearings. The individual rotational bearing components HTS and PM, their physical interaction and technology is reviewed. Characterisation experiments are conducted to understand the rotor dynamic behaviour. In terms of unbalance and critical speeds the suspended wheels and rotors compare favourably with conventional bearing devices. The rationale of our present bearing technology lies in the assembling of both low-speed magnetic bearings for centrifugal and wafer processing units up to 20,000 rpm as well as a high-speed optical mirror accelerated to rim speed of more than 500 m/s (174,000 rpm) confirming stable low-drag and low energy operation. Two new-type U shaped semicircle HTS bearings coupled each with a 6 W/80 K cryocooler of the Stirling type allow the contact-free operation of a Si wafer carrier in semiconductor wet processes.

Werfel, Frank N.; Flögel-Delor, Uta; Rothfeld, Rolf; Wippich, Dieter; Riedel, Thomas

2002-08-01

166

Good bearings reduce downtime  

SciTech Connect

Points out that a poorly maintained $100 bearing can hold up the operation of a $1-million conveyor. Of all the moving parts in a coal conveyor system, few cost less or last longer than anti-friction bearings. Most modern conveyor systems are equipped with 2 types of bearings: troughing idlers, spaced at regular intervals to support the conveyor belt as it travels throughout the system, and the adaptermounted spherical roller bearing pillow blocks that are used in the head, tail, bend and takeup pulleys that drive, alter the direction of, or regulate tension in the belt to allow for repairs or splicing. Explains how pillow blocks should handle radial or axial loads, how to mount bearings correctly, and how rings prevent infiltration. Concludes that by making certain that the proper bearing types are built into the system initially, or used as replacements in case of failures, paying close attention to installation procedures and devoting adequate time to maintenance, conveyor system bearings can provide decades of problem-free service.

Kinney, J.; Foster, J.

1982-12-01

167

Measuring Bearing-Cage Rotation  

NASA Technical Reports Server (NTRS)

Bearing slip measured optically. Concept for measuring rotational speed of bearing cage promises to be simple and accurate. Based on fiber optics, requires no contact between measuring device and bearing, and would not introduce wear.

Roschak, E. J.

1987-01-01

168

Magnetically-controlled bearing lubrication  

NASA Technical Reports Server (NTRS)

Proposed magnetic-lubricant ball-bearing assembly has permanently-magnetized bearing retainer fabricated of porous material. Pores of retainer are filled with ferrolubricant. Surface tension causes retainer to deliver sufficient lubricant to nonmagnetic ball bearings.

Whitaker, A. F.

1977-01-01

169

Ball and Roller Bearings. A Teaching Reference.  

ERIC Educational Resources Information Center

The manual provides a subject reference for ball and roller bearings. The following topics are included: (1) bearing nomenclature, (2) bearing uses, (3) bearing capacities, (4) shop area working conditions, (5) bearing removal, (6) bearing cleaning and inspection, (7) bearing replacement, (8) bearing lubrication, (9) bearing installation, (10)…

American Association for Vocational Instructional Materials, Athens, GA.

170

High hydrostatic pressure technology in dairy processing: a review.  

PubMed

Consumers demand high quality foods, which are fresh, tasty and nutritious; this has created considerable interest in the development of new food processing techniques. Presently, non-thermal techniques, including high hydrostatic pressure (HHP), are regarded with special interest by the food industry. Pressure ranges between 100 and 1200 MPa have been considered as effective to inactivate microorganisms including food-borne pathogens. HHP also improves rennet or acid coagulation of milk without any detrimental effect on flavour, body and texture and nutrients. Extended shelf-life and a "fresh-like" product presentation emphasize the need to take full account of food safety risks, alongside possible health benefits to consumers. These characteristics offer the dairy industry numerous practical applications to produce microbially safe and minimally processed dairy products with improved characteristics. Thus HHP is a powerful tool to develop novel dairy products of better nutritional and sensory quality, novel texture and increased shelf-life. PMID:23572744

Chawla, Rekha; Patil, Girdhari Ramdass; Singh, Ashish Kumar

2011-06-01

171

Cell Membranes Under Hydrostatic Pressure Subjected to Micro-Injection  

NASA Astrophysics Data System (ADS)

The work is concerned with the determination of the mechanical behaviour of cell membranes under uniform hydrostatic pressure subject to micro-injections. For that purpose, assuming that the shape of the deformed cell membrane is axisymmetric a variational statement of the problem is developed on the ground of the so-called spontaneous curvature model. In this setting, the cell membrane is regarded as an axisymmetric surface in the three-dimensional Euclidean space providing a stationary value of the shape energy functional under the constraint of fixed total area and fixed enclosed volume. The corresponding Euler-Lagrange equations and natural boundary conditions are derived, analyzed and used to express the forces and moments in the membrane. Several examples of such surfaces representing possible shapes of cell membranes under pressure subjected to micro injection are determined numerically.

Vassilev, Vassil M.; Kostadinov, Kostadin G.; Mladenov, Ivaïlo M.; Shulev, Assen A.; Stoilov, Georgi I.; Djondjorov, Peter A.

2011-04-01

172

Hydrostatic equilibrium and stellar structure in f(R) gravity  

NASA Astrophysics Data System (ADS)

We investigate the hydrostatic equilibrium of stellar structure by taking into account the modified Lané-Emden equation coming out from f(R) gravity. Such an equation is obtained in a metric approach by considering the Newtonian limit of f(R) gravity, which gives rise to a modified Poisson equation, and then introducing a relation between pressure and density with polytropic index n. The modified equation results an integro-differential equation, which, in the limit f(R)?R, becomes the standard Lané-Emden equation. We find the radial profiles of the gravitational potential by solving for some values of n. The comparison of solutions with those coming from general relativity shows that they are compatible and physically relevant.

Capozziello, S.; de Laurentis, M.; Odintsov, S. D.; Stabile, A.

2011-03-01

173

Ball Bearing Mechanics  

NASA Technical Reports Server (NTRS)

Load-deflection relationships for different types of elliptical contacts such as those found in a ball bearing are developed. Simplified expressions that allow quick calculations of deformation to be made simply from a knowledge of the applied load, the material properties, and the geometry of the contacting elements are presented. Ball bearings subjected to radial, thrust and combined ball loads are analyzed. A design criterion for fatigue life of ball bearings is developed. The section of a satisfactory lubricant, as well as describing systems that provide a constant flow of lubricant to the contact, is considered.

Hamrock, B. J.; Dowson, D.

1981-01-01

174

Enhancements to the Pellissier H5 Hydrostatic Level  

NASA Astrophysics Data System (ADS)

The Pellissier H5 Hydrostatic Level is used for applications requiring an order of magnitude improvement in accuracy over conventional optical leveling. The H5 has been used on such applications as the 32-meter radius track for the National Radio Astronomy Observatory (NRAO) Green Bank Telescope (GBT) alidade, the Final Focus Test Beam (FFTB) project at Stanford Linear Accelerator Center (SLAC), the Superconducting Super Collider (SSC), measurements of the Golden Gate Bridge, etc. For the GBT alidade track, 16 benchmarks on a 32-meter radius were measured 3 times over a 2-week period. In each case, the levels closed to better than 0.050 mm over the 200-meter run. The H5 has been well described in the literature by Imfeld, Pellissier, Plouffe, and Ruland [1], so a description will not be repeated in this article. The GBT metrology system [2,3] will employ 12 ground-based laser ranging instruments on a 120-meter radius, i.e., 12 monuments on 62-meter spacing (0.75 km loop). The metrology system will use measured distances only, so the 3-D coordinates of the instrument locations are required in order to do trilateration calculations. The goal is to establish the (x,y,z) coordinates to an accuracy of less than 0.1 mm. The x and y coordinates can be measured by the instruments, but due to the insensitivity of the monument geometry in the z direction, and the need to orient the ground instruments with respect to the gravity vector (to point the telescope), hydrostatic leveling is required.

Parker, David; Shelton, John W.; Radcliff, Bill

175

The water-bearing numerical model and its operational forecasting experiments part I: the water-bearing numerical model  

NASA Astrophysics Data System (ADS)

In first paper of articles, the physical and calculating schemes of the water-bearing numerical model are described. The model is developed by bearing all species of hydrometeors in a conventional numerical model in which the dynamic framework of hydrostatic equilibrium is taken. The main contributions are: the mixing ratios of all species of hydrometeors are added as the prognostic variables of model, the prognostic equations of these hydrometeors are introduced, the cloud physical framework is specially designed, some technical measures are used to resolve a series of physical, mathematical and computational problems arising from water-bearing; and so on. The various problems (in such aspects as the designs of physical and calculating schemes and the composition of computational programme) which are exposed in feasibility test, in sensibility test, and especially in operational forecasting experiments are successfully resolved using a lot of technical measures having been developed from researches and tests. Finally, the operational forecasting running of the water-bearing numerical model and its forecasting system is realized stably and reliably, and the fine forecasts are obtained. All of these mentioned above will be described in second paper.

Xia, Daqing; Xu, Youping

1998-06-01

176

PCs and Polar Bears  

NSDL National Science Digital Library

This article looks at the growing energy consumption from consumer electronics and the increases it may cause in greenhouse gases and global warming. The article appears in the free, online magazine Beyond Penguins and Polar Bears.

Fries-Gaither, Jessica

2011-01-01

177

Optimal Synchronizability of Bearings  

NASA Astrophysics Data System (ADS)

Bearings are mechanical dissipative systems that, when perturbed, relax toward a synchronized (bearing) state. Here we find that bearings can be perceived as physical realizations of complex networks of oscillators with asymmetrically weighted couplings. Accordingly, these networks can exhibit optimal synchronization properties through fine-tuning of the local interaction strength as a function of node degree [Motter, Zhou, and Kurths, Phys. Rev. E 71, 016116 (2005)PLEEE81539-3755]. We show that, in analogy, the synchronizability of bearings can be maximized by counterbalancing the number of contacts and the inertia of their constituting rotor disks through the mass-radius relation, m˜r?, with an optimal exponent ?=?× which converges to unity for a large number of rotors. Under this condition, and regardless of the presence of a long-tailed distribution of disk radii composing the mechanical system, the average participation per disk is maximized and the energy dissipation rate is homogeneously distributed among elementary rotors.

Araújo, N. A. M.; Seybold, H.; Baram, R. M.; Herrmann, H. J.; Andrade, J. S., Jr.

2013-02-01

178

Magnetic Bearing System.  

National Technical Information Service (NTIS)

A magnetic bearing system is described which includes a high magnetic permeability interior disc member that is symmetrical about a longitudinal z axis. An annular member of high magnetic permeability is coaxial with and surrounds the disc, but is mechani...

P. A. Studer

1975-01-01

179

Gear bearing drive  

NASA Technical Reports Server (NTRS)

A gear bearing drive provides a compact mechanism that operates as an actuator providing torque and as a joint providing support. The drive includes a gear arrangement integrating an external rotor DC motor within a sun gear. Locking surfaces maintain the components of the drive in alignment and provide support for axial loads and moments. The gear bearing drive has a variety of applications, including as a joint in robotic arms and prosthetic limbs.

Weinberg, Brian (Inventor); Mavroidis, Constantinos (Inventor); Vranish, John M. (Inventor)

2011-01-01

180

Investigation of Pressurized Wave Bearings  

NASA Technical Reports Server (NTRS)

The wave bearing has been pioneered and developed by Dr. Dimofte over the past several years. This bearing will be the main focus of this research. It is believed that the wave bearing offers a number of advantages over the foil bearing, which is the bearing that NASA is currently pursuing for turbomachinery applications. The wave bearing is basically a journal bearing whose film thickness varies around the circumference approximately sinusoidally, with usually 3 or 4 waves. Being a rigid geometry bearing, it provides precise control of shaft centerlines. The wave profile also provides good load capacity and makes the bearing very stable. Manufacturing techniques have been devised that should allow the production of wave bearings almost as cheaply as conventional full-circular bearings.

Keith, Theo G., Jr.; Dimofte, Florin

2003-01-01

181

Load responsive hydrodynamic bearing  

DOEpatents

A load responsive hydrodynamic bearing is provided in the form of a thrust bearing or journal bearing for supporting, guiding and lubricating a relatively rotatable member to minimize wear thereof responsive to relative rotation under severe load. In the space between spaced relatively rotatable members and in the presence of a liquid or grease lubricant, one or more continuous ring shaped integral generally circular bearing bodies each define at least one dynamic surface and a plurality of support regions. Each of the support regions defines a static surface which is oriented in generally opposed relation with the dynamic surface for contact with one of the relatively rotatable members. A plurality of flexing regions are defined by the generally circular body of the bearing and are integral with and located between adjacent support regions. Each of the flexing regions has a first beam-like element being connected by an integral flexible hinge with one of the support regions and a second beam-like element having an integral flexible hinge connection with an adjacent support region. A least one local weakening geometry of the flexing region is located intermediate the first and second beam-like elements. In response to application of load from one of the relatively rotatable elements to the bearing, the beam-like elements and the local weakening geometry become flexed, causing the dynamic surface to deform and establish a hydrodynamic geometry for wedging lubricant into the dynamic interface.

Kalsi, Manmohan S. (Houston, TX); Somogyi, Dezso (Sugar Land, TX); Dietle, Lannie L. (Stafford, TX)

2002-01-01

182

Thermal conductivity and compressive strain of foam neoprene insulation under hydrostatic pressure  

NASA Astrophysics Data System (ADS)

The purpose of this study was to show that the thermal properties of foam neoprene under hydrostatic pressure cannot be predicted by theoretical means, and that uni-axial pressure cannot simulate hydrostatic compression. The thermal conductivity and compressive strain of foam neoprene were measured under hydrostatic pressure. In parallel, uni-axial compressive strain data were collected. The experimental set-up and data were put into perspective with past published studies. It was shown that uni-axial compression yielded strains 20-25% greater than did hydrostatic compression. This suggests the need for direct hydrostatic pressure measurement. For comparison to hydrostatic experimental data, a series of thermal conductivity theories of two phase composites based on particulate phase geometry were utilized. Due to their dependence on the porosity and constituent thermal conductivities, a model to predict porosity under hydrostatic pressure was used and an empirical correlation was derived to calculate the thermal conductivity of pure neoprene rubber from experimental data. It was shown that, although some agreement between experimental data and thermal conductivity theories was present, no particular theory can be used because they all fail to model the complex structure of the pores. It was therefore concluded that an experimental programme, such as reported here, is necessary for direct measurement.

Bardy, Erik; Mollendorf, Joseph; Pendergast, David

2005-10-01

183

Vertical Discretization of Hydrostatic Primitive Equations with Finite Element Method  

NASA Astrophysics Data System (ADS)

A vertical finite element (VFE) discretization of hydrostatic primitive equations is developed for the dynamical core of a numerical weather prediction (NWP) system at KIAPS, which is horizontally discretized by a spectral element on a cubed-sphere grid. The governing equations are discretized on a hybrid pressure-based vertical coordinate [1]. Compared with a vertical finite difference (VFD) discretization, which is only first order accurate for non-uniform grids, the VFE has many advantages such that it gives more accurate results, all variables are defined in the same full level, the level of vertical noise might be reduced [2], and it is easily coupled with existing physics packages, developed for a Lorentz staggering grid system. Due to these reasons, we adopted the VFE scheme presented by Untch [2] for the vertical discretization. Instead of using semi-Lagrangian and semi-implicit schemes of ECMWF, we use the Eulerian equations and second-order Runge-Kutta scheme as the first step in implementing the VFE for the dynamical core of the KIAPS's NWP model. Since the Eulerian hydrostatic equations are used in this study, both integral and derivative operators are required to implement the VFE using the Galerkin method with b-splines as basis functions. To compare the accuracy of the VFE with the VFD, the two-dimensional test case of mountain waves is used where physical configuration and initial conditions are the same as that of Durran [3]. In this case, the horizontal and vertical velocities obtained by the analytical solution, VFD, VFE-linear and VFE-cubic are compared to understand their numerical features and the vertical flux of horizontal momentum is also presented as the measurement of solution accuracy since it is sensitive to errors in a solution [3]. It is shown that the VFE with a cubic b-spline function is more accurate than the VFD and VFE with a linear b-spline function as the vertical flux is closer to unity, which will be presented in the conference. Reference Simmons, A. J., Burridge, D. M., 1981: An energy and angular momentum conserving vertical finite difference scheme and hybrid vertical coordinates. Mon. Wea. Rev., 109, 758-766. Untch, A., Hortal, M., 2004: A finite-element schemes for the vertical discretization of the semi-Lagrangian version of the ECMWF forecast model. Q. J. R. Meteorol. Soc., 130, 1505-1530. Durran, D. R., Klemp, J. B., 1983: A compressible model for the simulation of moist mountain waves. Mon. Wea. Rev., 111, 2341-2361.

Yi, Tae-Hyeong; Park, Ja-Rin

2014-05-01

184

Fault tolerant magnetic bearings  

SciTech Connect

A fault tolerant magnetic bearing system was developed and demonstrated on a large flexible-rotor test rig. The bearing system comprises a high speed, fault tolerant digital controller, three high capacity radial magnetic bearings, one thrust bearing, conventional variable reluctance position sensors, and an array of commercial switching amplifiers. Controller fault tolerance is achieved through a very high speed voting mechanism which implements triple modular redundancy with a powered spare CPU, thereby permitting failure of up to three CPU modules without system failure. Amplifier/cabling/coil fault tolerance is achieved by using a separate power amplifier for each bearing coil and permitting amplifier reconfiguration by the controller upon detection of faults. This allows hot replacement of failed amplifiers without any system degradation and without providing any excess amplifier kVA capacity over the nominal system requirement. Implemented on a large (2440 mm in length) flexible rotor, the system shows excellent rejection of faults including the failure of three CPUs as well as failure of two adjacent amplifiers (or cabling) controlling an entire stator quadrant.

Maslen, E.H.; Sortore, C.K.; Gillies, G.T.; Williams, R.D.; Fedigan, S.J. [Univ. of Virginia, Charlottesville, VA (United States); Aimone, R.J. [Mobile Technology Co., Paulsboro, NJ (United States)

1999-07-01

185

P and W Cryogenic Fluid-Film Bearing and Seal Technology Development and Implementation  

NASA Technical Reports Server (NTRS)

This presentation will summarize Pratt & Whitney's past, present, and future activities toward cryogenic fluid-film bearing and seal technology development and implementation. The three major areas of focus for this technology are analytical models and design tools, component testing, and technology implementation. The analytical models and design tools area will include a summary of current tools along with an overview of P&W's new full 3-D Navier-Stokes solution for hydrostatic bearings, HYDROB3D. P&W's comprehensive component test program, including teaming with the Air Force Phillips Laboratory, NASA's Marshall Space Flight Center, and Carrier Corporation, will be outlined. Component test programs consisting of material development and testing, surface patterns/roughness, pocket and orifice geometry variations, and static and dynamic performance of both journal and thrust bearings will be summarized. Finally, the technology implementation area will show the benefits and plans for P&W to incorporate this technology into products.

Pelfrey, Philip C.

1996-01-01

186

Partial tooth gear bearings  

NASA Technical Reports Server (NTRS)

A partial gear bearing including an upper half, comprising peak partial teeth, and a lower, or bottom, half, comprising valley partial teeth. The upper half also has an integrated roller section between each of the peak partial teeth with a radius equal to the gear pitch radius of the radially outwardly extending peak partial teeth. Conversely, the lower half has an integrated roller section between each of the valley half teeth with a radius also equal to the gear pitch radius of the peak partial teeth. The valley partial teeth extend radially inwardly from its roller section. The peak and valley partial teeth are exactly out of phase with each other, as are the roller sections of the upper and lower halves. Essentially, the end roller bearing of the typical gear bearing has been integrated into the normal gear tooth pattern.

Vranish, John M. (Inventor)

2010-01-01

187

Radial Halbach Magnetic Bearings  

NASA Technical Reports Server (NTRS)

Radial Halbach magnetic bearings have been investigated as part of an effort to develop increasingly reliable noncontact bearings for future high-speed rotary machines that may be used in such applications as aircraft, industrial, and land-vehicle power systems and in some medical and scientific instrumentation systems. Radial Halbach magnetic bearings are based on the same principle as that of axial Halbach magnetic bearings, differing in geometry as the names of these two types of bearings suggest. Both radial and axial Halbach magnetic bearings are passive in the sense that unlike most other magnetic bearings that have been developed in recent years, they effect stable magnetic levitation without need for complex active control. Axial Halbach magnetic bearings were described in Axial Halbach Magnetic Bearings (LEW-18066-1), NASA Tech Briefs, Vol. 32, No. 7 (July 2008), page 85. In the remainder of this article, the description of the principle of operation from the cited prior article is recapitulated and updated to incorporate the present radial geometry. In simplest terms, the basic principle of levitation in an axial or radial Halbach magnetic bearing is that of the repulsive electromagnetic force between (1) a moving permanent magnet and (2) an electric current induced in a stationary electrical conductor by the motion of the magnetic field. An axial or radial Halbach bearing includes multiple permanent magnets arranged in a Halbach array ("Halbach array" is defined below) in a rotor and multiple conductors in the form of wire coils in a stator, all arranged so the rotary motion produces an axial or radial repulsion that is sufficient to levitate the rotor. A basic Halbach array (see Figure 1) consists of a row of permanent magnets, each oriented so that its magnetic field is at a right angle to that of the adjacent magnet, and the right-angle turns are sequenced so as to maximize the magnitude of the magnetic flux density on one side of the row while minimizing it on the opposite side. The advantage of this configuration is that it makes it possible to approach the theoretical maximum force per unit area that could be exerted by a given amount of permanent-magnet material. The configuration is named after physicist Klaus Halbach, who conceived it for use in particle accelerators. Halbach arrays have also been studied for use in magnetic-levitation ("maglev") railroad trains. In a radial Halbach magnetic bearing, the basic Halbach arrangement is modified into a symmetrical arrangement of sector-shaped permanent magnets mounted on the outer cylindrical surface of a drum rotor (see Figure 2). The magnets are oriented to concentrate the magnetic field on their radially outermost surface. The stator coils are mounted in a stator shell surrounding the rotor.

Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

2009-01-01

188

Blood Pump Bearing System  

NASA Technical Reports Server (NTRS)

An apparatus is provided for a blood pump bearing system within a pump housing to support long-term highspeed rotation of a rotor with an impeller blade having a plurality of individual magnets disposed thereon to provide a small radial air gap between the magnets and a stator of less than 0.025 inches. The bearing system may be mounted within a flow straightener, diffuser, or other pump element to support the shaft of a pump rotor. The bearing system includes a zirconia shaft having a radiused end. The radiused end has a first radius selected to be about three times greater than the radius of the zirconia shaft. The radiused end of the zirconia shaft engages a flat sapphire endstone. Due to the relative hardness of these materials a flat is quickly produced during break-in on the zirconia radiused end of precisely the size necessary to support thrust loads whereupon wear substantially ceases. Due to the selection of the first radius, the change in shaft end-play during pump break-in is limited to a total desired end-play of less than about 0.010 inches. Radial loads are supported by an olive hole ring jewel that makes near line contact around the circumference of the Ir shaft to support big speed rotation with little friction. The width of olive hole ring jewel is small to allow heat to conduct through to thereby prevent heat build-up in the bearing. A void defined by the bearing elements may fill with blood that then coagulates within the void. The coagulated blood is then conformed to the shape of the bearing surfaces.

Aber, Gregory S. (Inventor)

2000-01-01

189

Blood Pump Bearing System  

NASA Technical Reports Server (NTRS)

Methods and apparatus are provided for a blood pump bearing system within a pump housing to support long-term high-speed rotation of a rotor with an impeller blade having a plurality of individual magnets disposed thereon to provide a small radial air gap between the magnets and a stator of less than 0.025 inches. The bearing system may be mounted within a flow straightener, diffuser, or other pump element to support the shaft of a pump rotor. The bearing system includes a zirconia shaft having a radiused end. The radiused end has a first radius selected to be about three times greater than the radius of the zirconia shaft. The radiused end of the zirconia shaft engages a flat sapphire endstone. Due to the relative hardness of these materials a flat is quickly produced during break-in on the zirconia radiused end of precisely the size necessary to support thrust loads whereupon wear substantially ceases. Due to the selection of the first radius, the change in shaft end-play during pump break-in is limited to a total desired end-play of less than about 0.010 inches. Radial loads are supported by an olive hole ring jewel that makes near line contact around the circumference of the shaft to support high speed rotation with little friction. The width of olive hole ring jewel is small to allow heat to conduct through to thereby prevent heat build-up in the bearing. A void defined by the bearing elements may fill with blood that then coagulates within the void. The coagulated blood is then conformed to the shape of the bearing surfaces.

Aber, Gregory S. (Inventor)

1999-01-01

190

A CANDIDATE DETECTION OF THE FIRST HYDROSTATIC CORE  

SciTech Connect

The first hydrostatic core (FHSC) represents a very early phase in the low-mass star formation process, after collapse of the parent core has begun but before a true protostar has formed. This large (few AU), cool (100 K), pressure-supported core of molecular hydrogen is expected from theory, but has yet to be observationally verified. Here, we present observations of an excellent candidate for the FHSC phase: Per-Bolo 58, a dense core in Perseus that was previously believed to be starless. The 70 {mu}m flux of 65 mJy, from new deep Spitzer MIPS observations, is consistent with that expected for the FHSC. A low signal-to-noise detection at 24 {mu}m leaves open the possibility that Per-Bolo 58 could be a very low luminosity protostar, however. We utilize radiative transfer models to determine the best-fitting FHSC and protostar models to the spectral energy distribution and 2.9 mm visibilities of Per-Bolo 58. The source is consistent with an FHSC with some source of lower opacity through the envelope allowing 24 {mu}m emission to escape; a small outflow cavity and a cavity in the envelope are both possible. While we are unable to rule out the presence of a protostar, if present it would be one of the lowest luminosity protostellar objects yet observed, with an internal luminosity of {approx}0.01 L {sub sun}.

Enoch, Melissa L. [Department of Astronomy, University of California at Berkeley, 601 Campbell Hall, Berkeley, CA 94720 (United States); Lee, Jeong-Eun [Department of Astronomy and Space Science, Astrophysical Research Center for the Structure and Evolution of the Cosmos, Sejong University, Seoul 143-747 (Korea, Republic of); Harvey, Paul; Dunham, Michael M. [Department of Astronomy, University of Texas at Austin, 1 University Station, C1400, Austin, TX 78712 (United States); Schnee, Scott, E-mail: menoch@berkeley.ed [National Research Council Canada, Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria BC V9E 2E7 (Canada)

2010-10-10

191

Ordered states of URu2Si2 under hydrostatic pressure  

NASA Astrophysics Data System (ADS)

Oriented single crystalline samples of URu2Si2 have been synthesized and investigated under nearly hydrostatic pressure via electrical resistivity and ac susceptibility measurements. The heavy fermion compound URu2Si2 exhibits three distinct ordered states as a function of temperature and pressure: ``hidden order'' (HO), in which the order parameter has yet to be determined; antiferromagnetism (AFM), which seemingly develops out of the HO state at P <=15 kbar; and superconductivity (SC), which exists at ambient pressure. Careful measurements of the HO transition, occurring at THO˜16.5 K at ambient pressure, have been performed at several different pressures, yielding a P-T phase diagram for the HO state as a function of pressure. In addition, measurements of the superconducting critical temperature, Tc˜1.4 K at ambient pressure, and the upper critical field Hc2 have been performed at low temperatures using a ^3He-^4He dilution refrigerator, revealing the superconducting H-T-P phase diagram. Possible correlations between the HO, AFM, and SC states will be discussed. This research was supported by the National Nuclear Security Administration under the Stewardship Science Academic Alliances program through DOE Research Grant No. DE-FG52-03NA00068.

Jeffries, J. R.; Butch, N. P.; Paglione, J.; Maple, M. B.

2006-03-01

192

Performance of a Polyurethane Core Seal Tested in a Hydrostatic Chamber.  

National Technical Information Service (NTIS)

The National Institute for Occupational Safety and Health's Pittsburgh Research Laboratory conducted a full-scale test of a composite polyurethane-aggregate seal in a hydrostatic chamber at the Lake Lynn Experimental Mine. This composite seal consisted of...

D. R. Dolinar M. J. Sapko S. P. Harteis

2008-01-01

193

Sensitivity of Spores to Hydrostatic Pressure Mechanisms of Inactivation, Injury and Repair Phase II.  

National Technical Information Service (NTIS)

Over the past fifteen years, it has been established that high- hydrostatic pressure processing (HPP) has significant potential to function as an effective nonthermal method in the destruction of microorganisms in foods with little effect on the sensory q...

D. G. Hoover A. E. Shearer A. Sikes C. P. Dunne

2003-01-01

194

Installation and Test of a Hydrostatic Drive Transmission in a Government Furnished M-113 Vehicle.  

National Technical Information Service (NTIS)

A design effort was performed to install a Hydrostatic Drive Train with secondary regulation (constant pressure) in a 14 ton Military Tracked Vehicle. The system offered simplified control and utilizes a single variable displacement pump driven by the eng...

1986-01-01

195

46 CFR 131.585 - Periodic servicing of hydrostatic-release units.  

Code of Federal Regulations, 2010 CFR

...the vessel; and (2) In compliance with subpart 160.062 of this chapter. (b) The springs of each spring-tensioned gripe used with a hydrostatic-release unit must be renewed when the unit is serviced and...

2009-10-01

196

46 CFR 131.585 - Periodic servicing of hydrostatic-release units.  

Code of Federal Regulations, 2010 CFR

...the vessel; and (2) In compliance with subpart 160.062 of this chapter. (b) The springs of each spring-tensioned gripe used with a hydrostatic-release unit must be renewed when the unit is serviced and...

2010-10-01

197

String and Sticky Tape Experiments: Light Pipes, Hydrostatics, Surface Tension and a Milk Carton.  

ERIC Educational Resources Information Center

Describes a demonstration of light pipes using low-cost materials, relating it to fiber optics communication. Also provides several experiments in hydrostatics and hydrodynamics using the materials for light pipe. (JM)

Edge, R. D., Ed.

1984-01-01

198

General Instability of Conical Shells with Non-Uniformly Spaced Stiffeners under Hydrostatic Pressure.  

National Technical Information Service (NTIS)

The method of analysis of the general instability of stiffened conical shells, developed earlier by the authors for uniform and equally spaced stiffeners, is now extended to shells with non-uniformly spaced stiffeners. For hydrostatic pressure loading, ri...

M. Baruch J. Singer O. Harari

1964-01-01

199

Inelastic Buckling Tests of Ring-Stiffened Cylinders under Hydrostatic Pressure.  

National Technical Information Service (NTIS)

A series of small machined aluminum models were collapsed under external hydrostatic pressure to study the inelastic buckling of near-perfect ring-stiffened cylinders made of strain-hardening materials. The predominant modes of failure were general instab...

L. Boichot T. E. Reynolds

1965-01-01

200

Modular gear bearings  

NASA Technical Reports Server (NTRS)

A gearing system using modular gear bearing components. Each component is composed of a core, one or more modules attached to the core and two or more fastening modules rigidly attaching the modules to the core. The modules, which are attached to the core, may consist of gears, rollers or gear bearing components. The core orientation affects the orientation of the modules attached to the core. This is achieved via the keying arrangement of the core and the component modules that attach to the core. Such an arrangement will also facilitate the phase tuning of gear modules with respect to the core and other gear modules attached to the core.

Vranish, John M. (Inventor)

2009-01-01

201

An apparatus for the torsion testing of materials at high hydrostatic pressures  

NASA Astrophysics Data System (ADS)

It is shown how a previously developed apparatus for rupture testing at high hydrostatic pressures can be adapted to the torsional testing of materials at high hydrostatic pressures. The apparatus described here has been successfully used to obtain ductility diagrams for high-tin bronze, niobium, and a series of alloys based on precious metals. Details of the test procedure and the corresponding formulas are presented; a schematic diagram of the test apparatus is shown, and its main components are briefly described.

Kolpashnikov, A. I.; Fedorov, A. A.; Kucheriaev, B. V.; Bespalov, A. V.

202

Amos Bear Gets Hurt.  

ERIC Educational Resources Information Center

A three-day experiment set up by an early childhood teacher explored Piaget's view that children younger than age eight lack ability to take another's point of view. The experiment focused on a bear, the class mascot, and observations of children's empathetic behavior toward its "injury." Age-related differences in the children's responses were…

Read, Laurie

1995-01-01

203

The Teddy Bears' Disc.  

ERIC Educational Resources Information Center

Reports an evaluation of the Teddy Bear disc, an interactive videodisc developed at the Open University for a second-level course in metallurgy and materials technology. Findings from observation of students utilizing the videodisc are reviewed; successful design features and design problems are considered; and development costs are outlined. (MBR)

Laurillard, Diana

1985-01-01

204

History of ball bearings  

NASA Technical Reports Server (NTRS)

The familiar precision rolling-element bearings of the twentieth century are products of exacting technology and sophisticated science. Their very effectiveness and basic simplicity of form may discourage further interest in their history and development. Yet the full story covers a large portion of recorded history and surprising evidence of an early recognition of the advantages of rolling motion over sliding action and progress toward the development of rolling-element bearings. The development of rolling-element bearings is followed from the earliest civilizations to the end of the eighteenth century. The influence of general technological developments, particularly those concerned with the movement of large building blocks, road transportation, instruments, water-raising equipment, and windmills are discussed, together with the emergence of studies of the nature of rolling friction and the impact of economic factors. By 1800 the essential features of ball and rolling-element bearings had emerged and it only remained for precision manufacture and mass production to confirm the value of these fascinating machine elements.

Dowson, D.; Hamrock, B. J.

1981-01-01

205

Tardigrada (Water Bears)  

NSDL National Science Digital Library

This reference page offers a brief description of Tardigrades, also known as water bears. It includes information about their physical appearance, an explanation of their name, likely habitats, internal organs and other distinguishing features, and a few images. A diagram of a common tardigrade, Macrobiotus macronyx, is also provided via an internal link.

Micrographia

206

Magnetic Bearings For Turbopumps  

NASA Technical Reports Server (NTRS)

Report presents study of feasibility of magnetic bearings in turbopumps. Liquid-oxygen turbopump in space shuttle main engine selected for study. Other potential applications include manned and unmanned spacecraft, gas turbines for commercial and military aircraft, turbomachinery for petro-chemical and gas operations, suspension systems for precise machinery, and precise pointing and tracking systems.

Meeks, Crawford R.; Mendez, Antonio J.

1995-01-01

207

Flexure Bearing Reduces Startup Friction  

NASA Technical Reports Server (NTRS)

Design concept for ball bearing incorporates small pieces of shim stock, wire spokes like those in bicycle wheels, or other flexing elements to reduce both stiction and friction slope. In flexure bearing, flexing elements placed between outer race of ball bearing and outer ring. Elements flex when ball bearings encounter small frictional-torque "bumps" or even larger ones when bearing balls encounter buildups of grease on inner or outer race. Flexure of elements reduce high friction slopes of "bumps", helping to keep torque between outer ring and inner race low and more nearly constant. Concept intended for bearings in gimbals on laser and/or antenna mirrors.

Clingman, W. Dean

1991-01-01

208

Lubricant effects on bearing life  

NASA Technical Reports Server (NTRS)

Lubricant considerations for rolling-element bearings have within the last two decades taken on added importance in the design and operation of mechanical systems. The phenomenon which limits the useful life of bearings is rolling-element or surface pitting fatigue. The elastohydrodynamic (EHD) film thickness which separates the ball or roller surface from those of the raceways of the bearing directly affects bearing life. Chemical additives added to the lubricant can also significantly affect bearings life and reliability. The interaction of these physical and chemical effects is important to the design engineer and user of these systems. Design methods and lubricant selection for rolling-element bearings are presented and discussed.

Zaretsky, Erwin V.

1986-01-01

209

Bearing Line Tracking and Bearing-Only Target Motion Analysis  

Microsoft Academic Search

The framework of this paper is a passive sonar system, more precisely at the core of bearing estimation and bearings-only target motion analysis (BO-TMA). A cosine of relative bearing estimation and bearings v.s. time image is first obtained by a conventional frequency-domain beam-former [D.H Johnson et al, 1993]. Computing the first two moments of each line of this image, we

Fabien BONNETON; Claude JAUFFRET

2007-01-01

210

Magnetocaloric effect of Er5Si4 under hydrostatic pressure  

NASA Astrophysics Data System (ADS)

The magnetocaloric effect (MCE) of the compound Er5Si4 has been investigated as a function of the applied magnetic field (up to 50 kOe) and the hydrostatic pressure (from ambient pressure up to 9 kbar). At constant magnetic field change, increasing the pressure up to 1.4 kbar induces a global rise of the magnetic entropy change, |?Smag| , with the peak at TC?30K growing from 14.9 to 20.1J/kgK . Between 1.4 and 9 kbar, the size and shape of the |?Smag| vs T curve remain nearly constant but the peak moves to higher temperatures and stabilizes above 3.5 kbar at Ttilde 36K . Contrary to many other R5(SixGe1-x)4 compounds, the magnetocaloric effect in Er5Si4 does not originate from the simultaneous field-induced magnetic and structural transformations since previous studies of the compound have demonstrated that moderate steady magnetic fields are not strong enough to induce the M?O(I) transformation at the atmospheric pressure. However, the pressure dependence of the MCE is associated with pressure-induced M?O(I) structural transformation that takes place in Er5Si4 . The increase in the magnetic entropy change occurs because of a modification of the magnetic coupling derived from the differences in the interlayer bonding in the M and O(I) states. This gives rise to an enhancement of the ferromagnetic interactions in the O(I) phase with respect to the ambient pressure M state, resulting in a stronger saturation magnetization and a higher Curie temperature, i.e., TCM=30K and TCO(I)=36K .

Arnold, Z.; Magen, C.; Morellon, L.; Algarabel, P. A.; Kamarad, J.; Ibarra, M. R.; Pecharsky, V. K.; Gschneidner, K. A., Jr.

2009-04-01

211

Hydrostatic strain enhancement in laterally confined SiGe nanostripes  

NASA Astrophysics Data System (ADS)

Strain engineering in SiGe nanostructures is fundamental for the design of optoelectronic devices at the nanoscale. Here we explore a new strategy, where SiGe structures are laterally confined by the Si substrate, to obtain high tensile strain yet avoid the use of external stressors, thus improving the scalability. Spectromicroscopy techniques, finite element method simulations, and ab initio calculations are used to investigate the strain state of laterally confined Ge-rich SiGe nanostripes. Strain information is obtained by tip-enhanced Raman spectroscopy with an unprecedented lateral resolution of ˜30 nm. The nanostripes exhibit a large tensile hydrostatic strain component, which is maximal at the center of the top free surface and becomes very small at the edges. The maximum lattice deformation is larger than the typical values of thermally relaxed Ge/Si(001) layers. This strain enhancement originates from a frustrated relaxation in the out-of-plane direction, resulting from the combination of the lateral confinement induced by the substrate side walls and the plastic relaxation of the misfit strain in the (001) plane at the SiGe/Si interface. The effect of this tensile lattice deformation at the stripe surface is probed by work function mapping, which is performed with a spatial resolution better than 100 nm using x-ray photoelectron emission microscopy. The nanostripes exhibit a positive work function shift with respect to a bulk SiGe alloy, quantitatively confirmed by electronic structure calculations of tensile-strained configurations. The present results have a potential impact on the design of optoelectronic devices at a nanometer-length scale.

Vanacore, G. M.; Chaigneau, M.; Barrett, N.; Bollani, M.; Boioli, F.; Salvalaglio, M.; Montalenti, F.; Manini, N.; Caramella, L.; Biagioni, P.; Chrastina, D.; Isella, G.; Renault, O.; Zani, M.; Sordan, R.; Onida, G.; Ossikovski, R.; Drouhin, H.-J.; Tagliaferri, A.

2013-09-01

212

Hydrostatic equilibrium profiles for gas in elliptical galaxies  

NASA Astrophysics Data System (ADS)

We present an analytic formulation for the equilibrium gas density profile of early-type galaxies that explicitly includes the contribution of stars in the gravitational potential. We build a realistic model for an isolated elliptical galaxy and explore the equilibrium gas configurations as a function of multiple parameters. For an assumed central gas temperature kBT0 = 0.6 keV, we find that neglecting the gravitational effects of stars, which can contribute substantially in the innermost regions, leads to an underestimate of the enclosed baryonic gas mass by up to ~65 per cent at the effective radius and by up to ~15 per cent at the Navarro-Frenk-White (NFW) scale radius, depending on the stellar baryon fraction. This formula is therefore important for estimating the baryon fraction in an unbiased fashion. These new hydrostatic equilibrium solutions, derived for the isothermal and polytropic cases, can also be used to generate more realistic initial conditions for simulations of elliptical galaxies. Moreover, the new formulation is relevant when interpreting X-ray data. We compare our composite isothermal model to the standard ?-model used to fit X-ray observations of early-type galaxies, to determine the value of the NFW scale radius rs. Assuming a 10 per cent stellar baryon fraction, we find that the exclusion of stars from the gravitational potential leads to (i) an underestimate of rs by ~80 per cent and (ii) an overestimate of the enclosed dark matter at rs by a factor of ~2, compared to the equivalent ?-model fit results when stars are not taken into account. For higher stellar mass fractions, a ?-model is unable to accurately reproduce our solution, indicating that when the observed surface brightness profile of an isolated elliptical galaxy is found to be well fitted by a ?-model, the stellar mass fraction cannot be much greater than ~10 per cent.

Capelo, Pedro R.; Natarajan, Priyamvada; Coppi, Paolo S.

2010-09-01

213

Vygotsky and the Three Bears  

ERIC Educational Resources Information Center

Peggy Kulczewski, a kindergarten classroom teacher, remembers the day when students enjoyed a story she told them from the book "The Three Bears". The students' discussion about comparison of the bears was very helpful to the whole group.

Kulczewski, Peggy

2004-01-01

214

Nonlinear Control of Magnetic Bearings.  

National Technical Information Service (NTIS)

In this paper we present a variety of nonlinear controllers for the magnetic bearing that ensure both stability and robustness. We utilize techniques of discontinuous control to design novel control laws for the magnetic bearing. We present in particular ...

A. K. Pradeep R. Gurumoorthy

1994-01-01

215

Self-Lubricating Bearing Materials.  

National Technical Information Service (NTIS)

A survey is given of progress in the development of self-lubricating materials for load-carrying components (bearings and gears) or for transfer lubrication (rolling element bearing retainers). Various methods for producing composites of inorganic solid l...

J. K. Lancaster

1965-01-01

216

Aerospace Applications of Magnetic Bearings.  

National Technical Information Service (NTIS)

Magnetic bearings have traditionally been considered for use in aerospace applications only where performance advantages have been the primary, if not only, consideration. Conventional wisdom has been that magnetic bearings have certain performance advant...

J. Downer J. Goldie V. Gondhalekar R. Hockney

1994-01-01

217

Magnetic bearings grow more attractive  

SciTech Connect

Advances in materials and electronics have enabled designers to devise simpler, smaller magnetic bearings. As a result, costs have dropped, widening the applications for these very-low-friction devices. Avcon (Advanced Controls Technology) has patented a permanent-magnet bias actively controlled bearing. Here high-energy rare earth permanent-magnet materials supply the basic bearing load levitation, while servo-driven electromagnets generate stabilization and centering forces for motion contol. Previous heavy-duty magnetic bearings used electromagnets entirely for suspension and control, which led to large bearings and control systems with higher power requirements. Avcon has developed several types of permanent-magnet bias bearings. The simplest is the radial repulsion bearing. Avcon's homopolar permanent-magnet bias active bearing is the most versatile of the company's designs.

Not Available

1993-10-01

218

Leakage-free journal bearings  

NASA Technical Reports Server (NTRS)

A new concept of a journal bearing is developed which prevents side leakage of the lubricant, thus eliminating the need for sealing and collecting this leakage. The cooling of the bearing is accomplished by the prevailing circumferential flow. An analysis is performed and solutions are given for the bearing geometries and inlet pressures required to achieve the above purpose.

Pinkus, O.; Etsion, I.

1976-01-01

219

Magnetic bearings for cryogenic turbomachines  

Microsoft Academic Search

Magnetic bearings offer a number of advantages over gas bearings for the support of rotors in cryogenic turboexpanders and compressors. Their performance is relatively independent of the temperature or pressure of the process gas for a large range of conditions. Active magnetic bearing systems that use capacitive sensors have been developed for high speed compressors for use in cryogenic refrigerators.

Victor Iannello; Herbert Sixsmith

1991-01-01

220

Night of the Bear  

NSDL National Science Digital Library

The NOAA Ocean Exploration program strives to engage broad audiences to enhance America's environmental literacy through the excitement of ocean discovery. Increasing this literacy requires high-quality, effective collaborations between ocean explorers and America's teachers. NOAA is forming such collaborations to reach out in new ways to the public to improve the literacy of learners with respect to ocean issues. This site is a daily log of exploration in the Arctic and research on the Polar Bear.

Debenham, Casey; Timmermans, Mary-Louise

2002-08-25

221

Big Bear Solar Observatory  

NASA Astrophysics Data System (ADS)

Big Bear Solar Observatory (BBSO) is located at the end of a causeway in a mountain lake more than 2 km above sea level. The site has more than 300 sunny days a year and a natural inversion caused by the lake which makes for very clean images. BBSO is the only university observatory in the US making high-resolution observations of the Sun. Its daily images are posted at http://www.bbso.njit.e...

Murdin, P.

2000-11-01

222

Bitumen-bearing rocks  

Microsoft Academic Search

Bitumen-bearing rocks occur in many areas of the U.S., but few of the deposits have been evaluated for their energy potential or exploited. Those deposits which have been evaluated are a relatively small part of North American resources of tar sands and probably will not contribute to U.S. energy needs before 1985. Studies of known but unappraised deposits, especially extensive

Cashion

1973-01-01

223

Turbogear bearing analysis  

Microsoft Academic Search

To optimize process energy efficiency, many plants are considering variable-speed electric motor drives with speed-increasing gears for centrifugal compressors. Variable-speed systems are much more complex than fixed-speed systems, especially when power and speed change independently across the compressor performance map, for example, from start-of-run to end-of-run. There are more mechanical design issues that impact reliable operation. Bearing analysis of turbogears

Cassolato

1997-01-01

224

Bearing, gearing, and lubrication technology  

NASA Technical Reports Server (NTRS)

Results of selected NASA research programs on rolling-element and fluid-film bearings, gears, and elastohydrodynamic lubrication are reported. Advances in rolling-element bearing material technology, which have resulted in a significant improvement in fatigue life, and which make possible new applications for rolling bearings, are discussed. Research on whirl-resistant, fluid-film bearings, suitable for very high-speed applications, is discussed. An improved method for predicting gear pitting life is reported. An improved formula for calculating the thickness of elastohydrodynamic films (the existence of which help to define the operating regime of concentrated contact mechanisms such as bearings, gears, and cams) is described.

Anderson, W. J.

1978-01-01

225

Hybrid Bearing Prognostic Test Rig  

NASA Technical Reports Server (NTRS)

The NASA Glenn Research Center has developed a new Hybrid Bearing Prognostic Test Rig to evaluate the performance of sensors and algorithms in predicting failures of rolling element bearings for aeronautics and space applications. The failure progression of both conventional and hybrid (ceramic rolling elements, metal races) bearings can be tested from fault initiation to total failure. The effects of different lubricants on bearing life can also be evaluated. Test conditions monitored and recorded during the test include load, oil temperature, vibration, and oil debris. New diagnostic research instrumentation will also be evaluated for hybrid bearing damage detection. This paper summarizes the capabilities of this new test rig.

Dempsey, Paula J.; Certo, Joseph M.; Handschuh, Robert F.; Dimofte, Florin

2005-01-01

226

Anti-backlash gear bearings  

NASA Technical Reports Server (NTRS)

A gear bearing having a first gear and a second gear, each having a plurality of teeth. Each gear operates on two non-parallel surfaces of the opposing gear teeth to perform both gear and bearing functions simultaneously. The gears are moving at substantially the same speed at their contact points. The gears may be roller gear bearings or phase-shifted gear bearings, and may be arranged in a planet/sun system or used as a transmission. One preferred embodiment discloses and describes an anti-backlash feature to counter ''dead zones'' in the gear bearing movement.

Vranish, John M. (Inventor)

2009-01-01

227

Bearing for liquid metal pump  

DOEpatents

A liquid metal pump bearing support comprises a series of tangentially oriented spokes that connect the bearing cylinder to the pump internals structure. The spokes may be arranged in a plurality of planes extending from the bearing cylinder to the pump internals with the spokes in one plane being arranged alternately with those in the next plane. The bearing support structure provides the pump with sufficient lateral support for the bearing structure together with the capability of accommodating differential thermal expansion without adversely affecting pump performance.

Dickinson, Robert J. (Shaler Township, Allegheny County, PA); Wasko, John (Plum Borough, PA); Pennell, William E. (Unity Township, Allegheny County, PA)

1984-01-01

228

Stability of finite journal bearings from bearings--linear and nonlinear bearing forces  

Microsoft Academic Search

The paper investigates the relationship between the stability contour determined from the nonlinear simulation and that from the linear theory. The nonlinear bearing forces are directly obtained from the bearing pressure distribution which is solved from the Reynolds equation at each journal position. It is found that the critical speeds in the case of nonlinear bearing forces are the same

A. K. Tieu; Z. L. Qiu

1995-01-01

229

Simulation of non-hydrostatic gravity wave propagation in the upper atmosphere  

NASA Astrophysics Data System (ADS)

The high-frequency and small horizontal scale gravity waves may be reflected and ducted in non-hydrostatic simulations, but usually propagate vertically in hydrostatic models. To examine gravity wave propagation, a preliminary study has been conducted with a global ionosphere-thermosphere model (GITM), which is a non-hydrostatic general circulation model for the upper atmosphere. GITM has been run regionally with a horizontal resolution of 0.2° long × 0.2° lat to resolve the gravity wave with wavelength of 250 km. A cosine wave oscillation with amplitude of 30 m s-1 has been applied to the zonal wind at the low boundary, and both high-frequency and low-frequency waves have been tested. In the high-frequency case, the gravity wave stays below 200 km, which indicates that the wave is reflected or ducted in propagation. The results are consistent with the theoretical analysis from the dispersion relationship when the wavelength is larger than the cutoff wavelength for the non-hydrostatic situation. However, the low-frequency wave propagates to the high altitudes during the whole simulation period, and the amplitude increases with height. This study shows that the non-hydrostatic model successfully reproduces the high-frequency gravity wave dissipation.

Deng, Y.; Ridley, A. J.

2014-04-01

230

Performance of an Electro-Hydrostatic Actuator on the F-18 Systems Research Aircraft  

NASA Technical Reports Server (NTRS)

An electro-hydrostatic actuator was evaluated at NASA Dryden Flight Research Center, Edwards, California. The primary goal of testing this actuator system was the flight demonstration of power-by-wire technology on a primary flight control surface. The electro-hydrostatic actuator uses an electric motor to drive a hydraulic pump and relies on local hydraulics for force transmission. This actuator replaced the F-18 standard left aileron actuator on the F-18 Systems Research Aircraft and was evaluated throughout the Systems Research Aircraft flight envelope. As of July 24, 1997 the electro-hydrostatic actuator had accumulated 23.5 hours of flight time. This paper presents the electro-hydrostatic actuator system configuration and component description, ground and flight test plans, ground and flight test results, and lessons learned. This actuator performs as well as the standard actuator and has more load capability than required by aileron actuator specifications of McDonnell- Douglas Aircraft, St. Louis, Missouri. The electro-hydrostatic actuator system passed all of its ground tests with the exception of one power-off test during unloaded dynamic cycling.

Navarro, Robert

1997-01-01

231

Bearing construction for refrigeration compresssor  

DOEpatents

A hermetic refrigeration compressor has a cylinder block and a crankshaft rotatable about a vertical axis to reciprocate a piston in a cylinder on the cylinder block. A separate bearing housing is secured to the central portion of the cylinder block and extends vertically along the crankshaft, where it carries a pair of roller bearings to journal the crankshaft. The crankshaft has a radially extending flange which is journaled by a thrust-type roller bearing above the bearing housing to absorb the vertical forces on the crankshaft so that all three of the roller bearings are between the crankshaft and the bearing housing to maintain and control the close tolerances required by such bearings.

Middleton, Marc G. (Wyoming, MI) [Wyoming, MI; Nelson, Richard T. (Worthington, OH) [Worthington, OH

1988-01-01

232

Wave Journal Bearing with Compressible Lubricant—Part II: A Comparison of the Wave Bearing with a Wave-Groove Bearing and a Lobe Bearing  

Microsoft Academic Search

To identify the potential advantages of the wave journal bearing, a three-wave journal bearing was compared to both a three-wave-groove bearing (a wave bearing with axial grooves that isolate each wave) and a three-lobe bearing. The lobe bearing's profile was selected to approximate the wave journal bearing's profile. The lubricant was assumed to be compressible (gas). The bearing number, A,

Florin Dimofte

1995-01-01

233

History of Space Shuttle Main Engine Turbopump Bearing Testing at the Marshall Space Flight Center  

NASA Technical Reports Server (NTRS)

The Space Shuttle is propelled into orbit by two solid rocket motors and three liquid fed main engines. After the solid motors fall away, the shuttle engines continue to run for a total time of 8 minutes. These engines are fed propellants by low and high pressure turbopumps. A critical part of the turbopump is the main shaft that supports the drive turbine and the pump inducer and impeller. Rolling element bearings hold the shaft in place during rotation. If the bearings were to fail, the shaft would move, allowing components to rub in a liquid oxygen or hydrogen environment, which could have catastrophic results. These bearings are required to spin at very high speeds, support radial and axial loads, and have high wear resistance without the benefit of a conventional means of lubrication. The Rocketdyne built Shuttle turbopumps demonstrated their capability to perform during launches; however, the seven hour life requirement was not being met. One of the limiting factors was the bearings. In the late 1970's, an engineering team was formed at the Marshall Space Flight Center (MSFC), to develop a test rig and plan for testing the Shuttle s main engine high pressure oxygen turbopump (HPOTP) bearings. The goals of the program were to better understand the operation of bearings in a cryogenic environment and to further develop and refine existing computer models used to predict the operational limits of these bearings. In 1982, testing began in a rig named the Bearing and Seal Material Tester or BSMT as it was commonly called. The first testing investigated the thermal margin and thermal runaway limits of the HPOTP bearings. The test rig was later used to explore potential bearing improvements in the area of increased race curvatures, new cage materials for better lubrication, new wear resistant rolling element materials, and other ideas to improve wear life. The most notable improvements during this tester s time was the incorporation of silicon nitride balls and bronze filled polytetrafluoroethylene (PTFE) cage inserts into the bearings and the anchoring of the SHABERTH bearing model and SINDA thermal computer model for cryogenic bearing analysis. In the mid 1990's, Pratt and Whitney (P&W) won the contract to deliver new high pressure turbopumps for the Shuttle s engines. P&W used two new bearing materials for the rings, Cronidur 30 and AISI 9310 steel and testing was needed on these new materials. A test rig had been designed and delivered to MSFC for testing hydrostatic bearings but with the need by Pratt to validate their bearings, the rig was reconfigured for testing of two ball bearings or a ball bearing and a roller bearing. The P&W bearings are larger than the Rocketdyne bearings and could not be installed in the BSMT. This new test rig was called the LH2 test rig and began operation in 1995. The LH2 test rig accumulated 75,000 seconds of run time in hydrogen. This test rig was valuable in two areas: validating the use of silicon nitride balls and rollers in Alternate Turbopump Development (ATD) bearings, which Pratt eventually used, and in proving the robustness of the balls and rollers after river marks appeared on the surface of the rolling elements. Individual test reports have been presented at conferences and symposiums throughout the years. This paper is a comprehensive report of all the bearing testing done at Marshall. It represents thousands of hours of dedication and labor in all engineering and technical fields that made this program a success.

Gibson, Howard; Thom, Robert; Moore, Chip; Haluck, Dave

2010-01-01

234

On variable hydrostatic transmission for road vehicles, powered by supply of fluid at constant pressure  

NASA Technical Reports Server (NTRS)

Various hydrostatic power transmission systems for automotive applications with power supply at constant pressure and unrestricted flow and with a Volvo Flygmotor variable displacement motor as the principal unit were investigated. Two most promising concepts were analyzed in detail and their main components optimized for minimum power loss at the EPA Urban Driving Cycle. The best fuel consumption is less than 10 lit. per 100 kM for a 1542 kG vehicle with a hydrostatic motor and a two speed gear box in series (braking power not recovered). Realistic system pressure affects the fuel consumption just slightly, but the package volume/weight drastically. Back pressure increases losses significantly. Special attention was paid to description of the behavior and modeling of the losses of variable displacement hydrostatic machines.

Magi, M.; Freivald, A.; Andersson, I.; Ericsson, U.

1981-01-01

235

Microstructure and properties of ultrafine grain nickel 200 after hydrostatic extrusion processes  

NASA Astrophysics Data System (ADS)

This paper presents the results of the studies of the structure and properties of ultrafine grained nickel 200 obtained by hydrostatic extrusion processes. Microstructure was characterized by means of optical microscopy and electron transmission microscopy. Corrosion resistance was studied by impedance and potentiodynamic methods using an AutoLab PGSTAT 100 potentiostat in 0.1 M Na2SO4 solution and in acidified (by addition of H2SO4) 0.1 M NaCl solution at pH = 4.2 at room temperature. Microhardness tests were also performed. The results showed that hydrostatic extrusion produces a heterogeneous, ultrafine-grained microstructure in nickel 200. The corrosive resistance tests showed that the grain refinement by hydrostatic extrusion is accompanied by a decreased corrosive resistance of nickel 200.

Sitek, R.; Krajewski, C.; Kami?ski, J.; Spychalski, M.; Garbacz, H.; Pachla, W.; Kurzyd?owski, K. J.

2012-09-01

236

Antagonistic effects of hydrostatic pressure and osmotic pressure on cytochrome P-450cam spin transition.  

PubMed Central

The combined effects of hydrostatic pressure and osmotic pressure, generated by polyols, on the spin equilibrium of fenchone-bound cytochrome P-450cam were investigated. Hydrostatic pressure indices a high spin to low spin transition, whereas polyols induce the reversed reaction. Of the four solutes used, glycerol, glucose, stachyose, and sucrose, only the last two would act on the spin transition by osmotic stress. The spin volume changes measured by both techniques are different, 29 and -350 ml/mol for hydrostatic pressure and osmotic pressure, respectively. It suggests that even if the two are perturbing water molecules, different properties are probed. From the volume change induced by osmotic stress, 19 water molecules are deduced that would be implicated in the spin transition of the fenchone-bound protein. This result suggests that water molecules other than the well defined ones located in the active site play a key role in modulating the spin equilibrium of cytochrome P-450cam.

Di Primo, C; Deprez, E; Hoa, G H; Douzou, P

1995-01-01

237

Gold-bearing skarns  

USGS Publications Warehouse

In recent years, a significant proportion of the mining industry's interest has been centered on discovery of gold deposits; this includes discovery of additional deposits where gold occurs in skarn, such as at Fortitude, Nevada, and at Red Dome, Australia. Under the classification of Au-bearing skarns, we have modeled these and similar gold-rich deposits that have a gold grade of at least 1 g/t and exhibit distinctive skarn mineralogy. Two subtypes, Au-skarns and byproduct Au-skarns, can be recognized on the basis of gold, silver, and base-metal grades, although many other geological factors apparently are still undistinguishable largely because of a lack of detailed studies of the Au-skarns. Median grades and tonnage for 40 Au-skarn deposits are 8.6 g/t Au, 5.0 g/t Ag, and 213,000 t. Median grades and tonnage for 50 byproduct and Au-skarn deposits are 3.7 g/t Au, 37 g/t Ag, and 330,000 t. Gold-bearing skarns are generally calcic exoskarns associated with intense retrograde hydrosilicate alteration. These skarns may contain economic amounts of numerous other commodities (Cu, Fe, Pb, Zn, As, Bi, W, Sb, Co, Cd, and S) as well as gold and silver. Most Au-bearing skarns are found in Paleozoic and Cenozoic orogenic-belt and island-arc settings and are associated with felsic to intermediate intrusive rocks of Paleozoic to Tertiary age. Native gold, electru, pyrite, pyrrhotite, chalcopyrite, arsenopyrite, sphalerite, galena, bismuth minerals, and magnetite or hematite are the most common opaque minerals. Gangue minerals typically include garnet (andradite-grossular), pyroxene (diopside-hedenbergite), wollastonite, chlorite, epidote, quartz, actinolite-tremolite, and (or) calcite.

Theodore, Ted G.; Orris, Greta J.; Hammerstrom, Jane M.; Bliss, James D.

1991-01-01

238

Linear magnetic bearings  

NASA Technical Reports Server (NTRS)

A self regulating, nonfrictional, active magnetic bearing is disclosed which has an elongated cylindrical housing for containing a shaft type armature with quadrature positioned shaft position sensors and equidistantly positioned electromagnets located at one end of the housing. Each set of sensors is responsive to orthogonal displacement of the armature and is used to generate control signals to energize the electromagnets to center the armature. A bumper magnet assembly is located at one end of the housing for dampening any undesired axial movement of the armature or to axially move the armature either continuously or fixedly.

Goldowskiy, M. P.

1984-01-01

239

Dialogue for Kids Wild About Bears Sleepy Bear Lesson Plan  

NSDL National Science Digital Library

Each winter, bears hunker down, slow their metabolisms, and pretty much wait out the winter in the safety of some sort of den. This lesson plan, from Idaho Public Television, is a fun way to illustrate to children (probably elementary grades primarily) the process of hibernation. At this site, educators are given the complete lesson plan instructions as well as several links to all sorts of great resources, including links to information on: Bear Diet, Home Range, Reproduction, Bear Research, People and Bears, more Classroom Activities, and more. And, the great addition to the site is a link to a 30-minute video about bears. While the site is somewhat focused on Idaho-specific bear information, teachers should be able to easily integrate the lesson no matter where you are.

240

High Hydrostatic Pressure for Disinfection of Bone Grafts and Biomaterials: An Experimental Study  

PubMed Central

Background: Autoclaving, heat, irradiation or chemical detergents are used to disinfect autografts, allografts and biomaterials for tissue reconstruction. These methods are often associated with deterioration of mechanical, physical, and biological properties of the bone grafts and synthetic implants. High hydrostatic pressure has been proposed as a novel method preserving biomechanical and biological properties of bone, tendon and cartilage. This is the first study to assess the inactivation of clinically relevant bacteria on biomaterials and human bone by high hydrostatic pressure. Methods: Bacterial suspensions of Staphylococcus aureus, Pseudomonas aeruginosa and Enterococcus faecium, implants covered with infected blood, human bone infected in vitro, and biopsies of patients with chronic osteomyelitis were subjected to different protocols of high hydrostatic pressure up to 600 MPa. Bacterial survival after high hydrostatic pressure treatment was determined and compared with bacterial growth in untreated controls. Results: S. aureus and P. aeruginosa in suspension were completely inactivated by high hydrostatic pressure (> 5log levels), whereas E. faecium showed barotolerance up to 600 MPa. Blood and adherence to metal implants did not significantly alter inactivation of bacteria, and complete disinfection was achieved with barotolerant bacteria (S. aureus and P. aeruginosa). However, osteoarthritic bone demonstrated a non-homogeneous baroprotective effect, with single bone samples resistant to treatment resulting in unaltered bacterial growth, and complete disinfection of artificially infected bone specimens was achieved in 66% for S. aureus, 60% for P. aeruginosa and 0% for E. faecium. Human bone samples of patients with chronic osteomyelitis could be completely disinfected in 2 of 37 cases. Conclusion: High hydrostatic pressure offers new perspectives for disinfection of sensitive biomaterials and bone grafts, and contamination by blood did not significantly affect bacterial inactivation rates. However, a significant baroprotective effect was demonstrated in bone. Effectiveness is currently limited to colonization and / or infection with barosensitive micro-organisms.

Gollwitzer, Hans; Mittelmeier, Wolfram; Brendle, Monika; Weber, Patrick; Miethke, Thomas; Hofmann, Gunther O; Gerdesmeyer, Ludger; Schauwecker, Johannes; Diehl, Peter

2009-01-01

241

Aerospace applications of magnetic bearings  

NASA Technical Reports Server (NTRS)

Magnetic bearings have traditionally been considered for use in aerospace applications only where performance advantages have been the primary, if not only, consideration. Conventional wisdom has been that magnetic bearings have certain performance advantages which must be traded off against increased weight, volume, electric power consumption, and system complexity. These perceptions have hampered the use of magnetic bearings in many aerospace applications because weight, volume, and power are almost always primary considerations. This paper will review progress on several active aerospace magnetic bearings programs at SatCon Technology Corporation. The magnetic bearing programs at SatCon cover a broad spectrum of applications including: a magnetically-suspended spacecraft integrated power and attitude control system (IPACS), a magnetically-suspended momentum wheel, magnetic bearings for the gas generator rotor of a turboshaft engine, a vibration-attenuating magnetic bearing system for an airborne telescope, and magnetic bearings for the compressor of a space-rated heat pump system. The emphasis of these programs is to develop magnetic bearing technologies to the point where magnetic bearings can be truly useful, reliable, and well tested components for the aerospace community.

Downer, James; Goldie, James; Gondhalekar, Vijay; Hockney, Richard

1994-01-01

242

Bearing Dynamic Coefficients of Flexible-Pad Journal Bearings  

Microsoft Academic Search

The application of flexible-pad journal bearings for high-speed rotating machinery has recently gained attention from equipment manufacturers for its simplicity of one-piece design which can eliminate the manufacturing tolerance stack-up and possible lower functional power loss. This paper presents a general method for the calculation of bearing dynamic coefficients of flexible-pad journal bearings. These coefficients are critical to the rotor

Wen Jeng Chen

1995-01-01

243

Titan's Hydrostatic Figure and a Possible Dynamic Tidal Variation  

NASA Astrophysics Data System (ADS)

An archive of radio Doppler data from the Cassini mission can be found in NASA's PDS Atmospheres Node as a series of binary files called Orbit Data Files (ODF). We have downloaded six ODFs from the Cassini mission for six Titan gravity passes T11 (27-Feb-2006), T22 (28-Dec-2006), T33 (29-Jun-2007), T45 (31-Jul-2008), T68 (20-May-2010) and T74 (18-Feb-2011). After converting to text files with JPL space-navigation software (ODDUMP), we convert the observed Doppler shift for the Cassini spacecraft to radial velocity along the line of sight (LOS) at one-second sample interval. These data can be fit by a numerical integration of the equations of motion for the craft with respect to Titan, and a subsequent projection of the velocity so obtained along the LOS. The orbital parameters are represented by six standard Kepler elements with the plane of sky as the fundamental reference system, the system used for spectroscopic binary stars. While the systemic velocity Vs is taken as a constant for binary stars, it is represented for spacecraft by six parameters in a function developed for the Doppler detection of gravitational waves. We adopt well-determined values for the GM of Titan and Saturn and add a 13th gravity parameter C22 for an ellipsoidal hydrostatic Titan distorted by the Saturn tide and synchronous rotation (J2 = (10/3) C22). Also, we adopt the IAU definition for the pole and prime meridian of Titan in the ICRF/J2000 reference system. The interval of observation for each flyby is held to two hours, centered as closely as possible on the time of closest approach to Titan. This interval is sufficiently long for purposes of including all the detectable signal from C22, but short enough that spacecraft-generated translational forces can be neglected. By iterating on a linear least-squares system, 13 converged parameters and associated covariance matrix are found by singular-value decomposition of the least-squares design matrix for each of the six flybys. With reasonably good starting conditions from JPL's Horizons web site, convergence is achieved in about 10 iterations. The weighted mean of the six independent values of C22 is (10.479 ± 0.074) × 10-6, in good agreement with published values by the Cassini Radio Science Team, especially SOL1a at (10.121 ± 0.029) × 10-6. However, our independent analysis of the data does not result in a significantly improved fit when a 14th parameter, the Love number k2, is added to the parameter list. It seems that a dynamic tidal variation is not required in order to fit the data, even though it might very well represent a more realistic fitting model.

Anderson, J. D.; Schubert, G.

2012-12-01

244

Influence of dispersion on sensitivity of highly birefringent fibers to temperature and hydrostatic pressure.  

PubMed

The influence of dispersion on the sensitivity of highly birefringent fibers to temperature and hydrostatic pressure was experimentally investigated. In fibers with geometric birefringence that shows high dispersion, great differences were observed between group and phase sensitivities to temperature and hydrostatic pressure. This difference may reach 400% in the case of temperature response. In contrast, in weakly dispersive fibers with stress-induced birefringence these differences were of the order of 8% and 14%, respectively, for temperature and pressure. The influence of the dispersion effect on the temperature compensation of white-light interferometric sensors based on highly birefringent fibers was also discussed. PMID:18273266

Urbanczyk, W; Bock, W J

1998-05-20

245

Reduction in bearing size due to superconductors in magnetic bearings  

NASA Technical Reports Server (NTRS)

A design concept that reduces the size of magnetic bearings is assessed. The small size will enable magnetic bearings to fit into limited available bearing volume of cryogenic machinery. The design concept, called SUPERC, uses (high Tc) superconductors or high-purity aluminum conductors in windings instead of copper. The relatively high-current density of these conductors reduces the slot radial thickness for windings, which reduces the size of the bearings. MTI developed a sizing program called SUPERC that translates the high-current density of these conductors into smaller sized bearings. This program was used to size a superconducting bearing to carry a 500 lb. load. The sizes of magnetic bearings needed by various design concepts are as follows: SUPERC design concept = 3.75 in.; magnet-bias design concept = 5.25 in.; and all electromagnet design concept = 7.0 in. These results indicate that the SUPERC design concept can significantly reduce the size of the bearing. This reduction, in turn, reduces the weight and yields a lighter bearing. Since the superconductors have inherently near-zero resistance, they are also expected to save power needed for operation considerably.

Rao, Dantam K.; Lewis, Paul; Dill, James F.

1991-01-01

246

Effect of Bearing Cleaning on Long Term Bearing Life  

NASA Technical Reports Server (NTRS)

For many years chlorofluorocarbon (CFC ) based solvents, such as Freon and 1,1,1, Trichloroethane (TCA), were used as bearing cleaning solvents for space mechanisms. The 1995 ban on the production of ozone depleting chemicals (ODC) such as CFCs caused a change to new ODC-free cleaners for the precision bearing cleaning. With this change the question arises what effect if any do these new cleaners have on long term bearing life. The purpose of this study was to evaluate this effect. A one year test using 60 small electrical motors (two bearings per motor) was conducted in a high vacuum environment (2.0* 10(exp -6) torr) at a temperature of 90C. Prior to testing the bearings were cleaned with one of four cleaners. These cleaners included two aqueous based cleaners, a CFC based cleaner and supercritical carbon dioxide. Three space compatible greases were tested. After testing the mass of each lubricated bearing was measured both pre and post test. Along with mass loss measurements a profilometer trace of each bearing was taken to measure post test wear of the bearings. In addition the bearings were visually examined and analyzed using an optical microscope.

Jett, Timothy Raymond; Thom, Robert L.

1998-01-01

247

Analysis of Bearing Incidents in Aircraft Gas Turbine Mainshaft Bearings  

Microsoft Academic Search

An examination of approximately 200 bearing incidents in current aircraft engines has shown that damage in the bearing is initiated at the surface. Twenty-one cases were studied in detail, and five typical incidents are presented here. The initial damage was produced by abrasive particles, dents, grinding scores, skidding, large carbides and corrosion pits. The first phase of the failure mechanism

B. L. Averbach; E. N. Bamberger

1991-01-01

248

Superconducting levitating bearing  

NASA Technical Reports Server (NTRS)

A superconducting bearing assembly includes a coil field source that may be superconducting and a superconducting structure. The coil field source assembly and superconducting structure are positioned so as to enable relative rotary movement therebetween. The structure and coil field source are brought to a supercooled temperature before a power supply induces a current in the coil field source. A Meissner-like effect is thereby obtained and little or no penetration of the field lines is seen in the superconducting structure. Also, the field that can be obtained from the superconducting coil is 2-8 times higher than that of permanent magnets. Since the magnetic pressure is proportioned to the square of the field, magnetic pressures from 4 to 64 times higher are achieved.

Moon, Francis C. (Inventor)

1996-01-01

249

Small-Scale Processes in the Weddell Sea Modeled with Non-Hydrostatic Formulations of the MITgcm  

NASA Astrophysics Data System (ADS)

Ocean general circulation models are most frequently derived from the Navier-Stokes equations built from the hydrostatic primitive equations (HPEs). In these, the hydrostatic balance - the balance between the vertical pressure gradient and gravity - replaces the vertical momentum equation. HPEs also make the traditional approximation which includes the shallow atmosphere approximation and the elimination of the horizontal Coriolis force terms. While it is generally accepted that the hydrostatic equation is a very good approximation for motions in the ocean at global scales, at smaller scales, it is necessary to take into account the non-hydrostatic effects. In the Weddell Sea, the cyclonic sub-polar gyre leads to surface water divergence and upwelling of deep water. Sea ice area, thickness, and particularly the location and size of the intermittent Weddell Polynya have been shown to strongly influence non-hydrostatic deep convection in the gyre. We are using a fine resolution configuration of the MITgcm with hydrostatic (HPE), non-hydrostatic, and quasi-hydrostatic capabilities to test the impact of using these equations to model the Weddell Sea circulation and sea surface height. We force the model with sea ice concentration and thickness data to represent years in the Weddell Sea with a large polynya and years when there is very little open water. The deviations in sea ice conditions help to explain the extent to which sea ice amplifies effects of the non-hydrostatic model formulation. Results from these tests address how resolving non-hydrostatic motion in a region with small scale convection affects the modeled output.

Bernstein, E. R.; Geiger, C. A.; Deliberty, T. L.

2012-12-01

250

Pediatric Hydrostatic Intususcception Reduction - Still a Clinician's Enigma: A Case Report  

PubMed Central

We present a case of infantile intussusception treated successfully using hydrostatic reduction, highlighting the importance of non-surgical techniques as the first line of management for this entity. Physicians should strive for mastery over such techniques by extensive training to prevent unwanted surgical procedures in such cases.

Sood, Vikrant; Khanna, Rajeev; Jain, Deepak

2012-01-01

251

Accurate representation of geostrophic and hydrostatic balance in unstructured mesh finite element ocean modelling  

Microsoft Academic Search

Accurate representation of geostrophic and hydrostatic balance is an essential requirement for numerical modelling of geophysical flows. Potentially, unstructured mesh numerical methods offer significant benefits over conventional structured meshes, including the ability to conform to arbitrary bounding topography in a natural manner and the ability to apply dynamic mesh adaptivity. However, there is a need to develop robust schemes with

J. R. Maddison; D. P. Marshall; C. C. Pain; M. D. Piggott

2011-01-01

252

Effect of hydrostatic pressure on ADH induced osmotic water flow in toad bladder  

Microsoft Academic Search

The effect of hydrostatic pressure (HP) on antidiuretic hormone (ADH) stimulated osmotic water flow (Jv) across the toad urinary bladder was evaluated. Jv for ADH-stimulated bladders was significantly reduced by an elevation of the serosal HP gradient to 1 cm H2O. Subsequent elimination of the HP gradient resulted in a recovery of Jv. Serosal HP also caused a reversible increase

Bernard Rosenbaum; Gerard Lombardo; Vincent A. DiScala

1982-01-01

253

Simulation of meniscus stability in superhydrophobic granular surfaces under hydrostatic pressures  

Microsoft Academic Search

In this work, a series of numerical simulations has been devised to study the performance of granular superhydrophobic surfaces under elevated hydrostatic pressures. Using balance of forces, an analytical expression has also been developed to predict the critical pressure at which a submersed idealized granular superhydrophobic surface comprised of spherical particles, orderly packed next to one another, departs from the

B. Emami; T. M. Bucher; H. Vahedi Tafreshi; D. Pestov; M. Gad-el-Hak; G. C. Tepper

2011-01-01

254

Tuning of PbSe Lasers by Hydrostatic Pressure from 8 to 22 Micrometers.  

National Technical Information Service (NTIS)

This paper reports the tuning by hydrostatic pressure of the wavelength of emission of a PbSe laser from 7.5 to 22.3 micrometers in the infrared. Also discussed are the possibilities for further extension of the emission wavelength, the physical studies t...

J. M. Besson P. William A. R. Calawa

1968-01-01

255

Effect of high hydrostatic pressure on the physiology of Manila mango.  

PubMed

Manila mangoes (Mangifera indica L.) have sensory characteristics that make them attractive for consumption as a fresh fruit. A large portion of the annual yield of this fruit is infested by the Mexican fruit fly (Anastrepha ludens), adversely impacting the quality of the crop. Hence, it is necessary to develop economically viable postharvest treatments to reduce the damage caused by this insect. Currently, high hydrostatic pressures are used to guarantee the safety of many processed foods. The objective of this work was to assess the effects of high hydrostatic pressure on mangoes at their physiological maturity. High hydrostatic pressures were applied to mangoes at three levels: 50, 100 and 200 megapascals applied for four different time periods (0, 5, 10 and 20 min). Physiologically mature mangoes were more resistant to changes in response to the pressure of 50 MPa. Reduction of physiological activity by application of high hydrostatic pressure opens a new avenue for the research on treatments intended to enhance preservation of whole fresh fruit. PMID:23504511

Vargas-Ortiz, M A; De la Cruz-Medina, J; de Los Monteros, J J Espinosa; Oliart-Ros, R M; Rebolledo-Martinez, A; Ramírez, J A; García, H S

2013-06-01

256

First-principles simulations on bonding pathways of chemical transformations under hydrostatic compression  

NASA Astrophysics Data System (ADS)

High pressure as a thermodynamic parameter provides a strong structural constraint to lead chemical transformations with selective ways. Thus, chemical transformations under pressure can create novel materials which may not be accessible by covalent synthesis. However, bonding evolution toward high pressure chemical transformations can be a complex process and may happen over widely different pressures. To understand bonding evolution pathways of high pressure chemical transformations, first-principles simulations were performed following hydrostatic compression enthalpy minimization paths to obtain experimentally and theoretically established phase transitions of carbon. The results showed that the chemical transformations from hydrostatic compression carbon to single-bonded phases were characterized by a sudden decrease in principal stress components, indicating the onset of chemical transformation. On this basis, a number of hydrostatic compression chemical transformations from molecular precursors to novel materials were predicted, such as hydrocarbon graphane, a hydrogenated carbon nitride sheet, and carbon nitrides. All predicted hydrostatic compression transformations are featured as a sudden change in principal stress components, representing chemical bonding destruction and formation reactions with a cell volume collapse.

Hu, Anguang; Zhang, Fan

2012-02-01

257

Poisson's ratios of crystalline rocks as a function of hydrostatic confining pressure  

Microsoft Academic Search

The hydrostatic pressure (P) dependence of dynamic Poisson's ratios (?) has been investigated for 54 samples of the crystalline rocks from the Sulu-Dabie orogenic belt (China) using pulse transmission techniques. The Poisson's ratio of each sample was calculated from its mean P and S wave velocities from three orthogonal directions corresponding to the tectonic framework (X-Y-Z) defined by foliation and

Qian Wang; Shaocheng Ji

2009-01-01

258

Radial deformation and stability of single-wall carbon nanotubes under hydrostatic pressure  

Microsoft Academic Search

In this paper we have developed a theory of energetics for isolated single-wall carbon nanotubes (SWNTs) deformed in the radial direction, and applied this theory to investigate their deformation characteristics and stability under hydrostatic pressure. The starting point of the theory is the strain energy of SWNTs predicted by ab initio calculations based on the density functional theory (DFT), which

Masayuki Hasegawa; Kazume Nishidate

2006-01-01

259

Injury recovery of foodborne pathogens in high hydrostatic pressure treated milk during storage  

Microsoft Academic Search

Bacteria are expected to be injured or killed by high hydrostatic pressure (HHP). This depends on pressure levels, species and strain of the microorganism and subsequent storage. Injured bacteria may be repaired which could affect the microbiological quality of foodstuffs with an important safety consideration especially in low acid food products. In this study two Gram-positive (Listeria monocytogenes CA and

Faruk Bozoglu; Hami Alpas; Gönül Kaletunç

2004-01-01

260

High hydrostatic pressure activates transcription factors involved in Saccharomyces cerevisiae stress tolerance.  

PubMed

A number of transcriptional control elements are activated when Saccharomyces cerevisiae cells are submitted to various stress conditions, including high hydrostatic pressure (HHP). Exposure of Saccharomyces cerevisiae cells to HHP results in global transcriptional reprogramming, similar to that observed under other industrial stresses, such as temperature, ethanol and oxidative stresses. Moreover, treatment with a mild hydrostatic pressure renders yeast cells multistress tolerant. In order to identify transcriptional factors involved in coordinating response to high hydrostatic pressure, we performed a time series microarray expression analysis on a wild S. cerevisiae strain exposed to 50 MPa for 30 min followed by recovery at atmospheric pressure (0.1 MPa) for 5, 10 and 15 min. We identified transcription factors and corresponding DNA and RNA motifs targeted in response to hydrostatic pressure. Moreover, we observed that different motif elements are present in the promoters of induced or repressed genes during HHP treatment. Overall, as we have already published, mild HHP treatment to wild yeast cells provides multiple protection mechanisms, and this study suggests that the TFs and motifs identified as responding to HHP may be informative for a wide range of other biotechnological and industrial applications, such as fermentation, that may utilize HHP treatment. PMID:23072392

Bravim, Fernanda; da Silva, Lucas F; Souza, Diego T; Lippman, Soyeon I; Broach, James R; Fernandes, A Alberto R; Fernandes, Patricia M B

2012-12-01

261

SAS FAMILY OF HYDROSTATIC LEVEL AND TILT SENSORS FOR SLOW GROUND MOTION STUDIES AND PRECISE ALIGNMENT  

Microsoft Academic Search

The design and principle of operation of a family of hydrostatic Level and Tilt monitors (SAS & SAST) is described. These devices are intended for investigation and measurement of components movement of particle accelerators and storage rings and relative movement of ground parts. The SAS type monitor is intended for vertical displacement measurements in the 5 mm displacement range with

A. Chupyra; M. Kondaurov; A. Medvedko; S. Singatulin; E. Shubin

262

Light-scattering studies of the polymorphism of potassium cyanide under hydrostatic pressure  

Microsoft Academic Search

We measured the Raman spectrum of potassium cyanide under hydrostatic gas pressures up to 7 kbar at temperatures down to 75 K and found two new high-pressure phases with characteristic Raman spectra. The topology of the phase diagram of the alkali cyanides suggests that the orientation of the CN- molecules in these phases is probably a [111] direction of the

W. Dultz; H. Krause

1978-01-01

263

46 CFR 54.10-10 - Standard hydrostatic test (modifies UG-99).  

Code of Federal Regulations, 2011 CFR

...pressure vessel, multiplied by the ratio of the stress value “S” at the test temperature to the stress value “S” at the design temperature for...No ratio less than one shall be used. The stress resulting from the hydrostatic test...

2011-10-01

264

46 CFR 54.10-10 - Standard hydrostatic test (modifies UG-99).  

Code of Federal Regulations, 2012 CFR

...pressure vessel, multiplied by the ratio of the stress value “S” at the test temperature to the stress value “S” at the design temperature for...No ratio less than one shall be used. The stress resulting from the hydrostatic test...

2012-10-01

265

46 CFR 54.10-10 - Standard hydrostatic test (modifies UG-99).  

Code of Federal Regulations, 2010 CFR

...pressure vessel, multiplied by the ratio of the stress value “S” at the test temperature to the stress value “S” at the design temperature for...No ratio less than one shall be used. The stress resulting from the hydrostatic test...

2010-10-01

266

Functional Improvement of Milk Whey Proteins Induced by High Hydrostatic Pressure  

Microsoft Academic Search

High pressure is emerging as a new processing technology that produces particular changes in the molecular structure of proteins and thus gives rise to new properties inaccessible via conventional methods of protein modification. This review deals with the main effects of high hydrostatic pressure on the physicochemical characteristics of milk whey proteins and how modifications in their structural properties contribute

Rosina López-Fandiño

2006-01-01

267

A High Pressure Cell for Far Infrared Spectroscopy Under Truly Hydrostatic Pressures.  

National Technical Information Service (NTIS)

A high pressure far infrared cell operating to truly hydrostatic pressures of 8 kbars is described. Results of experiments on the collision induced absorption in nitrogen gas and on the pressure dependence of the q approx. 0 transverse optic phonon freque...

R. P. Lowndes

1974-01-01

268

46 CFR 54.10-10 - Standard hydrostatic test (modifies UG-99).  

Code of Federal Regulations, 2013 CFR

...pressure vessel, multiplied by the ratio of the stress value âSâ at the test temperature to the stress value âSâ at the design temperature for...No ratio less than one shall be used. The stress resulting from the hydrostatic test...

2013-10-01

269

Strength Differential Measured in Inconel 718: Effects of Hydrostatic Pressure Studied  

NASA Technical Reports Server (NTRS)

Aeropropulsion components, such as disks, blades, and shafts, are commonly subjected to multiaxial stress states at elevated temperatures. Experimental results from loadings as complex as those experienced in service are needed to help guide the development of accurate viscoplastic, multiaxial deformation models that can be used to improve the design of these components. During a recent study on multiaxial deformation (ref. 1) on a common aerospace material, Inconel 718, it was shown that the material in the aged state exhibits a strength differential effect (SDE), whereby the uniaxial compressive yield and subsequent flow behavior are significantly higher than those in uniaxial tension. Thus, this material cannot be described by a standard von Mises yield formulation. There have been other formulations postulated (ref. 2) that involve other combinations of the stress invariants, including the effect of hydrostatic stress. The question remained as to which invariants are necessary in the flow model. To capture the physical mechanisms occurring during deformation and reflect them in the plasticity formulation, researchers examined the flow of Inconel 718 under various amounts of hydrostatic stress to determine whether or not hydrostatic stress is needed in the formulation. Under NASA Grant NCC3-464, monitored by the NASA Glenn Research Center, a series of tensile tests were conducted at Case Western Reserve University on aged (precipitation hardened) Inconel 718 at 650 C and with superimposed hydrostatic pressure. Dogbone shaped tensile specimens (3-mm-diameter gauge by 16-mm gauge length) and cylindrical compression specimens (3-mm-diameter gauge by 6-mm gauge length) were strain gauged and loaded in a high-pressure testing apparatus. Hydrostatic pressures were obtained with argon and ranged from 210 to 630 MPa. The aged Inconel 718 showed a pronounced difference in the tension and compression yield strength (i.e., an SDE), as previously observed. Also, there were no significant effects of hydrostatic pressure on either the tensile and compressive yield strength (see the graph) or on the magnitude of the SDE. This behavior is not consistent with the pressure-dependent theory of the SDE, which postulates that the SDE is associated with pressure-dependent and/or internal friction dependent deformation associated with non-Schmid effects at the crystal level (refs. 3 and 4). Flow in Inconel 718 appears to be independent of hydrostatic pressure, suggesting that this invariant may be removed from the phenomenological constitutive model. As part of an ongoing effort to develop advanced constitutive models, Glenn s Life Prediction Branch coordinated this work with that of research on the multiaxial deformation behavior of Inconel 718 being conducted at Pennsylvania State University under NASA Grant NCC597.

Lewandowski, John J.; Wesseling, Paul; Prabhu, Nishad S.; Larose, Joel; Lissenden, Cliff J.; Lerch, Bradley A.

2003-01-01

270

Water stress and protein synthesis. II. Interaction between water stress, hydrostatic pressure, and abscisic acid on the pattern of protein synthesis in Avena coleoptiles  

Microsoft Academic Search

Water stress causes a reduction in hydrostatic pressure and can cause an increase in abscisic acid in plant tissues. To assess the possible role of abscisic acid and hydrostatic pressure in water stress effects, we have compared the effects of water stress, abscisic acid, and an imposed hydrostatic pressure on the rate and pattern of protein synthesis in Avena coleoptiles.

R. S. Dhindsa; R. E. Cleland

1975-01-01

271

Radial Clearance of Antifriction Bearings.  

National Technical Information Service (NTIS)

The article concerns in detail the radial clearance of different antifriction bearings which belong to important parameters which influence the longevity of the bearing to a certain extent. The effect of the influence of assembly and the wear on the radia...

V. Patocka

1968-01-01

272

Lubrication of rolling element bearings  

NASA Technical Reports Server (NTRS)

This paper is a broad survey of the lubrication of rolling-element bearings. Emphasis is on the critical design aspects related to speed, temperature, and ambient pressure environment. Types of lubrication including grease, jets, mist, wick, and through-the-race are discussed. The paper covers the historical development, present state of technology, and the future problems of rolling-element bearing lubrication.

Parker, R. J.

1980-01-01

273

Permanent-Magnet Meissner Bearing  

NASA Technical Reports Server (NTRS)

Permanent-magnet meissner bearing features inherently stable, self-centering conical configuration. Bearing made stiffer or less stiff by selection of magnets, springs, and spring adjustments. Cylindrical permanent magnets with axial magnetization stacked coaxially on rotor with alternating polarity. Typically, rare-earth magnets used. Magnets machined and fitted together to form conical outer surface.

Robertson, Glen A.

1994-01-01

274

Ion Implantation of Ceramic Bearings.  

National Technical Information Service (NTIS)

This report explores the use of ion implantation techniques to form solid lubricating surfaces on all ceramic (silicon nitride) and hybrid ball bearings. Techniques were developed to implant and/or cost silicon nitride and 52100 bearing steel with MoS2, B...

A. J. Armini S. N. Bunker

1989-01-01

275

Development And Application Of Non-Hydrostatic Model To The Coastal Engineering Problems  

NASA Astrophysics Data System (ADS)

The 3D non-hydrostatic free surface model developed by Kanarska and Maderich (2003) for stratified flows was further improved and has been used to simulate coastal processes. In the model the surface elevation, hydrostatic and non-hydrostatic components of pressure and velocity are calculated at sequential stages. Unlike most non-hydrostatic models, the 2-D depth-averaged momentum and continuity equations were integrated explicitly, whereas the 3-D equations were solved semi-implicitly at subsequent stages. The RANS and subgrid- scale eddy viscosity and diffusivity parameterization were implemented in the model to parameterize small-scale mixing. The model was applied to three coastal engineering problems. First, we used the model coupled with a 3D Lagrangian sediment transport model to predict scour caused by propeller jets of slowly maneuvering ships. The results of the simulations show good agreement with laboratory experiments and field ADCP measurements with tug boats. Second, the model was applied, while nested into the hydrostatic far-field counterpart model, for near-field simulation of cooling water discharge through submerged outfalls. Third, laboratory experiments and simulations were performed to estimate effects of large-amplitude internal solitary waves (ISW) on submerged structures and coastal bottom sediments. In the first series of experiments and simulations, the interaction of ISW-depressions with a rectangular bottom obstacle was investigated. In the second series, the ISW-depression was studied passing through a smooth local lateral constriction. The third series of laboratory experiments and simulations was conducted to investigate the dynamics of ISW of depressions reflecting from a steep slope. Contribution of V. Maderych in this work was supported by Hankuk University of Foreign Studies Research Fund of 2007.

Maderych, V.; Brovchenko, I.; Fenical, S.; Nikishov, V.; Terletska, K.

2007-12-01

276

Nonlinear control of magnetic bearings  

NASA Technical Reports Server (NTRS)

In this paper we present a variety of nonlinear controllers for the magnetic bearing that ensure both stability and robustness. We utilize techniques of discontinuous control to design novel control laws for the magnetic bearing. We present in particular sliding mode controllers, time optimal controllers, winding algorithm based controllers, nested switching controllers, fractional controllers, and synchronous switching controllers for the magnetic bearing. We show existence of solutions to systems governed by discontinuous control laws, and prove stability and robustness of the chosen control laws in a rigorous setting. We design sliding mode observers for the magnetic bearing and prove the convergence of the state estimates to their true values. We present simulation results of the performance of the magnetic bearing subject to the aforementioned control laws, and conclude with comments on design.

Pradeep, A. K.; Gurumoorthy, R.

1994-01-01

277

Geophagy by yellowstone grizzly bears  

USGS Publications Warehouse

We documented 12 sites in the Yellowstone ecosystem where grizzly bears (Ursus arctos horribilis) had purposefully consumed soil (an activity known as geophagy). We also documented soil in numerous grizzly bear feces. Geophagy primarily occurred at sites barren of vegetation where surficial geology had been modified by geothermal activity. There was no evidence of ungulate use at most sites. Purposeful consumption of soil by bears peaked first from March to May and again from August to October, synchronous with peaks in consumption of ungulate meat and mushrooms. Geophageous soils were distinguished from ungulate mineral licks and soils in general by exceptionally high concentrations of potassium (K) and high concentrations of magnesium (Mg) and sulphur (S). Our results do not support the hypotheses that bears were consuming soil to detoxify secondary compounds in grazed foliage, as postulated for primates, or to supplement dietary sodium, as known for ungulates. Our results suggest that grizzly bears could have been consuming soil as an anti-diarrheal.

Mattson, D. J.; Green, G. I.; Swalley, R.

1999-01-01

278

The physiological effects of hydrostatic pressure are not equivalent to those of helium pressure on Rana pipiens.  

PubMed Central

The effects of helium pressure and hydrostatic pressure on Rana pipiens were compared. Both agents caused paralysis at pressures greater than 135 atmospheres (1 atm = 101.325 kPa), but the median pressure for hydrostatic-pressure-induced paralysis was 35 atm less than that for helium pressure. When the ability of both pressurizing agents to reverse urethane-induced anaesthesia was compared, it was found that hydrostatic pressure raised the median dose for anaesthesia 2.2-fold more per atmosphere than did helium pressure. Animals that were lightly anaesthetized by urethane at 110 atm hydrostatic pressure became more deeply anaesthetized when helium was admitted isobarically into the pressure chamber. This difference in depth of anaesthesia between hydrostatic pressure and helium pressure is consistent with helium possessing an inherent anaesthetic effect. The abilities of other gases to pressure-reverse urethane anaesthesia were also determined. The degree of attenuation of the full pressure reversal effect observed with hydrostatic pressure was proportional to the lipid solubility of the gases, increasing in the order helium, neon, hydrogen, nitrogen and argon. Our data on the difference between hydrostatic and helium pressure are consistent with the critical volume hypothesis.

Dodson, B A; Furmaniuk, Z W; Miller, K W

1985-01-01

279

HYDROSTATIC GAS CONSTRAINTS ON SUPERMASSIVE BLACK HOLE MASSES: IMPLICATIONS FOR HYDROSTATIC EQUILIBRIUM AND DYNAMICAL MODELING IN A SAMPLE OF EARLY-TYPE GALAXIES  

SciTech Connect

We present new mass measurements for the supermassive black holes (SMBHs) in the centers of three early-type galaxies. The gas pressure in the surrounding, hot interstellar medium (ISM) is measured through spatially resolved spectroscopy with the Chandra X-ray Observatory, allowing the SMBH mass (M {sub BH}) to be inferred directly under the hydrostatic approximation. This technique does not require calibration against other SMBH measurement methods and its accuracy depends only on the ISM being close to hydrostatic, which is supported by the smooth X-ray isophotes of the galaxies. Combined with results from our recent study of the elliptical galaxy NGC 4649, this brings the number of galaxies with SMBHs measured in this way to four. Of these, three already have mass determinations from the kinematics of either the stars or a central gas disk, and hence join only a handful of galaxies with M {sub BH} measured by more than one technique. We find good agreement between the different methods, providing support for the assumptions implicit in both the hydrostatic and the dynamical models. The stellar mass-to-light ratios for each galaxy inferred by our technique are in agreement with the predictions of stellar population synthesis models assuming a Kroupa initial mass function (IMF). This concurrence implies that no more than {approx}10%-20% of the ISM pressure is nonthermal, unless there is a conspiracy between the shape of the IMF and nonthermal pressure. Finally, we compute Bondi accretion rates (M-dot{sub bondi}), finding that the two galaxies with the highest M-dot{sub bondi} exhibit little evidence of X-ray cavities, suggesting that the correlation with the active galactic nuclei jet power takes time to be established.

Humphrey, Philip J.; Buote, David A. [Department of Physics and Astronomy, University of California at Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697-4575 (United States); Brighenti, Fabrizio [Dipartimento di Astronomia, Universita di Bologna, Via Ranzani 1, Bologna 40127 (Italy); Gebhardt, Karl [Astronomy Department, University of Texas, Austin, TX 78712 (United States); Mathews, William G. [University of California Observatories, Lick Observatory, University of California, Santa Cruz, CA 95064 (United States)

2009-10-01

280

SSME turbopump bearing analytical study  

NASA Technical Reports Server (NTRS)

Three shuttle pump bearings operating under severe overspeed and shut-down conditions are evaluated. The specific parameters investigated include outer race stresses, cage stresses, cage-race drag, bearing heating, and crush loading. A quasi-dynamic version of the BASDAP computer code was utilized which involved the calculation of ball-race forces (inner and outer), contact pressures, contact dimensions, and contact angles as a function of (1) axial load, (2) radial load, and (3) centrifugal load on the bearing. Generally, radial loads on the order of 13,300 N (3000 pounds) per bearing or 26,700 N (6000 pounds) per bearing pair, could be expected to cause severe problems to any of the bearings with a 17,800 N (4000 pounds) axial load. Further, when possible temperature excursions are considered, even a load of 8900 N (2000 pounds) may be excessive. However, high momentary radial loads with a 3800 N (850 pounds) axial load would not be anticipated to cause catastrophic failure of the fuel pump bearing.

Kannel, J. W.; Merriman, T.

1980-01-01

281

Magnetic Bearings at Draper Laboratory  

NASA Technical Reports Server (NTRS)

Magnetic bearings, unlike traditional mechanical bearings, consist of a series of components mated together to form a stabilized system. The correct design of the actuator and sensor will provide a cost effective device with low power requirements. The proper choice of a control system utilizes the variables necessary to control the system in an efficient manner. The specific application will determine the optimum design of the magnetic bearing system including the touch down bearing. Draper for the past 30 years has been a leader in all these fields. This paper summarizes the results carried out at Draper in the field of magnetic bearing development. A 3-D radial magnetic bearing is detailed in this paper. Data obtained from recently completed projects using this design are included. One project was a high radial load (1000 pound) application. The second was a high speed (35,000 rpm), low loss flywheel application. The development of a low loss axial magnetic bearing is also included in this paper.

Kondoleon, Anthony S.; Kelleher, William P.; Possel, Peter D.

1996-01-01

282

Adaptive Spindle Balancing Using Magnetically Levitated Bearings.  

National Technical Information Service (NTIS)

A technological break through for supporting rotating shafts is the active magnetic bearing (AMB). Active magnetic bearings off some important advantages over conventional ball, roller, or journal bearings such as reduced frictional drag, no physical cont...

Barney Lauffer Petteys Redmond Sullivan

1999-01-01

283

Bearing Error and the Central Limit Theorem.  

National Technical Information Service (NTIS)

Bearings are frequently computed as the average of the number of readings. Most of fixing theory assumes that the bearing error is normal is distributed. Averages are usually much closer to bearing normally distributed than individual readings. The amount...

1987-01-01

284

Influence of Foreign Particles on Bearing Metals.  

National Technical Information Service (NTIS)

Incidents of damage to automobile engine bearings caused by foreign particles are discussed. Granular materials can cause cracks and intrusions into soft bearing surfaces, leaving scratches in the bearing metals.

S. Mori

1988-01-01

285

Surficial Deposits in the Bear Lake Basin.  

National Technical Information Service (NTIS)

Mapping and dating of surficial deposits in the Bear Lake drainage basin were undertaken to provide a geologic context for interpretation of cores taken from deposits beneath Bear Lake, which sometimes receives water and sediment from the glaciated Bear R...

M. C. Reheis B. J. C. Laabs R. M. Forester J. P. McGeehin D. S. Kaufman J. Bright

2005-01-01

286

Military and Commercial Aircraft Bearing Field Experience.  

National Technical Information Service (NTIS)

This report contains the results of a study performed on the field experience of aircraft bearings. The study pertains primarily to airframe bearings with emphasis on teflon and fabroid types. Source of field experience for evaluating these bearings was A...

W. C. Barnes

1969-01-01

287

Passive Magnetic Bearing with Ferrofluid Stabilization.  

National Technical Information Service (NTIS)

A new class of magnetic bearings is shown to exist analytically and is demonstrated experimentally. The class of magnetic bearings utilize a ferrofluid/solid magnet interaction to stabilize the axial degree of freedom of a permanent magnet radial bearing....

R. Jansen E. Dirusso

1996-01-01

288

Thermal Interactions in Rolling Bearing Dynamics.  

National Technical Information Service (NTIS)

Numerical enhancements to the established bearing dynamics computer code, Advanced Dynamics of Rolling Elements (ADORE), have been accomplished for improved computation of bearing heat generation and geometrical variation in bearing element dimensions. Th...

P. K. Gupta

2002-01-01

289

Effect of the hydrostatic pressure on the vertical distribution of Laminaria saccharina (L.) lamouroux in the Barents Sea  

NASA Astrophysics Data System (ADS)

An experimental study was undertaken to reveal the influence of the hydrostatic pressure on the early developmental stages of Laminaria saccharina, including the motile zoospores, the embryospores, and sprouting spores. The pressure did not affect the moving patterns and sinking rate of the zoospores. The sprouting spores were the most vulnerable among the other types; i.e., a pressure of 3 standard atmospheres (the hydrostatic pressure at the depth of 30 m) delayed or disturbed their development. The light conditions did not limit the vertical distribution of L. saccharina to greater depths. We assume that the hydrostatic pressure may significantly impact the vertical distribution of benthic macrophytes in the sublittoral zone.

Makarov, M. V.

2011-06-01

290

Conformational changes in human Hsp70 induced by high hydrostatic pressure produce oligomers with ATPase activity but without chaperone activity.  

PubMed

We investigated the folding of the 70 kDa human cytosolic inducible protein (Hsp70) in vitro using high hydrostatic pressure as a denaturing agent. We followed the structural changes in Hsp70 induced by high hydrostatic pressure using tryptophan fluorescence, molecular dynamics, circular dichroism, high-performance liquid chromatography gel filtration, dynamic light scattering, ATPase activity, and chaperone activity. Although monomeric, Hsp70 is very sensitive to hydrostatic pressure; after pressure had been removed, the protein did not return to its native sate but instead formed oligomeric species that lost chaperone activity but retained ATPase activity. PMID:24739062

Araujo, Thaís L S; Borges, Julio Cesar; Ramos, Carlos H; Meyer-Fernandes, José Roberto; Oliveira Júnior, Reinaldo S; Pascutti, Pedro G; Foguel, Debora; Palhano, Fernando L

2014-05-13

291

Numerical modeling of multidimensional flow in seals and bearings used in rotating machinery  

NASA Technical Reports Server (NTRS)

The rotordynamic behavior of turbomachinery is critically dependent on fluid dynamic rotor forces developed by various types of seals and bearings. The occurrence of self-excited vibrations often depends on the rotor speed and load. Misalignment and rotor wobbling motion associated with differential clearance were often attributed to stability problems. In general, the rotative character of the flowfield is a complex three dimensional system with secondary flow patterns that significantly alter the average fluid circumferential velocity. A multidimensional, nonorthogonal, body-fitted-grid fluid flow model is presented that describes the fluid dynamic forces and the secondary flow pattern development in seals and bearings. Several numerical experiments were carried out to demonstrate the characteristics of this complex flowfield. Analyses were performed by solving a conservation form of the three dimensional Navier-Stokes equations transformed to those for a rotating observer and using the general-purpose computer code PHOENICS with the assumptions that the rotor orbit is circular and that static eccentricity is zero. These assumptions have enabled a precise steady-state analysis to be used. Fluid injection from ports near the seal or bearing center increased fluid-film direct dynamic stiffness and, in some cases, significantly increased quadrature dynamic stiffness. Injection angle and velocity could be used for active rotordynamic control; for example, injection, when compared with no injection, increased direct dynamic stiffness, which is an important factor for hydrostatic bearings.

Hendricks, R. C.; Tam, L. T.; Przekwas, A.; Muszynska, A.; Braun, M. J.; Mullen, R. L.

1988-01-01

292

Random Bearings and Their Stability  

NASA Astrophysics Data System (ADS)

Self-similar space-filling bearings have been proposed some time ago as models for the motion of tectonic plates and appearance of seismic gaps. These models have two features which, however, seem unrealistic, namely, high symmetry in the arrangement of the particles, and lack of a lower cutoff in the size of the particles. In this work, an algorithm for generating random bearings in both two and three dimensions is presented. Introducing a lower cutoff for the sizes of the particles, the instabilities of the bearing under an external force such as gravity, are studied.

Baram, Reza Mahmoodi; Herrmann, Hans J.

2005-11-01

293

Random bearings and their stability.  

PubMed

Self-similar space-filling bearings have been proposed some time ago as models for the motion of tectonic plates and appearance of seismic gaps. These models have two features which, however, seem unrealistic, namely, high symmetry in the arrangement of the particles, and lack of a lower cutoff in the size of the particles. In this work, an algorithm for generating random bearings in both two and three dimensions is presented. Introducing a lower cutoff for the sizes of the particles, the instabilities of the bearing under an external force such as gravity, are studied. PMID:16384225

Mahmoodi Baram, Reza; Herrmann, Hans J

2005-11-25

294

Gas bearing operates in vacuum  

NASA Technical Reports Server (NTRS)

Bearing has restrictions to reduce air leaks and is connected to external pumpout facility which removes exhausted air. Token amount of air which is lost to vacuum is easily removed by conventional vacuum pump.

Perkins, G. S.

1975-01-01

295

Mixed-mu superconducting bearings  

DOEpatents

A mixed-mu superconducting bearing including a ferrite structure disposed for rotation adjacent a stationary superconductor material structure and a stationary permanent magnet structure. The ferrite structure is levitated by said stationary permanent magnet structure.

Hull, John R. (Hinsdale, IL); Mulcahy, Thomas M. (Western Springs, IL)

1998-01-01

296

A Passive Magnetic Bearing Flywheel  

NASA Technical Reports Server (NTRS)

A 100 percent passive magnetic bearing flywheel rig employing no active control components was designed, constructed, and tested. The suspension clothe rotor was provided by two sets of radial permanent magnetic bearings operating in the repulsive mode. The axial support was provided by jewel bearings on both ends of the rotor. The rig was successfully operated to speeds of 5500 rpm, which is 65 percent above the first critical speed of 3336 rpm. Operation was not continued beyond this point because of the excessive noise generated by the air impeller and because of inadequate containment in case of failure. Radial and axial stiffnesses of the permanent magnetic bearings were experimentally measured and then compared to finite element results. The natural damping of the rotor was measured and a damping coefficient was calculated.

Siebert, Mark; Ebihara, Ben; Jansen, Ralph; Fusaro, Robert L.; Morales, Wilfredo; Kascak, Albert; Kenny, Andrew

2002-01-01

297

Myrmecophagy by Yellowstone grizzly bears  

USGS Publications Warehouse

I used data collected during a study of radio-marked grizzly bears (Ursus arctos horribilis) in the Yellowstone region from 1977 to 1992 to investigate myrmecophagy by this population. Although generally not an important source of energy for the bears (averaging 8 mm long) nested in logs over small ants (6 mm long) nested under stones. Optimal conditions for consumption of ants occurred on the warmest sites with ample substrate suitable for ant nests. For ants in mounds, this occurred at low elevations at non-forested sites. For ants in logs, this occurred at low elevations or on southerly aspects where there was abundant, large-diameter, well-decomposed woody debris under an open forest canopy. Grizzly bears selected moderately decomposed logs 4a??5 dm in diameter at midpoint. Ants will likely become a more important food for Yellowstone's grizzly bears as currently important foods decline, owing to disease and warming of the regional climate.

Mattson, D. J.

2001-01-01

298

ATM CMG bearing failure analysis  

NASA Technical Reports Server (NTRS)

The cause or causes for the failure of ATM CMG S/N 5 (Skylab 1) and the anomalies associated with ATM CMG S/N 6 (Skylab 2) were investigated. Skylab telemetry data were reviewed and presented in the form of parameter distributions. The theory that the problems were caused by marginal bearing lubrication was studied along with the effects of orbital conditions on lubricants. Bearing tests were performed to investigate the effect of lubricant or lack of lubricant in the ATM CMG bearings and the dispersion and migration of the lubricant. The vacuum and weightless conditions of space were simulated in the bearing tests. Analysis of the results of the tests conducted points to inadequate lubrication as the predominant factor causing the failure of ATM CMG S/N 5 (Skylab 1) and the anomalies associated with ATM CMG S/N 6 (Skylab 2).

1975-01-01

299

Bearing capacity of desiccated tailings  

SciTech Connect

The development of matric suctions in soils contributes to their shear strength, resulting in an enhanced factor of safety against bearing-capacity failure. In this paper, matric suction profiles of desiccated mine tailings are predicted from a steady-state solution for evaporative conditions, and from an isothermal mathematical model that simulates liquid and vapor water flow through soils. The shear-strength envelope with respect to matric suction is established by testing reconstituted tailings samples in a modified triaxial cell, in which matric suction can be controlled. The contribution of matric suction to the shear strength is interpreted as an additional apparent cohesion for use in bearing-capacity calculations. Because of the nonlinearity of the shear-strength profile, a numerical method of analysis is adopted to predict the ultimate bearing capacity of the desiccated tailings. A subsequent decrease in bearing capacity following 2D water infiltration into a partially capped tailings deposit and accompanying suction loss is investigated.

Rassam, D.W.; Williams, D.J. [Univ. of Queensland, Brisbane, Queensland (Australia). Dept. of Civil Engineering] [Univ. of Queensland, Brisbane, Queensland (Australia). Dept. of Civil Engineering

1999-07-01

300

Mixed-mu superconducting bearings  

DOEpatents

A mixed-mu superconducting bearing is disclosed including a ferrite structure disposed for rotation adjacent a stationary superconductor material structure and a stationary permanent magnet structure. The ferrite structure is levitated by said stationary permanent magnet structure. 9 figs.

Hull, J.R.; Mulcahy, T.M.

1998-03-03

301

Analytic theory of hydrostatic stress effect on switching dynamics in ferroelectrics  

NASA Astrophysics Data System (ADS)

Polarization switching of ferroelectric materials is influenced by extensive variables such as electric field, temperature and stress. Currently a variety of theoretical approaches are used to gain a deeper understanding of the influence of extensive variables on the dynamic properties of ferroelectrics. In this paper a Landau-type model for second order bulk materials is used to study the extent to which hydrostatic stress affects the switching dynamic behaviours in ferroelectric material. Exact expressions for equilibrium polarization and switching time are derived analytically and then used to examine the dynamic behaviour in regimes of high electric field and hydrostatic stress. The second aspect of this work is to determine the relationship between empirical rules used to describe dynamic behaviour with the exact expressions derived from this model.

Loh, Kok-Khuan; Ong, Lye-Hock; Chew, Khian-Hooi

2014-07-01

302

Pressure distribution in a quasi-hydrostatic pressure medium: A finite element analysis  

NASA Astrophysics Data System (ADS)

The highest quality pressures on samples in a diamond anvil cell (DAC) at high pressures are produced using quasi-hydrostatic pressurization media such as helium or hydrogen. In this paper we carry out a finite element analysis of pressure distributions in a DAC using helium and non-hydrostatic argon pressurization media. We find that samples and ruby chips are at substantially higher pressures than the pressurization media, although this is sharply reduced by using helium, which has a low yield strength for the shear modulus. The deviations in pressure of the different samples (and ruby) from the pressurization media differ and depend on their elastic constants. Our observations may account for the distribution of pressures in metallic markers found in a recent calibration of the ruby scale to high pressures.

Tempere, Jacques; Silvera, Isaac F.

2011-12-01

303

Zinc phosphate chain length study under high hydrostatic pressure by Raman spectroscopy  

NASA Astrophysics Data System (ADS)

The aim of this study is to combine a diamond anvil cell with in-situ Raman spectroscopy to simulate and analyze the effect of pure pressure on the length of phosphate chains in an antiwear film formed in a tribological contact. In-situ Raman spectra of Zn2P2O7 glass, ?-Zn3(PO4)2, and ?-Zn2P2O7 crystals submitted to high hydrostatic pressure up to 20 GPa were recorded. Evolution of Raman spectra as a function of pressure was studied in the characteristic high frequency range of PO4 tetrahedra molecular resonance (650-1300 cm-1). When exposed to high pressure, the structure of the sample becomes less ordered. Phase transitions in ?-Zn3(PO4)2 structure are observed during compression from ambient pressure to 3 GPa. The length of the phosphate chains is conserved up to 20 GPa when samples are subjected to hydrostatic pressure.

Gauvin, M.; Dassenoy, F.; Minfray, C.; Martin, J. M.; Montagnac, G.; Reynard, B.

2007-03-01

304

Polarimetric and intermodal interference sensitivity to hydrostatic pressure, temperature, and strain of highly birefringent optical fibers.  

PubMed

The sensitivity to hydrostatic pressure, temperature, and strain of elliptical-core, D-shaped, bow-tie highly birefringent fibers is experimentally investigated. Both polarimetric and polarization sensitive LP(01)-LP(11) intermodal interferometric responses are studied. The sensitivities are expressed in terms of the experimental parameters T(x,j) describing a 2pi phase shift in the cosine response. It is found that bow-tie fibers exhibit a linear response to all the studied external perturbations except for the polarimetric response of the fundamental mode to temperature, while elliptical-core and D-shaped fibers are characterized by a nonlinear sensitivity to both temperature and hydrostatic pressure. The application to fiber-optic sensors of each type of fiber is discussed. PMID:19829467

Bock, W J; Eftimov, T A

1993-11-15

305

Hydrostatic pressure effects on mode propagation in highly birefringent two-mode bow-tie fibers.  

PubMed

An experimental study on the effects of high hydrostatic pressure of as much as 100 MPa on mode propagation in a highly birefringent two-mode bow-tie fiber is presented. Hydrostatic pressure is found to produce a large phase shift between both orthogonal polarizations in fundamental and second-order modes and also between the two lowest-order spatial modes in the highly birefringent two-mode bow-tie fiber. The pressure-induced effects are expressed in terms of birefringence changes and pressure phase sensitivity, both described by the experimental parameter T(p). The results indicate that pressure phase sensitivity between the two spatial modes, 1.3 rad/MPa-m, is approximately one order lower than for polarization modes. PMID:19771113

Bock, W J; Woli?ski, T R

1990-12-15

306

The Effect of Hydrostatic Pressure and Seismic Load on ITER Lower Cryopump Ports  

NASA Astrophysics Data System (ADS)

The lower cryopump ports in International Thermonuclear Experimental Reactor (ITER) as a part of the vacuum vessel play many important roles. As the boundary of vacuum it must be ensured against structural damage. In this study a finite element model of the lower cryopump ports was developed by ANSYS code with a purpose to evaluate the stress and displacement level on it. Two kinds of loads were taken into account. One was the hydrostatic pressure including the normal operation pressure and test pressure. The other was the seismic load. The analysis results show that the peak stress does not exceed the allowable stress for either the hydrostatic pressure or the seismic load according to the ITER structural design criterion, which indicates that the structure has a good safety margin.

Cai, Yingxiang; Yu, Jie; Wu, Songtao

2007-04-01

307

Lateral dampers for thrust bearings  

NASA Technical Reports Server (NTRS)

The development of lateral damping schemes for thrust bearings was examined, ranking their applicability to various engine classes, selecting the best concept for each engine class and performing an in-depth evaluation. Five major engine classes were considered: large transport, military, small general aviation, turboshaft, and non-manrated. Damper concepts developed for evaluation were: curved beam, constrained and unconstrained elastomer, hybrid boost bearing, hydraulic thrust piston, conical squeeze film, and rolling element thrust face.

Hibner, D. H.; Szafir, D. R.

1985-01-01

308

Teddy Bear Line-Up  

NSDL National Science Digital Library

This problem requires children to develop logical reasoning and promotes using visualization to plan ahead. Students are presented with a line of four blue, then four red followed by four yellow and finally four green bears and are asked to rearrange them using the least number of moves so that no two bears of the same color are next to each other. The Teachers' Notes page offers rationale, suggestions for implementation, discussion questions, and an idea for support and extension.

2009-04-01

309

Superconductivity under extreme hydrostatic pressures in lithium, magnesium boride and lanthanum neodymium strontium copper oxide  

Microsoft Academic Search

The lattice and electronic properties of a material change under pressure. The application of high pressure can have entirely different effects on the superconducting state of materials. Pressure can induce, destroy or enhance superconductivity. MgB2, lithium, sodium and potassium were studied under extreme hydrostatic pressure in a helium-loaded diamond-anvil cell using the AC susceptibility technique. MgB2 is an ambient-pressure superconductor

Shanti Deemyad

2004-01-01

310

Density Measurement of Tridecane by using Hydrostatic Weighing System at Density Laboratory, NML-SIRIM  

NASA Astrophysics Data System (ADS)

This paper presents the density measurement of tridecane by using hydrostatic weighing system, which is currently practised in Density Laboratory of National Metrology Laboratory (NML), SIRIM Berhad. This system weighed the crystal sphere while the crystal sphere was immersed in the tridecane. The volume and mass in air of the crystal sphere were calibrated at KRISS, Korea. The uncertainties of volume and mass in air of the crystal sphere were 4 ppm and 0.3 ppm respectively.

Nor, Mohd. Fazrul Hisyam Mohd.; Othman, Hafidzah; Abidin, Abd. Rashid Zainal

2009-07-01

311

Proteolysis of type III collagen by collagenase and cathepsin B under high hydrostatic pressure  

Microsoft Academic Search

The effects of high hydrostatic pressures on the kinetics of hydrolysis of type III collagen from calf skin by collagenase and cathepsin B were studied. Collagen hydrolysates sampled at different time intervals (0–90 min) and at different pressures (0.1–300 MPa) were analysed by reverse-phase high pressure liquid chromatography. The rate of collagen hydrolysis decreased up to 300 MPa for both

Eric Dufour; Michèle Dalgalarrondo; Guy Hervé; René Goutefongea; Tomasz Haertlé

1996-01-01

312

Kinetic analysis of Escherichia coli inactivation by high hydrostatic pressure in broth and foods  

Microsoft Academic Search

High hydrostatic pressure (HHP) inactivation kinetics of Escherichia coli in broth, milk, peach juice and orange juice were evaluated at a pressure range from 300 to 700MPa. E. coli inactivation followed first-order reaction kinetics. Decimal reduction times (D value) for E. coli were 3.94 and 1.35 at 400 and 600MPa, respectively, in broth. D values were 3.19 and 1.66min for

O. Erkmen; C. Do?an

2004-01-01

313

Destruction of Salmonella Enteriditis inoculated onto raw almonds by high hydrostatic pressure  

Microsoft Academic Search

The effects of continuous (50,000, 60,000 and 70,000psi with holding times of 5 and 10min) and discontinuous (oscillatory) (six cycles at 60,000psi with a holding time of 20s) high hydrostatic pressure (HHP) treatments on the viability of two Salmonella Enteriditis strains (FDA and PT30) inoculated onto raw almonds were evaluated at 25, 50, and 55°C. Complete inactivation of the S.

L. D. Goodridge; John Willford; N. Kalchayanand

2006-01-01

314

Kinetic Analysis of Zygosaccharomyces bailiiInactivation by High Hydrostatic Pressure  

Microsoft Academic Search

High hydrostatic pressure inactivation kinetics ofZygosaccharomyces bailiiin food model systems of pH 3.5 and water activities (aw) of 0.98 and 0.95 were evaluated at 21 °C and pressures from 241 to 517 MPa. The come-up time to reach a pressure exerts an important effect on the survival fraction ofZ. bailii. Yeast inactivation followed first order reaction kinetics, with inactivation rates

E. Palou; A. López-Malo; G. V. Barbosa-Cánovas; J. Welti-Chanes; B. G. Swanson

1997-01-01

315

Filtration coefficient of the axon membrane as measured with hydrostatic and osmotic methods.  

PubMed

The hydraulic conductivity of the membranes surrounding the giant axon of the squid, Dosidicus gigas, was measured. In some axons the axoplasm was partially removed by suction. Perfusion was then established by insertion of a second pipette. In other axons the axoplasm was left intact and only one pipette was inserted. In both groups hydrostatic pressure was applied by means of a water column in a capillary manometer. Displacement of the meniscus in time gave the rate of fluid flowing across the axon sheath. In both groups osmotic differences across the membrane were established by the addition of a test molecule to the external medium which was seawater. The hydraulic conductivity determined by application of hydrostatic pressure was 10.6 +/- 0.8.10(-8) cm/sec cm H(2)O in perfused axons and 3.2 +/- 0.6.10(-8) cm/sec cm H(2)O in intact axons. When the driving force was an osmotic pressure gradient the conductivity was 4.5 +/- 0.6 x 10(-10) cm/sec cm H(2)O and 4.8 +/- 0.9 x 10(-10) cm/sec cm H(2)O in perfused and intact axons, respectively. A comparable result was found when the internal solution was made hyperosmotic. The fluid flow was a linear function of the hydrostatic pressure up to 70 cm of water. Glycerol outflux and membrane conductance were increased 1.6 and 1.1 times by the application of hydrostatic pressure. These increments do not give an explanation of the difference between the filtration coefficients. Other possible explanations are suggested and discussed. PMID:5642470

Vargas, F F

1968-01-01

316

Filtration Coefficient of the Axon Membrane As Measured with Hydrostatic and Osmotic Methods  

PubMed Central

The hydraulic conductivity of the membranes surrounding the giant axon of the squid, Dosidicus gigas, was measured. In some axons the axoplasm was partially removed by suction. Perfusion was then established by insertion of a second pipette. In other axons the axoplasm was left intact and only one pipette was inserted. In both groups hydrostatic pressure was applied by means of a water column in a capillary manometer. Displacement of the meniscus in time gave the rate of fluid flowing across the axon sheath. In both groups osmotic differences across the membrane were established by the addition of a test molecule to the external medium which was seawater. The hydraulic conductivity determined by application of hydrostatic pressure was 10.6 ± 0.8.10-8 cm/sec cm H2O in perfused axons and 3.2 ± 0.6.10-8 cm/sec cm H2O in intact axons. When the driving force was an osmotic pressure gradient the conductivity was 4.5 ± 0.6 x 10-10 cm/sec cm H2O and 4.8 ± 0.9 x 10-10 cm/sec cm H2O in perfused and intact axons, respectively. A comparable result was found when the internal solution was made hyperosmotic. The fluid flow was a linear function of the hydrostatic pressure up to 70 cm of water. Glycerol outflux and membrane conductance were increased 1.6 and 1.1 times by the application of hydrostatic pressure. These increments do not give an explanation of the difference between the filtration coefficients. Other possible explanations are suggested and discussed.

Vargas, Fernando F.

1968-01-01

317

DETECTION OF A BIPOLAR MOLECULAR OUTFLOW DRIVEN BY A CANDIDATE FIRST HYDROSTATIC CORE  

SciTech Connect

We present new 230 GHz Submillimeter Array observations of the candidate first hydrostatic core Per-Bolo 58. We report the detection of a 1.3 mm continuum source and a bipolar molecular outflow, both centered on the position of the candidate first hydrostatic core. The continuum detection has a total flux density of 26.6 {+-} 4.0 mJy, from which we calculate a total (gas and dust) mass of 0.11 {+-} 0.05 M{sub Sun} and a mean number density of 2.0 {+-} 1.6 Multiplication-Sign 10{sup 7} cm{sup -3}. There is some evidence for the existence of an unresolved component in the continuum detection, but longer-baseline observations are required in order to confirm the presence of this component and determine whether its origin lies in a circumstellar disk or in the dense inner envelope. The bipolar molecular outflow is observed along a nearly due east-west axis. The outflow is slow (characteristic velocity of 2.9 km s{sup -1}), shows a jet-like morphology (opening semi-angles {approx}8 Degree-Sign for both lobes), and extends to the edges of the primary beam. We calculate the kinematic and dynamic properties of the outflow in the standard manner and compare them to several other protostars and candidate first hydrostatic cores with similarly low luminosities. We discuss the evidence both in support of and against the possibility that Per-Bolo 58 is a first hydrostatic core, and we outline future work needed to further evaluate the evolutionary status of this object.

Dunham, Michael M.; Chen Xuepeng; Arce, Hector G. [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520 (United States); Bourke, Tyler L. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Schnee, Scott [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Enoch, Melissa L., E-mail: michael.dunham@yale.edu [Department of Astronomy, University of California at Berkeley, 601 Campbell Hall, Berkeley, CA 94720 (United States)

2011-11-20

318

Optimal design of axially symmetrical shells under hydrostatic pressure with respect to their stability  

Microsoft Academic Search

.   In this paper, the problem of optimal design of axially symmetrical shells against instability is considered. We look for\\u000a the shape of middle surface as well as the thickness (constant or variable) of a shell, which ensure maximal value of the\\u000a critical hydrostatic pressure. As the equality constraints the volume of material and the capacity of a shell are

J. Kru?elecki; P. Trzeciak

2000-01-01

319

A three-dimensional spectral element model for the solution of the hydrostatic primitive equations  

Microsoft Academic Search

We present a spectral element model to solve the hydrostatic primitive equations governing large-scale geophysical flows. The highlights of this new model include unstructured grids, dual h–p paths to convergence, and good scalability characteristics on present day parallel computers including Beowulf-class systems. The behavior of the model is assessed on three process-oriented test problems involving wave propagation, gravitational adjustment, and

M. Iskandarani; D. B. Haidvogel; J. C. Levin

2003-01-01

320

The Effect of Hydrostatic Weighting on the Vertical Temperature Structure of the Solar Corona.  

PubMed

We investigate the effect of hydrostatic scale heights lambda(T) in coronal loops on the determination of the vertical temperature structure T&parl0;h&parr0; of the solar corona. Every method that determines an average temperature at a particular line of sight from optically thin emission (e.g., in EUV or soft X-ray wavelengths) of a mutlitemperature plasma is subject to the emission measure-weighted contributions dEM&parl0;T&parr0;&solm0;dT from different temperatures. Because most of the coronal structures (along open or closed field lines) are close to hydrostatic equilibrium, the hydrostatic temperature scale height introduces a height-dependent weighting function that causes a systematic bias in the determination of the temperature structure T&parl0;h&parr0; as function of altitude h. The net effect is that the averaged temperature seems to increase with altitude, dT&parl0;h&parr0;&solm0;dh>0, even if every coronal loop (of a multitemperature ensemble) is isothermal in itself. We simulate this effect with differential emission measure distributions observed by SERTS for an instrument with a broadband temperature filter such as Yohkoh/Soft X-Ray Telescope and find that the apparent temperature increase due to hydrostatic weighting is of order DeltaT approximately T0h&solm0;r middle dot in circle. We suggest that this effect largely explains the systematic temperature increase in the upper corona reported in recent studies (e.g., by Sturrock et al., Wheatland et al., or Priest et al.), rather than being an intrinsic signature of a coronal heating mechanism. PMID:10829008

Aschwanden; Nitta

2000-05-20

321

Induction of Shiga Toxin-Converting Prophage in Escherichia coli by High Hydrostatic Pressure  

Microsoft Academic Search

Since high hydrostatic pressure is becoming increasingly important in modern food preservation, its potential effects on microorganisms need to be thoroughly investigated. In this context, mild pressures (<200 MPa) have recently been shown to induce an SOS response in Escherichia coli MG1655. Due to this response, we observed a RecA- and LexA-dependent induction of lambda prophage upon treating E. coli

Abram Aertsen; David Faster; Chris W. Michiels

2005-01-01

322

Temperature-hydrostatic pressure cross-sensitivity effect in elliptical-core, highly birefringent fibers.  

PubMed

We determine the cross-sensitivity coefficient that represents the interaction between temperature and hydrostatic pressure in Corning elliptical-core, highly birefringent (HB) fiber. The measurement method we propose is especially useful to determine the cross-sensitivity effects in weakly sensitive HB fibers. The method involves registration of the residual temperature drift of thermally compensated polarimetric sensors at specially chosen values of pressure applied to the sensing fibers. PMID:21127652

Bock, W J; Urba?czyk, W

1996-11-01

323

Comparison of air displacement plethysmography to hydrostatic weighing for estimating total body density in children  

Microsoft Academic Search

: BACKGROUND: The purpose of this study was to examine the accuracy of total body density and percent body fat (% fat) using air displacement plethysmography (ADP) and hydrostatic weighing (HW) in children. METHODS: Sixty-six male and female subjects (40 males: 12.4 ± 1.3 yrs, 47.4 ± 14.8 kg, 155.4 ± 11.9 cm, 19.3 ± 4.1 kg\\/m2; 26 females: 12.0

Geo Claros; Holly R Hull; David A Fields

2005-01-01

324

Solid-state phase transitions in CuCl under hydrostatic pressures to 12. 8 GPa  

SciTech Connect

The phase transitions in solid CuCl under hydrostatic conditions at pressures to 12.8 GPa are examined. The transition at 4.4 GPa from zinc-blende to tetragonal is observed. Our negative observations for the upper transition at 8.2 GPa and for the formation of an opaque phase due to the disproportionation reaction support the contention that pressure gradients are important in affecting the behavior of pure CuCl.

Liebenberg, D.H.; Mills, R.L.; Huang, C.Y.; Olsen, C.; Schmidt, L.C.

1981-01-01

325

Numerical Simulation of Phase Change at High Hydrostatic Pressure under Variable-Gravity Environment  

Microsoft Academic Search

We present a numerical investigation of phase change of water at high hydrostatic pressure conditions occurring under a gravitational environment and a low-gravity environment. A computational model consists of conservation equations of mass, momentum, and energy. Phase-transition phenomena are modeled with an enthalpy–porosity approach. Numerical solutions are obtained for process stages dominated by free convection as well as by forced

W. Kowalczyk; A. Delgado

2007-01-01

326

Weighing Galaxy Clusters with Gas. I. On the Methods of Computing Hydrostatic Mass Bias  

NASA Astrophysics Data System (ADS)

Mass estimates of galaxy clusters from X-ray and Sunyeav-Zel'dovich observations assume the intracluster gas is in hydrostatic equilibrium with their gravitational potential. However, since galaxy clusters are dynamically active objects whose dynamical states can deviate significantly from the equilibrium configuration, the departure from the hydrostatic equilibrium assumption is one of the largest sources of systematic uncertainties in cluster cosmology. In the literature there have been two methods for computing the hydrostatic mass bias based on the Euler and the modified Jeans equations, respectively, and there has been some confusion about the validity of these two methods. The word "Jeans" was a misnomer, which incorrectly implies that the gas is collisionless. To avoid further confusion, we instead refer these methods as "summation" and "averaging" methods respectively. In this work, we show that these two methods for computing the hydrostatic mass bias are equivalent by demonstrating that the equation used in the second method can be derived from taking spatial averages of the Euler equation. Specifically, we identify the correspondences of individual terms in these two methods mathematically and show that these correspondences are valid to within a few percent level using hydrodynamical simulations of galaxy cluster formation. In addition, we compute the mass bias associated with the acceleration of gas and show that its contribution is small in the virialized regions in the interior of galaxy clusters, but becomes non-negligible in the outskirts of massive galaxy clusters. We discuss future prospects of understanding and characterizing biases in the mass estimate of galaxy clusters using both hydrodynamical simulations and observations and their implications for cluster cosmology.

Lau, Erwin T.; Nagai, Daisuke; Nelson, Kaylea

2013-11-01

327

Cholesteric Liquid Crystal Sensing of High Hydrostatic Pressure Utilizing Optical Fibers  

Microsoft Academic Search

A new method of sensing high hydrostatic pressure utilizing cholesteric liquid crystals (ChLCs) as a sensing element and optical fibers for communication with the high-pressure region is proposed and demonstrated the concept exploits the effect of pressure-induced changes in the peak light-reflection wavelength observed in ChLCs. Measurements were performed on an encapsulated ChLC sample obtained by dispersion of a mixture

T. R. Woli?ski; W. J. Bock

1991-01-01

328

Three-dimensional numerical modelling of free surface flows with non-hydrostatic pressure  

Microsoft Academic Search

A three-dimensional numerical model is developed for incompressible free surface flows. The model is based on the unsteady Reynolds-averaged Navier-Stokes equations with a non-hydrostatic pressure distribution being incorporated in the model. The governing equations are solved in the conventional sigma co-ordinate system, with a semi-implicit time discretization. A fractional step method is used to enable the pressure to be decomposed

Musteyde B. Koçyigit; Roger A. Falconer; Binliang Lin

2002-01-01

329

The effect of hydrostatic pressure on magnetic properties of partially crystallized Co-based amorphous alloy  

Microsoft Academic Search

Melt-spun Co66Nb9Cu1Si12B12 metallic glass ribbon (TC?150K) was used to produce nanocrystalline samples by annealing at 590°C and 610°C for 1 h. Their magnetic properties were measured in a superconducting quantum interference device (SQUID) magnetometer as a function of temperature (10–250 K) in fields to 3 kOe at zero and ?7 kbar hydrostatic pressure. The pressure shifts the Curie point of

H. K. Lachowicz; K. Zaveta; Z. Arnold; J. Kamarad; M. Marysko

2001-01-01

330

The effects of defects on copper melting under hydrostatic and shock loading  

SciTech Connect

With molecular dynamics (MD) simulations, we investigate the effects of defects on Cu melting under hydrostatic and shock wave loading. We explore preexistent defects including vacancies, stacking faults and grain boundaries, as well as shock-induced defects. Depending on defect characteristics (energy and concentration), defects may have negligible or considerable effects on melting at MD scales However, it is expected that defects have more pronounced effects at heating rates lower than the MD rates.

Luo, Shengnian [Los Alamos National Laboratory; An, Qi [Los Alamos National Laboratory; German, Timothy C [Los Alamos National Laboratory; Han, Li - Bo [USTC

2009-01-01

331

Hot isostatic pressing of Chevrel phase bulk and hydrostatically extruded wire samples  

Microsoft Academic Search

In order to lower final sintering temperatures for Chevrel phase (CP) wires, we have investigated low-temperature hot isostatic pressing (HIP'ing) of both bulk and wire samples. We have fabricated (Pb,Sn)-based Chevrel phase (CP) monofilament and 61 filament wires by hydrostatic extrusion of (Cu or Cu-Ni)\\/(Nb or V)\\/CP composites, followed by cold drawing. We have investigated the CP\\/barrier reaction during heat

Toinas C. Willis; Paul D. Jablonski; David C. Larbalestier; Sylvie Evcii-Boudjada; R. Chevrel; M. Sergent

1995-01-01

332

Structural effects of hydrostatic pressure in orthorhombic La2-xSrxCuO4  

Microsoft Academic Search

We have investigated the effect of hydrostatic pressure on the structure of orthorhombic La2-xSrxCuO4 between 1 atm and 0.6 GPa, using neutron powder diffraction. Increasing pressure causes the tilt angle of CuO6 octahedra to decrease, leading to a transition to tetragonal symmetry. There is a strong compressibility anisotropy for the orthorhombic structure. Order parameters for the transition versus pressure are

H. Takahashi; H. Shaked; B. A. Hunter; P. G. Radaelli; R. L. Hitterman; D. G. Hinks; J. D. Jorgensen

1994-01-01

333

Polyphenoloxidase activity and color changes during storage of high hydrostatic pressure treated avocado puree  

Microsoft Academic Search

The effects of high hydrostatic pressure (HHP) treatments of 345, 517, or 689MPa, for 10, 20, or 30min at initial pHs of 3.9, 4.1, or 4.3 on polyphenoloxidase (PPO) activity, color and microbial inactivation in avocado puree during storage at 5, 15, or 25°C were investigated and compared with untreated avocado puree. Standard plate as well as yeast and mold

A. López-Malo; E. Palou; G. V. Barbosa-Cánovas; J. Welti-Chanes; B. G. Swanson

1998-01-01

334

BiAxial Testing of Zinc and Zinc Alloy Sheets under Superimposed Hydrostatic Pressures  

Microsoft Academic Search

The effects of pressurization on the properties of metals has long been of interest to scientists. Bridgman found that in general, the ductility (ability of the metal to deform without fracture) increased with superimposed hydrostatic pressure. Pugh et al. confirmed similar findings.\\u000aThe effects of hydrostatistic pressure on the mechanical properties of thin anisotropic zinc, heat treated and non heat

Harjeet S. Sandhu

1973-01-01

335

Improved efficiency of a non-hydrostatic, unstructured grid, finite volume model  

NASA Astrophysics Data System (ADS)

An efficient depth-integrated non-hydrostatic unstructured grid finite volume model is presented and applied to several test cases, which involve the computation of free surface flows. The model solves the non-linear shallow water equations, with extra non-hydrostatic pressure terms to describe dispersion effects. The efficiency of the model is a major issue when it involves large spatial domains with high resolution meshes. Lumping of the pressure gradient of the horizontal velocities is employed, which reduces the number of non-zero elements in the sparse matrix of the Poisson equation by half. This greatly reduces both the memory requirements and the number of floating point operations required to solve the Poisson equations. In addition, for a model using a collocated grid, both the water surface and the non-hydrostatic pressure need to be defined at the incoming wave boundary. A non-hydrostatic pressure boundary, has been derived based on linear wave theory, that is accompanied with the regular incoming short wave for depth-integrated models. It can serve as a simple way to introduce short incoming waves in models with collocated grids. The model has been validated through several test problems including an oscillating basin, propagation of a solitary wave, wave propagation over a submerged bar, wave refraction and diffraction over an elliptical shoal, as well as solitary wave run-up on a conical island. The model gives good results for all test cases. We show that the lumping of the pressure gradient generates identical results to simulations without lumping, while the execution CPU time is reduced by around 30%, demonstrating a good computational efficiency of the model.

Cui, Haiyang; Pietrzak, J. D.; Stelling, G. S.

2012-09-01

336

Effects of Hydrostatic Pressure on the Location of PRODAN in Lipid Bilayers: A FT-IR Study.  

National Technical Information Service (NTIS)

The effects of hydrostatic pressure on the location of 6-propionyl-2-(dimethylamino)naphthalene (PRODAN), an environmentally sensitive fluorescent probe, in phosphatidylcholine lipid bilayers have been studied by Fourier-transform infrared spect (FT-IR) o...

P. Chong S. Capes P. T. Wong

1989-01-01

337

Electronic structure computation and differential capacitance profile in δ-doped FET as a function of hydrostatic pressure  

NASA Astrophysics Data System (ADS)

In this work we present the results obtained from the calculation of the level structure of a n-type delta-doped well Field Effect Transistor when is subjected to hydrostatic pressure. We study the energy level structure as a function of hydrostatic pressure within the range of 0 to 6 kbar for different Schottky barrier height (SBH). We use an analytical expression for the effect of hydrostatic pressure on the SBH and the pressure dependence of the basic parameters of the system as the effective mass m(P) and the dielectric constant ?(P) of GaAs. We found that due to the effects of hydrostatic pressure, in addition to electronic level structure alteration, the profile of the differential capacitance per unit area C-2 is affected.

Carlos-Pinedo, C.; Rodríguez-Vargas, I.; Martínez-Orozco, J. C.

2014-05-01

338

Hydrostatic and shear consolidation tests with permeability measurements on Waste Isolation Pilot Plant crushed salt  

SciTech Connect

Crushed natural rock salt is a primary candidate for use as backfill and barrier material at the Waste Isolation Pilot Plant (WIPP) and therefore Sandia National Laboratories (SNL) has been pursuing a laboratory program designed to quantify its consolidation properties and permeability. Variables that influence consolidation rate that have been examined include stress state and moisture content. The experimental results presented in this report complement existing studies and work in progress conducted by SNL. The experiments described in this report were designed to (1) measure permeabilities of consolidated specimens of crushed salt, (2) determine the influence of brine saturation on consolidation under hydrostatic loads, and 3) measure the effects of small applied shear stresses on consolidation properties. The laboratory effort consisted of 18 individual tests: three permeability tests conducted on specimens that had been consolidated at Sandia, six hydrostatic consolidation and permeability tests conducted on specimens of brine-saturated crushed WIPP salt, and nine shear consolidation and permeability tests performed on crushed WIPP salt specimens containing 3 percent brine by weight. For hydrostatic consolidation tests, pressures ranged from 1.72 MPa to 6.90 MPa. For the shear consolidation tests, confining pressures were between 3.45 MPa and 6.90 MPa and applied axial stress differences were between 0.69 and 4.14 MPa. All tests were run under drained conditions at 25{degrees}C.

Brodsky, N.S. [RE/SPEC, Inc., Rapid City, SD (United States)

1994-03-01

339

The effect of hydrostatic pressure on S-layer-supported lipid membranes.  

PubMed

We report on the behavior of unsupported and surface layer (S-layer)-supported lipid membranes at the application of a uniform hydrostatic pressure. At a hydrostatic pressure gradient higher than 6 N/m(2), unsupported lipid membranes, independent from which side pressurized and S-layer-supported lipid membranes pressurized from the lipid-faced side revealed a pronounced increase in capacitance. A maximal hydrostatic pressure gradient of 11.0 N/m(2) resulted in an almost doubling of the capacitance of the (composite) membranes. S-layer-supported lipid membranes showed a hysteresis in the capacitance versus pressure plot, indicating that this composite structure required a certain time to reorient when the pressure gradient acting from the lipid-faced side was balanced. By contrast, the S-layer-supported lipid membrane pressurized from the protein-faced side revealed only a minute increase in capacitance (C/C(0,max)=1.17+/-0.05), reflecting only minor pressure-induced area expansion. In addition, no hysteresis could be observed, indicating that no rearrangement of the composite membrane occurred. The maximal induced tension was with 4.3+/-0.2 mN/m, significantly higher than that of unsupported (2.5+/-0.3 mN/m) and S-layer-supported lipid membranes pressurized from the lipid-faced side (2.6+/-0.1 mN/m). PMID:12007622

Schuster, Bernhard; Sleytr, Uwe B

2002-06-13

340

Hyporheic flow path response to hydraulic jumps at river steps: Hydrostatic model simulations  

NASA Astrophysics Data System (ADS)

This research examined hydrostatic groundwater model (MODFLOW) predictive adequacy and sensitivity in simulating hyporheic flow paths across a river step with a hydraulic jump. In a companion paper, we used flume and hydrodynamic model analysis to develop a refined conceptual model depicting these flow paths with zones of downwelling and upstream-directed flux below the step. The previous coarse conceptual model predicted uniform downstream-directed upwelling below the step. The hydrostatic model accurately predicted the downwelling and upstream-directed fluxes beneath the wave and jump but failed to predict the plunge pool downwelling, which is driven by dynamic pressures. Sensitivity tests varied riverbed topography and water surface profile geometry for a river with 1% slopes, 10 cm flow depths, and 50-150 cm long jets and jumps. The flow paths below the jet-jump region were driven by hydrostatic pressures and were highly sensitive to water surface profile and riverbed topography parameters. Failure to simulate the hydraulic jump caused errors in hyporheic flow path predictions beneath the jump region (˜1 m long by ˜0.5 m deep). If the jump was poorly parameterized, several meters of riverbed flow paths could be erroneously modeled as pointing upstream. The hyporheic zone may contain a spatial mosaic of aerobic and anaerobic waters regulating nutrient transformations and biologic productivity. Accurate parameterization of hydraulic jumps in hyporheic simulation has the potential to improve predictions and explain heterogeneous subsurface flow paths and associated nutrient patterns and ecosystem functions.

Endreny, T.; Lautz, L.; Siegel, D.

2011-02-01

341

Hydrostatic pressure effect on micro air bubbles deposited on surfaces with a retreating tip.  

PubMed

The effect of hydrostatic pressure on 6 ?L air bubbles formed on micropillar structured PDMS and silicone surfaces using a 2 mm diameter stainless steel tip retreated at 1 mm/s was investigated. Dimensional analysis of the tip retraction process showed the experiments to be conducted in the condition where fluid inertial forces are comparable in magnitude with surface tension forces, while viscous forces were lower. Larger bubbles could be left behind on the structured PDMS surface. For hydrostatic pressures in excess of 20 mm H2O (196 Pa), the volume of bubble deposited was found to decrease progressively with pressure increase. The differences in width of the deposited bubbles (in contact with the substrate) were significant at any particular pressure but marginal in height. The attainable height before rupture reduced with pressure increase, thereby accounting for the reducing dispensed volume characteristic. On structured PDMS, the gaseous bridge width (in contact with the substrate) was invariant with tip retraction, while on silicone it was initially reducing before becoming invariant in the lead up to rupture. With silicone, hence, reductions in the contact width and height were both responsible for reduced volumes with pressure increase. Increased hydrostatic pressure was also found to restrict the growth in contact width on silicone during the stage when air was injected in through the tip. The ability to effect bubble size in such a simple manner may already be harnessed in nature and suggests possibilities in technological applications. PMID:24810460

Huynh, So Hung; Wang, Jingming; Yu, Yang; Ng, Tuck Wah

2014-06-01

342

Calpain: a molecule to induce AIF-mediated necroptosis in RGC-5 following elevated hydrostatic pressure  

PubMed Central

Background RIP3 (Receptor-interacting protein 3) pathway was mainly described as the molecular mechanism of necroptosis (programmed necrosis). But recently, non-RIP3 pathways were found to mediate necroptosis. We deliberate to investigate the effect of calpain, a molecule to induce necroptosis as reported (Cell Death Differ 19:245–256, 2012), in RGC-5 following elevated hydrostatic pressure. Results First, we identified the existence of necroptosis of RGC-5 after insult by using necrostatin-1 (Nec-1, necroptosis inhibitor) detected by flow cytometry. Immunofluorescence staining and western blot were used to detect the expression of calpain. Western blot analysis was carried out to describe the truncated AIF (tAIF) expression with or without pretreatment of ALLN (calpain activity inhibitor). Following elevated hydrostatic pressure, necroptotic cells pretreated with or without ALLN was stained by Annexin V/PI, The activity of calpain was also examined to confirm the inhibition effect of ALLN. The results showed that after cell injury there was an upregulation of calpain expression. Upon adding ALLN, the calpain activity was inhibited, and tAIF production was reduced upon injury along with the decreased number of necroptosis cells. Conclusion Our study found that calpain may induce necroptosis via tAIF-modulation in RGC-5 following elevated hydrostatic pressure.

2014-01-01

343

Application of high hydrostatic pressure to aloe vera ( Aloe barbadensis Miller) gel: Microbial inactivation and evaluation of quality parameters  

Microsoft Academic Search

High hydrostatic pressure (HHP) is an innovative technology which minimizes loss of physicochemical and nutritional quality matching consumer demands for fresh-like foods. The aim of this study was to investigate the effect of high hydrostatic pressure (300, 400 and 500MPa\\/1, 3 and 5min) on microbial inactivation and quality parameters of A. vera gel after 60days of storage. Shelf life was

Antonio Vega-Gálvez; Claudia Giovagnoli; Mario Pérez-Won; Juan E. Reyes; Judith Vergara; Margarita Miranda; Elsa Uribe; Karina Di Scala

344

The effect of temperature on the hydrostatic limit of 4:1 methanol-ethanol under pressure  

Microsoft Academic Search

We have investigated the pressure-induced solidification of 4:1 methanol–ethanol at 50 °C and 100 °C, using the ruby fluorescence technique and an externally heated diamond anvil cell. The hydrostatic limits of this pressure transmitting medium increases at a rate of 1 GPa per 11 °C to reach 17 GPa at 100 °C. This demonstrates that the hydrostatic limits can be considerably increased by modest heating.

S. Klotz; L. Paumier; G. Le March; P. Munsch

2009-01-01

345

Wear Resistance of Polyformaldehyde in Sleeve Bearings.  

National Technical Information Service (NTIS)

Tests showed, that sleeve bearings made of PFA are 3-4 times more wear resistant than caprone bearings, and 1.5 to 2 times than ceramet bushings and bearings. PFA bearings retain stability of dimensions and assure reliable operation of friction units.

V. N. Kestelman D. I. Feldman N. Y. Kestelman

1965-01-01

346

Liquid oxygen cooled bearing ignition potential assessment  

NASA Technical Reports Server (NTRS)

Space Shuttle Main Engine High Pressure Oxygen Turbopump bearings have shown evidence of heavy oxidation on the surfaces of the balls and races. Extensive analyses were performed to assess the ignition potential in the bearing system during normal and off-nominal operation. Test programs and analyses were used to determine the bearing thermal condition and bearing material ignition characteristics.

Page, Arthur T.; Goode, Brian K.; Owen, James W.

1990-01-01

347

Laser measurements in the motor bearing diagnostics  

Microsoft Academic Search

A b s t r a c t - Statistics say that bearings are this part of indu ction motors which is most susceptible to damage. That is why the issues connected with diagn ostics of bearings are so important. The equipment employed for bearing diagnostics usually makes use of vibrations as the criterion for technical condition of the bearings.

Ariel Dzwonkowski; Leon Sw

348

Cryogenic Magnetic Bearing Test Facility (CMBTF)  

NASA Technical Reports Server (NTRS)

The Cryogenic Magnetic Bearing Test Facility (CMBTF) was designed and built to evaluate compact, lightweight magnetic bearings for use in the SSME's (space shuttle main engine) liquid oxygen and liquid hydrogen turbopumps. State of the art and tradeoff studies were conducted which indicated that a hybrid permanent magnet bias homopolar magnetic bearing design would be smaller, lighter, and much more efficient than conventional industrial bearings. A test bearing of this type was designed for the test rig for use at both room temperature and cryogenic temperature (-320 F). The bearing was fabricated from state-of-the-art materials and incorporated into the CMBTF. Testing at room temperature was accomplished at Avcon's facility. These preliminary tests indicated that this magnetic bearing is a feasible alternative to older bearing technologies. Analyses showed that the hybrid magnetic bearing is one-third the weight, considerably smaller, and uses less power than previous generations of magnetic bearings.

1992-01-01

349

Wave journal bearing with compressible lubricant--Part 1: The wave bearing concept and a comparison to the plain circular bearing  

Microsoft Academic Search

To improve hydrodynamic journal bearing steady-state and dynamic performance, a new bearing concept, the wave journal bearing, was developed at the author's lab. This concept features a waved inner bearing diameter. Compared to other alternative bearing geometries used to improve bearing performance such as spiral or herring-bone grooves, steps, etc., the wave bearing's design is relatively simple and allows the

Florin Dimofte

1995-01-01

350

A Fatigue Life Comparison of Two-Row Tapered Roller Bearings and Spherical Roller Bearings  

Microsoft Academic Search

Tests were run to compare the fatigue life of two-row tapered roller bearings to that of spherical roller bearings. Both bearing types had an outer diameter of 110 mm with the spherical roller bearing having a 22 percent larger dynamic radial load rating than the tapered roller bearings. All tests were run at 165 percent of the respective two-row dynamic

Harry Zantopulos; Joel Z. Russell

1999-01-01

351

Magnetic bearings with zero bias  

NASA Technical Reports Server (NTRS)

A magnetic bearing operating without a bias field has supported a shaft rotating at speeds up to 12,000 rpm with the usual four power supplies and with only two. A magnetic bearing is commonly operated with a bias current equal to half of the maximum current allowable in its coils. This linearizes the relation between net force and control current and improves the force slewing rate and hence the band width. The steady bias current dissipates power, even when no force is required from the bearing. The power wasted is equal to two-thirds of the power at maximum force output. Examined here is the zero bias idea. The advantages and disadvantages are noted.

Brown, Gerald V.; Grodsinsky, Carlos M.

1991-01-01

352

Wave journal bearing. Part 1: Analysis  

NASA Technical Reports Server (NTRS)

A wave journal bearing concept features a waved inner bearing diameter of the non-rotating bearing side and it is an alternative to the plain journal bearing. The wave journal bearing has a significantly increased load capacity in comparison to the plain journal bearing operating at the same eccentricity. It also offers greater stability than the plain circular bearing under all operating conditions. The wave bearing's design is relatively simple and allows the shaft to rotate in either direction. Three wave bearings are sensitive to the direction of an applied stationary side load. Increasing the number of waves reduces the wave bearing's sensitivity to the direction of the applied load relative to the wave. However, the range in which the bearing performance can be varied decreases as the number of waves increases. Therefore, both the number and the amplitude of the waves must be properly selected to optimize the wave bearing design for a specific application. It is concluded that the stiffness of an air journal bearing, due to hydrodynamic effect, could be doubled and made to run stably by using a six or eight wave geometry with a wave amplitude approximately half of the bearing radial clearance.

Dimofte, Florin

1995-01-01

353

Efficacy and safety of hydrostatic balloon dilatation of ileocolonic Crohn's strictures: a prospective longterm analysis.  

PubMed Central

Preliminary reports have suggested that dilatation using hydrostatic through the scope balloons may be useful for the treatment of Crohn's strictures, A prospective longterm follow up (mean (SD) 33.6 (11.2) months) was carried out in 55 Crohn's patients with 59 ileocolonic strictures submitted to 78 dilatation procedures. Hydrostatic balloons were used (Rigiflator, Microvasive) with a diameter of 18 mm on inflation. As soon as the balloons became available dilatation up to a diameter of 20 and 25 mm was attempted. The dilatations were performed under general anaesthesia using propofol (Diprivan). The patients were kept for one night in the hospital after dilatation. Seventy (90%) procedures were technically successful and passage of the stricture with a 13.6 mm diameter colonoscope was possible after 73% of the dilatations. Complications occurred in six patients (11%; 8% of procedures), including sealed perforations (n = 2), retroperitoneal perforations (n = 2), and intraperitoneal perforations (n = 2). Two of the patients were treated surgically with a one stage resection of the stricture and recovered uneventfully. Four patients were treated conservatively with intravenous fluids and antibiotics. There was no mortality. Dilatation completely relieved obstructive symptoms in 20 patients after one procedure, in another 14 patients after two (n = 13) or three (n = 1) dilatations. Total longterm success rate was 34 of 55 patients (62%). Nineteen patients (38%) were operated on because of persistent obstructive symptoms. The data show that endoscopic dilatation using the through the scope hydrostatic balloon system relieves obstructive symptoms resulting from ileocolonic Crohn's strictures. The procedure, however, carries a definite risk of perforation.

Couckuyt, H; Gevers, A M; Coremans, G; Hiele, M; Rutgeerts, P

1995-01-01

354

Gas bearings for gas lasers  

Microsoft Academic Search

This patent describes a long-life transverse electric discharge laser assembly. It comprises: a housing for containing an excimer laser gas; means for electrically exciting the laser gas within the housing; means for circulating the laser gas within the housing; and gas bearings including means for supporting the circulating means on a cushion of laser gas to reduce friction and to

G. A. Murray; R. A. Golobic; S. G. Derrickson

1990-01-01

355

Intelligent Engine Systems: Bearing System  

NASA Technical Reports Server (NTRS)

The overall requirements necessary for sensing bearing distress and the related criteria to select a particular rotating sensor were established during the phase I. The current phase II efforts performed studies to evaluate the Robustness and Durability Enhancement of the rotating sensors, and to design, and develop the Built-in Telemetry System concepts for an aircraft engine differential sump. A generic test vehicle that can test the proposed bearing diagnostic system was designed, developed, and built. The Timken Company, who also assisted with testing the GE concept of using rotating sensors for the differential bearing diagnostics during previous phase, was selected as a subcontractor to assist General Electric (GE) for the design, and procurement of the test vehicle. A purchase order was prepared to define the different sub-tasks, and deliverables for this task. The University of Akron was selected to provide the necessary support for installing, and integrating the test vehicle with their newly designed test facility capable of simulating the operating environment for the planned testing. The planned testing with good and damaged bearings will be on hold pending further continuation of this effort during next phase.

Singh, Arnant P.

2008-01-01

356

Plain Facts About Plain Bearings.  

National Technical Information Service (NTIS)

This citation summarizes a one-page announcement of technology available for utilization. A special report has been prepared as a concise, practical, easy-to-read guide for anyone with an interest in or need for plain bearings. It begins with a brief hist...

1982-01-01

357

Bradycardia of the Polar Bear.  

National Technical Information Service (NTIS)

For several years two male polar bears have been studied by long-life implanted physiological radio capsules at the Naval Arctic Research Laboratory, at Point Barrow. A regular measurement has been the resting heart rate; for this we used the lowest heart...

G. E. Folk J. J. Berberich D. K. Sanders

1973-01-01

358

Tardigrades: Bears of the Moss  

NSDL National Science Digital Library

This online PowerPoint presentation is dedicated to the phylum Tardigrada. It discusses distinguishing characteristics of Tardigrades (also known as water bears), their relationship to arthropods and nematodes, internal structures, life stages, cryptobiosis, research opportunities, classification, identification, habitat, distribution, ease of study in the lab, and more. Each slide contains illustrations and descriptions of the microscopic animal.

Miller, William; College, Southwestern

359

Fuzzy control of magnetic bearings  

NASA Technical Reports Server (NTRS)

The use of an adaptive fuzzy control algorithm implemented on a VLSI chip for the control of a magnetic bearing was considered. The architecture of the adaptive fuzzy controller is similar to that of a neural network. The performance of the fuzzy controller is compared to that of a conventional controller by computer simulation.

Feeley, J. J.; Niederauer, G. M.; Ahlstrom, D. J.

1991-01-01

360

High performance rolling element bearing  

NASA Technical Reports Server (NTRS)

A high performance rolling element bearing (5) which is particularly suitable for use in a cryogenically cooled environment, comprises a composite cage (45) formed from glass fibers disposed in a solid lubricant matrix of a fluorocarbon polymer. The cage includes inserts (50) formed from a mixture of a soft metal and a solid lubricant such as a fluorocarbon polymer.

Bursey, Jr., Roger W. (Inventor); Olinger, Jr., John B. (Inventor); Owen, Samuel S. (Inventor); Poole, William E. (Inventor); Haluck, David A. (Inventor)

1993-01-01

361

The decrease in yield strength in NiAl due to hydrostatic pressure  

NASA Technical Reports Server (NTRS)

The decrease in yield strength in NiAl due to hydrostatic pressure is examined via a comparison of the tensile flow behavior in the low strain regime at 0.1 MPa for NiAl which was cast, extruded, and annealed for 2 hr at 827 C in argon and very slowly cooled to room temperature. Pressurization to 1.4 GPa produces a subsequent reduction at 0.1 MP in proportional limit by 40 percent as well as a 25-percent reduction in the 0.2-percent offset yield strength, while pressurization with lower pressures produces a similar reduction, although smaller in magnitude.

Margevicius, R. W.; Lewandowski, J. J.; Locci, I.

1992-01-01

362

Cell compressibility studies utilizing noncontact hydrostatic pressure measurements on single living cells in a microchamber  

NASA Astrophysics Data System (ADS)

A micro-optical-fluidic system (MOFS), which integrates a force generating device and an optical detector, is designed to measure the bulk modulus of a single living cell in real time under a controlled hydrostatic pressure. In this design, the accuracy of the bulk modulus measurement is improved because neither the force generating device nor the optical detector needs to be in contact with the cells. The MOFS device has been used to investigate the mechanotransduction of THP-1 human acute monocytic leukemia cells and the effects of the toxin lipopolysaccharide and colchicine on various properties of these cells.

Lin, L. A. G.; Liu, A. Q.; Yu, Y. F.; Zhang, C.; Lim, C. S.; Ng, S. H.; Yap, P. H.; Gao, H. J.

2008-06-01

363

A High Precision Double Tubed Hydrostatic Leveling System for Accelerator Alignment Applications  

SciTech Connect

Since 1998 several hydrostatic leveling systems (HLS) have been installed in different locations at Fermilab. This work was in collaboration with Budker Institute and SLAC. All systems were either half-filled pipe (HF) or full-filled pipe (FF). Issues assembling HLS are covered in this article. An improved and cost-effective water system with temperature stabilized of water media is presented. This proposal is a double-tube full-filled DT-FF system. Examples of hardware configurations are included for systems located at Fermilab.

Singatulin, Shavkat; Volk, J.; Shiltsev, V.; Chupyra, A.; Medvedko, A.; Kondaurov, M.

2006-09-01

364

Hydrostatic pressure in the inner ear fluid compartments and its effects on inner ear function.  

PubMed

The present study summarizes the experimental findings obtained on the pressure in the inner ear fluids and on the effects of pressure changes on cochlear function in the guinea pig. Two types of pressures have to be distinguished in the inner ear fluid compartments: (i) hydrostatic fluid pressure and (ii) superimposed hydrodynamic high frequency (> 100 Hz) sound pressure oscillations. Hydrostatic pressure in the inner ear fluids in guinea pigs is in the order of 200 Pa (2 cm H2O) and shows slow (< 5 Hz) respiratory and pulsatory oscillations as well as considerable physiological variations in the range of -100 to +700 Pa. In normal ears, hydrostatic pressure in the perilymph equals pressure in the endolymph, and pressure changes applied to one compartment are immediately transmitted to the other one. A high compliance of Reissner's membrane seems to be the cause of this endolymphatic-perilymphatic pressure equalization. In experimental endolymphatic hydrops, a unique animal model for Meniere's disease, endolymphatic pressure is higher (100 Pa and above) than perilymphatic pressure. These pressure gradients occur only in late stages of hydrops, probably when Reissner's membrane has lost its high compliance after long standing distension. Positive endolymphatic-perilymphatic pressure gradients are secondary to and not the primary cause of hydrops formation. Changes of hydrostatic pressure do not affect auditory function as long as they stay in the physiological range. This includes the sudden loss of positive inner ear pressure that occurs in perilymph fistulas. The rationale for surgical repair of perilymph fistulas in patients in order to restore the hearing function thus becomes questionable. Other aspects of surgical repair, however, as e.g. prevention of labyrinthitis due to permanently open fistula, could not be investigated in this model, because in guinea pigs even large fistulas heal spontaneously within a few days. In experimental endolymphatic hydrops, deterioration of auditory thresholds was partially correlated to the presence of positive endolymphatic-perilymphatic pressure gradients. A change in pressure, however, occurred later than the first deterioration in auditory function. Therefore positive endo-perilymphatic pressure gradients may contribute to, but are not the only cause of hearing impairment. PMID:8273452

Böhmer, A

1993-01-01

365

Atomistic simulation of a NiZr model metallic glass under hydrostatic pressure  

NASA Astrophysics Data System (ADS)

Compressive behavior of a model NiZr metallic glass under hydrostatic pressure is simulated using molecular dynamics. The equation of state obtained exhibits two distinct regimes, one at low and the other at high pressure, along with an intermediate region in between. The densification is associated with topological rearrangement of atoms at low pressure and hard-sphere-like compaction dictated by the strong interatomic repulsion at high pressure. Different from many isotropic materials, the atomic rearrangement in the metallic glass during compression is accompanied by strong local topological structure change and chemical short-range (re)ordering. The possibility of a pressure-induced phase transition is briefly discussed.

Guo, Yu-Zheng; Li, Mo

2009-02-01

366

Structural effects of hydrostatic pressure in Sr[sub 1[minus][ital x  

Microsoft Academic Search

Pressure effects on the tetragonal infinite-layer structure were studied in superconducting Sr[sub 0.9]La[sub 0.1]CuO[sub 2] (electron-doped) and Sr[sub 0.7]Ca[sub 0.3]CuO[sub 2] (hole-doped) samples, and in an insulating nonsuperconducting Sr[sub 0.14]Ca[sub 0.86]CuO[sub 2] sample, using time-of-flight neutron powder diffraction. Neutron-diffraction measurements, with the sample at room temperature, were performed at several hydrostatic pressures up to [approx]0.6 GPa on each of the

H. Shaked; Y. Shimakawa; B. A. Hunter; P. G. Radaelli; B. Dabrowski; R. L. Hitterman; J. D. Jorgensen; P. D. Han; D. A. Payne; S. Kikkawa; G. Er; F. Kanamaru

1994-01-01

367

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

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

368

Hydrostatic Level Sensors as High Precision Ground Motion Instrumentation for Tevatron and Other Energy Frontier Accelerators  

SciTech Connect

Particle accelerators require very tight tolerances on the alignment and stability of their elements: magnets, accelerating cavities, vacuum chambers, etc. In this article we describe the Hydrostatic Level Sensors (HLS) for very low frequency measurements used in a variety of facilities at Fermilab. We present design features of the sensors, outline their technical parameters, describe their test and calibration procedures, discuss different regimes of operation and give few illustrative examples of the experimental data. Detail experimental results of the ground motion measurements with these detectors will be presented in subsequent papers.

Volk, James; Hansen, Sten; Johnson, Todd; Jostlein, Hans; Kiper, Terry; Shiltsev, Vladimir; Chupyra, Andrei; Kondaurov, Mikhail; Medvedko, Anatoly; Parkhomchuk, Vasily; Singatulin, Shavkat

2012-01-01

369

Effect of the hydrostatic pressure on otolith growth of early juveniles of Nile tilapia Oreochromis niloticus.  

PubMed

Nile tilapia Oreochromis niloticus early juveniles were maintained for 2 weeks in a pressurized system under a controlled photoperiod, at constant salinity and temperature. Groups of fish were exposed to one of three absolute hydrostatic pressure (HP) regimes: (1) a constant normal atmospheric pressure (100 kPa), (2) a constant 40 m pressure (500 kPa) or (3) a semi-diurnal cyclic vertical migration (100-500 kPa). No significant differences were detected in otolith size and incremental periodicity among the three HP treatments, suggesting that HP does not affect otolith growth of early juveniles O. niloticus. PMID:22747823

Correia, A T; Coimbra, A M; Damasceno-Oliveira, A

2012-07-01

370

Theoretical studies of optical gain tuning by hydrostatic pressure in GaInNAs/GaAs quantum wells  

NASA Astrophysics Data System (ADS)

In order to describe theoretically the tuning of the optical gain by hydrostatic pressure in GaInNAs/GaAs quantum wells (QWs), the optical gain calculations within kp approach were developed and applied for N-containing and N-free QWs. The electronic band structure and the optical gain for GaInNAs/GaAs QW were calculated within the 10-band kp model which takes into account the interaction of electron levels in the QW with the nitrogen resonant level in GaInNAs. It has been shown that this interaction increases with the hydrostatic pressure and as a result the optical gain for GaInNAs/GaAs QW decreases by about 40% and 80% for transverse electric and transverse magnetic modes, respectively, for the hydrostatic pressure change from 0 to 40 kilobars. Such an effect is not observed for N-free QWs where the dispersion of electron and hole energies remains unchanged with the hydrostatic pressure. This is due to the fact that the conduction and valence band potentials in GaInAs/GaAs QW scale linearly with the hydrostatic pressure.

Gladysiewicz, M.; Kudrawiec, R.; Wartak, M. S.

2014-01-01

371

Journal and Wave Bearing Impedance Calculation Software  

NASA Technical Reports Server (NTRS)

The wave bearing software suite is a MALTA application that computes bearing properties for user-specified wave bearing conditions, as well as plain journal bearings. Wave bearings are fluid film journal bearings with multi-lobed wave patterns around the circumference of the bearing surface. In this software suite, the dynamic coefficients are outputted in a way for easy implementation in a finite element model used in rotor dynamics analysis. The software has a graphical user interface (GUI) for inputting bearing geometry parameters, and uses MATLAB s structure interface for ease of interpreting data. This innovation was developed to provide the stiffness and damping components of wave bearing impedances. The computational method for computing bearing coefficients was originally designed for plain journal bearings and tilting pad bearings. Modifications to include a wave bearing profile consisted of changing the film thickness profile given by an equation, and writing an algorithm to locate the integration limits for each fluid region. Careful consideration was needed to implement the correct integration limits while computing the dynamic coefficients, depending on the form of the input/output variables specified in the algorithm.

Hanford, Amanda; Campbell, Robert

2012-01-01

372

Short-bearing approximation for full journal bearings  

NASA Technical Reports Server (NTRS)

A short-bearing approximation of pressure distribution in the oil film is presented which is an extension of the pressure-distribution function of Michell and Cardullo and includes end-leakage effects. Equations giving applied load, attitude angle, location and magnitude of peak film pressure, friction, and required oil flow rate as functions of the eccentricity ratio are also given. The capacity number, a basic non dimensional quantity resulting from this analysis is the product of the Sommerfeld number and the square of the length-diameter ratio. Curves determined by this analysis are compared with previously published experimental data and theoretical curves of Sommerfeld and Cameron and Wood. Conclusions reached indicate that this approximation is of practical value for analysis of short bearings.

Ocvirk, F W

1952-01-01

373

Effects of bearing deadbands on bearing loads and rotor stability  

NASA Technical Reports Server (NTRS)

A generic model of a turbopump, simplified to bring out these effects is examined. This model demonstrates that bearing deadbands which are of the same order of magnitude or larger than the center-of-mass offset of a rotor due to mass imbalances cause significantly different dynamic behavior than would be expected of a linear, dynamical system. This fundamentally nonlinear behavior yields altered stability characteristics and altered bearing loading tendencies. It is shown that side forces can enhance system stability in the small, i.e., as long as the mass imbalance does not exceed some thresholds value or as long as no large, impulsive disturbances cause the motion to depart significantly from the region of stability. Limit cycles are investigated in this report and techniques for determining these limit cycles are developed. These limit cycles are the major source of bearing loading and appear in both synchronous and nonsynchronous forms. The synchronous limit cycles are driven by rotor imbalances. The nonsynchronous limit cycles (also called subsynchronous whirls) are self-excited and are the sources of instability.

1984-01-01

374

Use of Interstate Passageways by Black Bears.  

National Technical Information Service (NTIS)

Vehicle collisions account for up to forty black bear (Ursus americanus) deaths per year in Tennessee. Historically, a relatively high number of bear deaths have occurred on Interstate Highway 40 between mile marker 440 and the North Carolina state line. ...

F. T. Manen A. B. Coley M. R. Pelton

1995-01-01

375

Elastic orifice automatically regulates gas bearings  

NASA Technical Reports Server (NTRS)

Elastic, pressure-sensitive orifice is used to automatically regulate the rate of gas flow into bearings under varying loads. Formed of a molded elastomer, theses orifices increase the stability of gas bearings.

Batsch, F.; Laub, J. L.

1964-01-01

376

Bear-inflicted human injury and fatality.  

PubMed

This review attempts to summarize credible scientific information, and to dispel myths, regarding bear attacks. Publications in the scientific literature were sought through a Medline search and by reviewing the bibliographies of related books and scientific articles. Personal experience and interviews with authorities were also used in preparation of this review, although only published articles or books are cited. This is a summary of case series reported or observed elsewhere. Bear-inflicted human injury and death is rare. Brown bear attacks tend to be severe and to occur suddenly, without provocation. Black bear attacks usually result in minor injuries and tend to be predacious. Polar bear attacks are exceedingly rare, and the ferocity of polar bears has probably been overemphasized. Bear-inflicted wounds should be treated as major trauma in accordance with advanced trauma life support guidelines. This information may be useful in counseling patients with regard to prevention of injury or death from bear attack. PMID:10442155

Floyd, T

1999-01-01

377

Complex Demodulation for Bearing Fault Detection.  

National Technical Information Service (NTIS)

Vibration analysis using the high frequency resonance technique has been used successfully to detect incipient failure in rolling element bearings. This memo outlines a new method of obtaining the demodulated narrow band envelope of a bearing vibration si...

I. M. Howard

1989-01-01

378

Magnetic Perturbation Inspection of Inner Bearing Races.  

National Technical Information Service (NTIS)

Approximately 100 inner race bearings were inspected nondestructively prior to endurance testing. Two of the bearings which failed during testing spalled at the sites of subsurface inclusions previously detected by using magnetic field perturbation. At ot...

J. Lankford J. R. Barton

1972-01-01

379

Ultralow Friction in a Superconducting Magnetic Bearing.  

National Technical Information Service (NTIS)

Passive levitation by superconducting magnetic bearings can be utilized in flywheels for energy storage. Basic design criteria of such a bearing are high levitation force, sufficient vertical and horizontal stability and low friction. A test facility was ...

H. J. Bornemann M. Siegel O. Zaitsev M. Bareiss H. Laschuetza

1996-01-01

380

A Preliminary Foil Gas Bearing Performance Map  

NASA Technical Reports Server (NTRS)

Recent breakthrough improvements in foil gas bearing load capacity, high temperature tribological coatings and computer based modeling have enabled the development of increasingly larger and more advanced Oil-Free Turbomachinery systems. Successful integration of foil gas bearings into turbomachinery requires a step wise approach that includes conceptual design and feasibility studies, bearing testing, and rotor testing prior to full scale system level demonstrations. Unfortunately, the current level of understanding of foil gas bearings and especially their tribological behavior is often insufficient to avoid developmental problems thereby hampering commercialization of new applications. In this paper, a new approach loosely based upon accepted hydrodynamic theory, is developed which results in a "Foil Gas Bearing Performance Map" to guide the integration process. This performance map, which resembles a Stribeck curve for bearing friction, is useful in describing bearing operating regimes, performance safety margins, the effects of load on performance and limiting factors for foil gas bearings.

DellaCorte, Christopher; Radil, Kevin C.; Bruckner, Robert J.; Howard, S. Adam

2006-01-01

381

Hunting for 'bears' in the backyard  

NSDL National Science Digital Library

This Micscape Magazine article offers practical hints about how to collect and study tardigrades, or water bears, from mosses in your backyard. It features a general introduction of water bears, a video, and a section of references for further reading.

Walker, Dave; Magazine, Micscape

382

Cryogenic Fluid Film Bearing Tester Development Study.  

National Technical Information Service (NTIS)

Conceptual designs were developed for the determination of rotordynamic coefficients of cryogenic fluid film bearings. The designs encompassed the use of magnetic and conventional excitation sources as well as the use of magnetic bearings as support beari...

J. K. Scharrer B. T. Murphy L. A. Hawkins

1993-01-01

383

Happy Birthday Smokey Bear from Joe Acaba  

NASA Video Gallery

Expedition 32 Flight Engineer Joe Acaba wishes Smokey Bear a Happy Birthday. For 68 years Smokey Bear has been promoting fire safety and prevention through the message, â??Only You Can Prevent Wild...

384

Stable isotopes to detect food-conditioned bears and to evaluate human-bear management  

USGS Publications Warehouse

We used genetic and stable isotope analysis of hair from free-ranging black bears (Ursus americanus) in Yosemite National Park, California, USA to: 1) identify bears that consume human food, 2) estimate the diets of these bears, and 3) evaluate the Yosemite human–bear management program. Specifically, we analyzed the isotopic composition of hair from bears known a priori to be food-conditioned or non-food-conditioned and used these data to predict whether bears with an unknown management status were food-conditioned (FC) or non-food-conditioned (NFC). We used a stable isotope mixing model to estimate the proportional contribution of natural foods (plants and animals) versus human food in the diets of FC bears. We then used results from both analyses to evaluate proactive (population-level) and reactive (individual-level) human–bear management, and discussed new metrics to evaluate the overall human–bear management program in Yosemite. Our results indicated that 19 out of 145 (13%) unknown bears sampled from 2005 to 2007 were food-conditioned. The proportion of human food in the diets of known FC bears likely declined from 2001–2003 to 2005–2007, suggesting proactive management was successful in reducing the amount of human food available to bears. In contrast, reactive management was not successful in changing the management status of known FC bears to NFC bears, or in reducing the contribution of human food to the diets of FC bears. Nine known FC bears were recaptured on 14 occasions from 2001 to 2007; all bears were classified as FC during subsequent recaptures, and human–bear management did not reduce the amount of human food in the diets of FC bears. Based on our results, we suggest Yosemite continue implementing proactive human–bear management, reevaluate reactive management, and consider removing problem bears (those involved in repeated bear incidents) from the population.

Hopkins, John B., III; Koch, Paul L.; Schwartz, Charles C.; Ferguson, Jake M.; Greenleaf, Schuyler S.; Kalinowski, Steven T.

2012-01-01

385

Effect of horizontal and vertical resolution in a non-hydrostatic global model: An aquaplanet study  

NASA Astrophysics Data System (ADS)

The effect of the spatial resolution of numerical models on the atmospheric circulation has been a concern for some decades. In particular, the performance of physical processes in a global model is significantly affected by vertical resolution because processes in the most models are vertically one dimensional models. Nevertheless, systematic studies of how simulations are affected by finer vertical spacing have been limited, while many research groups have devoted to studies on horizontal resolution dependency. This study presents preliminary results related to the issue of how the simulation of overall large-scale features and precipitation by a non-hydrostatic global model depends on horizontal and vertical resolution. As a tool, a Non-hydrostatic Icosahedral Model (NIM), which has been developing at National Oceanic and Atmospheric Administration Earth System Research Laboratory (NOAA ESRL), is used. Aquaplanet simulations, forced by idealized zonally symmetric sea surface temperature (SST), are performed with systematically increasing resolutions. Verification of NIM aqua-planet simulation at low resolution with other published results, and the simulated results obtained from different resolution will be compared along with the discussion on the basic dependence of each physical process on horizontal and vertical model resolution.

Kim, J. E.; Lee, J.; Hong, S.

2013-12-01

386

Fourier analysis for hydrostatic pressure sensing in a polarization-maintaining photonic crystal fiber  

SciTech Connect

.We measured the hydrostatic pressure dependence of the birefringence and birefringent dispersion of a Sagnac interferometric sensor incorporating a length of highly birefringent photonic crystal fiber using Fourier analysis. Sensitivity of both the phase and chirp spectra to hydrostatic pressure is demonstrated. Using this analysis, phase-based measurements showed a good linearity with an effective sensitivity of 9.45nm/MPa and an accuracy of {+-}7.8kPa using wavelength-encoded data and an effective sensitivity of -55.7cm{sup -1}/MPa and an accuracy of {+-}4.4kPa using wavenumber-encoded data. Chirp-based measurements, though nonlinear in response, showed an improvement in accuracy at certain pressure ranges with an accuracy of {+-}5.5kPa for the full range of measured pressures using wavelength-encoded data and dropping to within {+-}2.5kPa in the range of 0.17 to 0.4MPa using wavenumber-encoded data. Improvements of the accuracy demonstrated the usefulness of implementing chirp-based analysis for sensing purposes.

Childs, Paul; Wong, Allan C. L.; Fu, H. Y.; Liao, Yanbiao; Tam, Hwayaw; Lu Chao; Wai, P. K. A.

2010-12-20

387

The effect of hydrostatic vs. shock pressure treatment of plant seeds  

NASA Astrophysics Data System (ADS)

The hydrostatic pressure and shock response of plant seeds has been investigated antecedently, primarily driven by interest in reducing bacterial contamination of crops and the theory of panspermia, respectively. However, comparisons have not previously been made between these two methods ofapplying pressure to plant seeds. Here such a comparison has been undertaken based on the premise that any correlations in collected data may provide a route to inform understanding of damage mechanisms in the seeds under test. In this work two varieties of plant seeds were subjected to hydrostatic pressure via a non-end-loaded piston cylinder setup and shock compression via employment of a 50 mm bore, single stage gas gun using the flyer plate technique. Results from germination tests of recovered seed samples have been compared and contrasted, and initial conclusions made regarding causes of trends in the resultant data-set. Data collected has shown that cress seeds are extremely resilient to static loading, whereas the difference in the two forms of loading is negligible for lettuce seeds. Germination time has been seen to extend dramatically following static loading of cress seeds to greater than 0.4 GPa. In addition, the cut-off pressure previously seen to cause 0% germination in dynamic experiments performed on cress seeds has now also been seen in lettuce seeds.

Mustey, A.; Leighs, J. A.; Appleby-Thomas, G. J.; Wood, D. C.; Hazael, R.; McMillan, P. F.; Hazell, P. J.

2014-05-01

388

Hydrostatic pressure effect on hydrophobic hydration and pairwise hydrophobic interaction of methane.  

PubMed

At room temperature, the Ben-Naim standard hydration Gibbs energy of methane is a positive quantity that increases markedly with hydrostatic pressure [M. S. Moghaddam and H. S. Chan, J. Chem. Phys. 126, 114507 (2007)]. This finding is rationalized by showing that the magnitude of the reversible work to create a suitable cavity in water increases with pressure due to both the increase in the volume packing density of water and the contribution of the pressure-volume work. According to the present approach, at room temperature, the Gibbs energy of the contact-minimum configuration of two methane molecules is a negative quantity that increases in magnitude with hydrostatic pressure. This result is not in line with the results of several computer simulation studies [T. Ghosh, A. E. Garcia, and S. Garde, J. Am. Chem. Soc. 123, 10997-11003 (2001)], and emerges because pairwise association causes a decrease in solvent-excluded volume that produces a gain of configurational/translational entropy of water molecules, whose magnitude increases with the volume packing density of the liquid phase. PMID:24606364

Graziano, Giuseppe

2014-03-01

389

A hydraulic hammer corer utilizing hydrostatic energy for hard seafloor sediment coring  

NASA Astrophysics Data System (ADS)

The paper presents the design and preliminary test results of a corer used for hard seafloor sediments sampling. Generally the sediment cores are provided by either gravity-type coring or deep-ocean drilling for a range of studies. However, in consideration of the operability and available sample length in collecting hard sediments, these methods exhibit no advantages. In this paper, a new corer which can exploit both hydrostatic energy and gravity energy for hard sediments coring is presented. The hydrostatic energy is provided by pressure differential between ambient seawater pressure and air pressure in an empty cavity. During sampling process, the corer penetrates into the sediment like a gravity corer and then automatically shifts to the percussion mode. The experiments in the laboratory indicate that the corer can complete 40 cycles in the sea with a cycle time of 2.8 seconds in percussion mode and impact the sample tube with the velocity of 0.2 m/s during each cycle. Besides, its adjustable falling velocity can make the corer achieve the maximum efficiency in coring different sediments.

Wang, Jian-Jun; Qin, Hua-Wei; Chen, Ying; Wei, Shuang-Feng

2011-06-01

390

Response of superconductivity and crystal structure of LiFeAs to hydrostatic pressure.  

PubMed

On the application of hydrostatic pressures of up to 1.3 GPa, the superconducting transition temperatures (T(c)) of samples of LiFeAs are lowered approximately monotonically at approximately -2 K GPa(-1). Measurements of the X-ray powder diffraction pattern at hydrostatic pressures of up to 17 GPa applied by a He gas pressure medium in a diamond anvil cell reveal a bulk modulus for LiFeAs of 57.3(6) GPa which is much smaller than that of other layered arsenide and oxyarsenide superconductors. LiFeAs also exhibits much more isotropic compression than other layered iron arsenide superconductors. The higher and more isotropic compressibility is presumably a consequence of the small size of the lithium ion. At ambient pressure the FeAs(4) tetrahedra are the most compressed in the basal plane of those in any of the superconducting iron arsenides. On increasing the pressure the Fe-Fe distance contracts more rapidly than the Fe-As distance so that the FeAs(4) tetrahedra become even more distorted from the ideal tetrahedral shape. The decrease in T(c) with applied pressure is therefore consistent with the observations that in the iron arsenides and related materials investigated thus far, T(c) is maximized for a particular electron count when the FeAs(4) tetrahedra are close to regular. PMID:19206468

Mito, Masaki; Pitcher, Michael J; Crichton, Wilson; Garbarino, Gaston; Baker, Peter J; Blundell, Stephen J; Adamson, Paul; Parker, Dinah R; Clarke, Simon J

2009-03-01

391

Crystallization of a Li2O2SiO2 Glass under High Hydrostatic Pressures  

NASA Technical Reports Server (NTRS)

The crystallization behavior of a Li2O.2SiO2 (LS2) glass subjected to a uniform hydrostatic pressure of 4.5 or 6 GPa was investigated between 550 and 800 C using XRD, IR, Raman, TEM, NMR, and DTA. The density of the glass subjected to 6 GPa was between 2.52 plus or minus 0.01 and 2.57 plus or minus 0.01 grams per cubic centimeters, depending upon the processing temperatures, and was higher than that of the stoichiometric LS2 crystals, 2.46 plus or minus 0.01 grams per cubic centimeter. Thus, crystallization in 6 GPa glass occurred in a condition of negative volume dilatation, deltaV = V(sub glass) - V(sub crystal), while that for the 4.5 GPa glass occurred in the condition deltaV greater than 0. For deltaV greater than 0, which also includes the control glass at ambient (one atmosphere) pressure, the glasses always crystallize Li2Si2O5 (orthorhombic, Ccc2) crystals, but for deltaV less than 0 (6 GPa), the glasses crystallize Li2SiO3 crystals with a slightly deformed structure. The crystal growth rate vs. temperature curve moved to higher temperature with increasing pressure, and was independent of the sign of deltaV. These results for the effect of hydrostatic pressure on the crystallization of LS2 glass were discussed from thermodynamic considerations.

Fuss, T.; Day, D. E.; Lesher, C. E.; Ray, C. S.

2004-01-01

392

True-slime-mould-inspired hydrostatically coupled oscillator system exhibiting versatile behaviours.  

PubMed

Behavioural diversity is an indispensable attribute of living systems, which makes them intrinsically adaptive and responsive to the demands of a dynamically changing environment. In contrast, conventional engineering approaches struggle to suppress behavioural diversity in artificial systems to reach optimal performance in given environments for desired tasks. The goals of this research include understanding the essential mechanism that endows living systems with behavioural diversity and implementing the mechanism in robots to exhibit adaptive behaviours. For this purpose, we have focused on an amoeba-like unicellular organism: the plasmodium of true slime mould. Despite the absence of a central nervous system, the plasmodium exhibits versatile spatiotemporal oscillatory patterns and switches spontaneously among these patterns. By exploiting this behavioural diversity, it is able to exhibit adaptive behaviour according to the situation encountered. Inspired by this organism, we built a real physical robot using hydrostatically coupled oscillators that produce versatile oscillatory patterns and spontaneous transitions among the patterns. The experimental results show that exploiting physical hydrostatic interplay—the physical dynamics of the robot—allows simple phase oscillators to promote versatile behaviours. The results can contribute to an understanding of how a living system generates versatile and adaptive behaviours with physical interplays among body parts. PMID:23981517

Umedachi, Takuya; Idei, Ryo; Ito, Kentaro; Ishiguro, Akio

2013-09-01

393

Weak hydrostatic forces in far-scanning ion conductance microscopy used to guide neuronal growth cones.  

PubMed

Scanning ion conductance microscopy (SICM) is currently used for high resolution topographic imaging of living cells. Recently, it has been also employed as a tool to deliver stimuli to the cells. In this work we have investigated the mechanical interaction occurring between the pipette tip and the sample during SICM operation. For the purpose, we have built a setup combining SICM with atomic force microscopy (AFM), where the AFM cantilever replaces the sample. Our data indicate that, operating in far-scanning mode with current decrease values below 2%, no force can be detected, provided that the level of the electrolyte filling the pipette is equal to that determined by the capillary tension. A filling level different from this value determines a hydrostatic pressure, a flux through the pipette tip and detectable forces, even in far-scanning mode. The absolute value of these forces depends on the pipette tip size. Therefore, a possible pitfall when using SICM for cell imaging is to imply zero-force working conditions. However the hydrostatic forces can be exploited in order to deliver weak mechanical stimuli and guide neuronal growth cones. Evidences of the effectiveness of this approach are herein given. PMID:21146567

Pellegrino, Mario; Orsini, Paolo; Pellegrini, Monica; Baschieri, Paolo; Dinelli, Franco; Petracchi, Donatella; Tognoni, Elisabetta; Ascoli, Cesare

2011-03-01

394

Validity conditions of the hydrostatic approach for self-gravitating systems: a microcanonical analysis  

NASA Astrophysics Data System (ADS)

We consider a system of hard spheres with gravitational interactions in a stationary state described in terms of the microcanonical ensemble. We introduce a set of similar auxiliary systems with increasing sizes and numbers of particles. The masses and radii of the hard spheres of the auxiliary systems are rescaled in such a way that the usual extensive properties are maintained despite the long-range nature of the gravitational interactions, while the mass density and packing fractions are kept fixed. We show, within that scaling limit, that a local thermalization spontaneously emerges as a consequence of both extensive properties and the relative smallness of the fluctuations. The resulting mass density profile for the infinite system can be determined within a hydrostatic approach, where the gradient of the local hard-sphere pressure is balanced by the average gravitational field. The derivation sheds light on the mechanisms which ensure that the local equilibrium in the infinite system is entirely controlled by hard-core interactions, while gravitational interactions can be treated at the mean-field level. This allows us to determine the conditions under which the hydrostatic approach is also valid for the actual finite system of interest. We provide simple tests of such conditions for a few astrophysical examples.

Champion, M.; Alastuey, A.; Dauxois, T.; Ruffo, S.

2014-06-01

395

Performance of a hybrid cylindrical roller bearing  

Microsoft Academic Search

A 206-size hybrid (ceramic\\/steel) cylindrical roller bearing was tested in MIL-L-23699 C oil at several speeds and loads. Heat-generation data was collected and subsequently correlated with bearing-analysis software. Bearing-cage slip data was also collected at various oil-flow rates, oil temperatures, and with both MIL-L-7808 J and MIL-L-23699 C oils. The hybrid bearing was tested in MIL-L-23699 C oil for for

Stephen M. Schrader

1992-01-01

396

Cartridge Bearing System for Space Applications  

NASA Technical Reports Server (NTRS)

Conventional spin axis ball bearings have been unreliable in spacecraft, often failing by two heretofore uncontrolled processes: ball retainer instability and lubricant breakdown. The Space Cartridge Bearing System (SCBS) addresses each of these mechanisms directly, leading to a bearing system with absolute freedom from retainer instability and negligible lubricant degradation rate. The result is a reliable plug-in bearing cartridge with a definite design life.

Kingsbury, Edward P.; Hanson, Robert A.; Jones, William R.; Mohr, Terry W.

1999-01-01

397

Research In Diagnosing Bearing Defects From Vibrations  

NASA Technical Reports Server (NTRS)

Report describes research in bearing-defect signature analysis - use of vibration-signal analysis to diagnose defects in roller and ball bearings. Experiments performed on bearings in good condition and other bearings in which various parts scratched to provide known defects correlated with vibration signals. Experiments performed on highly instrumented motor-driven rotor assembly at speeds up to 10,050 r/min, using accelerometers, velocity probes, and proximity sensors mounted at various locations on assembly to measure vibrations.

Zoladz, T.; Earhart, E.; Fiorucci, T.

1995-01-01

398

Hydrology of the Bear Lake Basin, Utah  

Microsoft Academic Search

Bear Lake’s natural watershed is made up of relatively low mountains covered with sagebrush at lower elevations and southern exposures and fir-aspen forests at higher elevations and northern exposures. The basin is traversed by the Bear River that begins high in the Unita Mountains and flows through Utah, Idaho, and Wyoming before feeding the Great Salt Lake. The Bear River

Patsy Palacios; Chris Luecke; Justin Robinson

2007-01-01

399

36 CFR 13.1236 - Bear orientation.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Bear orientation. 13.1236 Section 13...Brooks Camp Developed Area § 13.1236 Bear orientation. All persons visiting the BCDA must receive an NPS-approved Bear Orientation. Failure to receive an...

2010-07-01

400

36 CFR 13.1236 - Bear orientation.  

Code of Federal Regulations, 2010 CFR

...2009-07-01 2009-07-01 false Bear orientation. 13.1236 Section 13...Brooks Camp Developed Area § 13.1236 Bear orientation. All persons visiting the BCDA must receive an NPS-approved Bear Orientation. Failure to receive an...

2009-07-01

401

Teaching American History with Teddy's Bear.  

ERIC Educational Resources Information Center

Discusses the origins of "Teddy's bear," tracing back to a cartoon published in 1902. States that Teddy's bear can shed light on U.S. culture and society. Focuses on the role of Teddy's bear as a symbol of conservationism, an embodiment of male dominance and female nurturance, and a manifestation of white racial supremacy. (CMK)

Forman-Brunell, Miriam

2001-01-01

402

Minimizing electric bearing currents in ASD systems  

Microsoft Academic Search

During recent years, an increase in bearing failures has been seen in ASD-fed electric motors, as well as in gearboxes, and other connected machinery, caused by electric current flow through such bearings. The theories presented in this paper focus on bearing currents in ASDs of the voltage source pulse width modulated (PWM) type, for use with AC induction motors, although

P. J. Link

1999-01-01

403

Bearing-Mounting Concept Accommodates Thermal Expansion  

NASA Technical Reports Server (NTRS)

Pins or splines allow radial expansion without slippage. Design concept for mounting rotary bearing accommodates differential thermal expansion between bearing and any structure(s) to which bearing connected. Prevents buildup of thermal stresses by allowing thermal expansion to occur freely but accommodating expansion in such way not to introduce looseness. Pin-in-slot configuration also maintains concentricity.

Nespodzany, Robert; Davis, Toren S.

1995-01-01

404

Fixed-Wheel Gate Bearing Studies.  

National Technical Information Service (NTIS)

Tests to determine friction coefficients and bearing behavior in 3 types of bearings--2 self-lubricating and 1 plain bronze--show that increased allowable bearing pressures of 6,000 psi and a design coefficient of friction of 0.10 can be used for one of t...

G. I. Brooks, M. Lopez, D. B. Mountjoy

1964-01-01

405

Foil bearing lubrication theory including compressibility effects  

NASA Technical Reports Server (NTRS)

An analysis is presented to determine the film thickness in a foil bearing. Using the Reynolds equation and including the compressibility effects of the gas, an equation was developed applicable to the film thickness in a foil bearing. The bearing was divided into three regions, namely, the entrance region, middle region and exit region. Solutions are obtained for the film thickness in each region.

Gorla, Rama Subba Reddy; Catalano, Daniel A.

1987-01-01

406

Sliding bearings lubricated with magnetic fluids  

Microsoft Academic Search

Purpose – This paper seeks to present some new designs of sliding bearings lubricated with magnetic fluids (ferrofluids) and the possibility of using them in modern bearing technology, in new computer and audiovisual equipment among others. Design\\/methodology\\/approach – The paper presents new designs of journal, thrust and journal-thrust sliding bearings lubricated and sealed with magnetic fluids such as: magnetic fluid

W. Ocho?ski

2007-01-01

407

49 CFR 229.64 - Plain bearings.  

Code of Federal Regulations, 2013 CFR

...Transportation 4 2013-10-01 2013-10-01 false Plain bearings. 229.64 Section 229.64 Transportation...Safety Requirements Suspension System § 229.64 Plain bearings. A plain bearing box shall contain visible free oil and may...

2013-10-01

408

Optimum energy loss in electro magnetic bearing  

Microsoft Academic Search

This paper includes weight optimization method of rotor and analysis of total power loss in radial magnetic bearing consisting of four, eight and twelve poles. Weight optimization reduces copper loss in bearing since the electromagnetic force is reduced due to optimized rotor. Further numbers of poles in magnetic bearing are varied for same electromagnetic force 350 N and stator is

Santosh Shelke; R. V. Chalam

2011-01-01

409

Thin film superconductor magnetic bearings  

DOEpatents

A superconductor magnetic bearing includes a shaft (10) that is subject to a load (L) and rotatable around an axis of rotation, a magnet (12) mounted to the shaft, and a stator (14) in proximity to the shaft. The stator (14) has a superconductor thin film assembly (16) positioned to interact with the magnet (12) to produce a levitation force on the shaft (10) that supports the load (L). The thin film assembly (16) includes at least two superconductor thin films (18) and at least one substrate (20). Each thin film (18) is positioned on a substrate (20) and all the thin films are positioned such that an applied magnetic field from the magnet (12) passes through all the thin films. A similar bearing in which the thin film assembly (16) is mounted on the shaft (10) and the magnet (12) is part of the stator (14) also can be constructed.

Weinberger, Bernard R. (Avon, CT)

1995-12-26

410

The BEAR Beamline at Elettra  

SciTech Connect

The BEAR (Bending Magnet for Emission Absorption and Reflectivity) beamline is installed at the right exit of the 8.1 bending magnet at ELETTRA. The beamline - in operation since January 2003 - delivers linear and circularly polarized radiation in the 5 - 1600 eV energy range. The experimental station is composed of a UHV chamber for reflectivity, absorption, fluorescence and angle resolved photoemission measurements and a UHV chamber for in-situ sample preparation.

Nannarone, S.; Pasquali, L.; Selvaggi, G. [UdR-INFM Modena, Universita di Modena and Reggio Emilia, Via Vignolese 905, 41100 Modena (Italy); Borgatti, F.; DeLuisa, A.; Doyle, B.P.; Gazzadi, G.C.; Giglia, A.; Finetti, P.; Pedio, M. [TASC-INFM, MM building in Area Science Park, s.s.14 km 163.5, 34012 Basovizza, Trieste (Italy); Mahne, N. [TASC-INFM, Universita di Trieste, Trieste (Italy); Naletto, G.; Pelizzo, M.G.; Tondello, G. [LUXOR-INFM, Universita di Padova, Padua (Italy)

2004-05-12

411

Bearing capacity of desiccated tailings  

Microsoft Academic Search

The development of matric suctions in soils contributes to their shear strength, resulting in an enhanced factor of safety against bearing-capacity failure. In this paper, matric suction profiles of desiccated mine tailings are predicted from a steady-state solution for evaporative conditions, and from an isothermal mathematical model that simulates liquid and vapor water flow through soils. The shear-strength envelope with

Daud W. Rassam; David J. Williams

1999-01-01

412

Rolling element bearings in space  

NASA Technical Reports Server (NTRS)

Some of the advances in tribology that have been associated with aerospace mechanisms are discussed. The needs of aerospace have been the dominant forces leading to improvements in understanding and applying tribology technology. In the past two decades improvements in understanding bearing torque, elastohydrodynamic lubrication, lubricant distribution, cage stability, and transfer film lubricants have been made. It is anticipated that further developments will be made in response to future aerospace requirements.

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

1986-01-01

413

Neutron scattering study of a quasi-2D spin-1/2 dimer system Piperazinium Hexachlorodicuprate under hydrostatic pressure  

SciTech Connect

We report inelastic neutron scattering study of a quasi-two-dimensional S=1/2 dimer system piperazinium hexachlorodicuprate under hydrostatic pressure. The spin gap {Delta} becomes softened with the increase of the hydrostatic pressure up to P = 9.0 kbar. The observed threefold degenerate triplet excitation at P = 6.0 kbar is consistent with the theoretical prediction and the bandwidth of the dispersion relation is unaffected within the experimental uncertainty. At P = 9.0 kbar the spin gap is reduced to {Delta} = 0.55 meV from {Delta} = 1.0 meV at ambient pressure.

Hong, Tao [ORNL; Stock, C. [NIST Center for Neutron Research (NCRN), Gaithersburg, MD; Cabrera, I. [Johns Hopkins University; Broholm, C. [Johns Hopkins University; Qiu, Y. [National Institute of Standards and Technology (NIST); Leao, J. B. [National Institute of Standards and Technology (NIST); Poulton, S. J. [National Institute of Standards and Technology (NIST); Copley, J.R.D. [National Institute of Standards and Technology (NIST)

2010-01-01

414

Fault Tolerant Homopolar Magnetic Bearings  

NASA Technical Reports Server (NTRS)

Magnetic suspensions (MS) satisfy the long life and low loss conditions demanded by satellite and ISS based flywheels used for Energy Storage and Attitude Control (ACESE) service. This paper summarizes the development of a novel MS that improves reliability via fault tolerant operation. Specifically, flux coupling between poles of a homopolar magnetic bearing is shown to deliver desired forces even after termination of coil currents to a subset of failed poles . Linear, coordinate decoupled force-voltage relations are also maintained before and after failure by bias linearization. Current distribution matrices (CDM) which adjust the currents and fluxes following a pole set failure are determined for many faulted pole combinations. The CDM s and the system responses are obtained utilizing 1D magnetic circuit models with fringe and leakage factors derived from detailed, 3D, finite element field models. Reliability results are presented vs. detection/correction delay time and individual power amplifier reliability for 4, 6, and 7 pole configurations. Reliability is shown for two success criteria, i.e. (a) no catcher bearing contact following pole failures and (b) re-levitation off of the catcher bearings following pole failures. An advantage of the method presented over other redundant operation approaches is a significantly reduced requirement for backup hardware such as additional actuators or power amplifiers.

Li, Ming-Hsiu; Palazzolo, Alan; Kenny, Andrew; Provenza, Andrew; Beach, Raymond; Kascak, Albert

2003-01-01

415

The Design of Externally Pressurized Gas Lubricated Bearings by the Method of Bearing Equivalence  

Microsoft Academic Search

This paper presents the theoretical development and experimental verification of a simplified technique for the design of externally pressurized gas lubricated bearings. The general procedure is to establish an equivalent rectangular bearing which is the performance replica of an arbitrary gas bearing configuration. The resulting equivalent bearing has the same load support, clearance, area, source pressure, entrance losses, and mass

Richard C. Turnblade

1962-01-01

416

The effects of bearing distortion on the performance of hydrodynamic thrust bearings  

Microsoft Academic Search

Purpose – In this work, the performance characteristics of thrust bearings are studied by taking into account bearing distortions. Design\\/methodology\\/approach – The pressure distribution in the bearing is found using Reynolds' equation. Reynolds' equation is solved under isothermal conditions by assuming oil viscosity constant. The amount of deformation in the bearing is determined using constitute equations applied to linear elastic

Emin Güllü

2005-01-01

417

Oil Exchange Between Ball Bearings and Cotton-Phenolic Bail-Bearing Retainers  

Microsoft Academic Search

Experiments have been performed that determine for the first time the transfer of oil between cotton-phenolic ball-bearing retainers and operating ball bearings. A full retainer exchanges oil with the metal park of the bearing, probably by diffusional mixing. There is no net delivery of oil from the retrainer to the metal parts of the bearing. A partially filled retainer (such

P. A. Bertrand; D. J. Carré; Reinhold Bauer

1995-01-01

418

Effect of high hydrostatic pressure pretreatment on drying kinetics, antioxidant activity, firmness and microstructure of Aloe vera ( Aloe barbadensis Miller) gel  

Microsoft Academic Search

The effect of High Hydrostatic Pressure (HHP) and other pretreatments on the drying kinetics, antioxidant activity, firmness and microstructure of Aloe vera gel was investigated during convective drying at 70 °C. The pretreatments analyzed were high hydrostatic pressure, blanching, enzymatic and microwaves. Simulation of drying curves was studied through the application of several mathematical models such as Newton, Henderson and Pabis,

Antonio Vega-Gálvez; Elsa Uribe; Mario Perez; Gipsy Tabilo-Munizaga; Judith Vergara; Purificación Garcia-Segovia; Elena Lara; Karina Di Scala

2011-01-01

419

Valve assembly having remotely replaceable bearings  

DOEpatents

A valve assembly having remotely replaceable bearings is disclosed wherein a valve disc is supported within a flow duct for rotation about a pair of axially aligned bearings, one of which is carried by a spindle received within a diametral bore in the valve disc, and the other of which is carried by a bearing support block releasably mounted on the duct circumferentially of an annular collar on the valve disc coaxial with its diametrical bore. The spindle and bearing support block are adapted for remote removal to facilitate servicing or replacement of the valve disc support bearings.

Johnson, Evan R. (San Diego, CA) [San Diego, CA; Tanner, David E. (Poway, CA) [Poway, CA

1980-01-01

420

Automated Assistance for Designing Active Magnetic Bearings  

NASA Technical Reports Server (NTRS)

MagBear12 is a computer code that assists in the design of radial, heteropolar active magnetic bearings (AMBs). MagBear12 was developed to help in designing the system described in "Advanced Active-Magnetic-Bearing Thrust-Measurement System". Beyond this initial application, MagBear12 is expected to be useful for designing AMBs for a variety of rotating machinery. This program incorporates design rules and governing equations that are also implemented in other, proprietary design software used by AMB manufacturers. In addition, this program incorporates an advanced unpublished fringing-magnetic-field model that increases accuracy beyond that offered by the other AMB-design software.

Imlach, Joseph

2008-01-01

421

Servo Reduces Friction In Flexure Bearing  

NASA Technical Reports Server (NTRS)

Proposed servocontrol device reduces such resistive torques as stiction, friction, ripple, and cogging in flexure bearing described in LAR-14348, "Flexure Bearing Reduces Startup Friction". Reduces frictional "bump" torque encountered when bearing ball runs into buildup of grease on bearing race. Also used as cable follower to reduce torque caused by cable and hoses when they bend because of motion of bearing. New device includes torquer across ball race. Torquer controlled by servo striving to keep flexure at null, removing torque to outer ring. In effect, device is inner control loop reducing friction, but does not control platforms or any outer-control-loop functions.

Clingman, W. Dean

1991-01-01

422

Equations For Elastohydrodynamic Lubrication Of Bearings  

NASA Technical Reports Server (NTRS)

Equation for thickness of elastohydrodynamic (EHD) lubricant film in rolling-element bearing reduced to simplified form involving only inside and outside diameters of bearing, speed of rotation, parameter related to type of lubricant, and viscosity of lubricant at temperature of bearing. In addition, experimentally derived graph of EHD-film-thickness-reduction factor as function of contact-lubricant-flow number. Accounts for lubricant starvation within Hertzian contact. Graph relating ratio of minimum film thickness to composite roughness of bearing surfaces and to lubrication-life correction factor also provided. Life-correction factor used to determine resultant life of bearing.

Zaretsky, Erwin V.

1993-01-01

423

Polar Bears International: Wrangel Island, Russia  

NSDL National Science Digital Library

This site describes the ongoing research of the polar bears in the Russian High Arctic. Wrangel Island with neighboring small island, Herald Island, are the key reproductive areas for the Chukchi-Alaskan polar bear population. Marine areas and Wrangel and Herald islands provide optimum foraging habitats for polar bears, and polar bear densities in these marine habitats are high all year round. Approximately 350-500 pregnant female polar bears construct their maternity dens on Wrangel and Herald islands every fall, emerging with their cubs in spring. The research is described in terms of goals and objectives, structure, methods, equipment, staff, and implementations.

424

High-Load Multi-Rotational Bridge Bearings.  

National Technical Information Service (NTIS)

This report contains the results of a study on high-load multi-rotational bridge bearings. Information on various bearing types, including pot bearings, disk bearings, and polytetrafluorethylene (PTFE) sliding surfaces is included. Design and selection gu...

J. F. Stanton

1999-01-01

425

Design review of fluid film bearing testers  

NASA Technical Reports Server (NTRS)

The designs of three existing testers (Hybrid Bearing Tester, OTV Bearing Tester, and Long Life Bearing Tester) owned by NASA were reviewed for their capability to serve as a multi-purpose cryogenic fluid film bearing tester. The primary tester function is the validation of analytical predictions for fluid film bearing steady state and dynamic performance. Evaluation criteria were established for test bearing configurations, test fluids, instrumentation, and test objectives. Each tester was evaluated with respect to these criteria. A determination was made of design improvements which would allow the testers to meet the stated criteria. The cost and time required to make the design changes were estimated. A recommendation based on the results of this study was made to proceed with the Hybrid Bearing Tester.

Scharrer, Joseph K.

1993-01-01

426

Lubrication for high load duplex bearings  

SciTech Connect

Three ES and H-compatible lubricants (Environment, Safety and Health) for high load duplex bearing applications were evaluated and compared against trichlorotrifluoroethane (Freon) deposition of low molecular weight polytetrafluoroethylene (PTFE) bearing lubricant extracted from Vydax{trademark}. Vydax is a product manufactured by DuPont consisting of various molecular weights of PTFE suspended in trichlorotrifluoroethane (Freon) which is an ozone-depleting solvent. Bearings with Supercritical CO{sub 2} deposition of PTFE extracted from Vydax AR/IPA, bearings with titanium carbide coated balls, and bearings with diamond-like carbon races and retainers were evaluated. Bearings with Supercritical CO{sub 2} deposition of PTFE from Vydax AR/IPA performed as well as bearings with Freon deposition of PTFE from Freon-based Vydax.

Steinhoff, R.G.

1997-08-01

427

Pratt and Whitney cryogenic turbopump bearing experience  

NASA Technical Reports Server (NTRS)

Successful, reusable bearings require lubrication, traditionally, a transfer film from sacrificial cage wear. Early testing included materials screening programs to identify suitable cryogenic cage materials. A specially developed element tester that simulated the function of a ball bearing cage was used. Suitable materials must provide lubrication with an acceptably low wear rate, without abrading contacting surfaces. The most promising materials were tested in full scale bearings at speeds up to 4 MDN. Teflon, filled with 40 percent bronze powder, was the best performing material. A variety of bearings were designed and successfully tested in LH2 and LOX. Bearings with bronze filled Teflon cages were successfully tested for 150 hrs. In overload tests, the same design was tested for 5 hrs at maximum Hertz stresses above 450 ksi and an additional 5 hrs with a maximum Hertz stress exceeding 500 ksi. Four bearings were tested in LOX for 25 hrs, with a maximum time per bearing of 10 hrs.

Poole, W. E.; Bursey, R. W., Jr.

1988-01-01

428

Wave Journal Bearings Under Dynamic Loads  

NASA Technical Reports Server (NTRS)

The dynamic behavior of the wave journal bearing was determined by running a three-wave bearing with an eccentrically mounted shaft. A transient analysis was developed and used to predict numerical data for the experimental cases. The three-wave journal bearing ran stably under dynamic loads with orbits well inside the bearing clearance. The orbits were almost circular and nearly free of the influence of, but dynamically dependent on, bearing wave shape. Experimental observations for both the absolute bearing-housing-center orbits and the relative bearing-housing-center-to-shaft-center orbits agreed well with the predictions. Moreover, the subsynchronous whirl motion generated by the fluid film was found experimentally and predicted theoretically for certain speeds.

Hendricks, Robert C.; Dimofte, Florin

2002-01-01

429

Towards an energy-conserving quasi-hydrostatic deep-atmosphere dynamical core  

NASA Astrophysics Data System (ADS)

Towards an energy-conserving quasi-hydrostatic deep-atmosphere dynamical core Marine Tort1 & Thomas Dubos1 1 Laboratoire Météorologique Dynamique, Ecole Polytechnique, Palaiseau, FRANCE Atmosphere dynamics of our planet is quite well described by traditional primitive equations based on the so-called shallow-atmosphere approximation. Thus, the model is dynamically consistent (in the sense that it possesses conservation principles for mass, energy, potential vorticity and angular momentum) when certain metric terms and the cos? Coriolis terms are neglected (Phillips, 1966). Nevertheless, to simulate planetary atmospheres, the shallow-atmosphere approximation should be relaxed because of the low planet radius (such as Titan) or the depth of their atmospheres (such as Jupiter or Saturne). Non-traditional terms have some dynamical effects (Gerkema and al., 2008) but they are little-known and rarely integrated into general circulation dynamical cores (Wood and Staniforth, 2002). As an example, the french GCM of the Laboratoire Météorologique Dynamique (LMD-Z) integrates the traditional primitive equations discretized from their curl (vector-invariant) form based on a finite different scheme whose conserves exactly potential vorticity (Sadourny, 1975a,b). We considered an orthogonal curvilinear system and we first derived a curl form of global, deep-atmosphere quasi-hydrostatic model in which prognostic variable is absolute axial momentum instead of relative velocity vector. Given the close relationship between the curl form and Hamiltonian formulation of the previous equations, we generalized Sadourny's energy-conserving formulation by discretizing the Poisson bracket and the energy themselves (Salmon, 1983; Gassmann, 2013). The substantial computing infrastructure of the dynamical core is the same but the modification of the hydrostatic balance requires a mass-based vertical coordinate (Wood and Staniforth, 2003). The new discretization has been implemented into LMD-Z on a longitude-latitude horizontal grid and test cases (Held and Suarez, 1994; Ullrich et al., 2013) have been performed considering an idealized deep atmosphere (small like-Earth). They validate the accuracy and the numerical stability of the new dynamical core.

Tort, Marine; Dubos, Thomas

2014-05-01

430

Effect of hydrostatic pressure on water penetration and rotational dynamics in phospholipid-cholesterol bilayers.  

PubMed Central

The effect of high hydrostatic pressure on the lipid bilayer hydration, the mean order parameter, and rotational dynamics of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) cholesterol vesicles has been studied by time-resolved fluorescence spectroscopy up to 1500 bar. Whereas the degree of hydration in the lipid headgroup and interfacial region was assessed from fluorescence lifetime data using the probe 1-(4-trimethylammonium-phenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH), the corresponding information in the upper acyl chain region was estimated from its effect on the fluorescence lifetime of and 3-(diphenylhexatrienyl)propyl-trimethylammonium (TMAP-DPH). The lifetime data indicate a greater level of interfacial hydration for DPPC bilayers than for POPC bilayers, but there is no marked difference in interchain hydration of the two bilayer systems. The addition of cholesterol at levels from 30 to 50 mol% to DPPC has a greater effect on the increase of hydrophobicity in the interfacial region of the bilayer than the application of hydrostatic pressure of several hundred to 1000 bar. Although the same trend is observed in the corresponding system, POPC/30 mol% cholesterol, the observed effects are markedly less pronounced. Whereas the rotational correlation times of the fluorophores decrease in passing the pressure-induced liquid-crystalline to gel phase transition of DPPC, the wobbling diffusion coefficient remains essentially unchanged. The wobbling diffusion constant of the two fluorophores changes markedly upon incorporation of 30 mol% cholesterol, and increases at higher pressures, also in the case of POPC/30 mol% cholesterol. The observed effects are discussed in terms of changes in the rotational characteristics of the fluorophores and the phase-state of the lipid mixture. The results demonstrate the ability of cholesterol to adjust the structural and dynamic properties of membranes composed of different phospholipid components, and to efficiently regulate the motional freedom and hydrophobicity of membranes, so that they can withstand even drastic changes in environmental conditions, such as high external hydrostatic pressure.

Bernsdorff, C; Wolf, A; Winter, R; Gratton, E

1997-01-01

431

Calf stretching in non-weight bearing versus weight bearing.  

PubMed

Limited ankle dorsiflexion passive range of motion (DF PROM) has been associated with lower extremity overuse injuries. Therefore, clinicians often prescribe stretching exercises to increase ankle DF PROM. However, there is limited evidence to indicate if any particular gastrocnemius stretching exercise results in greater improvement in DF PROM. The aim of this study was to determine if gastrocnemius stretching in non-weight bearing (NWB) or weight bearing (WB) results in a greater increase of ankle DF PROM. 28 healthy volunteers, aged 18-55 years, who exhibited less than 10 degrees of ankle DF PROM completed the study. Participants were randomized into 2 stretching groups: NWB and WB. Both groups completed a 3-week home gastrocnemius stretching program, consisting of 5 repetitions held for 30 s each, 2 times daily. Participants' ankle DF PROM was measured with a blinded standard goniometer in NWB and WB positions before and after participation in a 3-week home gastrocnemius stretching program. Two 3-way mixed model ANOVAs demonstrated no significant difference in ankle DF PROM between the NWB and WB groups for either the NWB measurement condition (p=0.49) or WB measurement condition (p=0.86). Gastrocnemius stretching exercises performed in NWB or WB were equally effective in increasing ankle DF PROM. PMID:21181639

Dinh, N V; Freeman, H; Granger, J; Wong, S; Johanson, M

2011-03-01

432

Generation of large volume hydrostatic pressure to 8 GPa for ultrasonic studies  

NASA Astrophysics Data System (ADS)

The design and performance of a liquid-solid hybrid cell to generate high hydrostatic pressures in a relatively large volume (for use in measurements of the pressure dependence of the physical properties of materials) are reported. A 4:1 methanol-ethanol mixture is employed in 12-mm-side and 20-mm-side versions of an eight-cubic-anvil apparatus driven by a 10-kt press. Pressures up to 8 GPa are obtained safely in a 16-cu cm volume by applying uniaxial force of 3 kt. The cell is used to obtain measurements of the velocity of ultrasonic waves in fused quartz: the experimental setup is described, and sample results are presented graphically.

Kozuki, Yasushi; Yoneda, Akira; Fujimura, Akio; Sawamoto, Hiroshi; Kumazawa, Mineo

1986-09-01

433

Effect of intravenous contrast media on proximal and distal tubular hydrostatic pressure in the rat kidney.  

PubMed

The effect of i.v. injection of contrast media (CM, 1,600 mg I/kg b.w.) on proximal and distal tubular hydrostatic pressure (PTHP, DTHP) in the rat was investigated using a micropuncture technique. The PTHP and DTHP after injection of diatrizoate, iohexol, ioxaglate, or mannitol returned to control values within approximately 20 min. However, following iotrolan injection PTHP was still elevated above control levels after 35 min while DTHP remained elevated throughout the experiment (50 min). Iotrolan has a lower osmotic potential than the other CM when given in equivalent iodine doses. The concentration of iotrolan may thus increase more along the tubules than the other CM and consequently lead to a higher viscosity of urine, resulting in increases in PTHP and DTHP. The high intratubular pressure induced by iotrolan may explain our previous findings of reduced single nephron glomerular filtration rate caused by this CM. PMID:8427755

Ueda, J; Nygren, A; Hansell, P; Ulfendahl, H R

1993-01-01

434

Wave Response during Hydrostatic and Geostrophic Adjustment. Part I: Transient Dynamics.  

NASA Astrophysics Data System (ADS)

The adjustment of a compressible, stably stratified atmosphere to sources of hydrostatic and geostrophic imbalance is investigated using a linear model. Imbalance is produced by prescribed, time-dependent injections of mass, heat, or momentum that model those processes considered “external” to the scales of motion on which the linearization and other model assumptions are justifiable. Solutions are demonstrated in response to a localized warming characteristic of small isolated clouds, larger thunderstorms, and convective systems.For a semi-infinite atmosphere, solutions consist of a set of vertical modes of continuously varying wavenumber, each of which contains time dependencies classified as steady, acoustic wave, and buoyancy wave contributions. Additionally, a rigid lower-boundary condition implies the existence of a discrete mode—the Lamb mode— containing only a steady and acoustic wave contribution. The forced solutions are generalized in terms of a temporal Green's function, which represents the response to an instantaneous injection.The response to an instantaneous warming with geometry representative of a small, isolated cloud takes place in two stages. Within the first few minutes, acoustic and Lamb waves accomplish an expansion of the heated region. Within the first quarter-hour, nonhydrostatic buoyancy waves accomplish an upward displacement inside of the heated region with inflow below, outflow above, and weak subsidence on the periphery—all mainly accomplished by the lowest vertical wavenumber modes, which have the largest horizontal group speed. More complicated transient patterns of inflow aloft and outflow along the lower boundary are accomplished by higher vertical wavenumber modes. Among these is an outwardly propagating rotor along the lower boundary that effectively displaces the low-level inflow upward and outward.A warming of 20 min duration with geometry representative of a large thunderstorm generates only a weak acoustic response in the horizontal by the Lamb waves. The amplitude of this signal increases during the onset of the heating and decreases as the heating is turned off. The lowest vertical wavenumber buoyancy waves still dominate the horizontal adjustment, and the horizontal scale of displacements is increased by an order of magnitude. Within a few hours the transient motions remove the perturbations and an approximately trivial balanced state is established.A warming of 2 h duration with geometry representative of a large convective system generates a weak but discernible Lamb wave signal. The response to the conglomerate system is mainly hydrostatic. After several hours, the only signal in the vicinity of the heated region is that of inertia-gravity waves oscillating about a nontrivial hydrostatic and geostrophic state.This paper is the first of two parts treating the transient dynamics of hydrostatic and geostrophic adjustment. Part II examines the potential vorticity conservation and the partitioning of total energy.

Chagnon, Jeffrey M.; Bannon, Peter R.

2005-05-01

435

High structural stability of single wall carbon nanotube under quasi-hydrostatic high pressures  

SciTech Connect

In quasi-hydrostatic conditions, single wall carbon nanotubes (SWNTs) exhibit high structural stability to {approx}35 GPa, well beyond the stability of sp{sup 2} C{double_bond}C bonds in graphite, carbon fullerenes, benzene, and other hydrocarbons. The pressure-induced Raman changes of SWNT are completely reversible below 16 GPa, partially reversible between 16 and 35 GPa, and irreversible beyond 35 GPa where it turns into highly disordered graphite. We explain the high stability in terms of the pressure-induced structural modification to an interlinked configuration, which occurs reversibly under substantial sp{sup 3} hybridization ({approx}20%) and, thus, increases the stability of sp{sup 2} C{double_bond}C bonds in the SWNTs.

Chen, Jing-Yin; Kim, Minseob; Yoo, Choong-Shik; (WSU)

2009-11-23

436

Selective reduction of ketones using water as a hydrogen source under high hydrostatic pressure.  

PubMed

A selective reduction of a broad variety of ketones is described. The method is based on the combination of a Ni-Al alloy and high hydrostatic pressure (HHP, 2.8 kbar) in an aqueous medium. The reaction of the Ni-Al alloy with water provides in situ hydrogen generation and the high pressure ensures that the H(2) formed remains in the solution, thus the C=O reduction readily occurs. The application of the HHP resulted in selective formation of the desired products and the common problem of non-selective overhydrogenation could be avoided. In most cases the reductions resulted in high yields and excellent selectivities without the use of any base. PMID:22868406

Tomin, Anna; Lazarev, Alexander; Bere, Matthew P; Redjeb, Hana; Török, Béla

2012-09-28

437

A system for acoustical and optical analysis of encapsulated microbubbles at ultrahigh hydrostatic pressures.  

PubMed

Acoustics are commonly used for borehole (i.e., oil well) imaging applications, under conditions where temperature and pressure reach extremes beyond that of conventional medical ultrasonics. Recently, there has been an interest in the application of encapsulated microbubbles as borehole contrast agents for acoustic assessment of fluid composition and flow. Although such microbubbles are widely studied under physiological conditions for medical imaging applications, to date there is a paucity of information on the behavior of encapsulated gas-filled microbubbles at high pressures. One major limitation is that there is a lack of experimental systems to assess both optical and acoustic data of micrometer-sized particles data at these extremes. In this paper, we present the design and application of a high-pressure cell designed for acoustical and optical studies of microbubbles at hydrostatic pressures up to 27.5 MPa (271 atm). PMID:23742587

Zhushma, Aleksandr; Lebedeva, Natalia; Sen, Pabitra; Rubinstein, Michael; Sheiko, Sergei S; Dayton, Paul A

2013-05-01

438

Hydrostatic pressure effects on structural and electronic properties of TATB from first principles calculations  

NASA Astrophysics Data System (ADS)

The structural and electronic properties of crystalline 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) has been investigated within the framework of density functional theory including van der Waals interactions. The predicted crystal structure compares well with the experimental results at the ambient pressure. The computed lattice parameters and lattice energy have good agreement with experimental data. We study on the structural and electronic properties of the TATB under the hydrostatic pressure of 0-40 GPa. In addition, the electronic structure of the TATB has been studied as a function of uniaxial compression. The isothermal equations of state calculated from the results show good agreement with experiment in the pressure intervals studied. We have also calculated the quasiparticle band structure of TATB with the G0W0 approximation.

Fedorov, Igor A.; Zhuravlev, Yuriy N.

2014-06-01

439

The effect of high hydrostatic pressure on black truffle (tuber melanosporum) flavour compounds  

NASA Astrophysics Data System (ADS)

The effects of high hydrostatic pressure (HHP), at 4°C or -18°C, on black truffle flavour compounds, alteration enzymes (lipoxigenase (LOX), peroxidase (POD) and polyphenoloxidase (PPO)) and microbiological qualities were evaluated. The choosen analytes for this study are six alcohols, three aldehydes, one ketone and on sulfur component. The highest flavour stability was observed when samples were pressurized at 300 MPa / 4°C / 10 min. All the treatments induced a drastic decrease of LOX activity and a slight decrease of POD activity. On the other hand, the PPO was not inactivated by pressurization at sub-zero (200 MPa / -18°C / 10 min) and was strongly increased after the 300 MPa / 4°C / 10 min treatment. Pressurization at 300 and 550 MPa lead to an almost complete Pseudomonas fluorescens reduction (6 and 6.5 log destruction, respectively) whereas pressurization at -18°C (200MPa) allowed to obtain only 3 log reduction.

Verret, C.; Ballestra, P.; Cruz, C.; Pardon, P.; Largeteau, A.; Moueffak, A. H. E.

2008-07-01

440

Hydrostatically pressurized buckling of complete spherical shells filled with an elastic medium  

NASA Astrophysics Data System (ADS)

The critical buckling characteristics of hydrostatically pressurized complete spherical shells filled with an elastic medium are presented. A model based on small deflection thin shell theory, the equations of which are solved using exact methods in conjunction with variational principles, is presented. In the current formulation, axisymmetric and inextensional assumptions are not used initially and the elastic medium is modelled as a Winkler foundation, i.e.using uncoupled radial springs with a constant foundation modulus that is independent of wave numbers of shell buckling modes. Critical buckling pressures and characteristic modal shapes are demonstrated for a wide range of material and geometric parameters. A phase diagram is established to obtain the requisite thickness to radius, and stiffness ratios for a desired mode profile. The present formulation can be readily extended to apply to more general cases of non-axisymmetric buckling problems.

Sato, Motohiro; Wadee, M. Ahmer; Sekizawa, Takafumi; Iiboshi, Kohtaroh; Shima, Hiroyuki

441

Physical balances in non-hydrostatic balanced quasi-geostrophic equations  

NASA Astrophysics Data System (ADS)

A suite of high resolution DNS for Rotating Rayleigh Benard convection using the non-hydrostatic balanced geostophic equations (NHBGE) (Julien et al 1998, 2006) over a wide range of parameter space was conducted to allow for the analysis of the term-by-term balances of the prognostic equations. These reduced equations offer greater access to the Low Rossby limit of thermal convection in comparison to the DNS of incompressible Navier-Stokes. The result has been a greater understanding of the transition between three regimes (cellular, columns, geostrophic turbulence) in terms of physical balances. Particularly, analysis reveals a dynamically unstable thermal boundary layer that can be modeled and turbulent interiors for which scalings with thermal forcing can be understood. Further insight has been gained into the scaling and breakdown of the convective Taylor columns (CTCs) (Grooms et al PRL, 2011) and the equation balances inside and outside of the CTCs in regimes where they coexist with cellular solutions.

Julien, Keith; Rubio, Antonio; Grooms, Ian

2011-11-01

442

A coupled analytical model for hydrostatic response of 1-3 piezocomposites.  

PubMed

This study presents a fully coupled analysis of a unit cell of a 1-3 piezocomposite under hydrostatic loading. The governing equations for coupled axisymmetric electroelastic field of a transversely isotropic piezoelectric medium and a transversely isotropic elastic medium are used. A reduced form of the analytical general solutions expressed in terms of series of modified Bessel functions of the first and second kind are used. The solution of the boundary-value problem corresponding to a unit cell is presented. The effective properties of a 1-3 piezocomposite are obtained for different fiber volume fractions, polymer and piezoceramic properties, and fiber aspect ratios. Comparisons with previously reported simplified and uncoupled models are made. PMID:18986927

Rajapakse, Nimal; Chen, Yue

2008-08-01

443

High hydrostatic pressure effects investigated by neutron scattering on lipid multilamellar vesicles.  

PubMed

The effects of high hydrostatic pressure on the structure and dynamics of model membrane systems were investigated using neutron scattering. Diffraction experiments show shifts of the pre- and main-phase transitions of multilamellar vesicles of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) to higher temperatures with increased pressure which are close to results observed previously by other techniques, namely (10.4 ± 1.0) K kbar(-1) and (20.0 ± 0.5) K kbar(-1) for the two transitions. Backscattering spectroscopy reveals that the mean square displacements in the liquid phase are about 10% smaller at 300 bar and about 20% smaller at 600 bar compared to atmospheric pressure, whereas in the gel phase below the main phase transition the mean square displacements show a smaller difference in the dynamics of the three pressure values within the studied pressure range. PMID:24201561

Trapp, Marcus; Marion, Jérémie; Tehei, Moeava; Demé, Bruno; Gutberlet, Thomas; Peters, Judith

2013-12-28

444

High-Precision Simulation of the Gravity Field of Rapidly-Rotating Barotropes in Hydrostatic Equilibrium  

NASA Astrophysics Data System (ADS)

The so-called theory of figures (TOF) uses potential theory to solve for the structure of highly distorted rotating liquid planets in hydrostatic equilibrium. TOF is noteworthy both for its antiquity (Maclaurin 1742) and its mathematical complexity. Planned high-precision gravity measurements near the surfaces of Jupiter and Saturn (possibly detecting signals ~ microgal) will place unprecedented requirements on TOF, not because one expects hydrostatic equilibrium to that level, but because nonhydrostatic components in the surface gravity, at expected levels ~ 1 milligal, must be referenced to precise hydrostatic-equilibrium models. The Maclaurin spheroid is both a useful test of numerical TOF codes (Hubbard 2012, ApJ Lett 756:L15), and an approach to an efficient TOF code for arbitrary barotropes of variable density (Hubbard 2013, ApJ 768:43). For the latter, one trades off vertical resolution by replacing a continuous barotropic pressure-density relation with a stairstep relation, corresponding to N concentric Maclaurin spheroids (CMS), each of constant density. The benefit of this trade-off is that two-dimensional integrals over the mass distributions at each interface are reduced to one-dimensional integrals, quickly and accurately evaluated by Gaussian quadrature. The shapes of the spheroids comprise N level surfaces within the planet and at its surface, are gravitationally coupled to each other, and are found by self-consistent iteration, relaxing to a final configuration to within the computer's precision limits. The angular and radial variation of external gravity (using the usual geophysical expansion in multipole moments) can be found to the limit of typical floating point precision (~ 1.e-14), much better than the expected noise/signal for either the Juno or Cassini gravity experiments. The stairstep barotrope can be adjusted to fit a prescribed continuous or discontinuous interior barotrope, and can be made to approximate it to any required precision by increasing N. One can insert a higher density of CMSs toward the surface of an interior model in order to more accurately model high-order gravitational moments. The magnitude of high-order moments predicted by TOF declines geometrically with order number, and falls below the magnitude of expected non-hydrostatic terms produced by interior dynamics at ~ order 10 and above. Juno's sensitivity is enough to detect tidal gravity signals from Galilean satellites. The CMS method can be generalized to predict tidal zonal and tesseral terms consistent with an interior model fitted to measured zonal harmonics. For this purpose, two-dimensional Gaussian quadrature is necessary at each CMS interface. However, once the model is relaxed to equilibrium, one need not refit the model to the average zonal harmonics because of the smallness of the tidal terms. I will describe how the CMS method has been validated through comparisons with standard TOF models for which fully or partially analytic solutions exist, as well as through consistency checks. At this stage in software development in preparation for Jupiter orbit, we are focused on increasing the speed of the code in order to more efficiently search the parameter space of acceptable Jupiter interior models, as well as to interface it with advanced hydrogen-helium equations of state.

Hubbard, W. B.

2013-12-01

445

Density Measurement System for Weights of 1 kg to 20 kg Using Hydrostatic Weighing  

NASA Astrophysics Data System (ADS)

This paper presents a density measurement system to determine density of weights from 1 kg to 20 kg using hydrostatic weighing. The system works based on Archimedes principle. The density of reference liquid is determined using this setup while determining the density of the test weight. Density sphere is used as standard density ball to determine density of the reference liquid. A new immersion pan is designed for dual purpose to carry the density sphere and the cylindrical test weight for weighing in liquid. Main parts of the setup are an electronic balance, a thermostat controlled liquid bath, reference weights designed for bottom weighing, dual purpose immersion pans and stepping motors to load and unload in weighing process. The results of density measurement will be evaluated as uncertainties for weights of 1 kg to 20 kg.

Lee, Yong Jae; Lee, Woo Gab; Abdurahman, Mohammed; Kim, Kwang Pyo

446

Weighing Galaxy Clusters with Gas. II. On the Origin of Hydrostatic Mass Bias in ?CDM Galaxy Clusters  

NASA Astrophysics Data System (ADS)

The use of galaxy clusters as cosmological probes hinges on our ability to measure their masses accurately and with high precision. Hydrostatic mass is one of the most common methods for estimating the masses of individual galaxy clusters, which suffer from biases due to departures from hydrostatic equilibrium. Using a large, mass-limited sample of massive galaxy clusters from a high-resolution hydrodynamical cosmological simulation, in this work we show that in addition to turbulent and bulk gas velocities, acceleration of gas introduces biases in the hydrostatic mass estimate of galaxy clusters. In unrelaxed clusters, the acceleration bias is comparable to the bias due to non-thermal pressure associated with merger-induced turbulent and bulk gas motions. In relaxed clusters, the mean mass bias due to acceleration is small (lsim 3%), but the scatter in the mass bias can be reduced by accounting for gas acceleration. Additionally, this acceleration bias is greater in the outskirts of higher redshift clusters where mergers are more frequent and clusters are accreting more rapidly. Since gas acceleration cannot be observed directly, it introduces an irreducible bias for hydrostatic mass estimates. This acceleration bias places limits on how well we can recover cluster masses from future X-ray and microwave observations. We discuss implications for cluster mass estimates based on X-ray, Sunyaev-Zel'dovich effect, and gravitational lensing observations and their impact on cluster cosmology.

Nelson, Kaylea; Lau, Erwin T.; Nagai, Daisuke; Rudd, Douglas H.; Yu, Liang

2014-02-01

447

An experimental investigation into the design and performance of hydrostatically loaded floating wear plates in gear pumps  

Microsoft Academic Search

The design principles and the performance of hydrostatically loaded wear (end) plates in three high-pressure external gear pumps were examined experimentally while the pumps were running under typical operating conditions. The film thicknesses (clearances) between the gears and end closures (plates) in three different designs of floating plate gear pump were measured. It was found that at high delivery pressures

E. Koç; C. J. Hooke

1997-01-01

448

Review: Potential of High Hydrostatic Pressure and Pulsed Electric Fields for Energy Efficient and Environmentally Friendly Food Processing  

Microsoft Academic Search

The application of emerging, novel processing techniques such as high hydrostatic pressure or pulsed electric fields can be utilized to replace, enhance or modify conventional techniques of food production. In addition to quality improvements and consumer benefits by gentle microbial inactivation and improvement of mass transfer processes, their potential to improve energy efficiency and sustainability of food production will be

S. Toepfl; A. Mathys; V. Heinz; D. Knorr

2006-01-01

449

High hydrostatic pressure effects on mold flora, citrinin mycotoxin, hydroxytyrosol, oleuropein phenolics and antioxidant activity of black table olives  

Microsoft Academic Search

High hydrostatic pressure (HHP) as a non-thermal technology is an effective tool for microbiologically safe and shelf-stable fruits. Mycotoxin citrinin (CIT) is a toxic secondary metabolite, especially produced from filamentous fungus Penicillium citrinum and is also produced by other species of Penicillium, Aspergillus, and Monascus that are able to develop on olive after harvest, during brine and storage of olives.

Özlem Toku?o?lu; Hami Alpas; Faruk Bozo?lu

2010-01-01

450

Evolution of Quasiparticle Properties in UGe2 with Hydrostatic Pressure Studied via the de Haas-van Alphen Effect  

Microsoft Academic Search

We report measurements of the de Haas-van Alphen effect in UGe 2 under hydrostatic pressures up to 17.6 kbar, exceeding the critical pressure Pc for the suppression of ferromagnetism. A discontinuous change of the Fermi surface is found to occur across Pc. Substantially enhanced effective masses (~40me) are found near Pc on both the ferromagnetic and the paramagnetic sides.

T. Terashima; T. Matsumoto; C. Terakura; S. Uji; N. Kimura; M. Endo; T. Komatsubara; H. Aoki

2001-01-01

451

Effect of high hydrostatic pressure on functional properties and quality characteristics of Aloe vera gel ( Aloe barbadensis Miller)  

Microsoft Academic Search

The aim of this study was to evaluate the effects of high hydrostatic pressure treatment at three pressure levels (300, 400 and 500Mpa) on the functional and quality characteristics of Aloe vera gel including vitamin C and E, aloin, minerals, phenolic content and antioxidant activity. The results show that HHP exerted a clear influence on minerals content, vitamin C and

Antonio Vega-Gálvez; Margarita Miranda; Mario Aranda; Karem Henriquez; Judith Vergara; Gipsy Tabilo-Munizaga; Mario Pérez-Won

2011-01-01

452

Evolution of dilatancy and permeability in rock salt during hydrostatic compaction and triaxial deformation  

NASA Astrophysics Data System (ADS)

Combined gas permeability and P and S wave velocity measurements were carried out on rock salt samples from the Gorleben salt dome and the Morsleben salt mine under hydrostatic and triaxial loading condions, mostly at room temperature. Permeabilities in the as-received samples vary between 10-16 and 2×10-20 m2. The initial permeability is primarily due to decompaction induced by drilling, core retrieval and sample preparation. Hydrostatic loading gives rise to a marked decrease of permeability and a coeval significant increase of P and S wave velocities due to progressive closure of grain boundary cracks, tending to approach the in situ matrix permeability (<10-20 m2). The pore space sensitivity of P and S wave velocities is used to monitor the in situ state of the microstructure. Their reversals define the boundary in the state of stresses between dilatant and compactive domains (dilatancy boundary). Dilatancy during triaxial deformation of the compacted rock salt samples is found to evolve stress dependent in various stages. The crack initiation stress increases from ˜18 MPa differential stress at 10 MPa confining pressure to ˜30 MPa at confining pressures above ˜70 MPa. Dilatancy is due to the opening of grain boundary and (100) cleavage cracks and depends on the applied confining pressure. The orientation of the open cracks is primarily controlled by the loading geometry system (compression, extension). As a consequence, permeability increases dramatically with progressive dilatancy, followed by a period of plus/minus constant permeability during strain hardening up to 10% axial strain or even more. This suggests that the evolution of permeability is not only a function of dilatancy but also of microcrack linkage. Importantly, the anisotropic crack array within the samples causes a strong directional dependence of permeability.

Popp, Till; Kern, Hartmut; Schulze, Otto

2001-01-01

453

Effects of High Hydrostatic Pressure on Bacterial Growth on Human Ossicles Explanted from Cholesteatoma Patients  

PubMed Central

Background High hydrostatic pressure (HHP) treatment can eliminate cholesteatoma cells from explanted human ossicles prior to re-insertion. We analyzed the effects of HHP treatment on the microbial flora on ossicles and on the planktonic and biofilm states of selected isolates. Methodology Twenty-six ossicles were explanted from cholesteatoma patients. Five ossicles were directly analyzed for microbial growth without further treatment. Fifteen ossicles were cut into two pieces. One piece was exposed to HHP of 350 MPa for 10 minutes. Both the treated and untreated (control) pieces were then assessed semi-quantitatively. Three ossicles were cut into two pieces and exposed to identical pressure conditions with or without the addition of one of two different combinations of antibiotics to the medium. Differential effects of 10-minute in vitro exposure of planktonic and biofilm bacteria to pressures of 100 MPa, 250 MPa, 400 MPa and 540 MPa in isotonic and hypotonic media were analyzed using two patient isolates of Staphylococcus epidermidis and Neisseria subflava. Bacterial cell inactivation and biofilm destruction were assessed by colony counting and electron microscopy. Principal Findings A variety of microorganisms were isolated from the ossicles. Irrespective of the medium, HHP treatment at 350 MPa for 10 minutes led to satisfying but incomplete inactivation especially of Gram-negative bacteria. The addition of antibiotics increased the efficacy of elimination. A comparison of HHP treatment of planktonic and biofilm cells showed that the effects of HPP were reduced by about one decadic logarithmic unit when HPP was applied to biofilms. High hydrostatic pressure conditions that are suitable to inactivate cholesteatoma cells fail to completely sterilize ossicles even if antibiotics are added. As a result of the reduced microbial load and the viability loss of surviving bacteria, however, there is a lower risk of re-infection after re-insertion.

Ostwald, Jurgen; Lindner, Tobias; Zautner, Andreas Erich; Arndt, Kathleen; Pau, Hans Wilhelm; Podbielski, Andreas

2012-01-01

454

Radial deformation and stability of single-wall carbon nanotubes under hydrostatic pressure  

NASA Astrophysics Data System (ADS)

In this paper we have developed a theory of energetics for isolated single-wall carbon nanotubes (SWNTs) deformed in the radial direction, and applied this theory to investigate their deformation characteristics and stability under hydrostatic pressure. The starting point of the theory is the strain energy of SWNTs predicted by ab initio calculations based on the density functional theory (DFT), which shows the same behavior as that obtained for the continuum elastic shell model. We extend this result for inflated SWNTs with circular cross section to calculate the deformation energy of a deformed SWNT without performing further DFT calculations. This extension is then complemented by a van der Waals interaction, which is not fully taken into account in the DFT approximations currently in use but becomes important in highly deformed tubes. We find that the minimum pressure, P1 , for the radial deformation to occur is proportional to the inverse cube of tube diameter, D , in agreement with the recent theoretical predictions as well as the classical theory of buckling. The radial deformation of SWNTs with D<2.5nm is found to be elastic up to very high pressure and they hardly collapse. On the other hand, SWNTs with D>2.5nm show a plastic deformation and collapse if the applied hydrostatic pressure exceeds a critical value, which is about 30 40% higher than P1 and also varies as D-3 though approximately. These SWNTs with large D collapse when the cross-sectional area is about 60% reduced with respect to the circular one. It is also found that for SWNTs with D>7.0nm , the plastically deformed (collapsed) state is more stable than the inflated one. This critical value of D is somewhat larger than previously predicted.

Hasegawa, Masayuki; Nishidate, Kazume

2006-09-01

455

Hydrostatic pressure effect on magnetic hysteresis parameters of multidomain magnetite: Implication for crustal magnetization  

NASA Astrophysics Data System (ADS)

Hydrostatic pressure effects on magnetic parameters for crustal rock have been poorly investigated yet, while it is important for an understanding of source of long-wavelength magnetic anomaly, which is considered to reside in deep crust. In this study we have conducted the in situ magnetic hysteresis measurements on multidomain (MD) magnetite under high pressure up to 1 GPa. With special attention to hydrostatic condition and sample preparation, pressure dependences of its magnetic hysteresis parameters (saturation magnetization, Ms; saturation remanence, Mrs; coercivity, Bc; coercivity of remanence, Bcr) are revealed as follows: (1) Bc monotonically increases with pressure at a rate of +91%/GPa; (2) Ms is constant under high pressure up to 1 GPa; (3) Mrs increases with pressure up to 0.5 GPa by ?30% and reaches to saturation above the pressure; (4) Bcr is nearly constant at low pressure, and it increases above ?0.6 GPa; and (5) the changes in ratios Mrs/Ms and Bcr/Bc correlate with each other, resulting in systematic movement on the Day plot. These findings allow us to estimate change in a relaxation time of magnetic remanence carried by MD magnetite as a function of depth in the continental crust. In the model calculation, we consider no effect of plastic deformation on magnetic properties of magnetite, and the relaxation time is calculated using the theoretical thermal gradient. In consequence, the relaxation time monotonously decreases with depth, and primary remanence is considered to be replaced by a viscous remanent magnetization (VRM) over the Brunhes chron. Therefore, it is suggested that MD magnetite in deep crustal rocks can contribute to the source of the anomaly over the continental crust by VRM and induced magnetization.

Sato, Masahiko; Yamamoto, Yuhji; Nishioka, Takashi; Kodama, Kazuto; Mochizuki, Nobutatsu; Tsunakawa, Hideo

2014-08-01

456

Effects of a Planetary Gap on the Hydrostatic Structure of a Proto-planetary Disk  

NASA Astrophysics Data System (ADS)

We study the effects of a planetary gap on the hydrostatic structure of a proto-planetary disk. Such a gap produces a bright ring surrounding the dark gap in scattered light images because stellar radiation that would have been scattered (and absorbed) by material within in the gap is instead reprocessed by the disk wall at the outer edge of the gap (Varnière et al. 2005). The light absorbed by the outer wall raises its temperature, which increases the disk scale height at that location. As a result, the outer wall of the gap will shadow the outer region of the disk. Here we investigate whether or not this self-shadowing will lead to a collapse of the outer disk as suggested by Dullemond & Dominik (2004). Using a 3-D Monte Carlo radiation transfer code to determine the disk temperature and hydrostatic structure, we find that the disk scale height at the outer wall is indeed larger, but only over a rather small distance. In particular, we observe that the outer disk does not ``collapse''. This behavior is exactly analogous to that of the inner wall of the disk (at the dust destruction radius). As discussed by Walker et al. (2005), all disks are self-shadowed; collapse only occurs for steep power laws of the surface density (and not for steady-state accretion models). We conclude that the presence of the gap does not significantly alter the overall structure of the disk; it only affects the disk locally in the vicinity of the gap. This work was supported by NSF grants AST-0307686.

Bjorkman, J. E.; Whitney, B. A.; Wood, K.

2005-12-01

457

Suzaku Observations of the Outskirts of A1835: Deviation from Hydrostatic Equilibrium  

NASA Astrophysics Data System (ADS)

We present results of four-pointing Suzaku X-ray observations (total ~200 ks) of the intracluster medium (ICM) in the A1835 galaxy cluster (kT ~ 8 keV, z = 0.253) out to the virial radius (r vir ~ 2.9 Mpc) and beyond. Faint X-ray emission from the ICM out to r vir is detected. The temperature gradually decreases with radius from ~8 keV in the inner region to ~2 keV at r vir. The entropy profile is shown to flatten beyond r 500, in disagreement with the r 1.1 dependence predicted from the accretion shock heating model. The thermal pressure profile in the range 0.3r 500 <~ r <~ r vir agrees well with that obtained from the stacked Sunyaev-Zel'dovich effect observations with the Planck satellite. The hydrostatic mass profile in the cluster outskirts (r 500 <~ r <~ r vir) falls well short of the weak-lensing one derived from Subaru/Suprime-Cam observations, showing an unphysical decrease with radius. The gas mass fraction at r vir defined with the lensing total mass agrees with the cosmic baryon fraction from the Wilkinson Microwave Anisotropy Probe seven-year data. All these results indicate, rather than the gas-clumping effect, that the bulk of the ICM in the cluster outskirts is far from hydrostatic equilibrium and infalling matter retained some of its kinetic energy. Finally, combining with our recent Suzaku and lensing analysis of A1689, a cluster of similar mass, temperature, and redshift, we show that the cluster temperature distribution in the outskirts is significantly correlated with the galaxy density field in the surrounding large-scale environment at (1-2)r vir.

Ichikawa, Kazuya; Matsushita, Kyoko; Okabe, Nobuhiro; Sato, Kosuke; Zhang, Y.-Y.; Finoguenov, A.; Fujita, Yutaka; Fukazawa, Yasushi; Kawaharada, Madoka; Nakazawa, Kazuhiro; Ohashi, Takaya; Ota, Naomi; Takizawa, Motokazu; Tamura, Takayuki; Umetsu, Keiichi

2013-04-01

458

Transfer Lubrication For Cryogenic Bearings  

NASA Technical Reports Server (NTRS)

Report presents evaluation of bronze-filled polytetrafluoroethylene (PTFE), known as Salox M, as cage material for ball bearings in high-pressure turbopumps for liquid oxygen. Material evaluated as potentially longer-lived replacement for glass-filled PTFE, known as Armalon. Cage transfers PTFE to balls to form solid lubricant film. However, glass fibers in glass-filled material tend to interfere with transfer. Two cage-design concepts developed; one involves metal-reinforced cage of bronze-filled PTFE; other calls for bronze-filled PTFE inserts in metal structure.

Barber, S. A.; Kannel, J. W.; Dufrane, K. F.

1988-01-01

459

Precision magnetic suspension linear bearing  

NASA Technical Reports Server (NTRS)

We have shown the design and analyzed the electromechanics of a linear motor suitable for independently controlling two suspension degrees of freedom. This motor, at least on paper, meets the requirements for driving an X-Y stage of 10 Kg mass with about 4 m/sq sec acceleration, with travel of several hundred millimeters in X and Y, and with reasonable power dissipation. A conceptual design for such a stage is presented. The theoretical feasibility of linear and planar bearings using single or multiple magnetic suspension linear motors is demonstrated.

Trumper, David L.; Queen, Michael A.

1992-01-01

460

Hunting Bears with a Microscope  

NSDL National Science Digital Library

In this online activity, students use lichens and tardigrades (water bears) to investigate their use as bioindicators of key air pollutants. When lichens are exposed to some kinds of air pollutants, especially to sulfur dioxide, the lichens are injured and die. The lichen coverage in a specified area should be a good indicator of the level of air quality. The diversity of the tardigrade species on the lichens will be used to develop another level for bioindication of air quality. Sections of this activity include: introduction, sulfur dioxide and lichens, sampling procedure for lichen coverage, tardigrade sampling, sampling procedure for tardigrades, calculating diversity using the Simpson Diversity Index, interpretation of results, and references.

Case, Steve; Excellence, The N.

461

Phylum: Tardigrada (water bears, tardigrades)  

NSDL National Science Digital Library

This web page describes water bears, minute animals that can remain dormant in a dry state for over 100 years. The page addresses what they are, where they are found, their general biology, cryptobiosis, their ability to resist environmental extremes, implications and further research regarding their cryptobiosis, where they fit in with other animals, and their existence in South Africa. It also describes how someone could collect and see them. The page is part of Biodiversity Explorer, a web site hosted by Iziko Museums of Cape Town that features the diversity of life in South Africa.

Middleton, Roger; Town, Iziko M.

462

Current Status of Hybrid Bearing Damage Detection  

NASA Technical Reports Server (NTRS)

Advances in material development and processing have led to the introduction of ceramic hybrid bearings for many applications. The introduction of silicon nitride hybrid bearings into the high pressure oxidizer turbopump, on the space shuttle main engine, led NASA to solve a highly persistent and troublesome bearing problem. Hybrid bearings consist of ceramic balls and steel races. The majority of hybrid bearings utilize Si3N4 balls. The aerospace industry is currently studying the use of hybrid bearings and naturally the failure modes of these bearings become an issue in light of the limited data available. In today s turbine engines and helicopter transmissions, the health of the bearings is detected by the properties of the debris found in the lubrication line when damage begins to occur. Current oil debris sensor technology relies on the magnetic properties of the debris to detect damage. Since the ceramic rolling elements of hybrid bearings have no metallic properties, a new sensing system must be developed to indicate the system health if ceramic components are to be safely implemented in aerospace applications. The ceramic oil debris sensor must be capable of detecting ceramic and metallic component damage with sufficient reliability and forewarning to prevent a catastrophic failure. The objective of this research is to provide a background summary on what is currently known about hybrid bearing failure modes and to report preliminary results on the detection of silicon nitride debris, in oil, using a commercial particle counter.

Dempsey, Paula J.; Certo, Joseph M.; Morales, Wilfredo

2004-01-01

463

Interference Fit Life Factors for Roller Bearings  

NASA Technical Reports Server (NTRS)

The effect of hoop stresses in reducing cylindrical roller bearing fatigue life was determined for various classes of inner ring interference fit. Calculations were performed for up to seven interference fit classes for each of ten bearing sizes. Each fit was taken at tightest, average and loosest values within the fit class for RBEC-5 tolerance, thus requiring 486 separate analyses. The hoop stresses were superimposed on the Hertzian principal stresses created by the applied radial load to calculate roller bearing fatigue life. The method was developed through a series of equations to calculate the life reduction for cylindrical roller bearings based on interference fit. All calculated lives are for zero initial bearing internal clearance. Any reduction in bearing clearance due to interference fit was compensated by increasing the initial (unmounted) clearance. Results are presented as tables and charts of life factors for bearings with light, moderate and heavy loads and interference fits ranging from extremely light to extremely heavy and for bearing accuracy class RBEC 5 (ISO class 5). Interference fits on the inner bearing ring of a cylindrical roller bearing can significantly reduce bearing fatigue life. In general, life factors are smaller (lower life) for bearings running under light load where the unfactored life is highest. The various bearing series within a particular bore size had almost identical interference fit life factors for a particular fit. The tightest fit at the high end of the RBEC-5 tolerance band defined in ANSI/ABMA shaft fit tables produces a life factor of approximately 0.40 for an inner-race maximum Hertz stress of 1200 MPa (175 ksi) and a life factor of 0.60 for an inner-race maximum Hertz stress of 2200 MPa (320 ksi). Interference fits also impact the maximum Hertz stress-life relation.

Oswald, Fred B.; Zaretsky, Erwin V.; Poplawski, Joseph V.

2008-01-01

464

Mechanics of superconducting magnetic bearings  

SciTech Connect

Levitation forces and lateral forces in relation to the gaps in superconducting bearings were measured using a beam-and-camera system. Dynamic magnetic stiffness derived from vibration tests were compared to static magnetic stiffness. The relaxation of magnetic forces as a function of time was measured as well. The behavior of levitation forces at temperatures from 4.2 K to 77 K were studied. A rotor equipped with two superconducting bearings was fabricated and was spun up to 120,000 RPM. The drag torques acting on the rotor were measured at both atmospheric pressure and at a partial vacuum of a few mm Hg. Many high-temperature superconductors of different compositions fabricated through different processing techniques were investigated by measuring the magnetic force-gap relationships. The data indicated that YBa{sub 2}Cu{sub 3}O{sub 7} specimens made of melt-quench process produced the largest magnetic forces obtained in the laboratory so far. Models predicting the magnetic forces between superconductors and externally applied magnetic fields were studied. A numerical scheme based on the magnetization model was developed. The calculated levitation force-gap relationships showed a reasonable agreement with experimental results.

Chang, Peizen.

1991-01-01

465

The dual action gas thrust bearing - A new high load bearing concept  

NASA Technical Reports Server (NTRS)

The principle of utilizing hydrodynamic effects in diverging films for improving load capacity in gas thrust bearings is discussed. A new concept of dual action bearing based on that principle is described and analyzed. The potential of the new bearing is demonstrated both analytically for an infinitely long slider and by numerical solution for a flat sector shaped thrust bearing. It is shown that the dual action bearing can extend substantially the range of load carrying capacity in gas lubricated thrust bearings and improve their efficiency.

Etsion, I.

1976-01-01

466

Cryogenic fluid film bearing tester development study  

NASA Technical Reports Server (NTRS)

Conceptual designs were developed for the determination of rotordynamic coefficients of cryogenic fluid film bearings. The designs encompassed the use of magnetic and conventional excitation sources as well as the use of magnetic bearings as support bearings. Test article configurations reviewed included overhung, floating housing, and fixed housing. Uncertainty and forced response analyses were performed to assess quality of data and suitability of each for testing a variety of fluid film bearing designs. Development cost and schedule estimates were developed for each design. Facility requirements were reviewed and compared with existing MSFC capability. The recommended configuration consisted of a fixed test article housing centrally located between two magnetic bearings. The