WorldWideScience

Sample records for bearing tn10 tn10kan

  1. Induction of the Tn10 Precise Excision in E. coli Cells after Accelerated Heavy Ions Irradiation

    CERN Document Server

    Zhuravel, D V

    2003-01-01

    The influence of the irradiation of different kinds on the indication of the structural mutations in the bacteria Escherichia coli is considered. The regularities of the Tn10 precise excision after accelerated ^{4}He and ^{12}C ions irradiations with different linear energy transfer (LET) were investigated. Dose dependences of the survival and relative frequency of the Tn10 precise excision were obtained. It was shown, that the relative frequency of the Tn10 precise excision is the exponential function from the irradiation dose. Relative biological efficiency (RBE), and relative genetic efficiency (RGE) were calculated, and were treated as the function of the LET.

  2. Base flipping in tn10 transposition: an active flip and capture mechanism.

    Directory of Open Access Journals (Sweden)

    Julien Bischerour

    2009-07-01

    Full Text Available The bacterial Tn5 and Tn10 transposases have a single active site that cuts both strands of DNA at their respective transposon ends. This is achieved using a hairpin intermediate that requires the DNA to change conformation during the reaction. In Tn5 these changes are controlled in part by a flipped nucleoside that is stacked on a tryptophan residue in a hydrophobic pocket of the transposase. Here we have investigated the base flipping mechanism in Tn10 transposition. As in Tn5 transposition, we find that base flipping takes place after the first nick and is required for efficient hairpin formation and resolution. Experiments with an abasic substrate show that the role of base flipping in hairpin formation is to remove the base from the DNA helix. Specific interactions between the flipped base and the stacking tryptophan residue are required for hairpin resolution later in the reaction. We show that base flipping in Tn10 transposition is not a passive reaction in which a spontaneously flipped base is captured and retained by the protein. Rather, it is driven in part by a methionine probe residue that helps to force the flipped base from the base stack. Overall, it appears that base flipping in Tn10 transposition is similar to that in Tn5 transposition.

  3. Tetracycline alters gene expression in Salmonella strains that harbor the Tn10 transposon.

    Science.gov (United States)

    Hüttener, M; Prieto, A; Aznar, S; Dietrich, M; Paytubi, S; Juárez, A

    2018-04-01

    In this report, we show that bacterial plasmids that harbor the Tn10 transposon (i.e., the IncHI1 plasmid R27) modify expression of different Salmonella regulons responding to the presence of tetracycline (Tc) in the medium. By using as a model the Tc-dependent upregulation of the ibpAB operon (which belongs to the heat shock regulon), we have identified Tn10-tetA (coding for a Tc efflux pump) and adjacent tetC sequences as required for ibpAB upregulation. Characterization of transcripts in the tetAC region showed that tetA transcription can continue into tetC sequences, generating a long 3'UTR sequence, which can protect transcripts from RNA processing, thus increasing the expression of TetA protein. In the presence of Tc, the DnaK and IbpA chaperones are overexpressed and translocated to the periplasm and to the membrane fraction respectively. DnaK targeting unfolded proteins is known to induce heat shock by avoiding RpoH proteolysis. We correlate expression levels of Tn10-encoded TetA protein with heat shock induction in Salmonella, likely because TetA activity compromises protein secretion. © 2018 Society for Applied Microbiology and John Wiley & Sons Ltd.

  4. Hfq restructures RNA-IN and RNA-OUT and facilitates antisense pairing in the Tn10/IS10 system

    Science.gov (United States)

    Ross, Joseph A.; Ellis, Michael J.; Hossain, Shahan; Haniford, David B.

    2013-01-01

    Hfq functions in post-transcriptional gene regulation in a wide range of bacteria, usually by promoting base-pairing of mRNAs and trans-encoded sRNAs that share partial sequence complementarity. It is less clear if Hfq is required for pairing of cis-encoded RNAs (i.e., antisense RNAs) with their target mRNAs. In the current work, we have characterized the interactions between Escherichia coli Hfq and the components of the Tn10/IS10 antisense system, RNA-IN and RNA-OUT. We show that Hfq interacts with RNA-OUT through its proximal RNA-binding surface, as is typical for Hfq and trans-encoded sRNAs. In contrast, RNA-IN binds both proximal and distal RNA-binding surfaces in Hfq with a higher affinity for the latter, as is typical for mRNA interactions in canonical sRNA-mRNA pairs. Importantly, an amino acid substitution in Hfq that interferes with RNA binding to the proximal site negatively impacts RNA-IN:OUT pairing in vitro and suppresses the ability of Hfq to negatively regulate IS10 transposition in vivo. We also show that Hfq binding to RNA-IN and RNA-OUT alters secondary structure elements in both of these RNAs and speculate that this could be important in how Hfq facilitates RNA-IN:OUT pairing. Based on the results presented here, we suggest that Hfq could be involved in regulating RNA pairing in other antisense systems, including systems encoded by other transposable elements. PMID:23510801

  5. Bearing system

    Science.gov (United States)

    Kapich, Davorin D.

    1987-01-01

    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.

  6. Magnetic Bearing

    OpenAIRE

    Anbuselvan. T; Vinothkumar. K; Sai Vikash. M

    2013-01-01

    The use of bearings is essential to all types of machines, especially in marine aspects they provide the function of supporting heavier component in a desired position. These bearings have contact with the rotating part and causes surface wear which can be controlled by lubrication. Researches have raised the standards of performance for rotating equipment by providing robust, cost effective, easy to implement magnetic bearing solutions. Use of magnetic bearings in ships can be more advantag...

  7. Journal bearing

    Science.gov (United States)

    Menke, John R.; Boeker, Gilbert F.

    1976-05-11

    1. An improved journal bearing comprising in combination a non-rotatable cylindrical bearing member having a first bearing surface, a rotatable cylindrical bearing member having a confronting second bearing surface having a plurality of bearing elements, a source of lubricant adjacent said bearing elements for supplying lubricant thereto, each bearing element consisting of a pair of elongated relatively shallowly depressed surfaces lying in a cylindrical surface co-axial with the non-depressed surface and diverging from one another in the direction of rotation and obliquely arranged with respect to the axis of rotation of said rotatable member to cause a flow of lubricant longitudinally along said depressed surfaces from their distal ends toward their proximal ends as said bearing members are rotated relative to one another, each depressed surface subtending a radial angle of less than 360.degree., and means for rotating said rotatable bearing member to cause the lubricant to flow across and along said depressed surfaces, the flow of lubricant being impeded by the non-depressed portions of said second bearing surface to cause an increase in the lubricant pressure.

  8. GAS BEARING

    Science.gov (United States)

    Skarstrom, C.W.

    1960-09-01

    A gas lubricated bearing for a rotating shaft is described. The assembly comprises a stationary collar having an annular member resiliently supported thereon. The collar and annular member are provided with cooperating gas passages arranged for admission of pressurized gas which supports and lubricates a bearing block fixed to the rotatable shaft. The resilient means for the annular member support the latter against movement away from the bearing block when the assembly is in operation.

  9. Thrust bearing

    Science.gov (United States)

    Anderson, W. J. (Inventor)

    1976-01-01

    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.

  10. Polar Bears

    Science.gov (United States)

    Amstrup, Steven C.; Douglas, David C.; Reynolds, Patricia E.; Rhode, E.B.

    2002-01-01

    Polar bears (Ursus maritimus) are hunted throughout most of their range. In addition to hunting polar bears of the Beaufort Sea region are exposed to mineral and petroleum extraction and related human activities such as shipping road-building, and seismic testing (Stirling 1990).Little was known at the start of this project about how polar bears move about in their environment, and although it was understood that many bears travel across political borders, the boundaries of populations had not been delineated (Amstrup 1986, Amstrup et al. 1986, Amstrup and DeMaster 1988, Garner et al. 1994, Amstrup 1995, Amstrup et al. 1995, Amstrup 2000).As human populations increase and demands for polar bears and other arctic resources escalate, managers must know the sizes and distributions of the polar bear populations. Resource managers also need reliable estimates of breeding rates, reproductive intervals, litter sizes, and survival of young and adults.Our objectives for this research were 1) to determine the seasonal and annual movements of polar bears in the Beaufort Sea, 2) to define the boundaries of the population(s) using this region, 3) to determine the size and status of the Beaufort Sea polar bear population, and 4) to establish reproduction and survival rates (Amstrup 2000).

  11. Hydrodynamic bearings

    CERN Document Server

    Bonneau, Dominique; Souchet, Dominique

    2014-01-01

    This Series provides the necessary elements to the development and validation of numerical prediction models for hydrodynamic bearings. This book describes the rheological models and the equations of lubrication. It also presents the numerical approaches used to solve the above equations by finite differences, finite volumes and finite elements methods.

  12. Bearing structures

    International Nuclear Information System (INIS)

    Lee, A.S.; Preece, G.E.

    1988-01-01

    A hydrostatic bearing for the lower end of the vertical shaft of a sodium pump comprises a support shell encircling the shaft and a bush located between the shell and shaft. Liquid sodium is fed from the pump outlet to the bush/shaft and bush/shell interfaces to provide hydrostatic support. The bush outer surface and the shell inner surface are of complementary part-spherical shape and the bush floats relative to the shaft so that the bush can align itself with the shaft axis. Monitoring of the relative rotational speed of the bush with respect to the shaft (such rotation being induced by the viscous drag forces present) is also performed for the purposes of detecting abnormal operation of the bearing or partial seizure, at least one magnet is rotatable with the bush, and a magnetic sensor provides an output having a frequency related to the speed of the bush. (author)

  13. Camshaft bearing arrangement

    Energy Technology Data Exchange (ETDEWEB)

    Aoi, K.; Ozawa, T.

    1986-06-10

    A bearing arrangement is described for the camshaft of an internal combustion engine or the like which camshaft is formed along its length in axial order with a first bearing surface, a first cam lobe, a second bearing surface, a second cam lobe, a third bearing surface, a third cam lobe and a fourth bearing surface, the improvement comprising first bearing means extending around substantially the full circumference of the first bearing surface and journaling the first bearing surface, second bearing means extending around substantially less than the circumference of the second bearing surface and journaling the second bearing surface, third bearing means extending around substantially less than the circumference of the third bearing surface and journaling the third bearing surface, and fourth bearing means extending around substantially the full circumference of the fourth bearing surface and journaling the first bearing surface.

  14. Passive magnetic bearing configurations

    Science.gov (United States)

    Post, Richard F [Walnut Creek, CA

    2011-01-25

    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.

  15. Improved gas thrust bearings

    Science.gov (United States)

    Anderson, W. J.; Etsion, I.

    1979-01-01

    Two variations of gas-lubricated thrust bearings extend substantially load-carrying range over existing gas bearings. Dual-Action Gas Thrust Bearing's load-carrying capacity is more than ninety percent greater than that of single-action bearing over range of compressibility numbers. Advantages of Cantilever-mounted Thrust Bearing are greater tolerance to dirt ingestion, good initial lift-off characteristics, and operational capability over wide temperature range.

  16. Experiments with needle bearings

    Science.gov (United States)

    Ferretti, Pericle

    1933-01-01

    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.

  17. Teddy Bear Stories

    DEFF Research Database (Denmark)

    van Leeuwen, Theo; Caldas-Coulthardt, Carmen

    2014-01-01

    This paper presents a semiotic analysis of a key cultural artefact, the teddy bear. After introducing the iconography of the teddy bear, it analyses different kinds of stories to show how teddy bears are endowed with meaning in everyday life: stories from children's books, reminiscenses by adults...... about their childhood teddy bears, and children's accounts of what they do with teddy bears, both written for school and told 'out of school', The chapter sees teddy bears as artefacts that provide a cultural channeling for the child's need of a transitional object and argues that the meanings of teddy...... bears have traditionally centred on interpersonal relations within the nuclear family, but have recently been institutionalized and commercialized....

  18. Bearings: Technology and needs

    Science.gov (United States)

    Anderson, W. J.

    1982-01-01

    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.

  19. Polar bears, Ursus maritimus

    Science.gov (United States)

    Rode, Karyn D.; Stirling, Ian

    2017-01-01

    Polar bears are the largest of the eight species of bears found worldwide and are covered in a pigment-free fur giving them the appearance of being white. They are the most carnivorous of bear species consuming a high-fat diet, primarily of ice-associated seals and other marine mammals. They range throughout the circumpolar Arctic to the southernmost extent of seasonal pack ice.

  20. EcoBears

    DEFF Research Database (Denmark)

    Nielsen, Nick; Pedersen, Sandra Bleuenn; Sørensen, Jens Ager

    2015-01-01

    In this paper, we introduce the EcoBears concept that aims to augment household appliances with functional and aesthetic features to promote their "use'' and "longevity of use'' to prevent their disposal. The EcoBears also aim to support the communication of environmental issues in the home setting....... We present our initial design and implementation of the EcoBears that consist of two bear modules (a mother and her cub). We also present our preliminary concept validations and lessons learned to be considered for future directions....

  1. Fluorine lubricated bearing technology

    Science.gov (United States)

    Mallaire, F. R.

    1973-01-01

    An experimental program was conducted to evaluate and select materials for ball bearings intended for use in liquid fluorine and/or FLOX. The ability of three different ball-separator materials, each containing nickel, to form and transfer a nickel fluoride film to provide effective lubrication at the required areas of a ball bearing operating in liquid fluorine was evaluated. In addition, solid lubrication of a ball bearing operating in liquid fluorine by either a fused fluoride coating applied to all surfaces of the ball separator or by a fluoride impregnation of porous sintered material ball separators was evaluated. Less bearing wear occurred when tests were conducted in the less reactive FLOX. Bearings fabricated from any of the materials tested would have relatively short wear lives and would require frequent replacement in a reusable engine.

  2. Ultra-precision bearings

    CERN Document Server

    Wardle, F

    2015-01-01

    Ultra-precision bearings can achieve extreme accuracy of rotation, making them ideal for use in numerous applications across a variety of fields, including hard disk drives, roundness measuring machines and optical scanners. Ultraprecision Bearings provides a detailed review of the different types of bearing and their properties, as well as an analysis of the factors that influence motion error, stiffness and damping. Following an introduction to basic principles of motion error, each chapter of the book is then devoted to the basic principles and properties of a specific type of bearin

  3. Investigation of Bearing Technology

    National Research Council Canada - National Science Library

    Maciag, Walter

    1998-01-01

    .... They eliminate roller needles and balls in bearings. Since the GC design does not require lubrication maintenance, there is no need for the u-joint cross to contain lubrication reservoirs and distribution channels and their input fitting...

  4. DW_BEAR

    Data.gov (United States)

    Department of Homeland Security — Subset of BEAR (Bi-Weekly Examination Analysis and Reporting) data used for financial audit remediation reporting within the Coast Guard Business Intelligence (CGBI)...

  5. Gear bearing drive

    Science.gov (United States)

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

    2011-01-01

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

  6. Rolling bearing analysis

    CERN Document Server

    Harris, Tedric A

    2001-01-01

    One of the most well-known experts in the field brings cutting-edge research to practitioners in the new edition of this important reference. Covers the improved mathematical calculations for rolling bearing endurance developed by the American Society of Mechanical Engineers and the Society of Lubrication and Tribology Engineers. Updated with new material on Condition-Based Maintenance, new testing methods, and new bearing materials.

  7. Load responsive hydrodynamic bearing

    Science.gov (United States)

    Kalsi, Manmohan S.; Somogyi, Dezso; Dietle, Lannie L.

    2002-01-01

    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.

  8. Watchable Wildlife: The Black Bear

    Science.gov (United States)

    Lynn L. Rogers

    1992-01-01

    Black bears are the bears people most often encounter. Black bears live in forests over much of North America, unlike grizzlies that live only in Alaska, northern and western Canada, and the northern Rocky Mountains. This brochure presents the latest information on black bear life and how this species responds to an ever-increasing number of campers, hikers, and...

  9. Climate Drives Polar Bear Origins

    Science.gov (United States)

    In their provocative analysis of northern bears (“Nuclear genomic sequences reveal that polar bears are an old and distinct bear lineage,” Reports, 20 April, p. 344), F. Hailer et al. use independent nuclear loci to show that polar bears originated during the middle Pleistocene, rather than during t...

  10. Radial Halbach Magnetic Bearings

    Science.gov (United States)

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

    2009-01-01

    Radial Halbach magnetic bearings have been investigated as part of an effort to develop increasingly reliable noncontact bearings for future high-speed rotary machines that may be used in such applications as aircraft, industrial, and land-vehicle power systems and in some medical and scientific instrumentation systems. Radial Halbach magnetic bearings are based on the same principle as that of axial Halbach magnetic bearings, differing in geometry as the names of these two types of bearings suggest. Both radial and axial Halbach magnetic bearings are passive in the sense that unlike most other magnetic bearings that have been developed in recent years, they effect stable magnetic levitation without need for complex active control. Axial Halbach magnetic bearings were described in Axial Halbach Magnetic Bearings (LEW-18066-1), NASA Tech Briefs, Vol. 32, No. 7 (July 2008), page 85. In the remainder of this article, the description of the principle of operation from the cited prior article is recapitulated and updated to incorporate the present radial geometry. In simplest terms, the basic principle of levitation in an axial or radial Halbach magnetic bearing is that of the repulsive electromagnetic force between (1) a moving permanent magnet and (2) an electric current induced in a stationary electrical conductor by the motion of the magnetic field. An axial or radial Halbach bearing includes multiple permanent magnets arranged in a Halbach array ("Halbach array" is defined below) in a rotor and multiple conductors in the form of wire coils in a stator, all arranged so the rotary motion produces an axial or radial repulsion that is sufficient to levitate the rotor. A basic Halbach array (see Figure 1) consists of a row of permanent magnets, each oriented so that its magnetic field is at a right angle to that of the adjacent magnet, and the right-angle turns are sequenced so as to maximize the magnitude of the magnetic flux density on one side of the row while

  11. Hybrid superconductor magnet bearings

    Science.gov (United States)

    Chu, Wei-Kan

    1995-01-01

    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.

  12. Compliant hydrodynamic fluid journal bearing

    Science.gov (United States)

    Warren, E. L. (Inventor)

    1985-01-01

    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.

  13. Magnetic bearing and motor

    Science.gov (United States)

    Studer, Philip A. (Inventor)

    1983-01-01

    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.

  14. Passive magnetic bearing system

    Science.gov (United States)

    Post, Richard F.

    2014-09-02

    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.

  15. Government Risk-Bearing

    CERN Document Server

    1993-01-01

    The u.s. government bulks large in the nation's financial markets. The huge volume of government-issued and -sponsored debt affects the pricing and volume ofprivate debt and, consequently, resource allocation between competing alternatives. What is often not fully appreciated is the substantial influence the federal government wields overresource allocation through its provisionofcreditandrisk-bearing services to the private economy. Because peopleand firms generally seekto avoid risk, atsomeprice they are willing to pay another party to assume the risk they would otherwise face. Insurance companies are a class of private-sector firms one commonly thinks of as providing these services. As the federal government has expanded its presence in the U.S. economy during this century, it has increasingly developed programs aimed at bearing risks that the private sector either would not take on at any price, or would take on but atapricethoughtto besogreatthatmostpotentialbeneficiarieswouldnotpurchase the coverage. To...

  16. COMPOSITION OF BLACK BEAR MILK.

    Science.gov (United States)

    An analysis of black bear ( Ursus americanus Pallas) milk showed that the total solids, fat and protein were much higher and the lactose lower than...either cow or human milk. In comparison with polar bear (Thalarcotos maritimus ), the black bear milk was lower in fat, protein and total calories. (Author)

  17. Frictionless Bearing Uses Permanent Magnets

    Science.gov (United States)

    1965-01-01

    The purpose of this innovation was to develop a frictionless bearing for high speed, light load applications. The device involves the incorporation of permanent magnets in the bearing design. The repulsion of like magnetic poles provides concentric support of the inner member so that no metallic contact occurs between the bearing surfaces.

  18. Rotating plug bearing and seal

    International Nuclear Information System (INIS)

    Wade, E.E.

    1977-01-01

    Disclosed is a bearing and seal structure for nuclear reactors utilizing rotating plugs above the nuclear reactor vessel. The structure permits lubrication of bearings and seals of the rotating plugs without risk of the lubricant draining into the reactor vessel below. The structure permits lubrication by utilizing a rotating outer race bearing. 19 claims, 3 figures

  19. Radium bearing waste disposal

    International Nuclear Information System (INIS)

    Tope, W.G.; Nixon, D.A.; Smith, M.L.; Stone, T.J.; Vogel, R.A.; Schofield, W.D.

    1995-01-01

    Fernald radium bearing ore residue waste, stored within Silos 1 and 2 (K-65) and Silo 3, will be vitrified for disposal at the Nevada Test Site (NTS). A comprehensive, parametric evaluation of waste form, packaging, and transportation alternatives was completed to identify the most cost-effective approach. The impacts of waste loading, waste form, regulatory requirements, NTS waste acceptance criteria, as-low-as-reasonably-achievable principles, and material handling costs were factored into the recommended approach

  20. Bearing for liquid metal pump

    International Nuclear Information System (INIS)

    Dickinson, R.J.; Pennell, W.E.; Wasko, J.

    1984-01-01

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

  1. Bearing, gearing, and lubrication technology

    Science.gov (United States)

    Anderson, W. J.

    1978-01-01

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

  2. Bearing construction for refrigeration compresssor

    Science.gov (United States)

    Middleton, Marc G.; Nelson, Richard T.

    1988-01-01

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

  3. 77 FR 70423 - Black Bear Hydro Partners, LLC and Black Bear Development Holdings, LLC and Black Bear SO, LLC...

    Science.gov (United States)

    2012-11-26

    ... Bear Hydro Partners, LLC and Black Bear Development Holdings, LLC and Black Bear SO, LLC; Notice of..., 2012, Black Bear Hydro Partners, LLC, sole licensee (transferor) and Black Bear Development Holdings, LLC and Black Bear SO, LLC (transferees) filed an application for the partial the transfer of licenses...

  4. Introgressive hybridization: brown bears as vectors for polar bear alleles.

    Science.gov (United States)

    Hailer, Frank

    2015-03-01

    The dynamics and consequences of introgression can inform about numerous evolutionary processes. Biologists have therefore long been interested in hybridization. One challenge, however, lies in the identification of nonadmixed genotypes that can serve as a baseline for accurate quantification of admixture. In this issue of Molecular Ecology, Cahill et al. (2015) analyse a genomic data set of 28 polar bears, eight brown bears and one American black bear. Polar bear alleles are found to be introgressed into brown bears not only near a previously identified admixture zone on the Alaskan Admiralty, Baranof and Chichagof (ABC) Islands, but also far into the North American mainland. Elegantly contrasting admixture levels at autosomal and X chromosomal markers, Cahill and colleagues infer that male-biased dispersal has spread these introgressed alleles away from the Late Pleistocene contact zone. Compared to a previous study on the ABC Island population in which an Alaskan brown bear served as a putatively admixture-free reference, Cahill et al. (2015) utilize a newly sequenced Swedish brown bear as admixture baseline. This approach reveals that brown bears have been impacted by introgression from polar bears to a larger extent (up to 8.8% of their genome), than previously known, including the bear that had previously served as admixture baseline. No evidence for introgression of brown bear into polar bear is found, which the authors argue could be a consequence of selection. Besides adding new exciting pieces to the puzzle of polar/brown bear evolutionary history, the study by Cahill and colleagues highlights that wildlife genomics is moving from analysing single genomes towards a landscape genomics approach. © 2015 John Wiley & Sons Ltd.

  5. Computational design of rolling bearings

    CERN Document Server

    Nguyen-Schäfer, Hung

    2016-01-01

    This book comprehensively presents the computational design of rolling bearings dealing with many interdisciplinary difficult working fields. They encompass elastohydrodynamics (EHD), Hertzian contact theory, oil-film thickness in elastohydrodynamic lubrication (EHL), bearing dynamics, tribology of surface textures, fatigue failure mechanisms, fatigue lifetimes of rolling bearings and lubricating greases, Weibull distribution, rotor balancing, and airborne noises (NVH) in the rolling bearings. Furthermore, the readers are provided with hands-on essential formulas based on the up-to-date DIN ISO norms and helpful examples for computational design of rolling bearings. The topics are intended for undergraduate and graduate students in mechanical and material engineering, research scientists, and practicing engineers who want to understand the interactions between these working fields and to know how to design the rolling bearings for automotive industry and many other industries.

  6. Grease lubrication in rolling bearings

    CERN Document Server

    Lugt, Piet M

    2012-01-01

    The definitive book on the science of grease lubrication for roller and needle bearings in industrial and vehicle engineering. Grease Lubrication in Rolling Bearings provides an overview of the existing knowledge on the various aspects of grease lubrication (including lubrication systems) and the state of the art models that exist today. The book reviews the physical and chemical aspects of grease lubrication, primarily directed towards lubrication of rolling bearings. The first part of the book covers grease composition, properties and rheology, including thermal

  7. Improvement of bearing support lubrication

    Directory of Open Access Journals (Sweden)

    Shehovtseva E. V.

    2016-12-01

    Full Text Available Gas turbine engine bearing supports is an important part in providing product efficiency of general and special-purpose engineering industry. Attempts are being made to increase efficiency of bearing support. Such attempts are caused by the modern tendency of the development of engineering striving for compact machines and units possessing increased reliability and durability. Researches on finding discrepancies in operation of support for this purpose have been executed. The reasons of occurrence the fatigue crumbling on external bearing races at different stages development of working surface damage have been investigated. The basic constructions of support of shaft for the aviation gas turbine engine and methods of their lubrication have been considered. Shortcomings of existing methods of lubrication of bearing supports have been marked. The upgraded construction of the module of gas turbine bearing shaft, which allows to improve conditions of lubrication and bearing cooling as a result of a uniform oil feed to the contact zones of outside bearing race and rolling elements and forced oil removal from contact zones of inside bearing race and rolling elements has been suggested. The task of improving conditions of lubrication supply to an internal holder of the bearing has been solved. The developed design allows applying unconventional methods of lubrication and cooling of a bearing support. Thus it is recommended to use process of regulation of a microrough on working surfaces bearing support during grinding-in. It will allow to improve a stage grinding-in and to increase reliability and durability of bearing support.

  8. Hydrostatic and hybrid bearing design

    CERN Document Server

    Rowe, W B

    1983-01-01

    Hydrostatic and Hybrid Bearing Design is a 15-chapter book that focuses on the bearing design and testing. This book first describes the application of hydrostatic bearings, as well as the device pressure, flow, force, power, and temperature. Subsequent chapters discuss the load and flow rate of thrust pads; circuit design, flow control, load, and stiffness; and the basis of the design procedures and selection of tolerances. The specific types of bearings, their design, dynamics, and experimental methods and testing are also shown. This book will be very valuable to students of engineering des

  9. Autosizing Control Panel for Needle Bearing

    OpenAIRE

    Prof.A.R.Wadhekar,; Ms Jyoti R. Rajput

    2016-01-01

    A needle roller bearing is a bearing which uses small cylindrical rollers. Bearings are used to reduce friction of any rotating surface. Needle bearings have a large surface in contact with the bearing outer surfaces as compared to ball bearings. There is less added clearance(Diameter of the shaft and the diameter of the bearing are different) so they are much compact. The structure consists of a needle cage which contains the needle rollersthemselves and an outer race (The housin...

  10. Permanent-Magnet Meissner Bearing

    Science.gov (United States)

    Robertson, Glen A.

    1994-01-01

    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.

  11. Superconducting bearings for flywheel applications

    DEFF Research Database (Denmark)

    Abrahamsen, A.B.

    2001-01-01

    A literature study on the application of superconducting bearings in energy storage flywheel systems. The physics of magnetic levitation and superconductors are presented in the first part of the report, followed by a discussion of the literature found onthe applications of superconducting bearings...

  12. What about the Javan Bear?

    NARCIS (Netherlands)

    Jentink, F.A.

    1898-01-01

    The other day I read in a dutch popular periodical a paper dealing with the different species of Bears and their geographical distribution. To my great surprise the Malayan Bear was mentioned from Java: the locality Java being quite new to me I wrote to the author of that paper and asked him some

  13. Nonlinear control of magnetic bearings

    Science.gov (United States)

    Pradeep, A. K.; Gurumoorthy, R.

    1994-01-01

    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.

  14. Flywheel Challenge: HTS Magnetic Bearing

    International Nuclear Information System (INIS)

    Werfel, F N; Floegel-Delor, U; Riedel, T; Rothfeld, R; Wippich, D; Goebel, B

    2006-01-01

    A 200 mm cylindrical engineering prototype high temperature superconducting (HTS) was designed and fabricated. Measurements show that the 17 kg PM rotor can suspend safely 1000 kg in axial direction and 470 kg radially. The rationale for the bearing performance is to stabilize a 400 kg rotor of a new compact 5 kWh/280 kW flywheel energy storage system (COM - FESS). Measurements of the magnetic bearing force, stiffness and drag-torque are presented indicated the successful targeting a milestone in the HTS bearing technology. The influence of the PM configuration and the YBCO temperature on the bearing performance was experimentally studied, providing high-force or high-stiffness behaviour. The axial stiffness 5 kN/mm at 0.5 mm displacement is the highest value of a HTS bearing we know

  15. DESIGN HANDBOOK ON GAS BEARINGS FOR GYROSCOPES.

    Science.gov (United States)

    consisting of a plain journal for supporting radial loads flanked by two spiral-grooved thrust bearings to support double-acting thrust loads; (3) the spiral-grooved journal bearing ; and (4) the spiral-grooved conical bearing.

  16. Hybrid Hydrostatic/Transient Roller Bearing Assembly

    Science.gov (United States)

    Justak, John F.

    1992-01-01

    Proposed bearing assembly for shaft of high-speed turbopump includes both hydrostatic and rolling-element bearings. Rolling-element bearing unloaded at high speed by centrifugal expansion of outer race and transient retainer.

  17. Two pad axially grooved hydrostatic bearing

    Science.gov (United States)

    San Andres, Luis A. (Inventor)

    1995-01-01

    A hydrostatic bearing having two axial grooves on opposite sides of the bearing for breaking the rotational symmetry in the dynamic force coefficients thus reducing the whirl frequency ratio and increasing the damping and stiffness of the hydrostatic bearing.

  18. Deformation Analysis of Fixed Bearing Inclined Plane Thrust Bearing

    Directory of Open Access Journals (Sweden)

    LI Yong--hai

    2017-02-01

    Full Text Available According to the theory of lubrication,Numerical simulation of the deformation of the thrust bearing of the fixed inclined plane was carried out,by finite element numerical analysis method and using the ANSYS software. The mathematical model of the oil film shape control equations about of the deformation and bearing is established. Analytical result showed that the force caused the tile surface generating concave deformation,and convex deformation increased with the height and the size of the load and bearing;Tile surface temperature generated convex deformation and increased with the height and the size of the temperature of bearing bush;The actual deformation of the tile surface is the superposition of the force and the thermal deformation. This conclusion can provide reference for the design and the application of thrust bearing,to reduce the tile surface,which is not conducive to the carrying capacity of the concave deformation.

  19. EFFECT OF BEARING MACROGEOMETRY ON BEARING PERFORMANCE IN ELASTOHYDRODYNAMIC LUBRICATION

    Directory of Open Access Journals (Sweden)

    Emin GÜLLÜ

    2000-01-01

    Full Text Available During manufacturing, ideal dimension and mutual positioning of machine elements proposed in project desing can be achieved only within certain range of tolerances. These tolerances, being classified in two groups, related to micro and macro geometry of machine elements, don't have to effect the functioning of these elements. So, as for all machine elements, investigation of the effects of macro and micro tolerances for journal bearings is important. In this study, we have investigated the effect of macro geometric irregularities of journal bearings on performance characteristics. In this regard, we have studied the change of bearing performance in respect to deviation from ideal circle for an elliptic shaft with small ovality rolling in circular journal bearing.

  20. Bears, Big and Little. Young Discovery Library Series.

    Science.gov (United States)

    Pfeffer, Pierre

    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)…

  1. Non-contacting "snubber bearing" for passive magnetic bearing systems

    Science.gov (United States)

    Post, Richard F

    2017-08-22

    A new non-contacting magnetic "snubber" bearing is provided for application to rotating systems such as vehicular electromechanical battery systems subject to frequent accelerations. The design is such that in the equilibrium position the drag force of the snubber is very small (milliwatts). However in a typical case, if the rotor is displaced by as little as 2 millimeters a large restoring force is generated without any physical contact between the stationary and rotating parts of the snubber bearing.

  2. Thin Dense Chrome Bearing Insertion Program

    National Research Council Canada - National Science Library

    Rhoads, Mark

    1997-01-01

    .... TDC coated bearings demonstrated improved corrosion and contamination resistance. TDC coated bearings also demonstrated acceptable performance during thermal cycle, oil-off, and induced defect conditions...

  3. Mixed-mu superconducting bearings

    Science.gov (United States)

    Hull, John R.; Mulcahy, Thomas M.

    1998-01-01

    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.

  4. Simplified installation of thrust bearings

    Science.gov (United States)

    Sensenbaugh, N. D.

    1980-01-01

    Special handling sleeve, key to method of installing thrust bearings, was developed for assembling bearings on shaft of low-pressure oxygen turbo-pump. Method eliminates cooling and vacuum-drying steps which saves time, while also eliminating possibility of corrosion formation. Procedure saves energy because it requires no liquid nitrogen for cooling shaft and no natural gas or electric power for operating vacuum oven.

  5. Lateral dampers for thrust bearings

    Science.gov (United States)

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

    1985-01-01

    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.

  6. Radial magnetic bearings: An overview

    Directory of Open Access Journals (Sweden)

    Weiyu Zhang

    Full Text Available Radial magnetic bearings (RMBs are one of the most commonly used magnetic bearings. They are used widely in the field of ultra-high speed and ultra-precise numerical control machine tools, bearingless motors, high speed flywheels, artificial heart pumps, and molecular pumps, and they are being strengthened and extended in various important areas. In this paper, a comprehensive overview is given of different bearing topologies of RMBs with different stator poles that differ in their construction, the driving mode of electromagnets, power consumption, cost, magnetic circuits, and symmetry. RMBs with different poles and couplings between the two bearing axes in the radial direction responsible for cross-coupling generation are compared. In addition, different shaped rotors are compared, as the performances of magnetic bearing-rotor systems are of great concern to rotor constructions. Furthermore, the parameter design methods, the mathematical models and control strategies of the RMBs are described in detail. From the comparison of topologies, models and control methods for RMBs, the advantages, disadvantages and utilizable perspectives are also analyzed. Moreover, several possible development trends of the RMBs are discussed. Keywords: Radial magnetic bearings (RMBs, Topologies, Mathematical mode, Control strategies, Development trends

  7. 36 CFR 13.1236 - Bear orientation.

    Science.gov (United States)

    2010-07-01

    ... 36 Parks, Forests, and Public Property 1 2010-07-01 2010-07-01 false Bear orientation. 13.1236... Developed Area § 13.1236 Bear orientation. All persons visiting the BCDA must receive an NPS-approved Bear Orientation. Failure to receive an NPS-approved Bear Orientation is prohibited. ...

  8. 49 CFR 229.69 - Side bearings.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Side bearings. 229.69 Section 229.69....69 Side bearings. (a) Friction side bearings with springs designed to carry weight may not have more than 25 percent of the springs in any one nest broken. (b) Friction side bearings may not be run in...

  9. Heuristic Explanation of Journal Bearing Instability

    Science.gov (United States)

    1982-05-01

    A fluid-filled journal bearing is viewed as a powerful pump circulating fluid around the annular space between the journal and the bearing. A small...other simple explanations of journal - bearing instability. It is shown that for non-cavitating long bearings the hypothesis predicts instability onset

  10. Superconductor bearings, flywheels and transportation

    Science.gov (United States)

    Werfel, F. N.; Floegel-Delor, U.; Rothfeld, R.; Riedel, T.; Goebel, B.; Wippich, D.; Schirrmeister, P.

    2012-01-01

    This paper describes the present status of high temperature superconductors (HTS) and of bulk superconducting magnet devices, their use in bearings, in flywheel energy storage systems (FESS) and linear transport magnetic levitation (Maglev) systems. We report and review the concepts of multi-seeded REBCO bulk superconductor fabrication. The multi-grain bulks increase the averaged trapped magnetic flux density up to 40% compared to single-grain assembly in large-scale applications. HTS magnetic bearings with permanent magnet (PM) excitation were studied and scaled up to maximum forces of 10 kN axially and 4.5 kN radially. We examine the technology of the high-gradient magnetic bearing concept and verify it experimentally. A large HTS bearing is tested for stabilizing a 600 kg rotor of a 5 kWh/250 kW flywheel system. The flywheel rotor tests show the requirement for additional damping. Our compact flywheel system is compared with similar HTS-FESS projects. A small-scale compact YBCO bearing with in situ Stirling cryocooler is constructed and investigated for mobile applications. Next we show a successfully developed modular linear Maglev system for magnetic train operation. Each module levitates 0.25t at 10 mm distance during one-day operation without refilling LN2. More than 30 vacuum cryostats containing multi-seeded YBCO blocks are fabricated and are tested now in Germany, China and Brazil.

  11. Lubrication of sliding bearings for hydropower applications

    OpenAIRE

    McCarthy, Donald

    2005-01-01

    The term "sliding bearing" refers to types of bearing where two conformal surfaces (usually the stationary bearing and a moving shaft) slide relative to one another with load distributed directly across the interface. A suitable lubricant may be employed to reduce the friction between these two surfaces. In "fluid film" bearings, this lubricant builds up a layer of sufficient thickness such that the two surfaces are completely separated. Examples include journal and thrust bearings and shaft ...

  12. The Weight-Bearing Shoulder.

    Science.gov (United States)

    Patel, Ronak M; Gelber, Jonathan D; Schickendantz, Mark S

    2018-01-01

    The shoulder achieves a wide spectrum of motion, and in a subset of patients, including those who use manual wheelchairs and upper extremity walking aids, the shoulder also serves as the primary weight-bearing joint. Because the weight-bearing shoulder is subject to considerable joint reaction forces and overuse, a broad spectrum of pathology can affect the joint. The combination of muscle imbalance and repetitive trauma presents most commonly as subacromial impingement syndrome but can progress to other pathology. Patients with high-level spinal cord injury, leading to quadriplegia and motor deficits, have an increased incidence of shoulder pain. Understanding the needs of patients who use manual wheelchairs or walking aids can help the physician to better comprehend the pathology of and better manage the weight-bearing shoulder.

  13. Wave Journal Bearing. Part 1: Analysis

    Science.gov (United States)

    Dimofte, Florin

    1995-01-01

    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.

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

    OpenAIRE

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

    2015-01-01

    © 2014 The Authors. Molecular Ecology Published by John Wiley & Sons Ltd. 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...

  15. Satellite monitoring of black bear.

    Science.gov (United States)

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

    1971-01-01

    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.

  16. Little Bear Fire Summary Report

    Science.gov (United States)

    Sarah McCaffrey; Melanie Stidham; Hannah. Brenkert-Smith

    2013-01-01

    In June 2012, immediately after the Little Bear Fire burned outside Ruidoso, New Mexico, a team of researchers interviewed fire managers, local personnel, and residents to understand perceptions of the event itself, communication, evacuation, and pre-fire preparedness. The intensity of fire behavior and resulting loss of 242 homes made this a complex fire with a...

  17. BEAR AT THE BACK DOOR

    African Journals Online (AJOL)

    BEAR AT THE BACK DOOR. Deur generaal sir Walter Walker KCB, CBE,. D80. 8andton. Uitgegee deur Valiant Publis- hers. Verskyningsdatum Julie 1978. Prys R10.) Hierdie boek is 'n uitstekende aktuele geskrif ook. Suidelike Afrika se politieke en militere aspekte wat deur 'n a/gehele buitestaander nl 'n Britse. Generaal ...

  18. Climate Change, Polar Bears and their management

    OpenAIRE

    Derenchenko, Liza

    2010-01-01

    This is a literature study of polar bears in the context of climate change: what kind of creatures are polar bears, what are the main interpretations of current climate change, how might the polar bear adapt to these changes (feeding strategies) and how are the bears being managed (hunting)? These are relevant questions , since climate change is on the agenda, and polar bears being the apex predators of the Arctic are a key representation of the wildlife there. The third element of polar bear...

  19. Journal and Wave Bearing Impedance Calculation Software

    Science.gov (United States)

    Hanford, Amanda; Campbell, Robert

    2012-01-01

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

  20. Dynamics of gas-thrust bearings

    Science.gov (United States)

    Stiffler, A. K.; Tapia, R. R.

    1978-01-01

    Computer program calculates load coefficients, up to third harmonic, for hydrostatic gas thrust bearings. Program is useful in identification of industrial situations where gas-thrust bearings have potential applications.

  1. Rolling Element Bearing Stiffness Matrix Determination (Presentation)

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Y.; Parker, R.

    2014-01-01

    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.

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

    Science.gov (United States)

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

    2012-01-01

    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.

  3. Mercury in polar bears from Alaska

    Energy Technology Data Exchange (ETDEWEB)

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

    1987-04-01

    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.

  4. Technology development for indigenous water lubricated bearings

    International Nuclear Information System (INIS)

    Limaye, P.K.; Soni, N.L.; Agrawal, R.G.

    2010-01-01

    Water Lubricated Bearings (WLB) are used in various mechanisms of fuel handling systems of PHWRs and AHWR. Availability and random failures of these bearings was a major factor in refuelling operations. Indigenous development of these bearings was taken up and 7 types of antifriction bearings in various sizes (totaling 37 variants) for PHWR, AHWR and Dhruva applications were successfully developed. This paper deals with various aspects of WLB development. (author)

  5. Thin film superconductor magnetic bearings

    Science.gov (United States)

    Weinberger, Bernard R.

    1995-12-26

    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.

  6. Passive Thermal Management of Foil Bearings

    Science.gov (United States)

    Bruckner, Robert J. (Inventor)

    2015-01-01

    Systems and methods for passive thermal management of foil bearing systems are disclosed herein. The flow of the hydrodynamic film across the surface of bearing compliant foils may be disrupted to provide passive cooling and to improve the performance and reliability of the foil bearing system.

  7. 49 CFR 229.64 - Plain bearings.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Plain bearings. 229.64 Section 229.64 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION....64 Plain bearings. A plain bearing box shall contain visible free oil and may not be cracked to the...

  8. Cool Polar Bears: Dabbing on the Texture

    Science.gov (United States)

    O'Connell, Jean

    2011-01-01

    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.

  9. Hydrodynamic squeeze-film bearings for gyroscopes

    Science.gov (United States)

    Chiang, T.; Smith, R. L.

    1970-01-01

    Experimental tests are conducted on squeeze-film bearings by applying electricity to piezoelectric ceramics, causing vibrations at thousands or millions of Hz that are amplified and transmitted to the bearing. Rotor operation through 24,000 rpm without whirl instability proved bearing ability to support rotor weight without hydrodynamic action.

  10. 14 CFR 23.623 - Bearing factors.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Bearing factors. 23.623 Section 23.623... Bearing factors. (a) Each part that has clearance (free fit), and that is subject to pounding or vibration, must have a bearing factor large enough to provide for the effects of normal relative motion. (b) For...

  11. 14 CFR 25.623 - Bearing factors.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Bearing factors. 25.623 Section 25.623... STANDARDS: TRANSPORT CATEGORY AIRPLANES Design and Construction General § 25.623 Bearing factors. (a) Except... subject to pounding or vibration, must have a bearing factor large enough to provide for the effects of...

  12. 14 CFR 27.623 - Bearing factors.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Bearing factors. 27.623 Section 27.623... STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction General § 27.623 Bearing factors. (a) Except... subject to pounding or vibration, must have a bearing factor large enough to provide for the effects of...

  13. 14 CFR 29.623 - Bearing factors.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Bearing factors. 29.623 Section 29.623... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction General § 29.623 Bearing factors. (a... subject to pounding or vibration, must have a bearing factor large enough to provide for the effects of...

  14. Fractal analysis of polar bear hairs

    Directory of Open Access Journals (Sweden)

    Wang Qing-Li

    2015-01-01

    Full Text Available Hairs of a polar bear (Ursus maritimus are of superior properties such as the excellent thermal protection. Why do polar bears can resist such cold environment? The paper concludes that its fractal porosity plays an important role, and its fractal dimensions are very close to the golden mean, 1.618, revealing the possible optimal structure of polar bear hair.

  15. Microstructural degradation of bearing steels

    OpenAIRE

    Solano Alvarez, Wilberth

    2015-01-01

    The aim of the work presented in this thesis is to clarify one of the most fundamental aspects of fatigue damage in bearings steels through critical experiments, in particular whether damage in the form of cracks precedes hard “white-etching matter" formation, which is carbon supersaturated nanoscaled ferrite. Heat treatments have been designed to create four different crack types and distributions: scarce martensite plate cracks, fine grain boundary cracks, abundant martensite plate cracks, ...

  16. Scaling laws for radial foil bearings

    Science.gov (United States)

    Honavara Prasad, Srikanth

    The effects of fluid pressurization, structural deformation of the compliant members and heat generation in foil bearings make the design and analysis of foil bearings very complicated. The complex fluid-structural-thermal interactions in foil bearings also make modeling efforts challenging because these phenomena are governed by highly non-linear partial differential equations. Consequently, comparison of various bearing designs require detailed calculation of the flow fields (velocities, pressures), bump deflections (structural compliance) and heat transfer phenomena (viscous dissipation in the fluid, frictional heating, temperature profile etc.,) resulting in extensive computational effort (time/hardware). To obviate rigorous computations and aid in feasibility assessments of foil bearings of various sizes, NASA developed the "rule of thumb" design guidelines for estimation of journal bearing load capacity. The guidelines are based on extensive experimental data. The goal of the current work is the development of scaling laws for radial foil bearings to establish an analytical "rule of thumb" for bearing clearance and bump stiffness. The use of scale invariant Reynolds equation and experimentally observed NASA "rule of thumb" yield scale factors which can be deduced from first principles. Power-law relationships between: a. Bearing clearance and bearing radius, and b. bump stiffness and bearing radius, are obtained. The clearance and bump stiffness values obtained from scaling laws are used as inputs for Orbit simulation to study various cases. As the clearance of the bearing reaches the dimensions of the material surface roughness, asperity contact breaks the fluid film which results in wear. Similarly, as the rotor diameter increases (requiring larger bearing diameters), the load capacity of the fluid film should increase to prevent dry rubbing. This imposes limits on the size of the rotor diameter and consequently bearing diameter. Therefore, this thesis aims

  17. Improvement of journal bearing operation at heavy misalignment using bearing flexibility and compliant liners

    DEFF Research Database (Denmark)

    Thomsen, Kim; Klit, Peder

    2012-01-01

    A flexure journal bearing design is proposed that will improve operational behaviour of a journal bearing at pronounced misalignment. Using a thermoelastohydrodynamic model, it is shown that the proposed flexure journal bearing has vastly increased the hydrodynamic performance compared to the stiff...... bearing when misaligned. The hydrodynamic performance is evaluated on lubricant film thickness, pressure and temperature. Furthermore, the influence of a compliant bearing liner is investigated and it is found that it increases the hydrodynamic performance when applied to a stiff bearing, whereas...... the liner has practically no influence on the flexure journal bearing's performance....

  18. Bearing/Bypass Material-Testing System

    Science.gov (United States)

    Crews, John H., Jr.

    1988-01-01

    System developed to test specimens in compression as well as tension while maintaining constant bearing/bypass ration. Test specimen with centrally located hole is clamped between two bearing-guide plates using one bolt. Bearing-guide plates then secured to two bearing-load cells. Test specimen independently loaded at both ends, using two separate control systems identified as applied and bypass. If two end loads unequal, difference between them reacted as bolt-bearing load on specimen. Throughout test, two control systems synchronized by common input signal (increasing voltage). As result, loads remain proportional as they increase.

  19. [Advances in studies on bear bile powder].

    Science.gov (United States)

    Zhou, Chao-fan; Gao, Guo-jian; Liu, Ying

    2015-04-01

    In this paper, a detailed analysis was made on relevant literatures about bear bile powder in terms of chemical component, pharmacological effect and clinical efficacy, indicating bear bile powder's significant pharmacological effects and clinical application in treating various diseases. Due to the complex composition, bear bile powder is relatively toxic. Therefore, efforts shall be made to study bear bile powder's pharmacological effects, clinical application, chemical composition and toxic side-effects, with the aim to provide a scientific basis for widespread reasonable clinical application of bear bile powder.

  20. Valve assembly having remotely replaceable bearings

    International Nuclear Information System (INIS)

    Johnson, E.R.; Tanner, D.E.

    1980-01-01

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

  1. A motor with superconducting magnetic bearings

    International Nuclear Information System (INIS)

    Gladun, A.; Stoye, P.; Verges, P.; Gawalek, W.; Habisreuther, T.; Goernert, P.

    1993-01-01

    Superconducting bearings may be one of the most promising near term applications of HTSC. For use at liquid nitrogen temperature and below, they offer the advantage of lower energy consumption and higher reliability. Different bearing configurations have been proposed. But in order to substitute for conventional bearings a further increase in the critical current density of the superconductor and improved bearing concepts are necessary. For this it is necessary to take into account the peculiarities of the interaction between permanent magnets and bulk superconductors. As a contribution to this programme we present the model of a motor with superconducting magnetic bearings. (orig.)

  2. Heuristic explanation of journal bearing instability

    Science.gov (United States)

    Crandall, S. H.

    1982-01-01

    A fluid-filled journal bearing is viewed as a powerful pump circulating fluid around the annular space between the journal and the bearing. A small whirling motion of the journal generates a wave of thickness variation progressing around the channel. The hypothesis that the fluid flow drives the whirl whenever the mean of the pumped fluid velocity is greater than the peripheral speed of the thickness variation wave is discussed and compared with other simple explanations of journal bearing instability. It is shown that for non-cavitation long bearings the hypothesis predicts instability onset correctly for unloaded bearings but gradually overpredicts the onset speed as the load is increased.

  3. A reliability approach to machine tool bearings

    International Nuclear Information System (INIS)

    Jia Yazhou; Shen Guixiang; Jia Zhixin

    1995-01-01

    Based on the machine tool working characteristics, a method to determine the bearing dynamic load rating with a specified reliability is presented. Unlike the conventional methods for machine tool bearing design which are almost empirical, the proposed method is based on the bearing fatigue reliability. Also, unlike the common design methods of other industrial bearings which cannot consider the machine tool peculiarity, the obtained method is based on power and torque characteristics of machine tools. Designing the machine tool bearings by use of the method can obtain the expected reliability

  4. Ball Bearing Analysis with the ORBIS Tool

    Science.gov (United States)

    Halpin, Jacob D.

    2016-01-01

    Ball bearing design is critical to the success of aerospace mechanisms. Key bearing performance parameters, such as load capability, stiffness, torque, and life all depend on accurate determination of the internal load distribution. Hence, a good analytical bearing tool that provides both comprehensive capabilities and reliable results becomes a significant asset to the engineer. This paper introduces the ORBIS bearing tool. A discussion of key modeling assumptions and a technical overview is provided. Numerous validation studies and case studies using the ORBIS tool are presented. All results suggest the ORBIS code closely correlates to predictions on bearing internal load distributions, stiffness, deflection and stresses.

  5. Improvement of journal bearing operation at heavy misalignment using bearing flexibility and compliant liners

    OpenAIRE

    Thomsen, Kim; Klit, Peder

    2012-01-01

    A flexure journal bearing design is proposed that will improve operational behaviour of a journal bearing at pronounced misalignment. Using a thermoelastohydrodynamic model, it is shown that the proposed flexure journal bearing has vastly increased the hydrodynamic performance compared to the stiff bearing when misaligned. The hydrodynamic performance is evaluated on lubricant film thickness, pressure and temperature. Furthermore, the influence of a compliant bearing liner is investigated and...

  6. Coupled Dynamics of a Rotor-Journal Bearing System Equipped with Thrust Bearings

    OpenAIRE

    Yu Lie; R.B. Bhat

    1995-01-01

    The rotordynamic coefficients of fixed-pad thrust bearing are introduced and calculated by using the out-domain method, and a general analysis method is developed to investigate the coupled dynamics of a rotor equipped with journal and thrust bearings simultaneously. Considerations include the effects of static tilt parameters of the rotor on rotordynamic coefficients of thrust bearing and the action of thrust bearing on system dynamics. It is shown that thrust bearing changes the load distri...

  7. Chromatographic (TLC) differentiation of grizzly bear and black bear scats

    Science.gov (United States)

    Picton, Harold D.; Kendall, Katherine C.

    1994-01-01

    While past work concluded that thin-layer chromatography (TLC) was inadequate for the separation of grizzly (Ursus arctos horribilis) and black bear (U. americanus) scats, our study found differences adequate for species separation. A key was constructed using 19 of 40 data points recorded on each(N)=356 profiles of 178) know-species scat. Accuracy was best for late summer scats (94%). Methods for specimen preparation, analysis, and reading the TLC profiles are discussed. Factors involved in scat variation were tested.

  8. A prototype construction of bearing heater system

    International Nuclear Information System (INIS)

    Firman Silitonga

    2007-01-01

    A bearing heater system has been successfully constructed using transformer-like method of 1000 VA power, 220 V primary voltage, and 50 Hz electrical frequency. The bearing heater consists of primary coil 230 turns, U type and bar-type iron core with 36 cm 2 , 9 cm 2 ,and 3 cm 2 cross-section, and electrical isolation. The bearing heater is used to enlarge the diameter of the bearing so that it can be easily fixed on an electric motor shaft during replacement because the heating is conducted by treated the bearing as a secondary coil of a transformer. This bearing heater can be used for bearing with 3 and 6 cm of inner diameter and 12 cm of maximum outside diameter. (author)

  9. Noise of oil lubricated journal bearings

    International Nuclear Information System (INIS)

    Rho, Byoung Hoo; Kim, Kyung Woong

    2002-01-01

    The purpose of the paper is to provide a procedure to calculate the noise of oil lubricated journal bearings. To do this, the nonlinear transient analysis of rotor-bearing system including rotor imbalance is performed. Acoustical properties of the bearing are investigated through frequency analysis of the pressure fluctuation of the fluid film calculated from the nonlinear analysis. Furthermore, a transmission theory of plane waves on a boundary of the outer surface of the bearing is used to obtain the sound pressure level of the bearing. Results show that the sound pressure level of the bearing can be increased with the rotational speed of the rotor although the whirl amplitude of the rotor is decreased at high speed. Noise estimating procedures presented in this paper could be an aid in the evaluation and understanding of acoustical properties of oil lubricated journal bearings

  10. Evaluation of rotating, incompressibly lubricated, pressurized thrust bearings

    Science.gov (United States)

    Fleming, D. P.

    1971-01-01

    Program evaluates a series hybrid, fluid film ball bearing consisting of an orifice compensated pressurized thrust bearing in conjunction with a self-acting journal bearing. Oil viscosities corresponding to experimentally measured ball bearing outer-race temperatures were used.

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

    Science.gov (United States)

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

    2015-03-01

    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. © 2014 The Authors. Molecular Ecology Published by John Wiley & Sons Ltd.

  12. Kortervilla : elamu Kreutzwaldi tn. 10 Tallinnas = Apartment villa : residential building at F. R. Kreutzwaldi st. 10 in Tallinn / Urmas Oja

    Index Scriptorium Estoniae

    Oja, Urmas, 1981-2012

    2005-01-01

    Endise Eesti Telefoni keskjaama rekonstrueerimine korterelamuks. Projekteerija: Agabush, Endjärv & Truverk Arhitektid OÜ. Autorid: Eero Endjärv, Mattias Agabush, Illimar Truverk. Konstruktor Tõnu Peipman. Projekt 2003, valmis 2004. Ill.: II, III, IV ja V korruse plaanid, 2 värv. välis- ja 2 sisevaadet

  13. Conditioning of alpha bearing wastes

    International Nuclear Information System (INIS)

    1991-01-01

    Alpha bearing wastes are generated during the reprocessing of spent fuel, mixed oxide fuel fabrication, decommissioning and other activities. The safe and effective management of these wastes is of particular importance owing to the radiotoxicity and long lived characteristics of certain transuranic (TRU) elements. The management of alpha bearing wastes involves a number of stages which include collection, characterization, segregation, treatment, conditioning, transport, storage and disposal. This report describes the currently available matrices and technologies for the conditioning of alpha wastes and relates them to their compatibility with the other stages of the waste management process. The selection of a specific immobilization process is dependent on the waste treatment state and the subsequent handling, transport, storage and disposal requirements. The overall objectives of immobilization are similar for all waste producers and processors, which are to produce: (a) Waste forms with sufficient mechanical, physical and chemical stability to satisfy all stages of handling, transport and storage (referred to as the short term requirements), and (b) Waste forms which will satisfy disposal requirements and inhibit the release of radionuclides to the biosphere (referred to as the long term requirements). Cement and bitumen processes have already been successfully applied to alpha waste conditioning on the industrial scale in many of the IAEA Member States. Cement systems based on BFS and pozzolanic cements have emerged as the principal encapsulation matrices for the full range of alpha bearing wastes. Alternative technologies, such as polymers and ceramics, are being developed for specific waste streams but are unlikely to meet widespread application owing to cost and process complexity. The merits of alpha waste conditioning are improved performance in transport, storage and disposal combined with enhanced public perception of waste management operations. These

  14. Precision magnetic suspension linear bearing

    Science.gov (United States)

    Trumper, David L.; Queen, Michael A.

    1992-01-01

    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.

  15. Comparison of Alignment Correction Angles Between Fixed-Bearing and Mobile-Bearing UKA.

    Science.gov (United States)

    Inoue, Atsuo; Arai, Yuji; Nakagawa, Shuji; Inoue, Hiroaki; Yamazoe, Shoichi; Kubo, Toshikazu

    2016-01-01

    Good outcomes have been reported with both fixed-bearing and mobile-bearing unicompartmental knee arthroplasty (UKA). However, overcorrected alignment could induce the progression of arthritis on the non-arthroplasty side. Changes of limb alignment after UKA with both types of bearings (fixed bearing: 24 knees, mobile bearing: 28 knees) were investigated. The mean difference between the preoperative standing femoral-tibial angle (FTA) and postoperative standing FTA was significantly larger in mobile bearing UKA group. In fixed-bearing UKA, there must be some laxity in MCL tension so that a 2-mm tension gauge can be inserted. In mobile-bearing UKA, appropriate MCL tension is needed to prevent bearing dislocation. This difference in MCL tension may have caused the difference in the correction angle between the groups. Copyright © 2016 Elsevier Inc. All rights reserved.

  16. Seismic isolation rubber bearings for nuclear facilities

    International Nuclear Information System (INIS)

    Fujita, Takafumi

    1991-01-01

    This paper describes results of biaxial breaking tests by compression and shear and by tension and shear for seismic isolation rubber bearings with bolted-type connections. The bearings used in the tests were low-damping rubber bearings, high-damping rubber bearings, and lead-rubber bearings. Three modes of failure of the bolted-type bearings were observed in the tests. They are the breaking failure by tension and shear; the breaking failure by compression and shear; and the buckling failure by compression and shear. The first and the second modes of failures are almost independent of the types and the sizes of the bearings. The breaking conditions of those failure modes are described in the axial-stress-shear-strain plane. This expression is useful for the evaluation of safety margins of the bearings. The paper outlines the basic design of the nuclear-grade bearings which were used for large-scale rubber bearing tests in a research project for seismic isolation of FBR plants. It also discusses the protection method against aging and the quality control which are important for implementation. (orig./HP)

  17. Seismic isolation rubber bearings for nuclear facilities

    International Nuclear Information System (INIS)

    Fujita, Takafumi

    1989-01-01

    This paper describes results of biaxial breaking tests by compression and shear and by tension and shear for seismic isolation rubber bearings with bolted-type connections. The bearings used in the tests were low-damping rubber bearings, high-damping rubber bearings, and lead-rubber bearings. Three modes of failure of the bolted-type bearings were observed in the tests. They are the breaking failure by tension and shear; the breaking failure by compression and shear; and the buckling failure by compression and shear. The first and the second modes of failures are almost independent of the types and the sizes of the bearings. The breaking conditions of those failure modes are described in the axial stress-shear strain plane. This expression is useful for the evaluation of safety margins of the bearings. The paper outlines the basic design of the nuclear-grade bearings which were used for large-scale rubber bearing tests in a research project for seismic isolation of fast breeder reactor (FBR) plants. The paper also discusses the protection method against aging and the quality control which are important for implementation

  18. Coupled Dynamics of a Rotor-Journal Bearing System Equipped with Thrust Bearings

    Directory of Open Access Journals (Sweden)

    Yu Lie

    1995-01-01

    Full Text Available The rotordynamic coefficients of fixed-pad thrust bearing are introduced and calculated by using the out-domain method, and a general analysis method is developed to investigate the coupled dynamics of a rotor equipped with journal and thrust bearings simultaneously. Considerations include the effects of static tilt parameters of the rotor on rotordynamic coefficients of thrust bearing and the action of thrust bearing on system dynamics. It is shown that thrust bearing changes the load distribution of journal bearings and the static deflection of the rotor and delays the instability of the system considerably in lateral shaft vibration.

  19. The dual action gas thrust bearing - A new high load bearing concept

    Science.gov (United States)

    Etsion, I.

    1976-01-01

    The principle of utilizing hydrodynamic effects in diverging films for improving load capacity in gas thrust bearings is discussed. A new concept of dual action bearing based on that principle is described and analyzed. The potential of the new bearing is demonstrated both analytically for an infinitely long slider and by numerical solution for a flat sector shaped thrust bearing. It is shown that the dual action bearing can extend substantially the range of load carrying capacity in gas lubricated thrust bearings and improve their efficiency.

  20. Construction of gas suspended bearings (radial and axial gas ball bearings)

    International Nuclear Information System (INIS)

    Kaspar, G.

    1974-10-01

    This report contains practical and theoretical results that were obtained at IPP in the section of gas suspended bearings. The two air-cushioned, air-driven revolving mirrors and an air-cushioned, air measuring coil drive were built. The latter has a double radial bearing and a single axial bearing. The axial bearing is shaped in such a way that, with slight throttling of the air feed, i.e. at low air intake pressure, a relatively high bearing load can be imposed and the bearing remains at the same time free of the so-called air hammer effect. (orig.) [de

  1. Electron beam melting of bearing materials

    Energy Technology Data Exchange (ETDEWEB)

    Goldschmied, G.; Schuler, A. (Technische Univ., Vienna (Austria). Inst. fuer Allgemeine Elektrotechnik); Elsinger, G.; Koroschetz, F. (MIBA Gleitlager AG, Laakirchen (Austria)); Tschegg, E.K. (Technische Univ., Vienna (Austria). Inst. fuer Angewandte und Technische Physik)

    1990-06-01

    This paper reports on a surface treatment method for the bearing materials AlSn6 which permits the use of this material without the overlay usually required. Microstructural refinement is achieved by means of a surface melting technique using an electron beam with successive rapid solidification. Extremely fine tin precipitates are formed in the melted surface layer which lead to significantly better tribological properties of the bearing material. Tests compared the tribological properties for AlSn6 bearings treated by the surface melting technique with those of untreated bearings. Whereas all untreated bearings failed by seizure after only 2 h of testing, 30% of the tested bearings which had been surface melted survived the entire testing program without damage.

  2. Bearing Health Assessment Based on Chaotic Characteristics

    Directory of Open Access Journals (Sweden)

    Chen Lu

    2013-01-01

    Full Text Available Vibration signals extracted from rotating parts of machinery carry a lot of useful information about the condition of operating machine. Due to the strong non-linear, complex and non-stationary characteristics of vibration signals from working bearings, an accurate and reliable health assessment method for bearing is necessary. This paper proposes to utilize the selected chaotic characteristics of vibration signal for health assessment of a bearing by using self-organizing map (SOM. Both Grassberger-Procaccia algorithm and Takens' theory are employed to calculate the characteristic vector which includes three chaotic characteristics, such as correlation dimension, largest Lyapunov exponent and Kolmogorov entropy. After that, SOM is used to map the three corresponding characteristics into a confidence value (CV which represents the health state of the bearing. Finally, a case study based on vibration datasets of a group of testing bearings was conducted to demonstrate that the proposed method can reliably assess the health state of bearing.

  3. Are organohalogen contaminants a bears (Ursus maritimus)?

    DEFF Research Database (Denmark)

    Sonne, Christian; Dietz, Rune; Leifsson, PS

    2006-01-01

    Tissues of polar bears (Ursus maritimus) from East Greenland contain the highest concentrations of organohalogen contaminants (OHCs) among subpopulations of any mammalian species in the Arctic. Negative associations also have been found between OHC concentrations and bone mineral density and liver...... histology parameters for this subpopulation of polar bears. The present study examined the OHC concentrations and adverse effects on renal tissue for 75 polar bears collected during 1999 to 2002. Specific lesions were diffuse glomerular capillary wall thickening, mesangial glomerular deposits, tubular...

  4. Deterioration Assessment of Bridge Rubber Bearings

    OpenAIRE

    Gu, Haosheng; 伊藤, 義人; Itoh, Yoshito

    2005-01-01

    Natural rubber (NR) with lead plugs and high damping rubber (HDR) are often used for base-isolated rubber bearings. However, it is usually known that ageing causes rubber performance to drop. This research is to study the deterioration characteristics of these two kinds of bridge rubber bearings through accelerated thermal oxidation tests. The property variations inside the aged rubber blocks are investigated. For natural rubber bearing, the mechanical properties on the surface change the mos...

  5. BEARING TESTS FOR THE SPUR TURBOGENERATOR.

    Science.gov (United States)

    The results of the liquid-potassium journalbearing test program for the SPUR turbogenerator are presented. The activities described include the design, assembly and checkout of the bearing test rig, and the results of a successfully completed 250-h endurance test on a hydrodynamic journal bearing using 600 F liquid potassium as the lubricant. Unidirectional loads from 6 to 25 lbs were applied to the bearing operating at a speed of 24,000 rpm. (Author)

  6. Technical Development Path for Gas Foil Bearings

    Science.gov (United States)

    Dellacorte, Christopher

    2016-01-01

    Foil gas bearings are in widespread commercial use in air cycle machines, turbocompressors and microturbine generators and are emerging in more challenging applications such as turbochargers, auxiliary power units and propulsion gas turbines. Though not well known, foil bearing technology is well over fifty years old. Recent technological developments indicate that their full potential has yet to be realized. This paper investigates the key technological developments that have characterized foil bearing advances. It is expected that a better understanding of foil gas bearing development path will aid in future development and progress towards more advanced applications.

  7. Nuclear genomic sequences reveal that polar bears are an old and distinct bear lineage.

    Science.gov (United States)

    Hailer, Frank; Kutschera, Verena E; Hallström, Björn M; Klassert, Denise; Fain, Steven R; Leonard, Jennifer A; Arnason, Ulfur; Janke, Axel

    2012-04-20

    Recent studies have shown that the polar bear matriline (mitochondrial DNA) evolved from a brown bear lineage since the late Pleistocene, potentially indicating rapid speciation and adaption to arctic conditions. Here, we present a high-resolution data set from multiple independent loci across the nuclear genomes of a broad sample of polar, brown, and black bears. Bayesian coalescent analyses place polar bears outside the brown bear clade and date the divergence much earlier, in the middle Pleistocene, about 600 (338 to 934) thousand years ago. This provides more time for polar bear evolution and confirms previous suggestions that polar bears carry introgressed brown bear mitochondrial DNA due to past hybridization. Our results highlight that multilocus genomic analyses are crucial for an accurate understanding of evolutionary history.

  8. Experimental Evaluation of Journal Bearing Stability and New Gas Bearing Material

    Science.gov (United States)

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

    2001-01-01

    It has been estimated that the noise levels in aircraft engine transmissions can be reduced by as much as 10 dB through the use of journal bearings. The potential benefits of lower noise levels include reduced wear, longer gear life and enhanced comfort for passengers and crew. Based on this concept the journal-thrust wave bearing was analyzed and its performance was evaluated. Numerical codes, developed over the past 30 years by Dr. Dimofte, were used to predict the performance of the bearing. The wave bearing is a fluid film bearing and therefore was analyzed using the Reynolds pressure equation. The formulation includes turbulent flow concepts and possesses a viscosity-temperature correction. The centrifugal growth of the bearing diameter and the deformation of the bearing under gear loads were also incorporated into the code. An experimental rig was developed to test the journal-thrust wave bearing.

  9. Gearbox Reliability Collaborative Bearing Calibration

    Energy Technology Data Exchange (ETDEWEB)

    van Dam, J.

    2011-10-01

    NREL has initiated the Gearbox Reliability Collaborative (GRC) to investigate the root cause of the low wind turbine gearbox reliability. The GRC follows a multi-pronged approach based on a collaborative of manufacturers, owners, researchers and consultants. The project combines analysis, field testing, dynamometer testing, condition monitoring, and the development and population of a gearbox failure database. At the core of the project are two 750kW gearboxes that have been redesigned and rebuilt so that they are representative of the multi-megawatt gearbox topology currently used in the industry. These gearboxes are heavily instrumented and are tested in the field and on the dynamometer. This report discusses the bearing calibrations of the gearboxes.

  10. Treatment of alpha bearing wastes

    International Nuclear Information System (INIS)

    1988-01-01

    This report deals with the current state of the art of alpha waste treatment, which is an integral part of the overall nuclear waste management system. The International Atomic Energy Agency (IAEA) defines alpha bearing waste as 'waste containing one or more alpha emitting radionuclides, usually actinides, in quantities above acceptable limits'. The limits are established by national regulatory bodies. The limits above which wastes are considered as alpha contaminated refer to the concentrations of alpha emitters that need special consideration for occupational exposures and/or potential safety, health, or environmental impact during one or more steps from generation through disposal. Owing to the widespread use of waste segregation by source - that is, based upon the 'suspect origin' of the material - significant volumes of waste are being handled as alpha contaminated which, in fact, do not require such consideration by reason of risk or environmental concern. The quantification of de minimis concepts by national regulatory bodies could largely contribute to the safe reduction of waste volumes and associated costs. Other factors which could significantly contribute to the reduction of alpha waste arisings are an increased application of assaying and sorting, instrumentation and the use of feedback mechanisms to control or modify the processes which generate these wastes. Alpha bearing wastes are generated during fabrication and reprocessing of nuclear fuels, decommissioning of alpha contaminated facilities, and other activities. Most alpha wastes are contact handled, but a small portion may require shielding or remote handling because of high levels of neutron (n), beta (β), or gamma (γ) emissions associated with the waste material. This report describes the sources and characteristics of alpha wastes and strategies for alpha waste management. General descriptions of treatment processes for solid and liquid alpha wastes are included. 71 refs, 14 figs, 9 tabs

  11. Long-term bearing wear tests of conventional journal bearings and development of hydrostatic bearings for the LOFT drag-disc turbine transducer

    International Nuclear Information System (INIS)

    Fincke, J.R.

    1979-01-01

    The details of a two-year development program concerning materials for use as turbine bearings in a pressurized water reactor environment are reported. Two types of bearings have been examined, both conventional journal bearings and hydrostatic bearings. The results of long-term bearing wear tests conducted at 590 K and 15.1 MPa in water are presented. The feasibility of using hydrostatic bearings for the same transducer is demonstrated

  12. Rolling Bearing Life Prediction, Theory, and Application

    Science.gov (United States)

    Zaretsky, Erwin V.

    2016-01-01

    A tutorial is presented outlining the evolution, theory, and application of rolling-element bearing life prediction from that of A. Palmgren, 1924; W. Weibull, 1939; G. Lundberg and A. Palmgren, 1947 and 1952; E. Ioannides and T. Harris, 1985; and E. Zaretsky, 1987. Comparisons are made between these life models. The Ioannides-Harris model without a fatigue limit is identical to the Lundberg-Palmgren model. The Weibull model is similar to that of Zaretsky if the exponents are chosen to be identical. Both the load-life and Hertz stress-life relations of Weibull, Lundberg and Palmgren, and Ioannides and Harris reflect a strong dependence on the Weibull slope. The Zaretsky model decouples the dependence of the critical shear stress-life relation from the Weibull slope. This results in a nominal variation of the Hertz stress-life exponent. For 9th- and 8th-power Hertz stress-life exponents for ball and roller bearings, respectively, the Lundberg-Palmgren model best predicts life. However, for 12th- and 10th-power relations reflected by modern bearing steels, the Zaretsky model based on the Weibull equation is superior. Under the range of stresses examined, the use of a fatigue limit would suggest that (for most operating conditions under which a rolling-element bearing will operate) the bearing will not fail from classical rolling-element fatigue. Realistically, this is not the case. The use of a fatigue limit will significantly overpredict life over a range of normal operating Hertz stresses. (The use of ISO 281:2007 with a fatigue limit in these calculations would result in a bearing life approaching infinity.) Since the predicted lives of rolling-element bearings are high, the problem can become one of undersizing a bearing for a particular application. Rules had been developed to distinguish and compare predicted lives with those actually obtained. Based upon field and test results of 51 ball and roller bearing sets, 98 percent of these bearing sets had acceptable

  13. State Space Formulation of Nonlinear Vibration Responses Collected from a Dynamic Rotor-Bearing System: An Extension of Bearing Diagnostics to Bearing Prognostics

    Directory of Open Access Journals (Sweden)

    Peter W. Tse

    2017-02-01

    Full Text Available Bearings are widely used in various industries to support rotating shafts. Their failures accelerate failures of other adjacent components and may cause unexpected machine breakdowns. In recent years, nonlinear vibration responses collected from a dynamic rotor-bearing system have been widely analyzed for bearing diagnostics. Numerous methods have been proposed to identify different bearing faults. However, these methods are unable to predict the future health conditions of bearings. To extend bearing diagnostics to bearing prognostics, this paper reports the design of a state space formulation of nonlinear vibration responses collected from a dynamic rotor-bearing system in order to intelligently predict bearing remaining useful life (RUL. Firstly, analyses of nonlinear vibration responses were conducted to construct a bearing health indicator (BHI so as to assess the current bearing health condition. Secondly, a state space model of the BHI was developed to mathematically track the health evolution of the BHI. Thirdly, unscented particle filtering was used to predict bearing RUL. Lastly, a new bearing acceleration life testing setup was designed to collect natural bearing degradation data, which were used to validate the effectiveness of the proposed bearing prognostic method. Results show that the prediction accuracy of the proposed bearing prognostic method is promising and the proposed bearing prognostic method is able to reflect future bearing health conditions.

  14. Shaft Center Orbit in Dynamically Loaded Bearings

    DEFF Research Database (Denmark)

    Klit, Peder

    2005-01-01

    The aim of this work is to demonstrate how to utilize the bearings damping coe±cients to estimate the orbit for a dynamically loaded journal bearing. The classical method for this analysis was developed by Booker in 1965 [1]and described further in 1972 [2]. Several authors have re¯ned this metho...

  15. INVESTIGATION OF SHALLOW FOUNDATION SOIL BEARING ...

    African Journals Online (AJOL)

    This study investigated the soil bearing capacity and foundation settlement characteristics of Minna City Centre development site using standard penetration test (SPT) data obtained from10 SPT boreholes at 0.6, 2.1 and 3.6 m depths to correlate soil properties. Evaluation of foundation bearing capacity and settlement ...

  16. INVESTIGATION OF ANGULAR BALL BEARING WEAR

    Directory of Open Access Journals (Sweden)

    A. L. Savchenko

    2006-01-01

    Full Text Available Wearing process of balls in an angular ball bearing has been investigated in the paper. Force affecting a separator from the side of balls is determined theoretically. Wear rate may be calculated with a formula for abrasive wear while substituting numerical parameter values of the investigated ball bearing for formula symbols.

  17. On the dynamics of ball bearings

    NARCIS (Netherlands)

    Wensing, J.A.

    1998-01-01

    This investigation on the dynamic behaviour of ball bearings was motivated by the demand for silent bearings in noise-sensitive applications, especially in the household appliance and automotive industry. The present investigations are intended to provide a clear understanding of the role of the

  18. Hydrodynamic Lubrication Analysis Of Slider Bearings Lubricated ...

    African Journals Online (AJOL)

    Hydrodynamic Lubrication Analysis Of Slider Bearings Lubricated With Micropolar Fluids. ... In this paper, a theoretical study of the effect of micropolar lubricants on the performance characteristics of wide inclined slider bearings is presented. The finite element method and Gauss Seidel iterative procedure have been used ...

  19. 33 CFR 117.543 - Bear Creek.

    Science.gov (United States)

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Bear Creek. 117.543 Section 117.543 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY BRIDGES DRAWBRIDGE OPERATION REGULATIONS Specific Requirements Maryland § 117.543 Bear Creek. (a) The draws of the Baltimore...

  20. Friction coefficients of PTFE bearing liner

    Science.gov (United States)

    Daniels, C. M.

    1979-01-01

    Data discusses frictional characteristics of PTFE (polytetrafluoroethylene) under temperature extremes and in vacuum environment. Tests were also run on reduced scale hardware to determine effects of vacuum. Data is used as reference by designers of aircraft-control system rod-end bearings and for bearings used in polar regions.

  1. BEARING ANALYSIS FOR THE SPUR TURBOGENERATOR.

    Science.gov (United States)

    The results of the analysis of journal bearing configuration for the SPUR turbogenerator are presented in this report. For this analysis, a computer...laminar analysis agreed with existing solutions, thereby providing a check of the computer program. Several journal bearing mounting arrangements were considered, and a design was selected for initial testing. (Author)

  2. Protecting a Ball-Bearing-Deflection Monitor

    Science.gov (United States)

    Kuhr, George A.

    1987-01-01

    Deflectometer probe monitors deflection of ball-bearing race in liquid oxygen with aid of small window or diaphragm. Diaphragm or window isolates optical deflectometer from liquid oxygen or other fluid in ball bearing. At high pressures, diaphragm integral part of housing preferable to window, since there would be no leakage.

  3. Rotor Vibration Reduction via Active Hybrid Bearings

    DEFF Research Database (Denmark)

    Nicoletti, Rodrigo; Santos, Ilmar

    2002-01-01

    orifices machined in the bearing pads, one can alter the machine dynamic characteristics, thus enhancing its operational range. A mathematical model of the rotor-bearing system, as well as of the hydraulic system, is presented. Numerical results of the system frequency response show good agreement...

  4. Can polar bear hairs absorb environmental energy?

    OpenAIRE

    He Ji-Huan; Wang Qing-Li; Sun Jie

    2011-01-01

    A polar bear (Ursus maritimus) has superior ability to survive in harsh Arctic regions, why does the animal have such an excellent thermal protection? The present paper finds that the unique labyrinth cavity structure of the polar bear hair plays an important role. The hair can not only prevent body temperature loss but can also absorb energy from the environment.

  5. Can polar bear hairs absorb environmental energy?

    Directory of Open Access Journals (Sweden)

    He Ji-Huan

    2011-01-01

    Full Text Available A polar bear (Ursus maritimus has superior ability to survive in harsh Arctic regions, why does the animal have such an excellent thermal protection? The present paper finds that the unique labyrinth cavity structure of the polar bear hair plays an important role. The hair can not only prevent body temperature loss but can also absorb energy from the environment.

  6. TEMPERATURE DIAGNOSTICS OF GAS TURBINE ENGINE BEARINGS

    Directory of Open Access Journals (Sweden)

    R. V. Birukov

    2014-01-01

    Full Text Available The objective of the current research was to develop methodology for diagnosing industrial gas turbine engine bearings using the standard performance parameters. This paper presents mathematical thermal model of combined thrust and radial bearing and provides the model application examples for diagnostics.

  7. Gas Lubricated Foil Bearing Development for Advanced Turbomachines

    Science.gov (United States)

    1977-03-01

    Rear Journal Bearing Runner 29 3.1.6 Forward Journal Bearing Runner Stress and DefJection Analysis 32 3.1.7 Critical Speed Analysis 35 3.1.8 Thermal...Analysis 39 3.1.8.1 Journal Bearing Temperatures 42 3.1.8.2 Thrust Bearing Temperatures 50 3.2 Design 56 3.2.1 Baseline Bearing Design 56 3.2.1.1 Journal ... Bearing Baseline Design 57 3.2.1.2 Thrust Bearing Baseline Design 59 3.2.2 Thrust Bearing Test Rig Design 61 3.2.3 Journal Bearing Test Rig Design 63

  8. Transient response of two lobe aerodynamic journal bearing

    Directory of Open Access Journals (Sweden)

    Saurabh Kumar Yadav

    2018-03-01

    Full Text Available The dynamic behavior of a rotor-dynamic system is greatly affected by the performance of aerodynamic bearing and the performance of bearing is characterized by the stiffness and damping coefficients. In the present work, stiffness and damping coefficients of bearing are computed and the performance of the bearing is greatly changed with the change in bearing air film profile. The effect of lobe offset factors on the transient performance of aerodynamic bearing is presented. Bifurcation and Poincare diagrams of two lobe journal bearing have been presented for different offset factors. A bearing designer can judge the bearing performance based on bifurcation diagrams.

  9. The dynamic state monitoring of bearings system

    Directory of Open Access Journals (Sweden)

    Marek Krynke

    2015-03-01

    Full Text Available The article discusses the methods of dynamic state monitoring of bearings system. A vibration signal contains important technical information about the machine condition and is currently the most frequently used in diagnostic bearings systems. One of the main ad-vantages of machine condition monitoring is identifying the cause of failure of the bearings and taking preventative measures, otherwise the operation of such a machine will lead to frequent replacement of the bearings. Monitoring changes in the course of the operation of machin-ery repair strategies allows keeping the conditioned state of dynamic failure conditioned preventive repairs and repairs after-failure time. In addition, the paper also presents the fundamental causes of bearing failure and identifies mechanisms related to the creation of any type of damage.

  10. Trends in Controllable Oil Film Bearings

    DEFF Research Database (Denmark)

    Santos, Ilmar

    2011-01-01

    This work gives an overview about the theoretical and experimental achievements of mechatronics applied to oil film bearings, with the aim of: controlling the lateral vibration of flexible rotating shafts; modifying bearing dynamic characteristics, as stiffness and damping properties; increasing...... the rotational speed ranges by improving damping and eliminating instability problems, for example, by compensating cross-coupling destabilizing effects; reducing startup torque and energy dissipation in bearings; compensating thermal effects. It is shown that such controllable bearings can act as "smart......" components and be applied to rotating machines with the goal of avoiding unexpected stops of plants, performing rotordynamic tests and identifying model parameters "on site". Emphasis is given to the controllable lubrication (active lubrication) applied to different types of oil film bearings, i...

  11. Development of gadolinia bearing fuel for PWR

    International Nuclear Information System (INIS)

    Seki, Kazuichiro

    1986-01-01

    In the PWR power plants in Japan, the long-period operation cycle was extended legally to a maximum of 13 months from the conventional about 9 months in fiscal 1980. With this move, as a new type of fuel with burnable-poison-rod function, the development was started of gadolinia-bearing (gadolinium oxide) fuel, gadolinia being contained in the fuel pellets. The basic technology studies were completed in fiscal 1984. Actual irradiation of the fuel in Unit 2 of the Oi Power Station was then started in July 1984, demonstrating validity of the design. Meanwhile, the rapid power-up fest and the fuel center temperature measurement are conducted in an overseas reactor from fiscal 1983. The following are described: functions of the burnable absorber, the need for gadolinia-bearing fuel, experiences with gadolinia-bearing fuel, problems in the design and production of gadolinia-bearing fuel, the development of gadolinia-bearing fuel. (Mori, K.)

  12. Geology and geomorphology of Bear Lake Valley and upper Bear River, Utah and Idaho

    Science.gov (United States)

    Reheis, M.C.; Laabs, B.J.C.; Kaufman, D.S.

    2009-01-01

    Bear Lake, on the Idaho-Utah border, lies in a fault-bounded valley through which the Bear River flows en route to the Great Salt Lake. Surficial deposits in the Bear Lake drainage basin provide a geologic context for interpretation of cores from Bear Lake deposits. In addition to groundwater discharge, Bear Lake received water and sediment from its own small drainage basin and sometimes from the Bear River and its glaciated headwaters. The lake basin interacts with the river in complex ways that are modulated by climatically induced lake-level changes, by the distribution of active Quaternary faults, and by the migration of the river across its fluvial fan north of the present lake. The upper Bear River flows northward for ???150 km from its headwaters in the northwestern Uinta Mountains, generally following the strike of regional Laramide and late Cenozoic structures. These structures likely also control the flow paths of groundwater that feeds Bear Lake, and groundwater-fed streams are the largest source of water when the lake is isolated from the Bear River. The present configuration of the Bear River with respect to Bear Lake Valley may not have been established until the late Pliocene. The absence of Uinta Range-derived quartzites in fluvial gravel on the crest of the Bear Lake Plateau east of Bear Lake suggests that the present headwaters were not part of the drainage basin in the late Tertiary. Newly mapped glacial deposits in the Bear River Range west of Bear Lake indicate several advances of valley glaciers that were probably coeval with glaciations in the Uinta Mountains. Much of the meltwater from these glaciers may have reached Bear Lake via groundwater pathways through infiltration in the karst terrain of the Bear River Range. At times during the Pleistocene, the Bear River flowed into Bear Lake and water level rose to the valley threshold at Nounan narrows. This threshold has been modified by aggradation, downcutting, and tectonics. Maximum lake

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

    Science.gov (United States)

    Dimofte, Florin

    1995-01-01

    To improve hydrodynamic journal bearing steady-state and dynamic performance, a new bearing concept, the wave journal bearing, was developed at the author's lab. This concept features a waved inner bearing diameter. Compared to other alternative bearing geometries used to improve bearing performance such as spiral or herring-bone grooves, steps, etc., the wave bearing's design is relatively simple and allows the shaft to rotate in either direction. A three-wave bearing operating with a compressible lubricant, i.e., gas is analyzed using a numerical code. Its performance is compared to a plain (truly) circular bearing over a broad range of bearing working parameters, e.g., bearing numbers from 0.01 to 100.

  14. 49 CFR 230.102 - Tender plain bearing journal boxes.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Tender plain bearing journal boxes. 230.102... Locomotives and Tenders Running Gear § 230.102 Tender plain bearing journal boxes. Plain bearing journal boxes... expected to damage the bearing; or have a detrimental effect on the lubrication of the journal and bearing...

  15. 24 CFR 3285.202 - Soil classifications and bearing capacity.

    Science.gov (United States)

    2010-04-01

    ... 24 Housing and Urban Development 5 2010-04-01 2010-04-01 false Soil classifications and bearing... Soil classifications and bearing capacity. The soil classification and bearing capacity of the soil... bearing capacity must be determined by one or more of the following methods, unless the soil bearing...

  16. Hydrodynamic air lubricated compliant surface bearing for an automotive gas turbine engine. 1: Journal bearing performance

    Science.gov (United States)

    Ruscitto, D.; Mccormick, J.; Gray, S.

    1978-01-01

    A 38.1 mm (1.5 inch) diameter Hydresil Compliant Surface Air Lubricated Journal Bearing was designed and tested to obtain bearing performance characteristics at both room temperature and 315 C (600 F). Testing was performed at various speeds up to 60,000 rpm with varying loads. Rotating sensors provided an opportunity to examine the film characteristics of the compliant surface bearing. In addition to providing minimum film thickness values and profiles, many other insights into bearing operation were gained such as the influence of bearing fabrication accuracy and the influence of smooth foil deflection between the bumps.

  17. Failure of GIMBAL bearing in directional GYRO

    International Nuclear Information System (INIS)

    Pervaiz, R.; Baig, N.A.; Shahid, M.; Ahmad, A.; Chohan, G.Y.

    2003-01-01

    This paper relates to the directional gyro of a sensing device used in indigenously developed surface-to-surface missile. The assembling of more than one thousand components in the form of several sub assemblies including hundreds of silver solders of this device was done in the hundred-thousands-class clean room according to assembly procedure. Whereas more than twenty bearings including gimbals bearings were assembled in the ten-thousands-class clean room after inspection/ testing them on beating testing system as per routine. The device was entered in testing and adjustment phase after successful completion of assembly work. The directional gyro qualified all the tests except the most critical one, the drift-rate. The drift-rate of outer gimbal was 60% more than permissible limit whereas drift-rate of inner gimbal was found O.K. It was diagnosed that at least one inner gimbal bearing out of two had some problem. The results were same after rebalancing of gimbals three times. The directional gyro was disassembled in clean room and the radial-thrust-bearing was recovered and flange bearing which are inner gimbal bearings. They were checked on bearing testing system and it was found that flange-bearing had more friction than permissible limit and hence rejected but radial thrust bearing were declared O.K. The gyro was reassembled with new O.K. flange bearing and the assembly work was completed in all respects. The sensing device qualified all the tests including the drift-rate. This case study is being presented to emphasize the importance of careful assembly of gyro in clean environment. (author)

  18. Genomic evidence of widespread admixture from polar bears into brown bears during the last ice age.

    Science.gov (United States)

    Cahill, James A; Heintzman, Peter D; Harris, Kelley; Teasdale, Matthew D; Kapp, Joshua; Soares, André E Rodrigues; Stirling, Ian; Bradley, Daniel; Edwards, Ceiridwen J; Graim, Kiley; Kisleika, Aliaksandr A; Malev, Alexander V; Monaghan, Nigel; Green, Richard E; Shapiro, Beth

    2018-02-20

    Recent genomic analyses have provided substantial evidence for past periods of gene flow from polar bears (Ursus maritimus) into Alaskan brown bears (Ursus arctos), with some analyses suggesting a link between climate change and genomic introgression. However, because it has mainly been possible to sample bears from the present day, the timing, frequency, and evolutionary significance of this admixture remains unknown. Here, we analyze genomic DNA from three additional and geographically distinct brown bear populations, including two that lived temporally close to the peak of the last ice age. We find evidence of admixture in all three populations, suggesting that admixture between these species has been common in their recent evolutionary history. In addition, analyses of ten fossil bears from the now-extinct Irish population indicate that admixture peaked during the last ice age, when brown bear and polar bear ranges overlapped. Following this peak, the proportion of polar bear ancestry in Irish brown bears declined rapidly until their extinction. Our results support a model in which ice age climate change created geographically widespread conditions conducive to admixture between polar bears and brown bears, as is again occurring today. We postulate that this model will be informative for many admixing species pairs impacted by climate change. Our results highlight the power of paleogenomics to reveal patterns of evolutionary change that are otherwise masked in contemporary data.

  19. Bear-ly” learning: Limits of abstraction in black bear cognition

    Directory of Open Access Journals (Sweden)

    Jennifer Vonk

    2018-02-01

    Full Text Available We presented two American black bears (Ursus americanus with a serial list learning memory task, and one of the bears with a matching-to-sample task. After extended training, both bears demonstrated some success with the memory task but failed to generalize the overarching rule of the task to novel stimuli. Matching to sample proved even more difficult for our bear to learn. We conclude that, despite previous success in training bears to respond to natural categories, quantity discriminations, and other related tasks, that bears may possess a cognitive limitation with regards to learning abstract rules. Future tests using different procedures are necessary to determine whether this is a limit of bears’ cognitive capacities, or a limitation of the current tasks as presented. Future tests should present a larger number of varying stimuli. Ideally, bears of various species should be tested on these tasks to demonstrate species as well as individual differences.

  20. Vibration quenching in a large scale rotor-bearing system using journal bearings with variable geometry

    Science.gov (United States)

    Chasalevris, Athanasios; Dohnal, Fadi

    2014-03-01

    In large scale rotating machinery the resonance amplitude during the passage through resonance is a matter of consideration because of its influence in the surrounding environment of the rotational system and foundation. In this paper, a variable geometry journal bearing (VGJB), recently patented, is applied for the mounting of a large scale rotor bearing system operating at the range of medium speed. The simulation of the rotor-bearing system incorporates a recent method for simulation of a multi-segment continuous rotor in combination with nonlinear bearing forces. The use of the current bearing gives results that encourage the use of such a bearing in rotating machinery since the vibration amplitude during the passage through the critical speed can be reduced up to 60-70%. In the presented study, the developed amplitude and the rotor stresses are severely reduced compared to those of the system with normal cylindrical journal bearings during a virtual start up of the system.

  1. Vibration model of rolling element bearings in a rotor-bearing system for fault diagnosis

    Science.gov (United States)

    Cong, Feiyun; Chen, Jin; Dong, Guangming; Pecht, Michael

    2013-04-01

    Rolling element bearing faults are among the main causes of breakdown in rotating machines. In this paper, a rolling bearing fault model is proposed based on the dynamic load analysis of a rotor-bearing system. The rotor impact factor is taken into consideration in the rolling bearing fault signal model. The defect load on the surface of the bearing is divided into two parts, the alternate load and the determinate load. The vibration response of the proposed fault signal model is investigated and the fault signal calculating equation is derived through dynamic and kinematic analysis. Outer race and inner race fault simulations are realized in the paper. The simulation process includes consideration of several parameters, such as the gravity of the rotor-bearing system, the imbalance of the rotor, and the location of the defect on the surface. The simulation results show that different amplitude contributions of the alternate load and determinate load will cause different envelope spectrum expressions. The rotating frequency sidebands will occur in the envelope spectrum in addition to the fault characteristic frequency. This appearance of sidebands will increase the difficulty of fault recognition in intelligent fault diagnosis. The experiments given in the paper have successfully verified the proposed signal model simulation results. The test rig design of the rotor bearing system simulated several operating conditions: (1) rotor bearing only; (2) rotor bearing with loader added; (3) rotor bearing with loader and rotor disk; and (4) bearing fault simulation without rotor influence. The results of the experiments have verified that the proposed rolling bearing signal model is important to the rolling bearing fault diagnosis of rotor-bearing systems.

  2. Polar bears and sea ice habitat change

    Science.gov (United States)

    Durner, George M.; Atwood, Todd C.; Butterworth, Andy

    2017-01-01

    The polar bear (Ursus maritimus) is an obligate apex predator of Arctic sea ice and as such can be affected by climate warming-induced changes in the extent and composition of pack ice and its impacts on their seal prey. Sea ice declines have negatively impacted some polar bear subpopulations through reduced energy input because of loss of hunting habitats, higher energy costs due to greater ice drift, ice fracturing and open water, and ultimately greater challenges to recruit young. Projections made from the output of global climate models suggest that polar bears in peripheral Arctic and sub-Arctic seas will be reduced in numbers or become extirpated by the end of the twenty-first century if the rate of climate warming continues on its present trajectory. The same projections also suggest that polar bears may persist in the high-latitude Arctic where heavy multiyear sea ice that has been typical in that region is being replaced by thinner annual ice. Underlying physical and biological oceanography provides clues as to why polar bear in some regions are negatively impacted, while bears in other regions have shown no apparent changes. However, continued declines in sea ice will eventually challenge the survival of polar bears and efforts to conserve them in all regions of the Arctic.

  3. Genetic control of biennial bearing in apple

    Science.gov (United States)

    Guitton, Baptiste; Kelner, Jean-Jacques; Velasco, Riccardo; Gardiner, Susan E.; Chagné, David; Costes, Evelyne

    2012-01-01

    Although flowering in mature fruit trees is recurrent, floral induction can be strongly inhibited by concurrent fruiting, leading to a pattern of irregular fruiting across consecutive years referred to as biennial bearing. The genetic determinants of biennial bearing in apple were investigated using the 114 flowering individuals from an F1 population of 122 genotypes, from a ‘Starkrimson’ (strong biennial bearer)בGranny Smith’ (regular bearer) cross. The number of inflorescences, and the number and the mass of harvested fruit were recorded over 6 years and used to calculate 26 variables and indices quantifying yield, precocity of production, and biennial bearing. Inflorescence traits exhibited the highest genotypic effect, and three quantitative trait loci (QTLs) on linkage group (LG) 4, LG8, and LG10 explained 50% of the phenotypic variability for biennial bearing. Apple orthologues of flowering and hormone-related genes were retrieved from the whole-genome assembly of ‘Golden Delicious’ and their position was compared with QTLs. Four main genomic regions that contain floral integrator genes, meristem identity genes, and gibberellin oxidase genes co-located with QTLs. The results indicated that flowering genes are less likely to be responsible for biennial bearing than hormone-related genes. New hypotheses for the control of biennial bearing emerged from QTL and candidate gene co-locations and suggest the involvement of different physiological processes such as the regulation of flowering genes by hormones. The correlation between tree architecture and biennial bearing is also discussed. PMID:21963613

  4. Genomic sequencing of Pleistocene cave bears

    Energy Technology Data Exchange (ETDEWEB)

    Noonan, James P.; Hofreiter, Michael; Smith, Doug; Priest, JamesR.; Rohland, Nadin; Rabeder, Gernot; Krause, Johannes; Detter, J. Chris; Paabo, Svante; Rubin, Edward M.

    2005-04-01

    Despite the information content of genomic DNA, ancient DNA studies to date have largely been limited to amplification of mitochondrial DNA due to technical hurdles such as contamination and degradation of ancient DNAs. In this study, we describe two metagenomic libraries constructed using unamplified DNA extracted from the bones of two 40,000-year-old extinct cave bears. Analysis of {approx}1 Mb of sequence from each library showed that, despite significant microbial contamination, 5.8 percent and 1.1 percent of clones in the libraries contain cave bear inserts, yielding 26,861 bp of cave bear genome sequence. Alignment of this sequence to the dog genome, the closest sequenced genome to cave bear in terms of evolutionary distance, revealed roughly the expected ratio of cave bear exons, repeats and conserved noncoding sequences. Only 0.04 percent of all clones sequenced were derived from contamination with modern human DNA. Comparison of cave bear with orthologous sequences from several modern bear species revealed the evolutionary relationship of these lineages. Using the metagenomic approach described here, we have recovered substantial quantities of mammalian genomic sequence more than twice as old as any previously reported, establishing the feasibility of ancient DNA genomic sequencing programs.

  5. On Controllable Elastohydrodynamic Fluid Film Bearings

    DEFF Research Database (Denmark)

    Haugaard, Martin Asger

    This thesis gives a theoretical description of the active tilting-pad journal bearing (ATPJB). It provides the qualified reader with the tools to model an ATPJB, while staying clear of pitfalls. The model is based on well known techniques and allows for local stability analyses, harmonic stationary...... are performed for a tilting-pad journal bearing (TPJB) and an ATPJB under static conditions, followed by a generalisation to dynamic conditions (transient as well as stationary harmonic). These analyses will be of interest to experimentalists, since they permit experiments performed on scaled down test rigs...... the addition of a control system may just as well harm rotor-bearing performance as improve it....

  6. On the Characteristics of Misaligned Journal Bearings

    Directory of Open Access Journals (Sweden)

    Joon Young Jang

    2015-03-01

    Full Text Available Journal bearing misalignment arise generally from the shaft deformation under load, deflection of the shaft, manufacturing and assembly errors, improper installation, and asymmetric loading. During operations, misalignment has a considerable effect on the static and dynamic performances. It could cause wear, vibration and even system failure. In this article, a literature review of misalignment of the journal bearings is presented. The basic theory for the misalignment and some results for the circular journal bearing are also presented to show the general trends of the misalignment.

  7. Microeconomic analysis of military aircraft bearing restoration

    Science.gov (United States)

    Hein, G. F.

    1976-01-01

    The risk and cost of a bearing restoration by grinding program was analyzed. A microeconomic impact analysis was performed. The annual cost savings to U.S. Army aviation is approximately $950,000.00 for three engines and three transmissions. The capital value over an indefinite life is approximately ten million dollars. The annual cost savings for U.S. Air Force engines is approximately $313,000.00 with a capital value of approximately 3.1 million dollars. The program will result in the government obtaining bearings at lower costs at equivalent reliability. The bearing industry can recover lost profits during a period of reduced demand and higher costs.

  8. Camshaft bearing arrangement for overhead cam engine

    Energy Technology Data Exchange (ETDEWEB)

    Yoshikawa, M.

    1985-01-01

    In an assembly for an internal combustion engine comprising a cylinder block, a cylinder head detachably affixed to the cylinder block by a plurality of threaded fastening means, a plurality of poppet valves supported for reciprocation in the cylinder head and a camshaft for operating the poppet valves, the improvement is described comprising a cam carrier detachably affixed to the cylinder head and overlying the threaded fastening means, and a bearing cap affixed to the cam carrier. The cam carrier and the bearing cap have bearing surfaces for journaling the camshaft.

  9. Rotational decay torques of superconducting magnetic bearing

    International Nuclear Information System (INIS)

    Takahata, R.; Yotsuya, T.

    1991-01-01

    This paper proposes a superconducting magnetic bearing as one of application of a high critical temperature (Tc) oxide superconducting material. The authors have assembled new models of bearing with free rotation axis. In these models, superconductor, YBa 2 Cu 3 O X , prepared by the quench and melt growth (QMG) method was applied to the bearing section and a permanent magnet was used for a rotor. This development originated from the knowledge that YBa 2 Cu 3 O X prepared by QMG method had a stronger pinning force of magnetic flux than that of conventional superconductors

  10. Compressor ported shroud for foil bearing cooling

    Science.gov (United States)

    Elpern, David G [Los Angeles, CA; McCabe, Niall [Torrance, CA; Gee, Mark [South Pasadena, CA

    2011-08-02

    A compressor ported shroud takes compressed air from the shroud of the compressor before it is completely compressed and delivers it to foil bearings. The compressed air has a lower pressure and temperature than compressed outlet air. The lower temperature of the air means that less air needs to be bled off from the compressor to cool the foil bearings. This increases the overall system efficiency due to the reduced mass flow requirements of the lower temperature air. By taking the air at a lower pressure, less work is lost compressing the bearing cooling air.

  11. Public Perceptions of Bears and Management Interventions in Japan

    OpenAIRE

    Sakurai, Ryo; Jacobson, Susan K.

    2011-01-01

    Conservation of bears is a challenge globally. In Japan, Asiatic black bears (Ursus thibetanus) and brown bears (Ursus arctos) are considered a nuisance because of agricultural and property damage and personal human danger due to occasional human casualties. Reduction of human–bear conflicts in Japan would improve long-term conservation of bears and reduce risks to human health and safety. To understand Japanese perceptions of and experience with bears, we analyzed results of 5 public surveys...

  12. Management of brown bears (Ursus arctos) in Europe.

    OpenAIRE

    Klenzendorf, Sybille A.

    1997-01-01

    Management of Brown Bears (Ursus arctos) in Europe. Sybille A. Klenzendorf (Abstract) Successful conservation of brown bears (Ursus arctos) in Europe is associated with public acceptance of damages caused by bears. Recent increases in sheep depredation and beehive damage in central Austria resulted in the deaths of two bears there. Since bear numbers are low in most European populations, alternatives to the elimination of problem bears associated with dam...

  13. State Space Formulation of Nonlinear Vibration Responses Collected from a Dynamic Rotor-Bearing System: An Extension of Bearing Diagnostics to Bearing Prognostics

    OpenAIRE

    Peter W. Tse; Dong Wang

    2017-01-01

    Bearings are widely used in various industries to support rotating shafts. Their failures accelerate failures of other adjacent components and may cause unexpected machine breakdowns. In recent years, nonlinear vibration responses collected from a dynamic rotor-bearing system have been widely analyzed for bearing diagnostics. Numerous methods have been proposed to identify different bearing faults. However, these methods are unable to predict the future health conditions of bearings. To exten...

  14. Vibration Characteristics of Hydrodynamic Fluid Film Pocket Journal Bearings

    Directory of Open Access Journals (Sweden)

    N. S. Feng

    2010-01-01

    Full Text Available Theoretical analyses of hydrodynamic fluid film bearings with different bearing profiles rely on solutions of the Reynolds equation. This paper presents an approach used for analysing the so-called pocket bearings formed from a combination of offset circular bearing profiles. The results show that the variation of the dynamic bearing characteristics with different load inclinations for the pocket bearings is less than that for the elliptic bearing counterpart. It is shown that the natural frequencies as well as the critical speeds, and hence the vibrational behaviour, can also be significantly different for an industrial rotor supported by the different bearings.

  15. Molecular phylogeny and SNP variation of polar bears (Ursus maritimus), brown bears (U. arctos), and black bears (U. americanus) derived from genome sequences.

    Science.gov (United States)

    Cronin, Matthew A; Rincon, Gonzalo; Meredith, Robert W; MacNeil, Michael D; Islas-Trejo, Alma; Cánovas, Angela; Medrano, Juan F

    2014-01-01

    We assessed the relationships of polar bears (Ursus maritimus), brown bears (U. arctos), and black bears (U. americanus) with high throughput genomic sequencing data with an average coverage of 25× for each species. A total of 1.4 billion 100-bp paired-end reads were assembled using the polar bear and annotated giant panda (Ailuropoda melanoleuca) genome sequences as references. We identified 13.8 million single nucleotide polymorphisms (SNP) in the 3 species aligned to the polar bear genome. These data indicate that polar bears and brown bears share more SNP with each other than either does with black bears. Concatenation and coalescence-based analysis of consensus sequences of approximately 1 million base pairs of ultraconserved elements in the nuclear genome resulted in a phylogeny with black bears as the sister group to brown and polar bears, and all brown bears are in a separate clade from polar bears. Genotypes for 162 SNP loci of 336 bears from Alaska and Montana showed that the species are genetically differentiated and there is geographic population structure of brown and black bears but not polar bears.

  16. Mercury biomagnification in polar bears ( Ursus maritimus)

    Science.gov (United States)

    Horton, T. W.; Blum, J. D.; Xie, Z.; Hren, M.; Chamberlain, C. P.

    2007-12-01

    Mercury biomagnification occurs in a variety of ecosystems resulting in greater potential for toxicological effects in higher-level trophic feeders. However, Hg transport pathways through different foodweb channels are not well known, particularly in high-latitude systems affected by atmospheric Hg deposition associated with snow and ice. Stable carbon and nitrogen isotope ratios and Hg concentrations determined for 26 late 19th and early 20th century polar bear hair specimens collected from cataloged museum collections elucidate relationships between high latitude marine foodweb structure and Hg transport pathways. Nitrogen and carbon isotopic compositions suggest that polar bears derive nutrition from both open water (pelagic) and ice associated (sympagic) foodweb channels. Correlation between Hg concentrations and nitrogen isotope compositions indicate mercury biomagnification occurred in most of the polar bears investigated. Interpretation of stable isotope based foodweb structure in concert with Hg concentrations further suggests that Hg biomagnification occurred to a greater degree in polar bears participating in pelagic foodweb channels.

  17. Bearings for the HFIR control plates

    International Nuclear Information System (INIS)

    Abbatiello, A.A.

    1975-08-01

    Recent accelerated wear of HFIR bearings seems to be a more advanced stage of the situation encountered in 1967. The latest observations are in agreement with the hypothesis that high-frequency impact loads at a 30 0 angle on these bearings are the apparent basic cause of their short life. In view of the limited possibilities for change at this stage of HFIR operation, the region of best payoff seems to be an increase in the load-carrying area at some acceptable sacrifice of low rolling friction. On this basis three types of bearings are proposed for test--two of these are journal types and one is a slider type. The next planned shutdown for major parts replacement provides an opportunity to test these modified bearing types in the HFIR under full mechanical operating conditions but without nuclear operation. The program is recommended for consideration and adoption. (U.S.)

  18. LIGHT-WEIGHT LOAD-BEARING STRUCTURE

    DEFF Research Database (Denmark)

    2009-01-01

    The invention relates to a light-weight load-bearing structure (1) with optimized compression zone (2), where along one or more compression zones (2) in the structure (1) to be cast a core (3) of strong concrete is provided, which core (3) is surrounded by concrete of less strength (4) compared...... to the core (3) of strong concrete. The invention also relates to a method of casting of light-weight load-bearing structures (1) with optimized compression zone (2) where one or more channels, grooves, ducts, pipes and/or hoses (5) formed in the load-bearing structure (1) serves as moulds for moulding one...... or more cores (3) of strong concrete in the light-weight load-bearing structure (1)....

  19. How to live with black bears

    Science.gov (United States)

    Lynn L. Rogers

    1988-01-01

    A black bear in camp requires caution but is not cause for great alarm. Most are timid enough to be scared away by yelling, waving, and banging pans. But a few are too accustomed to people to be bothered.

  20. Ceramic Rail-Race Ball Bearings

    Science.gov (United States)

    Balzer, Mark A.; Mungas, Greg S.; Peters, Gregory H.

    2010-01-01

    Non-lubricated ball bearings featuring rail races have been proposed for use in mechanisms that are required to function in the presence of mineral dust particles in very low-pressure, dry environments with extended life. Like a conventional ball bearing, the proposed bearing would include an inner and an outer ring separated by balls in rolling contact with the races. However, unlike a conventional ball bearing, the balls would not roll in semi-circular or gothic arch race grooves in the rings: instead, the races would be shaped to form two or more rails (see figure). During operation, the motion of the balls would push dust particles into the spaces between the rails where the particles could not generate rolling resistance for the balls

  1. AX-5 space suit bearing torque investigation

    Science.gov (United States)

    Loewenthal, Stuart; Vykukal, Vic; Mackendrick, Robert; Culbertson, Philip, Jr.

    1990-01-01

    The symptoms and eventual resolution of a torque increase problem occurring with ball bearings in the joints of the AX-5 space suit are described. Starting torques that rose 5 to 10 times initial levels were observed in crew evaluation tests of the suit in a zero-g water tank. This bearing problem was identified as a blocking torque anomaly, observed previously in oscillatory gimbal bearings. A large matrix of lubricants, ball separator designs and materials were evaluated. None of these combinations showed sufficient tolerance to lubricant washout when repeatedly cycled in water. The problem was resolved by retrofitting a pressure compensated, water exclusion seal to the outboard side of the bearing cavity. The symptoms and possible remedies to blocking are discussed.

  2. Cavitation Peening of Aerospace Bearings, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — High-value bearings are a critical part of the safety, reliability, cost and performance of modern aircraft. A typical passenger jet will have 100 to 175 high-valve...

  3. Hydrostatic radial bearing of centrifugal pump

    International Nuclear Information System (INIS)

    Skalicky, A.

    1976-01-01

    A hydrostatic radial pump is described characterized by the fact that part of the medium off-taken from delivery is used as a lubricating medium. Two additional bodies are placed alongside a hydrostatic bearing with coils in between them and the pump shaft; the coils have an opposite pitch. The feed channel for the hydrostatic bearing pocket is linked to delivery. The coil outlets are connected to the pump suction unit. Two rotating coils placed alongside the hydrostatic bearing will considerably simplify the communication channel design and reduce the dependence on the pump shaft deflections. The addition of another rotating coil in the close vicinity of the pump shaft or directly on the shaft further increases the efficiency. The bearing can be used in designing vertical circulating pumps for the cooling circuits of nuclear reactors. (J.B.)

  4. Novel nano bearings constructed by physical adsorption

    Science.gov (United States)

    Zhang, Yongbin

    2015-09-01

    The paper proposes a novel nano bearing formed by the physical adsorption of the confined fluid to the solid wall. The bearing is formed between two parallel smooth solid plane walls sliding against one another, where conventional hydrodynamic lubrication theory predicted no lubricating effect. In this bearing, the stationary solid wall is divided into two subzones which respectively have different interaction strengths with the lubricating fluid. It leads to different physical adsorption and slip properties of the lubricating fluid at the stationary solid wall respectively in these two subzones. It was found that a significant load-carrying capacity of the bearing can be generated for low lubricating film thicknesses, because of the strong physical adsorption and non-continuum effects of the lubricating film.

  5. Development of hydrodynamic micro-bearings

    Science.gov (United States)

    Wang, P.; Zhang, J.; Spikes, H. A.; Reddyhoff, T.; Holmes, A. S.

    2016-11-01

    This paper describes the modelling and testing of mm-scale hydrodynamic bearings which are being developed to improve the efficiency of a cm-scale turbine energy harvester, whose efficiency was previously limited by poorly lubricated commercial jewel-bearings. The bearings were fabricated using DRIE and their performance was assessed using a custom built MEMS tribometer. Results demonstrate that acceptably low friction is achieved when low viscosity liquid lubricants are used in combination with an appropriate choice of friction modifier additive. Further reduction in friction is demonstrated when the step height of bearing is adjusted in accordance with hydrodynamic theory. In parallel with the experiments, hydrodynamic lubricant modelling has been carried out to predict and further optimize film thickness and friction performance. Modelling results are presented and validated against experimental friction data.

  6. Effect of Surface Roughness on Hydrodynamic Bearings

    Science.gov (United States)

    Majumdar, B. C.; Hamrock, B. J.

    1981-01-01

    A theoretical analysis on the performance of hydrodynamic oil bearings is made considering surface roughness effect. The hydrodynamic as well as asperity contact load is found. The contact pressure was calculated with the assumption that the surface height distribution was Gaussian. The average Reynolds equation of partially lubricated surface was used to calculate hydrodynamic load. An analytical expression for average gap was found and was introduced to modify the average Reynolds equation. The resulting boundary value problem was then solved numerically by finite difference methods using the method of successive over relaxation. The pressure distribution and hydrodynamic load capacity of plane slider and journal bearings were calculated for various design data. The effects of attitude and roughness of surface on the bearing performance were shown. The results are compared with similar available solution of rough surface bearings. It is shown that: (1) the contribution of contact load is not significant; and (2) the hydrodynamic and contact load increase with surface roughness.

  7. cyclic -perimeter hydrocarbon ruthenium complexes bearing ...

    Indian Academy of Sciences (India)

    - cyclic -perimeter hydrocarbon ruthenium complexes bearing functionalized pyridyl diketones: Isolation of complexes with 2-N∩O and 4-N∩O bonding modes of ligands. Saphidabha L Nongbri Babulal Das Mohan Rao Kollipara.

  8. Cavitation Peening of Aerospace Bearings, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — High-value bearings are a critical part of the safety, reliability, cost and performance of modern aircraft. A typical passenger jet will have 100 to 175 high-valve...

  9. Effects of fluid inertia and bearing flexibility on the performance of finite length journal bearing

    Science.gov (United States)

    Javorova, Juliana; Alexandrov, Vassil

    2017-02-01

    The paper describes the theoretical study concerning the effect of lubricant inertia forces and deformability of the bearing elastic layer on the performance of a plane journal bearing. The problem is investigated for a Newtonian lubricant under isothermal and isoviscous conditions. The analysis considers the generalized Reynolds equation governing the flow of lubricant in the clearance space and the linear elasticity equation governing the displacement field in the bearing shell. An iterative numerical procedure with successive over relaxation is used to pressure distribution within the lubricated conjunction. Bearing performance characteristics have been presented for typically selected values of generalized Reynolds number Re* and elasticity parameters of the elastic liner. It has been observed that the combined effect of fluid inertia forces and bearing flexibility affects the performance characteristics of dynamically loaded journal bearing.

  10. Genetic relationships of extant brown bears (Ursus arctos) and polar bears (Ursus maritimus).

    Science.gov (United States)

    Cronin, Matthew A; MacNeil, Michael D

    2012-01-01

    Polar bears (Ursus maritimus) and brown bears (Ursus arctos) are closely related species for which extensive mitochondrial and nuclear phylogenetic comparisons have been made. We used previously published genotype data for 8 microsatellite DNA loci from 930 brown bears in 19 populations and 473 polar bears in 16 populations to compare the population genetic relationships of extant populations of the species. Genetic distances (Nei standard distance = 1.157), the proportion of private alleles (52% of alleles are not shared by the species), and Bayesian cluster analysis are consistent with morphological and life-history characteristics that distinguish polar bears and brown bears as different species with little or no gene flow among extant populations.

  11. Flywheel energy storage with superconductor magnetic bearings

    Science.gov (United States)

    Weinberger, Bernard R.; Lynds, Jr., Lahmer; Hull, John R.

    1993-01-01

    A flywheel having superconductor bearings has a lower drag to lift ratio that translates to an improvement of a factor of ten in the rotational decay rate. The lower drag results from the lower dissipation of melt-processed YBCO, improved uniformity of the permanent magnet portion of the bearings, operation in a different range of vacuum pressure from that taught by the art, and greater separation distance from the rotating members of conductive materials.

  12. Is Polar Bear Hair Fiber Optic?

    Science.gov (United States)

    Koon, Daniel W.

    1998-05-01

    New direct measurement of high optical attenuation rates in polar bear hairs 2 8 dB mm in the visible and reanalysis of the data of Tributsch et al . Sol. Energy Mater. 21, 219 (1990) seem to rule out the UV waveguiding proposed by Grojean et al . Appl. Opt. 19, 339 (1980) . The case against fiber-optic polar bear hairs is summarized, and four conditions are given that any variation of the model of Grojean et al . would have to satisfy.

  13. KINEMATICS FRICTION PAIR FOR EXAMPLE NEEDLE BEARINGS

    OpenAIRE

    Jerzy NACHIMOWICZ; Robert KORBUT

    2014-01-01

    The present study concerns certain phenomena that take place in the needle roller bearing. The friction that generates the anti-torque of a friction pair is the major factor that influences the needle bearing’s wear. In the needle bearing there occur two predominant types of friction: the rolling friction and the sliding friction, and both are subject to examination. The study presents recordings and analysis of the movements of all needle bearing’s rolling elements. The examination was carri...

  14. Thermal effects in an accelerating thrust bearing

    Science.gov (United States)

    Doo, R.; Rodkiewicz, C. M.; Gupta, R. N.

    1985-01-01

    This study is mainly concerned with the development of transient temperatures in a thrust bearing. The effect of Prandtl number on temperatures was also investigated. All lubricant properties were assumed to be constant. It was found that the location of highest temperatures depended on the bearing ratio. The effect of Prandtl number on temperatures was small. However, its effect on the heat transfer at the surfaces was significant.

  15. Consumption choice by bears feeding on salmon.

    Science.gov (United States)

    Gende, S M; Quinn, T P; Willson, M F

    2001-05-01

    Consumption choice by brown (Ursus arctos) and black bears (U. americanus) feeding on salmon was recorded for over 20,000 bear-killed fish from 1994 to 1999 in Bristol Bay (sockeye salmon, Oncorhynchus nerka) and southeastern Alaska (pink, O. gorbuscha and chum salmon O. keta). These data revealed striking patterns of partial and selective consumption that varied with relative availability and attributes of the fish. As the availability of salmon decreased, bears consumed a larger proportion of each fish among both years and habitats. When availability was high (absolute number and density of salmon), bears consumed less biomass per captured fish, targeting energy-rich fish (those that had not spawned) or energy-rich body parts (eggs in females; brain in males). In contrast, individual fish were consumed to a much greater extent, regardless of sex or spawning status, in habitats or years of low salmon availability. The proportion of biomass consumed per fish was similar for males and females, when spawning status was statistically controlled, but bears targeted different body parts: the body flesh, brain and dorsal hump in males and the roe in females. Bears thus appeared to maximize energy intake by modifying the amount and body parts consumed, based on availability and attributes of spawning salmon.

  16. Rotordynamics and bearing design of turbochargers

    Science.gov (United States)

    Chen, Wen Jeng

    2012-05-01

    Turbochargers have gained significant attention in recent years. They are already widely used in automotive, locomotive, and marine applications with diesel engines. They are also applied in the aerospace application to increase the engine performance now. The turbochargers used in automotive and aerospace industry are very light-weight with operating speeds above 100,000 rpm. The turbochargers used in locomotive and marine applications are relatively heavy in size and power compared to the automotive and aerospace applications, and the maximum continuous operating speeds are around 30,000 rpm depending on the diesel engine power rating. Floating ring bushings, semi-floating dampers, ball bearings, and ball bearings with dampers are commonly used in automotive applications for small turbochargers. However, these bearings may not be appropriate for large turbochargers in locomotive and marine applications. Instead, multi-lobed bearings with and without squeeze film dampers are commonly used in these heavy-duty turbochargers. This paper deals with the rotordynamic characteristics of larger turbochargers in locomotive and marine applications. Various bearing designs are discussed. Bearing design parameters are studied and optimal values are suggested. Test results are also presented to support the analytical simulation.

  17. Adaptive Spindle Balancing Using Magnetically Levitated Bearings

    International Nuclear Information System (INIS)

    BARNEY, PATRICK S.; LAUFFER, JAMES P.; PETTEYS, REBECCA; REDMOND, JAMES M.; SULLIVAN, WILLIAM N.

    1999-01-01

    A technological break through for supporting rotating shafts is the active magnetic bearing (AMB). Active magnetic bearings offer some important advantages over conventional ball, roller or journal bearings such as reduced frictional drag, no physical contact in the bearing, no need for lubricants, compatibility with high vacuum and ultra-clean environments, and ability to control shaft position within the bearing. The disadvantages of the AMB system are the increased cost and complexity, reduced bearing stiffness and the need for a controller. Still, there are certain applications, such as high speed machining, biomedical devices, and gyroscopes, where the additional cost of an AMB system can be justified. The inherent actuator capabilities of the AMB offer the potential for active balancing of spindles and micro-shaping capabilities for machine tools, The work presented in this paper concentrates on an AMB test program that utilizes the actuator capability to dynamically balance a spindle. In this study, an unbalanced AMB spindle system was enhanced with an LMS (Least Mean Squares) algorithm combined with an existing PID (proportional, integral, differential) control. This enhanced controller significantly improved the concentricity of an intentionally unbalanced shaft. The study included dynamic system analysis, test validation, control design and simulation, as well as experimental implementation using a digital LMS controller

  18. Adaptive Spindle Balancing Using Magnetically Levitated Bearings

    Energy Technology Data Exchange (ETDEWEB)

    BARNEY,PATRICK S.; LAUFFER,JAMES P.; PETTEYS,REBECCA; REDMOND,JAMES M.; SULLIVAN,WILLIAM N.

    1999-09-20

    A technological break through for supporting rotating shafts is the active magnetic bearing (AMB). Active magnetic bearings offer some important advantages over conventional ball, roller or journal bearings such as reduced frictional drag, no physical contact in the bearing, no need for lubricants, compatibility with high vacuum and ultra-clean environments, and ability to control shaft position within the bearing. The disadvantages of the AMB system are the increased cost and complexity, reduced bearing stiffness and the need for a controller. Still, there are certain applications, such as high speed machining, biomedical devices, and gyroscopes, where the additional cost of an AMB system can be justified. The inherent actuator capabilities of the AMB offer the potential for active balancing of spindles and micro-shaping capabilities for machine tools, The work presented in this paper concentrates on an AMB test program that utilizes the actuator capability to dynamically balance a spindle. In this study, an unbalanced AMB spindle system was enhanced with an LMS (Least Mean Squares) algorithm combined with an existing PID (proportional, integral, differential) control. This enhanced controller significantly improved the concentricity of an intentionally unbalanced shaft. The study included dynamic system analysis, test validation, control design and simulation, as well as experimental implementation using a digital LMS controller.

  19. A semi-analytical bearing model considering outer race flexibility for model based bearing load monitoring

    Science.gov (United States)

    Kerst, Stijn; Shyrokau, Barys; Holweg, Edward

    2018-05-01

    This paper proposes a novel semi-analytical bearing model addressing flexibility of the bearing outer race structure. It furthermore presents the application of this model in a bearing load condition monitoring approach. The bearing model is developed as current computational low cost bearing models fail to provide an accurate description of the more and more common flexible size and weight optimized bearing designs due to their assumptions of rigidity. In the proposed bearing model raceway flexibility is described by the use of static deformation shapes. The excitation of the deformation shapes is calculated based on the modelled rolling element loads and a Fourier series based compliance approximation. The resulting model is computational low cost and provides an accurate description of the rolling element loads for flexible outer raceway structures. The latter is validated by a simulation-based comparison study with a well-established bearing simulation software tool. An experimental study finally shows the potential of the proposed model in a bearing load monitoring approach.

  20. Ancient DNA reveals differences in behaviour and sociality between brown bears and extinct cave bears.

    Science.gov (United States)

    Fortes, Gloria G; Grandal-d'Anglade, Aurora; Kolbe, Ben; Fernandes, Daniel; Meleg, Ioana N; García-Vázquez, Ana; Pinto-Llona, Ana C; Constantin, Silviu; de Torres, Trino J; Ortiz, Jose E; Frischauf, Christine; Rabeder, Gernot; Hofreiter, Michael; Barlow, Axel

    2016-10-01

    Ancient DNA studies have revolutionized the study of extinct species and populations, providing insights on phylogeny, phylogeography, admixture and demographic history. However, inferences on behaviour and sociality have been far less frequent. Here, we investigate the complete mitochondrial genomes of extinct Late Pleistocene cave bears and middle Holocene brown bears that each inhabited multiple geographically proximate caves in northern Spain. In cave bears, we find that, although most caves were occupied simultaneously, each cave almost exclusively contains a unique lineage of closely related haplotypes. This remarkable pattern suggests extreme fidelity to their birth site in cave bears, best described as homing behaviour, and that cave bears formed stable maternal social groups at least for hibernation. In contrast, brown bears do not show any strong association of mitochondrial lineage and cave, suggesting that these two closely related species differed in aspects of their behaviour and sociality. This difference is likely to have contributed to cave bear extinction, which occurred at a time in which competition for caves between bears and humans was likely intense and the ability to rapidly colonize new hibernation sites would have been crucial for the survival of a species so dependent on caves for hibernation as cave bears. Our study demonstrates the potential of ancient DNA to uncover patterns of behaviour and sociality in ancient species and populations, even those that went extinct many tens of thousands of years ago. © 2016 John Wiley & Sons Ltd.

  1. Polar bears: the fate of an icon.

    Science.gov (United States)

    Fitzgerald, Kevin T

    2013-11-01

    Polar bears are one of the most iconic animals on our planet. Worldwide, even people who would never see one are drawn to these charismatic arctic ice hunters. They are the world's largest terrestrial carnivore, and despite being born on land, they spend most of their lives out on the sea ice and are considered a marine mammal. Current global studies estimate there are around 20,000 animals in some 19 discrete circumpolar populations. Aside from pregnant females denning in the winter months to give birth, the white bears do not hibernate. They spend their winters on the sea ice hunting seals, an activity they are spectacularly adapted for. Research on these animals is incredibly difficult because of the inhospitable surroundings they inhabit and how inaccessible they make the bears. For many years, the sum of our understanding of the natural history of polar bears came from tracks, scats, the remains of their kills, abandoned dens, and anecdotal observations of native hunters, explorers, and early biologists. Nonetheless, the last 40 years have seen a much better picture of their biology emerge thanks to, first, dedicated Canadian researchers and, later, truly international efforts of workers from many countries. Veterinarians have contributed to our knowledge of the bears by delivering and monitoring anesthesia, obtaining blood samples, performing necropsies, investigating their reproduction, conducting radiotelemetry studies, and examining their behavior. Recently, new technologies have been developed that revolutionize the study of the lives and natural history of undisturbed polar bears. These advances include better satellite radiotelemetry equipment and the development of remote-controlled miniature devices equipped with high-definition cameras. Such new modalities provide dramatic new insights into the life of polar bears. The remarkable degree of specialized adaptation to life on the sea ice that allowed the bears to be successful is the very reason that

  2. Wave Journal Bearing. Part 2: Experimental Pressure Measurements and Fractional Frequency Whirl Threshold for Wave and Plain Journal Bearings

    Science.gov (United States)

    Walker, James F.; Dimofte, Florin; Addy, Harold E., Jr.

    1995-01-01

    A new hydrodynamic bearing concept, the wave journal bearing, is being developed because it has better stability characteristics than plain journal bearings while maintaining similar load capacity. An analysis code to predict the steady state and dynamic performance of the wave journal bearing is also part of the development. To verify numerical predictions and contrast the wave journal bearing's stability characteristics to a plain journal bearing, tests were conducted at NASA Lewis Research Center using an air bearing test rig. Bearing film pressures were measured at 16 ports located around the bearing circumference at the middle of the bearing length. The pressure measurements for both a plain journal bearing and a wave journal bearing compared favorably with numerical predictions. Both bearings were tested with no radial load to determine the speed threshold for self-excited fractional frequency whirl. The plain journal bearing started to whirl immediately upon shaft start-up. The wave journal did not incur self-excited whirl until 800 to 900 rpm as predicted by the analysis. Furthermore, the wave bearing's geometry limited the whirl orbit to less than the bearing's clearance. In contrast, the plain journal bearing did not limit the whirl orbit, causing it to rub.

  3. Mass Loss Rates of Fasting Polar Bears.

    Science.gov (United States)

    Pilfold, Nicholas W; Hedman, Daryll; Stirling, Ian; Derocher, Andrew E; Lunn, Nicholas J; Richardson, Evan

    2016-01-01

    Polar bears (Ursus maritimus) have adapted to an annual cyclic regime of feeding and fasting, which is extreme in seasonal sea ice regions of the Arctic. As a consequence of climate change, sea ice breakup has become earlier and the duration of the open-water period through which polar bears must rely on fat reserves has increased. To date, there is limited empirical data with which to evaluate the potential energetic capacity of polar bears to withstand longer fasts. We measured the incoming and outgoing mass of inactive polar bears (n = 142) that were temporarily detained by Manitoba Conservation and Water Stewardship during the open-water period near the town of Churchill, Manitoba, Canada, in 2009-2014. Polar bears were given access to water but not food and held for a median length of 17 d. Median mass loss rates were 1.0 kg/d, while median mass-specific loss rates were 0.5%/d, similar to other species with high adiposity and prolonged fasting capacities. Mass loss by unfed captive adult males was identical to that lost by free-ranging individuals, suggesting that terrestrial feeding contributes little to offset mass loss. The inferred metabolic rate was comparable to a basal mammalian rate, suggesting that while on land, polar bears can maintain a depressed metabolic rate to conserve energy. Finally, we estimated time to starvation for subadults and adult males for the on-land period. Results suggest that at 180 d of fasting, 56%-63% of subadults and 18%-24% of adult males in this study would die of starvation. Results corroborate previous assessments on the limits of polar bear capacity to withstand lengthening ice-free seasons and emphasize the greater sensitivity of subadults to changes in sea ice phenology.

  4. A circumpolar monitoring framework for polar bears

    Science.gov (United States)

    Vongraven, Dag; Aars, Jon; Amstrup, Steven C.; Atkinson, Stephen N.; Belikov, Stanislav; Born, Erik W.; DeBruyn, T.D.; Derocher, Andrew E.; Durner, George M.; Gill, Michael J.; Lunn, Nicholas J.; Obbard, Martyn E.; Omelak, Jack; Ovsyanikov, Nikita; Peacock, Elizabeth; Richardson, E.E.; Sahanatien, Vicki; Stirling, Ian; Wiig, Øystein

    2012-01-01

    Polar bears (Ursus maritimus) occupy remote regions that are characterized by harsh weather and limited access. Polar bear populations can only persist where temporal and spatial availability of sea ice provides adequate access to their marine mammal prey. Observed declines in sea ice availability will continue as long as greenhouse gas concentrations rise. At the same time, human intrusion and pollution levels in the Arctic are expected to increase. A circumpolar understanding of the cumulative impacts of current and future stressors is lacking, long-term trends are known from only a few subpopulations, and there is no globally coordinated effort to monitor effects of stressors. Here, we describe a framework for an integrated circumpolar monitoring plan to detect ongoing patterns, predict future trends, and identify the most vulnerable polar bear subpopulations. We recommend strategies for monitoring subpopulation abundance and trends, reproduction, survival, ecosystem change, human-caused mortality, human–bear conflict, prey availability, health, stature, distribution, behavioral change, and the effects that monitoring itself may have on polar bears. We assign monitoring intensity for each subpopulation through adaptive assessment of the quality of existing baseline data and research accessibility. A global perspective is achieved by recommending high intensity monitoring for at least one subpopulation in each of four major polar bear ecoregions. Collection of data on harvest, where it occurs, and remote sensing of habitat, should occur with the same intensity for all subpopulations. We outline how local traditional knowledge may most effectively be combined with the best scientific methods to provide comparable and complementary lines of evidence. We also outline how previously collected intensive monitoring data may be sub-sampled to guide future sampling frequencies and develop indirect estimates or indices of subpopulation status. Adoption of this framework

  5. What Can We Learn?--The Algonquin Bear Attack.

    Science.gov (United States)

    Strickland, Dan

    1992-01-01

    Describes a bear attack in Algonquin Park in Lake Opeongo (Canada) in which a man and woman were killed. Hypothesizes that the bear deliberately preyed on its victims and concludes that the bear was physically normal. Despite this isolated attack, the chance of being attacked by a black bear when camping is virtually nonexistent. (KS)

  6. 77 FR 77070 - Black Bear Hydro Partners, LLC;

    Science.gov (United States)

    2012-12-31

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Project No. 2727-086] Black Bear Hydro...: October 24, 2012. d. Submitted By: Black Bear Hydro Partners, LLC (Black Bear Hydro). e. Name of Project... designating Black Bear Hydro as the Commission's non-federal representative for carrying out informal...

  7. Wear numbers for ball cup and journal bearings

    NARCIS (Netherlands)

    Ligterink, D.J.; Moes, H.

    1980-01-01

    A wear number is defined for ball cup bearings and for journal bearings where the cup and the cylindrical bearing are made of soft material. This dimensionless wear number provides a relation between the following five quantities: the radius of the ball or the length of the journal bearing in

  8. Critical Pressures of the Thrust Bearing Using a Magnetic Fluid

    OpenAIRE

    長屋, 幸助; 武田, 定彦; 佐藤, 淳; 井開, 重男; 関口, 肇; 斉藤, 登

    1990-01-01

    This paper proposes a thrust bearing lubricated by a magnetic fluid under a magnetic field. The critical pressures of the bearing versus the magnitude of the magnetic flux densities have been investigated experimentally. It is clarified that the critical pressures of the proposed bearing are larger than those of the normal lubricant bearing under high speeds.

  9. Noise reduction of rotating machinery by viscoelastic bearing supports

    NARCIS (Netherlands)

    Tillema, H.G.

    2003-01-01

    The demand for silent rolling bearing applications, such as electric motors and gearboxes, has resulted in an investigation of viscoelastic bearing supports. By placing a thin viscoelastic layer between the bearing outer ring and the surrounding structure, vibrations of the shaft-bearing arrangement

  10. 46 CFR 61.20-23 - Tailshaft clearance; bearing weardown.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Tailshaft clearance; bearing weardown. 61.20-23 Section...; bearing weardown. (a) Water lubricated bearings, other than rubber, must be rebushed as follows: (1) Where the propelling machinery is located amidship, the after stern tube bearing must be rebushed when it is...

  11. Effect of Bearings on Vibration in Rotating Machinery

    Science.gov (United States)

    Daniel, Rudrapati Victor; Amit Siddhappa, Savale; Bhushan Gajanan, Savale; Vipin Philip, S.; Paul, P. Sam

    2017-08-01

    In rotary machines vibration is an inherent phenomenon which has the tendency to affect required performance. Amongst the different parameters that affect vibration, selection of appropriate bearing is the most critical component. In this work the effect of different types of bearing on vibration in rotary machines is studied and the magnitude of vibration produced by use of different set of bearings under the same condition of loads and rotational speeds were investigated. Bearings considered in this work were ball bearing, tapered roller bearing, thrust bearing and shaft material considered is of mild steel. From experimental result, it was noted that tapered roller bearing gives the highest amplitude of vibration among all the three bearings whereas the ball bearing gives least amplitude under similar operating conditions.

  12. Bearing assemblies, apparatuses, and motor assemblies using the same

    Science.gov (United States)

    Sexton, Timothy N.; Cooley, Craig H.; Knuteson, Cody W.

    2015-12-29

    Various embodiments of the invention relate to bearing assemblies, apparatuses and motor assemblies that include geometric features configured to impart a selected amount of heat transfer and/or hydrodynamic film formation. In an embodiment, a bearing assembly may include a plurality of superhard bearing pads distributed circumferentially about an axis. At least some of the plurality of superhard bearing pads may include a plurality of sub-superhard bearing elements defining a bearing surface. At least some of the plurality of sub-superhard bearing elements may be spaced from one another by one or more voids to impart a selected amount of heat transfer and hydrodynamic film formation thereon during operation. The bearing assembly may also include a support ring that carries the plurality of superhard bearing pads. In addition, at least a portion of the sub-superhard bearing elements may extend beyond the support ring.

  13. Local Attitudes towards Bear Management after Illegal Feeding and Problem Bear Activity.

    Science.gov (United States)

    Dubois, Sara; Fraser, David

    2013-09-12

    The "pot bears" received international media attention in 2010 after police discovered the intentional feeding of over 20 black bears during the investigation of an alleged marijuana-growing operation in Christina Lake, British Columbia, Canada. A two-phase random digit dialing survey of the community was conducted in 2011 to understand local perspectives on bear policy and management, before and after a summer of problem bear activity and government interventions. Of the 159 households surveyed in February 2011, most had neutral or positive attitudes towards bears in general, and supported the initial decision to feed the food-conditioned bears until the autumn hibernation. In contrast to wildlife experts however, most participants supported relocating the problem bears, or allowing them to remain in the area, ahead of killing; in part this arose from notions of fairness despite the acknowledged problems of relocation. Most locals were aware of the years of feeding but did not report it, evidently failing to see it as a serious form of harm, even after many bears had been killed. This underscores the importance of preventive action on wildlife feeding and the need to narrow the gap between public and expert opinion on the likely effects of relocation versus killing.

  14. Acoustic Emission Monitoring of Incipient in Journal Bearings - Part I : Detectability and measurement for bearing damages

    International Nuclear Information System (INIS)

    Yoon, Dong Jin; Kwon, Oh Yang; Chung, Min Hwa; Kim, Kyung Woong

    1994-01-01

    In contrast to the machinery using rolling element bearings, systems with journal bearings generally operate in large scale and under severe loading condition such as steam generator turbines and internal combustion engines. Failure of the bearings in these machinery can result in the system breakdown. To avoid the time consuming repair and considerable economic loss, the detection of incipient failure in journal bearings becomes very important. In this experimental approach, acoustic emission monitoring is applied to the detection of incipient failure caused by several types of abnormal operating condition most probable in the journal bearing systems. It has been known that the intervention of foreign materials, insufficient lubrication and misassembly etc. are principal factors to cause bearing failure and distress. The experiment was conducted under such designed conditions as hard particles in the lubrication layer, insufficient lubrication, and metallic contact in the simulated journal bearing system. The results showed that acoustic emission could be an effective tool to detect the incipient failure in journal bearings

  15. Nonlinear Dynamical Analysis for a Plain Bearing

    Directory of Open Access Journals (Sweden)

    Ali Belhamra

    2014-03-01

    Full Text Available This paper investigates the nonlinear dynamic behavior for a plain classic bearing (fluid bearing lubricated by a non-Newtonian fluid of a turbo machine rotating with high speed; this type of fluid contains additives viscosity (couple-stress fluid film. The solution of the nonlinear dynamic problem of this type of bearing is determined with a spatial discretisation of the modified Reynolds' equation written in dynamic mode by using the optimized short bearing theory and a temporal discretisation for equations of rotor motion by the help of Euler's explicit diagram. This study analyzes the dynamic behavior of a rotor supported by two couple-stress fluid film journal lubricant enhances the dynamic stability of the rotor-bearing system considerably compared to that obtained when using a traditional Newtonian lubricant. The analysis shows that the dynamic behavior of a shaft which turns with high velocities is strongly nonlinear even for poor eccentricities of unbalance; the presence of parameters of couple stress allows strongly attenuating the will synchrony (unbalance and asynchrony (whipping amplitudes of vibrations of the shaft which supports more severe conditions (large unbalances.

  16. Identifying lubricant options for compressor bearing designs

    Science.gov (United States)

    Karnaz, J.; Seeton, C.; Dixon, L.

    2017-08-01

    Today’s refrigeration and air conditioning market is not only driven by the environmental aspects of the refrigerants, but also by the energy efficiency and reliability of system operation. Numerous types of compressor designs are used in refrigeration and air conditioning applications which means that different bearings are used; and in some cases, multiple bearing types within a single compressor. Since only one lubricant is used, it is important to try to optimize the lubricant to meet the various demands and requirements for operation. This optimization entails investigating different types of lubricant chemistries, viscosities, and various formulation options. What makes evaluating these options more challenging is the refrigerant which changes the properties of the lubricant delivered to the bearing. Once the lubricant and refrigerant interaction are understood, through various test methods, then work can start on collaborating with compressor engineers on identifying the lubricant chemistry and formulation options. These interaction properties are important to the design engineer to make decisions on the adequacy of the lubricant before compressor tests are started. This paper will discuss the process to evaluate lubricants for various types of compressors and bearing design with focus on what’s needed for current refrigerant trends. In addition, the paper will show how the lubricant chemistry choice can be manipulated through understanding of the bearing design and knowledge of interaction with the refrigerant to maximize performance. Emphasis will be placed on evaluation of synthetic lubricants for both natural and synthetic low GWP refrigerants.

  17. Comparison of fixed-bearing and mobile-bearing total knee arthroplasty after high tibial osteotomy.

    Science.gov (United States)

    Hernigou, Philippe; Huys, Maxime; Pariat, Jacques; Roubineau, François; Flouzat Lachaniette, Charles Henri; Dubory, Arnaud

    2018-02-01

    There is no information comparing the results of fixed-bearing total knee replacement and mobile-bearing total knee replacement in the same patients previously treated by high tibial osteotomy. The purpose was therefore to compare fixed-bearing and mobile-bearing total knee replacements in patients treated with previous high tibial osteotomy. We compared the results of 57 patients with osteoarthritis who had received a fixed-bearing prosthesis after high tibial osteotomy with the results of 41 matched patients who had received a rotating platform after high tibial osteotomy. The match was made for length of follow-up period. The mean follow-up was 17 years (range, 15-20 years). The patients were assessed clinically and radiographically. The pre-operative knee scores had no statistically significant differences between the two groups. So was the case with the intra-operative releases, blood loss, thromboembolic complications and infection rates in either group. There was significant improvement in both groups of knees, and no significant difference was observed between the groups (i.e., fixed-bearing and mobile-bearing knees) for the mean Knee Society knee clinical score (95 and 92 points, respectively), or the Knee Society knee functional score (82 and 83 points, respectively) at the latest follow-up. However, the mean post-operative knee motion was higher for the fixed-bearing group (117° versus 110°). In the fixed-bearing group, one knee was revised because of periprosthetic fracture. In the rotating platform mobile-bearing group, one knee was revised because of aseptic loosening of the tibial component. The Kaplan-Meier survivorship for revision at ten years of follow-up was 95.2% for the fixed bearing prosthesis and 91.1% for the rotating platform mobile-bearing prosthesis. Although we did manage to detect significant differences mainly in clinical and radiographic results between the two groups, we found no superiority or inferiority of the mobile-bearing

  18. Method for changing removable bearing for a wind turbine generator

    Science.gov (United States)

    Bagepalli, Bharat Sampathkumaran [Niskayuna, NY; Jansen, Patrick Lee , Gadre; Dattatraya, Aniruddha [Rexford, NY

    2008-04-22

    A wind generator having removable change-out bearings includes a rotor and a stator, locking bolts configured to lock the rotor and stator, a removable bearing sub-assembly having at least one shrunk-on bearing installed, and removable mounting bolts configured to engage the bearing sub-assembly and to allow the removable bearing sub-assembly to be removed when the removable mounting bolts are removed.

  19. Transient thermal modelling of ball bearing using finite element method

    OpenAIRE

    Sibilli, Thierry; Igie, Uyioghosa

    2017-01-01

    Gas turbines are fitted with rolling element bearings, which transfer loads and supports the shafts. The interaction between the rotating and stationary parts in the bearing causes a conversion of some of the power into heat, influencing the thermal behaviour of the entire bearing chamber. To improve thermal modelling of bearing chambers, this work focused on modelling of the heat generated and dissipated around the bearings, in terms of magnitude and location, and the interaction with the co...

  20. A conventional point of view on active magnetic bearings

    Science.gov (United States)

    Chen, H. Ming; Dill, Jim

    1993-01-01

    Active magnetic bearings used in rotating machinery should be designed as locally controlled, independent devices similar to other types of bearings. The functions of control electronics and power amplifiers can be simply and explicitly related to general bearing properties such as load capacity, stiffness, and damping. The dynamics of a rotor and its supporting active magnetic bearings are analyzed in a modified conventional method with an extended state vector containing the bearing state variables.

  1. Superconducting Meissner Effect Bearings for Cryogenic Turbomachines. Phase 2

    Science.gov (United States)

    1994-02-01

    significant sources of damping being squeeze - film damping in the gap and any structural damping in the bearings . The first of these damping sources is dependent... bearing / damper , that the gas bearing could be stabilized at cryogenic temperatures. Figure 12 shows the hybrid gas/Meissner-effect bearing . The tilt-pad...Housing TurbomachineAssembly with T Meissner Dampers and Self-Acting Tilt-Pad Gas Bearings In-Une Heaters Manually Controlled Uquid Nitrogen -j T

  2. Performance studies of oil lubricated helical groove journal bearing

    OpenAIRE

    Khan, Muhammad Zubair

    1992-01-01

    This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University. The provision of helical grooves on the surface of a plain journal bearing can improve the stability of a rotor-bearing system. However, the improvement depends on the arrangement of the grooves along the axial length of the bearing. In order to verify this improved stability three types of helical groove bearing and a reference plain journal bearing were investigated. The helical groove jour...

  3. Modeling and simulation of porous journal bearings in multibody systems

    OpenAIRE

    Buuren, Sietze van

    2013-01-01

    A specific cost-efficient type of plain journal bearing is the porous journal bearing, which possesses a pervious bush that serves as a lubricant reservoir. The current work is concerned with modeling porous journal bearings in multibody systems, for which dynamical models are needed to investigate the bearing’s behavior. Such porous journal bearing models as well as models of elementary rotor-bearing systems including these, were developed and investigated during the course for this work.

  4. Removable bearing arrangement for a wind turbine generator

    Science.gov (United States)

    Bagepalli, Bharat Sampathkumaran; Jansen, Patrick Lee; Gadre, Aniruddha Dattatraya

    2010-06-15

    A wind generator having removable change-out bearings includes a rotor and a stator, locking bolts configured to lock the rotor and stator, a removable bearing sub-assembly having at least one shrunk-on bearing installed, and removable mounting bolts configured to engage the bearing sub-assembly and to allow the removable bearing sub-assembly to be removed when the removable mounting bolts are removed.

  5. Bear bile: dilemma of traditional medicinal use and animal protection

    Directory of Open Access Journals (Sweden)

    Nagamatsu Tadashi

    2009-01-01

    Full Text Available Abstract Bear bile has been used in Traditional Chinese Medicine (TCM for thousands of years. Modern investigations showed that it has a wide range of pharmacological actions with little toxicological side effect and the pure compounds have been used for curing hepatic and biliary disorders for decades. However, extensive consumption of bear bile made bears endangered species. In the 1980's, bear farming was established in China to extract bear bile from living bears with "Free-dripping Fistula Technique". Bear farming is extremely inhumane and many bears died of illness such as chronic infections and liver cancer. Efforts are now given by non-governmental organizations, mass media and Chinese government to end bear farming ultimately. At the same time, systematic research has to be done to find an alternative for bear bile. In this review, we focused on the literature, laboratory and clinical results related to bear bile and its substitutes or alternative in English and Chinese databases. We examined the substitutes or alternative of bear bile from three aspects: pure compounds derived from bear bile, biles from other animals and herbs from TCM. We then discussed the strategy for stopping the trading of bear bile and issues of bear bile related to potential alternative candidates, existing problems in alternative research and work to be done in the future.

  6. Bear bile: dilemma of traditional medicinal use and animal protection

    Science.gov (United States)

    Feng, Yibin; Siu, Kayu; Wang, Ning; Ng, Kwan-Ming; Tsao, Sai-Wah; Nagamatsu, Tadashi; Tong, Yao

    2009-01-01

    Bear bile has been used in Traditional Chinese Medicine (TCM) for thousands of years. Modern investigations showed that it has a wide range of pharmacological actions with little toxicological side effect and the pure compounds have been used for curing hepatic and biliary disorders for decades. However, extensive consumption of bear bile made bears endangered species. In the 1980's, bear farming was established in China to extract bear bile from living bears with "Free-dripping Fistula Technique". Bear farming is extremely inhumane and many bears died of illness such as chronic infections and liver cancer. Efforts are now given by non-governmental organizations, mass media and Chinese government to end bear farming ultimately. At the same time, systematic research has to be done to find an alternative for bear bile. In this review, we focused on the literature, laboratory and clinical results related to bear bile and its substitutes or alternative in English and Chinese databases. We examined the substitutes or alternative of bear bile from three aspects: pure compounds derived from bear bile, biles from other animals and herbs from TCM. We then discussed the strategy for stopping the trading of bear bile and issues of bear bile related to potential alternative candidates, existing problems in alternative research and work to be done in the future. PMID:19138420

  7. Experimental investigations of active air bearings

    DEFF Research Database (Denmark)

    Santos, Ilmar; Morosi, Stefano

    2012-01-01

    Along with traditional oil lubrication, increasing demand for high-speed applications has renewed attention to gas bearings technology. Traditional aerostatic and aerodynamic gas lubrication has been widely used in a variety of applications, ranging from high-speed spindles to micro and meso......-scale turbomachinery. The present paper deals with experimental rotordynamic testing of a flexible rotor supported by hybrid aerostaticaerodynamic gas journal bearing equipped with an electronic radial air injection system. From a rotordynamic point of view there are two phenomena that limit the widespread...... of traditional gas lubrication: 1) Low damping makes operation across critical speed dangerous, as even low level of unbalance can generate large vibration responses. This is especially problematic for gas bearing applications, which often operate in the supercritical region. Moreover, 2) An upper bound...

  8. DESIGN OPTIMIZATION OF ROTOR-BEARING SYSTEMS

    Directory of Open Access Journals (Sweden)

    Hamit SARUHAN

    2003-03-01

    Full Text Available This paper presents a brief study of the information from the published literature and author's works regarding rotor-bearing systems analysis with respect to optimization. The main goal of this work is to motivate and give an idea to designers who are willing to deal with optimization of rotor-bearing sytems. The results obtained and presented in this study are to provide a comparison with numerical optimum design methods such as gradientbased method, and to show the potential of genetic algorithms in optimization of rotor-bearing systems. Genetic algorithms have been used as optimization problem solving techniques. They are parameter search procedures based on the idea of natural selection and genetics. These robust methods have increasingly recognized and applied in many applications.

  9. KINEMATICS FRICTION PAIR FOR EXAMPLE NEEDLE BEARINGS

    Directory of Open Access Journals (Sweden)

    Jerzy NACHIMOWICZ

    2014-06-01

    Full Text Available The present study concerns certain phenomena that take place in the needle roller bearing. The friction that generates the anti-torque of a friction pair is the major factor that influences the needle bearing’s wear. In the needle bearing there occur two predominant types of friction: the rolling friction and the sliding friction, and both are subject to examination. The study presents recordings and analysis of the movements of all needle bearing’s rolling elements. The examination was carried out on a special examination stand that precisely emulates the real conditions of the needle bearing’s work. Carefully prepared examination methods enable recording and analyzing frictions in the bearing, estimating a sphere within which the load is shifted, and calculating the coefficient of friction.

  10. Active Magnetic Bearings – Magnetic Forces

    DEFF Research Database (Denmark)

    Kjølhede, Klaus

    2006-01-01

    Parameter identification procedures and model validation are major steps towards intelligent machines supported by active magnetic bearings (AMB). The ability of measuring the electromagnetic bearing forces, or deriving them from measuring the magnetic flux, strongly contributes to the model...... of the work is the characterization of magnetic forces by using two experimental different experimental approaches. Such approaches are investigated and described in details. A special test rig is designed where the 4 poles - AMB is able to generate forces up to 1900 N. The high precision characterization...... of the magnetic forces are led by using different experimental tests: (I) by using hall sensors mounted directly on the poles (precise measurements of the magnetic flux) and by an auxiliary system, composed of strain gages and flexible beams attached to the rotor; (II) by measuring the input current and bearing...

  11. Powder metallurgy bearings for advanced rocket engines

    Science.gov (United States)

    Fleck, J. N.; Killman, B. J.; Munson, H.E.

    1985-01-01

    Traditional ingot metallurgy was pushed to the limit for many demanding applications including antifriction bearings. New systems require corrosion resistance, better fatigue resistance, and higher toughness. With conventional processing, increasing the alloying level to achieve corrosion resistance results in a decrease in other properties such as toughness. Advanced powder metallurgy affords a viable solution to this problem. During powder manufacture, the individual particle solidifies very rapidly; as a consequence, the primary carbides are very small and uniformly distributed. When properly consolidated, this uniform structure is preserved while generating a fully dense product. Element tests including rolling contact fatigue, hot hardness, wear, fracture toughness, and corrosion resistance are underway on eleven candidate P/M bearing alloys and results are compared with those for wrought 440C steel, the current SSME bearing material. Several materials which offer the promise of a significant improvement in performance were identified.

  12. Drivers of hibernation in the brown bear.

    Science.gov (United States)

    Evans, A L; Singh, N J; Friebe, A; Arnemo, J M; Laske, T G; Fröbert, O; Swenson, J E; Blanc, S

    2016-01-01

    Hibernation has been a key area of research for several decades, essentially in small mammals in the laboratory, yet we know very little about what triggers or ends it in the wild. Do climatic factors, an internal biological clock, or physiological processes dominate? Using state-of-the-art tracking and monitoring technology on fourteen free-ranging brown bears over three winters, we recorded movement, heart rate (HR), heart rate variability (HRV), body temperature (Tb), physical activity, ambient temperature (TA), and snow depth to identify the drivers of the start and end of hibernation. We used behavioral change point analyses to estimate the start and end of hibernation and convergent cross mapping to identify the causal interactions between the ecological and physiological variables over time. To our knowledge, we have built the first chronology of both ecological and physiological events from before the start to the end of hibernation in the field. Activity, HR, and Tb started to drop slowly several weeks before den entry. Bears entered the den when snow arrived and when ambient temperature reached 0 °C. HRV, taken as a proxy of sympathetic nervous system activity, dropped dramatically once the bear entered the den. This indirectly suggests that denning is tightly coupled to metabolic suppression. During arousal, the unexpected early rise in Tb (two months before den exit) was driven by TA, but was independent of HRV. The difference between Tb and TA decreased gradually suggesting that bears were not thermoconforming. HRV increased only three weeks before exit, indicating that late activation of the sympathetic nervous system likely finalized restoration of euthermic metabolism. Interestingly, it was not until TA reached the presumed lower critical temperature, likely indicating that the bears were seeking thermoneutrality, that they exited the den. We conclude that brown bear hibernation was initiated primarily by environmental cues, but terminated by

  13. Big Bear Exploration Ltd. 1998 annual report

    International Nuclear Information System (INIS)

    1999-01-01

    During the first quarter of 1998 Big Bear completed a purchase of additional assets in the Rainbow Lake area of Alberta in which light oil purchase was financed with new equity and bank debt. The business plan was to immediately exploit these light oil assets, the result of which would be increased reserves, production and cash flow. Although drilling results in the first quarter on the Rainbow Lake properties was mixed, oil prices started to free fall and drilling costs were much higher than expected. As a result, the company completed a reduced program which resulted in less incremental loss and cash flow than it budgeted for. On April 29, 1998, Big Bear entered into agreement with Belco Oil and Gas Corp. and Moan Investments Ltd. for the issuance of convertible preferred shares at a gross value of $15,750,000, which shares were eventually converted at 70 cents per share to common equity. As a result of the continued plunge in oil prices, the lending value of the company's assets continued to fall, requiring it to take action in order to meet its financial commitments. Late in the third quarter Big Bear issued equity for proceeds of $11,032,000 which further reduced the company's debt. Although the company has been extremely active in identifying and pursuing acquisition opportunities, it became evident that Belco Oil and Gas Corp. and Big Bear did nor share common criteria for acquisitions, which resulted in the restructuring of their relationship in the fourth quarter. With the future of oil prices in question, Big Bear decided that it would change its focus to that of natural gas and would refocus ts efforts to acquire natural gas assets to fuel its growth. The purchase of Blue Range put Big Bear in a difficult position in terms of the latter's growth. In summary, what started as a difficult year ended in disappointment

  14. Wear Analysis of Wind Turbine Gearbox Bearings

    Energy Technology Data Exchange (ETDEWEB)

    Blau, Peter Julian [ORNL; Walker, Larry R [ORNL; Xu, Hanbing [ORNL; Parten, Randy J [ORNL; Qu, Jun [ORNL; Geer, Tom [ORNL

    2010-04-01

    The objective of this effort was to investigate and characterize the nature of surface damage and wear to wind turbine gearbox bearings returned from service in the field. Bearings were supplied for examination by S. Butterfield and J. Johnson of the National Wind Technology Center (NREL), Boulder, Colorado. Studies consisted of visual examination, optical and electron microscopy, dimensional measurements of wear-induced macro-scale and micro-scale features, measurements of macro- and micro-scale hardness, 3D imaging of surface damage, studies of elemental distributions on fracture surfaces, and examinations of polished cross-sections of surfaces under various etched and non-etched conditions.

  15. The sweet lung: Chewing gummi bear aspiration.

    Science.gov (United States)

    Tavladaki, Theonimfi; Fitrolaki, Michaela-Diana; Spanaki, Anna-Maria; Ilia, Staurula; Geromarkaki, Elissabet; Briassoulis, George

    2012-07-01

    Inhalation of foreign bodies, a leading cause of accidental death, is most common in preschool children. In this article we report our experience with a 5-year-old Greek girl who presented with a 24-hour history of sore throat, chest pain, and shortness of breath. Emergency bronchoscopy was performed and multiple small chewing gummi bear (HARIBO) particles impacted in the orifices of the right main bronchus and right lobar and segmentalinic bronchi were successfully removed and aspirated. Aspiration of gummi bears, which is for the first time reported, may cause a silent choking episode leading to life-threatening bronchi obstruction at multiple sites, even in children older than 4 years.

  16. Local Attitudes towards Bear Management after Illegal Feeding and Problem Bear Activity

    Directory of Open Access Journals (Sweden)

    David Fraser

    2013-09-01

    Full Text Available The “pot bears” received international media attention in 2010 after police discovered the intentional feeding of over 20 black bears during the investigation of an alleged marijuana-growing operation in Christina Lake, British Columbia, Canada. A two-phase random digit dialing survey of the community was conducted in 2011 to understand local perspectives on bear policy and management, before and after a summer of problem bear activity and government interventions. Of the 159 households surveyed in February 2011, most had neutral or positive attitudes towards bears in general, and supported the initial decision to feed the food-conditioned bears until the autumn hibernation. In contrast to wildlife experts however, most participants supported relocating the problem bears, or allowing them to remain in the area, ahead of killing; in part this arose from notions of fairness despite the acknowledged problems of relocation. Most locals were aware of the years of feeding but did not report it, evidently failing to see it as a serious form of harm, even after many bears had been killed. This underscores the importance of preventive action on wildlife feeding and the need to narrow the gap between public and expert opinion on the likely effects of relocation versus killing.

  17. Dynamic Analysis of a Rotor-Bearing-SFD System with the Bearing Inner Race Defect

    Directory of Open Access Journals (Sweden)

    Junhong Zhang

    2017-01-01

    Full Text Available In this paper, the dynamic behavior of a rotor-bearing-SFD system with the inner race defect of bearing is investigated. The contact force between the rolling element and the race is calculated in Hertzian contact and elastohydrodynamic lubrication condition. The supporting force of the SFD is simulated by integrating the pressure distribution derived from Reynolds’s equation. The equations of motion of the rotor-bearing-SFD system are derived and solved using the fourth-order Runge-Kutta method. The dynamic behavior and the fault characteristics are analyzed with two configurations of the SFD: (1 mounted on the unfaulted bearing and (2 mounted on the faulty bearing. According to the analysis of time-frequency diagram, waterfall plot, and spectral diagram, the results show that the characteristics of inner race defects on bearing frequencies are related to the characteristic multiple frequency of the inner race defect and the fundamental frequency. The speed and defect width have different influence on the distribution and amplitude of frequency. The SFD can enhance the system stability under the bearing fault but the enhancement decreases with the increasing speed. Meanwhile, the beneficial effect of the SFD varies according to the mounted position in the rotor system.

  18. A. Palmgren Revisited: A Basis for Bearing Life Prediction

    Science.gov (United States)

    Zaretsky, Erwin V.

    1997-01-01

    Bearing technology, as well as the bearing industry, began to develop with the invention of the bicycle in the 1850's. At the same time, high-quality steel was made possible by the Bessemer process. In 1881, H. Hertz published his contact stress analysis. By 1902, R. Stribeck had published his work based on Hertz theory to calculate the maximum load of a radially loaded ball bearing. By 1920, all of the rolling bearing types used today were being manufactured. AISI 52100 bearing steel became the material of choice for these bearings. Beginning in 1918, engineers directed their attention to predicting the lives of these bearings. In 1924, A. Palmgren published a paper outlining his approach to bearing life prediction. This paper was the basis for the Lundberg-Palmgren life theory published in 1947. A critical review of the 1924 Palmgren paper is presented here together with a discussion of its effect on bearing life prediction.

  19. Three-D CFD Analysis of Hydrostatic Bearings

    Science.gov (United States)

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

    1993-01-01

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

  20. Diet and morphology of extant and recently extinct northern bears

    Science.gov (United States)

    Mattson, David J.

    1998-01-01

    I examined the relationship of diets to skull morphology of extant northern bears and used this information to speculate on diets of the recently extinct cave (Ursus spelaeus) and short-faced (Arctodus simus) bears. Analyses relied upon published skull measurements and food habits of Asiatic (U. thibetanus) and American (U. americanus) black bears, polar bears (U. maritimus), various subspecies of brown bears (U. arctos), and the giant panda (Ailuropoda melanoleuca). Principal components analysis showed major trends in skull morphology related to size, crushing force, and snout shape. Giant pandas, short-faced bears, cave bears, and polar bears exhibited extreme features along these gradients. Diets of brown bears in colder, often non-forested environments were distinguished by large volumes of roots, foliage, and vertebrates, while diets of the 2 black bear species and brown bears occupying broadleaf forests contained greater volumes of mast and invertebrates and overlapped considerably. Fractions of fibrous foods in feces (foliage and roots) were strongly related to skull morphology (R2=0.97)">(R2=0.97). Based on this relationship, feces of cave and short-faced bears were predicted to consist almost wholly of foliage, roots, or both. I hypothesized that cave bears specialized in root grubbing. In contrast, based upon body proportions and features of the ursid digestive tract, I hypothesized that skull features associated with crushing force facilitated a carnivorous rather than herbivorous diet for short-faced bears.

  1. Spatial transposition tasks in Indian sloth bears (Melursus ursinus) and Bornean sun bears (Helarctos malayanus euryspilus).

    Science.gov (United States)

    Hartmann, Daniela; Davila-Ross, Marina; Wong, Siew Te; Call, Josep; Scheumann, Marina

    2017-11-01

    Spatial transposition tasks assess individuals' ability to represent nonvisible spatial object displacements. Several nonhuman mammal species have been tested on this task including primates, cats, and dogs, but to date, great apes seem the only taxon that has repeatedly and consistently solved spatial transposition tasks. The authors investigated the ability of captive sloth and sun bears to solve spatial transposition tasks. Both species belong to the same taxonomic group as cats and dogs, but unlike them and similar to apes, they have an omnivorous diet that requires them to keep track of fruit sources in space and time. The bears were first tested on a visible displacement task and those that succeeded were further tested on a spatial transposition task that involved a 180° transposition, followed by 2 tasks with two 360° transpositions. All 7 sloth bears and 7 out of 9 sun bears solved the visible displacement task. The 180° transposition task was solved by 6 out of 7 sloth bears and 1 out of the 5 tested sun bears. Three sloth bears were tested on all 4 experiments and even solved 2-chained 360° transpositions. Control conditions were conducted showing that the bears' performance did not rely on olfactory or auditory cues. The results provide the first indication that bears might be able to track invisible objects. Further studies will be necessary to confirm these results and to control the influence of associative learning. The present study emphasizes the importance of including different animal species in the investigation of what underlies the evolution of different cognitive skills. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  2. Design of an oil squeeze film damper bearing for a multimass flexible-rotor bearing system

    Science.gov (United States)

    Cunningham, R. E.; Gunter, E. J., Jr.; Fleming, D. P.

    1975-01-01

    A single-mass flexible-rotor analysis was used to optimize the stiffness and damping of a flexible support for a symmetric five-mass rotor. The flexible, damped support attenuates the amplitudes of motions and forces transmitted to the support bearings when the rotor operates through and above its first bending critical speed. An oil squeeze film damper was designed based on short bearing lubrication theory. The damper design was verified by an unbalance response computer program. Rotor amplitudes were reduced by a factor of 16 and loads reduced by a factor of 36 compared with the same rotor with rigid bearing supports.

  3. Experimental Evaluation of Journal Bearing Stability and New Gas Wave Bearing Materials

    Science.gov (United States)

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

    1998-01-01

    A gas journal bearing, with a wavy surfaces was tested in a range of speeds up to 18,000 RPM to determine its stability in an unloaded condition as a function of the wave amplitude. The bearing, was 50 mm in diameter, 58 mm long and had 0.01 65 mm radial clearance. Three waves were created on the inner surface by deforming the bearing sleeve. The ratio of the wave amplitude to the radial clearance (the wave amplitude ratio) was varied from zero to 0.3.

  4. Telemetry experiments with a hibernating black bear

    Science.gov (United States)

    Craighead, J. J.; Varney, J. R.; Sumner, J. S.; Craighead, F. C., Jr.

    1972-01-01

    The objectives of this research were to develop and test telemetry equipment suitable for monitoring physiological parameters and activity of a hibernating bear in its den, to monitor this data and other environmental information with the Nimbus 3 IRLS data collection system, and to refine immobilizing, handling, and other techniques required in future work with wild bears under natural conditions. A temperature-telemetering transmitter was implanted in the abdominal cavity of a captive black bear and body temperature data was recorded continuously during a 3 month hibernation period. Body temperatures ranging between 37.5 and 31.8 C were observed. Body temperature and overall activity were influenced by disturbances and ambient den temperature. Nychthemeral temperature changes were not noticable. A load cell weight recording device was tested for determining weight loss during hibernation. Monitoring of data by satellite was not attempted. The implanted transmitter was removed and the bear was released with a radiolocation collar at the conclusion of the experiment.

  5. An Interview About Hunting a Black Bear

    OpenAIRE

    G.yu lha

    2009-01-01

    The respondent describes the first time he killed a black bear while hunting. The fifty one audio and nine video files in this collection include: villages’ life stories, circle-dancing songs and performance, local history, folk tales, and interviews from Siyuewu Village, Puxi Township, Rangtang County, Aba Tibetan and Qiang Autonomous Prefecture, Sichuan Province, China. World Oral Literature Project

  6. Contact fatigue in rolling-element bearings

    CSIR Research Space (South Africa)

    Fernandes, PJL

    1997-06-01

    Full Text Available Surface contact fatigue is a common cause of failure in rolling-element bearings. The extent of damage observed depends on the contact loads, the curvature of the rolling elements, and the relative motion between the contacting surfaces...

  7. Self-lubricating fluid bearing assembly

    International Nuclear Information System (INIS)

    Kapich, D.D.

    1981-01-01

    A sealed self-lubricating fluid bearing assembly is described for circulating fluid in the form of a gas coolant in a nuclear reactor, the power for the circulator being provided by a shaft located within the primary containment vessel. In such a system the reactor coolant is isolated from the fluid region at the far end of the drive shaft. (U.K.)

  8. Load-Bearing Capacity of Roof Trusses

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Damkilde, Lars; Munch-Andersen, J.

    2004-01-01

    systems such as roof trusses are established and statistical characteristics of the load bearing capacity are determined. The results show that there is a significant increase in the characteristic (nominal) value and a reduction in the coefficient of variation (COV) for typical loads such as permanent...

  9. Extended Life Testing of Duplex Ball Bearings

    Science.gov (United States)

    Mobley, Jeffrey; Robertson, Michael; Hodges, Charles

    2016-01-01

    Sierra Nevada Corporation’s Space Systems performed bearing life testing for the Scan Mirror Motor/Encoder Assembly (SMMA), part of the Scan Mirror Assembly on-board the Aerosol Polarimetry Sensor (APS) on the NASA Glory Spacecraft. The baseline bearing life test duration extended beyond the launch date for the Glory Spacecraft; a risk that the program was willing to undertake with the understanding that if any anomalies or failures occurred before the required life was achieved, then the mission objectives or operating profile could be modified on orbit to take those results into account. Even though the Glory Spacecraft failed to reach orbit during its launch in March of 2011, the bearing life testing was continued through a mutual understanding of value between Sierra Nevada Corporation and our customer; with a revised goal of testing to failure rather than completing a required number of life cycles. Life testing thus far has not only exceeded the original mission required life, but has also exceeded the published test data for Cumulative Degradation Factor (CDF) from NASA/CR-2009-215681. Many lessons were learned along the way regarding long life testing. The bearing life test has been temporarily suspended due to test support equipment issues.

  10. Thermo-hydrodynamic lubrication in hydrodynamic bearings

    CERN Document Server

    Bonneau, Dominique; Souchet, Dominique

    2014-01-01

    This Series provides the necessary elements to the development and validation of numerical prediction models for hydrodynamic bearings. This book describes the thermo-hydrodynamic and the thermo-elasto-hydrodynamic lubrication. The algorithms are methodically detailed and each section is thoroughly illustrated.

  11. Eddy-Current Inspection of Ball Bearings

    Science.gov (United States)

    Bankston, B.

    1985-01-01

    Custom eddy-current probe locates surface anomalies. Low friction air cushion within cone allows ball to roll easily. Eddy current probe reliably detects surface and near-surface cracks, voids, and material anomalies in bearing balls or other spherical objects. Defects in ball surface detected by probe displayed on CRT and recorded on strip-chart recorder.

  12. Angular-momentum-bearing modes in fission

    International Nuclear Information System (INIS)

    Moretto, L.G.; Peaslee, G.F.; Wozniak, G.J.

    1989-03-01

    The angular-momentum-bearing degrees of freedom involved in the fission process are identified and their influence on experimental observables is discussed. The excitation of these modes is treated in the ''thermal'' limit, and the resulting distributions of observables are calculated. Experiments demonstrating the role of these modes are presented and discussed. 61 refs., 12 figs

  13. Weak and strong nonlinearities in magnetic bearings

    Czech Academy of Sciences Publication Activity Database

    Půst, Ladislav

    2004-01-01

    Roč. 39, č. 7 (2004), s. 779-795 ISSN 0094-114X R&D Projects: GA ČR GA101/00/1471; GA AV ČR IBS2076301 Institutional research plan: CEZ:AV0Z2076919 Keywords : weak nonlinearitiy * strong nonlinearity * magnetics bearings Subject RIV: BI - Acoustics Impact factor: 0.605, year: 2004

  14. Film Thickness in Grease Lubricated Rolling Bearings

    NARCIS (Netherlands)

    Lugt, Piet M.; Van Zoelen, M. T.; Venner, C. H.; Lugt, Piet M.

    2012-01-01

    In this chapter the theory from Chapter 9 will be applied to rolling bearings. The thin layer flow equations are used to describe the tangential and normal flow due to centrifugal forces. The interaction between the various contacts on inner ring and outer ring will be described followed by the

  15. Technique for improving hydrodynamic gyro bearings

    Science.gov (United States)

    Broussard, P., Jr.; Burch, J. L.

    1970-01-01

    Conical or spherical, spirally grooved grease bearings have an inclined surface which is machined inboard of the grooved surface. The indentation and inclined surface provide a reservoir for forced out lubricant, and when rotation begins, centrifugal force returns the lubricant to the grooved area.

  16. Heavy Bearings Exploitation Energy and Reduction Methods

    Science.gov (United States)

    Szekely, V. G.; Cioară, R.

    2016-11-01

    The global trend of resource conservation so as “not to compromise the ability of future generation's development” is the fundamental basis of the concept of sustainable development. Concordant with this, the energy efficiency of products is increasingly discussed and frequently taken into account in the design stage. In more cases a product is more appreciated and more attractive as the energy consumption and its associated materials are lower. In the production stage, said consumption advantages primarily the manufacturer, particularly through low consumption thereof. In the operational phase, low energy and materials consumption represents an user advantage and it's a major argument in the decision to purchase and use a particular product. Heavy bearings are frequent products used in wind turbines that are producing non-conventional “clean” energy, as windmills. An enhanced energy efficiency bearing contributes to the enhancement of the overall efficiency of the wind turbines. Based on a suitable mathematical model, this paper identifies and recommends courses of action to reduce the operating energy of heavy bearing through the “cage” - which is the subject of a much larger research - with the highest priority. The identified actions may constitute from a set of requirements for the design stage of the heavy bearing predominantly oriented towards innovation-invention.

  17. Additive Manufacturing for Low Volume Bearings

    Energy Technology Data Exchange (ETDEWEB)

    Tate, John G. [Schaeffler Group USA, Spartanburg, SC (United States); Richardson, Bradley S. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Love, Lonnie J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-09-01

    ORNL worked with the Schaeffler Group USA to explore additive manufacturing techniques that might be appropriate for prototyping of bearing cages. Multiple additive manufacturing techniques were investigated, including e-beam, binder jet and multiple laser based processes. The binder jet process worked best for the thin, detailed cages printed.

  18. The economics of roadside bear viewing

    Science.gov (United States)

    Richardson, Leslie; Rosen, Tatjana; Gunther, Kerry; Schwartz, Chuck

    2014-01-01

    Viewing bears along roadside habitats is a popular recreational activity in certain national parks throughout the United States. However, safely managing visitors during traffic jams that result from this activity often requires the use of limited park resources. Using unique visitor survey data, this study quantifies economic values associated with roadside bear viewing in Yellowstone National Park, monetary values that could be used to determine whether this continued use of park resources is warranted on economic grounds. Based on visitor expenditure data and results of a contingent visitation question, it is estimated that summer Park visitation would decrease if bears were no longer allowed to stay along roadside habitats, resulting in a loss of 155 jobs in the local economy. Results from a nonmarket valuation survey question indicate that on average, visitors to Yellowstone National Park are willing to pay around $41 more in Park entrance fees to ensure that bears are allowed to remain along roads within the Park. Generalizing this value to the relevant population of visitors indicates that the economic benefits of allowing this wildlife viewing opportunity to continue could outweigh the costs of using additional resources to effectively manage these traffic jams.

  19. Load Bearing Equipment for Bone and Muscle

    Science.gov (United States)

    Shackelford, Linda; Griffith, Bryan

    2015-01-01

    Resistance exercise on ISS has proven effective in maintaining bone mineral density and muscle mass. Exploration missions require exercise with similar high loads using equipment with less mass and volume and greater safety and reliability than resistance exercise equipment used on ISS (iRED, ARED, FWED). Load Bearing Equipment (LBE) uses each exercising person to create and control the load to the partner.

  20. Bearings and Seals. FOS: Fundamentals of Service.

    Science.gov (United States)

    John Deere Co., Moline, IL.

    This manual on bearings and seals is one of a series of power mechanics texts and visual aids for use in training for the servicing of automotive and off-the-road farm and industrial machines. Materials provide basic information and illustrations for use by vocational students and teachers as well as shop servicemen and laymen. Focusing on…

  1. Stability of multi orifice active tilting-pad journal bearings

    DEFF Research Database (Denmark)

    Haugaard, Asger M.; Santos, Ilmar

    2010-01-01

    The stability properties of actively lubricated tilting-pad journal bearings are investigated theoretically. The bearing preload factor and control system gains are varied, and stable and unstable regions are identified. It is seen, that the control system influences bearing stability, and that t......The stability properties of actively lubricated tilting-pad journal bearings are investigated theoretically. The bearing preload factor and control system gains are varied, and stable and unstable regions are identified. It is seen, that the control system influences bearing stability...

  2. Fault tolerant homopolar magnetic bearings with flux invariant control

    International Nuclear Information System (INIS)

    Na, Uhn Joo

    2006-01-01

    The theory for a novel fault-tolerant 4-active-pole homopolar magnetic bearing is developed. If any one coil of the four coils in the bearing actuator fail, the remaining three coil currents change via an optimal distribution matrix such that the same opposing pole, C-core type, control fluxes as those of the un-failed bearing are produced. The homopolar magnetic bearing thus provides unaltered magnetic forces without any loss of the bearing load capacity even if any one coil suddenly fails. Numerical examples are provided to illustrate the novel fault-tolerant, 4-active pole homopolar magnetic bearings

  3. Three-Wave Gas Journal Bearing Behavior With Shaft Runout

    Science.gov (United States)

    Dimofte, Florin; Hendricks, Robert C.

    1997-01-01

    Experimental orbits of a free-mounted, three-wave gas journal bearing housing were recorded and compared to transient predicted orbits. The shaft was mounted eccentric with a fixed runout. Experimental observations for both the absolute bearing housing center orbits and the relative bearing housing center to shaft center orbits are in good agreement with the predictions. The sub-synchronous whirl motion generated by the fluid film was found experimentally and predicted theoretically for certain speeds. A three-wave journal bearing can run stably under dynamic loads with orbits well inside the bearing clearance. Moreover, the orbits are almost circular free of the influence of bearing wave shape.

  4. Thermohydrodynamic analysis of cryogenic liquid turbulent flow fluid film bearings

    Science.gov (United States)

    Andres, Luis San

    1993-01-01

    A thermohydrodynamic analysis is presented and a computer code developed for prediction of the static and dynamic force response of hydrostatic journal bearings (HJB's), annular seals or damper bearing seals, and fixed arc pad bearings for cryogenic liquid applications. The study includes the most important flow characteristics found in cryogenic fluid film bearings such as flow turbulence, fluid inertia, liquid compressibility and thermal effects. The analysis and computational model devised allow the determination of the flow field in cryogenic fluid film bearings along with the dynamic force coefficients for rotor-bearing stability analysis.

  5. Dual-action gas thrust bearing for improving load capacity

    Science.gov (United States)

    Etsion, I.

    1976-01-01

    The principle of utilizing hydrodynamic effects in diverging films to improve the load carrying capacity in gas thrust bearings is discussed. A new concept of a dual action bearing based on that principle is described and analyzed. The potential of the new bearing is demonstrated both analytically for an infinitely long slider and by numerical solution for a flat sector shaped thrust bearing. It is shown that the dual action bearing can extend substantially the range of load carrying capacity in gas lubricated thrust bearings and can improve their efficiency.

  6. Bear maul craniocerebral trauma in Kashmir Valley.

    Science.gov (United States)

    Bashir, Sheikh Adil; Rasool, Altaf; Zaroo, Mohamad Inam; Wani, Adil Hafeez; Zargar, Haroon Rashid; Darzi, Mohammad Ashraf; Khursheed, Nayil

    2013-01-01

    Craniocerebral injuries constitute the bulk of the trauma patients in all the tertiary-care hospitals. Bear attacks as a cause of trauma to the brain and its protective covering are rare. This was a hospital-based retrospective (January 1990 to July 2005) and prospective study (August 2005 to December 2010). Craniocerebral trauma was seen in 49 patients of bear maul injuries. Loss of scalp tissue was seen in 17 patients, 13 of whom had exposed pericranium and needed split-thickness skin grafting, while 4 patients with exposed skull bones required scalp transposition flaps as an initial procedure. Skull bone fractures without associated brain injury were observed in 24 cases. Frontal bone was the site of fracture in the majority of cases (95%). Surgical intervention was needed in 18 patients for significantly depressed fractures. Three of these patients had depressed frontal bone fractures with underlying contusions and needed brain debridement and duraplasty. Injury to the brain was observed in 8 patients. Trauma to the brain and its protective coverings as a result of bear attacks is rarely known. Brain injury occurs less commonly as compared to soft tissue and bony injury. Craniocerebral trauma as a result of bear assaults has been a hitherto neglected area of trauma as the past reported incidence has been very low. Of late, the incidence and severity of such attacks has assumed grave proportions in areas adjacent to known bear habitats. An innocuous-looking surface wound might be the only presentation of an underlying severe brain trauma. Public awareness has to be generated to protect the people living in hilly areas.

  7. The role of human outdoor recreation in shaping patterns of grizzly bear-black bear co-occurrence.

    Directory of Open Access Journals (Sweden)

    Andrew Ladle

    Full Text Available Species' distributions are influenced by a combination of landscape variables and biotic interactions with other species, including people. Grizzly bears and black bears are sympatric, competing omnivores that also share habitats with human recreationists. By adapting models for multi-species occupancy analysis, we analyzed trail camera data from 192 trail camera locations in and around Jasper National Park, Canada to estimate grizzly bear and black bear occurrence and intensity of trail use. We documented (a occurrence of grizzly bears and black bears relative to habitat variables (b occurrence and intensity of use relative to competing bear species and motorised and non-motorised recreational activity, and (c temporal overlap in activity patterns among the two bear species and recreationists. Grizzly bears were spatially separated from black bears, selecting higher elevations and locations farther from roads. Both species co-occurred with motorised and non-motorised recreation, however, grizzly bears reduced their intensity of use of sites with motorised recreation present. Black bears showed higher temporal activity overlap with recreational activity than grizzly bears, however differences in bear daily activity patterns between sites with and without motorised and non-motorised recreation were not significant. Reduced intensity of use by grizzly bears of sites where motorised recreation was present is a concern given off-road recreation is becoming increasingly popular in North America, and can negatively influence grizzly bear recovery by reducing foraging opportunities near or on trails. Camera traps and multi-species occurrence models offer non-invasive methods for identifying how habitat use by animals changes relative to sympatric species, including humans. These conclusions emphasise the need for integrated land-use planning, access management, and grizzly bear conservation efforts to consider the implications of continued access for

  8. The role of human outdoor recreation in shaping patterns of grizzly bear-black bear co-occurrence.

    Science.gov (United States)

    Ladle, Andrew; Steenweg, Robin; Shepherd, Brenda; Boyce, Mark S

    2018-01-01

    Species' distributions are influenced by a combination of landscape variables and biotic interactions with other species, including people. Grizzly bears and black bears are sympatric, competing omnivores that also share habitats with human recreationists. By adapting models for multi-species occupancy analysis, we analyzed trail camera data from 192 trail camera locations in and around Jasper National Park, Canada to estimate grizzly bear and black bear occurrence and intensity of trail use. We documented (a) occurrence of grizzly bears and black bears relative to habitat variables (b) occurrence and intensity of use relative to competing bear species and motorised and non-motorised recreational activity, and (c) temporal overlap in activity patterns among the two bear species and recreationists. Grizzly bears were spatially separated from black bears, selecting higher elevations and locations farther from roads. Both species co-occurred with motorised and non-motorised recreation, however, grizzly bears reduced their intensity of use of sites with motorised recreation present. Black bears showed higher temporal activity overlap with recreational activity than grizzly bears, however differences in bear daily activity patterns between sites with and without motorised and non-motorised recreation were not significant. Reduced intensity of use by grizzly bears of sites where motorised recreation was present is a concern given off-road recreation is becoming increasingly popular in North America, and can negatively influence grizzly bear recovery by reducing foraging opportunities near or on trails. Camera traps and multi-species occurrence models offer non-invasive methods for identifying how habitat use by animals changes relative to sympatric species, including humans. These conclusions emphasise the need for integrated land-use planning, access management, and grizzly bear conservation efforts to consider the implications of continued access for motorised

  9. Yellowstone grizzly bear investigations: Annual report of the Interagency Grizzly Bear Study Team, 2006

    Science.gov (United States)

    Schwartz, Charles C.; Haroldson, Mark A.; West, Karrie K.

    2007-01-01

    The contents of this Annual Report summarize results of monitoring and research from the 2006 field season. The report also contains a summary of nuisance grizzly bear (Ursus arctos horribilis) management actions.

  10. Local Attitudes towards Bear Management after Illegal Feeding and Problem Bear Activity

    OpenAIRE

    David Fraser; Sara Dubois

    2013-01-01

    Simple Summary The “pot bears” received international media attention in 2010 after police discovered the intentional feeding of black bears during the investigation of an alleged marijuana-growing operation in Christina Lake, British Columbia. Residents of this small community were surveyed by phone twice over the following year, before and after government actions. This study aimed to understand local attitudes on how these bears should be managed and whether they differed from existing bea...

  11. The thermodynamic properties of a new type catcher bearing used in active magnetic bearings system

    International Nuclear Information System (INIS)

    Jin, Chaowu; Zhu, Yili; Xu, Longxiang; Xu, Yuanping; Zheng, Yantong

    2015-01-01

    Normally a rotor levitated by active magnetic bearings (AMBs) system would rotate without contacting with any stator component, but the possibility still remains that the supporting force might lose temporarily or permanently, thus requiring the Catcher bearings (CBs) to provide backup protection in case of the failure of AMBs. A new type CB with two separate rolling element bearing series could have the speed distribution between the inner race and intermediate race according to certain ratio, in which the speed of each roller element bearing decreases with the limit speed of the whole CB increasing, offering high capability to sustain its initial rotation speed. Based on the theory of heat transfer, tribology, and rotor dynamics, this paper analyzes the thermal structure of double-decker catcher bearing (DDCB) and single-decker catcher bearing (SDCB), respectively. Through this structure, the thermal resistances and equations of heat transfer can be obtained. Then we calculate the friction heat and temperature distribution in the various CBs upon rotor's dropping on SDCB or DDCB, followed by the discussion on the CBs temperature rise's effects on lubrication conditions and rotor dynamics parameters. Finally various experiments are carried out to measure the temperature rise of different CBs. The results obtained validate the theoretical analysis and also provide main methods to reduce heat generation. Using DDCB is proved to be effective to reduce the temperature rise. - Highlights: • The DDCB is a more suitable catcher bearing for AMBs. • Compared to SDCB, using DDCB, the temperature rise can decrease in the same states. • A lower viscosity of lubricant may induce a lower temperature rise. • The inner raceway temperature of the first layer bearing is the highest. • Reducing the unbalance mass of the rotor is a method to decrease the temperature rise

  12. Reduced Bearing Excursion After Mobile-Bearing Unicompartmental Knee Arthroplasty is Associated With Poor Functional Outcomes.

    Science.gov (United States)

    Wahal, Naman; Gaba, Sahil; Malhotra, Rajesh; Kumar, Vijay; Pegg, Elise C; Pandit, Hemant

    2018-02-01

    A small proportion of patients with mobile unicompartmental knee arthroplasty (UKA) report poor functional outcomes in spite of optimal component alignment on postoperative radiographs. The purpose of this study is to assess whether there is a correlation between functional outcome and knee kinematics. From a cohort of consecutive cases of 150 Oxford medial UKA, patients with fair/poor functional outcome at 1-year postsurgery (Oxford Knee Score [OKS] bearing position with knee flexion angle. Mean OKS in the fair/poor group was 29.9 and the mean OKS in the good/excellent group was 41.1. The tibial slope, time taken to complete the exercises, and patellar tendon angle trend over the flexion range were similar in both the groups; however, bearing position and the extent of bearing excursion differed significantly. The total bearing excursion in the OKS bearing was positioned 1.7 mm more posterior on the tibia in the OKS bearing excursion and positioning, are associated with worse functional outcomes after mobile UKA. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Nuclear fuel handling grapple carriage with self-lubricating bearing

    International Nuclear Information System (INIS)

    1977-01-01

    This invention relates to the provision of a fuel handling grapple carriage for a sodium cooled fast breeder reactor with sodium coolant lubricated bearings in which contamination of the bearings is prevented. (UK)

  14. Detection of outer raceway bearing defects in small induction motors ...

    Indian Academy of Sciences (India)

    MCSA) for detection of rolling element bearing damage from the outer raceway. In this work, MCSA and vibration analysis are applied to induction motor to detect outer raceway defects in faulty bearings. Data acquisition, recording,and fast ...

  15. Experimental Study and Dynamic Modeling of Metal Rubber Isolating Bearing

    International Nuclear Information System (INIS)

    Zhang, Ke; Zhou, Yanguo; Jiang, Jian

    2015-01-01

    In this paper, dynamic shear mechanical properties of a new metal rubber isolating bearing is tested and studied. The mixed damping model is provided for theoretical modeling of MR isolating bearing, the shear stiffness and damping characteristics of the MR bearing can be analyzed separately and easily discussed, and the mixed damping model is proved to be an rather effective approach. The test results indicate that loading frequency bears little impact over shear property of metal rubber isolating bearing, the total energy consumption of metal rubber isolating bearing increases with the increase in loading amplitude. With the increase in loading amplitude, the stiffness of the isolating bearing will reduce showing its “soft property”; and the type of damping force gradually changes to be close to dry friction. The features of “soft property” and dry friction energy consumption of metal rubber isolating bearing are very useful in practical engineering application. (paper)

  16. Trichinella and polar bears: a limited risk for humans.

    Science.gov (United States)

    Dupouy-Camet, J; Bourée, P; Yera, H

    2017-07-01

    In this review, we identified 63 cases reported since World War II of human trichinellosis linked to the consumption of parasitized polar bear (Ursus maritimus) meat. This low number contrasts to the numerous cases of human trichinellosis related to consumption of the meat of black (U. americanus) or brown bears (U. arctos). The prevalence of Trichinella infection is high in bears, but larval muscular burden is usually lower in polar bears compared to other bear species. Polar bears, therefore, seem to play a limited role in the transmission of trichinellosis to humans, as native residents living in the Arctic traditionally consume well-cooked bear meat, and travellers and foreign hunters have only limited access to this protected species due to the declining polar bear population.

  17. Self-Bearing Motor-Generator for Flywheels, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Self-bearing or ?bearingless? motors perform both motor and bearing support functions but such devices have not yet achieved speeds above 15,000 rpm. The innovation...

  18. SPECTRAL ANALYSIS OF GAS BEARING SYSTEMS FOR STABILITY STUDIES

    Science.gov (United States)

    latter case is given in terms of a herringbone-grooved journal bearing . This method of stability analysis is applicable to both thrust and journal bearings for both whirl and pneumatic-hammer instabilities.

  19. Interchangeable Bearings for Profile and Weight Trade Studies Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Air-Lock, Incorporated is proposing to design fully sealed shoulder and arm bearings with interchangeable bearing housings. The interchangeable housings shall be...

  20. Long life, high speed, thrust-load ball bearings

    Science.gov (United States)

    Signer, H.; Bamberger, E. N.; Zaretsky, E. V.

    1975-01-01

    Long-term bearing operation at three million DN can be achieved with high degree of reliability using full combination of sophisticated but currently available state-of-the-art bearing materials and designs, lubricants, and lubricating techniques.

  1. Blade Bearing Friction Estimation of Operating Wind Turbines

    DEFF Research Database (Denmark)

    Perisic, Nevena; Pedersen, Bo Juul; Kirkegaard, Poul Henning

    2012-01-01

    Blade root bearing on a wind turbine (WTG) enables pitching of blades for power control and rotor braking and is a WTG critical component. As the size of modern WTGs is constantly increasing, this leads to relatively less rigid bearings, more sensitive to deformations, thus WTG operational...... reliability can be increased by continuous monitoring of blade bearing. High blade bearing friction is undesirable, as it may be associated with excessive heating of the surfaces, damage and/or inefficient operation. Thus, continuous observation of bearing friction level is crucial for blade bearing health...... monitoring systems. A novel algorithm for online monitoring of bearing friction level is developed combining physical knowledge about pitch system dynamics with state estimator, i.e. observer theory and signal processing assuming realistic sensor availability. Results show estimation of bearing friction...

  2. Marking activity of the Kamchatka brown bear (Ursus arctos piscator)

    OpenAIRE

    Seryodkin, Ivan V.

    2014-01-01

    The marking activity of brown bears was studied in the Kronotsky Reserve (eastern shore of the Kamchatka Peninsula) between 2002 and 2005. The goal of this investigation was to document communication mechanisms within the species. We recorded descriptions of bears rubbing and marking trees, as well as individual marking behaviour of bears in the Valley of the Geysers. We recorded 203 marked trees in an area of 2.5 km2 . Bears marked mostly stone birches (Betula ermanii ) with a mean diameter ...

  3. Design and test of a magnetic thrust bearing

    Science.gov (United States)

    Allaire, P. E.; Mikula, A.; Banerjee, B.; Lewis, D. W.; Imlach, J.

    1993-01-01

    A magnetic thrust bearing can be employed to take thrust loads in rotating machinery. The design and construction of a prototype magnetic thrust bearing for a high load per weight application is described. The theory for the bearing is developed. Fixtures were designed and the bearing was tested for load capacity using a universal testing machine. Various shims were employed to have known gap thicknesses. A comparison of the theory and measured results is presented.

  4. Computer program for flat sector thrust bearing performance

    Science.gov (United States)

    Presler, A. F.; Etsion, I.

    1977-01-01

    A versatile computer program is presented which achieves a rapid, numerical solution of the Reynolds equation for a flat sector thrust pad bearing with either compressible or liquid lubricants. Program input includes a range in values of the geometric and operating parameters of the sector bearing. Performance characteristics are obtained from the calculated bearing pressure distribution. These are the load capacity, center of pressure coordinates, frictional energy dissipation, and flow rates of liquid lubricant across the bearing edges. Two sample problems are described.

  5. EXPERIMENTAL APPARATUS FOR EXAMINATION OF MAGNETIC FLUID LUBRICATED THURST BEARING

    Directory of Open Access Journals (Sweden)

    Józef SALWIŃSKI

    2014-06-01

    Full Text Available In recent years, there has been development of the structure of thrust bearing with magnetic fluids . The essence of this type of bearing is to maintain a liquid lubricant in a very narrow gap with magnetic fluid by a magnetic field. Such systems can act as the bearing lubrication and sealing. This paper presents description of the experimental apparatus for examination magnetic fluid lubricated thrust bearing. Description of the construction and characteristics of the measuring possibilities ware presented.

  6. Feature Extraction for Bearing Prognostics and Health Management (PHM) - A Survey (Preprint)

    National Research Council Canada - National Science Library

    Yan, Weizhong; Qiu, Hai; Iyer, Naresh

    2008-01-01

    Feature extraction in bearing PHM involves extracting characteristic signatures from the original sensor measurements, which are sensitive to bearing conditions and thus most useful in determining bearing faults...

  7. Static Load Distribution in Ball Bearings

    Science.gov (United States)

    Ricci, Mario

    2010-01-01

    A numerical procedure for computing the internal loading distribution in statically loaded, single-row, angular-contact ball bearings when subjected to a known combined radial and thrust load is presented. The combined radial and thrust load must be applied in order to avoid tilting between inner and outer rings. The numerical procedure requires the iterative solution of Z + 2 simultaneous nonlinear equations - where Z is the number of the balls - to yield an exact solution for axial and radial deflections, and contact angles. Numerical results for a 218 angular-contact ball bearing have been compared with those from the literature and show significant differences in the magnitudes of the ball loads, contact angles, and the extent of the loading zone.

  8. Self-Assembling Brush Polymers Bearing Multisaccharides.

    Science.gov (United States)

    Lee, Jongchan; Kim, Jin Chul; Lee, Hoyeol; Song, Sungjin; Kim, Heesoo; Ree, Moonhor

    2017-06-01

    Three different series of brush polymers bearing glucosyl, maltosyl, or maltotriosyl moiety at the bristle end are successfully prepared by using cationic ring-opening polymerization and two sequential postmodification reactions. All brush polymers, except for the polymer containing 100 mol% maltotriosyl moiety, demonstrate the formation of multibilayer structure in films, always providing saccharide-enriched surface. These self-assembling features are remarkable, regarding the bulkiness of saccharide moieties and the kink in the bristle due to the triazole linker. The saccharide-enriched film surfaces reveal exceptionally high specific binding affinity to concanavalin A but suppress nonspecific binding of plasma proteins severely. Overall, the brush polymers bearing saccharide moieties of various kinds in this study are highly suitable materials for biomedical applications including biosensors. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Combination radial and thrust magnetic bearing

    Science.gov (United States)

    Blumenstock, Kenneth A. (Inventor)

    2002-01-01

    A combination radial and thrust magnetic bearing is disclosed that allows for both radial and thrust axes control of an associated shaft. The combination radial and thrust magnetic bearing comprises a rotor and a stator. The rotor comprises a shaft, and first and second rotor pairs each having respective rotor elements. The stator comprises first and second stator elements and a magnet-sensor disk. In one embodiment, each stator element has a plurality of split-poles and a corresponding plurality of radial force coils and, in another embodiment, each stator element does not require thrust force coils, and radial force coils are replaced by double the plurality of coils serving as an outer member of each split-pole half.

  10. Trichinella surveillance in black bears (Ursus americanus) from Oregon, USA.

    Science.gov (United States)

    Mortenson, J A; Kent, M L; Fowler, D R; Chomel, B B; Immell, D A

    2014-01-01

    We used serology and muscle digestion to test black bears (Ursus americanus) from western Oregon, USA, for Trichinella. Results indicate black bears in Oregon are not part of a sylvatic cycle for Trichinella, and risk of human exposure to Trichinella larvae from eating black bear meat from Oregon appears low.

  11. Oak-Black Bear Relationships in Southeastern Uplands

    Science.gov (United States)

    Joseph D. Clark

    2004-01-01

    Bears (Ursus americanus) primarily occur in upland habitats in the Southeast because uplands were the last to be developed for agriculture and were more likely to become publicly owned. National parks and forests created in the early to mid-1900s served as sources to supply surrounding uplands with bears. Bears could not survive in southeastern...

  12. Identification of dynamic properties of radial air-foil bearings

    NARCIS (Netherlands)

    Arora, Vikas; Arora, V.; van der Hoogt, Peter; Aarts, Ronald G.K.M.; de Boer, Andries

    2010-01-01

    Air-foil bearings (AFBs) are self acting hydrodynamic bearings made from sheet metal foils comprised of at least two layers. The innermost “top foil” layer traps a gas pressure film that supports a load while the layer or layers underneath provide an elastic foundation. Air-foil bearings are

  13. 77 FR 73967 - Drawbridge Operation Regulation; Bear Creek, Dundalk, MD

    Science.gov (United States)

    2012-12-12

    ...-AA09 Drawbridge Operation Regulation; Bear Creek, Dundalk, MD AGENCY: Coast Guard, DHS. ACTION... Avenue across Bear Creek, mile 3.4, between Dundalk and Sparrows Point, MD. The proposed change would... Notice of Proposed Rulemaking entitled ``Drawbridge Operation Regulation; Bear Creek, Dundalk, MD'' in...

  14. 77 FR 5201 - Drawbridge Operation Regulation; Bear Creek, Dundalk, MD

    Science.gov (United States)

    2012-02-02

    ...-AA09 Drawbridge Operation Regulation; Bear Creek, Dundalk, MD AGENCY: Coast Guard, DHS. ACTION: Notice... operation of the Baltimore County highway bridge at Wise Avenue across Bear Creek, mile 3.4, between Dundalk... Avenue across Bear Creek, mile 3.4 between Dundalk and Sparrows Point, MD. This change would require the...

  15. 49 CFR 215.115 - Defective roller bearing.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Defective roller bearing. 215.115 Section 215.115... § 215.115 Defective roller bearing. (a) A railroad may not place or continue in service a car, if the car has— (1) A roller bearing that shows signs of having been overheated as evidenced by— (i...

  16. 49 CFR 215.111 - Defective plain bearing.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Defective plain bearing. 215.111 Section 215.111... § 215.111 Defective plain bearing. A railroad may not place or continue in service a car, if the car has a plain bearing— (a) That is missing, cracked, or broken; (b) On which the bearing liner— (1) Is...

  17. Marking behavior of Andean bears in an Ecuadorian cloud forest

    NARCIS (Netherlands)

    Filipczyková, Eva; Heitkonig, Ignas; Castellanos, Armando; Hantson, Wouter; Steyaert, Sam M.J.G.

    2017-01-01

    Very little is known about marking behavior of the endangered Andean bear (Tremarctos ornatus). Here, we present a first detailed description of Andean bear marking behavior obtained using camera traps. From November 2012 to April 2013, we inspected 16 bear trails in the Napo province of eastern

  18. The Imagined Bear | Bieder | Current Writing: Text and Reception in ...

    African Journals Online (AJOL)

    This spiritual power was often articulated through stories such as those presented here where bears are portrayed as powerful sacred spirits; as ancestors, healers, shape-shifters, lovers and mates. The stories, however, are not just about bears; the stories are also about cultures and how peoplo saw themselves in bears ...

  19. Coating Hydrostatic Bearings To Resist Ignition In Oxygen

    Science.gov (United States)

    Funkhouser, Merle E.

    1993-01-01

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

  20. Studies on Automobile Clutch Release Bearing Characteristics with Acoustic Emission

    Science.gov (United States)

    Chen, Guoliang; Chen, Xiaoyang

    Automobile clutch release bearings are important automotive driveline components. For the clutch release bearing, early fatigue failure diagnosis is significant, but the early fatigue failure response signal is not obvious, because failure signals are susceptible to noise on the transmission path and to working environment factors such as interference. With an improvement in vehicle design, clutch release bearing fatigue life indicators have increasingly become an important requirement. Contact fatigue is the main failure mode of release rolling bearing components. Acoustic emission techniques in contact fatigue failure detection have unique advantages, which include highly sensitive nondestructive testing methods. In the acoustic emission technique to detect a bearing, signals are collected from multiple sensors. Each signal contains partial fault information, and there is overlap between the signals' fault information. Therefore, the sensor signals receive simultaneous source information integration is complete fragment rolling bearing fault acoustic emission signal, which is the key issue of accurate fault diagnosis. Release bearing comprises the following components: the outer ring, inner ring, rolling ball, cage. When a failure occurs (such as cracking, pitting), the other components will impact damaged point to produce acoustic emission signal. Release bearings mainly emit an acoustic emission waveform with a Rayleigh wave propagation. Elastic waves emitted from the sound source, and it is through the part surface bearing scattering. Dynamic simulation of rolling bearing failure will contribute to a more in-depth understanding of the characteristics of rolling bearing failure, because monitoring and fault diagnosis of rolling bearings provide a theoretical basis and foundation.

  1. PROVIDING SERVICEABILITY OF STRUCTURAL BEARING TYPES FOR ROADWAY BRIDGES

    Directory of Open Access Journals (Sweden)

    R. I. Polyuga

    2010-03-01

    Full Text Available In the article the description of structural bearing types for roadway bridges and their classification is given. Special attention is paid to effective bearings with elastomeric materials – rubber, pot, spherical ones. Characteristic defects of structural bearings and demands of serviceability are noticed.

  2. 49 CFR 230.103 - Tender roller bearing journal boxes.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Tender roller bearing journal boxes. 230.103... Locomotives and Tenders Running Gear § 230.103 Tender roller bearing journal boxes. Tender roller bearing journal boxes shall be maintained in a safe and suitable condition. ...

  3. Nonlinear electromagnetic effects on magnetic bearing performance and power loss

    Science.gov (United States)

    Kenny, Andrew

    Magnetic bearings are now being used in many applications. One of their features is their ability to apply force without contact. Thus they do not wear out from friction and are quiet. Magnetic bearings have very low levels of parasitic drag torque and force, especially at lower speeds. Active magnetic bearings can utilize microprocessors and feedback to control or excite vibrations in a manner that is unique from all other types of bearings. This dissertation presents methods to design magnetic bearings and makes some advances to them. The circuit model equations for a homopolar bearing are presented and a solution is found including the effects of magnetic flux saturation and laminate stacking. Circuit model equations for thrust bearings are presented. Linearized frequency dependent reluctance elements are incorporated into these equations. The equations are arranged to predict the frequency dependence of thrust bearings and the predictions agree with measurements. Finite element models are used extensively to back up the circuit model results. The drag torque caused by high rotation speed is calculated by the finite element method. The accuracy of these calculations is confirmed by comparison to measurements available in previously published experiments. Predictions of the drag torque in homopolar bearing rotor spacers are presented. The finite element method is also used to confirm the performance equations derived for a novel thrust bearing and a novel radial bearing, and it is also used to confirm the advanced circuit equations which are demonstrated on homopolar bearings.

  4. Mechanical design problems associated with turbopump fluid film bearings

    Science.gov (United States)

    Evces, Charles R.

    1990-01-01

    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.

  5. 49 CFR 215.117 - Defective roller bearing adapter.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Defective roller bearing adapter. 215.117 Section... Suspension System § 215.117 Defective roller bearing adapter. A railroad may not place or continue in service a car, if the car has a roller bearing adapter that is— (a) Cracked or broken; (b) Not in its design...

  6. 49 CFR 215.113 - Defective plain bearing wedge.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Defective plain bearing wedge. 215.113 Section 215... Suspension System § 215.113 Defective plain bearing wedge. A railroad may not place or continue in service a car, if a plain bearing wedge on that car is— (a) Missing; (b) Cracked; (c) Broken; or (d) Not located...

  7. 7 CFR 761.53 - Interest bearing accounts.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 7 2010-01-01 2010-01-01 false Interest bearing accounts. 761.53 Section 761.53... AGRICULTURE SPECIAL PROGRAMS GENERAL PROGRAM ADMINISTRATION Supervised Bank Accounts § 761.53 Interest bearing accounts. (a) A supervised bank account, if possible, will be established as an interest bearing deposit...

  8. 77 FR 50716 - Tapered Roller Bearings From China

    Science.gov (United States)

    2012-08-22

    ... COMMISSION Tapered Roller Bearings From China Determination On the basis of the record \\1\\ developed in the... antidumping duty order on tapered roller bearings from China would be likely to lead to continuation or... Publication 4343 (August 2012), entitled Tapered Roller Bearings from China: Investigation No. 731-TA-344...

  9. THE DEVELOPMENT OF A GAS LUBRICATED BEARING BLOWER ASSEMBLY FOR USE IN AN AN/TED-9 RADIO TRANSMITTER.

    Science.gov (United States)

    effect of bearing geometry variations on the bearing performance of a cylindrical journal bearing . Several evaluations were also conducted on repulsive type permanent magnet thrust bearings. (Author)

  10. Annular Pressure Seals and Hydrostatic Bearings

    Science.gov (United States)

    2006-11-01

    scale). The equation below presents a close form expression for estimation of the added mass coefficient (MXX) in a seal or squeeze film damper [14...Arauz & L. San Andrés, “ASME Journal of Tribology, 120, pp. 221-233, 1998. [14] Squeeze Film Dampers : Operation, Models and Technical Issues, L. San...fluid film bearing technology with very low number of parts and no DN limit operation. Details on the bulk- flow analysis of turbulent flow

  11. Device Rotates Bearing Balls For Inspection

    Science.gov (United States)

    Burley, R. K.

    1988-01-01

    Entire surface of ball inspected automatically and quickly. Device holds and rotates bearing ball for inspection by optical or mechanical surface-quality probe, eddy-current probe for detection of surface or subsurface defects, or circumference-measuring tool. Ensures entire surface of ball moves past inspection head quickly. New device saves time and increases reliability of inspections of spherical surfaces. Simple to operate and provides quick and easy access for loading and unloading of balls during inspection.

  12. Thermal conductivity of hydrate-bearing sediments

    Science.gov (United States)

    Cortes, Douglas D.; Martin, Ana I.; Yun, Tae Sup; Francisca, Franco M.; Santamarina, J. Carlos; Ruppel, Carolyn D.

    2009-01-01

    A thorough understanding of the thermal conductivity of hydrate-bearing sediments is necessary for evaluating phase transformation processes that would accompany energy production from gas hydrate deposits and for estimating regional heat flow based on the observed depth to the base of the gas hydrate stability zone. The coexistence of multiple phases (gas hydrate, liquid and gas pore fill, and solid sediment grains) and their complex spatial arrangement hinder the a priori prediction of the thermal conductivity of hydrate-bearing sediments. Previous studies have been unable to capture the full parameter space covered by variations in grain size, specific surface, degree of saturation, nature of pore filling material, and effective stress for hydrate-bearing samples. Here we report on systematic measurements of the thermal conductivity of air dry, water- and tetrohydrofuran (THF)-saturated, and THF hydrate–saturated sand and clay samples at vertical effective stress of 0.05 to 1 MPa (corresponding to depths as great as 100 m below seafloor). Results reveal that the bulk thermal conductivity of the samples in every case reflects a complex interplay among particle size, effective stress, porosity, and fluid-versus-hydrate filled pore spaces. The thermal conductivity of THF hydrate–bearing soils increases upon hydrate formation although the thermal conductivities of THF solution and THF hydrate are almost the same. Several mechanisms can contribute to this effect including cryogenic suction during hydrate crystal growth and the ensuing porosity reduction in the surrounding sediment, increased mean effective stress due to hydrate formation under zero lateral strain conditions, and decreased interface thermal impedance as grain-liquid interfaces are transformed into grain-hydrate interfaces.

  13. Gas-Bearing Crucible for Shot Tower

    Science.gov (United States)

    Youngberg, C. L.; Miller, C. G.; Stephens, J. B.; Finnerty, A. A.

    1983-01-01

    Device protects molten drops from contamination and distortion. Gas flowing through levitator tube levitates small balls while they melt. Gas heated by filament extending through center of tube. Gas bearing crucible on tube has concave configuration to hold single relatively large ball or many recesses to hold many small balls. By time spheres reach foam, they are cooled sufficiently by radiation to retain their shape.

  14. Drivers of hibernation in the brown bear

    OpenAIRE

    Evans, Alina; Singh, N.J.; Arnemo, Jon Martin; Laske, T.G.; Fröbert, O.; Swenson, Jon; Blanc, S.

    2016-01-01

    Background Hibernation has been a key area of research for several decades, essentially in small mammals in the laboratory, yet we know very little about what triggers or ends it in the wild. Do climatic factors, an internal biological clock, or physiological processes dominate? Using state-of-the-art tracking and monitoring technology on fourteen free-ranging brown bears over three winters, we recorded movement, heart rate (HR), heart rate variability (HRV), body temperature (Tb), physical a...

  15. Activity monitoring of alpha-bearing wastes

    International Nuclear Information System (INIS)

    Birkhoff, G.; Bondar, L.

    1980-01-01

    The paper aims at the survey on the actual situation in activity monitoring of alpha-bearing wastes. Homogeneous materials such as liquid-, gaseous- and homogeneous solid wastes are amenable to destructive analyses of representative samples. Available destructive analyses methods are sensitive and precise enough to cope with all requirements in alpha-waste monitoring. The more difficult problems are encountered with alpha-contaminated solids, when representative sampling is not practicable. Non-destructive analysis techniques are applied for monitoring this category of solid wastes. The techniques for nondestructive analysis of alpha-bearing wastes are based on the detection of gamma and/or neutron-emission of actinides. Principles and a theory of non-destructive radiometric assay of plutonium contaminated solid waste streams are explained. Guidelines for the calibration of instruments and interpretation of experimental data are given. Current theoretical and experimental development work in this problem area is reviewed. Evaluations concerning capabilities and limitations of monitoring systems for alpha-bearing solid wastes are very complex and out of the scope of this paper

  16. EHD Effects in Lubricated Journal Bearing

    Directory of Open Access Journals (Sweden)

    Pavel Pavlovich Usov

    2018-01-01

    Full Text Available This paper presents a numerical analysis of the influence of deformation of infinite parallel cylindrical solids in partial journal bearing on the oil film characteristics. The stationary elastohydrodynamic EHD problems for three design models of bearings are considered: (1 The bearing in which the basic contribution to the elastic displacement of the surface brings the thin elastic liner; (2 The elastic cylinder and the elastic bushing which is modeled by the elastic space with a cylindrical cut; (3 The elastic cylinder and the elastic bushing in the presence of the thin elastic liner with a small module of elasticity. It is shown that when the minimum film thickness is fixed and deformations of the elastic solids increase, then the load capacity increases, reaches a maximum, and then decreases. The deformation of solids can raise load capacity many times over. When the deformation of solids increases from zero, the pressure distribution changes from the distribution of pressure in the case of rigid bodies to the distribution of pressure which takes place with the dry contact of elastic bodies.

  17. Fatigue Life Prediction in Journal Bearing

    Directory of Open Access Journals (Sweden)

    Irsyadi Yani

    2017-03-01

    Full Text Available Failure of fatigue is damaged materials where caused frequent load. Fatigue owing to some factors, which is Stress concentration on fatigue, Stress life, Effect size and surface, and Change properties of surface. The fatigue failure of a material is dependent on the interaction of a large stress with a critical flow. In essence, fatigue is controlled by the weakest link of the material, with the probability of a weak link increasing with material volume. This phenomenon is evident in the fatigue test results of a material using specimens of varying diameters. From this research we can get effect of concentration stress on strength fatigue with S-N method. On this method only count fatigue life or endurance limit from Journal bearing housing. By Finite Element Analysis, it is not so easy to determine fatigue life. When we find the first yield point, it means this point is in the highest stress state. Then we can refer S-N curve. In this paper, the effect of bearing and housing elasticity on the stress field, which could result in surface fatigue in journal bearing, has been investigated. This condition is proved with occurred slip lines on surface of specimen. These slip lines are caused on some thousands stress cycles. Additional crack is happened immediately and finally long enough crack. So that formed unstable crack that caused fracture of brittleness or fracture of toughness because section of specimen cannot keep

  18. Concurrent Initialization for Bearing-Only SLAM

    Directory of Open Access Journals (Sweden)

    Antoni Grau

    2010-03-01

    Full Text Available Simultaneous Localization and Mapping (SLAM is perhaps the most fundamental problem to solve in robotics in order to build truly autonomous mobile robots. The sensors have a large impact on the algorithm used for SLAM. Early SLAM approaches focused on the use of range sensors as sonar rings or lasers. However, cameras have become more and more used, because they yield a lot of information and are well adapted for embedded systems: they are light, cheap and power saving. Unlike range sensors which provide range and angular information, a camera is a projective sensor which measures the bearing of images features. Therefore depth information (range cannot be obtained in a single step. This fact has propitiated the emergence of a new family of SLAM algorithms: the Bearing-Only SLAM methods, which mainly rely in especial techniques for features system-initialization in order to enable the use of bearing sensors (as cameras in SLAM systems. In this work a novel and robust method, called Concurrent Initialization, is presented which is inspired by having the complementary advantages of the Undelayed and Delayed methods that represent the most common approaches for addressing the problem. The key is to use concurrently two kinds of feature representations for both undelayed and delayed stages of the estimation. The simulations results show that the proposed method surpasses the performance of previous schemes.

  19. Concurrent initialization for Bearing-Only SLAM.

    Science.gov (United States)

    Munguía, Rodrigo; Grau, Antoni

    2010-01-01

    Simultaneous Localization and Mapping (SLAM) is perhaps the most fundamental problem to solve in robotics in order to build truly autonomous mobile robots. The sensors have a large impact on the algorithm used for SLAM. Early SLAM approaches focused on the use of range sensors as sonar rings or lasers. However, cameras have become more and more used, because they yield a lot of information and are well adapted for embedded systems: they are light, cheap and power saving. Unlike range sensors which provide range and angular information, a camera is a projective sensor which measures the bearing of images features. Therefore depth information (range) cannot be obtained in a single step. This fact has propitiated the emergence of a new family of SLAM algorithms: the Bearing-Only SLAM methods, which mainly rely in especial techniques for features system-initialization in order to enable the use of bearing sensors (as cameras) in SLAM systems. In this work a novel and robust method, called Concurrent Initialization, is presented which is inspired by having the complementary advantages of the Undelayed and Delayed methods that represent the most common approaches for addressing the problem. The key is to use concurrently two kinds of feature representations for both undelayed and delayed stages of the estimation. The simulations results show that the proposed method surpasses the performance of previous schemes.

  20. The role of human outdoor recreation in shaping patterns of grizzly bear-black bear co-occurrence

    OpenAIRE

    Ladle, Andrew; Steenweg, Robin; Shepherd, Brenda; Boyce, Mark S.

    2018-01-01

    Species’ distributions are influenced by a combination of landscape variables and biotic interactions with other species, including people. Grizzly bears and black bears are sympatric, competing omnivores that also share habitats with human recreationists. By adapting models for multi-species occupancy analysis, we analyzed trail camera data from 192 trail camera locations in and around Jasper National Park, Canada to estimate grizzly bear and black bear occurrence and intensity of trail use....

  1. Conflict bear translocation: investigating population genetics and fate of bear translocation in Dachigam National Park, Jammu and Kashmir, India.

    Science.gov (United States)

    Mukesh; Sharma, Lalit Kumar; Charoo, Samina Amin; Sathyakumar, Sambandam

    2015-01-01

    The Asiatic black bear population in Dachigam landscape, Jammu and Kashmir is well recognized as one of the highest density bear populations in India. Increasing incidences of bear-human interactions and the resultant retaliatory killings by locals have become a serious threat to the survivorship of black bears in the Dachigam landscape. The Department of Wildlife Protection in Jammu and Kashmir has been translocating bears involved in conflicts, henceforth 'conflict bears' from different sites in Dachigam landscape to Dachigam National Park as a flagship activity to mitigate conflicts. We undertook this study to investigate the population genetics and the fate of bear translocation in Dachigam National Park. We identified 109 unique genotypes in an area of ca. 650 km2 and observed bear population under panmixia that showed sound genetic variability. Molecular tracking of translocated bears revealed that mostly bears (7 out of 11 bears) returned to their capture sites, possibly due to homing instincts or habituation to the high quality food available in agricultural croplands and orchards, while only four bears remained in Dachigam National Park after translocation. Results indicated that translocation success was most likely to be season dependent as bears translocated during spring and late autumn returned to their capture sites, perhaps due to the scarcity of food inside Dachigam National Park while bears translocated in summer remained in Dachigam National Park due to availability of surplus food resources. Thus, the current management practices of translocating conflict bears, without taking into account spatio-temporal variability of food resources in Dachigam landscape seemed to be ineffective in mitigating conflicts on a long-term basis. However, the study highlighted the importance of molecular tracking of bears to understand their movement patterns and socio-biology in tough terrains like Dachigam landscape.

  2. Conflict bear translocation: investigating population genetics and fate of bear translocation in Dachigam National Park, Jammu and Kashmir, India.

    Directory of Open Access Journals (Sweden)

    Mukesh

    Full Text Available The Asiatic black bear population in Dachigam landscape, Jammu and Kashmir is well recognized as one of the highest density bear populations in India. Increasing incidences of bear-human interactions and the resultant retaliatory killings by locals have become a serious threat to the survivorship of black bears in the Dachigam landscape. The Department of Wildlife Protection in Jammu and Kashmir has been translocating bears involved in conflicts, henceforth 'conflict bears' from different sites in Dachigam landscape to Dachigam National Park as a flagship activity to mitigate conflicts. We undertook this study to investigate the population genetics and the fate of bear translocation in Dachigam National Park. We identified 109 unique genotypes in an area of ca. 650 km2 and observed bear population under panmixia that showed sound genetic variability. Molecular tracking of translocated bears revealed that mostly bears (7 out of 11 bears returned to their capture sites, possibly due to homing instincts or habituation to the high quality food available in agricultural croplands and orchards, while only four bears remained in Dachigam National Park after translocation. Results indicated that translocation success was most likely to be season dependent as bears translocated during spring and late autumn returned to their capture sites, perhaps due to the scarcity of food inside Dachigam National Park while bears translocated in summer remained in Dachigam National Park due to availability of surplus food resources. Thus, the current management practices of translocating conflict bears, without taking into account spatio-temporal variability of food resources in Dachigam landscape seemed to be ineffective in mitigating conflicts on a long-term basis. However, the study highlighted the importance of molecular tracking of bears to understand their movement patterns and socio-biology in tough terrains like Dachigam landscape.

  3. Hydrodynamic sliding bearings vs. roller bearings. Segmented sliding bearings for higher rotational speed; Hydrodynamische Gleitlager versus Waelzlager. Segmentgleitlager fuer hoehere Drehzahlen

    Energy Technology Data Exchange (ETDEWEB)

    Hagenhoff, M.; Sauer, M. [Main-Metall-Giesserei Fritz Schorr GmbH und Co. KG, Altenglan (Germany)

    2004-10-01

    Hydrodynamic sliding bearings are considered only in cases when roller bearings reach their speed limits and there is no other solution. However, this view neglects the fact that there are modern, optimised sliding bearings which have more advantages over roller bearings than should be expected. Many producers of sliding bearings also have computer programs enabling them to offer customised solutions, i.e. optimal adaptation of the bearings to their specific operating conditions. (orig.) [German] Hydrodynamische Gleitlager werden oft erst dann in Betracht gezogen, wenn man an die Drehzahlgrenzen von Waelzlagern stoesst und keine andere sinnvolle Alternative mehr in Frage kommt. Dabei uebersieht man leicht, dass es moderne, optimierte Gleitlagerkonstruktionen gibt, die weitaus haeufiger ihre Staerken im Vergleich zu Waelzlagern ausspielen koennen als zunaechst vermutet. Viele Gleitlagerhersteller haben zudem heute Berechnungsprogramme zur Verfuegung, die eine optimale Anpassung der Lager an die speziellen Betriebsbedingungen erlauben. (orig.)

  4. 77 FR 59639 - Bear Lake National Wildlife Refuge, Bear Lake County, ID and Oxford Slough Waterfowl Production...

    Science.gov (United States)

    2012-09-28

    ... DEPARTMENT OF THE INTERIOR Fish and Wildlife Service [FWS-R1-R-2012-N095; 1265-0000-10137-S3] Bear Lake National Wildlife Refuge, Bear Lake County, ID and Oxford Slough Waterfowl Production Area... comprehensive conservation plan and environmental assessment (Draft CCP/EA) for the Bear Lake National Wildlife...

  5. Less anterior knee pain with a mobile-bearing prosthesis compared with a fixed-bearing prosthesis

    NARCIS (Netherlands)

    Breugem, Stefan J. M.; Sierevelt, Inger N.; Schafroth, Matthias U.; Blankevoort, Leendert; Schaap, Gerard R.; van Dijk, C. Niek

    2008-01-01

    Anterior knee pain is one of the major short-term complaints after TKA. Since the introduction of the mobile-bearing TKA, numerous studies have attempted to confirm the theoretical advantages of a mobile-bearing TKA over a fixed-bearing TKA but most show little or no actual benefits. The concept of

  6. Gas Foil Bearing Misalignment and Unbalance Effects

    Science.gov (United States)

    Howard, Samuel A.

    2008-01-01

    The effects of misalignment and unbalance on gas foil bearings are presented. The future of U.S. space exploration includes plans to conduct science missions aboard space vehicles, return humans to the Moon, and place humans on Mars. All of these endeavors are of long duration, and require high amounts of electrical power for propulsion, life support, mission operations, etc. One potential source of electrical power of sufficient magnitude and duration is a nuclear-fission-based system. The system architecture would consist of a nuclear reactor heat source with the resulting thermal energy converted to electrical energy through a dynamic power conversion and heat rejection system. Various types of power conversion systems can be utilized, but the Closed Brayton Cycle (CBC) turboalternator is one of the leading candidates. In the CBC, an inert gas heated by the reactor drives a turboalternator, rejects excess heat to space through a heat exchanger, and returns to the reactor in a closed loop configuration. The use of the CBC for space power and propulsion is described in more detail in the literature (Mason, 2003). In the CBC system just described, the process fluid is a high pressure inert gas such as argon, krypton, or a helium-xenon mixture. Due to the closed loop nature of the system and the associated potential for damage to components in the system, contamination of the working fluid is intolerable. Since a potential source of contamination is the lubricant used in conventional turbomachinery bearings, Gas Foil Bearings (GFB) have high potential for the rotor support system. GFBs are compliant, hydrodynamic journal and thrust bearings that use a gas, such as the CBC working fluid, as their lubricant. Thus, GFBs eliminate the possibility of contamination due to lubricant leaks into the closed loop system. Gas foil bearings are currently used in many commercial applications, both terrestrial and aerospace. Aircraft Air Cycle Machines (ACMs) and ground

  7. Bearing life in contaminated oil and oil passing into bearing for tapered roller bearing; Ensui koro jikuuke ni okeru ibutsu yuchu deno jumyo to kantsu yuryo

    Energy Technology Data Exchange (ETDEWEB)

    Asai, Y.; Oshima, H.; Sakamoto, K. [Koyo Seiko Co. Ltd., Osaka (Japan)

    1997-10-01

    In this paper a relationship between depth of dents, area of dents gathered and bearing life has been investigated for tapered roller bearings used in differential gear case. It is effective for the longer bearing life to reduce hard particles of Fe especially among several contaminations existing in the gear case. It is also effective to make oil level lower in the case from the view point for reduction of number of dents. 8 refs., 8 figs., 4 tabs.

  8. Nonlinear Control of Large Disturbances in Magnetic Bearing Systems

    Science.gov (United States)

    Jiang, Yuhong; Zmood, R. B.

    1996-01-01

    In this paper, the nonlinear operation of magnetic bearing control methods is reviewed. For large disturbances, the effects of displacement constraints and power amplifier current and di/dt limits on bearing control system performance are analyzed. The operation of magnetic bearings exhibiting self-excited large scale oscillations have been studied both experimentally and by simulation. The simulation of the bearing system has been extended to include the effects of eddy currents in the actuators, so as to improve the accuracy of the simulation results. The results of these experiments and simulations are compared, and some useful conclusions are drawn for improving bearing system robustness.

  9. Gerotor and bearing system for whirling mass orbital vibrator

    Energy Technology Data Exchange (ETDEWEB)

    Brett, James Ford; Westermark, Robert Victor; Turner, Jr., Joey Earl; Lovin, Samuel Scott; Cole, Jack Howard; Myers, Will

    2007-02-27

    A gerotor and bearing apparatus for a whirling mass orbital vibrator which generates vibration in a borehole. The apparatus includes a gerotor with an inner gear rotated by a shaft having one less lobe than an outer gear. A whirling mass is attached to the shaft. At least one bearing is attached to the shaft so that the bearing engages at least one sleeve. A mechanism is provided to rotate the inner gear, the mass and the bearing in a selected rotational direction in order to cause the mass, the inner gear, and the bearing to backwards whirl in an opposite rotational direction. The backwards whirling mass creates seismic vibrations.

  10. Oxford phase III meniscal bearing fracture: case report.

    Science.gov (United States)

    Lim, Hong-Chul; Shon, Won-Yong; Kim, Seung-Ju; Bae, Ji-Hoon

    2014-01-01

    Meniscal bearing fracture is a rare complication of phase III Oxford unicompartmental knee replacement (UKR). We report a case of a meniscal bearing fracture that occurred 7 years after phase III Oxford medial UKR. The meniscal bearing showed uneven delamination of the polyethylene in the thinnest articular surface and an impingement lesion. This lesion initiated a fatigue crack that propagated to cause failure of the meniscal bearing. This is the first report of a meniscal bearing fracture without a posterior marker wire. © 2013.

  11. Sudden venting test of an emergency bearing for the magnet bearing type compound molecular pump

    International Nuclear Information System (INIS)

    Hiroki, Seiji; Abe, Tetsuya; Murakami, Yoshio; Okamoto, Masatomo; Iguchi, Masashi; Nakamura, Jyunichi; Nakazeki, Tsugito.

    1995-01-01

    The vacuum evacuation system for nuclear fusion reactors bears the role of exhausting hydrogen isotopes in large quantity together with helium continuously for long hours, and as the high vacuum pumps for this purpose, the mechanical pumps which can do continuous evacuation and decrease the quantity of staying radioactive tritium, such as turbo molecular pumps and compound molecular pumps, are promising. Because of the compatibility with tritium, oil lubrication is not desirable, accordingly, the pumps with ceramic rotating vanes and magnetic bearings are demanded. As a part of the development of a magnetic bearing type mechanical pump which can be used for nuclear fusion reactors, the compound molecular pump, in which emergency bearings were incorporated, was made for trial, and the test of sudden air intrusion was carried out, as the results, various knowledges were obtained. The constitution of the testing setup, and the test results are reported. When air was injected at the pressure rise of 3.3x10 4 Pa/s from exhaust port side, after about 2.5 s, the maximum lift of 4.2x10 3 N arose. When air was injected at the pressure rise of 2.7x10 5 Pa/s from the suction part side, after about 0.4s, the maximum lift of 6.9x10 3 N arose. In the air injection alternately from the suction port and exhaust port sides, the emergency bearings functioned normally in 10 times of the test. (K.I.)

  12. Rolling Bearing Steels - A Technical and Historical Perspective

    Science.gov (United States)

    Zaretsky, Erwin V.

    2012-01-01

    Starting about 1920 it becomes easier to track the growth of bearing materials technology. Until 1955, with few exceptions, comparatively little progress was made in this area. AISI 52100 and some carburizing grades (AISI 4320, AISI 9310) were adequate for most applications. The catalyst to quantum advances in high-performance rolling-element bearing steels was the advent of the aircraft gas turbine engine. With improved bearing manufacturing and steel processing together with advanced lubrication technology, the potential improvements in bearing life can be as much as 80 times that attainable in the late 1950s or as much as 400 times that attainable in 1940. This paper summarizes the chemical, metallurgical and physical aspects of bearing steels and their effect on rolling bearing life and reliability. The single most important variable that has significantly increased bearing life and reliability is vacuum processing of bearing steel. Differences between through hardened, case carburized and corrosion resistant steels are discussed. The interrelation of alloy elements and carbides and their effect on bearing life are presented. An equation relating bearing life, steel hardness and temperature is given. Life factors for various steels are suggested and discussed. A relation between compressive residual stress and bearing life is presented. The effects of retained austenite and grain size are discussed.

  13. Analysis of thermoelastohydrodynamic performance of journal misaligned engine main bearings

    Science.gov (United States)

    Bi, Fengrong; Shao, Kang; Liu, Changwen; Wang, Xia; Zhang, Jian

    2015-05-01

    To understand the engine main bearings' working condition is important in order to improve the performance of engine. However, thermal effects and thermal effect deformations of engine main bearings are rarely considered simultaneously in most studies. A typical finite element model is selected and the effect of thermoelastohydrodynamic(TEHD) reaction on engine main bearings is investigated. The calculated method of main bearing's thermal hydrodynamic reaction and journal misalignment effect is finite difference method, and its deformation reaction is calculated by using finite element method. The oil film pressure is solved numerically with Reynolds boundary conditions when various bearing characteristics are calculated. The whole model considers a temperature-pressure-viscosity relationship for the lubricant, surface roughness effect, and also an angular misalignment between the journal and the bearing. Numerical simulations of operation of a typical I6 diesel engine main bearing is conducted and importance of several contributing factors in mixed lubrication is discussed. The performance characteristics of journal misaligned main bearings under elastohydrodynamic(EHD) and TEHD loads of an I6 diesel engine are received, and then the journal center orbit movement, minimum oil film thickness and maximum oil film pressure of main bearings are estimated over a wide range of engine operation. The model is verified through the comparison with other present models. The TEHD performance of engine main bearings with various effects under the influences of journal misalignment is revealed, this is helpful to understand EHD and TEHD effect of misaligned engine main bearings.

  14. Effects of exotic species on Yellowstone's grizzly bears

    Science.gov (United States)

    Reinhart, Daniel P.; Haroldson, Mark A.; Mattson, D.J.; Gunther, Kerry A.

    2001-01-01

    Humans have affected grizzly bears (Ursus arctos horribilis) by direct mortality, competition for space and resources, and introduction of exotic species. Exotic organisms that have affected grizzly bears in the Greater Yellowstone Area include common dandelion (Taraxacum officinale), nonnative clovers (Trifolium spp.), domesticated livestock, bovine brucellosis (Brucella abortus), lake trout (Salvelinus namaycush), and white pine blister rust (Cronartium ribicola). Some bears consume substantial amounts of dandelion and clover. However, these exotic foods provide little digested energy compared to higher-quality bear foods. Domestic livestock are of greater energetic value, but use of this food by bears often leads to conflicts with humans and subsequent increases in bear mortality. Lake trout, blister rust, and brucellosis diminish grizzly bears foods. Lake trout prey on native cutthroat trout (Oncorhynchus clarkii) in Yellowstone Lake; white pine blister rust has the potential to destroy native whitebark pine (Pinus albicaulis) stands; and management response to bovine brucellosis, a disease found in the Yellowstone bison (Bison bison) and elk (Cervus elaphus), could reduce populations of these 2 species. Exotic species will likely cause more harm than good for Yellowstone grizzly bears. Managers have few options to mitigate or contain the impacts of exotics on Yellowstone's grizzly bears. Moreover, their potential negative impacts have only begun to unfold. Exotic species may lead to the loss of substantial highquality grizzly bear foods, including much of the bison, trout, and pine seeds that Yellowstone grizzly bears currently depend upon.

  15. On the computation of electrical resistance of hydrodynamic journal bearing

    Directory of Open Access Journals (Sweden)

    Eleonora Pop

    2014-12-01

    Full Text Available The paper approaches the mathematical model of electrical resistance of hydrodynamic journal bearing under different parameters of operation so as to predict bearing performance and safe load carrying capacity. The currents circulating in the journal bearing of electrical machine causes reducing of lifespan by appearance of pitting on their surface and the degradation of the lubricant. In a hydrodynamic journal bearing, the zone of minimum film thickness, load-carrying oil film varies along the circumference of a bearing through its length. This has been found to form a capacitor of varying capacitance between the journal and the bearings dependent on permittivity of the lubricant used, the bearing length, the eccentricity ratio and the clearance ratio. Besides this, load-carrying on oil film offers resistance that depends on operating parameters and resistivity of the lubricant.

  16. Effect of fluid compressibility on journal bearing performance

    Science.gov (United States)

    Dimofte, Florin

    1993-01-01

    An analysis was undertaken to determine the effect of fluid film compressibility on the performance of fluid film bearings. A new version of the Reynolds equation was developed, using a polytropic expansion, for both steady-state and dynamic conditions. Polytropic exponents from 1 (isothermal) to 1000 (approaching an incompressible liquid) were evaluated for two bearing numbers, selected from a range of practical interest for cryogenic application, and without cavitation. Bearing loads were insensitive to fluid compressibility for low bearing numbers, as was expected. The effect of compressibility on attitude angle was significant, even when the bearing number was low. A small amount of fluid compressibility was enough to obtain stable running conditions. Incompressible liquid lacked stability at all conditions. Fluid compressibility can be used to control the bearing dynamic coefficients, thereby influencing the dynamic behavior of the rotor-bearing system.

  17. Foil Bearing Coating Behavior in CO2

    Energy Technology Data Exchange (ETDEWEB)

    Walker, Matthew [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Kruizenga, Alan Michael [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Pasch, James Jay [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Fleming, Darryn [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-08-01

    The Sandia S-CO2 Recompression Closed Brayton Cycle (RCBC) utilizes a series of gas foil bearings in its turbine-alternator-compressors. At high shaft rotational speed these bearings allow the shaft to ride on a cushion of air. Conversely, during startup and shutdown, the shaft rides along the foil bearing surface. Low-friction coatings are used on bearing surfaces in order to facilitate rotation during these periods. An experimental program was initiated to elucidate the behavior of coated bearing foils in the harsh environments of this system. A test configuration was developed enabling long duration exposure tests, followed by a range of analyses relevant to their performance in a bearing. This report provides a detailed overview of this work. The results contained herein provide valuable information in selecting appropriate coatings for more advanced future bearing-rig tests at the newly established test facility in Sandia-NM.

  18. Modeling of dynamically loaded hydrodynamic bearings at low Sommerfeld numbers

    DEFF Research Database (Denmark)

    Thomsen, Kim

    and failure risk of rolling element bearings do, however, grow exponentially with the size. Therefore hydrodynamic bearings can prove to be a competitive alternative to the current practice of rolling element bearings and ultimately help reducing the cost and carbon footprint of renewable energy generation....... The challenging main bearing operation conditions in a wind turbine pose a demanding development task for the design of a hydrodynamic bearing. In general these conditions include operation at low Reynolds numbers with frequent start and stop at high loads as well as difficult operating conditions dictated...... by environment and other wind turbine components. In this work a numerical multiphysics bearing model is developed in order to allow for accurate performance prediction of hydrodynamic bearings subjected to the challenging conditions that exist in modern wind turbines. This requires the coupling of several...

  19. Operation and design selection of high temperature superconducting magnetic bearings

    International Nuclear Information System (INIS)

    Werfel, F N; Floegel-Delor, U; Riedel, T; Rothfeld, R; Wippich, D; Goebel, B

    2004-01-01

    Axial and radial high temperature superconducting (HTS) magnetic bearings are evaluated by their parameters. Journal bearings possess advantages over thrust bearings. High magnetic gradients in a multi-pole permanent magnet (PM) configuration, the surrounding melt textured YBCO stator and adequate designs are the key features for increasing the overall bearing stiffness. The gap distance between rotor and stator determines the specific forces and has a strong impact on the PM rotor design. We report on the designing, building and measuring of a 200 mm prototype 100 kg HTS bearing with an encapsulated and thermally insulated melt textured YBCO ring stator. The encapsulation requires a magnetically large-gap (4-5 mm) operation but reduces the cryogenic effort substantially. The bearing requires 3 l of LN 2 for cooling down, and about 0.2 l LN 2 h -1 under operation. This is a dramatic improvement of the efficiency and in the practical usage of HTS magnetic bearings

  20. Vascular injuries after bear attacks: Incidence, surgical challenges and outcome.

    Science.gov (United States)

    Wani, Mohd Lateef; Ahangar, Abdul Gani; Lone, Gh Nabi; Lone, Reyaz Ahmad; Ashraf, Hakeem Zubair; Dar, Abdul Majeed; Bhat, M A; Singh, Shyam; Bijli, Akram Hussain; Irshad, Ifat

    2011-01-01

    Bear mauling is rarely reported in medical literature due to its rare occurrence. Present study was undertaken to describe the pattern and management of bear maul vascular injuries in Kashmir. Study of patients with bear maul vascular injury from 1(st) Jan 2004 to 31(st) Dec. 2008. Fifteen patients with bear maul vascular injury were studied. All patients of bear maul without vascular injury were excluded from the study. Most of the patients were treated by reverse saphenous vein graft or end to end anastomosis. Most common complication was wound infection (20%) followed by graft occlusion (13.33%). There was no operative death. Bear attacks are very common in Kashmir. Vascular injury due to bear maul needs prompt resuscitation and revascularization. Results are very good provided timely intervention for revascularization is done.

  1. Polar bear attacks on humans: Implications of a changing climate

    Science.gov (United States)

    Wilder, James; Vongraven, Dag; Atwood, Todd C.; Hansen, Bob; Jessen, Amalie; Kochnev, Anatoly A.; York, Geoff; Vallender, Rachel; Hedman, Daryll; Gibbons, Melissa

    2017-01-01

    Understanding causes of polar bear (Ursus maritimus) attacks on humans is critical to ensuring both human safety and polar bear conservation. Although considerable attention has been focused on understanding black (U. americanus) and grizzly (U. arctos) bear conflicts with humans, there have been few attempts to systematically collect, analyze, and interpret available information on human-polar bear conflicts across their range. To help fill this knowledge gap, a database was developed (Polar Bear-Human Information Management System [PBHIMS]) to facilitate the range-wide collection and analysis of human-polar bear conflict data. We populated the PBHIMS with data collected throughout the polar bear range, analyzed polar bear attacks on people, and found that reported attacks have been extremely rare. From 1870–2014, we documented 73 attacks by wild polar bears, distributed among the 5 polar bear Range States (Canada, Greenland, Norway, Russia, and United States), which resulted in 20 human fatalities and 63 human injuries. We found that nutritionally stressed adult male polar bears were the most likely to pose threats to human safety. Attacks by adult females were rare, and most were attributed to defense of cubs. We judged that bears acted as a predator in most attacks, and that nearly all attacks involved ≤2 people. Increased concern for both human and bear safety is warranted in light of predictions of increased numbers of nutritionally stressed bears spending longer amounts of time on land near people because of the loss of their sea ice habitat. Improved conflict investigation is needed to collect accurate and relevant data and communicate accurate bear safety messages and mitigation strategies to the public. With better information, people can take proactive measures in polar bear habitat to ensure their safety and prevent conflicts with polar bears. This work represents an important first step towards improving our understanding of factors influencing

  2. Performance of gas-lubricated nonconforming pivoted-pad journal bearings and a flexibly mounted spiral-groove thrust bearing

    Science.gov (United States)

    Ream, L. W.

    1973-01-01

    A test program was conducted to determine the performance characteristics of gas-lubricated nonconforming pivoted-pad journal bearings and a spiral-groove thrust bearing designed for the Brayton cycle rotating unit (BRU). Hydrostatic, hybrid (simultaneously hydrostatic and hydrodynamic), and hydrodynamic tests were conducted in argon gas at ambient pressure and temperature ranges representative of hydrostatic operation up to the 10.5-kWe BRU power-generating level. Performance of the gas lubricated bearings is presented, including hydrostatic gas flow rates, bearing clearances, bearing temperatures, and transient performance.

  3. Trophic cascades from wolves to grizzly bears or changing abundance of bears and alternate foods?

    Science.gov (United States)

    Barber-Meyer, Shannon M.

    2015-01-01

    This is a Forum article commenting on: Ripple, W. J., Beschta, R. L., Fortin, J. K., & Robbins, C. T. (2014) Trophic cascades from wolves to grizzly bears in Yellowstone. Journal of Animal Ecology, 83, 223–233. Comparisons Ripple et al. (2014) used to demonstrate increased fruit availability and consumption by grizzly bears post-wolf reintroduction are flawed and tenuous at best. Importantly, a more parsimonious (than trophic cascades) hypothesis, not sufficiently considered by Ripple et al., exists and is better supported by available data I review.

  4. Spectral properties and identification of aerostatic bearings

    Czech Academy of Sciences Publication Activity Database

    Kozánek, Jan; Půst, Ladislav

    2011-01-01

    Roč. 27, č. 1 (2011), s. 63-67 ISSN 0567-7718. [International Conference on Dynamical Systems - Theory and Applications /10./. Lodz, 07.12.2009-10.12.2009] R&D Projects: GA ČR GA101/09/1522 Institutional research plan: CEZ:AV0Z20760514 Keywords : aerostatic bearing * identification * stiffness * damping coefficients Subject RIV: BI - Acoustics Impact factor: 0.860, year: 2011 http://www.springerlink.com/content/34l382r75g8wu716/

  5. Bear Creek Project. Final environmental statement

    International Nuclear Information System (INIS)

    1977-06-01

    The Bear Creek Project consists of certain mining and milling operations involving uranium ore deposits located in Converse County, Wyoming. Mining of uranium from nine known ore bodies will take place over a period of ten years (estimated); a mill with a nominal capacity of 1000 tons per day of ore will be constructed and operated as long as ore is available. The waste material (tailings) from the mill, also produced at a rate of about 1000 tons per day, will be stored onsite in an impoundment. Environmental impacts and adverse effects are summarized

  6. Flexure Based Linear and Rotary Bearings

    Science.gov (United States)

    Voellmer, George M. (Inventor)

    2016-01-01

    A flexure based linear bearing includes top and bottom parallel rigid plates; first and second flexures connecting the top and bottom plates and constraining exactly four degrees of freedom of relative motion of the plates, the four degrees of freedom being X and Y axis translation and rotation about the X and Y axes; and a strut connecting the top and bottom plates and further constraining exactly one degree of freedom of the plates, the one degree of freedom being one of Z axis translation and rotation about the Z axis.

  7. Analysis of an all-metallic resilient pad gas-lubricated thrust bearing

    Science.gov (United States)

    Anderson, W. J.

    1974-01-01

    A new type of resilient pad gas thrust bearing that does not contain any elastomers in the bearing assembly is described and analyzed. The bearing consists of sector-shaped pads mounted asymmetrically on resilient foil beams. The effects of bearing design parameters on performance are shown. Performance of a resilient pad bearing is compared with that of a pivoted pad bearing.

  8. Analysis of an all-metallic resilient-pad gas-lubricated thrust bearing

    Science.gov (United States)

    Anderson, W. J.

    1974-01-01

    A resilient-pad gas thrust bearing that does not contain any elastomers in the bearing assembly is described and analyzed. The bearing consists of sector-shaped pads mounted asymmetrically on resilient foil beams. The effects of bearing design parameters on performance are shown. Performance of a resilient-pad bearing is compared with that of a pivoted-pad bearing.

  9. Qualification of high damping seismic isolation bearings for the ALMR

    International Nuclear Information System (INIS)

    Tajirian, F.F.; Gluekler, E.L.; Chen, W.P.; Kelly, J.M.

    1992-01-01

    The Advanced Liquid Metal Reactor (ALMR) seismic isolation system consists of high damping steel-laminated elastomeric bearings. This type of bearing is used worldwide to isolate buildings and large critical components. A comprehensive testing program has been developed to qualify the use of this system for the ALMR. The program includes material characterization tests, various scale bearing tests, full-size bearing tests, shake table tests, and long-term aging tests. The main tasks and objectives of this program are described in the paper. Additionally, a detailed assessment of completed ALMR bearing test results will be provided. This assessment will be mainly based on half-scale bearing tests performed at the Earthquake Engineering Research Center (EERC) of the University of California at Berkeley and at the Energy Technology Engineering Center (ETEC). These tests were funded by the U.S. Department of Energy (DOE). Both static and dynamic tests were performed. Bearings with two types of end connections were tested: dowelled and bolted. The parameters examined will include the vertical, horizontal stiffness and damping of the bearings under different loading conditions up to failure. This will determine the available margins in the bearings above the design vertical load and horizontal displacement. Additionally, the self-centering capability of the bearings after an earthquake will be addressed. On the basis of these findings, recommendations can be made if necessary, to improve current manufacturing procedures, quality control, and procurement specifications. (author)

  10. Experimental study on bearing preload optimum of machine tool spindle

    International Nuclear Information System (INIS)

    Xu Tao; Xu Guanghua; Zhang Qin; Hua Cheng; Zhang Hu; Jiang Kuosheng

    2012-01-01

    An experimental study is conducted to investigate the possibility and the effect of temperature rise and vibration level of bearing by adjusting axial preloads and radial loads in spindle bearing test rig. The shaft of the test rig is driven by a motorized high speed spindle at the range of 0∼20000 rpm. The axial preloads and radial loads on bearings are controlled by using hydraulic pressure which can be adjusted automatically. Temperature rise and radial vibration of test bearings are measured by thermocouples and Polytec portable laser vibrometer PDV100. Experiment shows that the temperature rise of bearings is nonlinear varying with the increase of radial loads, but temperature rise almost increases linearly with the increase of axial preload and rotating speed. In this paper, an alternate axial preload is used for bearings. When the rotating speed passes through the critical speed of the shaft, axial preload of bearings will have a remarkable effect. The low preload could reduce bearing vibration and temperature rise for bearings as well. At the others speed, the high preload could improve the vibration performance of high speed spindle and the bearing temperature was lower than that of the constant pressure preload spindle.

  11. Lubrication of an 85-mm ball bearing with RP-1

    Science.gov (United States)

    Addy, Harold E., Jr.; Schuller, Fredrick T.

    1993-01-01

    A parametric experimental investigation of an 85 millimeter bore angular contact ball bearing running in RP-1 fuel was performed at speeds of 10,000 to 24,000 rpm. Thrust loads were varied from 4450 to 17,800 Newtons (1000 to 4000 lbs.). Radial loads were varied from 1335 to 13,350 Newtons (300 to 3000 lbs.). RP-1 lubrication for the bearing was provided through a stationary jet ring located adjacent to the test bearing outer ring. Increases in both the thrust and radial loads resulted in increased bearing temperature, while increases in shaft speed resulted in much more dramatic increases in bearing temperature. These trends are typical for ball bearings operating under these types of conditions. Results are given for outer ring temperatures of the test bearing at the various test conditions employed. In addition, the heat energy removed from the bearing by the RP-1 was determined by measuring the increase in temperature as the RP-1 passed through the bearing. Results showed that the amount of heat energy removed by the RP-1 increased with both shaft speed and RP-1 flow rate to the bearing.

  12. Food availability and foraging near human developments by black bears

    Science.gov (United States)

    Merkle, Jerod A.; Robinson, Hugh S.; Krausman, Paul R.; Alaback, Paul B.

    2013-01-01

    Understanding the relationship between foraging ecology and the presence of human-dominated landscapes is important, particularly for American black bears (Ursus americanus), which sometimes move between wildlands and urban areas to forage. The food-related factors influencing this movement have not been explored, but can be important for understanding the benefits and costs to black bear foraging behavior and the fundamental origins of bear conflicts. We tested whether the scarcity of wildland foods or the availability of urban foods can explain when black bears forage near houses, examined the extent to which male bears use urban areas in comparison to females, and identified the most important food items influencing bear movement into urban areas. We monitored 16 collared black bears in and around Missoula, Montana, during 2009 and 2010, while quantifying the rate of change in green vegetation and the availability of 5 native berry-producing species outside the urban area, the rate of change in green vegetation, and the availability of apples and garbage inside the urban area. We used parametric time-to-event models in which an event was a bear location collected within 100 m of a house. We also visited feeding sites located near houses and quantified food items bears had eaten. The probability of a bear being located near a house was 1.6 times higher for males, and increased during apple season and the urban green-up. Fruit trees accounted for most of the forage items at urban feeding sites (49%), whereas wildland foods composed Black bears foraged on human foods near houses even when wildland foods were available, suggesting that the absence of wildland foods may not influence the probability of bears foraging near houses. Additionally, other attractants, in this case fruit trees, appear to be more important than the availability of garbage in influencing when bears forage near houses.

  13. Nonlinear dynamics of attractive magnetic bearings

    Science.gov (United States)

    Hebbale, K. V.; Taylor, D. L.

    1987-01-01

    The nonlinear dynamics of a ferromagnetic shaft suspended by the force of attraction of 1, 2, or 4 independent electromagnets is presented. Each model includes a state variable feedback controller which has been designed using the pole placement method. The constitutive relationships for the magnets are derived analytically from magnetic circuit theory, and the effects of induced eddy currents due to the rotation of the journal are included using Maxwell's field relations. A rotor suspended by four electro-magnets with closed loop feedback is shown to have nine equilibrium points within the bearing clearance space. As the rotor spin speed increases, the system is shown to pass through a Hopf bifurcation (a flutter instability). Using center manifold theory, this bifurcation can be shown to be of the subcritical type, indicating an unstable limit cycle below the critical speed. The bearing is very sensitive to initial conditions, and the equilibrium position is easily upset by transient excitation. The results are confirmed by numerical simulation.

  14. BEARS: Radioactive ion beams at LBNL

    International Nuclear Information System (INIS)

    Powell, J.; Guo, F.Q.; Haustein, P.E.

    1998-01-01

    BEARS (Berkeley Experiments with Accelerated Radioactive Species) is an initiative to develop a radioactive ion-beam capability at Lawrence Berkeley National Laboratory. The aim is to produce isotopes at an existing medical cyclotron and to accelerate them at the 88 inch Cyclotron. To overcome the 300-meter physical separation of these two accelerators, a carrier-gas transport system will be used. At the terminus of the capillary, the carrier gas will be separated and the isotopes will be injected into the 88 inch Cyclotron's Electron Cyclotron Resonance (ECR) ion source. The first radioactive beams to be developed will include 20-min 11 C and 70-sec 14 O, produced by (p,n) and (p,α) reactions on low-Z targets. A test program is currently being conducted at the 88 inch Cyclotron to develop the parts of the BEARS system. Preliminary results of these tests lead to projections of initial 11 C beams of up to 2.5 x 10 7 ions/sec and 14 O beams of 3 x 10 5 ions/sec

  15. The effect of external dynamic loads on the lifetime of rolling element bearings: accurate measurement of the bearing behaviour

    International Nuclear Information System (INIS)

    Jacobs, W; Boonen, R; Sas, P; Moens, D

    2012-01-01

    Accurate prediction of the lifetime of rolling element bearings is a crucial step towards a reliable design of many rotating machines. Recent research emphasizes an important influence of external dynamic loads on the lifetime of bearings. However, most lifetime calculations of bearings are based on the classical ISO 281 standard, neglecting this influence. For bearings subjected to highly varying loads, this leads to inaccurate estimations of the lifetime, and therefore excessive safety factors during the design and unexpected failures during operation. This paper presents a novel test rig, developed to analyse the behaviour of rolling element bearings subjected to highly varying loads. Since bearings are very precise machine components, their motion can only be measured in an accurately controlled environment. Otherwise, noise from other components and external influences such as temperature variations will dominate the measurements. The test rig is optimised to perform accurate measurements of the bearing behaviour. Also, the test bearing is fitted in a modular structure, which guarantees precise mounting and allows testing different types and sizes of bearings. Finally, a fully controlled multi-axial static and dynamic load is imposed on the bearing, while its behaviour is monitored with capacitive proximity probes.

  16. Individual effects of seasonal changes, visitor density, and concurrent bear behavior on stereotypical behaviors in captive polar bears (Ursus maritimus).

    Science.gov (United States)

    Kelly, Krista R; Harrison, Michelle L; Size, Daniele D; MacDonald, Suzanne E

    2015-01-01

    Stereotypical behaviors in captive polar bears (Ursus maritimus) can be detrimental to their welfare. These behaviors can be reduced through enrichment programs but are often not completely eliminated, so identifying potential triggers is important. The present study investigated the influences of seasonal changes, visitor density, and concurrent bear activity on stereotypical behaviors exhibited by 3 captive polar bears at the Toronto Zoo. All bears exhibited these behaviors; however, individual differences were found in duration and form. The male exhibited less stereotypical behavior during spring, and the females exhibited less stereotypical behavior during winter. An increase in visitor density was associated with more stereotypical behavior in 1 female but less stereotypical behavior in the other 2 bears. All bears engaged in more stereotypical behaviors when the other bears were inactive, and 1 female engaged in more stereotypical behaviors when the other bears were out of sight. Further, when conspecifics were active, all bears engaged in less stereotypical behaviors. Given the variability among individual bears, future enrichment programs must be tailored to the needs of individuals to maximize efficacy.

  17. Precision Magnetic Bearing Six Degree of Freedom Stage

    Science.gov (United States)

    Williams, M. E.; Trumper, David L.

    1996-01-01

    Magnetic bearings are capable of applying force and torque to a suspended object without rigidly constraining any degrees of freedom. Additionally, the resolution of magnetic bearings is limited only by sensors and control, and not by the finish of a bearing surface. For these reasons, magnetic bearings appear to be ideal for precision wafer positioning in lithography systems. To demonstrate this capability a linear magnetic bearing has been constructed which uses variable reluctance actuators to control the motion of a 14.5 kg suspended platen in five degrees of freedom. A Lorentz type linear motor of our own design and construction is used to provide motion and position control in the sixth degree of freedom. The stage performance results verify that the positioning requirements of photolithography can be met with a system of this type. This paper describes the design, control, and performance of the linear magnetic bearing.

  18. On the future of controllable fluid film bearings

    DEFF Research Database (Denmark)

    Santos, Ilmar

    2011-01-01

    This work gives an overview of the theoretical and experimental achievements of mechatronics applied to fluid film bearings. Compressible and uncompressible fluids are addressed. Rigid and elastic (deformable) bearing profiles are investigated. Hydraulic, pneumatic, magnetic and piezoelectric...... controllable fluid film bearings is to improve the overall machine performance by: controlling the lateral vibration of rigid and flexible rotating shafts; modifying bearing dynamic characteristics, such as stiffness and damping properties; increasing the rotational speed ranges by enhancing damping...... and eliminating instability problems, for example, by compensating cross-coupling destabilizing effects; reducing start-up torque and energy dissipation in bearings; compensating thermal effects. It is shown that such controllable fluid film bearings can act as “smart” machine components and be applied...

  19. Simulating fullerene ball bearings of ultra-low friction

    International Nuclear Information System (INIS)

    Li Xiaoyan; Yang Wei

    2007-01-01

    We report the direct molecular dynamics simulations for molecular ball bearings composed of fullerene molecules (C 60 and C 20 ) and multi-walled carbon nanotubes. The comparison of friction levels indicates that fullerene ball bearings have extremely low friction (with minimal frictional forces of 5.283 x 10 -7 and 6.768 x 10 -7 nN/atom for C 60 and C 20 bearings) and energy dissipation (lowest dissipation per cycle of 0.013 and 0.016 meV/atom for C 60 and C 20 bearings). A single fullerene inside the ball bearings exhibits various motion statuses of mixed translation and rotation. The influences of the shaft's distortion on the long-ranged potential energy and normal force are discussed. The phonic dissipation mechanism leads to a non-monotonic function between the friction and the load rate for the molecular bearings

  20. A study on synchronously whirling motion of hydrodynamic journal bearings

    International Nuclear Information System (INIS)

    Rho, Byoung Hoo; Kim, Kyung Woong

    2001-01-01

    In this paper, a control algorithm which is synchronously excitation the bearing with whirl speed of rotor is employed to suppress the whirl instability and unbalance response of the rotor-bearing system. Also, the cavitation algorithm implementing the Jakobsson-Floberg-Olsson boundary condition is adopted to predict cavitation regions in the fluid film more accurately than a conventional analysis with the Renolds condition. The stabilities and unbalance responses of the rotor-bearing system are investigated for various control gains and phase differences between the bearing and journal motion. It is shown that the unbalance response of the system can be greatly improved by synchronous control of the bearing, and there is an optimum phase difference, which gives the minimum unbalance response of the system, for given operating condition. It is also found that the onset speed of the instability can be greatly increased by synchronous control of the bearing

  1. Development of AE monitoring system for journal bearing

    International Nuclear Information System (INIS)

    Yoon, Dong Jin; Kwon, Oh Yang; Chung, Min Hwa

    1994-01-01

    For the purpose of monitoring of the bearing conditions in rotating machinery, a system for journal bearing diagnosis by AE was developed. Acoustic emission technique is used to detect abnormal conditions in the bearing system. And various data such as AE events, rms voltage level of AE signals, and AE parameters were acquired during experiments with the simulated journal bearing system. Based on the above results and practical application for power plant, algorithms and judgement criteria for diagnosis system was accomplished. Bearing diagnosis system is composed of four parts as follows : sensing part for AE sensor and preamplifier, signal processing part for rms-to-dc converting to measure AE rms voltage, interface part for connecting rms signal to PC using A/D converter, graphic display and software part for display of bearing condition and for managing of diagnosis program.

  2. Analysis of partially textured slider and journal bearing

    Science.gov (United States)

    Rao, T. V. V. L. N.; Rani, A. M. A.; Nagarajan, T.; Hashim, F. M.

    2012-06-01

    The partial texturing of bearing surfaces with different shapes of textures and at different locations is an effective approach to improve the performance of bearings. The present study examines the effects of texture configuration on improvement in load capacity and reduction in friction coefficient for slider and journal bearing. This work presents nondimensional pressure expressions for the partially textured slider and journal bearing. The nondimensional pressure expressions are derived taking into consideration of texture geometry and extent of partial texture on the bearing surface. The Reynolds boundary conditions are used in the analysis to predict nondimensional load capacity and coefficient of friction. Even for nominally parallel surfaces, partial texturing of bearing surfaces has a potential to generate load carrying capacity and reduce coefficient of friction.

  3. Enhancing stability of industrial turbines using adjustable partial arc bearings

    Science.gov (United States)

    Chasalevris, Athanasios; Dohnal, Fadi

    2016-09-01

    The paper presents the principal of operation, the simulation and the characteristics of two partial-arc journal bearings of variable geometry and adjustable/controllable stiffness and damping properties. The proposed journals are supposed to consist of a scheme that enables the periodical variation of bearing properties. Recent achievements of suppressing rotor vibrations using plain circular journal bearings of variable geometry motivate the further extension of the principle to bearings of applicable geometry for industrial turbines. The paper describes the application of a partial-arc journal bearing to enhance stability of high speed industrial turbines. The proposed partial-arc bearings with adjustable/controllable properties enhance stability and they introduce stable margins in speeds much higher than the 1st critical.

  4. Gearbox Instrumentation for the Investigation of Bearing Axial Cracking

    Energy Technology Data Exchange (ETDEWEB)

    Keller, Jonathan A [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Lambert, Scott R [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2018-03-27

    Failures in gearbox bearings have been the primary source of reliability issues for wind turbine drivetrains, leading to costly downtime and unplanned maintenance. The most common failure mode is attributed to so-called axial cracks or white-etching cracks, which primarily affect the intermediate and high-speed-stage bearings. The high-speed-shaft and bearing loads and sliding will be measured with a specially instrumented gearbox installed in a 1.5-megawatt turbine at the National Wind Technology Center in an upcoming test campaign. Additional instrumentation will also measure the tribological environment of these bearings, including bearing temperatures, lubricant temperature and water content, air temperature and humidity, and stray electrical current across the bearings. This paper fully describes the instrumentation package and summarizes initial results.

  5. Hibernating bears as a model for preventing disuse osteoporosis.

    Science.gov (United States)

    Donahue, Seth W; McGee, Meghan E; Harvey, Kristin B; Vaughan, Michael R; Robbins, Charles T

    2006-01-01

    The hibernating bear is an excellent model for disuse osteoporosis in humans because it is a naturally occurring large animal model. Furthermore, bears and humans have similar lower limb skeletal morphology, and bears walk plantigrade like humans. Black bears (Ursus americanus) may not develop disuse osteoporosis during long periods of disuse (i.e. hibernation) because they maintain osteoblastic bone formation during hibernation. As a consequence, bone volume, mineral content, porosity, and strength are not adversely affected by annual periods of disuse. In fact, cortical bone bending strength has been shown to increase with age in hibernating black bears without a significant change in porosity. Other animals require remobilization periods 2-3 times longer than the immobilization period to recover the bone lost during disuse. Our findings support the hypothesis that black bears, which hibernate for as long as 5-7 months annually, have evolved biological mechanisms to mitigate the adverse effects of disuse on bone porosity and strength.

  6. A study on synchronously whirling motion of hydrodynamic journal bearings

    Energy Technology Data Exchange (ETDEWEB)

    Rho, Byoung Hoo; Kim, Kyung Woong [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)

    2001-09-01

    In this paper, a control algorithm which is synchronously excitation the bearing with whirl speed of rotor is employed to suppress the whirl instability and unbalance response of the rotor-bearing system. Also, the cavitation algorithm implementing the Jakobsson-Floberg-Olsson boundary condition is adopted to predict cavitation regions in the fluid film more accurately than a conventional analysis with the Renolds condition. The stabilities and unbalance responses of the rotor-bearing system are investigated for various control gains and phase differences between the bearing and journal motion. It is shown that the unbalance response of the system can be greatly improved by synchronous control of the bearing, and there is an optimum phase difference, which gives the minimum unbalance response of the system, for given operating condition. It is also found that the onset speed of the instability can be greatly increased by synchronous control of the bearing.

  7. The R and D D's bearing test benches

    International Nuclear Information System (INIS)

    Vialettes, J.M.

    1997-01-01

    In power generation plants, rotating machines are involved in energy transformation processes and safety systems. The bearings supporting the rotors and the thrust bearings play a crucial role in the reliability of these machines. The phenomena encountered straddle several disciplines: hydrodynamics, tribology, thermomechanics, materials and vibrations in a specific environment, namely: thin fluid film, solid mechanical components and shaft rotation. Means of analysing the behaviour of these components (bearings and thrust bearings) have been developed and implemented. These consists of the EDYOS (Etude Dynamique des Organes de Supportage) code for dynamically studying bearing devices and several related bench tests. In reality, in order to understand the complex physical phenomena encountered in these components, it is vital to carry out analyses and experimental validations. Since these investigations cannot be carried out on actual machines, test benches have been built which can subject the sample bearings to the equivalent stresses. (author)

  8. Spatial Distribution of Black Bear Incident Reports in Michigan.

    Directory of Open Access Journals (Sweden)

    Jamie E McFadden-Hiller

    Full Text Available Interactions between humans and carnivores have existed for centuries due to competition for food and space. American black bears are increasing in abundance and populations are expanding geographically in many portions of its range, including areas that are also increasing in human density, often resulting in associated increases in human-bear conflict (hereafter, bear incidents. We used public reports of bear incidents in Michigan, USA, from 2003-2011 to assess the relative contributions of ecological and anthropogenic variables in explaining the spatial distribution of bear incidents and estimated the potential risk of bear incidents. We used weighted Normalized Difference Vegetation Index mean as an index of primary productivity, region (i.e., Upper Peninsula or Lower Peninsula, primary and secondary road densities, and percentage land cover type within 6.5-km2 circular buffers around bear incidents and random points. We developed 22 a priori models and used generalized linear models and Akaike's Information Criterion (AIC to rank models. The global model was the best compromise between model complexity and model fit (w = 0.99, with a ΔAIC 8.99 units from the second best performing model. We found that as deciduous forest cover increased, the probability of bear incident occurrence increased. Among the measured anthropogenic variables, cultivated crops and primary roads were the most important in our AIC-best model and were both positively related to the probability of bear incident occurrence. The spatial distribution of relative bear incident risk varied markedly throughout Michigan. Forest cover fragmented with agriculture and other anthropogenic activities presents an environment that likely facilitates bear incidents. Our map can help wildlife managers identify areas of bear incident occurrence, which in turn can be used to help develop strategies aimed at reducing incidents. Researchers and wildlife managers can use similar mapping

  9. Spatial Distribution of Black Bear Incident Reports in Michigan.

    Science.gov (United States)

    McFadden-Hiller, Jamie E; Beyer, Dean E; Belant, Jerrold L

    2016-01-01

    Interactions between humans and carnivores have existed for centuries due to competition for food and space. American black bears are increasing in abundance and populations are expanding geographically in many portions of its range, including areas that are also increasing in human density, often resulting in associated increases in human-bear conflict (hereafter, bear incidents). We used public reports of bear incidents in Michigan, USA, from 2003-2011 to assess the relative contributions of ecological and anthropogenic variables in explaining the spatial distribution of bear incidents and estimated the potential risk of bear incidents. We used weighted Normalized Difference Vegetation Index mean as an index of primary productivity, region (i.e., Upper Peninsula or Lower Peninsula), primary and secondary road densities, and percentage land cover type within 6.5-km2 circular buffers around bear incidents and random points. We developed 22 a priori models and used generalized linear models and Akaike's Information Criterion (AIC) to rank models. The global model was the best compromise between model complexity and model fit (w = 0.99), with a ΔAIC 8.99 units from the second best performing model. We found that as deciduous forest cover increased, the probability of bear incident occurrence increased. Among the measured anthropogenic variables, cultivated crops and primary roads were the most important in our AIC-best model and were both positively related to the probability of bear incident occurrence. The spatial distribution of relative bear incident risk varied markedly throughout Michigan. Forest cover fragmented with agriculture and other anthropogenic activities presents an environment that likely facilitates bear incidents. Our map can help wildlife managers identify areas of bear incident occurrence, which in turn can be used to help develop strategies aimed at reducing incidents. Researchers and wildlife managers can use similar mapping techniques to

  10. Seal and bearing arrangement for use in a nuclear reactor

    International Nuclear Information System (INIS)

    Kazan, J.M.; Ritz, W.C.; Sharbaugh, J.E.

    1982-01-01

    A combination seal and bearing arrangement for use in a nuclear reactor including a vessel and vessel cover is disclosed herein. The vessel cover itself includes at least one rotatable plug which serves to perform certain position related functions within the reactor vessel and the combination seal and bearing arrangement is provided for sealing the annular opening around the rotation plug while, at the same time, providing a bearing support for the latter

  11. A Simulation Study of Recessed Type Hydrostatic Journal Bearing

    Directory of Open Access Journals (Sweden)

    Wong Shih-Ming

    2016-01-01

    Full Text Available In this paper, a simulation model is established to study effects of the bearing system parameters on bearing performance. The static performance (such as load capacity, stiffness and flow about various dimensions of multi-recess type hydrostatic journal bearings with constant-resistant restrictor compensation was investigated. The parameters studied includes length/diameter ratio, number of recess, recess length ratio, recess width ratio, initial ratio between recess pressure to supply pressure, and eccentricity.

  12. Static Characteristics of Conical Hydrostatic Journal Bearing Under Micropolar Lubrication

    Science.gov (United States)

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

    2014-10-01

    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.

  13. Analysis for the cause of the condensate pump bearing failure

    International Nuclear Information System (INIS)

    Cheng Yiyan

    2012-01-01

    This paper discussed the influence of the foreign matters for the rolling bearing's service life, analyzed the reason, way and harm of soft foreign matters disabling the bearings. And some measures were brought forward to improve the maintenance quality, which could be used for reference to enhance the ability of estimating the failure of the motor's rolling bearings, and to improve the level of the maintenance work. (author)

  14. A Low Friction Thrust Bearing for Reciprocating Compressors

    OpenAIRE

    Nagata, Shuhei; Kousokabe, Hirokatsu; Sekiyama, Nobuya; Ono, Toshiaki

    2012-01-01

    A thrust bearing with a micro texture on its sliding surface that produces hydrodynamic pressure was developed for use in reciprocating compressors. Evaluation using an elemental friction test showed that its friction loss was 20–60 % lower than that of the current design. Measurement of the efficiency of a compressor with the developed thrust bearing showed that the coefficient of performance was 1.4 % higher than that of a compressor with a conventional thrust bearing.

  15. Backward whirl in a simple rotor supported on hydrodynamic bearings

    Science.gov (United States)

    Subbiah, R.; Rhat, R. B.; Sankar, T. S.; Rao, J. S.

    1985-01-01

    The asymmetric nature of the fluid film stiffness and damping properties in rotors supported on fluid film bearings causes a forward or a backward whirl depending on the bearing parameters and the speed of the rotor. A rotor was designed to exhibit backward synchronous whirl. The rotor-bearing system exhibited split criticals, and a backward whirl was observed between the split criticals. The orbital diagrams show the whirl pattern.

  16. Household Portfolios and Risk Bearing over Age and Time

    OpenAIRE

    Alessandro Bucciol; Raffaele Miniaci

    2011-01-01

    We exploit the US Survey of Consumer Finances from 1998 to 2007 to study households’ portfolio risk bearing. We compare four alternative measures of risk, two based on a financial portfolio and two based on a broader portfolio also including – as illiquid assets – human capital, real estate, business wealth and related debt. The measures provide a different ranking of household risk bearing, but they consistently show that risk bearing fell after 2001, and it positively correlates with wealth...

  17. The peculiarities of bear numbers dynamics in the Eastern Carpathians

    OpenAIRE

    Khoyetskyy, Pavlo

    2013-01-01

    There have been two periods of change in the dynamics of bear population in the Eastern Carpathians. The first period lasted over 50 years, starting in the late 1940s and ending in the year 2001. The second period started in the early 21st century. The bear population reached its maximum – of about 1100 individuals – in the early 1970s. Over 85% of recorded bear deaths have resulted from poaching.

  18. USING GENETICS TO STUDY ROAD IMPACTS ON BEARS IN FLORIDA

    OpenAIRE

    Simek, Stephanie L.; Eason, Thomas

    2003-01-01

    Funding source: Florida Department of Transportation Total Budget: $407,000 Project Period: April 2001 – April 2004 The Florida Fish and Wildlife Conservation Commission (FWC) has documented an increase in the number of transportation-related bear deaths (roadkill) since the late 1970’s. In addition to impacts on bear populations, vehicle collisions with bears often are traumatic for the people involved and may cause significant collateral damage and personal injury. For these reasons, and be...

  19. The peculiarities of bear numbers dynamics in the Eastern Carpathians

    OpenAIRE

    Khoyetskyy, Pavlo

    2013-01-01

    There have been two periods of change in the dynamics of bear population in the Eastern Carpathians. The first period lasted over 50 years, starting in the late 1940s and ending in the year 2001. The second period started in the early 21st century. The bear population reached its maximum- of about 1100 individuals - in the early 1970s. Over 85% of recorded bear deaths have resulted from poaching. Przemysław Szmit

  20. Bearing problems’ effects on the dynamic performance of pumping stations

    Directory of Open Access Journals (Sweden)

    Mostafa A. Abu-Zeid

    2013-09-01

    Pumping stations use large number of bearings with different types and applications. These bearings have a clear effect on the performance and efficiency of the pumps. Pump bearings in the arid regions are greatly affected by temperature, water quality, lubricants, and maintenance operations. This research focuses on analysis of damaged rolling element bearings of pumping system. The objective of the research is to enhance and control dynamic performance of pumping stations by avoiding damage and failure of bearings. The research proves that damaged bearings generate periodic, non-periodic, and transient forces causing high amplitude of vibration at high frequencies and increasing energy consumption. Bearing faults increase vibration level 85%, where power consumption increases 14% and pump efficiency decreases 18%. It is very important to take care of bearings during installation, alignment, balancing, and maintenance to assure safe and efficient pump operation for long period. As pump efficiency decreases, water power decreases and/or consumed power increases affecting water distribution and management system. Bearing faults break pumping system for long period affecting irrigation system. Optimum operation of pumping stations helps to save and manage water requirement for development and extension projects in arid regions. The measurements are performed on full scale model in the field, which proves reliable results on similar pumping stations.

  1. DC Control Effort Minimized for Magnetic-Bearing-Supported Shaft

    Science.gov (United States)

    Brown, Gerald V.

    2001-01-01

    A magnetic-bearing-supported shaft may have a number of concentricity and alignment problems. One of these involves the relationship of the position sensors, the centerline of the backup bearings, and the magnetic center of the magnetic bearings. For magnetic bearings with permanent magnet biasing, the average control current for a given control axis that is not bearing the shaft weight will be minimized if the shaft is centered, on average over a revolution, at the magnetic center of the bearings. That position may not yield zero sensor output or center the shaft in the backup bearing clearance. The desired shaft position that gives zero average current can be achieved if a simple additional term is added to the control law. Suppose that the instantaneous control currents from each bearing are available from measurements and can be input into the control computer. If each control current is integrated with a very small rate of accumulation and the result is added to the control output, the shaft will gradually move to a position where the control current averages to zero over many revolutions. This will occur regardless of any offsets of the position sensor inputs. At that position, the average control effort is minimized in comparison to other possible locations of the shaft. Nonlinearities of the magnetic bearing are minimized at that location as well.

  2. Modeling of Tilting-Pad Journal Bearings with Transfer Functions

    Directory of Open Access Journals (Sweden)

    J. A. Vázquez

    2001-01-01

    Full Text Available Tilting-pad journal bearings are widely used to promote stability in modern rotating machinery. However, the dynamics associated with pad motion alters this stabilizing capacity depending on the operating speed of the machine and the bearing geometric parameters, particularly the bearing preload. In modeling the dynamics of the entire rotor-bearing system, the rotor is augmented with a model of the bearings. This model may explicitly include the pad degrees of freedom or may implicitly include them by using dynamic matrix reduction methods. The dynamic reduction models may be represented as a set of polynomials in the eigenvalues of the system used to determine stability. All tilting-pad bearings can then be represented by a fixed size matrix with polynomial elements interacting with the rotor. This paper presents a procedure to calculate the coefficients of polynomials for implicit bearing models. The order of the polynomials changes to reflect the number of pads in the bearings. This results in a very compact and computationally efficient method for fully including the dynamics of tilting-pad bearings or other multiple degrees of freedom components that interact with rotors. The fixed size of the dynamic reduction matrices permits the method to be easily incorporated into rotor dynamic stability codes. A recursive algorithm is developed and presented for calculating the coefficients of the polynomials. The method is applied to stability calculations for a model of a typical industrial compressor.

  3. The development of cobalt-base alloy ball bearing

    International Nuclear Information System (INIS)

    Yu Xinshui; Chen Jianting; Wang Zaishu; Wang Ximei; Huang Chongming.

    1986-01-01

    The main technologies and experiences in developing a Cobalt-base alloy ball bearing are described. In the hardfacing of bearing races, a lower-hardness alloy of type St-6 is used rather than an alloy with hardness similar to that of the ball and finally the hardness of race is increased to match that of the ball by heat treatment. This improvement has certain advantages. The experience of whole developing technology indicates that strict control of the technology in the bearing-race hardfacing is the key problem in the quality assurance of bearings

  4. Recent research and development of bearings for helium circulator

    International Nuclear Information System (INIS)

    Taniguchi, S.; Ezaki, Z.; Kawaguchi, K.; Matsumura, N.; Kozima, M.

    1988-01-01

    This paper mainly describes recent studies and successful applications of water lubricated bearing and gas lubricated bearing. Both types of bearing seem to be suitable for a turbo machine installed in an atomic energy plant - such as the helium circulator of a HTGR - not to be affected by radioactivity, so we have been attracted by them for about 10 years. The former was investigated theoretically taking account of turbulent flow due to the low viscosity of water, and compared with the experimental data. Good agreement was obtained, and a successful example applied to a small-sized high speed air compressor is shown. The latter was investigated using a large-sized bearing test rig simulated to an actual machine. The tilting pad journal bearing and the tilting pad thrust bearing were taken and improved for some aspects. These bearings have been taken into service on an actual circulator and are now operating successfully. Currently, a magnetic bearing is being studied to pay special attention to endurance for an earthquake and catcher bearing system. We would like to have an opportunity to present these results in the near future. (author). 5 refs, 15 figs, 2 tabs

  5. Interaction of Reinforced Elastomeric Bearings in Bridge Construction

    Directory of Open Access Journals (Sweden)

    Nittmannová Ľubica

    2016-03-01

    Full Text Available The aim of this paper is to demonstrate the behavior of reinforced elastomeric bearings under various loads. They are made of special types of bearings. The experimental verification of these special bearings has been tested on various types of loading. The results of the experimental measurements are compared with the results of the numerical modeling and calculations according to the standard assumptions in STN EN 1337-3. In the conclusion, the results are summarized for the selected types of bearings.

  6. Numerical investigation of cavitation flow in journal bearing geometry

    Directory of Open Access Journals (Sweden)

    Stücke P.

    2013-04-01

    Full Text Available The appearance of cavitation is still a problem in technical and industrial applications. Especially in automotive internal combustion engines, hydrodynamic journal bearings are used due to their favourable wearing quality and operating characteristics. Cavitation flows inside the bearings reduces the load capacity and leads to a risk of material damages. Therefore an understanding of the complex flow phenomena inside the bearing is necessary for the design development of hydrodynamic journal bearings. Experimental investigations in the fluid domain of the journal bearing are difficult to realize founded by the small dimensions of the bearing. In the recent years more and more the advantages of the computational fluid dynamics (CFD are used to investigate the detail of the cavitation flows. The analysis in the paper is carried out in a two-step approach. At first an experimental investigation of journal bearing including cavitation is selected from the literature. The complex numerical model validated with the experimental measured data. In a second step, typically design parameters, such as a groove and feed hole, which are necessary to distribute the oil supply across the gap were added into the model. The paper reflects on the influence of the used design parameters and the variation of the additional supply flow rate through the feed hole regarding to cavitation effects in the bearing. Detailed pictures of the three-dimensional flow structures and the cavitation regions inside the flow film of the bearing are presented.

  7. Design optimization and probabilistic analysis of a hydrodynamic journal bearing

    Science.gov (United States)

    Liniecki, Alexander G.

    1990-01-01

    A nonlinear constrained optimization of a hydrodynamic bearing was performed yielding three main variables: radial clearance, bearing length to diameter ratio, and lubricating oil viscosity. As an objective function a combined model of temperature rise and oil supply has been adopted. The optimized model of the bearing has been simulated for population of 1000 cases using Monte Carlo statistical method. It appeared that the so called 'optimal solution' generated more than 50 percent of failed bearings, because their minimum oil film thickness violated stipulated minimum constraint value. As a remedy change of oil viscosity is suggested after several sensitivities of variables have been investigated.

  8. INVESTIGATION OF TRIBOLOGICAL PROPERTIES CuSn10 BEARING MATERIAL

    Directory of Open Access Journals (Sweden)

    Bekir Sadık ÜNLÜ

    2005-01-01

    Full Text Available Bronzes which copper based alloys is widely used because of properties physical, thermal and tribological as journal bearing material. This material that has tribological performance good conclusions gives at journal bearings. In this study, CuSn10 bronze that were manufactured journal bearings friction and wear properties has been examined and compared. SAE 1050 steel shaft has been used as counter abrader. Experiments have been carried out 10 N and 20 N loads, 750 and 1500 rpm, dry and lubricated conditions by using radial journal bearing wear test rig. As a results, high friction coefficient and weigh loss have been obtained at dry condition more than lubricated condition.

  9. On The Modelling Of Hybrid Aerostatic - Gas Journal Bearings

    DEFF Research Database (Denmark)

    Morosi, Stefano; Santos, Ilmar

    2011-01-01

    modeling for hybrid lubrication of a compressible fluid film journal bearing. Additional forces are generated by injecting pressurized air into the bearing gap through orifices located on the bearing walls. A modified form of the compressible Reynolds equation for active lubrication is derived. By solving......Gas journal bearing have been increasingly adopted in modern turbo-machinery applications, as they meet the demands of operation at higher rotational speeds, in clean environment and great efficiency. Due to the fact that gaseous lubricants, typically air, have much lower viscosity than more...

  10. On The Modeling Of Hybrid Aerostatic - Gas Journal Bearings

    DEFF Research Database (Denmark)

    Morosi, Stefano; Santos, Ilmar

    2010-01-01

    of a compressible fluid film journal bearing. Control forces are generated by injecting pressurized air into the bearing gap through orifices located on the bearing walls. A modified form of the compressible Reynolds equation for active lubrication is derived. By solving this equation, stiffness and damping......Gas journal bearing have been increasingly adopted in modern turbo-machinery applications, as they meet the demands of operation at higher rotational speeds, in clean environment and great efficiency. Due to the fact that gaseous lubricants, typically air, have much lower viscosity than more...

  11. Precise bearing support ditherer with piezoelectric drive means

    Science.gov (United States)

    Assard, G. L.; Moorcroft, A. L.

    1985-06-01

    A relatively solid mounting surface, which may be part of a leveling gimbal, supports a piezoelectric bearing mount which has the properties of an acoustic transducer. The transducer has electrodes thereon which are powered from multi-phase electrical sources causing the bearing mount, and a bearing jewel which is rigid therewith, to move so as to dither the jewel in a rotary or other preselected fashion, thereby reducing bearing friction. Bandwidth, level and phasing sequence of the power sources are adjustable permitting optimized average dynamic motion and corresponding increased readout accuracy.

  12. Research on Bored Bearing Characteristics in Xi’an

    Directory of Open Access Journals (Sweden)

    Zhang Lipeng

    2015-01-01

    Full Text Available To analyze the influence of different soil properties on pile foundation load-bearing characteristics, taking a section of railway in Xi’an and a bridge of Xi’an as test area, and by field static load test to study load transfer characteristics after the test piles under axial pressure, including the distribution of axial force, pile lateral friction, tip resistance traits, ultimate bearing capacity determine, and compare with the theory bearing capacity. Experimental results show that, adjacent soil properties change large, axial force and lateral friction mutation at the junction of corresponding soil layer. Silty clay in different parts is below ground, and its lateral friction plays much difference. Pile lateral friction plays an important role in bearing capacity, but the role of round gravel soil end bearing capacity to pile bearing capacity can’t be ignored. Tests calculate pile bearing capacity significantly larger than standardized formula calculation bearing capacity, which are respectively 55.35% and 119.1%. And give the similar project condition the suggested values of pile bearing capacity and soil friction, to provide reference for similar pile foundation design.

  13. Numerical investigation of cavitation flow in journal bearing geometry

    Science.gov (United States)

    Riedel, M.; Schmidt, M.; Stücke, P.

    2013-04-01

    The appearance of cavitation is still a problem in technical and industrial applications. Especially in automotive internal combustion engines, hydrodynamic journal bearings are used due to their favourable wearing quality and operating characteristics. Cavitation flows inside the bearings reduces the load capacity and leads to a risk of material damages. Therefore an understanding of the complex flow phenomena inside the bearing is necessary for the design development of hydrodynamic journal bearings. Experimental investigations in the fluid domain of the journal bearing are difficult to realize founded by the small dimensions of the bearing. In the recent years more and more the advantages of the computational fluid dynamics (CFD) are used to investigate the detail of the cavitation flows. The analysis in the paper is carried out in a two-step approach. At first an experimental investigation of journal bearing including cavitation is selected from the literature. The complex numerical model validated with the experimental measured data. In a second step, typically design parameters, such as a groove and feed hole, which are necessary to distribute the oil supply across the gap were added into the model. The paper reflects on the influence of the used design parameters and the variation of the additional supply flow rate through the feed hole regarding to cavitation effects in the bearing. Detailed pictures of the three-dimensional flow structures and the cavitation regions inside the flow film of the bearing are presented.

  14. Acquired umbilical hernias in four captive polar bears (Ursus maritimus).

    Science.gov (United States)

    Velguth, Karen E; Rochat, Mark C; Langan, Jennifer N; Backues, Kay

    2009-12-01

    Umbilical hernias are a common occurrence in domestic animals and humans but have not been well documented in polar bears. Surgical reduction and herniorrhaphies were performed to correct acquired hernias in the region of the umbilicus in four adult captive polar bears (Ursus maritimus) housed in North American zoos. Two of the four bears were clinically unaffected by their hernias prior to surgery. One bear showed signs of severe discomfort following acute enlargement of the hernia. In another bear, re-herniation led to acute abdominal pain due to gastric entrapment and strangulation. The hernias in three bears were surgically repaired by debridement of the hernia ring and direct apposition of the abdominal wall, while the large defect in the most severely affected bear was closed using polypropylene mesh to prevent excessive tension. The cases in this series demonstrate that while small hernias may remain clinically inconsequential for long periods of time, enlargement or recurrence of the defect can lead to incarceration and acute abdominal crisis. Umbilical herniation has not been reported in free-ranging polar bears, and it is suspected that factors such as body condition, limited exercise, or enclosure design potentially contribute to the development of umbilical hernias in captive polar bears.

  15. Gene transcription in polar bears (Ursus maritimus) from disparate populations

    Science.gov (United States)

    Bowen, Lizabeth; Miles, A. Keith; Waters, Shannon C.; Meyerson, Randi; Rode, Karyn D.; Atwood, Todd C.

    2015-01-01

    Polar bears in the Beaufort (SB) and Chukchi (CS) Seas experience different environments due primarily to a longer history of sea ice loss in the Beaufort Sea. Ecological differences have been identified as a possible reason for the generally poorer body condition and reproduction of Beaufort polar bears compared to those from the Chukchi, but the influence of exposure to other stressors remains unknown. We use molecular technology, quantitative PCR, to identify gene transcription differences among polar bears from the Beaufort and Chukchi Seas as well as captive healthy polar bears. We identified significant transcriptional differences among a priori groups (i.e., captive bears, SB 2012, SB 2013, CS 2013) for ten of the 14 genes of interest (i.e., CaM, HSP70, CCR3, TGFβ, COX2, THRα, T-bet, Gata3, CD69, and IL17); transcription levels of DRβ, IL1β, AHR, and Mx1 did not differ among groups. Multivariate analysis also demonstrated separation among the groups of polar bears. Specifically, we detected transcript profiles consistent with immune function impairment in polar bears from the Beaufort Sea, when compared with Chukchi and captive polar bears. Although there is no strong indication of differential exposure to contaminants or pathogens between CS and SB bears, there are clearly differences in important transcriptional responses between populations. Further investigation is warranted to refine interpretation of potential effects of described stress-related conditions for the SB population.

  16. Gearbox Reliability Collaborative Gearbox 3 Planet Bearing Calibration

    Energy Technology Data Exchange (ETDEWEB)

    Keller, Jonathan [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2017-03-24

    The Gearbox Reliability Collaborative gearbox was redesigned to improve its load-sharing characteristics and predicted fatigue life. The most important aspect of the redesign was to replace the cylindrical roller bearings with preloaded tapered roller bearings in the planetary section. Similar to previous work, the strain gages installed on the planet tapered roller bearings were calibrated in a load frame. This report describes the calibration tests and provides the factors necessary to convert the measured units from dynamometer testing to bearing loads, suitable for comparison to engineering models.

  17. Targeting Faulty Bearings for an Ocean Turbine Dynamometer

    Directory of Open Access Journals (Sweden)

    David J. Vendittis

    2013-01-01

    Full Text Available A real-time, vibrations-based condition monitoring method used to detect, localize, and identify a faulty bearing in an ocean turbine electric motor is presented in this paper. The electric motor is installed in a dynamometer emulating the functions of the actual ocean turbine. High frequency modal analysis and power trending are combined to assess the operational health of the dynamometer’s bearings across an array of accelerometers. Once a defect has been detected, envelope analysis is used to identify the exact bearing containing the defect. After a brief background on bearing fault detection, this paper introduces a simplified mathematical model of the bearing fault, followed with the signal processing approach used to detect, locate, and identify the fault. In the results section, effectiveness of the methods of bearing fault detection presented in this paper is demonstrated through processing data collected, first, from a controlled lathe setup and, second, from the dynamometer. By mounting a bearing containing a defect punched into its inner raceway to a lathe and placing an array of accelerometers along the length of lathe, the bearing fault is clearly detected, localized, and identified as an inner raceway defect. Through retroactively trending the data leading to the near-failure of one of the electric motors in the dynamometer, the authors identified a positive trend in energy levels for a specific frequency band present across the array of accelerometers and identify two bearings as possible sources of the fault.

  18. The current state of bearing surfaces in total hip replacement.

    Science.gov (United States)

    Rajpura, A; Kendoff, D; Board, T N

    2014-02-01

    We reviewed the literature on the currently available choices of bearing surface in total hip replacement (THR). We present a detailed description of the properties of articulating surfaces review the understanding of the advantages and disadvantages of existing bearing couples. Recent technological developments in the field of polyethylene and ceramics have altered the risk of fracture and the rate of wear, although the use of metal-on-metal bearings has largely fallen out of favour, owing to concerns about reactions to metal debris. As expected, all bearing surface combinations have advantages and disadvantages. A patient-based approach is recommended, balancing the risks of different options against an individual's functional demands.

  19. Platelet function in brown bear (Ursus arctos compared to man

    Directory of Open Access Journals (Sweden)

    Särndahl Eva

    2010-06-01

    Full Text Available Abstract Background Information on hemostasis and platelet function in brown bear (Ursus arctos is of importance for understanding the physiological, protective changes during hibernation. Objective The study objective was to document platelet activity values in brown bears shortly after leaving the den and compare them to platelet function in healthy humans. Methods Blood was drawn from immobilized wild brown bears 7-10 days after leaving the den in mid April. Blood samples from healthy human adults before and after clopidogrel and acetylsalicylic acid administration served as control. We analyzed blood samples by standard blood testing and platelet aggregation was quantified after stimulation with various agonists using multiple electrode aggregometry within 3 hours of sampling. Results Blood samples were collected from 6 bears (3 females between 1 and 16 years old and from 10 healthy humans. Results of adenosine diphosphate, aspirin, and thrombin receptor activating peptide tests in bears were all half or less of those in humans. Platelet and white blood cell counts did not differ between species but brown bears had more and smaller red blood cells compared with humans. Conclusion Using three different tests, we conclude that platelet function is lower in brown bears compared to humans. Our findings represent the first descriptive study on platelet function in brown bears and may contribute to explain how bears can endure denning without obvious thrombus building. However, the possibility that our findings reflect test-dependent and not true biological variations in platelet reactivity needs further studies.

  20. Handling of tritium-bearing wastes

    International Nuclear Information System (INIS)

    1981-01-01

    The generation of nuclear power and reprocessing of nuclear fuel results in the production of tritium and the possible need to control the release of tritium-contaminated effluents. In assessing the need for controls, it is necessary to know the production rates of tritium at different nuclear facilities, the technologies available for separating tritium from different gaseous and liquid streams, and the methods that are satisfactory for storage and disposal of tritiated wastes. The intention in applying such control technologies and methods is to avoid undesirable effects on the environment, and to reduce the radiation burden on operational personnel and the general population. This technical report is a result of the IAEA Technical Committee Meeting on Handling of Tritium-bearing Effluents and Wastes, which was held in Vienna, 4 - 8 December 1978. It summarizes the main topics discussed at the meeting and appends the more detailed reports on particular aspects that were prepared for the meeting by individual participants

  1. Bear Creek Project. Draft environmental statement

    International Nuclear Information System (INIS)

    1977-01-01

    The Bear Creek Project consists of mining and milling operations involving uranium ore deposits located in Converse County, Wyoming. Mining of uranium from six known ore bodies will take place over ten years; a 1000 tons ore/day will be constructed and operated as long as ore is available. The tailings will be stored onsite in an impoundment. The project would convert 2700 acres from grazing use to mining/milling activities for about ten years. Mining would disturb a total of 1600 acres but, because of reclamation, the max acreage disturbed at any one time would be about 1000 acres, the average being about 650 acres. Dose rates were computed for an individual in a ranch house at the nearest ranch. Conditions for the protection of the environment are proposed. Possible environmental impacts evaluated cover air, land, water, soil, vegetation, wildlife, and community. A benefit-cost analysis is made

  2. Evaluation of Grooved Solid Lubricated Bearings

    Science.gov (United States)

    1976-02-01

    support to this program; to Mr. D. B. El kins who balanced the solid lubri- cated bearing retainers and test rig drive shaft, and to various members...0.1 * ///o lo KY * el V M^° 3« ffr •> o-t z- i’fO * v • • /5T * 0-1 1/ 𔃻 14.4.U \\M» _5L? IVf c? a ft -a..( 1 7S°C Ml* fi H6 -o.« t 1 1 1... tifo ’’tMMMi psi LBS PSI i£f /./?. a^- RfADIMS /IY-OZ fifiw Hi 75 » 7f - - /«"". .Jfo lo ?•? tt 1 0.1 V oft" U - — • « n 󈧅 * 1 atoo - ’S

  3. The Polar BEAR magnetic field experiment

    Science.gov (United States)

    Bythrow, P. F.; Potemra, T. A.; Zanetti, L. J.; Mobley, F. F.; Scheer, L.; Radford, W. E.

    1987-09-01

    The objectives and the instrumentation of the Polar BEAR magnetic field experiment are described along with the preliminary results from simultaneous measurements of Birkeland currents and UV auroral emissions. The experiment consists of an integrated sensor head, analog electronics, and digital electronics. The sensor head is a single unit containing sensor windings for each of the three orthogonal axes, oriented parrallel to the spacecraft coordinates; to minimize interference from spacecraft-generated magnetic fields, the sensor unit is located at the end of the +y solar panel. The digital electronics package is essentially identical to that flown on HILAT. A signal processor digitizes the analog outputs of the three orthogonal axes of the flux-gate magnetometer to a 13-bit resolution, yielding a magnetic field range of + or - 63,000 nT and a resolution of 15.2 nT. The full-resolution magnetic field values are recovered by data processing techniques on the ground.

  4. THK: CLB Crossed Linear Bearing Seismic Isolators

    International Nuclear Information System (INIS)

    Toniolo, Roberto

    2008-01-01

    This text highlights the new seismic isolation technology called CLB (Crossed Linear Bearing), which is made of linear guides with recirculating steel ball technology. It describes specifications and building characteristics, provides examples of seismic isolation and application functionalities and shows experimental data. Since 1994, the constant commitment by Japan to develop diversified anti-seismic systems based on the precise needs of the structures to protect and the areas where they were built has led to the creation of important synergy between the research institutions of leading Japanese companies and THK's Centre for Research and Development. Their goal has been to develop new technology and solutions to allow seismic isolation to be effective in the following cases:

  5. Magnetic remanence of hematite-bearing murals

    Science.gov (United States)

    Lanza, R.; Zanella, E.; Saudino, S.

    2009-12-01

    We report on a series of experiments designed to test the ability of hematite-bearing colors to record the direction of the ambient magnetic field. Plasterboards accurately oriented with respect to the Earth's magnetic field were painted with red tempera colors prepared with hematite pigments. Magnetic measurements indicate that the color film retains a remanent magnetization and acquires a well developed magnetic fabric. The remanence direction is close to, yet slightly deviated from the Earth's magnetic field. The deviation is interpreted to result from preferential alignment of the pigment grains parallel to the plasterboard surface and depends on both its orientation with respect to magnetic north and the degree of magnetic anisotropy of the color film, which in turn varies according to the pigment used. Investigation of the magnetic remanence of murals may complement archaeomagnetic information derived from traditional materials such as baked and fired structures.

  6. Grizzly bears (Ursus arctos horribilis) and black bears (Ursus americanus) prevent trabecular bone loss during disuse (hibernation).

    Science.gov (United States)

    McGee-Lawrence, Meghan E; Wojda, Samantha J; Barlow, Lindsay N; Drummer, Thomas D; Castillo, Alesha B; Kennedy, Oran; Condon, Keith W; Auger, Janene; Black, Hal L; Nelson, O Lynne; Robbins, Charles T; Donahue, Seth W

    2009-12-01

    Disuse typically causes an imbalance in bone formation and bone resorption, leading to losses of cortical and trabecular bone. In contrast, bears maintain balanced intracortical remodeling and prevent cortical bone loss during disuse (hibernation). Trabecular bone, however, is more detrimentally affected than cortical bone in other animal models of disuse. Here we investigated the effects of hibernation on bone remodeling, architectural properties, and mineral density of grizzly bear (Ursus arctos horribilis) and black bear (Ursus americanus) trabecular bone in several skeletal locations. There were no differences in bone volume fraction or tissue mineral density between hibernating and active bears or between pre- and post-hibernation bears in the ilium, distal femur, or calcaneus. Though indices of cellular activity level (mineral apposition rate, osteoid thickness) decreased, trabecular bone resorption and formation indices remained balanced in hibernating grizzly bears. These data suggest that bears prevent bone loss during disuse by maintaining a balance between bone formation and bone resorption, which consequently preserves bone structure and strength. Further investigation of bone metabolism in hibernating bears may lead to the translation of mechanisms preventing disuse-induced bone loss in bears into novel treatments for osteoporosis.

  7. Gulf-Wide Information System, Environmental Sensitivity Index Bear Database, Geographic NAD83, LDWF (2001) [esi_bear_LDWF_2001

    Data.gov (United States)

    Louisiana Geographic Information Center — This data set contains sensitive biological resource data for the Louisiana black bear in coastal Louisiana. Vector polygons represent occupied habitat for this...

  8. Ancestral polymorphisms and sex-biased migration shaped the demographic history of brown bears and polar bears.

    Science.gov (United States)

    Nakagome, Shigeki; Mano, Shuhei; Hasegawa, Masami

    2013-01-01

    Recent studies have reported discordant gene trees in the evolution of brown bears and polar bears. Genealogical histories are different among independent nuclear loci and between biparentally inherited autosomal DNA (aDNA) and matrilineal mitochondrial DNA (mtDNA). Based on multi-locus genomic sequences from aDNA and mtDNA, we inferred the population demography of brown and polar bears and found that brown bears have 6 times (aDNA) or more than 14 times (mtDNA) larger population sizes than polar bears and that polar bear lineage is derived from within brown bear diversity. In brown bears, the effective population size ratio of mtDNA to aDNA was at least 0.62, which deviated from the expected value of 0.25, suggesting matriarchal population due to female philopatry and male-biased migration. These results emphasize that ancestral polymorphisms and sex-biased migration may have contributed to conflicting branching patterns in brown and polar bears across aDNA genes and mtDNA.

  9. Bearing load distribution studies in a multi bearing rotor system and a remote computing method based on the internet

    International Nuclear Information System (INIS)

    Yang, Zhao Jian; Peng, Ze Jun; Kim, Seock Sam

    2004-01-01

    A model in the form of a Bearing Load Distribution (BLD) matrix in the Multi Bearing Rotor System (MBRS) is established by a transfer matrix equation with the consideration of a bearing load, elevation and uniform load distribution. The concept of Bearing Load Sensitivity (BLS) is proposed and matrices for load and elevation sensitivity are obtained. In order to share MBRS design resources on the internet with remote customers, the basic principle of Remote Computing (RC) based on the internet is introduced ; the RC of the BLD and BLS is achieved by Microsoft Active Server Pages (ASP) technology

  10. The Effect of Non-Circular Bearing Shapes in Hydrodynamic Journal Bearings on the Vibration Behavior of Turbocharger Structures

    Directory of Open Access Journals (Sweden)

    Lukas Bernhauser

    2017-03-01

    Full Text Available Increasing quality demands of combustion engines require, amongst others, improvements of the engine’s acoustics and all (subcomponents mounted to the latter. A significant impact to the audible tonal noise spectrum results from the vibratory motions of fast-rotating turbocharger rotor systems in multiple hydrodynamic bearings such as floating bearing rings. Particularly, the study of self-excited non-linear vibrations of the rotor-bearing systems is crucial for the understanding, prevention or reduction of the noise and, consequently, for a sustainable engine acoustics development. This work presents an efficient modeling approach for the investigation, optimization, and design improvement of complex turbocharger rotors in hydrodynamic journal bearings, including floating bearing rings with circular and non-circular bearing geometries. The capability of tonal non-synchronous vibration prevention using non-circular bearing shapes is demonstrated with dynamic run-up simulations of the presented model. These findings and the performance of our model are compared and validated with results of a classical Laval/Jeffcott rotor-bearing model and a specific turbocharger model found in the literature. It is shown that the presented simulation method yields fast and accurate results and furthermore, that non-circular bearing shapes are an effective measure to reduce or even prevent self-excited tonal noise.

  11. Ancestral polymorphisms and sex-biased migration shaped the demographic history of brown bears and polar bears.

    Directory of Open Access Journals (Sweden)

    Shigeki Nakagome

    Full Text Available Recent studies have reported discordant gene trees in the evolution of brown bears and polar bears. Genealogical histories are different among independent nuclear loci and between biparentally inherited autosomal DNA (aDNA and matrilineal mitochondrial DNA (mtDNA. Based on multi-locus genomic sequences from aDNA and mtDNA, we inferred the population demography of brown and polar bears and found that brown bears have 6 times (aDNA or more than 14 times (mtDNA larger population sizes than polar bears and that polar bear lineage is derived from within brown bear diversity. In brown bears, the effective population size ratio of mtDNA to aDNA was at least 0.62, which deviated from the expected value of 0.25, suggesting matriarchal population due to female philopatry and male-biased migration. These results emphasize that ancestral polymorphisms and sex-biased migration may have contributed to conflicting branching patterns in brown and polar bears across aDNA genes and mtDNA.

  12. Passive magnetic bearing systems stabilizer/bearing utilizing time-averaging of a periodic magnetic field

    Science.gov (United States)

    Post, Richard F.

    2017-10-03

    A high-stiffness stabilizer/bearings for passive magnetic bearing systems is provide where the key to its operation resides in the fact that when the frequency of variation of the repelling forces of the periodic magnet array is large compared to the reciprocal of the growth time of the unstable motion, the rotating system will feel only the time-averaged value of the force. When the time-averaged value of the force is radially repelling by the choice of the geometry of the periodic magnet array, the Earnshaw-related unstable hit motion that would occur at zero rotational speed is suppressed when the system is rotating at operating speeds.

  13. Permanent magnet design for high-speed superconducting bearings

    Science.gov (United States)

    Hull, John R.; Uherka, Kenneth L.; Abdoud, Robert G.

    1996-01-01

    A high temperature superconducting bearing including a permanent magnet rotor levitated by a high temperature superconducting structure. The rotor preferably includes one or more concentric permanent magnet rings coupled to permanent magnet ring structures having substantially triangular and quadrangular cross-sections. Both alternating and single direction polarity magnet structures can be used in the bearing.

  14. 19 CFR 133.21 - Articles bearing counterfeit trademarks.

    Science.gov (United States)

    2010-04-01

    ... 19 Customs Duties 1 2010-04-01 2010-04-01 false Articles bearing counterfeit trademarks. 133.21... Recorded Trademarks or Recorded Trade Names § 133.21 Articles bearing counterfeit trademarks. (a... substantially indistinguishable from, a registered trademark. (b) Seizure. Any article of domestic or foreign...

  15. Detection of outer raceway bearing defects in small induction motors ...

    Indian Academy of Sciences (India)

    Abstract. We investigate the application of induction motor stator current spec- tral analysis (MCSA) for detection of rolling element bearing damage from the outer raceway. In this work, MCSA and vibration analysis are applied to induction motor to detect outer raceway defects in faulty bearings. Data acquisition, record-.

  16. Human disturbances of denning polar bears in Alaska

    Energy Technology Data Exchange (ETDEWEB)

    Amstrup, S.C. (Alaska Fish and Wildlife Research Center, Anchorage, AK (United States))

    1993-09-01

    Polar bears (Ursus maritimus) give birth in dens of snow and ice. The altricial neonates cannot leave the den for >2 months post-partum and are potentially vulnerable to disturbances near dens. The coastal plain (1002) area of Alaska's Arctic National Wildlife Refuge (ANWR) lies in a region of known polar bear denning and also may contain >9 billion barrels of recoverable oil. Polar bears in dens could be affected in many ways by hydrocarbon development. The distribution of dens on ANWR was documented between 1981 and 1992 and responses of bears in dens to various anthropogenic disturbances were observed. Of 44 dens located by radiotelemetry on the mainland coast of Alaska and Canada, 20 (45%) were on ANWR and 15 (34%) were within the 1002 area. Thus, development of ANWR will increase the potential that denning polar bears are disturbed by human activities. However, perturbations resulting from capture, marking, and radiotracking maternal bears did not affect litter sizes or stature of cubs produced. Likewise, 10 of 12 denned polar bears tolerated exposure to exceptional levels of activity. This tolerance and the fact that investment in the denning effort increases through the winter indicated that spatial and temporal restrictions on developments could prevent the potential for many disruptions of denned bears from being realized. 16 refs., 1 fig., 2 tabs.

  17. Biomechanical consequences of rapid evolution in the polar bear lineage.

    Directory of Open Access Journals (Sweden)

    Graham J Slater

    2010-11-01

    Full Text Available The polar bear is the only living ursid with a fully carnivorous diet. Despite a number of well-documented craniodental adaptations for a diet of seal flesh and blubber, molecular and paleontological data indicate that this morphologically distinct species evolved less than a million years ago from the omnivorous brown bear. To better understand the evolution of this dietary specialization, we used phylogenetic tests to estimate the rate of morphological specialization in polar bears. We then used finite element analysis (FEA to compare the limits of feeding performance in the polar bear skull to that of the phylogenetically and geographically close brown bear. Results indicate that extremely rapid evolution of semi-aquatic adaptations and dietary specialization in the polar bear lineage produced a cranial morphology that is weaker than that of brown bears and less suited to processing tough omnivorous or herbivorous diets. Our results suggest that continuation of current climate trends could affect polar bears by not only eliminating their primary food source, but also through competition with northward advancing, generalized brown populations for resources that they are ill-equipped to utilize.

  18. Evaluation of journal bearings characteristics using finite element ...

    African Journals Online (AJOL)

    Dynamic behavior of the rotor-bearings system exerts a considerable influence on rotating machine operating and stability. Indeed, vibrations in such machines may cause not only high level of noise but also wearing of moving components. Hydrodynamic journal bearings, which are among the best devices to prevent ...

  19. The quality of materials applied for slewing bearing raceway

    Directory of Open Access Journals (Sweden)

    Marek Krynke

    2012-09-01

    Full Text Available Selected slewing bearings and their application have been described in this article. Basic causes of the damage pitch surfaces of slewing bearings have been analysed and examples of the damage have been presented as well. Special attention was paid to these kinds of damage which appeared most often in the case of the pitch surfaces of the bearings and those ones which very often cause premature exchange of the bearing and its scrapping. On the basis of the conducted studies it was stated that the main cause of the damage to  the pitch surfaces of the bearings is the excessive load of rolling elements. Based on the results of the conducted analysis, actions limiting the occurrence of the damage to the pitch surfaces of the bearings, which lead to their premature exchange, have been proposed. One of the suggested actions, limiting the premature exchange of bearings, is the necessity of exceptionally thorough design and selection of the slewing bearings, including the conditions of their foundation

  20. Detection of outer raceway bearing defects in small induction motors ...

    Indian Academy of Sciences (India)

    an induction motor is of paramount importance in industrial, commercial, aerospace and military applications. Bearings play an important role in the reliability and performance of all motor systems. Due to the ... Bearing corrosion is produced by the presence of water, acids, deteriorated lubrication and even perspiration from ...

  1. Acoustic analysis of an induction motor with viscoelastic bearing supports

    NARCIS (Netherlands)

    Tillema, H.G.; Wensing, J.A.; Selamet, Ahmet

    2002-01-01

    The demand for silent bearing applications has resulted in the development of an effective damping layer between the outer ring of a rolling bearing and the surrounding structure. By means of numerical modeling using both FEM and BEM techniques an induction motor for household appliances is

  2. Biomechanical consequences of rapid evolution in the polar bear lineage.

    Science.gov (United States)

    Slater, Graham J; Figueirido, Borja; Louis, Leeann; Yang, Paul; Van Valkenburgh, Blaire

    2010-11-05

    The polar bear is the only living ursid with a fully carnivorous diet. Despite a number of well-documented craniodental adaptations for a diet of seal flesh and blubber, molecular and paleontological data indicate that this morphologically distinct species evolved less than a million years ago from the omnivorous brown bear. To better understand the evolution of this dietary specialization, we used phylogenetic tests to estimate the rate of morphological specialization in polar bears. We then used finite element analysis (FEA) to compare the limits of feeding performance in the polar bear skull to that of the phylogenetically and geographically close brown bear. Results indicate that extremely rapid evolution of semi-aquatic adaptations and dietary specialization in the polar bear lineage produced a cranial morphology that is weaker than that of brown bears and less suited to processing tough omnivorous or herbivorous diets. Our results suggest that continuation of current climate trends could affect polar bears by not only eliminating their primary food source, but also through competition with northward advancing, generalized brown populations for resources that they are ill-equipped to utilize.

  3. Performance of an active electric bearing for rotary micromotors

    International Nuclear Information System (INIS)

    Han, F T; Wang, L; Wu, Q P; Liu, Y F

    2011-01-01

    An electric bearing used to support a micromachined rotor of variable-capacitance motors was designed and tested in order to study the characteristics of this frictionless bearing. Electrostatic suspension of a ring-shaped rotor in five degrees of freedom is required to eliminate the mechanical bearing and thus the friction and wear between the rotor and the substrate. Bulk microfabrication-based glass/silicon/glass bonding is chosen for this device, allowing the fabrication of large area sense capacitors and rotor, which make the device potentially suitable for the development of an electrostatically suspended micromachined gyroscope. The device and its basic operating principle are described, as well as the dynamics of the rotor and basic design considerations of the electric bearing system. A theoretical relationship to relate the characteristics of a classical lag–lead compensator to the stiffness properties of the electric bearing is developed to explain the experimental bearing measurements. The experimental results of closed-loop frequency response, suspension stiffness and drive voltage effects are presented and discussed for the bearing operated initially in the atmospheric environment. The performance of a tri-axial electrostatic accelerometer has also been experimentally investigated on the prototype of the electric bearing system

  4. Permanent magnet design for high-speed superconducting bearings

    International Nuclear Information System (INIS)

    Hull, J.R.; Uherka, K.L.; Abdoud, R.G.

    1996-01-01

    A high temperature superconducting bearing including a permanent magnet rotor levitated by a high temperature superconducting structure is disclosed. The rotor preferably includes one or more concentric permanent magnet rings coupled to permanent magnet ring structures having substantially triangular and quadrangular cross-sections. Both alternating and single direction polarity magnet structures can be used in the bearing. 9 figs

  5. Black bear damage to northwestern conifers in California: a review

    Science.gov (United States)

    Kenneth O. Fulgham; Dennis Hosack

    2017-01-01

    A total of 789 black bear damaged trees were investigate over a multi-year period on 14 different study sites chosen on lands of four participating timber companies. The sites ranged from 30 to 50 years of age. Four different conifer species were found to have black bear damage: coastal redwood (Sequoia sempervirens (D. Don) Endl.), Douglas-fir (...

  6. 36 CFR 7.80 - Sleeping Bear Dunes National Lakeshore.

    Science.gov (United States)

    2010-07-01

    ... 36 Parks, Forests, and Public Property 1 2010-07-01 2010-07-01 false Sleeping Bear Dunes National Lakeshore. 7.80 Section 7.80 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR SPECIAL REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.80 Sleeping Bear Dunes National...

  7. Design optimization of deep groove ball bearings using crowding ...

    Indian Academy of Sciences (India)

    The considered objectives are maximizing dynamic and static load bearing capacities and minimizing elastohydrodynamic film thickness. The technique is applied to bearings used in transmission system of a tractor for the purpose of farming. Pareto optimal solutions are obtained using the proposed technique. The results ...

  8. External Coulomb-Friction Damping For Hydrostatic Bearings

    Science.gov (United States)

    Buckmann, Paul S.

    1992-01-01

    External friction device damps vibrations of shaft and hydrostatic ring bearing in which it turns. Does not rely on wear-prone facing surfaces. Hydrostatic bearing ring clamped in radially flexing support by side plates clamped against radial surfaces by spring-loaded bolts. Plates provide friction against radial motions of shaft.

  9. Human disturbances of denning polar bears in Alaska

    International Nuclear Information System (INIS)

    Amstrup, S.C.

    1993-01-01

    Polar bears (Ursus maritimus) give birth in dens of snow and ice. The altricial neonates cannot leave the den for >2 months post-partum and are potentially vulnerable to disturbances near dens. The coastal plain (1002) area of Alaska's Arctic National Wildlife Refuge (ANWR) lies in a region of known polar bear denning and also may contain >9 billion barrels of recoverable oil. Polar bears in dens could be affected in many ways by hydrocarbon development. The distribution of dens on ANWR was documented between 1981 and 1992 and responses of bears in dens to various anthropogenic disturbances were observed. Of 44 dens located by radiotelemetry on the mainland coast of Alaska and Canada, 20 (45%) were on ANWR and 15 (34%) were within the 1002 area. Thus, development of ANWR will increase the potential that denning polar bears are disturbed by human activities. However, perturbations resulting from capture, marking, and radiotracking maternal bears did not affect litter sizes or stature of cubs produced. Likewise, 10 of 12 denned polar bears tolerated exposure to exceptional levels of activity. This tolerance and the fact that investment in the denning effort increases through the winter indicated that spatial and temporal restrictions on developments could prevent the potential for many disruptions of denned bears from being realized. 16 refs., 1 fig., 2 tabs

  10. Development and Testing of an Axial Halbach Magnetic Bearing

    Science.gov (United States)

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

    2006-01-01

    The NASA Glenn Research Center has developed and tested a revolutionary Axial Halbach Magnetic Bearing. The objective of this work is to develop a viable non-contact magnetic thrust bearing utilizing Halbach arrays for all-electric flight, and many other applications. This concept will help to reduce harmful emissions, reduce the Nation s dependence on fossil fuels and mitigate many of the concerns and limitations encountered in conventional axial bearings such as bearing wear, leaks, seals and friction loss. The Axial Halbach Magnetic Bearing is inherently stable and requires no active feedback control system or superconductivity as required in many magnetic bearing designs. The Axial Halbach Magnetic Bearing is useful for very high speed applications including turbines, instrumentation, medical systems, computer memory systems, and space power systems such as flywheels. Magnetic fields suspend and support a rotor assembly within a stator. Advanced technologies developed for particle accelerators, and currently under development for maglev trains and rocket launchers, served as the basis for this application. Experimental hardware was successfully designed and developed to validate the basic principles and analyses. The report concludes that the implementation of Axial Halbach Magnetic Bearings can provide significant improvements in rotational system performance and reliability.

  11. Development and Testing of a Radial Halbach Magnetic Bearing

    Science.gov (United States)

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

    2006-01-01

    The NASA John H. Glenn Research Center has developed and tested a revolutionary Radial Halbach Magnetic Bearing. The objective of this work is to develop a viable non-contact magnetic bearing utilizing Halbach arrays for all-electric flight, and many other applications. This concept will help reduce harmful emissions, reduce the Nation s dependence on fossil fuels and mitigate many of the concerns and limitations encountered in conventional axial bearings such as bearing wear, leaks, seals and friction loss. The Radial Halbach Magnetic Bearing is inherently stable and requires no active feedback control system or superconductivity as required in many magnetic bearing designs. The Radial Halbach Magnetic Bearing is useful for very high speed applications including turbines, instrumentation, medical applications, manufacturing equipment, and space power systems such as flywheels. Magnetic fields suspend and support a rotor assembly within a stator. Advanced technologies developed for particle accelerators, and currently under development for maglev trains and rocket launchers, served as the basis for this application. Experimental hardware was successfully designed and developed to validate the basic principles and analyses. The report concludes that the implementation of Radial Halbach Magnetic Bearings can provide significant improvements in rotational system performance and reliability.

  12. Design optimization of deep groove ball bearings using crowding ...

    Indian Academy of Sciences (India)

    Aparna Duggirala

    2018-02-07

    Feb 7, 2018 ... Abstract. This paper presents a crowding distance particle swarm optimization technique to optimize the design parameters of deep groove ball bearings. The design optimization problem is multi-objective in nature. The considered objectives are maximizing dynamic and static load bearing capacities and ...

  13. Using preloading to protect bearings against lightning damage

    NARCIS (Netherlands)

    Leferink, Frank Bernardus Johannes; Blaj, M.A.; Hogeman, Edwin; Storck, Rob

    2015-01-01

    When a radar system onboard a ship is struck by lightning the current has to be conducted via defined paths to prevent damage. A key element to protect is the bearing system between the rotating and stationary part. The conventional way of protecting bearing is to provide a bypass current path via

  14. Bears Arouse Interest in Microbiota's Role in Health.

    Science.gov (United States)

    Dill-McFarland, Kimberly A; Suen, Garret; Carey, Hannah V

    2016-04-01

    The first report of the effect of hibernation on the gut microbiota of bears reveals trends both similar and distinct from those found in small hibernators. A model mouse system also suggested possible roles of the microbiota for healthy weight gain and insulin tolerance in bears during their active season. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Forecasting the condition of petroleum impregnated load bearing ...

    African Journals Online (AJOL)

    Petroleum products (PP) used in industrial processes systematically fall on the load-bearing CRC structures and gradually impregnate therein. Currently, available guidelines for the assessment of technical condition and reliability of load-bearing CRC structures do not fully take into account the effect of viscosity of PP that ...

  16. Vesuvianite–wollastonite–grossular-bearing calc-silicate rock near ...

    Indian Academy of Sciences (India)

    The enclave contains phlogopite-absent and phlogopite-bearing calc-silicate rocks, the latter being much more abundant than the former. The above assemblage occurs in the phlogopite-absent rock. Phlogopite-bearing rock contains the assemblage phlogopite + salite + microcline + plagioclase + quartz. A strong ...

  17. Avalanche transmission and critical behaviour in load-bearing ...

    Indian Academy of Sciences (India)

    The strength and stability properties of hierarchical load-bearing networks and their strengthened variants have been discussed in a recent work. Here, we study the avalanche time distributions on these load-bearing networks. The avalanche time distributions of the V-lattice, a unique realization of the networks, show ...

  18. Dynamic behaviour of ball bearing applications with constrained damping layers

    NARCIS (Netherlands)

    Tillema, Hedzer G.; Wicks, Alfred L.

    2001-01-01

    Rolling bearing noise has become an aspect of increasing importance for the performance of rotating machinery, like electric motors and gearboxes. Generally, two aspects are important with regard to bearing noise, i.e. the transmission characteristics and the vibration generation characteristics. A

  19. Rolling bearing monitoring algorithm by wavelet scaling comparison ...

    African Journals Online (AJOL)

    A rolling bearing is the most common element of any rotary mechanism design and, at the same time, the most vulnerable element that determines the operability and the durability of equipment. The purpose of the work is to develop the method of bearing condition control by vibration parameters on the basis of scale graph ...

  20. Analysis of bearing steel exposed to rolling contact fatigue

    DEFF Research Database (Denmark)

    Hansen, K. T.; Fæster, Søren; Natarajan, Anand

    2017-01-01

    The objective of this work is to characterize fatigue damage in roller bearings under conditions of high load and slippage. A test rig constructed for rolling contact fatigue tests of rings is described, and test results are presented for rings taken from two spherical roller bearings...

  1. Active magnetic bearings: As applied to centrifugal pumps

    Science.gov (United States)

    Nelik, Lev; Cooper, Paul; Jones, Graham; Galecki, Dennis; Pinckney, Frank; Kirk, Gordon

    1992-01-01

    Application of magnetic bearings to boiler feed pumps presents various attractive features, such as longer bearing life, lower maintenance costs, and improved operability through control of the rotordynamics. Magnetic bearings were fitted to an eight-stage, 600 hp boiler feed pump, which generates 2600 ft of heat at 680 gpm and 3560 rpm. In addition to the varied and severe operating environment in steady state operation of this pump in a power plant, it is also subjected to transient loads during frequent starts and stops. These loads can now be measured by the in-built instrumentation of the magnetic bearings. Following site installation, a follow-up bearing tune-up was performed, and pump transient response testing was conducted. The bearing response was completely satisfactory, ensuring trouble-free pump operation even in the range of reduced load. The experience gained so far through design and testing proves feasibility of magnetic bearings for boiler feed pumps, which sets the stage for application of even higher energy centrifugal pumps equipped with magnetic bearings.

  2. EVALUATION OF CARDIOLOGIC FUNCTIONS IN CAPTIVE EURASIAN BROWN BEARS (URSUS ARCTOS ARCTOS) IN TURKEY.

    Science.gov (United States)

    Cihan, Huseyin; Yilmaz, Zeki; Aytug, Nilufer

    2016-03-01

    The aim of this study was to evaluate the cardiac functions in healthy Eurasian brown bears (Ursus arctos arctos) living in a seminatural area during their active season. Twelve clinically healthy brown bears were selected based on their normal physical examination, hematologic, and serum biochemistry results. These bears were divided into two groups based on age; subadult (bears. Notching of QRS complexes and peaked T wave were also observed in both groups. Left ventricular diameter at systole and diastole in adult bears was wider (P bears. Subadult bears had reduced aortic diameter compared to adult bears (P bears.

  3. Steroid hormone profile in female polar bears (Ursus maritimus)

    DEFF Research Database (Denmark)

    Gustavson, Lisa; Jenssen, Bjorn Munro; Bytingsvik, Jenny

    2015-01-01

    -4 pathway in polar bears, similar to rodents. The large individual variability in steroid levels reported here most likely reflects the differences in reproductive status of the female polar bears during mating season. The steroid data establish reference values of steroid hormones and may...... is the first study to report circulating concentrations of nine steroid hormones (i.e., estrogens, androgens and progestagens) in female polar bears (Ursus maritimus). The aim of the study was to investigate the effects of age, condition, location and reproductive status on steroid profile in female polar...... bears. Levels of pregnenolone (PRE), progesterone, androstenedione (AN), dehydroepiandrosterone (DHEA), testosterone, dihydrotestosterone, estrone (E1), 17α-estradiol (αE2) and 17β-estradiol (βE2) were quantified in blood (serum) of free-living female polar bears (n = 15) from Svalbard, Norway, by gas...

  4. On the Design of Tilting-Pad Thrust Bearings

    DEFF Research Database (Denmark)

    Heinrichson, Niels

    2007-01-01

    Pockets are often machined in the surfaces of tilting-pad thrust bearings to allow for hydrostatic jacking in the start-up phase. Pockets and other recesses in the surfaces of bearing pads influence the pressure distribution and thereby the position of the pivot resulting in the most advantageous...... friction and a small pressure build-up. As in parallel-step bearings the recesses may also have a depth of the same order of magnitude as the oil film thickness. Such recesses are characterized by a strong pressure build-up caused by the reduction of the flow area at the end of the recess. Numerical models...... based on the Reynolds equation are used. They include the effects of variations of viscosity with temperature and the deformation of the bearing pads due to pressure and thermal gradients. The models are validated using measurements. Tilting-pad bearings of standard design are studied and the influences...

  5. Progress in development of high capacity magnetic HTS bearings

    International Nuclear Information System (INIS)

    Kummeth, P.; Nick, W.; Neumueller, H.-W.

    2005-01-01

    HTS magnetic bearings are inherently stable without an active feedback system. They provide low frictional losses, no wear and allow operation at high rotational speed without lubrication. So they are very promising for use in motors, generators and turbines. We designed and constructed an HTS radial bearing for use with a 400 kW HTS motor. It consists of alternating axially magnetized permanent magnet rings on the rotor and a segmented YBCO stator. Stator cooling is performed by liquid nitrogen, the temperature of the stator can be adjusted by varying the pressure in the cryogenic vessel. At 68 K maximum radial forces of more than 3.7 kN were found. These results range within the highest radial bearing capacities reported worldwide. The encouraging results lead us to develop a large heavy load HTS radial bearing. Currently a high magnetic gradient HTS bearing for a 4 MVA synchronous HTS generator is under construction

  6. Steroid hormone profile in female polar bears (Ursus maritimus)

    DEFF Research Database (Denmark)

    Gustavson, Lisa; Jenssen, Bjørn Munro; Bytingsvik, Jenny

    2015-01-01

    The polar bear is an iconic Arctic species, threatened by anthropogenic impacts such as pollution and climate change. Successful reproduction of polar bears depends on a functioning steroid hormone system, which is susceptible to effects of persistent organic pollutants. The present study...... is the first study to report circulating concentrations of nine steroid hormones (i.e., estrogens, androgens and progestagens) in female polar bears (Ursus maritimus). The aim of the study was to investigate the effects of age, condition, location and reproductive status on steroid profile in female polar...... bears. Levels of pregnenolone (PRE), progesterone, androstenedione (AN), dehydroepiandrosterone (DHEA), testosterone, dihydrotestosterone, estrone (E1), 17α-estradiol (αE2) and 17β-estradiol (βE2) were quantified in blood (serum) of free-living female polar bears (n = 15) from Svalbard, Norway, by gas...

  7. Magnetic bearings promise reduced operation and maintenance costs

    International Nuclear Information System (INIS)

    Jones, G.

    1990-01-01

    Magnetic bearings are being incorporated into the design of the US DoE modular high temperature gas cooled reactor. The virtually maintenance-free bearing technology may have potential in other nuclear applications. In an active magnetic bearing, a stationary electromagnet (stator) and a rotating ferrous material (rotor) are used to allow a shaft to be suspended in a magnetic field. The position of the shaft is maintained dynamically using position sensors to provide a continuous feedback through a control and amplifier system to the electromagnetic poles which are used to suspend the shaft. Two separate systems are required: an axial positioning system, or thrust bearing, and a pair of radial positioning systems, or journal bearings. (author)

  8. Auxiliary bearing design considerations for gas cooled reactors

    International Nuclear Information System (INIS)

    Penfield, S.R. Jr.; Rodwell, E.

    2001-01-01

    The need to avoid contamination of the primary system, along with other perceived advantages, has led to the selection of electromagnetic bearings (EMBs) in most ongoing commercial-scale gas cooled reactor (GCR) designs. However, one implication of magnetic bearings is the requirement to provide backup support to mitigate the effects of failures or overload conditions. The demands on these auxiliary or 'catcher' bearings have been substantially escalated by the recent development of direct Brayton cycle GCR concepts. Conversely, there has been only limited directed research in the area of auxiliary bearings, particularly for vertically oriented turbomachines. This paper explores the current state-of-the-art for auxiliary bearings and the implications for current GCR designs. (author)

  9. East Greenland and Barents Sea polar bears (Ursus maritimus)

    DEFF Research Database (Denmark)

    Pertoldi, Cino; Sonne, Christian; Wiig, Øystein

    2012-01-01

    A morphometric study was conducted on four skull traits of 37 male and 18 female adult East Greenland polar bears (Ursus maritimus) collected 18921968, and on 54 male and 44 female adult Barents Sea polar bears collected 19501969. The aim was to compare differences in size and shape of the bear...... and three clusters for Barents Sea females. East Greenland consisted of one female and one male cluster. A principal component analysis (PCA) conducted on the clusters defined by the mixture analysis, showed that East Greenland and Barents Sea polar bear populations overlapped to a large degree, especially...... and genetic factors seem to have contributed to the observed skull differences between the two populations. Overall, results indicate that many Barents Sea polar bears are morphometrically similar to the East Greenland ones, suggesting an exchange of individuals between the two populations. Furthermore...

  10. Plain bearing stresses due to forming and oil film pressure

    Energy Technology Data Exchange (ETDEWEB)

    Burke-Veliz, A; Reed, P A S; Syngellakis, S [University of Southampton, School of Engineering Sciences, Southampton SO17 1BJ (United Kingdom); Wang, D; Wahdy, N; Merritt, D, E-mail: allan.burke@itesm.m [MAHLE Engine Systems UK Ltd, 2 Central park Drive, Rugby CV23 0WE (United Kingdom)

    2009-08-01

    This paper describes a methodology for assessing critical stress ranges arising in automotive plain bearings during engine operations. An industry-produced and run simulation program provides information on oil film pressure and overall bearing deformation during accelerated performance tests. This code performs an elasto-hydrodynamic lubrication analysis accounting for the compliance of the housing and journal. Finite element analyses of a multilayer bearing are performed to assess the conditions responsible for possible fatigue damage over the bearing lining. The residual stresses arising from the forming and fitting process are first assessed. The stress analyses over the engine cycle show the intensity and distribution of cyclic tensile and compressive stresses in the bearing. The location of maximum stress range is found to be consistent with the damage observed in accelerated fatigue tests. Critical zones are identified in the lining for possible fatigue crack initiation and growth studies.

  11. Influence of Electric Discharges on Bearings of Electric Machines

    Directory of Open Access Journals (Sweden)

    Karel Chmelik

    2006-01-01

    Full Text Available I the last time many articles were found out discussed about shaft voltage, bearing currents and their influence on lifetime and reliability of electric machines bearings. This is associated with extension of use of static converters for control drives for DC motors feeding in the past and for induction motors feeding from frequency converters in the last time. It is known from our own experiences that not all failures assigned to bearing currents were their real reason and we also know how hardly the mentioned currents can be measured on real machines and how work-intensive and expensive is to detect real reason of the failure on damaged bearing. We will not concern with basics of classical bearing currents in this paper, because they were known and studied in the beginning of the last century but our own investigations will be presented.

  12. The application of dichotomy in equilibrium position of journal bearing

    Science.gov (United States)

    Wu, G. K.; Luo, X. Q.

    2016-05-01

    The fluid lubricant force in the journal bearing is an important factor for the stability and dynamic characteristics of rotating machine. In order to obtain the dynamic coefficients of journal bearing, the equilibrium position must be known for further calculation. In this paper, the Reynolds equation is solved by finite difference method and the dichotomy is applied to acquire the equilibrium position of journal bearing by means of double loop. The effects of length, radius and clearance of journal bearing on the equilibrium position are also researched. The calculated results show that the dichotomy is an effective method for the equilibrium position of journal bearing and the geometry parameters play an important effect on the equilibrium position.

  13. Tribological Behavior of Journal Bearing Material under Different Lubricants

    Directory of Open Access Journals (Sweden)

    S. Baskar

    2014-06-01

    Full Text Available The friction and wear behavior of journal bearing material has been investigated using pin on disc wear tester with three different lubricating oils i.e. synthetic lubricating oil (SAE20W40, chemically modified rapeseed oil (CMRO, chemically modified rapeseed oil with Nano CuO. Wear tests were carried out at maximum load of 200 N and sliding speeds of 2 – 10 m/s. The results showed that the friction and wear behavior of the journal bearing material have changed according to the sliding conditions and lubricating oils. The journal bearing material has a lower friction coefficient for CMRO with Nano CuO than other two oils. Higher wear of journal bearing material was observed in SAE 20W40 and CMRO. Worn surfaces of the journal bearing material with three lubricating oils were examined using scanning electron microscope (SEM and wear mechanisms were discussed.

  14. Controllable sliding bearings and controllable lubrication principles-an overview

    DEFF Research Database (Denmark)

    Santos, Ilmar F.

    2018-01-01

    Hydrodynamic and aerodynamic lubrication regimes in their controllable forms have been intensively investigated over the last two decades. With the aim of reducing friction and improving thermal, static, and dynamic characteristics of radial sliding bearings, different types of electro-mechanical...... about advantages and drawbacks of the different design solutions for controllable sliding bearings and the main challenges to be overcome towards industrial applications.......Hydrodynamic and aerodynamic lubrication regimes in their controllable forms have been intensively investigated over the last two decades. With the aim of reducing friction and improving thermal, static, and dynamic characteristics of radial sliding bearings, different types of electro....... In this framework, this paper gives one main original contribution to the state-of-the-art of radial sliding bearings and controllable lubrication: a comprehensive overview about the different types of controllable sliding bearings and principles used by several authors. The paper ends with some conclusive remarks...

  15. An Advanced Microturbine System with Water-Lubricated Bearings

    Directory of Open Access Journals (Sweden)

    Susumu Nakano

    2009-01-01

    Full Text Available A prototype of the next-generation, high-performance microturbine system was developed for laboratory evaluation. Its unique feature is its utilization of water. Water is the lubricant for the bearings in this first reported application of water-lubricated bearings in gas turbines. Bearing losses and limitations under usage conditions were found from component tests done on the bearings and load tests done on the prototype microturbine. The rotor system using the water-lubricated bearings achieved stable rotating conditions at a rated rotational speed of 51,000 rpm. An electrical output of 135 kW with an efficiency of more than 33% was obtained. Water was also utilized to improve electrical output and efficiency through water atomizing inlet air cooling (WAC and a humid air turbine (HAT. The operation test results for the WAC and HAT revealed the WAC and HAT operations had significant effects on both electrical output and electrical efficiency.

  16. Design and Analysis of an Electromagnetic Thrust Bearing

    Science.gov (United States)

    Banerjee, Bibhuti; Rao, Dantam K.

    1996-01-01

    A double-acting electromagnetic thrust bearing is normally used to counter the axial loads in many rotating machines that employ magnetic bearings. It essentially consists of an actuator and drive electronics. Existing thrust bearing design programs are based on several assumptions. These assumptions, however, are often violated in practice. For example, no distinction is made between maximum external loads and maximum bearing forces, which are assumed to be identical. Furthermore, it is assumed that the maximum flux density in the air gap occurs at the nominal gap position of the thrust runner. The purpose of this paper is to present a clear theoretical basis for the design of the electromagnetic thrust bearing which obviates such assumptions.

  17. Experimental Grey Box Model Identification of an Active Gas Bearing

    DEFF Research Database (Denmark)

    Theisen, Lukas Roy Svane; Pierart Vásquez, Fabián Gonzalo; Niemann, Hans Henrik

    2014-01-01

    Gas bearings have inherent dynamics that gives rise to low damping and potential instability at certain rotational speeds. Required damping and stabilization properties can be achieved by active ow control if bearing parameters are known. This paper deals with identifacation of parameters...... in a dynamic model of an active gas bearing and subsequent control loop design. A grey box model is determined based on experiments where piezo actuated valves are used to perturb the journal and hence excite the rotor-bearing system. Such modelling from actuator to output is shown to effciently support...... controller design, in contrast to impact models that focus on resonance dynamics. The identified model is able to accurately reproduce the lateral dynamics of the rotor-bearing system in a desired operating range, in this case around the first two natural frequencies. The identified models are validated...

  18. Review and critical analysis: Rolling-element bearings for system life and reliability

    Science.gov (United States)

    Irwin, A. S.; Anderson, W. J.; Derner, W. J.

    1985-01-01

    A ball and cylindrical roller bearing technical specification which incorporates the latest state-of-the-art advancements was prepared for the purpose of improving bearing reliability in U.S. Army aircraft. The current U.S. Army aviation bearing designs and applications, including life analyses, were analyzed. A bearing restoration and refurbishment specification was prepared to improve bearing availability.

  19. Uranium-bearing wastes and their radon emanation

    International Nuclear Information System (INIS)

    Sasaki, Tomozo; Imamura, Mitsutaka; Gunji, Yasuyoshi

    2007-01-01

    There are no data available with regard to radon emanation coefficients for uranium-bearing wastes; such data are needed for the assessment of radiation exposure from radon that will be generated in the distant future as one uranium progeny at shallow land disposal sites for uranium-bearing wastes. There are many kinds of uranium-bearing wastes. However, it is not necessary to measure the radon emanation coefficients for all of them for two reasons. First, the radon emanation coefficients for uranium-bearing wastes contaminated by dissolved uranium are determined by the uranium chemical form, the manner of uranium deposition on the waste matrix, and the size of the particles which constitute the waste matrix. Therefore, only a few representative measurements are sufficient for such uranium-bearing wastes. Second, it is possible to make theoretical calculations of radon emanation coefficients for uranium-bearing wastes contaminated by UO 2 particles before sintering. In the present study, simulated uranium-bearing wastes contaminated by dissolved uranium were prepared, their radon emanation coefficients were measured and radon emanation coefficients were calculated theoretically for uranium-bearing wastes contaminated by UO 2 particles before sintering. The obtained radon emanation coefficients are distributed at higher values than those for ubiquitous soils and rocks in the natural environment. Therefore, it is not correct to just compare uranium concentrations among uranium-bearing wastes, ubiquitous soils and rocks in terms of radiation exposure. The radon emanation coefficients obtained in the present study have to be employed together with the uranium concentration in uranium-bearing wastes in order to achieve proper assessment of radiation exposure. (author)

  20. Polar bear maternity denning in the Beaufort Sea

    Science.gov (United States)

    Amstrup, Steven C.; Gardner, Craig L.

    1994-01-01

    The distribution of polar bears (Ursus maritimus) is circumpolar in the NOrthern Hemisphere, but known locations of maternal dens are concentrated in relatively few, widely scattered locations. Denning is either uncommon or unknown within gaps. To understand effects of industrial development and propose increases in hunting, the temporal and spatial distribution of denning in the Beaufort Sea must be known. We caputred and radiocollared polar bears between 1981 and 1991 and determined tht denning in the Beaufort Sea region was sufficient to account for the estimated population there. Of 90 dend, 48 were on drifting pack ice, 38 on land, and 4 on land-fast ice. The portions of dens on land was higher (P= 0.029) in later compared with earlier years of the study. Bears denning on pack ice drifting as far as 997 km (x=385km) while in dens. there was no difference in cun production by bears denning on land and pack ice (P =0.66). Mean entry and exit dates were 11 November and 5 April for land dens and 22 November and 26 March for pack-ice dens. Female polar bears captured in the Beaufort Sea appeared to be isolated from those caught eat of Cape Bathurst in Canada. Of 35 polar bears that denned along the mainland coast of Alaska and Canada 80% denned between 137 00'W snf 146 59'W. Bears followed to >1 den did not reuse sites and consecutive dens were 20-1,304 km apart. However radio-collared bears are largely faithful to substrate (pack-ice, land, and land-fast ice) and the general geographic area of previous dens. Bears denning on land may be vunerable to human activities such as hunting and industrial development. However, predictable denning chronology and alck of site fidelity indicate that many potential impacts on denning polar bears could be mitigated.

  1. Methane Recovery from Hydrate-bearing Sediments

    Energy Technology Data Exchange (ETDEWEB)

    J. Carlos Santamarina; Costas Tsouris

    2011-04-30

    Gas hydrates are crystalline compounds made of gas and water molecules. Methane hydrates are found in marine sediments and permafrost regions; extensive amounts of methane are trapped in the form of hydrates. Methane hydrate can be an energy resource, contribute to global warming, or cause seafloor instability. This study placed emphasis on gas recovery from hydrate bearing sediments and related phenomena. The unique behavior of hydrate-bearing sediments required the development of special research tools, including new numerical algorithms (tube- and pore-network models) and experimental devices (high pressure chambers and micromodels). Therefore, the research methodology combined experimental studies, particle-scale numerical simulations, and macro-scale analyses of coupled processes. Research conducted as part of this project started with hydrate formation in sediment pores and extended to production methods and emergent phenomena. In particular, the scope of the work addressed: (1) hydrate formation and growth in pores, the assessment of formation rate, tensile/adhesive strength and their impact on sediment-scale properties, including volume change during hydrate formation and dissociation; (2) the effect of physical properties such as gas solubility, salinity, pore size, and mixed gas conditions on hydrate formation and dissociation, and it implications such as oscillatory transient hydrate formation, dissolution within the hydrate stability field, initial hydrate lens formation, and phase boundary changes in real field situations; (3) fluid conductivity in relation to pore size distribution and spatial correlation and the emergence of phenomena such as flow focusing; (4) mixed fluid flow, with special emphasis on differences between invading gas and nucleating gas, implications on relative gas conductivity for reservoir simulations, and gas recovery efficiency; (5) identification of advantages and limitations in different gas production strategies with

  2. Rotor Rolling over a Water-Lubricated Bearing

    Science.gov (United States)

    Shatokhin, V. F.

    2018-02-01

    The article presents the results of studying the effect of forces associated with secondary damping coefficients (gyroscopic forces) on the development of asynchronous rolling of the rotor over a water-lubricated bearing. The damping forces act against the background of other exciting forces in the rotor-supports system, in particular, the exciting forces of contact interaction between the rotor and bearing. The article considers a rotor resting on supports rubbing against the bearing and the occurrence of self-excited vibration in the form of asynchronous roll-over. The rotor supports are made in the form of plain-type water-lubricated bearings. The plain-type bearing's lubrication stiffness and damping forces are determined using the wellknown algorithms taking into account the physical properties of water serving as lubrication of the bearing. The bearing sliding pair is composed of refractory materials. The lubrication layer in such bearings is thinner than that used in oil-lubricated bearings with white metal lining, and there is no white metal layer in waterlubricated bearings. In case of possible deviations from normal operation of the installation, the rotating rotor comes into direct contact with the liner's rigid body. Unsteady vibrations are modeled using a specially developed software package for calculating the vibration of rotors that rub against the turbine (pump) stator elements. The stiffness of the bearing liner with the stator support structure is specified by a dependence in the force-deformation coordinate axes. In modeling the effect of damping forces, the time moment corresponding to the onset of asynchronous rolling-over with growing vibration amplitudes is used as the assessment criterion. With a longer period of time taken for the rolling-over to develop, it becomes possible to take the necessary measures in response to actuation of the equipment set safety system, which require certain time for implementing them. It is shown that the

  3. NASA Research Bearing on Jet Engine Reliability

    Science.gov (United States)

    Mason, S. S.; Ault, G. M.; Pinkel, B.

    1959-01-01

    Turbojet engine reliability has long been an intense interest to the military users of this type of aircraft propulsion. With the recent inauguration of commercial jet transport this subject has assumed a new dimension of importance. In January l96 the Lewis Research Center of the NASA (then the MACA) published the results of an extensive study on the factors that affect the opera- center dot tional reliability of turbojet engines (ref. 1). At that time the report was classified Confidential. In July l98 this report was declassified. It is thus appropriate at this time to present some of the highlights of the studies described in the NASA report. In no way is it intended to outline the complete contents of the report; rather it is hoped to direct attention to it among those who are center dot directly concerned with this problem. Since the publication of our study over three years ago, the NASA has completed a number of additional investigations that bear significantly on this center dot subject. A second object of this paper, therefore, is to summarize the results of these recent studies and to interpret their significance in relation to turbojet operational reliability.

  4. Transpermeance Amplifier Applied to Magnetic Bearings

    Directory of Open Access Journals (Sweden)

    Jossana Ferreira

    2017-02-01

    Full Text Available The most conventional approach of controlling magnetic forces in active magnetic bearings (AMBs is through current feedback amplifiers: transconductance. This enables the operation of the AMB to be understood in terms of a relatively simple current-based model as has been widely reported on in the literature. The alternative notion of using transpermeance amplifiers, which approximate the feedback of gap flux rather than current, has been in commercial use in some form for at least thirty years, however is only recently seeing more widespread acceptance as a commercial standard. This study explores how such alternative amplifiers should be modeled and then examines the differences in behavior between AMBs equipped with transconductance and transpermeance amplifiers. The focus of this study is on two aspects. The first is the influence of rotor displacement on AMB force, commonly modeled as a constant negative equivalent mechanical stiffness, and it is shown that either scheme actually leads to a finite bandwidth effect, but that this bandwidth is much lower when transpermeance is employed. The second aspect is the influence of eddy currents. Using a very simple model of eddy currents (a secondary short-circuited coil, it is demonstrated that transpermeance amplifiers can recover significant actuator bandwidth compared with transconductance, but at the cost of needing increased peak current headroom.

  5. Comparision of Fixed-Bearing and Mobile-Bearing Total Knee Arthroplasties: Short-Term Clinical Results

    Directory of Open Access Journals (Sweden)

    Burak Kaymaz

    2015-05-01

    Full Text Available Introduction: Mobile-bearing knee replacements were introduced as an alternative to fixed-bearing prosthesis to decrease the wear. Despite theoretical advantages of mobile bearings prosthesis, it is still controversial whether there is any clinically significant difference between the patients treated with fixed and mobile bearing prosthesis. The aim of this study is to compare the short-term clinical outcomes of fixed  versus mobile-bearing prosthesises.Methodology: Patients who were diagnosed as grade 4 gonartrosis and operated for total knee arthroplasty between years 2010-2014 were evaluated and 33 patients (40 knees were included in the study. From hospital medical and radiological databases, age and gender of the patients, duration of operation, number of blood tranfusions postoperatively and pre-operative range of motions (ROM of the operated knees were recorded and all the patients were assessed with  Knee Society Knee Score. Results:  Twenty-two knees (12 female, 10 male were present in fixed bearing group (Group I and 18 knees (13 female, 5 male were present in mobile bearing group (Group II. There was no statistically significant difference between the groups in terms of pre-operative range of motions (ROM, post-operative range of motions (ROM, number of blood transfusions. Knee Society Knee Score was 167.7±23.4 in Group I and 178.1±22.4 in Group II. Mobile bearing prosthesis group was found to have better knee score and this difference was near to statistically significance (p=0.055.Conclusions: Clinical outcomes of mobile bearing prosthesis seems to be better in short-term follow-up but long-term results should also be investigated before recommending the mobile bearing prosthesises.

  6. Migration and clinical outcome of mobile-bearing versus fixed-bearing single-radius total knee arthroplasty.

    Science.gov (United States)

    Van Hamersveld, Koen T; Marang-Van De Mheen, Perla J; Van Der Heide, Huub J L; Van Der Linden-Van Der Zwaag, Henrica M J; Valstar, Edward R; Nelissen, Rob G H H

    2018-04-01

    Background and purpose - Mobile-bearing total knee prostheses (TKPs) were developed in the 1970s in an attempt to increase function and improve implant longevity. However, modern fixed-bearing designs like the single-radius TKP may provide similar advantages. We compared tibial component migration measured with radiostereometric analysis (RSA) and clinical outcome of otherwise similarly designed cemented fixed-bearing and mobile-bearing single-radius TKPs. Patients and methods - RSA measurements and clinical scores were assessed in 46 randomized patients at baseline, 6 months, 1 year, and annually thereafter up to 6 years postoperatively. A linear mixed-effects model was used to analyze the repeated measurements. Results - Both groups showed comparable migration (p = 0.3), with a mean migration at 6-year follow-up of 0.90 mm (95% CI 0.49-1.41) for the fixed-bearing group compared with 1.22 mm (95% CI 0.75-1.80) for the mobile-bearing group. Clinical outcomes were similar between groups. 1 fixed-bearing knee was revised for aseptic loosening after 6 years and 2 knees (1 in each group) were revised for late infection. 2 knees (1 in each group) were suspected for loosening due to excessive migration. Another mobile-bearing knee was revised after an insert dislocation due to failure of the locking mechanism 6 weeks postoperatively, after which study inclusion was preliminary terminated. Interpretation - Fixed-bearing and mobile-bearing single-radius TKPs showed similar migration. The latter may, however, expose patients to more complex surgical techniques and risks such as insert dislocations inherent to this rotating-platform design.

  7. Genomic evidence for island population conversion resolves conflicting theories of polar bear evolution.

    Directory of Open Access Journals (Sweden)

    James A Cahill

    Full Text Available Despite extensive genetic analysis, the evolutionary relationship between polar bears (Ursus maritimus and brown bears (U. arctos remains unclear. The two most recent comprehensive reports indicate a recent divergence with little subsequent admixture or a much more ancient divergence followed by extensive admixture. At the center of this controversy are the Alaskan ABC Islands brown bears that show evidence of shared ancestry with polar bears. We present an analysis of genome-wide sequence data for seven polar bears, one ABC Islands brown bear, one mainland Alaskan brown bear, and a black bear (U. americanus, plus recently published datasets from other bears. Surprisingly, we find clear evidence for gene flow from polar bears into ABC Islands brown bears but no evidence of gene flow from brown bears into polar bears. Importantly, while polar bears contributed <1% of the autosomal genome of the ABC Islands brown bear, they contributed 6.5% of the X chromosome. The magnitude of sex-biased polar bear ancestry and the clear direction of gene flow suggest a model wherein the enigmatic ABC Island brown bears are the descendants of a polar bear population that was gradually converted into brown bears via male-dominated brown bear admixture. We present a model that reconciles heretofore conflicting genetic observations. We posit that the enigmatic ABC Islands brown bears derive from a population of polar bears likely stranded by the receding ice at the end of the last glacial period. Since then, male brown bear migration onto the island has gradually converted these bears into an admixed population whose phenotype and genotype are principally brown bear, except at mtDNA and X-linked loci. This process of genome erosion and conversion may be a common outcome when climate change or other forces cause a population to become isolated and then overrun by species with which it can hybridize.

  8. Genomic evidence for island population conversion resolves conflicting theories of polar bear evolution.

    Science.gov (United States)

    Cahill, James A; Green, Richard E; Fulton, Tara L; Stiller, Mathias; Jay, Flora; Ovsyanikov, Nikita; Salamzade, Rauf; St John, John; Stirling, Ian; Slatkin, Montgomery; Shapiro, Beth

    2013-01-01

    Despite extensive genetic analysis, the evolutionary relationship between polar bears (Ursus maritimus) and brown bears (U. arctos) remains unclear. The two most recent comprehensive reports indicate a recent divergence with little subsequent admixture or a much more ancient divergence followed by extensive admixture. At the center of this controversy are the Alaskan ABC Islands brown bears that show evidence of shared ancestry with polar bears. We present an analysis of genome-wide sequence data for seven polar bears, one ABC Islands brown bear, one mainland Alaskan brown bear, and a black bear (U. americanus), plus recently published datasets from other bears. Surprisingly, we find clear evidence for gene flow from polar bears into ABC Islands brown bears but no evidence of gene flow from brown bears into polar bears. Importantly, while polar bears contributed bear, they contributed 6.5% of the X chromosome. The magnitude of sex-biased polar bear ancestry and the clear direction of gene flow suggest a model wherein the enigmatic ABC Island brown bears are the descendants of a polar bear population that was gradually converted into brown bears via male-dominated brown bear admixture. We present a model that reconciles heretofore conflicting genetic observations. We posit that the enigmatic ABC Islands brown bears derive from a population of polar bears likely stranded by the receding ice at the end of the last glacial period. Since then, male brown bear migration onto the island has gradually converted these bears into an admixed population whose phenotype and genotype are principally brown bear, except at mtDNA and X-linked loci. This process of genome erosion and conversion may be a common outcome when climate change or other forces cause a population to become isolated and then overrun by species with which it can hybridize.

  9. Integral finite element analysis of turntable bearing with flexible rings

    Science.gov (United States)

    Deng, Biao; Liu, Yunfei; Guo, Yuan; Tang, Shengjin; Su, Wenbin; Lei, Zhufeng; Wang, Pengcheng

    2018-03-01

    This paper suggests a method to calculate the internal load distribution and contact stress of the thrust angular contact ball turntable bearing by FEA. The influence of the stiffness of the bearing structure and the plastic deformation of contact area on the internal load distribution and contact stress of the bearing is considered. In this method, the load-deformation relationship of the rolling elements is determined by the finite element contact analysis of a single rolling element and the raceway. Based on this, the nonlinear contact between the rolling elements and the inner and outer ring raceways is same as a nonlinear compression spring and bearing integral finite element analysis model including support structure was established. The effects of structural deformation and plastic deformation on the built-in stress distribution of slewing bearing are investigated on basis of comparing the consequences of load distribution, inner and outer ring stress, contact stress and other finite element analysis results with the traditional bearing theory, which has guiding function for improving the design of slewing bearing.

  10. Black bear density in Glacier National Park, Montana

    Science.gov (United States)

    Stetz, Jeff B.; Kendall, Katherine C.; Macleod, Amy C.

    2013-01-01

    We report the first abundance and density estimates for American black bears (Ursus americanus) in Glacier National Park (NP),Montana, USA.We used data from 2 independent and concurrent noninvasive genetic sampling methods—hair traps and bear rubs—collected during 2004 to generate individual black bear encounter histories for use in closed population mark–recapture models. We improved the precision of our abundance estimate by using noninvasive genetic detection events to develop individual-level covariates of sampling effort within the full and one-half mean maximum distance moved (MMDM) from each bear’s estimated activity center to explain capture probability heterogeneity and inform our estimate of the effective sampling area.Models including the one-halfMMDMcovariate received overwhelming Akaike’s Information Criterion support suggesting that buffering our study area by this distance would be more appropriate than no buffer or the full MMDM buffer for estimating the effectively sampled area and thereby density. Our modelaveraged super-population abundance estimate was 603 (95% CI¼522–684) black bears for Glacier NP. Our black bear density estimate (11.4 bears/100 km2, 95% CI¼9.9–13.0) was consistent with published estimates for populations that are sympatric with grizzly bears (U. arctos) and without access to spawning salmonids. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

  11. Modelling of Rotor-gas bearings for Feedback Controller Design

    DEFF Research Database (Denmark)

    Theisen, Lukas Roy Svane; Niemann, Hans Henrik

    2014-01-01

    Controllable rotor-gas bearings are popular oering adaptability, high speed operation, low friction and clean operation. Rotor-gas bearings are however highly sensitive to disturbances due to the low friction of the injected gas. These undesirable damping properties call for controllers, which ca...... and are shown to accurately describe the dynamical behaviour of the rotor-gas bearing. Design of a controller using the identied models is treated and experiments verify the improvement of the damping properties of the rotor-gas bearing.......Controllable rotor-gas bearings are popular oering adaptability, high speed operation, low friction and clean operation. Rotor-gas bearings are however highly sensitive to disturbances due to the low friction of the injected gas. These undesirable damping properties call for controllers, which can...... be designed from suitable models describing the relation from actuator input to measured shaft position. Current state of the art models of controllable gas bearings however do not provide such relation, which calls for alternative strategies. The present contribution discusses the challenges for feedback...

  12. Foil Bearing Starting Considerations and Requirements for Rotorcraft Engine Applications

    Science.gov (United States)

    Radil, Kevin C.; DellaCorte, Christopher

    2009-01-01

    Foil gas bearings under development for rotorcraft-sized, hot core engine applications have been susceptible to damage from the slow acceleration and rates typically encountered during the pre-ignition stage in conventional engines. Recent laboratory failures have been assumed to be directly linked to operating foil bearings below their lift-off speed while following conventional startup procedures for the engines. In each instance, the continuous sliding contact between the foils and shaft was believed to thermally overload the bearing and cause the engines to fail. These failures highlight the need to characterize required acceleration rates and minimum operating speeds for these applications. In this report, startup experiments were conducted with a large, rotorcraft engine sized foil bearing under moderate load and acceleration rates to identify the proper start procedures needed to avoid bearing failure. The results showed that a bearing under a 39.4 kPa static load can withstand a modest acceleration rate of 500 rpm/s and excessive loitering below the bearing lift-off speed provided an adequate solid lubricant is present.

  13. Dynamic behavior of hybrid sodium bearings. Theoretical and experimental studies

    International Nuclear Information System (INIS)

    Guidez, J.; Juignet, N.; Queval, M.

    1981-08-01

    The primary sodium pump shaft lower section of a fast breeder reactor is guided by a hydrostatic sodium bearing. This recess type bearing is supplied via orifices restrictors. Sodium is sampled at hight pressure at the diffuser outlet and is then centrifuged towards the orifices restrictors. Bearing stiffness and damping data is essential for the study of rotor dynamic behavior. Two points in particular may then be studied: - calculation of rotor instability ranges and critical speeds, - dynamic behavior of the rotor in the event of an earthquake. As regards the bearing design, the problem is to obtain the pressure fields in the liquid film. The integration of these pressure fields will then give the stiffness coefficients. The damping coefficients can then be obtained by the same calculation after slight displacement. The Reynolds equation can be used to study the liquid film (under any conditions for the turbulent and inertia effects). Then the computer code DELPAL is explained that solves the modified Reynolds equation using a finite element method. The presentation of tests conducted in 1981 on the Super-Phenix 1 full scall bearing (diameter 850 mm) in water is made. In conclusion this paper describes a method for calculating the stiffness and damping matrices of a hydrostatic bearing using the DELPAL calculation code and shows the loop of behavior tests on a bearing with sinusoidal excitation. The results, obtained by calculation and by testing, are indispensable when calculating the dynamic behavior of the shaft line

  14. Force and stiffness characteristics of superconducting bearing prototype

    International Nuclear Information System (INIS)

    Matveev, V.; Nizhelskiy, N.; Poluschenko, O.

    2004-01-01

    The radial-axial superconducting bearing prototype was designed, fabricated and tested. The YBaCuO high-temperature superconducting (HTS) monodomain disks diameter 28 mm and thickness of h = 4; 6; 8; 10 mm, capable to trap magnetic field 1 T, were fabricated to be employed in bearing prototype. Force interaction of single field cooled HTS disks with NdFeB magnets depending on disk thickness under 1 mm magnet air gap was studied. It was found that the increase in disk thickness results in reducing radial stiffness and in growing axial one. The results obtained were used for optimization of HTS-PM arrangement, and for developing the bearing design. The designed bearing incorporates a rotor with 7 HTS disks of 4 mm thickness, total mass 90 g, and stator with two pairs of permanent annular magnets of NdFeB. It is established that the force-displacement dependencies of the bearing have three zones: non-hysteresis (elastic) zone with high stiffness up to 560 N/mm; zone of elastic interaction with stiffness 190 N/mm; hysteretic zone with stiffness 150 N/mm in which a rotor residual displacement being observed after unloading. The outer bearing diameter is 130 mm, thickness 30 mm, and mass 1.8 kg. The maximal radial load capacity of the bearing is 190 N at the rotor displacement of 1.3 mm, and the maximal axial load capacity is 85 N at the displacement of 1 mm

  15. Stable blood lubricated hydrodynamic journal bearing with magnetic loading.

    Science.gov (United States)

    Malanoski, S B; Belawski, H; Horvath, D; Smith, W A; Golding, L R

    1998-01-01

    The Cleveland Clinic Foundation's Innovative Ventricular Assist System (IVAS) is distinguished by the use of a special hydrodynamic journal bearing to support the rotating assembly of the blood pump. In a permanently implanted blood pump, this bearing's characteristics of long life and high reliability are of paramount importance. In addition, this bearing's inherent self-pumping flow and the axial through flow caused by an imposed end-to-end pressure difference provides good washing, thus guarding against deposition. The basic computer analysis and preliminary testing results of this bearing were previously presented. This article reports the ongoing studies (both analytic and in vitro tests) on this innovative bearing as a component of the IVAS in general, with particular emphasis on its stable operating characteristics and reliability. The absence of vibration attributable to hydrodynamic instabilities related to the thick fluid film are both calculated and demonstrated during testing. A stable operating center of the rotor is shown to be inherent under magnetic side loads and resulting hydrodynamic bearing forces. A low shear as a result of large fluid-film thicknesses has been calculated, and low hemolysis has been shown by in vitro testing. Several unique design features of the bearing are believed to be responsible for this high level of performance.

  16. Bearing Fault Detection in Induction Motor-Gearbox Drivetrain

    International Nuclear Information System (INIS)

    Cibulka, Jaroslav; Ebbesen, Morten K; Robbersmyr, Kjell G

    2012-01-01

    The main contribution in the hereby presented paper is to investigate the fault detection capability of a motor current signature analysis by expanding its scope to include the gearbox, and not only the induction motor. Detecting bearing faults outside the induction motor through the stator current analysis represents an interesting alternative to traditional vibration analysis. Bearing faults cause changes in the stator current spectrum that can be used for fault diagnosis purposes. A time-domain simulation of the drivetrain model is developed. The drivetrain system consists of a loaded single stage gearbox driven by a line-fed induction motor. Three typical bearing faults in the gearbox are addressed, i.e. defects in the outer raceway, the inner raceway, and the rolling element. The interaction with the fault is modelled by means of kinematical and mechanical relations. The fault region is modelled in order to achieve gradual loss and gain of contact. A bearing fault generates an additional torque component that varies at the specific bearing defect frequency. The presented dynamic electromagnetic dq-model of an induction motor is adjusted for diagnostic purpose and considers such torque variations. The bearing fault is detected as a phase modulation of the stator current sine wave at the expected bearing defect frequency.

  17. Salmon poisoning disease in two Malayan sun bears.

    Science.gov (United States)

    Gai, Jackie J; Marks, Stanley L

    2008-02-15

    2 captive sun bears (Helarctos malayanus) were evaluated because of acute onset of vomiting, mucoid diarrhea, lethargy, and anorexia 1 week after eating live trout from a northern California reservoir. In 1 of the bears, a CBC and serum biochemical analyses revealed mild anemia, mild eosinophilia, moderate lymphopenia, moderate hypoalbuminemia, and high serum G-glutamyltransferase activity. Ultrasonographic examination of the same bear revealed ascites and mesenteric lymphadenopathy. Histologic examination of gastrointestinal tract biopsy specimens revealed moderate to severe lymphoplasmacytic and eosinophilic gastritis, enteritis, and colitis. Ova of Nanophyetus salmincola, the trematode vector of Neorickettsia helminthoeca (a rickettsial organism that causes salmon poisoning disease), were detected in fecal samples from both bears. The bears were treated with oxytetracycline, doxycycline, praziquantel, and famotidine. Within 1 week after initiation of treatment, the appetite and fecal consistency of each bear were considered normal. Fecal ova shedding began 4 days after onset of clinical signs and ceased 9 days later. Salmon poisoning disease can be rapidly fatal in untreated animals, but if diagnosed early and treated appropriately, full recovery can be achieved. Domestic dogs and captive exotic bears are highly susceptible to clinical disease after ingestion of trematode-infected fish. Salmon poisoning disease may develop outside the geographic range in which the causative organism is endemic as a result of the transplantation of infected fish for sport fishing; veterinarians practicing in areas where infected fish may be transplanted should be aware of appropriate diagnostic and treatment protocols.

  18. Hydrodynamic Analyses and Evaluation of New Fluid Film Bearing Concepts

    Science.gov (United States)

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

    1998-01-01

    Over the past several years, numerical and experimental investigations have been performed on a waved journal bearing. The research work was undertaken by Dr. Florin Dimofte, a Senior Research Associate in the Mechanical Engineering Department at the University of Toledo. Dr. Theo Keith, Distinguished University Professor in the Mechanical Engineering Department was the Technical Coordinator of the project. The wave journal bearing is a bearing with a slight but precise variation in its circular profile such that a waved profile is circumscribed on the inner bearing diameter. The profile has a wave amplitude that is equal to a fraction of the bearing clearance. Prior to this period of research on the wave bearing, computer codes were written and an experimental facility was established. During this period of research considerable effort was directed towards the study of the bearing's stability. The previously developed computer codes and the experimental facility were of critical importance in performing this stability research. A collection of papers and reports were written to describe the results of this work. The attached captures that effort and represents the research output during the grant period.

  19. GIS representation of coal-bearing areas in Antarctica

    Science.gov (United States)

    Merrill, Matthew D.

    2016-03-11

    Understanding the distribution of coal-bearing geologic units in Antarctica provides information that can be used in sedimentary, geomorphological, paleontological, and climatological studies. This report is a digital compilation of information on Antarctica’s coal-bearing geologic units found in the literature. It is intended to be used in small-scale spatial geographic information system (GIS) investigations and as a visual aid in the discussion of Antarctica’s coal resources or in other coal-based geologic investigations. Instead of using spatially insignificant point markers to represent large coal-bearing areas, this dataset uses polygons to represent actual coal-bearing lithologic units. Specific locations of coal deposits confirmed from the literature are provided in the attribution for the coal-bearing unit polygons. Coal-sample-location data were used to confirm some reported coal-bearing geology. The age and extent of the coal deposits indicated in the literature were checked against geologic maps ranging from local scale at 1:50,000 to Antarctic continental scale at 1:5,000,000; if satisfactory, the map boundaries were used to generate the polygons for the coal-bearing localities.

  20. Evaluation of cardiac function in active and hibernating grizzly bears.

    Science.gov (United States)

    Nelson, O Lynne; McEwen, Margaret-Mary; Robbins, Charles T; Felicetti, Laura; Christensen, William F

    2003-10-15

    To evaluate cardiac function parameters in a group of active and hibernating grizzly bears. Prospective study. 6 subadult grizzly bears. Indirect blood pressure, a 12-lead ECG, and a routine echocardiogram were obtained in each bear during the summer active phase and during hibernation. All measurements of myocardial contractility were significantly lower in all bears during hibernation, compared with the active period. Mean rate of circumferential left ventricular shortening, percentage fractional shortening, and percentage left ventricular ejection fraction were significantly lower in bears during hibernation, compared with the active period. Certain indices of diastolic function appeared to indicate enhanced ventricular compliance during the hibernation period. Mean mitral inflow ratio and isovolumic relaxation time were greater during hibernation. Heart rate was significantly lower for hibernating bears, and mean cardiac index was lower but not significantly different from cardiac index during the active phase. Contrary to results obtained in hibernating rodent species, cardiac index was not significantly correlated with heart rate. Cardiac function parameters in hibernating bears are opposite to the chronic bradycardic effects detected in nonhibernating species, likely because of intrinsic cardiac muscle adaptations during hibernation. Understanding mechanisms and responses of the myocardium during hibernation could yield insight into mechanisms of cardiac function regulation in various disease states in nonhibernating species.

  1. Probabilistic assessment of fuel channel bearing travel and end of bearing time

    International Nuclear Information System (INIS)

    Camacho, F.; Lam, R.; Goldberg, J.; Micuda, L.; Cho, D.

    2008-01-01

    Operators in Ontario have been assessing fuel channel elongation in nuclear generating units to ensure fuel channels remain on bearing at least until the next inspection in accordance with CSA N285.4. These assessments have so far been performed deterministically and, among other conservative assumptions, use the worst stack-up of tolerances for all relevant fuel channel components to calculate the end-of-bearing (EOB) times. Since the probability of having the worst stack-up of tolerances occurring is extremely small, a deterministic assessment provides a very conservative representation of the unit condition. The probabilistic assessment presented in this paper provides a more realistic representation of elongation and channel end-of-bearing times. For a given reactor, the probabilistic assessment used Monte Carlo techniques to generate values for fuel channel component dimensions, current fuel channel elongations, future elongations and elongation measurement errors from specified distributions. The simulated values are then used to obtain a distribution of EOB times at each lattice position in the reactor. The expected number of fuel channels reaching EOB in a given operating interval can then be compared to pre-established acceptance criteria to determine if the operating interval is acceptable. The methodology is illustrated with an example reactor. The results from 100,000 simulations at each lattice position show that the EOB times calculated in the deterministic assessment corresponded to a very low percentile of the EOB times calculated in the probabilistic assessment. This indicated that the deterministic assessment was very conservative. For the example reactor, no elongation maintenance would be necessary for approximately one year (8,000 effective full power hours) after the latest outage. (author)

  2. Bear-baiting may exacerbate wolf-hunting dog conflict.

    Directory of Open Access Journals (Sweden)

    Joseph K Bump

    Full Text Available BACKGROUND: The influence of policy on the incidence of human-wildlife conflict can be complex and not entirely anticipated. Policies for managing bear hunter success and depredation on hunting dogs by wolves represent an important case because with increasing wolves, depredations are expected to increase. This case is challenging because compensation for wolf depredation on hunting dogs as compared to livestock is less common and more likely to be opposed. Therefore, actions that minimize the likelihood of such conflicts are a conservation need. METHODOLOGY/PRINCIPAL FINDINGS: We used data from two US states with similar wolf populations but markedly different wolf/hunting dog depredation patterns to examine the influence of bear hunting regulations, bear hunter to wolf ratios, hunter method, and hunter effort on wolf depredation trends. Results indicated that the ratio of bear hunting permits sold per wolf, and hunter method are important factors affecting wolf depredation trends in the Upper Great Lakes region, but strong differences exist between Michigan and Wisconsin related in part to the timing and duration of bear-baiting (i.e., free feeding. The probability that a wolf depredated a bear-hunting dog increases with the duration of bear-baiting, resulting in a relative risk of depredation 2.12-7.22× greater in Wisconsin than Michigan. The net effect of compensation for hunting dog depredation in Wisconsin may also contribute to the difference between states. CONCLUSIONS/SIGNIFICANCE: These results identified a potential tradeoff between bear hunting success and wolf/bear-hunting dog conflict. These results indicate that management options to minimize conflict exist, such as adjusting baiting regulations. If reducing depredations is an important goal, this analysis indicates that actions aside from (or in addition to reducing wolf abundance might achieve that goal. This study also stresses the need to better understand the relationship

  3. Bear-baiting may exacerbate wolf-hunting dog conflict.

    Science.gov (United States)

    Bump, Joseph K; Murawski, Chelsea M; Kartano, Linda M; Beyer, Dean E; Roell, Brian J

    2013-01-01

    The influence of policy on the incidence of human-wildlife conflict can be complex and not entirely anticipated. Policies for managing bear hunter success and depredation on hunting dogs by wolves represent an important case because with increasing wolves, depredations are expected to increase. This case is challenging because compensation for wolf depredation on hunting dogs as compared to livestock is less common and more likely to be opposed. Therefore, actions that minimize the likelihood of such conflicts are a conservation need. We used data from two US states with similar wolf populations but markedly different wolf/hunting dog depredation patterns to examine the influence of bear hunting regulations, bear hunter to wolf ratios, hunter method, and hunter effort on wolf depredation trends. Results indicated that the ratio of bear hunting permits sold per wolf, and hunter method are important factors affecting wolf depredation trends in the Upper Great Lakes region, but strong differences exist between Michigan and Wisconsin related in part to the timing and duration of bear-baiting (i.e., free feeding). The probability that a wolf depredated a bear-hunting dog increases with the duration of bear-baiting, resulting in a relative risk of depredation 2.12-7.22× greater in Wisconsin than Michigan. The net effect of compensation for hunting dog depredation in Wisconsin may also contribute to the difference between states. These results identified a potential tradeoff between bear hunting success and wolf/bear-hunting dog conflict. These results indicate that management options to minimize conflict exist, such as adjusting baiting regulations. If reducing depredations is an important goal, this analysis indicates that actions aside from (or in addition to) reducing wolf abundance might achieve that goal. This study also stresses the need to better understand the relationship among baiting practices, the effect of compensation on hunter behavior, and depredation

  4. Immobilization of Wyoming bears using carfentanil and xylazine.

    Science.gov (United States)

    Kreeger, Terry J; Bjornlie, Dan; Thompson, Dan; Clapp, Justin; Clark, Colby; Hansen, Cole; Huizenga, Matt; Lockwood, Sam

    2013-07-01

    Seven grizzly (Ursus arctos; four male, three female) and three black (Ursus americanus; two male, one female) bears caught in culvert traps or leg snares were immobilized in northwestern Wyoming with carfentanil and xylazine at doses, respectively, of 0.011 ± 0.001 and 0.12 ± 0.01 mg/kg for grizzly bears and 0.014 ± 0.002 and 0.15 ± 0.04 mg/kg for black bears. These drugs were antagonized with 1 mg/kg naltrexone and 2 mg/kg tolazoline. Induction and recovery times, respectively, were 4.3 ± 0.5 and 7.1 ± 0.8 min for grizzly bears and 5.2 ± 0.4 and 9.1 ± 2.2 min for black bears. Inductions were smooth and uneventful. Recoveries were characterized initially by increased respiration followed by raising of the head, which quickly led to a full recovery, with the bears recognizing and avoiding humans and moving away, maneuvering around obstacles. All bears experienced respiratory depression, which did not significantly improve with supplemental oxygen on the basis of pulse oximetry (P=0.56). Rectal temperatures were normothermic. Carfentanil-xylazine immobilization of bears provided significant advantages over other drug regimens, including small drug volumes, predictable inductions, quick and complete recoveries, and lower costs. On the basis of these data, both grizzly and black bears can be immobilized effectively with 0.01 mg/kg carfentanil and 0.1 mg/kg xylazine.

  5. Dietary breadth of grizzly bears in the Greater Yellowstone Ecosystem

    Science.gov (United States)

    Gunther, Kerry A.; Shoemaker, Rebecca; Frey, Kevin L.; Haroldson, Mark A.; Cain, Steven L; van Manen, Frank T.; Fortin, Jennifer K.

    2014-01-01

    Grizzly bears (Ursus arctos) in the Greater Yellowstone Ecosystem (GYE) are opportunistic omnivores that eat a great diversity of plant and animal species. Changes in climate may affect regional vegetation, hydrology, insects, and fire regimes, likely influencing the abundance, range, and elevational distribution of the plants and animals consumed by GYE grizzly bears. Determining the dietary breadth of grizzly bears is important to document future changes in food resources and how those changes may affect the nutritional ecology of grizzlies. However, no synthesis exists of all foods consumed by grizzly bears in the GYE. We conducted a review of available literature and compiled a list of species consumed by grizzly bears in the GYE. We documented >266 species within 200 genera from 4 kingdoms, including 175 plant, 37 invertebrate, 34 mammal, 7 fungi, 7 bird, 4 fish, 1 amphibian, and 1 algae species as well as 1 soil type consumed by grizzly bears. The average energy values of the ungulates (6.8 kcal/g), trout (Oncorhynchus spp., 6.1 kcal/g), and small mammals (4.5 kcal/g) eaten by grizzlies were higher than those of the plants (3.0 kcal/g) and invertebrates (2.7 kcal/g) they consumed. The most frequently detected diet items were graminoids, ants (Formicidae), whitebark pine seeds (Pinus albicaulis), clover (Trifolium spp.), and dandelion (Taraxacum spp.). The most consistently used foods on a temporal basis were graminoids, ants, whitebark pine seeds, clover, elk (Cervus elaphus), thistle (Cirsium spp.), and horsetail (Equisetum spp.). Historically, garbage was a significant diet item for grizzlies until refuse dumps were closed. Use of forbs increased after garbage was no longer readily available. The list of foods we compiled will help managers of grizzly bears and their habitat document future changes in grizzly bear food habits and how bears respond to changing food resources.

  6. The urothelium of a hibernator: the American black bear.

    Science.gov (United States)

    Spector, David A; Deng, Jie; Coleman, Richard; Wade, James B

    2015-06-01

    The American black bear undergoes a 3-5 month winter hibernation during which time bears do not eat, drink, defecate, or urinate. During hibernation renal function (GFR) is 16-50% of normal but urine is reabsorbed across the urinary bladder (UB) urothelium thus enabling metabolic recycling of all urinary constituents. To elucidate the mechanism(s) whereby urine is reabsorbed, we examined the UBs of five nonhibernating wild bears using light, electron (EM), and confocal immunofluorescent (IF) microscopy-concentrating on two components of the urothelial permeability barrier - the umbrella cell apical membranes and tight junctions (TJ). Bear UB has the same tissue layers (serosa, muscularis, lamina propria, urothelia) and its urothelia has the same cell layers (basal, intermediate, umbrella cells) as other mammalians. By EM, the bear apical membrane demonstrated a typical mammalian scalloped appearance with hinge and plaque regions - the latter containing an asymmetric trilaminar membrane and, on IF, uroplakins Ia, IIIa, and IIIb. The umbrella cell TJs appeared similar to those in other mammals and also contained TJ proteins occludin and claudin - 4, and not claudin -2. Thus, we were unable to demonstrate urothelial apical membrane or TJ differences between active black bears and other mammals. Expression and localization of UT-B, AQP-1 and -3, and Na(+), K(+)-ATPase on bear urothelial membranes was similar to that of other mammals. Similar studies of urothelia of hibernating bears, including evaluation of the apical membrane lipid bilayer and GAGs layer are warranted to elucidate the mechanism(s) whereby hibernating bears reabsorb their daily urine output and thus ensure successful hibernation. © 2015 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.

  7. Vibration control of rotor-bearing system by controlled squeeze-film damper bearings

    Science.gov (United States)

    He, Erming; Gu, Jialiu

    1992-07-01

    A new vibration control scheme for rotor-bearing systems is presented which offers many advantages over the scheme proposed by Gu (1990). Due to the nonlinear state feedback, closed-loop control becomes possible. Thus control can be readily adjusted in accordance with transient state information. Optimal structure parameters are determined by the optimal control law. The control force is applied on line; by merely adjusting CSFDB structure parameters, control forces can be applied to the system. The feasibility of the present design is confirmed by simulation, which is performed for a flexible Jeffcott rotor elastically supported at both ends on identical CSFDBs.

  8. Prevalence of Trichinella spp. in black bears, grizzly bears, and wolves in the Dehcho Region, Northwest Territories, Canada, including the first report of T. nativa in a grizzly bear from Canada.

    Science.gov (United States)

    Larter, Nicholas C; Forbes, Lorry B; Elkin, Brett T; Allaire, Danny G

    2011-07-01

    Samples of muscle from 120 black bears (Ursus americanus), 11 grizzly bears (Ursus arctos), and 27 wolves (Canis lupus) collected in the Dehcho Region of the Northwest Territories from 2001 to 2010 were examined for the presence of Trichinella spp. larvae using a pepsin-HCl digestion assay. Trichinella spp. larvae were found in eight of 11 (73%) grizzly bears, 14 of 27 (52%) wolves, and seven of 120 (5.8%) black bears. The average age of positive grizzly bears, black bears, and wolves was 13.5, 9.9, and approximately 4 yr, respectively. Larvae from 11 wolves, six black bears, and seven grizzly bears were genotyped. Six wolves were infected with T. nativa and five with Trichinella T6, four black bears were infected with T. nativa and two with Trichinella T6, and all seven grizzly bears were infected with Trichinella T6 and one of them had a coinfection with T. nativa. This is the first report of T. nativa in a grizzly bear from Canada. Bears have been linked to trichinellosis outbreaks in humans in Canada, and black bears are a subsistence food source for residents of the Dehcho region. In order to assess food safety risk it is important to monitor the prevalence of Trichinella spp. in both species of bear and their cohabiting mammalian food sources.

  9. Non Linear Analysis on Multi Lobe Journal Bearings

    Science.gov (United States)

    Udaya Bhaskar, S.; Manzoor Hussian, M.; Yousuf Ali, Md.

    2017-08-01

    Multi lobe journal bearings are used in machines which operate at high speeds and high loads. In this paper the multi lobe bearing are analyzed to determine the effect of surface roughness during non linear loading. A non-linear time transient analysis is performed using the fourth order Runge Kutta method. The finite difference method is used to predict the pressure distribution over the bearing surface. The effect of eccentric ratio is studied and the variation of attitude angle is discussed. The journal center trajectories were calculated and plotted.

  10. Rotordynamic Characterization of a Hybrid Superconductor Magnet Bearing

    Science.gov (United States)

    Ma, Ki B.; Xia, Zule H.; Cooley, Rodger; Fowler, Clay; Chu, Wei-Kan

    1996-01-01

    A hybrid superconductor magnet bearing uses magnetic forces between permanent magnets to provide lift and the flux pinning force between permanent magnets and superconductors to stabilize against instabilities intrinsic to the magnetic force between magnets. We have constructed a prototype kinetic energy storage system, using a hybrid superconductor magnet bearing to support a 42 lb. flywheel at the center. With five sensors on the periphery of the flywheel, we have monitored the position and attitude of the flywheel during its spin down. The results indicate low values of stiffnesses for the bearing. The implications of this and other consequences will be discussed.

  11. Advanced Transmission Components Investigation Program. Bearing and Seal Development.

    Science.gov (United States)

    1980-08-01

    were fabricated from consumable-electrode vacuum- melt M50 steel (AMS649) and the inner rings were made from a bar of consunable-electrode ,acuum-melt...diatmeter, hut 11one Were reCorded inl thIre O ’aIta 111 bearing. Prior to thle stat of testing, a destructive rntaC,1lngic.1 e\\arnirratrnr ol one bar ...bearings replaced the test bearings at failure and were also used to compare the life-imptovement factor to V .\\SCO-X2 steel. TESI RLSUIAS The fatigue

  12. Modelling and Identification for Control of Gas Bearings

    DEFF Research Database (Denmark)

    Theisen, Lukas Roy Svane; Niemann, Hans Henrik; Santos, Ilmar

    2015-01-01

    Gas bearings are popular for their high speed capabilities, low friction and clean operation, but suffer from poor damping, which poses challenges for safe operation in presence of disturbances. Enhanced damping can be achieved through active lubrication techniques using feedback control laws...... to industrial rotating machinery with gas bearings and to allow for subsequent control design. The paper shows how piezoelectric actuators in a gas bearing are efficiently used to perturb the gas film for identification over relevant ranges of rotational speed and gas injection pressure. Parameter...

  13. Analyzing the use of pins in safety bearings

    DEFF Research Database (Denmark)

    da Fonseca, Cesar A. L. L.; Weber, Hans I.; Fleischer, Philip F.

    2015-01-01

    A new concept for safety bearings is analyzed: useful in emergency situations, it shall protect the bearing from destruction by the use of pins which impact with a disc, both capable of good energy dissipation. Results of work in progress are presented by validating partial stages......, the variation of energy content of the disc after each contact is considered. Actually, the validation of the clamped-free rotor is done. The main goal is to design an automatic system with the capability of changing the gap when necessary in order to avoid the rotor colliding with the inner part of the bearing....

  14. Prediction of Gas Lubricated Foil Journal Bearing Performance

    Science.gov (United States)

    Carpino, Marc; Talmage, Gita

    2003-01-01

    This report summarizes the progress in the first eight months of the project. The objectives of this research project are to theoretically predict the steady operating conditions and the rotor dynamic coefficients of gas foil journal bearings. The project is currently on or ahead of schedule with the development of a finite element code that predicts steady bearing performance characteristics such as film thickness, pressure, load, and drag. Graphical results for a typical bearing are presented in the report. Project plans for the next year are discussed.

  15. Effects of Active Vibration Control of Journal Bearings

    Directory of Open Access Journals (Sweden)

    Jiří Tůma

    2016-09-01

    Full Text Available The article deals with the stability of the movement of the journal inside the bushing of the hydrodynamic plain bearings, which limits the operational range of rotor rotational speed. The purpose of active vibration control using piezoactuators is to increase the limit of the rotor rotation speed without onset of a whirl. It is also required maintaining the bearing journal position without vibration and reducing friction losses at the steady-state rotation. The main topic is the presentation of the results of the test of the journal bearing with the use of a test bench.

  16. A technique to measure rotordynamic coefficients in hydrostatic bearings

    Science.gov (United States)

    Capaldi, Russell J.

    1993-01-01

    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.

  17. Performance of Simple Gas Foil Thrust Bearings in Air

    Science.gov (United States)

    Bruckner, Robert J.

    2012-01-01

    Foil bearings are self-acting hydrodynamics devices used to support high speed rotating machinery. The advantages that they offer to process fluid lubricated machines include: high rotational speed capability, no auxiliary lubrication system, non-contacting high speed operation, and improved damping as compared to rigid hydrodynamic bearings. NASA has had a sporadic research program in this technology for almost 6 decades. Advances in the technology and understanding of foil journal bearings have enabled several new commercial products in recent years. These products include oil-free turbochargers for both heavy trucks and automobiles, high speed electric motors, microturbines for distributed power generation, and turbojet engines. However, the foil thrust bearing has not received a complimentary level of research and therefore has become the weak link of oil-free turbomachinery. In an effort to both provide machine designers with basic performance parameters and to elucidate the underlying physics of foil thrust bearings, NASA Glenn Research Center has completed an effort to experimentally measure the performance of simple gas foil thrust bearing in air. The database includes simple bump foil supported thrust bearings with full geometry and manufacturing techniques available to the user. Test conditions consist of air at ambient pressure and temperatures up to 500 C and rotational speeds to 55,000 rpm. A complete set of axial load, frictional torque, and rotational speed is presented for two different compliant sub-structures and inter-pad gaps. Data obtained from commercially available foil thrust bearings both with and without active cooling is presented for comparison. A significant observation made possible by this data set is the speed-load capacity characteristic of foil thrust bearings. Whereas for the foil journal bearing the load capacity increases linearly with rotational speed, the foil thrust bearing operates in the hydrodynamic high speed limit. In

  18. Static properties of hydrostatic thrust gas bearings with curved surfaces.

    Science.gov (United States)

    Rehsteiner, F. H.; Cannon, R. H., Jr.

    1971-01-01

    The classical treatment of circular, hydrostatic, orifice-regulated thrust gas bearings, in which perfectly plane bearing plates are assumed, is extended to include axisymmetric, but otherwise arbitrary, plate profiles. Plate curvature has a strong influence on bearing load capability, static stiffness, tilting stiffness, and side force per unit misalignment angle. By a suitable combination of gas inlet impedance and concave plate profile, the static stiffness can be made almost constant over a wide load range, and to remain positive at the closure load. Extensive measurements performed with convex and concave plates agree with theory to within the experimental error throughout and demonstrate the practical feasibility of using curved plates.

  19. Instability thresholds for flexible rotors in hydrodynamic bearings

    Science.gov (United States)

    Allaire, P. E.; Flack, R. D.

    1980-01-01

    Two types of fixed pad hydrodynamic bearings (multilobe and pressure dam) were considered. Optimum and nonoptimum geometric configurations were tested. The optimum geometric configurations were determined by using a theoretical analysis and then the bearings were constructed for a flexible rotor test rig. It was found that optimizing bearings using this technique produces a 100% or greater increase in rotor stability. It is shown that this increase in rotor stability is carried out in the absence of certain types of instability mechanisms such as aerodynamic crosscoupling. However, the increase in rotor stability should greatly improve rotating machinery performance in the presence of such forces as well.

  20. The Influence of Time on Bearing Capacity of Driven Piles

    DEFF Research Database (Denmark)

    Jensen, J. Lysebjerg; Augustesen, A.; Sørensen, Carsten S.

    2004-01-01

    In Danish engineering practice, one of the ways to determine the ultimate bearing capacity of an axially loaded pile is by means of geostatic formulas. In the equation describing the contribution from the shaft friction to the total bearing capacity for piles located entirely or partly in clay......, a regeneration factor appears. The regeneration factor accounts for effects of dissipation of pore pressure due to pile driving and true time effects such as ageing on the ultimate bearing capacity. Normally the factor is 0.4 but in this paper, the influence of the undrained shear strength and time...