WorldWideScience

Sample records for expanded fastener holes

  1. Quick connect fastener

    Science.gov (United States)

    Weddendorf, Bruce

    1994-01-01

    A quick connect fastener and method of use is presented wherein the quick connect fastener is suitable for replacing available bolts and screws, the quick connect fastener being capable of installation by simply pushing a threaded portion of the connector into a member receptacle hole, the inventive apparatus being comprised of an externally threaded fastener having a threaded portion slidably mounted upon a stud or bolt shaft, wherein the externally threaded fastener portion is expandable by a preloaded spring member. The fastener, upon contact with the member receptacle hole, has the capacity of presenting cylindrical threads of a reduced diameter for insertion purposes and once inserted into the receiving threads of the receptacle member hole, are expandable for engagement of the receptacle hole threads forming a quick connect of the fastener and the member to be fastened, the quick connect fastener can be further secured by rotation after insertion, even to the point of locking engagement, the quick connect fastener being disengagable only by reverse rotation of the mated thread engagement.

  2. Discrimination between Fatigue Cracking and Mechanical Damage in Aircraft Fastener Holes by Eddy-Current Phase Rotation

    Science.gov (United States)

    2016-08-01

    Science and Technology Organisation) EDM Electrodischarge machining FSH Full Screen Height on an eddy - current instrument IVD Ion Vapour...electromagnetic skin depth δ is 0.15 mm in the fastener holes3. 4.1 Bolt Hole Eddy Current Inspection Procedure 4.1.1 Calibration on Machined ...UNCLASSIFIED UNCLASSIFIED Discrimination between Fatigue Cracking and Mechanical Damage in Aircraft Fastener Holes by Eddy - Current Phase

  3. A structural health monitoring fastener for tracking fatigue crack growth in bolted metallic joints

    Science.gov (United States)

    Rakow, Alexi Schroder

    Fatigue cracks initiating at fastener hole locations in metallic components are among the most common form of airframe damage. The fastener hole site has been surveyed as the second leading initiation site for fatigue related accidents of fixed wing aircraft. Current methods for inspecting airframes for these cracks are manual, whereby inspectors rely on non-destructive inspection equipment or hand-held probes to scan over areas of a structure. Use of this equipment often demands disassembly of the vehicle to search appropriate hole locations for cracks, which elevates the complexity and cost of these maintenance inspections. Improved reliability, safety, and reduced cost of such maintenance can be realized by the permanent integration of sensors with a structure to detect this damage. Such an integrated system of sensors would form a structural health monitoring (SHM) system. In this study, an Additive, Interleaved, Multi-layer Electromagnetic (AIME) sensor was developed and integrated with the shank of a fastener to form a SHM Fastener, a new SHM technology targeted at detection of fastener hole cracks. The major advantages of the SHM Fastener are its installation, which does not require joint layer disassembly, its capability to detect inner layer cracks, and its capability to operate in a continuous autonomous mode. Two methods for fabricating the proposed SHM Fastener were studied. The first option consisted of a thin flexible printed circuit film that was bonded around a thin metallic sleeve placed around the fastener shank. The second option consisted of coating sensor materials directly to the shank of a part in an effort to increase the durability of the sensor under severe loading conditions. Both analytical and numerical models were developed to characterize the capability of the sensors and provide a design tool for the sensor layout. A diagnostic technique for crack growth monitoring was developed to complete the SHM system, which consists of the

  4. Black holes in an expanding universe.

    Science.gov (United States)

    Gibbons, Gary W; Maeda, Kei-ichi

    2010-04-02

    An exact solution representing black holes in an expanding universe is found. The black holes are maximally charged and the universe is expanding with arbitrary equation of state (P = w rho with -1 < or = for all w < or = 1). It is an exact solution of the Einstein-scalar-Maxwell system, in which we have two Maxwell-type U(1) fields coupled to the scalar field. The potential of the scalar field is an exponential. We find a regular horizon, which depends on one parameter [the ratio of the energy density of U(1) fields to that of the scalar field]. The horizon is static because of the balance on the horizon between gravitational attractive force and U(1) repulsive force acting on the scalar field. We also calculate the black hole temperature.

  5. Dynamical 3-Space: Black Holes in an Expanding Universe

    Directory of Open Access Journals (Sweden)

    Rothall D. P.

    2013-10-01

    Full Text Available Black holes are usually studied without including effects of the expanding universe. However in some recent studies black holes have been embedded in an expanding universe, in order to determine the interplay, if any, of these two dynamical processes. Dynamical 3-space theory contains time independent solutions for black holes, which are spatial in-flows, and separately the time dependent Hubble expansion. This theory has explained numerous puzzles in observational astrophysics and contains 3 constants; G, - which from experimental data turns out to be the fine structure constant, and - which is a small but nonzero distance, possibly a Planck-type length. The Hubble expansion in the dynamical 3-space theory cannot be “switched o”, forcing the study, first, of isolated black holes coexisting with the expanding universe. It is shown that a time dependent black hole and expanding universe solution exists. The nature and implications of these solutions are discussed as they evolve over time. A dynamical network of black holes and induced linking cosmic filaments forming bubble structures is discussed, as a consequence of dynamical 3-space undergoing a dynamical breakdown of homogeneity and isotropy, even in the absence of baryonic matter.

  6. Scalar-Tensor Black Holes Embedded in an Expanding Universe

    Science.gov (United States)

    Tretyakova, Daria; Latosh, Boris

    2018-02-01

    In this review we focus our attention on scalar-tensor gravity models and their empirical verification in terms of black hole and wormhole physics. We focus on a black hole, embedded in an expanding universe, describing both cosmological and astrophysical scales. We show that in scalar-tensor gravity it is quite common that the local geometry is isolated from the cosmological expansion, so that it does not backreact on the black hole metric. We try to extract common features of scalar-tensor black holes in an expanding universe and point out the gaps that must be filled.

  7. Scalar-Tensor Black Holes Embedded in an Expanding Universe

    Directory of Open Access Journals (Sweden)

    Daria Tretyakova

    2018-02-01

    Full Text Available In this review, we focus our attention on scalar-tensor gravity models and their empirical verification in terms of black hole and wormhole physics. We focus on black holes, embedded in an expanding universe, describing both cosmological and astrophysical scales. We show that in scalar-tensor gravity it is quite common that the local geometry is isolated from the cosmological expansion, so that it does not backreact on the black hole metric. We try to extract common features of scalar-tensor black holes in an expanding universe and point out the issues that are not fully investigated.

  8. Instantaneous mechanical fastening of quasi-isotropic CFRP laminates by a self-piercing rivet

    OpenAIRE

    上田, 政人; 三宅, 崇太郎; 長谷川, 寛幸; 平野, 義鎭; Ueda, Masahito; Miyake, Sotaro; Hasegawa, Hiroyuki; Hirano, Yoshiyasu

    2012-01-01

    A modified self-piercing rivet (SPR) has been proposed to mechanically fasten CFRP laminates. The modified SPR consists of a rivet body and two flat washers. The two flat washers were used to suppress delamination in the CFRP laminates at the point of piercing. The advantages of the modified SPR for fastening CFRP laminates are instantaneous process time and low cost. Any pretreatments such as surface treatments or hole drilling are not required. In this study, the viability of the modified S...

  9. The Automated Threaded Fastening Based on On-line Identification

    Directory of Open Access Journals (Sweden)

    Nicolas Ivan Giannoccaro

    2008-11-01

    Full Text Available The principle of the thread fastenings have been known and used for decades with the purpose of joining one component to another. Threaded fastenings are popular because they permit easy disassembly for maintenance, repair, relocation and recycling. Screw insertions are typically carried out manually. It is a difficult problem to automat. As a result there is very little published research on automating threaded fastenings, and most research on automated assembly focus on the peg-in-hole assembly problem. This paper investigates the problem of automated monitoring of the screw insertion process. The monitoring problem deals with predicting integrity of a threaded insertion, based on the torque vs. insertion depth curve generated during the insertions. The authors have developed an analytical model to predict the torque signature signals during self-tapping screw insertions. However, the model requires parameters on the screw dimensions and plate material properties are difficult to measure. This paper presents a study on on-line identification during screw fastenings. An identification methodology for two unknown parameter estimation during a self-tapping screw insertion process is presented. It is shown that friction and screw properties required by the model can be reliably estimated on-line. Experimental results are presented to validate the identification procedure.

  10. Titanium fasteners. [for aircraft industry

    Science.gov (United States)

    Phillips, J. L.

    1972-01-01

    Titanium fasteners are used in large quantities throughout the aircraft industry. Most of this usage is in aluminum structure; where titanium structure exists, titanium fasteners are logically used as well. Titanium fasteners offer potential weight savings to the designer at a cost of approximately $30 per pound of weight saved. Proper and least cost usage must take into consideration type of fastener per application, galvanic couples and installation characteristics of protective coatings, cosmetic appearance, paint adhesion, installation forces and methods available and fatigue performance required.

  11. Expanding plasmas from anti de Sitter black holes

    Energy Technology Data Exchange (ETDEWEB)

    Camilo, Giancarlo [Instituto de Fisica, Universidade de Sao Paulo, Departamento de Fisica Matematica, Sao Paulo (Brazil)

    2016-12-15

    We introduce a new foliation of AdS{sub 5} black holes such that the conformal boundary takes the form of a 4-dimensional FLRW spacetime with scale factor a(t). The foliation employs Eddington-Finkelstein-like coordinates and is applicable to a large class of AdS black holes, supported by matter fields or not, considerably extending previous efforts in the literature. We argue that the holographic dual picture of a CFT plasma on a FLRW background provides an interesting prototype to study the nonequilibrium dynamics of expanding plasmas and use holographic renormalization to extract the renormalized energy-momentum tensor of the dual plasma. We illustrate the procedure for three black holes of interest, namely AdS-Schwarzschild, AdS-Gauss-Bonnet, and AdS-Reissner-Nordstroem. For the latter, as a by-product, we show that the nonequilibrium dynamics of a CFT plasma subject to a quench in the chemical potential (i.e., a time-dependent chemical potential) resembles a cosmological evolution with the scale factor a(t) being inversely related to the quench profile μ(t). (orig.)

  12. Expanding plasmas from anti de Sitter black holes

    International Nuclear Information System (INIS)

    Camilo, Giancarlo

    2016-01-01

    We introduce a new foliation of AdS_5 black holes such that the conformal boundary takes the form of a 4-dimensional FLRW spacetime with scale factor a(t). The foliation employs Eddington-Finkelstein-like coordinates and is applicable to a large class of AdS black holes, supported by matter fields or not, considerably extending previous efforts in the literature. We argue that the holographic dual picture of a CFT plasma on a FLRW background provides an interesting prototype to study the nonequilibrium dynamics of expanding plasmas and use holographic renormalization to extract the renormalized energy-momentum tensor of the dual plasma. We illustrate the procedure for three black holes of interest, namely AdS-Schwarzschild, AdS-Gauss-Bonnet, and AdS-Reissner-Nordstroem. For the latter, as a by-product, we show that the nonequilibrium dynamics of a CFT plasma subject to a quench in the chemical potential (i.e., a time-dependent chemical potential) resembles a cosmological evolution with the scale factor a(t) being inversely related to the quench profile μ(t). (orig.)

  13. Welding, Bonding and Fastening, 1984

    Science.gov (United States)

    Buckley, J. D. (Editor); Stein, B. A. (Editor)

    1985-01-01

    A compilation of papers presented in a joint NASA, American Society for Metals, The George Washington University, American Welding Soceity, and Society of Manufacturing Engineers conference on Welding, Bonding, and Fastening at Langley Research Center, Hampton, VA, on October 23 to 25, 1984 is given. Papers were presented on technology developed in current research programs relevant to welding, bonding, and fastening of structural materials required in fabricating structures and mechanical systems used in the aerospace, hydrospace, and automotive industries. Topics covered in the conference included equipment, hardware and materials used when welding, brazing, and soldering, mechanical fastening, explosive welding, use of unique selected joining techniques, adhesives bonding, and nondestructive evaluation. A concept of the factory of the future was presented, followed by advanced welding techniques, automated equipment for welding, welding in a cryogenic atmosphere, blind fastening, stress corrosion resistant fasteners, fastening equipment, explosive welding of different configurations and materials, solid-state bonding, electron beam welding, new adhesives, effects of cryogenics on adhesives, and new techniques and equipment for adhesive bonding.

  14. Probability of detection for bolt hole eddy current in extracted from service aircraft wing structures

    Science.gov (United States)

    Underhill, P. R.; Uemura, C.; Krause, T. W.

    2018-04-01

    Fatigue cracks are prone to develop around fasteners found in multi-layer aluminum structures on aging aircraft. Bolt hole eddy current (BHEC) is used for detection of cracks from within bolt holes after fastener removal. In support of qualification towards a target a90/95 (detect 90% of cracks of depth a, 95% of the time) of 0.76 mm (0.030"), a preliminary probability of detection (POD) study was performed to identify those parameters whose variation may keep a bolt hole inspection from attaining its goal. Parameters that were examined included variability in lift-off due to probe type, out-of-round holes, holes with diameters too large to permit surface-contact of the probe and mechanical damage to the holes, including burrs. The study examined the POD for BHEC of corner cracks in unfinished fastener holes extracted from service material. 68 EDM notches were introduced into two specimens of a horizontal stabilizer from a CC-130 Hercules aircraft. The fastener holes were inspected in the unfinished state, simulating potential inspection conditions, by 7 certified inspectors using a manual BHEC setup with an impedance plane display and also with one inspection conducted utilizing a BHEC automated C-Scan apparatus. While the standard detection limit of 1.27 mm (0.050") was achieved, given the a90/95 of 0.97 mm (0.039"), the target 0.76 mm (0.030") was not achieved. The work highlighted a number of areas where there was insufficient information to complete the qualification. Consequently, a number of recommendations were made. These included; development of a specification for minimum probe requirements; criteria for condition of the hole to be inspected, including out-of-roundness and presence of corrosion pits; statement of range of hole sizes; inspection frequency and data display for analysis.

  15. RFID Torque Sensing Tag System for Fasteners

    Science.gov (United States)

    Fink, Patrick W. (Inventor); Lin, Gregory Y. (Inventor); Ngo, Phong H. (Inventor); Kennedy, Timothy F. (Inventor)

    2016-01-01

    The present invention provides an RFID-based torque sensor that can be used to quickly monitor off the shelf fasteners including fasteners that are used in expensive satellites or other uses where fastener failure can be very costly. In one embodiment, an antenna, RFID ring and spring comprise a sensor tag that can be interrogated with an interrogation signal produced by an interrogator device. When sufficient torque is applied to the fastener, an RFID circuit is connected, and produces a radio frequency (RF) signal that can be read by the interrogator. In one embodiment, the RFID circuit does not transmit when the spring member is not compressed, thereby indicating insufficient tensioning of the fastener. The present invention offers the ability to remotely, quickly, and inexpensively verify that any number of fasteners are torqued properly upon initial installation. Where applicable, the present invention allows low cost monitoring over the life of the fastener.

  16. Physics of Rotating and Expanding Black Hole Universe

    Directory of Open Access Journals (Sweden)

    Seshavatharam U. V. S.

    2010-04-01

    Full Text Available Throughout its journey universe follows strong gravity. By unifying general theory of relativity and quantum mechanics a simple derivation is given for rotating black hole's temperature. It is shown that when the rotation speed approaches light speed temperature approaches Hawking's black hole temperature. Applying this idea to the cosmic black hole it is noticed that there is "no cosmic temperature" if there is "no cosmic rotation". Starting from the Planck scale it is assumed that universe is a rotating and expanding black hole. Another key assumption is that at any time cosmic black hole rotates with light speed. For this cosmic sphere as a whole while in light speed rotation "rate of decrease" in temperature or "rate of increase" in cosmic red shift is a measure of "rate of cosmic expansion". Since 1992, measured CMBR data indicates that, present CMB is same in all directions equal to $2.726^circ$ K, smooth to 1 part in 100,000 and there is no continuous decrease! This directly indicates that, at present rate of decrease in temperature is practically zero and rate of expansion is practically zero. Universe is isotropic and hence static and is rotating as a rigid sphere with light speed. At present galaxies are revolving with speeds proportional to their distances from the cosmic axis of rotation. If present CMBR temperature is $2.726^circ$ K, present value of obtained angular velocity is $2.17 imes 10^{-18}$ rad/sec $cong$ 67 Km/sec$imes$Mpc. Present cosmic mass density and cosmic time are fitted with a $ln (volume ratio$ parameter. Finally it can be suggested that dark matter and dark energy are ad-hoc and misleading concepts.

  17. Physics of Rotating and Expanding Black Hole Universe

    Directory of Open Access Journals (Sweden)

    Seshavatharam U. V. S.

    2010-04-01

    Full Text Available Throughout its journey universe follows strong gravity. By unifying general theory of relativity and quantum mechanics a simple derivation is given for rotating black hole’s temperature. It is shown that when the rotation speed approaches light speed temperature approaches Hawking’s black hole temperature. Applying this idea to the cosmic black hole it is noticed that there is “no cosmic temperature” if there is “no cosmic rotation”. Starting from the Planck scale it is assumed that- universe is a rotating and expanding black hole. Another key assumption is that at any time cosmic black hole rotates with light speed. For this cosmic sphere as a whole while in light speed rotation “rate of decrease” in temperature or “rate of increase” in cosmic red shift is a measure of “rate of cosmic expansion”. Since 1992, measured CMBR data indicates that, present CMB is same in all directions equal to 2 : 726 K ; smooth to 1 part in 100,000 and there is no continuous decrease! This directly indicates that, at present rate of decrease in temperature is practically zero and rate of expansion is practically zero. Universe is isotropic and hence static and is rotating as a rigid sphere with light speed. At present galaxies are revolving with speeds proportional to their distances from the cosmic axis of rotation. If present CMBR temperature is 2 : 726 K, present value of obtained angular velocity is 2 : 17 10 Present cosmic mass density and cosmic time are fitted with a ln ( volume ratio parameter. Finally it can be suggested that dark matter and dark energy are ad-hoc and misleading concepts.

  18. Carbon nanotube plane fastener

    Directory of Open Access Journals (Sweden)

    Kaori Hirahara

    2011-12-01

    Full Text Available We report a feature of carbon nanotubes (CNTs that arises when the surfaces of two vertically-aligned CNT brushes are pressed together. Adhesion between the CNTs creates a plane fastener-like device. Observations from scanning electron microscopy and measurements of adhesion properties indicate a device-dependence on CNT density and shape near the tip region. Among other applications, such fasteners have the potential to attach small components onto micron-sized electronic devices.

  19. Stress-intensity factors for cracks emanating from the loaded fastener hole

    Science.gov (United States)

    Shivakumar, V.; Hsu, Y. C.

    1977-01-01

    Using a series approach and the Muskhelishvili formulation in the two-dimensional theory of elasticity, stress-intensity factors K are derived for problems in which cracks emanate radially from the boundary of an arbitrarily loaded internal circular hole in an infinite plate. Numerical values are obtained for K(I) and K(II) for radial cracks from a hole containing a loose-fitted pin or rivet that is pulled perpendicular to the crack direction in the plane of the plate. The method is a general one for determining K for a set of symmetrically emanating radial cracks for a variety of concentrated or distributed tractions on the circular hole.

  20. Improvements in remote equipment torquing and fastening

    International Nuclear Information System (INIS)

    Garin, J.

    1978-01-01

    Remote torquing and fastening is a requirement of generic interest for application in an environment not readily accessible to man. The developments over the last 30 years in torque-controlled equipment above 200 nm (150 ft/lb) have not been emphasized. The development of specialized subassemblies to torque and fasten equipment in a remotely controlled environment is an integral part of the Advanced Fuel Recycle Program at Oak Ridge National Laboratory. Commercially available subassemblies have been adapted into a system that would provide remote torquing and fastening in the range of 200 to 750 nm (150 to 550 ft/lb). 9 figures

  1. Precision hole punching on composite fiber reinforced polymer panels

    Science.gov (United States)

    Abdullah, A. B.; Zain, M. S. M.; Chan, H. Y.; Samad, Z.

    2017-12-01

    Structural materials, such as composite panels, can only be assembled, and in most cases through the use of fasteners, which are fitted into the drilled holes. However, drilling is costly and time consuming, thus affecting productivity. This research aims to develop an alternative method to drilling. In this paper, the precision of the holes was measured and the effects of the die clearance to the areas around the holes were evaluated. Measurement and evaluation were performed based on the profile of the holes constructed using Alicona IFM, a 3D surface measurement technique. Results showed that punching is a potential alternative to drilling but still requires improvements.

  2. Removal of T-fasteners 2 days after gastrostomy is feasible.

    LENUS (Irish Health Repository)

    Foster, A

    2009-03-01

    T-fastener gastropexy is widely performed as part of gastrostomy insertion. The current literature recommends removal of T-fasteners at 2 weeks. We present a series of patients in whom T-fasteners were removed at 2 days with no major complications. We removed T-fasteners in 109 patients (male-to-female ratio 59:50, age range 18 to 88 years, mean age 62 years) at 2 days after gastrostomy insertion. Indications for gastrostomy included amytrophic lateral sclerosis, cerebrovascular accidents, head and neck carcinoma, multiple sclerosis, and others, including brain tumours and chronic inflammatory demyelinating polyneuropathy. No peritubal leaks or other major complications were seen in the study population. In the study group, 15 minor complications were recorded (14%), including localised infection and pain, both of which resolved on removal of T-fasteners. We conclude that it is feasible and safe to remove T-fasteners at 2 days.

  3. Removal of bound metal fasteners

    Science.gov (United States)

    Kramer, R. F.

    1981-04-01

    This project explored the removal of bound metal fasteners through the use of ultrasonically assisted wrenches. Two wrenches were designed, fabricated and tested. Previous studies had indicated an increase in thread tension for a given torque application under the influence of ultrasonics. Based on this, the loosening of seized and corroded fasteners with the aid of ultrasonics was explored. Experimental data confirmed our prior analysis of the torque-tension relationship under the influence of ultrasonics; however, our progress did not satisfy the requirements necessary to loosen seized studs in a shipyard environment.

  4. Degradation of fastener in reactor internal of PWR

    Energy Technology Data Exchange (ETDEWEB)

    Kim, D. W.; Ryu, W. S.; Jang, J. S.; Kim, S. H.; Kim, W. G.; Chung, M. K.; Han, C. H

    2000-03-01

    Main component degraded in reactor internal structure of PWR is fastener such as bolts, stud, cap screw, and pins. The failure of these components may damage nuclear fuel and limits the operation of nuclear reactor. In foreign reactors operated more than 10 years, an increasing number of incidents of degraded thread fasteners have been reported. The degradation of these components impair the integrity of reactor internal structure and limit the life extension of nuclear power plant. To solve the problem of fastener failure, the incidents of failure and main mechanisms should be investigated. the purpose of this state-of-the -art report is to investigate the failure incidents and mechanisms of fastener in foreign and domestic PWR and make a guide to select a proper materials. There is no intent to describe each event in detail in this report. This report covers the failures of fastener and damage mechanisms reported by the licensees of operating nuclear power plants and the applications of plants constructed after 1964. This information is derived from pertinent licensee event report, reportable occurrence reports, operating reactor event memoranda, failure analysis reports, and other relevant documents. (author)

  5. Development of high temperature fasteners using directionally solidified eutectic alloys

    Science.gov (United States)

    George, F. D.

    1972-01-01

    The suitability of the eutectics for high temperature fasteners was investigated. Material properties were determined as a function of temperature, and included shear parallel and perpendicular to the growth direction and torsion parallel to it. Techniques for fabricating typical fastener shapes included grinding, creep forming, and direct casting. Both lamellar Ni3Al-Ni3Nb and fibrous (Co,Cr,Al)-(Cr,Co)7C3 alloys showed promise as candidate materials for high temperature fastener applications. A brief evaluation of the performance of the best fabricated fastener design was made.

  6. Cylinder head fastening structure for internal combustion engines

    Energy Technology Data Exchange (ETDEWEB)

    Futakuchi, Y.; Oshiro, N.

    1988-01-26

    In a construction for an overhead cam internal combustion engine comprising a cylinder head adapted to be affixed to another component of the engine by at least one fastener having a tool receiving portion for tightening thereof and having a bearing cap affixed to the cylinder head and rotatably journaling the overhead camshaft, the improvement is described comprising the bearing cap having a portion overlying the fastener tool receiving portion, and means defining an access opening passing through the bearing cap and adapted to pass a tool for tightening of the fastener without removal of the bearing cap.

  7. Hydraulic screw fastening devices - design, maintenance, operational experience

    International Nuclear Information System (INIS)

    Lachner.

    1976-01-01

    With hydraulic screw fastening devices, pretension values with a maximum deviation of +-2.5% from the rated value can be achieved. This high degree of pretension accuracy is of considerable importance with regard to the safety factor required for the screw connection between reactor vessel head and reactor vessel. The operating rhythm of a nuclear power station with its refuelling art regular intervals makes further demands on the screw fastening device, in particular in connection with the transport of screws and for nuts. The necessary installations extend the screw fastening device into a combination of a high-pressure hydraulic cylinder system with an electrical or pneumoelectrical driving unit and an electrical control unit. Maintenance work is complicated by the large number of identical, highly stressed structural elements in connection with an unfavourable relation operating time/outage time. The problems have been perpetually reduced by close cooperation between the manufacturers and users of screw fastening devices. (orig./AK) [de

  8. Threaded-fastener experience in nuclear power plants

    International Nuclear Information System (INIS)

    Koo, W.H.

    1983-01-01

    This report identifies 44 incidents of threaded-fastener degradation and failure in nuclear power plants from October 1964 to March 1982. It provides an overview of some of the threaded-fastener problems that have occurred since 1964. Safety implications of these incidents are discussed, and short-term regulatory actions and ongoing long-term regulatory actions are described. Information included in this report represents the current NRC staff understanding of each issue

  9. Development of an anti-loosening fastener and comparing its ...

    Indian Academy of Sciences (India)

    Bikash Panja

    2017-09-08

    Sep 8, 2017 ... MS received 13 November 2013; revised 20 June 2016; accepted 30 April ... However, threaded fasteners may have the problem of loosening under vibrating ..... [7] Junker G H 1969 New criteria for self-loosening of fasteners.

  10. Fastener tightening in a radioactive (hot) cell

    International Nuclear Information System (INIS)

    Kalk, J.J.

    1986-01-01

    Accurate remote tightening of fasteners in a radioactive (Hot) cell can be a very exasperating experience. Viewing can be difficult (in many places) and work sometimes must be done using mirrors and/or cameras. If electro mechanical manipulators are used, the operator has no ''feel,'' which often can result in cross threading, or improper torquing of fasteners. At the Interim Examination and Maintenance (IEM) Cell, where reactor components from the Fast Flux Test Facility (FFTF) are disassembled, these problems are prevalent because three of the IEM Cell walls have no windows. Electric impact wrenches were first proposed and tested for the IEM Cell, but the combined effects of radiation, dry argon atmosphere and poor visibility radically altered the cell tool development philosophy. This change in philosophy is reflected in the development of several simple fastener tightening devices

  11. Fastener tightening in a radioactive (hot) cell

    International Nuclear Information System (INIS)

    Kalk, J.J.

    1987-01-01

    Accurate remote tightening of fasteners in a radioactive (hot) cell can be a very exasperating experience. Viewing can be difficult (in many places) and work sometimes must be done using mirrors and/or cameras. If electro mechanical manipulators are used, the operator has no feel, which often can result in cross threading, or improper torquing of fasteners. At the Interim Examination and Maintenance (IEM) Cell, where reactor components from the Fast Flux Testing Facility (FFTF) are disassembled, these problems are prevalent because three of the IEM Cell walls have no windows. Electric impact wrenches were first proposed and tested for the IEM Cell, but the combined effects of radiation, dry argon atmosphere and poor visibility radically altered the cell tool development philosophy. This change in philosophy is reflected in the development of several simple fastener tightening devices

  12. Theory of timber connections with slender dowel type fasteners

    DEFF Research Database (Denmark)

    Svensson, Staffan; Munch-Andersen, Jørgen

    2018-01-01

    A theory on the lateral load-carrying capacity of timber connections with slender fasteners is presented. The base of the theory is the coupled mechanical phenomena acting in the connection, while the wood and the slender fastener deform and yield prior to failure. The objective is to derive...... a sufficient description of actions and responses which have determining influence on the load-carrying capacity of timber connections with slender fasteners. Model assumptions are discussed and made, but simplifications are left out. Even so, simple mathematical equations describing the lateral capacity......-carrying capacity of the tested connections....

  13. Double fastener-type contamination protective cloth

    International Nuclear Information System (INIS)

    Nomura, Norio.

    1996-01-01

    In the cloth of the present invention, a hood portion covering the entire of a head and a suit portion having an upper half body portion and a lower half body portion connected to the upper half portion for covering from a neck to ankles are made integrated. The suit portion has long sleeves at the upper half body portion, and has strait leg portions at the lower half body portion. Two linear sliding fasteners are disposed from the neck portion on the front surface of the suit portion to the lower edges of both ankle portions. The sliding fasteners have a double structure having a folded portion at the inner side. Slits are formed on the outer side surfaces of each of the ankle portions and openable/closable face fasteners are attached. A rubber is incorporated in the wrist portions at the top ends of the long sleeves to be in close contact with the wrists. An operator can easily put on and off the cloth without withdrawing legs. Accordingly, radioactive contamination can be prevented upon putting on and off the cloth. (I.N.)

  14. Corrosion rates of fasteners in treated wood exposed to 100% relative humidity

    Science.gov (United States)

    Samuel L. Zelinka; Douglas R. Rammer

    2009-01-01

    In the past, gravimetric corrosion data for fasteners exposed to treated wood has been reported as a percent weight loss. Although percent weight loss is a valid measure of corrosion for comparing identical fasteners, it can distort the corrosion performance of fasteners with different geometries and densities. This report reevaluates a key report on the corrosiveness...

  15. A novel method for detecting second harmonic ultrasonic components generated from fastened bolts

    Science.gov (United States)

    Fukuda, Makoto; Imano, Kazuhiko

    2012-09-01

    This study examines the use of ultrasonic second harmonic components in the quality control of bolt-fastened structures. An improved method for detecting the second harmonic components, from a bolt fastened with a nut, using the transmission method is constructed. A hexagon head iron bolt (12-mm diameter and 25-mm long) was used in the experiments. The bolt was fastened using a digital torque wrench. The second harmonic component increased by approximately 20 dB before and after the bolt was fastened. The sources of second harmonic components were contact acoustic nonlinearity in the screw thread interfaces of the bolt-nut and were the plastic deformation in the bolt with fastening bolt. This result was improved by approximately 10 dB compared with previous our method. Consequently, usefulness of the novel method for detecting second harmonic ultrasonic components generated from fastened bolt was confirmed.

  16. Investigation of Fastening Performance of Subminiature Serrated Bolt

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Myung Guen; Jeong, Jin Hwan; Jang, Yeon Hui; Kim, Hee Cheol; Kim, Jong-Bong [Seoul Nat’l Univ. of Science & Tech, Seoul (Korea, Republic of)

    2017-04-15

    As the size of electric products such as mobile phones and smart watches decrease, the bolts used to assemble these products should also be miniaturized. A miniature-sized bolt has to provide sufficient joining torque and anti-releasing torque to keep the components together. We studied a serrated bolt as a candidate for a miniature-sized fastener to increase the anti-releasing torque. In a serrated bolt, a serrated shape is formed on the bottom surface of the bolt head to create an obstacle to releasing. In this study, finite element analyses for the joining and releasing of bolts were carried out, and the anti-releasing performance was predicted. Based on the results of analyses using various numbers of serrations and fastening depths, the effects of the number of serrations and fastening depth on the anti-releasing performance were investigated.

  17. Investigation of Fastening Performance of Subminiature Serrated Bolt

    International Nuclear Information System (INIS)

    Jang, Myung Guen; Jeong, Jin Hwan; Jang, Yeon Hui; Kim, Hee Cheol; Kim, Jong-Bong

    2017-01-01

    As the size of electric products such as mobile phones and smart watches decrease, the bolts used to assemble these products should also be miniaturized. A miniature-sized bolt has to provide sufficient joining torque and anti-releasing torque to keep the components together. We studied a serrated bolt as a candidate for a miniature-sized fastener to increase the anti-releasing torque. In a serrated bolt, a serrated shape is formed on the bottom surface of the bolt head to create an obstacle to releasing. In this study, finite element analyses for the joining and releasing of bolts were carried out, and the anti-releasing performance was predicted. Based on the results of analyses using various numbers of serrations and fastening depths, the effects of the number of serrations and fastening depth on the anti-releasing performance were investigated.

  18. Factors influencing power hand tool fastening accuracy and reaction forces.

    Science.gov (United States)

    Radwin, Robert G; Chourasia, Amrish O; Howery, Robert S; Fronczak, Frank J; Yen, Thomas Y; Subedi, Yashpal; Sesto, Mary E

    2014-06-01

    A laboratory study investigated the relationship between power hand tool and task-related factors affecting threaded fastener torque accuracy and associated handle reaction force. We previously developed a biodynamic model to predict handle reaction forces. We hypothesized that torque accuracy was related to the same factors that affect operator capacity to react against impulsive tool forces, as predicted by the model. The independent variables included tool (pistol grip on a vertical surface, right angle on a horizontal surface), fastener torque rate (hard, soft), horizontal distance (30 cm and 60 cm), and vertical distance (80 cm, 110 cm, and 140 cm). Ten participants (five male and five female) fastened 12 similar bolts for each experimental condition. Average torque error (audited - target torque) was affected by fastener torque rate and operator position. Torque error decreased 33% for soft torque rates, whereas handle forces greatly increased (170%). Torque error also decreased for the far horizontal distance 7% to 14%, when vertical distance was in the middle or high, but handle force decreased slightly 3% to 5%. The evidence suggests that although both tool and task factors affect fastening accuracy, they each influence handle reaction forces differently. We conclude that these differences are attributed to different parameters each factor influences affecting the dynamics of threaded faster tool operation. Fastener torque rate affects the tool dynamics, whereas posture affects the spring-mass-damping biodynamic properties of the human operator. The prediction of handle reaction force using an operator biodynamic model may be useful for codifying complex and unobvious relationships between tool and task factors for minimizing torque error while controlling handle force.

  19. Velcro-like fasteners based on NiTi micro-hook arrays

    International Nuclear Information System (INIS)

    Vokoun, D; Pilch, J; Majtás, D; Šittner, P; Sedlák, P; Frost, M

    2011-01-01

    A recently developed Velcro-like fastener utilizes superelastic deformation of two interlocked NiTi hooks when pulled apart. This work focuses on experimental analysis (evaluation of normal detachment force at different temperatures) and modeling (simulation by a finite element implemented SMA model) of the unhooking process. It is claimed that nonlinear superelastic deformation of NiTi leads to unique properties of the NiTi hook fasteners such as high strength (∼15 000 kg m −2 ), a significant increase of strength with increasing temperature, absorption of impact loads, damping of mechanical vibrations, forceless contact or silent release and better functioning in dirty environments compared to conventional Velcro fasteners

  20. Fastening, coupling and joining technique between diaspora and irredenta

    Science.gov (United States)

    Bauer, C.-O.

    1980-06-01

    The problem of eliminating the present divergence and shattering (diaspora) in the treatment of problems of the fastening, coupling, and joining technique on different technical branches is examined. It is shown that by an appropriate independence the fastening, coupling and joining techniques can recognize and consequently utilize the numerous performance reserves which are concealed by the present organization and action due to the lack of systematically tended works.

  1. Compilation of fastener testing data received in response to NRC Compliance Bulletin 87-02

    International Nuclear Information System (INIS)

    Cwalina, G.C.; Conway, J.T.; Parker, L.B.

    1989-06-01

    On November 6, 1987, the Nuclear Regulatory Commission (NRC) issued Bulletin 87-02, ''Fastener Testing to Determine Conformance With Applicable Material Specifications,'' to all holders of operating licenses or construction permits for nuclear power reactors (licensees). The bulletin was issued so that the NRC staff could gather data to determine whether counterfeit fasteners are a problem in the nuclear power industry. The bulletin requested nuclear power plant owners to determine whether fasteners obtained from suppliers and/or manufacturers for use in their facilities meet the mechanical and chemical specifications stipulated in the procurement documents. The licensees were requested to sample a minimum of 10 safety-related and 10 non-safety-related fasteners (studs, bolts, and/or cap screws) and a sample of typical nuts that would be used with each fastener and to report the testing results to the NRC. The results of this study did not indicate a safety concern relating to the use of mismarked or counterfeit fasteners in the nuclear industry, but they did indicate a nonconformance rate of 8 to 12 percent for fasteners. The NRC staff is considering taking action to improve the effectiveness of receipt inspection and testing programs for all materials at nuclear power plants

  2. Prevailing Torque Locking Feature in Threaded Fasteners Using Anaerobic Adhesive

    Science.gov (United States)

    Hernandez, Alan; Hess, Daniel P.

    2016-01-01

    This paper presents results from tests to assess the use of anaerobic adhesive for providing a prevailing torque locking feature in threaded fasteners. Test procedures are developed and tests are performed on three fastener materials, four anaerobic adhesives, and both unseated assembly conditions. Five to ten samples are tested for each combination. Tests for initial use, reuse without additional adhesive, and reuse with additional adhesive are performed for all samples. A 48-hour cure time was used for all initial use and reuse tests. Test data are presented as removal torque versus removal angle with the specification required prevailing torque range added for performance assessment. Percent specification pass rates for the all combinations of fastener material, adhesive, and assembly condition are tabulated and reveal use of anaerobic adhesive as a prevailing torque locking feature is viable. Although not every possible fastener material and anaerobic adhesive combination provides prevailing torque values within specification, any combination can be assessed using the test procedures presented. Reuse without additional anaerobic adhesive generally provides some prevailing torque, and in some cases within specification. Reuse with additional adhesive often provides comparable removal torque data as in initial use.

  3. Component assembly with shape memory polymer fastener for microrobots

    Science.gov (United States)

    Kim, Ji-Suk; Lee, Dae-Young; Koh, Je-Sung; Jung, Gwang-Pil; Cho, Kyu-Jin

    2014-01-01

    Adhesives are generally used for the assembly of microrobots, whereas bolts, screws, or rivets are used for larger robots. Although adhesives are easy to apply, lightweight, and small, they cannot be used for repeated assembly and disassembly of parts. In this paper, we present a novel microfastener composed of a polyurethane-based shape memory polymer (SMP) that is lightweight and small but that is easily detached for disassembly. This was achieved by using the shape recovery and modulus change of the SMP. A sheet of macromolded SMP was laser machined into an I-beam-shaped rivet, and notches were added to the structure to prevent stress concentration. Pull-off tests showed that, as the notch radius increased, the disengagement strength of the rivet fastener decreased and the reusability increased. Through the elastoplastic model, a single SMP rivet was calculated to have maximum disengagement strength of 150 N cm-2 in the elastic range, depending on the notch radius. The fasteners were applied to a jumping microrobot. The legs and body were assembled with ten fasteners, which showed no permanent deformation after impact during jumping movements. The legs were easily replaced with ones of different stiffness by heating the engaged sites to make the fasteners compliant and detachable. The proposed detachable SMP microfasteners are particularly useful for testing the isolated performance of microrobot components to determine the optimal designs for these components.

  4. Fastener investigation in JET

    Energy Technology Data Exchange (ETDEWEB)

    Bunting, P., E-mail: patrick.bunting@ccfe.ac.uk; Thompson, V.; Riccardo, V.

    2016-11-15

    Highlights: • Experimental work to identify the cause of a bolt seizure inside the JET vessel. • Taguchi method used to reduce tests to 16 while covering 5 parameters. • Experimental work was unable to reproduce bolt seizure. • Thread contamination had little effect on the bolt performance. - Abstract: JET is an experimental fusion reactor consisting of magnetically confined, high temperature plasma inside a large ultra-high vacuum chamber. The inside of the chamber is protected from the hot plasma with tiles made from beryllium, tungsten, carbon composites and other materials bolted to the vessel wall. The study was carried out in response to a JET fastener seizing inside the vacuum vessel. The following study looks at characterising the magnitude of the individual factors affecting the fastener break away torque. This was carried out using a statistical approach, the Taguchi method: isolating the net effect of individual factors present in a series of tests [1](Grove and Davis, 1992). Given the severe environment within the JET vessel due to the combination of heat, ultra-high vacuum and the high contact pressure in bolt threads, the contributions of localised diffusion bonding is assessed in conjunction with various combinations of bolt and insert material.

  5. Fastener Corrosion: A Result of Moisture Problems in the Building Envelope

    Science.gov (United States)

    Samuel L. Zelinka

    2013-01-01

    This paper reviews recent literature on the corrosion of metals embedded in wood and highlights the link be-tween moisture accumulation in wood and fastener cor-rosion. Mechanisms of fastener corrosion are described including dependence upon wood moisture content. These fundamental concepts are applied to practical examples by explaining how hygrothermal models can be...

  6. Numerical Analysis of Thermal Stresses around Fasteners in Composite Metal Foils

    Science.gov (United States)

    Nammi, S. K.; Butt, J.; –L Mauricette, J.; Shirvani, H.

    2017-12-01

    The process of composite metal foil manufacturing (CMFM) has reduced a number of limitations associated with commercial additive manufacturing (AM) methods. The existing metal AM machines are restricted by their build envelope and there is a growing market for the manufacture of large parts using AM. These parts are subsequently manufactured in fragments and are fastened together. This paper analyses the thermal stresses around cylindrical fasteners for three layered metal composite parts consisting of aluminium foil, brazing paste and copper foil layers. The investigation aims to examine the mechanical integrity of the metallurgically bonded aluminium/copper foils of 100 micron thickness manufactured in a disc shape. A cylindrical fastener set at an elevated temperature of 100 °C is fitted in the middle of the disc which results in a steady-state thermal distribution. Radial and shear stresses are computed using finite element method which shows that non-zero shear stresses developed by the copper layer inhibit the axial slippage of the fastener and thereby establishing the suitability of rivet joints for CMFM parts.

  7. Component assembly with shape memory polymer fastener for microrobots

    International Nuclear Information System (INIS)

    Kim, Ji-Suk; Lee, Dae-Young; Koh, Je-Sung; Jung, Gwang-Pil; Cho, Kyu-Jin

    2014-01-01

    Adhesives are generally used for the assembly of microrobots, whereas bolts, screws, or rivets are used for larger robots. Although adhesives are easy to apply, lightweight, and small, they cannot be used for repeated assembly and disassembly of parts. In this paper, we present a novel microfastener composed of a polyurethane-based shape memory polymer (SMP) that is lightweight and small but that is easily detached for disassembly. This was achieved by using the shape recovery and modulus change of the SMP. A sheet of macromolded SMP was laser machined into an I-beam-shaped rivet, and notches were added to the structure to prevent stress concentration. Pull-off tests showed that, as the notch radius increased, the disengagement strength of the rivet fastener decreased and the reusability increased. Through the elastoplastic model, a single SMP rivet was calculated to have maximum disengagement strength of 150 N cm −2 in the elastic range, depending on the notch radius. The fasteners were applied to a jumping microrobot. The legs and body were assembled with ten fasteners, which showed no permanent deformation after impact during jumping movements. The legs were easily replaced with ones of different stiffness by heating the engaged sites to make the fasteners compliant and detachable. The proposed detachable SMP microfasteners are particularly useful for testing the isolated performance of microrobot components to determine the optimal designs for these components. (paper)

  8. Solid expandable systems put deepwater targets within reach

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Roca, Eduardo [Enventure Global Technology L.L.C., Houston, TX (United States). Latin America; Fristch, Jerry [Enventure Global Technology L.L.C., Houston, TX (United States)

    2008-07-01

    Enabling technologies that take drilling operations to deeper objectives have made a significant impact on the practicality of many projects, especially deep water offshore targets. Increasing vertical depth and lateral reach requires adequate hole size to attain the desired objectives of the well bore. Solid expandable technology can maintain and retain hole size to address both the physical limitations and the economic feasibility of deep water operations. With each and every casing point, the potential for adequate hole size at total depth (TD) decreases. Solid expandable open hole liners and single-diameter systems reduce and eliminate, respectively, the well bore tapering that dictates hole size at TD and subsequent completion size. Successful mitigation of this tapering, whether through the entire well bore or through select zones, enables operators to gain access to previously unreachable reserves. Solid expandable systems have proven to be reliable and effective with over 1,000 installations in a myriad of conditions and environments worldwide. To date, over 115 of those applications have been in deep water environments. The current operating envelope for solid expandable systems include the deepest installation at {approx}28,750 ft (8,763 m) and the longest at 6,867 ft (2,083 m) in water depth over 3,150 ft (960 m). This record-length application consisted of an open hole liner installed and expanded in a single run. This paper will discuss the effectiveness of solid expandable systems in deep water operations and how the technology brings value to offshore projects especially when planned into the initial design. Case histories will be used to further illustrate the features, advantages, and benefits of expandable technology. In addition, this paper will examine the state of the solid expandable technology and its continuing evolution to provide even more drilling solutions. (author)

  9. Reversible fastener clamp load monitor with continuous visual or remote readout

    Science.gov (United States)

    Hodge, Malcolm H.; Kausel, Theodore C., Jr.; Begley, Matthew R.

    1998-03-01

    SIMS has developed a simple means for detecting and monitoring both absolute and relative clamp load, or bolt tension, in fastener systems. More than twenty-five percent of automotive failures are known to be due to undetected loss of fastener clamp load. While the equivalent aerospace maintenance statistics are not known, the average automobile has 3,500 fasteners while a Boeing 747 has closer to one million. It is therefore anticipated that the new SensaBolt clamp load tracking system could find wide applications in the aerospace arena. We describe a visually-evident and retrofitted clamp load monitoring design which is based on the differential joint substrate compression at, and immediately adjacent to, the fastener location. This intrinsically-accurate indicator does not necessarily require alteration in either the bolt or nut geometries, thereby facilitating product introduction and retrofit in aging aircraft applications. In addition, SensaBolt's sole reliance on substrate compression renders it more accurate then torque wrench or turn-of-nut techniques. Readout may be accomplished by any of three principal methods: for those applications with ease of access to the sensor, loss of tension can be determined by direct visual inspection. Application of a standard wrench can then be made to restore the fastener's proper tightness, per the SensaBolt indicators. In those instances where line-of-sight is unimpeded and more formal inspection is desired, the SensaBolt may be interrogated by a laser scanner bar code reader. Finally, SensaBolt may be addressed by the SIMS fiber optic harness for those instances where full-time remote interrogation is desired.

  10. Were all white holes in the early Universe converted into black holes?

    International Nuclear Information System (INIS)

    Dey, T.K.; Banerji, S.

    1991-01-01

    It has been claimed that in the early Universe any white hole must have been converted to a black hole. But taking the simple case of an expanding homogeneous dust sphere colliding with a homogeneous spherical shell of dust which are mutually noninteracting, we find that the mean motion of the combined system will be expanding or contracting to a distant observer according as the combined radius at the instant of collision is less than or greater than the Schwarzschild radius

  11. Review of Bolt Preload and Torque for Assembling Threaded Fasteners in Nuclear Power Plant

    International Nuclear Information System (INIS)

    Lee, Yong-Sung; Lee, Jae-Gon; Kang, Yong-Chul; Shin, Ki-Jong

    2007-01-01

    There are numerous threaded fasteners such as bolts, studs, nuts, cap screws and anchor bolts used in nuclear power plants(NPPs). The major applications of threaded fasteners are reactor coolant pressure boundary components, their internals and supports. With the increase of commercial operation period of NPPs, the incidents caused by degradation of threaded fasteners have been occurred. A large number of reported incidents are involved in the pressure boundary and major component supports. The degradation and failure of threaded fasteners is affected by material, preload and torque value at assembly, bolting practice, etc. It is very important to select appropriate bolt preload and decide assembly torque value because torque control using a torque wrench is the most common method in a power plant to assemble a bolted flange connection. Many researches have been studied to define the proper bolt preload and desired torque value with regard to the integrity of bolted connections including pressure boundary joints by EPRI and other plant industry. But in domestic NPPs, considerably few works are done on the bolted joint assembly in spite of increasing events related with threaded faster. Therefore we investigated degradation or failure of the threaded fasteners used in NPPs, also examined the codes, standards and technical trends concerning bolt preload and assembly torque in NPPs. It is the purpose of this study to provide proper technical information for assuring integrity of the threaded fasteners

  12. Alloy and composition dependence of hydrogen embrittlement susceptibility in high-strength steel fasteners

    Science.gov (United States)

    Brahimi, S. V.; Yue, S.; Sriraman, K. R.

    2017-06-01

    High-strength steel fasteners characterized by tensile strengths above 1100 MPa are often used in critical applications where a failure can have catastrophic consequences. Preventing hydrogen embrittlement (HE) failure is a fundamental concern implicating the entire fastener supply chain. Research is typically conducted under idealized conditions that cannot be translated into know-how prescribed in fastener industry standards and practices. Additionally, inconsistencies and even contradictions in fastener industry standards have led to much confusion and many preventable or misdiagnosed fastener failures. HE susceptibility is a function of the material condition, which is comprehensively described by the metallurgical and mechanical properties. Material strength has a first-order effect on HE susceptibility, which increases significantly above 1200 MPa and is characterized by a ductile-brittle transition. For a given concentration of hydrogen and at equal strength, the critical strength above which the ductile-brittle transition begins can vary due to second-order effects of chemistry, tempering temperature and sub-microstructure. Additionally, non-homogeneity of the metallurgical structure resulting from poorly controlled heat treatment, impurities and non-metallic inclusions can increase HE susceptibility of steel in ways that are measurable but unpredictable. Below 1200 MPa, non-conforming quality is often the root cause of real-life failures. This article is part of the themed issue 'The challenges of hydrogen and metals'.

  13. Resolved, expanding jets in the Galactic black hole candidate XTE J1908+094

    Science.gov (United States)

    Rushton, A. P.; Miller-Jones, J. C. A.; Curran, P. A.; Sivakoff, G. R.; Rupen, M. P.; Paragi, Z.; Spencer, R. E.; Yang, J.; Altamirano, D.; Belloni, T.; Fender, R. P.; Krimm, H. A.; Maitra, D.; Migliari, S.; Russell, D. M.; Russell, T. D.; Soria, R.; Tudose, V.

    2017-07-01

    Black hole X-ray binaries undergo occasional outbursts caused by changing inner accretion flows. Here we report high angular resolution radio observations of the 2013 outburst of the black hole candidate X-ray binary system XTE J1908+094, using data from the Very Long Baseline Array and European VLBI Network. We show that following a hard-to-soft state transition, we detect moving jet knots that appear asymmetric in morphology and brightness, and expand to become laterally resolved as they move away from the core, along an axis aligned approximately -11° east of north. We initially see only the southern component, whose evolution gives rise to a 15-mJy radio flare and generates the observed radio polarization. This fades and becomes resolved out after 4 days, after which a second component appears to the north, moving in the opposite direction. From the timing of the appearance of the knots relative to the X-ray state transition, a 90° swing of the inferred magnetic field orientation, the asymmetric appearance of the knots, their complex and evolving morphology, and their low speeds, we interpret the knots as working surfaces where the jets impact the surrounding medium. This would imply a substantially denser environment surrounding XTE J1908+094 than has been inferred to exist around the microquasar sources GRS 1915+105 and GRO J1655-40.

  14. Automation of calculation of fastening of non-standard freights on sea vessels

    Directory of Open Access Journals (Sweden)

    Андрій Валерійович Пархотько

    2015-11-01

    Full Text Available Correct positioning and fastening of freights are important safety conditions of navigation. Unreliable positioning and fastening of freights results in shipwreck and is the reason for injuries and losses of human lives both in the sea and during loading and unloading. To solve the above-mentioned problems, the International Maritime Organization publishes manuals in the form of either the Assembly resolutions, or the circulars approved by Maritime Safety Committee. The correct definition of necessary quantity of lashings and their positioning has the greatest impact on safe fastening of freights. The sea being rough, the vessel is accelerated both in longitudinal, and vertical and prevailing cross directions. The forces created by these accelerations generate the majority of the problems in fastening. The order of calculations of the force moments and forces acting upon the freights being shipped by sea vessels has been shown in the article. To know the proper number of lashings the calculations of the forces acting upon the freights being shipped as compared with the forces holding the freights and taking into account the strength, the number and the fastening angle of the lashings must be made. Оption of realization of algorithm of calculation with use of the а computer program to make these calculations has been offered. Some recommendations so that the program could be used by the management of the vessel, the surveyor companies and technologists of the port have been given as well as an example of such a calculation

  15. Three-Dimensional Heat Transfer Analysis of Metal Fasteners in Roofing Assemblies

    Directory of Open Access Journals (Sweden)

    Manan Singh

    2016-11-01

    Full Text Available Heat transfer analysis was performed on typical roofing assemblies using HEAT3, a three-dimensional heat transfer analysis software. The difference in heat transferred through the roofing assemblies considered is compared between two cases—without any steel fasteners and with steel fasteners. In the latter case, the metal roofing fasteners were arranged as per Factor Mutual Global (FMG approvals, in the field, perimeter, and corner zones of the roof. The temperature conditions used for the analysis represented summer and winter conditions for three separate Climate Zones (CZ namely Climate Zone 2 or CZ2 represented by Orlando, FL; CZ3 represented by Atlanta, GA; and CZ6 zone represented by St. Paul, MN. In all the climatic conditions, higher energy transfer was observed with increase in the number of metal fasteners attributed to high thermal conductivity of metals as compared to the insulation and other materials used in the roofing assembly. This difference in heat loss was also quantified in the form of percentage change in the overall or effective insulation of the roofing assembly for better understanding of the practical aspects. Besides, a comparison of 2D heat transfer analysis (using THERM software and 3D analysis using HEAT3 is also discussed proving the relevance of 3D over 2D heat transfer analysis.

  16. Effects of long-term exposure on LDEF fastener assemblies

    Science.gov (United States)

    Spear, Steve; Dursch, Harry

    1992-09-01

    This presentation summarizes the Systems Special Investigations Group (SIG) findings from testing and analysis of fastener assemblies used on the Long Duration Exposure Facility (LDEF) structure, the tray mounting clamps, and by the various experimenters. The LDEF deintegration team and several experimenters noted severe fastener damage and hardware removal difficulties during post-flight activities. The System SIG has investigated all reported instances, and in all cases examined to date, the difficulties were attributed to galling during installation or post-flight removal. To date, no evidence of coldwelding was found. Correct selection of materials and lubricants as well as proper mechanical procedures is essential to ensure successful on-orbit or post-flight installation and removal of hardware.

  17. Tempering of martensitic steel for fasteners: Effects of micro-alloying on microstructure and mechanical property evolution

    OpenAIRE

    Öhlund, C.E.I.C.

    2015-01-01

    The research presented in this thesis aims to deepen our understanding of the effect of micro-alloying on the microstructure and mechanical property evolution during tempering of martensitic steel for fasteners. The ongoing trend of engine down-sizing has led to the need for stronger and more temperature resistant fasteners than currently available according to international standards. A new martensitic fastener steel called KNDS4 has been developed, that combines higher strength with improve...

  18. Torque Tension Testing of Fasteners used for NASA Flight Hardware Applications

    Science.gov (United States)

    Hemminger, Edgar G.; Posey, Alan J.; Dube, Michael J.

    2014-01-01

    The effect of various lubricants and other compounds on fastener torque-tension relationships is evaluated. Testing was performed using a unique test apparatus developed by Posey at the NASA Goddard Space Flight Center. A description of the test methodology, including associated data collection and analysis will be presented. Test results for 300 series CRES and A286 heat resistant fasteners, torqued into various types of inserts will be presented. The primary objective of this testing was to obtain torque-tension data for use on NASA flight projects.

  19. Mounting Systems for Structural Members, Fastening Assemblies Thereof, and Vibration Isolation Systems Including the Same

    Science.gov (United States)

    Young, Ken (Inventor); Hindle, Timothy (Inventor); Barber, Tim Daniel (Inventor)

    2016-01-01

    Mounting systems for structural members, fastening assemblies thereof, and vibration isolation systems including the same are provided. Mounting systems comprise a pair of mounting brackets, each clamped against a fastening assembly forming a mounting assembly. Fastening assemblies comprise a spherical rod end comprising a spherical member having a through opening and an integrally threaded shaft, first and second seating members on opposite sides of the spherical member and each having a through opening that is substantially coaxial with the spherical member through opening, and a partially threaded fastener that threadably engages each mounting bracket forming the mounting assembly. Structural members have axial end portions, each releasably coupled to a mounting bracket by the integrally threaded shaft. Axial end portions are threaded in opposite directions for permitting structural member rotation to adjust a length thereof to a substantially zero strain position. Structural members may be vibration isolator struts in vibration isolation systems.

  20. Primary black holes

    International Nuclear Information System (INIS)

    Novikov, I.; Polnarev, A.

    1981-01-01

    Proves are searched for of the formation of the so-called primary black holes at the very origin of the universe. The black holes would weigh less than 10 13 kg. The formation of a primary black hole is conditional on strong fluctuations of the gravitational field corresponding roughly to a half of the fluctuation maximally permissible by the general relativity theory. Only big fluctuations of the gravitational field can overcome the forces of the hot gas pressure and compress the originally expanding matter into a black hole. Low-mass black holes have a temperature exceeding that of the black holes formed from stars. A quantum process of particle formation, the so-called evaporation takes place in the strong gravitational field of a black hole. The lower the mass of the black hole, the shorter the evaporation time. The analyses of processes taking place during the evaporation of low-mass primary black holes show that only a very small proportion of the total mass of the matter in the universe could turn into primary black holes. (M.D.)

  1. Finite element analysis of adanced composite structures containing mechanically fastened joints

    International Nuclear Information System (INIS)

    Baumann, E.

    1982-01-01

    Although the usual engineering practice is to ignore joint effects in finite element models of overall structures, there are times when the inclusion of fastener effects in a model is necessary for accurate analysis. This paper describes some simple but accurate methods for accommodating this modeling requirement. The approach involves correlation of test results from a few composite mechanically fastened joints with finite element analyses of joints. It is assumed that if the fastener actions in the test articles can be properly predicted by simple finite element techniques, then these same techniques can be applied to large overall structure models. During the course of this test-analysis effort it was determined that it is possible to obtain correct results for overall structure-joint analyses by using simple modeling concepts provided special care is employed. Also, some emphasis is given in this paper to the importance of properly reducing test data in order to obtain meaningful correlations with finite element analysis. Finally, for those interested, the appendix contains brief descriptions of the test results and failure modes explored in the test program. (orig.)

  2. NRC Bulletin No. 87-02, Supplement 1: Fastener testing to determine conformance with applicable material specifications

    International Nuclear Information System (INIS)

    Rossi, C.E.

    1992-01-01

    Item 5 of NRC Compliance Bulletin 87-02 requested that all holders of operating licenses or construction permits for nuclear power reactors information regarding the identity of the suppliers and manufacturers of the safety-related and non-safety-related fasteners selected for testing. After further consideration, the NRC has determined that it needs information regarding the identity of all vendors from which safety-related and non-safety-related fasteners have been obtained within the past 10 years, a reasonable period which will not put undue burden on addressees. This information will assist the NRC in determining whether nuclear facility fasteners in use have been supplied in accordance with their intended use. In addition, this information is needed so that the NRC can properly coordinate information with other government agencies concerned with problems identified in the quality of fasteners

  3. Smart fastener for KC-135 structural integrity monitoring

    Science.gov (United States)

    Schoess, Jeffrey N.; Seifert, Greg

    1997-06-01

    Hidden and inaccessible corrosion in aircraft structures is the number-one logistics problem for the U.S. Air Force, with an estimated maintenance cost in excess of $DOL1.0 billion per year in 1990-equivalent dollars. The Smart Aircraft Fastener Evaluation (SAFE) system is being developed to provide early warning detection of corrosion- related symptoms in hidden locations of aircraft structures. The SAFE incorporates an in situ measurement approach that measures and autonomously records several environmental conditions (i.e., pH, temperature, chloride, free potential, time-of-wetness) within a Hi-Lok aircraft fastener that could cause corrosion to occur. The SAFE system integrates a miniature electrochemical microsensor array and a time-of- wetness sensor with an ultra-low-power 8-bit microcontroller and 5-Mbyte solid-state FLASH archival memory to measure the evidence of active corrosion. A summary of the technical approach, system design definition, software architecture, and future field test plans will be presented.

  4. Device for measuring hole elongation in a bolted joint

    Science.gov (United States)

    Wichorek, Gregory R. (Inventor)

    1987-01-01

    A device to determine the operable failure mode of mechanically fastened lightweight composite joints by measuring the hole elongation of a bolted joint is disclosed. The double-lap joint test apparatus comprises a stud, a test specimen having a hole, two load transfer plates, and linear displacement measuring instruments. The test specimen is sandwiched between the two load transfer plates and clamped together with the stud. Spacer washers are placed between the test specimen and each load transfer plate to provide a known, controllable area for the determination of clamping forces around the hole of the specimen attributable to bolt torque. The spacer washers also provide a gap for the mounting of reference angles on each side of the test specimen. Under tensile loading, elongation of the hole of the test specimen causes the stud to move away from the reference angles. This displacement is measured by the voltage output of two linear displacement measuring instruments that are attached to the stud and remain in contact with the reference angles throughout the tensile loading. The present invention obviates previous problems in obtaining specimen deformation measurements by monitoring the reference angles to the test specimen and the linear displacement measuring instruments to the stud.

  5. Initial experience with percutaneous endoscopic gastrostomy with T-fastener fixation in pediatric patients

    Science.gov (United States)

    Kvello, Morten; Knatten, Charlotte Kristensen; Perminow, Gøri; Skari, Hans; Engebretsen, Anders; Schistad, Ole; Emblem, Ragnhild; Bjørnland, Kristin

    2018-01-01

    Background and study aims  Insertion of a percutaneous endoscopic gastrostomy (PEG) with push-through technique and T-fastener fixation (PEG-T) has recently been introduced in pediatric patients. The T-fasteners allow a primary insertion of a balloon gastrostomy. Due to limited data on the results of this technique in children, we have investigated peri- and postoperative outcomes after implementation of PEG-T in our department. Patients and methods  This retrospective chart review included all patients below 18 years who underwent PEG-T placement from 2010 to 2014. Main outcomes were 30-day postoperative complications and late gastrostomy-related complications. Results  In total, 87 patients were included, and median follow-up time was 2.4 years (1 month – 4.9 years). Median age and weight at PEG-T insertion were 1.9 years (9.4 months – 16.4 years) and 10.4 kg (5.4 – 33.0 kg), respectively. Median operation time was 28 minutes (10 – 65 minutes), and 6 surgeons and 3 endoscopists performed the procedures. During the first 30 days, 54 complications occurred in 41 patients (47 %). Most common were peristomal infections treated with either local antibiotics in 11 patients (13 %) or systemic antibiotics in 11 other patients (13 %). 9 patients (10 %) experienced tube dislodgment. Late gastrostomy-related complications occurred in 33 patients (38 %). The T-fasteners caused early and late complications in 9 (10 %) and 11 patients (13 %), respectively. Of these, 4 patients (5 %) had subcutaneously migrated T-fasteners which were removed under general anesthesia. Conclusion  We found a high rate of complications after PEG-T. In particular, problems with the T-fasteners and tube dislodgment occurred frequently after PEG-T insertion. PMID:29399615

  6. Detection of fastener loosening in simple lap joint based on ultrasonic wavefield imaging

    Science.gov (United States)

    Gooda Sahib, M. I.; Leong, S. J.; Chia, C. C.; Mustapha, F.

    2017-12-01

    Joints in aero-mechanical structures are critical elements that ensure the structural integrity but they are prone to damages. Inspection of such joints that have no prior baseline data is really challenging but it can be possibly done using the Ultrasonic Propagation Imager (UPI). The feasibility of applying UPI for detection of loosened fastener is investigated in this study. A simple lap joint specimen made by connecting two pieces of 2.5mm thick SAE304 stainless steel plates using five M6 screws and nuts has been used in this study. All fasteners are tightened to 10Nm but one of them is completely loosened to simulate the damage. The wavefield data is processed into ultrasonic wavefield propagation video and a series of spectral amplitude images. The spectral images showed noticeable amplitude difference at the loosened fastener, hence confirmed the feasibility of using UPI for structural joints inspection. A simple contrast maximization method is also introduced to improve the result.

  7. Black holes in an expanding universe and supersymmetry

    Directory of Open Access Journals (Sweden)

    Dietmar Klemm

    2016-02-01

    Full Text Available This paper analyzes the supersymmetric solutions to five and six-dimensional minimal (ungauged supergravities for which the bilinear Killing vector constructed from the Killing spinor is null. We focus on the spacetimes which admit an additional SO(1,1 boost symmetry. Upon the toroidal dimensional reduction along the Killing vector corresponding to the boost, we show that the solution in the ungauged case describes a charged, nonextremal black hole in a Friedmann–Lemaître–Robertson–Walker (FLRW universe with an expansion driven by a massless scalar field. For the gauged case, the solution corresponds to a charged, nonextremal black hole embedded conformally into a Kantowski–Sachs universe. It turns out that these dimensional reductions break supersymmetry since the bilinear Killing vector and the Killing vector corresponding to the boost fail to commute. This represents a new mechanism of supersymmetry breaking that has not been considered in the literature before.

  8. Nonlinear Coupled Dynamics of a Rod Fastening Rotor under Rub-Impact and Initial Permanent Deflection

    Directory of Open Access Journals (Sweden)

    Liang Hu

    2016-10-01

    Full Text Available A nonlinear coupled dynamic model of a rod fastening rotor under rub-impact and initial permanent deflection was developed in this paper. The governing motion equation was derived by the D’Alembert principle considering the contact characteristic between disks, nonlinear oil-film force, rub-impact force, unbalance mass, etc. The contact effects between disks was modeled as a flexural spring with cubical nonlinear stiffness. The coupled nonlinear dynamic phenomena of the rub-impact rod fastening rotor bearing system with initial permanent deflection were investigated by the fourth-order Runge-Kutta method. Bifurcation diagram, vibration waveform, frequency spectrum, shaft orbit and Poincaré map are used to illustrate the rich diversity of the system response with complicated dynamics. The studies indicate that the coupled dynamic responses of the rod fastening rotor bearing system under rub-impact and initial permanent deflection exhibit a rich nonlinear dynamic diversity, synchronous periodic-1 motion, multiple periodic motion, quasi-periodic motion and chaotic motion can be observed under certain conditions. Larger radial stiffness of the stator will simplify the system motion and make the oil whirl weaker or even disappear at a certain rotating speed. With the increase of initial permanent deflection length, the instability speed of the system gradually rises, and the chaotic motion region gets smaller and smaller. The corresponding results can provide guidance for the fault diagnosis of a rub-impact rod fastening rotor with initial permanent deflection and contribute to the further understanding of the nonlinear dynamic characteristics of the rod fastening rotor bearing system.

  9. Performance of Rail Fastening Systems on an Open-Deck Bridge

    Science.gov (United States)

    2018-02-01

    Transportation Technology Center, Inc. (TTCI) monitored the performance of rail fasteners on an open-deck bridge and its approaches, located at Norfolk Southern Corporations (NS's) eastern mega site. The project was co-sponsored by the Federal Rai...

  10. Deep Defect Detection within Thick Multilayer Aircraft Structures Containing Steel Fasteners Using a Giant-Magneto Resistive (GMR) Sensor (Preprint)

    National Research Council Canada - National Science Library

    Ko, Ray T; Steffes, Gary J

    2007-01-01

    Defect detection within thick multilayer structures containing steel fasteners is a challenging task in eddy current testing due to the magnetic permeability of the fasteners and overall thickness of the structure...

  11. Evaluation of the seat fastening in the frame of a road bus submitted to frontal impact

    Directory of Open Access Journals (Sweden)

    Márcio Walber

    Full Text Available The collective intercity transportation by bus is currently a mean of locomotion much sought after by people. Security in accidents is a very important factor that must be taken into account in design of bus body structure, being the evaluation of passenger safety of this type of vehicle is an important subject that should be checked, because in many accidents occur disconnection between seats and fastening members causing serious passengers injury, often fatal. This work aims at evaluation the behavior of frame fixing of seats of intercity bus bodies, submitted to the frontal impact situation in a rigid wall of 100% offset, through evaluation by finite element method (FEM. This study uses a numerical model corresponding to the body structure and chassis, developed through flexible beam elements, combining with shell elements for the structure of the seats and its fastening members, with the objective of not missing the essential aspects of the problem, allowing the solution with a reduced computational time. The numerical model of bus body and seat was impacted against a rigid wall at a speed of 8.89 m/s, being its validation according to the deceleration curve established by Regulation 80. Then it was gotten the Von Mises stress in fastening members of the seat structure in bus body. It is also presented a proposal to improve the fastening of the seat structure, comparing the results of the stress gotten in the two types fastening submitted to the frontal impact.

  12. Black and white holes

    International Nuclear Information System (INIS)

    Zeldovich, Ya.; Novikov, I.; Starobinskij, A.

    1978-01-01

    The theory is explained of the origination of white holes as a dual phenomenon with regard to the formation of black holes. Theoretically it is possible to derive the white hole by changing the sign of time in solving the general theory of relativity equation implying the black hole. The white hole represents the amount of particles formed in the vicinity of a singularity. For a distant observer, matter composed of these particles expands and the outer boundaries of this matter approach from the inside the gravitational radius Rsub(r). At t>>Rsub(r)/c all radiation or expulsion of matter terminates. For the outside observer the white hole exists for an unlimited length of time. In fact, however, it acquires the properties of a black hole and all processes in it cease. The qualitative difference between a white hole and a black hole is in that a white hole is formed as the result of an inner quantum explosion from the singularity to the gravitational radius and not as the result of a gravitational collapse, i.e., the shrinkage of diluted matter towards the gravitational radius. (J.B.)

  13. Black and white holes

    Energy Technology Data Exchange (ETDEWEB)

    Zeldovich, Ya; Novikov, I; Starobinskii, A

    1978-07-01

    The theory is explained of the origination of white holes as a dual phenomenon with regard to the formation of black holes. Theoretically it is possible to derive the white hole by changing the sign of time in solving the general theory of relativity equation implying the black hole. The white hole represents the amount of particles formed in the vicinity of a singularity. For a distant observer, matter composed of these particles expands and the outer boundaries of this matter approach from the inside the gravitational radius R/sub r/. At t>>R/sub r//c all radiation or expulsion of matter terminates. For the outside observer the white hole exists for an unlimited length of time. In fact, however, it acquires the properties of a black hole and all processes in it cease. The qualitative difference between a white hole and a black hole is in that a white hole is formed as the result of an inner quantum explosion from the singularity to the gravitational radius and not as the result of a gravitational collapse, i.e., the shrinkage of diluted matter towards the gravitational radius.

  14. A New Cosmological Model: Black Hole Universe

    Directory of Open Access Journals (Sweden)

    Zhang T. X.

    2009-07-01

    Full Text Available A new cosmological model called black hole universe is proposed. According to this model, the universe originated from a hot star-like black hole with several solar masses, and gradually grew up through a supermassive black hole with billion solar masses to the present state with hundred billion-trillion solar masses by accreting ambient mate- rials and merging with other black holes. The entire space is structured with infinite layers hierarchically. The innermost three layers are the universe that we are living, the outside called mother universe, and the inside star-like and supermassive black holes called child universes. The outermost layer is infinite in radius and limits to zero for both the mass density and absolute temperature. The relationships among all layers or universes can be connected by the universe family tree. Mathematically, the entire space can be represented as a set of all universes. A black hole universe is a subset of the en- tire space or a subspace. The child universes are null sets or empty spaces. All layers or universes are governed by the same physics - the Einstein general theory of relativity with the Robertson-walker metric of spacetime - and tend to expand outward physically. The evolution of the space structure is iterative. When one universe expands out, a new similar universe grows up from its inside. The entire life of a universe begins from the birth as a hot star-like or supermassive black hole, passes through the growth and cools down, and expands to the death with infinite large and zero mass density and absolute temperature. The black hole universe model is consistent with the Mach principle, the observations of the universe, and the Einstein general theory of relativity. Its various aspects can be understood with the well-developed physics without any difficulty. The dark energy is not required for the universe to accelerate its expansion. The inflation is not necessary because the black hole universe

  15. Expanding the catalog of binary black-hole simulations: aligned-spin configurations

    Science.gov (United States)

    Chu, Tony; Pfeiffer, Harald; Scheel, Mark; Szilagyi, Bela; SXS Collaboration

    2015-04-01

    A major goal of numerical relativity is to model the inspiral and merger of binary black holes through sufficiently accurate and long simulations, to enable the successful detection of gravitational waves. However, covering the full parameter space of binary configurations is a computationally daunting task. The SXS Collaboration has made important progress in this direction recently, with a catalog of 174 publicly available binary black-hole simulations [black-holes.org/waveforms]. Nevertheless, the parameter-space coverage remains sparse, even for non-precessing binaries. In this talk, I will describe an addition to the SXS catalog to improve its coverage, consisting of 95 new simulations of aligned-spin binaries with moderate mass ratios and dimensionless spins as high as 0.9. Some applications of these new simulations will also be mentioned.

  16. Flexible Multi-Body Spacecraft Simulator: Design, Construction, and Experiments

    Science.gov (United States)

    2017-12-01

    required analysis. The first step in applying Pontryagin’s Principle is writing the control Hamiltonian: ( , , , ) ( , , ) ( , , )TH x u t F x u t f...of holes allows the adapter plate to be fastened to the MBSS top plate. 26 The base and link are designed to be modular and expandable. The link...https://www.quanser.com/products/2-dof-serial-flexible-joint/ 79 INITIAL DISTRIBUTION LIST 1. Defense Technical Information Center Ft. Belvoir

  17. Delamination measurement of a laminates composite panel due to hole punching based on the focus variation technique

    Science.gov (United States)

    Abdullah, A. B.; Zain, M. S. M.; Abdullah, M. S.; Samad, Z.

    2017-07-01

    Structural materials, such as composite panels, must be assembled, and such panels are typically constructed via the insertion of a fastener through a drilled hole. The main problem encountered in drilling is delamination, which affects assembly strength. The cost of drilling is also high because of the severe wear on drill bits. The main goal of this research is to develop a new punching method as an alternative to drilling during hole preparation. In this study, the main objective is to investigate the effect of different puncher profiles on the quality of holes punched into carbon fiber reinforcement polymer (CFRP) composite panels. Six types of puncher profiles were fabricated with minimum die clearance (1%), and two quality aspects, namely, incomplete shearing and delamination factor, were measured. The conical puncher incurred the least defects in terms of delamination and yielded an acceptable amount of incomplete shearing in comparison with the other punchers.

  18. 77 FR 38547 - Airworthiness Directives; The Boeing Company Airplanes

    Science.gov (United States)

    2012-06-28

    ... (including cracking, misdrilled fastener holes, elongated fastener holes, corrosion, oil-cans, and existing..., corrosion, oil-cans, and existing repairs), or for certain discrepancies, contacting Boeing for repair... Designated Engineering Representative (DER). We have revised the date of the document specified in paragraph...

  19. Black Hole Universe Model and Dark Energy

    Science.gov (United States)

    Zhang, Tianxi

    2011-01-01

    Considering black hole as spacetime and slightly modifying the big bang theory, the author has recently developed a new cosmological model called black hole universe, which is consistent with Mach principle and Einsteinian general relativity and self consistently explains various observations of the universe without difficulties. According to this model, the universe originated from a hot star-like black hole and gradually grew through a supermassive black hole to the present universe by accreting ambient material and merging with other black holes. The entire space is infinitely and hierarchically layered and evolves iteratively. The innermost three layers are the universe that we lives, the outside space called mother universe, and the inside star-like and supermassive black holes called child universes. The outermost layer has an infinite radius and zero limits for both the mass density and absolute temperature. All layers or universes are governed by the same physics, the Einstein general relativity with the Robertson-Walker metric of spacetime, and tend to expand outward physically. When one universe expands out, a new similar universe grows up from its inside black holes. The origin, structure, evolution, expansion, and cosmic microwave background radiation of black hole universe have been presented in the recent sequence of American Astronomical Society (AAS) meetings and published in peer-review journals. This study will show how this new model explains the acceleration of the universe and why dark energy is not required. We will also compare the black hole universe model with the big bang cosmology.

  20. Effects of specialized drill bits on hole defects of CFRP laminates

    Science.gov (United States)

    Li, Chao; Xu, Jinyang; Chen, Ming

    2018-05-01

    Drilling is a conventional machining process widely applied to carbon fiber reinforced plastics (CFRP) for the riveting and fastening purposes in the aerospace and automotive industries. However, the machining mechanism of CFRP composites differ significantly from that of homogeneous metal alloys owing to their prominent anisotropy and heterogeneity. Serious hole defects such as fiber pullout, matrix debonding and delamination are generally produced during the hole-making process, resulting in the poor machined surface quality, low fatigue durability or even the part rejections. In order to minimize the defects especially the delamination damage in composites drilling, specialized drill bits are often a primary choice being widely adopted in a real production. This paper aims to study the effects of two drills differing in geometrical characteristics during the drilling of CFRP laminates. A number of drilling experiments were carried out with the aim to evaluate the drilling performance of different drill bits. A scanning electron microscope (SEM) was used to observe the drilled surfaces to study the surface roughness. A high frequency scanning acoustic microscope (SAM) was applied to characterize the drilled hole morphologies with a particular focus on the delamination damage occurring in the CFRP laminates. The obtained results indicate that the fiber orientation relative to the cutting direction is a key factor affecting hole morphology and hole wall defects can be reduced by utilizing specialized drill geometries. Moreover, the dagger drill was confirmed outperforming the brad spur drill from the aspect of reducing drilling-induced delamination.

  1. Black holes in the Universe: Generalized Lemaitre-Tolman-Bondi solutions

    International Nuclear Information System (INIS)

    Gao Changjun; Chen Xuelei; Shen Yougen; Faraoni, Valerio

    2011-01-01

    We present new exact solutions which presumably describe black holes in the background of a spatially flat, pressureless dark-matter- or dark matter plus dark energy (DM+DE)- or quintom-dominated Universe. These solutions generalize Lemaitre-Tolman-Bondi metrics. For a dark-matter- or (DM+DE)-dominated universe, the area of the black hole apparent horizon (AH) decreases with the expansion of the Universe while that of the cosmic AH increases. However, for a quintom-dominated universe, the black hole AH first shrinks and then expands, while the cosmic AH first expands and then shrinks. A (DM+DE)-dominated universe containing a black hole will evolve to the Schwarzschild-de Sitter solution with both AHs approaching constant size. In a quintom-dominated universe, the black hole and cosmic AHs will coincide at a certain time, after which the singularity becomes naked, violating cosmic censorship.

  2. Test results of smart aircraft fastener for KC-135 structural integrity

    Science.gov (United States)

    Schoess, Jeffrey N.; Seifert, Greg

    1998-07-01

    Hidden and inaccessible corrosion in aircraft structures is the number one logistics problem for the US Air Force, with an estimated maintenance cost in excess of $LR 1.0B per year in 1990-equivalent dollars. The Smart Aircraft Fastener Evaluation (SAFE) system was developed to provide early warning detection of corrosion-related symptoms in hidden locations of aircraft structures. The SAFE system incorporates an in situ measurement approach that measures and autonomously records several environmental conditions within a Hi-Lok aircraft fastener that could cause corrosion. The SAFE system integrates a miniature electrochemical microsensor array and a time-of-wetness sensor with an ultra low power 8-bit microcontroller and 4- Mbyte solid-state FLASH archival memory to measure evidence of active corrosion. A summary of the technical approach and a detailed analysis of the KC-135 lap joint test coupon results are presented.

  3. B-scan technique for localization and characterization of fatigue cracks around fastener holes in multi-layered structures

    Science.gov (United States)

    Hopkins, Deborah; Datuin, Marvin; Aldrin, John; Warchol, Mark; Warchol, Lyudmila; Forsyth, David

    2018-04-01

    The work presented here aims to develop and transition angled-beam shear-wave inspection techniques for crack localization at fastener sites in multi-layer aircraft structures. This requires moving beyond detection to achieve reliable crack location and size, thereby providing invaluable information for maintenance actions and service-life management. The technique presented is based on imaging cracks in "True" B-scans (depth view projected in the sheets along the beam path). The crack traces that contribute to localization in the True B-scans depend on small, diffracted signals from the crack edges and tips that are visible in simulations and experimental data acquired with sufficient gain. The most recent work shows that cracks rotated toward and away from the central ultrasonic beam also yield crack traces in True B-scans that allow localization in simulations, even for large obtuse angles where experimental and simulation results show very small or no indications in the C-scans. Similarly, for two sheets joined by sealant, simulations show that cracks in the second sheet can be located in True B-scans for all locations studied: cracks that intersect the front or back wall of the second sheet, as well as relatively small mid-bore cracks. These results are consistent with previous model verification and sensitivity studies that demonstrate crack localization in True B-scans for a single sheet and cracks perpendicular to the ultrasonic beam.

  4. Mechanical fasteners used in historical Siberian shipbuilding: perspectives for metallurgical analysis

    Science.gov (United States)

    Goncharov, A. E.; Mednikov, D. M.; Karelin, N. M.; Nasyrov, I. R.

    2017-10-01

    Recent discoveries of shipwrecked vessels in the northern reaches of the river Yenisei led to a number of questions concerning the history of shipbuilding in Siberia and the technical features of the first vessels of the industrial era to navigate the Northern Sea Route and the Yenisei. One of these questions addresses the features of mechanical fasteners used in the construction of the Siberian vessels. The answer to this question may provide information on how the first vessels, constructed in Siberia during the 1870’s, were able to sail the high seas of the Arctic Ocean and reach European ports. In this paper, we provide a description of iron mechanical fasteners obtained from one shipwrecked vessel and discuss on the perspectives of a metallurgical analysis This research has been funded by a grant of the Russian Fund of Humanities Research (Russian Fund of Fundamental Research) and the Krasnoyarsk Regional Science Fund under Grant number 16-11-24010.

  5. Dowel-type fastener connections in timber structures subjected to short-term loading

    DEFF Research Database (Denmark)

    Lauritzen Jensen, J.

    Design of dowel-type fastener connections in framed timber structures usually involves a two-step analysis: determination of the distribution of the sectional forces, and design of the eccentrically loaded connections. This report presents an integrated model for design of framed timber structures...

  6. Testing of Compact Bolted Fasteners with Insulation and Friction-Enhanced Shims for NCSX

    International Nuclear Information System (INIS)

    Dudek, L.E.; Chrzanowski, J.H.; Gettelfinger, G.; Heitzenroeder, P.; Jurczynski, S.; Viola, M.; Freudenberg, K.

    2009-01-01

    The fastening of the National Compact Stellarator Experiment's (NCSX) modular coils presented a number of engineering and manufacturing challenges due to the high magnetic forces, need to control induced currents, tight tolerances and restrictive space envelope. A fastening method using high strength studs, jack nuts, insulating spacers, bushings and alumina coated shims was developed which met the requirements. A test program was conducted to verify the design. The tests included measurements of flatness of the spacers, determination of contact area, torque vs. tension of the studs and jack nuts, friction coefficient tests on the alumina and G-10 insulators, electrical tests, and tension relaxation tests due to temperature excursions from room temperature to liquid nitrogen temperatures. This paper will describe the design and the results of the test program.

  7. Exposure testing of fasteners in preservative treated wood: Gravimetric corrosion rates and corrosion product analyses

    Energy Technology Data Exchange (ETDEWEB)

    Zelinka, Samuel L., E-mail: szelinka@fs.fed.u [USDA Forest Products Laboratory, One Gifford Pinchot Drive, Madison, WI 53726 (United States); Sichel, Rebecca J. [College of Engineering, University of Wisconsin, Madison, WI 53706 (United States); Stone, Donald S. [Department of Materials Science and Engineering, College of Engineering, University of Wisconsin, Madison, WI 53706 (United States)

    2010-12-15

    Research highlights: {yields} The composition of the corrosion products was similar for the nail head and shank. {yields} Reduced copper was not detected on any of the fasteners. {yields} Measured corrosion rates were between 1 and 35 {mu}m year{sup -1}. - Abstract: Research was conducted to determine the corrosion rates of metals in preservative treated wood and also understand the mechanism of metal corrosion in treated wood. Steel and hot-dip galvanized steel fasteners were embedded in wood treated with one of six preservative treatments and exposed to 27 {sup o}C at 100% relative humidity for 1 year. The corrosion rate was determined gravimetrically and the corrosion products were analyzed with scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. Although the accepted mechanism of corrosion in treated wood involves the reduction of cupric ions from the wood preservative, no reduced copper was found on the corrosion surfaces. The galvanized corrosion products contained sulfates, whereas the steel corrosion products consisted of iron oxides and hydroxides. The possible implications and limitations of this research on fasteners used in building applications are discussed.

  8. Velcro-like fasteners based on NiTi micro-hook arrays

    Czech Academy of Sciences Publication Activity Database

    Vokoun, David; Sedlák, Petr; Frost, Miroslav; Pilch, Jan; Majtás, Dušan; Šittner, Petr

    2011-01-01

    Roč. 20, č. 8 (2011), 085027/1-085027/13 ISSN 0964-1726 R&D Projects: GA ČR GAP108/10/1296; GA ČR GA106/09/1573 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z20760514 Keywords : Nitinol * martensitic transformation * Finite Element Method * Velcro-like fastener Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.089, year: 2011

  9. Comparison of the corrosion of fasteners embedded in wood measured in outdoor exposure with the predictions from a combined hygrothermal-corrosion model

    Science.gov (United States)

    Samuel L. Zelinka; Samuel V. Glass; Charles R. Boardman; Dominique Derome

    2016-01-01

    This paper examines the accuracy of a recently developed hygrothermal-corrosion model which predictsthe corrosion of fasteners embedded in wood by comparing the results of the model to a one year fieldtest. Steel and galvanized steel fasteners were embedded into untreated and preservative treated woodand exposed outdoors while weather data were collected. Qualitatively...

  10. Distorted black holes in terms of multipole moments

    International Nuclear Information System (INIS)

    Suen, W.

    1986-01-01

    In terms of a multipole-moment formalism previously developed for non-asymptotically-flat systems in general relativity, the metric of a Schwarzschild black hole in an external quadrupolar gravitational field is studied. Among other results, we find that the black hole develops an induced quadrupole moment, which in turn generates a tidal field opposing the applied field. This effect, plus the fact that the horizon cannot expand when a quasistatic tidal force is applied, can be described in terms of effective 2-dimensional elastic moduli for the black-hole horizon. The bulk modulus is kappa = ∞, and the shear modulus is mu = -63/(20πM), where M is the hole's mass

  11. Cross-linkable liposomes stabilize a magnetic resonance contrast-enhancing polymeric fastener.

    Science.gov (United States)

    Smith, Cartney E; Kong, Hyunjoon

    2014-04-08

    Liposomes are commonly used to deliver drugs and contrast agents to their target site in a controlled manner. One of the greatest obstacles in the performance of such delivery vehicles is their stability in the presence of serum. Here, we demonstrate a method to stabilize a class of liposomes that load gadolinium, a magnetic resonance (MR) contrast agent, as a model cargo on their surfaces. We hypothesized that the sequential adsorption of a gadolinium-binding chitosan fastener on the liposome surface followed by covalent cross-linking of the lipid bilayer would provide enhanced stability and improved MR signal in the presence of human serum. To investigate this hypothesis, liposomes composed of diyne-containing lipids were assembled and functionalized via chitosan conjugated with a hydrophobic anchor and diethylenetriaminepentaacetic acid (DTPA). This postadsorption cross-linking strategy served to stabilize the thermodynamically favorable association between liposome and polymeric fastener. Furthermore, the chitosan-coated, cross-linked liposomes proved more effective as delivery vehicles of gadolinium than uncross-linked liposomes due to the reduced liposome degradation and chitosan desorption. Overall, this study demonstrates a useful method to stabilize a broad class of particles used for systemic delivery of various molecular payloads.

  12. Black holes and the multiverse

    International Nuclear Information System (INIS)

    Garriga, Jaume; Vilenkin, Alexander; Zhang, Jun

    2016-01-01

    Vacuum bubbles may nucleate and expand during the inflationary epoch in the early universe. After inflation ends, the bubbles quickly dissipate their kinetic energy; they come to rest with respect to the Hubble flow and eventually form black holes. The fate of the bubble itself depends on the resulting black hole mass. If the mass is smaller than a certain critical value, the bubble collapses to a singularity. Otherwise, the bubble interior inflates, forming a baby universe, which is connected to the exterior FRW region by a wormhole. A similar black hole formation mechanism operates for spherical domain walls nucleating during inflation. As an illustrative example, we studied the black hole mass spectrum in the domain wall scenario, assuming that domain walls interact with matter only gravitationally. Our results indicate that, depending on the model parameters, black holes produced in this scenario can have significant astrophysical effects and can even serve as dark matter or as seeds for supermassive black holes. The mechanism of black hole formation described in this paper is very generic and has important implications for the global structure of the universe. Baby universes inside super-critical black holes inflate eternally and nucleate bubbles of all vacua allowed by the underlying particle physics. The resulting multiverse has a very non-trivial spacetime structure, with a multitude of eternally inflating regions connected by wormholes. If a black hole population with the predicted mass spectrum is discovered, it could be regarded as evidence for inflation and for the existence of a multiverse

  13. Black holes and the multiverse

    Energy Technology Data Exchange (ETDEWEB)

    Garriga, Jaume [Departament de Fisica Fonamental i Institut de Ciencies del Cosmos, Universitat de Barcelona, Marti i Franques, 1, Barcelona, 08028 Spain (Spain); Vilenkin, Alexander; Zhang, Jun, E-mail: jaume.garriga@ub.edu, E-mail: vilenkin@cosmos.phy.tufts.edu, E-mail: jun.zhang@tufts.edu [Institute of Cosmology, Tufts University, 574 Boston Ave, Medford, MA, 02155 (United States)

    2016-02-01

    Vacuum bubbles may nucleate and expand during the inflationary epoch in the early universe. After inflation ends, the bubbles quickly dissipate their kinetic energy; they come to rest with respect to the Hubble flow and eventually form black holes. The fate of the bubble itself depends on the resulting black hole mass. If the mass is smaller than a certain critical value, the bubble collapses to a singularity. Otherwise, the bubble interior inflates, forming a baby universe, which is connected to the exterior FRW region by a wormhole. A similar black hole formation mechanism operates for spherical domain walls nucleating during inflation. As an illustrative example, we studied the black hole mass spectrum in the domain wall scenario, assuming that domain walls interact with matter only gravitationally. Our results indicate that, depending on the model parameters, black holes produced in this scenario can have significant astrophysical effects and can even serve as dark matter or as seeds for supermassive black holes. The mechanism of black hole formation described in this paper is very generic and has important implications for the global structure of the universe. Baby universes inside super-critical black holes inflate eternally and nucleate bubbles of all vacua allowed by the underlying particle physics. The resulting multiverse has a very non-trivial spacetime structure, with a multitude of eternally inflating regions connected by wormholes. If a black hole population with the predicted mass spectrum is discovered, it could be regarded as evidence for inflation and for the existence of a multiverse.

  14. The effect of moisture content on the corrosion of fasteners embedded in wood subjected to alkaline copper quaternary treatment

    International Nuclear Information System (INIS)

    Zelinka, Samuel L.; Glass, Samuel V.; Derome, Dominique

    2014-01-01

    Highlights: • We examine the dependence of metal corrosion on wood moisture content. • Corrosion of steel and galvanized steel in treated wood were measured. • Corrosion products were analyzed across moisture contents using X-ray diffraction. • The corrosion rate has a sigmoidal dependence on moisture content. • The data herein can be used to improve combined hygrothermal–corrosion models. - Abstract: This paper characterizes the corrosion rate of embedded fasteners as a function of wood moisture content using gravimetric and electrochemical measurements. The results indicated that the corrosion rate increased with moisture content before reaching a plateau. The phases present in the corrosion products, as analyzed using X-ray diffraction, are generally consistent with previous work. Uniform corrosion was observed for all fasteners and all conditions except steel fasteners embedded in water-saturated wood. Data of dependence of corrosion rate on moisture content, presented herein, are necessary to ensure the accuracy of combined hygrothermal/corrosion models used to predict durability of wood structures

  15. Black-hole production from ultrarelativistic collisions

    International Nuclear Information System (INIS)

    Rezzolla, Luciano; Takami, Kentaro

    2013-01-01

    Determining the conditions under which a black hole can be produced is a long-standing and fundamental problem in general relativity. We use numerical simulations of colliding self-gravitating fluid objects to study the conditions of black-hole formation when the objects are boosted to ultrarelativistic speeds. Expanding on the previous work, we show that the collision is characterized by a type-I critical behaviour, with a black hole being produced for masses above a critical value, M c , and a partially bound object for masses below the critical one. More importantly, we show for the first time that the critical mass varies with the initial effective Lorentz factor 〈γ〉 following a simple scaling of the type M c ∼ K〈γ〉 −1.0 , thus indicating that a black hole of infinitesimal mass is produced in the limit of a diverging Lorentz factor. Furthermore, because a scaling is present also in terms of the initial stellar compactness, we provide a condition for black-hole formation in the spirit of the hoop conjecture. (fast track communication)

  16. "Service Recovery: The Effects of Complaint Handling on Post-complaint Relationship Intention and Customer Switching Behaviour in the Taiwan Fastener Industry"

    OpenAIRE

    Hwang, Jui-Chin

    2005-01-01

    Abstract In recent decades, many industries have started to realize the importance of relationship marketing and effective complaint handling as part of their customer retention strategies. This includes the traditional Taiwan fastener industry, which used to be considered as more technically focused rather than service-oriented. One of the main reasons for this industry to move toward a service orientation is that Taiwanese fastener trading companies have become highly customer-focused, ...

  17. Experimental Research on the Elastic Deformation Mode of S235JR Rolled Steel Fastened between the Centers of a Universal Lathe

    Science.gov (United States)

    Tabacaru, LL; Axinte, E.; Musca, G.

    2016-11-01

    Elastic deformations of the technological system occur during the mechanical treatment of a blank, regardless of the manner in which it is fastened. The elastic deformation of the blank is significant especially when machining shaft-like parts. The purpose of our research is to compare the mathematical model of blank deformation to the experimental model when the blank, which is a part belonging to the shaft class, is fastened between centers.

  18. Quasinormal modes of Kerr-de Sitter black holes

    International Nuclear Information System (INIS)

    Yoshida, Shijun; Uchikata, Nami; Futamase, Toshifumi

    2010-01-01

    We calculate the fundamental quasinormal modes of the Kerr-de Sitter black hole for the first time. In order to calculate the quasinormal modes, we employ the master equations derived by Suzuki, Takasugi, and Umetsu, who transform the Teukolsky equations for the Kerr-de Sitter black hole into the standard form of the Heun's equation. The transformed functions are expanded around the outer horizon of the black hole or the symmetric axis in the Froebenius series whose coefficients satisfy a three-term recurrence relation. These three-term recurrence relations allow us to use Leaver's continued fraction method to calculate the angular separation constant and the quasinormal mode frequency. Any unstable fundamental quasinormal mode is not found in this paper. It is also observed that for some black holes characterized by a large mass parameter, some retrograde modes in the slow rotation limit become prograde as the black hole spin increases. This phenomenon does not occur for the fundamental modes of the Kerr black hole.

  19. Comparison study of multistep forging and injection forging of automobile fasteners

    OpenAIRE

    Chen Senyong; Qin Yi

    2015-01-01

    In order to improve production efficiency, injection forging as a feasible approach was introduced to automobile fasteners production. In the study reported in this paper, two forging approaches, traditional multistep forging and injection forging, were analysed by using a finite element method. Using ABAQUS and DEFORM, some significant factors, namely, forging force, energy consumption, component accuracy and stress distribution in the die, were compared to explore the potential and challeng...

  20. IMPLEMENTATION OF THE LEAN-KAIZEN APPROACH IN FASTENER INDUSTRIES USING THE DATA ENVELOPMENT ANALYSIS

    Directory of Open Access Journals (Sweden)

    Sunil Kumar

    2017-04-01

    Full Text Available This research paper is an attempt to improve the quality system of ten small scale fastener manufacturing industries through the implementation of the Lean-Kaizen approach using the Data Envelopment Analysis (DEA Charnes Cooper & Rhodes (CCR model with constant returns to scale (CRS. Output maximization is taken as the objective function to identify the percentage scope of improvements. The data is collected by paying personal visits to the selected industries for three inputs (manpower, maintenance, and training of employees and two outputs (quality, on-time delivery of their quality system. The DEA CCR model is applied to identify efficiency scores of the quality system by taking the most efficient industry as a benchmark for the rest of the organizations. The Lean-Kaizen approach is applied to identify waste / non-value added activities in outputs of the selected industries. Four Kaizen events are proposed to eliminate waste / non-value added activities in their quality system. The data collected after the Kaizen events are further analyzed by the DEA CCR model. The improvements in efficiency scores of the selected industries are presented as findings in this research paper. Two fastener industries became 100% efficient while the rest of the organizations reported 8% to 49% improvements in their efficiency scores of the quality system. The conclusions are made as the Lean-Kaizen using DEA is found to be an effective approach to improve the quality system of fastener industries. This study will be beneficial for researchers, practitioners and academicians for tackling the inefficiencies in the organization.

  1. Simulation of magnetic holes formation in the magnetosheath

    Science.gov (United States)

    Ahmadi, Narges; Germaschewski, Kai; Raeder, Joachim

    2017-12-01

    Magnetic holes have been frequently observed in the Earth's magnetosheath and are believed to be the consequence of the nonlinear evolution of the mirror instability. Mirror mode perturbations mainly form as magnetic holes in regions where the plasma is marginally mirror stable with respect to the linear instability criterion. We present an expanding box particle-in-cell simulation to mimic the changing conditions in the magnetosheath as the plasma is convected through it that produces mirror mode magnetic holes. We show that in the initial nonlinear evolution, where the plasma conditions are mirror unstable, the magnetic peaks are dominant, while later, as the plasma relaxes toward marginal stability, the fluctuations evolve into deep magnetic holes. While the averaged plasma parameters in the simulation remain close to the mirror instability threshold, the local plasma in the magnetic holes is highly unstable to mirror instability and locally mirror stable in the magnetic peaks.

  2. Black holes and structure in an oscillating universe

    International Nuclear Information System (INIS)

    Saslaw, W.C.

    1991-01-01

    If black holes exist in the contracting phase of a closed universe, they will give rise to a pressure and entropy catastrophe. First, the black holes absorb all the radiation; then their apparent horizons merge, and coalesce with the cosmological apparent horizon. All external observers become internal observers. It is possible that the internal metric of some of the merging black holes will be contracting, and others expanding. I suggest here that the resulting violent inhomogeneities can lead to a re-expansion in a significant portion of the universe. Global re-expansion, prompted by the merging of black holes, may thus begin in a semi-classical rather than fully quantum gravitational era, at densities greater than those at which nucleosynthesis occurs. Surviving black holes and inhomogeneities could initiate the formation of structures such as galaxies in the 'new' universe. The behaviour of such an oscillating universe would differ in detail from cycle to cycle. (author)

  3. Automatic Defect Detection of Fasteners on the Catenary Support Device Using Deep Convolutional Neural Network

    NARCIS (Netherlands)

    Chen, Junwen; Liu, Zhigang; Wang, H.; Nunez Vicencio, Alfredo; Han, Zhiwei

    2018-01-01

    The excitation and vibration triggered by the long-term operation of railway vehicles inevitably result in defective states of catenary support devices. With the massive construction of high-speed electrified railways, automatic defect detection of diverse and plentiful fasteners on the catenary

  4. Assessment of a Boat Fractured Steering Wheel

    Directory of Open Access Journals (Sweden)

    Vukelic Goran

    2016-09-01

    Full Text Available During regular use of the steering wheel mounted on a boat, two cracks emanating from a fastener hole were noticed which, consequently, caused final fracture of the wheel. To determine the behavior of a boat steering wheel with cracks present, assessment of a fractured wheel was performed. Torque moments of the fasteners were measured prior to removing the steering wheel from the boat. Visual and dye penetrant inspection followed along with the material detection. Besides using experimental procedures, assessment of the fractured wheel was performed using finite element analysis, i.e. stress intensity factor values were numerically determined. Variation of stress intensity factor with crack length is presented. Possible causes of crack occurrence are given and they include excessive values of fastener torque moments coupled with fretting between fastener and fastener hole that was poorly machined. Results obtained by this assessment can be taken for predicting fracture behavior of a cracked steering wheel and as a reference in the design, mounting and exploitation process of steering wheels improving that way their safety in transportation environment.

  5. 76 FR 28626 - Airworthiness Directives; Lockheed Martin Corporation/Lockheed Martin Aeronautics Company Model...

    Science.gov (United States)

    2011-05-18

    ... LM Aero believed that there should be a differentiation between the repetitive inspection intervals for Taper-Lok fastened joints (original production configuration) and the inspection intervals for Hi-Tigue fasteners installed in cold-worked holes. LM Aero pointed out that this differentiation is...

  6. Solar wind acceleration in coronal holes

    International Nuclear Information System (INIS)

    Kopp, R.A.

    1978-01-01

    Past attempts to explain the large solar wind velocities in high speed streams by theoretical models of the expansion have invoked either extended nonthermal heating of the corona, heat flux inhibition, or direct addition of momentum to the expanding coronal plasma. Several workers have shown that inhibiting the heat flux at low coronal densities is probably not adequate to explain quantitatively the observed plasma velocities in high speed streams. It stressed that, in order to account for both these large plasma velocities and the low densities found in coronal holes (from which most high speed streams are believed to emanate), extended heating by itself will not suffice. One needs a nonthermal mechanism to provide the bulk acceleration of the high wind plasma close to the sun, and the most likely candidate at present is direct addition of the momentum carried by outward-propagating waves to the expanding corona. Some form of momentum addition appears to be absolutely necessary if one hopes to build quantitatively self-consistent models of coronal holes and high speed solar wind streams

  7. Advanced Modelling of Trusses with Punched Metal Plate Fasteners

    DEFF Research Database (Denmark)

    Ellegaard, Peter; Nielsen, Jacob

    Most of the finite element programs for design of timber trusses with punched metal fasteners are based on models using beam and fictitious elements. Different models have been used for different types of joints. Common problems for all the models are how to calculate the forces in the nail groups...... and the plates and furthermore, how big 'the deformations in the joints are. By developing an advanced model that includes all parts of the joint, i.e. plate, nail groups and contact it is possible to give a better description of the joint. An advanced model with these properties is presented. The advanced model...

  8. Special servicing equipment for reactor pressurized vessel stud hole and stud accessories

    International Nuclear Information System (INIS)

    Li Jianglian

    1999-01-01

    The author briefly introduces the design and manufacture of nuclear island special servicing equipment of Nuclear Power Institute of China. Maintenance process of reactor pressurized vessel (RPV) stud hold and stud accessories the special servicing equipment include RPV flange dummy, closed-circuit television (CCTV) inspection equipment, RPV stud hole expandable comb, RPV stud hole polisher, RPV stud hold thread lubricating equipment, RPV stud hole thread miller and RPV stud hole camera. It is presented how eight kinds of special servicing equipment perform the maintenance process concerning their function, structure, and characteristics, their practical use on site is also introduced

  9. An Integrated Approach to Assess Exposure and Health-Risk from Polycyclic Aromatic Hydrocarbons (PAHs in a Fastener Manufacturing Industry

    Directory of Open Access Journals (Sweden)

    Hsin-I Hsu

    2014-09-01

    Full Text Available An integrated approach was developed to assess exposure and health-risk from polycyclic aromatic hydrocarbons (PAHs contained in oil mists in a fastener manufacturing industry. One previously developed model and one new model were adopted for predicting oil mist exposure concentrations emitted from metal work fluid (MWF and PAHs contained in MWF by using the fastener production rate (Pr and cumulative fastener production rate (CPr as predictors, respectively. By applying the annual Pr and CPr records to the above two models, long-term workplace PAH exposure concentrations were predicted. In addition, true exposure data was also collected from the field. The predicted and measured concentrations respectively served as the prior and likelihood distributions in the Bayesian decision analysis (BDA, and the resultant posterior distributions were used to determine the long-term exposure and health-risks posed on workers. Results show that long term exposures to PAHs would result in a 3.1%, 96.7%, and 73.4% chance of exceeding the PEL-TWA (0.2 mg/m3, action level (0.1 mg/m3, and acceptable health risk (10−3, respectively. In conclusion, preventive measures should be taken immediately to reduce workers’ PAH exposures.

  10. Bolt and nut evaluator

    Science.gov (United States)

    Kerley, James J.; Burkhardt, Raymond; White, Steven

    1994-02-01

    A device for testing fasteners such as nuts and bolts is described which consists of a fixed base plate having a number of threaded and unthreaded holes of varying size for receiving the fasteners to be tested, a torque marking paper taped on top the fixed base plate for marking torque-angle indicia, a torque wrench for applying torque to the fasteners being tested, and an indicator for showing the torque applied to the fastener. These elements provide a low cost, nondestructive device for verifying the strength of bolts and nuts.

  11. Charged black holes in quadratic gravity

    International Nuclear Information System (INIS)

    Matyjasek, Jerzy; Tryniecki, Dariusz

    2004-01-01

    Iterative solutions to fourth-order gravity describing static and electrically charged black holes are constructed. The obtained solutions are parametrized by two integration constants which are related to the electric charge and the exact location of the event horizon. Special emphasis is put on the extremal black holes. It is explicitly demonstrated that in the extremal limit the exact location of the (degenerate) event horizon is given by r + =|e|. Similarly to the classical Reissner-Nordstroem solution, the near-horizon geometry of the charged black holes in quadratic gravity, when expanded into the whole manifold, is simply that of Bertotti and Robinson. Similar considerations have been carried out for boundary conditions of the second type which employ the electric charge and the mass of the system as seen by a distant observer. The relations between results obtained within the framework of each method are briefly discussed

  12. Smart aircraft fastener evaluation (SAFE) system: a condition-based corrosion detection system for aging aircraft

    Science.gov (United States)

    Schoess, Jeffrey N.; Seifert, Greg; Paul, Clare A.

    1996-05-01

    The smart aircraft fastener evaluation (SAFE) system is an advanced structural health monitoring effort to detect and characterize corrosion in hidden and inaccessible locations of aircraft structures. Hidden corrosion is the number one logistics problem for the U.S. Air Force, with an estimated maintenance cost of $700M per year in 1990 dollars. The SAFE system incorporates a solid-state electrochemical microsensor and smart sensor electronics in the body of a Hi-Lok aircraft fastener to process and autonomously report corrosion status to aircraft maintenance personnel. The long-term payoff for using SAFE technology will be in predictive maintenance for aging aircraft and rotorcraft systems, fugitive emissions applications such as control valves, chemical pipeline vessels, and industrial boilers. Predictive maintenance capability, service, and repair will replace the current practice of scheduled maintenance to substantially reduce operational costs. A summary of the SAFE concept, laboratory test results, and future field test plans is presented.

  13. A real-time visual inspection method of fastening bolts in freight car operation

    Science.gov (United States)

    Nan, Guo; Yao, JunEn

    2015-10-01

    A real-time inspection of the key components is necessary for ensuring safe operation of freight car. While traditional inspection depends on the trained human inspectors, which is time-consuming and lower efficient. With the development of machine vision, vision-based inspection methods get more railway on-spot applications. The cross rod end fastening bolts are important components on both sides of the train body that fixing locking plates together with the freight car main structure. In our experiment, we get the images containing fastening bolt components, and accurately locate the locking plate position using a linear Support Vector Machine (SVM) locating model trained with Histograms of Oriented Gradients (HOG) features. Then we extract the straight line segment using the Line Segment Detector (LSD) and encoding them in a range, which constitute a straight line segment dataset. Lastly we determine the locking plate's working state by the linear pattern. The experiment result shows that the localization accurate rate is over 99%, the fault detection rate is over 95%, and the module implementation time is 2f/s. The overall performance can completely meet the practical railway safety assurance application.

  14. Estimation for bolt fastening conditions of thin aluminum structure using PZT sensors

    International Nuclear Information System (INIS)

    Hong, Yong; Han, Byeong Hee; Kim, Byung Jin; Hong, Dong Pyo; Kim, Young Moon

    2007-01-01

    This work presents a study on PZT impedance-based method, it is one of the NDT(Non-Destructive Technique). We study about assessment of the square-structure health condition by impedance-based technique using PZT patches, associated with longitudinal wave propagation. Health conditions of the square-structure controlled by bolt fastening condition is adjusted by torque wrench. In order to estimate the damage condition numerically, we suggest the evaluation method of impedance peak frequency shift

  15. Decarburisation Effect on Hardened Strip Steel Fastening Components

    Directory of Open Access Journals (Sweden)

    Karli JAASON

    2016-05-01

    Full Text Available Heat treatment is widely used for high reliability fastening components such as buckles and brackets. The current study focuses on mass production of safety components which are fineblanked from sheet metal, austempered and chromium electroplated. Electroplating together with stamping defects may lead to unexpected brittle failure of the component. It is widely known that during austenitisation, decarburisation could avoid brittle failure and, therefore, slight decarburisation is recommended. There is little information how much mass production is influenced by decarburisation and where the limits are. The current study has two goals. The first one focuses on the extent of decarburisation effect on the part properties, and the second aims to find the optimum furnace setting for the product type used in the study. Also, it is necessary to choose a reliable decarburisation control method for austempered components. The effect on material grades was analyzed by using three steel alloys with carbon content of 0.37 wt.%, 0.47 wt.% and 0.62 wt.%. The specimens were austempered to hardness 45 – 51 HRC under endothermic protective atmosphere. To gain different decarburisation levels, two gas set-ups were used. Infrared gas analyzer was used to measure CO and CO2 content in the furnace gas. Three characteristics of the specimens were evaluated: hardness, rupture strength and brittleness. The depth of the decarburisation was determined by three different approaches according to standard EN ISO 3887. Based on the results, the spectrographic method is the most reliable for determining the depth of decarburisation. This study reveals that higher surface decarburisation has a positive effect on the ductility and no effect on the rupture strength of the component. The material with carbon content of 0.62 wt.% is the most sensitive to decarburisation. During mass production, the inaccuracy of hardness measuring raises which results in the inaccuracy of

  16. Experimental Study on Environment Friendly Tap Hole Clay for Blast Furnace

    Science.gov (United States)

    Siva kumar, R.; Mohammed, Raffi; Srinivasa Rao, K.

    2018-03-01

    Blast furnace (BF) is the best possible route of iron production available. Blast furnace is a high pressure vessel where iron ore is melted and liquid iron is produced. The liquid iron is tapped through the hole in Blast Furnace called tap hole. The tapped liquid metal flowing through the tap hole is plugged using a clay called tap hole clay. Tap hole clay (THC) is a unshaped refractory used to plug the tap hole. The tap hole clay extruded through the tap hole using a gun. The tap hole clay is designed to expand and plug the tap hole. The tap hole filled with clay is drilled using drill bit and the hole made through the tap hole to tap the liquid metal accumulated inside the furnace. The number of plugging and drilling varies depending on the volume of the furnace. The tap hole clay need to have certain properties to avoid problems during plugging and drilling. In the present paper tap hole clay properties in industrial use was tested and studied. The problems were identified related to tap hole clay manufacturing. Experiments were conducted in lab scale to solve the identified problems. The present composition was modified with experimental results. The properties of the modified tap hole clay were found suitable and useful for blast furnace operation with lab scale experimental results.

  17. From laboratory corrosion tests to a corrosion lifetime for wood fasteners : progress and challenges

    Science.gov (United States)

    Samuel L. Zelinka; Dominique Derome; Samuel V. Glass

    2010-01-01

    Determining a “corrosion-lifetime” for fasteners embedded in wood treated with recently adopted preservative systems depends upon successfully relating results of laboratory tests to in-service conditions. In contrast to laboratory tests where metal is embedded in wood at constant temperature and moisture content, the in-service temperature and moisture content of wood...

  18. Influence of panel fastening on the acoustic performance of light-weight building elements: Study by sound transmission and laser scanning vibrometry

    Science.gov (United States)

    Roozen, N. B.; Muellner, H.; Labelle, L.; Rychtáriková, M.; Glorieux, C.

    2015-06-01

    Structural details and workmanship can cause considerable differences in sound insulation properties of timber frame partitions. In this study, the influence of panel fastening is investigated experimentally by means of standardized sound reduction index measurements, supported by detailed scanning laser Doppler vibrometry. In particular the effect of the number of screws used to fasten the panels to the studs, and the tightness of the screws, is studied using seven different configurations of lightweight timber frame building elements. In the frequency range from 300 to 4000 Hz, differences in the weighted sound reduction index RW as large as 10 dB were measured, suggesting that the method of fastening can have a large impact on the acoustic performance of building elements. Using the measured vibrational responses of the element, its acoustic radiation efficiency was computed numerically by means of a Rayleigh integral. The increased radiation efficiency partly explains the reduced sound reduction index. Loosening the screws, or reducing the number of screws, lowers the radiation efficiency, and significantly increases the sound reduction index of the partition.

  19. Comprehensive and Highly Accurate Measurements of Crane Runways, Profiles and Fastenings.

    Science.gov (United States)

    Dennig, Dirk; Bureick, Johannes; Link, Johannes; Diener, Dmitri; Hesse, Christian; Neumann, Ingo

    2017-05-13

    The process of surveying crane runways has been continually refined due to the competitive situation, modern surveying instruments, additional sensors, accessories and evaluation procedures. Guidelines, such as the International Organization for Standardization (ISO) 12488-1, define target values that must be determined by survey. For a crane runway these are for example the span, the position and height of the rails. The process has to be objective and reproducible. However, common processes of surveying crane runways do not meet these requirements sufficiently. The evaluation of the protocols, ideally by an expert, requires many years of experience. Additionally, the recording of crucial parameters, e.g., the wear of the rail, or the condition of the rail fastening and rail joints, is not regulated and for that reason are often not considered during the measurement. To solve this deficit the Advanced Rail Track Inspection System (ARTIS) was developed. ARTIS is used to measure the 3D position of crane rails, the cross-section of the crane rails, joints and, for the first time, the (crane-rail) fastenings. The system consists of a monitoring vehicle and an external tracking sensor. It makes kinematic observations with the tracking sensor from outside the rail run, e.g., the floor of an overhead crane runway, possible. In this paper we present stages of the development process of ARTIS, new target values, calibration of sensors and results of a test measurement.

  20. 76 FR 3561 - Airworthiness Directives; The Boeing Company Model 777-200 and -300 Series Airplanes Equipped...

    Science.gov (United States)

    2011-01-20

    ... studs, blanket studs, and temporary fasteners; replacement of sealant if necessary; and related... installed Doing a detailed inspection of the T/R panel wall inner bolt holes for elongation Doing a general... click bond stud, blanket stud, and temporary fastener is loose, damaged, or missing Doing an NDT (eddy...

  1. Cosmic microwave background radiation of black hole universe

    Science.gov (United States)

    Zhang, T. X.

    2010-11-01

    Modifying slightly the big bang theory, the author has recently developed a new cosmological model called black hole universe. This new cosmological model is consistent with the Mach principle, Einsteinian general theory of relativity, and observations of the universe. The origin, structure, evolution, and expansion of the black hole universe have been presented in the recent sequence of American Astronomical Society (AAS) meetings and published recently in a scientific journal: Progress in Physics. This paper explains the observed 2.725 K cosmic microwave background radiation of the black hole universe, which grew from a star-like black hole with several solar masses through a supermassive black hole with billions of solar masses to the present universe with hundred billion-trillions of solar masses. According to the black hole universe model, the observed cosmic microwave background radiation can be explained as the black body radiation of the black hole universe, which can be considered as an ideal black body. When a hot and dense star-like black hole accretes its ambient materials and merges with other black holes, it expands and cools down. A governing equation that expresses the possible thermal history of the black hole universe is derived from the Planck law of black body radiation and radiation energy conservation. The result obtained by solving the governing equation indicates that the radiation temperature of the present universe can be ˜2.725 K if the universe originated from a hot star-like black hole, and is therefore consistent with the observation of the cosmic microwave background radiation. A smaller or younger black hole universe usually cools down faster. The characteristics of the original star-like or supermassive black hole are not critical to the physical properties of the black hole universe at present, because matter and radiation are mainly from the outside space, i.e., the mother universe.

  2. Tempering of martensitic steel for fasteners : Effects of micro-alloying on microstructure and mechanical property evolution

    NARCIS (Netherlands)

    Öhlund, C.E.I.C.

    2015-01-01

    The research presented in this thesis aims to deepen our understanding of the effect of micro-alloying on the microstructure and mechanical property evolution during tempering of martensitic steel for fasteners. The ongoing trend of engine down-sizing has led to the need for stronger and more

  3. The Fate of Massive Black Holes in Gas-Rich Galaxy Mergers

    Science.gov (United States)

    Escala, A.; Larson, R. B.; Coppi, P. S.; Mardones, D.

    2006-06-01

    Using SPH numerical simulations, we investigate the effects of gas on the inspiral and merger of a massive black hole binary. This study is motivated by the very massive nuclear gas disks observed in the central regions of merging galaxies. Here we present results that expand on the treatment in previous works (Escala et al. 2004, 2005), by studying the evolution of a binary with different black holes masses in a massive gas disk.

  4. Characterization and optimization of spiral eddy current coils for in-situ crack detection

    Science.gov (United States)

    Mandache, Catalin

    2018-03-01

    In-situ condition-based maintenance is making strides in the aerospace industry and it is seen as an alternative to scheduled, time-based maintenance. With fatigue cracks originating from fastener holes as the main reason for structural failures, embedded eddy current coils are a viable non-invasive solution for their timely detection. The development and potential broad use of these coils are motivated by a few consistent arguments: (i) inspection of structures of complicated geometries and hard to access areas, that often require disassembly, (ii) alternative to regular inspection actions that could introduce inadvertent damage, (iii) for structures that have short inspection intervals, and (iv) for repaired structures where fastener holes contain bushings and prevent further bolt-hole inspections. Since the spiral coils are aiming at detecting radial cracks emanating from the fastener holes, their design parameters should allow for high inductance, low ohmic losses and power requirements, as well as optimal size and high sensitivity to discontinuities. In this study, flexible, surface conformable, spiral eddy current coils are empirically investigated on mock-up specimens, while numerical analysis is performed for their optimization and design improvement.

  5. Rapid Strengthening of Full-Sized Concrete Beams with Powder-Actuated fastening Systems and Fiber-Reinforced Polymer (FRP) Composite Materials

    National Research Council Canada - National Science Library

    Bank, Lawrence

    2002-01-01

    A research study was conducted to determine if the method of retrofitting reinforced concrete beams with powder-actuated fasteners and composite materials was applicable to full-scale flexural members...

  6. A polymeric fastener can easily functionalize liposome surfaces with gadolinium for enhanced magnetic resonance imaging.

    Science.gov (United States)

    Smith, Cartney E; Shkumatov, Artem; Withers, Sarah G; Yang, Binxia; Glockner, James F; Misra, Sanjay; Roy, Edward J; Wong, Chun-Ho; Zimmerman, Steven C; Kong, Hyunjoon

    2013-11-26

    Common methods of loading magnetic resonance imaging (MRI) contrast agents into nanoparticles often suffer from challenges related to particle formation, complex chemical modification/purification steps, and reduced contrast efficiency. This study presents a simple, yet advanced process to address these issues by loading gadolinium, an MRI contrast agent, exclusively on a liposome surface using a polymeric fastener. The fastener, so named for its ability to physically link the two functional components together, consisted of chitosan substituted with diethylenetriaminepentaacetic acid (DTPA) to chelate gadolinium, as well as octadecyl chains to stabilize the modified chitosan on the liposome surface. The assembly strategy, mimicking the mechanisms by which viruses and proteins naturally anchor to a cell, provided greater T1 relaxivity than liposomes loaded with gadolinium in both the interior and outer leaflet. Gadolinium-coated liposomes were ultimately evaluated in vivo using murine ischemia models to highlight the diagnostic capability of the system. Taken together, this process decouples particle assembly and functionalization and, therefore, has considerable potential to enhance imaging quality while alleviating many of the difficulties associated with multifunctional particle fabrication.

  7. Temporary percutaneous T-fastener gastropexy and continuous decompressive gastrostomy in dogs with experimentally induced gastric dilatation.

    Science.gov (United States)

    Fox-Alvarez, W Alexander; Case, J Brad; Cooke, Kirsten L; Garcia-Pereira, Fernando L; Buckley, Gareth J; Monnet, Eric; Toskich, Beau B

    2016-07-01

    OBJECTIVE To evaluate a percutaneous, continuous gastric decompression technique for dogs involving a temporary T-fastener gastropexy and self-retaining decompression catheter. ANIMALS 6 healthy male large-breed dogs. PROCEDURES Dogs were anesthetized and positioned in dorsal recumbency with slight left-lateral obliquity. The gastric lumen was insufflated endoscopically until tympany was evident. Three T-fasteners were placed percutaneously into the gastric lumen via the right lateral aspect of the abdomen, caudal to the 13th rib and lateral to the rectus abdominis muscle. Through the center of the T-fasteners, a 5F locking pigtail catheter was inserted into the gastric lumen and attached to a device measuring gas outflow and intragastric pressure. The stomach was insufflated to 23 mm Hg, air was allowed to passively drain from the catheter until intraluminal pressure reached 5 mm Hg for 3 cycles, and the catheter was removed. Dogs were hospitalized and monitored for 72 hours. RESULTS Mean ± SD catheter placement time was 3.3 ± 0.5 minutes. Mean intervals from catheter placement to a ≥ 50% decrease in intragastric pressure and to ≤ 6 mm Hg were 2.1 ± 1.3 minutes and 8.4 ± 5.1 minutes, respectively. After catheter removal, no gas or fluid leakage at the catheter site was visible laparoscopically or endoscopically. All dogs were clinically normal 72 hours after surgery. CONCLUSIONS AND CLINICAL RELEVANCE The described technique was performed rapidly and provided continuous gastric decompression with no evidence of postoperative leakage in healthy dogs. Investigation is warranted to evaluate its effectiveness in dogs with gastric dilatation-volvulus.

  8. Exposure testing of fasteners in preservative treated wood : gravimetric corrosion rates and corrosion product analyses

    Science.gov (United States)

    Samuel L. Zelinka; Rebecca J. Sichel; Donald S. Stone

    2010-01-01

    Research was conducted to determine the corrosion rates of metals in preservative treated wood and also understand the mechanism of metal corrosion in treated wood. Steel and hot-dip galvanized steel fasteners were embedded in wood treated with one of six preservative treatments and exposed to 27oC at 100% relative humidity for 1 year. The...

  9. Enhancing results : solid expandable tubulars facilitate high-temperature oil recovery

    Energy Technology Data Exchange (ETDEWEB)

    Noel, G.; Nylund, J.; Flaming, S. [Enventure Global Technology LLC, Calgary, AB (Canada)

    2010-07-01

    Steam-based recovery methods can provide a cost-effective approach to developing heavy oil and oil sands energy resources. This paper described a solid expandable tubular system designed to prevent damage without decreases in hole size. The pipe's permanent deformation creates an energized seal that cases off damaged tubulars. The new sealing systems allow for operations in the range of 270 degrees C. The system was comprised of mechanical retainers designed to hold the multi-component, high-temperature seal in place on the expandable casing. The seals are held in place by retainer rings designed to protect the seal in the hole as well as to provide increased anchoring capacity when the pipe is expanded and clad onto the base casing. The retainers are wrapped with a redundant standard seal material. The weight and size of the casings are individually configured for specific wells and are also designed to maintain consistency across multiple weight ranges. Details of the testing protocol used to ensure that the sealing system operated well in various oil production scenarios were presented, as well as the results of case studies conducted to demonstrate the system in the field. 6 refs., 1 tab., 2 figs.

  10. Hole growth dynamics in a two dimensional Leidenfrost droplet

    Science.gov (United States)

    Raufaste, Christophe; Celestini, Franck; Barzyk, Alexandre; Frisch, Thomas

    2015-03-01

    We studied the behaviors of Leidenfrost droplets confined in a Hele-Shaw cell. These droplets are unstable above a critical size and a hole grows at their center. We experimentally investigate two different systems for which the hole growth dynamics exhibits peculiar features that are driven by capillarity and inertia. We report a first regime characterized by the liquid reorganization from a liquid sheet to a liquid torus with similarities to the burst of micron-thick soap films. In the second regime, the liquid torus expands and thins before fragmentation. Finally, we propose models to account for the experimental results.

  11. Longitudinal coupling impedance of a hole in an infinite plane screen

    International Nuclear Information System (INIS)

    Chae, Yong-Chul.

    1995-01-01

    An analytical formula for the longitudinal coupling impedance of a hole is developed using a variational method. We show that the coupling impedance can be expressed as a sum of functional series, whose argument is the dimensionless quantity kd alone, where k is the free-space wave number and d is the radius of the hole. When expanded in powers of kd, we recover the long wavelength result as a limiting case. The numerical evaluation reveals that the impedance can be well modeled by an RLC-resonator circuit. We also show the qualitatively good agreement between the theory and the MAFIA-T3 simulation for the geometry of a hole in a coupled waveguide with rectangular cross section

  12. The Mixed Phase of Charged AdS Black Holes

    Directory of Open Access Journals (Sweden)

    Piyabut Burikham

    2016-01-01

    Full Text Available We study the mixed phase of charged AdS black hole and radiation when the total energy is fixed below the threshold to produce a stable charged black hole branch. The coexistence conditions for the charged AdS black hole and radiation are derived for the generic case when radiation particles carry charge. The phase diagram of the mixed phase is demonstrated for both fixed potential and charge ensemble. In the dual gauge picture, they correspond to the mixed phase of quark-gluon plasma (QGP and hadron gas in the fixed chemical potential and density ensemble, respectively. In the nuclei and heavy-ion collisions at intermediate energies, the mixed phase of exotic QGP and hadron gas could be produced. The mixed phase will condense and evaporate into the hadron gas as the fireball expands.

  13. Corrosion fatigue of high strength fastener materials in seawater

    Science.gov (United States)

    Tipton, D. G.

    1983-12-01

    Environmental effects which significantly reduce the fatigue life of metals are discussed. Corrosion fatigue is a major concern in the engineering application of high strength fasteners in marine environments. The corrosion fatigue failure of an AISI 41L4O high strength steel blade to hub attachment bolt at the MOD-OA 200 kW wind turbine generator was investigated. The reduction of fatigue strength of AISI 41L4O in marine environments and to obtain similar corrosion fatigue data for candidate replacement materials was studied. The AISI 4140, PH 13-8Mo stainless steel, alloy 718 and alloy MP-35N were tested in axial fatigue at a frequency of 20 Hz in dry air and natural seawater. The fatigue data are fitted by regression equations to allow determination of fatigue strength for a given number of cycles to failure.

  14. Study on antioxidant experiment on forged steel tube sheet and tube hole for steam generator

    International Nuclear Information System (INIS)

    Zong Hai; Wang Detai; Ding Yang

    2012-01-01

    Antioxidant experiment on forged steel tube sheet and tube hole for steam generator was studied and the influence of different simulated heat treatments on the antioxidant performance of tube sheet and tube hole was made. The influence of different antioxidant methods on the size of tube hole was drawn. Furthermore, the change of size and weight of 18MnD5 forged steel tube sheet on the condition of different simulated heat treatments was also studied. The analytical results have proved reference information for the use of 18MnD5 material and for key processes of processing tube hole and wearing and expanding U-style tube. (authors)

  15. [Functional load distribution in cases of different types of removable dentures fastening].

    Science.gov (United States)

    Zhulev, E N; Klokov, A A

    2007-01-01

    Questions of studying of a biomechanics of system prosthesis - prosthetic region using of mathematical modelling are surveyed. The original way of definition of physical parameters of a mucosa of an edentulous alveolar process is offered. Modelling of a leaky adhering of prosthesis basis to a mucosa as free saddle situation shows, that a abutment teeth and an edentulous alveolar part of a jaw are in an optimum situation at sliding resilient fastening of a removable partial denture. Rigid bond in the given situation on the contrary promotes development of an overload of abutment teeth and their inclination distally.

  16. Black supernovae and black holes in non-local gravity

    Energy Technology Data Exchange (ETDEWEB)

    Bambi, Cosimo [Center for Field Theory and Particle Physics and Department of Physics, Fudan University,200433 Shanghai (China); Theoretical Astrophysics, Eberhard-Karls Universität Tübingen,72076 Tübingen (Germany); Malafarina, Daniele [Department of Physics, Nazarbayev University,010000 Astana (Kazakhstan); Modesto, Leonardo [Center for Field Theory and Particle Physics and Department of Physics, Fudan University,200433 Shanghai (China)

    2016-04-22

    In a previous paper, we studied the interior solution of a collapsing body in a non-local theory of gravity super-renormalizable at the quantum level. We found that the classical singularity is replaced by a bounce, after which the body starts expanding. A black hole, strictly speaking, never forms. The gravitational collapse does not create an event horizon but only an apparent one for a finite time. In this paper, we solve the equations of motion assuming that the exterior solution is static. With such an assumption, we are able to reconstruct the solution in the whole spacetime, namely in both the exterior and interior regions. Now the gravitational collapse creates an event horizon in a finite comoving time, but the central singularity is approached in an infinite time. We argue that these black holes should be unstable, providing a link between the scenarios with and without black holes. Indeed, we find a non catastrophic ghost-instability of the metric in the exterior region. Interestingly, under certain conditions, the lifetime of our black holes exactly scales as the Hawking evaporation time.

  17. Enthalpy and the mechanics of AdS black holes

    International Nuclear Information System (INIS)

    Kastor, David; Traschen, Jennie; Ray, Sourya

    2009-01-01

    We present geometric derivations of the Smarr formula for static AdS black holes and an expanded first law that includes variations in the cosmological constant. These two results are further related by a scaling argument based on Euler's theorem. The key new ingredient in the constructions is a two-form potential for the static Killing field. Surface integrals of the Killing potential determine the coefficient of the variation of Λ in the first law. This coefficient is proportional to a finite, effective volume for the region outside the AdS black hole horizon, which can also be interpreted as minus the volume excluded from a spatial slice by the black hole horizon. This effective volume also contributes to the Smarr formula. Since Λ is naturally thought of as a pressure, the new term in the first law has the form of effective volume times change in pressure that arises in the variation of the enthalpy in classical thermodynamics. This and related arguments suggest that the mass of an AdS black hole should be interpreted as the enthalpy of the spacetime.

  18. On the Size of the Antarctic Ozone Hole

    Science.gov (United States)

    Newman, Paul A.; Nash, Eric R.; Kawa, S. Randolph

    2002-01-01

    The Antarctic ozone hole is a region of extremely large ozone depletion that is roughly centered over the South Pole. Since 1979, the area coverage of the ozone hole has grown from near zero size to over 24 Million sq km. In the 8-year period from 1981 to 1989, the area expanded by 18 Million sq km. During the last 5 years, the hole has been observed to exceed 25 Million sq km over brief periods. In the spring of 2002, the size of the ozone hole barely reached 20 Million sq km for only a couple of days. We will review these size observations, the size trends, and the interannual variability of the size. The area is derived from the area enclosed by the 220 DU total ozone contour. We will discuss the rationale for the choice of 220 DU: 1) it is located near the steep gradient between southern mid-latitudes and the polar region, and 2) 220 DU is a value that is lower than the pre-1979 ozone observations over Antarctica during the spring period. The phenomenal growth of the ozone hole was directly caused by the increases of chlorine and bromine compounds in the stratosphere. In this talk, we will show the relationship of the ozone hole's size to the interannual variability of Antarctic spring temperatures. In addition, we will show the relationship of these same temperatures to planetary-scale wave forcings.

  19. White holes and eternal black holes

    International Nuclear Information System (INIS)

    Hsu, Stephen D H

    2012-01-01

    We investigate isolated white holes surrounded by vacuum, which correspond to the time reversal of eternal black holes that do not evaporate. We show that isolated white holes produce quasi-thermal Hawking radiation. The time reversal of this radiation, incident on a black hole precursor, constitutes a special preparation that will cause the black hole to become eternal. (paper)

  20. Effective theories and black hole production in warped compactifications

    International Nuclear Information System (INIS)

    Giddings, Steven B.; Katz, Emanuel

    2001-01-01

    We investigate aspects of the four-dimensional (4D) effective description of brane world scenarios based on warped compactification on anti-de Sitter space. The low-energy dynamics is described by visible matter gravitationally coupled to a ''dark'' conformal field theory. We give the linearized description of the 4D stress tensor corresponding to an arbitrary 5D matter distribution. In particular a 5D falling particle corresponds to a 4D expanding shell, giving a 4D interpretation of a trajectory that misses a black hole only by moving in the fifth dimension. Breakdown of the effective description occurs when either five-dimensional physics or strong gravity becomes important. In scenarios with a TeV brane, the latter can happen through the production of black holes near the TeV scale. This could provide an interesting experimental window on quantum black hole dynamics

  1. Evaluation of anti-migration properties of biliary covered self-expandable metal stents.

    Science.gov (United States)

    Minaga, Kosuke; Kitano, Masayuki; Imai, Hajime; Harwani, Yogesh; Yamao, Kentaro; Kamata, Ken; Miyata, Takeshi; Omoto, Shunsuke; Kadosaka, Kumpei; Sakurai, Toshiharu; Nishida, Naoshi; Kudo, Masatoshi

    2016-08-14

    To assess anti-migration potential of six biliary covered self-expandable metal stents (C-SEMSs) by using a newly designed phantom model. In the phantom model, the stent was placed in differently sized holes in a silicone wall and retracted with a retraction robot. Resistance force to migration (RFM) was measured by a force gauge on the stent end. Radial force (RF) was measured with a RF measurement machine. Measured flare structure variables were the outer diameter, height, and taper angle of the flare (ODF, HF, and TAF, respectively). Correlations between RFM and RF or flare variables were analyzed using a linear correlated model. Out of the six stents, five stents were braided, the other was laser-cut. The RF and RFM of each stent were expressed as the average of five replicate measurements. For all six stents, RFM and RF decreased as the hole diameter increased. For all six stents, RFM and RF correlated strongly when the stent had not fully expanded. This correlation was not observed in the five braided stents excluding the laser cut stent. For all six stents, there was a strong correlation between RFM and TAF when the stent fully expanded. For the five braided stents, RFM after full stent expansion correlated strongly with all three stent flare structure variables (ODF, HF, and TAF). The laser-cut C-SEMS had higher RFMs than the braided C-SEMSs regardless of expansion state. RF was an important anti-migration property when the C-SEMS did not fully expand. Once fully expanded, stent flare structure variables plays an important role in anti-migration.

  2. Strength Behaviour of Fatigue Cracked Lugs (Festigkeitsverhalten von Rissbehafteten Augenstaeben),

    Science.gov (United States)

    1981-01-01

    either surface cracks or corner cracks at holes. NASA TN 1)-8244 64 A.F. Grandt Stress intensity factors for some through fracked fastener holes...with Hydropuise L~ngszylinder longitudinal cylinder Druckblversorgung =pressure oil Supply Hydraulikaggregat = hydraulic control unit Fig 7.5 Plan of

  3. What Controls the Size of the Antarctic Ozone Hole?

    Science.gov (United States)

    Bhartia, P. K. (Technical Monitor); Newman, Paul A.; Kawa, S. Randolph; Nash, Eric R.

    2002-01-01

    The Antarctic ozone hole is a region of extremely large ozone depletion that is roughly centered over the South Pole. Since 1979, the area coverage of the ozone hole has grown from near zero size to over 24 Million square kilometers. In the 8-year period from 1981 to 1989, the area expanded by 18 Million square kilometers. During the last 5 years, the hole has been observed to exceed 25 Million square kilometers over brief periods. We will review these size observations, the size trends, and the interannual variability of the size. The area is derived from the area enclosed by the 220 DU total ozone contour. We will discuss the rationale for the choice of 220 DU: 1) it is located near the steep gradient between southern mid-latitudes and the polar region, and 2) 220 DU is a value that is lower than the pre- 1979 ozone observations over Antarctica during the spring period. The phenomenal growth of the ozone hole was directly caused by the increases of chlorine and bromine compounds in the stratosphere. In this talk, we will show the relationship of the ozone hole's size to the interannual variability of Antarctic spring temperatures. In addition, we will show the relationship of these same temperatures to planetary-scale wave forcings.

  4. Quasar Formation and Energy Emission in Black Hole Universe

    Directory of Open Access Journals (Sweden)

    Zhang T. X.

    2012-07-01

    . The entire space evolves itera- tively. When one universe expands out, a new similar universe is formed from its inside star-like or supermassive black holes.

  5. Electrochemical impedance spectroscopy (EIS) as a tool for measuring corrosion of polymer-coated fasteners used in treated wood

    Science.gov (United States)

    Samuel L. Zelinka; Lorraine Ortiz-Candelaria; Donald S. Stone; Douglas R. Rammer

    2009-01-01

    Currently, many of the polymer-coated fasteners on the market are designed for improved corrosion performance in treated wood; yet, there is no way to evaluate their corrosion performance. In this study, a common technique for measuring the corrosion performance of polymer-coated metals, electrochemical impedance spectroscopy (EIS), was used to evaluate commercial...

  6. Use of an Automated Suture Fastening Device in Minimally Invasive Aortic Valve Replacement.

    Science.gov (United States)

    Beute, Tyler J; Orem, Matthew D; Schiller, Timothy M; Goehler, Matthew; Parker, Jessica; Willekes, Charles L; Timek, Tomasz

    2018-03-01

    Minimally invasive aortic valve replacement (mAVR) is gaining clinical acceptance, however, it is associated with increased operative times due to limited surgical field and access. The Cor-Knot is an automated fastening device designed to facilitate suture fastening, but clinical data in mAVR are lacking. From May 2014 to February 2017, 92 patients underwent mAVR at our center with 39 valves secured with manually-tied (MT) sutures and 53 valves entirely secured with the Cor-Knot (CK). Pre-operative characteristics and 30-day outcomes data were extracted from our local Society of Thoracic Surgeons database and the electronic medical record. Survival data were obtained from the Michigan State Social Security Death Index. No significant difference in pre-operative characteristics were noted between the two groups. Aortic cross-clamp time (72±12 min vs 82±15 min, p=0.001) was significantly shorter with CK. There was no difference in post-operative mortality (0% vs 0%), stroke (0% vs 1.9%), atrial fibrillation (28% vs 33%), renal failure (0% vs 3.8%), or pacemaker implantation (5.1% vs 5.7%) between MT and CK. Valve function on post-operative echocardiography and 1-year patient survival were similar. In minimally invasive aortic valve replacement, the Cor-Knot device was associated with reduced aortic cross-clamp time while providing equivalent clinical outcomes. Larger studies are needed to confirm efficacy, safety, and cost-effectiveness of the Cor-Knot device in minimally invasive aortic valve surgery. Copyright © 2018 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

  7. Nanowire surface fastener fabrication on flexible substrate

    Science.gov (United States)

    Toku, Yuhki; Uchida, Keita; Morita, Yasuyuki; Ju, Yang

    2018-07-01

    The market for wearable devices has increased considerably in recent years. In response to this demand, flexible electronic circuit technology has become more important. The conventional bonding technology in electronic assembly depends on high-temperature processes such as reflow soldering, which result in undesired thermal damages and residual stress at a bonding interface. In addition, it exhibits poor compatibility with bendable or stretchable device applications. Therefore, there is an urgent requirement to attach electronic parts on printed circuit boards with good mechanical and electrical properties at room temperature. Nanowire surface fasteners (NSFs) are candidates for resolving these problems. This paper describes the fabrication of an NSF on a flexible substrate, which can be used for room temperature conductive bonding. The template method is used for preparing high-density nanowire arrays. A Cu thin film is layered on the template as the flexible substrate. After etching the template, a Cu NSF is obtained on the Cu film substrate. In addition, the electrical and mechanical properties of the Cu NSF are studied under various fabrication conditions. The Cu NSF exhibits high shear adhesion strength (∼234 N cm‑2) and low contact resistivity (2.2 × 10‑4 Ω cm2).

  8. Development of a 3-D model for eddy current testing: application for fastened structures in aeronautics

    International Nuclear Information System (INIS)

    Paillard, S.

    2007-12-01

    One of the Eddy Current Testing issues in aeronautics is the inspection of fastened structures to detect flaws nearby rivets which can grow because of mechanical stress. EADS and the CEA LIST have started a collaborative work with the support of the Ile-de-France Region to develop a simulation tool of EC fastened structures testing, integrated to the CIVA platform, aimed at conceiving testing methods, optimizing and qualifying it. The volume integral method using the Green dyadics formalism has been chosen in order to get a fast resolution of Maxwell equations. A first milestone was to build a simulation model of multilayer structures testing, thanks to the use of the multilayer Green dyads. Because of the rivet volume, 60 times bigger than the one of a typical flaw, a large number of discretization cells are needed. Therefore an iterative method has been developed in order to numerically solve large calculation zones. Finally, the flaw response simulation mostly has to cope with a scale issue between the size of the rivet and the one of the flaw, the latter being much smaller in a direction than the former. The whole model has been experimentally validated and compared to other simulation models at the important development steps: multilayer configuration, iteration resolution, and flaw signature. (author)

  9. Can static regular black holes form from gravitational collapse?

    International Nuclear Information System (INIS)

    Zhang, Yiyang; Zhu, Yiwei; Modesto, Leonardo; Bambi, Cosimo

    2015-01-01

    Starting from the Oppenheimer-Snyder model, we know how in classical general relativity the gravitational collapse of matter forms a black hole with a central spacetime singularity. It is widely believed that the singularity must be removed by quantum-gravity effects. Some static quantum-inspired singularity-free black hole solutions have been proposed in the literature, but when one considers simple examples of gravitational collapse the classical singularity is replaced by a bounce, after which the collapsing matter expands for ever. We may expect three possible explanations: (i) the static regular black hole solutions are not physical, in the sense that they cannot be realized in Nature, (ii) the final product of the collapse is not unique, but it depends on the initial conditions, or (iii) boundary effects play an important role and our simple models miss important physics. In the latter case, after proper adjustment, the bouncing solution would approach the static one. We argue that the ''correct answer'' may be related to the appearance of a ghost state in de Sitter spacetimes with super Planckian mass. Our black holes have indeed a de Sitter core and the ghost would make these configurations unstable. Therefore we believe that these black hole static solutions represent the transient phase of a gravitational collapse but never survive as asymptotic states. (orig.)

  10. Examination of pulsed eddy current for inspection of second layer aircraft wing lap-joint structures using outlier detection methods

    Energy Technology Data Exchange (ETDEWEB)

    Butt, D.M., E-mail: Dennis.Butt@forces.gc.ca [Royal Military College of Canada, Dept. of Chemistry and Chemical Engineering, Kingston, Ontario (Canada); Underhill, P.R.; Krause, T.W., E-mail: Thomas.Krause@rmc.ca [Royal Military College of Canada, Dept. of Physics, Kingston, Ontario (Canada)

    2016-09-15

    Ageing aircraft are susceptible to fatigue cracks at bolt hole locations in multi-layer aluminum wing lap-joints due to cyclic loading conditions experienced during typical aircraft operation, Current inspection techniques require removal of fasteners to permit inspection of the second layer from within the bolt hole. Inspection from the top layer without fastener removal is desirable in order to minimize aircraft downtime while reducing the risk of collateral damage. The ability to detect second layer cracks without fastener removal has been demonstrated using a pulsed eddy current (PEC) technique. The technique utilizes a breakdown of the measured signal response into its principal components, each of which is multiplied by a representative factor known as a score. The reduced data set of scores, which represent the measured signal, are examined for outliers using cluster analysis methods in order to detect the presence of defects. However, the cluster analysis methodology is limited by the fact that a number of representative signals, obtained from fasteners where defects are not present, are required in order to perform classification of the data. Alternatively, blind outlier detection can be achieved without having to obtain representative defect-free signals, by using a modified smallest half-volume (MSHV) approach. Results obtained using this approach suggest that self-calibrating blind detection of cyclic fatigue cracks in second layer wing structures in the presence of ferrous fasteners is possible without prior knowledge of the sample under test and without the use of costly calibration standards. (author)

  11. Examination of pulsed eddy current for inspection of second layer aircraft wing lap-joint structures using outlier detection methods

    International Nuclear Information System (INIS)

    Butt, D.M.; Underhill, P.R.; Krause, T.W.

    2016-01-01

    Ageing aircraft are susceptible to fatigue cracks at bolt hole locations in multi-layer aluminum wing lap-joints due to cyclic loading conditions experienced during typical aircraft operation, Current inspection techniques require removal of fasteners to permit inspection of the second layer from within the bolt hole. Inspection from the top layer without fastener removal is desirable in order to minimize aircraft downtime while reducing the risk of collateral damage. The ability to detect second layer cracks without fastener removal has been demonstrated using a pulsed eddy current (PEC) technique. The technique utilizes a breakdown of the measured signal response into its principal components, each of which is multiplied by a representative factor known as a score. The reduced data set of scores, which represent the measured signal, are examined for outliers using cluster analysis methods in order to detect the presence of defects. However, the cluster analysis methodology is limited by the fact that a number of representative signals, obtained from fasteners where defects are not present, are required in order to perform classification of the data. Alternatively, blind outlier detection can be achieved without having to obtain representative defect-free signals, by using a modified smallest half-volume (MSHV) approach. Results obtained using this approach suggest that self-calibrating blind detection of cyclic fatigue cracks in second layer wing structures in the presence of ferrous fasteners is possible without prior knowledge of the sample under test and without the use of costly calibration standards. (author)

  12. Finite-Element Modeling of Timber Joints with Punched Metal Plate Fasteners

    DEFF Research Database (Denmark)

    Ellegaard, Peter

    2006-01-01

    The focus of this paper is to describe the idea and the theory behind a finite-element model developed for analysis of timber trusses with punched metal plate fasteners (nail plates). The finite-element model includes the semirigid and nonlinear behavior of the joints (nonlinear nail and plate...... elements) and contact between timber beams, if any (bilinear contact elements). The timber beams have linear-elastic properties. The section forces needed for design of the joints are given directly by the finite-element model, since special elements are used to model the nail groups and the nail plate...... the behavior of the joints very well at lower load levels. At higher load levels the stiffness is overestimated due to development of cracks in the timber and the linear-elastic timber properties in the finite-element model....

  13. Generation of Electron Whistler Waves at the Mirror Mode Magnetic Holes: MMS Observations and PIC Simulation

    Science.gov (United States)

    Ahmadi, N.; Wilder, F. D.; Usanova, M.; Ergun, R.; Argall, M. R.; Goodrich, K.; Eriksson, S.; Germaschewski, K.; Torbert, R. B.; Lindqvist, P. A.; Le Contel, O.; Khotyaintsev, Y. V.; Strangeway, R. J.; Schwartz, S. J.; Giles, B. L.; Burch, J.

    2017-12-01

    The Magnetospheric Multiscale (MMS) mission observed electron whistler waves at the center and at the gradients of magnetic holes on the dayside magnetosheath. The magnetic holes are nonlinear mirror structures which are anti-correlated with particle density. We used expanding box Particle-in-cell simulations and produced the mirror instability magnetic holes. We show that the electron whistler waves can be generated at the gradients and the center of magnetic holes in our simulations which is in agreement with MMS observations. At the nonlinear regime of mirror instability, the proton and electron temperature anisotropy are anti-correlated with the magnetic hole. The plasma is unstable to electron whistler waves at the minimum of the magnetic field structures. In the saturation regime of mirror instability, when magnetic holes are dominant, electron temperature anisotropy develops at the edges of the magnetic holes and electrons become isotropic at the magnetic field minimum. We investigate the possible mechanism for enhancing the electron temperature anisotropy and analyze the electron pitch angle distributions and electron distribution functions in our simulations and compare it with MMS observations.

  14. Porous expandable device for attachment to bone tissue

    Science.gov (United States)

    Rybicki, Edmund F.; Wheeler, Kenneth Ray; Hulbert, Lewis E.; Karagianes, Manuel Tom; Hassler, Craig R.

    1977-01-01

    A device for attaching to substantially solid living bone tissue, comprising a body member having an outer surface shaped to fit approximately into an empty space in the tissue and having pores into which the tissue can grow to strengthen the bond between the device and the tissue, and adjustable means for expanding the body member against the tissue to an extent such as to provide a compressive stress capable of maintaining a snug and stable fit and of enhancing the growth of the tissue into the pores in the body member. The expanding means is adjustable to provide a stress between the tissue and the body member in the range of about 150 to 750 psi, typically 150 to 350 psi. Typically the body member comprises an expandable cylindrical portion having at least one radial slit extending longitudinally from a first end to the vicinity of the opposite (second) end thereof, at least one radial slit extending longitudinally from the second end to the vicinity of the first end thereof, and a tapered cylindrical hole extending coaxially from a wider circular opening in the first end to a narrower circular opening communicating with the second end.

  15. Black holes

    International Nuclear Information System (INIS)

    Feast, M.W.

    1981-01-01

    This article deals with two questions, namely whether it is possible for black holes to exist, and if the answer is yes, whether we have found any yet. In deciding whether black holes can exist or not the central role in the shaping of our universe played by the forse of gravity is discussed, and in deciding whether we are likely to find black holes in the universe the author looks at the way stars evolve, as well as white dwarfs and neutron stars. He also discusses the problem how to detect a black hole, possible black holes, a southern black hole, massive black holes, as well as why black holes are studied

  16. Performance Characterization of Loctite (Registered Trademark) 242 and 271 Liquid Locking Compounds (LLCs) as a Secondary Locking Feature for International Space Station (ISS) Fasteners

    Science.gov (United States)

    Dube, Michael J.; Gamwell, Wayne R.

    2011-01-01

    Several International Space Station (ISS) hardware components use Loctite (and other polymer based liquid locking compounds (LLCs)) as a means of meeting the secondary (redundant) locking feature requirement for fasteners. The primary locking method is the fastener preload, with the application of the Loctite compound which when cured is intended to resist preload reduction. The reliability of these compounds has been questioned due to a number of failures during ground testing. The ISS Program Manager requested the NASA Engineering and Safety Center (NESC) to characterize and quantify sensitivities of Loctite being used as a secondary locking feature. The findings and recommendations provided in this investigation apply to the anaerobic LLCs Loctite 242 and 271. No other anaerobic LLCs were evaluated for this investigation. This document contains the findings and recommendations of the NESC investigation

  17. σ-holes and π-holes: Similarities and differences.

    Science.gov (United States)

    Politzer, Peter; Murray, Jane S

    2018-04-05

    σ-Holes and π-holes are regions of molecules with electronic densities lower than their surroundings. There are often positive electrostatic potentials associated with them. Through these potentials, the molecule can interact attractively with negative sites, such as lone pairs, π electrons, and anions. Such noncovalent interactions, "σ-hole bonding" and "π-hole bonding," are increasingly recognized as being important in a number of different areas. In this article, we discuss and compare the natures and characteristics of σ-holes and π-holes, and factors that influence the strengths and locations of the resulting electrostatic potentials. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  18. Matched filtering of numerical relativity templates of spinning binary black holes

    International Nuclear Information System (INIS)

    Vaishnav, Birjoo; Hinder, Ian; Herrmann, Frank; Shoemaker, Deirdre

    2007-01-01

    Tremendous progress has been made towards the solution of the binary-black-hole problem in numerical relativity. The waveforms produced by numerical relativity will play a role in gravitational wave detection as either test beds for analytic template banks or as template banks themselves. As the parameter space explored by numerical relativity expands, the importance of quantifying the effect that each parameter has on first the detection of gravitational waves and then the parameter estimation of their sources increases. In light of this, we present a study of equal-mass, spinning binary-black-hole evolutions through matched filtering techniques commonly used in data analysis. We study how the match between two numerical waveforms varies with numerical resolution, initial angular momentum of the black holes, and the inclination angle between the source and the detector. This study is limited by the fact that the spinning black-hole binaries are oriented axially and the waveforms only contain approximately two and a half orbits before merger. We find that for detection purposes, spinning black holes require the inclusion of the higher harmonics in addition to the dominant mode, a condition that becomes more important as the black-hole spins increase. In addition, we conduct a preliminary investigation of how well a template of fixed spin and inclination angle can detect target templates of arbitrary but nonprecessing spin and inclination for the axial case considered here

  19. Energy Neutral Wireless Bolt for Safety Critical Fastening.

    Science.gov (United States)

    Seyoum, Biruk B; Rossi, Maurizio; Brunelli, Davide

    2017-09-26

    Thermoelectric generators (TEGs) are now capable of powering the abundant low power electronics from very small (just a few degrees Celsius) temperature gradients. This factor along with the continuously lowering cost and size of TEGs, has contributed to the growing number of miniaturized battery-free sensor modules powered by TEGs. In this article, we present the design of an ambient-powered wireless bolt for high-end electro-mechanical systems. The bolt is equipped with a temperature sensor and a low power RF chip powered from a TEG. A DC-DC converter interfacing the TEG with the RF chip is used to step-up the low TEG voltage. The work includes the characterizations of different TEGs and DC-DC converters to determine the optimal design based on the amount of power that can be generated from a TEG under different loads and at temperature gradients typical of industrial environments. A prototype system was implemented and the power consumption of this system under different conditions was also measured. Results demonstrate that the power generated by the TEG at very low temperature gradients is sufficient to guarantee continuous wireless monitoring of the critical fasteners in critical systems such as avionics, motorsport and aerospace.

  20. Energy Neutral Wireless Bolt for Safety Critical Fastening

    Directory of Open Access Journals (Sweden)

    Biruk B. Seyoum

    2017-09-01

    Full Text Available Thermoelectric generators (TEGs are now capable of powering the abundant low power electronics from very small (just a few degrees Celsius temperature gradients. This factor along with the continuously lowering cost and size of TEGs, has contributed to the growing number of miniaturized battery-free sensor modules powered by TEGs. In this article, we present the design of an ambient-powered wireless bolt for high-end electro-mechanical systems. The bolt is equipped with a temperature sensor and a low power RF chip powered from a TEG. A DC-DC converter interfacing the TEG with the RF chip is used to step-up the low TEG voltage. The work includes the characterizations of different TEGs and DC-DC converters to determine the optimal design based on the amount of power that can be generated from a TEG under different loads and at temperature gradients typical of industrial environments. A prototype system was implemented and the power consumption of this system under different conditions was also measured. Results demonstrate that the power generated by the TEG at very low temperature gradients is sufficient to guarantee continuous wireless monitoring of the critical fasteners in critical systems such as avionics, motorsport and aerospace.

  1. Dance of Two Monster Black Holes

    Science.gov (United States)

    Kohler, Susanna

    2016-03-01

    This past December, researchers all over the world watched an outburst from the enormous black hole in OJ 287 an outburst that had been predicted years ago using the general theory of relativity.Outbursts from Black-Hole OrbitsOJ 287 is one of the largest supermassive black holes known, weighing in at 18 billion solar masses. Located about 3.5 billion light-years away, this monster quasar is bright enough that it was first observed as early as the 1890s. What makes OJ 287 especially interesting, however, is that its light curve exhibits prominent outbursts roughly every 12 years.Diagram illustrating the orbit of the secondary black hole (shown in blue) in OJ 287 from 2000 to 2023. We see outbursts (the yellow bubbles) every time the secondary black hole crosses the accretion disk (shown in red, ina side view) surrounding the primary (the black circle). [Valtonen et al. 2016]What causes the outbursts? Astronomers think that there is a second supermassive black hole, ~100 times smaller, inspiraling as it orbits the central monster and set to merge within the next 10,000 years. In this model, the primary black hole of OJ 287 is surrounded by a hot accretion disk. As the secondary black hole orbits the primary, it regularly punches through this accretion disk, heating the material and causing the release of expanding bubbles of hot gas pulled from the disk. This gas then radiates thermally, causing the outbursts we see.Attempts to model this scenario using Newtonian orbits all fail; the timing of the secondary black holes crossings through the accretion disk (as measured by when we see the outbursts) can only be explained by a model incorporating general-relativistic effects on the orbit. Careful observations and precise timing of these outbursts therefore provide an excellent test of general relativity.Watching a Predicted CrossingThe model of OJ 287 predicted another disk crossing in December 2015, so professional and amateur astronomers around the world readied more

  2. Influencing Factors and Simplified Model of Film Hole Irrigation

    Directory of Open Access Journals (Sweden)

    Yi-Bo Li

    2017-07-01

    Full Text Available Film hole irrigation is an advanced low-cost and high-efficiency irrigation method, which can improve water conservation and water use efficiency. Given its various advantages and potential applications, we conducted a laboratory study to investigate the effects of soil texture, bulk density, initial soil moisture, irrigation depth, opening ratio (ρ, film hole diameter (D, and spacing on cumulative infiltration using SWMS-2D. We then proposed a simplified model based on the Kostiakov model for infiltration estimation. Error analyses indicated SWMS-2D to be suitable for infiltration simulation of film hole irrigation. Additional SWMS-2D-based investigations indicated that, for a certain soil, initial soil moisture and irrigation depth had the weakest effects on cumulative infiltration, whereas ρ and D had the strongest effects on cumulative infiltration. A simplified model with ρ and D was further established, and its use was then expanded to different soils. Verification based on seven soil types indicated that the established simplified double-factor model effectively estimates cumulative infiltration for film hole irrigation, with a small mean average error of 0.141–2.299 mm, a root mean square error of 0.177–2.722 mm, a percent bias of −2.131–1.479%, and a large Nash–Sutcliffe coefficient that is close to 1.0.

  3. Black hole astrophysics

    International Nuclear Information System (INIS)

    Blandford, R.D.; Thorne, K.S.

    1979-01-01

    Following an introductory section, the subject is discussed under the headings: on the character of research in black hole astrophysics; isolated holes produced by collapse of normal stars; black holes in binary systems; black holes in globular clusters; black holes in quasars and active galactic nuclei; primordial black holes; concluding remarks on the present state of research in black hole astrophysics. (U.K.)

  4. Quantum vacuum energy near a black hole: the Maxwell field

    International Nuclear Information System (INIS)

    Elster, T.

    1984-01-01

    A quantised Maxwell field is considered propagating in the gravitational field of a Schwarzschild black hole. The vector Hartle-Hawking propagator is defined on the Riemannian section of the analytically continued space-time and expanded in terms of four-dimensional vector spherical harmonics. The equations for the radial functions appearing in the expansion are derived for both odd and even parity. Using the expansion of the vector Hartle-Hawking propagator, the point-separated expectation value of the Maxwellian energy-momentum tensor in the Hartle-Hawking vacuum is derived. The renormalised values of radial pressure, tangential pressure and energy density are obtained near the horizon of the black hole. In contrast to the scalar field, the Maxwell field exhibits a positive energy density near the horizon in the Hartle-Hawking vacuum state. (author)

  5. Geodesics of black holes with dark energy

    Science.gov (United States)

    Ghaderi, K.

    2017-12-01

    Dark energy is the most popular hypothesis to explain recent observations suggesting that the world will increasingly expand. One of the models of dark energy is quintessence which is highly plausible. In this paper, we investigate the effect of dark energy on the null geodesics of Schwarzschild, Reissner-Nordström, Schwarzschild-de Sitter and Bardeen black holes. Using the definition of effective potential, the radius of the circular orbits, the period, the instability of the circular orbits, the force exerted on the photons and the deviation angle of light in quintessence field are calculated and the results are analyzed and discussed.

  6. SHORT-PULSE ELECTROMAGNETIC TRANSPONDER FOR HOLE-TO-HOLE USE.

    Science.gov (United States)

    Wright, David L.; Watts, Raymond D.; Bramsoe, Erik

    1983-01-01

    Hole-to-hole observations were made through nearly 20 m of granite using an electromagnetic transponder (an active reflector) in one borehole and a single-hole short-pulse radar in another. The transponder is inexpensive, operationally simple, and effective in extending the capability of a short-pulse borehole radar system to allow hole-to-hole operation without requiring timing cables. A detector in the transponder senses the arrival of each pulse from the radar. Each pulse detection triggers a kilovolt-amplitude pulse for retransmission. The transponder 'echo' may be stronger than that of a passive reflector by a factor of as much as 120 db. The result is an increase in range capability by a factor which depends on attenuation in the medium and hole-to-hole wavepath geometry.

  7. Black holes

    OpenAIRE

    Brügmann, B.; Ghez, A. M.; Greiner, J.

    2001-01-01

    Recent progress in black hole research is illustrated by three examples. We discuss the observational challenges that were met to show that a supermassive black hole exists at the center of our galaxy. Stellar-size black holes have been studied in x-ray binaries and microquasars. Finally, numerical simulations have become possible for the merger of black hole binaries.

  8. Fastener locking device for attaching guide thimble to fuel assembly bottom nozzle

    International Nuclear Information System (INIS)

    Widener, W.H.

    1987-01-01

    This patent describes a nuclear reactor fuel assembly including an end nozzle and at least one longitudinally-extending guide thimble projecting away from the end nozzle. The end nozzle has at least one passageway defined therethrough and a ledge defined within the passageway so as to face away from the guide thimble and divide the passageway into a first portion extending from the ledge toward the guide thimble. A second portion extends from the ledge away from the guide thimble. The second passageway portion has a larger cross-sectional size than the first passageway portion, the end nozzle also having recess means defined thereon in the second portion of the passageway. The guide thimble has an end disposed adjacent to the first portion of the passageway with threaded means defined thereon and a fastener locking device

  9. Neutrino constraints that transform black holes into grey holes

    International Nuclear Information System (INIS)

    Ruderfer, M.

    1982-01-01

    Existing black hole theory is found to be defective in its neglect of the physical properties of matter and radiation at superhigh densities. Nongravitational neutrino effects are shown to be physically relevant to the evolution of astronomical black holes and their equations of state. Gravitational collapse to supernovae combined with the Davis and Ray vacuum solution for neutrinos limit attainment of a singularity and require black holes to evolve into ''grey holes''. These allow a better justification than do black holes for explaining the unique existence of galactic masses. (Auth.)

  10. Black hole perturbations in vector-tensor theories: the odd-mode analysis

    Science.gov (United States)

    Kase, Ryotaro; Minamitsuji, Masato; Tsujikawa, Shinji; Zhang, Ying-li

    2018-02-01

    In generalized Proca theories with vector-field derivative couplings, a bunch of hairy black hole solutions have been derived on a static and spherically symmetric background. In this paper, we formulate the odd-parity black hole perturbations in generalized Proca theories by expanding the corresponding action up to second order and investigate whether or not black holes with vector hair suffer ghost or Laplacian instabilities. We show that the models with cubic couplings G3(X), where X=‑AμAμ/2 with a vector field Aμ, do not provide any additional stability condition as in General Relativity. On the other hand, the exact charged stealth Schwarzschild solution with a nonvanishing longitudinal vector component A1, which originates from the coupling to the Einstein tensor GμνAμ Aν equivalent to the quartic coupling G4(X) containing a linear function of X, is unstable in the vicinity of the event horizon. The same instability problem also persists for hairy black holes arising from general quartic power-law couplings G4(X) ⊃ β4 Xn with the nonvanishing A1, while the other branch with A1=0 can be consistent with conditions for the absence of ghost and Laplacian instabilities. We also discuss the case of other exact and numerical black hole solutions associated with intrinsic vector-field derivative couplings and show that there exists a wide range of parameter spaces in which the solutions suffer neither ghost nor Laplacian instabilities against odd-parity perturbations.

  11. From binary black hole simulation to triple black hole simulation

    International Nuclear Information System (INIS)

    Bai Shan; Cao Zhoujian; Han, Wen-Biao; Lin, Chun-Yu; Yo, Hwei-Jang; Yu, Jui-Ping

    2011-01-01

    Black hole systems are among the most promising sources for a gravitational wave detection project. Now, China is planning to construct a space-based laser interferometric detector as a follow-on mission of LISA in the near future. Aiming to provide some theoretical support to this detection project on the numerical relativity side, we focus on black hole systems simulation in this work. Considering the globular galaxy, multiple black hole systems also likely to exist in our universe and play a role as a source for the gravitational wave detector we are considering. We will give a progress report in this paper on our black hole system simulation. More specifically, we will present triple black hole simulation together with binary black hole simulation. On triple black hole simulations, one novel perturbational method is proposed.

  12. Retaining Ring Fastener for Solar Panels

    Science.gov (United States)

    Wilson, A. H.

    1983-01-01

    Simple articulating linkage secures solar panels into supporting framework. Five element linkage collapses into W-shape for easy placement into framework, then expands to form rectangle of same dimensions as those of panel.

  13. Phase transition for black holes with scalar hair and topological black holes

    International Nuclear Information System (INIS)

    Myung, Yun Soo

    2008-01-01

    We study phase transitions between black holes with scalar hair and topological black holes in asymptotically anti-de Sitter spacetimes. As the ground state solutions, we introduce the non-rotating BTZ black hole in three dimensions and topological black hole with hyperbolic horizon in four dimensions. For the temperature matching only, we show that the phase transition between black hole with scalar hair (Martinez-Troncoso-Zanelli black hole) and topological black hole is second-order by using differences between two free energies. However, we do not identify what order of the phase transition between scalar and non-rotating BTZ black holes occurs in three dimensions, although there exists a possible decay of scalar black hole to non-rotating BTZ black hole

  14. Walking speed, rather than Expanded Disability Status Scale, relates to long-term patient-reported impact in progressive MS

    NARCIS (Netherlands)

    Bosma, L.V.A.E.; Kragt, J.J.; Polman, C.H.; Uitdehaag, B.M.J.

    2013-01-01

    Objective: To study the relationships between 1-2 year changes in well-known physician-rated measurements (Expanded Disability Status Scale (EDSS), Timed 25-Foot Walk (T25FW), 9-Hole Peg Test (9HPT)) and the long-term (= 5 years) outcome in patient-reported outcome (PRO) measures (Multiple Sclerosis

  15. Black Holes

    OpenAIRE

    Townsend, P. K.

    1997-01-01

    This paper is concerned with several not-quantum aspects of black holes, with emphasis on theoretical and mathematical issues related to numerical modeling of black hole space-times. Part of the material has a review character, but some new results or proposals are also presented. We review the experimental evidence for existence of black holes. We propose a definition of black hole region for any theory governed by a symmetric hyperbolic system of equations. Our definition reproduces the usu...

  16. The search for massive black hole binaries with LISA

    International Nuclear Information System (INIS)

    Cornish, Neil J; Porter, Edward K

    2007-01-01

    In this work we focus on the search and detection of massive black hole binary (MBHB) systems, including systems at high redshift. As well as expanding on previous works where we used a variant of Markov chain Monte Carlo (MCMC), called Metropolis-Hastings Monte Carlo, with simulated annealing, we introduce a new search method based on frequency annealing which leads to a more rapid and robust detection. We compare the two search methods on systems where we do and do not see the merger of the black holes. In the non-merger case, we also examine the posterior distribution exploration using a 7D MCMC algorithm. We demonstrate that this method is effective in dealing with the high correlations between parameters, has a higher acceptance rate than previously proposed methods and produces posterior distribution functions that are close to the prediction from the Fisher information matrix. Finally, after carrying out searches where there is only one binary in the data stream, we examine the case where two black hole binaries are present in the same data stream. We demonstrate that our search algorithm can accurately recover both binaries, and more importantly showing that we can safely extract the MBHB sources without contaminating the rest of the data stream

  17. Investigation Analysis of Crack Growth Arresting with Fasteners in Hybrid Laminated Skin-Stiffener Joint

    Science.gov (United States)

    Jeevan Kumar, N.; Ramesh Babu, P.

    2018-02-01

    In recent years carbon fibre-reinforced polymers (CFRP) emerged its increasing demand in aerospace engineering. Due to their high specific strength to weight ratio, these composites offer more characteristics and considerable advantages compared to metals. Metals, unlike composites, offer plasticity effects to evade high stress concentrations during postbuckling. Under compressive load, composite structures show a wide range of damage mechanisms where a set of damage modes combined together might lead to the eventual structural collapse. Crack is one of the most critical damages in fiber composites, which are being employed in primary aircraft structures. A parametric study is conducted to investigate the arrest mechanism of the delamination or crack growth with installation of multiple fasteners when the delamination is embedded in between the skin and stiffener interface.

  18. Oxasmaragdyrins as New and Efficient Hole-Transporting Materials for High-Performance Perovskite Solar Cells.

    Science.gov (United States)

    Mane, Sandeep B; Sutanto, Albertus Adrian; Cheng, Chih-Fu; Xie, Meng-Yu; Chen, Chieh-I; Leonardus, Mario; Yeh, Shih-Chieh; Beyene, Belete Bedemo; Diau, Eric Wei-Guang; Chen, Chin-Ti; Hung, Chen-Hsiung

    2017-09-20

    The high performance of the perovskite solar cells (PSCs) cannot be achieved without a layer of efficient hole-transporting materials (HTMs) to retard the charge recombination and transport the photogenerated hole to the counterelectrode. Herein, we report the use of boryl oxasmaragdyrins (SM01, SM09, and SM13), a family of aromatic core-modified expanded porphyrins, as efficient hole-transporting materials (HTMs) for perovskite solar cells (PSCs). These oxasmaragdyrins demonstrated complementary absorption spectra in the low-energy region, good redox reversibility, good thermal stability, suitable energy levels with CH 3 NH 3 PbI 3 perovskite, and high hole mobility. A remarkable power conversion efficiency of 16.5% (V oc = 1.09 V, J sc = 20.9 mA cm -2 , fill factor (FF) = 72%) is achieved using SM09 on the optimized PSCs device employing a planar structure, which is close to that of the state-of-the-art hole-transporting materials (HTMs), spiro-OMeTAD of 18.2% (V oc = 1.07 V, J sc = 22.9 mA cm -2 , FF = 74%). In contrast, a poor photovoltaic performance of PSCs using SM01 is observed due to the interactions of terminal carboxylic acid functional group with CH 3 NH 3 PbI 3 .

  19. Low-mass black holes as the remnants of primordial black hole formation.

    Science.gov (United States)

    Greene, Jenny E

    2012-01-01

    Bridging the gap between the approximately ten solar mass 'stellar mass' black holes and the 'supermassive' black holes of millions to billions of solar masses are the elusive 'intermediate-mass' black holes. Their discovery is key to understanding whether supermassive black holes can grow from stellar-mass black holes or whether a more exotic process accelerated their growth soon after the Big Bang. Currently, tentative evidence suggests that the progenitors of supermassive black holes were formed as ∼10(4)-10(5) M(⊙) black holes via the direct collapse of gas. Ongoing searches for intermediate-mass black holes at galaxy centres will help shed light on this formation mechanism.

  20. Hole dephasing caused by hole-hole interaction in a multilayered black phosphorus.

    Science.gov (United States)

    Li, Lijun; Khan, Muhammad Atif; Lee, Yoontae; Lee, Inyeal; Yun, Sun Jin; Youn, Doo-Hyeb; Kim, Gil-Ho

    2017-11-01

    We study the magnetotransport of holes in a multilayered black phosphorus in a temperature range of 1.9 to 21.5 K. We observed a negative magnetoresistance at magnetic fields up to 1.5 T. This negative magetoresistance was analyzed by weak localization theory in diffusive regime. At the lowest temperature and the highest carrier density we found a phase coherence length of 48 nm. The linear temperature dependence of the dephasing rate shows that the hole-hole scattering processes with small energy transfer are the dominant contribution in breaking the carrier phase coherence.

  1. The Use of Explosive Forming for Fastening and Joining Structural and Pressure Components

    Science.gov (United States)

    Schroeder, J. W.

    1985-01-01

    Explosive expansion of tubes into tubesheets has been used for over 20 years in the fabrication and repair of shell and tube heat exchangers. The use of explosives to perform these expansions has offered several distinct advantages over other methods. First, the process is fast and economical and can be performed with minimal training of personnel. Secondly, explosive forming does not cause the deleterious metallurgical effects which often result from other forming operations. In addition, the process can be performed remotely without the need for sophisticated handling equipment. The expansion of tubes into tubesheets is only one of many possible fastening and joining applications for which explosive forming can be used to achieve highly successful results. The explosive forming process and where it has been used are described. In addition, some possible adaptations to other joining applications are identified and discussed.

  2. Bifurcation from stable holes to replicating holes in vibrated dense suspensions.

    Science.gov (United States)

    Ebata, H; Sano, M

    2013-11-01

    In vertically vibrated starch suspensions, we observe bifurcations from stable holes to replicating holes. Above a certain acceleration, finite-amplitude deformations of the vibrated surface continue to grow until void penetrates fluid layers, and a hole forms. We studied experimentally and theoretically the parameter dependence of the holes and their stabilities. In suspensions of small dispersed particles, the circular shapes of the holes are stable. However, we find that larger particles or lower surface tension of water destabilize the circular shapes; this indicates the importance of capillary forces acting on the dispersed particles. Around the critical acceleration for bifurcation, holes show intermittent large deformations as a precursor to hole replication. We applied a phenomenological model for deformable domains, which is used in reaction-diffusion systems. The model can explain the basic dynamics of the holes, such as intermittent behavior, probability distribution functions of deformation, and time intervals of replication. Results from the phenomenological model match the linear growth rate below criticality that was estimated from experimental data.

  3. Elasto-Plastic 3D Finite Element Contact Analysis of a Hole Containing a Circular Insert in a Fatigue Test Coupon

    Science.gov (United States)

    2015-08-01

    Australian Air Force (RAAF) airframes. An aluminium - alloy fatigue test coupon (see Figure 1) has been designed and applied in support of the validation of...manufactured from aerospace aluminium alloy material (see Section 4 for further details). Unloaded close-fit fasteners of small diametric clearance were...Abaqus elasto–plastic input data requirements The aluminium and titanium alloys used in the coupon and fastener material display linear- elastic

  4. Black Holes

    OpenAIRE

    Horowitz, Gary T.; Teukolsky, Saul A.

    1998-01-01

    Black holes are among the most intriguing objects in modern physics. Their influence ranges from powering quasars and other active galactic nuclei, to providing key insights into quantum gravity. We review the observational evidence for black holes, and briefly discuss some of their properties. We also describe some recent developments involving cosmic censorship and the statistical origin of black hole entropy.

  5. Black hole levitron

    International Nuclear Information System (INIS)

    Arsiwalla, Xerxes D.; Verlinde, Erik P.

    2010-01-01

    We study the problem of spatially stabilizing four dimensional extremal black holes in background electric/magnetic fields. Whilst looking for stationary stable solutions describing black holes placed in external fields we find that taking a continuum limit of Denef et al.'s multicenter supersymmetric black hole solutions provides a supergravity description of such backgrounds within which a black hole can be trapped within a confined volume. This construction is realized by solving for a levitating black hole over a magnetic dipole base. We comment on how such a construction is akin to a mechanical levitron.

  6. Blastema Tissue Formed at Experimentally-Created Rabbit Ear Hole

    Directory of Open Access Journals (Sweden)

    Mohamadreza Baghaban Eslaminejad

    2013-02-01

    Full Text Available   Objective(s: Throughout evolution, mammalians have increasingly lost their ability to regenerate structures however rabbits are exceptional since they develop a blastema in their ear wound for regeneration purposes. Blastema consists of a group of undifferentiated cells capable of dividing and differentiating into the ear tissue. The objective of the present study is to isolate, culture expand, and characterize blastema progenitor cells in terms of their in vitro differentiation capacity.   Materials and Methods: Five New Zealand white male rabbits were used in the present study. Using a punching apparatus, a 4-mm hole was created in the animal ears. Following 4 days, the blastema ring which was created in the periphery of primary hole in the ears was removed and cultivated. The cells migrated from the blastema were expanded through 3 successive subcultures and characterized in terms of their potential differentiation, growth characteristics, and culture requirements. Results: The primary cultures tended to be morphologically heterogeneous having spindly-shaped fibroblast-like cells as well as flattened cells. Fibroblast-like cells survived and dominated the cultures. These cells tended to have the osteogenic, chondrogenic, and adipogenic differentiation potentials. They were highly colonogenic and maximum proliferation was achieved when the cells were plated at density of 100 cells/cm2 in a medium which contained 10% fetal bovine serum (FBS. Conclusion: Taken together, blastema tissue-derived stem cells from rabbit ear are of mesenchymal stem cell-like population. Studies similar to this will assist scientist better understanding the nature of blastema tissue formed at rabbit ear to regenerate the wound.

  7. Noncommutative black holes

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-DomInguez, J C [Instituto de Fisica de la Universidad de Guanajuato PO Box E-143, 37150 Leoen Gto. (Mexico); Obregon, O [Instituto de Fisica de la Universidad de Guanajuato PO Box E-143, 37150 Leoen Gto. (Mexico); RamIrez, C [Facultad de Ciencias FIsico Matematicas, Universidad Autonoma de Puebla, PO Box 1364, 72000 Puebla (Mexico); Sabido, M [Instituto de Fisica de la Universidad de Guanajuato PO Box E-143, 37150 Leoen Gto. (Mexico)

    2007-11-15

    We study noncommutative black holes, by using a diffeomorphism between the Schwarzschild black hole and the Kantowski-Sachs cosmological model, which is generalized to noncommutative minisuperspace. Through the use of the Feynman-Hibbs procedure we are able to study the thermodynamics of the black hole, in particular, we calculate Hawking's temperature and entropy for the 'noncommutative' Schwarzschild black hole.

  8. Black hole critical phenomena without black holes

    Indian Academy of Sciences (India)

    large values of Ф, black holes do form and for small values the scalar field ... on the near side of the ridge ultimately evolve to form black holes while those configu- ... The inset shows a bird's eye view looking down on the saddle point.

  9. Search for black holes

    International Nuclear Information System (INIS)

    Cherepashchuk, Anatolii M

    2003-01-01

    Methods and results of searching for stellar mass black holes in binary systems and for supermassive black holes in galactic nuclei of different types are described. As of now (June 2002), a total of 100 black hole candidates are known. All the necessary conditions Einstein's General Relativity imposes on the observational properties of black holes are satisfied for candidate objects available, thus further assuring the existence of black holes in the Universe. Prospects for obtaining sufficient criteria for reliably distinguishing candidate black holes from real black holes are discussed. (reviews of topical problems)

  10. Axisymmetric black holes allowing for separation of variables in the Klein-Gordon and Hamilton-Jacobi equations

    Science.gov (United States)

    Konoplya, R. A.; Stuchlík, Z.; Zhidenko, A.

    2018-04-01

    We determine the class of axisymmetric and asymptotically flat black-hole spacetimes for which the test Klein-Gordon and Hamilton-Jacobi equations allow for the separation of variables. The known Kerr, Kerr-Newman, Kerr-Sen and some other black-hole metrics in various theories of gravity are within the class of spacetimes described here. It is shown that although the black-hole metric in the Einstein-dilaton-Gauss-Bonnet theory does not allow for the separation of variables (at least in the considered coordinates), for a number of applications it can be effectively approximated by a metric within the above class. This gives us some hope that the class of spacetimes described here may be not only generic for the known solutions allowing for the separation of variables, but also a good approximation for a broader class of metrics, which does not admit such separation. Finally, the generic form of the axisymmetric metric is expanded in the radial direction in terms of the continued fractions and the connection with other black-hole parametrizations is discussed.

  11. Angle-Beam Shear Wave Scattering from Buried Crack-like Defects in Bonded Specimens (Postprint)

    Science.gov (United States)

    2017-02-01

    defects: such as understanding the scattering behavior of fatigue cracks emanating from fastener holes in aluminum structural components [2]. Angle...Ultrasonic NDE techniques using angle-beam wedges coupled to PZT transducers have also been utilized in measuring the depth of surface-breaking cracks

  12. A Dancing Black Hole

    Science.gov (United States)

    Shoemaker, Deirdre; Smith, Kenneth; Schnetter, Erik; Fiske, David; Laguna, Pablo; Pullin, Jorge

    2002-04-01

    Recently, stationary black holes have been successfully simulated for up to times of approximately 600-1000M, where M is the mass of the black hole. Considering that the expected burst of gravitational radiation from a binary black hole merger would last approximately 200-500M, black hole codes are approaching the point where simulations of mergers may be feasible. We will present two types of simulations of single black holes obtained with a code based on the Baumgarte-Shapiro-Shibata-Nakamura formulation of the Einstein evolution equations. One type of simulations addresses the stability properties of stationary black hole evolutions. The second type of simulations demonstrates the ability of our code to move a black hole through the computational domain. This is accomplished by shifting the stationary black hole solution to a coordinate system in which the location of the black hole is time dependent.

  13. Heat Loads Due To Small Penetrations In Multilayer Insulation Blankets

    Science.gov (United States)

    Johnson, W. L.; Heckle, K. W.; E Fesmire, J.

    2017-12-01

    The main penetrations (supports and piping) through multilayer insulation systems for cryogenic tanks have been previously addressed by heat flow measurements. Smaller penetrations due to fasteners and attachments are now experimentally investigated. The use of small pins or plastic garment tag fasteners to ease the handling and construction of multilayer insulation (MLI) blankets goes back many years. While it has long been understood that penetrations and other discontinuities degrade the performance of the MLI blanket, quantification of this degradation has generally been lumped into gross performance multipliers (often called degradation factors or scale factors). Small penetrations contribute both solid conduction and radiation heat transfer paths through the blanket. The conduction is down the stem of the structural element itself while the radiation is through the hole formed during installation of the pin or fastener. Analytical models were developed in conjunction with MLI perforation theory and Fourier’s Law. Results of the analytical models are compared to experimental testing performed on a 10 layer MLI blanket with approximately 50 small plastic pins penetrating the test specimen. The pins were installed at ∼76-mm spacing inches in both directions to minimize the compounding of thermal effects due to localized compression or lateral heat transfer. The testing was performed using a liquid nitrogen boil-off calorimeter (Cryostat-100) with the standard boundary temperatures of 293 K and 78 K. Results show that the added radiation through the holes is much more significant than the conduction down the fastener. The results are shown to be in agreement with radiation theory for perforated films.

  14. XFEM Modelling of Multi-holes Plate with Single-row and Staggered Holes Configurations

    Directory of Open Access Journals (Sweden)

    Supar Khairi

    2017-01-01

    Full Text Available Joint efficiency is the key to composite structures assembly design, good structures response is dependent upon multi-holes behavior as subjected to remote loading. Current benchmarking work were following experimental testing series taken from literature on multi-holes problem. Eleven multi-hole configurations were investigated with various pitch and gage distance of staggered holes and non-staggered holes (single-row holes. Various failure modes were exhibited, most staggered holes demonstrates staggered crack path but non-staggered holes series displayed crack path along net-section plane. Stress distribution were carried out and good agreement were exhibited in experimental observation as reported in the respective literature. Consequently, strength prediction work were carried out under quasi-static loading, most showed discrepancy between 8% -31%, better prediction were exhibited in thicker and non-staggered holes plate combinations.

  15. Black holes will break up solitons and white holes may destroy them

    International Nuclear Information System (INIS)

    Akbar, Fiki T.; Gunara, Bobby E.; Susanto, Hadi

    2017-01-01

    Highlights: • What happens if a soliton collides with a black or white hole? • Solitons can pass through black hole horizons, but they will break up into several solitons after the collision. • In the interaction with a white hole horizon, solitons either pass through the horizon or will be destroyed by it. - Abstract: We consider a quantum analogue of black holes and white holes using Bose–Einstein condensates. The model is described by the nonlinear Schrödinger equation with a ‘stream flow’ potential, that induces a spatial translation to standing waves. We then mainly consider the dynamics of dark solitons in a black hole or white hole flow analogue and their interactions with the event horizon. A reduced equation describing the position of the dark solitons was obtained using variational method. Through numerical computations and comparisons with the analytical approximation we show that solitons can pass through black hole horizons even though they will break up into several solitons after the collision. In the interaction with a white hole horizon, we show that solitons either pass through the horizon or will be destroyed by it.

  16. Black holes will break up solitons and white holes may destroy them

    Energy Technology Data Exchange (ETDEWEB)

    Akbar, Fiki T., E-mail: ftakbar@fi.itb.ac.id [Theoretical Physics Laboratory, Theoretical High Energy Physics and Instrumentation Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha no. 10, Bandung, 40132 (Indonesia); Gunara, Bobby E., E-mail: bobby@fi.itb.ac.id [Theoretical Physics Laboratory, Theoretical High Energy Physics and Instrumentation Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha no. 10, Bandung, 40132 (Indonesia); Susanto, Hadi, E-mail: hsusanto@essex.ac.uk [Department of Mathematical Sciences, University of Essex, Colchester, CO4 3SQ (United Kingdom)

    2017-06-15

    Highlights: • What happens if a soliton collides with a black or white hole? • Solitons can pass through black hole horizons, but they will break up into several solitons after the collision. • In the interaction with a white hole horizon, solitons either pass through the horizon or will be destroyed by it. - Abstract: We consider a quantum analogue of black holes and white holes using Bose–Einstein condensates. The model is described by the nonlinear Schrödinger equation with a ‘stream flow’ potential, that induces a spatial translation to standing waves. We then mainly consider the dynamics of dark solitons in a black hole or white hole flow analogue and their interactions with the event horizon. A reduced equation describing the position of the dark solitons was obtained using variational method. Through numerical computations and comparisons with the analytical approximation we show that solitons can pass through black hole horizons even though they will break up into several solitons after the collision. In the interaction with a white hole horizon, we show that solitons either pass through the horizon or will be destroyed by it.

  17. Caged black holes: Black holes in compactified spacetimes. I. Theory

    International Nuclear Information System (INIS)

    Kol, Barak; Sorkin, Evgeny; Piran, Tsvi

    2004-01-01

    In backgrounds with compact dimensions there may exist several phases of black objects including a black hole and a black string. The phase transition between them raises questions and touches on fundamental issues such as topology change, uniqueness, and cosmic censorship. No analytic solution is known for the black hole, and moreover one can expect approximate solutions only for very small black holes, while phase transition physics happens when the black hole is large. Hence we turn to numerical solutions. Here some theoretical background to the numerical analysis is given, while the results will appear in a subsequent paper. The goals for a numerical analysis are set. The scalar charge and tension along the compact dimension are defined and used as improved order parameters which put both the black hole and the black string at finite values on the phase diagram. The predictions for small black holes are presented. The differential and the integrated forms of the first law are derived, and the latter (Smarr's formula) can be used to estimate the 'overall numerical error'. Field asymptotics and expressions for physical quantities in terms of the numerical values are supplied. The techniques include the 'method of equivalent charges', free energy, dimensional reduction, and analytic perturbation for small black holes

  18. Alternate Explosions: Collapse and Accretion Events with Red Holes instead of Black Holes

    OpenAIRE

    Graber, James S.

    1999-01-01

    A red hole is "just like a black hole" except it lacks an event horizon and a singularity. As a result, a red hole emits much more energy than a black hole during a collapse or accretion event. We consider how a red hole solution can solve the "energy crisis" and power extremely energetic gamma ray bursts and hypernovae.

  19. Astrophysical black holes

    CERN Document Server

    Gorini, Vittorio; Moschella, Ugo; Treves, Aldo; Colpi, Monica

    2016-01-01

    Based on graduate school lectures in contemporary relativity and gravitational physics, this book gives a complete and unified picture of the present status of theoretical and observational properties of astrophysical black holes. The chapters are written by internationally recognized specialists. They cover general theoretical aspects of black hole astrophysics, the theory of accretion and ejection of gas and jets, stellar-sized black holes observed in the Milky Way, the formation and evolution of supermassive black holes in galactic centers and quasars as well as their influence on the dynamics in galactic nuclei. The final chapter addresses analytical relativity of black holes supporting theoretical understanding of the coalescence of black holes as well as being of great relevance in identifying gravitational wave signals. With its introductory chapters the book is aimed at advanced graduate and post-graduate students, but it will also be useful for specialists.

  20. Mechanism of Film Cooling with One Inlet and Double Outlet Hole Injection at Various Turbulence Intensities

    Science.gov (United States)

    Li, Guangchao; Chen, Yukai; Kou, Zhihai; Zhang, Wei; Zhang, Guochen

    2018-03-01

    The trunk-branch hole was designed as a novel film cooling concept, which aims for improving film cooling performance by producing anti-vortex. The trunk-branch hole is easily manufactured in comparison with the expanded hole since it consists of two cylindrical holes. The effect of turbulence on the film cooling effectiveness with a trunk-branch hole injection was investigated at the blowing ratios of 0.5, 1.0, 1.5 and 2.0 by numerical simulation. The turbulence intensities from 0.4 % to 20 % were considered. The realizable graphic id="j_tjj-2016-0024_ingr_001" xlink.href="graphic/j_tjj-2016-0024_inline1.png" />k-ɛ k - ɛ turbulence model and the enhanced wall function were used. The more effective anti-vortex occurs at the low blowing ratio of 0.5 %. The high turbulence intensity causes the effectiveness evenly distributed in the spanwise direction. The increase of turbulence intensity leads to a slight decrease of the spanwise averaged effectiveness at the low blowing ratio of 0.5, but a significant increase at the high blowing ratios of 1.5 and 2.0. The optimal blowing ratio of the averaged surface effectiveness is improved from 1.0 to 1.5 when the turbulence intensity increases from 0.4 % to 20 %.

  1. ExpandED Options: Learning beyond High School Walls

    Science.gov (United States)

    ExpandED Schools, 2014

    2014-01-01

    Through ExpandED Options by TASC, New York City high school students get academic credit for learning career-related skills that lead to paid summer jobs. Too many high school students--including those most likely to drop out--are bored or see classroom learning as irrelevant. ExpandED Options students live the connection between mastering new…

  2. Exploring Jets from a Supermassive Black Hole

    Science.gov (United States)

    Kohler, Susanna

    2018-06-01

    collaborators observations span the enormous radial distance of a thousand to a billion times the radius of the black hole, or about 54 light-days to more than a million light-years.Scale for ChangeThe width of the jet as a function of radial distance from the black hole, for NGC 4261 (red) compared to the few other jets from nearby supermassive black holes that weve measured. NGC 4261s jets transition from parabolic to conical at around 10,000 times the radius of the black hole (RS). [Nakahara et al. 2018]The authors observations of NGC 4261s jets indicate that a transition occurs at 10,000 times the radius of the black hole (thats a little over a light-year from the black hole). At this point, the jets structures change from parabolic (becoming more tightly beamed) to conical (expanding freely). Around the same location, Nakahara and collaborators also see the radiation profile of one of the jets change, suggesting the physical conditions in the jets transition here as well.This is the first time weve been able to examine jet width this closely for both of the jets emitted from a supermassive black hole. The fact that the structure changes at the same distance for both jets indicates that the shape of these powerful streams is likely governed by global properties of the environment surrounding the galaxys nucleus, or properties of the jets themselves, rather than by a local condition.The authors next hope to pin down velocities inside NGC 4261s jets to determine where the jets accelerate and decelerate. This nearby powerhouse is clearly going to be a useful laboratory in the future, helping to unveil the secrets of more distant, feeding monsters.BonusCurious what these hungry supermassive black holes look like? Check out this artists imagining of NGC 4261, which shows how it feeds from a large, swirling accretion disk and emits fast-moving, collimated jets. [Original video credit to Dana Berry, Space Telescope Science Institute]CitationSatomi Nakahara et al 2018 ApJ 854 148

  3. Black holes in binary stars

    NARCIS (Netherlands)

    Wijers, R.A.M.J.

    1996-01-01

    Introduction Distinguishing neutron stars and black holes Optical companions and dynamical masses X-ray signatures of the nature of a compact object Structure and evolution of black-hole binaries High-mass black-hole binaries Low-mass black-hole binaries Low-mass black holes Formation of black holes

  4. The stable problem of the black-hole connected region in the Schwarzschild black hole

    OpenAIRE

    Tian, Guihua

    2005-01-01

    The stability of the Schwarzschild black hole is studied. Using the Painlev\\'{e} coordinate, our region can be defined as the black-hole-connected region(r>2m, see text) of the Schwarzschild black hole or the white-hole-connected region(r>2m, see text) of the Schwarzschild black hole. We study the stable problems of the black-hole-connected region. The conclusions are: (1) in the black-hole-connected region, the initially regular perturbation fields must have real frequency or complex frequen...

  5. Rotating black holes at future colliders. III. Determination of black hole evolution

    International Nuclear Information System (INIS)

    Ida, Daisuke; Oda, Kin-ya; Park, Seong Chan

    2006-01-01

    TeV scale gravity scenario predicts that the black hole production dominates over all other interactions above the scale and that the Large Hadron Collider will be a black hole factory. Such higher-dimensional black holes mainly decay into the standard model fields via the Hawking radiation whose spectrum can be computed from the greybody factor. Here we complete the series of our work by showing the greybody factors and the resultant spectra for the brane-localized spinor and vector field emissions for arbitrary frequencies. Combining these results with the previous works, we determine the complete radiation spectra and the subsequent time evolution of the black hole. We find that, for a typical event, well more than half a black hole mass is emitted when the hole is still highly rotating, confirming our previous claim that it is important to take into account the angular momentum of black holes

  6. Black holes. Chapter 6

    International Nuclear Information System (INIS)

    Penrose, R.

    1980-01-01

    Conditions for the formation of a black hole are considered, and the properties of black holes. The possibility of Cygnus X-1 as a black hole is discussed. Einstein's theory of general relativity in relation to the formation of black holes is discussed. (U.K.)

  7. Statistical black-hole thermodynamics

    International Nuclear Information System (INIS)

    Bekenstein, J.D.

    1975-01-01

    Traditional methods from statistical thermodynamics, with appropriate modifications, are used to study several problems in black-hole thermodynamics. Jaynes's maximum-uncertainty method for computing probabilities is used to show that the earlier-formulated generalized second law is respected in statistically averaged form in the process of spontaneous radiation by a Kerr black hole discovered by Hawking, and also in the case of a Schwarzschild hole immersed in a bath of black-body radiation, however cold. The generalized second law is used to motivate a maximum-entropy principle for determining the equilibrium probability distribution for a system containing a black hole. As an application we derive the distribution for the radiation in equilibrium with a Kerr hole (it is found to agree with what would be expected from Hawking's results) and the form of the associated distribution among Kerr black-hole solution states of definite mass. The same results are shown to follow from a statistical interpretation of the concept of black-hole entropy as the natural logarithm of the number of possible interior configurations that are compatible with the given exterior black-hole state. We also formulate a Jaynes-type maximum-uncertainty principle for black holes, and apply it to obtain the probability distribution among Kerr solution states for an isolated radiating Kerr hole

  8. Analysis and Experiments on Sea Load and Fastened Mechanics on Pipe Clamps

    Directory of Open Access Journals (Sweden)

    Wang Zhuo

    2017-08-01

    Full Text Available When an offshore oil field completed and put into production, new subsea pipelines and the new cable need to be established. Cable protection pipe clamp is used to fix cable protection pipe on the jacket. In order to avoid the problem of traditional steel structure clamp splice, counterpoint, fastening difficulty when installed cable protection pipe under water, reduce the risk and workload of under water, This paper develop a new type of portable connecting riser clamp -“backpack clamp” which solve the riser cable protection pipe difficult underwater installation problem. The main structure of backpack clamp used three valves type structure. The load characteristic of a clamping device was determined by the Morison equation which was a classical theory. Clamp device underwater mechanics analysis model was established. The minimum tension pre-tightening force was determined. The results show that the strength of the base meets the requirements after strength analysis with finite element analysis method, stability and strength experiments, which means the clamp based on resin matrix composite is feasible.

  9. Black hole hair removal

    International Nuclear Information System (INIS)

    Banerjee, Nabamita; Mandal, Ipsita; Sen, Ashoke

    2009-01-01

    Macroscopic entropy of an extremal black hole is expected to be determined completely by its near horizon geometry. Thus two black holes with identical near horizon geometries should have identical macroscopic entropy, and the expected equality between macroscopic and microscopic entropies will then imply that they have identical degeneracies of microstates. An apparent counterexample is provided by the 4D-5D lift relating BMPV black hole to a four dimensional black hole. The two black holes have identical near horizon geometries but different microscopic spectrum. We suggest that this discrepancy can be accounted for by black hole hair - degrees of freedom living outside the horizon and contributing to the degeneracies. We identify these degrees of freedom for both the four and the five dimensional black holes and show that after their contributions are removed from the microscopic degeneracies of the respective systems, the result for the four and five dimensional black holes match exactly.

  10. Brane holes

    International Nuclear Information System (INIS)

    Frolov, Valeri P.; Mukohyama, Shinji

    2011-01-01

    The aim of this paper is to demonstrate that in models with large extra dimensions under special conditions one can extract information from the interior of 4D black holes. For this purpose we study an induced geometry on a test brane in the background of a higher-dimensional static black string or a black brane. We show that, at the intersection surface of the test brane and the bulk black string or brane, the induced metric has an event horizon, so that the test brane contains a black hole. We call it a brane hole. When the test brane moves with a constant velocity V with respect to the bulk black object, it also has a brane hole, but its gravitational radius r e is greater than the size of the bulk black string or brane r 0 by the factor (1-V 2 ) -1 . We show that bulk ''photon'' emitted in the region between r 0 and r e can meet the test brane again at a point outside r e . From the point of view of observers on the test brane, the events of emission and capture of the bulk photon are connected by a spacelike curve in the induced geometry. This shows an example in which extra dimensions can be used to extract information from the interior of a lower-dimensional black object. Instead of the bulk black string or brane, one can also consider a bulk geometry without a horizon. We show that nevertheless the induced geometry on the moving test brane can include a brane hole. In such a case the extra dimensions can be used to extract information from the complete region of the brane-hole interior. We discuss thermodynamic properties of brane holes and interesting questions which arise when such an extra-dimensional channel for the information mining exists.

  11. Black holes are warm

    International Nuclear Information System (INIS)

    Ravndal, F.

    1978-01-01

    Applying Einstein's theory of gravitation to black holes and their interactions with their surroundings leads to the conclusion that the sum of the surface areas of several black holes can never become less. This is shown to be analogous to entropy in thermodynamics, and the term entropy is also thus applied to black holes. Continuing, expressions are found for the temperature of a black hole and its luminosity. Thermal radiation is shown to lead to explosion of the black hole. Numerical examples are discussed involving the temperature, the mass, the luminosity and the lifetime of black mini-holes. It is pointed out that no explosions corresponding to the prediction have been observed. It is also shown that the principle of conservation of leptons and baryons is broken by hot black holes, but that this need not be a problem. The related concept of instantons is cited. It is thought that understanding of thermal radiation from black holes may be important for the development of a quantified gravitation theory. (JIW)

  12. Effects of hole tapering on cone-beam collimation for brain SPECT imaging

    International Nuclear Information System (INIS)

    Park, Mi-Ae; Kijewski, Marie Foley; Moore, Stephen C.

    2006-01-01

    New collimator manufacturing technologies, such as photoetching, electrical discharge machining, and stereolithography, expand the range of possible cone-beam collimator configurations. For example, it might now be possible for brain SPECT to make a short-focusing cone-beam collimator with tapered holes that increase in size with distance from the collimator surface; conventional lead-casting techniques produce holes of constant size and, consequently, varying septal thicknesses. Moreover, the changes in hole shape and loss of close packing due to focusing leads to thicker septa in the collimator periphery, especially for shorter focal lengths. We investigated the potential advantages of new cone-beam collimator manufacturing processes, and proposed a new design for very short focal-length collimators for brain SPECT imaging. We compared three cone-beam collimators, a conventional collimator manufactured using casting techniques (CC), a novel collimator with uniform hole sizes on the collimator surface and constant hole size through the collimator thickness (FC), and a novel collimator with uniform hole sizes and tapered holes (TC). We determined the resolution of each collimator analytically for focal lengths ranging from 20-50 cm, and adjusted the entrance hole sizes of FC and TC to equalize resolution of all collimators. Sensitivity was calculated at several locations by Monte Carlo simulation. Sensitivity was higher at all points for TC and FC than for CC, and higher for TC than for FC. The differences in sensitivity were larger for shorter focal lengths. For a point on the focal line at 10 cm in front of the collimator entrance surface, the sensitivity gain for TC compared to CC was 7% and 45% for focal lengths of 50 and 20 cm, respectively. The sensitivity gain for a 20-cm focal length, compared to CC, averaged over all locations, was 44% for TC and 23% for FC. We have shown that the new collimator designs made possible by new manufacturing techniques will

  13. Hole history, rotary hole DC-3

    International Nuclear Information System (INIS)

    1977-10-01

    Purpose of hole DC-3 was to drill into the Umtanum basalt flow using both conventional rotary and core drilling methods. The borehole is to be utilized for geophysical logging, future hydrological testing, and the future installation of a borehole laboratory for long-term pressure, seismic, and moisture migration or accumulation recording in the Umtanum basalt flow in support of the Basalt Waste Isolation Program. Hole DC-3 is located east of the 200 West barricaded area on the Hanford reservation

  14. Quantum aspects of black holes

    CERN Document Server

    2015-01-01

    Beginning with an overview of the theory of black holes by the editor, this book presents a collection of ten chapters by leading physicists dealing with the variety of quantum mechanical and quantum gravitational effects pertinent to black holes. The contributions address topics such as Hawking radiation, the thermodynamics of black holes, the information paradox and firewalls, Monsters, primordial black holes, self-gravitating Bose-Einstein condensates, the formation of small black holes in high energetic collisions of particles, minimal length effects in black holes and small black holes at the Large Hadron Collider. Viewed as a whole the collection provides stimulating reading for researchers and graduate students seeking a summary of the quantum features of black holes.

  15. Black holes and beyond

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2002-02-01

    Belief in the existence of black holes is the ultimate act of faith for a physicist. First suggested by the English clergyman John Michell in the year 1784, the gravitational pull of a black hole is so strong that nothing - not even light - can escape. Gravity might be the weakest of the fundamental forces but black-hole physics is not for the faint-hearted. Black holes present obvious problems for would-be observers because they cannot, by definition, be seen with conventional telescopes - although before the end of the decade gravitational-wave detectors should be able to study collisions between black holes. Until then astronomers can only infer the existence of a black hole from its gravitational influence on other matter, or from the X-rays emitted by gas and dust as they are dragged into the black hole. However, once this material passes through the 'event horizon' that surrounds the black hole, we will never see it again - not even with X-ray specs. Despite these observational problems, most physicists and astronomers believe that black holes do exist. Small black holes a few kilometres across are thought to form when stars weighing more than about two solar masses collapse under the weight of their own gravity, while supermassive black holes weighing millions of solar masses appear to be present at the centre of most galaxies. Moreover, some brave physicists have proposed ways to make black holes - or at least event horizons - in the laboratory. The basic idea behind these 'artificial black holes' is not to compress a large amount of mass into a small volume, but to reduce the speed of light in a moving medium to less than the speed of the medium and so create an event horizon. The parallels with real black holes are not exact but the experiments could shed new light on a variety of phenomena. The first challenge, however, is to get money for the research. One year on from a high-profile meeting on artificial black holes in London, for

  16. Investigation of Spiral and Sweeping Holes

    Science.gov (United States)

    Thurman, Douglas; Poinsatte, Philip; Ameri, Ali; Culley, Dennis; Raghu, Surya; Shyam, Vikram

    2015-01-01

    Surface infrared thermography, hotwire anemometry, and thermocouple surveys were performed on two new film cooling hole geometries: spiral/rifled holes and fluidic sweeping holes. The spiral holes attempt to induce large-scale vorticity to the film cooling jet as it exits the hole to prevent the formation of the kidney shaped vortices commonly associated with film cooling jets. The fluidic sweeping hole uses a passive in-hole geometry to induce jet sweeping at frequencies that scale with blowing ratios. The spiral hole performance is compared to that of round holes with and without compound angles. The fluidic hole is of the diffusion class of holes and is therefore compared to a 777 hole and Square holes. A patent-pending spiral hole design showed the highest potential of the non-diffusion type hole configurations. Velocity contours and flow temperature were acquired at discreet cross-sections of the downstream flow field. The passive fluidic sweeping hole shows the most uniform cooling distribution but suffers from low span-averaged effectiveness levels due to enhanced mixing. The data was taken at a Reynolds number of 11,000 based on hole diameter and freestream velocity. Infrared thermography was taken for blowing rations of 1.0, 1.5, 2.0, and 2.5 at a density ration of 1.05. The flow inside the fluidic sweeping hole was studied using 3D unsteady RANS.

  17. Black Hole Area Quantization rule from Black Hole Mass Fluctuations

    OpenAIRE

    Schiffer, Marcelo

    2016-01-01

    We calculate the black hole mass distribution function that follows from the random emission of quanta by Hawking radiation and with this function we calculate the black hole mass fluctuation. From a complete different perspective we regard the black hole as quantum mechanical system with a quantized event horizon area and transition probabilities among the various energy levels and then calculate the mass dispersion. It turns out that there is a perfect agreement between the statistical and ...

  18. Black Holes Lead Galaxy Growth, New Research Shows

    Science.gov (United States)

    2009-01-01

    as they were in the first billion years after the Big Bang, and the evidence suggests that the constant ratio seen nearby may not hold in the early Universe. The black holes in these young galaxies are much more massive compared to the bulges than those seen in the nearby Universe," said Fabian Walter of the Max-Planck Institute for Astronomy (MPIfA) in Germany. "The implication is that the black holes started growing first." The next challenge is to figure out how the black hole and the bulge affect each others' growth. "We don't know what mechanism is at work here, and why, at some point in the process, the 'standard' ratio between the masses is established," Riechers said. New telescopes now under construction will be key tools for unraveling this mystery, Carilli explained. "The Expanded Very Large Array (EVLA) and the Atacama Large Millimeter/submillimeter Array (ALMA) will give us dramatic improvements in sensitivity and the resolving power to image the gas in these galaxies on the small scales required to make detailed studies of their dynamics," he said. "To understand how the Universe got to be the way it is today, we must understand how the first stars and galaxies were formed when the Universe was young. With the new observatories we'll have in the next few years, we'll have the opportunity to learn important details from the era when the Universe was only a toddler compared to today's adult," Carilli said. Carilli, Riechers and Walter worked with Frank Bertoldi of Bonn University; Karl Menten of MPIfR; and Pierre Cox and Roberto Neri of the Insitute for Millimeter Radio Astronomy (IRAM) in France.

  19. Harvesting multiple electron-hole pairs generated through plasmonic excitation of Au nanoparticles.

    Science.gov (United States)

    Kim, Youngsoo; Smith, Jeremy G; Jain, Prashant K

    2018-05-07

    Multi-electron redox reactions, although central to artificial photosynthesis, are kinetically sluggish. Amidst the search for synthetic catalysts for such processes, plasmonic nanoparticles have been found to catalyse multi-electron reduction of CO 2 under visible light. This example motivates the need for a general, insight-driven framework for plasmonic catalysis of such multi-electron chemistry. Here, we elucidate the principles underlying the extraction of multiple redox equivalents from a plasmonic photocatalyst. We measure the kinetics of electron harvesting from a gold nanoparticle photocatalyst as a function of photon flux. Our measurements, supported by theoretical modelling, reveal a regime where two-electron transfer from the excited gold nanoparticle becomes prevalent. Multiple electron harvesting becomes possible under continuous-wave, visible-light excitation of moderate intensity due to strong interband transitions in gold and electron-hole separation accomplished using a hole scavenger. These insights will help expand the utility of plasmonic photocatalysis beyond CO 2 reduction to other challenging multi-electron, multi-proton transformations such as N 2 fixation.

  20. Monopole Black Hole Skyrmions

    OpenAIRE

    Moss, Ian G; Shiiki, N; Winstanley, E

    2000-01-01

    Charged black hole solutions with pion hair are discussed. These can be\\ud used to study monopole black hole catalysis of proton decay.\\ud There also exist\\ud multi-black hole skyrmion solutions with BPS monopole behaviour.

  1. Leak isolation self-repairing tape for a water storage vessel and piping against holes

    International Nuclear Information System (INIS)

    Nagaya, Kosuke; Sekiguchi, Takahiro; Chen, Zhichao; Murakami, Iwanori

    2007-01-01

    A new type taping for a water storage vessel or piping is presented, in which water leakage is isolated automatically by its self-repairing mechanism against holes. The self-repairing unit (sealant layer) is consisting of three pieces of net with polymer particles inside lattices. Polymer particles, which expand their volume with water, is used for having self-repairing forces. In ordinary tapes, water leaks along the boundary between the tape and the vessel. In order to retain the leak isolation force, this article first discusses a method for making the sealant tape, then develops a method for fixing the sealant to the vessel. The portion of water leakage can be checked on this tape, and the method of detecting the hole or crack portion of the vessel is also presented by using the tape. (author)

  2. Skyrmion black hole hair: Conservation of baryon number by black holes and observable manifestations

    Energy Technology Data Exchange (ETDEWEB)

    Dvali, Gia [Arnold Sommerfeld Center, Ludwig-Maximilians-Universität, 80333 München (Germany); Max-Planck-Institut für Physik, Werner-Heisenberg-Institut, 80805 München (Germany); Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Gußmann, Alexander, E-mail: alexander.gussmann@physik.uni-muenchen.de [Arnold Sommerfeld Center, Ludwig-Maximilians-Universität, 80333 München (Germany)

    2016-12-15

    We show that the existence of black holes with classical skyrmion hair invalidates standard proofs that global charges, such as the baryon number, cannot be conserved by a black hole. By carefully analyzing the standard arguments based on a Gedankenexperiment in which a black hole is seemingly-unable to return the baryon number that it swallowed, we identify inconsistencies in this reasoning, which does not take into the account neither the existence of skyrmion black holes nor the baryon/skyrmion correspondence. We then perform a refined Gedankenexperiment by incorporating the new knowledge and show that no contradiction with conservation of baryon number takes place at any stage of black hole evolution. Our analysis also indicates no conflict between semi-classical black holes and the existence of baryonic gauge interaction arbitrarily-weaker than gravity. Next, we study classical cross sections of a minimally-coupled massless probe scalar field scattered by a skyrmion black hole. We investigate how the skyrmion hair manifests itself by comparing this cross section with the analogous cross section caused by a Schwarzschild black hole which has the same ADM mass as the skyrmion black hole. Here we find an order-one difference in the positions of the characteristic peaks in the cross sections. The peaks are shifted to smaller scattering angles when the skyrmion hair is present. This comes from the fact that the skyrmion hair changes the near horizon geometry of the black hole when compared to a Schwarzschild black hole with same ADM mass. We keep the study of this second aspect general so that the qualitative results which we obtain can also be applied to black holes with classical hair of different kind.

  3. Entropy of quasiblack holes

    International Nuclear Information System (INIS)

    Lemos, Jose P. S.; Zaslavskii, Oleg B.

    2010-01-01

    We trace the origin of the black hole entropy S, replacing a black hole by a quasiblack hole. Let the boundary of a static body approach its own gravitational radius, in such a way that a quasihorizon forms. We show that if the body is thermal with the temperature taking the Hawking value at the quasihorizon limit, it follows, in the nonextremal case, from the first law of thermodynamics that the entropy approaches the Bekenstein-Hawking value S=A/4. In this setup, the key role is played by the surface stresses on the quasihorizon and one finds that the entropy comes from the quasihorizon surface. Any distribution of matter inside the surface leads to the same universal value for the entropy in the quasihorizon limit. This can be of some help in the understanding of black hole entropy. Other similarities between black holes and quasiblack holes such as the mass formulas for both objects had been found previously. We also discuss the entropy for extremal quasiblack holes, a more subtle issue.

  4. Black holes without firewalls

    Science.gov (United States)

    Larjo, Klaus; Lowe, David A.; Thorlacius, Larus

    2013-05-01

    The postulates of black hole complementarity do not imply a firewall for infalling observers at a black hole horizon. The dynamics of the stretched horizon, that scrambles and reemits information, determines whether infalling observers experience anything out of the ordinary when entering a large black hole. In particular, there is no firewall if the stretched horizon degrees of freedom retain information for a time of the order of the black hole scrambling time.

  5. The effect of particle-hole interaction on the XPS core-hole spectrum

    International Nuclear Information System (INIS)

    Ohno, Masahide; Sjoegren, Lennart

    2004-01-01

    How the effective particle-hole interaction energy, U, or the polarization effect on a secondary electron in a final two-hole one-particle (2h1p) state created by the Coster-Kronig (CK) transition can solely affect the density of the CK particle states and consequently the core-hole spectral function, is discussed. The X-ray photoelectron spectroscopy (XPS) core-hole spectrum is predominantly governed by the unperturbed initial core-hole energy relative to the zero-point energy. At the latter energy, the real part of the initial core-hole self-energy becomes zero (no relaxation energy shift) and the imaginary part (the lifetime broadening) approximately maximizes. The zero-point energy relative to the double-ionization threshold energy is governed by the ratio of U relative to the bandwidth of the CK continuum. As an example, we study the 5p XPS spectra of atomic Ra (Z=88), Th (Z=90) and U (Z=92). The spectra are interpreted in terms of the change in the unperturbed initial core-hole energy relative to the zero-point energy. We explain why in general an ab initio atomic many-body calculation can provide an overall good description of solid-state spectra predominantly governed by the atomic-like localized core-hole dynamics. We explain this in terms of the change from free atom to metal in both U and the zero-point energy (self-energy)

  6. Over spinning a black hole?

    Energy Technology Data Exchange (ETDEWEB)

    Bouhmadi-Lopez, Mariam; Cardoso, Vitor; Nerozzi, Andrea; Rocha, Jorge V, E-mail: mariam.bouhmadi@ist.utl.pt, E-mail: vitor.cardoso@ist.utl.pt, E-mail: andrea.nerozzi@ist.utl.pt, E-mail: jorge.v.rocha@ist.utl.pt [CENTRA, Department de Fisica, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049 Lisboa (Portugal)

    2011-09-22

    A possible process to destroy a black hole consists on throwing point particles with sufficiently large angular momentum into the black hole. In the case of Kerr black holes, it was shown by Wald that particles with dangerously large angular momentum are simply not captured by the hole, and thus the event horizon is not destroyed. Here we reconsider this gedanken experiment for black holes in higher dimensions. We show that this particular way of destroying a black hole does not succeed and that Cosmic Censorship is preserved.

  7. New Challenges to the automotive fasteners and cold formed parts in the chinese markets

    Directory of Open Access Journals (Sweden)

    Chen Jin Guang

    2015-01-01

    Full Text Available Despite of substantial cold forming related R&D, innovations and new inventions have been achieved and reported by research institutes and famous industrial organisations, many small and medium size enterprises in the third world or developing countries considering this R&D activities is too luxury. Most of the third world cold forming factories still dependent on previously successful experiences by using trial an error methods. The author does not make attempt to write a scientific research paper on metal forming processes but, instead, to report the effect, application and impact of the previous and on-going metal forming related research work to the cold forming industry in China. This paper highlights the effect of 1 efficient manufacturing practices, 2 upgrading in process technology and 3improved machines capabilities in upgrading the cold forming operation. Three real-life cold forming examples from Ritai are illustrated showing the transformation from an automotive fasteners maker into a cold formed parts manufacturer.

  8. Numerical Analysis of Stress Concentration in Isotropic and Laminated Plates with Inclined Elliptical Holes

    Science.gov (United States)

    Khechai, Abdelhak; Tati, Abdelouahab; Belarbi, Mohamed Ouejdi; Guettala, Abdelhamid

    2018-03-01

    The design of high-performance composite structures frequently includes discontinuities to reduce the weight and fastener holes for joining. Understanding the behavior of perforated laminates is necessary for structural design. In the current work, stress concentrations taking place in laminated and isotropic plates subjected to tensile load are investigated. The stress concentrations are obtained using a recent quadrilateral finite element of four nodes with 32 DOFs. The present finite element (PE) is a combination of two finite elements. The first finite element is a linear isoparametric membrane element and the second is a high precision Hermitian element. One of the essential objectives of the current investigation is to confirm the capability and efficiency of the PE for stress determination in perforated laminates. Different geometric parameters, such as the cutout form, sizes and cutout orientations, which have a considerable effect on the stress values, are studied. Using the present finite element formulation, the obtained results are found to be in good agreement with the analytical findings, which validates the capability and the efficiency of the proposed formulation. Finally, to understand the material parameters effect such as the orientation of fibers and degree of orthotropy ratio on the stress values, many figures are presented using different ellipse major to minor axis ratio. The stress concentration values are considerably affected by increasing the orientation angle of the fibers and degree of orthotropy.

  9. Accreting Black Holes

    OpenAIRE

    Begelman, Mitchell C.

    2014-01-01

    I outline the theory of accretion onto black holes, and its application to observed phenomena such as X-ray binaries, active galactic nuclei, tidal disruption events, and gamma-ray bursts. The dynamics as well as radiative signatures of black hole accretion depend on interactions between the relatively simple black-hole spacetime and complex radiation, plasma and magnetohydrodynamical processes in the surrounding gas. I will show how transient accretion processes could provide clues to these ...

  10. Naked black holes

    International Nuclear Information System (INIS)

    Horowitz, G.T.; Ross, S.F.

    1997-01-01

    It is shown that there are large static black holes for which all curvature invariants are small near the event horizon, yet any object which falls in experiences enormous tidal forces outside the horizon. These black holes are charged and near extremality, and exist in a wide class of theories including string theory. The implications for cosmic censorship and the black hole information puzzle are discussed. copyright 1997 The American Physical Society

  11. Impact Driver With Integral Sliding Hammer

    Science.gov (United States)

    Wallace, Bilby J.

    1987-01-01

    Tool combines impact driver with sliding dead-blow hammer. Used for any purpose for which ordinary impact driver used; tightening fasteners or driving starter holes for drill. Tool protects user from accidental injury and surrounding equipment from damage that might occur from ordinary arm-wielded hammer. Especially useful in underwater work.

  12. Ballistic hole magnetic microscopy

    NARCIS (Netherlands)

    Haq, E.; Banerjee, T.; Siekman, M.H.; Lodder, J.C.; Jansen, R.

    2005-01-01

    A technique to study nanoscale spin transport of holes is presented: ballistic hole magnetic microscopy. The tip of a scanning tunneling microscope is used to inject hot electrons into a ferromagnetic heterostructure, where inelastic decay creates a distribution of electron-hole pairs.

  13. Black-hole driven winds

    International Nuclear Information System (INIS)

    Punsly, B.M.

    1988-01-01

    This dissertation is a study of the physical mechanism that allows a large scale magnetic field to torque a rapidly rotating, supermassive black hole. This is an interesting problem as it has been conjectured that rapidly rotating black holes are the central engines that power the observed extragalactic double radio sources. Axisymmetric solutions of the curved space-time version of Maxwell's equations in the vacuum do not torque black holes. Plasma must be introduced for the hole to mechanically couple to the field. The dynamical aspect of rotating black holes that couples the magnetic field to the hole is the following. A rotating black hole forces the external geometry of space-time to rotate (the dragging of inertial frames). Inside of the stationary limit surface, the ergosphere, all physical particle trajectories must appear to rotate in the same direction as the black hole as viewed by the stationary observers at asymptotic infinity. In the text, it is demonstrated how plasma that is created on field lines that thread both the ergosphere and the equatorial plane will be pulled by gravity toward the equator. By the aforementioned properties of the ergosphere, the disk must rotate. Consequently, the disk acts like a unipolar generator. It drives a global current system that supports the toroidal magnetic field in an outgoing, magnetically dominated wind. This wind carries energy (mainly in the form of Poynting flux) and angular momentum towards infinity. The spin down of the black hole is the ultimate source of this energy and angular momentum flux

  14. Regulation of black-hole accretion by a disk wind during a violent outburst of V404 Cygni.

    Science.gov (United States)

    Muñoz-Darias, T; Casares, J; Mata Sánchez, D; Fender, R P; Armas Padilla, M; Linares, M; Ponti, G; Charles, P A; Mooley, K P; Rodriguez, J

    2016-06-02

    Accretion of matter onto black holes is universally associated with strong radiative feedback and powerful outflows. In particular, black-hole transients have outflows whose properties are strongly coupled to those of the accretion flow. This includes X-ray winds of ionized material, expelled from the accretion disk encircling the black hole, and collimated radio jets. Very recently, a distinct optical variability pattern has been reported in the transient stellar-mass black hole V404 Cygni, and interpreted as disrupted mass flow into the inner regions of its large accretion disk. Here we report observations of a sustained outer accretion disk wind in V404 Cyg, which is unlike any seen hitherto. We find that the outflowing wind is neutral, has a large covering factor, expands at one per cent of the speed of light and triggers a nebular phase once accretion drops sharply and the ejecta become optically thin. The large expelled mass (>10(-8) solar masses) indicates that the outburst was prematurely ended when a sizeable fraction of the outer disk was depleted by the wind, detaching the inner regions from the rest of the disk. The luminous, but brief, accretion phases shown by transients with large accretion disks imply that this outflow is probably a fundamental ingredient in regulating mass accretion onto black holes.

  15. Black holes are hot

    International Nuclear Information System (INIS)

    Gibbons, G.

    1976-01-01

    Recent work, which has been investigating the use of the concept of entropy with respect to gravitating systems, black holes and the universe as a whole, is discussed. The resulting theory of black holes assigns a finite temperature to them -about 10 -7 K for ordinary black holes of stellar mass -which is in complete agreement with thermodynamical concepts. It is also shown that black holes must continuously emit particles just like ordinary bodies which have a certain temperature. (U.K.)

  16. Intermediate-Mass Black Holes

    Science.gov (United States)

    Miller, M. Coleman; Colbert, E. J. M.

    2004-01-01

    The mathematical simplicity of black holes, combined with their links to some of the most energetic events in the universe, means that black holes are key objects for fundamental physics and astrophysics. Until recently, it was generally believed that black holes in nature appear in two broad mass ranges: stellar-mass (M~3 20 M⊙), which are produced by the core collapse of massive stars, and supermassive (M~106 1010 M⊙), which are found in the centers of galaxies and are produced by a still uncertain combination of processes. In the last few years, however, evidence has accumulated for an intermediate-mass class of black holes, with M~102 104 M⊙. If such objects exist they have important implications for the dynamics of stellar clusters, the formation of supermassive black holes, and the production and detection of gravitational waves. We review the evidence for intermediate-mass black holes and discuss future observational and theoretical work that will help clarify numerous outstanding questions about these objects.

  17. Black hole multiplicity at particle colliders (Do black holes radiate mainly on the brane?)

    International Nuclear Information System (INIS)

    Cavaglia, Marco

    2003-01-01

    If gravity becomes strong at the TeV scale, we may have the chance to produce black holes at particle colliders. In this Letter we revisit some phenomenological signatures of black hole production in TeV-gravity theories. We show that the bulk-to-brane ratio of black hole energy loss during the Hawking evaporation phase depends crucially on the black hole greybody factors and on the particle degrees of freedom. Since the greybody factors have not yet been calculated in the literature, and the particle content at trans-Planckian energies is not known, it is premature to claim that the black hole emits mainly on the brane. We also revisit the decay time and the multiplicity of the decay products of black hole evaporation. We give general formulae for black hole decay time and multiplicity. We find that the number of particles produced during the evaporation phase may be significantly lower than the average multiplicity which has been used in the past literature

  18. String-Corrected Black Holes

    Energy Technology Data Exchange (ETDEWEB)

    Hubeny, V.

    2005-01-12

    We investigate the geometry of four dimensional black hole solutions in the presence of stringy higher curvature corrections to the low energy effective action. For certain supersymmetric two charge black holes these corrections drastically alter the causal structure of the solution, converting seemingly pathological null singularities into timelike singularities hidden behind a finite area horizon. We establish, analytically and numerically, that the string-corrected two-charge black hole metric has the same Penrose diagram as the extremal four-charge black hole. The higher derivative terms lead to another dramatic effect--the gravitational force exerted by a black hole on an inertial observer is no longer purely attractive. The magnitude of this effect is related to the size of the compactification manifold.

  19. Microstructure and Properties of Ti-5553 Alloy for Aerospace Fasteners

    Directory of Open Access Journals (Sweden)

    ZHAO Qing-yun

    2017-10-01

    Full Text Available The effect of heat treatment on microstructure and mechanical properties of Ti-5553 alloy was investigated by scanning electron microscopy (SEM and transmission electron microscopy (TEM. The results show that when the alloy is treated in α+β phase zone, tensile strength decreases with raising solution temperature due to decreasing the content of primary α-phase and increasing the size and volume fraction of β phase. A lot of secondary α-phase precipitates from grain boundary and intragranular with β phase transformation during aging treatment. The size of secondary α-phase has significant influence on tensile strength, secondary α-phase coarsens gradually with the increase of aging temperature, resulting in the decrease of tensile strength. It is suggested that for 1240MPa aerospace fasteners the solution temperature of Ti-5553 should be under Tβ, thus adequate β phase, where a lot of secondary α phase precipitates from, is good for the required high strength. Meanwhile, a certain percentage of primary α-phase is kept for acquiring good ductility and toughness. After solution treatment at 810-820℃ for 1.5h, water quenching plus aging at 510℃ for 10h, Ti-5553 shows a better mechanical property with tensile strength 1500MPa, elongation 14.8% and reduction of cross-section area 38.6%. Lots of dimples can be found in tensile fracture after solution treatment and solution+aging treatment, which demonstrate Ti-5553 with good ductility and toughness.

  20. Video studies of passage by Anopheles gambiae mosquitoes through holes in a simulated bed net: effects of hole size, hole orientation and net environment.

    Science.gov (United States)

    Sutcliffe, James; Colborn, Kathryn L

    2015-05-13

    Holes in netting provide potential routes for mosquitoes to enter ITNs. Despite this, there is little information on how mosquitoes respond to holes in bed nets and how their responses are affected by hole size, shape and orientation or by ambient conditions around the net. Female Anopheles gambiae (G3) were recorded in a simulated bed net consisting of two sizes of untreated netting-covered behavioural arenas placed above and beside (to simulate the bed net roof and sides respectively) the experimenter who was a source of host cues from 'inside' the net. A round hole of 9 mm or 13 mm diameter was cut into the centre of the netting of each arena. Videos of unfed female mosquitoes in arenas were analysed for time spent flying, walking and standing still and for exit through the hole. The effects of the experimenter on temperature and relative humidity around the simulated net were also measured. Mosquitoes were significantly more active in overhead arenas than in arenas to the side. Hole passage was significantly more likely in smaller arenas than larger ones and for larger holes than smaller ones. In arenas to the side, hole passage rate through small holes was about 50% less likely than what could be explained by area alone. Passage rate through holes in overhead arenas was consistent with hole area. Temperature in arenas did not strongly reflect the experimenter's presence in the simulated net. Relative humidity and absolute humidity in overhead arenas, but not in arenas to the side, were immediately affected by experimenter presence. Higher levels of activity in overhead arenas than in arenas to the side were likely due to the rising heat and humidity plume from the experimenter. Lower than expected passage rates through smaller vertically oriented holes may have been be due to an edge effect that does not apply to horizontally oriented holes. Results suggest that current methods of assessing the importance of physical damage to ITNs may not accurately reflect

  1. Structural differences between glycosylated, disulfide-linked heterodimeric Knob-into-Hole Fc fragment and its homodimeric Knob-Knob and Hole-Hole side products.

    Science.gov (United States)

    Kuglstatter, A; Stihle, M; Neumann, C; Müller, C; Schaefer, W; Klein, C; Benz, J

    2017-09-01

    An increasing number of bispecific therapeutic antibodies are progressing through clinical development. The Knob-into-Hole (KiH) technology uses complementary mutations in the CH3 region of the antibody Fc fragment to achieve heavy chain heterodimerization. Here we describe the X-ray crystal structures of glycosylated and disulfide-engineered heterodimeric KiH Fc fragment and its homodimeric Knob-Knob and Hole-Hole side products. The heterodimer structure confirms the KiH design principle and supports the hypothesis that glycosylation stabilizes a closed Fc conformation. Both homodimer structures show parallel Fc fragment architectures, in contrast to recently reported crystal structures of the corresponding aglycosylated Fc fragments which in the absence of disulfide mutations show an unexpected antiparallel arrangement. The glycosylated Knob-Knob Fc fragment is destabilized as indicated by variability in the relative orientation of its CH3 domains. The glycosylated Hole-Hole Fc fragment shows an unexpected intermolecular disulfide bond via the introduced Y349C Hole mutation which results in a large CH3 domain shift and a new CH3-CH3 interface. The crystal structures of glycosylated, disulfide-linked KiH Fc fragment and its Knob-Knob and Hole-Hole side products reported here will facilitate further design of highly efficient antibody heterodimerization strategies. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  2. Wall insulation system

    Energy Technology Data Exchange (ETDEWEB)

    Kostek, P.T.

    1987-08-11

    In a channel specially designed to fasten semi-rigid mineral fibre insulation to masonry walls, it is known to be constructed from 20 gauge galvanized steel or other suitable material. The channel is designed to have pre-punched holes along its length for fastening of the channel to the drywall screw. The unique feature of the channel is the teeth running along its length which are pressed into the surface of the butted together sections of the insulation providing a strong grip between the two adjacent pieces of insulation. Of prime importance to the success of this system is the recent technological advancements of the mineral fibre itself which allow the teeth of the channel to engage the insulation fully and hold without mechanical support, rather than be repelled or pushed back by the inherent nature of the insulation material. After the insulation is secured to the masonry wall by concrete nail fastening systems, the drywall is screwed to the channel.

  3. FEASTING BLACK HOLE BLOWS BUBBLES

    Science.gov (United States)

    2002-01-01

    A monstrous black hole's rude table manners include blowing huge bubbles of hot gas into space. At least, that's the gustatory practice followed by the supermassive black hole residing in the hub of the nearby galaxy NGC 4438. Known as a peculiar galaxy because of its unusual shape, NGC 4438 is in the Virgo Cluster, 50 million light-years from Earth. These NASA Hubble Space Telescope images of the galaxy's central region clearly show one of the bubbles rising from a dark band of dust. The other bubble, emanating from below the dust band, is barely visible, appearing as dim red blobs in the close-up picture of the galaxy's hub (the colorful picture at right). The background image represents a wider view of the galaxy, with the central region defined by the white box. These extremely hot bubbles are caused by the black hole's voracious eating habits. The eating machine is engorging itself with a banquet of material swirling around it in an accretion disk (the white region below the bright bubble). Some of this material is spewed from the disk in opposite directions. Acting like high-powered garden hoses, these twin jets of matter sweep out material in their paths. The jets eventually slam into a wall of dense, slow-moving gas, which is traveling at less than 223,000 mph (360,000 kph). The collision produces the glowing material. The bubbles will continue to expand and will eventually dissipate. Compared with the life of the galaxy, this bubble-blowing phase is a short-lived event. The bubble is much brighter on one side of the galaxy's center because the jet smashed into a denser amount of gas. The brighter bubble is 800 light-years tall and 800 light-years across. The observations are being presented June 5 at the American Astronomical Society meeting in Rochester, N.Y. Both pictures were taken March 24, 1999 with the Wide Field and Planetary Camera 2. False colors were used to enhance the details of the bubbles. The red regions in the picture denote the hot gas

  4. Internal structure of black holes

    International Nuclear Information System (INIS)

    Cvetic, Mirjam

    2013-01-01

    Full text: We review recent progress that sheds light on the internal structure of general black holes. We first summarize properties of general multi-charged rotating black holes both in four and five dimensions. We show that the asymptotic boundary conditions of these general asymptotically flat black holes can be modified such that a conformal symmetry emerges. These subtracted geometries preserve the thermodynamic properties of the original black holes and are of the Lifshitz type, thus describing 'a black hole in the asymptotically conical box'. Recent efforts employ solution generating techniques to construct interpolating geometries between the original black hole and their subtracted geometries. Upon lift to one dimension higher, these geometries lift to AdS 3 times a sphere, and thus provide a microscopic interpretation of the black hole entropy in terms of dual two-dimensional conformal field theory. (author)

  5. What is black hole?

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. What is black hole? Possible end phase of a star: A star is a massive, luminous ball of plasma having continuous nuclear burning. Star exhausts nuclear fuel →. White Dwarf, Neutron Star, Black Hole. Black hole's gravitational field is so powerful that even ...

  6. Quantum effects in black holes

    International Nuclear Information System (INIS)

    Frolov, V.P.

    1979-01-01

    A strict definition of black holes is presented and some properties with regard to their mass are enumerated. The Hawking quantum effect - the effect of vacuum instability in the black hole gravitational field, as a result of shich the black hole radiates as a heated body is analyzed. It is shown that in order to obtain results on the black hole radiation it is sufficient to predetermine the in-vacuum state at a time moment in the past, when the collapsing body has a large size, and its gravitational field can be neglected. The causes and the place of particle production by the black hole, and also the space-time inside the black hole, are considered

  7. Simulation of friction stir drilling process

    Science.gov (United States)

    Vijayabaskar, P.; Hynes, N. Rajesh Jesudoss

    2018-05-01

    The project is the study of the thermal drilling process. The process is a hole forming process in the sheet metals using the heat generated by means of friction. The main advantage of the process over the conventional drilling process is that the holes formed using this process does not need any backing arrangements such as weld nuts, rivet nuts etc. Because the extruded bush itself acts as a supporting structure for the fasteners. This eliminates the need for the access to the backside of the work material for fastening operations. The major factors contributing the thermal drilling operation are the spindle speed and the thrust force required for forming a hole. The process of finding out the suitable thrust force and the speed for drilling a particular material with particular thickness is a tedious process. The process can be simplified by forming a mathematical model by combining the empirical formulae from the literature. These formulae were derived in the literature from the experimental trials by following certain assumptions. In this paper a suitable mathematical model is formed by replicating the experiments and tried to be validated by the results from numerical analysis. The numerical analysis of the model is done using the ANSYS software.

  8. A small-animal imaging system capable of multipinhole circular/helical SPECT and parallel-hole SPECT

    International Nuclear Information System (INIS)

    Qian Jianguo; Bradley, Eric L.; Majewski, Stan; Popov, Vladimir; Saha, Margaret S.; Smith, Mark F.; Weisenberger, Andrew G.; Welsh, Robert E.

    2008-01-01

    We have designed and built a small-animal single-photon emission computed tomography (SPECT) imaging system equipped with parallel-hole and multipinhole collimators and capable of circular or helical SPECT. Copper-beryllium parallel-hole collimators suitable for imaging the ∼35 keV photons from the decay of 125 I have been built and installed to achieve useful spatial resolution over a range of object-detector distances and to reduce imaging time on our dual-detector array. To address the resolution limitations in the parallel-hole SPECT and the sensitivity and limited field of view of single-pinhole SPECT, we have incorporated multipinhole circular and helical SPECT in addition to expanding the parallel-hole SPECT capabilities. The pinhole SPECT system is based on a 110 mm diameter circular detector equipped with a pixellated NaI(Tl) scintillator array (1x1x5 mm 3 /pixel). The helical trajectory is accomplished by two stepping motors controlling the rotation of the detector-support gantry and displacement of the animal bed along the axis of rotation of the gantry. Results obtained in SPECT studies of various phantoms show an enlarged field of view, very good resolution and improved sensitivity using multipinhole circular or helical SPECT. Collimators with one, three and five, 1-mm-diameter pinholes have been implemented and compared in these tests. Our objective is to develop a system on which one may readily select a suitable mode of either parallel-hole SPECT or pinhole circular or helical SPECT for a variety of small animal imaging applications

  9. Tissue expander infections in children: look beyond the expander pocket.

    Science.gov (United States)

    Mason, A C; Davison, S P; Manders, E K

    1999-11-01

    Infection of the expander pocket is the most common complication encountered with soft-tissue expansion. It is usually due to direct inoculation with skin flora either at the time of expander insertion or from extrusion of the device. The authors report two cases of infection of tissue expanders in which the children had concomitant infected sites distant from the prosthesis. Etiological bacteria of common pediatric infections like otitis media and pharyngitis were cultured from the infected expander pocket, raising suspicion that translocation of the organism to the expander had occurred. Aggressive antibiotic treatment, removal of the prosthesis, and flap advancement is advocated.

  10. An evaluation of ACI 349 code for design of the fastening system at nuclear power plant

    International Nuclear Information System (INIS)

    Jang, J.-B.; Suh, Y.-P.; Lee, J.-R.

    2005-01-01

    ACI 349 Code, revised on 2001, is only available for the anchor with diameter not exceeding 2 in. and tensile embedment not exceeding 25 in. in depth. So, ACI 349 Code can't be applied to the design of the large sized anchor with diameter exceeding 2 in. and tensile embedment exceeding 25 in. in depth which fastens the SG, RV, RCP, PZR, etc. at containment building. Therefore, an application of ACI 349 Code was investigated for the design of the small and large sized anchors under tensile load using the numerical analysis model which was developed on a basis of the various test data of cast-in-place anchor in this study. In conclusion, it is proved that ACI 349 Code is available for the design of the small and large sized cast-in-place anchor. (authors)

  11. 30 CFR 57.7055 - Intersecting holes.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Intersecting holes. 57.7055 Section 57.7055... Jet Piercing Drilling-Surface and Underground § 57.7055 Intersecting holes. Holes shall not be drilled where there is a danger of intersecting a misfired hole or a hole containing explosives, blasting agents...

  12. Self consistent MHD modeling of the solar wind from polar coronal holes

    International Nuclear Information System (INIS)

    Stewart, G. A.; Bravo, S.

    1996-01-01

    We have developed a 2D self consistent MHD model for solar wind flow from antisymmetric magnetic geometries. We present results in the case of a photospheric magnetic field which has a dipolar configuration, in order to investigate some of the general characteristics of the wind at solar minimum. As in previous studies, we find that the magnetic configuration is that of a closed field region (a coronal helmet belt) around the solar equator, extending up to about 1.6 R · , and two large open field regions centred over the poles (polar coronal holes), whose magnetic and plasma fluxes expand to fill both hemispheres in interplanetary space. In addition, we find that the different geometries of the magnetic field lines across each hole (from the almost radial central polar lines to the highly curved border equatorial lines) cause the solar wind to have greatly different properties depending on which region it flows from. We find that, even though our simplified model cannot produce realistic wind values, we can obtain a polar wind that is faster, less dense and hotter than equatorial wind, and found that, close to the Sun, there exists a sharp transition between the two wind types. As these characteristics coincide with observations we conclude that both fast and slow solar wind can originate from coronal holes, fast wind from the centre, slow wind from the border

  13. Electromagnetic Counterparts to Black Hole Mergers

    Science.gov (United States)

    Schnittman, Jeremy D.

    2011-01-01

    During the final moments of a binary black hole (BH) merger, the gravitational wave (GW) luminosity of the system is greater than the combined electromagnetic (EM) output of the entire observable universe. However, the extremely weak coupling between GWs and ordinary matter makes these waves very difficult to detect directly. Fortunately, the inspirating BH system will interact strongly-on a purely Newtonian level-with any surrounding material in the host galaxy, and this matter can in turn produce unique EM signals detectable at Earth. By identifying EM counterparts to GW sources, we will be able to study the host environments of the merging BHs, in turn greatly expanding the scientific yield of a mission like LISA. Here we present a comprehensive review of the recent literature on the subject of EM counterparts, as well as a discussion of the theoretical and observational advances required to fully realize the scientific potential of the field.

  14. 30 CFR 56.7055 - Intersecting holes.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Intersecting holes. 56.7055 Section 56.7055... Piercing Drilling § 56.7055 Intersecting holes. Holes shall not be drilled where there is a danger of intersecting a misfired hole or a hole containing explosives blasting agents, or detonators. [56 FR 46508, Sept...

  15. Lifshitz topological black holes

    International Nuclear Information System (INIS)

    Mann, R.B.

    2009-01-01

    I find a class of black hole solutions to a (3+1) dimensional theory gravity coupled to abelian gauge fields with negative cosmological constant that has been proposed as the dual theory to a Lifshitz theory describing critical phenomena in (2+1) dimensions. These black holes are all asymptotic to a Lifshitz fixed point geometry and depend on a single parameter that determines both their area (or size) and their charge. Most of the solutions are obtained numerically, but an exact solution is also obtained for a particular value of this parameter. The thermodynamic behaviour of large black holes is almost the same regardless of genus, but differs considerably for small black holes. Screening behaviour is exhibited in the dual theory for any genus, but the critical length at which it sets in is genus-dependent for small black holes.

  16. The Aftermath of GW170817: Neutron Star or Black Hole?

    Science.gov (United States)

    Kohler, Susanna

    2018-06-01

    shock wave expands and slams into the surrounding interstellar medium. The earliest X-ray detection from GW170817 around 9 days after the merger likely indicated the moment when that interaction began. GW170817s X-ray emission continued to grow over the first 100 days post-merger, expected as the shock continues to expand.If the merger had produced a neutron star, however, there should be an additional source of X-ray radiation besides the shock: the neutron star itself. This emission should, by now, have started to dominate over the emission from the propagating shock. Instead, Pooley and collaborators find that the observed X-ray flux from GW170817 falls significantly short of whats needed to justify the presence of a highly magnetized, spinning neutron star. For this reason, the authors conclude that GW170817 likely produced a black hole.Future ConfirmationHow can we be sure? Pooley and collaborators point out that we can confirm this theory just by observing GW170817 for another year. Around this time, energy released from the spin-down of a central neutron star would catch up to the decelerating shock front, causing a dramatic brightening in GW170817s X-ray flux.If we dont see this brightening, the authors argue that we can conclude with certainty that GW170817s remnant is a black hole. Either way, continued observations of this remnant are sure to provide a wealth of information about the physics of mergers, shocks, and outflows that we can hope to mine for years to come.CitationDavid Pooley et al 2018 ApJL 859 L23. doi:10.3847/2041-8213/aac3d6

  17. Black hole decay as geodesic motion

    International Nuclear Information System (INIS)

    Gupta, Kumar S.; Sen, Siddhartha

    2003-01-01

    We show that a formalism for analyzing the near-horizon conformal symmetry of Schwarzschild black holes using a scalar field probe is capable of describing black hole decay. The equation governing black hole decay can be identified as the geodesic equation in the space of black hole masses. This provides a novel geometric interpretation for the decay of black holes. Moreover, this approach predicts a precise correction term to the usual expression for the decay rate of black holes

  18. UNIVERSE IN A BLACK HOLE IN EINSTEIN–CARTAN GRAVITY

    Energy Technology Data Exchange (ETDEWEB)

    Popławski, Nikodem, E-mail: NPoplawski@newhaven.edu [Department of Mathematics and Physics, University of New Haven, 300 Boston Post Road, West Haven, CT 06516 (United States)

    2016-12-01

    The conservation law for the angular momentum in curved spacetime, consistent with relativistic quantum mechanics, requires that the antisymmetric part of the affine connection (torsion tensor) is a variable in the principle of least action. The coupling between the spin of elementary particles and torsion in the Einstein–Cartan theory of gravity generates gravitational repulsion at extremely high densities in fermionic matter, approximated as a spin fluid, and thus avoids the formation of singularities in black holes. The collapsing matter in a black hole should therefore bounce at a finite density and then expand into a new region of space on the other side of the event horizon, which may be regarded as a nonsingular, closed universe. We show that quantum particle production caused by an extremely high curvature near a bounce can create enormous amounts of matter, produce entropy, and generate a finite period of exponential expansion (inflation) of this universe. This scenario can thus explain inflation without a scalar field and reheating. We show that, depending on the particle production rate, such a universe may undergo several nonsingular bounces until it has enough matter to reach a size at which the cosmological constant starts cosmic acceleration. The last bounce can be regarded as the big bang of this universe.

  19. Universe in a Black Hole in Einstein-Cartan Gravity

    Science.gov (United States)

    Popławski, Nikodem

    2016-12-01

    The conservation law for the angular momentum in curved spacetime, consistent with relativistic quantum mechanics, requires that the antisymmetric part of the affine connection (torsion tensor) is a variable in the principle of least action. The coupling between the spin of elementary particles and torsion in the Einstein-Cartan theory of gravity generates gravitational repulsion at extremely high densities in fermionic matter, approximated as a spin fluid, and thus avoids the formation of singularities in black holes. The collapsing matter in a black hole should therefore bounce at a finite density and then expand into a new region of space on the other side of the event horizon, which may be regarded as a nonsingular, closed universe. We show that quantum particle production caused by an extremely high curvature near a bounce can create enormous amounts of matter, produce entropy, and generate a finite period of exponential expansion (inflation) of this universe. This scenario can thus explain inflation without a scalar field and reheating. We show that, depending on the particle production rate, such a universe may undergo several nonsingular bounces until it has enough matter to reach a size at which the cosmological constant starts cosmic acceleration. The last bounce can be regarded as the big bang of this universe.

  20. Drilling miniature holes, Part III

    Energy Technology Data Exchange (ETDEWEB)

    Gillespie, L.K.

    1978-07-01

    Miniature components for precision electromechanical mechanisms such as switches, timers, and actuators typically require a number of small holes. Because of the precision required, the workpiece materials, and the geometry of the parts, most of these holes must be produced by conventional drilling techniques. The use of such techniques is tedious and often requires considerable trial and error to prevent drill breakage, minimize hole mislocation and variations in hole diameter. This study of eight commercial drill designs revealed that printed circuit board drills produced better locational and size repeatability than did other drills when centerdrilling was not used. Boring holes 1 mm in dia, or less, as a general rule did not improve hole location in brass or stainless steel. Hole locations of patterns of 0.66-mm holes can be maintained within 25.4-..mu..m diametral positional tolerance if setup misalignments can be eliminated. Size tolerances of +- 3.8 ..mu..m can be maintained under some conditions when drilling flat plates. While these levels of precision are possible with existing off-the-shelf drills, they may not be practical in many cases.

  1. Simplified computational methods for elastic and elastic-plastic fracture problems

    Science.gov (United States)

    Atluri, Satya N.

    1992-01-01

    An overview is given of some of the recent (1984-1991) developments in computational/analytical methods in the mechanics of fractures. Topics covered include analytical solutions for elliptical or circular cracks embedded in isotropic or transversely isotropic solids, with crack faces being subjected to arbitrary tractions; finite element or boundary element alternating methods for two or three dimensional crack problems; a 'direct stiffness' method for stiffened panels with flexible fasteners and with multiple cracks; multiple site damage near a row of fastener holes; an analysis of cracks with bonded repair patches; methods for the generation of weight functions for two and three dimensional crack problems; and domain-integral methods for elastic-plastic or inelastic crack mechanics.

  2. Acceleration of black hole universe

    Science.gov (United States)

    Zhang, T. X.; Frederick, C.

    2014-01-01

    Recently, Zhang slightly modified the standard big bang theory and developed a new cosmological model called black hole universe, which is consistent with Mach's principle, governed by Einstein's general theory of relativity, and able to explain all observations of the universe. Previous studies accounted for the origin, structure, evolution, expansion, and cosmic microwave background radiation of the black hole universe, which grew from a star-like black hole with several solar masses through a supermassive black hole with billions of solar masses to the present state with hundred billion-trillions of solar masses by accreting ambient matter and merging with other black holes. This paper investigates acceleration of the black hole universe and provides an alternative explanation for the redshift and luminosity distance measurements of type Ia supernovae. The results indicate that the black hole universe accelerates its expansion when it accretes the ambient matter in an increasing rate. In other words, i.e., when the second-order derivative of the mass of the black hole universe with respect to the time is positive . For a constant deceleration parameter , we can perfectly explain the type Ia supernova measurements with the reduced chi-square to be very close to unity, χ red˜1.0012. The expansion and acceleration of black hole universe are driven by external energy.

  3. Super-horizon primordial black holes

    International Nuclear Information System (INIS)

    Harada, Tomohiro; Carr, B.J.

    2005-01-01

    We discuss a new class of solutions to the Einstein equations which describe a primordial black hole (PBH) in a flat Friedmann background. Such solutions arise if a Schwarzschild black hole is patched onto a Friedmann background via a transition region. They are possible providing the black hole event horizon is larger than the cosmological apparent horizon. Such solutions have a number of strange features. In particular, one has to define the black hole and cosmological horizons carefully and one then finds that the mass contained within the black hole event horizon decreases when the black hole is larger than the Friedmann cosmological apparent horizon, although its area always increases. These solutions involve two distinct future null infinities and are interpreted as the conversion of a white hole into a black hole. Although such solutions may not form from gravitational collapse in the same way as standard PBHs, there is nothing unphysical about them, since all energy and causality conditions are satisfied. Their conformal diagram is a natural amalgamation of the Kruskal diagram for the extended Schwarzschild solution and the conformal diagram for a black hole in a flat Friedmann background. In this paper, such solutions are obtained numerically for a spherically symmetric universe containing a massless scalar field, but it is likely that they exist for more general matter fields and less symmetric systems

  4. NASA Observatory Confirms Black Hole Limits

    Science.gov (United States)

    2005-02-01

    The very largest black holes reach a certain point and then grow no more, according to the best survey to date of black holes made with NASA's Chandra X-ray Observatory. Scientists have also discovered many previously hidden black holes that are well below their weight limit. These new results corroborate recent theoretical work about how black holes and galaxies grow. The biggest black holes, those with at least 100 million times the mass of the Sun, ate voraciously during the early Universe. Nearly all of them ran out of 'food' billions of years ago and went onto a forced starvation diet. Focus on Black Holes in the Chandra Deep Field North Focus on Black Holes in the Chandra Deep Field North On the other hand, black holes between about 10 and 100 million solar masses followed a more controlled eating plan. Because they took smaller portions of their meals of gas and dust, they continue growing today. "Our data show that some supermassive black holes seem to binge, while others prefer to graze", said Amy Barger of the University of Wisconsin in Madison and the University of Hawaii, lead author of the paper describing the results in the latest issue of The Astronomical Journal (Feb 2005). "We now understand better than ever before how supermassive black holes grow." One revelation is that there is a strong connection between the growth of black holes and the birth of stars. Previously, astronomers had done careful studies of the birthrate of stars in galaxies, but didn't know as much about the black holes at their centers. DSS Optical Image of Lockman Hole DSS Optical Image of Lockman Hole "These galaxies lose material into their central black holes at the same time that they make their stars," said Barger. "So whatever mechanism governs star formation in galaxies also governs black hole growth." Astronomers have made an accurate census of both the biggest, active black holes in the distance, and the relatively smaller, calmer ones closer by. Now, for the first

  5. 77 FR 73265 - Airworthiness Directives; Erickson Air-Crane Incorporated Helicopters

    Science.gov (United States)

    2012-12-10

    ... attention to the fastener attachment holes, as shown in Figure 1, Detail B, of the Accomplishment...-66340-043 or -044, for a crack. Pay particular attention to the circled areas shown in Figure 2 of the... Office, M-30, West Building Ground Floor, Room W12- 140, 1200 New Jersey Avenue SE., Washington, DC 20590...

  6. Supportability in Aircraft Systems through Technology and Acquisition Strategy Applications.

    Science.gov (United States)

    1987-09-01

    structures is their corrosion resistance. These integral structures are water impregnable. Also, the absence of rivet and fastener hole eliminates the...REPCRT SECURITY CLASS,F,CAT ON lb RESTR;CTIVE MARK.NGSU",CLAS S I7 F 15E Za. SECURITY CLASSiFICAT;ON AUTHORITY 3 DISTRiBUTiQN/ AVAILABILIT ’ OF REPORT

  7. Green's tensor calculations of plasmon resonances of single holes and hole pairs in thin gold films

    International Nuclear Information System (INIS)

    Alegret, Joan; Kaell, Mikael; Johansson, Peter

    2008-01-01

    We present numerical calculations of the plasmon properties of single-hole and hole-pair structures in optically thin gold films obtained with the Green's tensor formalism for stratified media. The method can be used to obtain the optical properties of a given hole system, without problems associated with the truncation of the infinite metal film. The calculations are compared with previously published experimental data and an excellent agreement is found. In particular, the calculations are shown to reproduce the evolution of the hole plasmon resonance spectrum as a function of hole diameter, film thickness and hole separation.

  8. Curvature invariant characterization of event horizons of four-dimensional black holes conformal to stationary black holes

    Science.gov (United States)

    McNutt, David D.

    2017-11-01

    We introduce three approaches to generate curvature invariants that transform covariantly under a conformal transformation of a four-dimensional spacetime. For any black hole conformally related to a stationary black hole, we show how a set of conformally covariant invariants can be combined to produce a conformally covariant invariant that detects the event horizon of the conformally related black hole. As an application we consider the rotating dynamical black holes conformally related to the Kerr-Newman-Unti-Tamburino-(anti)-de Sitter spacetimes and construct an invariant that detects the conformal Killing horizon along with a second invariant that detects the conformal stationary limit surface. In addition, we present necessary conditions for a dynamical black hole to be conformally related to a stationary black hole and apply these conditions to the ingoing Kerr-Vaidya and Vaidya black hole solutions to determine if they are conformally related to stationary black holes for particular choices of the mass function. While two of the three approaches cannot be generalized to higher dimensions, we discuss the existence of a conformally covariant invariant that will detect the event horizon for any higher dimensional black hole conformally related to a stationary black hole which admits at least two conformally covariant invariants, including all vacuum spacetimes.

  9. Statistical mechanics of black holes

    International Nuclear Information System (INIS)

    Harms, B.; Leblanc, Y.

    1992-01-01

    We analyze the statistical mechanics of a gas of neutral and charged black holes. The microcanonical ensemble is the only possible approach to this system, and the equilibrium configuration is the one for which most of the energy is carried by a single black hole. Schwarzschild black holes are found to obey the statistical bootstrap condition. In all cases, the microcanonical temperature is identical to the Hawking temperature of the most massive black hole in the gas. U(1) charges in general break the bootstrap property. The problems of black-hole decay and of quantum coherence are also addressed

  10. Fatigue crack growth monitoring in multi-layered structures using guided ultrasonic waves

    International Nuclear Information System (INIS)

    Kostson, E; Fromme, P

    2009-01-01

    This contribution investigates the application of low frequency guided ultrasonic waves for monitoring fatigue crack growth at fastener holes in the 2nd layer of multi-layered plate structures, a common problem in aerospace industry. The model multi-layered structure investigated consists of two aluminum plate-strips adhesively bonded using a structural paste adhesive. Guided ultrasonic waves were excited using multiple piezoelectric discs bonded to the surface of the multi-layered structure. The wave propagation in the tensile specimen was measured using a laser interferometer and compared to numerical simulations. Thickness and width mode shapes of the excited flexural waves were identified from Semi-Analytical Finite Element (SAFE) calculations. Experiments and 3D Finite Element (FE) simulations show a change in the scattered field around fastener holes caused by a defect in the 2nd layer. The amplitude of the guided ultrasonic wave was monitored during fatigue experiments at a single point. The measured changes in the amplitude of the ultrasonic signal due to fatigue crack growth agree well with FE simulations.

  11. Regular black hole in three dimensions

    OpenAIRE

    Myung, Yun Soo; Yoon, Myungseok

    2008-01-01

    We find a new black hole in three dimensional anti-de Sitter space by introducing an anisotropic perfect fluid inspired by the noncommutative black hole. This is a regular black hole with two horizons. We compare thermodynamics of this black hole with that of non-rotating BTZ black hole. The first-law of thermodynamics is not compatible with the Bekenstein-Hawking entropy.

  12. RC Beams Strengthened with Mechanically Fastened Composites: Experimental Results and Numerical Modeling

    Directory of Open Access Journals (Sweden)

    Enzo Martinelli

    2014-03-01

    Full Text Available The use of mechanically-fastened fiber-reinforced polymer (MF-FRP systems has recently emerged as a competitive solution for the flexural strengthening of reinforced concrete (RC beams and slabs. An overview of the experimental research has proven the effectiveness and the potentiality of the MF-FRP technique which is particularly suitable for emergency repairs or when the speed of installation and immediacy of use are imperative. A finite-element (FE model has been recently developed by the authors with the aim to simulate the behavior of RC beams strengthened in bending by MF-FRP laminates; such a model has also been validated by using a wide experimental database collected from the literature. By following the previous study, the FE model and the assembled database are considered herein with the aim of better exploring the influence of some specific aspects on the structural response of MF-FRP strengthened members, such as the bearing stress-slip relationship assumed for the FRP-concrete interface, the stress-strain law considered for reinforcing steel rebars and the cracking process in RC members resulting in the well-known tension stiffening effect. The considerations drawn from this study will be useful to researchers for the calibration of criteria and design rules for strengthening RC beams through MF-FRP laminates.

  13. Black hole levitron

    NARCIS (Netherlands)

    Arsiwalla, X.D.; Verlinde, E.P.

    2010-01-01

    We study the problem of spatially stabilizing four dimensional extremal black holes in background electric/magnetic fields. Whilst looking for stationary stable solutions describing black holes placed in external fields we find that taking a continuum limit of Denef et al.’s multicenter

  14. Is there life inside black holes?

    International Nuclear Information System (INIS)

    Dokuchaev, V I

    2011-01-01

    Bound inside rotating or charged black holes, there are stable periodic planetary orbits, which neither come out nor terminate at the central singularity. Stable periodic orbits inside black holes exist even for photons. These bound orbits may be defined as orbits of the third kind, following the Chandrasekhar classification of particle orbits in the black hole gravitational field. The existence domain for the third-kind orbits is rather spacious, and thus there is place for life inside supermassive black holes in the galactic nuclei. Interiors of the supermassive black holes may be inhabited by civilizations, being invisible from the outside. In principle, one can get information from the interiors of black holes by observing their white hole counterparts. (paper)

  15. Black Hole Grabs Starry Snack

    Science.gov (United States)

    2006-01-01

    [figure removed for brevity, see original site] Poster Version This artist's concept shows a supermassive black hole at the center of a remote galaxy digesting the remnants of a star. NASA's Galaxy Evolution Explorer had a 'ringside' seat for this feeding frenzy, using its ultraviolet eyes to study the process from beginning to end. The artist's concept chronicles the star being ripped apart and swallowed by the cosmic beast over time. First, the intact sun-like star (left) ventures too close to the black hole, and its own self-gravity is overwhelmed by the black hole's gravity. The star then stretches apart (middle yellow blob) and eventually breaks into stellar crumbs, some of which swirl into the black hole (cloudy ring at right). This doomed material heats up and radiates light, including ultraviolet light, before disappearing forever into the black hole. The Galaxy Evolution Explorer was able to watch this process unfold by observing changes in ultraviolet light. The area around the black hole appears warped because the gravity of the black hole acts like a lens, twisting and distorting light.

  16. A nonsingular rotating black hole

    International Nuclear Information System (INIS)

    Ghosh, Sushant G.

    2015-01-01

    The spacetime singularities in classical general relativity are inevitable, as predicated by the celebrated singularity theorems. However, it is a general belief that singularities do not exist in Nature and that they are the limitations of the general relativity. In the absence of a welldefined quantum gravity, models of regular black holes have been studied. We employ a probability distribution inspired mass function m(r) to replace the Kerr black hole mass M to represent a nonsingular rotating black hole that is identified asymptotically (r >> k, k > 0 constant) exactly as the Kerr-Newman black hole, and as the Kerr black hole when k = 0. The radiating counterpart renders a nonsingular generalization of Carmeli's spacetime as well as Vaidya's spacetime, in the appropriate limits. The exponential correction factor changing the geometry of the classical black hole to remove the curvature singularity can also be motivated by quantum arguments. The regular rotating spacetime can also be understood as a black hole of general relativity coupled to nonlinear electrodynamics. (orig.)

  17. Thermodynamic theory of black holes

    Energy Technology Data Exchange (ETDEWEB)

    Davies, P C.W. [King' s Coll., London (UK). Dept. of Mathematics

    1977-04-21

    The thermodynamic theory underlying black hole processes is developed in detail and applied to model systems. It is found that Kerr-Newman black holes undergo a phase transition at a = 0.68M or Q = 0.86M, where the heat capacity has an infinite discontinuity. Above the transition values the specific heat is positive, permitting isothermal equilibrium with a surrounding heat bath. Simple processes and stability criteria for various black hole situations are investigated. The limits for entropically favoured black hole formation are found. The Nernst conditions for the third law of thermodynamics are not satisfied fully for black holes. There is no obvious thermodynamic reason why a black hole may not be cooled down below absolute zero and converted into a naked singularity. Quantum energy-momentum tensor calculations for uncharged black holes are extended to the Reissner-Nordstrom case, and found to be fully consistent with the thermodynamic picture for Q < M. For Q < M the model predicts that 'naked' collapse also produces radiation, with such intensity that the collapsing matter is entirely evaporated away before a naked singularity can form.

  18. Erratic Black Hole Regulates Itself

    Science.gov (United States)

    2009-03-01

    New results from NASA's Chandra X-ray Observatory have made a major advance in explaining how a special class of black holes may shut off the high-speed jets they produce. These results suggest that these black holes have a mechanism for regulating the rate at which they grow. Black holes come in many sizes: the supermassive ones, including those in quasars, which weigh in at millions to billions of times the mass of the Sun, and the much smaller stellar-mass black holes which have measured masses in the range of about 7 to 25 times the Sun's mass. Some stellar-mass black holes launch powerful jets of particles and radiation, like seen in quasars, and are called "micro-quasars". The new study looks at a famous micro-quasar in our own Galaxy, and regions close to its event horizon, or point of no return. This system, GRS 1915+105 (GRS 1915 for short), contains a black hole about 14 times the mass of the Sun that is feeding off material from a nearby companion star. As the material swirls toward the black hole, an accretion disk forms. This system shows remarkably unpredictable and complicated variability ranging from timescales of seconds to months, including 14 different patterns of variation. These variations are caused by a poorly understood connection between the disk and the radio jet seen in GRS 1915. Chandra, with its spectrograph, has observed GRS 1915 eleven times since its launch in 1999. These studies reveal that the jet in GRS 1915 may be periodically choked off when a hot wind, seen in X-rays, is driven off the accretion disk around the black hole. The wind is believed to shut down the jet by depriving it of matter that would have otherwise fueled it. Conversely, once the wind dies down, the jet can re-emerge. "We think the jet and wind around this black hole are in a sort of tug of war," said Joseph Neilsen, Harvard graduate student and lead author of the paper appearing in the journal Nature. "Sometimes one is winning and then, for reasons we don

  19. Nonsingular black hole

    Energy Technology Data Exchange (ETDEWEB)

    Chamseddine, Ali H. [American University of Beirut, Physics Department, Beirut (Lebanon); I.H.E.S., Bures-sur-Yvette (France); Mukhanov, Viatcheslav [Niels Bohr Institute, Niels Bohr International Academy, Copenhagen (Denmark); Ludwig-Maximilians University, Theoretical Physics, Munich (Germany); MPI for Physics, Munich (Germany)

    2017-03-15

    We consider the Schwarzschild black hole and show how, in a theory with limiting curvature, the physical singularity ''inside it'' is removed. The resulting spacetime is geodesically complete. The internal structure of this nonsingular black hole is analogous to Russian nesting dolls. Namely, after falling into the black hole of radius r{sub g}, an observer, instead of being destroyed at the singularity, gets for a short time into the region with limiting curvature. After that he re-emerges in the near horizon region of a spacetime described by the Schwarzschild metric of a gravitational radius proportional to r{sub g}{sup 1/3}. In the next cycle, after passing the limiting curvature, the observer finds himself within a black hole of even smaller radius proportional to r{sub g}{sup 1/9}, and so on. Finally after a few cycles he will end up in the spacetime where he remains forever at limiting curvature. (orig.)

  20. Axion-dilation black holes

    International Nuclear Information System (INIS)

    Kallosh, R.

    1993-01-01

    In this talk some essential features of stringy black holes are described. The author considers charged U(1) and U(1) x U(1) four-dimensional axion-dilaton black holes. The Hawking temperature and the entropy of all solutions are shown to be simple functions of the squares of supercharges, defining the positivity bounds. Spherically symmetric and multi black hole solutions are presented. The extreme solutions with zero entropy (holons) represent a ground state of the theory and are characterized by elementary dilaton, axion, electric, and magnetic charges. The attractive gravitational and axion-dilaton force is balanced by the repulsive electromagnetic force. The author discusses the possibility of splitting of nearly extreme black holes. 11 refs

  1. What Can We Learn About Black-Hole Formation from Black-Hole X-ray Binaries?

    NARCIS (Netherlands)

    Nelemans, G.A.

    2007-01-01

    I discuss the effect of the formation of a black hole on a (close) binary and show some of the current constraints that the observed properties of black hole X-ray binaries put on the formation of black holes. In particular, I discuss the evidence for and against asymmetric kicks imparted on the

  2. Quantum capacity of quantum black holes

    Science.gov (United States)

    Adami, Chris; Bradler, Kamil

    2014-03-01

    The fate of quantum entanglement interacting with a black hole has been an enduring mystery, not the least because standard curved space field theory does not address the interaction of black holes with matter. We discuss an effective Hamiltonian of matter interacting with a black hole that has a precise analogue in quantum optics and correctly reproduces both spontaneous and stimulated Hawking radiation with grey-body factors. We calculate the quantum capacity of this channel in the limit of perfect absorption, as well as in the limit of a perfectly reflecting black hole (a white hole). We find that the white hole is an optimal quantum cloner, and is isomorphic to the Unruh channel with positive quantum capacity. The complementary channel (across the horizon) is entanglement-breaking with zero capacity, avoiding a violation of the quantum no-cloning theorem. The black hole channel on the contrary has vanishing capacity, while its complement has positive capacity instead. Thus, quantum states can be reconstructed faithfully behind the black hole horizon, but not outside. This work sheds new light on black hole complementarity because it shows that black holes can both reflect and absorb quantum states without violating the no-cloning theorem, and makes quantum firewalls obsolete.

  3. Anyon black holes

    Science.gov (United States)

    Aghaei Abchouyeh, Maryam; Mirza, Behrouz; Karimi Takrami, Moein; Younesizadeh, Younes

    2018-05-01

    We propose a correspondence between an Anyon Van der Waals fluid and a (2 + 1) dimensional AdS black hole. Anyons are particles with intermediate statistics that interpolates between a Fermi-Dirac statistics and a Bose-Einstein one. A parameter α (0 quasi Fermi-Dirac statistics for α >αc, but a quasi Bose-Einstein statistics for α quasi Bose-Einstein statistics. For α >αc and a range of values of the cosmological constant, there is, however, no event horizon so there is no black hole solution. Thus, for these values of cosmological constants, the AdS Anyon Van der Waals black holes have only quasi Bose-Einstein statistics.

  4. ULTRAMASSIVE BLACK HOLE COALESCENCE

    International Nuclear Information System (INIS)

    Khan, Fazeel Mahmood; Holley-Bockelmann, Kelly; Berczik, Peter

    2015-01-01

    Although supermassive black holes (SMBHs) correlate well with their host galaxies, there is an emerging view that outliers exist. Henize 2-10, NGC 4889, and NGC 1277 are examples of SMBHs at least an order of magnitude more massive than their host galaxy suggests. The dynamical effects of such ultramassive central black holes is unclear. Here, we perform direct N-body simulations of mergers of galactic nuclei where one black hole is ultramassive to study the evolution of the remnant and the black hole dynamics in this extreme regime. We find that the merger remnant is axisymmetric near the center, while near the large SMBH influence radius, the galaxy is triaxial. The SMBH separation shrinks rapidly due to dynamical friction, and quickly forms a binary black hole; if we scale our model to the most massive estimate for the NGC 1277 black hole, for example, the timescale for the SMBH separation to shrink from nearly a kiloparsec to less than a parsec is roughly 10 Myr. By the time the SMBHs form a hard binary, gravitational wave emission dominates, and the black holes coalesce in a mere few Myr. Curiously, these extremely massive binaries appear to nearly bypass the three-body scattering evolutionary phase. Our study suggests that in this extreme case, SMBH coalescence is governed by dynamical friction followed nearly directly by gravitational wave emission, resulting in a rapid and efficient SMBH coalescence timescale. We discuss the implications for gravitational wave event rates and hypervelocity star production

  5. When Supermassive Black Holes Wander

    Science.gov (United States)

    Kohler, Susanna

    2018-05-01

    Are supermassive black holes found only at the centers of galaxies? Definitely not, according to a new study in fact, galaxies like the Milky Way may harbor several such monsters wandering through their midst.Collecting Black Holes Through MergersIts generally believed that galaxies are built up hierarchically, growing in size through repeated mergers over time. Each galaxy in a major merger likely hosts a supermassive black hole a black hole of millions to billions of times the mass of the Sun at its center. When a pair of galaxies merges, their supermassive black holes will often sink to the center of the merger via a process known as dynamical friction. There the supermassive black holes themselves will eventually merge in a burst of gravitational waves.Spatial distribution and velocities of wandering supermassive black holes in three of the authors simulated galaxies, shown in edge-on (left) and face-on (right) views of the galaxy disks. Click for a closer look. [Tremmel et al. 2018]But if a galaxy the size of the Milky Way was built through a history of many major galactic mergers, are we sure that all its accumulated supermassive black holes eventually merged at the galactic center? A new study suggests that some of these giants might have escaped such a fate and they now wander unseen on wide orbits through their galaxies.Black Holes in an Evolving UniverseLed by Michael Tremmel (Yale Center for Astronomy Astrophysics), a team of scientists has used data from a large-scale cosmological simulation, Romulus25, to explore the possibility of wandering supermassive black holes. The Romulus simulations are uniquely suited to track the formation and subsequent orbital motion of supermassive black holes as galactic halos are built up through mergers over the history of the universe.From these simulations, Tremmel and collaborators find an end total of 316 supermassive black holes residing within the bounds of 26 Milky-Way-mass halos. Of these, roughly a third are

  6. Black holes: the membrane paradigm

    International Nuclear Information System (INIS)

    Thorne, K.S.; Price, R.H.; Macdonald, D.A.

    1986-01-01

    The physics of black holes is explored in terms of a membrane paradigm which treats the event horizon as a two-dimensional membrane embedded in three-dimensional space. A 3+1 formalism is used to split Schwarzschild space-time and the laws of physics outside a nonrotating hole, which permits treatment of the atmosphere in terms of the physical properties of thin slices. The model is applied to perturbed slowly or rapidly rotating and nonrotating holes, and to quantify the electric and magnetic fields and eddy currents passing through a membrane surface which represents a stretched horizon. Features of tidal gravitational fields in the vicinity of the horizon, quasars and active galalctic nuclei, the alignment of jets perpendicular to accretion disks, and the effects of black holes at the center of ellipsoidal star clusters are investigated. Attention is also given to a black hole in a binary system and the interactions of black holes with matter that is either near or very far from the event horizon. Finally, a statistical mechanics treatment is used to derive a second law of thermodynamics for a perfectly thermal atmosphere of a black hole

  7. Stationary black holes: large D analysis

    International Nuclear Information System (INIS)

    Suzuki, Ryotaku; Tanabe, Kentaro

    2015-01-01

    We consider the effective theory of large D stationary black holes. By solving the Einstein equations with a cosmological constant using the 1/D expansion in near zone of the black hole we obtain the effective equation for the stationary black hole. The effective equation describes the Myers-Perry black hole, bumpy black holes and, possibly, the black ring solution as its solutions. In this effective theory the black hole is represented as an embedded membrane in the background, e.g., Minkowski or Anti-de Sitter spacetime and its mean curvature is given by the surface gravity redshifted by the background gravitational field and the local Lorentz boost. The local Lorentz boost property of the effective equation is observed also in the metric itself. In fact we show that the leading order metric of the Einstein equation in the 1/D expansion is generically regarded as a Lorentz boosted Schwarzschild black hole. We apply this Lorentz boost property of the stationary black hole solution to solve perturbation equations. As a result we obtain an analytic formula for quasinormal modes of the singly rotating Myers-Perry black hole in the 1/D expansion.

  8. Drilling history core hole DC-8

    International Nuclear Information System (INIS)

    1978-10-01

    Core hole DC-8 was completed in August, 1978 by Boyles Brothers Drilling Company, Spokane, Washington, under subcontract to Fenix and Scission, Inc. The hole was cored for the US Department of Energy and the Rockwell Hanford Operations' Basalt Waste Isolation Program. Fenix and Scisson, Inc. furnished the engineering, daily supervision of the core drilling activities, and geologic core logging for hole DC-8. Core hole DC-8 is located on the Hanford Site near the Wye Barricade and 50 feet northwest of rotary hole DC-7. The Hanford Site vation coordinates for DC-8 are North 14,955.94 feet and West 14,861.92 coordinates for DC-8 are North 14,955.94 feet and West 14,861.92 mean sea level. The purpose of core hole DC-8 was to core drill vertically through the basalt and interbed units for stratigraphic depth determination and core collection, and to provide a borehole for hydrologic testing and cross-hole seismic shear and pressure wave velocity studies with rotary hole DC-7. The total depth of core hole DC-8 was 4100.5 feet. Core recovery exceeded 97 percent of the total footage cored

  9. Drilling history core hole DC-8

    Energy Technology Data Exchange (ETDEWEB)

    1978-10-01

    Core hole DC-8 was completed in August, 1978 by Boyles Brothers Drilling Company, Spokane, Washington, under subcontract to Fenix and Scission, Inc. The hole was cored for the US Department of Energy and the Rockwell Hanford Operations' Basalt Waste Isolation Program. Fenix and Scisson, Inc. furnished the engineering, daily supervision of the core drilling activities, and geologic core logging for hole DC-8. Core hole DC-8 is located on the Hanford Site near the Wye Barricade and 50 feet northwest of rotary hole DC-7. The Hanford Site vation coordinates for DC-8 are North 14,955.94 feet and West 14,861.92 coordinates for DC-8 are North 14,955.94 feet and West 14,861.92 mean sea level. The purpose of core hole DC-8 was to core drill vertically through the basalt and interbed units for stratigraphic depth determination and core collection, and to provide a borehole for hydrologic testing and cross-hole seismic shear and pressure wave velocity studies with rotary hole DC-7. The total depth of core hole DC-8 was 4100.5 feet. Core recovery exceeded 97 percent of the total footage cored.

  10. Particle creation by black holes

    International Nuclear Information System (INIS)

    Hawking, S.W.

    1975-01-01

    In the classical theory black holes can only absorb and not emit particles. However it is shown that quantum mechanical effects cause black holes to create and emit particles. This thermal emission leads to a slow decrease in the mass of the black hole and to its eventual disappearance: any primordial black hole of mass less than about 10 15 g would have evaporated by now. Although these quantum effects violate the classical law that the area of the event horizon of a black hole cannot decrease, there remains a Generalized Second Law: S + 1/4 A never decreases where S is the entropy of matter outside black holes and A is the sum of the surface areas of the event horizons. This shows that gravitational collapse converts the baryons and leptons in the collapsing body into entropy. It is tempting to speculate that this might be the reason why the Universe contains so much entropy per baryon. (orig.) [de

  11. The 2002 Antarctic Ozone Hole

    Science.gov (United States)

    Newman, P. A.; Nash, E. R.; Douglass, A. R.; Kawa, S. R.

    2003-01-01

    Since 1979, the ozone hole has grown from near zero size to over 24 Million km2. This area is most strongly controlled by levels of inorganic chlorine and bromine oncentrations. In addition, dynamical variations modulate the size of the ozone hole by either cooling or warming the polar vortex collar region. We will review the size observations, the size trends, and the interannual variability of the size. Using a simple trajectory model, we will demonstrate the sensitivity of the ozone hole to dynamical forcing, and we will use these observations to discuss the size of the ozone hole during the 2002 Austral spring. We will further show how the Cly decreases in the stratosphere will cause the ozone hole to decrease by 1-1.5% per year. We will also show results from a 3-D chemical transport model (CTM) that has been continuously run since 1999. These CTM results directly show how strong dynamics acts to reduce the size of the ozone hole.

  12. Black Hole's 1/N Hair

    CERN Document Server

    Dvali, Gia

    2013-01-01

    According to the standard view classically black holes carry no hair, whereas quantum hair is at best exponentially weak. We show that suppression of hair is an artifact of the semi-classical treatment and that in the quantum picture hair appears as an inverse mass-square effect. Such hair is predicted in the microscopic quantum description in which a black hole represents a self-sustained leaky Bose-condensate of N soft gravitons. In this picture the Hawking radiation is the quantum depletion of the condensate. Within this picture we show that quantum black hole physics is fully compatible with continuous global symmetries and that global hair appears with the strength B/N, where B is the global charge swallowed by the black hole. For large charge this hair has dramatic effect on black hole dynamics. Our findings can have interesting astrophysical consequences, such as existence of black holes with large detectable baryonic and leptonic numbers.

  13. Procedure and device for extracting the end of a tube inserted into a hole in a tube plate

    International Nuclear Information System (INIS)

    1980-01-01

    When constructing heat exchangers and steam generators, particularly in the construction of steam generators for nuclear power stations, many small diameter tubes have to be secured into a very thick tube plate for instance 600 mm thick. This crimping or expanding of the tube is generally performed by rolling the internal surface of the tube inside a hole drilled right through the tube plate and slightly greater in diameter than the external diameter of the tube before the tube is rolled. To check the tubes for defects, it is necessary to extract certain tubes from the tube plate in order to move the tube to a testing and inspection point and examine the part of it that was secured in the plate hole. The invention concerns the uncrimping of these tubes [fr

  14. Black holes a very short introduction

    CERN Document Server

    Blundell, Katherine

    2015-01-01

    Black holes are a constant source of fascination to many due to their mysterious nature. Black Holes: A Very Short Introduction addresses a variety of questions, including what a black hole actually is, how they are characterized and discovered, and what would happen if you came too close to one. It explains how black holes form and grow—by stealing material that belongs to stars—as well as how many there may be in the Universe. It also explores the large black holes found in the centres of galaxies, and how black holes power quasars and lie behind other spectacular phenomena in the cosmos.

  15. "Iron-Clad" Evidence For Spinning Black Hole

    Science.gov (United States)

    2003-09-01

    Telltale X-rays from iron may reveal if black holes are spinning or not, according to astronomers using NASA's Chandra X-ray Observatory and the European Space Agency's XMM-Newton Observatory. The gas flows and bizarre gravitational effects observed near stellar black holes are similar to those seen around supermassive black holes. Stellar black holes, in effect, are convenient `scale models' of their much larger cousins. Black holes come in at least two different sizes. Stellar black holes are between five and 20 times the mass of the Sun. At the other end of the size scale, supermassive black holes contain millions or billions times the mass of our Sun. The Milky Way contains both a supermassive black hole at its center, as well as a number of stellar black holes sprinkled throughout the Galaxy. At a press conference at the "Four Years of Chandra" symposium in Huntsville, Ala., Jon Miller of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. discussed recent results on the X-ray spectra, or distribution of X-rays with energy, from the iron atoms in gas around three stellar black holes in the Milky Way. "Discovering the high degree of correspondence between stellar and supermassive black holes is a real breakthrough," said Miller. "Because stellar black holes are smaller, everything happens about a million times faster, so they can be used as a test-bed for theories of how spinning black holes affect the space and matter around them." X-rays from a stellar black hole are produced when gas from a nearby companion star is heated to tens of millions of degrees as it swirls toward the black hole. Iron atoms in this gas produce distinctive X-ray signals that can be used to study the orbits of particles around the black hole. For example, the gravity of a black hole can shift the X-rays to lower energies. "The latest work provides the most precise measurements yet of the X-ray spectra for stellar black holes," said Miller. "These data help rule out

  16. Epiretinal proliferation in lamellar macular holes and full-thickness macular holes: clinical and surgical findings.

    Science.gov (United States)

    Lai, Tso-Ting; Chen, San-Ni; Yang, Chung-May

    2016-04-01

    To report the clinical findings and surgical outcomes of lamellar macular holes (LMH) with or without lamellar hole-associated epiretinal proliferation (LHEP), and those of full-thickness macular holes (FTMH) presenting with LHEP. From 2009 to 2013, consecutive cases of surgically treated LMH, and all FTMH cases with LHEP were reviewed, given a follow-up time over 1 year. In the LMH group (43 cases), those with LHEP (19 cases) had significantly thinner bases and larger openings than those without (24 cases). The rate of disrupted IS/OS line was higher in the LHEP subgroup preoperatively (68.4 % vs 37.5 %), but similar between subgroups postoperatively (36.8 % and 33.3 %). The preoperative and postoperative visual acuity showed no significant difference between two subgroups. In the FTMH group (13 cases), the average hole size was 219.2 ± 92.1 μm. Permanent or transient spontaneous hole closure was noted in 69.2 % of cases. An intact IS-OS line was found in only 23 % of cases at the final follow-up. In the LMH group, LHEP was associated with a more severe defect but didn't affect surgical outcomes. In the FTMH group, spontaneous hole closure was frequently noted. Despite small holes, disruption of IS-OS line was common after hole closure.

  17. Nonextremal stringy black hole

    International Nuclear Information System (INIS)

    Suzuki, K.

    1997-01-01

    We construct a four-dimensional BPS saturated heterotic string solution from the Taub-NUT solution. It is a nonextremal black hole solution since its Euler number is nonzero. We evaluate its black hole entropy semiclassically. We discuss the relation between the black hole entropy and the degeneracy of string states. The entropy of our string solution can be understood as the microscopic entropy which counts the elementary string states without any complications. copyright 1997 The American Physical Society

  18. The search for black holes

    International Nuclear Information System (INIS)

    Torn, K.

    1976-01-01

    Conceivable experimental investigations to prove the existence of black holes are discussed. Double system with a black hole turning around a star-satellite are in the spotlight. X-radiation emmited by such systems and resulting from accretion of the stellar gas by a black hole, and the gas heating when falling on the black hole might prove the model suggested. A source of strong X-radiation observed in the Cygnus star cluster and referred to as Cygnus X-1 may be thus identified as a black hole. Direct registration of short X-ray pulses with msec intervals might prove the suggestion. The lack of appropriate astrophysic facilities is pointed out to be the major difficulty on the way of experimental verifications

  19. Stability of squashed Kaluza-Klein black holes

    International Nuclear Information System (INIS)

    Kimura, Masashi; Ishihara, Hideki; Murata, Keiju; Soda, Jiro

    2008-01-01

    The stability of squashed Kaluza-Klein black holes is studied. The squashed Kaluza-Klein black hole looks like a five-dimensional black hole in the vicinity of horizon and looks like a four-dimensional Minkowski spacetime with a circle at infinity. In this sense, squashed Kaluza-Klein black holes can be regarded as black holes in the Kaluza-Klein spacetimes. Using the symmetry of squashed Kaluza-Klein black holes, SU(2)xU(1)≅U(2), we obtain master equations for a part of the metric perturbations relevant to the stability. The analysis based on the master equations gives strong evidence for the stability of squashed Kaluza-Klein black holes. Hence, the squashed Kaluza-Klein black holes deserve to be taken seriously as realistic black holes in the Kaluza-Klein spacetime.

  20. Black-hole bomb and superradiant instabilities

    International Nuclear Information System (INIS)

    Cardoso, Vitor; Dias, Oscar J.C.; Lemos, Jose P.S.; Yoshida, Shijun

    2004-01-01

    A wave impinging on a Kerr black hole can be amplified as it scatters off the hole if certain conditions are satisfied, giving rise to superradiant scattering. By placing a mirror around the black hole one can make the system unstable. This is the black-hole bomb of Press and Teukolsky. We investigate in detail this process and compute the growing time scales and oscillation frequencies as a function of the mirror's location. It is found that in order for the system black hole plus mirror to become unstable there is a minimum distance at which the mirror must be located. We also give an explicit example showing that such a bomb can be built. In addition, our arguments enable us to justify why large Kerr-AdS black holes are stable and small Kerr-AdS black holes should be unstable

  1. Interior structure of rotating black holes. III. Charged black holes

    International Nuclear Information System (INIS)

    Hamilton, Andrew J. S.

    2011-01-01

    This paper extends to the case of charged rotating black holes the conformally stationary, axisymmetric, conformally separable solutions presented for uncharged rotating black holes in a companion paper. In the present paper, the collisionless fluid accreted by the black hole may be charged. The charge of the black hole is determined self-consistently by the charge accretion rate. As in the uncharged case, hyper-relativistic counterstreaming between ingoing and outgoing streams drives inflation at (just above) the inner horizon, followed by collapse. If both ingoing and outgoing streams are charged, then conformal separability holds during early inflation, but fails as inflation develops. If conformal separability is imposed throughout inflation and collapse, then only one of the ingoing and outgoing streams can be charged: the other must be neutral. Conformal separability prescribes a hierarchy of boundary conditions on the ingoing and outgoing streams incident on the inner horizon. The dominant radial boundary conditions require that the incident ingoing and outgoing number densities be uniform with latitude, but the charge per particle must vary with latitude such that the incident charge densities vary in proportion to the radial electric field. The subdominant angular boundary conditions require specific forms of the incident number- and charge-weighted angular motions. If the streams fall freely from outside the horizon, then the prescribed angular conditions can be achieved by the charged stream, but not by the neutral stream. Thus, as in the case of an uncharged black hole, the neutral stream must be considered to be delivered ad hoc to just above the inner horizon.

  2. 30 CFR 57.9360 - Shelter holes.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Shelter holes. 57.9360 Section 57.9360 Mineral....9360 Shelter holes. (a) Shelter holes shall be— (1) Provided at intervals adequate to assure the safety... farthest projection of moving equipment. (b) Shelter holes shall not be used for storage unless a 40-inch...

  3. Turbulent black holes.

    Science.gov (United States)

    Yang, Huan; Zimmerman, Aaron; Lehner, Luis

    2015-02-27

    We demonstrate that rapidly spinning black holes can display a new type of nonlinear parametric instability-which is triggered above a certain perturbation amplitude threshold-akin to the onset of turbulence, with possibly observable consequences. This instability transfers from higher temporal and azimuthal spatial frequencies to lower frequencies-a phenomenon reminiscent of the inverse cascade displayed by (2+1)-dimensional fluids. Our finding provides evidence for the onset of transitory turbulence in astrophysical black holes and predicts observable signatures in black hole binaries with high spins. Furthermore, it gives a gravitational description of this behavior which, through the fluid-gravity duality, can potentially shed new light on the remarkable phenomena of turbulence in fluids.

  4. Information Retention by Stringy Black Holes

    CERN Document Server

    Ellis, John

    2015-01-01

    Building upon our previous work on two-dimensional stringy black holes and its extension to spherically-symmetric four-dimensional stringy black holes, we show how the latter retain information. A key r\\^ole is played by an infinite-dimensional $W_\\infty$ symmetry that preserves the area of an isolated black-hole horizon and hence its entropy. The exactly-marginal conformal world-sheet operator representing a massless stringy particle interacting with the black hole necessarily includes a contribution from $W_\\infty$ generators in its vertex function. This admixture manifests the transfer of information between the string black hole and external particles. We discuss different manifestations of $W_\\infty$ symmetry in black-hole physics and the connections between them.

  5. Shaping Globular Clusters with Black Holes

    Science.gov (United States)

    Kohler, Susanna

    2018-03-01

    How many black holes lurk within the dense environments of globular clusters, and how do these powerful objects shape the properties of the cluster around them? One such cluster, NGC 3201, is now helping us to answer these questions.Hunting Stellar-Mass Black HolesSince the detection of merging black-hole binaries by the Laser Interferometer Gravitational-Wave Observatory (LIGO), the dense environments of globular clusters have received increasing attention as potential birthplaces of these compact binary systems.The central region of the globular star cluster NGC 3201, as viewed by Hubble. The black hole is in orbit with the star marked by the blue circle. [NASA/ESA]In addition, more and more stellar-mass black-hole candidates have been observed within globular clusters, lurking in binary pairs with luminous, non-compact companions. The most recent of these detections, found in the globular cluster NGC 3201, stands alone as the first stellar-mass black hole candidate discovered via radial velocity observations: the black holes main-sequence companion gave away its presence via a telltale wobble.Now a team of scientists led by Kyle Kremer (CIERA and Northwestern University) is using models of this system to better understand the impact that black holes might have on their host clusters.A Model ClusterThe relationship between black holes and their host clusters is complicated. Though the cluster environment can determine the dynamical evolution of the black holes, the retention rate of black holes in a globular cluster (i.e., how many remain in the cluster when they are born as supernovae, rather than being kicked out during the explosion) influences how the host cluster evolves.Kremer and collaborators track this complex relationship by modeling the evolution of a cluster similar to NGC 3201 with a Monte Carlo code. The code incorporates physics relevant to the evolution of black holes and black-hole binaries in globular clusters, such as two-body relaxation

  6. Black holes matter

    DEFF Research Database (Denmark)

    Kragh, Helge Stjernholm

    2016-01-01

    Review essay, Marcia Bartusiak, Black Hole: How an Idea Abandoned by Newtonians, Hated by Einstein, and Gambled On by Hawking Became Loved (New Haven: Yale University Press, 2015).......Review essay, Marcia Bartusiak, Black Hole: How an Idea Abandoned by Newtonians, Hated by Einstein, and Gambled On by Hawking Became Loved (New Haven: Yale University Press, 2015)....

  7. Newborn Black Holes

    Science.gov (United States)

    Science Teacher, 2005

    2005-01-01

    Scientists using NASA's Swift satellite say they have found newborn black holes, just seconds old, in a confused state of existence. The holes are consuming material falling into them while somehow propelling other material away at great speeds. "First comes a blast of gamma rays followed by intense pulses of x-rays. The energies involved are much…

  8. 30 CFR 77.1010 - Collaring holes.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Collaring holes. 77.1010 Section 77.1010... Control § 77.1010 Collaring holes. (a) Starter steels shall be used when collaring holes with hand-held drills. (b) Men shall not hold the drill steel while collaring holes, or rest their hands on the chuck or...

  9. Statistical clustering of primordial black holes

    Energy Technology Data Exchange (ETDEWEB)

    Carr, B J [Cambridge Univ. (UK). Inst. of Astronomy

    1977-04-01

    It is shown that Meszaros theory of galaxy formation, in which galaxies form from the density perturbations associated with the statistical fluctuation in the number density of primordial black holes, must be modified if the black holes are initially surrounded by regions of lower radiation density than average (as is most likely). However, even in this situation, the sort of effect Meszaros envisages does occur and could in principle cause galactic mass-scales to bind at the conventional time. In fact, the requirement that galaxies should not form prematurely implies that black holes could not have a critical density in the mass range above 10/sup 5/ M(sun). If the mass spectrum of primordial black holes falls off more slowly than m/sup -3/ (as expected), then the biggest black holes have the largest clustering effect. In this case the black hole clustering theory of galaxy formation reduces to the black hole seed theory of galaxy formation, in which each galaxy becomes bound under the gravitational influence of a single black hole nucleus. The seed theory could be viable only if the early Universe had a soft equation of state until a time exceeding 10/sup -4/ s or if something prevented black hole formation before 1 s.

  10. Suppressing star formation in quiescent galaxies with supermassive black hole winds.

    Science.gov (United States)

    Cheung, Edmond; Bundy, Kevin; Cappellari, Michele; Peirani, Sébastien; Rujopakarn, Wiphu; Westfall, Kyle; Yan, Renbin; Bershady, Matthew; Greene, Jenny E; Heckman, Timothy M; Drory, Niv; Law, David R; Masters, Karen L; Thomas, Daniel; Wake, David A; Weijmans, Anne-Marie; Rubin, Kate; Belfiore, Francesco; Vulcani, Benedetta; Chen, Yan-mei; Zhang, Kai; Gelfand, Joseph D; Bizyaev, Dmitry; Roman-Lopes, A; Schneider, Donald P

    2016-05-26

    Quiescent galaxies with little or no ongoing star formation dominate the population of galaxies with masses above 2 × 10(10) times that of the Sun; the number of quiescent galaxies has increased by a factor of about 25 over the past ten billion years (refs 1-4). Once star formation has been shut down, perhaps during the quasar phase of rapid accretion onto a supermassive black hole, an unknown mechanism must remove or heat the gas that is subsequently accreted from either stellar mass loss or mergers and that would otherwise cool to form stars. Energy output from a black hole accreting at a low rate has been proposed, but observational evidence for this in the form of expanding hot gas shells is indirect and limited to radio galaxies at the centres of clusters, which are too rare to explain the vast majority of the quiescent population. Here we report bisymmetric emission features co-aligned with strong ionized-gas velocity gradients from which we infer the presence of centrally driven winds in typical quiescent galaxies that host low-luminosity active nuclei. These galaxies are surprisingly common, accounting for as much as ten per cent of the quiescent population with masses around 2 × 10(10) times that of the Sun. In a prototypical example, we calculate that the energy input from the galaxy's low-level active supermassive black hole is capable of driving the observed wind, which contains sufficient mechanical energy to heat ambient, cooler gas (also detected) and thereby suppress star formation.

  11. Black holes and quantum processes in them

    International Nuclear Information System (INIS)

    Frolov, V.P.

    1976-01-01

    The latest achievements in the physics of black holes are reviewed. The problem of quantum production in a strong gravitational field of black holes is considered. Another parallel discovered during investigation of interactions between black holes and between black holes and surrounding media, is also drawn with thermodynamics. A gravitational field of rotating black holes is considered. Some cosmological aspects of evaporation of small black holes are discussed as well as possibilities to observe them

  12. Expandable stents.

    Science.gov (United States)

    Nesbitt, J C; Carrasco, H

    1996-05-01

    Expandable metallic stents are effective in selected patients with malignant or benign airway stenoses. When used for malignant lesions, the primary purpose of the stent is to improve the quality of life; stents are usually chosen for palliation of symptoms in recognition of the low likelihood of success for other therapy. For patients with benign stenoses, the stents provide a permanent source of structural support to alleviate the narrowed segment. The advantages of the expandable metallic stents are as follows: (1) they can be inserted through an endotracheal tube or under local anesthesia with relative simplicity under fluoroscopic guidance; (2) they do not impair the drainage of sputum because ciliary movement is not interrupted; (3) over a period of a few weeks, the meshwork is gradually covered with mucosa as the stent becomes incorporated into the airway wall; (4) ventilation usually is not impaired if the metallic mesh stent covers another nonstenosed bronchus, because the interstices of the stent are nonobstructive; and (5) they are dynamic and continue to expand over time, particularly if concurrent treatment achieves an effect on the lesion that caused stenosis. Disadvantages of the expandable stent include (1) they often are only temporarily effective for tracheobronchial stenosis due to intraluminal tumor or granulation tissue, both of which can grow between the wires; (2) they are considered permanent stents because removal is difficult; and (3) they can be poorly positioned during placement or can become displaced by progressive migration after placement, and they cannot be repositioned. A relative contraindication to insertion is an inflammatory process or infection that can predispose to granulation formation, particularly at the points of maximal contact pressure of the stent to the airway mucosa. In the presence of inflammation, it may be better to use a silicone prosthesis until the inflammatory process subsides and fibrosis occurs. Granulation

  13. Black holes and everyday physics

    International Nuclear Information System (INIS)

    Bekenstein, J.D.

    1982-01-01

    Black holes have piqued much curiosity. But thus far they have been important only in ''remote'' subjects like astrophysics and quantum gravity. It is shown that the situation can be improved. By a judicious application of black hole physics, one can obtain new results in ''everyday physics''. For example, black holes yield a quantum universal upper bound on the entropy-to-energy ratio for ordinary thermodynamical systems which was unknown earlier. It can be checked, albeit with much labor, by ordinary statistical methods. Black holes set a limitation on the number of species of elementary particles-quarks, leptons, neutrinos - which may exist. And black holes lead to a fundamental limitation on the rate at which information can be transferred for given message energy by any communication system. (author)

  14. Black hole final state conspiracies

    International Nuclear Information System (INIS)

    McInnes, Brett

    2009-01-01

    The principle that unitarity must be preserved in all processes, no matter how exotic, has led to deep insights into boundary conditions in cosmology and black hole theory. In the case of black hole evaporation, Horowitz and Maldacena were led to propose that unitarity preservation can be understood in terms of a restriction imposed on the wave function at the singularity. Gottesman and Preskill showed that this natural idea only works if one postulates the presence of 'conspiracies' between systems just inside the event horizon and states at much later times, near the singularity. We argue that some AdS black holes have unusual internal thermodynamics, and that this may permit the required 'conspiracies' if real black holes are described by some kind of sum over all AdS black holes having the same entropy

  15. Black hole shadow in an asymptotically flat, stationary, and axisymmetric spacetime: The Kerr-Newman and rotating regular black holes

    Science.gov (United States)

    Tsukamoto, Naoki

    2018-03-01

    The shadow of a black hole can be one of the strong observational evidences for stationary black holes. If we see shadows at the center of galaxies, we would say whether the observed compact objects are black holes. In this paper, we consider a formula for the contour of a shadow in an asymptotically-flat, stationary, and axisymmetric black hole spacetime. We show that the formula is useful for obtaining the contour of the shadow of several black holes such as the Kerr-Newman black hole and rotating regular black holes. Using the formula, we can obtain new examples of the contour of the shadow of rotating black holes if assumptions are satisfied.

  16. K-shell-hole production, multiple-hole production, charge transfer, and antisymmetry

    International Nuclear Information System (INIS)

    Reading, J.F.; Ford, A.L.

    1980-01-01

    In calculating K-shell-hole production when an ion collides with an atom, account must be taken of the fact that processes involving electrons other than the K-shell electron can occur. For example, after making a K-shell hole an L-shell electron may be knocked into it, or an L-shell vacancy may be produced and the K-shell electron promoted to that vacancy in the ''Fermi sea'' of the target-atom orbitals. In 1973 a theorem was proved by one of the present authors demonstrating that all these multielectron processes cancel in an independent-particle model for the target atom. In this paper it is shown that the same thing occurs for hole production by charge transfer to the ion. The authors demonstrate that multihole production does not obey this simple rule and that the probability for multihole production is not the product of independent single-electron probabilities. The correct expressions that should be used for these processes are given, together with new results for charge-transfer processes accompanied by hole production

  17. Drilling history core hole DC-4

    International Nuclear Information System (INIS)

    1978-12-01

    Core hole DC-4 was completed at a depth of 3998 feet in December, 1978 by Boyles Brothers Drilling Company, Spokane, Washington, under subcontract to Fenix and Scission, Inc. The hole was cored for the US Department of Energy and the Rockwell Hanford Operations' Basalt Waste Isolation Program. Fenix and Sicsson, Inc. furnished the engineering, daily supervision of the cable tool and core drilling activities, and geological core logging for DC-4. Core hole DC-4 is located on the Hanford Site about 3 miles east of the Yakima Barricade and approximately 103 feet southwest of rotary hole DC-5, which was completed to 3990 feet in February, 1978. Hanford Site coordinates reported for hole DC-4 are north 49,385.62 feet and west 85,207.63 feet, and Washington State coordinates are north 454,468.73 feet and east 2,209,990.87 feet. No elevation survey is available for hole DC-4, but it is approximately 745 feet above mean sea level based upon the survey of hole DC-5, which has a reported elevation of 745.16 feet on the top of the 3-inch flange. The purpose of core hole DC-4 was to core drill vertically through the basalt and interbed units for stratigraphic depth determination and core collection, and to provide a borehole for hydrologic testing, cross-hole seismic shear, and pressure wave velocity studies with rotary hole DC-5. Hole DC-4 was drilled through the overburden into basalt bedrock by cable tool methods (0-623 feet) and continuously cored through the final interval (623 to 3998 feet).Core recovery was 95.8 percent of the total footage cored

  18. Warped products and black holes

    International Nuclear Information System (INIS)

    Hong, Soon-Tae

    2005-01-01

    We apply the warped product space-time scheme to the Banados-Teitelboim-Zanelli black holes and the Reissner-Nordstroem-anti-de Sitter black hole to investigate their interior solutions in terms of warped products. It is shown that there exist no discontinuities of the Ricci and Einstein curvatures across event horizons of these black holes

  19. Atomic structure in black hole

    International Nuclear Information System (INIS)

    Nagatani, Yukinori

    2006-01-01

    We propose that any black hole has atomic structure in its inside and has no horizon as a model of black holes. Our proposal is founded on a mean field approximation of gravity. The structure of our model consists of a (charged) singularity at the center and quantum fluctuations of fields around the singularity, namely, it is quite similar to that of atoms. Any properties of black holes, e.g. entropy, can be explained by the model. The model naturally quantizes black holes. In particular, we find the minimum black hole, whose structure is similar to that of the hydrogen atom and whose Schwarzschild radius is approximately 1.1287 times the Planck length. Our approach is conceptually similar to Bohr's model of the atomic structure, and the concept of the minimum Schwarzschild radius is similar to that of the Bohr radius. The model predicts that black holes carry baryon number, and the baryon number is rapidly violated. This baryon number violation can be used as verification of the model. (author)

  20. Mechanical alignment of substrates to a mask

    Science.gov (United States)

    Webb, Aaron P.; Carlson, Charles T.; Honan, Michael; Amato, Luigi G.; Grant, Christopher Neil; Strassner, James D.

    2016-11-08

    A plurality of masks is attached to the underside of a mask frame. This attachment is made such that each mask can independently move relative to the mask frame in three directions. This relative movement allows each mask to adjust its position to align with respective alignment pins disposed on a working surface. In one embodiment, each mask is attached to the mask frame using fasteners, where the fasteners have a shaft with a diameter smaller than the diameter of the mounting hole disposed on the mask. A bias element may be used to allow relative movement between the mask and the mask frame in the vertical direction. Each mask may also have kinematic features to mate with the respective alignment pins on the working surface.

  1. Gamma ray bursts of black hole universe

    Science.gov (United States)

    Zhang, T. X.

    2015-07-01

    Slightly modifying the standard big bang theory, Zhang recently developed a new cosmological model called black hole universe, which has only a single postulate but is consistent with Mach's principle, governed by Einstein's general theory of relativity, and able to explain existing observations of the universe. In the previous studies, we have explained the origin, structure, evolution, expansion, cosmic microwave background radiation, quasar, and acceleration of black hole universe, which grew from a star-like black hole with several solar masses through a supermassive black hole with billions of solar masses to the present state with hundred billion-trillions of solar masses by accreting ambient matter and merging with other black holes. This study investigates gamma ray bursts of black hole universe and provides an alternative explanation for the energy and spectrum measurements of gamma ray bursts according to the black hole universe model. The results indicate that gamma ray bursts can be understood as emissions of dynamic star-like black holes. A black hole, when it accretes its star or merges with another black hole, becomes dynamic. A dynamic black hole has a broken event horizon and thus cannot hold the inside hot (or high-frequency) blackbody radiation, which flows or leaks out and produces a GRB. A star when it collapses into its core black hole produces a long GRB and releases the gravitational potential energy of the star as gamma rays. A black hole that merges with another black hole produces a short GRB and releases a part of their blackbody radiation as gamma rays. The amount of energy obtained from the emissions of dynamic star-like black holes are consistent with the measurements of energy from GRBs. The GRB energy spectra derived from this new emission mechanism are also consistent with the measurements.

  2. Simulations of nearly extremal binary black holes

    Science.gov (United States)

    Giesler, Matthew; Scheel, Mark; Hemberger, Daniel; Lovelace, Geoffrey; Kuper, Kevin; Boyle, Michael; Szilagyi, Bela; Kidder, Lawrence; SXS Collaboration

    2015-04-01

    Astrophysical black holes could have nearly extremal spins; therefore, nearly extremal black holes could be among the binaries that current and future gravitational-wave observatories will detect. Predicting the gravitational waves emitted by merging black holes requires numerical-relativity simulations, but these simulations are especially challenging when one or both holes have mass m and spin S exceeding the Bowen-York limit of S /m2 = 0 . 93 . Using improved methods we simulate an unequal-mass, precessing binary black hole coalescence, where the larger black hole has S /m2 = 0 . 99 . We also use these methods to simulate a nearly extremal non-precessing binary black hole coalescence, where both black holes have S /m2 = 0 . 994 , nearly reaching the Novikov-Thorne upper bound for holes spun up by thin accretion disks. We demonstrate numerical convergence and estimate the numerical errors of the waveforms; we compare numerical waveforms from our simulations with post-Newtonian and effective-one-body waveforms; and we compare the evolution of the black-hole masses and spins with analytic predictions.

  3. Instability of ultra-spinning black holes

    International Nuclear Information System (INIS)

    Emparan, Roberto; Myers, Robert C.

    2003-01-01

    It has long been known that, in higher-dimensional general relativity, there are black hole solutions with an arbitrarily large angular momentum for a fixed mass. We examine the geometry of the event horizon of such ultra-spinning black holes and argue that these solutions become unstable at large enough rotation. Hence we find that higher-dimensional general relativity imposes an effective 'Kerr-bound' on spinning black holes through a dynamical decay mechanism. Our results also give indications of the existence of new stationary black holes with 'rippled' horizons of spherical topology. We consider various scenarios for the possible decay of ultra-spinning black holes, and finally discuss the implications of our results for black holes in braneworld scenarios. (author)

  4. Braneworld black holes and entropy bounds

    Directory of Open Access Journals (Sweden)

    Y. Heydarzade

    2018-01-01

    Full Text Available The Bousso's D-bound entropy for the various possible black hole solutions on a 4-dimensional brane is checked. It is found that the D-bound entropy here is apparently different from that of obtained for the 4-dimensional black hole solutions. This difference is interpreted as the extra loss of information, associated to the extra dimension, when an extra-dimensional black hole is moved outward the observer's cosmological horizon. Also, it is discussed that N-bound entropy is hold for the possible solutions here. Finally, by adopting the recent Bohr-like approach to black hole quantum physics for the excited black holes, the obtained results are written also in terms of the black hole excited states.

  5. Black holes new horizons

    CERN Document Server

    Hayward, Sean Alan

    2013-01-01

    Black holes, once just fascinating theoretical predictions of how gravity warps space-time according to Einstein's theory, are now generally accepted as astrophysical realities, formed by post-supernova collapse, or as supermassive black holes mysteriously found at the cores of most galaxies, powering active galactic nuclei, the most powerful objects in the universe. Theoretical understanding has progressed in recent decades with a wider realization that local concepts should characterize black holes, rather than the global concepts found in textbooks. In particular, notions such as trapping h

  6. Asphalt Mixture for the First Asphalt Concrete Directly Fastened Track in Korea

    Directory of Open Access Journals (Sweden)

    Seong-Hyeok Lee

    2015-01-01

    Full Text Available The research has been initiated to develop the asphalt mixtures which are suitable for the surface of asphalt concrete directly fastened track (ADFT system and evaluate the performance of the asphalt mixture. Three aggregate gradations which are upper (finer, medium, and below (coarser. The nominal maximum aggregate size of asphalt mixture was 10 mm. Asphalt mixture design was conducted at 3 percent air voids using Marshall mix design method. To make impermeable asphalt mixture surface, the laboratory permeability test was conducted for asphalt mixtures of three different aggregate gradations using asphalt mixture permeability tester. Moisture susceptibility test was conducted based on AASHTO T 283. The stripping percentage of asphalt mixtures was measured using a digital camera and analyzed based on image analysis techniques. Based on the limited research results, the finer aggregate gradation is the most suitable for asphalt mixture for ADFT system with the high TSR value and the low stripping percentage and permeable coefficient. Flow number and beam fatigue tests for finer aggregate asphalt mixture were conducted to characterize the performance of asphalt mixtures containing two modified asphalt binders: STE-10 which is styrene-butadiene-styrene (SBS polymer and ARMA which is Crum rubber modified asphalt. The performance tests indicate that the STE-10 shows the higher rutting life and fatigue life.

  7. Quantum information erasure inside black holes

    International Nuclear Information System (INIS)

    Lowe, David A.; Thorlacius, Larus

    2015-01-01

    An effective field theory for infalling observers in the vicinity of a quasi-static black hole is given in terms of a freely falling lattice discretization. The lattice model successfully reproduces the thermal spectrum of outgoing Hawking radiation, as was shown by Corley and Jacobson, but can also be used to model observations made by a typical low-energy observer who enters the black hole in free fall at a prescribed time. The explicit short distance cutoff ensures that, from the viewpoint of the infalling observer, any quantum information that entered the black hole more than a scrambling time earlier has been erased by the black hole singularity. This property, combined with the requirement that outside observers need at least of order the scrambling time to extract quantum information from the black hole, ensures that a typical infalling observer does not encounter drama upon crossing the black hole horizon in a theory where black hole information is preserved for asymptotic observers.

  8. Interaction of poly(amidoamine) dendrimers with supported lipid bilayers and cells: hole formation and the relation to transport.

    Science.gov (United States)

    Hong, Seungpyo; Bielinska, Anna U; Mecke, Almut; Keszler, Balazs; Beals, James L; Shi, Xiangyang; Balogh, Lajos; Orr, Bradford G; Baker, James R; Banaszak Holl, Mark M

    2004-01-01

    We have investigated poly(amidoamine) (PAMAM) dendrimer interactions with supported 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipid bilayers and KB and Rat2 cell membranes using atomic force microscopy (AFM), enzyme assays, flow cell cytometry, and fluorescence microscopy. Amine-terminated generation 7 (G7) PAMAM dendrimers (10-100 nM) were observed to form holes of 15-40 nm in diameter in aqueous, supported lipid bilayers. G5 amine-terminated dendrimers did not initiate hole formation but expanded holes at existing defects. Acetamide-terminated G5 PAMAM dendrimers did not cause hole formation in this concentration range. The interactions between PAMAM dendrimers and cell membranes were studied in vitro using KB and Rat 2 cell lines. Neither G5 amine- nor acetamide-terminated PAMAM dendrimers were cytotoxic up to a 500 nM concentration. However, the dose dependent release of the cytoplasmic proteins lactate dehydrogenase (LDH) and luciferase (Luc) indicated that the presence of the amine-terminated G5 PAMAM dendrimer decreased the integrity of the cell membrane. In contrast, the presence of acetamide-terminated G5 PAMAM dendrimer had little effect on membrane integrity up to a 500 nM concentration. The induction of permeability caused by the amine-terminated dendrimers was not permanent, and leaking of cytosolic enzymes returned to normal levels upon removal of the dendrimers. The mechanism of how PAMAM dendrimers altered cells was investigated using fluorescence microscopy, LDH and Luc assays, and flow cytometry. This study revealed that (1) a hole formation mechanism is consistent with the observations of dendrimer internalization, (2) cytosolic proteins can diffuse out of the cell via these holes, and (3) dye molecules can be detected diffusing into the cell or out of the cell through the same membrane holes. Diffusion of dendrimers through holes is sufficient to explain the uptake of G5 amine-terminated PAMAM dendrimers into cells and is consistent

  9. Statistical Hair on Black Holes

    International Nuclear Information System (INIS)

    Strominger, A.

    1996-01-01

    The Bekenstein-Hawking entropy for certain BPS-saturated black holes in string theory has recently been derived by counting internal black hole microstates at weak coupling. We argue that the black hole microstate can be measured by interference experiments even in the strong coupling region where there is clearly an event horizon. Extracting information which is naively behind the event horizon is possible due to the existence of statistical quantum hair carried by the black hole. This quantum hair arises from the arbitrarily large number of discrete gauge symmetries present in string theory. copyright 1996 The American Physical Society

  10. On black hole horizon fluctuations

    International Nuclear Information System (INIS)

    Tuchin, K.L.

    1999-01-01

    A study of the high angular momentum particles 'atmosphere' near the Schwarzschild black hole horizon suggested that strong gravitational interactions occur at invariant distance of the order of 3 √M [2]. We present a generalization of this result to the Kerr-Newman black hole case. It is shown that the larger charge and angular momentum black hole bears, the larger invariant distance at which strong gravitational interactions occur becomes. This invariant distance is of order 3 √((r + 2 )/((r + - r - ))). This implies that the Planckian structure of the Hawking radiation of extreme black holes is completely broken

  11. Thermodynamics of Accelerating Black Holes.

    Science.gov (United States)

    Appels, Michael; Gregory, Ruth; Kubizňák, David

    2016-09-23

    We address a long-standing problem of describing the thermodynamics of an accelerating black hole. We derive a standard first law of black hole thermodynamics, with the usual identification of entropy proportional to the area of the event horizon-even though the event horizon contains a conical singularity. This result not only extends the applicability of black hole thermodynamics to realms previously not anticipated, it also opens a possibility for studying novel properties of an important class of exact radiative solutions of Einstein equations describing accelerated objects. We discuss the thermodynamic volume, stability, and phase structure of these black holes.

  12. Geometry of higher-dimensional black hole thermodynamics

    International Nuclear Information System (INIS)

    Aaman, Jan E.; Pidokrajt, Narit

    2006-01-01

    We investigate thermodynamic curvatures of the Kerr and Reissner-Nordstroem (RN) black holes in spacetime dimensions higher than four. These black holes possess thermodynamic geometries similar to those in four-dimensional spacetime. The thermodynamic geometries are the Ruppeiner geometry and the conformally related Weinhold geometry. The Ruppeiner geometry for a d=5 Kerr black hole is curved and divergent in the extremal limit. For a d≥6 Kerr black hole there is no extremality but the Ruppeiner curvature diverges where one suspects that the black hole becomes unstable. The Weinhold geometry of the Kerr black hole in arbitrary dimension is a flat geometry. For the RN black hole the Ruppeiner geometry is flat in all spacetime dimensions, whereas its Weinhold geometry is curved. In d≥5 the Kerr black hole can possess more than one angular momentum. Finally we discuss the Ruppeiner geometry for the Kerr black hole in d=5 with double angular momenta

  13. Compressibility of rotating black holes

    International Nuclear Information System (INIS)

    Dolan, Brian P.

    2011-01-01

    Interpreting the cosmological constant as a pressure, whose thermodynamically conjugate variable is a volume, modifies the first law of black hole thermodynamics. Properties of the resulting thermodynamic volume are investigated: the compressibility and the speed of sound of the black hole are derived in the case of nonpositive cosmological constant. The adiabatic compressibility vanishes for a nonrotating black hole and is maximal in the extremal case--comparable with, but still less than, that of a cold neutron star. A speed of sound v s is associated with the adiabatic compressibility, which is equal to c for a nonrotating black hole and decreases as the angular momentum is increased. An extremal black hole has v s 2 =0.9 c 2 when the cosmological constant vanishes, and more generally v s is bounded below by c/√(2).

  14. Black holes with halos

    Science.gov (United States)

    Monten, Ruben; Toldo, Chiara

    2018-02-01

    We present new AdS4 black hole solutions in N =2 gauged supergravity coupled to vector and hypermultiplets. We focus on a particular consistent truncation of M-theory on the homogeneous Sasaki–Einstein seven-manifold M 111, characterized by the presence of one Betti vector multiplet. We numerically construct static and spherically symmetric black holes with electric and magnetic charges, corresponding to M2 and M5 branes wrapping non-contractible cycles of the internal manifold. The novel feature characterizing these nonzero temperature configurations is the presence of a massive vector field halo. Moreover, we verify the first law of black hole mechanics and we study the thermodynamics in the canonical ensemble. We analyze the behavior of the massive vector field condensate across the small-large black hole phase transition and we interpret the process in the dual field theory.

  15. Black hole as a wormhole factory

    Directory of Open Access Journals (Sweden)

    Sung-Won Kim

    2015-12-01

    Full Text Available There have been lots of debates about the final fate of an evaporating black hole and the singularity hidden by an event horizon in quantum gravity. However, on general grounds, one may argue that a black hole stops radiation at the Planck mass (ħc/G1/2∼10−5 g, where the radiated energy is comparable to the black hole's mass. And also, it has been argued that there would be a wormhole-like structure, known as “spacetime foam”, due to large fluctuations below the Planck length (ħG/c31/2∼10−33 cm. In this paper, as an explicit example, we consider an exact classical solution which represents nicely those two properties in a recently proposed quantum gravity model based on different scaling dimensions between space and time coordinates. The solution, called “Black Wormhole”, consists of two different states, depending on its mass parameter M and an IR parameter ω: For the black hole state (with ωM2>1/2, a non-traversable wormhole occupies the interior region of the black hole around the singularity at the origin, whereas for the wormhole state (with ωM2<1/2, the interior wormhole is exposed to an outside observer as the black hole horizon is disappearing from evaporation. The black hole state becomes thermodynamically stable as it approaches the merging point where the interior wormhole throat and the black hole horizon merges, and the Hawking temperature vanishes at the exact merge point (with ωM2=1/2. This solution suggests the “Generalized Cosmic Censorship” by the existence of a wormhole-like structure which protects the naked singularity even after the black hole evaporation. One could understand the would-be wormhole inside the black hole horizon as the result of microscopic wormholes created by “negative” energy quanta which have entered the black hole horizon in Hawking radiation process; the quantum black hole could be a wormhole factory! It is found that this speculative picture may be consistent with the

  16. Black-hole creation in quantum cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Zhong Chao, Wu [Rome, Univ. `La Sapienza` (Italy). International Center for Relativistic Astrophysics]|[Specola Vaticana, Vatican City State (Vatican City State, Holy See)

    1997-11-01

    It is proven that the probability of a black hole created from the de Sitter space-time background, at the Wkb level, is the exponential of one quarter of the sum of the black hole and cosmological horizon areas, or the total entropy of the universe. This is true not only for the spherically symmetric cases of the Schwarzschild or Reissner-Nordstroem black holes, but also for the rotating cases of the Kerr black hole and the rotating charged case of the Newman black hole. The de Sitter metric is the most probable evolution at the Planckian era of the universe.

  17. What Expands in an Expanding Universe?

    Science.gov (United States)

    Pacheco, José A De Freitas

    2015-01-01

    In the present investigation, the possible effects of the expansion of the Universe on systems bonded either by gravitational or electromagnetic forces, are reconsidered. It will be shown that the acceleration (positive or negative) of the expanding background, is the determinant factor affecting planetary orbits and atomic sizes. In the presently accepted cosmology (ΛCDM) all bonded systems are expanding at a decreasing rate that tends to be zero as the universe enters in a de Sitter phase. It is worth mentioning that the estimated expansion rates are rather small and they can be neglected for all practical purposes.

  18. What Expands in an Expanding Universe?

    Directory of Open Access Journals (Sweden)

    JOSÉ A. DE FREITAS PACHECO

    2015-12-01

    Full Text Available ABSTRACT In the present investigation, the possible effects of the expansion of the Universe on systems bonded either by gravitational or electromagnetic forces, are reconsidered. It will be shown that the acceleration (positive or negative of the expanding background, is the determinant factor affecting planetary orbits and atomic sizes. In the presently accepted cosmology (ΛCDM all bonded systems are expanding at a decreasing rate that tends to be zero as the universe enters in a de Sitter phase. It is worth mentioning that the estimated expansion rates are rather small and they can be neglected for all practical purposes.

  19. Black Holes in Higher Dimensions

    Directory of Open Access Journals (Sweden)

    Reall Harvey S.

    2008-09-01

    Full Text Available We review black-hole solutions of higher-dimensional vacuum gravity and higher-dimensional supergravity theories. The discussion of vacuum gravity is pedagogical, with detailed reviews of Myers–Perry solutions, black rings, and solution-generating techniques. We discuss black-hole solutions of maximal supergravity theories, including black holes in anti-de Sitter space. General results and open problems are discussed throughout.

  20. Effect of Chord Splice Joints on Force Distribution and Deformations in Trusses with Punched Metal Plate Fasteners

    DEFF Research Database (Denmark)

    Ellegaard, Peter

    2007-01-01

    The span of roof trusses with punched metal plate fasteners (nail plates) makes it often necessary to use splice joints in the top and bottom chords. In the finite element models used for design of the trusses these splice joints are normally assumed to be either rotationally stiff or pinned....... Timber-to-timber contact and non-linear elastic behaviour are included in the model. Results from tests with joints under fourpoint bending are compared with predictions given by TrussLab, and a good agreement is found. Splice joints in trusses with nail plates may be assumed to be rotationally stiff...... if their deformation has no significant effect upon the distribution of member forces according to Eurocode 5. Two simple guidelines for the design and location of splice joints are given in Eurocode 5 for treating the splice joints as rotationally stiff. The reasonability of these guidelines and the influence...

  1. Plasma electron hole kinematics. I. Momentum conservation

    Energy Technology Data Exchange (ETDEWEB)

    Hutchinson, I. H.; Zhou, C. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2016-08-15

    We analyse the kinematic properties of a plasma electron hole: a non-linear self-sustained localized positive electric potential perturbation, trapping electrons, which behaves as a coherent entity. When a hole accelerates or grows in depth, ion and electron plasma momentum is changed both within the hole and outside, by an energization process we call jetting. We present a comprehensive analytic calculation of the momentum changes of an isolated general one-dimensional hole. The conservation of the total momentum gives the hole's kinematics, determining its velocity evolution. Our results explain many features of the behavior of hole speed observed in numerical simulations, including self-acceleration at formation, and hole pushing and trapping by ion streams.

  2. Evolving Coronal Holes and Interplanetary Erupting Stream ...

    Indian Academy of Sciences (India)

    prominences, have a significantly higher rate of occurrence in the vicinity of coronal .... coronal holes due to the birth of new holes or the growth of existing holes. .... Statistics of newly formed coronal hole areas (NFOCHA) associated with ...

  3. Quantum black holes

    OpenAIRE

    Hooft, G. 't

    1987-01-01

    This article is divided into three parts. First, a systematic derivation of the Hawking radiation is given in three different ways. The information loss problem is then discussed in great detail. The last part contains a concise discussion of black hole thermodynamics. This article was published as chapter $6$ of the IOP book "Lectures on General Relativity, Cosmology and Quantum Black Holes" (July $2017$).

  4. Black holes and cosmic censorship

    International Nuclear Information System (INIS)

    Hiscock, W.A.

    1979-01-01

    It is widely accepted that the complete gravitational collapse of a body always yields a black hole, and that naked singularities are never produced (the cosmic censorship hypothesis). The local (or strong) cosmic censorship hypothesis states that singularities which are even locally naked (e.g., to an observer inside a black hole) are never produced. This dissertation studies the validity of these two conjectures. The Kerr-Newman metrics describes the black holes only when M 2 greater than or equal to Q 2 + P 2 , where M is the mass of the black hole, a = J/M its specific angular momentum, Q its electric charge, and P its magnetic charge. In the first part of this dissertation, the possibility of converting an extreme Kerr-Newman black hole (M 2 = a 2 + Q 2 + P 2 ) into a naked singularity by the accretion of test particles is considered. The motion of test particles is studied with a large angular momentum to energy ratio, and also test particles with a large charge to energy ratio. The final state is always found to be a black hole if the angular momentum, electric charge, and magnetic charge of the black hole are all much greater than the corresponding angular momentum, electric charge, and magnetic charge of the test particle. In Part II of this dissertation possible black hole interior solutions are studied. The Cauchy horizons and locally naked timelike singularities of the charged (and/or rotating) solutions are contrasted with the spacelike all-encompassing singularity of the Schwarzschild solution. It is determined which portions of the analytic extension of the Reissner-Nordstroem solution are relevant to realistic gravitational collapse

  5. Instability of charged anti-de Sitter black holes

    International Nuclear Information System (INIS)

    Gwak, Bogeun; Lee, Bum-Hoon; Ro, Daeho

    2016-01-01

    We have studied the instability of charged anti-de Sitter black holes in four- or higher-dimensions under fragmentation. The unstable black holes under fragmentation can be broken into two black holes. Instability depends not only on the mass and charge of the black hole but also on the ratio between the fragmented black hole and its predecessor. We have found that the near extremal black holes are unstable, and Schwarzschild-AdS black holes are stable. These are qualitatively similar to black holes in four dimensions and higher. The detailed instabilities are numerically investigated.

  6. Spin One Hawking Radiation from Dirty Black Holes

    OpenAIRE

    Petarpa Boonserm; Tritos Ngampitipan; Matt Visser

    2013-01-01

    A “clean” black hole is a black hole in vacuum such as the Schwarzschild black hole. However in real physical systems, there are matter fields around a black hole. Such a black hole is called a “dirty black hole”. In this paper, the effect of matter fields on the black hole and the greybody factor is investigated. The results show that matter fields make a black hole smaller. They can increase the potential energy to a black hole to obstruct Hawking radiation to propagate. This causes the gre...

  7. Advances in moment transfering dvw reinforced timber connections : analysis and experimental verification, Part 1

    NARCIS (Netherlands)

    Leijten, A.J.M.; Brandon, D.

    2013-01-01

    Considerable advances in the moment transferring capacity of timber connections are achieved by using densified veneer wood reinforcement and expanded tube fasteners. This study focuses on the rotational stiffness of two dvw reinforced connections joined in series by a steel plate in a splice and

  8. Advantages of DVW reinforced moment transmitting timber joints with steel flitch plates for colum-beam application

    NARCIS (Netherlands)

    Leijten, A.J.M.; Brandon, D.; Haddad, Y.M.

    2013-01-01

    This paper presents a study into the moment-rotation aspects of dvw (densified veneer wood) reinforced timber connections with an inter-connecting flitch plate used as middle member. Previous studies showed that reinforcing dowel-type timber connections with dvw and using expanded tube fasteners

  9. Tracking black holes in numerical relativity

    International Nuclear Information System (INIS)

    Caveny, Scott A.; Anderson, Matthew; Matzner, Richard A.

    2003-01-01

    This work addresses the problem of generically tracking black hole event horizons in computational simulation of black hole interactions. Solutions of the hyperbolic eikonal equation, solved on a curved spacetime manifold containing black hole sources, are employed in development of a robust tracking method capable of continuously monitoring arbitrary changes of topology in the event horizon as well as arbitrary numbers of gravitational sources. The method makes use of continuous families of level set viscosity solutions of the eikonal equation with identification of the black hole event horizon obtained by the signature feature of discontinuity formation in the eikonal's solution. The method is employed in the analysis of the event horizon for the asymmetric merger in a binary black hole system. In this first such three dimensional analysis, we establish both qualitative and quantitative evidence for our method and its application to the asymmetric problem. We focus attention on (1) the topology of the throat connecting the holes following merger, (2) the time of merger, and (3) continuing to account for the surface of section areas of the black hole sources

  10. Interface state generation after hole injection

    International Nuclear Information System (INIS)

    Zhao, C. Z.; Zhang, J. F.; Groeseneken, G.; Degraeve, R.; Ellis, J. N.; Beech, C. D.

    2001-01-01

    After terminating electrical stresses, the generation of interface states can continue. Our previous work in this area indicates that the interface state generation following hole injection originates from a defect. These defects are inactive in a fresh device, but can be excited by hole injection and then converted into interface states under a positive gate bias after hole injection. There is little information available on these defects. This article investigates how they are formed and attempts to explain why they are sensitive to processing conditions. Roles played by hydrogen and trapped holes will be clarified. A detailed comparison between the interface state generation after hole injection in air and that in forming gas is carried out. Our results show that there are two independent processes for the generation: one is caused by H 2 cracking and the other is not. The rate limiting process for the interface state generation after hole injection is discussed and the relation between the defects responsible for this generation and hole traps is explored. [copyright] 2001 American Institute of Physics

  11. Testing quantum gravity through dumb holes

    Energy Technology Data Exchange (ETDEWEB)

    Pourhassan, Behnam, E-mail: b.pourhassan@du.ac.ir [School of Physics, Damghan University, Damghan (Iran, Islamic Republic of); Faizal, Mir, E-mail: f2mir@uwaterloo.ca [Department of Physics and Astronomy, University of Lethbridge, Lethbridge, AB T1K 3M4 (Canada); Irving K. Barber School of Arts and Sciences, University of British Columbia - Okanagan, Kelowna, BC V1V 1V7 (Canada); Capozziello, Salvatore, E-mail: capozzie@na.infn.it [Dipartimento di Fisica, Università di Napoli ”Frederico II” Complesso Universitario di Monte S. Angelo, Edificio G, Via Cinthia, I-80126 Napoli (Italy); Gran Sasso Science Institute (INFN), Via F. Crispi 7, I-67100 L’ Aquila (Italy)

    2017-02-15

    We propose a method to test the effects of quantum fluctuations on black holes by analyzing the effects of thermal fluctuations on dumb holes, the analogs for black holes. The proposal is based on the Jacobson formalism, where the Einstein field equations are viewed as thermodynamical relations, and so the quantum fluctuations are generated from the thermal fluctuations. It is well known that all approaches to quantum gravity generate logarithmic corrections to the entropy of a black hole and the coefficient of this term varies according to the different approaches to the quantum gravity. It is possible to demonstrate that such logarithmic terms are also generated from thermal fluctuations in dumb holes. In this paper, we claim that it is possible to experimentally test such corrections for dumb holes, and also obtain the correct coefficient for them. This fact can then be used to predict the effects of quantum fluctuations on realistic black holes, and so it can also be used, in principle, to experimentally test the different approaches to quantum gravity.

  12. Black Hole Paradoxes

    International Nuclear Information System (INIS)

    Joshi, Pankaj S.; Narayan, Ramesh

    2016-01-01

    We propose here that the well-known black hole paradoxes such as the information loss and teleological nature of the event horizon are restricted to a particular idealized case, which is the homogeneous dust collapse model. In this case, the event horizon, which defines the boundary of the black hole, forms initially, and the singularity in the interior of the black hole at a later time. We show that, in contrast, gravitational collapse from physically more realistic initial conditions typically leads to the scenario in which the event horizon and space-time singularity form simultaneously. We point out that this apparently simple modification can mitigate the causality and teleological paradoxes, and also lends support to two recently suggested solutions to the information paradox, namely, the ‘firewall’ and ‘classical chaos’ proposals. (paper)

  13. Merging Black Holes

    Science.gov (United States)

    Centrella, Joan

    2012-01-01

    The final merger of two black holes is expected to be the strongest source of gravitational waves for both ground-based detectors such as LIGO and VIRGO, as well as future. space-based detectors. Since the merger takes place in the regime of strong dynamical gravity, computing the resulting gravitational waveforms requires solving the full Einstein equations of general relativity on a computer. For many years, numerical codes designed to simulate black hole mergers were plagued by a host of instabilities. However, recent breakthroughs have conquered these instabilities and opened up this field dramatically. This talk will focus on.the resulting 'gold rush' of new results that is revealing the dynamics and waveforms of binary black hole mergers, and their applications in gravitational wave detection, testing general relativity, and astrophysics

  14. Dramatic Outburst Reveals Nearest Black Hole

    Science.gov (United States)

    2000-01-01

    Scientists have discovered the closest black hole yet, a mere 1,600 light years from Earth. Its discovery was heralded by four of the most dramatic rapid X-ray intensity changes ever seen from one star. Astronomers from the Massachusetts Institute of Technology (MIT) and the National Science Foundation's National Radio Astronomy Observatory (NRAO) announced their findings at the American Astronomical Society's meeting in Atlanta. The black hole in the constellation Sagittarius, along with a normal star dubbed V4641 Sgr, form a violent system that briefly flooded part of our Milky Way Galaxy with X-rays and ejected subatomic particles moving at nearly the speed of light one day last September. At the peak of its X-ray output, V4641 Sgr was the brightest X-ray emitter in the sky. Astronomers call this type of system an X-ray nova because it suddenly becomes a bright source of X-rays, but this object shows characteristics never seen in an X-ray nova. "V4641 Sgr turns on and off so fast that it seems to represent a new subclass of X-ray novae," said Donald A. Smith, postdoctoral associate in MIT's Center for Space Research. Smith worked on data from this object with MIT principal research scientist Ronald Remillard and NRAO astronomer Robert Hjellming. "In X-rays, the intensity rose by a factor of more than 1,000 in seven hours, then dropped by a factor of 100 in two hours," Remillard said. The radio emission was seen as an image of an expanding "jet" of particles shooting out from the binary system. After reaching a maximum, the radio intensity dropped by a factor of nearly 40 within two days. "Radio telescopes give us a quick glimpse of something moving at a fantastically high velocity," Hjellming said. Black holes harbor enormous gravitational force that can literally rip the gas away from a nearby star. This transfer of gas is visible in many forms of radiation. Both orbiting X-ray telescopes and ground-based radio and optical telescopes saw the outburst of V4641

  15. BOOK REVIEW: Introduction to Black Hole Physics Introduction to Black Hole Physics

    Science.gov (United States)

    Tanaka, Takahiro

    2012-07-01

    Introduction to Black Hole Physics is a large volume (504 pages), and yet despite this it is still really an introductory text. The book gives an introduction to general relativity, but most of the text is dedicated to attracting the reader's attention to the interesting world of black hole physics. In this sense, the book is very distinct from other textbooks on general relativity. We are told that it was based on the lectures given by Professor Frolov, one of the authors, over the last 30 years. One can obtain the basic ideas about black holes, and also the necessary tips to understand general relativity at a very basic level. For example, in the discussion about particle motion in curved space, the authors start with a brief review on analytical mechanics. The book does not require its readers to have a great deal of knowledge in advance. If you are familiar with such a basic subject, you can simply omit that section. The reason why I especially picked up on this topic as an example is that the book devotes a significant number of pages to geodesic motions in black hole spacetime. One of the main motivations to study black holes is related to how they will actually be observed, once we develop the ability to observe them clearly. The book does explain such discoveries as, for instance, how the motion of a particle is related to a beautiful mathematical structure arising from the hidden symmetry of spacetime, which became transparent via the recent progress in the exploration of black holes in higher dimensions; a concise introduction to this latest topic is deferred to Appendix D, so as not to distract the reader with its mathematical complexities. It should be also mentioned that the book is not limited to general relativistic aspects: quantum fields on a black hole background and Hawking radiation are also covered. Also included are current hot topics, for instance the gravitational waves from a system including black holes, whose first direct detection is

  16. Magnetohydrodynamics near a black hole

    International Nuclear Information System (INIS)

    Wilson, J.R.

    1975-01-01

    A numerical computer study of hydromagnetic flow near a black hole is presented. First, the equations of motion are developed to a form suitable for numerical computations. Second, the results of calculations describing the magnetic torques exerted by a rotating black hole on a surrounding magnetic plasma and the electric charge that is induced on the surface of the black hole are presented. (auth)

  17. What is a black hole

    International Nuclear Information System (INIS)

    Tipler, F.J.

    1979-01-01

    A definition of a black hole is proposed that should work in any stably causal space-time. This is that a black hole is the closure of the smaller future set that contains all noncosmological trapped surfaces and which has its boundary generated by null geodesic segments that are boundary generators of TIPs. This allows precise definitions of cosmic censorship and white holes. (UK)

  18. Black holes escaping from domain walls

    International Nuclear Information System (INIS)

    Flachi, Antonino; Sasaki, Misao; Pujolas, Oriol; Tanaka, Takahiro

    2006-01-01

    Previous studies concerning the interaction of branes and black holes suggested that a small black hole intersecting a brane may escape via a mechanism of reconnection. Here we consider this problem by studying the interaction of a small black hole and a domain wall composed of a scalar field and simulate the evolution of this system when the black hole acquires an initial recoil velocity. We test and confirm previous results, however, unlike the cases previously studied, in the more general set-up considered here, we are able to follow the evolution of the system also during the separation, and completely illustrate how the escape of the black hole takes place

  19. Black Holes Have Simple Feeding Habits

    Science.gov (United States)

    2008-06-01

    The biggest black holes may feed just like the smallest ones, according to data from NASA’s Chandra X-ray Observatory and ground-based telescopes. This discovery supports the implication of Einstein's relativity theory that black holes of all sizes have similar properties, and will be useful for predicting the properties of a conjectured new class of black holes. The conclusion comes from a large observing campaign of the spiral galaxy M81, which is about 12 million light years from Earth. In the center of M81 is a black hole that is about 70 million times more massive than the Sun, and generates energy and radiation as it pulls gas in the central region of the galaxy inwards at high speed. In contrast, so-called stellar mass black holes, which have about 10 times more mass than the Sun, have a different source of food. These smaller black holes acquire new material by pulling gas from an orbiting companion star. Because the bigger and smaller black holes are found in different environments with different sources of material to feed from, a question has remained about whether they feed in the same way. Using these new observations and a detailed theoretical model, a research team compared the properties of M81's black hole with those of stellar mass black holes. The results show that either big or little, black holes indeed appear to eat similarly to each other, and produce a similar distribution of X-rays, optical and radio light. AnimationMulti-wavelength Images of M81 One of the implications of Einstein's theory of General Relativity is that black holes are simple objects and only their masses and spins determine their effect on space-time. The latest research indicates that this simplicity manifests itself in spite of complicated environmental effects. "This confirms that the feeding patterns for black holes of different sizes can be very similar," said Sera Markoff of the Astronomical Institute, University of Amsterdam in the Netherlands, who led the study

  20. Entropy of black holes with multiple horizons

    Science.gov (United States)

    He, Yun; Ma, Meng-Sen; Zhao, Ren

    2018-05-01

    We examine the entropy of black holes in de Sitter space and black holes surrounded by quintessence. These black holes have multiple horizons, including at least the black hole event horizon and a horizon outside it (cosmological horizon for de Sitter black holes and "quintessence horizon" for the black holes surrounded by quintessence). Based on the consideration that the two horizons are not independent each other, we conjecture that the total entropy of these black holes should not be simply the sum of entropies of the two horizons, but should have an extra term coming from the correlations between the two horizons. Different from our previous works, in this paper we consider the cosmological constant as the variable and employ an effective method to derive the explicit form of the entropy. We also try to discuss the thermodynamic stabilities of these black holes according to the entropy and the effective temperature.

  1. Black hole entropy, curved space and monsters

    International Nuclear Information System (INIS)

    Hsu, Stephen D.H.; Reeb, David

    2008-01-01

    We investigate the microscopic origin of black hole entropy, in particular the gap between the maximum entropy of ordinary matter and that of black holes. Using curved space, we construct configurations with entropy greater than the area A of a black hole of equal mass. These configurations have pathological properties and we refer to them as monsters. When monsters are excluded we recover the entropy bound on ordinary matter S 3/4 . This bound implies that essentially all of the microstates of a semiclassical black hole are associated with the growth of a slightly smaller black hole which absorbs some additional energy. Our results suggest that the area entropy of black holes is the logarithm of the number of distinct ways in which one can form the black hole from ordinary matter and smaller black holes, but only after the exclusion of monster states

  2. Bosonic instability of charged black holes

    International Nuclear Information System (INIS)

    Gaina, A.B.; Ternov, I.M.

    1986-01-01

    The processes of spontaneous and induced production and accumulation of charged bosons on quasibound superradiant levels in the field of Kerr-Newman black hole is analysed. It is shown that bosonic instability may be caused exclusively by the rotation of the black hole. Particulary, the Reissner-Nordstrom configuration is stable. In the case of rotating and charged black hole the bosonic instability may cause an increase of charge of the black hole

  3. Measuring the spins of accreting black holes

    International Nuclear Information System (INIS)

    McClintock, Jeffrey E; Narayan, Ramesh; Gou, Lijun; Kulkarni, Akshay; Penna, Robert F; Steiner, James F; Davis, Shane W; Orosz, Jerome A; Remillard, Ronald A

    2011-01-01

    A typical galaxy is thought to contain tens of millions of stellar-mass black holes, the collapsed remnants of once massive stars, and a single nuclear supermassive black hole. Both classes of black holes accrete gas from their environments. The accreting gas forms a flattened orbiting structure known as an accretion disk. During the past several years, it has become possible to obtain measurements of the spins of the two classes of black holes by modeling the x-ray emission from their accretion disks. Two methods are employed, both of which depend upon identifying the inner radius of the accretion disk with the innermost stable circular orbit, whose radius depends only on the mass and spin of the black hole. In the Fe Kα method, which applies to both classes of black holes, one models the profile of the relativistically broadened iron line with a special focus on the gravitationally redshifted red wing of the line. In the continuum-fitting (CF) method, which has so far only been applied to stellar-mass black holes, one models the thermal x-ray continuum spectrum of the accretion disk. We discuss both methods, with a strong emphasis on the CF method and its application to stellar-mass black holes. Spin results for eight stellar-mass black holes are summarized. These data are used to argue that the high spins of at least some of these black holes are natal, and that the presence or absence of relativistic jets in accreting black holes is not entirely determined by the spin of the black hole.

  4. Black holes at neutrino telescopes

    International Nuclear Information System (INIS)

    Kowalski, M.; Ringwald, A.; Tu, H.

    2002-01-01

    In scenarios with extra dimensions and TeV-scale quantum gravity, black holes are expected to be produced in the collision of light particles at center-of-mass energies above the fundamental Planck scale with small impact parameters. Black hole production and evaporation may thus be studied in detail at the large hadron collider (LHC). But even before the LHC starts operating, neutrino telescopes such as AMANDA/IceCube, ANTARES, Baikal, and RICE have an opportunity to search for black hole signatures. Black hole production in the scattering of ultrahigh energy cosmic neutrinos on nucleons in the ice or water may initiate cascades and through-going muons with distinct characteristics above the Standard Model rate. In this Letter, we investigate the sensitivity of neutrino telescopes to black hole production and compare it to the one expected at the Pierre Auger Observatory, an air shower array currently under construction, and at the LHC. We find that, already with the currently available data, AMANDA and RICE should be able to place sensible constraints in black hole production parameter space, which are competitive with the present ones from the air shower facilities Fly's Eye and AGASA. In the optimistic case that a ultrahigh energy cosmic neutrino flux significantly higher than the one expected from cosmic ray interactions with the cosmic microwave background radiation is realized in nature, one even has discovery potential for black holes at neutrino telescopes beyond the reach of LHC. (orig.)

  5. Formation and Coalescence of Electron Solitary Holes

    DEFF Research Database (Denmark)

    Saeki, K.; Michelsen, Poul; Pécseli, H. L.

    1979-01-01

    Electron solitary holes were observed in a magnetized collisionless plasma. These holes were identified as Bernstein-Green-Kruskal equilibria, thus being purely kinetic phenomena. The electron hole does not damp even though its velocity is close to the electron thermal velocity. Two holes attract...

  6. Notes on Phase Transition of Nonsingular Black Hole

    International Nuclear Information System (INIS)

    Ma Meng-Sen; Zhao Ren

    2015-01-01

    On the belief that a black hole is a thermodynamic system, we study the phase transition of nonsingular black holes. If the black hole entropy takes the form of the Bekenstein—Hawking area law, the black hole mass M is no longer the internal energy of the black hole thermodynamic system. Using the thermodynamic quantities, we calculate the heat capacity, thermodynamic curvature and free energy. It is shown that there will be a larger black hole/smaller black hole phase transition for the nonsingular black hole. At the critical point, the second-order phase transition appears. (paper)

  7. Sizes of Black Holes Throughout the Universe

    Science.gov (United States)

    Kohler, Susanna

    2018-05-01

    What is the distribution of sizes of black holes in our universe? Can black holes of any mass exist, or are there gaps in their possible sizes? The shape of this black-hole mass function has been debated for decades and the dawn of gravitational-wave astronomy has only spurred further questions.Mind the GapsThe starting point for the black-hole mass function lies in the initial mass function (IMF) for stellar black holes the beginning size distribution of black holes after they are born from stars. Instead of allowing for the formation of stellar black holes of any mass, theoretical models propose two gaps in the black-hole IMF:An upper mass gap at 50130 solar masses, due to the fact that stellar progenitors of black holes in this mass range are destroyed by pair-instability supernovae.A lower mass gap below 5 solar masses, which is argued to arise naturally from the mechanics of supernova explosions.Missing black-hole (BH) formation channels due to the existence of the lower gap (LG) and the upper gap (UG) in the initial mass function. a) The number of BHs at all scales are lowered because no BH can merge with BHs in the LG to form a larger BH. b) The missing channel responsible for the break at 10 solar masses, resulting from the LG. c) The missing channel responsible for the break at 60 solar masses, due to the interaction between the LG and the UG. [Christian et al. 2018]We can estimate the IMF for black holes by scaling a typical IMF for stars and then adding in these theorized gaps. But is this initial distribution of black-hole masses the same as the distribution that we observe in the universe today?The Influence of MergersBased on recent events, the answer appears to be no! Since the first detections of gravitational waves in September 2015, we now know that black holes can merge to form bigger black holes. An initial distribution of black-hole masses must therefore evolve over time, as mergers cause the depletion of low-mass black holes and an increase in

  8. Lectures on Black Hole Quantum Mechanics

    Science.gov (United States)

    Wilczek, Frank

    The lectures that follow were originally given in 1992, and written up only slightly later. Since then there have been dramatic developments in the quantum theory of black holes, especially in the context of string theory. None of these are reflected here. The concept of quantum hair, which is discussed at length in the lectures, is certainly of permanent interest, and I continue to believe that in some generalized form it will prove central to the whole question of how information is stored in black holes. The discussion of scattering and emission modes from various classes of black holes could be substantially simplified using modern techniques, and from currently popular perspectives the choice of examples might look eccentric. On the other hand fashions have changed rapidly in the field, and the big questions as stated and addressed here, especially as formulated for "real" black holes (nonextremal, in four-dimensional, asymptotically flat space-time, with supersymmetry broken), remain pertinent even as the tools to address them may evolve. The four lectures I gave at the school were based on two lengthy papers that have now been published, "Black Holes as Elementary Particles," Nuclear Physics B380, 447 (1992) and "Quantum Hair on Black Holes," Nuclear Physics B378, 175 (1992). The unifying theme of this work is to help make plausible the possibility that black holes, although they are certainly unusual and extreme states of matter, may be susceptible to a description using concepts that are not fundamentally different from those we use in describing other sorts of quantum-mechanical matter. In the first two lectures I discussed dilaton black holes. The fact that apparently innocuous changes in the "matter" action can drastically change the properties of a black hole is already very significant: it indicates that the physical properties of small black holes cannot be discussed reliably in the abstract, but must be considered with due regard to the rest of

  9. Black-Hole Mass Measurements

    DEFF Research Database (Denmark)

    Vestergaard, Marianne

    2004-01-01

    The applicability and apparent uncertainties of the techniques currently available for measuring or estimating black-hole masses in AGNs are briefly summarized.......The applicability and apparent uncertainties of the techniques currently available for measuring or estimating black-hole masses in AGNs are briefly summarized....

  10. Accretion, primordial black holes and standard cosmology

    Indian Academy of Sciences (India)

    Primordial black holes evaporate due to Hawking radiation. We find that the evaporation times of primordial black holes increase when accretion of radiation is included. Thus, depending on accretion efficiency, more primordial black holes are existing today, which strengthens the conjecture that the primordial black holes ...

  11. Black holes: a slanted overview

    International Nuclear Information System (INIS)

    Vishveshwara, C.V.

    1988-01-01

    The black hole saga spanning some seventy years may be broadly divided into four phases, namely, (a) the dark ages when little was known about black holes even though they had come into existence quite early through the Schwarzschild solution, (b) the age of enlightenment bringing in deep and prolific discoveries, (c) the age of fantasy that cast black holes in all sorts of extraordinary roles, and (d) the golden age of relativistic astrophysics - to some extent similar to Dirac's characterisation of the development of quantum theory - in which black holes have been extensively used to elucidate a number of astrophysical phenomena. It is impossible to give here even the briefest outline of the major developments in this vast area. We shall only attempt to present a few aspects of black hole physics which have been actively pursued in the recent past. Some details are given in the case of those topics that have not found their way into text books or review articles. (author)

  12. Do stringy corrections stabilize colored black holes?

    International Nuclear Information System (INIS)

    Kanti, P.; Winstanley, E.

    2000-01-01

    We consider hairy black hole solutions of Einstein-Yang-Mills-dilaton theory, coupled to a Gauss-Bonnet curvature term, and we study their stability under small, spacetime-dependent perturbations. We demonstrate that stringy corrections do not remove the sphaleronic instabilities of colored black holes with the number of unstable modes being equal to the number of nodes of the background gauge function. In the gravitational sector and in the limit of an infinitely large horizon, colored black holes are also found to be unstable. Similar behavior is exhibited by magnetically charged black holes while the bulk of neutral black holes are proved to be stable under small, gauge-dependent perturbations. Finally, electrically charged black holes are found to be characterized only by the existence of a gravitational sector of perturbations. As in the case of neutral black holes, we demonstrate that for the bulk of electrically charged black holes no unstable modes arise in this sector. (c) 2000 The American Physical Society

  13. Mass inflation in the loop black hole

    International Nuclear Information System (INIS)

    Brown, Eric G.; Mann, Robert; Modesto, Leonardo

    2011-01-01

    In classical general relativity the Cauchy horizon within a two-horizon black hole is unstable via a phenomenon known as mass inflation, in which the mass parameter (and the spacetime curvature) of the black hole diverges at the Cauchy horizon. Here we study this effect for loop black holes - quantum gravitationally corrected black holes from loop quantum gravity - whose construction alleviates the r=0 singularity present in their classical counterparts. We use a simplified model of mass inflation, which makes use of the generalized Dray-'t Hooft relation, to conclude that the Cauchy horizon of loop black holes indeed results in a curvature singularity similar to that found in classical black holes. The Dray-'t Hooft relation is of particular utility in the loop black hole because it does not directly rely upon Einstein's field equations. We elucidate some of the interesting and counterintuitive properties of the loop black hole, and corroborate our results using an alternate model of mass inflation due to Ori.

  14. Entropy of black holes with multiple horizons

    Directory of Open Access Journals (Sweden)

    Yun He

    2018-05-01

    Full Text Available We examine the entropy of black holes in de Sitter space and black holes surrounded by quintessence. These black holes have multiple horizons, including at least the black hole event horizon and a horizon outside it (cosmological horizon for de Sitter black holes and “quintessence horizon” for the black holes surrounded by quintessence. Based on the consideration that the two horizons are not independent each other, we conjecture that the total entropy of these black holes should not be simply the sum of entropies of the two horizons, but should have an extra term coming from the correlations between the two horizons. Different from our previous works, in this paper we consider the cosmological constant as the variable and employ an effective method to derive the explicit form of the entropy. We also try to discuss the thermodynamic stabilities of these black holes according to the entropy and the effective temperature.

  15. Electromagnetic ``black holes'' in hyperbolic metamaterials

    Science.gov (United States)

    Smolyaninov, Igor

    2013-03-01

    We demonstrate that spatial variations of the dielectric tensor components in a hyperbolic metamaterial may lead to formation of electromagnetic ``black holes'' inside this metamaterial. Similar to real black holes, horizon area of the electromagnetic ``black holes'' is quantized in units of the effective ``Planck scale'' squared. Potential experimental realizations of such electromagnetic ``black holes'' will be considered. For example, this situation may be realized in a hyperbolic metamaterial in which the dielectric component exhibits critical opalescence.

  16. Black hole Berry phase

    NARCIS (Netherlands)

    de Boer, J.; Papadodimas, K.; Verlinde, E.

    2009-01-01

    Supersymmetric black holes are characterized by a large number of degenerate ground states. We argue that these black holes, like other quantum mechanical systems with such a degeneracy, are subject to a phenomenon which is called the geometric or Berry’s phase: under adiabatic variations of the

  17. Black hole accretion: the quasar powerhouse

    International Nuclear Information System (INIS)

    Anon.

    1983-01-01

    A program is described which calculates the effects of material falling into the curved space-time surrounding a rotation black hole. The authors have developed a two-dimensional, general-relativistic hydrodynamics code to simulate fluid flow in the gravitational field of a rotating black hole. Such calculations represent models that have been proposed for the energy sources of both quasars and jets from radiogalaxies. In each case, the black hole that powers the quasar or jet would have a mass of about 100 million times the mass of the sun. The black hole would be located in the center of a galaxy whose total mass is 1000 time greater than the black hole mass. (SC)

  18. Charged black holes with scalar hair

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Zhong-Ying; Lü, H. [Center for Advanced Quantum Studies, Department of Physics,Beijing Normal University, Beijing 100875 (China)

    2015-09-10

    We consider a class of Einstein-Maxwell-Dilaton theories, in which the dilaton coupling to the Maxwell field is not the usual single exponential function, but one with a stationary point. The theories admit two charged black holes: one is the Reissner-Nordstrøm (RN) black hole and the other has a varying dilaton. For a given charge, the new black hole in the extremal limit has the same AdS{sub 2}×Sphere near-horizon geometry as the RN black hole, but it carries larger mass. We then introduce some scalar potentials and obtain exact charged AdS black holes. We also generalize the results to black p-branes with scalar hair.

  19. Black hole thermodynamics with conical defects

    Energy Technology Data Exchange (ETDEWEB)

    Appels, Michael [Centre for Particle Theory, Durham University,South Road, Durham, DH1 3LE (United Kingdom); Gregory, Ruth [Centre for Particle Theory, Durham University,South Road, Durham, DH1 3LE (United Kingdom); Perimeter Institute,31 Caroline Street North, Waterloo, ON, N2L 2Y5 (Canada); Kubiznák, David [Perimeter Institute,31 Caroline Street North, Waterloo, ON, N2L 2Y5 (Canada)

    2017-05-22

    Recently we have shown https://www.doi.org/10.1103/PhysRevLett.117.131303 how to formulate a thermodynamic first law for a single (charged) accelerated black hole in AdS space by fixing the conical deficit angles present in the spacetime. Here we show how to generalise this result, formulating thermodynamics for black holes with varying conical deficits. We derive a new potential for the varying tension defects: the thermodynamic length, both for accelerating and static black holes. We discuss possible physical processes in which the tension of a string ending on a black hole might vary, and also map out the thermodynamic phase space of accelerating black holes and explore their critical phenomena.

  20. Black hole evaporation: a paradigm

    International Nuclear Information System (INIS)

    Ashtekar, Abhay; Bojowald, Martin

    2005-01-01

    A paradigm describing black hole evaporation in non-perturbative quantum gravity is developed by combining two sets of detailed results: (i) resolution of the Schwarzschild singularity using quantum geometry methods and (ii) time evolution of black holes in the trapping and dynamical horizon frameworks. Quantum geometry effects introduce a major modification in the traditional spacetime diagram of black hole evaporation, providing a possible mechanism for recovery of information that is classically lost in the process of black hole formation. The paradigm is developed directly in the Lorentzian regime and necessary conditions for its viability are discussed. If these conditions are met, much of the tension between expectations based on spacetime geometry and structure of quantum theory would be resolved

  1. Do Hypervolumes Have Holes?

    Science.gov (United States)

    Blonder, Benjamin

    2016-04-01

    Hypervolumes are used widely to conceptualize niches and trait distributions for both species and communities. Some hypervolumes are expected to be convex, with boundaries defined by only upper and lower limits (e.g., fundamental niches), while others are expected to be maximal, with boundaries defined by the limits of available space (e.g., potential niches). However, observed hypervolumes (e.g., realized niches) could also have holes, defined as unoccupied hyperspace representing deviations from these expectations that may indicate unconsidered ecological or evolutionary processes. Detecting holes in more than two dimensions has to date not been possible. I develop a mathematical approach, implemented in the hypervolume R package, to infer holes in large and high-dimensional data sets. As a demonstration analysis, I assess evidence for vacant niches in a Galapagos finch community on Isabela Island. These mathematical concepts and software tools for detecting holes provide approaches for addressing contemporary research questions across ecology and evolutionary biology.

  2. When Black Holes Collide

    Science.gov (United States)

    Baker, John

    2010-01-01

    Among the fascinating phenomena predicted by General Relativity, Einstein's theory of gravity, black holes and gravitational waves, are particularly important in astronomy. Though once viewed as a mathematical oddity, black holes are now recognized as the central engines of many of astronomy's most energetic cataclysms. Gravitational waves, though weakly interacting with ordinary matter, may be observed with new gravitational wave telescopes, opening a new window to the universe. These observations promise a direct view of the strong gravitational dynamics involving dense, often dark objects, such as black holes. The most powerful of these events may be merger of two colliding black holes. Though dark, these mergers may briefly release more energy that all the stars in the visible universe, in gravitational waves. General relativity makes precise predictions for the gravitational-wave signatures of these events, predictions which we can now calculate with the aid of supercomputer simulations. These results provide a foundation for interpreting expect observations in the emerging field of gravitational wave astronomy.

  3. Does black-hole entropy make sense

    International Nuclear Information System (INIS)

    Wilkins, D.

    1979-01-01

    Bekenstein and Hawking saved the second law of thermodynamics near a black hole by assigning to the hole an entropy Ssub(h) proportional to the area of its event horizon. It is tempting to assume that Ssub(h) possesses all the features commonly associated with the physical entropy. Kundt has shown, however, that Ssub(h) violates several reasonable physical expectations. This criticism is reviewed, augmenting it as follows: (a) Ssub(h) is a badly behaved state function requiring knowledge of the hole's future history; and (b) close analogs of event horizons in other space-times do not possess an 'entropy'. These questions are also discussed: (c) Is Ssub(h) suitable for all regions of a black-hole space-time. And (b) should Ssub(h) be attributed to the exterior of a white hole. One can retain Ssub(h) for the interior (respectively, exterior) of a black (respectively, white) hole, but is rejected as contrary to the information-theoretic derivation of horizon entropy given by Berkenstein. The total entropy defined by Kundt (all ordinary entropy on space-section cutting through the hole, no horizon term) and that of Bekenstein-Hawking (ordinary entropy outside horizon plus horizon term) appear to be complementary concepts with separate domains of validity. In the most natural choice, an observer inside a black hole will use Kundt's entropy, and one remaining outside that of Bekenstein-Hawking. (author)

  4. Stationary black holes as holographs

    Energy Technology Data Exchange (ETDEWEB)

    Racz, Istvan [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-01 (Japan); MTA KFKI, Reszecske- es Magfizikai Kutatointezet, H-1121 Budapest, Konkoly Thege Miklos ut 29-33 (Hungary)

    2007-11-21

    Smooth spacetimes possessing a (global) one-parameter group of isometries and an associated Killing horizon in Einstein's theory of gravity are investigated. No assumption concerning the asymptotic structure is made; thereby, the selected spacetimes may be considered as generic distorted stationary black holes. First, spacetimes of arbitrary dimension, n {>=} 3, with matter satisfying the dominant energy condition and allowing a non-zero cosmological constant are investigated. In this part, complete characterization of the topology of the event horizon of 'distorted' black holes is given. It is shown that the topology of the event horizon of 'distorted' black holes is allowed to possess a much larger variety than that of the isolated black hole configurations. In the second part, four-dimensional (non-degenerate) electrovac distorted black hole spacetimes are considered. It is shown that the spacetime geometry and the electromagnetic field are uniquely determined in the black hole region once the geometry of the bifurcation surface and one of the electromagnetic potentials are specified there. Conditions guaranteeing the same type of determinacy, in a neighbourhood of the event horizon, on the domain of outer communication side are also investigated. In particular, they are shown to be satisfied in the analytic case.

  5. Time dependent black holes and scalar hair

    International Nuclear Information System (INIS)

    Chadburn, Sarah; Gregory, Ruth

    2014-01-01

    We show how to correctly account for scalar accretion onto black holes in scalar field models of dark energy by a consistent expansion in terms of a slow roll parameter. At leading order, we find an analytic solution for the scalar field within our Hubble volume, which is regular on both black hole and cosmological event horizons, and compute the back reaction of the scalar on the black hole, calculating the resulting expansion of the black hole. Our results are independent of the relative size of black hole and cosmological event horizons. We comment on the implications for more general black hole accretion, and the no hair theorems. (paper)

  6. Quantum Black Holes As Elementary Particles

    OpenAIRE

    Ha, Yuan K.

    2008-01-01

    Are black holes elementary particles? Are they fermions or bosons? We investigate the remarkable possibility that quantum black holes are the smallest and heaviest elementary particles. We are able to construct various fundamental quantum black holes: the spin-0, spin 1/2, spin-1, and the Planck-charge cases, using the results in general relativity. Quantum black holes in the neighborhood of the Galaxy could resolve the paradox posed by the Greisen-Zatsepin-Kuzmin limit on the energy of cosmi...

  7. Internal limiting membrane flap transposition for surgical repair of macular holes in primary surgery and in persistent macular holes.

    Science.gov (United States)

    Leisser, Christoph; Hirnschall, Nino; Döller, Birgit; Varsits, Ralph; Ullrich, Marlies; Kefer, Katharina; Findl, Oliver

    2018-03-01

    Classical or temporal internal limiting membrane (ILM) flap transposition with air or gas tamponade are current trends with the potential to improve surgical results, especially in cases with large macular holes. A prospective case series included patients with idiopathic macular holes or persistent macular holes after 23-G pars plana vitrectomy (PPV) and ILM peeling with gas tamponade. In all patients, 23-G PPV and ILM peeling with ILM flap transposition with gas tamponade and postoperative face-down position was performed. In 7 of 9 eyes, temporal ILM flap transposition combined with pedicle ILM flap could be successfully performed and macular holes were closed in all eyes after surgery. The remaining 2 eyes were converted to pedicle ILM flap transposition with macular hole closure after surgery. Three eyes were scheduled as pedicle ILM flap transposition due to previous ILM peeling. In 2 of these eyes, the macular hole could be closed with pedicle ILM flap transposition. In 3 eyes, free ILM flap transposition was performed and in 2 of these eyes macular hole could be closed after surgery, whereas in 1 eye a second surgery, performed as pedicle ILM flap transposition, was performed and led to successful macular hole closure. Use of ILM flaps in surgical repair of macular hole surgery is a new option of treatment with excellent results independent of the diameter of macular holes. For patients with persistent macular holes, pedicle ILM flap transposition or free ILM flap transposition are surgical options.

  8. NASA's Chandra Finds Black Holes Are "Green"

    Science.gov (United States)

    2006-04-01

    Black holes are the most fuel efficient engines in the Universe, according to a new study using NASA's Chandra X-ray Observatory. By making the first direct estimate of how efficient or "green" black holes are, this work gives insight into how black holes generate energy and affect their environment. The new Chandra finding shows that most of the energy released by matter falling toward a supermassive black hole is in the form of high-energy jets traveling at near the speed of light away from the black hole. This is an important step in understanding how such jets can be launched from magnetized disks of gas near the event horizon of a black hole. Illustration of Fuel for a Black Hole Engine Illustration of Fuel for a Black Hole Engine "Just as with cars, it's critical to know the fuel efficiency of black holes," said lead author Steve Allen of the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University, and the Stanford Linear Accelerator Center. "Without this information, we cannot figure out what is going on under the hood, so to speak, or what the engine can do." Allen and his team used Chandra to study nine supermassive black holes at the centers of elliptical galaxies. These black holes are relatively old and generate much less radiation than quasars, rapidly growing supermassive black holes seen in the early Universe. The surprise came when the Chandra results showed that these "quiet" black holes are all producing much more energy in jets of high-energy particles than in visible light or X-rays. These jets create huge bubbles, or cavities, in the hot gas in the galaxies. Animation of Black Hole in Elliptical Galaxy Animation of Black Hole in Elliptical Galaxy The efficiency of the black hole energy-production was calculated in two steps: first Chandra images of the inner regions of the galaxies were used to estimate how much fuel is available for the black hole; then Chandra images were used to estimate the power required to produce

  9. Charged spinning black holes as particle accelerators

    International Nuclear Information System (INIS)

    Wei Shaowen; Liu Yuxiao; Guo Heng; Fu Chune

    2010-01-01

    It has recently been pointed out that the spinning Kerr black hole with maximal spin could act as a particle collider with arbitrarily high center-of-mass energy. In this paper, we will extend the result to the charged spinning black hole, the Kerr-Newman black hole. The center-of-mass energy of collision for two uncharged particles falling freely from rest at infinity depends not only on the spin a but also on the charge Q of the black hole. We find that an unlimited center-of-mass energy can be approached with the conditions: (1) the collision takes place at the horizon of an extremal black hole; (2) one of the colliding particles has critical angular momentum; (3) the spin a of the extremal black hole satisfies (1/√(3))≤(a/M)≤1, where M is the mass of the Kerr-Newman black hole. The third condition implies that to obtain an arbitrarily high energy, the extremal Kerr-Newman black hole must have a large value of spin, which is a significant difference between the Kerr and Kerr-Newman black holes. Furthermore, we also show that, for a near-extremal black hole, there always exists a finite upper bound for center-of-mass energy, which decreases with the increase of the charge Q.

  10. Thermodynamics of the Schwarzschild-de Sitter black hole: Thermal stability of the Nariai black hole

    International Nuclear Information System (INIS)

    Myung, Yun Soo

    2008-01-01

    We study the thermodynamics of the Schwarzschild-de Sitter black hole in five dimensions by introducing two temperatures based on the standard and Bousso-Hawking normalizations. We use the first-law of thermodynamics to derive thermodynamic quantities. The two temperatures indicate that the Nariai black hole is thermodynamically unstable. However, it seems that black hole thermodynamics favors the standard normalization and does not favor the Bousso-Hawking normalization

  11. Magnonic black holes

    OpenAIRE

    Roldán-Molina, A.; Nunez, A.S.; Duine, R. A.

    2017-01-01

    We show that the interaction between spin-polarized current and magnetization dynamics can be used to implement black-hole and white-hole horizons for magnons - the quanta of oscillations in the magnetization direction in magnets. We consider three different systems: easy-plane ferromagnetic metals, isotropic antiferromagnetic metals, and easy-plane magnetic insulators. Based on available experimental data, we estimate that the Hawking temperature can be as large as 1 K. We comment on the imp...

  12. Familial trends in a population with macular holes.

    Science.gov (United States)

    Kay, Christine Nichols; Pavan, Peter Reed; Small, Laurie Buccina; Zhang, Tao; Zamba, Gideon K D; Cohen, Steven Myles

    2012-04-01

    To determine if patients with macular hole report an increased family history of macular hole compared with control patients and compare the report of family history between patients with unilateral and bilateral macular holes. This was a multicenter case-control study. Charts of patients coded with diagnosis of macular hole were reviewed, and the diagnosis of idiopathic full-thickness macular hole was ascertained in 166 patients. The control group comprised 136 patients without macular hole or trauma who presented with senile cataract. Family history was obtained from all patients through a telephone interview. Six of 166 (3.6%) macular hole patients surveyed reported a history of macular hole in a primary relative compared with none of 136 (0.0%) control patients (odds ratio is infinity, with 95% confidence interval 1.295 to infinity); however, this finding may be explained by confounders such as age and number of family members. Two of the 142 (1.4%) patients with unilateral holes versus 4 of the 24 (16.7%) patients with bilateral holes reported a family history (odds ratio is 0.0714, with 95% confidence interval 0.0063 to 0.5537), and this finding remains significant when logistic regression is performed to evaluate variables of age and number of family members as potential confounders. There is an increased report of familial occurrence of macular hole in patients with macular holes compared with control patients; however, logistic regression relates this finding to variables of age and number of family members. Patients with bilateral macular holes are more likely to report a family history of macular hole than patients with unilateral macular holes, and this finding remains significant in the presence of age and number of family members. These findings may suggest a familial component to macular hole.

  13. Charged topological black hole pair creation

    International Nuclear Information System (INIS)

    Mann, R.B.

    1998-01-01

    I examine the pair creation of black holes in space-times with a cosmological constant of either sign. I consider cosmological C-metrics and show that the conical singularities in this metric vanish only for three distinct classes of black hole metric, two of which have compact event horizons on each spatial slice. One class is a generalization of the Reissner-Nordstroem (anti-)de Sitter black holes in which the event horizons are the direct product of a null line with a 2-surface with topology of genus g. The other class consists of neutral black holes whose event horizons are the direct product of a null conoid with a circle. In the presence of a domain wall, black hole pairs of all possible types will be pair created for a wide range of mass and charge, including even negative mass black holes. I determine the relevant instantons and Euclidean actions for each case. (orig.)

  14. The membrane paradigm for black holes

    International Nuclear Information System (INIS)

    Price, R.H.; Thorne, K.S.

    1988-01-01

    It is now widely accepted that black holes exist and have an astrophysical role, in particular as the likely power source of quasars. To understand this role with ease, the authors and their colleagues have developed a new paradigm for black holes - a new way to picture, think about and describe them. As far as possible it treats black holes as ordinary astrophysical objects, made of real material. A black hole in this description is a spherical or oblate surface made of a thin, electrically conducting membrane. It was the author's quest to understand the Blandford-Znajek process intuitively that led them to create the membrane paradigm. Their strategy was to translate the general-relativistic mathematics of black holes into the same language of three-dimensional space that is used for magnetized plasmas and to create a new set of black-hole diagrams and pictures to go along with the language. 9 figs

  15. Seeding black holes in cosmological simulations

    Science.gov (United States)

    Taylor, P.; Kobayashi, C.

    2014-08-01

    We present a new model for the formation of black holes in cosmological simulations, motivated by the first star formation. Black holes form from high density peaks of primordial gas, and grow via both gas accretion and mergers. Massive black holes heat the surrounding material, suppressing star formation at the centres of galaxies, and driving galactic winds. We perform an investigation into the physical effects of the model parameters, and obtain a `best' set of these parameters by comparing the outcome of simulations to observations. With this best set, we successfully reproduce the cosmic star formation rate history, black hole mass-velocity dispersion relation, and the size-velocity dispersion relation of galaxies. The black hole seed mass is ˜103 M⊙, which is orders of magnitude smaller than that which has been used in previous cosmological simulations with active galactic nuclei, but suggests that the origin of the seed black holes is the death of Population III stars.

  16. Calcium K-line network in coronal holes

    Energy Technology Data Exchange (ETDEWEB)

    Marsh, K A [Hale Observatories, Pasadena, Calif. (USA)

    1977-05-01

    Microphotometry of calcium K-line photographs in the regions of polar coronal holes shows that the chromospheric network exterior to a hole has a slightly broader intensity distribution than that inside the hole itself, a fact which can be attributed to a greater number of bright network elements outside the hole. These bright elements presumably represent the enhanced network resulting from the dispersal of magnetic flux from old active regions, a hypothesis which is consistent with current ideas of coronal hole formation.

  17. Greybody factors for d-dimensional black holes

    DEFF Research Database (Denmark)

    Harmark, Troels; Natário, José; Schiappa, Ricardo

    2010-01-01

    Gravitational greybody factors are analytically computed for static, spherically symmetric black holes in d-dimensions, including black holes with charge and in the presence of a cosmological constant (where a proper definition of greybody factors for both asymptotically de Sitter and anti...... of the details of the black hole. For asymptotically de Sitter black holes the greybody factor is different for even or odd spacetime dimension, and proportional to the ratio of the areas of the event and cosmological horizons. For asymptotically Ads black holes the greybody factor has a rich structure in which...... universality is hidden in the transmission and reflection coefficients. For either charged or asymptotically de Sitter black holes the greybody factors are given by non-trivial functions, while for asymptotically Ads black holes the greybody factor precisely equals one (corresponding to pure blackbody emission)....

  18. DYNAMIC MODELLING OF VIBRATIONS ASSISTED DRILLING

    Directory of Open Access Journals (Sweden)

    Mathieu LADONNE

    2015-05-01

    Full Text Available The number of multi-materials staking configurations for aeronautical structures is increasing, with the evolution of composite and metallic materials. For drilling the fastening holes, the processes of Vibration Assisted Drilling (VAD expand rapidly, as it permits to improve reliability of drilling operations on multilayer structures. Among these processes of VAD, the solution with forced vibrations added to conventional feed to create a discontinuous cutting is the more developed in industry. The back and forth movement allows to improve the evacuation of chips by breaking it. This technology introduces two new operating parameters, the frequency and the amplitude of the oscillation. To optimize the process, the choice of those parameters requires first to model precisely the operation cutting and dynamics. In this paper, a kinematic modelling of the process is firstly proposed. The limits of the model are analysed through comparison between simulations and measurements. The proposed model is used to develop a cutting force model that allows foreseeing the operating conditions which ensure good chips breaking and tool life improvement.

  19. High precision, rapid laser hole drilling

    Science.gov (United States)

    Chang, Jim J.; Friedman, Herbert W.; Comaskey, Brian J.

    2013-04-02

    A laser system produces a first laser beam for rapidly removing the bulk of material in an area to form a ragged hole. The laser system produces a second laser beam for accurately cleaning up the ragged hole so that the final hole has dimensions of high precision.

  20. Entropy evaporated by a black hole

    International Nuclear Information System (INIS)

    Zurek, W.H.

    1982-01-01

    It is shown that the entropy of the radiation evaporated by an uncharged, nonrotating black hole into vacuum in the course of its lifetime is approximately (4/3) times the initial entropy of this black hole. Also considered is a thermodynamically reversible process in which an increase of black-hole entropy is equal to the decrease of the entropy of its surroundings. Implications of these results for the generalized second law of thermodynamics and for the interpretation of black-hole entropy are pointed out

  1. Rotating black holes and Coriolis effect

    Directory of Open Access Journals (Sweden)

    Chia-Jui Chou

    2016-10-01

    Full Text Available In this work, we consider the fluid/gravity correspondence for general rotating black holes. By using the suitable boundary condition in near horizon limit, we study the correspondence between gravitational perturbation and fluid equation. We find that the dual fluid equation for rotating black holes contains a Coriolis force term, which is closely related to the angular velocity of the black hole horizon. This can be seen as a dual effect for the frame-dragging effect of rotating black hole under the holographic picture.

  2. Rotating black holes and Coriolis effect

    Energy Technology Data Exchange (ETDEWEB)

    Chou, Chia-Jui, E-mail: agoodmanjerry.ep02g@nctu.edu.tw [Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan, ROC (China); Wu, Xiaoning, E-mail: wuxn@amss.ac.cn [Institute of Mathematics, Academy of Mathematics and System Science, CAS, Beijing, 100190 (China); Yang, Yi, E-mail: yiyang@mail.nctu.edu.tw [Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan, ROC (China); Yuan, Pei-Hung, E-mail: phyuan.py00g@nctu.edu.tw [Institute of Physics, National Chiao Tung University, Hsinchu, Taiwan, ROC (China)

    2016-10-10

    In this work, we consider the fluid/gravity correspondence for general rotating black holes. By using the suitable boundary condition in near horizon limit, we study the correspondence between gravitational perturbation and fluid equation. We find that the dual fluid equation for rotating black holes contains a Coriolis force term, which is closely related to the angular velocity of the black hole horizon. This can be seen as a dual effect for the frame-dragging effect of rotating black hole under the holographic picture.

  3. Black Hole Complementary Principle and Noncommutative Membrane

    International Nuclear Information System (INIS)

    Wei Ren

    2006-01-01

    In the spirit of black hole complementary principle, we have found the noncommutative membrane of Scharzchild black holes. In this paper we extend our results to Kerr black hole and see the same story. Also we make a conjecture that spacetimes are noncommutative on the stretched membrane of the more general Kerr-Newman black hole.

  4. Dual jets from binary black holes.

    Science.gov (United States)

    Palenzuela, Carlos; Lehner, Luis; Liebling, Steven L

    2010-08-20

    The coalescence of supermassive black holes--a natural outcome when galaxies merge--should produce gravitational waves and would likely be associated with energetic electromagnetic events. We have studied the coalescence of such binary black holes within an external magnetic field produced by the expected circumbinary disk surrounding them. Solving the Einstein equations to describe black holes interacting with surrounding plasma, we present numerical evidence for possible jets driven by these systems. Extending the process described by Blandford and Znajek for a single, spinning black hole, the picture that emerges suggests that the electromagnetic field extracts energy from the orbiting black holes, which ultimately merge and settle into the standard Blandford-Znajek scenario. Emissions along these jets could potentially be observable at large distances.

  5. Optimal management of idiopathic macular holes.

    Science.gov (United States)

    Madi, Haifa A; Masri, Ibrahim; Steel, David H

    2016-01-01

    This review evaluates the current surgical options for the management of idiopathic macular holes (IMHs), including vitrectomy, ocriplasmin (OCP), and expansile gas use, and discusses key background information to inform the choice of treatment. An evidence-based approach to selecting the best treatment option for the individual patient based on IMH characteristics and patient-specific factors is suggested. For holes without vitreomacular attachment (VMA), vitrectomy is the only option with three key surgical variables: whether to peel the inner limiting membrane (ILM), the type of tamponade agent to be used, and the requirement for postoperative face-down posturing. There is a general consensus that ILM peeling improves primary anatomical hole closure rate; however, in small holes (holes, but large (>400 µm) and chronic holes (>1-year history) are usually treated with long-acting gas and posturing. Several studies on posturing and gas choice were carried out in combination with ILM peeling, which may also influence the gas and posturing requirement. Combined phacovitrectomy appears to offer more rapid visual recovery without affecting the long-term outcomes of vitrectomy for IMH. OCP is licensed for use in patients with small- or medium-sized holes and VMA. A greater success rate in using OCP has been reported in smaller holes, but further predictive factors for its success are needed to refine its use. It is important to counsel patients realistically regarding the rates of success with intravitreal OCP and its potential complications. Expansile gas can be considered as a further option in small holes with VMA; however, larger studies are required to provide guidance on its use.

  6. Black Holes at the LHC: Progress since 2002

    International Nuclear Information System (INIS)

    Park, Seong Chan

    2008-01-01

    We review the recent noticeable progresses in black hole physics focusing on the up-coming super-collider, the LHC. We discuss the classical formation of black holes by particle collision, the greybody factors for higher dimensional rotating black holes, the deep implications of black hole physics to the 'energy-distance' relation, the security issues of the LHC associated with black hole formation and the newly developed Monte-Carlo generators for black hole events.

  7. Five-hole pitot probe measurements of swirl, confinement and nozzle effects on confined turbulent flow

    Science.gov (United States)

    Lilley, D. G.; Scharrer, G. L.

    1984-01-01

    The results of a time-mean flow characterization of nonswirling and swirling inert flows in a combustor are reported. The five-hole pitot probe technique was used in axisymmetric test sections with expansion ratios of 1 and 1.5. A prominent corner recirculation zone identified in nonswirling expanding flows decreased in size with swirling flows. The presence of a downstream nozzle led to an adverse pressure gradient at the wall and a favorable gradient near the centerline. Reducing the expansion ratio reduced the central recirculation length. No significant effect was introduced in the flowfield by a gradual expansion.

  8. Boosting jet power in black hole spacetimes.

    Science.gov (United States)

    Neilsen, David; Lehner, Luis; Palenzuela, Carlos; Hirschmann, Eric W; Liebling, Steven L; Motl, Patrick M; Garrett, Travis

    2011-08-02

    The extraction of rotational energy from a spinning black hole via the Blandford-Znajek mechanism has long been understood as an important component in models to explain energetic jets from compact astrophysical sources. Here we show more generally that the kinetic energy of the black hole, both rotational and translational, can be tapped, thereby producing even more luminous jets powered by the interaction of the black hole with its surrounding plasma. We study the resulting Poynting jet that arises from single boosted black holes and binary black hole systems. In the latter case, we find that increasing the orbital angular momenta of the system and/or the spins of the individual black holes results in an enhanced Poynting flux.

  9. Filling bore-holes with explosive

    Energy Technology Data Exchange (ETDEWEB)

    Alfredsson, S H

    1965-03-02

    In this device for filling boreholes formed in a rock formation with particulate explosive, the explosive is conveyed into the hole by means of a pressure fluid through a tube which has a lesser diameter than the hole. The tube is characterized by a lattice work arranged externally on it, and having a structure adapted to allow passage of a pressure fluid returning between the tube and the wall of the hole, but retaining particles of explosive entrained by the returning pressure fluid. In another arrangement of the device, the lattice work has the form of a brush, including filaments or bristles which are dimensioned to bridge the spacing between the tube and the wall of the hole. (12 claims)

  10. Expanding subjectivities

    DEFF Research Database (Denmark)

    Lundgaard Andersen, Linda; Soldz, Stephen

    2012-01-01

    A major theme in recent psychoanalytic thinking concerns the use of therapist subjectivity, especially “countertransference,” in understanding patients. This thinking converges with and expands developments in qualitative research regarding the use of researcher subjectivity as a tool......-Saxon and continental traditions, this special issue provides examples of the use of researcher subjectivity, informed by psychoanalytic thinking, in expanding research understanding....

  11. Hawking radiation and strong gravity black holes

    International Nuclear Information System (INIS)

    Qadir, A.; Sayed, W.A.

    1979-01-01

    It is shown that the strong gravity theory of Salam et al. places severe restrictions on black hole evaporation. Two major implications are that: mini blck holes (down to masses approximately 10 -16 kg) would be stable in the present epoch; and that some suggested mini black hole mechanisms to explain astrophysical phenomena would not work. The first result implies that f-gravity appears to make black holes much safer by removing the possibility of extremely violent black hole explosions suggested by Hawking. (Auth.)

  12. Loop quantum corrected Einstein Yang-Mills black holes

    Science.gov (United States)

    Protter, Mason; DeBenedictis, Andrew

    2018-05-01

    In this paper, we study the homogeneous interiors of black holes possessing SU(2) Yang-Mills fields subject to corrections inspired by loop quantum gravity. The systems studied possess both magnetic and induced electric Yang-Mills fields. We consider the system of equations both with and without Wilson loop corrections to the Yang-Mills potential. The structure of the Yang-Mills Hamiltonian, along with the restriction to homogeneity, allows for an anomaly-free effective quantization. In particular, we study the bounce which replaces the classical singularity and the behavior of the Yang-Mills fields in the quantum corrected interior, which possesses topology R ×S2 . Beyond the bounce, the magnitude of the Yang-Mills electric field asymptotically grows monotonically. This results in an ever-expanding R sector even though the two-sphere volume is asymptotically constant. The results are similar with and without Wilson loop corrections on the Yang-Mills potential.

  13. The statistical clustering of primordial black holes

    International Nuclear Information System (INIS)

    Carr, B.J.

    1977-01-01

    It is shown that Meszaros theory of galaxy formation, in which galaxies form from the density perturbations associated with the statistical fluctuation in the number density of primordial black holes, must be modified if the black holes are initially surrounded by regions of lower radiation density than average (as is most likely). However, even in this situation, the sort of effect Meszaros envisages does occur and could in principle cause galactic mass-scales to bind at the conventional time. In fact, the requirement that galaxies should not form prematurely implies that black holes could not have a critical density in the mass range above 10 5 M(sun). If the mass spectrum of primordial black holes falls off more slowly than m -3 (as expected), then the biggest black holes have the largest clustering effect. In this case the black hole clustering theory of galaxy formation reduces to the black hole seed theory of galaxy formation, in which each galaxy becomes bound under the gravitational influence of a single black hole nucleus. The seed theory could be viable only if the early Universe had a soft equation of state until a time exceeding 10 -4 s or if something prevented black hole formation before 1 s. (orig.) [de

  14. Plasma horizons of a charged black hole

    International Nuclear Information System (INIS)

    Hanni, R.S.

    1977-01-01

    The most promising way of detecting black holes seems to be through electromagnetic radiation emitted by nearby charged particles. The nature of this radiation depends strongly on the local electromagnetic field, which varies with the charge of the black hole. It has often been purported that a black hole with significant charge will not be observed, because, the dominance of the Coulomb interaction forces its neutralization through selective accretion. This paper shows that it is possible to balance the electric attraction of particles whose charge is opposite that of the black hole with magnetic forces and (assuming an axisymmetric, stationary solution) covariantly define the regions in which this is possible. A Kerr-Newman hole in an asymptotically uniform magnetic field and a current ring centered about a Reissner-Nordstroem hole are used as examples, because of their relevance to processes through which black holes may be observed. (Auth.)

  15. Supersymmetric black holes

    OpenAIRE

    de Wit, Bernard

    2005-01-01

    The effective action of $N=2$, $d=4$ supergravity is shown to acquire no quantum corrections in background metrics admitting super-covariantly constant spinors. In particular, these metrics include the Robinson-Bertotti metric (product of two 2-dimensional spaces of constant curvature) with all 8 supersymmetries unbroken. Another example is a set of arbitrary number of extreme Reissner-Nordstr\\"om black holes. These black holes break 4 of 8 supersymmetries, leaving the other 4 unbroken. We ha...

  16. LIGO Finds Lightest Black-Hole Binary

    Science.gov (United States)

    Kohler, Susanna

    2017-11-01

    Wednesdayevening the Laser Interferometer Gravitational-wave Observatory (LIGO) collaboration quietly mentioned that theyd found gravitational waves from yet another black-hole binary back in June. This casual announcement reveals what is so far the lightest pair of black holes weve watched merge opening the door for comparisons to the black holes weve detected by electromagnetic means.A Routine DetectionThe chirp signal of GW170608 detected by LIGO Hanford and LIGO Livingston. [LIGO collaboration 2017]After the fanfare of the previous four black-hole-binary merger announcements over the past year and a half as well as the announcement of the one neutron-star binary merger in August GW170608 marks our entry into the era in which gravitational-wave detections are officially routine.GW170608, a gravitational-wave signal from the merger of two black holes roughly a billion light-years away, was detected in June of this year. This detection occurred after wed already found gravitational waves from several black-hole binaries with the two LIGO detectors in the U.S., but before the Virgo interferometer came online in Europe and increased the joint ability of the detectors to localize sources.Mass estimates for the two components of GW170608 using different models. [LIGO collaboration 2017]Overall, GW170608 is fairly unremarkable: it was detected by both LIGO Hanford and LIGO Livingston some 7 ms apart, and the signal looks not unlike those of the previous LIGO detections. But because were still in the early days of gravitational-wave astronomy, every discovery is still remarkable in some way! GW170608 stands out as being the lightest pair of black holes weve yet to see merge, with component masses before the merger estimated at 12 and 7 times the mass of the Sun.Why Size MattersWith the exception of GW151226, the gravitational-wave signal discovered on Boxing Day last year, all of the black holes that have been discovered by LIGO/Virgo have been quite large: the masses

  17. Black-hole astrophysics

    Energy Technology Data Exchange (ETDEWEB)

    Bender, P. [Univ. of Colorado, Boulder, CO (United States); Bloom, E. [Stanford Linear Accelerator Center, Menlo Park, CA (United States); Cominsky, L. [Sonoma State Univ., Rohnert Park, CA (United States). Dept. of Physics and Astronomy] [and others

    1995-07-01

    Black-hole astrophysics is not just the investigation of yet another, even if extremely remarkable type of celestial body, but a test of the correctness of the understanding of the very properties of space and time in very strong gravitational fields. Physicists` excitement at this new prospect for testing theories of fundamental processes is matched by that of astronomers at the possibility to discover and study a new and dramatically different kind of astronomical object. Here the authors review the currently known ways that black holes can be identified by their effects on their neighborhood--since, of course, the hole itself does not yield any direct evidence of its existence or information about its properties. The two most important empirical considerations are determination of masses, or lower limits thereof, of unseen companions in binary star systems, and measurement of luminosity fluctuations on very short time scales.

  18. Cosmology with primordial black holes

    International Nuclear Information System (INIS)

    Lindley, D.

    1981-09-01

    Cosmologies containing a substantial amount of matter in the form of evaporating primordial black holes are investigated. A review of constraints on the numbers of such black holes, including an analysis of a new limit found by looking at the destruction of deuterium by high energy photons, shows that there must be a negligible population of small black holes from the era of cosmological nucleosynthesis onwards, but that there are no strong constraints before this time. The major part of the work is based on the construction of detailed, self-consistent cosmological models in which black holes are continually forming and evaporating The interest in these models centres on the question of baryon generation, which occurs via the asymmetric decay of a new type of particle which appears as a consequence of the recently developed Grand Unified Theories of elementary particles. Unfortunately, there is so much uncertainty in the models that firm conclusions are difficult to reach; however, it seems feasible in principle that primordial black holes could be responsible for a significant part of the present matter density of the Universe. (author)

  19. Black holes with Yang-Mills hair

    International Nuclear Information System (INIS)

    Kleihaus, B.; Kunz, J.; Sood, A.; Wirschins, M.

    1998-01-01

    In Einstein-Maxwell theory black holes are uniquely determined by their mass, their charge and their angular momentum. This is no longer true in Einstein-Yang-Mills theory. We discuss sequences of neutral and charged SU(N) Einstein-Yang-Mills black holes, which are static spherically symmetric and asymptotically flat, and which carry Yang-Mills hair. Furthermore, in Einstein-Maxwell theory static black holes are spherically symmetric. We demonstrate that, in contrast, SU(2) Einstein-Yang-Mills theory possesses a sequence of black holes, which are static and only axially symmetric

  20. Tidal interactions with Kerr black holes

    International Nuclear Information System (INIS)

    Hiscock, W.A.

    1977-01-01

    The tidal deformation of an extended test body falling with zero angular momentum into a Kerr black hole is calculated. Numerical results for infall along the symmetry axis and in the equatorial plane of the black hole are presented for a range of values of a, the specific angular momentum of the black hole. Estimates of the tidal contribution to the gravitational radiation are also given. The tidal contribution in equatorial infall into a maximally rotating Kerr black hole may be of the same order as the center-of-mass contribution to the gravitational radiation

  1. Noncommutative Black Holes at the LHC

    Science.gov (United States)

    Villhauer, Elena Michelle

    2017-12-01

    Based on the latest public results, 13 TeV data from the Large Hadron Collider at CERN has not indicated any evidence of hitherto tested models of quantum black holes, semiclassical black holes, or string balls. Such models have predicted signatures of particles with high transverse momenta. Noncommutative black holes remain an untested model of TeV-scale gravity that offers the starkly different signature of particles with relatively low transverse momenta. Considerations for a search for charged noncommutative black holes using the ATLAS detector will be discussed.

  2. Destroying black holes with test bodies

    Energy Technology Data Exchange (ETDEWEB)

    Jacobson, Ted [Center for Fundamental Physics, University of Maryland, College Park, MD 20742-4111 (United States); Sotiriou, Thomas P, E-mail: jacobson@umd.ed, E-mail: T.Sotiriou@damtp.cam.ac.u [Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge, CB3 0WA (United Kingdom)

    2010-04-01

    If a black hole can accrete a body whose spin or charge would send the black hole parameters over the extremal limit, then a naked singularity would presumably form, in violation of the cosmic censorship conjecture. We review some previous results on testing cosmic censorship in this way using the test body approximation, focusing mostly on the case of neutral black holes. Under certain conditions a black hole can indeed be over-spun or over-charged in this approximation, hence radiative and self-force effects must be taken into account to further test cosmic censorship.

  3. Charged black holes in phantom cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Jamil, Mubasher; Qadir, Asghar; Rashid, Muneer Ahmad [National University of Sciences and Technology, Center for Advanced Mathematics and Physics, Rawalpindi (Pakistan)

    2008-11-15

    In the classical relativistic regime, the accretion of phantom-like dark energy onto a stationary black hole reduces the mass of the black hole. We have investigated the accretion of phantom energy onto a stationary charged black hole and have determined the condition under which this accretion is possible. This condition restricts the mass-to-charge ratio in a narrow range. This condition also challenges the validity of the cosmic-censorship conjecture since a naked singularity is eventually produced due to accretion of phantom energy onto black hole. (orig.)

  4. Destroying black holes with test bodies

    International Nuclear Information System (INIS)

    Jacobson, Ted; Sotiriou, Thomas P

    2010-01-01

    If a black hole can accrete a body whose spin or charge would send the black hole parameters over the extremal limit, then a naked singularity would presumably form, in violation of the cosmic censorship conjecture. We review some previous results on testing cosmic censorship in this way using the test body approximation, focusing mostly on the case of neutral black holes. Under certain conditions a black hole can indeed be over-spun or over-charged in this approximation, hence radiative and self-force effects must be taken into account to further test cosmic censorship.

  5. Topics in black-hole physics: geometric constraints on noncollapsing, gravitating systems, and tidal distortions of a Schwarzschild black hole

    International Nuclear Information System (INIS)

    Redmount, I.H.

    1984-01-01

    This dissertation consists of two studies on the general-relativistic theory of black holes. The first work concerns the fundamental issue of black-hole formation: in it geometric constraints are sought on gravitating matter systems, in the special case of axial symmetry, which determine whether or not those systems undergo gravitational collapse to form black holes. The second project deals with mechanical behavior of a black hole: specifically, the tidal deformation of a static black hole is studied by the gravitational fields of external bodies

  6. Entropy of charged dilaton-axion black hole

    International Nuclear Information System (INIS)

    Ghosh, Tanwi; SenGupta, Soumitra

    2008-01-01

    Using the brick wall method, the entropy of the charged dilaton-axion black hole is determined for both asymptotically flat and nonflat cases. The entropy turns out to be proportional to the horizon area of the black hole confirming the Bekenstein-Hawking area-entropy formula for black holes. The leading order logarithmic corrections to the entropy are also derived for such black holes.

  7. Slowly balding black holes

    International Nuclear Information System (INIS)

    Lyutikov, Maxim; McKinney, Jonathan C.

    2011-01-01

    The 'no-hair' theorem, a key result in general relativity, states that an isolated black hole is defined by only three parameters: mass, angular momentum, and electric charge; this asymptotic state is reached on a light-crossing time scale. We find that the no-hair theorem is not formally applicable for black holes formed from the collapse of a rotating neutron star. Rotating neutron stars can self-produce particles via vacuum breakdown forming a highly conducting plasma magnetosphere such that magnetic field lines are effectively ''frozen in'' the star both before and during collapse. In the limit of no resistivity, this introduces a topological constraint which prohibits the magnetic field from sliding off the newly-formed event horizon. As a result, during collapse of a neutron star into a black hole, the latter conserves the number of magnetic flux tubes N B =eΦ ∞ /(πc(ℎ/2π)), where Φ ∞ ≅2π 2 B NS R NS 3 /(P NS c) is the initial magnetic flux through the hemispheres of the progenitor and out to infinity. We test this theoretical result via 3-dimensional general relativistic plasma simulations of rotating black holes that start with a neutron star dipole magnetic field with no currents initially present outside the event horizon. The black hole's magnetosphere subsequently relaxes to the split-monopole magnetic field geometry with self-generated currents outside the event horizon. The dissipation of the resulting equatorial current sheet leads to a slow loss of the anchored flux tubes, a process that balds the black hole on long resistive time scales rather than the short light-crossing time scales expected from the vacuum no-hair theorem.

  8. Reversible Carnot cycle outside a black hole

    International Nuclear Information System (INIS)

    Xi-Hao, Deng; Si-Jie, Gao

    2009-01-01

    A Carnot cycle outside a Schwarzschild black hole is investigated in detail. We propose a reversible Carnot cycle with a black hole being the cold reservoir. In our model, a Carnot engine operates between a hot reservoir with temperature T 1 and a black hole with Hawking temperature T H . By naturally extending the ordinary Carnot cycle to the black hole system, we show that the thermal efficiency for a reversible process can reach the maximal efficiency 1 – T H /T 1 . Consequently, black holes can be used to determine the thermodynamic temperature by means of the Carnot cycle. The role of the atmosphere around the black hole is discussed. We show that the thermal atmosphere provides a necessary mechanism to make the process reversible. (general)

  9. Tunnelling from Goedel black holes

    International Nuclear Information System (INIS)

    Kerner, Ryan; Mann, R. B.

    2007-01-01

    We consider the spacetime structure of Kerr-Goedel black holes, analyzing their parameter space in detail. We apply the tunnelling method to compute their temperature and compare the results to previous calculations obtained via other methods. We claim that it is not possible to have the closed timelike curve (CTC) horizon in between the two black hole horizons and include a discussion of issues that occur when the radius of the CTC horizon is smaller than the radius of both black hole horizons

  10. Visual outcomes of macular hole surgery

    International Nuclear Information System (INIS)

    Khaqan, H.A.; Muhammad, F.J.

    2016-01-01

    To determine the mean visual improvement after internal limiting membrane (ILM) peeling assisted with brilliant blue staining of ILM in macular hole, and stratify the mean visual improvement in different stages of macular hole. Study Design: Quasi-experimental study. Place and Duration of Study: Eye outpatient department (OPD), Lahore General Hospital, Lahore from October 2013 to December 2014. Methodology: Patients with macular hole underwent measurement of best corrected visual acuity (BCVA) and fundus examination with indirect slit lamp biomicroscopy before surgery. The diagnosis of all patients was confirmed on optical coherence tomography. All patients had 23G trans-conjunctival three ports pars plana vitrectomy, ILM peeling, and endotamponade of SF6. The mean visual improvement of different stages of macular hole was noted. Paired t-test was applied. Results: There were 30 patients, 15 males and 15 females (50%). The mean age was 62 ± 10.95 years. They presented with low mean preoperative visual acuity (VA) of 0.96 ± 0.11 logMar. The mean postoperative VA was 0.63 ± 0.24 logMar. The mean visual increase was 0.33 0.22 logMar (p < 0.001). In patients with stage 2 macular hole, mean visual increase was 0.35 ± 0.20 logMar (p < 0.001). In patients with stage 3 macular hole, mean visual increase was 0.44 ± 0.21 logMar (p < 0.001), and in patients with stage 4 macular hole it was 0.13 ± 0.1 logMar (p = 0.004). Conclusion: ILM peeling assisted with brilliant blue is a promising surgery for those patients who have decreased vision due to macular hole, in 2 - 4 stages of macular hole. (author)

  11. 49 CFR 230.38 - Telltale holes.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Telltale holes. 230.38 Section 230.38... Staybolts § 230.38 Telltale holes. (a) Staybolts less than 8 inches long. All staybolts shorter than 8 inches, except flexible bolts, shall have telltale holes 3/16 inch to 7/32 inch diameter and at least 11...

  12. Compensating Scientism through "The Black Hole."

    Science.gov (United States)

    Roth, Lane

    The focal image of the film "The Black Hole" functions as a visual metaphor for the sacred, order, unity, and eternal time. The black hole is a symbol that unites the antinomic pairs of conscious/unconscious, water/fire, immersion/emersion, death/rebirth, and hell/heaven. The black hole is further associated with the quest for…

  13. Collision of two rotating Hayward black holes

    Energy Technology Data Exchange (ETDEWEB)

    Gwak, Bogeun [Sejong University, Department of Physics and Astronomy, Seoul (Korea, Republic of)

    2017-07-15

    We investigate the spin interaction and the gravitational radiation thermally allowed in a head-on collision of two rotating Hayward black holes. The Hayward black hole is a regular black hole in a modified Einstein equation, and hence it can be an appropriate model to describe the extent to which the regularity effect in the near-horizon region affects the interaction and the radiation. If one black hole is assumed to be considerably smaller than the other, the potential of the spin interaction can be analytically obtained and is dependent on the alignment of angular momenta of the black holes. For the collision of massive black holes, the gravitational radiation is numerically obtained as the upper bound by using the laws of thermodynamics. The effect of the Hayward black hole tends to increase the radiation energy, but we can limit the effect by comparing the radiation energy with the gravitational waves GW150914 and GW151226. (orig.)

  14. Rotating dilaton black holes with hair

    International Nuclear Information System (INIS)

    Kleihaus, Burkhard; Kunz, Jutta; Navarro-Lerida, Francisco

    2004-01-01

    We consider stationary rotating black holes in SU(2) Einstein-Yang-Mills theory, coupled to a dilaton. The black holes possess nontrivial non-Abelian electric and magnetic fields outside their regular event horizon. While generic solutions carry no non-Abelian magnetic charge, but non-Abelian electric charge, the presence of the dilaton field allows also for rotating solutions with no non-Abelian charge at all. As a consequence, these special solutions do not exhibit the generic asymptotic noninteger power falloff of the non-Abelian gauge field functions. The rotating black hole solutions form sequences, characterized by the winding number n and the node number k of their gauge field functions, tending to embedded Abelian black holes. The stationary non-Abelian black hole solutions satisfy a mass formula, similar to the Smarr formula, where the dilaton charge enters instead of the magnetic charge. Introducing a topological charge, we conjecture that black hole solutions in SU(2) Einstein-Yang-Mills-dilaton theory are uniquely characterized by their mass, their angular momentum, their dilaton charge, their non-Abelian electric charge, and their topological charge

  15. Black holes by analytic continuation

    CERN Document Server

    Amati, Daniele

    1997-01-01

    In the context of a two-dimensional exactly solvable model, the dynamics of quantum black holes is obtained by analytically continuing the description of the regime where no black hole is formed. The resulting spectrum of outgoing radiation departs from the one predicted by the Hawking model in the region where the outgoing modes arise from the horizon with Planck-order frequencies. This occurs early in the evaporation process, and the resulting physical picture is unconventional. The theory predicts that black holes will only radiate out an energy of Planck mass order, stabilizing after a transitory period. The continuation from a regime without black hole formation --accessible in the 1+1 gravity theory considered-- is implicit in an S matrix approach and provides in this way a possible solution to the problem of information loss.

  16. Six-dimensional localized black holes: Numerical solutions

    International Nuclear Information System (INIS)

    Kudoh, Hideaki

    2004-01-01

    To test the strong-gravity regime in Randall-Sundrum braneworlds, we consider black holes bound to a brane. In a previous paper, we studied numerical solutions of localized black holes whose horizon radii are smaller than the AdS curvature radius. In this paper, we improve the numerical method and discuss properties of the six-dimensional (6D) localized black holes whose horizon radii are larger than the AdS curvature radius. At a horizon temperature T≅1/2πl, the thermodynamics of the localized black hole undergo a transition with its character changing from a 6D Schwarzschild black hole type to a 6D black string type. The specific heat of the localized black holes is negative, and the entropy is greater than or nearly equal to that of the 6D black strings with the same thermodynamic mass. The large localized black holes show flattened horizon geometries, and the intrinsic curvature of the horizon four-geometry becomes negative near the brane. Our results indicate that the recovery mechanism of lower-dimensional Einstein gravity on the brane works even in the presence of the black holes

  17. Evaluation of responses to IE Bulletin 82-02: degradation of threaded fasteners in reactor coolant pressure boundary of pressurized-water-reactor plants

    International Nuclear Information System (INIS)

    Anderson, W.; Sterner, P.

    1985-05-01

    IE Bulletin 82-02 was issued by the NRC on June 2, 1982, to notify licensees about incidents of severe degradation of threaded fasteners. The bulletin required appropriate action including submittal of information from pressurized water reactors having an operating license. Responses from 41 licensees included their recent experience with degradation of threaded fasteners in primary system components. Data from recent regular inspections of reactor coolant pressure boundary component connections of 6-in. size and larger are compiled for technical evaluation. Statistical analysis is used to determine significant factors related to frequency of leakage incidents in connections, occurrence of degradation of bolts and studs, and the need for bolt replacement. Factors examined include the age of the plant, types of components, use of lubricants and sealants, and differences between plants. The compiled data indicate that, on the average, 10% of the bolted connections show evidence of leaking during an 18-month period. Also, 80% of the connections that show evidence of leakage undergo some degradation of the bolting. Results of the analysis show a significant decrease in the occurrence of bolting degradation events as the age of the plant increases. The data also show that valves are less subject to bolting corrosion. A group of 5 of the 41 plants accounted for about one-half of the reported leakage and corrosion events. The common characteristic found for four of these five plants was the lubricant used. The use of nickel-graphite based lubricants appears to offer a significantly reduced incidence of leakage and corrosion, based on late corrections to the reported data. The data also permit the conclusion that the use of molybdenum-disulfide-based lubricants and graphite-based lubricants results in a significantly increased incidence of leakage and corrosion. Reporting of data on lubricants was of poor quality and detracted from the value of the bulletin responses

  18. Relativistic hydrodynamic evolutions with black hole excision

    International Nuclear Information System (INIS)

    Duez, Matthew D.; Shapiro, Stuart L.; Yo, H.-J.

    2004-01-01

    We present a numerical code designed to study astrophysical phenomena involving dynamical spacetimes containing black holes in the presence of relativistic hydrodynamic matter. We present evolutions of the collapse of a fluid star from the onset of collapse to the settling of the resulting black hole to a final stationary state. In order to evolve stably after the black hole forms, we excise a region inside the hole before a singularity is encountered. This excision region is introduced after the appearance of an apparent horizon, but while a significant amount of matter remains outside the hole. We test our code by evolving accurately a vacuum Schwarzschild black hole, a relativistic Bondi accretion flow onto a black hole, Oppenheimer-Snyder dust collapse, and the collapse of nonrotating and rotating stars. These systems are tracked reliably for hundreds of M following excision, where M is the mass of the black hole. We perform these tests both in axisymmetry and in full 3+1 dimensions. We then apply our code to study the effect of the stellar spin parameter J/M 2 on the final outcome of gravitational collapse of rapidly rotating n=1 polytropes. We find that a black hole forms only if J/M 2 2 >1, the collapsing star forms a torus which fragments into nonaxisymmetric clumps, capable of generating appreciable 'splash' gravitational radiation

  19. Quantum Mechanics of Black Holes

    OpenAIRE

    Giddings, Steven B.

    1994-01-01

    These lectures give a pedagogical review of dilaton gravity, Hawking radiation, the black hole information problem, and black hole pair creation. (Lectures presented at the 1994 Trieste Summer School in High Energy Physics and Cosmology)

  20. On black holes and gravitational waves

    CERN Document Server

    Loinger, Angelo

    2002-01-01

    Black holes and gravitational waves are theoretical entities of today astrophysics. Various observed phenomena have been associated with the concept of black hole ; until now, nobody has detected gravitational waves. The essays contained in this book aim at showing that the concept of black holes arises from a misinterpretation of general relativity and that gravitational waves cannot exist.

  1. Spacetime and orbits of bumpy black holes

    International Nuclear Information System (INIS)

    Vigeland, Sarah J.; Hughes, Scott A.

    2010-01-01

    Our Universe contains a great number of extremely compact and massive objects which are generally accepted to be black holes. Precise observations of orbital motion near candidate black holes have the potential to determine if they have the spacetime structure that general relativity demands. As a means of formulating measurements to test the black hole nature of these objects, Collins and Hughes introduced ''bumpy black holes'': objects that are almost, but not quite, general relativity's black holes. The spacetimes of these objects have multipoles that deviate slightly from the black hole solution, reducing to black holes when the deviation is zero. In this paper, we extend this work in two ways. First, we show how to introduce bumps which are smoother and lead to better behaved orbits than those in the original presentation. Second, we show how to make bumpy Kerr black holes--objects which reduce to the Kerr solution when the deviation goes to zero. This greatly extends the astrophysical applicability of bumpy black holes. Using Hamilton-Jacobi techniques, we show how a spacetime's bumps are imprinted on orbital frequencies, and thus can be determined by measurements which coherently track the orbital phase of a small orbiting body. We find that in the weak field, orbits of bumpy black holes are modified exactly as expected from a Newtonian analysis of a body with a prescribed multipolar structure, reproducing well-known results from the celestial mechanics literature. The impact of bumps on strong-field orbits is many times greater than would be predicted from a Newtonian analysis, suggesting that this framework will allow observations to set robust limits on the extent to which a spacetime's multipoles deviate from the black hole expectation.

  2. Chandra Sees Wealth Of Black Holes In Star-Forming Galaxies

    Science.gov (United States)

    2001-06-01

    -like galaxy as we watch. In NGC 253, Chandra may have found the causal connection between starburst activity and quasars." Chandra detected variability and a relatively large ratio of high- to low-energy X-rays in these sources - two characteristics of superheated gas falling into black holes. When combined with extreme luminosities, this tells astronomers that some of these objects must have masses many times greater than ordinary stellar black holes, if they radiate energy uniformly in all directions. Scenarios for the formation of such "intermediate-mass" black holes include the direct collapse of a single, massive cloud of gas into a black hole, or the coalescence of a cluster of stellar black holes, but no uniformly accepted model exists. M82-True Color Image True Color Image of M82 Credit: NASA/SAO/G.Fabbiano et al. Press Image and Caption An alternative possibility, mentioned by Giuseppina Fabbiano of the Harvard-Smithsonian team, is that the X-rays from such highly luminous sources are beamed toward us -- perhaps by a funnel formed by the infalling matter. This would imply that the mass of the underlying black hole is only about ten times the mass of the Sun, in line with the known black hole sources in our galaxy. In this event, they would represent a short-lived but common stage in the evolution of black holes in close binary star systems. Long-term monitoring of the very luminous X-ray sources should distinguish between these possibilities. Andrew Ptak, led a team from Carnegie-Mellon University in Pittsburgh, PA, and Penn State University, University Park, PA, that used Chandra data to survey 37 galaxies. Ptak’s team found that 25 percent of galaxies, which were chosen for their suspected central supermassive black holes and areas of star formation, had these very luminous X-ray sources. The team plans to expand their survey with Chandra to assess the probability of finding these very bright X-ray sources in other types of galaxies. NASA's Marshall Space Flight

  3. Black holes and quantum mechanics

    CERN Document Server

    Wilczek, Frank

    1995-01-01

    1. Qualitative introduction to black holes : classical, quantum2. Model black holes and model collapse process: The Schwarzschild and Reissner-Nordstrom metrics, The Oppenheimer-Volkov collapse scenario3. Mode mixing4. From mode mixing to radiance.

  4. Quantum-gravity fluctuations and the black-hole temperature

    Energy Technology Data Exchange (ETDEWEB)

    Hod, Shahar [The Ruppin Academic Center, Emeq Hefer (Israel); The Hadassah Institute, Jerusalem (Israel)

    2015-05-15

    Bekenstein has put forward the idea that, in a quantum theory of gravity, a black hole should have a discrete energy spectrum with concomitant discrete line emission. The quantized black-hole radiation spectrum is expected to be very different from Hawking's semi-classical prediction of a thermal black-hole radiation spectrum. One naturally wonders: Is it possible to reconcile the discrete quantum spectrum suggested by Bekenstein with the continuous semi-classical spectrum suggested by Hawking? In order to address this fundamental question, in this essay we shall consider the zero-point quantum-gravity fluctuations of the black-hole spacetime. In a quantum theory of gravity, these spacetime fluctuations are closely related to the characteristic gravitational resonances of the corresponding black-hole spacetime. Assuming that the energy of the black-hole radiation stems from these zero-point quantum-gravity fluctuations of the black-hole spacetime, we derive the effective temperature of the quantized black-hole radiation spectrum. Remarkably, it is shown that this characteristic temperature of the discrete (quantized) black-hole radiation agrees with the well-known Hawking temperature of the continuous (semi-classical) black-hole spectrum. (orig.)

  5. Quantum-gravity fluctuations and the black-hole temperature

    International Nuclear Information System (INIS)

    Hod, Shahar

    2015-01-01

    Bekenstein has put forward the idea that, in a quantum theory of gravity, a black hole should have a discrete energy spectrum with concomitant discrete line emission. The quantized black-hole radiation spectrum is expected to be very different from Hawking's semi-classical prediction of a thermal black-hole radiation spectrum. One naturally wonders: Is it possible to reconcile the discrete quantum spectrum suggested by Bekenstein with the continuous semi-classical spectrum suggested by Hawking? In order to address this fundamental question, in this essay we shall consider the zero-point quantum-gravity fluctuations of the black-hole spacetime. In a quantum theory of gravity, these spacetime fluctuations are closely related to the characteristic gravitational resonances of the corresponding black-hole spacetime. Assuming that the energy of the black-hole radiation stems from these zero-point quantum-gravity fluctuations of the black-hole spacetime, we derive the effective temperature of the quantized black-hole radiation spectrum. Remarkably, it is shown that this characteristic temperature of the discrete (quantized) black-hole radiation agrees with the well-known Hawking temperature of the continuous (semi-classical) black-hole spectrum. (orig.)

  6. Dyonic black hole in heterotic string theory

    International Nuclear Information System (INIS)

    Jatkar, D.P.; Mukherji, S.

    1997-01-01

    We study some features of the dyonic black hole solution in heterotic string theory on a six-torus. This solution has 58 parameters. Of these, 28 parameters denote the electric charge of the black hole, another 28 correspond to the magnetic charge, and the other two parameters are the mass and the angular momentum of the black hole. We discuss the extremal limit and show that in various limits it reduces to the known black hole solutions. The solutions saturating the Bogomolnyi bound are identified. An explicit solution is presented for the non-rotating dyonic black hole. (orig.)

  7. Quantum tunneling from three-dimensional black holes

    International Nuclear Information System (INIS)

    Ejaz, Asiya; Gohar, H.; Lin, Hai; Saifullah, K.; Yau, Shing-Tung

    2013-01-01

    We study Hawking radiation from three-dimensional black holes. For this purpose the emission of charged scalar and charged fermionic particles is investigated from charged BTZ black holes, with and without rotation. We use the quantum tunneling approach incorporating WKB approximation and spacetime symmetries. Another class of black holes which is asymptotic to a Sol three-manifold has also been investigated. This procedure gives us the tunneling probability of outgoing particles, and we compute the temperature of the radiation for these black holes. We also consider the quantum tunneling of particles from black hole asymptotic to Sol geometry

  8. Modified dispersion relations and black hole physics

    International Nuclear Information System (INIS)

    Ling Yi; Li Xiang; Hu Bo

    2006-01-01

    A modified formulation of the energy-momentum relation is proposed in the context of doubly special relativity. We investigate its impact on black hole physics. It turns out that such a modification will give corrections to both the temperature and the entropy of black holes. In particular, this modified dispersion relation also changes the picture of Hawking radiation greatly when the size of black holes approaches the Planck scale. It can prevent black holes from total evaporation, as a result providing a plausible mechanism to treat the remnant of black holes as a candidate for dark matter

  9. Black hole gravitohydromagnetics

    CERN Document Server

    Punsly, Brian

    2008-01-01

    Black hole gravitohydromagnetics (GHM) is developed from the rudiments to the frontiers of research in this book. GHM describes plasma interactions that combine the effects of gravity and a strong magnetic field, in the vicinity (ergosphere) of a rapidly rotating black hole. This topic was created in response to the astrophysical quest to understand the central engines of radio loud extragalactic radio sources. The theory describes a "torsional tug of war" between rotating ergospheric plasma and the distant asymptotic plasma that extracts the rotational inertia of the black hole. The recoil from the struggle between electromagnetic and gravitational forces near the event horizon is manifested as a powerful pair of magnetized particle beams (jets) that are ejected at nearly the speed of light. These bipolar jets feed large-scale magnetized plasmoids on scales as large as millions of light years (the radio lobes of extragalactic radio sources). This interaction can initiate jets that transport energy fluxes exc...

  10. Black hole evaporation in conformal gravity

    Energy Technology Data Exchange (ETDEWEB)

    Bambi, Cosimo; Rachwał, Lesław [Center for Field Theory and Particle Physics and Department of Physics, Fudan University, 220 Handan Road, 200433 Shanghai (China); Modesto, Leonardo [Department of Physics, Southern University of Science and Technology, 1088 Xueyuan Road, Shenzhen 518055 (China); Porey, Shiladitya, E-mail: bambi@fudan.edu.cn, E-mail: lmodesto@sustc.edu.cn, E-mail: shilp@iitk.ac.in, E-mail: rachwal@fudan.edu.cn [Department of Physics, Indian Institute of Technology, 208016 Kanpur (India)

    2017-09-01

    We study the formation and the evaporation of a spherically symmetric black hole in conformal gravity. From the collapse of a spherically symmetric thin shell of radiation, we find a singularity-free non-rotating black hole. This black hole has the same Hawking temperature as a Schwarzschild black hole with the same mass, and it completely evaporates either in a finite or in an infinite time, depending on the ensemble. We consider the analysis both in the canonical and in the micro-canonical statistical ensembles. Last, we discuss the corresponding Penrose diagram of this physical process.

  11. Black holes - a way out of the universe

    International Nuclear Information System (INIS)

    Hartvigsen, Y.

    1975-01-01

    Following a general discussion of the phenomenon of gravitational collapse and the formation of dwarf stars, neutron stars and black holes, the characteristics of black holes are discussed in more detail. The nature of a black hole in the space-time continuum of the general relativity theory is described and the 'Einstein-Rosen bridge', or 'snake-pit', is presented. The concept that matter drawn into a black hole in our universe may be emitted from a 'white hole' on the 'other side' is also presented. Evidence for the existence of black holes in the universe is discussed and the X-ray source in Cygnus X-1 is cited as a possible example. Finally the interesting possibility is mentioned that our universe itself may be a black hole, having its origin in a white hole, which mathematically could represent the 'big bang' theory. (JIW)

  12. Quantum tunneling radiation from self-dual black holes

    International Nuclear Information System (INIS)

    Silva, C.A.S.; Brito, F.A.

    2013-01-01

    Black holes are considered as objects that can reveal quantum aspects of spacetime. Loop Quantum Gravity (LQG) is a theory that propose a way to model the quantum spacetime behavior revealed by a black hole. One recent prediction of this theory is the existence of sub-Planckian black holes, which have the interesting property of self-duality. This property removes the black hole singularity and replaces it with another asymptotically flat region. In this work, we obtain the thermodynamical properties of this kind of black holes, called self-dual black holes, using the Hamilton–Jacobi version of the tunneling formalism. Moreover, using the tools of the tunneling approach, we investigate the emission spectrum of self-dual black holes, and investigate if some information about the black hole initial state can be recovered during the evaporation process. Back-reaction effects are included

  13. Black holes - a way out of the universe

    Energy Technology Data Exchange (ETDEWEB)

    Hartvigsen, Y [Oslo Univ. (Norway). Institutt for Teoretisk Fysikk

    1975-01-01

    Following a general discussion of the phenomenon of gravitational collapse and the formation of dwarf stars, neutron stars and black holes, the characteristics of black holes are discussed in more detail. The nature of a black hole in the space-time continuum of the general relativity theory is described and the 'Einstein-Rosen bridge', or 'snake-pit', is presented. The concept that matter drawn into a black hole in our universe may be emitted from a 'white hole' on the 'other side' is also presented. Evidence for the existence of black holes in the universe is discussed and the X-ray source in Cygnus X-1 is cited as a possible example. Finally the interesting possibility is mentioned that our universe itself may be a black hole, having its origin in a white hole, which mathematically could represent the 'big bang' theory.

  14. The Thermodynamic Relationship between the RN-AdS Black Holes and the RN Black Hole in Canonical Ensemble

    Directory of Open Access Journals (Sweden)

    Yu-Bo Ma

    2017-01-01

    Full Text Available In this paper, by analyzing the thermodynamic properties of charged AdS black hole and asymptotically flat space-time charged black hole in the vicinity of the critical point, we establish the correspondence between the thermodynamic parameters of asymptotically flat space-time and nonasymptotically flat space-time, based on the equality of black hole horizon area in the two different types of space-time. The relationship between the cavity radius (which is introduced in the study of asymptotically flat space-time charged black holes and the cosmological constant (which is introduced in the study of nonasymptotically flat space-time is determined. The establishment of the correspondence between the thermodynamics parameters in two different types of space-time is beneficial to the mutual promotion of different time-space black hole research, which is helpful to understand the thermodynamics and quantum properties of black hole in space-time.

  15. Fermion tunneling from higher-dimensional black holes

    International Nuclear Information System (INIS)

    Lin Kai; Yang Shuzheng

    2009-01-01

    Via the semiclassical approximation method, we study the 1/2-spin fermion tunneling from a higher-dimensional black hole. In our work, the Dirac equations are transformed into a simple form, and then we simplify the fermion tunneling research to the study of the Hamilton-Jacobi equation in curved space-time. Finally, we get the fermion tunneling rates and the Hawking temperatures at the event horizon of higher-dimensional black holes. We study fermion tunneling of a higher-dimensional Schwarzschild black hole and a higher-dimensional spherically symmetric quintessence black hole. In fact, this method is also applicable to the study of fermion tunneling from four-dimensional or lower-dimensional black holes, and we will take the rainbow-Finsler black hole as an example in order to make the fact explicit.

  16. Hawking temperature of constant curvature black holes

    International Nuclear Information System (INIS)

    Cai Ronggen; Myung, Yun Soo

    2011-01-01

    The constant curvature (CC) black holes are higher dimensional generalizations of Banados-Teitelboim-Zanelli black holes. It is known that these black holes have the unusual topology of M D-1 xS 1 , where D is the spacetime dimension and M D-1 stands for a conformal Minkowski spacetime in D-1 dimensions. The unusual topology and time-dependence for the exterior of these black holes cause some difficulties to derive their thermodynamic quantities. In this work, by using a globally embedding approach, we obtain the Hawking temperature of the CC black holes. We find that the Hawking temperature takes the same form when using both the static and global coordinates. Also, it is identical to the Gibbons-Hawking temperature of the boundary de Sitter spaces of these CC black holes.

  17. Holographic duals of Kaluza-Klein black holes

    International Nuclear Information System (INIS)

    Azeyanagi, Tatsuo; Ogawa, Noriaki; Terashima, Seiji

    2009-01-01

    We apply Brown-Henneaux's method to the 5D extremal rotating Kaluza-Klein black holes essentially following the calculation of the Kerr/CFT correspondence, which is not based on supersymmetry nor string theory. We find that there are two completely different Virasoro algebras that can be obtained as the asymptotic symmetry algebras according to appropriate boundary conditions. The microscopic entropies are calculated by using the Cardy formula for both boundary conditions and they perfectly agree with the Bekenstein-Hawking entropy. The rotating Kaluza-Klein black holes contain a 4D dyonic Reissner-Nordstroem black hole and Myers-Perry black hole. Since the D-brane configurations corresponding to these black holes are known, we expect that our analysis will shed some light on deeper understanding of chiral CFT 2 's dual to extremal black holes.

  18. Chandra Data Reveal Rapidly Whirling Black Holes

    Science.gov (United States)

    2008-01-01

    A new study using results from NASA's Chandra X-ray Observatory provides one of the best pieces of evidence yet that many supermassive black holes are spinning extremely rapidly. The whirling of these giant black holes drives powerful jets that pump huge amounts of energy into their environment and affects galaxy growth. A team of scientists compared leading theories of jets produced by rotating supermassive black holes with Chandra data. A sampling of nine giant galaxies that exhibit large disturbances in their gaseous atmospheres showed that the central black holes in these galaxies must be spinning at near their maximum rates. People Who Read This Also Read... NASA’s Swift Satellite Catches First Supernova in The Act of Exploding Black Holes Have Simple Feeding Habits Jet Power and Black Hole Assortment Revealed in New Chandra Image Erratic Black Hole Regulates Itself "We think these monster black holes are spinning close to the limit set by Einstein's theory of relativity, which means that they can drag material around them at close to the speed of light," said Rodrigo Nemmen, a visiting graduate student at Penn State University, and lead author of a paper on the new results presented at American Astronomical Society in Austin, Texas. The research reinforces other, less direct methods previously used which have indicated that some stellar and supermassive black holes are spinning rapidly. According to Einstein's theory, a rapidly spinning black hole makes space itself rotate. This effect, coupled with gas spiraling toward the black hole, can produce a rotating, tightly wound vertical tower of magnetic field that flings a large fraction of the inflowing gas away from the vicinity of the black hole in an energetic, high-speed jet. Computer simulations by other authors have suggested that black holes may acquire their rapid spins when galaxies merge, and through the accretion of gas from their surroundings. "Extremely fast spin might be very common for large

  19. Mass formula for quasi-black holes

    International Nuclear Information System (INIS)

    Lemos, Jose P. S.; Zaslavskii, Oleg B.

    2008-01-01

    A quasi-black hole, either nonextremal or extremal, can be broadly defined as the limiting configuration of a body when its boundary approaches the body's quasihorizon. We consider the mass contributions and the mass formula for a static quasi-black hole. The analysis involves careful scrutiny of the surface stresses when the limiting configuration is reached. It is shown that there exists a strict correspondence between the mass formulas for quasi-black holes and pure black holes. This perfect parallelism exists in spite of the difference in derivation and meaning of the formulas in both cases. For extremal quasi-black holes the finite surface stresses give zero contribution to the total mass. This leads to a very special version of Abraham-Lorentz electron in general relativity in which the total mass has pure electromagnetic origin in spite of the presence of bare stresses.

  20. Surface effects in black hole physics

    International Nuclear Information System (INIS)

    Damour, T.

    1982-01-01

    This contribution reviews briefly the various analogies which have been drawn between black holes and ordinary physical objects. It is shown how, by concentrating on the properties of the surface of a black hole, it is possible to set up a sequence of tight analogies allowing one to conclude that a black hole is, qualitatively and quantitatively, similar to a fluid bubble possessing a negative surface tension and endowed with finite values of the electrical conductivity and of the shear and bulk viscosities. These analogies are valid simultaneously at the levels of electromagnetic, mechanical and thermodynamical laws. Explicit applications of this framework are worked out (eddy currents, tidal drag). The thermostatic equilibrium of a black hole electrically interacting with its surroundings is discussed, as well as the validity of a minimum entropy production principle in black hole physics. (Auth.)

  1. BSW process of the slowly evaporating charged black hole

    OpenAIRE

    Wang, Liancheng; He, Feng; Fu, Xiangyun

    2015-01-01

    In this paper, we study the BSW process of the slowly evaporating charged black hole. It can be found that the BSW process will also arise near black hole horizon when the evaporation of charged black hole is very slow. But now the background black hole does not have to be an extremal black hole, and it will be approximately an extremal black hole unless it is nearly a huge stationary black hole.

  2. Visualizing, Approximating, and Understanding Black-Hole Binaries

    Science.gov (United States)

    Nichols, David A.

    Numerical-relativity simulations of black-hole binaries and advancements in gravitational-wave detectors now make it possible to learn more about the collisions of compact astrophysical bodies. To be able to infer more about the dynamical behavior of these objects requires a fuller analysis of the connection between the dynamics of pairs of black holes and their emitted gravitational waves. The chapters of this thesis describe three approaches to learn more about the relationship between the dynamics of black-hole binaries and their gravitational waves: modeling momentum flow in binaries with the Landau-Lifshitz formalism, approximating binary dynamics near the time of merger with post-Newtonian and black-hole-perturbation theories, and visualizing spacetime curvature with tidal tendexes and frame-drag vortexes. In Chapters 2--4, my collaborators and I present a method to quantify the flow of momentum in black-hole binaries using the Landau-Lifshitz formalism. Chapter 2 reviews an intuitive version of the formalism in the first-post-Newtonian approximation that bears a strong resemblance to Maxwell's theory of electromagnetism. Chapter 3 applies this approximation to relate the simultaneous bobbing motion of rotating black holes in the superkick configuration---equal-mass black holes with their spins anti-aligned and in the orbital plane---to the flow of momentum in the spacetime, prior to the black holes' merger. Chapter 4 then uses the Landau-Lifshitz formalism to explain the dynamics of a head-on merger of spinning black holes, whose spins are anti-aligned and transverse to the infalling motion. Before they merge, the black holes move with a large, transverse, velocity, which we can explain using the post-Newtonian approximation; as the holes merge and form a single black hole, we can use the Landau-Lifshitz formalism without any approximations to connect the slowing of the final black hole to its absorbing momentum density during the merger. In Chapters 5

  3. Discrete quantum spectrum of black holes

    Energy Technology Data Exchange (ETDEWEB)

    Lochan, Kinjalk, E-mail: kinjalk@iucaa.in; Chakraborty, Sumanta, E-mail: sumanta@iucaa.in

    2016-04-10

    The quantum genesis of Hawking radiation is a long-standing puzzle in black hole physics. Semi-classically one can argue that the spectrum of radiation emitted by a black hole look very much sparse unlike what is expected from a thermal object. It was demonstrated through a simple quantum model that a quantum black hole will retain a discrete profile, at least in the weak energy regime. However, it was suggested that this discreteness might be an artifact of the simplicity of eigen-spectrum of the model considered. Different quantum theories can, in principle, give rise to different complicated spectra and make the radiation from black hole dense enough in transition lines, to make them look continuous in profile. We show that such a hope from a geometry-quantized black hole is not realized as long as large enough black holes are dubbed with a classical mass area relation in any gravity theory ranging from GR, Lanczos–Lovelock to f(R) gravity. We show that the smallest frequency of emission from black hole in any quantum description, is bounded from below, to be of the order of its inverse mass. That leaves the emission with only two possibilities. It can either be non-thermal, or it can be thermal only with the temperature being much larger than 1/M.

  4. Before Inflation and after Black Holes

    Science.gov (United States)

    Stoltenberg, Henry

    This dissertation covers work from three research projects relating to the physics before the start of inflation and information after the decay of a black hole. For the first project, we analyze the cosmological role of terminal vacua in the string theory landscape, and point out that existing work on this topic makes very strong assumptions about the properties of the terminal vacua. We explore the implications of relaxing these assumptions (by including "arrival" as well as "departure" terminals) and demonstrate that the results in earlier work are highly sensitive to their assumption of no arrival terminals. We use our discussion to make some general points about tuning and initial conditions in cosmology. The second project is a discussion of the black hole information problem. Under certain conditions the black hole information puzzle and the (related) arguments that firewalls are a typical feature of black holes can break down. We first review the arguments of Almheiri, Marolf, Polchinski and Sully (AMPS) favoring firewalls, focusing on entanglements in a simple toy model for a black hole and the Hawking radiation. By introducing a large and inaccessible system entangled with the black hole (representing perhaps a de Sitter stretched horizon or inaccessible part of a landscape) we show complementarity can be restored and firewalls can be avoided throughout the black hole's evolution. Under these conditions black holes do not have an "information problem". We point out flaws in some of our earlier arguments that such entanglement might be generically present in some cosmological scenarios, and call out certain ways our picture may still be realized. The third project also examines the firewall argument. A fundamental limitation on the behavior of quantum entanglement known as "monogamy" plays a key role in the AMPS argument. Our goal is to study and apply many-body entanglement theory to consider the entanglement among different parts of Hawking radiation and

  5. Black holes in the universe

    International Nuclear Information System (INIS)

    Camenzind, M.

    2005-01-01

    While physicists have been grappling with the theory of black holes (BH), as shown by the many contributions to the Einstein year, astronomers have been successfully searching for real black holes in the Universe. Black hole astrophysics began in the 1960s with the discovery of quasars and other active galactic nuclei (AGN) in distant galaxies. Already in the 1960s it became clear that the most natural explanation for the quasar activity is the release of gravitational energy through accretion of gas onto supermassive black holes. The remnants of this activity have now been found in the centers of about 50 nearby galaxies. BH astrophysics received a new twist in the 1970s with the discovery of the X-ray binary (XRB) Cygnus X-1. The X-ray emitting compact object was too massive to be explained by a neutron star. Today, about 20 excellent BH candidates are known in XRBs. On the extragalactic scale, more than 100.000 quasars have been found in large galaxy surveys. At the redshift of the most distant ones, the Universe was younger than one billion year. The most enigmatic black hole candidates identified in the last years are the compact objects behind the Gamma-Ray Bursters. The formation of all these types of black holes is accompanied by extensive emission of gravitational waves. The detection of these strong gravity events is one of the biggest challenges for physicists in the near future. (author)

  6. Aspects of hairy black holes

    Energy Technology Data Exchange (ETDEWEB)

    Anabalón, Andrés, E-mail: andres.anabalon-at@uai.cl [Departamento de Ciencias, Facultad de Artes Liberales y Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Viña del Mar (Chile); Astefanesei, Dumitru [Instituto de Física, Pontificia Universidad Católica de Valparaíso, Casilla 4059, Valparaíso (Chile)

    2015-03-26

    We review the existence of exact hairy black holes in asymptotically flat, anti-de Sitter and de Sitter space-times. We briefly discuss the issue of stability and the charging of the black holes with a Maxwell field.

  7. Post-Kerr black hole spectroscopy

    Science.gov (United States)

    Glampedakis, Kostas; Pappas, George; Silva, Hector O.; Berti, Emanuele

    2017-09-01

    One of the central goals of the newborn field of gravitational wave astronomy is to test gravity in the highly nonlinear, strong field regime characterizing the spacetime of black holes. In particular, "black hole spectroscopy" (the observation and identification of black hole quasinormal mode frequencies in the gravitational wave signal) is expected to become one of the main tools for probing the structure and dynamics of Kerr black holes. In this paper we take a significant step toward that goal by constructing a "post-Kerr" quasinormal mode formalism. The formalism incorporates a parametrized but general perturbative deviation from the Kerr metric and exploits the well-established connection between the properties of the spacetime's circular null geodesics and the fundamental quasinormal mode to provide approximate, eikonal limit formulas for the modes' complex frequencies. The resulting algebraic toolkit can be used in waveform templates for ringing black holes with the purpose of measuring deviations from the Kerr metric. As a first illustrative application of our framework, we consider the Johannsen-Psaltis deformed Kerr metric and compute the resulting deviation in the quasinormal mode frequency relative to the known Kerr result.

  8. Noise generated by cavitating single-hole and multi-hole orifices in a water pipe

    NARCIS (Netherlands)

    Testud, P.; Moussou, P.; Hirschberg, A.; Aurégan, Y.

    2007-01-01

    This paper presents an experimental study of the acoustical effects of cavitation caused by a water flow through an orifice. A circular-centered single-hole orifice and a multi-hole orifice are tested. Experiments are performed under industrial conditions: the pressure drop across the orifice varies

  9. Nonlinear evolutions of bosonic clouds around black holes

    International Nuclear Information System (INIS)

    Okawa, Hirotada

    2015-01-01

    Black holes are a laboratory not only for testing the theory of gravity but also for exploring the properties of fundamental fields. Fundamental fields around a supermassive black hole give rise to extremely long-lived quasi-bound states which can in principle extract the energy and angular momentum from the black hole. To investigate the final state of such a system, the backreaction onto the spacetime becomes important because of the nonlinearity of the Einstein equation. In this paper, we review the numerical method to trace the evolution of massive scalar fields in the vicinity of black holes, how such a system originates from scalar clouds initially in the absence of black holes or from the capture of scalar clouds by a black hole, and the evolution of quasi-bound states around both a non-rotating black hole and a rotating black hole including the backreaction. (paper)

  10. Relativistic three-body effects in black hole coalescence

    International Nuclear Information System (INIS)

    Campanelli, Manuela; Dettwyler, Miranda; Lousto, Carlos O.; Hannam, Mark

    2006-01-01

    Three-body interactions are expected to be common in globular clusters and in galactic cores hosting supermassive black holes. We consider an equal-mass binary black hole system in the presence of a third black hole. Using numerically generated binary black hole initial data sets, and first and second-order post-Newtonian (1PN and 2PN) techniques, we find that the presence of the third black hole has non-negligible relativistic effects on the location of the binary's innermost stable circular orbit (ISCO), and that these effects arise at 2PN order. For a stellar-mass black hole binary in orbit about a supermassive black hole, the massive black hole has stabilizing effects on the orbiting binary, leading to an increase in merger time and a decrease of the terminal orbital frequency, and an amplification of the gravitational radiation emitted from the binary system by up to 6%

  11. Orbital resonances around black holes.

    Science.gov (United States)

    Brink, Jeandrew; Geyer, Marisa; Hinderer, Tanja

    2015-02-27

    We compute the length and time scales associated with resonant orbits around Kerr black holes for all orbital and spin parameters. Resonance-induced effects are potentially observable when the Event Horizon Telescope resolves the inner structure of Sgr A*, when space-based gravitational wave detectors record phase shifts in the waveform during the resonant passage of a compact object spiraling into the black hole, or in the frequencies of quasiperiodic oscillations for accreting black holes. The onset of geodesic chaos for non-Kerr spacetimes should occur at the resonance locations quantified here.

  12. Black holes and Higgs stability

    CERN Document Server

    Tetradis, Nikolaos

    2016-09-20

    We study the effect of primordial black holes on the classical rate of nucleation of AdS regions within the standard electroweak vacuum. We find that the energy barrier for transitions to the new vacuum, which characterizes the exponential suppression of the nucleation rate, can be reduced significantly in the black-hole background. A precise analysis is required in order to determine whether the the existence of primordial black holes is compatible with the form of the Higgs potential at high temperature or density in the Standard Model or its extensions.

  13. Quantum mechanics of black holes.

    Science.gov (United States)

    Witten, Edward

    2012-08-03

    The popular conception of black holes reflects the behavior of the massive black holes found by astronomers and described by classical general relativity. These objects swallow up whatever comes near and emit nothing. Physicists who have tried to understand the behavior of black holes from a quantum mechanical point of view, however, have arrived at quite a different picture. The difference is analogous to the difference between thermodynamics and statistical mechanics. The thermodynamic description is a good approximation for a macroscopic system, but statistical mechanics describes what one will see if one looks more closely.

  14. Gravitational polarizability of black holes

    International Nuclear Information System (INIS)

    Damour, Thibault; Lecian, Orchidea Maria

    2009-01-01

    The gravitational polarizability properties of black holes are compared and contrasted with their electromagnetic polarizability properties. The 'shape' or 'height' multipolar Love numbers h l of a black hole are defined and computed. They are then compared to their electromagnetic analogs h l EM . The Love numbers h l give the height of the lth multipolar 'tidal bulge' raised on the horizon of a black hole by faraway masses. We also discuss the shape of the tidal bulge raised by a test-mass m, in the limit where m gets very close to the horizon.

  15. BLACK HOLE-GALAXY CORRELATIONS WITHOUT SELF-REGULATION

    International Nuclear Information System (INIS)

    Anglés-Alcázar, Daniel; Özel, Feryal; Davé, Romeel

    2013-01-01

    Recent models of black hole growth in a cosmological context have forwarded a paradigm in which the growth is self-regulated by feedback from the black hole itself. Here we use cosmological zoom simulations of galaxy formation down to z = 2 to show that such strong self-regulation is required in the popular spherical Bondi accretion model, but that a plausible alternative model in which black hole growth is limited by galaxy-scale torques does not require self-regulation. Instead, this torque-limited accretion model yields black holes and galaxies evolving on average along the observed scaling relations by relying only on a fixed, 5% mass retention rate onto the black hole from the radius at which the accretion flow is fed. Feedback from the black hole may (and likely does) occur, but does not need to couple to galaxy-scale gas in order to regulate black hole growth. We show that this result is insensitive to variations in the initial black hole mass, stellar feedback, or other implementation details. The torque-limited model allows for high accretion rates at very early epochs (unlike the Bondi case), which if viable can help explain the rapid early growth of black holes, while by z ∼ 2 it yields Eddington factors of ∼1%-10%. This model also yields a less direct correspondence between major merger events and rapid phases of black hole growth. Instead, growth is more closely tied to cosmological disk feeding, which may help explain observational studies showing that, at least at z ∼> 1, active galaxies do not preferentially show merger signatures.

  16. Numerical analysis of drilling hole work-hardening effects in hole-drilling residual stress measurement

    Science.gov (United States)

    Li, H.; Liu, Y. H.

    2008-11-01

    The hole-drilling strain gage method is an effective semi-destructive technique for determining residual stresses in the component. As a mechanical technique, a work-hardening layer will be formed on the surface of the hole after drilling, and affect the strain relaxation. By increasing Young's modulus of the material near the hole, the work-hardening layer is simplified as a heterogeneous annulus. As an example, two finite rectangular plates submitted to different initial stresses are treated, and the relieved strains are measured by finite element simulation. The accuracy of the measurement is estimated by comparing the simulated residual stresses with the given initial ones. The results are shown for various hardness of work-hardening layer. The influence of the relative position of the gages compared with the thickness of the work-hardening layer, and the effect of the ratio of hole diameter to work-hardening layer thickness are analyzed as well.

  17. Micro black holes and the democratic transition

    International Nuclear Information System (INIS)

    Dvali, Gia; Pujolas, Oriol

    2009-01-01

    Unitarity implies that the evaporation of microscopic quasiclassical black holes cannot be universal in different particle species. This creates a puzzle, since it conflicts with the thermal nature of quasiclassical black holes, according to which all of the species should see the same horizon and be produced with the same Hawking temperatures. We resolve this puzzle by showing that for the microscopic black holes, on top of the usual quantum evaporation time, there is a new time scale which characterizes a purely classical process during which the black hole loses the ability to differentiate among the species and becomes democratic. We demonstrate this phenomenon in a well-understood framework of large extra dimensions, with a number of parallel branes. An initially nondemocratic black hole is the one localized on one of the branes, with its high-dimensional Schwarzschild radius being much shorter than the interbrane distance. Such a black hole seemingly cannot evaporate into the species localized on the other branes that are beyond its reach. We demonstrate that in reality the system evolves classically in time, in such a way that the black hole accretes the neighboring branes. The end result is a completely democratic static configuration, in which all of the branes share the same black hole and all of the species are produced with the same Hawking temperature. Thus, just like their macroscopic counterparts, the microscopic black holes are universal bridges to the hidden sector physics.

  18. When will the Antarctic Ozone Hole Recover?

    Science.gov (United States)

    Newman, Paul A.; Nash, Eric R.; Kawa, S. Randolph; Montzka, Steve

    2006-01-01

    The Antarctic ozone hole develops each year and culminates by early Spring. Antarctic ozone values have been monitored since 1979 using satellite observations from the .TOMS instrument. The severity of the hole has been assessed from TOMS using the minimum total ozone value from the October monthly mean (depth of the hole) and by calculating the average size during the September-October period. Ozone is mainly destroyed by halogen catalytic cycles, and these losses are modulated by temperature variations in the collar of the polar lower stratospheric vortex. In this presentation, we show the relationships of halogens and temperature to, both the size and depth of the hole. Because atmospheric halogen levels are responding to international agreements that limit or phase out production, the amount of halogens in the stratosphere should decrease over the next few decades. Using projections of halogen levels combined with age-of-air estimates, we find that the ozone hole is recovering at an extremely slow rate and that large ozone holes will regularly recur over the next 2 decades. The ozone hole will begin to show first signs of recovery in about 2023, and the hole will fully recover to pre-1980 levels in approximately 2070. This 2070 recovery is 20 years later than recent projections.

  19. Grumblings from an Awakening Black Hole

    Science.gov (United States)

    Kohler, Susanna

    2015-11-01

    In June of this year, after nearly three decades of sleep, the black hole V404 Cygni woke up and began grumbling. Scientists across the globe scrambled to observe the sudden flaring activity coming from this previously peaceful black hole. And now were getting the first descriptions of what weve learned from V404 Cygs awakening!Sudden OutburstV404 Cyg is a black hole of roughly nine solar masses, and its in a binary system with a low-mass star. The black hole pulls a stream of gas from the star, which then spirals in around the black hole, forming an accretion disk. Sometimes the material simply accumulates in the disk but every two or three decades, the build-up of gas suddenly rushes toward the black hole as if a dam were bursting.The sudden accretion in these events causes outbursts of activity from the black hole, its flaring easily visible to us. The last time V404 Cyg exhibited such activity was in 1989, and its been rather quiet since then. Our telescopes are of course much more powerful and sensitive now, nearly three decades later so when the black hole woke up and began flaring in June, scientists were delighted at the chance to observe it.The high variability of V404 Cyg is evident in this example set of spectra, where time increases from the bottom panel to the top. [King et al. 2015]Led by Ashley King (Einstein Fellow at Stanford University), a team of scientists observed V404 Cyg with the Chandra X-ray Observatory, obtaining spectra of the black hole during its outbursts. The black hole flared so brightly during its activity that the team had to take precautions to protect the CCDs in their detector from radiation damage! Now the group has released the first results from their analysis.Windy DiskThe primary surprise from V404 Cyg is its winds. Many stellar-mass black holes have outflows of mass, either in the form of directed jets emitted from their centers, or in the form of high-energy winds isotropically emitted from their accretion disks. But V404

  20. Black holes in Lorentz-violating gravity theories

    International Nuclear Information System (INIS)

    Barausse, Enrico; Sotiriou, Thomas P

    2013-01-01

    Lorentz symmetry and the notion of light cones play a central role in the definition of horizons and the existence of black holes. Current observations provide strong indications that astrophysical black holes do exist in Nature. Here we explore what happens to the notion of a black hole in gravity theories where local Lorentz symmetry is violated, and discuss the relevant astrophysical implications. Einstein-aether theory and Hořava gravity are used as the theoretical background for addressing this question. We review earlier results about static, spherically symmetric black holes, which demonstrate that in Lorentz-violating theories there can be a new type of horizon and, hence, a new notion of black hole. We also present both known and new results on slowly rotating black holes in these theories, which provide insights on how generic these new horizons are. Finally, we discuss the differences between black holes in Lorentz-violating theories and in General Relativity, and assess to what extent they can be probed with present and future observations. (paper)

  1. Production of spinning black holes at colliders

    International Nuclear Information System (INIS)

    Park, S. C.; Song, H. S.

    2003-01-01

    When the Planck scale is as low as TeV, there will be chances to produce Black holes at future colliders. Generally, black holes produced via particle collisions can have non-zero angular momenta. We estimate the production cross-section of rotating Black holes in the context of low energy gravitation theories by taking the effects of rotation into account. The production cross section is shown to be enhanced by a factor of 2 - 3 over the naive estimate σ = π ∼ R S 2 , where R S denotes the Schwarzschild radius of black hole for a given energy. We also point out that the decay spectrum may have a distinguishable angular dependence through the grey-body factor of a rotating black hole. The angular dependence of decaying particles may give a clear signature for the effect of rotating black holes.

  2. Thin accretion disk around regular black hole

    Directory of Open Access Journals (Sweden)

    QIU Tianqi

    2014-08-01

    Full Text Available The Penrose′s cosmic censorship conjecture says that naked singularities do not exist in nature.So,it seems reasonable to further conjecture that not even a singularity exists in nature.In this paper,a regular black hole without singularity is studied in detail,especially on its thin accretion disk,energy flux,radiation temperature and accretion efficiency.It is found that the interaction of regular black hole is stronger than that of the Schwarzschild black hole. Furthermore,the thin accretion will be more efficiency to lost energy while the mass of black hole decreased. These particular properties may be used to distinguish between black holes.

  3. Accretion and evaporation of modified Hayward black hole

    International Nuclear Information System (INIS)

    Debnath, Ujjal

    2015-01-01

    We assume the most general static spherically symmetric black hole metric. The accretion of any general kind of fluid flow around the black hole is investigated. The accretion of the fluid flow around the modified Hayward black hole is analyzed, and we then calculate the critical point, the fluid's four-velocity, and the velocity of sound during the accretion process. Also the nature of the dynamical mass of the black hole during accretion of the fluid flow, taking into consideration Hawking radiation from the black hole, i.e., evaporation of the black hole, is analyzed. (orig.)

  4. Accretion onto some well-known regular black holes

    International Nuclear Information System (INIS)

    Jawad, Abdul; Shahzad, M.U.

    2016-01-01

    In this work, we discuss the accretion onto static spherically symmetric regular black holes for specific choices of the equation of state parameter. The underlying regular black holes are charged regular black holes using the Fermi-Dirac distribution, logistic distribution, nonlinear electrodynamics, respectively, and Kehagias-Sftesos asymptotically flat regular black holes. We obtain the critical radius, critical speed, and squared sound speed during the accretion process near the regular black holes. We also study the behavior of radial velocity, energy density, and the rate of change of the mass for each of the regular black holes. (orig.)

  5. Accretion onto some well-known regular black holes

    Energy Technology Data Exchange (ETDEWEB)

    Jawad, Abdul; Shahzad, M.U. [COMSATS Institute of Information Technology, Department of Mathematics, Lahore (Pakistan)

    2016-03-15

    In this work, we discuss the accretion onto static spherically symmetric regular black holes for specific choices of the equation of state parameter. The underlying regular black holes are charged regular black holes using the Fermi-Dirac distribution, logistic distribution, nonlinear electrodynamics, respectively, and Kehagias-Sftesos asymptotically flat regular black holes. We obtain the critical radius, critical speed, and squared sound speed during the accretion process near the regular black holes. We also study the behavior of radial velocity, energy density, and the rate of change of the mass for each of the regular black holes. (orig.)

  6. Accretion onto some well-known regular black holes

    Science.gov (United States)

    Jawad, Abdul; Shahzad, M. Umair

    2016-03-01

    In this work, we discuss the accretion onto static spherically symmetric regular black holes for specific choices of the equation of state parameter. The underlying regular black holes are charged regular black holes using the Fermi-Dirac distribution, logistic distribution, nonlinear electrodynamics, respectively, and Kehagias-Sftesos asymptotically flat regular black holes. We obtain the critical radius, critical speed, and squared sound speed during the accretion process near the regular black holes. We also study the behavior of radial velocity, energy density, and the rate of change of the mass for each of the regular black holes.

  7. Ineffective higher derivative black hole hair

    Science.gov (United States)

    Goldstein, Kevin; Mashiyane, James Junior

    2018-01-01

    Inspired by the possibility that the Schwarzschild black hole may not be the unique spherically symmetric vacuum solution to generalizations of general relativity, we consider black holes in pure fourth order higher derivative gravity treated as an effective theory. Such solutions may be of interest in addressing the issue of higher derivative hair or during the later stages of black hole evaporation. Non-Schwarzschild solutions have been studied but we have put earlier results on a firmer footing by finding a systematic asymptotic expansion for the black holes and matching them with known numerical solutions obtained by integrating out from the near-horizon region. These asymptotic expansions can be cast in the form of trans-series expansions which we conjecture will be a generic feature of non-Schwarzschild higher derivative black holes. Excitingly we find a new branch of solutions with lower free energy than the Schwarzschild solution, but as found in earlier work, solutions only seem to exist for black holes with large curvatures, meaning that one should not generically neglect even higher derivative corrections. This suggests that one effectively recovers the nonhair theorems in this context.

  8. Black hole chemistry: thermodynamics with Lambda

    International Nuclear Information System (INIS)

    Kubizňák, David; Mann, Robert B; Teo, Mae

    2017-01-01

    We review recent developments on the thermodynamics of black holes in extended phase space, where the cosmological constant is interpreted as thermodynamic pressure and treated as a thermodynamic variable in its own right. In this approach, the mass of the black hole is no longer regarded as internal energy, rather it is identified with the chemical enthalpy. This leads to an extended dictionary for black hole thermodynamic quantities; in particular a notion of thermodynamic volume emerges for a given black hole spacetime. This volume is conjectured to satisfy the reverse isoperimetric inequality—an inequality imposing a bound on the amount of entropy black hole can carry for a fixed thermodynamic volume. New thermodynamic phase transitions naturally emerge from these identifications. Namely, we show that black holes can be understood from the viewpoint of chemistry, in terms of concepts such as Van der Waals fluids, reentrant phase transitions, and triple points. We also review the recent attempts at extending the AdS/CFT dictionary in this setting, discuss the connections with horizon thermodynamics, applications to Lifshitz spacetimes, and outline possible future directions in this field. (topical review)

  9. Progress towards 3D black hole merger simulations

    International Nuclear Information System (INIS)

    Seidel, E.

    2001-01-01

    I review recent progress in 3D numerical relativity, focused on simulations involving black holes evolved with singularity avoiding slicings, but also touching on recent results in advanced techniques like black hole excision. After a long series of axisymmetric and perturbative studies of distorted black holes and black hole collisions, similar studies were carried out with full 3D codes. The results showed that such black hole simulations can be carried out extremely accurately, although instabilities plague the simulation at uncomfortably early times. However, new formulations of Einstein's equations allow much more stable 3D evolutions than ever before, enabling the first studies of 3D gravitational collapse to a black hole. With these new formulations, for example, it has been possible to perform the first detailed simulations of 3D grazing collisions of black holes with unequal mass, spin, and with orbital angular momentum. I discuss the 3D black hole physics that can now be studied, and prospects for the future, which look increasingly bright due to recent progress in formulations, black hole excision, new gauge conditions, and larger computers. Simulations may soon be able to provide information about the final plunge of two black holes, of relevance for gravitational wave astronomy. (author)

  10. Charge Fluctuations of an Uncharged Black Hole

    OpenAIRE

    Schiffer, Marcelo

    2016-01-01

    In this paper we calculate charge fluctuations of a Schwarzschild black-hole of mass $M$ confined within a perfectly reflecting cavity of radius R in thermal equilibrium with various species of radiation and fermions . Charge conservation is constrained by a Lagrange multiplier (the chemical potential). Black hole charge fluctuations are expected owing to continuous absorption and emission of particles by the black hole. For black holes much more massive than $10^{16} g$ , these fluctuations ...

  11. Catastrophic Instability of Small Lovelock Black Holes

    OpenAIRE

    Takahashi, Tomohiro; Soda, Jiro

    2010-01-01

    We study the stability of static black holes in Lovelock theory which is a natural higher dimensional generalization of Einstein theory. We show that Lovelock black holes are stable under vector perturbations in all dimensions. However, we prove that small Lovelock black holes are unstable under tensor perturbations in even-dimensions and under scalar perturbations in odd-dimensions. Therefore, we can conclude that small Lovelock black holes are unstable in any dimensions. The instability is ...

  12. Magnetized black holes and nonlinear electrodynamics

    Science.gov (United States)

    Kruglov, S. I.

    2017-08-01

    A new model of nonlinear electrodynamics with two parameters is proposed. We study the phenomenon of vacuum birefringence, the causality and unitarity in this model. There is no singularity of the electric field in the center of pointlike charges and the total electrostatic energy is finite. We obtain corrections to the Coulomb law at r →∞. The weak, dominant and strong energy conditions are investigated. Magnetized charged black hole is considered and we evaluate the mass, metric function and their asymptotic at r →∞ and r → 0. The magnetic mass of the black hole is calculated. The thermodynamic properties and thermal stability of regular black holes are discussed. We calculate the Hawking temperature of black holes and show that there are first-order and second-order phase transitions. The parameters of the model when the black hole is stable are found.

  13. STU Black Holes and String Triality

    Energy Technology Data Exchange (ETDEWEB)

    Shmakova, Marina

    2003-05-23

    We found double-extreme black holes associated with the special geometry of the Calabi-Yau moduli space with the prepotential F = STU. The area formula is STU-moduli independent and has [SL(2, Z)]{sup 3} symmetry in space of charges. The dual version of this theory without prepotential treats the dilaton S asymmetric versus T,U-moduli. We display the dual relation between new (STU) black holes and stringy (S|TU) black holes using particular Sp(8,Z) transformation. The area formula of one theory equals the area formula of the dual theory when expressed in terms of dual charges. We analyze the relation between (STU) black holes to string triality of black holes: (S|TU), (T|US), (U|ST) solutions. In democratic STU-symmetric version we find that all three S and T and U duality symmetries are non-perturbative and mix electric and magnetic charges.

  14. Kerr black holes are not fragile

    Energy Technology Data Exchange (ETDEWEB)

    McInnes, Brett, E-mail: matmcinn@nus.edu.sg [Centro de Estudios Cientificos (CECs), Valdivia (Chile); National University of Singapore (Singapore)

    2012-04-21

    Certain AdS black holes are 'fragile', in the sense that, if they are deformed excessively, they become unstable to a fundamental non-perturbative stringy effect analogous to Schwinger pair-production [of branes]. Near-extremal topologically spherical AdS-Kerr black holes, which are natural candidates for string-theoretic models of the very rapidly rotating black holes that have actually been observed to exist, do represent a very drastic deformation of the AdS-Schwarzschild geometry. One therefore has strong reason to fear that these objects might be 'fragile', which in turn could mean that asymptotically flat rapidly rotating black holes might be fragile in string theory. Here we show that this does not happen: despite the severe deformation implied by near-extremal angular momenta, brane pair-production around topologically spherical AdS-Kerr-Newman black holes is always suppressed.

  15. Mass of a Black Hole Firewall

    Science.gov (United States)

    Abramowicz, M. A.; Kluźniak, W.; Lasota, J.-P.

    2014-03-01

    Quantum entanglement of Hawking radiation has been supposed to give rise to a Planck density "firewall" near the event horizon of old black holes. We show that Planck density firewalls are excluded by Einstein's equations for black holes of mass exceeding the Planck mass. We find an upper limit of 1/(8πM) to the surface density of a firewall in a Schwarzschild black hole of mass M, translating for astrophysical black holes into a firewall density smaller than the Planck density by more than 30 orders of magnitude. A strict upper limit on the firewall density is given by the Planck density times the ratio MPl/(8πM).

  16. Particle accelerators inside spinning black holes.

    Science.gov (United States)

    Lake, Kayll

    2010-05-28

    On the basis of the Kerr metric as a model for a spinning black hole accreting test particles from rest at infinity, I show that the center-of-mass energy for a pair of colliding particles is generically divergent at the inner horizon. This shows not only that classical black holes are internally unstable, but also that Planck-scale physics is a characteristic feature within black holes at scales much larger that the Planck length. The novel feature of the divergence discussed here is that the phenomenon is present only for black holes with rotation, and in this sense it is distinct from the well-known Cauchy horizon instability.

  17. New entropy formula for Kerr black holes

    Directory of Open Access Journals (Sweden)

    González Hernán A.

    2018-01-01

    Full Text Available We introduce a new entropy formula for Kerr black holes inspired by recent results for 3-dimensional black holes and cosmologies with soft Heisenberg hair. We show that also Kerr–Taub–NUT black holes obey the same formula.

  18. Expanding Thurston maps

    CERN Document Server

    Bonk, Mario

    2017-01-01

    This monograph is devoted to the study of the dynamics of expanding Thurston maps under iteration. A Thurston map is a branched covering map on a two-dimensional topological sphere such that each critical point of the map has a finite orbit under iteration. It is called expanding if, roughly speaking, preimages of a fine open cover of the underlying sphere under iterates of the map become finer and finer as the order of the iterate increases. Every expanding Thurston map gives rise to a fractal space, called its visual sphere. Many dynamical properties of the map are encoded in the geometry of this visual sphere. For example, an expanding Thurston map is topologically conjugate to a rational map if and only if its visual sphere is quasisymmetrically equivalent to the Riemann sphere. This relation between dynamics and fractal geometry is the main focus for the investigations in this work.

  19. Moulting Black Holes

    OpenAIRE

    Bena, Iosif; Chowdhury, Borun D.; de Boer, Jan; El-Showk, Sheer; Shigemori, Masaki

    2011-01-01

    We find a family of novel supersymmetric phases of the D1-D5 CFT, which in certain ranges of charges have more entropy than all known ensembles. We also find bulk BPS configurations that exist in the same range of parameters as these phases, and have more entropy than a BMPV black hole; they can be thought of as coming from a BMPV black hole shedding a "hair" condensate outside of the horizon. The entropy of the bulk configurations is smaller than that of the CFT phases, which indicates that ...

  20. Virtual Black Holes

    OpenAIRE

    Hawking, Stephen W.

    1995-01-01

    One would expect spacetime to have a foam-like structure on the Planck scale with a very high topology. If spacetime is simply connected (which is assumed in this paper), the non-trivial homology occurs in dimension two, and spacetime can be regarded as being essentially the topological sum of $S^2\\times S^2$ and $K3$ bubbles. Comparison with the instantons for pair creation of black holes shows that the $S^2\\times S^2$ bubbles can be interpreted as closed loops of virtual black holes. It is ...