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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

Design of a low cost hydrostatic bearing  

E-print Network

This thesis presents the design and manufacturing method for a new surface self compensating hydrostatic bearing. A lumped resistance model was used to analyze the performance of the bearing and provide guidance on laying ...

Wong, Anthony Raymond

2012-01-01

3

Design, dynamic modeling, simulation and feedback control of hydrostatic bearing  

E-print Network

A hydrostatic bearing carriage (Hydrocline) that uses an open face linear motor to drive the carriage as well as to preload the hydrostatic bearings has been developed by Professor Alexander Slocum and Gerald Rothenhöfer ...

Rothenhöfer, Gerald S. (Gerald Sven)

2007-01-01

4

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.

Fincke, James R. (Rigby, ID)

1982-01-01

5

Hybrid hydrostatic/ball bearings in high-speed turbomachinery  

NASA Technical Reports Server (NTRS)

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 original conventional ball bearing packages. The design, analysis, turbopump modification, assembly, and testing of the turbopump with hybrid bearings is presented here. Initial design considerations and rotordynamic performance analysis was made to define expected turbopump operating characteristics and are reported. The results of testing the turbopump to speeds of 9215 rad/s (88,000 rpm) using a wide range of hydrostatic bearing supply pressures are presented. The hydrostatic bearing test data and the rotordynamic behavior of the turbopump was closely analyzed and are included in the report. The testing of hybrid hydrostatic/ball bearings on a turbopump to the high speed requirements has indicated the configuration concept is feasible. The program has presented a great deal of information on the technology requirements of integrating the hybrid bearing into high speed turbopump designs for improved bearing life.

Nielson, C. E.

1983-01-01

6

Static Characteristics of Conical Hydrostatic Journal Bearing Under Micropolar Lubrication  

NASA Astrophysics Data System (ADS)

A theoretical analysis for static characteristics of a conical hydrostatic journal bearing for a multirecess constant flow valve compensated under micropolar lubrication has been carried out in this work. The numerical solution of the modified Reynolds equation for the conical bearing has been done using Finite Element Method (FEM) using necessary boundary conditions. The various static characteristics have been presented to analyze the performance of bearing at zero speed.

Rana, N. K.; Gautam, S. S.; Verma, S.

2014-10-01

7

Static Characteristics of Conical Hydrostatic Journal Bearing Under Micropolar Lubrication  

NASA Astrophysics Data System (ADS)

A theoretical analysis for static characteristics of a conical hydrostatic journal bearing for a multirecess constant flow valve compensated under micropolar lubrication has been carried out in this work. The numerical solution of the modified Reynolds equation for the conical bearing has been done using Finite Element Method (FEM) using necessary boundary conditions. The various static characteristics have been presented to analyze the performance of bearing at zero speed.

Rana, N. K.; Gautam, S. S.; Verma, S.

2014-08-01

8

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

9

A technique to measure rotordynamic coefficients in hydrostatic bearings  

NASA Technical Reports Server (NTRS)

An experimental technique is described for measuring the rotordynamic coefficients of fluid film journal bearings. The bearing tester incorporates a double-spool shaft assembly that permits independent control over the journal spin speed and the frequency of an adjustable-magnitude circular orbit. This configuration yields data that enables determination of the full linear anisotropic rotordynamic coefficient matrices. The dynamic force measurements were made simultaneously with two independent systems, one with piezoelectric load cells and the other with strain gage load cells. Some results are presented for a four-recess, oil-fed hydrostatic journal bearing.

Capaldi, Russell J.

1993-01-01

10

Synchronous critical speed tracking in hydrostatic bearing supported rotors  

NASA Technical Reports Server (NTRS)

Hydrostatic bearings used in advanced turbopump designs use the pumped propellant as the working fluid and supply the propellant to the bearing from pump discharge. The resulting rotordynamic coefficients are highly speed-dependent and in some instances can cause system natural frequencies to coincide with spin speed over a wide speed range. This paper discusses this 'synchronous tracking' phenomenon. The factors affecting it are defined, and specific examples are presented. Methods which identify synchronous tracking issues early in the design process are reported, and techniques for eliminating this undesirable characteristic are addressed.

Henderson, Thomas W.; Scharrer, Joseph K.

1989-01-01

11

Dynamic force response of spherical hydrostatic journal bearings for cryogenic applications  

Microsoft Academic Search

Hydrostatic journal bearings are ideal elements to replace roller bearings as rotor support elements in cryogenic turbomachinery. These bearings will be used for primary space-power applications due to their long lifetime, low friction and wear, large load capacity, and direct stiffness and damping force coefficients. The performance characteristics of turbulent flow, orifice compensated, spherical hydrostatic journal bearings are presented. These

Luis San Andres

1994-01-01

12

Dynamic Force Response of Spherical Hydrostatic Journal Bearings for Cryogenic Applications  

Microsoft Academic Search

Hydrostatic journal bearings are ideal elements to replace roller bearings as rotor support elements in cryogenic lurbomachinery. These bearings will be used for primary space-power applications due to their long lifetime, low friction and wear, large load capacity, and direct stiffness and damping force coefficients. The performance characteristics of turbulent flow, orifice compensated, spherical hydrostatic journal bearings are presented. These

Luis San Andres

1994-01-01

13

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

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

DEVELOPMENT OF A HYDROSTATIC JOURNAL BEARING WITH SLIT-STEP COMPENSATION  

SciTech Connect

This paper describes the mathematical modeling and initial testing of an oil-hydrostatic bearing that derives compensation from both a central radial slit where fluid enters and stepped clearances near each end. Bearings using either a radial slit or stepped clearances for compensation were well studied over forty years ago by Donaldson. These bearings have smooth bores uninterrupted with multiple recesses around the circumference. The present slit-step bearing achieves the best of both types with somewhat higher hydrostatic stiffness than the slit bearing and fluid shear drag lower than the step bearing. This is apparent in TABLE 1, which compares calculated values of initial (i.e., centered) hydrostatic stiffness for each type. The slit-step bearing is one of several types being studied at Lawrence Livermore National Laboratory for possible use on the Precision Optical Grinder and Lathe (POGAL).

Hale, L C; Donaldson, R R; Castro, C; Chung, C A; Hopkins, D J

2006-07-28

16

Dynamic force response of spherical hydrostatic journal bearing for cryogenic applications  

Microsoft Academic Search

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

Luis Sanandres

1994-01-01

17

Theoretical and experimental study of the dynamic transient characteristics of a hydrostatic bearing  

NASA Astrophysics Data System (ADS)

The transient characteristics of a hydrostatic bearing under a step load have been studied by considering the compressibility of oil (containing air bubbles). The characteristic equations of the beating during the transient stage have been set up, the duration of the transient stage has been obtained and the effects of the main parameters of the bearing system on the transient characteristics have been analyzed. This study provides a new theoretical basis for improving the dynamic support precision of high quality bearings.

Pang, Zhicheng; Wang, Shuguo; Liu, Qingming; Chi, Wei

1993-01-01

18

Dynamic force response of spherical hydrostatic journal bearings for cryogenic applications  

NASA Astrophysics Data System (ADS)

Hydrostatic journal bearings are ideal elements to replace roller bearings as rotor support elements in cryogenic turbomachinery. These bearings will be used for primary space-power applications due to their long lifetime, low friction and wear, large load capacity, and direct stiffness and damping force coefficients. The performance characteristics of turbulent flow, orifice compensated, spherical hydrostatic journal bearings are presented. These bearing allow tolerance for shaft misalignment without force degradation and are able to support axial loads, thus providing a design configuration which could be used efficiently on high-performance turbomachinery. Bulk-flow mass and momentum equations for the motion of a variable properties liquid on the thin film bearing lands are solved numerically. Predictions of load capacity and force coefficients for a six recess, spherical hydrostatic bearing in a liquid oxygen environment are presented. Fluid film axial forces and dynamic coefficients of a magnitude about 20 percent of the radial load capacity are calculated for the case analyzed. Fluid inertia effects, advective and centrifugal, are found to greatly affect the static and dynamic force characteristics of the bearing studied.

Andres, Luis San

1994-07-01

19

Study on Flowability of the Gap Oil Film of the Multi-oil Pad Hydrostatic Bearing with Variable Viscosity  

Microsoft Academic Search

According to the large size multi-oil pad hydrostatic bearing, the mathematical model of three-dimensional flow of the gap oil film of the hydrostatic bearing is established in considering the influence of variable viscosity and centrifugal force condition. The finite element method and the finite volume method are used to simulate the flow field of the gap oil film of the

Junpeng Shao; Hongmei Li; Xiaodong Yang; Yanqin Zhang; Xiaodong Yu; Hui Jiang

2009-01-01

20

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

21

Vibration of a hydrostatic gas bearing due to supply pressure oscillations  

NASA Technical Reports Server (NTRS)

The vibration of a statically loaded, inherently compensated hydrostatic journal bearing due to oscillating supply 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 the sleeve is solved numerically 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 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. The results are compared with the results of an earlier study involving the response of a similar bearing to oscillating exhaust pressure.

Branch, H. D.; Watkins, C. B.; Eronini, I. E.

1984-01-01

22

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

23

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

24

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

NASA Technical Reports Server (NTRS)

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.

Watkins, C. B.; Eronini, I. E.; Branch, H. D.

1984-01-01

25

Oil pocket's bearing capacity analysis of liquid hydrostatic worktable in Gantry Moving Milling Center  

NASA Astrophysics Data System (ADS)

Durning the design process of hydrostatic rotary worktable, the processing and assembly tolerance, (the offset of worktable and the gap of the oil film's thickness) is ignored. But it will cause that the real bearing of oil pocket deviates from the initial design value, and then the performance of rotary worktable will be reduced significantly. Up to now, no effort is found toward the research of influence of the processing and assembly tolerance on the performance of the rotary worktable. So the hydrostatic oil film is assumed as the elastomer in this paper, and then the bearing capacity of the oil pocket is studied with and without the mass offset of the worktable by taking an expression between the bearing capacity and the oil film's thickness of the oil pocket as the deform compatibility equation. The influence of the processing tolerance of the oil sealing belt's gap on the bearing capacity of the oil pocket is analyzed. In the light of the liquid hydrostatic worktable of Gantry Moving Milling Center using on the scene, the oil pocket's pressure of the worktable is tested using Rotary Worktable Test System under the circumstance of the mass offset of the worktable and the gap tolerance of the oil sealing belt, and then the equivalent offset of worktable, the average pressure of the oil pocket and the actual thickness of the oil film are analyzed respectively. The test results show that the bearing capacity component of the oil pocket caused by G is consistent, and the component caused by M is relative to the position of the oil pocket. When the oil sealing belt's gap is larger than the theoretical value, the bearing capacity of the oil pocket is smaller than the others; whereas the bearing capacity of the oil pocket is larger than the others. The maximum and minimum equivalent offsets are 0.256 4 mm and 0.047 5 mm, respectively, and the average oil pocket pressure varies from 0.345 MPa to 0.460 MPa, the maximum and minimum value of the actual oil film thickness are 109.976 ?m (No. 7 oil pocket) and 93.467 ?m (No. 10 oil pocket), respectively. The research results can be used to detect the offset of the worktable and the actual thickness of the oil film under processing and assembly tolerance, and provides a basis way for detecting the processing and assembly tolerance of rotary worktable signing reasonably of Gantry Moving Milling Center.

Zhao, Jianhua; Liang, Yingna; Gao, Dianrong

2014-09-01

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

Development of a polymetric grout for the hydrostatic bearing at DSS 14  

NASA Technical Reports Server (NTRS)

Results of an investigation into the causes of the deterioration and premature failure of the grout under the hydrostatic bearing runner at DSS 14 are reported. Generic types of materials were screened and tested to find a grout material more resistive to the causes of grout failure. Emphasis was placed on the physical properties, strength, modulus of elasticity, and resistance to erosion and chemical attack by oil and unique requirements imposed by each material for mixing, placing, compacting, and cooling. The polymetric grout developed to replace the dry grout is described.

Mcclung, C. E.; Schwendeman, J. L.; Ball, G. L., III; Jenkins, G. H.; Casperson, R. D.; Gale, G. P.; Riewe, A. A.

1981-01-01

28

NASTRAN Structural Model for the Large 64-meter Antenna Pedestal. Part 3: Applications to Hydrostatic Bearing Oil Film  

NASA Technical Reports Server (NTRS)

Investigations are conducted on the 64-meter antenna hydrostatic bearing oil film thickness under a variety of loads and elastic moduli. These parametric studies use a NASTRAN pedestal structural model to determine the deflections under the hydrostatic bearing pad. The deflections form the input for a computer program to determine the hydrostatic bearing oil film thickness. For the future 64-meter to 70-meter antenna extension and for the 2.2-meter (86-in.) haunch concrete replacement cases, safe oil film thickness (greater than 0.13 mm (0.005 in.) at the corners of the pad) are predicted. The effects of varying moduli of elasticity for different sections of the pedestal and the film height under distressed runner conditions are also studied.

Chian, C. T.; Schonfeld, D.

1984-01-01

29

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

30

Predicted characteristics of an optimized series-hybrid conical hydrostatic ball bearing  

NASA Technical Reports Server (NTRS)

Optimized series-hybrid fluid-film ball bearings are described and operating characteristics are calculated and discussed. It is predicted that a series-hybrid bearing may be constructed which will reduce ball-bearing speed by 30 percent thereby increasing bearing fatigue life by factors of up to 5.9. Flow rates required are less than 9 kilograms per minute.

Nypan, L. J.; Hamrock, B. J.; Scibbe, H. W.; Anderson, W. J.

1971-01-01

31

Extending the life of the SSME HPOTP through the use of annular hydrostatic bearings  

NASA Astrophysics Data System (ADS)

A new fluid film bearing package is presented for incorporation into the Space Shuttle Main Engine High Pressure Oxygen Turbopump. This fluid film element functions as both the pump end bearing and the preburner pump rear wear ring seal. Most importantly, it replaces the duplex ball bearing package which has been the primary life limiting component in the turbopump. The design constraints and solutions are presented along with the effects of the bearing package on the hydrodynamic and rotordynamic performance of the turbopump.

Scharrer, Joseph K.; Hibbs, Robert I., Jr.; Nolan, Steven A.; Tabibzadeh, Ramin

1992-07-01

32

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

33

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

34

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 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

35

The 3,6 m Indo-Belgian Devasthal Optical Telescope: the hydrostatic azimuth bearing  

NASA Astrophysics Data System (ADS)

AMOS SA has been awarded of the contract for the design, manufacturing, assembly, tests and on site installation (Devasthal, Nainital in central Himalayan region) of the 3.6 m Indo-Belgian Devasthal Optical Telescope (IDOT). The telescope has a Ritchey-Chrétien optical configuration with a Cassegrain focus equipped with one axial port and two side ports. The primary mirror is a meniscus active mirror. The mount is an Alt-Az type with for the azimuth axis a 5 m diameter hydrostatic track. This paper presents the solution adopted by AMOS to meet the specific requirements for the azimuth axis. The track is designed to be able to control the positioning of the telescope around the azimuth axis with an accuracy of 0.05 arc second for all tracking configurations. The challenge came from this tight accuracy with a mass in rotation weighting 125 tons. The azimuth track was mounted and tested in AMOS workshop; the tests and performances are also discussed.

de Ville, Jonathan; Piérard, Maxime; Bastin, Christian

2012-09-01

36

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

37

Measurements versus Predictions for a Hybrid (Hydrostatic plus Hydrodynamic Thrust Bearing for a Range of Orifice Diameters  

E-print Network

all decreased with decreasing orifice diameters and bearing axial clearances. In most cases, the bearings with larger orifice diameters exhibit higher recess pressure ratios, operating clearances, and flow rates. The largest orifice diameter...

Esser, Paul R.

2011-08-08

38

Effect of design parameter variations on hybrid (combination hydrostatic and hydrodynamic) bearings for use in high speed turbomachinery  

E-print Network

and wear, and ability to use low viscosity fluids. However, very little work has been done in determining the rotordynamic performance of hybrid journal bearings. This thesis presents theoretical and experimental results for radial-injection, orifice...

Mosher, Phillip Andrew

2012-06-07

39

Bears  

NSDL National Science Digital Library

What are the characteristics of grizzly/brown bears and black bears? As you view the websites, please use this chart to record what you are learning about grizzly bears and black bears. For each bear, you should list 5 characteristics. Grizzly Bear and Black Bear Chart We will first begin by learning about black bears. Please go to these websites to learn some important facts about black bears. Black Bears Facts and Image Black Bear Facts for Kids Now that you have learned ...

Bledsoe, Miss

2011-04-07

40

Bears, Bears, Bears!  

NSDL National Science Digital Library

What are some things you learned about bears? Use these websites to find out about bears: Parts of a Bear Polar Bears Real Story of the Three Bears The truth about bears Brown Bears Now fill in your chart! Bear Fact Sheet Listen to your teacher for further instruction on completing a book about bears! ...

Ms.beason

2011-04-16

41

The Giant Magellan Telescope (GMT): hydrostatic constraints  

NASA Astrophysics Data System (ADS)

The Giant Magellan Telescope (GMT) is an optical-infrared 25 Meter ELT to be located in Chile. It is being designed and constructed by a group of U.S. and international universities and research institutions1. Structural performance of large telescopes can be enhanced significantly with the added stiffness that results from distributing loads to many points in the structure. In defining the two rotating assemblies in an altitude-over-azimuth mount more than a kinematic set of constraints can lead to hydrostatic bearing oil film failure due to unintended forces that result from runner bearing irregularities. High Frequency Over Constraint (HFOC) increases stiffness without risk of oil film failure. It was used successfully on the Magellan 6.5 Meter Telescopes. GMT will employ this and two additional methods to enhance stiffness at frequencies from DC wind up through the telescope primary mode frequencies of ~11 Hz. This will be achieved without excessive hydrostatic bearing pad forces. Detailed discussion of GMT's hydrostatic constraints, azimuth track and optics support structure (OSS) runner bearing illustrations, and performance criteria are provided for the design.

Gunnels, Steve

2010-07-01

42

Rotordynamic evaluation of a roughened-land hybrid bearing  

E-print Network

Hybrid bearings (combinations of hydrostatic and hydrodynamic bearings) represent an attractive alternative to ball bearings for use in high-speed cryogenic turbopumps. However, the internally-developed cross-coupled forces can generate...

Fayolle, Patrice Gerard

2012-06-07

43

BIOMACROMOLECULES UNDER HIGH HYDROSTATIC PRESSURE  

E-print Network

BIOMACROMOLECULES UNDER HIGH HYDROSTATIC PRESSURE A Dissertation Presented to the Faculty HIGH HYDROSTATIC PRESSURE Nozomi Ando, Ph.D. Cornell University 2009 Protein pressure denaturation denaturation studies. Recent studies imply that the mechanism of pressure denaturation is the penetration

Gruner, Sol M.

44

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

45

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

46

Lift-off performance in flexure pivot pad and hybrid bearings  

E-print Network

Three flexure pivot pad bearings (FPBs) with different preloads are evaluated for use in high performance applications by comparing them to a hybrid hydrostatic bearing (HHB). One application of these bearings is in turbopumps for liquid rocket...

Mertz, David Hunter

2009-05-15

47

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

48

SSME Long-life Bearings  

NASA Technical Reports Server (NTRS)

Hybrid hydrostatic/ball bearings for LH2 and LO2 service in turbopumps were studied as a means of improving speed and life capabilities. Four hybrid bearing configurations were designed with emphasis on achieving maximum stiffness and damping. Parallel load bearings were tested at steady-state and transient conditions with LH2 (externally fed) and LN2 (internally fed). The hydrostatic elements were tested with Freon 113 for empirical determination of dynamic characteristics. Tests using an eccentric journal for loading showed the externally and internally fed hydrostatic bearings to have significant separated coefficients of direct stiffness and damping. For the internally fed bearing, the strongly speed-dependent cross-coupling stiffness arising from fluid swirl, along with significant cross-coupling damping, resulted in low net effective stiffness and damping. The test method used can produce separated coefficients with a sufficiently elliptic journal orbit; otherwise, only net effective coefficients combining direct and cross-coupling terms can be determined. Testing with nonsynchronous excitation is recommended to avoid this restriction. Investigation of hard materials, including ceramics, is recommended as a means of eliminating the need for the rolling bearing for startup and shutdown support. The testing was performed in 1984 (LH2), 1985 (LN2) and 1985-86 (Freon).

Butner, M. F.; Murphy, B. T.

1986-01-01

49

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

50

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, including the treatment of medical conditions. 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 available in the developing world for the treatment of a variety of medical conditions. Specifically, hyperbaric oxygen therapy is highly-desired as a possibly curative treatment for Buruli Ulcer, an infectious condition that afflicts children in sub-Saharan Africa. Hyperbaric oxygen therapy is simply too expensive and too dangerous to implement in the developing world using standard equipment. The hydrostatic hyperbaric chamber 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 that will provide controlled pressurization of the system, and provide 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.

Sargusingh, Miriam M.

2011-01-01

51

PELLISSIER H5 HYDROSTATIC LEVEL  

SciTech Connect

Conventional spirit leveling using double scale invar rods has been in use at SLAC for some time as the standard method of obtaining very precise height difference information. Typical accuracy of {+-} 100 {micro}m and better can routinely be achieved. Procedures and software have evolved to the point where the method is relatively fast and reliable. However, recent projects such as the Final Focus Test Beam have pushed the requested vertical positioning tolerances for alignment of quadrupoles to the 30 {mu}m level. It is apparent that conventional spirit leveling cannot achieve this level of accuracy. To meet the challenge, the alignment group contracted with Pellissier, Inc. to develop a portable hydrostatic leveling system. The H5 grew out of this development effort and is expected to provide the needed accuracy and ease of use required for such vertical positioning projects. The H5 hydrostatic level is a portable instrument that under ideal operating conditions will provide elevation differences with an accuracy of +/- 5 {mu}m over double leg closed loop surveys. The H5 incorporates several features that eliminate problems common with hydrostatic leveling, primarily errors due to thermal gradients along the fluid tube. It utilizes self-checking software and automatic water level detection to reduce observational errors. Design features also have made the instrument reasonably quick and easy to operate when used on a flat surface. The instrument can be adapted for use in a wide variety of environments by using support fixtures and brackets. The H5 is robust and operators require little training to become proficient in its use. It has been successfully employed on several projects including the FFTB project at SLAC, as well as the Green Bank Telescope project for the NRAO and the SSC project in Texas.

Imfeld, Hans L.

2003-05-01

52

Mechanical response of collagen molecule under hydrostatic compression.  

PubMed

Proteins like collagen are the basic building blocks of various body tissues (soft and hard). Collagen molecules find their presence in the skeletal system of the body where they bear mechanical loads from different directions, either individually or along with hydroxy-apatite crystals. Therefore, it is very important to understand the mechanical behavior of the collagen molecule which is subjected to multi-axial state of loading. The estimation of strains of collagen molecule along different directions resulting from the changes in hydrostatic pressure magnitude, can provide us new insights into its mechanical behavior. In the present work, full atomistic simulations have been used to study global (volumetric) as well as local (along different directions) mechanical properties of the hydrated collagen molecule which is subjected to different hydrostatic pressure magnitudes. To estimate the local mechanical properties, the strains of collagen molecule along its longitudinal and transverse directions have been acquired at different hydrostatic pressure magnitudes. In spite of non-homogeneous distribution of atoms within the collagen molecule, the calculated values of local mechanical properties have been found to carry the same order of magnitude along the longitudinal and transverse directions. It has been demonstrated that the values of global mechanical properties like compressibility, bulk modulus, etc. as well as local mechanical properties like linear compressibility, linear elastic modulus, etc. are functions of magnitudes of applied hydrostatic pressures. The mechanical characteristics of collagen molecule based on the atomistic model have also been compared with that of the continuum model in the present work. The comparison showed up orthotropic material behavior for the collagen molecule. The information on collagen molecule provided in the present study can be very helpful in designing the future bio-materials. PMID:25687001

Saini, Karanvir; Kumar, Navin

2015-04-01

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

Bearing system  

DOEpatents

A bearing system includes backup bearings for supporting a rotating shaft upon failure of primary bearings. In the preferred embodiment, the backup bearings are rolling element bearings having their rolling elements disposed out of contact with their associated respective inner races during normal functioning of the primary bearings. Displacement detection sensors are provided for detecting displacement of the shaft upon failure of the primary bearings. Upon detection of the failure of the primary bearings, the rolling elements and inner races of the backup bearings are brought into mutual contact by axial displacement of the shaft.

Kapich, Davorin D. (Carlsbad, CA)

1987-01-01

55

49 CFR 178.814 - Hydrostatic pressure test.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Hydrostatic pressure test. 178.814 Section 178.814...Testing of IBCs § 178.814 Hydrostatic pressure test. (a) General. The hydrostatic pressure test must be conducted for the...

2011-10-01

56

49 CFR 178.605 - Hydrostatic pressure test.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Hydrostatic pressure test. 178.605 Section 178.605...and Packages § 178.605 Hydrostatic pressure test. (a) General. The hydrostatic pressure test must be conducted for the...

2011-10-01

57

49 CFR 178.814 - Hydrostatic pressure test.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Hydrostatic pressure test. 178.814 Section 178.814...Testing of IBCs § 178.814 Hydrostatic pressure test. (a) General. The hydrostatic pressure test must be conducted for the...

2013-10-01

58

49 CFR 178.605 - Hydrostatic pressure test.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Hydrostatic pressure test. 178.605 Section 178.605...and Packages § 178.605 Hydrostatic pressure test. (a) General. The hydrostatic pressure test must be conducted for the...

2010-10-01

59

49 CFR 178.814 - Hydrostatic pressure test.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Hydrostatic pressure test. 178.814 Section 178.814...Testing of IBCs § 178.814 Hydrostatic pressure test. (a) General. The hydrostatic pressure test must be conducted for the...

2010-10-01

60

49 CFR 178.605 - Hydrostatic pressure test.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Hydrostatic pressure test. 178.605 Section 178.605...and Packages § 178.605 Hydrostatic pressure test. (a) General. The hydrostatic pressure test must be conducted for the...

2012-10-01

61

49 CFR 178.814 - Hydrostatic pressure test.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Hydrostatic pressure test. 178.814 Section 178.814...Testing of IBCs § 178.814 Hydrostatic pressure test. (a) General. The hydrostatic pressure test must be conducted for the...

2012-10-01

62

49 CFR 178.605 - Hydrostatic pressure test.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Hydrostatic pressure test. 178.605 Section 178.605...and Packages § 178.605 Hydrostatic pressure test. (a) General. The hydrostatic pressure test must be conducted for the...

2013-10-01

63

Solid-Lubricant Entrainment in Hydrostatic Extrusion  

Microsoft Academic Search

The upper-bound model developed by Wilson and Halliday for solid-lubricant entrainment in metalforming operations is refined to include the effect of workpiece rounding at the die entrance on lubricant entrainment in hydrostatic extrusion. The analysis is verified by means of film thickness measurements on hydrostatic extrusions with a variety of workpiece materials, lubricants and die angles. The model is shown

David R. White; William R. D. Wilson

1980-01-01

64

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

65

Polar Bear Polar Bear  

NSDL National Science Digital Library

In this lesson, students will listen for key details in a nonfiction text about polar bears. They will work at completing a graphic organizer with the teacher to help organize their thinking and understanding of key details about a text. They will also complete an independent assignment where they will draw or write two things that they learned about the topic.

Burgess, Kelly

2012-09-11

66

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

67

Influence of elastic effects on the performance of slot-entry journal bearings  

Microsoft Academic Search

Modern high-performance machines require bearings to operate under stringent conditions. For bearings operating under heavy loads, the bearing deformations can no longer be neglected as they are comparable to the order of magnitude of the fluid film thickness. This paper describes the performance of slot-entry hydrostatic\\/hybrid journal bearings by considering bearing shell flexibility in the analysis. The relevant governing equations

Satish C Sharma; S. C Jain; N. Madhu Mohan Reddy

1999-01-01

68

Bear Scratch  

USGS Multimedia Gallery

When looking for a place to set up a trapping location, scientists look for existing bear sign such as scratches on trees and bear scat. Sometimes traps are set in areas that have no obvious bear sign to determine if indeed bears are present....

69

46 CFR 64.83 - Hydrostatic test.  

Code of Federal Regulations, 2012 CFR

...PORTABLE TANKS AND CARGO HANDLING SYSTEMS Periodic Inspections and Tests...fitted with an internal heating coil, the heating coil passing a hydrostatic test at...above the rated pressure of the coil, whichever is greater....

2012-10-01

70

46 CFR 64.83 - Hydrostatic test.  

Code of Federal Regulations, 2013 CFR

...PORTABLE TANKS AND CARGO HANDLING SYSTEMS Periodic Inspections and Tests...fitted with an internal heating coil, the heating coil passing a hydrostatic test at...above the rated pressure of the coil, whichever is greater....

2013-10-01

71

46 CFR 64.83 - Hydrostatic test.  

Code of Federal Regulations, 2011 CFR

...PORTABLE TANKS AND CARGO HANDLING SYSTEMS Periodic Inspections and Tests...fitted with an internal heating coil, the heating coil passing a hydrostatic test at...above the rated pressure of the coil, whichever is greater....

2011-10-01

72

46 CFR 64.83 - Hydrostatic test.  

Code of Federal Regulations, 2010 CFR

...PORTABLE TANKS AND CARGO HANDLING SYSTEMS Periodic Inspections and Tests...fitted with an internal heating coil, the heating coil passing a hydrostatic test at...above the rated pressure of the coil, whichever is greater....

2010-10-01

73

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

74

Demagnetization of terrestrial and extraterrestrial rocks under hydrostatic pressure up to 1.2 GPa  

NASA Astrophysics Data System (ADS)

We carried out hydrostatic pressure demagnetization experiments up to 1.24 GPa on samples of terrestrial and extraterrestrial rocks and minerals of different lithologies as well as on synthetic samples. The magnetic remanence of samples was measured directly under pressure using a non-magnetic high-pressure cell of piston-cylinder type that was inserted into a high sensitivity SQUID magnetometer. In order to bring light on the pressure demagnetization effect, we investigated 50 samples with different magnetic mineralogies, remanent coercivities ( Bcr) and hysteresis parameters. The samples consisted of pyrrhotite-, magnetite- and titanomagnetite-bearing Martian meteorites, taenite-, tetrataenite- and kamacite-bearing ordinary chondrites and pyrrhotite-bearing Rumuruti chondrite; magnetite- and titanomagnetite-bearing basalts, andesites, ignimbrites, obsidians and granites; a variety of pyrrhotite- and hematite-bearing rocks and minerals (jasper, schist, rhyolite, radiolarite); samples of goethite and greigite as well as synthetic samples of dispersed powders of magnetite, hematite, pyrrhotite and native iron set into epoxy resin. Under hydrostatic pressure of 1.24 GPa, applied in a low magnetic field (<5 ?T), the samples lost up to 84% of their initial saturation isothermal remanent magnetization (SIRM) without any changes in their intrinsic magnetic properties. We found that the efficiency of the pressure demagnetization is not exclusively controlled by the magnetic hardness of the samples ( Bcr), but that it is strongly dependent on their magnetic mineralogy. For a given magnetic mineralogy the resistance to hydrostatic pressure is roughly proportional to ln( Bcr). It was shown that there is no simple equivalence between pressure demagnetization and alternating field demagnetization effects. The pressure demagnetization was shown to be time-independent but repeated application of the same pressure level resulted in further demagnetization.

Bezaeva, Natalia S.; Gattacceca, Jérôme; Rochette, Pierre; Sadykov, Ravil A.; Trukhin, Vladimir I.

2010-03-01

75

The elastic stability, bifurcation and ideal strength of gold under hydrostatic stress: an ab initio calculation  

NASA Astrophysics Data System (ADS)

In this paper, we employ an ab initio density functional theory calculation to investigate the elastic stability of face-centered cubic Au under hydrostatic deformation. We identify the elastic stiffness constant Bijkl as the coefficient in the stress-strain relation for an arbitrary deformed state, and use it to test the stability condition. We show that this criterion bears the same physics as that proposed earlier by Frenkel and Orowan and agrees with the Born-Hill criterion. The results from those two approaches agree well with each other. We show that the stability limit, or instability, of the perfect Au crystal under hydrostatic expansion is not associated with the bulk stiffness modulus as predicted in the previous work; rather it is caused by a shear instability associated with the vanishing rhombohedral shear stiffness modulus. The deviation of the deformation mode from the primary hydrostatic loading path signals a bifurcation or symmetry breaking in the ideal crystal. The corresponding ideal hydrostatic strength for Au is 19.2 GPa at the Lagrangian expansion strain of ~0.06. In the case of compression, Au remains stable over the entire pressure range in our calculation.

Wang, Hao; Li, Mo

2009-11-01

76

The elastic stability, bifurcation and ideal strength of gold under hydrostatic stress: an ab initio calculation.  

PubMed

In this paper, we employ an ab initio density functional theory calculation to investigate the elastic stability of face-centered cubic Au under hydrostatic deformation. We identify the elastic stiffness constant B(ijkl) as the coefficient in the stress-strain relation for an arbitrary deformed state, and use it to test the stability condition. We show that this criterion bears the same physics as that proposed earlier by Frenkel and Orowan and agrees with the Born-Hill criterion. The results from those two approaches agree well with each other. We show that the stability limit, or instability, of the perfect Au crystal under hydrostatic expansion is not associated with the bulk stiffness modulus as predicted in the previous work; rather it is caused by a shear instability associated with the vanishing rhombohedral shear stiffness modulus. The deviation of the deformation mode from the primary hydrostatic loading path signals a bifurcation or symmetry breaking in the ideal crystal. The corresponding ideal hydrostatic strength for Au is 19.2 GPa at the Lagrangian expansion strain of ?0.06. In the case of compression, Au remains stable over the entire pressure range in our calculation. PMID:21694011

Wang, Hao; Li, Mo

2009-11-11

77

Phase stability limit of c-BN under hydrostatic and non-hydrostatic pressure conditions  

SciTech Connect

Phase stability limit of cubic boron nitride (c-BN) has been investigated by the crystal structure search technique. It indicated that this limit is ?1000 GPa at hydrostatic pressure condition. Above this pressure, c-BN turns into a metastable phase with respect to rocksalt type boron nitride (rs-BN). However, rs-BN cannot be retained at 0 GPa owing to its instability at pressure below 250 GPa. For non-hydrostatic pressure conditions, the phase stability limit of c-BN is substantially lower than that under hydrostatic pressure conditions and it is also dramatically different for other pressure mode.

Xiao, Jianwei; Du, Jinglian; Wen, Bin, E-mail: wenbin@ysu.edu.cn; Zhang, Xiangyi [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China)] [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Melnik, Roderick [M2NeT Lab, Wilfrid Laurier University, Waterloo25, 75 University Ave. West, Ontario, Canada N2L 3C5 (Canada)] [M2NeT Lab, Wilfrid Laurier University, Waterloo25, 75 University Ave. West, Ontario, Canada N2L 3C5 (Canada); Kawazoe, Yoshiyuki [New Industry Creation Hatchery Center, Tohoku University, 6-6-4 Aramaki-aza-Aoba, Aoba-ku, Sendai 980-8579, Japan and Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, 1, Lavyrentyev Avenue, Novosibirsk 630090 (Russian Federation)] [New Industry Creation Hatchery Center, Tohoku University, 6-6-4 Aramaki-aza-Aoba, Aoba-ku, Sendai 980-8579, Japan and Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, 1, Lavyrentyev Avenue, Novosibirsk 630090 (Russian Federation)

2014-04-28

78

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

79

49 CFR 230.36 - Hydrostatic testing of boilers.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 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...

2010-10-01

80

49 CFR 230.36 - Hydrostatic testing of boilers.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 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...

2012-10-01

81

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

82

49 CFR 230.36 - Hydrostatic testing of boilers.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 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...

2011-10-01

83

Coal-fired Stirling engine hydrostatic locomotive  

SciTech Connect

In view of the increasing price of diesel oil, there is a need to consider alternative fuels, such as coal, which is available in relative abundance and lower costs. A case is made to establish a 1000 hp 80 ton 2 bogie 4-axle coal-burning free-piston Stirling engine hydrostatic locomotive for shunting duty.

Srinivasan, V.; Walker, C.; Fauvel, R.

1982-01-01

84

Comment on "Piezoelectricity under Hydrostatic Pressure"  

NASA Astrophysics Data System (ADS)

It is shown that the special termination of the atoms on (111) surfaces of zinc-blende crystals cannot lead to the "hydrostatic piezoelectric effect" proposed by Woo. The present results are a special case of a more general proof given elsewhere and agree with the traditional bulk theory of piezoelectricity.

Martin, Richard M.

1972-12-01

85

46 CFR 61.30-10 - Hydrostatic test.  

Code of Federal Regulations, 2010 CFR

...INSPECTIONS Tests and Inspections of Fired Thermal Fluid Heaters § 61.30-10 Hydrostatic test. All new installations of thermal fluid heaters must be given a hydrostatic...accessible parts under pressure. The thermal fluid may be used as the hydrostatic...

2010-10-01

86

Hydrostatic pressure-regulated ion transport in bladder uroepithelium  

E-print Network

Hydrostatic pressure-regulated ion transport in bladder uroepithelium Edward C. Y. Wang,1,2 Jey Bridges, and Gerard Apodaca. Hydrostatic pressure-regulated ion transport in bladder uroepithelium. Am J.2002.--The effect of hydrostatic pressure on ion transport in the bladder uroepithelium was investigated

Apodaca, Gerard

87

Polar Bear  

USGS Publications Warehouse

Polar bears are long-lived, late-maturing carnivores that have relatively low rates of reproduction and natural mortality. Their populations are susceptible to disturbance from human activities, such as the exploration and development of mineral resources or hunting. Polar bear populations have been an important renewable resource available to coastal communities throughout the Arctic for thousands of years.

Amstrup, S.D.; DeMaster

1988-01-01

88

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

89

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

90

On hydrostatic flows in isentropic coordinates  

NASA Astrophysics Data System (ADS)

The hydrostatic primitive equations of motion which have been used in large-scale weather prediction and climate modelling over the last few decades are analysed with variational methods in an isentropic Eulerian framework. The use of material isentropic coordinates for the Eulerian hydrostatic equations is known to have distinct conceptual advantages since fluid motion is, under inviscid and statically stable circumstances, confined to take place on quasi-horizontal isentropic surfaces. First, an Eulerian isentropic Hamilton's principle, expressed in terms of fluid parcel variables, is therefore derived by transformation of a Lagrangian Hamilton's principle to an Eulerian one. This Eulerian principle explicitly describes the boundary dynamics of the time-dependent domain in terms of advection of boundary isentropes sB; these are the values the isentropes have at their intersection with the (lower) boundary. A partial Legendre transform for only the interior variables yields an Eulerian ‘action’ principle. Secondly, Noether's theorem is used to derive energy and potential vorticity conservation from the Eulerian Hamilton's principle. Thirdly, these conservation laws are used to derive a wave-activity invariant which is second-order in terms of small-amplitude disturbances relative to a resting or moving basic state. Linear stability criteria are derived but only for resting basic states. In mid-latitudes a time- scale separation between gravity and vortical modes occurs. Finally, this time-scale separation suggests that conservative geostrophic and ageostrophic approximations can be made to the Eulerian action principle for hydrostatic flows. Approximations to Eulerian variational principles may be more advantageous than approximations to Lagrangian ones because non-dimensionalization and scaling tend to be based on Eulerian estimates of the characteristic scales involved. These approximations to the stratified hydrostatic formulation extend previous approximations to the shallow- water equations. An explicit variational derivation is given of an isentropic version of Hoskins & Bretherton's model for atmospheric fronts.

Bokhove, Onno

2000-01-01

91

Nonlinear dynamics of hydrostatic internal gravity waves  

Microsoft Academic Search

Stratified hydrostatic fluids have linear internal gravity waves with different phase speeds and vertical profiles. Here a\\u000a simplified set of partial differential equations (PDE) is derived to represent the nonlinear dynamics of waves with different\\u000a vertical profiles. The equations are derived by projecting the full nonlinear equations onto the vertical modes of two gravity\\u000a waves, and the resulting equations are

Samuel N. Stechmann; Andrew J. Majda; Boualem Khouider

2008-01-01

92

Foil bearings  

NASA Astrophysics Data System (ADS)

The rolling element bearings (REB's) which support many turbomachinery rotors offer high load capacity, low power requirements, and durability. Two disadvantages of REB's are: (1) rolling or sliding contact within the bearing has life-limiting consequences; and (2) REB's provide essentially no damping. The REB's in the Space Shuttle Main Engine (SSME) turbopumps must sustain high static and dynamic loads, at high speeds, with a cryogenic fluid as lubricant and coolant. The pump end ball bearings limit the life of the SSME high pressure oxygen turbopump (HPOTP). Compliant foil bearing (CFB) manufacturers have proposed replacing turbopump REB's with CFB's CFB's work well in aircraft air cycle machines, auxiliary power units, and refrigeration compressors. In a CFB, the rotor only contracts the foil support structure during start up and shut down. CFB damping is higher than REB damping. However, the load capacity of the CFB is low, compared to a REB. Furthermore, little stiffness and damping data exists for the CFB. A rotordynamic analysis for turbomachinery critical speeds and stability requires the input of bearing stiffness and damping coefficients. The two basic types of CFB are the tension-dominated bearing and the bending-dominated bearing. Many investigators have analyzed and measured characteristics of tension-dominated foil bearings, which are applied principally in magnetic tape recording. The bending-dominated CFB is used more in rotating machinery. This report describes the first phase of a structural analysis of a bending-dominated, multileaf CFB. A brief discussion of CFB literature is followed by a description and results of the present analysis.

Elrod, David A.

1993-11-01

93

Foil bearings  

NASA Technical Reports Server (NTRS)

The rolling element bearings (REB's) which support many turbomachinery rotors offer high load capacity, low power requirements, and durability. Two disadvantages of REB's are: (1) rolling or sliding contact within the bearing has life-limiting consequences; and (2) REB's provide essentially no damping. The REB's in the Space Shuttle Main Engine (SSME) turbopumps must sustain high static and dynamic loads, at high speeds, with a cryogenic fluid as lubricant and coolant. The pump end ball bearings limit the life of the SSME high pressure oxygen turbopump (HPOTP). Compliant foil bearing (CFB) manufacturers have proposed replacing turbopump REB's with CFB's CFB's work well in aircraft air cycle machines, auxiliary power units, and refrigeration compressors. In a CFB, the rotor only contracts the foil support structure during start up and shut down. CFB damping is higher than REB damping. However, the load capacity of the CFB is low, compared to a REB. Furthermore, little stiffness and damping data exists for the CFB. A rotordynamic analysis for turbomachinery critical speeds and stability requires the input of bearing stiffness and damping coefficients. The two basic types of CFB are the tension-dominated bearing and the bending-dominated bearing. Many investigators have analyzed and measured characteristics of tension-dominated foil bearings, which are applied principally in magnetic tape recording. The bending-dominated CFB is used more in rotating machinery. This report describes the first phase of a structural analysis of a bending-dominated, multileaf CFB. A brief discussion of CFB literature is followed by a description and results of the present analysis.

Elrod, David A.

1993-01-01

94

Hydrostatic Adjustment in Vertically Stratified Atmospheres  

NASA Technical Reports Server (NTRS)

Hydrostatic adjustment due to diabatic heat in two nonisothermal atmospheres is examined. In the first case the temperature stratification is continuous; in the second case the atmosphere is composed of a warm, isothermal troposphere and a colder, isothermal semi-infinitely deep stratosphere.In both cases hydrostatic adjustment, to a good approximation, follows the pattern found in the Lamb problem (semi-infinitely deep. isothermal atmosphere): Initially we have acoustic waves with the kinetic energy increasing or decreasing at the expense of available elastic energy. After this initial period the acoustic waves evolve into acoustic-gravity waves with the kinetic, available potential and available elastic energies interacting with each other. Relaxation to hydrostatic balance occurs within a few oscillations. Stratification in an atmosphere with a continuous temperature profile affects primarily the shape and amplitude of the disturbances. In the two-layer atmosphere, a certain amount of energy is trapped in the tropospheric waveguide as disturbances reflect off the tropopause and back into the troposphere. With each internal reflection a portion of this trapped energy escapes and radiates to infinity.

Duffy, Dean G.

2000-01-01

95

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

96

Cave Bear  

NSDL National Science Digital Library

Decoding an ancient cave bear. A two-ton, thirteen-foot cave bear, extinct for ten thousand years, has just experienced a rebirth of sorts. From a tooth and a bone, scientists have recovered its entire genetic code.Eddy Rubin, director of the Department of Energy's Joint Genome Institute, says finding genuine cave bear DNA was like looking for a needle in a haystack. The haystack were all the other organisms that were living in the bones and in the tooth of this ancient creature. And the needle was the little bit of the ancient creature's genome DNA, or genes.They used state-of-the-art computer technology to separate the bear genes from the clutter. Jurassic Park fans should note that they can't clone a new cave bear, nor can they recover DNA from creatures as old as the dinosaurs. But they do hope to reconstruct the genetic code of Neanderthals, our closest non-human relatives, to better understand how our own species evolved. This resource contains detailed text description of the research as well as likes for further inquiry.

American Association for the Advancement of Science (; )

2005-08-15

97

Mechanical design problems associated with turbopump fluid film bearings  

NASA Technical Reports Server (NTRS)

Most high speed cryogenic turbopumps for liquid propulsion rocket engines currently use ball or roller contact bearings for rotor support. The operating speeds, loads, clearances, and environments of these pumps combine to make bearing wear a limiting factor on turbopump life. An example is the high pressure oxygen turbopump (HPOTP) used in the Space Shuttle Main Engine (SSME). Although the HPOTP design life is 27,000 seconds at 30,000 rpms, or approximately 50 missions, bearings must currently be replaced after 2 missions. One solution to the bearing wear problem in the HPOTP, as well as in future turbopump designs, is the utilization of fluid film bearings in lieu of continuous contact bearings. Hydrostatic, hydrodynamic, and damping seal bearings are all replacement candidates for contact bearings in rocket engine high speed turbomachinery. These three types of fluid film bearings have different operating characteristics, but they share a common set of mechanical design opportunities and difficulties. Results of research to define some of the mechanical design issues are given. Problems considered include transient strat/stop rub, non-operational rotor support, bearing wear inspection and measurement, and bearing fluid supply route. Emphasis is given to the HPOTP preburner pump (PBP) bearing, but the results are pertinent to high-speed cryogenic turbomachinery in general.

Evces, Charles R.

1990-01-01

98

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

99

Tooling Converts Stock Bearings To Custom Bearings  

NASA Technical Reports Server (NTRS)

Technique for reworking stock bearings saves time and produces helicopter-rotor bearings ground more precisely. Split tapered ring at one end of threaded bolt expands to hold inside of inner race bearing assembly; nut, at other end of bolt, adjusts amount of spring tension. Piece of hardware grasps bearing firmly without interfering with grinding operation. Operation produces bearing of higher quality than commercially available bearings.

Fleenor, E. N., Jr.

1983-01-01

100

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

101

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

102

Hydrostatic Hamiltonian particle-mesh (HPM) methods for atmospheric modeling.  

E-print Network

Hydrostatic Hamiltonian particle-mesh (HPM) methods for atmospheric modeling. Seoleun Shin Sebastian Reich Jason Frank August 19, 2011 Abstract We develop a hydrostatic Hamiltonian particle-mesh (HPM) method for efficient long-term numerical integration of the atmosphere. In the HPM method, the hydro

Reich, Sebastian

103

Hydrostatic Hamiltonian particle mesh (HPM) methods for atmospheric modeling.  

E-print Network

Hydrostatic Hamiltonian particle mesh (HPM) methods for atmospheric modeling. Seoleun Shin Sebastian Reich Jason Frank March 17, 2011 Abstract We develop a hydrostatic Hamiltonian particle mesh (HPM) method for efficient long-term numerical integration of the atmosphere. In the HPM method, the hydro

Frank, Jason

104

Secular love numbers and hydrostatic equilibrium of planets  

Microsoft Academic Search

The secular Love numbers of planets and of the Moon have been computed by use of the recent satellite data. It has been demonstrated that Venus, Mercury, and the Moon are far from the ideal hydrostatic equilibrium; the angular velocities (rotation periods) which correspond to the hydrostatic equilibrium have been computed.

M. Bursa

1984-01-01

105

Polar Bear  

NSDL National Science Digital Library

In this episode of the Podcast of Life, host Ari Daniel Shapiro relates two close calls with polar bears. Listen as Heather Cray recalls how, dumped by a storm on a small Arctic island without a shotgun, she got an unexpected wake-up call. And when researcher Steve Amstrup accidentally crashed through the roof of a polar bearâs den, no one could predict what happened next. Also included is a Learn More section that provides background information on the scientists recorded in the podcast, lessons, images, and cool facts.

2009-01-01

106

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

107

Magnetic bearings for free-piston Stirling engines  

NASA Technical Reports Server (NTRS)

The feasibility and efficacy 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 efficiency 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.; Fleming, D. P.; Rao, D. K.; Wilson, D. S.

1992-01-01

108

Magnetic bearings for free-piston Stirling engines  

NASA Astrophysics Data System (ADS)

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.

109

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

110

Designing a high-efficiency hydrostatic bicycle transmission  

E-print Network

Hydrostatic bicycle drives use a working fluid instead of the common roller-chain to transmit power to the drive wheel. These transmissions are typically considered too inefficient for human power applications. An experiment ...

Socks, Matthew T. (Matthew Tristram)

2006-01-01

111

Hydrostatic photoionization models of the Orion Bar  

NASA Astrophysics Data System (ADS)

Due to its proximity to the Earth and its nearly edge-on geometry, the Orion Bar provides an excellent testbed for detailed models of the structure of H II regions and the surrounding photon-dominated regions. In this study, a self-consistent model of the structure of the Orion Nebula in the vicinity of the Bar is built under the assumption of approximate ionization, thermal and hydrostatic equilibrium. It is found that a fairly simple geometry is able to describe the surface brightness profiles of the emission lines tracing the ionized H II region with a remarkable accuracy, independent of the prescription adopted to set the magnetic field or the population of cosmic rays. Although we consider different scenarios for these non-thermal components, none of the models is able to provide a fully satisfactory match to the observational data for the atomic layer, and the predicted column densities of several molecular species are always well above the measured abundances. Contrary to previous studies, we conclude that a more elaborate model is required in order to match all the available data.

Ascasibar, Y.; Obreja, A. C.; Díaz, A. I.

2011-09-01

112

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

113

Hydrostatic Pressure Influences HIF-2 Alpha Expression in Chondrocytes  

PubMed Central

Hypoxia-inducible factor (HIF)-2? is considered to play a major role in the progression of osteoarthritis. Recently, it was reported that pressure amplitude influences HIF-2? expression in murine endothelial cells. We examined whether hydrostatic pressure is involved in expression of HIF-2? in articular chondrocytes. Chondrocytes were cultured and stimulated by inflammation or hydrostatic pressure of 0, 5, 10, or 50 MPa. After stimulation, heat shock protein (HSP) 70, HIF-2?, nuclear factor kappa B (NF-?B), matrix metalloproteinase (MMP)-13, MMP-3, and vascular endothelial growth factor (VEGF) gene expression were evaluated. The levels of all gene expression were increased by inflammatory stress. When chondrocytes were exposed to a hydrostatic pressure of 5 MPa, HIF-2?, MMP-13, and MMP-3 gene expression increased significantly although those of HSP70 and NF-?B were not significantly different from the control group. In contrast, HIF-2? gene expression did not increase under a hydrostatic pressure of 50 MPa although HSP70 and NF-?B expression increased significantly compared to control. We considered that hydrostatic pressure of 5 MPa could regulate HIF-2? independent of NF-?B, because the level of HIF-2? gene expression increased significantly without upregulation of NF-?B expression at 5 MPa. Hydrostatic pressure may influence cartilage degeneration, inducing MMP-13 and MMP-3 expression through HIF-2?. PMID:25569085

Inoue, Hiroaki; Arai, Yuji; Kishida, Tsunao; Terauchi, Ryu; Honjo, Kuniaki; Nakagawa, Shuji; Tsuchida, Shinji; Matsuki, Tomohiro; Ueshima, Keiichirou; Fujiwara, Hiroyoshi; Mazda, Osam; Kubo, Toshikazu

2015-01-01

114

Optimal Synchronizability of Bearings  

E-print Network

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 ...

Seybold, Hansjorg

115

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. PMID:19645529

Frieboes, Laura R.

2009-01-01

116

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

117

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

118

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

119

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)

2011-01-25

120

Bearings for Your Whirligig  

NSDL National Science Digital Library

Experiment with friction and make bearings for a whirligig! This activity is a nice introduction to friction and bearings and demonstrates why bearings are useful for spinning. A related video show Vollis Simpson, an artist who creates kinetic sculptures and whirligigs, explain how he uses bearings in all of his spinning pieces so that they move smoothly.

Science Musuem of Minnesota

1995-01-01

121

Restoration of bearings  

NASA Technical Reports Server (NTRS)

Process consisting of grinding raceways to oversize but original quality condition and installing new oversize balls or bearings restores wornout ball and roller bearings to original quality, thereby doubling their operating life. Evaluations reveal process results in restoration of 90% of replaced bearings at less than 50% of new-bearing costs.

Parker, R. J.; Zaretsky, E. V.; Hanau, H.

1977-01-01

122

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

123

Theory for hydrostatic gas journal bearings for micro-electro-mechanical systems  

E-print Network

The goal of the MIT micro-engine project is to develop high-speed rotating Power MEMS (Micro-Electro-Mechanical Systems) using computer chip fabrication technologies. To produce high power (10-50 W) in a small volume (less ...

Liu, Lixian, Ph. D. Massachusetts Institute of Technology

2005-01-01

124

Orbital transfer vehicle oxygen turbopump technology. Volume 1: Design, fabrication, and hydrostatic bearing testing  

NASA Technical Reports Server (NTRS)

The design, fabrication, and initial testing of a rocket engine turbopump (TPA) for the delivery of high pressure liquid oxygen using hot oxygen for the turbine drive fluid are described. This TPA is basic to the dual expander engine which uses both oxygen and hydrogen as working fluids. Separate tasks addressed the key issue of materials for this TPA. All materials selections emphasized compatibility with hot oxygen. The OX TPA design uses a two-stage centrifugal pump driven by a single-stage axial turbine on a common shaft. The design includes ports for three shaft displacement/speed sensors, various temperature measurements, and accelerometers.

Buckmann, P. S.; Hayden, W. R.; Lorenc, S. A.; Sabiers, R. L.; Shimp, N. R.

1990-01-01

125

Orbital transfer vehicle oxygen turbopump technology. Volume 1: Design, fabrication, and hydrostatic bearing testing. Final Report  

SciTech Connect

The design, fabrication, and initial testing of a rocket engine turbopump (TPA) for the delivery of high pressure liquid oxygen using hot oxygen for the turbine drive fluid are described. This TPA is basic to the dual expander engine which uses both oxygen and hydrogen as working fluids. Separate tasks addressed the key issue of materials for this TPA. All materials selections emphasized compatibility with hot oxygen. The OX TPA design uses a two-stage centrifugal pump driven by a single-stage axial turbine on a common shaft. The design includes ports for three shaft displacement/speed sensors, various temperature measurements, and accelerometers.

Buckmann, P.S.; Hayden, W.R.; Lorenc, S.A.; Sabiers, R.L.; Shimp, N.R.

1990-12-01

126

Notes 12. (a) Annular pressure (damper) seals, and (b) Hydrostatic journal bearings  

E-print Network

/D=0.2 D=152.4 mm c =0.190 mm ?=0.792 cPoise ?=995 kg/m3 26 Whirl ratio vs shaft speed 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.0 1000.0 2000.0 3000.0 4000.0 5000.0 6000.0 Rotor Speed (RPM) Wh irl freq u e n cy r a tio Nominal clearance (with swirl) "" no swirl... Speed (RPM) Flow r a te Nominal clearance (C) Twice clearance (worn) No effect of inlet swirl kg/s operating speed 3600 rpm water seal, L/D=0.50, c=0.190 mm, D=152 mm L/D=0.50 Leakage vs shaft speed 0 2 4 6 8 10 12 14 16 18 0 1000 2000 3000 4000 5000...

San Andres, Luis

2009-01-01

127

Wheel drives for large telescopes: save the cost and keep the performance over hydrostatic bearings  

NASA Astrophysics Data System (ADS)

The use of steel wheels on steel tracks has been around since steel was invented, and before that it was iron wheels on iron tracks. Not to be made obsolete by the passage of time, this approach for moving large objects is still valid, even optimal, but the detailed techniques for achieving high performance and long life have been much improved. The use of wheel-and-track designs has been very popular in radio astronomy for the largest of the large radio telescopes (RT), including such notables as the 305m Arecibo RT, the 100m telescopes at Effelsberg, Germany (at 3600 tonnes) and the Robert C. Byrd, Greenbank Telescope (GBT, 7600 tonnes) at Greenbank, West Virginia. Of course, the 76m Lovell Telescope at Jodrell Bank is the grandfather of all large aperture radio telescopes that use wheel drives. Smaller sizes include NRAO's Very Long Baseline Array (VLBA) telescopes at 25m and others. Wheel drives have also been used on large radars of significance such as the 410 tonne Ground Based Radar-Prototype (GBR-P) and the 150 foot (45.7m) Altair Radar, and the 2130 tonne Sea Based X-Band Radar (SBX). There are also many examples of wheel driven communications antennas of 18 meters and larger. All of these instruments have one thing in common: they all use steel wheels that run in a circle on one or more flat, level, steel tracks. This paper covers issues related to designing for wheel driven systems. The intent is for managing motion to sub arc-second levels, and for this purpose it is primary for the designer to manage measurement and alignment errors, and to establish repeatability through dimensional control, structural and drive stiffness management, adjustability and error management. In a practical sense, there are very few, if any, fabricators that can machine structural and drive components to sufficiently small decimal places to matter. In fact, coming within 2-3 orders of magnitude of the precision needed is about the best that can be expected. Further, it is incumbent on the design team to develop the servo control system features, correction algorithms and structural features in concert with each other. Telescope designers are generally adept at many of these practices, so the scope of this paper is not that, but is limited to those items that pertain to a precision wheel driven system.

Campbell, Marvin F.

2014-07-01

128

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

129

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

130

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

131

A hydrostatic stress-dependent anisotropic model of viscoplasticity  

NASA Technical Reports Server (NTRS)

A hydrostatic stress-dependent, anisotropic model of viscoplasticity is formulated as an extension of Bodner's model. This represents a further extension of the isotropic Bodner model over that made to anisotropy by Robinson and MitiKavuma. Account is made of the inelastic deformation that can occur in metallic composites under hydrostatic stress. A procedure for determining the material parameters is identified that is virtually identical to the established characterization procedure for the original Bodner model. Characterization can be achieved using longitudinal/transverse tensile and shear tests and hydrostatic stress tests; alternatively, four off-axis tensile tests can be used. Conditions for a yield stress minimum under off-axis tension are discussed. The model is applied to a W/Cu composite; characterization is made using off-axis tensile data generated at NASA Lewis Research Center (LeRC).

Robinson, D. N.; Tao, Q.; Verrilli, M. J.

1994-01-01

132

Hydrostatic levelling systems: Measuring at the system limits  

NASA Astrophysics Data System (ADS)

Three hydrostatic displacement monitoring system applications in Switzerland are discussed; the first concerns experience gained monitoring the foundation of the Albigna dam, the second relating to the underground stability of the Swiss Light Source synchrotron and the third concerning the deformation of a bridge near the city of Lucerne. Two different principles were applied, the Hydrostatic Levelling System (HLS) using the “half-filled pipe principle” developed by the Paul Scherrer Institute and the Large Area Settlement System (LAS) using the “differential pressure principle”. With both systems ground deformations induced by tidal forces can be seen. However, high accuracy of single sensors is not sufficient. A well-designed configuration of the complete system is equally important. On the other hand there are also limits imposed by installation logistics and by the environmental conditions. An example is the bridge monitoring application, where the acceleration along the bridge due to the passage of heavy trucks limits the feasibility of using hydrostatic levelling measurements.

Meier, Edi; Geiger, Alain; Ingensand, Hilmar; Licht, Hans; Limpach, Philippe; Steiger, Andreas; Zwyssig, Roger

2010-09-01

133

Accurate pressure gradient calculations in hydrostatic atmospheric models  

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

134

Pairwise association of neopentane as a function of hydrostatic pressure  

NASA Astrophysics Data System (ADS)

It is shown that the contact-minimum configuration of two neopentane molecules is favoured on increasing hydrostatic pressure over the range 1-4000 atm, at room temperature, in line with the methane results (Graziano, 2014). This is due to the decrease in water accessible surface area accompanying the association, that leads to a gain in configurational/translational entropy of water molecules, whose magnitude increases with hydrostatic pressure. Of course, the strengthening of pairwise hydrophobic interaction cannot shed light on the pressure-induced denaturation of globular proteins.

Graziano, Giuseppe

2014-11-01

135

Bearing Failure Detection  

NASA Technical Reports Server (NTRS)

Shaker Research Corporation, under a contract with NASA, produced a test vehicle that measures resonant frequency of railroad roller bearings to identify source of bearings defects. Marshall scientists have developed a detection concept based on fact that bearing defects themselves excite resonant frequency of rolling elements of bearing as they impact the defect. By detecting resonant frequency and subsequently analyzing character of the signal, bearing defects may be detected and identified as to source. The bearing fault detector will help eliminate this cause of derailments.

1976-01-01

136

Comparison of hydrostatic and hydrodynamic pressure to inactivate foodborne viruses  

Technology Transfer Automated Retrieval System (TEKTRAN)

The effect of high hydrostatic pressure (HPP) and hydrodynamic pressure (HDP), in combination with chemical treatments, was evaluated for inactivation of foodborne viruses and non-pathogenic surrogates in a pork sausage product. Sausages were immersed in water, 100 ppm EDTA, or 2 percent lactoferrin...

137

Electrical breakdown of polyethylene terephthalate under hydrostatic pressure  

NASA Astrophysics Data System (ADS)

Measurements of dc dielectric breakdown strength were made on polyethylene terephthalate films of 50 micrometers in thickness at temperatures of 35, 70, and 100 C under hydrostatic pressure ranging from 50 to 500 bar. It has been found that the electrical breakdown field E(sub b) increases with pressure and decreases with temperature. It is suggested that thermal breakdown is the dominant process.

Zebouchi, N.; Essolbi, R.; Malec, D.; Giam, Hoang The; Ai, Bui; Bendaoud, M.

1994-12-01

138

Wind resource assessment with a mesoscale non-hydrostatic model  

E-print Network

Wind resource assessment with a mesoscale non- hydrostatic model Vincent Guénard, Center for Energy is developed for assessing the wind resource and its uncertainty. The work focuses on an existing wind farm mast measurements. The wind speed and turbulence fields are discussed. It is shown that the k

Boyer, Edmond

139

Hydrometer calibration by hydrostatic weighing with automated liquid surface positioning  

Microsoft Academic Search

We describe an automated apparatus for calibrating hydrometers by hydrostatic weighing (Cuckow's method) in tridecane, a liquid of known, stable density, and with a relatively low surface tension and contact angle against glass. The apparatus uses a laser light sheet and a laser power meter to position the tridecane surface at the hydrometer scale mark to be calibrated with an

Jesus Aguilera; John D. Wright; Vern E. Bean

2008-01-01

140

Non-hydrostatic general circulation model of the Venus atmosphere  

Microsoft Academic Search

We present the first non-hydrostatic global circulation model of the Venus atmosphere based on the complete set of gas dynamics equations. The model employs a spatially uniform triangular mesh that allows to avoid artificial damping of the dynamical processes in the polar regions, with altitude as a vertical coordinate. Energy conversion from the solar flux into atmospheric motion is described

Alexander V. Rodin; Igor Mingalev; Konstantin Orlov; Nikolay Ignatiev

2010-01-01

141

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

142

Ab initio calculation of hydrostatic absolute deformation potential of semiconductors  

E-print Network

on the wavefunction characters of the energy levels.3 It is now well accepted that the difference of the volume. ii The kinetic energy- induced band broadening. When the volume decreases, the bandwidth increasesAb initio calculation of hydrostatic absolute deformation potential of semiconductors Yong-Hua Li

Gong, Xingao

143

Experiments with needle bearings  

NASA Technical Reports Server (NTRS)

Experiments and results are presented in testing needle bearings, especially in comparison with roller bearings. Reduction in coefficient of friction is discussed as well as experimental methods and recording devices.

Ferretti, Pericle

1933-01-01

144

Tracking Polar Bears  

NSDL National Science Digital Library

In this interactive activity adapted from the USGS Alaska Science Center, track the movements of a polar bear as it migrates across the changing Arctic sea ice and compare the paths of four different polar bears.

Foundation, Wgbh E.

2008-01-17

145

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

146

ENSC 283: Center of Pressure and Hydrostatic Force on a submerged body School of Engineering Science  

E-print Network

ENSC 283: Center of Pressure and Hydrostatic Force on a submerged body 1 School of Engineering and bottom faces are concentric circular arcs centered on the pivot so that the resultant hydrostatic force of the apparatus. #12;ENSC 283: Center of Pressure and Hydrostatic Force on a submerged body 2 School

Bahrami, Majid

147

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

148

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

149

Good bearings reduce downtime  

Microsoft Academic Search

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

J. Kinney; J. Foster

1982-01-01

150

Grizzly bears and forestry  

Microsoft Academic Search

Today's growing demand for timber is increasing road development in once roadless forest ecosystems. Roads create both local changes in plant communities and landscape-level changes in forest connectivity. Roads also increase human access, which can be detrimental to species such as grizzly bears. Because most grizzly bear mortalities occur near roads, we examined grizzly bear attractants near roads, which could

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

2008-01-01

151

1-Way Bearing  

NASA Technical Reports Server (NTRS)

A one-way bearing is provided having sprags and rolling bearings both disposed between an inner and an outer race. The sprags may comprise three-dimensional sprags for preventing rotation in a non-preferential direction. The roll- ing bearings may comprise thrust rollers for transmitting axial, tilt, and radial loads between the inner and outer races.

Vranish, John M. (Inventor)

2003-01-01

152

Supertough Stainless Bearing Steel  

NASA Technical Reports Server (NTRS)

Composition and processing of supertough stainless bearing steel designed with help of computer-aided thermodynamic modeling. Fracture toughness and hardness of steel exceeds those of other bearing steels like 440C stainless bearing steel. Developed for service in fuel and oxidizer turbopumps on Space Shuttle main engine. Because of strength and toughness, also proves useful in other applications like gears and surgical knives.

Olson, Gregory B.

1995-01-01

153

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

154

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

155

Analysis of ?-phase RDX vibrational lattice modes under hydrostatic pressure  

NASA Astrophysics Data System (ADS)

Calculations employing density functional theory are performed on ?-phase RDX using the all-electron CRYSTAL06 program. The lowest frequency infrared active lattice modes are investigated as a function of hydrostatic pressure from ambient conditions up to 3 GPa. The strength of coupling between lattice and molecular modes as a function of pressure is examined. The anharmonic deviation of each mode from simple harmonic behavior as a function of pressure is also illustrated.

Slough, William; Perger, Warren

2009-06-01

156

Rectangular Shell Plating Under Uniformly Distributed Hydrostatic Pressure  

NASA Technical Reports Server (NTRS)

A check of the calculation methods used by Foppl and Henky for investigating the reliability of shell plating under hydrostatic pressure has proved that the formulas yield practical results within the elastic range of the material. Foppl's approximate calculation leaves one on the safe side. It further was found on the basis of the marked ductility of the shell plating under tensile stress that the strength is from 50 to 100 percent higher in the elastic range than expected by either method.

Neubert, M; Sommer, A

1940-01-01

157

A New Inversion for the Hydrostatic Stratification of the Sun  

NASA Astrophysics Data System (ADS)

Inversions for the spherically symmetric component of the hydrostatic stratification of the Sun are presented. These employ the Backus-Gilbert optimally localized averaging procedure applied to oscillation multiplet frequencies in the range 1.5 - 3 mHz of modes with 4 l 140 determined by Libbrecht et al. (1990) from observations carried out in 1986. We also obtain an estimate of the helium abundance in the solar convective envelope.

Däppen, W.; Gough, D. O.; Kosovichev, A. G.; Thompson, M. J.

158

Magnetotransport studies of FeSe under hydrostatic pressure  

NASA Astrophysics Data System (ADS)

The discoveries of iron-based superconductors with relatively high transition temperature are under intense experimental and theoretical investigation. Here we present magnetotransport measurements on FeSe superconductor under hydrostatic pressure. We show that in Fe-deficient tetragonal FeSe binary compound, the onset of superconducting transition is almost doubled under 1.98 GPa pressure and the estimated upper critical field of 26.7 Tesla is increased to 47.5 Tesla.

Tiwari, Brajesh; Jha, Rajveer; Awana, V. P. S.

2014-06-01

159

High hydrostatic pressure technology in dairy processing: a review  

Microsoft Academic Search

Consumers demand high quality foods, which are fresh, tasty and nutritious; this has created considerable interest in the\\u000a development of new food processing techniques. Presently, non-thermal techniques, including high hydrostatic pressure (HHP),\\u000a are regarded with special interest by the food industry. Pressure ranges between 100 and 1200 MPa have been considered as\\u000a effective to inactivate microorganisms including food-borne pathogens. HHP also

Rekha Chawla; Girdhari Ramdass Patil; Ashish Kumar Singh

2011-01-01

160

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

161

Non-equilibration of hydrostatic pressure in blebbing cells.  

PubMed

Current models for protrusive motility in animal cells focus on cytoskeleton-based mechanisms, where localized protrusion is driven by local regulation of actin biochemistry. In plants and fungi, protrusion is driven primarily by hydrostatic pressure. For hydrostatic pressure to drive localized protrusion in animal cells, it would have to be locally regulated, but current models treating cytoplasm as an incompressible viscoelastic continuum or viscous liquid require that hydrostatic pressure equilibrates essentially instantaneously over the whole cell. Here, we use cell blebs as reporters of local pressure in the cytoplasm. When we locally perfuse blebbing cells with cortex-relaxing drugs to dissipate pressure on one side, blebbing continues on the untreated side, implying non-equilibration of pressure on scales of approximately 10 microm and 10 s. We can account for localization of pressure by considering the cytoplasm as a contractile, elastic network infiltrated by cytosol. Motion of the fluid relative to the network generates spatially heterogeneous transients in the pressure field, and can be described in the framework of poroelasticity. PMID:15902261

Charras, Guillaume T; Yarrow, Justin C; Horton, Mike A; Mahadevan, L; Mitchison, T J

2005-05-19

162

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

163

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

164

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

165

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

166

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

167

Linear magnetic bearing  

NASA Technical Reports Server (NTRS)

A linear magnetic bearing system having electromagnetic vernier flux paths in shunt relation with permanent magnets, so that the vernier flux does not traverse the permanent magnet, is described. Novelty is believed to reside in providing a linear magnetic bearing having electromagnetic flux paths that bypass high reluctance permanent magnets. Particular novelty is believed to reside in providing a linear magnetic bearing with a pair of axially spaced elements having electromagnets for establishing vernier x and y axis control. The magnetic bearing system has possible use in connection with a long life reciprocating cryogenic refrigerator that may be used on the space shuttle.

Studer, P. A. (inventor)

1983-01-01

168

A feasibility assessment of magnetic bearings for free-piston Stirling space power converters  

NASA Astrophysics Data System (ADS)

This report describes a design and analysis study performed by Mechanical Technology Incorporated (MTI) under NASA Contract NAS3-26061. The objective of the study was to assess the feasibility and efficacy of applying magnetic bearings to free-piston Stirling-cycle power conversion machinery of the type currently being evaluated for possible use in long-term space missions. The study was performed for a 50-kWe Reference Stirling Space Power Converter (RSSPC) system consisting of two 25-kWe free-piston Stirling engine modules. Two different versions of the RSSPC engine modules have been defined under NASA Contract NAS3-25463. These modules currently use hydrostatic gas bearings to support the reciprocating displacer and power piston assemblies. Results of this study show that active magnetic bearings of the attractive electromagnetic type are technically feasible for RSSPC application provided that wire insulation with 60,000-hr life capability at 300 C can be developed for the bearing coils. From a design integration standpoint, both versions of the RSSPC were found to be conceptually amenable to magnetic support of the power piston assembly. However, only one version of the RSSPC was found to be amendable to magnetic support of the displacer assembly. Unacceptable changes to the basic engine design would be required to incorporate magnetic displacer bearings into the second version. Complete magnetic suspension of the RSSPC can potentially increase overall efficiency of the Stirling cycle power converter by 0.53 to 1.4 percent (0.15 to 0.4 efficiency points). Magnetic bearings will also overcome several operational concerns associated with hydrostatic gas bearing systems. However, these advantages are accompanied by a 5 to 8 percent increase in specific mass of the RSSPC, depending on the RSSPC version employed. Additionally, magnetic bearings are much more complex, both mechanically and particularly electronically, than hydrostatic bearings. Accordingly, long-term stability and reliability represent areas of uncertainty for magnetic bearings. Considerable development effort will be required to establish the long-term suitability of these bearings for Stirling space power applications.

Curwen, Peter W.; Rao, Dantam K.; Wilson, Donald R.

1992-06-01

169

Investigation of a Hydrostatic Weighing Method for a 1 kg Mass Comparator  

NASA Astrophysics Data System (ADS)

A mass comparator for the comparison of 1 kg weights was built according to a hydrostatic weighing principle, where the buoyancy in a liquid serves to compensate the force due to gravity. In accordance with the method known for hydrometers or areometers, the immersion depth of a float is measured as a function of the force due to gravity, using a laser interferometer. The substitution principle can thus be quite simply realized at constant load. An essential advantage of this weighing method compared with the mechanical beam balance results from the frictionless and vibration-resistant bearing of the float in the liquid. For achieving a high accuracy with this technique, two prerequisites were important: the reduction of the influence of temperature by adapting the coefficients of expansion of buoyant body and liquid to each other, and the improvement of the wetting property of the liquid by adding a surfactant. The accuracy was further improved by the use of an electromagnetic feedback control to keep the immersion depth constant. By this method, a relative standard deviation of the weighings of better than 5 × 10-9 could be achieved.

Probst, R.; Kochsiek, M.

1984-01-01

170

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

171

Hollow rolling element bearings  

NASA Technical Reports Server (NTRS)

A low mass rolling element with a lightweight core and hollow center was developed for use in bearings. The core is plated so as to provide a hard surface and increase the life and reliability of the high speed ball bearings.

Parker, R. J. (inventor)

1973-01-01

172

Grizzly bears and forestry  

Microsoft Academic Search

We assessed the occurrence and fruit production of 13 grizzly bear foods in west-central Alberta, Canada, to better understand use of clearcuts by grizzly bears. Comparisons were made between clearcuts and upland forest stands, while specific models describing food or fruit occurrence within clearcuts were developed from canopy, clearcut age, scarification, and terrain-related variables using logistic regression. Ants, Equisetum spp.,

S. E. Nielsen; R. H. M. Munro; E. L. Bainbridge; G. B. Stenhouse; M. S. Boyce

2004-01-01

173

ALASKAN POLAR BEAR DENNING  

Microsoft Academic Search

Abstract: Information on 35 overwinter maternity dens of Alaskan polar bears (Ursus maritimnus Phipps) and on 101 female polar bears with cubs, recently emerged from dens, was obtained by aerial and ground surveys, interviews with Arctic coast residents, and literature review. Pregnant females form snow dens in October and November and give birth in December and January. Females and cubs

Jack W. Lentfer; Richard J. Hensel

174

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

175

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

176

OTV bearing deflection investigation  

NASA Technical Reports Server (NTRS)

The primary goal of the Bearing Deflectometer Investigation was to gain experience in the use of fiber optic displacement probe technology for bearing health monitoring in a liquid hydrogen turbo pump. The work specified in this Task Order was conducted in conjunction with Air Force Rocket Propulsion Laboratory Contract F04611-86-C-0010. APD conducted the analysis and design coordination to provide a displacement probe design compatible with the XLR-134 liquid hydrogen turbo pump assembly (TPA). Specifications and requirements of the bearing deflectometer were established working with Mechanical Technology Instruments, Inc. (MTI). The TPA design accommodated positioning of the probe to measure outer race cyclic deflections of the pump inlet bearing. The fiber optic sensor was installed as required in the TPA and sensor output was recorded during the TPA testing. Data review indicated that no bearing deflection signature could be differentiated from the inherent system noise. Alternate sensor installations were not investigated, but might yield different results.

Reimer, B. L.; Diepenbrock, R. T.; Millis, M. G.

1993-01-01

177

Touchdown Ball-Bearing System for Magnetic Bearings  

NASA Technical Reports Server (NTRS)

The torque-limited touchdown bearing system (TLTBS) is a backup mechanical-bearing system for a high-speed rotary machine in which the rotor shaft is supported by magnetic bearings in steady-state normal operation. The TLTBS provides ball-bearing support to augment or supplant the magnetic bearings during startup, shutdown, or failure of the magnetic bearings. The TLTBS also provides support in the presence of conditions (in particular, rotational acceleration) that make it difficult or impossible to control the magnetic bearings or in which the magnetic bearings are not strong enough (e.g., when the side load against the rotor exceeds the available lateral magnetic force).

Kingsbury, Edward P.; Price, Robert; Gelotte, Erik; Singer, Herbert B.

2003-01-01

178

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.

179

New double beam spectrophotometer for microsamples. Application to hydrostatic pressure experiments  

E-print Network

New double beam spectrophotometer for microsamples. Application to hydrostatic pressure experiments) This article describes a new double beam spectrophotometer specially conceived for optical absorption

Rodríguez, Fernando

180

Analysis of ?-PHASE Rdx Vibrational Lattice Modes Under Hydrostatic Pressur  

NASA Astrophysics Data System (ADS)

Calculations using the all-electron CRYSTAL06 program employing density functional theory are used to calculate the terahertz vibrational frequencies of ?-phase RDX. The lowest frequency infrared active lattice modes are investigated as a function of hydrostatic pressure from ambient conditions up to 3 GPa. A given mode may be composed of both external and internal vibration contributions, with the composition changing as a function of pressure. The anharmonic deviation of each mode from simple harmonic behavior as a function of pressure is also explored.

Slough, W. J.; Perger, W. F.

2009-12-01

181

Steel pressure vessels for hydrostatic pressures to 50 kilobars.  

PubMed

Cylindrical steel pressure vessels are described that can be used for hydrostatic pressures up to 50 kilobars. Monoblock vessels of 350 maraging steel can be used to 40 kilobars and compound vessels with an inner vessel of 350 maraging steel and an outer vessel of 300 maraging steel to 50 kilobars. Neither requires the cylinder to be end loaded, and so they are much easier to use than the more usual compound vessels with a tungsten carbide inner and steel outer vessel. PMID:18699223

Lavergne, A; Whalley, E

1978-07-01

182

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

183

The Polar Bear Tracker  

NSDL National Science Digital Library

This new Web site from the World Wildlife Fund (WWF) International explores how polar bears are affected by global warming. Data on the movements of two radio-collared bears can be viewed, along with the ice status, through a series of online maps. This is an interesting site with valuable information and a nice balance of maps, photos, and text. The animation of the polar bear tracking data is a really neat feature, but is best viewed by advancing through the stages manually because the rapid speed of the film makes it difficult to comprehend.

2002-01-01

184

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

185

Photomultiplier tube failure under hydrostatic pressure in future neutrino detectors  

NASA Astrophysics Data System (ADS)

Failure of photomultiplier tubes (PMTs) under hydrostatic pressure is a concern in neutrino detection, specifically, in the proposed Long-Baseline Neutrino Experiment (LBNE) project. Controlled hydrostatic implosion tests were performed on prototypic PMT bulbs of 10-inch diameter and recorded using high-speed filming techniques to capture failures in detail. These high-speed videos were analyzed frame-by-frame in order to identify the origin of a crack, measure the progression of individual crack along the surface of the bulb as it propagates through the glass, and estimate crack velocity. Crack velocity was calculated for each individual crack and an average velocity was determined for all measurable cracks on each bulb. Overall, 32 cracks were measured in 9 different bulbs tested. Finite element modeling (FEM) of crack formation and growth in prototypic PMT shows stress concentration near the middle section of the PMT bulbs that correlates well with our crack velocity measurements in that section. The FEM model predicts a crack velocity value that is close to the terminal crack velocity reported. Our measurements also reveal significantly reduced crack velocities compared to terminal crack velocities measured in glasses using fracture mechanics testing and reported in literature.

Chambliss, K.; Sundaram, S. K.; Simos, N.; Diwan, M. V.

2014-10-01

186

Deformation texture of hydrostatically extruded polycrystalline NiAl  

SciTech Connect

NiAl is currently a candidate for high temperature structural applications because of its high melting temperature, low density, and excellent oxidation resistance. Polycrystalline NiAl possesses low ductility at ambient temperatures, but it has a brittle-to-ductile transition temperature (BDTT) of approximately 573 K (1,2). Its high melting temperature, however, puts limits on its formability, usually requiring it to be processed at high temperatures. High temperature processing can lead to diffusive effects which may nullify the benefits of deformation processing. Processing of NiAl at lower temperatures, yet above its BDTT, might yield the conditions necessary for large amounts of strain to be attained from processing but might also limit the amount of diffusion related phenomena that would occur either during or following high temperature deformation. Deformation textures give insight into the modes of deformation that result from processing. When extruded below approximately 1,173 K, NiAl typically develops a (110) fiber texture. When extruded at higher temperatures or subsequently annealed, a (111) recrystallization temperature develops. The first successful low temperature hydrostatic extrusion of NiAl has been reported recently. It is the purpose of this paper to give the details of the resulting deformation texture and relate it to the potential benefits of processing of NiAl with the use of hydrostatic pressure.

Margevicius, R.W. (Los Alamos National Lab., NM (United States)); Lewandowski, J.J. (Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Materials Science and Engineering)

1993-12-15

187

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

188

High speed hybrid bearing comprising a fluid bearing and a rolling bearing convected in series  

NASA Technical Reports Server (NTRS)

A description is given of an antifriction bearing and a process by which its fatigue life may be extended. The method involves a rotating shaft supported by a fluid bearing and a rolling element bearing coupled in series. Each bearing turns at a fraction of the rotational speed of the shaft. The fluid bearing is preferably conical, thereby providing thrust and radial load support in a single bearing structure.

Anderson, W. J. (inventor)

1973-01-01

189

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

190

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

191

New spherical roller bearings  

Microsoft Academic Search

Describes SKF’s three new spherical roller bearings, E for smoother running, VA 405 to resist vibration and CARB for axial displacement and misalignment. Gives a paper mill as an example of the successful use of CARB.

Bill Wilson

1995-01-01

192

Protecting Bear While Tranqualized  

USGS Multimedia Gallery

The kerchief over the bear's eyes protects it from dust and debris and reduces visual stimulation. The small tubing in its nose, known as a nasal cannula, delivers oxygen to the animal while it is tranquilized....

193

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

194

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

195

The Great Bear Rainforest Spirit Bears, Grizzlies and Ancient Forests  

E-print Network

The Great Bear Rainforest Spirit Bears, Grizzlies and Ancient Forests September 16 ­ 22, 2015 the verdant coastline of British Columbia. Migrating salmon and hungry coastal bears go together like popcorn at the movies and the Great Bear Rainforest is one of the world's best places to witness this primordial drama

de Leon, Alex R.

196

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

197

Magnetic bearing and motor  

NASA Technical Reports Server (NTRS)

A magnetic bearing for passively suspending a rotatable element subjected to axial and radial thrust forces is disclosed. The magnetic bearing employs a taut wire stretched along the longitudinal axis of the bearing between opposed end pieces and an intermediate magnetic section. The intermediate section is segmented to provide oppositely directed magnetic flux paths between the end pieces and may include either an axially polarized magnets interposed between the segments. The end pieces, separated from the intermediate section by air gaps, control distribution of magnetic flux between the intermediate section segments. Coaxial alignment of the end pieces with the intermediate section minimizes magnetic reluctance in the flux paths endowing the bearing with self-centering characteristics when subjected to radial loads. In an alternative embodiment, pairs of oppositely wound armature coils are concentrically interposed between segments of the intermediate section in concentric arcs adjacent to radially polarized magnets to equip a magnetic bearing as a torsion drive motor. The magnetic suspension bearing disclosed provides long term reliability without maintenance with application to long term space missions such as the VISSR/VAS scanning mirror instrument in the GOES program.

Studer, P. A. (inventor)

1983-01-01

198

Impact of non-hydrostatic effects and trapped lee waves on mountain wave drag  

E-print Network

Impact of non-hydrostatic effects and trapped lee waves on mountain wave drag in directionally;AcceptedArticle Impact of non-hydrostatic effects and trapped lee waves on mountain wave drag gravity wave drag produced in flow over an axisymmetric mountain when both vertical wind shear and non

Wirosoetisno, Djoko

199

ERK activation is required for hydrostatic pressure induced-tensile changes in engineered articular cartilage  

PubMed Central

The objective of this study was to identify the ERK 1/2 involvement in the changes in compressive and tensile mechanical properties associated with hydrostatic pressure treatment of self-assembled cartilage constructs. In study 1, ERK 1/2 phosphorylation was detected by immunoblot following application of hydrostatic pressure (1 hour of static 10MPa) applied at day 10-14 of self-assembly culture. In study 2, ERK 1/2 activation was blocked during hydrostatic pressure application on days 10-14. With pharmacological inhibition of the ERK pathway by the MEK1/ERK inhibitor U0126 during hydrostatic pressure application on days 10-14, the increase in Young’s modulus induced by hydrostatic pressure was blocked. Furthermore, this reduction in Young’s modulus with U0126 treatment during hydrostatic pressure application corresponded with a decrease in total collagen expression. However, U0126 did not inhibit the increase in aggregate modulus or GAG induced by hydrostatic pressure. These findings demonstrate a link between hydrostatic pressure application, ERK signaling, and changes in biomechanical properties of a tissue engineered construct. PMID:23255524

DuRaine, G D; Athanasiou, K A

2015-01-01

200

Mechanoluminescence of ZnS:Mn phosphors excited by hydrostatic pressure steps and pressure pulses  

NASA Astrophysics Data System (ADS)

When a hydrostatic pressure step is applied rapidly on ZnS:Mn phosphor introduced into a pressure cell as oil suspension, initially the mechanoluminescence (ML) intensity increases linearly with time, attains a peak value for a particular time, and then it decreases with time (G. Alzetta, N. Minnaja, S. Santucci, Nuovo Cimento 23, 1962, 910). When a hydrostatic pressure pulse is applied onto ZnS:Mn phosphor, then two ML pulses of equal intensity are emitted; one during the application of pressure and the other during the release of pressure. In case of ZnS:Mn phosphor, at low hydrostatic pressure the energy produced during the electron-hole recombination excites the Mn2+ centres; however, at high hydrostatic pressure, the impact of accelerated electrons with the Mn2+ centres causes the light emission. Considering the piezoelectrically-induced detrapping model of ML at low pressure and the piezoelectrically-induced impact excitation model of ML at high pressure, expressions are derived for different characteristics of ML, in which a good agreement is found between the theoretical and experimental results. At low hydrostatic pressure in the range from 3 MPa to 40 MPa, piezoelectrically-induced detrapping model of ML becomes applicable in ZnS:Mn phosphors; while at high hydrostatic pressure beyond 40 MPa, the piezoelectrically-induced impact excitation model of ML becomes applicable. The ML induced by hydrostatic pressure can be used for sensing both the magnitude and rise time of applied hydrostatic pressure.

Chandra, V. K.; Chandra, B. P.; Jha, Piyush

2014-11-01

201

The hydrostatic corer Selcore--a tool for sediment sampling and geophysical site characterization  

E-print Network

energy potential represented by the difference between ambient hydrostatic pressure and atmospheric are driven into the seabed by the kinetic energy of the corer released from a short distance (; accepted 15 February 2006 Abstract Hydrostatic energy is used to power an active device for sediment

Kristoffersen, Yngve

202

Phloem hydrostatic pressure relates to solute loading rate: a direct test of the Münch hypothesis  

Microsoft Academic Search

According to the M¨ unch hypothesis, a flow of solution through the sieve tubes is driven by a hydrostatic pressure difference between the source (or collection) phloem and the sink (or release) phloem. A high hydrostatic pressure is maintained in the collection phloem by the active uptake of sugar and other solutes, with a concomitant inflow of water. A lower

Nick GouldA; Michael R. ThorpeB; Olga Koroleva; Peter E. H. Minchin

2005-01-01

203

Failure monitoring in a high performance hydrostatic actuation system using the extended Kalman filter  

Microsoft Academic Search

This paper describes the development and evaluation of a fault detection strategy for a high performance hydrostatic actuation system, the electrohydraulic actuator (EHA). The approach makes use of the extended Kalman filter (EKF) technique for parameter estimation purposes and changes in the estimated system parameters were related to faults in the EHA. The hydrostatic system has potential applications in the

Y. Chinniah; R. Burton; S. Habibi

2006-01-01

204

American Black Bear: Ursus americanus  

E-print Network

3/21/2011 1 USFWS American Black Bear: Ursus americanus www.bear.org LDWF Historic Distribution Bear: Ursus americanus Louisiana Florida Eastern Olympic New Mexico California Cinnamon Mexican: Ursus americanus luteolus American black bear Historically abundant in Louisiana, eastern Texas

Gray, Matthew

205

Splined Ball-Bearing Carrier  

NASA Technical Reports Server (NTRS)

Ball-bearing carrier includes splined outer surface mating with slightly larger splined inner surface of housing and provides constant deadband, unaffected by movements of other components. Deadband needed to establish radial spring rate and provide for axial movement of bearing for thrust balance. Bearing carrier and bearing intended for use in high-pressure turbopump.

Moore, Jerry H.

1992-01-01

206

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. PMID:22559784

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

2012-01-01

207

Hydrostatic factors affect the gravity responses of algae and roots  

NASA Technical Reports Server (NTRS)

The hypothesis of Wayne et al. (1990) that plant cells perceive gravity by sensing a pressure differential between the top and the bottom of the cell was tested by subjecting rice roots and cells of Caracean algae to external solutions of various densities. It was found that increasing the density of the external medium had a profound effect on the polar ratio (PR, the ratio between velocities of the downwardly and upwardly streaming cytoplasm) of the Caracean algae cells. When these cells were placed in solutions of denser compound, the PR decreased to less than 1, as the density of the external medium became higher than that of the cell; thus, the normal gravity-induced polarity was reversed, indicating that the osmotic pressure of the medium affects the cell's ability to respond to gravity. In rice roots, an increase of the density of the solution inhibited the rate of gravitropism. These results agree with predictions of a hydrostatic model for graviperception.

Staves, Mark P.; Wayne, Randy; Leopold, A. C.

1991-01-01

208

Hydrometer calibration by hydrostatic weighing with automated liquid surface positioning  

NASA Astrophysics Data System (ADS)

We describe an automated apparatus for calibrating hydrometers by hydrostatic weighing (Cuckow's method) in tridecane, a liquid of known, stable density, and with a relatively low surface tension and contact angle against glass. The apparatus uses a laser light sheet and a laser power meter to position the tridecane surface at the hydrometer scale mark to be calibrated with an uncertainty of 0.08 mm. The calibration results have an expanded uncertainty (with a coverage factor of 2) of 100 parts in 106 or less of the liquid density. We validated the apparatus by comparisons using water, toluene, tridecane and trichloroethylene, and found agreement within 40 parts in 106 or less. The new calibration method is consistent with earlier, manual calibrations performed by NIST. When customers use calibrated hydrometers, they may encounter uncertainties of 370 parts in 106 or larger due to surface tension, contact angle and temperature effects.

Aguilera, Jesus; Wright, John D.; Bean, Vern E.

2008-01-01

209

Ultrahigh hydrostatic pressure extraction of flavonoids from Epimedium koreanum Nakai  

NASA Astrophysics Data System (ADS)

Herba Epimedii is one of the most famous Chinese herbal medicines listed in the Pharmacopoeia of the People's Republic of China, as one of the representatives of traditional Chinese herb, it has been widely applied in the field of invigorate the kidney and strengthen 'Yang'. The attention to Epimedium extract has more and more increased in recent years. In this work, a novel extraction technique, ultra-high hydrostatic pressure extraction (UPE) technology was applied to extract the total flavonoids of E. koreanum. Three factors (pressure, ethanol concentration and extraction time) were chosen as the variables of extraction experiments, and the optimum UPE conditions were pressure 350 MPa; ethanol concentration 50% (v/v); extraction time 5 min. Compared with Supercritical CO2 extraction, Reflux extraction and Ultrasonic-assisted extraction, UPE has excellent advantages (shorter extraction time, higher yield, better antioxidant activity, lower energy consumption and eco-friendly).

Hou, Lili; Zhang, Shouqin; Dou, Jianpeng; Zhu, Junjie; Liang, Qing

2011-02-01

210

Role of osmotic and hydrostatic pressures in bacteriophage genome ejection  

E-print Network

A critical step in the bacteriophage life cycle is genome ejection into host bacteria. The ejection process for double-stranded DNA phages has been studied thoroughly \\textit{in vitro}, where after triggering with the cellular receptor the genome ejects into a buffer. The experimental data have been interpreted in terms of the decrease in free energy of the densely packed DNA associated with genome ejection. Here we detail a simple model of genome ejection in terms of the hydrostatic and osmotic pressures inside the phage, a bacterium, and a buffer solution/culture medium. We argue that the hydrodynamic flow associated with the water movement from the buffer solution into the phage capsid and further drainage into the bacterial cytoplasm, driven by the osmotic gradient between the bacterial cytoplasm and culture medium, provides an alternative mechanism for phage genome ejection \\textit{in vivo}; the mechanism is perfectly consistent with phage genome ejection \\textit{in vitro}.

Serge G. Lemay; Debabrata Panja; Ian J. Molineux

2013-02-21

211

Role of osmotic and hydrostatic pressures in bacteriophage genome ejection  

NASA Astrophysics Data System (ADS)

A critical step in the bacteriophage life cycle is genome ejection into host bacteria. The ejection process for double-stranded DNA phages has been studied thoroughly in vitro, where after triggering with the cellular receptor the genome ejects into a buffer. The experimental data have been interpreted in terms of the decrease in free energy of the densely packed DNA associated with genome ejection. Here we detail a simple model of genome ejection in terms of the hydrostatic and osmotic pressures inside the phage, a bacterium, and a buffer solution or culture medium. We argue that the hydrodynamic flow associated with the water movement from the buffer solution into the phage capsid and further drainage into the bacterial cytoplasm, driven by the osmotic gradient between the bacterial cytoplasm and culture medium, provides an alternative mechanism for phage genome ejection in vivo; the mechanism is perfectly consistent with phage genome ejection in vitro.

Lemay, Serge G.; Panja, Debabrata; Molineux, Ian J.

2013-02-01

212

Effect of hydrostatic pressure on ligand binding to hemoglobin.  

PubMed

Increase in hydrostatic pressure to 1000 atm increased the affinity of human and menhaden (Brevoortia tyrannus) hemoglobins for oxygen. With necessary assumptions about the form of the equilibrium curve, and after correction for changes in pH and volume due to pressure, the increase in affinity is about 2-fold for both hemoglobins. At pH 6.5, Hill's n for menhaden hemoglobin is near 1, and it is believed to remain in the T state, whereas human hemoglobin undergoes a T to R transition. This suggests that the R-T equilibrium is not disturbed by pressure. In direct experiments the binding of a fluorescent effector (8 hydroxy-1,3,6-pyrene (trisulfonic acid) to deoxyhemoglobin was not changed by pressure. The binding of n-butylisocyanide to hemoglobin and to myoglobin is also greater at high pressures, similarly suggesting that the R-T transition is not involved in the pressure effect. PMID:16924

Carey, F G; Knowles, F; Gibson, Q H

1977-06-25

213

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

214

Effect of high hydrostatic pressures on 20S proteasome activity.  

PubMed

The 20S proteasome is the catalytic core of the ubiquitin proteolytic pathway, which is implicated in many cellular processes. The cylindrical structure of this complex consists of four stacked rings of seven subunits each. The central cavity is formed by two beta catalytic subunit rings in which protein substrates are progressively degraded. The 20S proteasome is isolated in a latent form which can be activated in vitro by various chemical and physical treatments. In this study, the effects of high hydrostatic pressures on 20S proteasome enzymatic activity were investigated. When proteasomes were subjected to increasing hydrostatic pressures, a progressive loss of peptidase activities was observed between 75 and 150 MPa. The inactivation also occurred when proteasomes were pressurized in the presence of synthetic peptide substrates; this may be the result of the dissociation of the 20S particle into its subunits under pressure, as was shown by PAGE. Pressurized proteasomes also lost their caseinolytic activity. In contrast, in the presence of casein, the pressure-induced inactivation and the dissociation of the 20S particles were prevented. In addition, in comparison to that observed at atmospheric pressure, their caseinolytic activity was increased under pressure. Following depressurization, the caseinolytic activity returned to basal levels but was further enhanced following an additional pressurization treatment. Thus, the structure of the 20S particle exhibits a certain degree of plasticity. This pressure-induced activation of the 20S proteasome is discussed in relation to its hollow structure, its currently accepted proteolytic mechanism and the general effect of high pressures on the biochemical reactions and structures of biopolymers. PMID:10411654

Gardrat, F; Fraigneau, B; Montel, V; Raymond, J; Azanza, J L

1999-06-01

215

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

216

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

217

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

218

BEARS conference UC Berkeley  

NSDL National Science Digital Library

The Berkeley EECS Annual Research Symposium (BEARS) is a conference hosted by UC Berkeley's Electrical Engineering and Computer Sciences department in the College of Engineering. This website provides the agenda for the 2005 BEARS (held on February 10 and 11) along with information on the presenters and abstracts and video footage of their presentations. The conference highlights work from EECS scientists on "advances enabling computing and communications to connect diverse aspects of our world." Topics include: wireless networks, optical communication, the future of the internet, embedded software, machine learning, security, and trust.

219

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

220

Bearing-Cartridge Damping Seal  

NASA Technical Reports Server (NTRS)

In proposed design for improved ball-bearing cartridge, damping seal in form of thin-layer fluid journal bearing incorporated into cartridge. Damping seal acts as auxiliary bearing, relieving bearing balls of significant portions of both static and dynamic bearing loads. Damping from seal reduces dynamic loads even further by reducing amplitude of vibrations in second vibrational mode of rotor, which mode occurs when rotor turning at nearly full operating speed. Intended for use in high-pressure-oxygen turbopump of Space Shuttle main engine, also applicable to other turbomachinery bearings.

Goggins, David G.; Scharrer, Joseph K.; Chen, Wei C.

1991-01-01

221

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

222

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

223

Bear vs Bee  

NSDL National Science Digital Library

This interactive Java applet is a game that challenges a student to solve problems by using logic and rudimentary engineering skills. The goal in each case is to create a conveyance that gets the bear to the pot of honey, avoiding the bees. The game has 32 stages of increasing complexity.

2012-01-01

224

Hybrid superconductor magnet bearings  

NASA Technical Reports Server (NTRS)

Hybrid superconductor magnet bearings (HSMB's) utilize high temperature superconductors (HTS's) together with permanent magnets to form a frictionless interface between relatively rotating parts. They are low mass, stable, and do not incur expenditure of energy during normal operation. There is no direct physical contact between rotor and stator, and hence there is no wear and tear. However, just as any other applications of HTS's, it requires a very cold temperature to function. Whereas this might be perceived as a disadvantage on earth, it is of no great concern in space or on the moon. To astronomers, the moon is an excellent site for an observatory, but the cold and dusty vacuum environment on the moon precludes the use of mechanical bearings on the telescope mounts. Furthermore, drive mechanisms with very fine steps, and hence bearings with extremely low friction are needed to track a star from the moon, because the moon rotates very slowly. All aspects considered, the HSMB is about the only candidate that fits in naturally. Here, we present a design for one such bearing, capable of supporting a telescope that weighs about 3 lbs on Earth.

Chu, Wei-Kan

1995-01-01

225

Magnetically leviated superconducting bearing  

DOEpatents

A magnetically levitated superconducting bearing includes a magnet (2) mounted on a shaft (12) that is rotatable around an axis of rotation and a Type II superconductor (6) supported on a stator (14) in proximity to the magnet (2). The superconductor (6) is positioned so that when it is cooled to its superconducting state in the presence of a magnetic field, it interacts with the magnet (2) to produce an attractive force that levitates the magnet (2) and supports a load on the shaft (12). The interaction between the superconductor (6) and magnet(2) also produces surface screening currents (8) that generate a repulsive force perpendicular to the load. The bearing also has means for maintaining the superconductor at a temperature below its critical temperature (16, 18). The bearing could also be constructed so the magnet (2) is supported on the stator (14) and the superconductor (6) is mounted on the shaft (12). The bearing can be operated by cooling the superconductor (6) to its superconducting state in the presence of a magnetic field.

Weinberger, Bernard R. (Avon, CT); Lynds, Jr., Lahmer (Glastonbury, CT)

1993-01-01

226

Introduction to magnetic bearings  

Microsoft Academic Search

Multi-axis suspension has several advantages over single axis system, in that it provides control of an object with precision in two or three orthogonal axes. In this report, we discuss the primary use of magnetic-bearing suspension and it's relevance to what was formally known as NASA's Annular Suspension and Pointing System (ASPS). This system is an experimental pointing system with

Lori Skowronski; Anne Bisese

1993-01-01

227

Oregon Zoo Polar Bear  

USGS Multimedia Gallery

Tasul, an Oregon Zoo polar bear, sports a high-tech collar that will help researchers study her endangered wild counterparts in the Arctic. Photo by Michael Durham, courtesy of the Oregon Zoo. Photo by Michael Durham, courtesy of the Oregon Zoo....

228

Measurements of hydrostatic pressure and temperature sensitivity in birefringent holey fibers  

NASA Astrophysics Data System (ADS)

We report on experimental studies of polarimetric sensitivity to temperature and hydrostatic pressure in two highly birefringent index guided photonic crystal fibers. Our results confirm earlier theoretical predictions indicating that polarimetric sensitivity to temperature in highly birefringent PCF with specific constriction can be very low. Proper choice of constructional parameters of the PCF can lead to complete temperature desensitization. On the other hand, relatively high polarimetric sensitivity to hydrostatic pressure in the analyzed structures make them good candidates for applications as active elements in hydrostatic pressure sensors.

Martynkien, Tadeusz; Statkiewicz, Gabriela; Szpulak, Marcin; Olszewski, Jacek; Urbanczyk, Waclaw; Wojcik, Jan; Mergo, Pawel; Makara, Mariusz; Nasilowski, Tomasz; Berghmans, Francis; Thienpont, Hugo

2006-04-01

229

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

230

Measuring ball-bearing loads  

NASA Technical Reports Server (NTRS)

Contour of wear-path boundary in bearing race gives precise information about magnitude, direction and imbalance of load. Simple tool measures height of path perimeter as bearing race is rotated manually on flat surface.

Butner, M. F.

1980-01-01

231

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

232

A self-lubricating bearing  

NASA Technical Reports Server (NTRS)

An improved bearing structure is described which includes a permanently magnetized porous body filled with an interstitial magnetic lubricant for extending the operational life of self-lubricating bearings. The bearing structure is characterized by a permanently magnetized retainer formed of a porous material and filled with an interstitial magnetic lubricant, whereby the pores serve as lubricant reservoirs from which the lubricant continuously is delivered to a film disposed between contiguous bearing surfaces.

Whitaker, A. F. (inventor)

1974-01-01

233

Compliant hydrodynamic fluid journal bearing  

NASA Technical Reports Server (NTRS)

An air bearing structure is described that prevents destructive bending moments within the top foil. Welds are eliminated by mounting the top bearing foil in the bearing cartridge sleeve without using a space block. Tabs or pins at the end of the top bearing foil are restrained by slots or stops formed in the cartridge sleeve. These structural members are free to move in a direction normal to the shaft while being restrained from movement in the direction of shaft rotation.

Warren, E. L. (inventor)

1985-01-01

234

First order ball bearing kinematics  

NASA Technical Reports Server (NTRS)

Two first order equations are given connecting geometry and internal motions in an angular contact ball bearing. Total speed, kinematic equivalence, basic speed ratio, and modal speed ratio are defined and discussed; charts are given for the speed ratios covering all bearings and all rotational modes. Instances where specific first order assumptions might fail are discussed, and the resulting effects on bearing performance reviewed.

Kingbury, E.

1984-01-01

235

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

236

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

SciTech Connect

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{sup ?2} is affected.

Carlos-Pinedo, C.; Rodríguez-Vargas, I.; Martínez-Orozco, J. C. [Unidad Académica de Física. Universidad Autónoma de Zacatecas. Calzada Solidaridad Esquina con Paseo la Bufa S/N. C.P. 98060, Zacatecas, Zac. (Mexico)

2014-05-15

237

Success with hydrostatic reduction of intussusception in relation to duration of symptoms  

PubMed Central

Background: It is widely believed that hydrostatic reduction of intussusception is less successful in children with prolonged symptoms prior to presentation. Aim: To prospectively evaluate success in relation to duration of symptoms. Methods: Prospective study in which children, regardless of symptom duration, underwent an attempt at hydrostatic reduction. Results: Of 113 children presenting with intussusception, 16 had peritonitis and required immediate laparotomy. A hydrostatic reduction was attempted in 97 and was successful in 77 (79%). There were 26 successful reductions with symptoms <12 hours (81%), 30 with symptoms for 12–24 hours (81%), and 21 with symptoms >24 hours (75%). Conclusion: The success rate with hydrostatic reduction was not significantly influenced by symptom duration. PMID:15941773

van den Ende, E D; Allema, J; Hazebroek, F; Breslau, P

2005-01-01

238

HIGH HYDROSTATIC PRESSURE PROCESSING: A POTENTIAL SOLUTION FOR SHELLFISH-BORNE VIRUSES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Molluscan shellfish bioconcentrate enteric viruses from human wastes that are present in the growing waters. Consequently, the consumption of raw shellfish poses considerable risk for contracting illnesses associated with these viruses. High hydrostatic pressure is a new nonthermal sanitizing proc...

239

Forming of magnesium alloys at 100 °C by hydrostatic extrusion  

NASA Astrophysics Data System (ADS)

Magnesium wrought alloys are of special interest for use as structural parts due to the possibility of obtaining improved and more homogeneous microstructure and mechanical properties compared with cast components. The market for magnesium wrought alloys is still relatively small, and they are only used for special applications due to the high cost of the feedstock. Currently, with the decreasing prices for the primary magnesium extrusion, magnesium has become competitive with aluminum, and is important for upcoming research and development activities. In this study hydrostatic extrusion, as a quite rarely applied technique, was used for deformation of commercial magnesium alloys at 100 °C, which is significantly below the temperature necessary for activation of new gliding systems. All experiments were carried out using typical industrial extrusion parameters like extrusion rate and extrusion ratio but with the objective of obtaining extremely fine-grained materials as are received typically from equal channel angular extrusion processing. These experiments show that the processing of magnesium alloys is possible even at a temperature of 100 °C. The limitations of this processing and the influence of process parameters on the microstructure and mechanical properties of extruded profiles will be discussed.

Swiostek, J.; Göken, J.; Letzig, D.; Kainer, K. U.

2006-12-01

240

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

241

High hydrostatic pressure and biology: a brief history.  

PubMed

Pressure as a thermodynamical parameter was successively introduced in physics, hydrometallurgy, geochemistry, and biology. In all cases, the main objective was to recreate a natural phenomenon (gas or liquid compressibility, synthesis or crystal growth of minerals, survival of deep sea microorganisms…). The introduction of high hydrostatic pressure (HHP) in Biology was an important scientific feature over the last hundred years. This paper describes the different steps that have led to the spreading of pressure in biology and the opening of new frontiers either in basic and applied researches due to the specific characteristics of the pressure parameter. Because of the low energy conveyed by this parameter, leading to the preservation of most organoleptic properties of foods, and its ability to inactivate many pathogens, the use of HHP began to spread at the end of the twentieth century into the food industry, in particular for the development of pathogen inactivation processes. Today, even if this field is still the first application domain for HHP, more and more research works have shown that this parameter could be of great interest in health and medicine sciences. PMID:21184058

Demazeau, Gérard; Rivalain, Nolwennig

2011-03-01

242

L1448 IRS2E: A candidate first hydrostatic core  

E-print Network

Intermediate between the prestellar and Class 0 protostellar phases, the first core is a quasi-equilibrium hydrostatic object with a short lifetime and an extremely low luminosity. Recent MHD simulations suggest that the first core can even drive a molecular outflow before the formation of the second core (i.e., protostar). Using the Submillimeter Array and the Spitzer Space Telescope, we present high angular resolution observations towards the embedded dense core IRS2E in L1448. We find that source L1448 IRS2E is not visible in the sensitive Spitzer infrared images (at wavelengths from 3.6 to 70 um), and has weak (sub-)millimeter dust continuum emission. Consequently, this source has an extremely low bolometric luminosity (< 0.1 L_sun). Infrared and (sub-)millimeter observations clearly show an outflow emanating from this source; L1448 IRS2E represents thus far the lowest luminosity source known to be driving a molecular outflow. Comparisons with prestellar cores and Class 0 protostars suggest that L1448 ...

Chen, Xuepeng; Zhang, Qizhou; Bourke, Tyler L; Launhardt, Ralf; Schmalz, Markus; Henning, Thomas

2010-01-01

243

Low hydrostatic head electrolyte addition to fuel cell stacks  

SciTech Connect

A fuel cell and system for supply electrolyte, as well as fuel and an oxidant to a fuel cell stack having at least two fuel cells, each of the cells having a pair of spaced electrodes and a matrix sandwiched therebetween, fuel and oxidant paths associated with a bipolar plate separating each pair of adjacent fuel cells and an electrolyte fill path for adding electrolyte to the cells and wetting said matrices. Electrolyte is flowed through the fuel cell stack in a back and forth fashion in a path in each cell substantially parallel to one face of opposite faces of the bipolar plate exposed to one of the electrodes and the matrices to produce an overall head uniformly between cells due to frictional pressure drop in the path for each cell free of a large hydrostatic head to thereby avoid flooding of the electrodes. The bipolar plate is provided with channels forming paths for the flow of the fuel and oxidant on opposite faces thereof, and the fuel and the oxidant are flowed along a first side of the bipolar plate and a second side of the bipolar plate through channels formed into the opposite faces of the bipolar plate, the fuel flowing through channels formed into one of the opposite faces and the oxidant flowing through channels formed into the other of the opposite faces.

Kothmann, R.E.

1983-05-10

244

Scaling of the hydrostatic skeleton in the earthworm Lumbricus terrestris.  

PubMed

The structural and functional consequences of changes in size or scale have been well studied in animals with rigid skeletons, but relatively little is known about scale effects in animals with hydrostatic skeletons. We used glycol methacrylate histology and microscopy to examine the scaling of mechanically important morphological features of the earthworm Lumbricus terrestris over an ontogenetic size range from 0.03 to 12.89 g. We found that L. terrestris becomes disproportionately longer and thinner as it grows. This increase in the length to diameter ratio with size means that, when normalized for mass, adult worms gain ~117% mechanical advantage during radial expansion, compared with hatchling worms. We also found that the cross-sectional area of the longitudinal musculature scales as body mass to the ~0.6 power across segments, which is significantly lower than the 0.66 power predicted by isometry. The cross-sectional area of the circular musculature, however, scales as body mass to the ~0.8 power across segments, which is significantly higher than predicted by isometry. By modeling the interaction of muscle cross-sectional area and mechanical advantage, we calculate that the force output generated during both circular and longitudinal muscle contraction scales near isometry. We hypothesize that the allometric scaling of earthworms may reflect changes in soil properties and burrowing mechanics with size. PMID:24871920

Kurth, Jessica A; Kier, William M

2014-06-01

245

Hydrostatic gas distributions: global estimates of temperature and abundance  

E-print Network

Estimating the temperature and metal abundance of the intracluster and the intragroup media is crucial to determine their global metal content and to determine fundamental cosmological parameters. When a spatially resolved temperature or abundance profile cannot be recovered from observations (e.g., for distant objects), or deprojection is difficult (e.g., due to a significant non-spherical shape), only global average temperature and abundance are derived. After introducing a general technique to build hydrostatic gaseous distributions of prescribed density profile in potential wells of any shape, we compute the global mass weighted and emission weighted temperature and abundance for a large set of barotropic equilibria and an observationally motivated abundance gradient. We also compute the spectroscopic-like temperature that is recovered from a single temperature fit of observed spectra. The derived emission weighted abundance and temperatures are higher by 50% to 100% than the corresponding mass weighted quantities, with overestimates that increase with the gas mean temperature. Spectroscopic temperatures are intermediate between mass and luminosity weighted temperatures. Dark matter flattening does not lead to significant differences in the values of the average temperatures or abundances with respect to the corresponding spherical case (except for extreme cases).

L. Ciotti; S. Pellegrini

2008-04-10

246

Low hydrostatic head electrolyte addition to fuel cell stacks  

DOEpatents

A fuel cell and system for supply electrolyte, as well as fuel and an oxidant to a fuel cell stack having at least two fuel cells, each of the cells having a pair of spaced electrodes and a matrix sandwiched therebetween, fuel and oxidant paths associated with a bipolar plate separating each pair of adjacent fuel cells and an electrolyte fill path for adding electrolyte to the cells and wetting said matrices. Electrolyte is flowed through the fuel cell stack in a back and forth fashion in a path in each cell substantially parallel to one face of opposite faces of the bipolar plate exposed to one of the electrodes and the matrices to produce an overall head uniformly between cells due to frictional pressure drop in the path for each cell free of a large hydrostatic head to thereby avoid flooding of the electrodes. The bipolar plate is provided with channels forming paths for the flow of the fuel and oxidant on opposite faces thereof, and the fuel and the oxidant are flowed along a first side of the bipolar plate and a second side of the bipolar plate through channels formed into the opposite faces of the bipolar plate, the fuel flowing through channels formed into one of the opposite faces and the oxidant flowing through channels formed into the other of the opposite faces.

Kothmann, Richard E. (Churchill Boro, PA)

1983-01-01

247

System for ESR measurements at hydrostatic pressures to 60 kilobars.  

PubMed

A single-crystal sapphire serves both as a solid microwave cavity (X band) and an anvil in a Bridgman-anvil pressure geometry. A metal gasket is used in a manner similar to its use in the diamond-anvil pressure cell, and single-crystal samples are subject to purely hydrostatic pressures. The ruby-fluorescence pressure-measurement technique is utilized. Sample size is limited to a disk approximately 0.6 mm in diameter and 0.1 mm thick. ESR data on Cr(3+) in ruby to 60 kilobars are given as an illustration of the precision and data quality. Line widths and profiles, as well as line positions, are meaningful. Very little degradation of the data is experienced at the higher pressures. The first and second derivatives of the zero-field splitting (delta) of the states in ruby with pressure are measured as ddelta/dP= (6.70+/-0.08) x 10(-4) cm(-1) kilobar(-1) and d(2)delta/dP(2)= (-2.44+/-0.30) x10(-6) cm(-1) kilobar(-2) at P=0. The gyromagnetic ratio g(11) is shown to experience a fractional change less than 2 x 10(-4) to 60 kilobars. PMID:18699095

Barnett, J D; Tyagi, S D; Nelson, H M

1978-03-01

248

Hydrostatic pressure sensation in cells: integration into the tensegrity model.  

PubMed

Hydrostatic pressure (HP) is a mechanical stimulus that has received relatively little attention in the field of the cell biology of mechanotransduction. Generalized models, such as the tensegrity model, do not provide a detailed explanation of how HP might be detected. This is significant, because HP is an important mechanical stimulus, directing cell behaviour in a variety of tissues, including cartilage, bone, airways, and the vasculature. HP sensitivity may also be an important factor in certain clinical situations, as well as under unique environmental conditions such as microgravity. While downstream cellular effects have been well characterized, the initial HP sensation mechanism remains unclear. In vitro evidence shows that HP affects cytoskeletal polymerization, an effect that may be crucial in triggering the cellular response. The balance between free monomers and cytoskeletal polymers is shifted by alterations in HP, which could initiate a cellular response by releasing and (or) activating cytoskeleton-associated proteins. This new model fits well with the basic tenets of the existing tensegrity model, including mechanisms in which cellular HP sensitivity could be tuned to accommodate variable levels of stress. PMID:17901896

Myers, Kenneth A; Rattner, Jerome B; Shrive, Nigel G; Hart, David A

2007-10-01

249

Optimization of hydrostatic transmissions by means of virtual instrumentation technique  

NASA Astrophysics Data System (ADS)

Obtaining mathematical models, as close as possible to physical phenomena which are intended to be replicated or improved, help us in deciding how to optimize them. The introduction of computers in monitoring and controlling processes caused changes in technological systems. With support from the methods for identification of processes and from the power of numerical computing equipment, researchers and designers can shorten the period for development of applications in various fields by generating a solution as close as possible to reality, since the design stage [1]. The paper presents a hybrid solution of modeling / simulation of a hydrostatic transmission with mixed adjustment. For simulation and control of the examined process we have used two distinct environments, AMESim and LabVIEW. The proposed solution allows coupling of the system's model to the software control modules developed using virtual instrumentation. Simulation network of the analyzed system was "tuned" and validated by an actual model of the process. This paper highlights some aspects regarding energy and functional advantages of hydraulic transmissions based on adjustable volumetric machines existing in their primary and secondary sectors [2].

Ion Guta, Dragos Daniel; Popescu, Teodor Costinel; Dumitrescu, Catalin

2010-11-01

250

Passive magnetic bearing system  

DOEpatents

An axial stabilizer for the rotor of a magnetic bearing provides external control of stiffness through switching in external inductances. External control also allows the stabilizer to become a part of a passive/active magnetic bearing system that requires no external source of power and no position sensor. Stabilizers for displacements transverse to the axis of rotation are provided that require only a single cylindrical Halbach array in its operation, and thus are especially suited for use in high rotation speed applications, such as flywheel energy storage systems. The elimination of the need of an inner cylindrical array solves the difficult mechanical problem of supplying support against centrifugal forces for the magnets of that array. Compensation is provided for the temperature variation of the strength of the magnetic fields of the permanent magnets in the levitating magnet arrays.

Post, Richard F.

2014-09-02

251

Centrifugally decoupling touchdown bearings  

DOEpatents

Centrifugally decoupling mechanical bearing systems provide thin tensioned metallic ribbons contained in a support structure. This assembly rotates around a stationary shaft being centered at low speeds by the action of the metal ribbons. Tension springs are connected on one end to the ribbons and on the other end to the support structure. The ribbons pass through slots in the inner ring of the support structure. The spring preloading thus insures contact (or near-contact) between the ribbons and the shaft at rotation speeds below the transition speed. Above this speed, however, the centrifugal force on the ribbons produces a tensile force on them that exceeds the spring tensile force so that the ribbons curve outward, effectively decoupling them from mechanical contact with the shaft. They still remain, however, in position to act as a touchdown bearing in case of abnormally high transverse accelerations.

Post, Richard F

2014-06-24

252

Magnetic bearing and motor  

NASA Technical Reports Server (NTRS)

A magnetic bearing assembly (10) has an intermediate rotatable section (33) having an outer cylindrical member (30) coaxially suspended by a torsion wire (72) around an axially polarized cylindrical magnet (32). Axial alignment between the pole faces (40-43) of the intermediate section (33) and end surfaces (50-53) of opposed end bells (20, 22) provides a path of least reluctance across intervening air gaps (60-63) for the magnetic flux emanating from magnet (32). Radial dislocation increases the reluctance and creates a radial restoring force. Substitution of radially polarized magnets 107 fixed to a magnetically permeable cylinder (32') and insertion of pairs of armature coil windings (109-112) between the cylinder pair (33') provides an integral magnetic bearing and torsion motor (100) able to provide arcuately limited rotational drive.

Studer, Philip A. (Inventor)

1983-01-01

253

Effect of hydrostatic pressure and salinity on the stability of gas hydrates  

Microsoft Academic Search

The distribution of gas in the hydrate and the liquid phases for the two-phase systems methane hydrate-water and methane hydrate-seawater has been calculated as a function of hydrostatic pressure. It is found that at hydrostatic pressures higher than the three-phase hydrate-liquid-gas equilibrium pressure, a two-phase hydrate-liquid equilibrium exists in which the hydrate phase is increasingly enriched in and the liquid

Y. Paul. Handa

1990-01-01

254

Use of high hydrostatic pressure to produce high quality and safe fresh pork sausage  

E-print Network

USE OF HIGH HYDROSTATIC PRESSURE TO PRODUCE HIGH QUALITY AND SAFE FRESH PORK SAUSAGE A Thesis by MEI HUANG Submitted to the Office of Graduate Studies of Texas AkM University in partial fulfillment of the requirements for the degree... of MASTER OF SCIENCE December 1997 Major Subject: Agricultural Engineering USE OF HIGH HYDROSTATIC PRESSURE TO PRODUCE HIGH QUALITY AND SAFE FRESH PORK SAUSAGE A Thesis by MEI HUANG Submitted to the Office of Graduate Studies of Texas A6'c...

Huang, Mei

2012-06-07

255

EVOLUTION OF THE MERGER-INDUCED HYDROSTATIC MASS BIAS IN GALAXY CLUSTERS  

SciTech Connect

In this work, we examine the effects of mergers on the hydrostatic mass estimate of galaxy clusters using high-resolution Eulerian cosmological simulations. We utilize merger trees to isolate the last merger for each cluster in our sample and follow the time evolution of the hydrostatic mass bias as the systems relax. We find that during a merger, a shock propagates outward from the parent cluster, resulting in an overestimate in the hydrostatic mass bias. After the merger, as a cluster relaxes, the bias in hydrostatic mass estimate decreases but remains at a level of -5%-10% with 15%-20% scatter within r{sub 500}. We also investigate the post-merger evolution of the pressure support from bulk motions, a dominant cause of this residual mass bias. At r{sub 500}, the contribution from random motions peaks at 30% of the total pressure during the merger and quickly decays to {approx}10%-15% as a cluster relaxes. Additionally, we use a measure of the random motion pressure to correct the hydrostatic mass estimate. We discover that 4 Gyr after mergers, the direct effects of the merger event on the hydrostatic mass bias have become negligible. Thereafter, the mass bias is primarily due to residual bulk motions in the gas which are not accounted for in the hydrostatic equilibrium equation. We present a hydrostatic mass bias correction method that can recover the unbiased cluster mass for relaxed clusters with 9% scatter at r{sub 500} and 11% scatter in the outskirts, within r{sub 200}.

Nelson, Kaylea; Nagai, Daisuke [Department of Astronomy, Yale University, New Haven, CT 06520 (United States); Rudd, Douglas H.; Shaw, Laurie, E-mail: kaylea.nelson@yale.edu [Department of Physics, Yale University, New Haven, CT 06520 (United States)

2012-06-01

256

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

257

The Polar Bear Game  

NSDL National Science Digital Library

In this game, which is similar to Petals Around the Rose (cataloged separately), a player rolls 5 dice and asks the participants, âHow many polar bears are around the ice holes?â The participants try to figure out the riddle (rules of the game) by studying the dice arrangements and the answers that correspond. This webpage extends the game to have players also determine the number of fish and plankton.

2010-10-24

258

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

259

Laser glazed bearings  

SciTech Connect

In the past decade high power, reliable, carbon dioxide lasers have become commercially available. Laser glazing is a process in which a focused laser beam is used to melt a very small portion of a component. As the beam moves away from the melted region, the underlying mass of the component causes the liquid pool to rapidly solidify. A major advantage of laser glazing is that the refined structure is only created in areas where high load carrying capacity is required. Initially rods manufactured from BG 42 and M 50 steels were laser glazed. Laser glazing transformed the normal, fine grain, martensitic steel matrix into a very fine dendritic microstructure. The carbides in the laser glazed material were greatly reduced in size due to very rapid solidification. Using a standard ball/rod rolling contact fatigue tester, enhanced rolling contact fatigue life was realized from the laser glazing process. LM 12749 tapered roller bearing cones were fabricated from M 50 high speed steel and laser glazed. At 200% catalog load, the L{sub 15.9%} life of the laser glazed M 50 bearings was 370% greater than the wrought cones. Similarly, when tested at 300% catalog load, the laser glazed bearings had L{sub 15.9%} life 580% greater than the wrought cones. Laser processing has been applied to 440 C stainless steel. In this alloy similar reduction in the size and distribution of large chromium carbides was achieved. The glazed 440 C was approximately 20 Knoop hardness points higher than the wrought alloy. Examples and properties of glazed microstructures in ball bearings and other alloy systems are discussed.

Hetzner, D.W. [Timken Co., Canton, OH (United States)

1998-12-31

260

Bears in a Boat  

NSDL National Science Digital Library

In this math activity, learners are challenged to create aluminum foil boats that will hold plastic bears until the boats sink. The lesson serves as a fun, hands-on way to collect data. Data from two attempts is collected and used to make two class box-and-whisker plots with some surprising results. This lesson guide includes questions for learners, assessment options, extensions, and reflection questions.

Rubillo, Jim

2012-01-01

261

Grizzly bears and forestry  

Microsoft Academic Search

We examined if clearcuts were selected as habitats by grizzly bears (Ursus arctos L.) in west-central Alberta during three seasons: hypophagia, early hyperphagia, and late hyperphagia. Our objectives were to describe seasonal habitat selection of clearcuts using resource selection functions at two scales. At the first scale, we assessed patch or third-order selection by comparing use (radiotelemetry) with study area-wide

Scott E. Nielsen; Mark S. Boyce; Gordon B. Stenhouse

2004-01-01

262

Day-Night Variations in Malate Concentration, Osmotic Pressure, and Hydrostatic Pressure in Cereus validus1  

PubMed Central

Malate concentration and stem osmotic pressure concomitantly increase during nighttime CO2 fixation and then decrease during the daytime in the obligate Crassulacean acid metabolism (CAM) plant, Cereus validus (Cactaceae). Changes in malate osmotic pressure calculated using the Van't Hoff relation match the changes in stem osmotic pressure, indicating that changes in malate level affected the water relations of the succulent stems. In contrast to stem osmotic pressure, stem water potential showed little day-night changes, suggesting that changes in cellular hydrostatic pressure occurred. This was corroborated by direct measurements of hydrostatic pressure using the Jülich pressure probe where a small oil-filled micropipette is inserted directly into chlorenchyma cells, which indicated a 4-fold increase in hydrostatic pressure from dusk to dawn. A transient increase of hydrostatic pressure at the beginning of the dark period was correlated with a short period of stomatal closing between afternoon and nighttime CO2 fixation, suggesting that the rather complex hydrostatic pressure patterns could be explained by an interplay between the effects of transpiration and malate levels. A second CAM plant, Agave deserti, showed similar day-night changes in hydrostatic pressure in its succulent leaves. It is concluded that, in addition to the inverted stomatal rhythm, the oscillations of malate markedly affect osmotic pressures and hence water relations of CAM plants. PMID:16663708

Lüttge, Ulrich; Nobel, Park S.

1984-01-01

263

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

264

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

265

The transition from hydrostatic to greater than hydrostatic fluid pressure in presently active continental hydrothermal systems in crystalline rock  

SciTech Connect

Fluid flow at hydrostatic pressure (P{sub h}) is relatively common through fractures in silicic and in mafic crystalline rocks where temperatures are less than about 350-370C. In contrast, pore-fluid pressure (P{sub f}) > P{sub h} has been encountered at the bottom of 3 geothermal exploration wells that attained temperatures >370C (at Larderello, Italy, at Nesjavellir, Iceland, and at The Geysers, California). Chemical sealing by deposition of minerals in veins appears to have allowed the development of the high P{sub f} encountered in the above wells. The upper limit for the magnitude of P{sub f} that can be attained is controlled by either the onset of shear fracturing (where differential stress is relatively high) that reopens clogged veins, or the hydraulic opening of new or old fractures (at relatively low values of differential stress). The brittle-plastic transition for silicic rocks can occur at temperatures as high as 370-400C in tectonically active regions. In regions where high-temperature geothermal systems develop and persist, it appears that either strain rates commonly are in the range 10{sup {minus}12} to 10{sup {minus}13}, or that silicic rocks in the shallow crust generally behave rheologically more like wet quartz diorite than wet Westerly granite.

Fournier, R.O. (Geological Survey, Menlo Park, CA (United States))

1991-05-01

266

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

267

Hydrostatic and osmotic pressure activated channel in plant vacuole  

PubMed Central

The vacuolar membrane of red beet vacuoles contains a channel which was not gated by voltage or Ca2+ ions. Its unit conductance was 20 pS in 200 mM symmetrical KCl solutions. It was stretch activated: the conductance remained constant but the probability of opening was increased by suction or pressure applied to a membrane patch. A 1.5-kNm-2 suction applied to isolated patches or a 0.08-kNm-2 pressure applied to a 45-?m diameter vacuole induced an e-fold change in the mean current. A 75% inhibition of the channel current was obtained with 10 ?M Gd3+ on the cytoplasmic side. The channel was more permeable for K+ than for Cl- (PK/PCl ? 3). A possible clustering for this channel was suggested by the recordings of the patch current. The channel properties were not significantly affected by a change in sorbitol osmolality in the solutions under isoosmotic conditions, between 0.6 and 1 mol/kg sorbitol. However, the channel was very sensitive to an osmotic gradient. A 0.2-mol/kg sorbitol gradient induced a two-fold increase in unit conductance and a thirty-fold increase in the mean patch current of the channel. A current was measured, when the osmotic gradient was the only driving force applied to the vacuolar membrane. The hydrostatic and osmotic pressure (HOP) activated channel described in this paper could be gated in vivo condition by a change in osmolality, without the need of a change in the turgor pressure in the cell. The HOP channel represents a possible example of an osmoreceptor for plant cells. PMID:19431814

Alexandre, Joel; Lassalles, Jean-Paul

1991-01-01

268

Development of hybrid bearing system with thrust superconducting magnetic bearing and radial active electromagnetic bearing  

NASA Astrophysics Data System (ADS)

A superconducting/electromagnetic hybrid bearing system is currently under development and test. This system consists of a thrust superconducting magnetic bearing and a double radial active electromagnetic bearing/motor devices. The thrust bearing has been designed using NdFeB permanent magnets levitating on a set of superconducting monoliths of YBCO, prepared by top seeded melt texturing technique, which supports the weight of the rotor. The bearing/motor devices were conceived as 4-pole 2-phase induction machine using stator windings for delivering torque and radial positioning simultaneously. Using this superconducting axial bearing and the active bearings for the rotor radial positioning, a fully levitating vertical-shaft inductive machine has been tested. The tests were successful in reaching a controlled levitation up to 6,300 rpm.

Nicolsky, R.; Pereira, A. S.; de Andrade, R.; David, D. F. B.; Santisteban, J. A.; Stephan, R. M.; Ripper, A.; Gawalek, W.; Habisreuther, T.; Strasser, T.

269

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.

270

Aerospace applications of magnetic bearings  

NASA Astrophysics Data System (ADS)

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

1994-05-01

271

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

272

PNA bearing 5-azidomethyluracil  

PubMed Central

Fmoc- and Boc-protected modified monomers bearing 5-azidomethyluracil nucleobase were synthesized. Four different solid-phase synthetic strategies were tested in order to evaluate the application of this series of monomers for the solid-phase synthesis of modified PNA. The azide was used as masked amine for the introduction of amide-linked functional groups, allowing the production of a library of compounds starting from a single modified monomer. The azide function was also exploited as reactive group for the modification of PNA in solution via azide-alkyne click cycloaddition. PMID:22772040

Manicardi, Alex; Accetta, Alessandro; Tedeschi, Tullia; Sforza, Stefano; Marchelli, Rosangela; Corradini, Roberto

2012-01-01

273

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

274

Numerical studies of flow over a sill: sensitivity of the non-hydrostatic effects to the grid size  

Microsoft Academic Search

A non-hydrostatic terrain-following model in cross sectional form is applied to study the processes in the lee of a sill in\\u000a an idealized stratified fjord during super-critical tidal inflow. A sequence of numerical studies with horizontal grid sizes\\u000a in the range from 100 to 1.5625 m are performed. All experiments are repeated using both hydrostatic and non-hydrostatic versions\\u000a of the

Jarle Berntsen; Jiuxing Xing; Alan M. Davies

2009-01-01

275

Experimental investigation of the flow in a simplified model of water lubricated axial thrust bearing  

NASA Astrophysics Data System (ADS)

In hydropower plants the axial thrust bearing takes up the hydraulic axial thrust of the runner and, in case of vertical shafts, the entire weight of all rotating masses. The use of water lubricated bearings can eliminate the oil leakage risk possibly contaminating the environment. A complex flow is generated by the smaller film thickness due to the lower viscosity of water compared with oil. Measurements on a simplified hydrostatic axial trust bearing model were accomplished for validating CFD analysis of water lubricated bearings. In this simplified model, fixed pads are implemented and the width of the gap was enlarged to create a higher resolution in space for the measurements. Most parts of the model were manufactured from acrylic glass to get optical access for measurement with PIV. The focus of these measurements is on the flow within the space between two pads. Additional to the PIV- measurement, the pressure on the wall of the rotating disk is captured by pressure transducers. The model bearing measurement results are presented for varied operating conditions.

Kirschner, O.; Ruprecht, A.; Riedelbauch, S.

2014-12-01

276

Primarily Pro-bear-bility  

NSDL National Science Digital Library

In this probability lesson plan students make predictions about the color of the bear they are likely to draw from a bag, and then draw and record the color of the bear they actually draw. Students complete this activity in cooperative learning groups and take turns removing a bear, without replacing it, and seeing if their predictions become more accurate. The lesson plan includes four student activity worksheets and extension questions and suggestions (PDF).

2006-01-01

277

The epsilon Aurigae Secondary: A Hydrostatically Supported Disk  

NASA Astrophysics Data System (ADS)

Epsilon Aurigae is an F supergiant in a spectroscopic binary system that undergoes a flat-bottomed partial eclipse of 2 yr duration every 27 yr. The spectrum appears to be single-lined, aside from extra absorption features detected during and shortly after eclipse. Eclipse characteristics indicate that the secondary is a very elongated object 5-10 AU in dimension parallel to its orbit. Orbital characteristics and the spectral properties of the primary are consistent with two different models of the system, with the secondary having a mass of either ˜15 Msun or ˜4 Msun. We have modeled the cool, dark secondary in the E Aurigae system as a geometrically thin circumstellar disk of gas and dust (surrounding one or two unseen stars, at or near its center), which is rotationally supported about its short axis and pressure supported perpendicular to its midplane. We assume that the midplane of the disk is coplanar with the orbital plane of the system. The gross features of the eclipse light curve observed at any single wavelength are easily reproduced, using a variety of disk scale heights and optical depths, provided that we are viewing within ˜3° of the symmetry plane of the system. Central holes in the disk only affect the eclipse profile for models with low optical depth (and correspondingly large pressure scale height). The observed grayness of the eclipse in the visible and near-IR implies that the particles in the disk are significantly larger than those in the typical ISM. Either particles of radius ? 5 ?m are almost completely absent, or the disk must be very opaque. If the disk is very opaque, then the observed eclipse depth implies a small scale height for the disk, equal to roughly 3% of the disk's radius at the outer edge. This is a factor of ˜1.5-2 smaller than the value expected for the low-mass model from hydrostatic balance with the disk temperature measured in the thermal-IR, suggesting that the high-mass model of the system is correct and/or the dust particles have settled into a thinner disk than the pressure-supported gas. We have also constructed a quasi-hydrodynamic model of the expansion of the material in the outermost edge of the disk secondary in response to the heating that it receives as it rotates into view of the luminous primary. Light curves computed using this model reproduce the basic features of absorption lines, which are observed to be deepest subsequent to the middle of the continuum eclipse and to persist after fourth contact.

Lissauer, Jack J.; Wolk, Scott J.; Griffith, Caitlin A.; Backman, Dana E.

1996-07-01

278

Evaluation of shuttle turbopump bearings  

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

279

Spin bearing retainer design optimization  

NASA Technical Reports Server (NTRS)

The dynamics behavior of spin bearings for momentum wheels (control-moment gyroscope, reaction wheel assembly) is critical to satellite stability and life. Repeated bearing retainer instabilities hasten lubricant deterioration and can lead to premature bearing failure and/or unacceptable vibration. These instabilities are typically distinguished by increases in torque, temperature, audible noise, and vibration induced by increases into the bearing cartridge. Ball retainer design can be optimized to minimize these occurrences. A retainer was designed using a previously successful smaller retainer as an example. Analytical methods were then employed to predict its behavior and optimize its configuration.

Boesiger, Edward A.; Warner, Mark H.

1991-01-01

280

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

281

Ecological overlap of sympatric sun bears and Asiatic black bears in tropical forest, Thailand.  

E-print Network

??Asiatic black bears (Ursus thibetanus) and sun bears (Helarctos malayanus) are ecologically similar species with broadly overlapping distributions in mainland Southeast Asia. Using bear sign… (more)

Steinmetz, Robert George

2009-01-01

282

The polar bear phenomena  

SciTech Connect

Results from measuring the thermal profile of polar bear pelts, reflectiveness of the pelts, and total thermal conversion data lead to the conclusion that the pelts from an ultra-efficient thermal diode for solar-thermal conversion. The transfer of the thermal energy from the surface of the fur to the skin where it is absorbed cannot be thermal, and therefore must be radiative. This process must have an efficiency of better than 90:0090 percent to account for measured values. The radiative transfer process is not known at present. To understand it, a detailed knowledge of the microscopic parameters of the pelts must be obtained. This is the current thrust of the polar solar research. If the process can be understood and synthesized,it will provide a major breakthrough in the area of solar-thermal energy conversion.

Maw, P.K. (United Kingdom Ingersoll-Rand Sales Company, Ltd., Horwich, Bolton Lancashire, BL6 6JN (GB)); Lane, M.T.

1990-02-01

283

Remanent magnetization and coercivity of rocks under hydrostatic pressure up to 1.4 GPa  

NASA Astrophysics Data System (ADS)

We designed an Isothermal Remanent Magnetization (IRM) acquisition system based on permanent magnets and sized to accommodate an amagnetic hydrostatic pressure cell. This pressure cell fits in a superconducting rock magnetometer, allowing for the measurement of remanent magnetization of pressurized samples. With this system, we determined the coercivity of remanence (Bcr) at different hydrostatic pressures up to 1.4 GPa for rock and dispersed mineral samples with various magnetic mineralogy and domain state. IRM and Bcr are nearly identical before compression and after decompression, indicating no permanent changes in the magnetic properties during pressure cycling. Hydrostatic pressure up to 1.4 GPa does not significantly increases IRM under pressure except for multidomain pyrrhotite and magnetite which show an increase of about 40%. Relative increase of Bcr under pressure is mild, except for a near single domain titanomagnetite where Bcr doubles.

Demory, F.; Rochette, P.; Gattacceca, J.; Gabriel, T.; Bezaeva, N. S.

2013-08-01

284

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

285

Numerical Simulation of Damage during Forging with Superimposed Hydrostatic Pressure by Active Media  

SciTech Connect

The effective reduction of energy consumption and a reasonable treatment of resources can be achieved by minimizing a component's weight using lightweight metals. In this context, aluminum alloys play a major role. Due to their material-sided restricted formability, the mentioned aluminum materials are difficult to form. The plasticity of a material is ascertained by its maximum forming limit. It is attained, when the deformation causes mechanical damage within the material. Damage of that sort is reached more rapidly, the greater the tensile strength rate in relation to total tension rate. A promising approach of handling these low ductile, high-strength aluminum alloys within a forming process, is forming with a synchronized superposition of comprehensive stress by active media such as by controlling oil pressure. The influence of superimposed hydrostatic pressure on the flow stress was analyzed as well as the formability for different procedures at different hydrostatic pressures and temperature levels. It was observed that flow stress is independent of superimposed hydrostatic pressure. Neither the superimposed pressure has an influence on the plastic deformation, nor does a pressure dependent material hardening due to increasing hydrostatic pressure take place. The formability increases with rising hydrostatic pressure. The relative gain at room temperature and increase of the superimposed pressure from 0 to 600 bar for tested materials was at least 140 % and max. 220 %. Therefore in this paper, based on these experimental observations, it is the intended to develop a numerical simulation in order to predict ductile damage that occurs in the bulk forging process with superimposed hydrostatic pressure based Lemaitre's damage model.

Behrens, B.-A.; Hagen, T.; Roehr, S.; Sidhu, K. B. [Institute for Metal Forming and Metal-Forming Machines, Leibniz University of Hanover, An der Universitaet 2, 30823 Garbsen (Germany)

2007-05-17

286

Combined use of infrared and Raman spectra in the characterization of orthoclase under various hydrostatic pressures.  

PubMed

Colorless and pink orthoclase from Balikun granite body, East Zhunger in Xinjiang, served as the samples for the research on hydrostatic pressure experiment. The in-situ hydrostatic pressure test for orthoclases was conducted at the room temperature and pressures from 100 to 600 MPa using cubic zirconia anvil cell, with quartz as pressure gauge. The water located in the orthoclases for the conditions of different hydrostatic pressures was characterized through the methods of Fourier transform infrared (FTIR) and Raman spectra. The results showed that there was a linear correlation between the shifting of Raman bands and hydrostatic pressure applied to the feldspar. All of vibration peaks of M-O structural groups in orthoclases, the bending vibration peaks of Si(Al(IV))-O-Si bond and tetrahedron groups of [SiO4] in Raman spectra shifted toward the higher frequency regularly, the drift distance is 2, 2.19 and less than 2 cm(-1) respectively. The spectra of FTIR suggested that there was more water in colorless orthoclases than the pink one under certain conditions of hydrostatic pressure. The intensity and integral area centered at 3420 cm(-1) in FTIR spectra increased with the rising of hydrostatic pressure. The integral area for colorless and pink feldspar in FTIR spectra rose from 120, 1383 cm(-1) under normal pressure to 1570, 2001 cm(-1) at 600 MPa respectively. The experimental results might indicate that the water in the earth crust could enter the orthoclases in certain condition of the aqueous confining pressure. PMID:24822414

Liu, Rui; Wang, Zhi-Hua; Xu, Qiang; Yu, Na; Cao, Miao-Cong

2014-02-01

287

Differential Stability of Dimeric and Monomeric Cytochrome c Oxidase Exposed to Elevated Hydrostatic Pressure†  

PubMed Central

Detergent-solubilized dimeric and monomeric cytochrome c oxidase (CcO) have significantly different quaternary stability when exposed to 2?3 kbar of hydrostatic pressure. Dimeric, dodecyl maltoside-solubilized cytochrome c oxidase is very resistant to elevated hydrostatic pressure with almost no perturbation of its quaternary structure or functional activity after release of pressure. In contrast to the stability of dimeric CcO, 3 kbar of hydrostatic pressure triggers multiple structural and functional alterations within monomeric cytochrome c oxidase. The perturbations are either irreversible or slowly reversible since they persist after the release of high pressure. Therefore, standard biochemical analytical procedures could be used to quantify the pressure-induced changes after the release of hydrostatic pressure. The electron transport activity of monomeric cytochrome c oxidase decreases by as much as 60% after exposure to 3 kbar of hydrostatic pressure. The irreversible loss of activity occurs in a time- and pressure-dependent manner. Coincident with the activity loss is a sequential dissociation of four subunits as detected by sedimentation velocity, high-performance ion-exchange chromatography, and reversed-phase and SDS–PAGE subunit analysis. Subunits VIa and VIb are the first to dissociate followed by subunits III and VIIa. Removal of subunits VIa and VIb prior to pressurization makes the resulting 11-subunit form of CcO even more sensitive to elevated hydrostatic pressure than monomeric CcO containing all 13 subunits. However, dimeric CcO, in which the association of VIa and VIb is stabilized, is not susceptible to pressure-induced inactivation. We conclude that dissociation of subunit III and/or VIIa must be responsible for pressure-induced inactivation of CcO since VIa and VIb can be removed from monomeric CcO without significant activity loss. These results are the first to clearly demonstrate an important structural role for the dimeric form of cytochrome c oxidase, i.e., stabilization of its quaternary structure. PMID:17530783

Stani?ová, Jana; Sedlák, Erik; Musatov, Andrej; Robinson, Neal C.

2007-01-01

288

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. PMID:19516918

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

2009-01-01

289

Polar Bears and Climate Change  

NSDL National Science Digital Library

The issue-focused, peer reviewed article discusses how a warming climate is altering sea ice conditions, which affects polar bears in many ways, including more difficulty in getting to and hunting prey, fewer den areas and lower cub survival, increased interactions between bears and humans, and lower survival rate of the species in general.

Andrew E. Derocher (University of Alberta, Canada;)

2008-05-01

290

Carbon Nanotube Linear Bearing Nanoswitches  

E-print Network

Carbon Nanotube Linear Bearing Nanoswitches V. V. Deshpande, H.-Y. Chiu, H. W. Ch. Postma, C. Miko-friction bearing capabilities of multiwalled carbon nanotubes (MWNTs) to realize nanoelectromechanical switches geometry remain important obstacles to the miniaturization of me- chanical systems. Carbon nanotubes

Bockrath, Marc

291

High-Performance Ball Bearing  

NASA Technical Reports Server (NTRS)

High-performance bearing features strong, lightweight, self-lubricating cage with self-lubricating liners in ball apertures. Designed to operate at high speed (tens of thousands of revolutions per minute) in cryogenic environment like liquid-oxygen or liquid-hydrogen turbopump. Includes inner race, outer race, and cage keeping bearing balls equally spaced.

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

1995-01-01

292

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

293

Thermally Activated Seizure of Angular Contact Bearings  

Microsoft Academic Search

Equations have been developed relating friction-power to bearing element temperatures for the particular case of prelubricated or lightly lubricated ball bearings. An expression is derived for the change in relative dimensions of an angular contact bearing, as determined by the temperature gradient across the bearing. A second expression is found for the accommodation of the bearing to expansion, this accommodation

R. A. Burton; H. E. Staph

1967-01-01

294

HUMAN IMPACTS ON BEAR HABITAT USE1  

Microsoft Academic Search

Human effects on bear habitat use are mediated through food biomass changes, bear tolerance of humans and their impacts, and human tolerance of bears. Large- scale changes in bear food biomass have been caused by conversion of wildlands and waterways to intensive human use, and by the introduction of exotic pathogens. Bears consume virtually all human foods that have been

DAVID J. MATTSON

295

Space Station alpha joint bearing  

NASA Technical Reports Server (NTRS)

Perhaps the most critical structural system aboard the Space Station is the Solar Alpha Rotary Joint which helps align the power generation system with the sun. The joint must provide structural support and controlled rotation to the outboard transverse booms as well as power and data transfer across the joint. The Solar Alpha Rotary Joint is composed of two transition sections and an integral, large diameter bearing. Alpha joint bearing design presents a particularly interesting problem because of its large size and need for high reliability, stiffness, and on orbit maintability. The discrete roller bearing developed is a novel refinement to cam follower technology. It offers thermal compensation and ease of on-orbit maintenance that are not found in conventional rolling element bearings. How the bearing design evolved is summarized. Driving requirements are reviewed, alternative concepts assessed, and the selected design is described.

Everman, Michael R.; Jones, P. Alan; Spencer, Porter A.

1987-01-01

296

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

297

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

298

[X-ray diffraction study of high hydrostatic pressure on crystalline structure of different type starches].  

PubMed

Crystalline changes of different type starches after high hydrostatic pressure treated under 300, 450, 600 MPa were studied by X-ray diffraction. Waxy maize (A type, 100% amylopectin), hylon VII (B type, 30% amylopectin) and tapioca starch (C type, 83% amylopectin) were chosen. The results indicated that for waxy maize starch, annealing effect was observed at 300 MPa, disappearance of crystalline structure happened at 450 MPa and retrogradation at 600 MPa. The results proved that the granule under high hydrostatic pressure processing experiences "three development stages" including annealling effect, disappearance of crystalline structure and recrystalline after granule disintegration. PMID:23240443

Liu, Pei-Ling; Shen, Qun; Hu, Xiao-Song; Wu, Ji-Hong

2012-09-01

299

Nonlinear Control of Wind Turbines with Hydrostatic Transmission Based on Takagi-Sugeno Model  

NASA Astrophysics Data System (ADS)

A nonlinear model-based control concept for wind turbines with hydrostatic transmission is proposed. The complete mathematical model of a wind turbine drive train with variable displacement pump and variable displacement motor is presented. The controller design takes into consideration the nonlinearity of the aerodynamic maps and hydrostatic drive train by an convex combination of state space controller with measurable generator speed and hydraulic motor displacement as scheduling parameters. The objectives are the set point control of generator speed and tracking control of the rotor speed to reach the maximum power according to the power curve in the partial-load region.

Schulte, Horst; Georg, Soren

2014-06-01

300

77 FR 70423 - Black Bear Hydro Partners, LLC and Black Bear Development Holdings, LLC and Black Bear SO, LLC...  

Federal Register 2010, 2011, 2012, 2013

...Federal Energy Regulatory Commission [Project Nos. 2710-061; 2712-078] Black Bear Hydro Partners, LLC and Black Bear Development Holdings, LLC and Black Bear SO, LLC; Notice of Application for Partial Transfer of Licenses, and...

2012-11-26

301

Prediction of relationships between hydrostatic coefficients and processing parameters of porous PZT ceramics by radial basis function  

Microsoft Academic Search

The high hydrostatic coefficients of porous piezoelectric materials provide the reduced acoustic impedance for the effective coupling with water medium as well as biological tissues. The hydrostatic strain coefficient (dh), voltage coefficients (gh) and longitudinal piezoelectric coefficient (d33) of porous piezoelectric materials has a strong dependence on processing parameters such as porosity parameter, polymer percentage, density and poling voltage. In

B. Praveenkumar; C. Vijayakumar; H. H. Kumar; D. K. Kharat

2009-01-01

302

Bears, Big and Little. Young Discovery Library Series.  

ERIC Educational Resources Information Center

This book is written for children 5 through 10. Part of a series designed to develop their curiosity, fascinate them and educate them, this volume describes: (1) the eight species of bears, including black bear, brown bear, grizzly bear, spectacled bear, sun bear, sloth bear, polar bear, and giant panda; (2) geographical habitats of bears; (3)…

Pfeffer, Pierre

303

USGS Scientist Taking Measurements Along Bear Creek  

USGS Multimedia Gallery

USGS Scientist Taking Measurements Along Bear Creek - Photo taken by Heidi Koontz, USGS Communications, Friday, Sept. 13. USGS scientist Ben Glass conducting current profiler measurements along Bear Creek near Bear Creek Lake in Morrison, Colo....

304

Alex the Bear Goes to Child Care  

MedlinePLUS Videos and Cool Tools

... Tools » Meet Alex the Bear Meet Alex the Bear, a new friend of Child Care Aware® Going ... experience for both children and parents. Alex the Bear, the newest friend of Child Care Aware®, seeks ...

305

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

306

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

307

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

308

Experimental analysis of journal bearings  

SciTech Connect

This study presents a comprehensive technique which could be applied to almost any rotating equipment to identify and diagnose journal bearing problems that relate to metal-to-metal bearing surface contact. Orbital measurements that describe bearing parameters in different modes of operation were experimentally obtained and analyzed. Such parameters may include: attitude angle, minimum oil film thickness, and the possibility of metal-to-metal rubbing occurrence. The general outline of the presented experimental technique was substantiated using the Raimondi-Boyd well documented design charts and good correlation between experimental and analytical results was obtained.

Elkholy, A.H. [United Arab Emirates Univ., Al-Ain (United Arab Emirates). Dept. of Mechanical Engineering; Elshakweer, A. [Global Engineering Technology, Kitchener, Ontario (Canada)

1994-12-31

309

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

NASA Astrophysics Data System (ADS)

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.

310

Thermal fluid-solid interaction model and experimental validation for hydrostatic mechanical face seals  

NASA Astrophysics Data System (ADS)

Hydrostatic mechanical face seals for reactor coolant pumps are very important for the safety and reliability of pressurized-water reactor power plants. More accurate models on the operating mechanism of the seals are needed to help improve their performance. The thermal fluid-solid interaction (TFSI) mechanism of the hydrostatic seal is investigated in this study. Numerical models of the flow field and seal assembly are developed. Based on the mechanism for the continuity condition of the physical quantities at the fluid-solid interface, an on-line numerical TFSI model for the hydrostatic mechanical seal is proposed using an iterative coupling method. Dynamic mesh technology is adopted to adapt to the changing boundary shape. Experiments were performed on a test rig using a full-size test seal to obtain the leakage rate as a function of the differential pressure. The effectiveness and accuracy of the TFSI model were verified by comparing the simulation results and experimental data. Using the TFSI model, the behavior of the seal is presented, including mechanical and thermal deformation, and the temperature field. The influences of the rotating speed and differential pressure of the sealing device on the temperature field, which occur widely in the actual use of the seal, are studied. This research proposes an on-line and assembly-based TFSI model for hydrostatic mechanical face seals, and the model is validated by full-sized experiments.

Huang, Weifeng; Liao, Chuanjun; Liu, Xiangfeng; Suo, Shuangfu; Liu, Ying; Wang, Yuming

2014-07-01

311

Hydrostatic Pressure Affects In Vitro Maturation of Oocytes and Follicles and Increases Granulosa Cell Death  

PubMed Central

Objective: This study examines the effects of hydrostatic pressure on in vitro maturation (IVM) of oocytes derived from in vitro grown follicles. Materials and Methods: In this experimental study, preantral follicles were isolated from 12-day-old female NMRI mice. Each follicle was cultured individually in Alpha Minimal Essential Medium (?-MEM) under mineral oil for 12 days. Then, follicles were induced for IVM and divided into two groups, control and experiment. In the experiment group follicles were subjected to 20 mmHg pressure for 30 minutes and cultured for 24-48 hours. We assessed for viability and IVM of the oocytes. The percentage of apoptosis in cumulus cells was determined by the TUNEL assay. A comparison between groups was made using the student’s t test. Results: The percentage of metaphase II oocytes (MII) increased in hydrostatic pressuretreated follicles compared to controls (p<0.05). Cumulus cell viability reduced in hydrostatic pressure-treated follicles compared to controls (p<0.05). Exposure of follicles to pressure increased apoptosis in cumulus cells compared to controls (p<0.05). Conclusion: Hydrostatic pressure, by inducing apoptosis in cumulus cells, participates in the cumulus oocyte coupled relationship with oocyte maturation. PMID:24381852

Rashidi, Zahra; Azadbakht, Mehri; Amini, Ali; Karimi, Isac

2014-01-01

312

Inactivation of Colletotrichum gloeosporioides spores by high hydrostatic pressure combined with citral or lemongrass essential oil  

Microsoft Academic Search

Anthracnose, caused by the fungus Colletotrichum gloeosporioides, is the main post-harvest disease of the papaya. Inactivation of the spores of C. gloeosporioides in saline solution by the use of high hydrostatic pressure, citral oil and lemongrass oil, alone and in combination, was studied. C. gloeosporioides spores were efficiently inhibited after a pressure treatment of 350 MPa for 30 min. When

Fernando L Palhano; Thabita T. B Vilches; Reginaldo B Santos; Marcos T. D Orlando; J. Aires Ventura; Patricia M. B Fernandes

2004-01-01

313

COMPARATIVE STUDY OF ADAPTATIONS FOR CONTINUOUS SWIMMING AND HYDROSTATIC EQUILIBRIUM OF  

E-print Network

COMPARATIVE STUDY OF ADAPTATIONS FOR CONTINUOUS SWIMMING AND HYDROSTATIC EQUILIBRIUM OF SCOMBROID AND XIPHOID FISHES JOHN J. MAGNUSON1, 2 ABSTRACT Scombroid fishes swim continuously with pectoral fins on the lifting area of extended pc.:toral fins and the weight of the fish in water. Lifting areas of

314

Thermal fluid-solid interaction model and experimental validation for hydrostatic mechanical face seals  

NASA Astrophysics Data System (ADS)

Hydrostatic mechanical face seals for reactor coolant pumps are very important for the safety and reliability of pressurized-water reactor power plants. More accurate models on the operating mechanism of the seals are needed to help improve their performance. The thermal fluid-solid interaction (TFSI) mechanism of the hydrostatic seal is investigated in this study. Numerical models of the flow field and seal assembly are developed. Based on the mechanism for the continuity condition of the physical quantities at the fluid-solid interface, an on-line numerical TFSI model for the hydrostatic mechanical seal is proposed using an iterative coupling method. Dynamic mesh technology is adopted to adapt to the changing boundary shape. Experiments were performed on a test rig using a full-size test seal to obtain the leakage rate as a function of the differential pressure. The effectiveness and accuracy of the TFSI model were verified by comparing the simulation results and experimental data. Using the TFSI model, the behavior of the seal is presented, including mechanical and thermal deformation, and the temperature field. The influences of the rotating speed and differential pressure of the sealing device on the temperature field, which occur widely in the actual use of the seal, are studied. This research proposes an on-line and assembly-based TFSI model for hydrostatic mechanical face seals, and the model is validated by full-sized experiments.

Huang, Weifeng; Liao, Chuanjun; Liu, Xiangfeng; Suo, Shuangfu; Liu, Ying; Wang, Yuming

2014-09-01

315

Argon gas permeability of New Mexico rock salt under hydrostatic compression  

Microsoft Academic Search

Laboratory measurements of the argon gas permeability for rock salt specimens from the Waste Isolation Pilot Plant (WIPP) site in Southeast New Mexico (SENM) are obtained by using a transient, pressure step technique. Permeabilities of seven specimens are investigated as a function of hydrostatic compression and time. These data, when evaluated with the results of other authors, lead to the

H. J. Sutherland; S. P. Cave

1980-01-01

316

Effects of hydrostatic pressure, agitation and CO2 stress on Phytophthora nicotianae zoospore survival  

Technology Transfer Automated Retrieval System (TEKTRAN)

Phytophthora nicotianae Breda de Haan was used as a model pathogen to investigate the effects of hydrostatic pressure, agitation, and aeration with CO2 or breathable air on the survival of Phytophthora zoospores in water. Injecting CO2 into 2 liters of zoospore-infested water for 5 min at 110.4 ml ...

317

Inactivation of human norovirus in contaminated oysters and clams by high-hydrostatic pressure  

Technology Transfer Automated Retrieval System (TEKTRAN)

Human norovirus (NoV) is the most frequent causative agent of foodborne disease associated with shellfish consumption. In this study, the effect of high-hydrostatic pressure (HHP) on inactivation of NoV was determined. Genogroup I.1 (GI.1) or Genogroup II.4 (GII.4) NoV were inoculated into oyster ho...

318

ERK activation is required for hydrostatic pressure-induced tensile changes in  

E-print Network

ERK activation is required for hydrostatic pressure-induced tensile changes in engineered articular, Davis, CA, USA Abstract The objective of this study was to identify ERK 1/2 involvement in the changes-assembled cartilage constructs. In study 1, ERK 1/2 phosphorylation was detected by immunoblot, following application

Athanasiou, Kyriacos

319

On the Modeling and Simulation of Non-Hydrostatic Dam Break Flows  

E-print Network

On the Modeling and Simulation of Non-Hydrostatic Dam Break Flows Alexandre Caboussat S´ebastien Boyaval Alexandre Masserey January 1, 2013 Abstract The numerical simulation of three-dimensional dam analytically. The numerical experiments on actual topographies, in particular the Malpasset dam break

Paris-Sud XI, Université de

320

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

321

Potential for High Hydrostatic Pressure Processing to Control Quarantine Insects in Fruit  

Technology Transfer Automated Retrieval System (TEKTRAN)

Tests were conducted to determine the potential for high hydrostatic pressure (HPP) to control codling moth, Cydia pomonella (L.) and Western cherry fruit fly, Rhagoletis indifferens Curran. Apples with larvae or eggs of codling moth were treated 24 h and 72 h, respectively, after infestation at a s...

322

Transcriptomics Reveal Several Gene Expression Patterns in the Piezophile Desulfovibrio hydrothermalis in Response to Hydrostatic Pressure  

PubMed Central

RNA-seq was used to study the response of Desulfovibrio hydrothermalis, isolated from a deep-sea hydrothermal chimney on the East-Pacific Rise at a depth of 2,600 m, to various hydrostatic pressure growth conditions. The transcriptomic datasets obtained after growth at 26, 10 and 0.1 MPa identified only 65 differentially expressed genes that were distributed among four main categories: aromatic amino acid and glutamate metabolisms, energy metabolism, signal transduction, and unknown function. The gene expression patterns suggest that D. hydrothermalis uses at least three different adaptation mechanisms, according to a hydrostatic pressure threshold (HPt) that was estimated to be above 10 MPa. Both glutamate and energy metabolism were found to play crucial roles in these mechanisms. Quantitation of the glutamate levels in cells revealed its accumulation at high hydrostatic pressure, suggesting its role as a piezolyte. ATP measurements showed that the energy metabolism of this bacterium is optimized for deep-sea life conditions. This study provides new insights into the molecular mechanisms linked to hydrostatic pressure adaptation in sulfate-reducing bacteria. PMID:25215865

Amrani, Amira; Bergon, Aurélie; Holota, Hélène; Tamburini, Christian; Garel, Marc; Ollivier, Bernard; Imbert, Jean; Dolla, Alain; Pradel, Nathalie

2014-01-01

323

Nuclear Technology. Course 26: Nondestructive Examination (NDE) Techniques I. Module 26-3, Hydrostatic Tests.  

ERIC Educational Resources Information Center

This third in a series of seven modules for a course titled Nondestructive Examination (NDE) Techniques I describes the principles and practices associated with hydrostatic testing. The module follows a typical format that includes the following sections: (1) introduction, (2) module prerequisites, (3) objectives, (4) notes to instructor/student,…

Pelton, Rick; Espy, John

324

Non-Hydrostatic Wave Model NHWAVE User's Guide for Modeling Submarine Landslide Tsunami  

E-print Network

Non-Hydrostatic Wave Model NHWAVE User's Guide for Modeling Submarine Landslide Tsunami ( Version 1 of submarine landslide-induced tsunami waves. NHWAVE was de- veloped by Ma et al. (2012) for modeling fully landslide can be directly simulated by taking advantage of the coordinate system. The model assumes

Kirby, James T.

325

Hydrostatic and uniaxial behavior of a high density polyurethane foam (FR-3720) at various temperatures  

SciTech Connect

This report describes the foam testing program designed to support a constitutive material response model. Experimental techniques were developed for hydrostatic pressure and uniaxial testing of high density polyurethane foam from ambient to 150 C with deformation greater than 50%. Two chambers were developed to perform the tests.

Lu, W.Y.; Korellis, J.S.; Lee, K.L.; Grishaber, R.

1993-03-01

326

Silica gel media for isolating and studying bacteria under hydrostatic pressure.  

PubMed Central

Individual colonies of micrococcus euryhalis and of a marine bacterial isolate were grown in pour tubes under hydrostatic pressure. The medium was prepared in a silica sol, and gelation was effected at 4 degrees C by addition of salts to achieve concentrations found in seawater. PMID:32836

Dietz, A S; Yayanos, A A

1978-01-01

327

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

328

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

329

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

330

Testing and Lubrication for Single Race Bearings  

SciTech Connect

Three ES and H-compatible lubricants (Environment, Safety and Health) for single race bearing applications and one hybrid-material single race bearings were evaluated and compared against single race bearings with 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. Vydax has been used as a bearing lubricant in stronglink mechanisms since 1974. Hybrid bearings with silicon nitride balls and molded glass-nylon-Teflon retainers, bearings lubricated with titanium carbide (TiC) on the balls, bearings lubricated with sputtered MoS{sub 2} on races and retainers, and bearings lubricated with electrophoretically deposited MoS{sub 2} were evaluated. The bearings were maintained in a preloaded state in bearing cartridges during cycling and vibration tests. Bearings with electrophoretically deposited MoS{sub 2} performed as well as bearings lubricated with Vydax and were the best performing candidate. All candidates were suitable for low preload applications. Bearings with TiC coated balls and bearings lubricated with sputtered MoS{sub 2} on the races and retainers performed well at high preloads, though not as well as bearings lubricated with electrophoretic deposition of MoS{sub 2}. Bearings with silicon nitride balls were not suitable for high preload applications.

Steinhoff, R.G.

1998-03-04

331

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

332

An efficient semi-implicit method for three-dimensional non-hydrostatic flows in compliant arterial vessels.  

PubMed

Blood flow in arterial systems can be described by the three-dimensional Navier-Stokes equations within a time-dependent spatial domain that accounts for the elasticity of the arterial walls. In this article, blood is treated as an incompressible Newtonian fluid that flows through compliant vessels of general cross section. A three-dimensional semi-implicit finite difference and finite volume model is derived so that numerical stability is obtained at a low computational cost on a staggered grid. The key idea of the method consists in a splitting of the pressure into a hydrostatic and a non-hydrostatic part, where first a small quasi-one-dimensional nonlinear system is solved for the hydrostatic pressure and only in a second step the fully three-dimensional non-hydrostatic pressure is computed from a three-dimensional nonlinear system as a correction to the hydrostatic one. The resulting algorithm is robust, efficient, locally and globally mass conservative, and applies to hydrostatic and non-hydrostatic flows in one, two and three space dimensions. These features are illustrated on nontrivial test cases for flows in tubes with circular or elliptical cross section where the exact analytical solution is known. Test cases of steady and pulsatile flows in uniformly curved rigid and elastic tubes are presented. Wherever possible, axial velocity development and secondary flows are shown and compared with previously published results. PMID:24842268

Fambri, Francesco; Dumbser, Michael; Casulli, Vincenzo

2014-11-01

333

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

334

Damping Seals And Bearings For A Turbomachine  

NASA Technical Reports Server (NTRS)

Improved design for support of rotor in turbopump integrates ball bearings with damping seals and damping bearings. Reduces radial (side) loads on ball bearings, making it possible to increase contact angles to withstand increased transient axial loads. Service lives of bearings prolonged.

Von Pragenau, George L.

1990-01-01

335

Ball-and-Socket-Bearing Wear Test  

NASA Technical Reports Server (NTRS)

Series of experiments to measure wear life of spherical bearing summarized. Report designed to establish clearance, contour, finish, and lubricant parameters for highly-loaded, compact plain spherical bearing. Information useful in design of bearings for helicopter control linkages, business machines, nuclear reactor, and rotor bearings.

Graham, W. G.

1984-01-01

336

International Workshop on Interfaces at Bear Creek  

E-print Network

International Workshop on Interfaces at Bear Creek October 20 ­ 24, 2009 Bear Creek Mountain Resort of Community and Economic Development #12;International Workshop on Interfaces at Bear Creek October 20-24, 2009 Bear Creek Mountain Resort Macungie, PA USA WORKSHOP PROGRAM TUESDAY, OCTOBER 20, 2009 3:00 p

Gilchrist, James F.

337

Hunting for grizzly bears By Andrew Findlay  

E-print Network

Hunting for grizzly bears By Andrew Findlay Publish Date: June 26, 2008 The Zodiac glides along environmentalists, First Nations, and bear-viewing companies believe the province is risking international shame for grizzly bears." Armed with the results of the poll, conservationists, First Nations, and grizzly-bear

Gross, Mart

338

SMOKEY THE BEAR SUTRA Gary Snyder  

E-print Network

SMOKEY THE BEAR SUTRA Gary Snyder Once in the Jurassic about 150 million years ago, the Great Sun THE BEAR. A handsome smokey­colored brown bear standing on his hind legs, show­ ing that he is aroused and watchful. Bearing in his right paw the Shovel that digs to the truth beneath ap­ pearances; cuts the roots

Alexander, Roger K.

339

The effect of hydrostatic pressure on subband structure and optical transitions in modulation-doped quantum well  

NASA Astrophysics Data System (ADS)

Within the framework of effective-mass approximation, we have calculated theoretically the effects of hydrostatic pressure and doping concentration on subband structure and optical transitions in modulation-doped GaAs/Al xGa 1-xAs quantum well for different well widths. The electronic structure of modulation-doped quantum well under the hydrostatic pressure is determined by solving the Schrödinger and Poisson equations self-consistently. The results obtained show that intersubband transitions and the subband energy levels in the modulation-doped quantum well can be significantly modified and controlled by the well width, donor concentration and hydrostatic pressure.

Ungan, F.; Yesilgul, U.; Sakiroglu, S.; Kasapoglu, E.; Sari, H.; Sökmen, I.

2011-06-01

340

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

341

Investigations of a bearing fault detector for railroad bearings  

NASA Technical Reports Server (NTRS)

The laboratory tests are described which were conducted on new and damaged bearings to determine the feasibility of using high-frequency vibration as a diagnostic tool. A high-frequency band pass filter and demodulator was assembled to permit field measurements of the high-frequency vibrations. Field tests were conducted on an actual truck and on an axle assembly run in a grease test rig. These field tests were directed toward demonstration of the suitability and capabilities of the high-frequency technique for field application. Two specific areas of field application were identified as being cost effective for railroad use. One area is the examination of railroad roller bearings at a derailment site, and the second is as a wayside detector to supplement present hot box detectors for defective roller bearings.

Wilson, D. S.; Frarey, J. L.

1975-01-01

342

Bearing Cartridge Designed To Reduce Wear  

NASA Technical Reports Server (NTRS)

Bearing cartridge holding outer races of two ball bearings in turbopump designed to prevent unloading of bearings during operating transients. Cartridge and bearings replace two ball bearings, whose outer races mounted in cylinder called "isolator" and preloaded by single spring mount holding isolator and reacting radial loads. Cartridge slides axially in bore of isolator during transients and forces outer races to move as pair. Necessary to eliminate unloading because unloading initiates wear.

Krieg, Eric J.

1992-01-01

343

International Workshop on Interfaces at Bear Creek  

E-print Network

International Workshop on Interfaces at Bear Creek October 2­5, 2012 Bear Creek Mountain Resort Workshop on Interfaces at Bear Creek October 2­5, 2012 Bear Creek Mountain Resort Macungie, PA USA WORKSHOP PROGRAM TUESDAY, OCTOBER 2, 2012 3:00 p.m. - 6:00 p.m. Arrival at the Inn at Bear Creek 6:00 p.m. - 8:00 p

Gilchrist, James F.

344

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

345

Function and hydrostatics in the telson of the Burgess Shale arthropod Burgessia  

PubMed Central

Burgessia bella is a characteristic Burgess Shale arthropod (508?Ma), but the unusual preservation of its telson in both straight and bent modes leads to contradictory interpretations of its function. A reinvestigation of the fossil material, including burial attitudes, combined with a comparison with the decay sequence and mechanics of the telson in living Limulus, demonstrates that the telson of Burgessia was flexible in its relaxed state but could be stiffened in life. Evidence of fluid within the telson indicates that this manoeuvrability was achieved by changes in hydrostatic pressure and muscular control. The dual mode in the Burgessia telson is, to my knowledge, the first documented among fossil arthropods. It indicates that the requirement for a rigid telson, which is resolved by a thick sclerotized cuticle in most arthropods, may first have been achieved by hydrostatic means. PMID:19324649

Lin, Jih-Pai

2009-01-01

346

Acute Uterine Inversion: A Simple Modification of Hydrostatic Method of Treatment  

PubMed Central

Background: Hydrostatic method for reducing acute uterine inversion is simple method, if advocated properly. Aim: The aim of this study is to reduce the failures in technique in O’Sullivan's method in acute puerperal uterine inversion hence reducing maternal mortality and morbidity. Subjects and Methods: This study was conducted over a f 6 year period s from 2007 to 2013. Women with acute uterine inversion immediately after delivered were included in the study. Repositioning of acute uterine inversion in six patients in emergency was done using trans-urethral resection of prostate set (TURP set), used in endoscopic resection of prostate, and two 3 L saline bags. Results: The repositioning was successful in all requiring no anesthesia. Conclusions: This technique modification is improvisation of hydrostatic pressure with a trans-urethral resection of prostate set (TURP set) and 3 L saline bags and it is simple and effective and will definitely save women's lives; thus, reducing maternal morbidity and mortality. PMID:24761250

Gupta, P; Sahu, R L; Huria, A

2014-01-01

347

The Effect of Hydrostatic Pressure and Temperature on Sonoluminescence of Metal Atoms from Aqueous Salt Solutions  

NASA Astrophysics Data System (ADS)

We have measured the spectra of multi-bubble sonoluminescence from aqueous LiCl, NaCl, MgCl2, CaCl2, CuSO4 solutions, saturated with argon, at the frequency 22 kHz. The spectra were collected at different hydrostatic pressures for all salts and in the ambient temperature range of 1-20 °C for NaCl solutions. Total absorbed ultrasonic power was 41 W. The results show that line emission from exited state metal atoms grows rapidly with the increase of hydrostatic pressure and at low ambient temperature. In all cases the increase of the intensity of underlying continuum and OH-radical emission was much lower than that of atomic emission at the same experimental conditions. The observed effects can be explained assuming higher temperature inside the cavitation bubbles during collapse in case of increased static pressure or decreased vapor pressure.

Gordeychuk, Tatyana V.; Kazachek, Mikhail V.

2008-06-01

348

Controlled hydrostatic sinus elevation: a novel method of elevating the sinus membrane.  

PubMed

Maxillary sinus elevation surgery has been practiced successfully over the past several decades with good outcomes, but tears and perforations still occur in significant numbers. The presumed cause of these problems is the fact that all methods currently used place "point sources" of lifting pressure on the Schneiderian membrane. A new procedure, controlled hydrostatic sinus lift, is presented herein as a safer, more controlled "lifting pressure" which simultaneously places equal force per square millimeter of bone-membrane interface. Hydraulic pressure in a closed system places equal pressure on all surfaces within the system, thereby eliminating "point sources" of pressure and gently elevating the Schneiderian membrane equally at all points of attachment. This controlled hydrostatic sinus lift procedure is accomplished by using a calibrated, hand-controlled pump and in-line pressure sensor meter. PMID:22067599

Kao, Daniel W K; DeHaven, Harold A

2011-12-01

349

'Dodo' and 'Baby Bear' Trenches  

NASA Technical Reports Server (NTRS)

NASA's Phoenix Mars Lander's Surface Stereo Imager took this image on Sol 11 (June 5, 2008), the eleventh day after landing. It shows the trenches dug by Phoenix's Robotic Arm. The trench on the left is informally called 'Dodo' and was dug as a test. The trench on the right is informally called 'Baby Bear.' The sample dug from Baby Bear will be delivered to the Phoenix's Thermal and Evolved-Gas Analyzer, or TEGA. The Baby Bear trench is 9 centimeters (3.1 inches) wide and 4 centimeters (1.6 inches) deep.

The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

2008-01-01

350

Disinfection Procedure for Water Distribution Pipelines Drinking water contamination can be prevented by hydrostatic testing and disinfection of  

E-print Network

Disinfection Procedure for Water Distribution Pipelines Drinking water contamination can be prevented by hydrostatic testing and disinfection of potable water distribution pipelines before connecting system with potable water after connecting pipelines EHS will provide technical guidance, approve

de Lijser, Peter

351

Characterization of High-Hydrostatic-Pressure Effects on Fresh Produce Using Chlorophyll Fluorescence Image Analysis  

Microsoft Academic Search

High hydrostatic pressure has the potential to affect food-related enzymes and microorganisms while retaining the produce’s\\u000a characteristic properties. Although many studies on effects of high pressure on quality attributes of fruit and vegetables\\u000a have been published, experimental results on the impact of high-pressure treatment on the physiological activity of products\\u000a are rare. To characterize changes of the samples fast and

Oliver Schlüter; Julia Foerster; Martin Geyer; Dietrich Knorr; Werner B. Herppich

2009-01-01

352

Effect of High Hydrostatic Pressure on Physicochemical and Structural Properties of Rice Starch  

Microsoft Academic Search

Rice starch–water suspension (20%) were subjected to high hydrostatic pressure (HHP) treatment at 120, 240, 360, 480, and\\u000a 600 MPa for 30 min. Polarizing light microscope, scanning electron microscopy (SEM), rapid visco analyzer (RVA), differential\\u000a scanning calorimeter (DSC), and X-ray diffraction were used to investigate the physicochemical and structural changes of starch.\\u000a Microscopy studies showed that the treatment of starch with HHP

Wenhao Li; Yunfei Bai; Saleh A. S. Mousaa; Qing Zhang; Qun Shen

353

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

354

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

355

HYDROSTATIC WEIGHING SYSTEM AT THE INRiM FOR CALIBRATING HYDROMETERS  

Microsoft Academic Search

Hydrometers are simple but effective instruments fo r measuring the density of liquids. In this work, we present the new hydrostatic weighing system developed at the INRiM, formerly IMGC - CNR, for the calibration of hydrometers in the range 500 kg.m -3 to 2000 kg.m -3 . The apparatus which uses a method to automatically align specific scale-marks for the

356

Environmental Constraints on the Mechanics of Crawling and Burrowing Using Hydrostatic Skeletons  

Microsoft Academic Search

Mechanics, kinematics, and energetics of crawling and burrowing by limbless organisms using hydrostatic skeletons depend on\\u000a the medium and mode in which the organism is moving. Whether the animal is moving over or through a solid has long been considered\\u000a important enough to distinguish crawling and burrowing as different terms, and in fact the mechanics are very different. Crawlers\\u000a use

K. M. Dorgan

2010-01-01

357

Influence of hydrostatic pressure on l-glutamate dehydrogenase from the Antarctic fish Chaenocephalus aceratus  

Microsoft Academic Search

The influence of hydrostatic pressure on the stability and activity of glutamate dehydrogenase (GDH) from the liver of the\\u000a Antarctic fish Chaenocephalus aceratus (Notothenioidei: Channichthyidae) has been investigated using the homologous bovine enzyme for comparison. At gradually increasing\\u000a pressure, the fish GDH retains all activity up to 140?MPa, whereas in the same pressure range the bovine enzyme is slightly\\u000a inactivated.

M. A. Ciardiello; B. Schmitt; G. di Prisco; G. Hervé

1999-01-01

358

Method for correcting laboratory model deep-well disposal system data for hydrostatic pressure effects.  

PubMed

A pressure chamber for determining the effect of increased hydrostatic pressure on growth and metabolic activities of groundwater bacteria is described. The chamber was used to show that moderate increases in pressure (to about 100 atmospheres) result in increased growth of mixed cultures of industrial-injection-well bacteria and in the more complete degradation of formate and nitrate by these bacteria, as compared with identical cultures at atmospheric pressure. PMID:16345295

Horvath, E; Elkan, G H

1978-06-01

359

Evolution of dilatancy and permeability in rock salt during hydrostatic compaction and triaxial deformation  

Microsoft Academic Search

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 2×10-20m2. The initial permeability is primarily due to decompaction induced by drilling, core retrieval

Till Popp; Hartmut Kern; Otto Schulze

2001-01-01

360

Donor impurity in vertically-coupled quantum-dots under hydrostatic pressure and applied electric field  

Microsoft Academic Search

In this work we make a predictive study on the binding energy of the ground state for hydrogenic donor impurity in vertically-coupled\\u000a quantum-dot structure, considering the combined effects of hydrostatic pressure and in growth-direction applied electric field.\\u000a The approach uses a variational method within the effective mass approximation. The low dimensional structure consists of\\u000a three cylindrical shaped GaAs quantum-dots, grown

C. M. Duque; M. G. Barseghyan; C. A. Duque

2010-01-01

361

Donor impurity in vertically-coupled quantum-dots under hydrostatic pressure and applied electric field  

Microsoft Academic Search

In this work we make a predictive study on the binding energy of the ground state for hydrogenic donor impurity in vertically-coupled quantum-dot structure, considering the combined effects of hydrostatic pressure and in growth-direction applied electric field. The approach uses a variational method within the effective mass approximation. The low dimensional structure consists of three cylindrical shaped GaAs quantum-dots, grown

C. M. Duque; M. G. Barseghyan; C. A. Duque

2010-01-01

362

Compression heating of selected pressure transmitting fluids and liquid foods during high hydrostatic pressure treatment  

Microsoft Academic Search

Three pressure transmitting fluids (water, ethylene glycol, and ethanol) and three liquid foods (orange juice, whole, and skim milk) were pressurized at 100–400MPa and at 5, 20 and 35°C, using different compression rates (100, 200, and 300MPa\\/min) to evaluate the adiabatic heating phenomena during high hydrostatic pressure (HHP) processing. A pressure vessel (3L volume) in which liquid foods could be

Sencer Buzrul; Hami Alpas; Alain Largeteau; Faruk Bozoglu; Gérard Demazeau

2008-01-01

363

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

SciTech Connect

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 [National Metrology Laboratory, SIRIM Berhad (Malaysia)

2009-07-07

364

An Update on High Hydrostatic Pressure, from the Laboratory to Industrial Applications  

Microsoft Academic Search

High hydrostatic pressure has become an industrial reality, and although there are still many aspects under research, today\\u000a it is possible to buy high-pressurized products in many countries. Indeed, pasteurization of food products using elevated\\u000a pressure at room temperature has been accepted by regulatory agencies for commercial use. The quality displayed in such products\\u000a includes better nutritional retention, fresh-like flavor,

Daniela Bermúdez-Aguirre; Gustavo V. Barbosa-Cánovas

2011-01-01

365

COORDINATION OF RESPIRATORY AND HYDROSTATIC FUNCTIONS OF THE SWIMBLADDER IN THE CENTRAL MUDMINNOW, UMBRA LIMI  

Microsoft Academic Search

SUMMARY 1. Observations of behaviour and changes in buoyancy of Umbra limi, a facultative air-breathing fish, were studied to understand coordination of respiratory and hydrostatic functions of the swimbladder. 2. Fish were exposed to either normoxic or hypoxic water in either undisturbed or disturbed (simulating predator presence) conditions. Declines in swimbladder volume occurred between air-breaths as O2 was removed. These

JOHN H. GEE

366

The gross hydrostatic-pressure effect as related to foil and wire strain gages  

Microsoft Academic Search

An analysis of gross pressure effect for strain gages is presented. This is defined as the difference between the predicted\\u000a hydrostatic strain and the experimental strain. Values of the theoretical strain per unit pressure are based on the Voigt-Reuss-Hill\\u000a approximation using published values of elastic moduli and compliances. These theoretical values are adjusted by the pressure\\u000a effect calculated from an

R. Vincent Milligan

1967-01-01

367

Effects of solutes on solubilization and refolding of proteins from inclusion bodies with high hydrostatic pressure  

Microsoft Academic Search

High hydrostatic pressure (HHP)-mediated solubilization and refolding of five inclusion bodies (IBs) produced from bacteria, three Gram-negative binding proteins (GNBP1, GNBP2, and GNBP3) from Drosophila, and two phosphatases from human were investigated in combination of a redox-shuffling agent (2 mM DTT and 6 mM GSSG) and various additives. HHP (200 MPa) combined with the redox- shuffling agent resulted in solubilization

SEUNG-HYUN LEE; JOHN F. CARPENTER; BYEONG S. CHANG; THEODORE W. RANDOLPH; YONG-SUNG KIM

2006-01-01

368

WEIGHING GALAXY CLUSTERS WITH GAS. I. ON THE METHODS OF COMPUTING HYDROSTATIC MASS BIAS  

SciTech Connect

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 [Department of Physics, Yale University, New Haven, CT 06520 (United States); Nelson, Kaylea, E-mail: erwin.lau@yale.edu [Department of Astronomy, Yale University, New Haven, CT 06520 (United States)

2013-11-10

369

75 FR 3444 - Ball Bearings and Parts Thereof From Germany: Initiation of Antidumping Duty Changed...  

Federal Register 2010, 2011, 2012, 2013

...bearings, cylindrical roller bearings, and spherical plain bearings and parts...Bearings, Cylindrical Roller Bearings, and Spherical Plain Bearings and Parts...orders on cylindrical roller bearings and spherical plain bearings and...

2010-01-21

370

Study of Catcher Bearings for High Temperature Magnetic Bearing Application  

E-print Network

the mechanical integrity of the components of the test rig. ? Due to extremely small air gap (about 0.030 inches or 30 mils) the magnetic bearings need to be installed with very little tolerance for concentricity. ? Study of the properties of Graphalloy...

Narayanaswamy, Ashwanth

2011-08-08

371

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

372

Subunit interaction of vacuolar H+-pyrophosphatase as determined by high hydrostatic pressure.  

PubMed

Vacuolar H+-pyrophosphatase (H+-PPase) from etiolated hypocotyls of mung bean (Vigna radiata L.) is a homodimer with a molecular mass of 145 kDa. The vacuolar H+-PPase was subjected to high hydrostatic pressure to investigate its structure and function. The inhibition of H+-PPase activity by high hydrostatic pressure has a pressure-, time- and protein-concentration-dependent manner. The Vmax value of vacuolar H+-PPase was dramatically decreased by pressurization from 293.9 to 70.2 micromol of PPi (pyrophosphate) consumed/h per mg of protein, while the Km value decreased from 0.35 to 0.08 mM, implying that the pressure treatment increased the affinity of PPi to vacuolar H+-PPase but decreased its hydrolysis. The physiological substrate and its analogues enhance high pressure inhibition of vacuolar H+-PPase. The HPLC profile reveals high pressure treatment of H+-PPase provokes the subunit dissociation from an active into inactive form. High hydrostatic pressure also induces the conformational change of vacuolar H+-PPase as determined by spectroscopic techniques. Our results indicate the importance of protein-protein interaction for this novel proton-translocating enzyme. Working models are proposed to interpret the pressure inactivation of vacuolar H+-PPase. We also suggest that association of identical subunits of vacuolar H+-PPase is not random but proceeds in a specific manner. PMID:9531476

Yang, S J; Ko, S J; Tsai, Y R; Jiang, S S; Kuo, S Y; Hung, S H; Pan, R L

1998-04-15

373

Optimal dispersion with minimized Poisson equations for non-hydrostatic free surface flows  

NASA Astrophysics Data System (ADS)

A non-hydrostatic shallow-water model is proposed to simulate the wave propagation in situations where the ratio of the wave length to the water depth is small. It exploits the reduced-size stencil in the Poisson pressure solver to make the model less expensive in terms of memory and CPU time. We refer to this new technique as the minimized Poisson equations formulation. In the simplest case when the method applied to a two-layer model, the new model requires the same computational effort as depth-integrated non-hydrostatic models, but can provide a much better description of dispersive waves. To allow an easy implementation of the new method in depth-integrated models, the governing equations are transformed into a depth-integrated system, in which the velocity difference serves as an extra variable. The non-hydrostatic shallow-water model with minimized Poisson equations formulation produces good results in a series of numerical experiments, including a standing wave in a basin, a non-linear wave test, solitary wave propagation in a channel and a wave propagation over a submerged bar.

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

2014-09-01

374

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

375

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. PMID:24884644

2014-01-01

376

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

377

Influence of electric field, hydrostatic pressure and temperature on the electronic states in a Pöschl-Teller quantum well  

Microsoft Academic Search

Influence of the electric field and hydrostatic pressure on the electronic states in a Pöschl-Teller quantum well is studied.\\u000a In the framework of variational method the dependences of the ground state energy on the electric field and hydrostatic pressure\\u000a are calculated for different values of the potential parameters and the temperature. It is shown that the increase in the\\u000a electric

A. Hakimyfard; M. G. Barseghyan; C. A. Duque; A. A. Kirakosyan

2010-01-01

378

Estimating Wear Of Installed Ball Bearings  

NASA Technical Reports Server (NTRS)

Simple inspection and measurement technique makes possible to estimate wear of balls in ball bearing, without removing bearing from shaft on which installed. To perform measurement, one observes bearing cage while turning shaft by hand to obtain integral number of cage rotations and to measure, to nearest 2 degrees, number of shaft rotations producing cage rotations. Ratio between numbers of cages and shaft rotations depends only on internal geometry of bearing and applied load. Changes in turns ratio reflect changes in internal geometry of bearing provided measurements made with similar bearing loads. By assuming all wear occurs on balls, one computes effective value for this wear from change in turns ratio.

Keba, John E.; Mcvey, Scott E.

1993-01-01

379

Active magnetic bearings give systems a lift  

NASA Astrophysics Data System (ADS)

While the active magnetic bearings currently being used in such specialized applications as centrifugal compressors for natural gas pumps are more expensive than conventional bearings, they furnish improved machine service life, controlled damping of high-speed rotors to eliminate critical-speed vibrations, and the obviation of lubrication systems. Attention is presently given to magnetic bearings used by the electric power industry, homopolar magnetic radial and thrust bearings, weapon-system and gas turbine engine applications of magnetic bearings, and the benefits of magnetic bearings for energy-storage flywheels.

O'Connor, Leo

1992-07-01

380

Gradient Tempering Of Bearing Races  

NASA Technical Reports Server (NTRS)

Gradient-tempering process increases fracture toughness and resistance to stress-corrosion cracking of ball-bearing races made of hard, strong steels and subject to high installation stresses and operation in corrosive media. Also used in other applications in which local toughening of high-strength/low-toughness materials required.

Parr, Richardson A.

1991-01-01

381

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

382

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

383

Toxicity of Polar Bear Liver  

Microsoft Academic Search

ACCORDING to information from the Eskimos, and records from Arctic travellers, bad effects may follow the consumption, by men and dogs, of the livers of polar bear, bearded seal, Greenland fox and Eskimo huskies, whereas livers of other Arctic mammals can usually be eaten without injury.

Kaare Rodahl

1949-01-01

384

Satellite monitoring of black bear.  

NASA Technical Reports Server (NTRS)

Description of a feasibility experiment recently performed to test the use of a satellite system for telemetering environmental and physiological data from the winter den of a 'hibernating' black bear, Ursus americanus. The instrumentation procedure and evaluations of the equipment performance and sensory data obtained are discussed in detail.

Craighead, J. J.; Craighead, F. C., Jr.; Varney, J. R.; Cote, C. E.

1971-01-01

385

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

386

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

387

Robust and intelligent bearing estimation  

SciTech Connect

As the monitoring thresholds of global and regional networks are lowered, bearing estimates become more important to the processes which associate (sparse) detections and which locate events. Current methods of estimating bearings from observations by 3-component stations and arrays lack both accuracy and precision. Methods are required which will develop all the precision inherently available in the arrival, determine the measurability of the arrival, provide better estimates of the bias induced by the medium, permit estimates at lower SNRs, and provide physical insight into the effects of the medium on the estimates. Initial efforts have focused on 3-component stations since the precision is poorest there. An intelligent estimation process for 3-component stations has been developed and explored. The method, called SEE for Search, Estimate, and Evaluation, adaptively exploits all the inherent information in the arrival at every step of the process to achieve optimal results. In particular, the approach uses a consistent and robust mathematical framework to define the optimal time-frequency windows on which to make estimates, to make the bearing estimates themselves, and to withdraw metrics helpful in choosing the best estimate(s) or admitting that the bearing is immeasurable. The approach is conceptually superior to current methods, particular those which rely on real values signals. The method has been evaluated to a considerable extent in a seismically active region and has demonstrated remarkable utility by providing not only the best estimates possible but also insight into the physical processes affecting the estimates. It has been shown, for example, that the best frequency at which to make an estimate seldom corresponds to the frequency having the best detection SNR and sometimes the best time interval is not at the onset of the signal. The method is capable of measuring bearing dispersion, thereby withdrawing the bearing bias as a function of frequency. The lowest measurable frequency in the dispersion pattern is often a near error free bearing. These latter features should be helpful in calibrating the stations for frequency dependent biases induced by the earth. Future efforts will enhance the SEE algorithm and will also evaluate it using larger station data sets.

Claassen, J.P.

1998-07-01

388

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

389

High Temperature, Permanent Magnet Biased Magnetic Bearings  

E-print Network

The Electron Energy Corporation (EEC) along with the National Aeronautics and Space Administration (NASA) is researching magnetic bearings. The purpose of this research was to design and develop a high-temperature (1000?F) magnetic bearing system...

Gandhi, Varun R.

2010-07-14

390

Detecting Wear In Ball Bearings During Operation  

NASA Technical Reports Server (NTRS)

Strain-gauge signals at harmonics of ball-bearing-cage frequencies signify wear. Brief report describes experiments in continuing effort to interpret vibrations of machinery in terms of wear in ball bearing.

Hine, Michael J.

1988-01-01

391

Rubber bearings for precision positioning systems  

E-print Network

In this thesis we investigate the use of thin rubber sheets or laminates of metal and rubber sheets as bearings in precision positioning systems. Such bearings have the potential to replace more conventional flexures ...

Barton Martinelli, Augusto E

2005-01-01

392

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

393

Self-bearing motor design & control  

E-print Network

This thesis presents the design, implementation and control of a new class of self-bearing motors. The primary thesis contributions include the design and experimental demonstration of hysteresis self-bearing motors, novel ...

Imani Nejad, Mohammad

2013-01-01

394

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

395

Rolling Element Bearing Stiffness Matrix Determination (Presentation)  

SciTech Connect

Current theoretical bearing models differ in their stiffness estimates because of different model assumptions. In this study, a finite element/contact mechanics model is developed for rolling element bearings with the focus of obtaining accurate bearing stiffness for a wide range of bearing types and parameters. A combined surface integral and finite element method is used to solve for the contact mechanics between the rolling elements and races. This model captures the time-dependent characteristics of the bearing contact due to the orbital motion of the rolling elements. A numerical method is developed to determine the full bearing stiffness matrix corresponding to two radial, one axial, and two angular coordinates; the rotation about the shaft axis is free by design. This proposed stiffness determination method is validated against experiments in the literature and compared to existing analytical models and widely used advanced computational methods. The fully-populated stiffness matrix demonstrates the coupling between bearing radial, axial, and tilting bearing deflections.

Guo, Y.; Parker, R.

2014-01-01

396

Mercury in polar bears from Alaska  

SciTech Connect

Alaskan polar bear (Ursus maritimus) muscle and liver samples collected in 1972 were analyzed for total mercury. Bears north of Alaska had more mercury than bears west of Alaska. The only difference between young and adult animals was in the northern area where adults had more mercury in liver tissue than young animals. Levels were probably not high enough to be a serious threat to bears.

Lentfer, J.W.; Galster, W.A.

1987-04-01

397

Predation of Svalbard reindeer by polar bears  

Microsoft Academic Search

Polar bears (Ursus maritimus) are believed to be obligate predators on marine mammals, and particularly, on two species of seals. This paper reports on\\u000a observations of polar bears preying (n=7) and scavenging (n=6) on Svalbard reindeer (Rangifer tarandus platyrhyncus). Similar to their closest evolutionary ancestor, the brown bear (U. arctos), polar bears are opportunistic and will prey on ungulates. Reindeer

Andrew E. Derocher; Øystein Wiig; Georg Bangjord

2000-01-01

398

Bearing fault diagnosis based on rough set  

Microsoft Academic Search

Bearing defects were categorized as localized and distributed. For on-line bearing fault diagnosis, in this paper, the time-domain kurtosis calculation and the frequency domain wavelet analysis were used to extract the transitory features of non-stationary vibration signal produced by the bearing distributed defects. To distributed defects, bearing fault diagnosis was built on the reducing decision based on rough set. According

Chen Xin; Yuhua Chen; Guofeng Wang; Hu Dong

2010-01-01

399

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

400

49 CFR 229.69 - Side bearings.  

Code of Federal Regulations, 2010 CFR

... Suspension System § 229.69 Side bearings. (a) Friction side bearings with springs designed to carry weight may not...than 25 percent of the springs in any one nest broken. (b) Friction side bearings may not be run in contact unless designed to...

2010-10-01

401

49 CFR 229.69 - Side bearings.  

Code of Federal Regulations, 2012 CFR

... Suspension System § 229.69 Side bearings. (a) Friction side bearings with springs designed to carry weight may not...than 25 percent of the springs in any one nest broken. (b) Friction side bearings may not be run in contact unless designed to...

2012-10-01

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 Wear in Large Thermal Gradients  

NASA Technical Reports Server (NTRS)

Report presents results of study of bearing distress resulting from malfunction of spring-preloading arrangements. Study examined effect of thermal growth on wear depth of bearing. Report considers bearing-failure modes, relationships between growth and wear, maximum stresses as function of load, and effect of thermal growth on spring-load deflections.

Kannel, J. W.

1984-01-01

404

Induction Motors Bearing Failures Detection and Diagnosis  

E-print Network

331 1 Induction Motors Bearing Failures Detection and Diagnosis Using a RBF ANN Park Pattern Based Method I. Y. Ã?nel, I. enol and M. E. H. Benbouzid Abstract--This paper deals with the problem of bearing detection and diagnosis process. Experimental tests with artificial bearing damages results show

Boyer, Edmond

405

Cool Polar Bears: Dabbing on the Texture  

ERIC Educational Resources Information Center

In this article, the author describes how her second-graders created their cool polar bears. The students used the elements of shape and texture to create the bears. They used Monet's technique of dabbing paint so as to give the bear some texture on his fur.

O'Connell, Jean

2011-01-01

406

36 CFR 13.1236 - Bear orientation.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 2012-07-01 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...

2012-07-01

407

36 CFR 13.1236 - Bear orientation.  

...2014-07-01 2014-07-01 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...

2014-07-01

408

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

409

36 CFR 13.1236 - Bear orientation.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 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...

2011-07-01

410

Bear Gulch: An Exceptional Upper Carboniferous Plattenkalk  

E-print Network

9 Bear Gulch: An Exceptional Upper Carboniferous Plattenkalk James W. Hagadorn T he upper mississippian bear gulch beds of central Montana constitute one of the lesser-known conservation Lager- stätten in this deposit. The Bear Gulch Beds are a lensoidal unit of fine-grained limestone, or Plattenkalk, very similar

Hagadorn, Whitey

411

Philanthropy fuels Cal's future Bears without borders  

E-print Network

Philanthropy fuels Cal's future Bears without borders Hope for Japan BerkeleyThePromiseof S p r i n: Philanthropy fuels Cal's future 9 Bears without borders: Berkeley's impact around the world Cal Campus to Cal 29 Making Connections 32 Bear Perspective Around the world at Berkeley #12;Around Cal Milestone

Kammen, Daniel M.

412

36 CFR 13.1236 - Bear orientation.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 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...

2013-07-01

413

THE UNIVERSITY OF EDINBURGH. Hudson Beare Building.  

E-print Network

THE UNIVERSITY OF EDINBURGH. Hudson Beare Building. (King's Buildings). A GUIDE TO ACCESS AND FACILITIES. Address: Hudson Beare Building, King's Buildings, Edinburgh, E,H,9 3,J,F. Telephone number: 0131 650 5687. Campus map link: http://www.ed.ac.uk/maps/buildings/hudson-beare-building #12;Page 1

Edinburgh, University of

414

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

415

White-etching matter in bearing steel Part 2: Distinguishing cause and eect in bearing steel  

E-print Network

White-etching matter in bearing steel Part 2: Distinguishing cause and eect in bearing steel of Cambridge, U.K Abstract The premature failure of large bearings of the type used in wind turbines, possibly as reported observations on real bearings. Evidence suggests that the formation mechanism of the white

Cambridge, University of

416

Bear Necessities: Myrmecophagy by grizzly bears in north-central British Columbia.  

E-print Network

Bear Necessities: Myrmecophagy by grizzly bears in north-central British Columbia. B. Staffan George, BC, Canada 2University of Alberta, Edmonton, AB, Canada Introduction ·The grizzly bear (Ursus Grizzly Bear Habitat Inventory Project (http://web.unbc.ca/parsnip-grizzly/), an ambitious multi

Lindgren, Staffan

417

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

418

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

419

RUBBER BEARINGS FOR DOWNHOLE PUMPS  

Microsoft Academic Search

Synopsis of project activity: 1998--Awarded cost share grant from DOE. 1st Qtr 1999--Developed fail safe lubricating system. 2nd Qtr 1999--Performed first large scale test with nitrile based bearings. It failed due to material swelling. Failure was blamed on improper tolerance. 3rd Qtr 1999--Material tests were performed with autoclaves and exposure tests to Casa Diablo fluids. Testing of Viton materials began.

Bob Sullivan Mammoth Pacific

2005-01-01

420

Thermal influence of the Couette flow in a hydrostatic spindle on the machining precision  

NASA Astrophysics Data System (ADS)

Hydrostatic spindles are increasingly used in precision machine tools. Thermal error is the key factor affecting the machining accuracy of the spindle, and research has focused on spindle thermal errors through examination of the influence of the temperature distribution, thermal deformation and spindle mode. However, seldom has any research investigated the thermal effects of the associated Couette flow. To study the heat transfer mechanism in spindle systems, the criterion of the heat transfer direction according to the temperature distribution of the Couette flow at different temperatures is deduced. The method is able to deal accurately with the significant phenomena occurring at every place where thermal energy flowed in such a spindle system. The variation of the motion error induced by thermal effects on a machine work-table during machining is predicated by establishing the thermo-mechanical error model of the hydrostatic spindle for a high precision machine tool. The flow state and thermal behavior of a hydrostatic spindle is analyzed with the evaluated heat power and the coefficients of the convective heat transfer over outer surface of the spindle are calculated, and the thermal influence on the oil film stiffness is evaluated. Thermal drift of the spindle nose is measured with an inductance micrometer, the thermal deformation data 1.35 ?m after running for 4 h is consistent with the value predicted by the finite element analysis's simulated result 1.28 ?m, and this demonstrates that the simulation method is feasible. The thermal effects on the processing accuracy from the flow characteristics of the fluid inside the spindle are analyzed for the first time.

Chen, Dongju; Fan, Jinwei; Li, Haiyong; Wang, Xiaofeng; Zhang, Feihu

2013-05-01

421

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.

422

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.

2007-12-12

423

Analytical and experimental investigations of hybrid air foil bearings  

E-print Network

Air foil bearings offer several advantages over oil-lubricated bearings in high speed micro-turbomachinery. With no contact between the rotor and bearings, the air foil bearings have higher service life and consequently lesser standstills between...

Kumar, Manish

2009-05-15

424

Antiferromagnetic critical pressure in URu2Si2 under hydrostatic conditions  

NASA Astrophysics Data System (ADS)

The onset of antiferromagnetic order in URu2Si2 has been studied via neutron diffraction in a helium pressure medium, which most closely approximates hydrostatic conditions. The antiferromagnetic critical pressure is 0.80 GPa, considerably higher than values previously reported. Complementary electrical resistivity measurements imply that the hidden-order-antiferromagnetic bicritical point falls between 1.3 and 1.5 GPa. Moreover, the redefined pressure-temperature phase diagram suggests that the superconducting and antiferromagnetic phase boundaries actually meet at a common critical pressure at zero temperature.

Butch, Nicholas P.; Jeffries, Jason R.; Chi, Songxue; Leão, Juscelino Batista; Lynn, Jeffrey W.; Maple, M. Brian

2010-08-01

425

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

426

Development of a Smart Bicycle Based on a Hydrostatic Automatic Transmission  

NASA Astrophysics Data System (ADS)

This paper develops a newly bicycle concept named smart bicycle (SBIC) with automatic transmission and energy recuperating ability. The SBIC operation is based on a hydrostatic transmission (HST). Several HST designs have been proposed. Moreover, a use of energy converting and storing devices is an optional design for the SBIC to recovery energy during the deceleration or going downhill process, and to support this energy to the hydraulic system during the acceleration or going uphill process. The working efficiency of the bicycle is then increased and could become competitive with the roller-chain technology. Simulations have been carried out to evaluate the working performances of the proposed SBIC concepts.

Truong, Dinh Quang; Ahn, Kyoung Kwan; Khoa, Le Duy; Thinh, Do Hoang

427

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

428

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

429

Moist processes and the quasi-hydrostatic approximation in a mesoscale numerical model  

E-print Network

for the diagnosed variables, pressure (at the model top) and the vertical velocity on the lateral boundaries. g. Inclusion of moisture One of the most important effects of moisture on the dynamics of the atmosphere is through the release of latent hear... is diagnosed from below using a combination of the hydrostatic equation (4) and the equation of state (7). The pressure must be diagnosed so that changes in the mean virtual temperature of the layers of the model can be taken into account. The process...

Kennedy, Charles Joseph

2012-06-07

430

Ice age True Polar Wander in a compressible and non-hydrostatic Earth  

NASA Astrophysics Data System (ADS)

Issues related to long timescale instability in the Earth's rotation, named True Polar Wander (TPW), have continuously been debated, after the pioneering works of the sixties. We show ice age TPW results from a newly developed compressible model, based on the numerical integration in the radial variable of the momentum and Poisson equations and on the contour integration in the Laplace domain which allows us to deal with the non-modal contribution from continuous radial rheological variations. We thus fully exploit the long term behaviour of the Earth's rotation and we quantify the effects of the compressible rheology, compared to the widely used incompressible one. We discuss the so-called `traditional approach' to the Earth's rotation developed during the eighties and nineties, both for ice age and mantle convection TPW and we explain within this approach the sensitivity of TWP predictions to the elastic and viscoelastic rheologies of the lithosphere. We agree on the necessity to include the effects of the non-hydrostatic bulge from mantle convection to obtain realistic ice age TPW rates in the lower mantle viscosity range [1021,1022] Pa s, as first indicated by Mitrovica et al. Their analysis represents a first attempt to couple the effects on TPW from mantle convection and glacial forcing, by including the non-hydrostatic bulge due to mantle convection but not the other time-dependent driving terms. This partial coupling freezes in space the non-hydrostatic contribution due to mantle convection, thus damping the present-day ice age TPW and forcing the axis of instantaneous rotation to come back to its initial position when ice ages started as discussed in Mitrovica et al. We also describe a peculiar behavior of the new ice age TPW predictions exhibiting a dampened pendulum motion, with the axis of instantaneous rotation overcrossing the position it had before ice ages started. We argue that a viscoelastic rather than elastic lithosphere should be adopted in the modelling of TPW although, on the time of ice ages, it is difficult to disentangle the effects of lithospheric rheology and of mantle convection. We discuss the implication of self-consistent convection calculations of the non-hydrostatic contribution and its impact on the long term Earth's rotation stability during ice ages. The ice age TPW cannot account for more than 70 per cent of the observed one, at least for lower mantle viscosities lower than 1022 Pa s: mantle convection must therefore contribute to the observed TPW.

Cambiotti, Gabriele; Ricard, Yanick; Sabadini, Roberto

2010-12-01

431

Wormgear geometry adopted for implementing hydrostatic lubrication and formulation of the lubrication problem  

NASA Technical Reports Server (NTRS)

The geometrical parameters for a wormgear intended to be used as the transmission in advanced helicopters are finalized. The resulting contact pattern of the meshing tooth surfaces is suitable for the implementation of hydrostatic lubrication Fluid film lubrication of the contact is formulated considering external pressurization as well as hydrodynamic wedge and squeeze actions. The lubrication analysis is aimed at obtaining the oil supply pressure needed to separate the worm and gear surfaces by a prescribed minimum film thickness. The procedure of solving the mathematical problem is outlined.

Sun, D. C.; Yuan, Qin

1995-01-01

432

hydrostatic pressurisation  

E-print Network

, in superfluid turbulence the kinetic energy should cascade do. Introduction: motivations.. ­ If cooled below a critical temperature (T 2.18 K in 4 He and Tc 10-3 K in at 3 such as water or air is that, in helium, vorticity is constrained to vortex line singularities of fixed circula

Paris-Sud XI, Université de

433

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

SciTech Connect

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.; Wartak, M. S. [Institute of Physics, Wroclaw University of Technology, 50-370 Wroclaw, Wybrzeze Wyspianskiego 27 (Poland); Department of Physics and Computer Science, Wilfrid Laurier University, Waterloo, Ontario N2L 3C5 (Canada); Kudrawiec, R. [Institute of Physics, Wroclaw University of Technology, 50-370 Wroclaw, Wybrzeze Wyspianskiego 27 (Poland)

2014-01-21

434

Genomic evidence of geographically widespread effect of gene flow from polar bears into brown bears.  

PubMed

Polar bears are an arctic, marine adapted species that is closely related to brown bears. Genome analyses have shown that polar bears are distinct and genetically homogeneous in comparison to brown bears. However, these analyses have also revealed a remarkable episode of polar bear gene flow into the population of brown bears that colonized the Admiralty, Baranof, and Chichagof Islands (ABC Islands) of Alaska. Here, we present an analysis of data from a large panel of polar bear and brown bear genomes that includes brown bears from the ABC Islands, the Alaskan mainland and Europe. Our results provide clear evidence that gene flow between the two species had a geographically wide impact, with polar bear DNA found within the genomes of brown bears living both on the ABC Islands and in the Alaskan mainland. Intriguingly, while brown bear genomes contain up to 8.8% polar bear ancestry, polar bear genomes appear to be devoid of brown bear ancestry, suggesting the presence of a barrier to gene flow in that direction. This article is protected by copyright. All rights reserved. PMID:25490862

Cahill, James A; Stirling, Ian; Kistler, Logan; Salamzade, Rauf; Ersmark, Erik; Fulton, Tara L; Stiller, Mathias; Green, Richard E; Shapiro, Beth

2014-12-01

435

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

436

Determination of ball bearing dynamic stiffness  

NASA Technical Reports Server (NTRS)

The dynamic radial stiffness characteristics of rolling element bearings are currently determined by analytical methods that have not been experimentally verified. These bearing data are vital to rotating machinery design integrity because accurate critical speeds and rotor stability predictions are highly dependent on the bearing stiffness. A tester was designed capable of controlling the bearing axial preload, speed, and rotor unbalance. The rotor and support structures were constructed to permit critical speeds that are predominantly determined by a 57 mm test bearing. A curve of calculated critical speed versus stiffness was used to determine the actual bearing stiffness from the empirical data. The results of extensive testing are used to verify analytical predictions, increase confidence in existing bearing computer programs, and to serve as a data base for efforts to correct these programs.

Beatty, R. F.; Rowan, B. F.

1982-01-01

437

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

438

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

439

Modeling of rolling element bearing mechanics. Computer program user's manual  

Microsoft Academic Search

This report provides the user's manual for the Rolling Element Bearing Analysis System (REBANS) analysis code which determines the quasistatic response to external loads or displacement of three types of high-speed rolling element bearings: angular contact ball bearings, duplex angular contact ball bearings, and cylindrical roller bearings. The model includes the defects of bearing ring and support structure flexibility. It

Lyn M. Greenhill; David H. Merchant

1994-01-01

440

Modeling of rolling element bearing mechanics. Theoretical manual  

Microsoft Academic Search

This report documents the theoretical basis for the Rolling Element Bearing Analysis System (REBANS) analysis code which determines the quasistatic response to external loads or displacement of three types of high-speed rolling element bearings: angular contact ball bearings; duplex angular contact ball bearings; and cylindrical roller bearings. The model includes the effects of bearing ring and support structure flexibility. It

David H. Merchant; Lyn M. Greenhill

1994-01-01

441

Efficient well-balanced hydrostatic upwind schemes for shallow-water equations  

NASA Astrophysics Data System (ADS)

The proposed work concerns the numerical approximations of the shallow-water equations with varying topography. The main objective is to introduce an easy and systematic technique to enforce the well-balance property and to make the scheme able to deal with dry areas. To access such an issue, the derived numerical method is obtained by involving the free surface instead of the water height and this produces the scheme well-balanced independently from the numerical flux function associated with the homogeneous problem. As a consequence, we obtain an easy well-balanced scheme which preserves non-negative water height. When compared with the well-known hydrostatic reconstruction, the presented topography discretization does not involve any max function known to introduce some numerical errors as soon as the topography admits very strong variations or discontinuities. A second-order MUSCL accurate reconstruction is adopted. The proposed hydrostatic upwind scheme is next extended for considering 2D simulations performed over unstructured meshes. Several 1D and 2D numerical experiments are performed to exhibit the relevance of the scheme.

Berthon, Christophe; Foucher, Françoise

2012-06-01

442

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

443

Cryogenic strength and microstructure of a hydrostatically extruded austenitic steel 1.4429 (AISI 316LN)  

NASA Astrophysics Data System (ADS)

The as-received material with the average equivalent grain diameter of 45 ?m was subjected to a hydrostatic extrusion process to a total true strain of 0.25, 0.84 and 1.36. Static tensile tests of the extruded material, performed at the room temperature, in liquid nitrogen and liquid helium. The material extruded to the strain of 1.36 and tested in liquid helium revealed ultimate strength 2.6 GPa. The results obtained for strengthened material were compared with the properties of as-received state. The effect of extrusion on the structure of this material was examined by transmission and scanning electron microscopy. The presence of necking and the nature of fracture surfaces in the specimens subjected to tensile tests confirm ductile behaviour of the extruded material even at liquid helium temperature, despite limited ductility. The results show that the hydrostatically extruded austenitic stainless steel is a promising material for relatively small, heavy loaded components working at cryogenic conditions.

Czarkowski, P.; Krawczy?ska, A. T.; Brynk, T.; Nowacki, M.; Lewandowska, M.; Kurzyd?owski, K. J.

2014-11-01

444

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

NASA Astrophysics Data System (ADS)

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.

Graziano, Giuseppe

2014-03-01

445

An operator-splitting time integration scheme for Discontinuous Galerkin non-hydrostatic model  

NASA Astrophysics Data System (ADS)

The non-hydrostatic (NH) atmospheric model is very important for mesoscale dynamics and cloud-resolving climate modeling. A Discontinuous Galerkin (DG) non-hydrostatic model based on compressible Navier-Stokes system has been developed. The DG-NH model employs moderate order of polynomials for spacial discretization, and the time-stepping is based on an explicit Runge-Kutta scheme. However, the vertical fast-moving acoustic wave and gravity wave together with high aspect ratio between horizontal and vertical spacial discretization impose a stringent restriction on explicit time-step size for the resulting ODE system. While an explicit time solver is acceptable for the slow evolving horizontal waves, a semi-implicit or full-implicit time integration scheme is desirable for the vertical portion of the dynamics. An operator-splitting time integration scheme has been developed for the DG model, which treats the vertical time discretization implicitly while handling horizontal part explicitly. The efficiency and performance of the proposed time-stepping scheme will be presented using several benchmark tests.

Bao, L.; Nair, R.; Kloefkorn, R.

2013-12-01

446

Physicochemical properties of natural actomyosin from threadfin bream (Nemipterus spp.) induced by high hydrostatic pressure.  

PubMed

Changes of physicochemical properties in natural actomyosin (NAM) from threadfin bream (Nemipterus spp.) induced by high hydrostatic pressure (200, 400, 600MPa for 10, 30, 50min) were studied. The increase in turbidity of NAM was coincidental with the decrease in protein solubility with increasing pressure and time, suggesting the formation of protein aggregates. SDS-PAGE showed that polymerisation and degradation of myosin heavy chain were induced by high pressure. Ca(2+)-ATPase activity of NAM treated by high pressure was lost, suggesting the denaturation of myosin and the dissociation of actomyosin complex. Surface hydrophobicity of NAM increased when the pressure and pressurization time increased, indicating that the exposed hydrophobic residues increased upon application of high pressure. Decrease in total sulfhydryl content and increase in surface-reactive sulfhydryl content of NAM samples were observed with the extension of pressurizing time, indicating the formation of disulphide bonds through oxidation of SH groups or disulphide interchanges. The above changes of physicochemical properties suggested conformational changes of NAM from muscle of threadfin bream induced by high hydrostatic pressure. PMID:24629987

Zhou, Aimei; Lin, Liying; Liang, Yan; Benjakul, Soottawat; Shi, Xiaoling; Liu, Xin

2014-08-01

447

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

448

Hydrogenic impurity states in a parabolic quantum dot: Hydrostatic pressure and electric field effects  

NASA Astrophysics Data System (ADS)

The binding energy of hydrogenic impurity associated with the ground state and some low-lying states in a GaAs spherical parabolic quantum dot with taking into account hydrostatic pressure and electric field are theoretically studied by using the configuration-integration method. The binding energies of these low-lying states of the impurity depend sensitively on the hydrostatic pressure, electric field and the strength of the parabolic confinement. Based on the analysis of these impurity states, we propose a way for preparation of quantum bit (qubit) by using the strong quantum confinement to the impurity in the quantum dot. Also we calculate the wave functions of some low-lying states to discuss the oscillator strength which is related to the electronic dipole-allowed transitions from 0s state to 0p state. The results show that the electronic dipole-allowed transitions mostly happen between the 0s state and 0p state, especially for the quantum confinement large enough.

Yuan, Jian-Hui; Zhang, Yan; Li, Meng; Wu, Zhi-Hui; Mo, Hua

2014-10-01

449

Prediction of acid lactic-bacteria growth in turkey ham processed by high hydrostatic pressure  

PubMed Central

High hydrostatic pressure (HHP) has been investigated and industrially applied to extend shelf life of meat-based products. Traditional ham packaged under microaerophilic conditions may sometimes present high lactic acid bacteria population during refrigerated storage, which limits shelf life due to development of unpleasant odor and greenish and sticky appearance. This study aimed at evaluating the shelf life of turkey ham pressurized at 400 MPa for 15 min and stored at 4, 8 and 12 °C, in comparison to the non pressurized product. The lactic acid bacteria population up to 107 CFU/g of product was set as the criteria to determine the limiting shelf life According to such parameter the pressurized sample achieved a commercial viability within 75 days when stored at 4 °C while the control lasted only 45 days. Predictive microbiology using Gompertz and Baranyi and Roberts models fitted well both for the pressurized and control samples. The results indicated that the high hydrostatic pressure treatment greatly increased the turkey ham commercial viability in comparison to the usual length, by slowing down the growth of microorganisms in the product. PMID:24159279

Mathias, S.P.; Rosenthal, A.; Gaspar, A.; Aragão, G.M.F.; Slongo-Marcusi, A.

2013-01-01

450

Damage in Escherichia coli Cells Treated with a Combination of High Hydrostatic Pressure and Subzero Temperature?  

PubMed Central

The relationship between membrane permeability, changes in ultrastructure, and inactivation in Escherichia coli strain K-12TG1 cells subjected to high hydrostatic pressure treatment at room and subzero temperatures was studied. Propidium iodide staining performed before and after pressure treatment made it possible to distinguish between reversible and irreversible pressure-mediated cell membrane permeabilization. Changes in cell ultrastructure were studied using transmission electron microscopy (TEM), which showed noticeable condensation of nucleoids and aggregation of cytosolic proteins in cells fixed after decompression. A novel technique used to mix fixation reagents with the cell suspension in situ under high hydrostatic pressure (HHP) and subzero-temperature conditions made it possible to show the partial reversibility of pressure-induced nucleoid condensation. However, based on visual examination of TEM micrographs, protein aggregation did not seem to be reversible. Reversible cell membrane permeabilization was noticeable, particularly for HHP treatments at subzero temperature. A correlation between membrane permeabilization and cell inactivation was established, suggesting different mechanisms at room and subzero temperatures. We propose that the inactivation of E. coli cells under combined HHP and subzero temperature occurs mainly during their transiently permeabilized state, whereas HHP inactivation at room temperature is related to a balance of transient and permanent permeabilization. The correlation between TEM results and cell inactivation was not absolute. Further work is required to elucidate the effects of pressure-induced damage on nucleoids and proteins during cell inactivation. PMID:17766454

Moussa, Marwen; Perrier-Cornet, Jean-Marie; Gervais, Patrick

2007-01-01

451

Lens intracellular hydrostatic pressure is generated by the circulation of sodium and modulated by gap junction coupling  

PubMed Central

We recently modeled fluid flow through gap junction channels coupling the pigmented and nonpigmented layers of the ciliary body. The model suggested the channels could transport the secretion of aqueous humor, but flow would be driven by hydrostatic pressure rather than osmosis. The pressure required to drive fluid through a single layer of gap junctions might be just a few mmHg and difficult to measure. In the lens, however, there is a circulation of Na+ that may be coupled to intracellular fluid flow. Based on this hypothesis, the fluid would cross hundreds of layers of gap junctions, and this might require a large hydrostatic gradient. Therefore, we measured hydrostatic pressure as a function of distance from the center of the lens using an intracellular microelectrode-based pressure-sensing system. In wild-type mouse lenses, intracellular pressure varied from ?330 mmHg at the center to zero at the surface. We have several knockout/knock-in mouse models with differing levels of expression of gap junction channels coupling lens fiber cells. Intracellular hydrostatic pressure in lenses from these mouse models varied inversely with the number of channels. When the lens’ circulation of Na+ was either blocked or reduced, intracellular hydrostatic pressure in central fiber cells was either eliminated or reduced proportionally. These data are consistent with our hypotheses: fluid circulates through the lens; the intracellular leg of fluid circulation is through gap junction channels and is driven by hydrostatic pressure; and the fluid flow is generated by membrane transport of sodium. PMID:21624945

Gao, Junyuan; Sun, Xiurong; Moore, Leon C.; White, Thomas W.; Brink, Peter R.

2011-01-01

452

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

453

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

2010-02-10

454

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.

455

Hydrostaticity and hidden order: effects of experimental conditions on the temperature-pressure phase diagram of URu2Si2  

NASA Astrophysics Data System (ADS)

The pressure-dependence of the hidden order phase transition of URu2Si2 is shown to depend sensitively upon the quality of hydrostatic pressure conditions during electrical resistivity measurements. Hysteresis in pressure is demonstrated for two choices of pressure medium: the commonly-used mixture of 1:1 Fluorinert FC70/FC77 and pure FC75. In contrast, no hysteresis is observed when the pressure medium is a 1:1 mixture of n-pentane/isoamyl alcohol, as it remains hydrostatic over the entire studied pressure range. Possible ramifications for the interpretation of the temperature-pressure phase diagram of URu2Si2 are discussed.

Butch, N. P.; Jeffries, J. R.; Zocco, D. A.; Maple, M. B.

2009-06-01

456

Simultaneous measurement of temperature, hydrostatic pressure and acoustic signal using a single distributed Bragg reflector fiber laser  

NASA Astrophysics Data System (ADS)

A fiber-optic sensor based on a dual polarization fiber grating laser for simultaneous measurement of temperature, hydrostatic pressure and acoustic signal is proposed and experimentally demonstrated. The acoustic wave induces a frequency modulation (FM) of the carrier in radio frequency (RF) range generated by the fiber laser and can be easily extracted by using the FM demodulation technique. The temperature can be determined by the laser wavelength. The hydrostatic pressure can be determined by monitoring the static shift of the carrier frequency and deducting the effect of the temperature.

Tan, Yan-Nan; Zhang, Yang; Guan, Bai-Ou

2011-05-01

457

Anesthetic antagonism of the effects of high hydrostatic pressure on locomotory activity of the brine shrimp Artemia.  

PubMed

The locomotory activity of small groups of brine shrimp (Artemia salina) was studied under conditions of high hydrostatic pressure, varying temperatures and exposure to several gaseous anesthetics. Both compression and exposure to anesthesia reduced the animal's swimming activity, while temperature increased or decreased activity as it was raised or lowered from ambient. The effect of the anesthetics was less during periods of simultaneous exposure to high hydrostatic pressure. It is concluded that pressure antagonism of anesthesia is demonstrable in invertebrate organisms and may represent a fundamental interaction of these parameters in biological systems. PMID:6135537

Simon, S A; Parmentier, J L; Bennett, P B

1983-01-01

458

Simultaneous effects of hydrostatic pressure and temperature and effect of spin-orbit interaction on the third harmonic generation  

NASA Astrophysics Data System (ADS)

We have studied the simultaneous effects of hydrostatic pressure and temperature and effect of spin-orbit interaction on the third harmonic generation in a Winternitz-Smorodinsky potential quantum ring. The role of magnetic field strength on spin-orbit splitting energies and the third harmonic generation has also been investigated. The results indicate that an increment in hydrostatic pressure or temperature brings about opposite influence on the resonant peak values, and gives the red and blue shift of the peak positions of the third harmonic generation, respectively. In addition, a red shift of the third harmonic generation is observed due to the spin-orbit interaction.

Jin, Mingge; Xie, Wenfang

2014-09-01

459

Unstable polar mode and minimum of the dielectric constant in cubic BaSnO3 under hydrostatic pressure  

NASA Astrophysics Data System (ADS)

From first-principles density-functional theory calculations, we show that above a given hydrostatic pressure, an unstable TO mode appears in the cubic perovskite barium stannate (BaSnO3) at ? . Below this critical pressure, we predict an interesting lowering of the dielectric response of this compound due to a change in the sign of this TO mode effective charge. The results are compared to recent calculations on perovskites under high pressure (titanates, zirconates, and niobates), which exhibit a different mechanism at the origin of the soft mode, and to magnesium silicate (MgSiO3) that does not undergo any ferroelectric transition under hydrostatic pressure.

Bévillon, Émile; Geneste, Grégory

2007-06-01

460

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 magnetic bearings would also serve as the excitation source.

Scharrer, Joseph K. (editor); Murphy, Brian T.; Hawkins, Lawrence A.

1993-01-01

461

Cryogenic fluid film bearing tester development study  

NASA Astrophysics Data System (ADS)

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 magnetic bearings would also serve as the excitation source.

Scharrer, Joseph K.; Murphy, Brian T.; Hawkins, Lawrence A.

1993-06-01

462

Two High-Temperature Foil Journal Bearings  

NASA Technical Reports Server (NTRS)

An enlarged, high-temperature-compliant foil bearing has been built and tested to demonstrate the feasibility of such bearings for use in aircraft gas turbine engines. Foil bearings are attractive for use in some machines in which (1) speeds of rotation, temperatures, or both exceed maximum allowable values for rolling-element bearings; (2) conventional lubricants decompose at high operating temperatures; and/or (3) it is necessary or desirable not to rely on conventional lubrication systems. In a foil bearing, the lubricant is the working fluid (e.g., air or a mixture of combustion gases) in the space between the journal and the shaft in the machine in which the bearing is installed.

Zak, Michail

2006-01-01

463

Rocketdyne LOX bearing tester program  

NASA Technical Reports Server (NTRS)

The cause, or causes, for the Space Shuttle Main Engine ball wear were unknown, however, several mechanisms were suspected. Two testers were designed and built for operation in liquid oxygen to empirically gain insight into the problems and iterate solutions in a timely and cost efficient manner independent of engine testing. Schedules and test plans were developed that defined a test matrix consisting of parametric variations of loading, cooling or vapor margin, cage lubrication, material, and geometry studies. Initial test results indicated that the low pressure pump thrust bearing surface distress is a function of high axial load. Initial high pressure turbopump bearing tests produced the wear phenomenon observed in the turbopump and identified an inadequate vapor margin problem and a coolant flowrate sensitivity issue. These tests provided calibration data of analytical model predictions to give high confidence in the positive impact of future turbopump design modification for flight. Various modifications will be evaluated in these testers, since similar turbopump conditions can be produced and the benefit of the modification will be quantified in measured wear life comparisons.

Keba, J. E.; Beatty, R. F.

1988-01-01

464

Effects of hydrostatic pressure and temperature on interband optical transitions in InAs\\/GaAs vertically coupled double quantum dots  

Microsoft Academic Search

We consider the effect of hydrostatic pressure, temperature and the variations of structure's sizes on interband transition energy and absorption coefficient in InAs\\/GaAs vertically coupled double quantum dots. The threshold energy of interband optical transitions is examined as a function of hydrostatic pressure and temperature for the different geometries of the structure. We also investigated the dependencies of the interband

H M Baghramyan; M G Barseghyan; A A Kirakosyan

2012-01-01

465

Simultaneous effects of hydrostatic pressure and temperature on donor binding energy and photoionization cross section in Pöschl–Teller quantum well  

Microsoft Academic Search

We consider the effects of hydrostatic pressure and temperature on the binding energy and photoionization cross section of hydrogen-like impurity in Pöschl–Teller quantum well. The ground state energy and the impurity wave function are calculated using the variational method. The binding energy dependencies on the width of the quantum well, the hydrostatic pressure, the impurity position and the temperature are

M. G. Barseghyan; Alireza Hakimyfard; S. Y. López; C. A. Duque; A. A. Kirakosyan

2010-01-01

466

Simultaneous effects of hydrostatic pressure and temperature on donor binding energy and photoionization cross section in Pöschl-Teller quantum well  

Microsoft Academic Search

We consider the effects of hydrostatic pressure and temperature on the binding energy and photoionization cross section of hydrogen-like impurity in Pöschl-Teller quantum well. The ground state energy and the impurity wave function are calculated using the variational method. The binding energy dependencies on the width of the quantum well, the hydrostatic pressure, the impurity position and the temperature are

M. G. Barseghyan; Alireza Hakimyfard; S. Y. López; C. A. Duque; A. A. Kirakosyan

2010-01-01

467

First-Order Ball-Bearing Kinematics  

Microsoft Academic Search

Two first-order equations are given connecting geometry and internal motions in an angular-contact ball bearing. Total speed, kinematic equivalence, basic speed ratio, and modal speed ratio are defined and discussed; charts are given for the speed ratios covering all bearings and all rotational modes. Instances where specific first-order assumptions might fail are discussed, and the resulting effects on bearing performance

Edward Kingsbury

1985-01-01

468

Ceramic Materials in Hybrid Ball Bearings  

Microsoft Academic Search

A computational study was conducted to make comparisons regarding heat generation, frictional torque, and ball wear between conventional all steel bearings using M50 steel balls and hybrid bearings using silicon nitride (Si3N4) ceramic balls. Both were modeled using M50 steel races and the study was accomplished for radially loaded bearings only. Although most realistic applications also include axial loads on

Pete Cento; Don W. Dareing

1999-01-01

469

First-order ball-bearing kinematics  

NASA Technical Reports Server (NTRS)

Two first-order equations are given connecting geometry and internal motions in an angular-contact ball bearing. Total speed, kinematic equivalence, basic speed ratio, and modal speed ratio are defined and discussed; charts are given for the speed ratios covering all bearings and all rotational modes. Instances where specific first-order assumptions might fail are discussed, and the resulting effects on bearing performance reviewed.

Kingsbury, E.

1985-01-01

470

Permanent Magnetic Bearing for Spacecraft Applications  

NASA Technical Reports Server (NTRS)

A permanent, totally passive magnetic bearing rig was designed, constructed, and tested. The suspension of the 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 using an air impeller. 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.

Morales, Winfredo; Fusaro, Robert; Kascak, Albert

2008-01-01

471

Bearing optimization for SSME HPOTP application  

NASA Technical Reports Server (NTRS)

The space shuttle main engine (SSME) high-pressure oxygen turbopumps (HPOTP) have not experienced the service life required of them. To improve the life of the existing turbopump bearings, modifications to the bearings that could be retrofitted into the present bearing cavity are being investigated. Several bearing parameters were optimized using the computer program SHABERTH, which performs a thermomechanical simulation of a load support system. The computer analysis showed that improved bearing performance is feasible if low friction coefficients can be attained. Bearing geometries were optimized considering heat generation, equilibrium temperatures, and relative life. Two sets of curvatures were selected from the optimization: an inner-raceway curvature of 0.54, an outer-raceway curvature of 0.52, and an inner-raceway curvature of 0.55, an outer-raceway curvature of 0.53. A contact angle of 16 deg was also selected. Thermal gradients through the bearings were found to be lower with liquid lubrication than with solid film lubrication. As the coolant flowrate through the bearing increased, the ball temperature decreased but at a continuously decreasing rate. The optimum flowrate was approximately 4 kg/s. The analytical modeling used to determine these feasible modifications to improve bearing performance is described.

Armstrong, Elizabeth S.; Coe, Harold H.

1988-01-01

472

Polar Bears International: Vital Maternity Den Study  

NSDL National Science Digital Library

This report describes a journalist's participation in a study of polar bear denning sites in the Alaska National Wildlife Refuge (ANWR). It is thought that cubs born in those dens play an important role in maintaining the Beaufort Sea population of polar bears. Prior to the study, no complete map existed pinpointing the ANWR's denning areas. The study data will be available to manage human activities, thus protecting the sensitive areas in which a mother polar bear may den. The study will also provide baseline data to assess how climate change may alter the distribution of polar-bear denning habitat.

473

Fractional Whirl Motion in Wave Journal Bearings  

NASA Technical Reports Server (NTRS)

Unloaded gas, plain journal bearings experience sub-synchronous whirl motion due to fluid film instabilities and wall contact usually occurs immediately after the onset of the whirl motion. An alternative is the wave journal bearing which significantly improves bearing stability. The predicted threshold where the sub-synchronous whirl motion starts was well confirmed by the experimental observation. In addition, both a two-wave and a three-wave journal bearing can operate free of sub-synchronous whirl motion over a large range in speeds. When the sub-synchronous whirl motion occurs, both the two-wave and three-wave bearing can run in a whirl orbit well within the bearing clearance. At large clearances and wave amplitudes a two-wave bearing, unliKe other bearings, can exhibit a sub-synchronous whirl movement at both low and high speeds, but can run extremely stable and without whirl at intermediate speeds. Moreover, in these cases, the whirl frequencies are close to a quarter of the synchronous speed. The three-wave bearing can exhibit sub-synchronous whirl motion only after a specific threshold when the speed increases and the whirl frequencies are close to half of the synchronous speed.

Dimofte, Florin; Hendricks, Robert C.

1996-01-01

474

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

475

Dynamic modelling and response characteristics of a magnetic bearing rotor system including auxiliary bearings  

NASA Technical Reports Server (NTRS)

Auxiliary bearings are a critical feature of any magnetic bearing system. They protect the soft iron core of the magnetic bearing during an overload or failure. An auxiliary bearing typically consists of a rolling element bearing or bushing with a clearance gap between the rotor and the inner race of the support. The dynamics of such systems can be quite complex. It is desired to develop a rotor-dynamic model and assess the dynamic behavior of a magnetic bearing rotor system which includes the effects of auxiliary bearings. Of particular interest is the effects of introducing sideloading into such a system during failure of the magnetic bearing. A model is developed from an experimental test facility and a number of simulation studies are performed. These results are presented and discussed.

Free, April M.; Flowers, George T.; Trent, Victor S.

1993-01-01

476

Dynamic modelling and response characteristics of a magnetic bearing rotor system with auxiliary bearings  

NASA Technical Reports Server (NTRS)

Auxiliary bearings are a critical feature of any magnetic bearing system. They protect the soft iron core of the magnetic bearing during an overload or failure. An auxiliary bearing typically consists of a rolling element bearing or bushing with a clearance gap between the rotor and the inner race of the support. The dynamics of such systems can be quite complex. It is desired to develop a rotordynamic model which describes the dynamic behavior of a flexible rotor system with magnetic bearings including auxiliary bearings. The model is based upon an experimental test facility. Some simulation studies are presented to illustrate the behavior of the model. In particular, the effects of introducing sideloading from the magnetic bearing when one coil fails is studied.

Free, April M.; Flowers, George T.; Trent, Victor S.

1995-01-01

477

Evaluation of bearing configurations using the single bearing tester in liquid nitrogen  

NASA Technical Reports Server (NTRS)

Various bearing configurations were tested using the Marshall Space Flight Center single bearing tester with LN2 as the cryogenic coolant. The baseline was one Rocketdyne phase one high pressure oxidizer turbopump (HPOTP) pump end 45-mm bore bearing. The bearing configurations that were tested included a Salox/M cage configuration, a silicon nitride ball configuration, an elongated cage configuration, and a Bray 601 grease configuration.

Jett, T.; Hall, P.; Thom, R.

1991-01-01

478

Effects of hydrostatic pressure on the nonlinear optical properties of a donor impurity in a GaAs quantum ring  

NASA Astrophysics Data System (ADS)

The effects of hydrostatic pressure, size quantization and impurity position on the binding energies of a hydrogenic-like donor impurity in a two-dimensional GaAs quantum ring and together with the linear and nonlinear intraband optical absorption and the relative refractive index changes are studied using the variational method and effective-mass approximation. The binding energies of 1s and 2s states are examined as functions of the structure (inner and outer radii), impurity position and hydrostatic pressure. We have also investigated the dependencies of the linear, nonlinear, and total optical absorption coefficients and relative index changes as a function of incident photon energy for different geometric configurations, hydrostatic pressure and impurity position. It is found that the variation of distinct sizes of the structure and impurity position leads to either a redshift and/or a blueshift of the resonant peaks of the intraband optical absorption and relative refractive index change spectrum. In addition we have found that the application of a hydrostatic pressure leads to a blueshift.

Restrepo, R. L.; Barseghyan, M. G.; Mora-Ramos, M. E.; Duque, C. A.

2013-06-01

479

Hydrostatic treatment of alpha-aluminum oxide powders part 2. Evaluation of the mechanisms of sintering acceleration  

Microsoft Academic Search

The effects of different mechanisms of mechanical activation of powders on the subsequent sintering are considered. Expressions for estimating the contribution to acceleration of the sintering process by the mechanisms of dislocation sliding and climbing, fracturing of the particles, and self-diffusion in dislocation pipes are obtained. It is shown that the expansion of hydrostatically pressed specimens of alumina in the

V. V. Storozh; G. Ya. Akimov

1994-01-01

480

Hydrostatic pressure, temperature and electric field effects on donor binding energy in Pöschl–Teller quantum well  

Microsoft Academic Search

We consider the effects of hydrostatic pressure, temperature, and applied electric field on the binding energy of a donor-impurity in Pöschl–Teller quantum well. The ground state energy and the wave function of electron in the presence of the applied electric field and the impurity center are calculated using the variational method and the effective mass and parabolic band approximations. The

M. G. Barseghyan; Alireza Hakimyfard; S. Y. López; C. A. Duque; A. A. Kirakosyan

2010-01-01

481

Electronic states in a Pöschl-Teller-like quantum well: Combined effects of electric field, hydrostatic pressure, and temperature  

Microsoft Academic Search

The work is devoted to present a theoretical study of the influences of external probes, such as applied electric field and hydrostatic pressure, on the electron and hole states in a Pöschl-Teller quantum well. The calculations have been done in the framework of the variational method. The dependence of the ground state energy of an electron and\\/or hole confined in

C. A. Duque; M. E. Mora-Ramos; M. G. Barseghyan

2011-01-01

482

Hydrostatic pressure, temperature and electric field effects on donor binding energy in Pöschl-Teller quantum well  

Microsoft Academic Search

We consider the effects of hydrostatic pressure, temperature, and applied electric field on the binding energy of a donor-impurity in Pöschl-Teller quantum well. The ground state energy and the wave function of electron in the presence of the applied electric field and the impurity center are calculated using the variational method and the effective mass and parabolic band approximations. The

M. G. Barseghyan; Alireza Hakimyfard; S. Y. López; C. A. Duque; A. A. Kirakosyan

2010-01-01

483

Electronic states in a Pöschl–Teller-like quantum well: Combined effects of electric field, hydrostatic pressure, and temperature  

Microsoft Academic Search

The work is devoted to present a theoretical study of the influences of external probes, such as applied electric field and hydrostatic pressure, on the electron and hole states in a Pöschl–Teller quantum well. The calculations have been done in the framework of the variational method. The dependence of the ground state energy of an electron and\\/or hole confined in

C. A. Duque; M. E. Mora-Ramos; M. G. Barseghyan

2011-01-01

484

Hydrostatic pressure treatment during the first mitosis does not suppress the first cleavage but the second one  

Microsoft Academic Search

Suppression of cell division causes chromosome set doubling. Some chemical agents or physical shocks such as temperature or hydrostatic pressure are effective tools for suppression of cell division. As spindles are obviously inactivated or disorganized by these treatments, it has been supposed that inactivation or disassembly of spindles blocks the anaphase movement of chromosomes and a duplicated nucleus is formed

Xuelian Zhang; Hiroshi Onozato

2004-01-01

485

Evaluation of the Growth Environment of a Hydrostatic Force Bioreactor for Preconditioning of Tissue-Engineered Constructs  

PubMed Central

Bioreactors have been widely acknowledged as valuable tools to provide a growth environment for engineering tissues and to investigate the effect of physical forces on cells and cell-scaffold constructs. However, evaluation of the bioreactor environment during culture is critical to defining outcomes. In this study, the performance of a hydrostatic force bioreactor was examined by experimental measurements of changes in dissolved oxygen (O2), carbon dioxide (CO2), and pH after mechanical stimulation and the determination of physical forces (pressure and stress) in the bioreactor through mathematical modeling and numerical simulation. To determine the effect of hydrostatic pressure on bone formation, chick femur skeletal cell-seeded hydrogels were subjected to cyclic hydrostatic pressure at 0–270?kPa and 1?Hz for 1?h daily (5 days per week) over a period of 14 days. At the start of mechanical stimulation, dissolved O2 and CO2 in the medium increased and the pH of the medium decreased, but remained within human physiological ranges. Changes in physiological parameters (O2, CO2, and pH) were reversible when medium samples were placed in a standard cell culture incubator. In addition, computational modeling showed that the distribution and magnitude of physical forces depends on the shape and position of the cell-hydrogel constructs in the tissue culture format. Finally, hydrostatic pressure was seen to enhance mineralization of chick femur skeletal cell-seeded hydrogels. PMID:24967717

Reinwald, Yvonne; Leonard, Katherine H.L.; Henstock, James R.; Whiteley, Jonathan P.; Osborne, James M.; Waters, Sarah L.; Levesque, Philippe

2015-01-01

486

Changes in the microstructure and location of some bioactive compounds in persimmons treated by high hydrostatic pressure  

Microsoft Academic Search

Persimmon fruit are an important source of phenolic compounds, dietary fibre, and carotenoids. However, the location of these elements in the tissue is directly connected with processing techniques used. The aim of this work was to study the effect of high hydrostatic pressure (HHP) on the microstructure of persimmon fruit cv. ‘Rojo Brillante’ during different ripening stages and the relationship

J. L. Vázquez-Gutiérrez; A. Quiles; I. Hernando; I. Pérez-Munuera

2011-01-01

487

Adaptive laboratory evolution of Escherichia coli K-12 MG1655 for growth at high hydrostatic pressure  

PubMed Central

Much of microbial life on Earth grows and reproduces under the elevated hydrostatic pressure conditions that exist in deep-ocean and deep-subsurface environments. In this study adaptive laboratory evolution (ALE) experiments were conducted to investigate the possible modification of the piezosensitive Escherichia coli for improved growth at high pressure. After approximately 500 generations of selection, a strain was isolated that acquired the ability to grow at pressure non-permissive for the parental strain. Remarkably, this strain displayed growth properties and changes in the proportion and regulation of unsaturated fatty acids that indicated the acquisition of multiple piezotolerant properties. These changes developed concomitantly with a change in the gene encoding the acyl carrier protein, which is required for fatty acid synthesis. PMID:25610434

Marietou, Angeliki; Nguyen, Alice T. T.; Allen, Eric E.; Bartlett, Douglas H.

2015-01-01

488

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

489

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 piez