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Sample records for dynamic hopkinson bar

  1. Beyond Hopkinson's bar.

    PubMed

    Pierron, F; Zhu, H; Siviour, C

    2014-08-28

    In order to perform experimental identification of high strain rate material models, engineers have only a very limited toolbox based on test procedures developed decades ago. The best example is the so-called split Hopkinson pressure bar based on the bar concept introduced 100 years ago by Bertram Hopkinson to measure blast pulses. The recent advent of full-field deformation measurements using imaging techniques has allowed novel approaches to be developed and exciting new testing procedures to be imagined for the first time. One can use this full-field information in conjunction with efficient numerical inverse identification tools such as the virtual fields method (VFM) to identify material parameters at high rates. The underpinning novelty is to exploit the inertial effects developed in high strain rate loading. This paper presents results from a new inertial impact test to obtain stress-strain curves at high strain rates (here, up to 3000 s(-1)). A quasi-isotropic composite specimen is equipped with a grid and images are recorded with the new HPV-X camera from Shimadzu at 5 Mfps and the SIMX16 camera from Specialised Imaging at 1 Mfps. Deformation, strain and acceleration fields are then input into the VFM to identify the stiffness parameters with unprecedented quality.

  2. A regularized model for impact in explicit dynamics applied to the split Hopkinson pressure bar

    NASA Astrophysics Data System (ADS)

    Otto, Peter; De Lorenzis, Laura; Unger, Jörg F.

    2016-07-01

    In the numerical simulation of impact phenomena, artificial oscillations can occur due to an instantaneous change of velocity in the contact area. In this paper, a nonlinear penalty regularization is used to avoid these oscillations. A particular focus is the investigation of higher order methods in space and time to increase the computational efficiency. The spatial discretization is realized by higher order spectral element methods that are characterized by a diagonal mass matrix. The time integration scheme is based on half-explicit Runge-Kutta scheme of fourth order. For the conditionally stable scheme, the critical time step is influenced by the penalty regularization. A framework is presented to adjust the penalty stiffness and the time step for a specific mesh to avoid oscillations. The methods presented in this paper are applied to 1D-simulations of a split Hopkinson pressure bar, which is commonly used for the investigation of materials under dynamic loading.

  3. A regularized model for impact in explicit dynamics applied to the split Hopkinson pressure bar

    NASA Astrophysics Data System (ADS)

    Otto, Peter; De Lorenzis, Laura; Unger, Jörg F.

    2016-10-01

    In the numerical simulation of impact phenomena, artificial oscillations can occur due to an instantaneous change of velocity in the contact area. In this paper, a nonlinear penalty regularization is used to avoid these oscillations. A particular focus is the investigation of higher order methods in space and time to increase the computational efficiency. The spatial discretization is realized by higher order spectral element methods that are characterized by a diagonal mass matrix. The time integration scheme is based on half-explicit Runge-Kutta scheme of fourth order. For the conditionally stable scheme, the critical time step is influenced by the penalty regularization. A framework is presented to adjust the penalty stiffness and the time step for a specific mesh to avoid oscillations. The methods presented in this paper are applied to 1D-simulations of a split Hopkinson pressure bar, which is commonly used for the investigation of materials under dynamic loading.

  4. Determination of Dynamic Compressive and Tensile Behavior of Rocks from Numerical Tests of Split Hopkinson Pressure and Tension Bars

    NASA Astrophysics Data System (ADS)

    Liao, Z. Y.; Zhu, J. B.; Xia, K. W.; Tang, C. A.

    2016-10-01

    FEM-based numerical testing systems of the split Hopkinson pressure bar (SHPB) and the split Hopkinson tensile bar (SHTB) are established to study the characteristics of rock materials under dynamic compressive and tensile loadings. First of all, the accuracy and applicability of the numerical testing system are validated and calibrated through comparison between the laboratory measurements and the simulation results. Subsequently, the dynamic behavior of rock is analyzed in detail with the numerical testing system followed by the underlying physical mechanism. For the SHPB tests, the simulation results demonstrate that the incident waveform is determined by the striker length, the striker shape and the pulse shaper. The dynamic increase factor (DIF) of the rock specimen varies with different impact velocities, which is attributed to the strain rate effect. The rock specimen size and bar size also have effects on the DIF. In addition, the interfacial friction between the rock specimen and the bars cannot be ignored. For the SHTB tests, it is found that the incident waveform is dependent on the striker tube length and the striker tube thickness. In addition, similar to the SHPB tests, the impact velocity, rock specimen size and bar size all have strong effects on the rock dynamic tensile strength.

  5. High speed synchrotron x-ray phase contrast imaging of dynamic material response to split Hopkinson bar loading

    NASA Astrophysics Data System (ADS)

    Hudspeth, M.; Claus, B.; Dubelman, S.; Black, J.; Mondal, A.; Parab, N.; Funnell, C.; Hai, F.; Qi, M. L.; Fezzaa, K.; Luo, S. N.; Chen, W.

    2013-02-01

    The successful process of amalgamating both the time-resolved imaging capabilities present at the Advanced Photon Source beamline 32ID-B and the proficiency of high-rate loading offered by the split Hopkinson or Kolsky compression/tension bar apparatus is discussed and verification of system effectiveness is expressed via dynamic experiments on various material systems. Single particle sand interaction along with glass cracking during dynamic compression, and fiber-epoxy interfacial failure, ligament-bone debonding, and single-crystal silicon fragmentation due to dynamic tension, were imaged with 0.5 μs temporal resolution and μm-level spatial resolution. Synchrotron x-ray phase contrast imaging of said material systems being loaded with the Kolsky bar apparatus demonstratively depicts the effectiveness of the novel union between these two powerful techniques, thereby allowing for in situ analysis of the interior of the material system during high-rate loading for a variety of applications.

  6. High speed synchrotron x-ray phase contrast imaging of dynamic material response to split Hopkinson bar loading

    SciTech Connect

    Hudspeth, M.; Claus, B.; Dubelman, S.; Black, J.; Mondal, A.; Parab, N.; Funnell, C.; Hai, F.; Chen, W.; Qi, M. L.; Fezzaa, K.; Luo, S. N.

    2013-02-15

    The successful process of amalgamating both the time-resolved imaging capabilities present at the Advanced Photon Source beamline 32ID-B and the proficiency of high-rate loading offered by the split Hopkinson or Kolsky compression/tension bar apparatus is discussed and verification of system effectiveness is expressed via dynamic experiments on various material systems. Single particle sand interaction along with glass cracking during dynamic compression, and fiber-epoxy interfacial failure, ligament-bone debonding, and single-crystal silicon fragmentation due to dynamic tension, were imaged with 0.5 {mu}s temporal resolution and {mu}m-level spatial resolution. Synchrotron x-ray phase contrast imaging of said material systems being loaded with the Kolsky bar apparatus demonstratively depicts the effectiveness of the novel union between these two powerful techniques, thereby allowing for in situ analysis of the interior of the material system during high-rate loading for a variety of applications.

  7. Experimental issues and interpretation of the necking phenomena in the dynamic characterization via Hopkinson bar

    NASA Astrophysics Data System (ADS)

    Mirone, Giuseppe; Corallo, Domenico

    2015-09-01

    The usual procedures for processing experimental data from Hopkinson bars (HB) are based on modeling hypotheses which, in some cases, may lead to considerable approximations. The effects of the specimen geometry and of the necking are analysed, both experimentally and by FE analyses, for assessing how much the conventional values of strain rate, strain and stress, based on strain gauges readings along the HB, are affected by approximations in different testing conditions. Also, from the way the necking affects the load/area ratio, useful considerations arise about the hardening response of metal alloys under high strain rates. The sensitivity of stress-strain curves to the time-translations of strain waves along the bars is assessed by comparing the above curves to others where the strain, the strain rate and the current cross section come from speed camera image analyses. This clearly shows that the effective strain rate in the most strained areas of the specimens is many times higher than the nominal value, and also allows to explore how much the engineering curve is poorly representative of the material response, due to strain localization in the post-necking phase. The necking-affected length compared to the total gauge length is also found to significantly influence the strain response of the specimens, in a way that can easily mislead the experimenters in the derivation of the material ductility. An empirical relationship, already found to be valid in the post-necking quasi-static regime for transforming the true stress (load / current area) into an estimation of the cross section-averaged equivalent stress, is also found to apply at high strain rates if only the appropriate considerations are done on the way the equivalent stress is considered.

  8. Blast Quantification Using Hopkinson Pressure Bars.

    PubMed

    Clarke, Samuel D; Fay, Stephen D; Rigby, Samuel E; Tyas, Andrew; Warren, James A; Reay, Jonathan J; Fuller, Benjamin J; Gant, Matthew T A; Elgy, Ian D

    2016-07-05

    Near-field blast load measurement presents an issue to many sensor types as they must endure very aggressive environments and be able to measure pressures up to many hundreds of megapascals. In this respect the simplicity of the Hopkinson pressure bar has a major advantage in that while the measurement end of the Hopkinson bar can endure and be exposed to harsh conditions, the strain gauge mounted to the bar can be affixed some distance away. This allows protective housings to be utilized which protect the strain gauge but do not interfere with the measurement acquisition. The use of an array of pressure bars allows the pressure-time histories at discrete known points to be measured. This article also describes the interpolation routine used to derive pressure-time histories at un-instrumented locations on the plane of interest. Currently the technique has been used to measure loading from high explosives in free air and buried shallowly in various soils.

  9. Split Hopkinson pressure bar technique: Experiments, analyses and applications

    NASA Astrophysics Data System (ADS)

    Gama, Bazle Anwer

    A critical review of the Hopkinson bar experimental technique is performed to identify the validity and applicability of the classic one-dimensional theory. A finite element model of the Hopkinson bar experiment is developed in three-dimensions and is used in detailed numerical analyses. For a small diameter hard specimen, the bar-specimen interfaces are non-planar, which predicts higher specimen strain and, thus, lower initial modulus in the linear elastic phase of deformation. In such cases, the stress distribution in the specimen is not uni-axial and a chamfered specimen geometry is found to provide better uni-axial stress condition in the specimen. In addition, a new Hopkinson bar with transmission tube is found suitable for small strain measurement of small diameter specimens. A one-dimensional exact Hopkinson bar theory considering the stress wave propagation in an equal diameter specimen has been formulated which predicts physically meaningful results in all extreme cases as compared to classic theory. In light of the theoretical and numerical investigations, an experimental methodology for rate dependent modulus and strength is developed. Quasi-static and dynamic behavior of plain weave (15 x 15) S-2 glass/SC15 composites has been investigated. A new circular-rectangular prism specimen (C-RPS) geometry is found suitable for testing laminated composites in the in-plane directions. Rate sensitive strength, non-linear strain and elastic modulus parameters for plain-weave (15 x 15) S-2 glass/SC15 composites have been experimentally determined.

  10. Numerical Investigation of Dynamic Rock Fracture Toughness Determination Using a Semi-Circular Bend Specimen in Split Hopkinson Pressure Bar Testing

    NASA Astrophysics Data System (ADS)

    Xu, Y.; Dai, F.; Xu, N. W.; Zhao, T.

    2016-03-01

    The International Society for Rock Mechanics (ISRM) has suggested a notched semi-circular bend technique in split Hopkinson pressure bar (SHPB) testing to determine the dynamic mode I fracture toughness of rock. Due to the transient nature of dynamic loading and limited experimental techniques, the dynamic fracture process associated with energy partitions remains far from being fully understood. In this study, the dynamic fracturing of the notched semi-circular bend rock specimen in SHPB testing is numerically simulated for the first time by the discrete element method (DEM) and evaluated in both microlevel and energy points of view. The results confirm the validity of this DEM model to reproduce the dynamic fracturing and the feasibility to simultaneously measure key dynamic rock fracture parameters, including initiation fracture toughness, fracture energy, and propagation fracture toughness. In particular, the force equilibrium of the specimen can be effectively achieved by virtue of a ramped incident pulse, and the fracture onset in the vicinity of the crack tip is found to synchronize with the peak force, both of which guarantee the quasistatic data reduction method employed to determine the dynamic fracture toughness. Moreover, the energy partition analysis indicates that simplifications, including friction energy neglect, can cause an overestimation of the propagation fracture toughness, especially under a higher loading rate.

  11. Improved specimen recovery in tensile split Hopkinson bar

    PubMed Central

    Isakov, Matti; Hiermaier, Stefan; Kuokkala, Veli-Tapani

    2014-01-01

    This paper presents an improved specimen recovery method for the tensile split Hopkinson bar (TSHB) technique. The method is based on the trapping of residual stress waves with the use of momentum trap bars. As is well known, successful momentum trapping in TSHB is highly sensitive to experimental uncertainties, especially on the incident bar side of the set-up. However, as is demonstrated in this paper, significant improvement in the reliability of specimen recovery is obtained by using two momentum trap bars in contact with the incident bar. This makes the trapping of the reflected wave insensitive to striker speed and removes the need for a precision set gap between the incident bar and the momentum trap. PMID:25071235

  12. Calibration of a Hopkinson Bar with a Transfer Standard

    DOE PAGES

    Bateman, Vesta I.; Leisher, William B.; Brown, Fred A.; Davie, Neil T.

    1993-01-01

    A program requirement for field test temperatures that are beyond the test accelerometer operational limits of −30° F and +150° F required the calibration of accelerometers at high shock levels and at the temperature extremes of −50° F and +160° F. The purposes of these calibrations were to insure that the accelerometers operated at the field test temperatures and to provide an accelerometer sensitivity at each test temperature. Because there is no National Institute of Standards and Technology traceable calibration capability at shock levels of 5,000–15,000 g for the temperature extremes of −50° F and +160° F, a method for calibrating and certifying the Hopkinson barmore » with a transfer standard was developed. Time domain and frequency domain results are given that characterize the Hopkinson bar. The National Institute of Standards and Technology traceable accuracy for the standard accelerometer in shock is ±5%. The Hopkinson bar has been certified with an uncertainty of 6%.« less

  13. Biomechanics Determination of dynamic material properties for poly(L-lactic acid)/ poly(ɛ-caprolactone) blends: Experiments and simulation using split Hopkinson pressure bars

    NASA Astrophysics Data System (ADS)

    Nishida, M.; Ito, Y.; Gustafsson, G.; Häggblad, H.-Å.; Jonsén, P.; Takayama, T.; Todo, M.

    2012-08-01

    Coefficients of Cowper-Symonds constitutive equation for PLLA/PCL = 80/20 were determined using the results of compressive tests at high and low strain rates. The simulation of split Hopkinson pressure bar using the coefficients was carried out under the same condition as the experiments. The diameter and thickness of specimens were measured by a high-speed video camera. The stress and strain histories of specimens, the thickness and the diameter in the simulations at high strain rate were compared with those in the experiments.

  14. Using the split Hopkinson pressure bar to validate material models.

    PubMed

    Church, Philip; Cornish, Rory; Cullis, Ian; Gould, Peter; Lewtas, Ian

    2014-08-28

    This paper gives a discussion of the use of the split-Hopkinson bar with particular reference to the requirements of materials modelling at QinetiQ. This is to deploy validated material models for numerical simulations that are physically based and have as little characterization overhead as possible. In order to have confidence that the models have a wide range of applicability, this means, at most, characterizing the models at low rate and then validating them at high rate. The split Hopkinson pressure bar (SHPB) is ideal for this purpose. It is also a very useful tool for analysing material behaviour under non-shock wave loading. This means understanding the output of the test and developing techniques for reliable comparison of simulations with SHPB data. For materials other than metals comparison with an output stress v strain curve is not sufficient as the assumptions built into the classical analysis are generally violated. The method described in this paper compares the simulations with as much validation data as can be derived from deployed instrumentation including the raw strain gauge data on the input and output bars, which avoids any assumptions about stress equilibrium. One has to take into account Pochhammer-Chree oscillations and their effect on the specimen and recognize that this is itself also a valuable validation test of the material model. PMID:25071238

  15. Using the split Hopkinson pressure bar to validate material models

    PubMed Central

    Church, Philip; Cornish, Rory; Cullis, Ian; Gould, Peter; Lewtas, Ian

    2014-01-01

    This paper gives a discussion of the use of the split-Hopkinson bar with particular reference to the requirements of materials modelling at QinetiQ. This is to deploy validated material models for numerical simulations that are physically based and have as little characterization overhead as possible. In order to have confidence that the models have a wide range of applicability, this means, at most, characterizing the models at low rate and then validating them at high rate. The split Hopkinson pressure bar (SHPB) is ideal for this purpose. It is also a very useful tool for analysing material behaviour under non-shock wave loading. This means understanding the output of the test and developing techniques for reliable comparison of simulations with SHPB data. For materials other than metals comparison with an output stress v strain curve is not sufficient as the assumptions built into the classical analysis are generally violated. The method described in this paper compares the simulations with as much validation data as can be derived from deployed instrumentation including the raw strain gauge data on the input and output bars, which avoids any assumptions about stress equilibrium. One has to take into account Pochhammer–Chree oscillations and their effect on the specimen and recognize that this is itself also a valuable validation test of the material model. PMID:25071238

  16. On backward dispersion correction of Hopkinson pressure bar signals

    PubMed Central

    Tyas, A.; Ozdemir, Z.

    2014-01-01

    Elastic theory shows that wide spectrum signals in the Hopkinson pressure bar suffer two forms of distortion as they propagate from the loaded bar face. These must be accounted for if accurate determination of the impact load is to be possible. The first form of distortion is the well-known phase velocity dispersion effect. The second form, which can be equally deleterious, is the prediction that at high frequencies, the stress and strain generated in the bar varies with radial position on the cross section, even for a uniformly applied loading. We consider the consequences of these effects on our ability to conduct accurate backward dispersion correction of bar signals, that is, to derive the impact face load from the dispersed signal recorded at some other point on the bar. We conclude that there is an upper limit on the frequency for which the distortion effects can be accurately compensated, and that this can significantly affect the accuracy of experimental results. We propose a combination of experimental studies and detailed numerical modelling of the impact event and wave propagation along the bar to gain better understanding of the frequency content of the impact event, and help assess the accuracy of experimental predictions of impact face load. PMID:25071236

  17. Advances in the Hopkinson bar testing of irradiated/non-irradiated nuclear materials and large specimens.

    PubMed

    Albertini, Carlo; Cadoni, Ezio; Solomos, George

    2014-05-13

    A brief review of the technological advances of the Hopkinson bar technique in tension for the study of irradiated/non-irradiated nuclear materials and the development of this technology for large specimens is presented. Comparisons are made of the dynamic behaviour of non-irradiated and irradiated materials previously subjected to creep, low cycle fatigue and irradiation (2, 10 and 30 displacements per atom). In particular, complete results of the effect of irradiation on the dynamic mechanical properties of AISI304L steel, tested at 20, 400 and 550°C are presented. These high strain rate tests have been performed with a modified Hopkinson bar (MHB), installed inside a hot cell. Examples of testing large nuclear steel specimens with a very large Hopkinson bar are also shown. The results overall demonstrate the capability of the MHB to efficiently reproduce the material stress conditions in case of accidental internal and external dynamic loadings in nuclear reactors, thus contributing to the important process of their structural assessment.

  18. Hopkinson bar techniques for the intermediate strain rate testing of bovine cortical bone

    PubMed Central

    Cloete, T. J.; Paul, G.; Ismail, E. B.

    2014-01-01

    Detailed knowledge of the dynamic viscoelastic properties of bone is required to understand the mechanisms of macroscopic bone fracture in humans, and other terrestrial mammals, during impact loading events (e.g. falls, vehicle accidents, etc.). While the dynamic response of bone has been studied for several decades, high-quality data remain limited, and it is only within the last decade that techniques for conducting dynamic compression tests on bone at near-constant strain rates have been developed. Furthermore, there appears to be a lack of published bone data in the intermediate strain rate (ISR) range (i.e. 1–100 s−1), which represents a regime in which many dynamic bone fractures occur. In this paper, preliminary results for the dynamic compression of bovine cortical bone in the ISR regime are presented. The results are obtained using two Hopkinson-bar-related techniques, namely the conventional split Hopkinson bar arrangement incorporating a novel cone-in-tube striker design, and the recently developed wedge bar apparatus. The experimental results show a rapid transition in the strain rate sensitive behaviour of bovine cortical bone in the ISR range. Finally, a new viscoelastic model is proposed that captures the observed transition behaviour. PMID:24711493

  19. The use of a beryllium Hopkinson bar to characterize a piezoresistive accelerometer in shock environments

    SciTech Connect

    Bateman, V.I.; Brown, F.A.; Davie, N.T.

    1996-03-01

    The characteristics of a piezoresistive accelerometer in shock environments are being studied at Sandia National Laboratories in the Mechanical Shock Testing Laboratory. A Hopkinson bar capability has been developed to extend our understanding of the piezoresistive accelerometer, in two mechanical configurations, in the high frequency, high shock environments where measurements are being made. In this paper, the beryllium Hopkinson bar configuration with a laser doppler vibrometer as the reference measurement is described. The in-axis performance of the piezoresistive accelerometer for frequencies of dc-50 kHz and shock magnitudes of up to 70,000 g as determined from measurements with a beryllium Hopkinson bar are presented. Preliminary results of characterizations of the accelerometers subjected to cross-axis shocks in a split beryllium Hopkinson bar configuration are presented.

  20. Split-Hopkinson Pressure Bar Tests on Pure Tantalum

    NASA Astrophysics Data System (ADS)

    Dick, Richard D.; Armstrong, Ronald W.

    1997-07-01

    Pure tantalum was loaded in compression by a split-Hopkinson pressure bar (SHPB) apparatus to strain rates from 450 to 6350 s-1. These stress-strain data were added to data collected previously to evaluate and improve the constitutive equations for tantalum(Armstrong, et al., 1997, Final report to the U.S. Army Research Laboratory, Aberdeen Proving Ground, MD.). In particular, the high strain rate data were compared to SHPB data of Armstrong, et al.(Armstrong, et al., 1997, Tantalum, Published by Minerals, Metals, and Mining Society, Warrendale, PA.) for commercially prepared tantalum. The main conclusions are: 1) the flow stress - log strain rate data agree well with the Zerilli - Armstrong constitutive model for pure tantalum, 2) uniform strain exponents computed for pure tantalum are significantly smaller than for commercial tantalum relating to the presence of impurities, 3) a plot of the uniform strain exponent versus log strain rate shows good agreement with the curve predicted by Zerilli and Armstrong at strain rates above 2000 s-1, and 4) the ductility of commercial tantalum is enhanced at high strain rates because of added dislocation generation.

  1. Two-wave photon Doppler velocimetry measurements in direct impact Hopkinson pressure bar experiments

    NASA Astrophysics Data System (ADS)

    Lea, Lewis J.; Jardine, Andrew P.

    2015-09-01

    Direct impact Hopkinson pressure bar systems offer many potential advantages over split Hopkinson pressure bars, including access to higher strain rates, higher strains for equivalent striker velocity and system length, lower dispersion and faster achievement of force equilibrium. Currently advantages are gained at a significant cost: the fact that input bar data is unavailable removes all information about the striker impacted specimen face, preventing the determination of force equilibrium, and requiring approximations to be made on the sample deformation history. Recently photon Doppler velocimetry methods have been developed, which can replace strain gauges on Hopkinson bars. In this paper we discuss an experimental method and complementary data analysis for using Doppler velocimetry to measure surface velocities of the striker and output bars in a direct impact bar experiment, allowing similar data to be recorded as in a split bar system, with the same level of convenience. We discuss extracting velocity and force measurements, and improving the accuracy and convenience of Doppler velocimetry on Hopkinson bars. Results obtained using the technique are compared to equivalent split bar tests, showing improved stress measurements for the lowest and highest strains.

  2. High Strain Rate Response Testing with the Split Hopkinson Pressure Bar Technique

    NASA Astrophysics Data System (ADS)

    Zwiessler, R.; Kenkmann, T.; Poelchau, M. H.; Nau, S.; Hess, S.

    2016-08-01

    We present a newly developed split Hopkinson pressure bar which is used to quantify the rate dependent uniaxial stress-strain response of rocks in the high strain rate regime as well as results of our first study on a sandstone and Carrara marble.

  3. Challenges in the Hydrocode Modelling of Hopkinson Bar Tests on Polymeric specimens

    NASA Astrophysics Data System (ADS)

    Cornish, Rory; Church, Phil; Gould, Peter; Camrbidge University Shock Physics Team; QinetiQ Hopkinson bar Team; QinetiQ WES Team

    2011-06-01

    QinetiQ has developed physically based material models that can predict the mechanical and failure response of polymer composites, at high and low levels of stress and strain rate. Previous experience of using the Hopkinson bar to validate such models has suggested that direct comparison with the measured wave output is preferable due to the lack of equilibrium during the test. The presence of large oscillations in the predicted stress strain results are explained in terms of Poisson's ratio. A Bancroft dispersion analysis demonstrates that the source of these oscillations is Pochhammer-Chree waves generated in the Hopkinson bars. The intermittent and rare nature of similar oscillations observed experimentally is suggested to be due to the precise conditions of impact and shape of the striker and incident bars. It is shown that by accounting for these effects and by refining the validation process, excellent levels of agreement between prediction and experiment are obtained.

  4. Application of the Split Hopkinson Resonant Bar Test for Seismic Property Characterization of Hydrate-bearing Sand Undergoing Water Saturation

    SciTech Connect

    Nakagawa, S.; Kneafsey, T.J.

    2011-05-03

    Conventional resonant bar tests allow the measurement of seismic properties of rocks and sediments at low frequencies (several kilohertz). However, the tests require a long, slender sample which is often difficult to obtain from the deep subsurface and weak and fractured formations. We present an alternative low-frequency measurement technique to the conventional resonant bar tests. This technique involves a jacketed core sample placed between a pair of long, metal extension rods with attached seismic source and receiver—the same geometry as the split Hopkinson pressure bar test for large-strain, dynamic impact experiments. Because of the added length and mass to the sample, the resonance frequency of the entire system can be lowered significantly, compared to the sample alone. The proposed “Split Hopkinson Resonant Bar (SHRB)” test is applied in two steps. In the first step, extension and torsion-mode resonance frequencies and attenuation of the system are measured. Then, numerical inversions for the compressional and shear wave velocities and attenuation are performed. We initially applied the SHRB test to synthetic materials (plastics) for testing its accuracy, then used it for measuring the seismic velocities and attenuation of a rock core containing supercritical CO{sub 2}, and a sediment core while methane hydrate formed in the pore space.

  5. Image-based stress and strain measurement of wood in the split-Hopkinson pressure bar

    NASA Astrophysics Data System (ADS)

    Moilanen, C. S.; Saarenrinne, P.; Engberg, B. A.; Björkqvist, T.

    2015-08-01

    The properties of wood must be considered when designing mechanical pulping machinery. The composition of wood within the annual ring is important. This paper proposes a novel image-based method to measure stress and planar strain distribution in soft, heterogeneous materials. The main advantage of this method in comparison to traditional methods that are based on strain gauges is that it captures local strain gradients and not only average strains. Wood samples were subjected to compression at strain rates of 1000-2500 s-1 in an encapsulated split-Hopkinson device. High-speed photography captured images at 50 000-100 000 Hz and different magnifications to achieve spatial resolutions of 2.9 to 9.7 µm pixels-1. The image-based analysis utilized an image correlation technique with a method that was developed for particle image velocimetry. The image analysis gave local strain distribution and average stress as a function of time. Two stress approximations, using the material properties of the split-Hopkinson bars and the displacement of the transmitter bar/sample interface, are presented. Strain gauges on the bars of the split-Hopkinson device give the reference average stress and strain. The most accurate image-based stress approximation differed from the strain gauge result by 5%.

  6. Application of photon Doppler velocimetry to direct impact Hopkinson pressure bars.

    PubMed

    Lea, Lewis J; Jardine, Andrew P

    2016-02-01

    Direct impact Hopkinson pressure bar systems offer many potential advantages over split Hopkinson pressure bars, including access to higher strain rates, higher strains for equivalent striker velocity and system length, lower dispersion, and faster achievement of force equilibrium. Currently, these advantages are gained at the expense of all information about the striker impacted specimen face, preventing the experimental determination of force equilibrium, and requiring approximations to be made on the sample deformation history. In this paper, we discuss an experimental method and complementary data analysis for using photon Doppler velocimetry to measure surface velocities of the striker and output bars in a direct impact bar experiment, allowing similar data to be recorded as in a split bar system. We discuss extracting velocity and force measurements, and the precision of measurements. Results obtained using the technique are compared to equivalent split bar tests, showing improved stress measurements for the lowest and highest strains in fully dense metals, and improvement for all strains in slow and non-equilibrating materials.

  7. Evaluation of a Hopkinson bar fly-away technique for high amplitude shock accelerometer calibration

    SciTech Connect

    Togami, T.C.; Bateman, V.I.; Brown, F.A.

    1997-11-01

    A split Hopkinson bar technique has been developed to evaluate the performance of accelerometers that measure large amplitude pulses. An evaluation of this technique has been conducted in the Mechanical Shock Laboratory at Sandia National Laboratories (SNL) to determine its use in the practical calibration of accelerometers. This evaluation consisted of three tasks. First, the quartz crystal was evaluated in a split Hopkinson bar configuration to evaluate the quartz gage`s sensitivity and frequency response at force levels of 18,000, 35,000 and 53,000 N at ambient temperature, {minus}48 C and +74 C. Secondly, the fly away technique was evaluated at shock amplitudes of 50,000, 100,000, 150,000 and 200,000 G (1 G = 9.81 m/s{sup 2}) at ambient temperature, {minus}48 C and +74 C. Lastly, the technique was performed using a NIST calibrated reference accelerometer. Comparisons of accelerations calculated from the quartz gage data and the measured acceleration data have shown very good agreement. Based on this evaluation, the authors expect this split Hopkinson fly away technique to be certified by the SNL Primary Standards Laboratory.

  8. High Strain Rate Characterization of Plastics and Foams Using Polymeric Split Hopkinson Bar

    NASA Astrophysics Data System (ADS)

    Sawas, Omar; Brar, N. S.

    1997-07-01

    High strain rate and high/low temperature response of engineered plastics and foams is relevant and important for the design and development of fighter aircraft canopies, submarine interiors and automobile exterior and interior systems. The mechanical impedance of conventional split Hopkinson bar materials (aluminum or steel) is extremely large compared to those of plastic or foam specimens. To overcome this difficulty of impedance mismatch we have developed the Polymeric Split Hopkinson Bar (PSHB). A viscoelastic model for cast acrylic bar material, which relates stresses and strains as well as particle velocity and strain, is developed to account for the wave dispersion along the bar. The model is verified by comparing the stress strain data on 1100 aluminum and polycarbonate specimens obtained using PSHB and conventional aluminum SHB. Stress-strain data at a strain rate of 103/s on low strength polyurethane foam (density = 0.57 g/cm3) following this technique show that the foam has a recoverable compressive strain of 0.4 at a stress of 2.9 MPa. High strain rate (2x102-2x103/s) data on polycarbonate, generic elastomer, and styrofoam will also be presented.

  9. Experimental and numerical investigations on the use of polymer Hopkinson pressure bars.

    PubMed

    Harrigan, John J; Ahonsi, Bright; Palamidi, Elisavet; Reid, Steve R

    2014-08-28

    Split Hopkinson pressure bar (SHPB) testing has traditionally been carried out using metal bars. For testing low stiffness materials such as rubbers or low strength materials such as low density cellular solids considered primarily herein, there are many advantages to replacing the metal bars with polymer bars. An investigation of a number of aspects associated with the accuracy of SHPB testing of these materials is reported. Test data are used to provide qualitative comparisons of accuracy using different bar materials and wave-separation techniques. Sample results from SHPB tests are provided for balsa, Rohacell foam and hydroxyl-terminated polybutadiene. The techniques used are verified by finite-element (FE) analysis. Experimentally, the material properties of the bars are determined from impact tests in the form of a complex elastic modulus without curve fitting to a rheological model. For the simulations, a rheological model is used to define the bar properties by curve fitting to the experimentally derived properties. Wave propagation in a polymer bar owing to axial impact of a steel bearing ball is simulated. The results indicate that the strain histories can be used to determine accurately the viscoelastic properties of polymer bars. An FE model of the full viscoelastic SHPB set-up is then used to simulate tests on hyperelastic materials.

  10. Experimental and numerical investigations on the use of polymer Hopkinson pressure bars.

    PubMed

    Harrigan, John J; Ahonsi, Bright; Palamidi, Elisavet; Reid, Steve R

    2014-08-28

    Split Hopkinson pressure bar (SHPB) testing has traditionally been carried out using metal bars. For testing low stiffness materials such as rubbers or low strength materials such as low density cellular solids considered primarily herein, there are many advantages to replacing the metal bars with polymer bars. An investigation of a number of aspects associated with the accuracy of SHPB testing of these materials is reported. Test data are used to provide qualitative comparisons of accuracy using different bar materials and wave-separation techniques. Sample results from SHPB tests are provided for balsa, Rohacell foam and hydroxyl-terminated polybutadiene. The techniques used are verified by finite-element (FE) analysis. Experimentally, the material properties of the bars are determined from impact tests in the form of a complex elastic modulus without curve fitting to a rheological model. For the simulations, a rheological model is used to define the bar properties by curve fitting to the experimentally derived properties. Wave propagation in a polymer bar owing to axial impact of a steel bearing ball is simulated. The results indicate that the strain histories can be used to determine accurately the viscoelastic properties of polymer bars. An FE model of the full viscoelastic SHPB set-up is then used to simulate tests on hyperelastic materials. PMID:25071237

  11. Split Hopkinson Resonant Bar Test for Sonic-Frequency Acoustic Velocity and Attenuation Measurements of Small, Isotropic Geologic Samples

    SciTech Connect

    Nakagawa, S.

    2011-04-01

    Mechanical properties (seismic velocities and attenuation) of geological materials are often frequency dependent, which necessitates measurements of the properties at frequencies relevant to a problem at hand. Conventional acoustic resonant bar tests allow measuring seismic properties of rocks and sediments at sonic frequencies (several kilohertz) that are close to the frequencies employed for geophysical exploration of oil and gas resources. However, the tests require a long, slender sample, which is often difficult to obtain from the deep subsurface or from weak and fractured geological formations. In this paper, an alternative measurement technique to conventional resonant bar tests is presented. This technique uses only a small, jacketed rock or sediment core sample mediating a pair of long, metal extension bars with attached seismic source and receiver - the same geometry as the split Hopkinson pressure bar test for large-strain, dynamic impact experiments. Because of the length and mass added to the sample, the resonance frequency of the entire system can be lowered significantly, compared to the sample alone. The experiment can be conducted under elevated confining pressures up to tens of MPa and temperatures above 100 C, and concurrently with x-ray CT imaging. The described Split Hopkinson Resonant Bar (SHRB) test is applied in two steps. First, extension and torsion-mode resonance frequencies and attenuation of the entire system are measured. Next, numerical inversions for the complex Young's and shear moduli of the sample are performed. One particularly important step is the correction of the inverted Young's moduli for the effect of sample-rod interfaces. Examples of the application are given for homogeneous, isotropic polymer samples and a natural rock sample.

  12. High Strain Rate Testing of Rocks using a Split-Hopkinson-Pressure Bar

    NASA Astrophysics Data System (ADS)

    Zwiessler, Ruprecht; Kenkmann, Thomas; Poelchau, Michael; Nau, Siegfried; Hess, Sebastian

    2016-04-01

    Dynamic mechanical testing of rocks is important to define the onset of rate dependency of brittle failure. The strain rate dependency occurs through the propagation velocity limit (Rayleigh wave speed) of cracks and their reduced ability to coalesce, which, in turn, significantly increases the strength of the rock. We use a newly developed pressurized air driven Split-Hopkinson-Pressure Bar (SHPB), that is specifically designed for the investigation of high strain rate testing of rocks, consisting of several 10 to 50 cm long strikers and bar components of 50 mm in diameter and 2.5 meters in length each. The whole set up, composed of striker, incident- and transmission bar is available in aluminum, titanium and maraging steel to minimize the acoustic impedance contrast, determined by the change of density and speed of sound, to the specific rock of investigation. Dynamic mechanical parameters are obtained in compression as well as in spallation configuration, covering a wide spectrum from intermediate to high strain rates (100-103 s-1). In SHPB experiments [1] one-dimensional longitudinal compressive pulses of diverse shapes and lengths - formed with pulse shapers - are used to generate a variety of loading histories under 1D states of stress in cylindrical rock samples, in order to measure the respective stress-strain response at specific strain rates. Subsequent microstructural analysis of the deformed samples is aimed at quantification fracture orientation, fracture pattern, fracture density, and fracture surface properties as a function of the loading rate. Linking mechanical and microstructural data to natural dynamic deformation processes has relevance for the understanding of earthquakes, landslides, impacts, and has several rock engineering applications. For instance, experiments on dynamic fragmentation help to unravel super-shear rupture events that pervasively pulverize rocks up to several hundred meters from the fault core [2, 3, 4]. The dynamic, strain

  13. High Strain Rate Testing of Rocks using a Split-Hopkinson-Pressure Bar

    NASA Astrophysics Data System (ADS)

    Zwiessler, Ruprecht; Kenkmann, Thomas; Poelchau, Michael; Nau, Siegfried; Hess, Sebastian

    2016-04-01

    Dynamic mechanical testing of rocks is important to define the onset of rate dependency of brittle failure. The strain rate dependency occurs through the propagation velocity limit (Rayleigh wave speed) of cracks and their reduced ability to coalesce, which, in turn, significantly increases the strength of the rock. We use a newly developed pressurized air driven Split-Hopkinson-Pressure Bar (SHPB), that is specifically designed for the investigation of high strain rate testing of rocks, consisting of several 10 to 50 cm long strikers and bar components of 50 mm in diameter and 2.5 meters in length each. The whole set up, composed of striker, incident- and transmission bar is available in aluminum, titanium and maraging steel to minimize the acoustic impedance contrast, determined by the change of density and speed of sound, to the specific rock of investigation. Dynamic mechanical parameters are obtained in compression as well as in spallation configuration, covering a wide spectrum from intermediate to high strain rates (100-103 s‑1). In SHPB experiments [1] one-dimensional longitudinal compressive pulses of diverse shapes and lengths - formed with pulse shapers - are used to generate a variety of loading histories under 1D states of stress in cylindrical rock samples, in order to measure the respective stress-strain response at specific strain rates. Subsequent microstructural analysis of the deformed samples is aimed at quantification fracture orientation, fracture pattern, fracture density, and fracture surface properties as a function of the loading rate. Linking mechanical and microstructural data to natural dynamic deformation processes has relevance for the understanding of earthquakes, landslides, impacts, and has several rock engineering applications. For instance, experiments on dynamic fragmentation help to unravel super-shear rupture events that pervasively pulverize rocks up to several hundred meters from the fault core [2, 3, 4]. The dynamic

  14. A new Hopkinson bar method to investigate the compacting behaviour of fresh concrete

    NASA Astrophysics Data System (ADS)

    Pattofatto, S.; Zhao, H.; Poitou, A.

    2006-08-01

    A new experimental test, based on the Hopkinson bar measurement technique is used in order to analyze the compaction process of a fresh concrete under successive impacts. The use of this modified Hopkinson bar technique allows for the measurement of the compacting stresses during one impact. In fact, the measurement device allows to measure the stress/time response of the material during each shock independently. In particular, the study is focused on the analysis of the stress/time curve during the first shock on the freshly-mixed concrete specimen. It happens that the stress response exhibits the occurrence of the equivalent of a phase change for the granular material. It is therefore possible to measure at what moment this phenomenon happens. Then, we show that, considering a model of shock front for the propagation of the compacting wave, the phase change occurs at a density that depends on the impact velocity. The results shows that the increase of the impact velocity leads to an increase of the phase change density.

  15. Copper damage modeling with the tensile hopkinson bar and gas gun

    SciTech Connect

    Tonks, D. L.; Thissell, W. R.; Trujillo, C. P.; Schwartz, D. S.

    2004-01-01

    Ductile damage nucleation in recovered copper tensile Hopkinson bar specimens has been modeled using the 2D EPIC code. The model has also been successfully applied to spallation gas gun data to greatly expand the pressure range. The split tensile Hopkinson pressure bar permits the creation of damage at fairly high strain rates (10{sup 4}/s) with large plastic strains (100%). Careful momentum trapping allows incipient damage states to be arrested and recovered for metallurgical examination. The use of notched samples allows the pressure - flow stress, or triaxiality, to be varied from 1/3 to about 1.2 to study the interplay of pressure and deviatoric stress. In this paper, we will concentrate on modeling the nucleation of ductile damage in pure copper (Hitachi). With the same material, we also study spallation in a gas gun experiment to obtain the nucleation stress under high pressure and small plastic strain. The goal of the modeling is to obtain a unified nucleation model suitable for both.

  16. Resolving Mechanical Response of Plastic Bonded Explosives at High Strain-Rate Using Split Hopkinson Pressure Bar

    NASA Astrophysics Data System (ADS)

    Joshi, Vasant S.; Lee, Richard J.

    2002-07-01

    The mechanical properties of two explosives (PBXN-110 and PBXW-128) were determined using a split-Hopkinson pressure bar at strain rates between 103 /s and 104 /s. The stress-strain data for 1, 2 and 3-wave analysis were compared to determine when stress equalization was achieved in the test samples. PBXN-110 behaved similar to conventional Hopkinson bar samples, i.e., stress equalization was maintained for most of the loading cycle. Stress equalization was not achieved until late in the loading cycle for PBXW-128. This behavior eventually terminates during the compression process yielding a uniform response.

  17. A modified Hopkinson pressure bar experiment to evaluate a damped piezoresistive MEMS accelerometer.

    SciTech Connect

    Frew, Danny Joe; Duong, Henry

    2009-03-01

    We conducted a series of modified Hopkinson pressure bar (HPB) experiments to evaluate a new, damped, high-shock accelerometer that has recently been developed by PCB Piezotronics Inc. Pulse shapers were used to create a long duration, non-dispersive stress pulse in an aluminum bar that interacted with a tungsten disk at the end of the incident bar. We measured stress at the aluminum bar-disk interface with a quartz gage and measured acceleration at the free-end of the disk with an Endevco brand 7270A and the new PCB 3991 accelerometers. The rise-time of the incident stress pulse in the aluminum bar was long enough and the disk length short enough so that the response of the disk can be approximated closely as rigid-body motion; an experimentally verified analytical model has been shown previously to support this assumption. Since the cross-sectional area and mass of the disk were known, we calculated acceleration of the rigid-disk from the quartz-gage force measurement and Newton's Second Law of Motion. Comparisons of accelerations calculated from the quartz-gage data and measured acceleration data show excellent agreement for acceleration pulses with the PCB accelerometer for peak amplitudes between 4,000 and 40,000 Gs , rise times as short as 40 microsec, and pulse durations between 150 and 320 microsec.

  18. The Use of a Beryllium Hopkinson Bar to Characterize In-Axis and Cross-Axis Accelerometer Response in Shock Environments

    SciTech Connect

    Bateman, V.I.; Brown, F.A.

    1999-01-01

    The characteristics of a piezoresistive accelerometer in shock environments have been studied at Sandia National Laboratories in the Mechanical Shock Laboratory. A beryllium Hopkinson bar capability with diameters of 0.75 in. and 2.0 in has been developed to extend our understanding of the piezoresistive accelerometer, in two mechanical configurations, in the high frequency, high shock environments where measurements are being made. The in-axis performance of the piezoresistive accelerometer determined from measurements with a beryllium Hopkinson bar and a certified laser doppler vibrometer as the reference measurement is presented. The cross-axis performance of the accelerometer subjected to static compression on a beryllium cylinder, static strain on a steel beam, dynamic strain on a steel beam (ISA-RP 37.2, Paragraph 6.6), and compressive shocks in a split beryllium Hopkinson bar configuration is also presented. The performance of the accelerometer in a combined in-axis and cross-axis shock environment is shown for one configuration. Finally, a failure analysis conducted in cooperation with ENDEVCO gives a cause for the occasional unexplained failures that have occurred in some applications.

  19. Split Hopkinson bar measurement using high-speed full-spectrum fiber Bragg grating interrogation.

    PubMed

    Seng, Frederick; Hackney, Drew; Goode, Tyler; Shumway, LeGrand; Hammond, Alec; Shoemaker, George; Pankow, Mark; Peters, Kara; Schultz, Stephen

    2016-09-01

    The development and validation of a high-speed, full-spectrum measurement technique is described for fiber Bragg grating (FBG) sensors. A FBG is surface-mounted to a split-Hopkinson tensile bar specimen to induce high strain rates. The high strain gradients and large strains that indicate material failure are analyzed under high strain rates up to 500  s-1. The FBG is interrogated using a high-speed full-spectrum solid-state interrogator with a repetition rate of 100 kHz. The captured deformed spectra are analyzed for strain gradients using a default interior point algorithm in combination with the modified transfer matrix approach. This paper shows that by using high-speed full-spectrum interrogation of an FBG and the modified transfer matrix method, highly localized strain gradients and discontinuities can be measured without a direct line of sight.

  20. Split Hopkinson bar measurement using high-speed full-spectrum fiber Bragg grating interrogation.

    PubMed

    Seng, Frederick; Hackney, Drew; Goode, Tyler; Shumway, LeGrand; Hammond, Alec; Shoemaker, George; Pankow, Mark; Peters, Kara; Schultz, Stephen

    2016-09-01

    The development and validation of a high-speed, full-spectrum measurement technique is described for fiber Bragg grating (FBG) sensors. A FBG is surface-mounted to a split-Hopkinson tensile bar specimen to induce high strain rates. The high strain gradients and large strains that indicate material failure are analyzed under high strain rates up to 500  s-1. The FBG is interrogated using a high-speed full-spectrum solid-state interrogator with a repetition rate of 100 kHz. The captured deformed spectra are analyzed for strain gradients using a default interior point algorithm in combination with the modified transfer matrix approach. This paper shows that by using high-speed full-spectrum interrogation of an FBG and the modified transfer matrix method, highly localized strain gradients and discontinuities can be measured without a direct line of sight. PMID:27607299

  1. Strain localization during tensile Hopkinson bar testing of commercially pure titanium and Ti6Al4V titanium alloy

    NASA Astrophysics Data System (ADS)

    Moćko, Wojciech; Kruszka, Leopold; Brodecki, Adam

    2015-09-01

    The goal of the analysis was to determine the strain localization for various specimen shapes (type A and type B according to PN-EN ISO 26203-1 standard) and different loading conditions, i.e. quasi- static and dynamic. Commercially pure titanium (Grade 2) and titanium alloy Ti6Al4V (Grade 5) were selected for the tests. Tensile loadings were applied out using servo-hydraulic testing machine and tensile Hopkinson bar with pre-tension. The results were recorded using ARAMIS system cameras and fast camera Phantom V1210, respectively at quasi-static and dynamic loading conditions. Further, specimens outline was determined on the basis of video data using TEMA MOTION software. The strain distribution on the specimen surface was estimated using digital image correlation method. The larger radius present in the specimen of type B in comparison to specimen of type A, results in slight increase of the elongation for commercially pure titanium at both quasi-static and dynamic loading conditions. However this effect disappears for Ti6Al4V alloy. The increase of the elongation corresponds to the stronger necking effect. Material softening due to increase of temperature induced by plastic work was observed at dynamic loading conditions. Moreover lower elongation at fracture point was found at high strain rates for both materials.

  2. Recent Developments In Shear Ignition Of Energetic Materials Using Hybrid Drop Weight-Hopkinson Bar

    NASA Astrophysics Data System (ADS)

    Joshi, Vasant

    2007-06-01

    The sensitivity and mechanical behavior and of energetic material is highly dependent on its constituents. Cast as well as cured (like PBX) types of explosives have mechanical properties significantly different from metals and the assumption of isotropic behavior may not be valid beyond a finite strain. While Split Hopkinson Pressure Bar (SHPB) can be successfully used to obtain mechanical properties of these soft explosives at strain rates up to 5,000/sec, ignition conditions are seldom achieved in SHPB tests. In very sensitive explosives, if ignition occurs in very small sample at extremely high strain rates, it would be very difficult to calculate the energy and energy rate that led to successful ignition. In contrast to the SHPB test, the drop-weight test, uses gravitational acceleration to impart a nearly constant velocity at the instant of impact. The Drop weight test is intended to obtain ignition, only as a go-no go condition, due to the variation of velocity, either due to change in the initial height or small changes in friction or drag. Due to lack of quantifiable parameters, the result from this test is not suitable for modeling, which is important in development of new explosive formulation. In order to overcome this barrier and allow evaluation of the susceptibility of the different formulations to ignition, a new test was recently developed. This test is called Hybrid Hopkinson Bar Drop Weight test, which overcomes shortcomings of two systems. When an explosive sample is compressed between two rigid flat surfaces and the material freely slides on the rigid plates without pinning, the mechanical energy is uniformly dissipated throughout the sample. In absence of any pressure gradient, pure-shear conditions apply throughout the sample. The ignition in this case, will not be localized at the edges, which is the basis for obtaining ignition condition in the new apparatus. Using this method, hydroxy-terminated poly butadiene (HTPB) bonded explosives, PBXN

  3. The use of a beryllium Hopkinson bar to characterize in-axis and cross-axis accelerometer response in shock environments

    SciTech Connect

    Bateman, V.I.; Brown, F.A.

    1997-05-01

    The characteristics of a piezoresistive accelerometer in shock environments are being studied at Sandia National Laboratories in the Mechanical Shock Testing Laboratory. A beryllium Hopkinson bar capability has been developed to extend the understanding of the piezoresistive accelerometer, in two mechanical configurations and with and without mechanical isolation, in the high frequency, high shock environments where measurements are being made. In this paper, recent measurements with beryllium single and split-Hopkinson bar configurations are described. The in axis performance of the piezoresistive accelerometer in mechanical isolation for frequencies of dc-30 kHz and shock magnitudes of up to 6,000 g as determined from measurements with a beryllium Hopkinson bar with a certified laser doppler vibrometer as the reference measurement are presented. Results of characterizations of the accelerometers subjected to cross axis shocks in a split beryllium Hopkinson bar configuration are also presented.

  4. Characterization and modeling of mechanical behavior of single crystal titanium deformed by split-Hopkinson pressure bar

    DOE PAGES

    Morrow, B. M.; Lebensohn, R. A.; Trujillo, C. P.; Martinez, D. T.; Addessio, F. L.; Bronkhorst, C. A.; Lookman, T.; Cerreta, E. K.

    2016-03-28

    Single crystal titanium samples were dynamically loaded using split-Hopkinson pressure bar (SHPB) and the resulting microstructures were examined. Characterization of the twins and dislocations present in the microstructure was conducted to understand the pathway for observed mechanical behavior. Electron backscatter diffraction (EBSD) was used to measure textures and quantify twinning. Microstructures were profusely twinned after loading, and twin variants and corresponding textures were different as a function of initial orientation. Focused ion beam (FIB) foils were created to analyze dislocation content using transmission electron microscopy (TEM). Large amounts of dislocations were present, indicating that plasticity was achieved through slip andmore » twinning together. Viscoplastic self-consistent (VPSC) modeling was used to confirm the complex order of operations during deformation. The activation of different mechanisms was highly dependent upon crystal orientation. For [0001] and View the MathML source[101¯1]-oriented crystals, compressive twinning was observed, followed by secondary tensile twinning. Furthermore, dislocations though prevalent in the microstructure, contributed to final texture far less than twinning.« less

  5. High-strain rate tensile characterization of graphite platelet reinforced vinyl ester based nanocomposites using split-Hopkinson pressure bar

    NASA Astrophysics Data System (ADS)

    Pramanik, Brahmananda

    The dynamic response of exfoliated graphite nanoplatelet (xGnP) reinforced and carboxyl terminated butadiene nitrile (CTBN) toughened vinyl ester based nanocomposites are characterized under both dynamic tensile and compressive loading. Dynamic direct tensile tests are performed applying the reverse impact Split Hopkinson Pressure Bar (SHPB) technique. The specimen geometry for tensile test is parametrically optimized by Finite Element Analysis (FEA) using ANSYS Mechanical APDLRTM. Uniform stress distribution within the specimen gage length has been verified using high-speed digital photography. The on-specimen strain gage installation is substituted by a non-contact Laser Occlusion Expansion Gage (LOEG) technique for infinitesimal dynamic tensile strain measurements. Due to very low transmitted pulse signal, an alternative approach based on incident pulse is applied for obtaining the stress-time history. Indirect tensile tests are also performed combining the conventional SHPB technique with Brazilian disk test method for evaluating cylindrical disk specimens. The cylindrical disk specimen is held snugly in between two concave end fixtures attached to the incident and transmission bars. Indirect tensile stress is estimated from the SHPB pulses, and diametrical transverse tensile strain is measured using LOEG. Failure diagnosis using high-speed digital photography validates the viability of utilizing this indirect test method for characterizing the tensile properties of the candidate vinyl ester based nanocomposite system. Also, quasi-static indirect tensile response agrees with previous investigations conducted using the traditional dog-bone specimen in quasi-static direct tensile tests. Investigation of both quasi-static and dynamic indirect tensile test responses show the strain rate effect on the tensile strength and energy absorbing capacity of the candidate materials. Finally, the conventional compressive SHPB tests are performed. It is observed that both

  6. A modified split Hopkinson torsional bar system for correlated study of τ–γ relations, shear localization and microstructural evolution

    PubMed Central

    Yang, Rong; Zhang, Husheng; Shen, Letian; Xu, Yongbo; Bai, Yilong; Dodd, Bradley

    2014-01-01

    The conventional split Hopkinson torsional bar (SHTB) system consists of two bars, which can successfully produce the data for the construction of dynamic torsional shear stress and strain relationships. However, the system cannot provide reliable information on the progression of the deformed micro-structure during the test. The reverberation of waves in the bars and the tested specimen can spoil the microstructural pattern formed during the effective loading. This paper briefly reviews a modified version of the SHTB system consisting of four bars that has been developed. This modified system can eliminate the reverberation of waves in the specimen and provide only a single rectangular torsional stress pulse, thus it can properly freeze the microstructure formed during the effective period of loading in the specimen. By using the advantage of the modified SHTB system, together with a new design of specimen, it is possible to perform a correlated study of the dynamic stress–strain response, shear localization and the evolution of the microstructure at a fixed view-field (position) on a given specimen during the sequence of the loading time. The principles, experimental set-up and procedure, calibration and some preliminary results of the correlated study are reported in this paper. PMID:24711492

  7. Geomechanics of penetration :laboratory analog experiments using a modified split hopkinson pressure bar/impact testing procedure.

    SciTech Connect

    Holcomb, David Joseph; Gettemy, Glen L.; Bronowski, David R.

    2005-11-01

    This research continues previous efforts to re-focus the question of penetrability away from the behavior of the penetrator itself and toward understanding the dynamic, possibly strain-rate dependent, behavior of the affected materials. A modified split Hopkinson pressure bar technique is prototyped to determine the value of reproducing the stress states, and mechanical responses, of geomaterials observed in actual penetrator tests within a laboratory setting. Conceptually, this technique simulates the passage of the penetrator surface past any fixed point in the penetrator trajectory by allowing for a controlled stress-time function to be transmitted into a sample, thereby mimicking the 1D radial projection inherent to analyses of the cavity expansion problem. Test results from a suite of weak (unconfined compressive strength, or UCS, of 22 MPa) concrete samples, with incident strain rates of 100-250 s{sup -1}, show that the complex mechanical response includes both plastic and anelastic wave propagation, and is critically dependent on incident particle velocity and saturation state. For instance, examination of the transmitted stress-time data, and post-test volumetric measurements of pulverized material, provide independent estimates of the plasticized zone length (1-2 cm) formed for incident particle velocity of {approx}16.7 m/s. The results also shed light on the elastic or energy propagation property changes that occur in the concrete. For example, the pre- and post-test zero-stress elastic wave propagation velocities show that the Young's modulus drops from {approx}19 GPa to <8 GPa for material within the first centimeter from the plastic transition front, while the Young's modulus of the dynamically confined, axially-stressed (in 6-18 MPa range) plasticized material drops to 0.5-0.6 GPa. The data also suggest that the critical particle velocity for formation of a plastic zone in the weak concrete is 13-15 m/s, with increased saturation tending to increase

  8. Dynamical mechanisms supporting barred-spiral structures

    NASA Astrophysics Data System (ADS)

    Patsis, P. A.

    We review some recent results of the orbital theory, related with the dynamics of barred-spiral galaxies. The method we use is to study the responses of stellar and gaseous disks when time-independent, external potentials are imposed. These potentials are directly estimated from near-infrared images of disk galaxies. The goal of the work is to detect dynamical mechanisms that reinforce the bars and the spirals in realistic systems. Besides the known mechanism for building bars by quasiperiodic orbits trapped around stable orbits of the {xx} family, we find cases where bars can be supported, to a large extent, by chaotic orbits. These bars are of the ``ansae'' type and their effective potentials are characterized by multiple Lagrangian points roughly along the major axis of the bar. On the other hand the spirals are supported mainly by chaotic orbits and extend usually beyond corotation. We find that the spirals and the outer parts of the bars share the same orbital content. However, we have found also barred-spiral systems with spirals inside corotation, consisting mainly by chaotic orbits. Finally we indicate, that in barred-spiral systems with different pattern speeds for the two components, the dynamics of the spirals can be similar to the dynamics of the spirals of normal spiral galaxies.

  9. Development of a new testing equipment that combines the working principles of both the split Hopkinson bar and the drop weight testers.

    PubMed

    Adas, Rateb; Haiba, Majed

    2016-01-01

    In the current work, a new high strain rate tensile testing equipment is proposed. The equipment uses a pendulum device to generate an impact load and a three-bar mechanism to bring that load to act upon a specially designed specimen. As the standard impact testing apparatus uses pendulum device and the well-known SHB high strain rate tester adopts the above-mentioned mechanism, the introduced equipment can be dealt with as an impact apparatus in which the base that supports the V-shape specimen is replaced with the three-bar configuration that the traditional SHB uses. In order to demonstrate the applicability of the new tester, virtual design tools were used to determine the most appropriate configuration for it. Then, a detailed design was created, and a full-scale prototype was produced, calibrated, instrumented and tested. The obtained results demonstrate that the new tester is capable of axially straining steel specimens up to failure at a maximum rate of about 250 s(-1), which is reasonable when compared with a more established high strain rate testers. PMID:27504253

  10. Development of new Hopkinson's device dedicated to rib's bone characterisation

    NASA Astrophysics Data System (ADS)

    Mayeur, O.; Haugou, G.; Chaâri, F.; Delille, R.; Drazetic, P.; Markiewicz, E.

    2012-08-01

    This study presents an original approach for the design of adapted Hopkinson device dedicated to the characterisation of human ribs' cortical bone. The quasi-static study carried out on flat samples coming from this anatomical part highlighted the importance of the critical effect of sample shape and location on the accuracy of identify mechanical behaviour. The access to higher rates of strains, Hopkinson bars technique are classically required whatever compression or tension loadings. Classical designs of measurement bars are not suitable for this purpose due to the complexity of specimen's geometry (thickness variation). In this context, a new design of SHTB is studied here on the basis on a Finite Element approach of the set measurement bars/biological coupon. Finite Element simulations have been conducted using Abaqus explicit code by varying the design configuration. The comparison on input and output elastic waves suggests a set of small diameter bars in polyamide 66 for a better signal measurement.

  11. Bertram Hopkinson's pioneering work and the dislocation mechanics of high rate deformations and mechanically induced detonations.

    PubMed

    Armstrong, Ronald W

    2014-05-13

    Bertram Hopkinson was prescient in writing of the importance of better measuring, albeit better understanding, the nature of high rate deformation of materials in general and, in particular, of the importance of heat in initiating detonation of explosives. This report deals with these subjects in terms of post-Hopkinson crystal dislocation mechanics applied to high rate deformations, including impact tests, Hopkinson pressure bar results, Zerilli-Armstrong-type constitutive relations, shock-induced deformations, isentropic compression experiments, mechanical initiation of explosive crystals and shear banding in metals.

  12. Introducing a New 3D Dynamical Model for Barred Galaxies

    NASA Astrophysics Data System (ADS)

    Jung, Christof; Zotos, Euaggelos E.

    2015-11-01

    The regular or chaotic dynamics of an analytical realistic three dimensional model composed of a spherically symmetric central nucleus, a bar and a flat disk is investigated. For describing the properties of the bar, we introduce a new simple dynamical model and we explore the influence on the character of orbits of all the involved parameters of it, such as the mass and the scale length of the bar, the major semi-axis and the angular velocity of the bar, as well as the energy. Regions of phase space with ordered and chaotic motion are identified in dependence on these parameters and for breaking the rotational symmetry. First, we study in detail the dynamics in the invariant plane z = pz = 0 using the Poincaré map as a basic tool and then study the full three-dimensional case using the Smaller Alignment index method as principal tool for distinguishing between order and chaos. We also present strong evidence obtained through the numerical simulations that our new bar model can realistically describe the formation and the evolution of the observed twin spiral structure in barred galaxies.

  13. A comparative study on the restrictions of dynamic test methods

    NASA Astrophysics Data System (ADS)

    Majzoobi, GH.; Lahmi, S.

    2015-09-01

    Dynamic behavior of materials is investigated using different devices. Each of the devices has some restrictions. For instance, the stress-strain curve of the materials can be captured at high strain rates only with Hopkinson bar. However, by using a new approach some of the other techniques could be used to obtain the constants of material models such as Johnson-Cook model too. In this work, the restrictions of some devices such as drop hammer, Taylor test, Flying wedge, Shot impact test, dynamic tensile extrusion and Hopkinson bars which are used to characterize the material properties at high strain rates are described. The level of strain and strain rate and their restrictions are very important in examining the efficiency of each of the devices. For instance, necking or bulging in tensile and compressive Hopkinson bars, fragmentation in dynamic tensile extrusion and petaling in Taylor test are restricting issues in the level of strain rate attainable in the devices.

  14. The Effect of Alternating Bars Migration on River Bifurcation Dynamics

    NASA Astrophysics Data System (ADS)

    Miori, S.; Bertoldi, W.; Repetto, R.; Zanoni, L.; Tubino, M.

    2007-12-01

    Recent theoretical analysis, field and laboratory observations pointed out that fluvial bifurcation show an intrinsic instability, leading to the establishment of an unbalanced flow and sediments distribution in the downstream branches. The existence of equilibrium configurations has been proved, which mainly depend on the hydraulic and morphologic conditions of the upstream flow. However, flow and sediment transport in braided networks are highly unsteady, so that the bifurcation can hardly reach an equilibrium configuration. One of the main causes of temporal fluctuations is the migration of alternate bars in the upstream channel, that can affect and control the flow partition in the distributaries. We analysed the bar - bifurcation interactions by experimental and analytical investigations. We performed a set of flume experiments on a Y shaped fixed banks and movable bed bifurcation. Laboratory results show that bar formation in the upstream channel perturbs the discharge distribution with a series of fluctuations strictly related to the period of bar migration. Four different behaviours have been identified, characterised by small perturbations of the equilibrium state (balanced or unbalanced), by the occurrence of large fluctuations or by the closure of one of the distributaries. The character of the bifurcation is controlled by the amplitude and speed of alternate bars that directly influence the amplitude and period of discharge oscillations. Consequently, at large values of the aspect ratio (high bars) and low sediment mobility (slow bars) the bifurcation dynamics is likely to be dominated by bars migration. Extending the one-dimensional model proposed by Bolla Pittaluga et al. (2003), we introduce the effect of bars migrating in the upstream channel. In the present model, the bifurcation is forced with spatial crosswise fluctuations of feeding conditions, in order to reproduce the transverse distribution of sediment and water of an alternate bar pattern as

  15. The Development of a Dual-Warhead Impact System for Dynamic Linearity Measurement of a High-g Micro-Electro-Mechanical-Systems (MEMS) Accelerometer.

    PubMed

    Shi, Yunbo; Yang, Zhicai; Ma, Zongmin; Cao, Huiliang; Kou, Zhiwei; Zhi, Dan; Chen, Yanxiang; Feng, Hengzhen; Liu, Jun

    2016-01-01

    Despite its extreme significance, dynamic linearity measurement for high-g accelerometers has not been discussed experimentally in previous research. In this study, we developed a novel method using a dual-warhead Hopkinson bar to measure the dynamic linearity of a high-g acceleration sensor with a laser interference impact experiment. First, we theoretically determined that dynamic linearity is a performance indicator that can be used to assess the quality merits of high-g accelerometers and is the basis of the frequency response. We also found that the dynamic linearity of the dual-warhead Hopkinson bar without an accelerometer is 2.5% experimentally. Further, we verify that dynamic linearity of the accelerometer is 3.88% after calibrating the Hopkinson bar with the accelerometer. The results confirm the reliability and feasibility of measuring dynamic linearity for high-g accelerometers using this method. PMID:27338383

  16. The Development of a Dual-Warhead Impact System for Dynamic Linearity Measurement of a High-g Micro-Electro-Mechanical-Systems (MEMS) Accelerometer

    PubMed Central

    Shi, Yunbo; Yang, Zhicai; Ma, Zongmin; Cao, Huiliang; Kou, Zhiwei; Zhi, Dan; Chen, Yanxiang; Feng, Hengzhen; Liu, Jun

    2016-01-01

    Despite its extreme significance, dynamic linearity measurement for high-g accelerometers has not been discussed experimentally in previous research. In this study, we developed a novel method using a dual-warhead Hopkinson bar to measure the dynamic linearity of a high-g acceleration sensor with a laser interference impact experiment. First, we theoretically determined that dynamic linearity is a performance indicator that can be used to assess the quality merits of high-g accelerometers and is the basis of the frequency response. We also found that the dynamic linearity of the dual-warhead Hopkinson bar without an accelerometer is 2.5% experimentally. Further, we verify that dynamic linearity of the accelerometer is 3.88% after calibrating the Hopkinson bar with the accelerometer. The results confirm the reliability and feasibility of measuring dynamic linearity for high-g accelerometers using this method. PMID:27338383

  17. Dynamic high-temperature Kolsky tension bar techniques

    SciTech Connect

    Song, Bo; Nelson, Kevin; Lipinski, Ronald; Bignell, John; Ulrich, George B; George, Easo P

    2015-01-01

    Kolsky tension bar techniques were modified for dynamic high-temperature tensile characterization of thin-sheet alloys. An induction coil heater was used to heat the specimen while a cooling system was applied to keep the bars at room temperature during heating. A preload system was developed to generate a small pretension load in the bar system during heating in order to compensate for the effect of thermal expansion generated in the high-temperature tensile specimen. A laser system was applied to directly measure the displacements at both ends of the tensile specimen in order to calculate the strain in the specimen. A pair of high-sensitivity semiconductor strain gages was used to measure the weak transmitted force due to the low flow stress in the thin specimen at elevated temperatures. As an example, the high-temperature Kolsky tension bar was used to characterize a DOP-26 iridium alloy in high-strain-rate tension at 860 s(-1)/1030 degrees C.

  18. Dynamic high-temperature Kolsky tension bar techniques

    NASA Astrophysics Data System (ADS)

    Song, Bo; Nelson, Kevin; Lipinski, Ronald; Bignell, John; Ulrich, G. B.; George, E. P.

    2015-09-01

    Kolsky tension bar techniques were modified for dynamic high-temperature tensile characterization of thin-sheet alloys. An induction coil heater was used to heat the specimen while a cooling system was applied to keep the bars at room temperature during heating. A preload system was developed to generate a small pretension load in the bar system during heating in order to compensate for the effect of thermal expansion generated in the high-temperature tensile specimen. A laser system was applied to directly measure the displacements at both ends of the tensile specimen in order to calculate the strain in the specimen. A pair of high-sensitivity semiconductor strain gages was used to measure the weak transmitted force due to the low flow stress in the thin specimen at elevated temperatures. As an example, the high-temperature Kolsky tension bar was used to characterize a DOP-26 iridium alloy in high-strain-rate tension at 860 s-1/1030 ∘C.

  19. Beam Dynamics Studies of Parallel-Bar Deflecting Cavities

    SciTech Connect

    S. Ahmed, G. Krafft, K. Detrick, S. Silva, J. Delayen, M. Spata ,M. Tiefenback, A. Hofler ,K. Beard

    2011-03-01

    We have performed three-dimensional simulations of beam dynamics for parallel-bar transverse electromagnetic mode (TEM) type RF separators: normal- and super-conducting. The compact size of these cavities as compared to conventional TM$_{110}$ type structures is more attractive particularly at low frequency. Highly concentrated electromagnetic fields between the parallel bars provide strong electrical stability to the beam for any mechanical disturbance. An array of six 2-cell normal conducting cavities or a one- or two-cell superconducting structure are enough to produce the required vertical displacement at the Lambertson magnet. Both the normal and super-conducting structures show very small emittance dilution due to the vertical kick of the beam.

  20. Gas as a tracer of barred spiral dynamics

    SciTech Connect

    Sanders, R.H.; Tubbs, A.D.

    1980-02-01

    The gravitational field of a barred spiral galaxy is described by a simple model consisting of two variable components: a central or nuclear disk and a homogeneous triaxial spheroid: and one fixed component: an extended disk or halo. The model is characterized by five free dimensionless parameters: the ratio of bar mass to central disk mass, two axial ratios of the spheroid, the ratio of the central disk length scale to the spheroid semimajor axis, and the corotation radius in units of the spheroid semimajor axis. Two-dimensional, time-dependent gas dynamical calculations are carried out in the gravitational field resulting from this mass model in order to generate a grid of hydrodynamical models on the five-dimensional parameter space. It is found that over a well-defined domain of this parameter space, the steady-state gas density and velocity distributions resemble the observed morphology and kinematics of the gas in actual SBb galaxies.

  1. Dynamic and quasi-static measurements of C-4 and primasheet P1000 explosives

    SciTech Connect

    Brown, Geoffrey W; Thompson, Darla G; De Luca, Racci; Rae, Philip J; Cady, Carl M; Todd, Steven N

    2010-01-01

    We have measured dynamic and quasi-static mechanical properties of C-4 and Primasheet P1000 explosive materials to provide input data for modeling efforts. Primasheet P1000 is a pentaerythritol tetranitrate-based rubberized explosive. C-4 is a RDX-based moldable explosive. Dynamic measurements included acoustic and split-Hopkinson pressure bar tests. Quasi-static testing was done in compression on load frames and on a dynamic mechanical analyzer. Split-Hopkinson and quasi-static tests were done at five temperatures from -50 C to 50 C. Acoustic velocities were measured at, above, and below room temperature.

  2. Gas dynamics of the barred spiral galaxy NGC 3359

    SciTech Connect

    Ball, J.R.

    1984-01-01

    A detailed study was conducted of the dynamics of the neutral hydrogen gas in the bright northern barred spiral galaxy NGC 3359. Observations of the 21 cm line at the Very Large Array were reduced to give single-channel maps with spatial resolution of 18'', and a velocity resolution of 25 km/s. The acquisition, calibration, and reduction of the data are discussed in some detail. Maps of the integrated column density and mean velocity of the atomic hydrogen, derived from the channel maps, provide the principal data for an investigation of the dynamics associated with the spiral structure of the galaxy. On scales comparable to the resolution of this survey, approximately 1 kpc at the distance of NGC 3359, the gas is broken up into a somewhat chaotic distribution of local maxima and minima. However, on larger scales the column density shows a smooth, grand design spiral pattern with two principal spiral arms. The extent and density of these two arms are roughly equal in the 21 cm map, unlike the optical image. These neutral hydrogen arms are very well correlated with the position of H II regions.

  3. Dynamic fragmentation of ferroelectric ceramics using the torsional Kolsky bar

    SciTech Connect

    Costin, L S; Grady, D E

    1983-10-01

    This paper studied the dynamic loading and subsequent fragmentation of four different load zirconate titanate (95/5 PZT) ferroelectric ceramics using a torsional Kolsky bar apparatus. Solid cylinders of the four materials were loaded in torsion at shear strain rates in the range 10/sup 2/ to 10/sup 3/s/sup -1/. Using the strain gage recordings of the incident, reflected and transmitted pulses, the energy required to fragment the specimen was determined for each test. In addition, the fragments resulting from each test were collected and analyzed by various technciques to determine their mass and size distributions. Results show some differences in particle distributions between the different batches of material. However, there is a more significant and consistent difference between the dynamic strength (as measured by the maximum shear stress) and the fragment mass distributions of the virgin material and the pressure depoled material, despite the fact that no differences were detected in the energy of fragmentation. Using earlier analytical results which relate the local kinetic energy of a potential fragment to the surface energy required to create that fragment, a relationship between the distribution of fragments from a test and material properties was derived. Results of tests on PZT as well as other materials such as oil shale, graphite, uranium dioxide and glass indicate a good correlation between the fragment distribution parameter, n, and material properties as predicted by the theory. Finally, the results are analyzed to determine the potential effects of internal stresses on the dynamic strength of the material and its fragmentation characteristics.

  4. Dynamic tensile characterization of a 4330-V steel with kolsky bar techniques.

    SciTech Connect

    Song, Bo; Antoun, Bonnie R.; Connelly, Kevin

    2010-09-01

    There has been increasing demand to understand the stress-strain response as well as damage and failure mechanisms of materials under impact loading condition. Dynamic tensile characterization has been an efficient approach to acquire satisfactory information of mechanical properties including damage and failure of the materials under investigation. However, in order to obtain valid experimental data, reliable tensile experimental techniques at high strain rates are required. This includes not only precise experimental apparatus but also reliable experimental procedures and comprehensive data interpretation. Kolsky bar, originally developed by Kolsky in 1949 [1] for high-rate compressive characterization of materials, has been extended for dynamic tensile testing since 1960 [2]. In comparison to Kolsky compression bar, the experimental design of Kolsky tension bar has been much more diversified, particularly in producing high speed tensile pulses in the bars. Moreover, instead of directly sandwiching the cylindrical specimen between the bars in Kolsky bar compression bar experiments, the specimen must be firmly attached to the bar ends in Kolsky tensile bar experiments. A common method is to thread a dumbbell specimen into the ends of the incident and transmission bars. The relatively complicated striking and specimen gripping systems in Kolsky tension bar techniques often lead to disturbance in stress wave propagation in the bars, requiring appropriate interpretation of experimental data. In this study, we employed a modified Kolsky tension bar, newly developed at Sandia National Laboratories, Livermore, CA, to explore the dynamic tensile response of a 4330-V steel. The design of the new Kolsky tension bar has been presented at 2010 SEM Annual Conference [3]. Figures 1 and 2 show the actual photograph and schematic of the Kolsky tension bar, respectively. As shown in Fig. 2, the gun barrel is directly connected to the incident bar with a coupler. The cylindrical

  5. Dynamic force measurements for a high bar using 3D motion capturing.

    PubMed

    Cagran, C; Huber, P; Müller, W

    2010-03-01

    The displacement of a calibrated horizontal bar is used as a measure for forces acting on the bar itself during dynamic performances in artistic gymnastics. The high bar is loaded with known forces and the displacement is monitored by means of a Vicon motion capturing system. The calibration results are fitted according to the Euler-Bernoulli beam theory. After calibration, forces can straightforwardly be measured by multiplication of the bar displacement with the determined fit parameter. This approach is also able to account for non-central force application (two hands on the bar) and the effect of the bar's inertia. Uncertainties in measured forces are assessed to be +/-25 N plus an additional 1% for the unknown weight distribution between the two hands. PMID:19906379

  6. Dynamics of membrane nanotubes coated with I-BAR.

    PubMed

    Barooji, Younes F; Rørvig-Lund, Andreas; Semsey, Szabolcs; Reihani, S Nader S; Bendix, Poul M

    2016-07-21

    Membrane deformation is a necessary step in a number of cellular processes such as filopodia and invadopodia formation and has been shown to involve membrane shaping proteins containing membrane binding domains from the IRSp53-MIM protein family. In reconstituted membranes the membrane shaping domains can efficiently deform negatively charged membranes into tubules without any other proteins present. Here, we show that the IM domain (also called I-BAR domain) from the protein ABBA, forms semi-flexible nanotubes protruding into Giant Unilamellar lipid Vesicles (GUVs). By simultaneous quantification of tube intensity and tubular shape we find both the diameter and stiffness of the nanotubes. I-BAR decorated tubes were quantified to have a diameter of ~50 nm and exhibit no stiffening relative to protein free tubes of the same diameter. At high protein density the tubes are immobile whereas at lower density the tubes diffuse freely on the surface of the GUV. Bleaching experiments of the fluorescently tagged I-BAR confirmed that the mobility of the tubes correlates with the mobility of the I-BAR on the GUV membrane. Finally, at low density of I-BAR the protein upconcentrates within tubes protruding into the GUVs. This implies that I-BAR exhibits strong preference for negatively curved membranes.

  7. Dynamics of membrane nanotubes coated with I-BAR.

    PubMed

    Barooji, Younes F; Rørvig-Lund, Andreas; Semsey, Szabolcs; Reihani, S Nader S; Bendix, Poul M

    2016-01-01

    Membrane deformation is a necessary step in a number of cellular processes such as filopodia and invadopodia formation and has been shown to involve membrane shaping proteins containing membrane binding domains from the IRSp53-MIM protein family. In reconstituted membranes the membrane shaping domains can efficiently deform negatively charged membranes into tubules without any other proteins present. Here, we show that the IM domain (also called I-BAR domain) from the protein ABBA, forms semi-flexible nanotubes protruding into Giant Unilamellar lipid Vesicles (GUVs). By simultaneous quantification of tube intensity and tubular shape we find both the diameter and stiffness of the nanotubes. I-BAR decorated tubes were quantified to have a diameter of ~50 nm and exhibit no stiffening relative to protein free tubes of the same diameter. At high protein density the tubes are immobile whereas at lower density the tubes diffuse freely on the surface of the GUV. Bleaching experiments of the fluorescently tagged I-BAR confirmed that the mobility of the tubes correlates with the mobility of the I-BAR on the GUV membrane. Finally, at low density of I-BAR the protein upconcentrates within tubes protruding into the GUVs. This implies that I-BAR exhibits strong preference for negatively curved membranes. PMID:27444356

  8. Dynamics of membrane nanotubes coated with I-BAR

    PubMed Central

    Barooji, Younes F.; Rørvig-Lund, Andreas; Semsey, Szabolcs; Reihani, S. Nader S.; Bendix, Poul M.

    2016-01-01

    Membrane deformation is a necessary step in a number of cellular processes such as filopodia and invadopodia formation and has been shown to involve membrane shaping proteins containing membrane binding domains from the IRSp53-MIM protein family. In reconstituted membranes the membrane shaping domains can efficiently deform negatively charged membranes into tubules without any other proteins present. Here, we show that the IM domain (also called I-BAR domain) from the protein ABBA, forms semi-flexible nanotubes protruding into Giant Unilamellar lipid Vesicles (GUVs). By simultaneous quantification of tube intensity and tubular shape we find both the diameter and stiffness of the nanotubes. I-BAR decorated tubes were quantified to have a diameter of ~50 nm and exhibit no stiffening relative to protein free tubes of the same diameter. At high protein density the tubes are immobile whereas at lower density the tubes diffuse freely on the surface of the GUV. Bleaching experiments of the fluorescently tagged I-BAR confirmed that the mobility of the tubes correlates with the mobility of the I-BAR on the GUV membrane. Finally, at low density of I-BAR the protein upconcentrates within tubes protruding into the GUVs. This implies that I-BAR exhibits strong preference for negatively curved membranes. PMID:27444356

  9. Dynamics of membrane nanotubes coated with I-BAR

    NASA Astrophysics Data System (ADS)

    Barooji, Younes F.; Rørvig-Lund, Andreas; Semsey, Szabolcs; Reihani, S. Nader S.; Bendix, Poul M.

    2016-07-01

    Membrane deformation is a necessary step in a number of cellular processes such as filopodia and invadopodia formation and has been shown to involve membrane shaping proteins containing membrane binding domains from the IRSp53-MIM protein family. In reconstituted membranes the membrane shaping domains can efficiently deform negatively charged membranes into tubules without any other proteins present. Here, we show that the IM domain (also called I-BAR domain) from the protein ABBA, forms semi-flexible nanotubes protruding into Giant Unilamellar lipid Vesicles (GUVs). By simultaneous quantification of tube intensity and tubular shape we find both the diameter and stiffness of the nanotubes. I-BAR decorated tubes were quantified to have a diameter of ~50 nm and exhibit no stiffening relative to protein free tubes of the same diameter. At high protein density the tubes are immobile whereas at lower density the tubes diffuse freely on the surface of the GUV. Bleaching experiments of the fluorescently tagged I-BAR confirmed that the mobility of the tubes correlates with the mobility of the I-BAR on the GUV membrane. Finally, at low density of I-BAR the protein upconcentrates within tubes protruding into the GUVs. This implies that I-BAR exhibits strong preference for negatively curved membranes.

  10. Transient dynamics of invasive competition: barred owls, spotted owls, habitat, and the demons of competition present.

    PubMed

    Dugger, Katie M; Anthony, Robert G; Andrews, Lawrence S

    2011-10-01

    The recent range expansion of Barred Owls (Strix varia) into the Pacific Northwest, where the species now co-occurs with the endemic Northern Spotted Owl (Strix occidentalis caurina), resulted in a unique opportunity to investigate potential competition between two congeneric, previously allopatric species. The primary criticism of early competition research was the use of current species' distribution patterns to infer past processes; however, the recent expansion of the Barred Owl and the ability to model the processes that result in site occupancy (i.e., colonization and extinction) allowed us to address the competitive process directly rather than inferring past processes through current patterns. The purpose of our study was to determine whether Barred Owls had any negative effects on occupancy dynamics of nesting territories by Northern Spotted Owls and how these effects were influenced by habitat characteristics of Spotted Owl territories. We used single-species, multi-season occupancy models and covariates quantifying Barred Owl detections and habitat characteristics to model extinction and colonization rates of Spotted Owl pairs in southern Oregon, USA. We observed a strong, negative association between Barred Owl detections and colonization rates and a strong positive effect of Barred Owl detections on extinction rates of Spotted Owls. We observed increased extinction rates in response to decreased amounts of old forest at the territory core and higher colonization rates when old-forest habitat was less fragmented. Annual site occupancy for pairs reflected the strong effects of Barred Owls on occupancy dynamics with much lower occupancy rates predicted for territories where Barred Owls were detected. The strong Barred Owl and habitat effects on occupancy dynamics of Spotted Owls provided evidence of interference competition between the species. These effects increase the importance of conserving large amounts of contiguous, old-forest habitat to maintain

  11. The Dynamical Relationship between the Bar and Spiral Patterns of NGC 1365

    NASA Astrophysics Data System (ADS)

    Speights, Jason C.; Rooke, Paul C.

    2016-07-01

    Theories that attempt to explain the dynamical relationship between bar and spiral patterns in galactic disks make different predictions about the radial profile of the pattern speed. These are tested for the H-alpha bar and spiral patterns of NGC 1365. The radial profile of the pattern speed is measured by fitting mathematical models that are based on the Tremaine-Weinberg method. The results show convincing evidence for the bar rotating at a faster rate than the spiral pattern, inconsistent with a global wave mode or a manifold. There is evidence for mode coupling of the bar and spiral patterns at the overlap of corotation and inner Lindblad resonances (ILRs), but the evidence is unreliable and inconsistent. The results are the most consistent with the bar and spiral patterns being dynamically distinct features. The pattern speed of the bar begins near an ILR and ends near the corotation resonance (CR). The radial profile of the pattern speed beyond the bar most closely resembles what is expected for coupled spiral modes and tidal interactions.

  12. The Dynamical Relationship between the Bar and Spiral Patterns of NGC 1365

    NASA Astrophysics Data System (ADS)

    Speights, Jason C.; Rooke, Paul C.

    2016-07-01

    Theories that attempt to explain the dynamical relationship between bar and spiral patterns in galactic disks make different predictions about the radial profile of the pattern speed. These are tested for the H-alpha bar and spiral patterns of NGC 1365. The radial profile of the pattern speed is measured by fitting mathematical models that are based on the Tremaine–Weinberg method. The results show convincing evidence for the bar rotating at a faster rate than the spiral pattern, inconsistent with a global wave mode or a manifold. There is evidence for mode coupling of the bar and spiral patterns at the overlap of corotation and inner Lindblad resonances (ILRs), but the evidence is unreliable and inconsistent. The results are the most consistent with the bar and spiral patterns being dynamically distinct features. The pattern speed of the bar begins near an ILR and ends near the corotation resonance (CR). The radial profile of the pattern speed beyond the bar most closely resembles what is expected for coupled spiral modes and tidal interactions.

  13. The Dynamical Relationship Between the Bar and Spiral Patterns of NGC 1365

    NASA Astrophysics Data System (ADS)

    Speights, Jason

    2016-01-01

    Theories describing the dynamical relationship between bar and spiral patterns in galaxy disks make different predictions about the radial profile of the pattern speed. The purpose of this poster is to test these predictions for the bar and spiral patterns of NGC 1365. The pattern speed is measured by fitting different forms of the Tremaine-Weinberg equations to H-alpha intensity and velocity maps. The results are the most consistent with the currently observed bar and spiral patterns being dynamically distinct features. They show compelling evidence for the bar rotating faster than the spiral pattern, inconsistent with a global wave mode or a manifold. The evidence for mode coupling of the bar and spiral patterns is weak due to inconsistencies in the results for different solution methods. The bar pattern speed is approximately constant between the inner Lindblad and corotation resonances, demonstrating that the solutions can detect large-scale, rigid patterns. Beyond the bar, the results resemble what is expected for coupled spiral modes and tidal interactions.

  14. Membrane Sculpting by F-BAR Domains Studied by Molecular Dynamics Simulations

    PubMed Central

    Yu, Hang; Schulten, Klaus

    2013-01-01

    Interplay between cellular membranes and their peripheral proteins drives many processes in eukaryotic cells. Proteins of the Bin/Amphiphysin/Rvs (BAR) domain family, in particular, play a role in cellular morphogenesis, for example curving planar membranes into tubular membranes. However, it is still unclear how F-BAR domain proteins act on membranes. Electron microscopy revealed that, in vitro, F-BAR proteins form regular lattices on cylindrically deformed membrane surfaces. Using all-atom and coarse-grained (CG) molecular dynamics simulations, we show that such lattices, indeed, induce tubes of observed radii. A 250 ns all-atom simulation reveals that F-BAR domain curves membranes via the so-called scaffolding mechanism. Plasticity of the F-BAR domain permits conformational change in response to membrane interaction, via partial unwinding of the domains 3-helix bundle structure. A CG simulation covering more than 350 µs provides a dynamic picture of membrane tubulation by lattices of F-BAR domains. A series of CG simulations identified the optimal lattice type for membrane sculpting, which matches closely the lattices seen through cryo-electron microscopy. PMID:23382665

  15. On the link between central black holes, bar dynamics and dark matter haloes in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Treuthardt, Patrick; Seigar, Marc S.; Sierra, Amber D.; Al-Baidhany, Ismaeel; Salo, Heikki; Kennefick, Daniel; Kennefick, Julia; Lacy, Claud H. S.

    2012-07-01

    The discovery of a relationship between supermassive black hole (SMBH) mass and spiral arm pitch angle (P) is evidence that SMBHs are tied to the overall secular evolution of a galaxy. The discovery of SMBHs in late-type galaxies with little or no bulge suggests that an underlying correlation between the dark matter halo concentration and SMBH mass (MBH) exists, rather than between the bulge mass and MBH. In this paper we measure P using a two-dimensional fast Fourier transform and estimate the bar pattern speeds of 40 barred spiral galaxies from the Carnegie-Irvine Galaxy Survey. The pattern speeds were derived by estimating the gravitational potentials of our galaxies from Ks-band images and using them to produce dynamical simulation models. The pattern speeds allow us to identify those galaxies with low central dark halo densities, or fast rotating bars, while P provides an estimate of MBH. We find that a wide range of MBH exists in galaxies with low central dark matter halo densities, which appears to support other theoretical results. We also find that galaxies with low central dark halo densities appear to follow more predictable trends in P versus de Vaucouleurs morphological type (T) and bar strength versus T than barred galaxies in general. The empirical relationship between MBH and total gravitational mass of a galaxy (Mtot) allows us to predict the minimum Mtot that will be observationally measured of our fast bar galaxies. These predictions will be investigated in a subsequent paper.

  16. Development of a miniature tensile Kolsky bar for dynamic testing of thin films

    NASA Astrophysics Data System (ADS)

    Paul, Jastin V.

    Mechanical properties such as yield stress and ultimate strength are most commonly obtained under quasi-static (strain rate of 10--4 s--1) loading conditions Materials such as metals, ceramics, and polymers may exhibit significant changes in mechanical response when subjected to high strain rate (102 --105 per second) conditions. The loading rate or strain rate can affect the material properties such as elastic modulus, yield strength, work hardening, and ductility. To ensure product quality and reliability under impact conditions, the mechanical responses of materials under dynamic loading conditions must be characterized. A Kolsky bar is a tool that can be used to study the uniaxial compressive constitutive behavior of materials under high strain rates. The goal of this thesis is to develop a miniature Tensile Kolsky bar that can be used to test materials with thickness on the order of 200 micrometers (thin foils). The system consists of a cylindrical launch tube with an internal striker, a rectangular incident bar and a transmitted bar. The specimen is held in pockets that were milled directly into the incident and transmitted bar. The rectangular incident and transmitted bars facilitate specimen and strain gage mounting. The rectangular section also provides a reduced cross sectional bar area compared to a bar of circular cross section with diameter equivalent to the width of the rectangular bar, which increases the system sensitivity. This thesis presents the detailed description of the miniature Kolsky bar device, specimen geometry, diagnostic techniques and different calibration and validation techniques used for developing the system. The Kolsky bar setup was used to test 99.9 percent pure magnesium at two different strain rates (5000 and 10000 per second). Specimens were cut from billets processed via the 4Bc equal channel angular extrusion route and were tested in three different directions: extrusion, longitudinal and transverse. The results from the

  17. Dynamical models - the barred spiral galaxy NGC 1300

    SciTech Connect

    England, M.N. )

    1989-09-01

    The results of hydrodynamical model calculations for the classic SBb(s) system NGC 1300 are presented and compared to high-resolution H I observations reported by England (1989). The effects of the various galactic components are investigated, and composite models are constructed in order to reproduce the gas observations and provide dynamical information on the galaxy. The models only partially reproduce the observations but nevertheless provide bounds for various dynamical parameters. The results indicate that either the models are too simplistic or nondynamical effects are important in the galaxy. 42 refs.

  18. Advances in experimental assessment of dynamic tensile strength of concrete by the spalling technique. …in tribute to Janusz Roman Klepaczko, Emeritus Professor at the Université Paul Verlaine in Metz, passed away on August 15, 2008.

    NASA Astrophysics Data System (ADS)

    Brara, Ahmed

    2015-09-01

    An experimental method to test concrete in dynamic tension by spalling with a Hopkinson bar as loading and measuring tool was developed in 1999. The dynamic strength of concrete specimen and strain rate were indirectly derived from an accurate data processing of the signals measured on the Hopkinson bar surface. This method suggested by late Prof. Klepaczko, allowed for reaching the highest strain rate reported in literature for which an intriguing tensile strength increase was highlighted. This simple and efficient technique has been adopted by many researchers around the world. Some significant improvements in terms of definition and reproducibility of the incident loading pulse travelling along the bar and direct and/or contactless measurements on concrete specimens have been introduced. The very high rate sensitivity of concrete tensile strength was corroborated by the additional experimental data obtained with this experimental technique during the last fifteen years.

  19. Dynamic and quasi-static measurements of PBXN-5 and comp-B explosives

    SciTech Connect

    Brown, Geoffrey W; Ten Cate, James A; Deluca, Racci; Rae, Philip J; Todd, Steven N

    2009-03-12

    We have measured dynamic and quasi-static mechanical properties of PBXN-5 and Comp-B explosive materials to provide input data for modeling efforts. Dynamic measurements included acoustic and split-Hopkinson pressure bar tests. Quasi-static testing was done in compression on a load frame. Hopkinson bar and quasistatic testing was done at five temperatures from -50{sup o}C to 50{sup o}C. Our results were dominated by the low density of the samples and showed up as low acoustic velocities and lower strengths, as compared to other materials of the same or similar formulations. The effects seem to be consistent with the high porosity of the materials. The data do provide useful input to models that include density as a parameter and suggest caution when using measurements of ideal materials to predict behavior of damaged materials.

  20. Dynamic Characterization and Modeling of Potting Materials for Electronics Assemblies

    NASA Astrophysics Data System (ADS)

    Joshi, Vasant; Lee, Gilbert; Santiago, Jaime

    2015-06-01

    Prediction of survivability of encapsulated electronic components subject to impact relies on accurate modeling. Both static and dynamic characterization of encapsulation material is needed to generate a robust material model. Current focus is on potting materials to mitigate high rate loading on impact. In this effort, encapsulation scheme consists of layers of polymeric material Sylgard 184 and Triggerbond Epoxy-20-3001. Experiments conducted for characterization of materials include conventional tension and compression tests, Hopkinson bar, dynamic material analyzer (DMA) and a non-conventional accelerometer based resonance tests for obtaining high frequency data. For an ideal material, data can be fitted to Williams-Landel-Ferry (WLF) model. A new temperature-time shift (TTS) macro was written to compare idealized temperature shift factor (WLF model) with experimental incremental shift factors. Deviations can be observed by comparison of experimental data with the model fit to determine the actual material behavior. Similarly, another macro written for obtaining Ogden model parameter from Hopkinson Bar tests indicates deviations from experimental high strain rate data. In this paper, experimental results for different materials used for mitigating impact, and ways to combine data from resonance, DMA and Hopkinson bar together with modeling refinements will be presented.

  1. BAR Proteins PSTPIP1/2 Regulate Podosome Dynamics and the Resorption Activity of Osteoclasts

    PubMed Central

    Sztacho, Martin; Segeletz, Sandra; Sanchez-Fernandez, Maria Arantzazu; Czupalla, Cornelia; Niehage, Christian; Hoflack, Bernard

    2016-01-01

    Bone resorption in vertebrates relies on the ability of osteoclasts to assemble F-actin-rich podosomes that condense into podosomal belts, forming sealing zones. Sealing zones segregate bone-facing ruffled membranes from other membrane domains, and disassemble when osteoclasts migrate to new areas. How podosome/sealing zone dynamics is regulated remains unknown. We illustrate the essential role of the membrane scaffolding F-BAR-Proline-Serine-Threonine Phosphatase Interacting Proteins (PSTPIP) 1 and 2 in this process. Whereas PSTPIP2 regulates podosome assembly, PSTPIP1 regulates their disassembly. PSTPIP1 recruits, through its F-BAR domain, the protein tyrosine phosphatase non-receptor type 6 (PTPN6) that de-phosphophorylates the phosphatidylinositol 5-phosphatases SHIP1/2 bound to the SH3 domain of PSTPIP1. Depletion of any component of this complex prevents sealing zone disassembly and increases osteoclast activity. Thus, our results illustrate the importance of BAR domain proteins in podosome structure and dynamics, and identify a new PSTPIP1/PTPN6/SHIP1/2-dependent negative feedback mechanism that counterbalances Src and PI(3,4,5)P3 signalling to control osteoclast cell polarity and activity during bone resorption. PMID:27760174

  2. Spatial dynamics of bar-headed geese migration in the context of H5N1

    PubMed Central

    Bourouiba, L.; Wu, Jianhong; Newman, S.; Takekawa, J.; Natdorj, T.; Batbayar, N.; Bishop, C. M.; Hawkes, L. A.; Butler, P. J.; Wikelski, M.

    2010-01-01

    Virulent outbreaks of highly pathogenic avian influenza (HPAI) since 2005 have raised the question about the roles of migratory and wild birds in the transmission of HPAI. Despite increased monitoring, the role of wild waterfowl as the primary source of the highly pathogenic H5N1 has not been clearly established. The impact of outbreaks of HPAI among species of wild birds which are already endangered can nevertheless have devastating consequences for the local and non-local ecology where migratory species are established. Understanding the entangled dynamics of migration and the disease dynamics will be key to prevention and control measures for humans, migratory birds and poultry. Here, we present a spatial dynamic model of seasonal migration derived from first principles and linking the local dynamics during migratory stopovers to the larger scale migratory routes. We discuss the effect of repeated epizootic at specific migratory stopovers for bar-headed geese (Anser indicus). We find that repeated deadly outbreaks of H5N1 on stopovers during the autumn migration of bar-headed geese could lead to a larger reduction in the size of the equilibrium bird population compared with that obtained after repeated outbreaks during the spring migration. However, the opposite is true during the first few years of transition to such an equilibrium. The age-maturation process of juvenile birds which are more susceptible to H5N1 reinforces this result. PMID:20472636

  3. Spatial dynamics of bar-headed geese migration in the context of H5N1

    USGS Publications Warehouse

    Bourouiba, L.; Wu, Jianhong; Newman, S.; Takekawa, J.; Natdorj, T.; Batbayar, N.; Bishop, C.M.; Hawkes, L.A.; Butler, P.J.; Wikelski, M.

    2010-01-01

    Virulent outbreaks of highly pathogenic avian influenza (HPAI) since 2005 have raised the question about the roles of migratory and wild birds in the transmission of HPAI. Despite increased monitoring, the role of wild waterfowl as the primary source of the highly pathogenic H5N1 has not been clearly established. The impact of outbreaks of HPAI among species of wild birds which are already endangered can nevertheless have devastating consequences for the local and non-local ecology where migratory species are established. Understanding the entangled dynamics of migration and the disease dynamics will be key to prevention and control measures for humans, migratory birds and poultry. Here, we present a spatial dynamic model of seasonal migration derived from first principles and linking the local dynamics during migratory stopovers to the larger scale migratory routes. We discuss the effect of repeated epizootic at specific migratory stopovers for bar-headed geese (Anser indicus). We find that repeated deadly outbreaks of H5N1 on stopovers during the autumn migration of bar-headed geese could lead to a larger reduction in the size of the equilibrium bird population compared with that obtained after repeated outbreaks during the spring migration. However, the opposite is true during the first few years of transition to such an equilibrium. The age-maturation process of juvenile birds which are more susceptible to H5N1 reinforces this result.

  4. Dynamics of nonmigrating mid-channel bar and superimposed dunes in a sandy-gravelly river (Loire River, France)

    NASA Astrophysics Data System (ADS)

    Wintenberger, Coraline L.; Rodrigues, Stéphane; Claude, Nicolas; Jugé, Philippe; Bréhéret, Jean-Gabriel; Villar, Marc

    2015-11-01

    A field study was carried out to investigate the dynamics during floods of a nonmigrating, mid-channel bar of the Loire River (France) forced by a riffle and renewed by fluvial management works. Interactions between the bar and superimposed dunes developed from an initial flat bed were analyzed during floods using frequent mono- and multibeam echosoundings, Acoustic Doppler Profiler measurements, and sediment grain-size analysis. When water left the bar, terrestrial laser scanning and sediment sampling documented the effect of post-flood sediment reworking. During floods a significant bar front elongation, spreading (on margins), and swelling was shown, whereas a stable area (no significant changes) was present close to the riffle. During low flows and falling limbs of floods, intense sediment reworking on the top of the bar and lateral scouring occurred. Hydrological variations controlled the sediment supply (in terms of phasing, quantity, and grain size) delivered by surrounding channels during floods and thus superimposed dune development. Their development was also linked to the sediment availability (armor layers, riffle proximity). Their relatively constant height highlights a preferential adaptation on dune length during floods. The role of each morphological forcing parameters (riffle vs. channel widening and curvature) on the bar dynamics and evolution is stage dependent; the shape, dynamics, and long-term morphological evolution of the bar and of the river reach (surrounding islands, channel translation) mainly depends on the presence of the natural riffle.

  5. Incremental dynamic analysis of concrete moment resisting frames reinforced with shape memory composite bars

    NASA Astrophysics Data System (ADS)

    Zafar, Adeel; Andrawes, Bassem

    2012-02-01

    Fiber reinforced polymer (FRP) reinforcing bars have been used in concrete structures as an alternative to conventional steel reinforcement, in order to overcome corrosion problems. However, due to the linear behavior of the commonly used reinforcing fibers, they are not considered in structures which require ductility and damping characteristics. The use of superelastic shape memory alloy (SMA) fibers with their nonlinear elastic behavior as reinforcement in the composite could potentially provide a solution for this problem. Small diameter SMA wires are coupled with polymer matrix to produce SMA-FRP composite, which is sought in this research as reinforcing bars. SMA-FRP bars are sought in this study to enhance the seismic performance of reinforced concrete (RC) moment resisting frames (MRFs) in terms of reducing their residual inter-story drifts while still maintaining the elastic characteristics associated with conventional FRP. Three story one bay and six story two bay RC MRF prototype structures are designed with steel, SMA-FRP and glass-FRP reinforcement. The incremental dynamic analysis technique is used to investigate the behaviors of the two frames with the three different reinforcement types under a suite of ground motion records. It is found that the frames with SMA-FRP composite reinforcement exhibit higher performance levels including lower residual inter-story drifts, high energy dissipation and thus lower damage, which are important for structures in highly seismic zones.

  6. Necking evolution in dynamically stretched bars: New experimental and computational insights

    NASA Astrophysics Data System (ADS)

    Vaz-Romero, A.; Rotbaum, Y.; Rodríguez-Martínez, J. A.; Rittel, D.

    2016-06-01

    This paper presents new results on dynamic neck evolution in steel bars of varying diameters. Dynamic tensile tests were carried out in a Kolsky apparatus using cylindrical steel specimens with various cross-section diameters ranging from 1.5 mm to 4 mm. A high speed digital camera was used to record the deformation of the specimen during the loading process. Video recording of the tests enabled accurate experimental measurements of the necking evolution, specifically its growth rate as a function of the diameter. The experiments show that increasing the specimen cross-section slows down the neck development. This behavior has been further investigated using two different kinds of numerical calculations: (1) axisymmetric finite element simulations and (2) one-dimensional finite difference computations. While the finite difference model only considers the normal stress along the longitudinal direction of the bar, the finite element model does not entail any simplification on the stress state of the specimen during the loading process. In agreement with the experiments, the finite element calculations show a decrease of the necking growth rate with the increase in the cross-section of the sample. On the contrary, the damping effect of the specimen cross-section on the necking evolution is not captured by the finite difference computations. We postulate that this result comes from the one-dimensional nature of the finite difference model. This work uncovers, by means of combined experiments and modelling, the key role played by stress multiaxiality in the growth rate of dynamic necks.

  7. Computer simulations of channel meandering and the formation of point bars: Linking channel dynamics to the preserved stratigraphy

    NASA Astrophysics Data System (ADS)

    Sun, T.; Covault, J. A.; Pyrcz, M.; Sullivan, M.

    2012-12-01

    Meandering rivers are probably one of the most recognizable geomorphic features on earth. As they meander across alluvial and delta plains, channels migrate laterally and develop point bars, splays, levees and other geomorphic and sedimentary features that compose substantial portions of the fill within many sedimentary basins. These basins can include hydrocarbon producing fields. Therefore, a good understanding of the processes of meandering channels and their associated deposits is critical for exploiting these reservoirs in the subsurface. In the past couple of decades, significant progress has been made in our understanding of the morphodynamics of channel meandering. Basic fluid dynamics and sediment transport (Ikeda and Parker, 1981; Howard, 1992) has shown that many characteristic features of meandering rivers, such as the meandering wavelength, growth rate and downstream migration rate, can be predicted quantitatively. As a result, a number of variations and improvement of the theory have emerged (e.g., Blondeaux and Seminara, 1985; Parker and Andrews, 1985, 1986; and Sun et al., 2001a, b).The main improvements include the recognition of so called "bar-bend" interactions, where the development of bars on the channel bed and their interactions with the channel bend is recognized as a primary cause for meandering channels to develop greater complexity than the classic goose-neck meander bend shapes, such as compound bend. Recently, Sun and others have shown that the spatial patterns of width variations in meandering channels can be explained by an extrinsic periodic flow variations coupled with the intrinsic bend instability dynamics. In contrast to the significant improvement of our understanding of channel meandering, little work has been done to link the geomorphic features of meandering channels to the geometry and heterogeneity of the deposits they form and ultimately preserves. A computer simulation model based on the work of Sun and others (1996, 2001

  8. MASSIVE CLUSTERS IN THE INNER REGIONS OF NGC 1365: CLUSTER FORMATION AND GAS DYNAMICS IN GALACTIC BARS

    SciTech Connect

    Elmegreen, Bruce G.; Galliano, Emmanuel; Alloin, Danielle E-mail: egallian@on.b

    2009-10-01

    Cluster formation and gas dynamics in the central regions of barred galaxies are not well understood. This paper reviews the environment of three 10{sup 7} M {sub sun} clusters near the inner Lindblad resonance (ILR) of the barred spiral NGC 1365. The morphology, mass, and flow of H I and CO gas in the spiral and barred regions are examined for evidence of the location and mechanism of cluster formation. The accretion rate is compared with the star formation rate to infer the lifetime of the starburst. The gas appears to move from inside corotation in the spiral region to looping filaments in the interbar region at a rate of approx6 M {sub sun} yr{sup -1} before impacting the bar dustlane somewhere along its length. The gas in this dustlane moves inward, growing in flux as a result of the accretion to approx40 M {sub sun} yr{sup -1} near the ILR. This inner rate exceeds the current nuclear star formation rate by a factor of 4, suggesting continued buildup of nuclear mass for another approx0.5 Gyr. The bar may be only 1-2 Gyr old. Extrapolating the bar flow back in time, we infer that the clusters formed in the bar dustlane outside the central dust ring at a position where an interbar filament currently impacts the lane. The ram pressure from this impact is comparable to the pressure in the bar dustlane, and both are comparable to the pressure in the massive clusters. Impact triggering is suggested. The isothermal assumption in numerical simulations seems inappropriate for the rarefaction parts of spiral and bar gas flows. The clusters have enough lower-mass counterparts to suggest they are part of a normal power-law mass distribution. Gas trapping in the most massive clusters could explain their [Ne II] emission, which is not evident from the lower-mass clusters nearby.

  9. An interrupted tensile testing at high strain rates for pure copper bars

    SciTech Connect

    Ma Dongfang; Chen Danian; Wu Shanxing; Wang Huanran; Hou Yanjun; Cai Canyuan

    2010-12-01

    A high-speed tensile facility (HSTF) invented by us was applied to interrupting the tests for pure copper specimen bars controlled locally at different levels of elongation. It was realized to isolate and identify the different stages of the dynamic fracture process of the pure copper specimen bar under impact tension. The results of scanning electron microscopical (SEM) investigation of the recovered pure copper specimens show that the void evolution near the surface of the minimum cross-section of the necking area is more severe than that at the middle of the necking area, which may be connected with the findings discussed by Alves and Jones [J. Mech. Phys. Solids 47, 643 (1999)]. The constitutive models in a certain range of strain determined from the tensile split Hopkinson bar optimized by us were employed and adjusted in numerically simulating the large deformation of the pure copper specimen in the interrupted tensile tests on HSTF. The dependence of the instability strain of thermoviscoplastic materials in simple tension on material parameters delineated by Batra and Wei [Int. J. Impact Eng. 34, 448 (2007)] was inspected in predicting the diffuse necking of the specimen bar. The axisymmetric necking rod model with a central void under static tension presented by Ragab [Eng. Fract. Mech. 71, 1515 (2004)] was extended to predicting the local necking and fracture of the specimen bar under impact tension.

  10. Nonaxisymmetric Dynamic Instabilities of Rotating Polytropes. II. Torques, Bars, and Mode Saturation with Applications to Protostars and Fizzlers

    NASA Astrophysics Data System (ADS)

    Imamura, James N.; Durisen, Richard H.; Pickett, Brian K.

    2000-01-01

    Dynamic nonaxisymmetric instabilities in rapidly rotating stars and protostars have a range of potential applications in astrophysics, including implications for binary formation during protostellar cloud collapse and for the possibility of aborted collapse to neutron star densities at late stages of stellar evolution (``fizzlers''). We have recently presented detailed linear analyses for polytropes of the most dynamically unstable global modes, the barlike modes. These produce bar distortions in the regions near the rotation axis but have trailing spiral arms toward the equator. In this paper, we use our linear eigenfunctions to predict the early nonlinear behavior of the dynamic instability and compare these ``quasi-linear'' predictions with several fully nonlinear hydrodynamics simulations. The comparisons demonstrate that the nonlinear saturation of the barlike instability is due to the self-interaction gravitational torques between the growing central bar and the spiral arms, where angular momentum is transferred outward from bar to arms. We also find a previously unsuspected resonance condition that accurately predicts the mass of the bar regions in our own simulations and in those published by other researchers. The quasi-linear theory makes other accurate predictions about consequences of instability, including properties of possible end-state bars and increases in central density, which can be large under some conditions. We discuss in some detail the application of our results to binary formation during protostellar collapse and to the formation of massive rotating black holes.

  11. BaLROG: The Influence of Bars on the Dynamical Structure in Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Seidel, M. K.; Falcón-Barroso, J.; Martínez-Valpuesta, I.; Díaz-García, S.; Laurikainen, E.; Salo, H.; Knapen, J. H.

    2016-10-01

    Using the BaLROG (Bars in Low Redshift Optical Galaxies) sample of 16 morphologically distinct barred spirals, we constrain the influence of bars on nearby galaxies observationally. Our sample appears small compared to ongoing IFU surveys, but offers a tenfold sharper spatial resolution (˜100 pc) as each galaxy is a mosaic of several pointings observed with the IFU spectrograph SAURON. We demonstrate a correlation between the bar strength Qb determined from classical torque analysis using 3.6 μm Spitzer (S4G) images, with Qkin, a kinematic torque, calculated via our new method based solely on the kinematics. Using a large number of N-body simulations, we verify this correlation and the measurement of Qb. We also determine bar strengths from ionized gas kinematics and find that they are ˜2.5 larger than those measured from stellar kinematics. Further, inner kinematic features related to bars as predicted by simulations seem to be stronger for stronger bars. We find a stellar angular momentum dip at 0.2±0.1 bar lengths. In these central regions, about half of our sample also exhibits an anti-correlation of h3 - stellar velocity (v/σ). An increased flattening of the stellar σ gradient with increasing bar strength supports the notion of bar-induced orbit mixing. Our results constrain the spatial scales and magnitude of a kinematic influence of bar-driven secular evolution in present day galaxies.

  12. Bar dimensions and bar shapes in estuaries

    NASA Astrophysics Data System (ADS)

    Leuven, Jasper; Kleinhans, Maarten; Weisscher, Steven; van der Vegt, Maarten

    2016-04-01

    Estuaries cause fascinating patterns of dynamic channels and shoals. Intertidal sandbars are valuable habitats, whilst channels provide access to harbors. We still lack a full explanation and classification scheme for the shapes and dimensions of bar patterns in natural estuaries, in contrast with bars in rivers. Analytical physics-based models suggest that bar length in estuaries increases with flow velocity, tidal excursion length or estuary width, depending on which model. However, these hypotheses were never validated for lack of data and experiments. We present a large dataset and determine the controls on bar shape and dimensions in estuaries, spanning bar lengths from centimeters (experiments) to 10s of kilometers length. First, we visually identified and classified 190 bars, measured their dimensions (width, length, height) and local braiding index. Data on estuarine geometry and tidal characteristics were obtained from governmental databases and literature on case studies. We found that many complex bars can be seen as simple elongated bars partly cut by mutually evasive ebb- and flood-dominated channels. Data analysis shows that bar dimensions scale with estuary dimensions, in particular estuary width. Breaking up the complex bars in simple bars greatly reduced scatter. Analytical bar theory overpredicts bar dimensions by an order of magnitude in case of small estuarine systems. Likewise, braiding index depends on local width-to-depth ratio, as was previously found for river systems. Our results suggest that estuary dimensions determine the order of magnitude of bar dimensions, while tidal characteristics modify this. We will continue to model bars numerically and experimentally. Our dataset on tidal bars enables future studies on the sedimentary architecture of geologically complex tidal deposits and enables studying effects of man-induced perturbations such as dredging and dumping on bar and channel patterns and habitats.

  13. Structure and dynamics of helix-0 of the N-BAR domain in lipid micelles and bilayers.

    PubMed

    Löw, Christian; Weininger, Ulrich; Lee, Hwankyu; Schweimer, Kristian; Neundorf, Ines; Beck-Sickinger, Annette G; Pastor, Richard W; Balbach, Jochen

    2008-11-01

    Bin/Amphiphysin/Rvs-homology (BAR) domains generate and sense membrane curvature by binding the negatively charged membrane to their positively charged concave surfaces. N-BAR domains contain an N-terminal extension (helix-0) predicted to form an amphipathic helix upon membrane binding. We determined the NMR structure and nano-to-picosecond dynamics of helix-0 of the human Bin1/Amphiphysin II BAR domain in sodium dodecyl sulfate and dodecylphosphocholine micelles. Molecular dynamics simulations of this 34-amino acid peptide revealed electrostatic and hydrophobic interactions with the detergent molecules that induce helical structure formation from residues 8-10 toward the C-terminus. The orientation in the micelles was experimentally confirmed by backbone amide proton exchange. The simulation and the experiment indicated that the N-terminal region is disordered, and the peptide curves to adopted the micelle shape. Deletion of helix-0 reduced tubulation of liposomes by the BAR domain, whereas the helix-0 peptide itself was fusogenic. These findings support models for membrane curving by BAR domains in which helix-0 increases the binding affinity to the membrane and enhances curvature generation. PMID:18658220

  14. A technique for combined dynamic compression-shear test

    NASA Astrophysics Data System (ADS)

    Zhao, P. D.; Lu, F. Y.; Chen, R.; Lin, Y. L.; Li, J. L.; Lu, L.; Sun, G. L.

    2011-03-01

    It is critically important to study the dynamic response of materials under a combined compression-shear loading for developing constitutive laws more accurately and fully. We present a novel technique to achieve the combined compression and shear loadings at high strain rates. The main apparatus consists of a strike bar, an incident bar, and two transmission bars. The close-to-specimen end of the incident bar is wedge-shaped with 90°. In each experiment, there are two identical specimens, respectively, agglutinated between one side of the wedge and one of transmission bars. When a loading impulse travels to specimens along the incident bar, because of the special geometrical shape, the specimen-incident bar interface gets an axial and a transverse velocity. Specimens endure a combined compression-shear loading at high strain rates. The compression stress and strain of the specimens are deduced from signals recorded by strain gages mounted on the bars. The shear stress is measured by two piezoelectric transducers of quartz (Y-cut with rotation angle 17.7°) embedded at the close-to-specimen end of transmission bars; the shear strain is measured with a novel optical technique, which is based on the luminous flux method. An analytic model was proposed and validated by the numerical simulations. The simulation results yield good agreement with the analytic results. The proposed technique was then validated through experiments carried out on lead specimens, by comparing experimental results with that of the split Hopkinson pressure bar experiments.

  15. Gas dynamics in barred spirals - Gaseous density waves and galactic shocks

    NASA Technical Reports Server (NTRS)

    Roberts, W. W., Jr.; Van Albada, G. D.; Huntley, J. M.

    1979-01-01

    Steady-state gasdynamical studies, previously limited to tightly wound normal spiral galaxies, are extended to models of barred spirals with a 5% to 10% perturbing potential. The models show that a strong wave manifestation is an important constituent of the bar structure in many barred spirals and that a density-wave shock wave can form a bar structure as pronounced as the narrow bars often evident in optical photographs of barred spirals. The dark narrow dust lanes often observed along the leading edges of bar structures are identified as tracers of shocks, and it is found that strong shocks along a bar structure during even a small part of a galaxy's lifetime might easily deplete a large enough proportion of the gas to cause a lack of gas in the inner annuli encompassing the bar by the time of the present epoch. It is emphasized that even moderate-amplitude barlike perturbations in the disk can drive large noncircular gas motions, typically 50 to 150 km/s.

  16. Studies on Dynamic Damage Evolution for Pp/pa Polymer Blends Under High Strain Rates

    NASA Astrophysics Data System (ADS)

    Sun, Zi-Jian; Wang, Li-Li

    The dynamic damage evolution for PP/PA blends with different compatibilizers is studied in high strain rates from two different approaches, namely by determining the unloading elastic modulus of specimen experienced impact deformation and by combining the split Hopkinson pressure bar (SHPB) experimental technique with the back-propagation (BP) neural network. The results obtained by both approaches consistently show that a threshold strain ɛth exists for dynamic damage evolution, and both the damage evolution and ɛth are dependent on strain and strain rate. For non-linear visco-elastic materials, the damage evolution determined by the unloading elastic modulus provides an underestimation of real damage evolution.

  17. Rotational reorientation dynamics at high pressures: rhodamine 6G in ethanol from 1 bar to 6 kbar

    SciTech Connect

    Philips, L.A.; Webb, S.P.; Yeh, S.W.; Clark, J.H.

    1985-01-03

    Picosecond, time-resolved fluorescence depolarization spectroscopy has been used to measure the rotational reorientation time (tau/sub or/) of electronically excited rhodamine 6G. When the dependence of tau/sub or/ on solvent viscosity for a series of linear alcohols is compared with that for ethanol as a function of pressure over the range from 1 bar to 6 kbar, substantially different rotational reorientation dynamics are found for identical macroscopic viscosities. 31 references, 2 figures, 2 tables.

  18. Dynamics of a nearshore bar system in the northern Adriatic: A video-based morphological classification

    NASA Astrophysics Data System (ADS)

    Armaroli, Clara; Ciavola, Paolo

    2011-03-01

    The aim of this paper is to define a simplified morphodynamic classification suitable for low energy beaches exposed to microtidal conditions. The study site is located in the northern Adriatic (in Italy), it is an almost 2 km-long rectilinear beach bordered at the northern edge by coastal structures and at the southern end by a small river inlet. The mechanisms related to the evolution of the submerged part of the beach were derived from video-monitoring using Argus technology. The morphodynamic evolution of the system was studied using an automatic procedure on images for the characterisation of nearshore bars that showed good correspondence with hand-based (visual) interpretation. To apply this automatic procedure, the bar's plan crest shape was mapped using cross-shore pixel luminosity transects traced on time-averaged video images. A careful sensitivity analysis was undertaken to determine the best spacing between transects for the correct tracing of the shape of the bar crest. The error associated to a transect spacing every 25 m resulted in being comparable with the pixel resolution in the area and with the error found comparing the video interpretation with bathymetric surveys. From the study of a four and a half year dataset (February 2003-May 2007), the submerged beach was found to be characterised by the presence of a single bar in the area next to coastal protection structures. However, moving southwards of these, inner and outer bars were present. The morphodynamics of the outer bar and its plan shape modifications were dominated by rhythmic forms. Occasionally, after high energy events, the bar became rectilinear but during the following lower energy periods rhythmicity was re-established, supporting the hypothesis of self-organization mechanisms. The cross-shore position of the bar's crests only showed limited cross-shore mobility through time.

  19. The influence of the rotary inertia on the dynamic behavior of viscoelastic non-cylindrical helicoidal bars

    NASA Astrophysics Data System (ADS)

    Ermiş, Merve; Eratlı, Nihal; Omurtag, Mehmet H.

    2015-12-01

    The objective of this study is to investigate the influence of the rotary inertia on the dynamic behavior of linear viscoelastic non-cylindrical helicoidal bars due to variation of the active turns. Dynamic analysis is performed in the Laplace space by using the mixed finite element method. The standard model is used for defining the viscoelastic material behavior and by using the correspondence principle, the material constants are replaced with their complex counterparts in the Laplace space. The solution under the rectangular impulsive type loading is carried out in the Laplace space and then the results are transformed back to time domain numerically by the Modified Durbin's transformation algorithm. Some original numerical results for the dynamic behavior of linear viscoelastic non-cylindrical helices with rectangular cross-section are presented.

  20. Dynamical behavior of octahedrite from the Henbury meteorite

    SciTech Connect

    Furnish, M.D.; Gray, G.T. III; Remo, J.L.

    1993-08-01

    A suite of dynamic property measurements and characterization studies on an iron-nickel single crystal from the Henbury octahedrite containing Widmanstaetten intergrowths of kamacite and taenite (initial density 7.810) has been performed. These measurements include six impact tests (wave profile compression/release) over the stress range 2-20 GPa, metallography, quasi-static and Hopkinson bar mechanical testing, and ultrasonic mapping and sound velocity measurements. A cryogenic impact test was included to evaluate effects of a brittle/ductile transition which has been reported at 200K. Temperature sensitivity of the dynamic behavior was measured at high and low strain rates. The impact test results show loading strength (HEL), Hugoniot and {alpha} {yields} {var_epsilon} transition signatures to be similar to those for Armco iron, and do not show evidence for a ductile-brittle transition at these extremely high strain rates. Metallographic analyses, quasi-static and Hopkinson bar testing suggest that the material is in a work-hardened state and that kamacite properties dominate the bulk octahedrite properties.

  1. Dynamics of Braided Channels, Bars, and Associated Deposits Under Experimental Density Currents

    NASA Astrophysics Data System (ADS)

    Limaye, A. B. S.; Jean-Louis, G.; Paola, C.

    2015-12-01

    Turbidity currents are the principal agents that transfer clastic sediment from continental margins to the deep ocean. The extensive sedimentary deposits that result can record influences from fluvial transport, ocean currents, and seafloor bathymetry; decoding these controls is key to understanding long-term continental denudation and the formation of hydrocarbon reservoirs. Experimental turbidity currents often use pre-formed, single-thread channels, but more recent experiments and seafloor observations suggest that braided channels also develop in submarine environments. Yet controls on the formation of submarine braided channels and relationships between these channels and stratigraphic evolution remain largely untested. We have conducted a series of experiments to determine the conditions conducive to forming braided submarine channels, and to relate channel geometry and kinematics to deposit architecture. Dissolved salt supplies the excess density of the experimental turbidity currents, which transport plastic, sand-sized sediment as bedload across a test section two meters long and one meter wide. Our experiments indicate that braided channels can form as constructional features without prior erosion for a range of input water and sediment fluxes. Channel migration, avulsion, and aggradation construct sedimentary deposits with bars at a variety of scales. Bar geometry and channel kinematics are qualitatively similar under subaerial and subaqueous experiments with other parameters fixed. We will present quantitative analyses of the relationships between channel geometry and mobility and deposit architecture, at scales from individual bars to the entire deposit, and compare these results to control experiments with subaerial braiding. These experimental results suggest parallels between subaerial and subaqueous braiding, and help to constrain forward models for stratigraphic evolution and inverse methods for estimating flow conditions from turbidites.

  2. Neuromuscular onset succession of high level gymnasts during dynamic leg acceleration phases on high bar.

    PubMed

    von Laßberg, Christoph; Rapp, Walter; Mohler, Betty; Krug, Jürgen

    2013-10-01

    In several athletic disciplines there is evidence that for generating the most effective acceleration of a specific body part the transfer of momentum should run in a "whip-like" consecutive succession of body parts towards the segment which shall be accelerated most effectively (e.g. the arm in throwing disciplines). This study investigated the question how this relates to the succession of neuromuscular activation to induce such "whip like" leg acceleration in sports like gymnastics with changed conditions concerning the body position and momentary rotational axis of movements (e.g. performing giant swings on high bar). The study demonstrates that during different long hang elements, performed by 12 high level gymnasts, the succession of the neuromuscular activation runs primarily from the bar (punctum fixum) towards the legs (punctum mobile). This demonstrates that the frequently used teaching instruction, first to accelerate the legs for a successful realization of such movements, according to a high level kinematic output, is contradictory to the neuromuscular input patterns, being used in high level athletes, realizing these skills with high efficiency. Based on these findings new approaches could be developed for more direct and more adequate teaching methods regarding to an earlier optimization and facilitation of fundamental movement requirements.

  3. The fate of Salicaceae seedlings related to the dynamics of alluvial bars during floods: differentiating bed erosion, uprooting and burying.

    NASA Astrophysics Data System (ADS)

    Wintenberger, C. L.; Rodrigues, S.; Bréhéret, J. G.; Juge, P.; Villar, M.

    2014-12-01

    Riparian vegetation is a key factor of the morphological evolution of river. In Europe, riparian Salicaceae is declining following the loss of potential recruitment areas associated with river management. As an exception for lowland rivers, the Loire River (France) shows, in its middle reaches, an efficient sexual regeneration of Populus nigra and Salix alba on bare sediments deposited during flood events. In the literature, the influence of hydrological patterns as a key factor of the seedlings survival is well documented. Some studies focused on seedlings ability to withstand flood constraints and detailed the effect of duration and intensity of floods but few studies characterized precisely the processes applied on seedlings. As a working hypothesis, we consider that three types of flood stresses can induce mortality of seedlings: (i) uprooting by drag applied on the seedlings without sediment erosion, (ii) erosion of the recruited areas and (iii) burying. The distinction of these three processes allows identifying the importance of survival factors due to a strong sediment dynamics (e.g. erosion height > root height) or to the anchorage and resprouting ability. The main issues are: what are the governing processes (type and intensity) determining survival or death of seedlings and which factor (fluvial dynamics vs. own characteristics of seedlings) controls their survival? In-situ measurements were performed on a forced alluvial bar (20.000 m2) to detail the bar dynamics (bathymetry, topography, scour/fill processes, grain size surveys, flow velocity) and to survey the associated recruitment. On 48 plots (1.410 m2) the density, height and species (P. nigra and S. alba) were surveyed the year of recruitment (after dry period) and the next year after flood period. We highlight the following phases of processes during floods. The erosion of substrate dominates at the beginning of the rising limb. The erosion or uprooting processes depend of the balance between

  4. Dynamic Compression of Aluminum Foam Processed by a Freeform Fabrication Technique

    NASA Astrophysics Data System (ADS)

    Dannemann, Kathryn A.; Lankford, James; Nicholls, Arthur E.; Vaidyanathan, Ranji; Green, Catherine

    2004-07-01

    The compressive deformation behavior of a new type of aluminum foam was assessed under static and dynamic loading conditions. The aluminum foam investigated was processed by Advanced Ceramics Research using an extrusion freeform fabrication technique. The foam contained approximately 50 to 60 % porosity. The dynamic compression response was evaluated in air using a split Hopkinson pressure bar (SHPB) system with aluminum bars, and strain rates ranging from 600 s-1 to 2000 s-1. Compression tests were also conducted at lower strain rates (10-3 s-1 to 4 s-1) to determine the extent of strain rate strengthening. The low strain rate tests were performed with a servo-controlled hydraulic test machine. The results were analyzed as a function of foam density, structure, and process conditions.

  5. Finite Element Simulations to Explore Assumptions in Kolsky Bar Experiments.

    SciTech Connect

    Crum, Justin

    2015-08-05

    The chief purpose of this project has been to develop a set of finite element models that attempt to explore some of the assumptions in the experimental set-up and data reduction of the Kolsky bar experiment. In brief, the Kolsky bar, sometimes referred to as the split Hopkinson pressure bar, is an experimental apparatus used to study the mechanical properties of materials at high strain rates. Kolsky bars can be constructed to conduct experiments in tension or compression, both of which are studied in this paper. The basic operation of the tension Kolsky bar is as follows: compressed air is inserted into the barrel that contains the striker; the striker accelerates towards the left and strikes the left end of the barrel producing a tensile stress wave that propogates first through the barrel and then down the incident bar, into the specimen, and finally the transmission bar. In the compression case, the striker instead travels to the right and impacts the incident bar directly. As the stress wave travels through an interface (e.g., the incident bar to specimen connection), a portion of the pulse is transmitted and the rest reflected. The incident pulse, as well as the transmitted and reflected pulses are picked up by two strain gauges installed on the incident and transmitted bars as shown. By interpreting the data acquired by these strain gauges, the stress/strain behavior of the specimen can be determined.

  6. Towards the prediction of multiple necking during dynamic extension of round bar : linear stability approach versus finite element calculations

    NASA Astrophysics Data System (ADS)

    El Maï, S.; Mercier, S.; Petit, J.; Molinari, A.

    2014-05-01

    The fragmentation of structures subject to dynamic conditions is a matter of interest for civil industries as well as for Defence institutions. Dynamic expansions of structures, such as cylinders or rings, have been performed to obtain crucial information on fragment distributions. Many authors have proposed to capture by FEA the experimental distribution of fragment size by introducing in the FE model a perturbation. Stability and bifurcation analyses have also been proposed to describe the evolution of the perturbation growth rate. In the proposed contribution, the multiple necking of a round bar in dynamic tensile loading is analysed by the FE method. A perturbation on the initial flow stress is introduced in the numerical model to trigger instabilities. The onset time and the dominant mode of necking have been characterized precisely and showed power law evolutions, with the loading velocities and moderately with the amplitudes and the cell sizes of the perturbations. In the second part of the paper, the development of linear stability analysis and the use of salient criteria in terms of the growth rate of perturbations enabled comparisons with the numerical results. A good correlation in terms of onset time of instabilities and of number of necks is shown.

  7. Orbital and escape dynamics in barred galaxies - II. The 3D system: Exploring the role of the normally hyperbolic invariant manifolds

    NASA Astrophysics Data System (ADS)

    Jung, Christof; Zotos, Euaggelos E.

    2016-09-01

    A three degrees of freedom (3-dof) barred galaxy model composed of a spherically symmetric nucleus, a bar, a flat disc and a spherically symmetric dark matter halo is used for investigating the dynamics of the system. We use colour-coded plots to demonstrate how the value of the semi-major axis of the bar influences the regular or chaotic dynamics of the 3-dof system. For distinguishing between ordered and chaotic motion we use the Smaller ALingment Index (SALI) method, a fast yet very accurate tool. Undoubtedly, the most important elements of the dynamics are the normally hyperbolic invariant manifolds (NHIMs) located in the vicinity of the index 1 Lagrange points L2 and L3. These manifolds direct the flow of stars over the saddle points, while they also trigger the formation of rings and spirals. The dynamics in the neighbourhood of the saddle points is visualized by bifurcation diagrams of the Lyapunov orbits as well as by the restriction of the Poincaré map to the NHIMs. In addition, we reveal how the semi-major axis of the bar influences the structure of these manifolds which determine the final stellar structure (rings or spirals). Our numerical simulations suggest that in galaxies with weak bars the formation of R1 rings or R_1^' } pseudo-rings is favoured. In the case of galaxies with intermediate and strong bars the invariant manifolds seem to give rise to R1R2 rings and twin spiral formations, respectively. We also compare our numerical outcomes with earlier related work and with observational data.

  8. Dynamic Tensile Strength of Coal under Dry and Saturated Conditions

    NASA Astrophysics Data System (ADS)

    Zhao, Yixin; Liu, Shimin; Jiang, Yaodong; Wang, Kai; Huang, Yaqiong

    2016-05-01

    The tensile failure characterization of dry and saturated coals under different impact loading conditions was experimentally investigated using a Split Hopkinson pressure bar. Indirect dynamic Brazilian disc tension tests for coals were carried out. The indirect tensile strengths for different bedding angles under different impact velocities, strain rates and loading rates are analyzed and discussed. A high-speed high-resolution digital camera was employed to capture and record the dynamic failure process of coal specimens. Based on the experimental results, it was found that the saturated specimens have stronger loading rate dependence than the dry specimens. The bedding angle has a smaller effect on the dynamic indirect tensile strength compared to the impact velocity. Both shear and tensile failures were observed in the tested coal specimens. Saturated coal specimens have higher indirect tensile strength than dry ones.

  9. Dark Matter Trapping by Stellar Bars: The Shadow Bar

    NASA Astrophysics Data System (ADS)

    Petersen, Michael S.; Weinberg, Martin D.; Katz, Neal

    2016-09-01

    We investigate the complex interactions between the stellar disc and the dark-matter halo during bar formation and evolution using N-body simulations with fine temporal resolution and optimally chosen spatial resolution. We find that the forming stellar bar traps dark matter in the vicinity of the stellar bar into bar-supporting orbits. We call this feature the shadow bar. The shadow bar modifies both the location and magnitude of the angular momentum transfer between the disc and dark matter halo and adds 10 per cent to the mass of the stellar bar over 4 Gyr. The shadow bar is potentially observable by its density and velocity signature in spheroid stars and by direct dark matter detection experiments. Numerical tests demonstrate that the shadow bar can diminish the rate of angular momentum transport from the bar to the dark matter halo by more than a factor of three over the rate predicted by dynamical friction with an untrapped dark halo, and thus provides a possible physical explanation for the observed prevalence of fast bars in nature.

  10. The Dynamic Tensile Behavior of Railway Wheel Steel at High Strain Rates

    NASA Astrophysics Data System (ADS)

    Jing, Lin; Han, Liangliang; Zhao, Longmao; Zhang, Ying

    2016-10-01

    The dynamic tensile tests on D1 railway wheel steel at high strain rates were conducted using a split Hopkinson tensile bar (SHTB) apparatus, compared to quasi-static tests. Three different types of specimens, which were machined from three different positions (i.e., the rim, web and hub) of a railway wheel, were prepared and examined. The rim specimens were checked to have a higher yield stress and ultimate tensile strength than those web and hub specimens under both quasi-static and dynamic loadings, and the railway wheel steel was demonstrated to be strain rate dependent in dynamic tension. The dynamic tensile fracture surfaces of all the wheel steel specimens are cup-cone-shaped morphology on a macroscopic scale and with the quasi-ductile fracture features on the microscopic scale.

  11. Dynamic Tensile Failure of the Rock Interface Between Tuff and Basalt

    NASA Astrophysics Data System (ADS)

    Yan, Fei; Feng, Xia-Ting; Chen, Rong; Xia, Kaiwen; Jin, Changyu

    2012-05-01

    The dynamic tensile strength properties of the rock interface and its host rocks sampled from the Baihetan Hydropower Station from Western China were measured using a split Hopkinson pressure bar (SHPB). The results were compared with those for its two host rocks. The dynamic tensile strengths of the two host rocks, tuff and basalt have typical loading rate dependence. However, the dynamic response of the rock interface is much more complicated and at a given loading rate, varies between those of tuff and basalt. To explain the observation, numerical simulation using the discrete element method (DEM) was conducted to determine the detailed tensile failure process of the rock interface. The numerical simulation verifies that the variation of the dynamic tensile strength of the rock interface is a result of the variation of the interface geometry.

  12. Dynamic Strength of Tantalum under impact

    NASA Astrophysics Data System (ADS)

    Glam, Benny; Werdiger, Meir; Pistinner, Shlomi

    2013-06-01

    Plane impact experiments of double shock and shock-rarefaction in Tantalum were carried out in a gas gun. VISAR diagnostics has been implemented to measure the particle velocity and the free surface velocity. The VISAR information was utilized to study the dynamic strength of Tantalum under compression and tension. The pressure in the experiments was below 35 GPa. In this pressure range the dominant mechanism is expected to be dislocation motion. A 1-d hydrodynamic code was used in order to match various strength models. As expected, both the Johnson-Cook and the Guinan-Steinberg models do not reproduce the experimental results. Therefore in this paper we compare the Zerilli-Armstrong model which has been recently calibrated at strain rate of 6 x 103 s-1 using the split Kowalsky-Hopkinson bar to our experimental results at strain rate of 106 s-1.

  13. A dynamic ball compression test for understanding rock crushing.

    PubMed

    Huang, S; Liu, H; Xia, K

    2014-12-01

    During crushing, rock particles are subjected to complicated loading. It is desired to establish the relation between the loading and the fragmentation parameters for better understanding rock crushing mechanism. In this work, a split Hopkinson pressure bar system in combination with high speed cameras is utilized in the dynamic ball compression test, in which the spherical rock sample is adopted to avoid the shape effect. Using elasticity theory, the loading rate and the dynamic indirect tensile strength are first calculated. With the aid of the moment-trap technique and high speed cameras, the surface energy is determined for each sample. The relations between the loading rate and the fragmentation parameters, i.e., the number of fragments and the surface energy are established. The application of this method to a granitic rock shows that it is flexible and can be applied to the crushing study of generic brittle solids.

  14. Application of the dynamic characterization of metals in automotive industry

    NASA Astrophysics Data System (ADS)

    D'Aiuto, Fabio; De Caro, Daniele; Federici, Claudio; Tedesco, Michele M.; Ziggiotti, Alessandro; Cadoni, Ezio

    2015-09-01

    This paper presents the experimental methodology used by R&D EMEA - Global Materials Labs Department to test metals at high strain rate of 500 s-1. The implementation of dynamic results in commercial FEM Software LS - DYNA for crash simulation are presented. The effects of the strain rate on the tensile properties of metals, used in automotive field, are evaluated using results obtained from a direct tension split Hopkinson bar, built in collaboration with the University of Applied Sciences of Southern Switzerland DynaMat Lab. Finally the complete mechanical characterization of the Magnesium alloy AZ31B is presented, from static up to dynamic tests, showing its applications in FCA (Fiat Chrysler Automobiles), problems and future developments.

  15. Measurement of the $B^+\\rightarrow p \\bar{p} K^{+}$ Branching Fraction and Study of the Decay Dynamics

    SciTech Connect

    Aubert, B.; Barate, R.; Boutigny, D.; Couderc, F.; Karyotakis, Y.; Lees, J.P.; Poireau, V.; Tisserand, V.; Zghiche, A.; Grauges, E.; Palano, A.; Pappagallo, M.; Pompili, A.; Chen, J.C.; Qi, N.D.; Rong, G.; Wang, P.; Zhu, Y.S.; Eigen, G.; Ofte, I.; Stugu, B. /Bergen U. /LBL, Berkeley /UC, Berkeley /Birmingham U. /Ruhr U., Bochum /Bristol U. /British Columbia U. /Brunel U. /Novosibirsk, IYF /UC, Irvine /UCLA /UC, Riverside /UC, San Diego /UC, Santa Barbara /UC, Santa Cruz /Caltech /Cincinnati U. /Colorado U. /Colorado State U. /Dortmund U. /Dresden, Tech. U. /Ecole Polytechnique /Edinburgh U. /Ferrara U. /INFN, Ferrara /Frascati /Genoa U. /INFN, Genoa /Harvard U. /Heidelberg U. /Imperial Coll., London /Iowa U. /Iowa State U. /Orsay, LAL /LLNL, Livermore /Liverpool U. /Queen Mary, U. of London /Royal Holloway, U. of London /Louisville U. /Manchester U. /Maryland U. /Massachusetts U., Amherst /MIT, LNS /McGill U. /Milan U. /INFN, Milan /Mississippi U. /Montreal U. /Mt. Holyoke Coll. /Naples U. /INFN, Naples /NIKHEF, Amsterdam /Notre Dame U. /Ohio State U. /Oregon U. /Padua U. /INFN, Padua /Paris U., VI-VII /Pennsylvania U. /Perugia U. /INFN, Perugia /Pisa U. /INFN, Pisa /Prairie View A-M /Princeton U. /Rome U. /INFN, Rome /Rostock U. /Rutherford /DAPNIA, Saclay /South Carolina U. /SLAC /Stanford U., Phys. Dept. /SUNY, Stony Brook /Tennessee U. /Texas U. /Texas U., Dallas /Turin U. /INFN, Turin /Trieste U. /INFN, Trieste /Valencia U., IFIC /Vanderbilt U. /Victoria U. /Warwick U. /Wisconsin U., Madison /Yale U.

    2005-07-06

    With a sample of 232 x 10{sup 6} {Upsilon}(4S) {yields} B{bar B} events collected with the BABAR detector, we study the decay B{sup +} {yields} p{bar p}K{sup +} excluding charmonium decays to p{bar p}. We measure a branching fraction {Beta}(B{sup +} {yields} p{bar p}K{sup +}) = (6.7 {+-} 0.5 {+-} 0.4) x 10{sup -6}. An enhancement at low p{bar p} mass is observed and the Dalitz plot asymmetry suggests dominance of the penguin amplitude in this B decay. We search for a pentaquark candidate {Theta}*{sup ++} decaying into pK{sup +} in the mass range 1.43 to 2.00 GeV/c{sup 2} and set limits on {Beta}(B{sup +} {yields} {Theta}*{sup ++} {bar p}) x {Beta}({Theta}*{sup ++} {yields} pK{sup +}) at the 10{sup -7} level.

  16. Numerical Simulations of the Kolsky Compression Bar Test

    SciTech Connect

    Corona, Edmundo

    2015-10-01

    The Kolsky compression bar, or split Hopkinson pressure bar (SHPB), is an ex- perimental apparatus used to obtain the stress-strain response of material specimens at strain rates in the order of 10 2 to 10 4 1/s. Its operation and associated data re- duction are based on principles of one-dimensional wave propagation in rods. Second order effects such as indentation of the bars by the specimen and wave dispersion in the bars, however, can significantly affect aspects of the measured material response. Finite element models of the experimental apparatus were used here to demonstrate these two effects. A procedure proposed by Safa and Gary (2010) to account for bar indentation was also evaluated and shown to improve the estimation of the strain in the bars significantly. The use of pulse shapers was also shown to alleviate the effects of wave dispersion. Combining the two can lead to more reliable results in Kolsky compression bar testing.

  17. Numerical SHPB Tests of Rocks Under Combined Static and Dynamic Loading Conditions with Application to Dynamic Behavior of Rocks Under In Situ Stresses

    NASA Astrophysics Data System (ADS)

    Zhu, J. B.; Liao, Z. Y.; Tang, C. A.

    2016-10-01

    A modified split Hopkinson pressure bar (SHPB) numerical testing system is established to study the characteristics of rocks under simultaneous static and dynamic loading conditions following verification of the capability of the SHPB numerical system through comparison with laboratory measurements (Liao et al. in Rock Mech Rock Eng, 2016. doi: 10.1007/s00603-016-0954-8). Three different methods are employed in this numerical testing system to address the contact problem between a rock specimen and bars. The effects of stand-alone static axial pressure, stand-alone lateral confining pressures, and a combination of them are analyzed. It is determined that the rock total strength and the dynamic strength are greatly dependent on the static axial and confining pressures. Moreover, the friction along the interfaces between the rock specimen and bars cannot be ignored, particularly for high axial pressure conditions. Subsequently, the findings are applied to determine the dynamic behavior of rocks with in situ stresses. The effects of the magnitude of horizontal and vertical initial stresses at varied depths and their ratios are investigated. It is observed that the dynamic strength of deep rocks increases with increasing depth or the ratio of horizontal-to-vertical initial stresses ( K). The dynamic behavior of deeper rocks is more sensitive to K, and the rock dynamic strength increases faster with depth in areas with higher K.

  18. Size and Geometry Effects on the Mechanical Properties of Carrara Marble Under Dynamic Loadings

    NASA Astrophysics Data System (ADS)

    Zou, Chunjiang; Wong, Louis Ngai Yuen

    2016-05-01

    The effects of specimen size and geometry on the dynamic mechanical properties of Carrara marble including compressive strength, failure strain and elastic modulus are investigated in this research. Four different groups of specimens of different sizes and cross-sectional geometries are loaded under a wide range of strain rates by the split Hopkinson pressure bar setup. The experimental results indicate that all these mechanical properties are significantly influenced by the specimen size and geometry to different extent, hence highlighting the importance of taking into account of the specimen size and geometry in dynamic tests on rock materials. In addition, the transmission coefficient and the determination of strain rate under dynamic tests are discussed in detail.

  19. Dynamic High-Temperature Characterization of an Iridium Alloy in Compression at High Strain Rates

    SciTech Connect

    Song, Bo; Nelson, Kevin; Lipinski, Ronald J.; Bignell, John L.; Ulrich, G. B.; George, E. P.

    2014-06-01

    Iridium alloys have superior strength and ductility at elevated temperatures, making them useful as structural materials for certain high-temperature applications. However, experimental data on their high-temperature high-strain-rate performance are needed for understanding high-speed impacts in severe elevated-temperature environments. Kolsky bars (also called split Hopkinson bars) have been extensively employed for high-strain-rate characterization of materials at room temperature, but it has been challenging to adapt them for the measurement of dynamic properties at high temperatures. Current high-temperature Kolsky compression bar techniques are not capable of obtaining satisfactory high-temperature high-strain-rate stress-strain response of thin iridium specimens investigated in this study. We analyzed the difficulties encountered in high-temperature Kolsky compression bar testing of thin iridium alloy specimens. Appropriate modifications were made to the current high-temperature Kolsky compression bar technique to obtain reliable compressive stress-strain response of an iridium alloy at high strain rates (300 – 10000 s-1) and temperatures (750°C and 1030°C). Uncertainties in such high-temperature high-strain-rate experiments on thin iridium specimens were also analyzed. The compressive stress-strain response of the iridium alloy showed significant sensitivity to strain rate and temperature.

  20. Experimental analysis of quasi-static and dynamic fracture initiation toughness of gy4 armor steel material

    NASA Astrophysics Data System (ADS)

    Ren, Peng; Guo, Zitao

    Quasi-static and dynamic fracture initiation toughness of gy4 armour steel material are investigated using three point bend specimen. The modified split Hopkinson pressure bar (SHPB) apparatus with digital image correlation (DIC) system is applied to dynamic loading experiments. Full-field deformation measurements are obtained by using DIC to elucidate on the strain fields associated with the mechanical response. A series of experiments are conducted at different strain rate ranging from 10-3 s-1 to 103 s-1, and the loading rate on the fracture initiation toughness is investigated. Specially, the scanning electron microscope imaging technique is used to investigate the fracture failure micromechanism of fracture surfaces. The gy4 armour steel material fracture toughness is found to be sensitive to strain rate and higher for dynamic loading as compared to quasi-static loading. This work is supported by National Nature Science Foundation under Grant 51509115.

  1. Servohydraulic methods for mechanical testing in the Sub-Hopkinson rate regime up to strain rates of 500 1/s.

    SciTech Connect

    Crenshaw, Thomas B.; Boyce, Brad Lee

    2005-10-01

    Tensile and compressive stress-strain experiments on metals at strain rates in the range of 1-1000 1/s are relevant to many applications such as gravity-dropped munitions and airplane accidents. While conventional test methods cover strain rates up to {approx}10 s{sup -1} and split-Hopkinson and other techniques cover strain rates in excess of {approx}1000 s{sup -1}, there are no well defined techniques for the intermediate or ''Sub-Hopkinson'' strain-rate regime. The current work outlines many of the challenges in testing in the Sub-Hopkinson regime, and establishes methods for addressing these challenges. The resulting technique for obtaining intermediate rate stress-strain data is demonstrated in tension on a high-strength, high-toughness steel alloy (Hytuf) that could be a candidate alloy for earth penetrating munitions and in compression on a Au-Cu braze alloy.

  2. Dynamic compressive properties of bovine knee layered tissue

    NASA Astrophysics Data System (ADS)

    Nishida, Masahiro; Hino, Yuki; Todo, Mitsugu

    2015-09-01

    In Japan, the most common articular disease is knee osteoarthritis. Among many treatment methodologies, tissue engineering and regenerative medicine have recently received a lot of attention. In this field, cells and scaffolds are important, both ex vivo and in vivo. From the viewpoint of effective treatment, in addition to histological features, the compatibility of mechanical properties is also important. In this study, the dynamic and static compressive properties of bovine articular cartilage-cancellous bone layered tissue were measured using a universal testing machine and a split Hopkinson pressure bar method. The compressive behaviors of bovine articular cartilage-cancellous bone layered tissue were examined. The effects of strain rate on the maximum stress and the slope of stress-strain curves of the bovine articular cartilage-cancellous bone layered tissue were discussed.

  3. Influence of vegetation cover on bars morpho-dynamics in sinuous gravel-bed channels of the Northern Marche rivers (central Italy): cues for research.

    NASA Astrophysics Data System (ADS)

    Tiberi, Valentina

    2010-05-01

    Sinuous gravel-bed channels are well represented in the Northern Marche river basins (central Italy), both in main streams and along several tributaries. In both cases, lozenge bars divide flow into a main branch (always active) and secondary channels (characterized by episodic reactivations). In the study area, this fluvial pattern characterized several river reaches during the last three decades and seems to be evolved from wandering configurations. Researches in progress are mainly investigating the role played by catchment controls (i.e. land use and climate changes, gravel removal, human alterations of longitudinal profiles) on major channel transformations (i.e. with regard to bankfull width, channel downcutting, pattern changes) applying a geomorphological methodology but, detailed studies carried out in order to define sinuous gravel-bed channel at the reach scale, suggest the need of an eco-morphological approach. These considerations result particularly appropriate for the Foglia River Basin where, in some cases, vegetation covers up to the 70% of the channel surface and shows a high stability during several bankfull discharge occurrences. Field surveys and monitoring also seem to demonstrate an impulsive evolution of meso-morphologies and different time-space behaviours of vegetate bars compared to the non-vegetate ones. The aim of this contribution is to provide some preliminary considerations about influence of vegetation cover on bars morpho-dynamics of some sinuous gravel-bed channels and promote specific eco-morphologic researches.

  4. Strain-rate-dependent model for the dynamic compression of elastoplastic spheres

    NASA Astrophysics Data System (ADS)

    Burgoyne, Hayden A.; Daraio, Chiara

    2014-03-01

    We present a force-displacement contact model for the compressive loading of elastoplastic spheres. This model builds from the well known Hertz contact law for elastic, quasistatic compression to incorporate a material's strain-rate-dependent plasticity in order to describe collisions between particles. In the quasistatic regime, finite-element analysis is used to derive an empirical function of the material properties. A Johnson-Cook strain rate dependence is then included into the model to study dynamic effects. We validate the model using split Hopkinson bar experiments and show that the model can accurately simulate the force-displacement response of strain-rate-dependent elastoplastic spheres during dynamic compression and unloading.

  5. Strain-rate-dependent model for the dynamic compression of elastoplastic spheres.

    PubMed

    Burgoyne, Hayden A; Daraio, Chiara

    2014-03-01

    We present a force-displacement contact model for the compressive loading of elastoplastic spheres. This model builds from the well known Hertz contact law for elastic, quasistatic compression to incorporate a material's strain-rate-dependent plasticity in order to describe collisions between particles. In the quasistatic regime, finite-element analysis is used to derive an empirical function of the material properties. A Johnson-Cook strain rate dependence is then included into the model to study dynamic effects. We validate the model using split Hopkinson bar experiments and show that the model can accurately simulate the force-displacement response of strain-rate-dependent elastoplastic spheres during dynamic compression and unloading. PMID:24730833

  6. Modeling and Characterization of Dynamic Failure of Glasses Under High Speed Impact

    SciTech Connect

    Liu, Wenning N.; Sun, Xin

    2011-08-23

    : In this chapter, the impact-induced dynamic failure of a glass block is studied using an integrated experimental/analytical approach. Both soda-lime and borosilicate glass materials are investigated. The Split Hopkinson Pressure Bar (SHPB) technique is used to conduct dynamic failure test of soda-lime glass first. The damage growth patterns and stress histories are reported for various glass specimen designs. Making use of a continuum damage mechanics (CDM)-based constitutive model, the initial failure and subsequent stiffness reduction of glass are simulated and investigated. Explicit finite element analyses are used to simulate the glass specimen impact event. A maximum shear stress-based damage evolution law is used in describing the glass damage process under combined compression/shear loading. The impact test results are used to quantify the critical shear stress for the soda-lime glass under examination.

  7. Modeling and Characterization of Dynamic Failure of Soda-lime Glass Under High Speed Impact

    SciTech Connect

    Liu, Wenning N.; Sun, Xin; Chen, Weinong W.; Templeton, Douglas W.

    2012-05-27

    In this paper, the impact-induced dynamic failure of a soda-lime glass block is studied using an integrated experimental/analytical approach. The Split Hopkinson Pressure Bar (SHPB) technique is used to conduct dynamic failure test of soda-lime glass first. The damage growth patterns and stress histories are reported for various glass specimen designs. Making use of a continuum damage mechanics (CDM)-based constitutive model, the initial failure and subsequent stiffness reduction of glass are simulated and investigated. Explicit finite element analyses are used to simulate the glass specimen impact event. A maximum shear stress-based damage evolution law is used in describing the glass damage process under combined compression/shear loading. The impact test results are used to quantify the critical shear stress for the soda-lime glass under examination.

  8. Strain-induced kinetics of intergrain defects as the mechanism of slow dynamics in the nonlinear resonant response of humid sandstone bars.

    PubMed

    Vakhnenko, Oleksiy O; Vakhnenko, Vyacheslav O; Shankland, Thomas J; Ten Cate, James A

    2004-01-01

    A closed-form description is proposed to explain nonlinear and slow dynamics effects exhibited by sandstone bars in longitudinal resonance experiments. Along with the fast subsystem of longitudinal nonlinear displacements we examine the strain-dependent slow subsystem of broken intergrain and interlamina cohesive bonds. We show that even the simplest but phenomenologically correct modeling of their mutual feedback elucidates the main experimental findings typical for forced longitudinal oscillations of sandstone bars, namely, (i) hysteretic behavior of a resonance curve on both its upward and downward slopes, (ii) linear softening of resonant frequency with an increase of driving level, and (iii) gradual recovery (increase) of resonant frequency at low dynamical strain after the sample was conditioned by high strain. In order to reproduce the highly nonlinear elastic features of sandstone grained structure a realistic nonperturbative form of stress-strain relation was adopted. In our theory slow dynamics associated with the experimentally observed memory of peak strain history are attributed to strain-induced kinetic changes in concentration of ruptured intergrain and interlamina cohesive bonds, causing a net hysteretic effect on the elastic Young's modulus. Finally, we explain how enhancement of hysteretic phenomena originates from an increase in equilibrium concentration of ruptured cohesive bonds that are due to water saturation.

  9. Inner shelf morphologic controls on the dynamics of the beach and bar system, Fire Island, New York

    USGS Publications Warehouse

    Hapke, Cheryl J.; Schwab, William C.; Gayes, P.; McCoy, Clay; Viso, Richard; Lentz, Erika E.

    2011-01-01

    he mechanism of sediment exchange between offshore sand ridges and the beach at Fire Island, New York is largely unknown. However, recent evidence from repeat nearshore bathymetry surveys, coupled with the complex but consistent bar morphology and patterns of shoreline change demonstrate that there is a feedback occurring between the regional geologic framework and modern processes. Analysis of bathymetric survey data provides direct confirmation that the offshore ridges are connected to the shoreface and are spatially persistent. The fixed nature of the nearshore morphology is further supported by time series camera data that indicate persistent bars with breaks that re-form in the same locations. A long-term time series of shoreline change shows distinct zones of erosion and accretion that are pervasive over time scales greater than a half-century, and their length-scales are similar to the spacing of the offshore ridge-trough system. The first-order geologic framework is responsible for the existence and locations of the ridges and troughs, which then influence the morphodynamics of the beach and bar system.

  10. Dynamic Brazilian Test of Rock Under Intermediate Strain Rate: Pendulum Hammer-Driven SHPB Test and Numerical Simulation

    NASA Astrophysics Data System (ADS)

    Zhu, W. C.; Niu, L. L.; Li, S. H.; Xu, Z. H.

    2015-09-01

    The tensile strength of rock subjected to dynamic loading constitutes many engineering applications such as rock drilling and blasting. The dynamic Brazilian test of rock specimens was conducted with the split Hopkinson pressure bar (SHPB) driven by pendulum hammer, in order to determine the indirect tensile strength of rock under an intermediate strain rate ranging from 5.2 to 12.9 s-1, which is achieved when the incident bar is impacted by pendulum hammer with different velocities. The incident wave excited by pendulum hammer is triangular in shape, featuring a long rising time, and it is considered to be helpful for achieving a constant strain rate in the rock specimen. The dynamic indirect tensile strength of rock increases with strain rate. Then, the numerical simulator RFPA-Dynamics, a well-recognized software for simulating the rock failure under dynamic loading, is validated by reproducing the Brazilian test of rock when the incident stress wave retrieved at the incident bar is input as the boundary condition, and then it is employed to study the Brazilian test of rock under the higher strain rate. Based on the numerical simulation, the strain-rate dependency of tensile strength and failure pattern of the Brazilian disc specimen under the intermediate strain rate are numerically simulated, and the associated failure mechanism is clarified. It is deemed that the material heterogeneity should be a reason for the strain-rate dependency of rock.

  11. Effects of laser power density on static and dynamic mechanical properties of dissimilar stainless steel welded joints

    NASA Astrophysics Data System (ADS)

    Wei, Yan-Peng; Li, Mao-Hui; Yu, Gang; Wu, Xian-Qian; Huang, Chen-Guang; Duan, Zhu-Ping

    2012-10-01

    The mechanical properties of laser welded joints under impact loadings such as explosion and car crash etc. are critical for the engineering designs. The hardness, static and dynamic mechanical properties of AISI304 and AISI316 L dissimilar stainless steel welded joints by CO2 laser were experimentally studied. The dynamic strain-stress curves at the strain rate around 103 s-1 were obtained by the split Hopkinson tensile bar (SHTB). The static mechanical properties of the welded joints have little changes with the laser power density and all fracture occurs at 316 L side. However, the strain rate sensitivity has a strong dependence on laser power density. The value of strain rate factor decreases with the increase of laser power density. The welded joint which may be applied for the impact loading can be obtained by reducing the laser power density in the case of welding quality assurance.

  12. Dynamic High-temperature Testing of an Iridium Alloy in Compression at High-strain Rates: Dynamic High-temperature Testing

    SciTech Connect

    Song, B.; Nelson, K.; Lipinski, R.; Bignell, J.; Ulrich, G.; George, E. P.

    2014-08-21

    Iridium alloys have superior strength and ductility at elevated temperatures, making them useful as structural materials for certain high-temperature applications. However, experimental data on their high-strain -rate performance are needed for understanding high-speed impacts in severe environments. Kolsky bars (also called split Hopkinson bars) have been extensively employed for high-strain -rate characterization of materials at room temperature, but it has been challenging to adapt them for the measurement of dynamic properties at high temperatures. In our study, we analyzed the difficulties encountered in high-temperature Kolsky bar testing of thin iridium alloy specimens in compression. We made appropriate modifications using the current high-temperature Kolsky bar technique in order to obtain reliable compressive stress–strain response of an iridium alloy at high-strain rates (300–10 000 s-1) and temperatures (750 and 1030°C). The compressive stress–strain response of the iridium alloy showed significant sensitivity to both strain rate and temperature.

  13. Dynamic High-temperature Testing of an Iridium Alloy in Compression at High-strain Rates: Dynamic High-temperature Testing

    DOE PAGES

    Song, B.; Nelson, K.; Lipinski, R.; Bignell, J.; Ulrich, G.; George, E. P.

    2014-08-21

    Iridium alloys have superior strength and ductility at elevated temperatures, making them useful as structural materials for certain high-temperature applications. However, experimental data on their high-strain -rate performance are needed for understanding high-speed impacts in severe environments. Kolsky bars (also called split Hopkinson bars) have been extensively employed for high-strain -rate characterization of materials at room temperature, but it has been challenging to adapt them for the measurement of dynamic properties at high temperatures. In our study, we analyzed the difficulties encountered in high-temperature Kolsky bar testing of thin iridium alloy specimens in compression. We made appropriate modifications using themore » current high-temperature Kolsky bar technique in order to obtain reliable compressive stress–strain response of an iridium alloy at high-strain rates (300–10 000 s-1) and temperatures (750 and 1030°C). The compressive stress–strain response of the iridium alloy showed significant sensitivity to both strain rate and temperature.« less

  14. Molecular dynamics investigation on the adsorption behaviors of H2O, CO2, CH4 and N2 gases on calcite (1 1 bar 0) surface

    NASA Astrophysics Data System (ADS)

    Wang, Shimeng; Zhou, Guanggang; Ma, Yue; Gao, Lei; Song, Ranran; Jiang, Guancheng; Lu, Guiwu

    2016-11-01

    Molecular dynamics simulations (MD) were carried out to investigate the adsorption behaviors of H2O, CO2, CH4 and N2 gases, which are the main and important components in gas wells, on the calcite surface at reservoir conditions. By analyzing the binding energy and Helmholtz free energy, we found that the preferential adsorption order of these four gases is: H2O > CO2 > CH4 > N2. Moreover, we have also calculated the radial distribution function profiles of the system. It shows that the H2O molecules will form two compact adsorbed layers on the surface, which denotes the calcite (1 1 bar 0) surface is hydrophilic. The CO2 molecules can also form a adsorbed layer on the surface, while there are no significant features indicating that the CH4 and N2 molecules were apparently adsorbed on calcite (1 1 bar 0) surface. Our calculations results can not only give a microscopic insight into the wettability of gas reservoirs but also provide theoretical instructions for hydrate risk evaluation of enhanced gas recovery.

  15. Measurement of intergranular stress and porosity during dynamic compaction of porous beds of cyclotetramethylene tetranitramine

    NASA Astrophysics Data System (ADS)

    Greenaway, M. W.

    2005-05-01

    The dynamic compaction of granular beds of the propellant cyclotetramethylene tetranitramine (HMX) has been investigated using a modified split Hopkinson pressure bar system. Intergranular stress and bed porosity were simultaneously measured during controlled loading. The importance of grain size was investigated by comparing conventional HMX (mean particle size ˜260μm) to microfine HMX (<5μm). Samples were radially confined and compression was predetermined using special end caps. Initial porosity was varied by hydraulically pressing the beds prior to testing. With large grains, resistance to compaction increased with the solid volume fraction. Microfine HMX behaved like low porosity conventional HMX beds in all cases. Porosity was typically reduced by 5%-10% during compaction and intergranular stresses below the yield stress were ensured. Energy dissipation to plastic flow and fracture were largely eliminated. Optical particle size analysis and electron microscopy support the experimental observations.

  16. Dynamic-tensile-extrusion response of fluoropolymers

    SciTech Connect

    Brown, Eric N; Trujillo, Carl P; Gray, George T

    2009-01-01

    The current work applies the recently developed Dynamic-Tensile-Extrusion (Dyn-Ten-Ext) technique to polytetrafluoroethylene (PTFE) and polychlorotrifluoroethylene (PCTFE). Similar to the Taylor Impact Rod, Dynamic-Tensile-Extrusion is a strongly integrated test, probing a wide range of strain rates and stress states. However, the stress state is primarily tensile enabling investigation of dynamic tensile failure modes. Here we investigate the influence of this propensity to neck or not between PCTFE and PTFE on their response under dynamic tensile extrusion loading. The results of the Dyn-Ten-Ext technique are compared with two classic techniques. Both polymers have been investigated using Tensile Split Hopkinson Pressure Bar. The quasistatic and dynamic responses of both fluoro-polymers have been extensively characterized. The two polymers exhibit significantly different failure behavior under tensile loading at moderate strain rates. Polytetrafluoroethylene resists formation of a neck and exhibits significant strain hardening. Independent of temperature or strain rate, PTFE sustains true strains to failure of approximately 1.5. Polychlorotrifluoroethylene, on the other hand, consistently necks at true strains of approximately 0.05.

  17. Thermal imaging of metals in a Kolsky-bar apparatus

    NASA Astrophysics Data System (ADS)

    Yoon, Howard W.; Basak, Debasis; Rhorer, Richard L.; Whitenton, Eric; Burns, Timothy J.; Fields, Richard; Levine, Lyle

    2003-04-01

    Since the modeling of machining processes relies on high-strain-rate, high-temperature material properties, NIST has built a split-Hopkinson (or Kolsky) bar to determine the stress-strain behavior of rapidly heated materials at high temperatures. Our Kolsky bar has been constructed in the NIST high current pulse-heating facility, which enables electrically heating the samples within ~ 100 milliseconds time duration, immediately before the mechanical impact in the bar. Due to the rapid heating, we avoid possible structural changes in the sample, and a stress-strain relationship can be determined at different temperatures for various test materials. We describe the design and the development of the resistively-heated Kolsky-bar apparatus. The incident and the transmitted bars are constructed of 1.5 m long, 15 mm diameter maraging steel, and a typical sample is a 4 mm-diameter, 2 mm-long cylinder of 1045 steel. The sample is placed between the bars and held by friction. The current is transmitted through the graphite-sleeve bushings of the two bars. The non-contact temperatures are measured using an InGaAs near-infrared micro-pyrometer (NIMPY) and an InSb focal-plane (320 by 256) array (thermal camera). The NIMPY and the thermal camera are both calibrated using a variable-temperature blackbody, and the thermodynamic temperature of the metal is determined using the emissivity determined from the measured infrared spectral reflectance of the metal. Thermal videos of the electrically-heated and the room-temperature impacts will be shown with 1 kHz frame rates, and the changes in the stress-strain curves with the temperature of the samples will be discussed.

  18. Bar Impact Tests on Alumina (AD995)

    NASA Astrophysics Data System (ADS)

    Cazamias, James U.; Reinhart, William D.; Konrad, Carl H.; Chhabildas, Lalit C.; Bless, Stephan J.

    2002-07-01

    Dynamic strength may be inferred from bar impact tests, although interpretation of the data is affected by the time-to-failure of the target bar. To clarify the mechanics, tests with graded density impactors were conducted on bare and confined bars, 12 and 19 mm in diameter, cut from blocks of AD995 alumina. Manganin gauge and VISAR diagnostics were employed. Larger rods displayed higher strength. In some tests the "true" yield stress of ˜4.5 GPa was achieved.

  19. An Experimental Study of Dynamic Tensile Failure of Rocks Subjected to Hydrostatic Confinement

    NASA Astrophysics Data System (ADS)

    Wu, Bangbiao; Yao, Wei; Xia, Kaiwen

    2016-10-01

    It is critical to understand the dynamic tensile failure of confined rocks in many rock engineering applications, such as underground blasting in mining projects. To simulate the in situ stress state of underground rocks, a modified split Hopkinson pressure bar system is utilized to load Brazilian disc (BD) samples hydrostatically, and then exert dynamic load to the sample by impacting the striker on the incident bar. The pulse shaper technique is used to generate a slowly rising stress wave to facilitate the dynamic force balance in the tests. Five groups of Laurentian granite BD samples (with static BD tensile strength of 12.8 MPa) under the hydrostatic confinement of 0, 5, 10, 15, and 20 MPa were tested with different loading rates. The result shows that the dynamic tensile strength increases with the hydrostatic confining pressure. It is also observed that under the same hydrostatic pressure, the dynamic tensile strength increases with the loading rate, revealing the so-called rate dependency for engineering materials. Furthermore, the increment of the tensile strength decreases with the hydrostatic confinement, which resembles the static tensile behavior of rock under confining pressure, as reported in the literature. The recovered samples are examined using X-ray micro-computed tomography method and the observed crack pattern is consistent with the experimental result.

  20. A Method for Selecting Software for Dynamic Event Analysis II: the Taylor Anvil and Dynamic Brazilian Tests

    SciTech Connect

    W. D. Richins; J. M. Lacy; T. K. Larson; S. R. Novascone

    2008-05-01

    New nuclear power reactor designs will require resistance to a variety of possible malevolent attacks as well as traditional dynamic accident scenarios. The design/analysis team may be faced with a broad range of phenomena including air and ground blasts, high-velocity penetrators or shaped charges, and vehicle or aircraft impacts. With a host of software tools available to address these high-energy events, the analysis team must evaluate and select the software most appropriate for their particular set of problems. The accuracy of the selected software should then be validated with respect to the phenomena governing the interaction of the threat and structure. Several software codes are available for the study of blast, impact, and other shock phenomena. At the Idaho National Laboratory (INL), a study is underway to investigate the comparative characteristics of a group of shock and high-strain rate physics codes including ABAQUS, LS-DYNA, CTH, ALEGRA, and ALE-3D. In part I of this report, a series of five benchmark problems to exercise some important capabilities of the subject software was identified. The benchmark problems selected are a Taylor cylinder test, a split Hopkinson pressure bar test, a free air blast, the dynamic splitting tension (Brazilian) test, and projectile penetration of a concrete slab. Part II-- this paper-- reports the results of two of the benchmark problems: the Taylor cylinder and the dynamic Brazilian test. The Taylor cylinder test is a method to determine the dynamic yield properties of materials. The test specimen is a right circular cylinder which is impacted against a theoretically rigid target. The cylinder deforms upon impact, with the final shape depending upon the dynamic yield stress, in turn a function of strain and strain rate. The splitting tension test, or Brazilian test, is a method to measure the tensile strength of concrete using a cylindrical specimen. The specimen is loaded diametrically in compression, producing a

  1. {bar K}-NUCLEAR Deeply Bound States?

    NASA Astrophysics Data System (ADS)

    Gal, Avraham

    Following the prediction by Akaishi and Yamazaki of relatively narrow {bar K}-nuclear states, deeply bound by over 100 MeV where the main decay channel {bar K} N -> π Σ is closed, several experimental signals in stopped K- reactions on light nuclei have been interpreted recently as due to such states. In this talk I review (i) the evidence from K--atom data for a deep bar K-nucleus potential, as attractive as V{bar K}(ρ 0) ˜ -(150 - 200) MeV at nuclear matter density, that could support such states; and (ii) the theoretical arguments for a shallow potential, V{bar K}(ρ 0) ˜ -(40 - 60) MeV. I then review a recent work by Mareš, Friedman and Gal in which {bar K}-nuclear bound states are generated dynamically across the periodic table, using a RMF Lagrangian that couples the {bar K} to the scalar and vector meson fields mediating the nuclear interactions. The reduced phase space available for {bar K} absorption from these bound states is taken into account by adding a density- and energy-dependent imaginary term, underlying the corresponding {bar K}-nuclear level widths, with a strength constrained by K--atom fits. Substantial polarization of the core nucleus is found for light nuclei, with central nuclear densities enhanced by almost a factor of two. The binding energies and widths calculated in this dynamical model differ appreciably from those calculated for a static nucleus. These calculations provide a lower limit of Γ {bar K} ˜ 50 ± 10 MeV on the width of nuclear bound states for {bar K} binding energy in the range B{bar K} = 100 - 200 MeV.

  2. Microsecond Time-Resolved Pyrometry during Rapid Resistive Heating of Samples in a Kolsky Bar Apparatus

    NASA Astrophysics Data System (ADS)

    Basak, D.; Yoon, H. W.; Rhorer, R.; Burns, T.

    2003-09-01

    Analysis of machining processes is important in the understanding and improving of manufacturing methods. The modeling of machining processes relies on high-strain rate, high-temperature material properties. A split-Hopkinson pressure bar (or Kolsky bar) is being installed in a NIST high-current pulse-heating facility. By heating the material sample rapidly with a controlled current pulse immediately before the mechanical impact in the bar, structural changes in the sample are inhibited, thus better simulating conditions during machining. A stress-strain relationship can be determined at various temperatures for test materials. We describe the design and the development of a millisecond-resolution split-Hopkinson apparatus, where the sample is resistively heated by the passage of a sub-second-duration electric current pulse. The impact bar is constructed out of maraging steel and the sample is a cylinder of AISI 1045 steel. The current is transmitted through the oiled-bronze sleeve bushing of the impact bar. The temperature measurements are performed using a near-infrared micro-pyrometer (NIMPY). The NIMPY consists of a refractive 5× microscope objective with a numerical aperture of 0.14 attached to a traditional microscope body. The thermal measurement is performed with an InGaAs detector with ˜ 1 μs response time. The procedure used to calibrate the pyrometer with a variable temperature blackbody is described. A brief description of a model of the pulse heating process is given and the predicted sample temperature history is compared with measured temperature data.

  3. Dynamic behaviour of HPFRCC in tension

    NASA Astrophysics Data System (ADS)

    Cadoni, E.; Caverzani, A.; di Priscoi, M.

    2012-08-01

    High Performance Fiber Reinforced Cementitious Composites belong to a new class of structural materials characterized by high strength and ductility. Thanks to the high energy absorbed during the fracture process, due to multiple cracking and pull-out phenomena, they are often suggested for dynamic loading applications. Current understanding of the dynamic response is very limited because of very few investigations have been actually carried out. An experimental research aimed at contributing to the understanding of the behaviour of advanced fiber-reinforced cementitious composites subjected to low and high strain rates was carried out. The material investigated is a High Performance Fiber Reinforced Cementitious Composites. Straight high carbon steel micro-fibers were used. The material behaviour was investigated at several strain rates and the tests results were compared with their static behaviour. Tests at intermediate strain rates were carried out by means of a hydro-pneumatic machine (HPM), while high strain rates were investigated by exploiting a Split Hopkinson Tensile Bar (SHTB). A comparison between static and dynamic tests highlighted several relevant aspects regarding the influence of fibers on the peak strength and post-peak behaviour at high strain rates. Finally, this material will be employed in the construction of an innovative tunnel segment designed for extreme conditions (high temperature and shock).

  4. Time-resolved x-ray diffraction techniques for bulk polycrystalline materials under dynamic loading

    PubMed Central

    Lambert, P. K.; Hustedt, C. J.; Vecchio, K. S.; Huskins, E. L.; Casem, D. T.; Gruner, S. M.; Tate, M. W.; Philipp, H. T.; Woll, A. R.; Purohit, P.; Weiss, J. T.; Kannan, V.; Ramesh, K. T.; Kenesei, P.; Okasinski, J. S.; Almer, J.; Zhao, M.; Ananiadis, A. G.; Hufnagel, T. C.

    2014-01-01

    We have developed two techniques for time-resolved x-ray diffraction from bulk polycrystalline materials during dynamic loading. In the first technique, we synchronize a fast detector with loading of samples at strain rates of ∼103–104 s−1 in a compression Kolsky bar (split Hopkinson pressure bar) apparatus to obtain in situ diffraction patterns with exposures as short as 70 ns. This approach employs moderate x-ray energies (10–20 keV) and is well suited to weakly absorbing materials such as magnesium alloys. The second technique is useful for more strongly absorbing materials, and uses high-energy x-rays (86 keV) and a fast shutter synchronized with the Kolsky bar to produce short (∼40 μs) pulses timed with the arrival of the strain pulse at the specimen, recording the diffraction pattern on a large-format amorphous silicon detector. For both techniques we present sample data demonstrating the ability of these techniques to characterize elastic strains and polycrystalline texture as a function of time during high-rate deformation. PMID:25273733

  5. Time-resolved x-ray diffraction techniques for bulk polycrystalline materials under dynamic loading

    SciTech Connect

    Lambert, P. K.; Hustedt, C. J.; Zhao, M.; Ananiadis, A. G.; Hufnagel, T. C.; Vecchio, K. S.; Huskins, E. L.; Casem, D. T.; Gruner, S. M.; Tate, M. W.; Philipp, H. T.; Purohit, P.; Weiss, J. T.; Woll, A. R.; Kannan, V.; Ramesh, K. T.; Kenesei, P.; Okasinski, J. S.; Almer, J.

    2014-09-15

    We have developed two techniques for time-resolved x-ray diffraction from bulk polycrystalline materials during dynamic loading. In the first technique, we synchronize a fast detector with loading of samples at strain rates of ∼10{sup 3}–10{sup 4} s{sup −1} in a compression Kolsky bar (split Hopkinson pressure bar) apparatus to obtain in situ diffraction patterns with exposures as short as 70 ns. This approach employs moderate x-ray energies (10–20 keV) and is well suited to weakly absorbing materials such as magnesium alloys. The second technique is useful for more strongly absorbing materials, and uses high-energy x-rays (86 keV) and a fast shutter synchronized with the Kolsky bar to produce short (∼40 μs) pulses timed with the arrival of the strain pulse at the specimen, recording the diffraction pattern on a large-format amorphous silicon detector. For both techniques we present sample data demonstrating the ability of these techniques to characterize elastic strains and polycrystalline texture as a function of time during high-rate deformation.

  6. Time-resolved x-ray diffraction techniques for bulk polycrystalline materials under dynamic loading.

    PubMed

    Lambert, P K; Hustedt, C J; Vecchio, K S; Huskins, E L; Casem, D T; Gruner, S M; Tate, M W; Philipp, H T; Woll, A R; Purohit, P; Weiss, J T; Kannan, V; Ramesh, K T; Kenesei, P; Okasinski, J S; Almer, J; Zhao, M; Ananiadis, A G; Hufnagel, T C

    2014-09-01

    We have developed two techniques for time-resolved x-ray diffraction from bulk polycrystalline materials during dynamic loading. In the first technique, we synchronize a fast detector with loading of samples at strain rates of ~10(3)-10(4) s(-1) in a compression Kolsky bar (split Hopkinson pressure bar) apparatus to obtain in situ diffraction patterns with exposures as short as 70 ns. This approach employs moderate x-ray energies (10-20 keV) and is well suited to weakly absorbing materials such as magnesium alloys. The second technique is useful for more strongly absorbing materials, and uses high-energy x-rays (86 keV) and a fast shutter synchronized with the Kolsky bar to produce short (~40 μs) pulses timed with the arrival of the strain pulse at the specimen, recording the diffraction pattern on a large-format amorphous silicon detector. For both techniques we present sample data demonstrating the ability of these techniques to characterize elastic strains and polycrystalline texture as a function of time during high-rate deformation.

  7. Hot Disks and Delayed Bar Formation

    NASA Astrophysics Data System (ADS)

    Sheth, Kartik; Melbourne, Jason; Elmegreen, Debra Meloy; Elmegreen, Bruce G.; Athanassoula, E.; Abraham, Roberto G.; Weiner, Benjamin J.

    2012-10-01

    We present observational evidence for the inhibition of bar formation in dispersion-dominated (dynamically hot) galaxies by studying the relationship between galactic structure and host galaxy kinematics in a sample of 257 galaxies between 0.1 < z <= 0.84 from the All-Wavelength Extended Groth Strip International Survey and the Deep Extragalactic Evolutionary Probe 2 survey. We find that bars are preferentially found in galaxies that are massive and dynamically cold (rotation-dominated) and on the stellar Tully-Fisher relationship, as is the case for barred spirals in the local universe. The data provide at least one explanation for the steep (×3) decline in the overall bar fraction from z = 0 to z = 0.84 in L* and brighter disks seen in previous studies. The decline in the bar fraction at high redshift is almost exclusively in the lower mass (10 < log M *(M ⊙) < 11), later-type, and bluer galaxies. A proposed explanation for this "downsizing" of the bar formation/stellar structure formation is that the lower mass galaxies may not form bars because they could be dynamically hotter than more massive systems from the increased turbulence of accreting gas, elevated star formation, and/or increased interaction/merger rate at higher redshifts. The evidence presented here provides observational support for this hypothesis. However, the data also show that not every disk galaxy that is massive and cold has a stellar bar, suggesting that mass and dynamic coldness of a disk are necessary but not sufficient conditions for bar formation—a secondary process, perhaps the interaction history between the dark matter halo and the baryonic matter, may play an important role in bar formation.

  8. Effects of Thermal Treatment on the Dynamic Mechanical Properties of Coal Measures Sandstone

    NASA Astrophysics Data System (ADS)

    Li, Ming; Mao, Xianbiao; Cao, Lili; Pu, Hai; Mao, Rongrong; Lu, Aihong

    2016-09-01

    Many projects such as the underground gasification of coal seams and coal-bed methane mining (exploitation) widely involve the dynamic problems of coal measures sandstone achieved via thermal treatment. This study examines the dynamic mechanical properties of coal measures sandstone after thermal treatment by means of an MTS653 high-temperature furnace and Split Hopkinson pressure bar test system. Experimental results indicate that 500 °C is a transition point for the dynamic mechanical parameters of coal measures sandstone. The dynamic elastic modulus and peak strength increase linearly from 25 to 500 °C while the dynamic peak strain decreases linearly over the same temperature range. The dynamic elastic modulus and peak strength drop quickly from 500 to 800 °C, with a significant increase in the dynamic peak strain over the same temperature range. The rock mechanics are closely linked to material composition and mesoscopic structure. Analysis by X-ray diffraction and scanning electron microscopy indicate that the molecules inside the sandstone increase in density due to the thermal expansion of the material particles, which effectively improves the deformation resistance and carrying capacity of the sandstone and reduces the likelihood of axial deformation. With heat treatment that exceeds 500 °C, the dynamic mechanical properties rapidly weaken due to the decomposition of kaolinite; additionally, hot cracking of the mineral particles within the materials arises from coal sandstone internal porosity, and other defects gradually appear.

  9. Ensemble Canonical Correlation Prediction of Seasonal Precipitation Over the United States: Raising the Bar for Dynamical Model Forecasts

    NASA Technical Reports Server (NTRS)

    Lau, William K. M.; Kim, Kyu-Myong; Shen, S. P.

    2001-01-01

    This paper presents preliminary results of an ensemble canonical correlation (ECC) prediction scheme developed at the Climate and Radiation Branch, NASA/Goddard Space Flight Center for determining the potential predictability of regional precipitation, and for climate downscaling studies. The scheme is tested on seasonal hindcasts of anomalous precipitation over the continental United States using global sea surface temperature (SST) for 1951-2000. To maximize the forecast skill derived from SST, the world ocean is divided into non-overlapping sectors. The canonical SST modes for each sector are used as the predictor for the ensemble hindcasts. Results show that the ECC yields a substantial (10-25%) increase in prediction skills for all the regions of the US in every season compared to traditional CCA prediction schemes. For the boreal winter, the tropical Pacific contributes the largest potential predictability to precipitation in the southwestern and southeastern regions, while the North Pacific and the North Atlantic are responsible to the enhanced forecast skills in the Pacific Northwest, the northern Great Plains and Ohio Valley. Most importantly, the ECC increases skill for summertime precipitation prediction and substantially reduces the spring predictability barrier over all the regions of the US continent. Besides SST, the ECC is designed with the flexibility to include any number of predictor fields, such as soil moisture, snow cover and additional local observations. The enhanced ECC forecast skill provides a new benchmark for evaluating dynamical model forecasts.

  10. A study on the dynamic behavior of the Meuse/Haute-Marne argillite

    NASA Astrophysics Data System (ADS)

    Cai, M.; Kaiser, P. K.; Suorineni, F.; Su, K.

    Excavation of underground tunnels can be conducted by tunnel boring machines (TBM) or drill-and-blast. TBMs cause minimum damage to excavation walls. Blasting effects on excavation walls depend on the care with which the blasting is executed. For blast-induced damage in excavation walls, two issues have to be addressed: rate of loss of confinement (rate of excavation) and dynamic loading from wave propagation that causes both intended and unintended damage. To address these two aspects, laboratory dynamic tests were conducted for the determination of the dynamic properties of the Meuse/Haute-Marne argillite. In the present study, 17 tensile (Brazilian) and 15 compression split Hopkinson pressure bar (SHPB) tests were conducted. The test revealed that the dynamic strengths of the argillite are strain rate dependent. The average dynamic increase factors (ratio of dynamic strength to static strength) for tensile and compressive strength are about 3.3 and 2.4, respectively. A high-speed video camera was used to visualize the initiation of failure and subsequent deformation of the specimens. The direct compression specimens were found to deform and fail uniformly around the circumference of the specimen, by a spalling process. The SHPB Brazilian tests indicated that failure occurred in tension along the line of load application. Radial fractures were also observed. The test results can be used for the development of a dynamic constitutive model for the argillite for the prediction of damage in underground excavation utilizing the drill-and blast method.

  11. Static and dynamic moduli of posterior dental resin composites under compressive loading.

    PubMed

    Tanimoto, Yasuhiro; Hirayama, Satoshi; Yamaguchi, Masaru; Nishiwaki, Tsuyoshi

    2011-10-01

    Dental resin composites are commonly used as restorative materials for dental treatment. To comprehend the static and dynamic moduli of dental resin composites, we investigated the mechanical behaviors of resin composites under static and dynamic loading conditions. Four commercially available resin composites for posterior restorations were evaluated. The percentages, by weight, of inorganic fillers of resin composites were examined by the ashing technique. The static compressive tests were undertaken with a constant loading speed of 1.0 mm/min using a computer-controlled INSTRON testing machine. The dynamic properties of composites were determined using the split Hopkinson pressure bar (SHPB) technique. When inorganic filler content was increased, a remarkable increase in the static modulus and dynamic modulus were observed. Furthermore, there was a strong relationship between the static modulus and dynamic modulus (r(2) = 0.947). The SHPB technique clearly demonstrated the dynamic properties of composites, and was a useful technique for determining the mechanical behavior of composites under dynamic compressive loading.

  12. Dynamics of wave-induced currents over an alongshore non-uniform multiple-barred sandy beach on the Aquitanian Coast, France

    NASA Astrophysics Data System (ADS)

    Castelle, Bruno; Bonneton, Philippe; Sénéchal, Nadia; Dupuis, Hélène; Butel, Rémi; Michel, Denis

    2006-01-01

    This paper presents field investigation and numerical modelling of waves and wave-induced currents on a wave-dominated and non-alongshore uniform multiple barred beach. This study aims at establishing the first analysis of the dynamics of horizontal flows on the French Aquitanian coast. The spectral wave program SWAN is coupled with the time- and depth-averaged (2DH) coastal area model MORPHODYN. This coupled-model is applied to Truc Vert Beach, and results are compared with field data. From the 14th to the 19th of October 2001, a field experiment was carried out in order to characterize hydrodynamics and sediment transport over a complex bathymetry in the presence of oceanic wave conditions. From this data we calibrated three parameters: the bottom friction for wave propagation from the Aquitanian continental shelf to the nearshore zone, the spatially constant bottom friction coefficient due to waves and currents, and lateral mixing. Despite model approximations and the fact that the offshore wave boundary condition was located 15 km off the coast, the model is in good agreement with measurements. During weak wind conditions, computed waves and longshore currents fit well with field data on the ridge and runnel system. The strong tidal modulation of surf zone processes over this system is revealed. Hydrodynamics are strongly controlled by the beach morphology. For near-normally incident swells, the ridge and runnel system is responsible for a strong rip current located at the runnel outlet, associated with a circulation cell. Prediction of the tidal modulation and the sensitivity of the rip current to offshore wave conditions are in agreement with observations. Maximum rip current flow velocities occur approximately at mid-tide, which differs from what most researchers have found in other environments.

  13. Constraints from microlensing on the COBE bar

    NASA Astrophysics Data System (ADS)

    Zhao, H. S.

    Since the first review of converging evidences for a bar in the center of the Galaxy by de Zeeuw (1992) at the IAU Sym. 153 in Gent five years ago, the Galactic bar idea has been put on a solid footing by an influx of new data (COBE/DIRBE maps, star count data of bulge red clump giants, microlensing optical depth, and bulge stellar proper motions, etc.) and a burst of increasingly sophisticated theoretical models (triaxial luminosity models of Dwek et al. 1994, and Binney, Gerhard & Spergel 1997, steady state stellar bar dynamical model of Zhao 1996, combined luminosity, microlensing and gas kinematics models of Zhao, Rich & Spergel 1996, and Bissantz et al. 1997, etc.), which fit new data and improve upon earlier simple bulge/bar models (Kent 1992, Binney et al. 1991, Blitz & Spergel 1991). While research in this field shifts more and more to constraining the exact phase space and parameter space of the bar, both the non-uniqueness of and the mismatches among bars from different datasets start to show up. I compare the bar from microlensing data with the COBE bar and point out the effects the non-uniqueness.

  14. Interferometry-based Kolsky bar apparatus

    NASA Astrophysics Data System (ADS)

    Avinadav, C.; Ashuach, Y.; Kreif, R.

    2011-07-01

    A new experimental approach of the Kolsky bar system using optical interferometry is presented for determination of dynamic behavior of materials. Conventional measurements in the Kolsky bar system are based on recording the strain histories on the incident and transmitter bars with two strain gauges, and require good adhesion between the gauge and the bar. We suggest an alternative approach, based on measuring the actual velocities of the bars by using fiber-based velocity interferometry. Two fiber focusers illuminate the bars at a small angle and collect reflected Doppler-shifted light, which is interfered with a reference beam. Velocities are calculated from short-time Fourier transform and phase-based analysis, and the dynamic stress-strain curve is derived directly from the measured velocity traces. We demonstrate that the results coincide with those obtained by conventional strain gauge measurements. The new method is non-intervening and thus not affected by bar impacts, making it more robust and reliable than strain gauges.

  15. The four bars problem

    NASA Astrophysics Data System (ADS)

    Mauroy, Alexandre; Taslakian, Perouz; Langerman, Stefan; Jungers, Raphaël

    2016-09-01

    A four-bar linkage is a mechanism consisting of four rigid bars which are joined by their endpoints in a polygonal chain and which can rotate freely at the joints (or vertices). We assume that the linkage lies in the 2-dimensional plane so that one of the bars is held horizontally fixed. In this paper we consider the problem of reconfiguring a four-bar linkage using an operation called a pop. Given a four-bar linkage, a pop reflects a vertex across the line defined by its two adjacent vertices along the polygonal chain. Our main result shows that for certain conditions on the lengths of the bars, the neighborhood of any configuration that can be reached by smooth motion can also be reached by pops. The proof relies on the fact that pops are described by a map on the circle with an irrational number of rotation.

  16. Composite carrier bar device

    SciTech Connect

    Felder, D.W.

    1981-09-01

    A composite carrier bar is disclosed for oil well pumping units that utilize sucker rod to operate bottom hole pumps. The bar includes a recessed cavity for receiving a hydraulic ram to operate as a polish rod jack and also a secondary carrier bar for receiving a secondary polish rod clamp for use in respacing bottom hole pumps and serve as a safety clamp during operation.

  17. Gap Formations Along Specimen-Bar Interfaces in Numerical Simulations of SHPB Tests on Elastic Materials Soft in Shear

    NASA Astrophysics Data System (ADS)

    Raftenberg, Martin N.; Scheidler, Mike

    2009-06-01

    Simulations of split Hopkinson pressure bar (SHPB) tests on elastic materials were performed using LS-DYNA. The specimens were much stiffer in dilatation than in shear. A compressible form of Mooney-Rivlin elasticity was applied with parameters evaluated from ballistic gelatin data. The bars were aluminum. The velocity prescribed on the incident bar increased over a rise time until attaining a steady-state value corresponding to a nominal strain rate of 2500/s. The rise time was varied to observe effects of pulse shaping. All calculations were 2D axisymmetric. A penalty-based contact algorithm was applied at the specimen-bar interfaces. This algorithm introduced a stiffness and a viscosity parameter. In sensitivity studies we varied the radius of the bars, the specimen's mesh, and the two contact parameters. In all calculations with the Mooney-Rivlin model, gaps formed at both specimen-bar interfaces over a wide range of strains. This gap phenomenon appears not to have been previously reported in the SHPB literature. We replaced the Mooney-Rivlin model with linear elasticity in order to explore whether the gaps were associated with material nonlinearity. We fixed Young's modulus at a value much smaller than that of aluminum. For sufficiently large Poisson ratios, we again observed gap formations at both specimen-bar interfaces.

  18. Bar Code Labels

    NASA Technical Reports Server (NTRS)

    1988-01-01

    American Bar Codes, Inc. developed special bar code labels for inventory control of space shuttle parts and other space system components. ABC labels are made in a company-developed anodizing aluminum process and consecutively marketed with bar code symbology and human readable numbers. They offer extreme abrasion resistance and indefinite resistance to ultraviolet radiation, capable of withstanding 700 degree temperatures without deterioration and up to 1400 degrees with special designs. They offer high resistance to salt spray, cleaning fluids and mild acids. ABC is now producing these bar code labels commercially or industrial customers who also need labels to resist harsh environments.

  19. Microlensing by the galactic bar

    NASA Technical Reports Server (NTRS)

    Zhao, Hongsheng; Spergel, David N.; Rich, R. Michael

    1995-01-01

    We compute the optical depth and duration distribution of microlensing events towrd Baade's window in a model composed of a Galactic disk and a bar. The bar model is a self-consistent dynamical model built out of individual orbits that has been populated to be consistent with the COBE maps of the Galaxy and kinematic observations of the Galactic bulge. We find that most of the lenses are in the bulge with a line-of-sight distance 6.25 kpc (adopting R(sub 0) = 8 kpc). The microlensing optical depth of a 2 x 10(exp 10) solar mass bar plus a truncated disk is (2.2 +/- 0.45) x 10(exp -6), consistent with the large optical depth (3.2 +/- 1.2) x 10(exp -6) found by Udalski et al. (1994). This model optical depth is enhanced over the predictions of axisymmetric models by Kiraga & Paczynski (1994) by slightly more than a factor of 2, since the bar is elongated along the line of sight. The large Einstein radius and small transverse velocity dispersion also predict a longer event duration in the self-consistent bar model than in the Kiraga-Paczynski model. The event rate and duration distribution also depend on the lower mass cutoff of the lens mass function. With a 0.1 solar mass cutoff, five to seven events (depending on the contribution of disk lenses) with a logarithmic mean duration of 20 days are expected for the Optical Gravitational Lensing Experiment (OGLE) according to our model, while Udalski et al. (1994) observed nine events with durations from 8 to 62 days. On the other hand, if most of the lenses are brown dwarfs, our model predicts too many short-duration events. A Kolmogorov-Smirnov test finds only 7% probability for the model with 0.01 solar mass cutoff to be consistent with current data.

  20. Static and Dynamic Flexural Strength Anisotropy of Barre Granite

    NASA Astrophysics Data System (ADS)

    Dai, F.; Xia, K.; Zuo, J. P.; Zhang, R.; Xu, N. W.

    2013-11-01

    Granite exhibits anisotropy due to pre-existing microcracks under tectonic loadings; and the mechanical property anisotropy such as flexural/tensile strength is vital to many rock engineering applications. In this paper, Barre Granite is studied to understand the flexural strength anisotropy under a wide range of loading rates using newly proposed semi-circular bend tests. Static tests are conducted with a MTS hydraulic servo-control testing machine and dynamic tests with a split Hopkinson pressure bar (SHPB) system. Six samples groups are fabricated with respect to the three principle directions of Barre granite. Pulse shaping technique is used in all dynamic SHPB tests to facilitate dynamic stress equilibrium. Finite element method is utilized to build up equations calculating the flexural tensile strength. For samples in the same orientation group, a loading rate dependence of the flexural tensile strength is observed. The measured flexural tensile strength is higher than the tensile strength measured using Brazilian disc method at given loading rate and this scenario has been rationalized using a non-local failure theory. The flexural tensile strength anisotropy features obvious dependence on the loading rates, the higher the loading rate, the less the anisotropy and this phenomenon may be explained considering the interaction of the preferentially oriented microcracks.

  1. Enhanced surveillance program annual report FY98. Dynamic behavior of Pu and U (intermediate strain rates) -- LA12

    SciTech Connect

    Blumenthal, W.R.

    1998-12-31

    The Kolsky-Hopkinson Bar Dynamic Test Facility in Building PF-4 at TA-55 recently became operational and the first series of plutonium samples from a baseline alloy were successfully tested on December 8, 1997 through the dedicated efforts of a large number of people in groups NMT-9, NMT-11, MST-8, NMT-5, and JCI. The Enhanced Surveillance Program provided the necessary support for this achievement. The Kolsky-Hopkinson bar is an instrument designed to measure the uniaxial compression stress-strain characteristics of special nuclear materials (SNM) in a glovebox environment at intermediate strain rates (typically 500 s{sup {minus}1} to 10,000 s{sup {minus}1}), over a wide temperature range (cryogenic up to near-melting temperatures), and up to strains of about 50% per test. Due to radiation contamination hazards, SNM samples are contained within a specially designed glovebox with only a small portion of the bar system. The uniaxial high-strain-rate deformation behavior of SNM materials is revealed by stress-strain-strain rate curves calculated from strain signals acquired by gauges on the pressure bars. The compressive stress-strain mechanical behavior of a range of weapons-relevant SNM materials (both baseline and stockpile-aged plutonium and enriched uranium), measured over a wide range of strain rates and temperatures, is necessary to support the development of predictive constitutive models and allows assessment of the mechanical response of SNM as a function of age, processing, and composition. Accurate constitutive material models are essential for simulating the high-rate deformation response of weapon materials. Most FY98 milestones and deliverables were successfully met or were partially completed on schedule. In the case of enriched uranium, testing began six months ahead of schedule. Upgrading the testing temperature capability took six months more than originally planned as a result of the highly formalized and rigorous design change plan (DCP

  2. Effect of Ductile Agents on the Dynamic Behavior of SiC3D Network Composites

    NASA Astrophysics Data System (ADS)

    Zhu, Jingbo; Wang, Yangwei; Wang, Fuchi; Fan, Qunbo

    2016-07-01

    Co-continuous SiC ceramic composites using pure aluminum, epoxy, and polyurethane (PU) as ductile agents were developed. The dynamic mechanical behavior and failure mechanisms were investigated experimentally using the split Hopkinson pressure bar (SHPB) method and computationally by finite element (FE) simulations. The results show that the SiC3D/Al composite has the best overall performance in comparison with SiC3D/epoxy and SiC3D/PU composites. FE simulations are generally consistent with experimental data. These simulations provide valuable help in predicting mechanical strength and in interpreting the experimental results and failure mechanisms. They may be combined with micrographs for fracture characterizations of the composites. We found that interactions between the SiC phase and ductile agents under dynamic compression in the SHPB method are complex, and that interfacial condition is an important parameter that determines the mechanical response of SiC3D composites with a characteristic interlocking structure during dynamic compression. However, the effect of the mechanical properties of ductile agents on dynamic behavior of the composites is a second consideration in the production of the composites.

  3. Dynamic compressive behavior of Pr-Nd alloy at high strain rates and temperatures

    SciTech Connect

    Wang Huanran; Cai Canyuan; Chen Danian; Ma Dongfang

    2012-07-01

    Based on compressive tests, static on 810 material test system and dynamic on the first compressive loading in split Hopkinson pressure bar (SHPB) tests for Pr-Nd alloy cylinder specimens at high strain rates and temperatures, this study determined a J-C type [G. R. Johnson and W. H. Cook, in Proceedings of Seventh International Symposium on Ballistics (The Hague, The Netherlands, 1983), pp. 541-547] compressive constitutive equation of Pr-Nd alloy. It was recorded by a high speed camera that the Pr-Nd alloy cylinder specimens fractured during the first compressive loading in SHPB tests at high strain rates and temperatures. From high speed camera images, the critical strains of the dynamic shearing instability for Pr-Nd alloy in SHPB tests were determined, which were consistent with that estimated by using Batra and Wei's dynamic shearing instability criterion [R. C. Batra and Z. G. Wei, Int. J. Impact Eng. 34, 448 (2007)] and the determined compressive constitutive equation of Pr-Nd alloy. The transmitted and reflected pulses of SHPB tests for Pr-Nd alloy cylinder specimens computed with the determined compressive constitutive equation of Pr-Nd alloy and Batra and Wei's dynamic shearing instability criterion could be consistent with the experimental data. The fractured Pr-Nd alloy cylinder specimens of compressive tests were investigated by using 3D supper depth digital microscope and scanning electron microscope.

  4. Experimental study on the dynamic mechanical properties of titanium alloy after thermal oxidation

    NASA Astrophysics Data System (ADS)

    Niu, Xiaoyan; Yu, Yingjie; Ma, Lianhua; Chen, Liangbiao

    2016-06-01

    In this study, the dynamic compressive properties of thermally oxidized TC4 (Ti-6Al-4V) titanium alloys were studied with split Hopkinson pressure bar. The dynamic tests were conducted under multiple strain rates from 400 to 2000 s-1 and different testing temperatures from 25 to 200 °C. Data for the true stress-strain curves of thermally oxidized TC4 titanium alloy are presented. They show that the thermal oxidation increases both the dynamic compressive strength of TC4 titanium and the rate of strain hardening. Higher compressive strengths of the material were obtained by applying higher strain rates. Under a strain rate of 2000 s-1, the stress-strain curves of TC4 titanium alloys exhibit both strain-rate-hardening behavior and thermal softening behavior. The oxidation temperature has little effect on dynamic properties of TC4 titanium alloy, but choosing different holding time for oxidation could greatly affect the initiation of plastic deformation and thus might potentially improve the ductility of the treated material. Furthermore, the data show that the increase in the testing temperature results in much lower yield stresses of the treated material.

  5. Dependence of Dynamic Tensile Strength of Longyou Sandstone on Heat-Treatment Temperature and Loading Rate

    NASA Astrophysics Data System (ADS)

    Yao, Wei; Xu, Ying; Wang, Wei; Kanopolous, Patrick

    2016-10-01

    As a material for famous historical underground rock caverns, Longyou sandstone (LS) may fail under the combination of high loading rate and high temperature. The thermal damage induced by various heat-treatment temperatures (150, 250, 350, 450, 600 and 850 °C) is first characterized by X-ray Micro-computed tomography (CT) method. The damage variable derived from the average CT value for heat-treated LS specimen and reference specimen without heat treatment was used to quantify the thermal damage. The dynamic tensile strengths of these LS samples under different dynamic loading rates (ranging from 24 to 540 GPa/s) were then obtained using the split Hopkinson pressure bar (SHPB) system. The dynamic tensile strength of LS increases with the loading rate at a given heat-treatment temperature, and the tensile strength at the same loading rate decreases with the heat-treatment temperature except for 450 °C. Based on the experimental data, an empirical equation was established to relate the dynamic tensile strength of LS to the loading rate and the heat-treatment temperature.

  6. The role of the modified taylor impact test in dynamic material research

    NASA Astrophysics Data System (ADS)

    Bagusat, Frank; Rohr, Ingmar

    2015-09-01

    Dynamic material research with strain rates of more than 1000 1/s is experimentally very often done with a Split-Hopkinson Bar, Taylor impact tests or planar plate impact test investigations. At the Ernst-Mach-Institut (EMI), a variant of an inverted classical Taylor impact test is used by application of velocity interferometers of the VISAR type ("Modified Taylor Impact Test", MTT). The conduction of the experiments is similar to that of planar plate impact tests. The data reduction and derivation of dynamic material data can also be restricted to an analysis of the VISAR signal. Due to these properties, nearly each highly dynamic material characterization in our institute done by planar plate investigations is usually accompanied by MTT experiments. The extended possibilities and usefulness of a combined usage of these two highly dynamic characterization methods are explained. Recently, further developed MTT experiments with very small specimen sizes are presented. For the first time, Taylor impact and planar impact specimen can be used for which the load directions even in case of thin plate test material are identical and not perpendicular to each other. Consequences for testing construction elements are discussed.

  7. Effect of Ductile Agents on the Dynamic Behavior of SiC3D Network Composites

    NASA Astrophysics Data System (ADS)

    Zhu, Jingbo; Wang, Yangwei; Wang, Fuchi; Fan, Qunbo

    2016-10-01

    Co-continuous SiC ceramic composites using pure aluminum, epoxy, and polyurethane (PU) as ductile agents were developed. The dynamic mechanical behavior and failure mechanisms were investigated experimentally using the split Hopkinson pressure bar (SHPB) method and computationally by finite element (FE) simulations. The results show that the SiC3D/Al composite has the best overall performance in comparison with SiC3D/epoxy and SiC3D/PU composites. FE simulations are generally consistent with experimental data. These simulations provide valuable help in predicting mechanical strength and in interpreting the experimental results and failure mechanisms. They may be combined with micrographs for fracture characterizations of the composites. We found that interactions between the SiC phase and ductile agents under dynamic compression in the SHPB method are complex, and that interfacial condition is an important parameter that determines the mechanical response of SiC3D composites with a characteristic interlocking structure during dynamic compression. However, the effect of the mechanical properties of ductile agents on dynamic behavior of the composites is a second consideration in the production of the composites.

  8. The dynamic mechanical behavior of insaturated clay under quasi-one-dimensional strain state

    NASA Astrophysics Data System (ADS)

    Jing, Song-ji; Lu, Fang-yun; Chen, Rong; Qin, Jin-gui; Pang, Chun-jing

    2008-11-01

    An improved split Hopkinson pressure bar (SHPB) method with passive confined pressure was used to study the dynamic mechanical behaviors of an insaturated clay under quasi-one dimensional strain state. Experimental results show that both modulus of elasticity and yield strength of the clay were sensitive to strain rates. The confined pressures of the specimens were also obtained from the dynamic tests. In addition, the quasi-static responses of the clay were obtained with the unconsolidated and undrained (UU) test with confined pressure from 0.1MPa to 1MPa. Results of the quasi-static experiments show that the yield strength of clay increased with the confined pressure. The quasi-static and dynamic stress-strain behavior of the clay under confinement exhibited an elastic-plastic-like response. Based on the results of both dynamic and quasi-static tests, a phenomenological elastic-plastic type of material model was employed to describe the strain-rate-dependent properties of the clay under tri-axial state of stress, which agreed well with the experimental results.

  9. Dynamic response of fiber bundle under transverse impact.

    SciTech Connect

    Lu, Wei-Yang; Song, Bo

    2010-03-01

    There has been a very high demand in developing efficient soft body armors to protect the military and law enforcement personnel from ballistic or explosive attack. As a basic component in the soft body armor, fibers or fiber bundles play a key role in the performance against ballistic impact. In order to study the ballistic-resistant mechanism of the soft body armor, it is desirable to understand the dynamic response of the fiber bundle under transverse impact. Transverse wave speed is one important parameter because a faster transverse wave speed can make the impact energy dissipate more quickly. In this study, we employed split Hopkinson pressure bar (SHPB) to generate constant high-speed impact on a Kevlar fiber bundle in the transverse direction. The deformation of the fiber bundle was photographed with high-speed digital cameras. The transverse wave speeds were experimentally measured at various transverse impact velocities. The experimental results can also be used to quantitatively verify the current analytical models or to develop new models to describe the dynamic response of fiber bundle under transverse impact.

  10. Determination of dynamic fracture toughness using a new experimental technique

    NASA Astrophysics Data System (ADS)

    Cady, Carl M.; Liu, Cheng; Lovato, Manuel L.

    2015-09-01

    In other studies dynamic fracture toughness has been measured using Charpy impact and modified Hopkinson Bar techniques. In this paper results will be shown for the measurement of fracture toughness using a new test geometry. The crack propagation velocities range from ˜0.15 mm/s to 2.5 m/s. Digital image correlation (DIC) will be the technique used to measure both the strain and the crack growth rates. The boundary of the crack is determined using the correlation coefficient generated during image analysis and with interframe timing the crack growth rate and crack opening can be determined. A comparison of static and dynamic loading experiments will be made for brittle polymeric materials. The analysis technique presented by Sammis et al. [1] is a semi-empirical solution, however, additional Linear Elastic Fracture Mechanics analysis of the strain fields generated as part of the DIC analysis allow for the more commonly used method resembling the crack tip opening displacement (CTOD) experiment. It should be noted that this technique was developed because limited amounts of material were available and crack growth rates were to fast for a standard CTOD method.

  11. Effect of a special carbohydrate-protein bar and tomato juice supplementation on oxidative stress markers and vascular endothelial dynamics in ultra-marathon runners.

    PubMed

    Samaras, Antonios; Tsarouhas, Konstantinos; Paschalidis, Eleftherios; Giamouzis, Grigorios; Triposkiadis, Filippos; Tsitsimpikou, Christina; Becker, Aphrodite Tousia; Goutzourelas, Nikolaos; Kouretas, Demetrios

    2014-07-01

    It is well established that exercise induces excessive production of reactive species leading to oxidative stress, which has been implicated in oxidative damage of macromolecules, immune dysfunction, muscle damage and fatigue. The present study examined the effect of supplementation of ultra-marathon runners for a two-months-period with a special whey protein bar containing carbohydrates and protein in a specific ratio (1:1) (N=16), prepared using as starting material the by-products of cheese manufacturing, and supplementation with commercially available tomato juice (N=15). Thiobarbituric-acid reactive substances and protein carbonyls were significantly decreased in both supplementation groups, while a pronounced increased in reduced glutathione was observed in the protein bar group. Total anti-oxidant activity remained unchanged in both groups. Flow-mediated dilatation, used as an estimate of endothelial function, was increased in both groups, with a significant rise observed only in the tomato juice administration group. In conclusion, supplementation of ultra marathon runners for a two-months-period with a special protein bar and tomato juice significantly improved the oxidative status of the subjects, while tomato juice also improved vascular endothelial function in these athletes.

  12. Mass modeling for bars

    NASA Technical Reports Server (NTRS)

    Butler, Thomas G.

    1987-01-01

    Methods of modeling mass for bars are surveyed. A method for extending John Archer's concept of consistent mass beyond just translational inertia effects is included. Recommendations are given for various types of modeling situations.

  13. Short Nuss bar procedure

    PubMed Central

    2016-01-01

    The Nuss procedure is now the preferred operation for surgical correction of pectus excavatum (PE). It is a minimally invasive technique, whereby one to three curved metal bars are inserted behind the sternum in order to push it into a normal position. The bars are left in situ for three years and then removed. This procedure significantly improves quality of life and, in most cases, also improves cardiac performance. Previously, the modified Ravitch procedure was used with resection of cartilage and the use of posterior support. This article details the new modified Nuss procedure, which requires the use of shorter bars than specified by the original technique. This technique facilitates the operation as the bar may be guided manually through the chest wall and no additional stabilizing sutures are necessary. PMID:27747185

  14. Dynamic mechanical response of magnesium single crystal under compression loading: Experiments, model, and simulations

    NASA Astrophysics Data System (ADS)

    Li, Qizhen

    2011-05-01

    Magnesium single crystal samples are compressed at room temperature under quasistatic (˜0.001 s-1) loading in a universal testing machine and dynamic (430, 1000, and 1200 s-1) loading in a split Hopkinson pressure bar system. Stress-strain curves show that (a) the fracture strain slightly increases with the strain rate; and (b) the maximum strength and strain hardening rate increase significantly when the testing changes from quasistatic to dynamic, although they do not vary much when the strain rate for dynamic testing varies in the range of 430-1200 s-1. The operation of the secondary pyramidal slip system is the dominating deformation mechanism, which leads to a fracture surface with an angle of ˜42° with respect to the loading axial direction. A theoretical material model based on Johnson-Cook law is also derived. The model includes the strain hardening and strain rate hardening terms, and provides the stress-strain relations matching with the experimental results. Finite element simulations for the strain rates used in the experiments predict the mechanical responses of the material that agree well with the experimental data.

  15. Dynamic versus quasi-static loading of X65 offshore steel pipes

    NASA Astrophysics Data System (ADS)

    Kristoffersen, M.; Børvik, T.; Langseth, M.; Hopperstad, O. S.

    2016-05-01

    Anchors or trawl gear occasionally impact offshore pipelines, resulting in large local and global deformations. Impact velocities are typically less than 5 m/s, but local strain rates may be very high. In this study strain rate effects in an X65 offshore material was characterised by split Hopkinson bar tests, while the cross-section homogeneity and possible anisotropic behaviour were determined by quasi-static material tests. Further, dynamic impact tests at prescribed velocities were carried out on simply supported full scale X65 steel pipes. Next, deformation-controlled quasi-static tests with the same boundary conditions were conducted. The level of deformation in the quasi-static tests was set to be equal to that attained in the dynamic tests. Finally, an assessment of the differences between the dynamically and quasi-statically loaded pipes was made in terms of force-displacement response, energy absorbed, and fracture. An optical light microscope and a scanning electron microscope were used to investigate fracture surfaces arising from the various tests.

  16. Comparative experimental study of dynamic compressive strength of mortar with glass and basalt fibres

    NASA Astrophysics Data System (ADS)

    Kruszka, Leopold; Moćko, Wojciech; Fenu, Luigi; Cadoni, Ezio

    2015-09-01

    Specimen reinforced with glass and basalt fibers were prepared using Standard Portland cement (CEM I, 52.5 R as prescribed by EN 197-1) and standard sand, in accordance with EN 196-1. From this cementitious mixture, a reference cement mortar without fibers was first prepared. Compressive strength, modulus of elasticity, and mod of fracture were determined for all specimens. Static and dynamic properties were investigated using Instron testing machine and split Hopkinson pressure bar, respectively. Content of the glass fibers in the mortar does not influence the fracture stress at static loading conditions in a clearly observed way. Moreover at dynamic range 5% content of the fiber results in a significant drop of fracture stress. Analysis of the basalt fibers influence on the fracture stress shows that optimal content of this reinforcement is equal to 3% for both static and dynamic loading conditions. Further increase of the fiber share gives the opposite effect, i.e. drop of the fracture stress.

  17. A new experimental setup to characterize the dynamic mechanical behaviour of ballistic yarns

    NASA Astrophysics Data System (ADS)

    Chevalier, C.; Kerisit, C.; Boussu, F.; Coutellier, D.; Faderl, N.; Klavzar, A.

    2016-10-01

    Fabrics have been widely used as part of ballistic protections since the 1970s and the development of new ballistic solutions made from fabrics need numerical simulations, in order to predict the performance of the ballistic protection. The performances and the induced mechanisms in ballistic fabrics during an impact depend on the weaving parameters and also on the inner parameters of the yarns used inside these structures. Thus, knowing the dynamic behaviour of yarn is essential to determine the ballistic behaviour of fabrics during an impact. Two major experimental devices exist and are used to test ballistic yarns in a dynamic uniaxial tension. The first one corresponds to the Split Hopkinson Tensile Bars device, which is commonly used to characterize the mechanical properties of materials in uniaxial tension and under high loading. The second one is the transversal impact device. The real conditions of ballistic impact can be realized with this device. Then, this paper deals with a new experimental setup developed in our laboratory and called the ‘tensile impact test for yarn’ (TITY) device. With this device, specific absorbed energy measurements of para-aramid yarns (336 Tex, Twaron™, 1000 filaments) have been carried out and revealed that static and dynamic properties of para-aramid are different.

  18. Dynamic fracturing by successive coseismic loadings leads to pulverization in active fault zones

    NASA Astrophysics Data System (ADS)

    Aben, F. M.; Doan, M.-L.; Mitchell, T. M.; Toussaint, R.; Reuschlé, T.; Fondriest, M.; Gratier, J.-P.; Renard, F.

    2016-04-01

    Previous studies show that pulverized rocks observed along large faults can be created by single high-strain rate loadings in the laboratory, provided that the strain rate is higher than a certain pulverization threshold. Such loadings are analogous to large seismic events. In reality, pulverized rocks have been subject to numerous seismic events rather than one single event. Therefore, the effect of successive "milder" high-strain rate loadings on the pulverization threshold is investigated by applying loading conditions below the initial pulverization threshold. Single and successive loading experiments were performed on quartz-monzonite using a Split Hopkinson Pressure Bar apparatus. Damage-dependent petrophysical properties and elastic moduli were monitored by applying incremental strains. Furthermore, it is shown that the pulverization threshold can be reduced by successive "milder" dynamic loadings from strain rates of ~180 s-1 to ~90 s-1. To do so, it is imperative that the rock experiences dynamic fracturing during the successive loadings prior to pulverization. Combined with loading conditions during an earthquake rupture event, the following generalized fault damage zone structure perpendicular to the fault will develop: furthest from the fault plane, there is a stationary outer boundary that bounds a zone of dynamically fractured rocks. Closer to the fault, a pulverization boundary delimits a band of pulverized rock. Consecutive seismic events will cause progressive broadening of the band of pulverized rocks, eventually creating a wider damage zone observed in mature faults.

  19. Dynamic Fracture Initiation Toughness at Elevated Temperatures With Application to the New Generation of Titanium Aluminide Alloys. Chapter 8

    NASA Technical Reports Server (NTRS)

    Shazly, Mostafa; Prakash, Vikas; Draper, Susan; Shukla, Arun (Editor)

    2006-01-01

    Recently, a new generation of titanium aluminide alloy, named Gamma-Met PX, has been developed with better rolling and post-rolling characteristics. I'revious work on this alloy has shown the material to have higher strengths at room and elevated temperatures when compared with other gamma titanium aluminides. In particular, this new alloy has shown increased ductility at elevated temperatures under both quasi-static and high strain rate uniaxial compressive loading. However, its high strain rate tensile ductility at room and elevated temperatures is limited to approx. 1%. In the present chapter, results of a study to investigate the effects of loading rate and test temperature on the dynamic fracture initiation toughness in Gamma-Met PX are presented. Modified split Hopkinson pressure bar was used along with high-speed photography to determine the crack initiation time. Three-point bend dynamic fracture experiments were conducted at impact speeds of approx. 1 m/s and tests temperatures of up-to 1200 C. The results show that thc dynamic fracture initiation toughness decreases with increasing test temperatures beyond 600 C. Furthermore, thc effect of long time high temperature air exposure on the fracture toughness was investigated. The dynamic fracture initiation toughness was found to decrease with increasing exposure time. The reasons behind this drop are analyzed and discussed.

  20. Bar pattern speed evolution over the last 7 Gyr

    NASA Astrophysics Data System (ADS)

    Pérez, I.; Aguerri, J. A. L.; Méndez-Abreu, J.

    2012-04-01

    Context. The tumbling pattern of a bar is the main parameter characterising its dynamics. From numerical simulations, its evolution since bar formation is tightly linked to the dark halo in which the bar is formed through dynamical friction and angular momentum exchange. Observational measurements of the bar pattern speed with redshift can restrict models of galaxy formation and bar evolution. Aims: We aim to determine for the first time the bar pattern speed evolution with redshift based on morphological measurements. Methods: We have selected a sample of 44 low-inclination ringed galaxies from the SDSS and COSMOS surveys covering the redshift range 0 < z < 0.8 to investigate the evolution of the bar pattern speed. We derived morphological ratios between the deprojected outer ring radius (Rring) and the bar size (Rbar). This quantity is related to the parameter ℛ = RCR/Rbar used for classifiying bars in slow and fast rotators, and allows us to investigate possible differences with redshift. Results: We obtain a similar distribution of R at all redshifts. We do not find any systematic effect that could be forcing this result. Conclusions: The results obtained here are compatible with the main bulk of the bar population (~70%) being fast-rotators and with no evolution of the pattern speed with redshift. We argue that if bars are long-lasting structures, the results presented here imply that there has not been a substantial angular momentum exchange between the bar and halo, as predicted by numerical simulations. In consequence, this might imply that the discs of these high surface-brightness galaxies are maximal. The appendix is available in electronic form at http://www.aanda.orgBased on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555.

  1. Experimental study on the dynamic mechanical behaviors of polycarbonate

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Gao, Yubo; Cai, Xuanming; Ye, Nan; Huang, Wei; Hypervelocity Impact Research Center Team

    2015-06-01

    Polycarbonate (PC) is a widely used engineering material in aerospace field, since it has excellent mechanical and optical property. In present study, both compress and tensile tests of PC were conducted at high strain rates by using a split Hopkinson pressure bar. The high-speed camera and 2D digital speckle correlation method (DIC) were used to analyze the dynamic deformation behavior of PC. Meanwhile, the plate impact experiment was carried out to measure the equation of state of PC in a single-stage gas gun, which consists of asymmetric impact technology, manganin gauges, PVDF, electromagnetic particle velocity gauges. The results indicate that the yield stress of PC increased with the strain rates. The strain softening occurred when the stress over yield point except the tensile tests in the strain rates of 1076s-1 and 1279s-1. The ZWT model can describe the constitutive behaviors of PC accurately in different strain rates by contrast with the results of 2D-DIC. At last, The D-u Hugoniot curve of polycarbonate in high pressure was fitted by the least square method. And the final results showed more closely to Cater and Mash than other previous data.

  2. Experimental study on dynamic splitting of recycled concrete using SHPB

    NASA Astrophysics Data System (ADS)

    Lu, Yubin; Yu, Shuisheng; Cai, Yong

    2015-09-01

    To study the recycled concrete splitting tensile properties and fracture state with various recycled coarse aggregate replacement percentage (i.e. 0%, 25%, 50%, 75% and 100%), the dynamic splitting test of recycled concrete was carried out using large diameter (75 mm) split Hopkinson pressure bar (SHPB). The results show that the recycled concrete splitting tensile strength increases with the increase of loading rate, and the loading rate also affects the recycled concrete fracture state, which indicates that the recycled concrete has obvious rate sensitivity. The damage state of the recycled concrete is not only the destruction of the interface between coarse aggregate and cement mortar, but also associates with the fracture damage of aggregates. Under the same water cement ratio, when the replacement percentage of coarse aggregates is around 50%-75%, the gradation of natural and recycled coarse aggregate is optimal, and thus the splitting tensile strength is the largest. This study offers theoretical basis for the engineering applications of recycled concrete.

  3. Toll Bar on Sea

    ERIC Educational Resources Information Center

    Hunter, Dave

    2008-01-01

    In the summer of 2007 the United Kingdom experienced some of the heaviest rainfall since records began. Toll Bar in South Yorkshire featured prominently in media coverage as the village and the homes surrounding it began to flood. Many people lost everything: their homes, their furniture, their possessions. In an effort to come to terms with what…

  4. BARS/SSC/SPHINX

    SciTech Connect

    Herrmann, W. )

    1993-06-06

    BARS is a program which allows retrieval of information from suitable bibliographic databases. Two databases are included, SSC and SPHINX, which together list bibliographic information for some 12,000 references related to the fields of shock compression of condensed media, high rate deformation of solids, and detonation.

  5. BARS/SSC/SPHINX

    SciTech Connect

    Herrmann, W. )

    1993-06-06

    BARS is a program which allows retrieval of information from suitable bibliographic databases. Two databases are included, SSC and SPHINX, which together list bibliographic information for some 12,000 references related to the fields of shoch compression of condensed media, high rate deformation of solids, and detonation.

  6. Bar code usage in nuclear materials accountability

    SciTech Connect

    Mee, W.T.

    1983-07-01

    The age old method of physically taking an inventory of materials by listing each item's identification number has lived beyond its usefulness. In this age of computerization, which offers the local grocery store a quick, sure, and easy means to inventory, it is time for nuclear materials facilities to automate accountability activities. The Oak Ridge Y-12 Plant began investigating the use of automated data collection devices in 1979. At that time, bar code and optical-character-recognition (OCR) systems were reviewed with the purpose of directly entering data into DYMCAS (Dynamic Special Nuclear Materials Control and Accountability System). Both of these systems appeared applicable; however, other automated devices already employed for production control made implementing the bar code and OCR seem improbable. However, the DYMCAS was placed on line for nuclear material accountability, a decision was made to consider the bar code for physical inventory listings. For the past several months a development program has been underway to use a bar code device to collect and input data to the DYMCAS on the uranium recovery operations. Programs have been completed and tested, and are being employed to ensure that data will be compatible and useful. Bar code implementation and expansion of its use for all nuclear material inventory activity in Y-12 is presented.

  7. Bar code usage in nuclear materials accountability

    SciTech Connect

    Mee, W.T.

    1983-01-01

    The Oak Ridge Y-12 Plant began investigating the use of automated data collection devices in 1979. At this time, bar code and optical-character-recognition (OCR) systems were reviewed with the purpose of directly entering data into DYMCAS (Dynamic Special Nuclear Materials Control and Accountability System). Both of these systems appeared applicable, however, other automated devices already employed for production control made implementing the bar code and OCR seem improbable. However, the DYMCAS was placed on line for nuclear material accountability, a decision was made to consider the bar code for physical inventory listings. For the past several months a development program has been underway to use a bar code device to collect and input data to the DYMCAS on the uranium recovery operations. Programs have been completed and tested, and are being employed to ensure that data will be compatible and useful. Bar code implementation and expansion of its use for all nuclear material inventory activity in Y-12 is presented.

  8. Warp evidence in precessing galactic bar models

    NASA Astrophysics Data System (ADS)

    Sánchez-Martín, P.; Romero-Gómez, M.; Masdemont, J. J.

    2016-04-01

    Most galaxies have a warped shape when they are seen edge-on. The reason for this curious form is not completely known so far, so in this work we apply dynamical system tools to contribute to its explanation. Starting from a simple, but realistic model formed by a bar and a disc, we study the effect of a small misalignment between the angular momentum of the system and its angular velocity. To this end, a precession model was developed and considered, assuming that the bar behaves like a rigid body. After checking that the periodic orbits inside the bar continue to be the skeleton of the inner system even after inflicting a precession to the potential, we computed the invariant manifolds of the unstable periodic orbits departing from the equilibrium points at the ends of the bar to find evidence of their warped shapes. As is well known, the invariant manifolds associated with these periodic orbits drive the arms and rings of barred galaxies and constitute the skeleton of these building blocks. Looking at them from a side-on viewpoint, we find that these manifolds present warped shapes like those recognised in observations. Lastly, test particle simulations have been performed to determine how the stars are affected by the applied precession, this way confirming the theoretical results.

  9. Predictions for the $$\\bar{B}^{0}\\rightarrow \\bar{K}^{\\ast 0}$$ X(YZ) and $$\\bar{B}^{0}_{s}\\rightarrow\\phi$$ X(YZ) with X(4160), Y(3940), Z(3930)

    DOE PAGES

    Liang, Wei -Hong; Molina, R.; Xie, Ju -Jun; Doring, M.; Oset, E.

    2015-05-22

    We investigate the decay ofmore » $$\\bar B^0 \\to \\bar K^{*0} R$$ and $$\\bar B^0_s \\to \\phi R$$ with $R$ being the $X(4160)$, $Y(3940)$, $Z(3930)$ resonances. Under the assumption that these states are dynamically generated from the vector-vector interaction, as has been concluded from several theoretical studies, we use a reaction mechanism of quark production at the elementary level, followed by hadronization of one final $$q \\bar q$$ pair into two vectors and posterior final state interaction of this pair of vector mesons to produce the resonances. With this procedure we are able to predict five ratios for these decays, which are closely linked to the dynamical nature of these states, and also predict the order of magnitude of the branching ratios which we find of the order of $$10^{-4}$$, well within the present measurable range. In order to further test the dynamical nature of these resonances we study the $$\\bar B^0_s \\to \\phi D^* \\bar D^*$$ and $$\\bar B^0_s \\to \\phi D_s^* \\bar D_s^*$$ decays close to the $$D^* \\bar D^*$$ and $$D_s^* \\bar D_s^*$$ thresholds and make predictions for the ratio of the mass distributions in these decays and the $$\\bar B^0_s \\to \\phi R$$ decay widths. In conclusion, the measurement of these decays rates can help unravel the nature of these resonances.« less

  10. Predictions for the $\\bar{B}^{0}\\rightarrow \\bar{K}^{\\ast 0}$ X(YZ) and $\\bar{B}^{0}_{s}\\rightarrow\\phi$ X(YZ) with X(4160), Y(3940), Z(3930)

    SciTech Connect

    Liang, Wei -Hong; Molina, R.; Xie, Ju -Jun; Doring, M.; Oset, E.

    2015-05-22

    We investigate the decay of $\\bar B^0 \\to \\bar K^{*0} R$ and $\\bar B^0_s \\to \\phi R$ with $R$ being the $X(4160)$, $Y(3940)$, $Z(3930)$ resonances. Under the assumption that these states are dynamically generated from the vector-vector interaction, as has been concluded from several theoretical studies, we use a reaction mechanism of quark production at the elementary level, followed by hadronization of one final $q \\bar q$ pair into two vectors and posterior final state interaction of this pair of vector mesons to produce the resonances. With this procedure we are able to predict five ratios for these decays, which are closely linked to the dynamical nature of these states, and also predict the order of magnitude of the branching ratios which we find of the order of $10^{-4}$, well within the present measurable range. In order to further test the dynamical nature of these resonances we study the $\\bar B^0_s \\to \\phi D^* \\bar D^*$ and $\\bar B^0_s \\to \\phi D_s^* \\bar D_s^*$ decays close to the $D^* \\bar D^*$ and $D_s^* \\bar D_s^*$ thresholds and make predictions for the ratio of the mass distributions in these decays and the $\\bar B^0_s \\to \\phi R$ decay widths. In conclusion, the measurement of these decays rates can help unravel the nature of these resonances.

  11. THE MASS PROFILE AND SHAPE OF BARS IN THE SPITZER SURVEY OF STELLAR STRUCTURE IN GALAXIES (S{sup 4}G): SEARCH FOR AN AGE INDICATOR FOR BARS

    SciTech Connect

    Kim, Taehyun; Lee, Myung Gyoon; Sheth, Kartik; Muñoz-Mateos, Juan-Carlos; Zaritsky, Dennis; Elmegreen, Bruce G.; Athanassoula, E.; Bosma, Albert; Holwerda, Benne; Ho, Luis C.; Comerón, Sébastien; Laurikainen, Eija; Salo, Heikki; Knapen, Johan H.; Erroz-Ferrer, Santiago; Hinz, Joannah L.; Buta, Ronald J.; Kim, Minjin; Madore, Barry F.; and others

    2015-01-20

    We have measured the radial light profiles and global shapes of bars using two-dimensional 3.6 μm image decompositions for 144 face-on barred galaxies from the Spitzer Survey of Stellar Structure in Galaxies. The bar surface brightness profile is correlated with the stellar mass and bulge-to-total (B/T) ratio of their host galaxies. Bars in massive and bulge-dominated galaxies (B/T > 0.2) show a flat profile, while bars in less massive, disk-dominated galaxies (B/T ∼ 0) show an exponential, disk-like profile with a wider spread in the radial profile than in the bulge-dominated galaxies. The global two-dimensional shapes of bars, however, are rectangular/boxy, independent of the bulge or disk properties. We speculate that because bars are formed out of disks, bars initially have an exponential (disk-like) profile that evolves over time, trapping more disk stars to boxy bar orbits. This leads bars to become stronger and have flatter profiles. The narrow spread of bar radial profiles in more massive disks suggests that these bars formed earlier (z > 1), while the disk-like profiles and a larger spread in the radial profile in less massive systems imply a later and more gradual evolution, consistent with the cosmological evolution of bars inferred from observational studies. Therefore, we expect that the flatness of the bar profile can be used as a dynamical age indicator of the bar to measure the time elapsed since the bar formation. We argue that cosmic gas accretion is required to explain our results on bar profile and the presence of gas within the bar region.

  12. Dynamic Fracture Properties of Rocks Subjected to Static Pre-load Using Notched Semi-circular Bend Method

    NASA Astrophysics Data System (ADS)

    Chen, Rong; Li, Kang; Xia, Kaiwen; Lin, Yuliang; Yao, Wei; Lu, Fangyun

    2016-10-01

    A dynamic load superposed on a static pre-load is a key problem in deep underground rock engineering projects. Based on a modified split Hopkinson pressure bar test system, the notched semi-circular bend (NSCB) method is selected to investigate the fracture initiation toughness of rocks subjected to pre-load. In this study, a two-dimensional ANSYS finite element simulation model is developed to calculate the dimensionless stress intensity factor. Three groups of NSCB specimen are tested under a pre-load of 0, 37 and 74 % of the maximum static load and with the loading rate ranging from 0 to 60 GPa m1/2 s-1. The results show that under a given pre-load, the fracture initiation toughness of rock increases with the loading rate, resembling the typical rate dependence of materials. Furthermore, the dynamic rock fracture toughness decreases with the static pre-load at a given loading rate. The total fracture toughness, defined as the sum of the dynamic fracture toughness and initial stress intensity factor calculated from the pre-load, increases with the pre-load at a given loading rate. An empirical equation is used to represent the effect of loading rate and pre-load force, and the results show that this equation can depict the trend of the experimental data.

  13. Effects of Dynamic Multi-directional Loading on the Microstructural Evolution and Thermal Stability of Pure Aluminum

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Zhang, Hua; Chen, Yadong

    2016-09-01

    Microstructural evolution and thermal stability of 1050 commercial pure aluminum processed by means of split Hopkinson pressure bar and Instron-3369 mechanical testing machine to an accumulated strain of 3.6 were investigated. The nominal strain rates reached up to 3.0 × 103 and 1 × 10-3/s, respectively. Samples in the deformed state and annealed in the temperature interval 423-523 K for 1 h were characterized by transmission electron microscopy (TEM). TEM observations reveal that the initial coarse grains are refined significantly, and the deformed structures mainly consist of equiaxed subgrains and dislocation cells with a high density of interior dislocation. In addition, the average subgrain/cell sizes of these two kinds of deformed samples are nearly the same. As to recovery behavior, recovered subgrains are observed at 473 (dynamic) versus 523 K (quasi-static), that is to say, recovery is fairly slow in the quasi-static deformed samples. It is therefore to be expected that thermal stability of this dynamic deformed aluminum is weaker than that of the quasi-static compressed one, which is due to the higher density of dislocation and nonequilibrium dislocation configurations produced during dynamic loading.

  14. Quantitative analysis of morphology of the fracture surface AlMg6 alloy with consecutive dynamic and gigacycle loading

    NASA Astrophysics Data System (ADS)

    Oborin, Vladimir; Sokovikov, Mikhail; Bilalov, Dmitry; Naimark, Oleg

    2015-10-01

    In this paper we investigated the influence of consecutive dynamic and gigacycle fatigue loads on the lifetime of aluminum-magnesium alloy AlMg6. Preloading of samples was achieved during dynamic tensile tests in the split-Hopkinson bar device. Fatigue tests were conducted on Shimadzu USF-2000 ultrasonic fatigue testing machine. The New-View 5010 interferometer-profiler of high structural resolution (resolution of 0.1 nm) was used for qualitative fracture surface analysis, which provided the data allowing us to find correlation between mechanical properties and scale-invariant characteristics of damage induced roughness formed under dynamic and gigacycle fatigue loading conditions. Original form of the kinetic equation was proposed, which links the rate of the fatigue crack growth and the stress intensity factor using the scale invariant parameters of fracture surface roughness. The scale invariance characterizes the correlated behavior of multiscale damage provides the link of crack growth kinetics and the power exponent of the modified Paris law.

  15. Effects of Dynamic Multi-directional Loading on the Microstructural Evolution and Thermal Stability of Pure Aluminum

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Zhang, Hua; Chen, Yadong

    2016-07-01

    Microstructural evolution and thermal stability of 1050 commercial pure aluminum processed by means of split Hopkinson pressure bar and Instron-3369 mechanical testing machine to an accumulated strain of 3.6 were investigated. The nominal strain rates reached up to 3.0 × 103 and 1 × 10-3/s, respectively. Samples in the deformed state and annealed in the temperature interval 423-523 K for 1 h were characterized by transmission electron microscopy (TEM). TEM observations reveal that the initial coarse grains are refined significantly, and the deformed structures mainly consist of equiaxed subgrains and dislocation cells with a high density of interior dislocation. In addition, the average subgrain/cell sizes of these two kinds of deformed samples are nearly the same. As to recovery behavior, recovered subgrains are observed at 473 (dynamic) versus 523 K (quasi-static), that is to say, recovery is fairly slow in the quasi-static deformed samples. It is therefore to be expected that thermal stability of this dynamic deformed aluminum is weaker than that of the quasi-static compressed one, which is due to the higher density of dislocation and nonequilibrium dislocation configurations produced during dynamic loading.

  16. Full Field Measurement of The Dynamic Response of AA6061-T6 Aluminum Alloy under High Strain Rate Compression and Torsion Loads

    NASA Astrophysics Data System (ADS)

    Odoh, Daniel Oghenekewhe Oluwatobi

    The dynamic response of AA6061-T6 aluminum alloy under high strain rate loading in compression and torsion loading conditions was studied using the split Hopkinson pressure bar, the Kolsky torsion bar, and the high speed digital image correlation system. AA6061-T6 alloy, the most widely used in the AA6000 series, is a multi-purpose Al-Mg-Si-Cu alloy containing about 0.4 % wt. of Cu and other alloying additives. The properties of AA6061-T6 aluminum alloy including medium to high strength, good fracture toughness, and high corrosion resistance make it to find application in high performance structures such as the automotive parts, panels, and armored carriers. In this work, the effect of strain rate during dynamic test on formation of adiabatic shear bands in AA6061-T6 alloy was investigated. A post deformation analysis of the tested specimen was performed in order to determine the damage evolution and strain localization along the narrow adiabatic shear bands within the specimen. The formation of an adiabatic shear band in the aluminum alloy tested was found to depend on the strain rate at which the test was conducted. Stress, strain, and strain rate data obtained from the elastic waves in the compression and torsion bar tests were also compared with those obtained using the high speed digital cameras. Results show good agreement between both measurement techniques with the 3D digital image correlation technique giving a slightly lower result. Scanning and electron microscopy results show that both deformed and transformed bands can be formed in AA6061-T6 alloy during dynamic loading. The type of adiabatic shear band formed depends on the strain rate at which test was performed.

  17. Effects of Temperature on Dynamic Properties of a Biodegradable Polymer Made from Corn Starch

    NASA Astrophysics Data System (ADS)

    Nishida, Masahiro; Ito, Noriomi; Kawase, Hiroyuki; Tanaka, Koichi

    The effect of strain rate on compressive properties of starch-based biodegradable plastics (Nihon Cornstarch Co., CPR-M2) was examined. Dynamic stress-strain curves of starch-based biodegradable plastics were measured over a wide range of strain rates from 10-5 s-1 to 104 s-1, using a quasi-static compression testing machine and a split Hopkinson pressure bar (SHPB) system. The strain rate slightly affected Young's modulus and considerably increased 7% flow stress. Empirical equation for 7% flow stress was derived for the strain rates from 10-5 s-1 to 104 s-1. In addition, the effect of temperature on Young's modulus and flow stress was also examined in a range from 4°C to 63°C. A master curve of 7% flow stress, reduced to 24°C, was made. The values of activation energies related to the α and β relaxation processes were respectively estimated from the master curve of 7% flow stress and from the best fit of equations based on Ree-Eyring theory and Bauwens' treatment. Temperature measurement of specimens was also made using thermocouples during dynamic compression.

  18. Experimental study of energy absorption in a close-celled aluminum foam under dynamic loading

    SciTech Connect

    Mukai, T.; Kanahashi, H.; Higashi, K.; Miyoshi, T.; Mabuchi, M.; Nieh, T.G.

    1999-03-19

    Recently, there is a high interest in using light-weight metallic foams (e.g., Al and Mg) for automotive, railway and aerospace applications where weight reduction and improvement in comfort are needed. Metallic foams also have a potential for absorbing impact energy during the crashing of a vehicle either against another vehicle or a pedestrian. To effectively absorb the impact energy, a material is required to exhibit an extended stress plateau. In order to evaluate the impact energy absorption, the relation between the compressive stress and strain at a dynamic strain rate must be characterized. The stress-strain behavior at dynamic strain rates is often characterized by using the split Hopkinson pressure bar (SHPB) method. A previous study suggested that, to evaluate reliably the mechanical properties of cellular materials, the height of a specimen should be ten or twenty times larger than the cell diameter to minimize the scatter of measurements. In the present study, therefore, the authors first determined the minimum height of aluminum foam specimens for compression test at a quasi-static strain rate by comparing the specific yield stress (i.e., yield stress per (relative density){sup 3/2}) of the foam with the other data previously reported. The relative stress of the aluminum foam as a function of relative density was also calculated and compared with those of other aluminum foams, along with the plot of Gibson and Ashby.

  19. Investigation of Dynamic Crack Coalescence Using a Gypsum-Like 3D Printing Material

    NASA Astrophysics Data System (ADS)

    Jiang, Chao; Zhao, Gao-Feng; Zhu, Jianbo; Zhao, Yi-Xin; Shen, Luming

    2016-10-01

    Dynamic crack coalescence attracts great attention in rock mechanics. However, specimen preparation in experimental study is a time-consuming and difficult procedure. In this work, a gypsum-like material by powder bed and inkjet 3D printing technique was applied to produce specimens with preset cracks for split Hopkinson pressure bar (SHPB) test. From micro X-ray CT test, it was found that the 3D printing technique could successfully prepare specimens that contain preset cracks with width of 0.2 mm. Basic mechanical properties of the 3D printing material, i.e., the elastic modulus, the Poisson's ratio, the density, the compressive strength, the indirect tensile strength, and the fracture toughness, were obtained and reported. Unlike 3D printed specimens using polylactic acid, these gypsum-like specimens can produce failure patterns much closer to those observed in classical rock mechanical tests. Finally, the dynamic crack coalescence of the 3D printed specimens with preset cracks were captured using a high-speed camera during SHPB tests. Failure patterns of these 3D printed specimens are similar to the specimens made by Portland cement concrete. Our results indicate that sample preparation by 3D printing is highly competitive due to its quickness in prototyping, precision and flexibility on the geometry, and high material homogeneity.

  20. Dynamic fracture resilience of elk antler: Biomimetic inspiration for improved crashworthiness

    NASA Astrophysics Data System (ADS)

    Kulin, Robb M.; Chen, Po-Yu; Jiang, Fengchun; McKittrick, Joanna; Vecchio, Kenneth S.

    2010-01-01

    The antler of the North American elk has been shown to have impressive fracture resistance under quasi-static loads, but given its viscoelastic behavior and impact nature of loading, questions remain as to its mechanical, and in particular, fracture behavior under dynamic loading. Samples were tested using a unique split-pressure Hopkin-son bar (SPHB) for four-point bending experiments in order to measure the fracture toughness of this material Interestingly, the hierarchical structure of antler had a strong influence on crack propagation characteristics, and cracks tended to propagate along the osteonal growth direction, whether loaded parallel or perpendicular to the osteonal growth direction. This occurred to such a degree so as to stop all crack propagation through the sample on transverse specimens, thus inhibiting the ability to measure a valid crack initiation toughness and demonstrating the extreme resilience of antler to resist dynamic fracture. The high resilience of antler to impact loading may serve as biomimetic inspiration to future material development for crashworthiness and defense applications.

  1. On the bar formation mechanism in galaxies with cuspy bulges

    NASA Astrophysics Data System (ADS)

    Polyachenko, E. V.; Berczik, P.; Just, A.

    2016-08-01

    We show by numerical simulations that a purely stellar dynamical model composed of an exponential disc, a cuspy bulge, and an NFW halo with parameters relevant to the Milky Way Galaxy is subject to bar formation. Taking into account the finite disc thickness, the bar formation can be explained by the usual bar instability, in spite of the presence of an inner Lindblad resonance, that is believed to damp any global modes. The effect of replacing the live halo and bulge by a fixed external axisymmetric potential (rigid models) is studied. It is shown that while the e-folding time of bar instability increases significantly (from 250 to 500 Myr), the bar pattern speed remains almost the same. For the latter, our average value of 55 km/s/kpc agrees with the assumption that the Hercules stream in the solar neighbourhood is an imprint of the bar-disc interaction at the outer Lindblad resonance of the bar. Vertical averaging of the radial force in the central disc region comparable to the characteristic scale length allows us to reproduce the bar pattern speed and the growth rate of the rigid models, using normal mode analysis of linear perturbation theory in a razor thin disc. The strong increase of the e-folding time with decreasing disc mass predicted by the mode analysis suggests that bars in galaxies similar to the Milky Way have formed only recently.

  2. On the bar formation mechanism in galaxies with cuspy bulges

    NASA Astrophysics Data System (ADS)

    Polyachenko, E. V.; Berczik, P.; Just, A.

    2016-11-01

    We show by numerical simulations that a purely stellar dynamical model composed of an exponential disc, a cuspy bulge, and a Navarro-Frenk-White halo with parameters relevant to the Milky Way is subject to bar formation. Taking into account the finite disc thickness, the bar formation can be explained by the usual bar instability, in spite of the presence of an inner Lindblad resonance, that is believed to damp any global modes. The effect of replacing the live halo and bulge by a fixed external axisymmetric potential (rigid models) is studied. It is shown that while the e-folding time of bar instability increases significantly (from 250 to 500 Myr), the bar pattern speed remains almost the same. For the latter, our average value of 55 km s-1 kpc-1 agrees with the assumption that the Hercules stream in the solar neighbourhood is an imprint of the bar-disc interaction at the outer Lindblad resonance of the bar. Vertical averaging of the radial force in the central disc region comparable to the characteristic scale length allows us to reproduce the bar pattern speed and the growth rate of the rigid models, using normal mode analysis of linear perturbation theory in a razor-thin disc. The strong increase of the e-folding time with decreasing disc mass predicted by the mode analysis suggests that bars in galaxies similar to the Milky Way have formed only recently.

  3. Musculoskeletal demands of progressions for the longswing on high bar.

    PubMed

    Irwin, Gareth; Kerwin, David G

    2007-09-01

    Kinetic analyses of the chalked bar longswing on high bar and its associated progressions were used to explain musculoskeletal contributions during the performance of these skills. Data on four international male gymnasts performing three series of chalked bar longswings and eight progressions were recorded. Customized body segment inertia parameters, two-dimensional kinematics (50 Hz), and bar forces (1000 Hz) were used as input to inverse dynamic modelling. The analysis focused on the relative contributions of the knees, hips, and shoulders with root mean squared differences between the chalked bar longswing and the progressions being used to rank the progressions. Seventy per cent of the total work occurred between 200 degrees and 240 degrees of angular rotation in the longswing, 67% of which was contributed by the shoulders. The shoulders were also dominant in all progressions, with the largest such contribution occurring in the looped bar longswing with "no action". The least similar progression was the looped bar pendulum swing, while the most similar was the chalked bar bent knee longswing. This study provides a useful means for ranking progressions based on their kinetic similarity to the chalked bar longswing and builds on earlier research in identifying that progressions can be classified into those similar in physical demand (kinetics) and those similar in geometry (kinematics).

  4. Musculoskeletal demands of progressions for the longswing on high bar.

    PubMed

    Irwin, Gareth; Kerwin, David G

    2007-09-01

    Kinetic analyses of the chalked bar longswing on high bar and its associated progressions were used to explain musculoskeletal contributions during the performance of these skills. Data on four international male gymnasts performing three series of chalked bar longswings and eight progressions were recorded. Customized body segment inertia parameters, two-dimensional kinematics (50 Hz), and bar forces (1000 Hz) were used as input to inverse dynamic modelling. The analysis focused on the relative contributions of the knees, hips, and shoulders with root mean squared differences between the chalked bar longswing and the progressions being used to rank the progressions. Seventy per cent of the total work occurred between 200 degrees and 240 degrees of angular rotation in the longswing, 67% of which was contributed by the shoulders. The shoulders were also dominant in all progressions, with the largest such contribution occurring in the looped bar longswing with "no action". The least similar progression was the looped bar pendulum swing, while the most similar was the chalked bar bent knee longswing. This study provides a useful means for ranking progressions based on their kinetic similarity to the chalked bar longswing and builds on earlier research in identifying that progressions can be classified into those similar in physical demand (kinetics) and those similar in geometry (kinematics). PMID:17933198

  5. Measurements of vertical bar Vcb vertical bar and vertical bar Vub vertical bar at BaBar

    SciTech Connect

    Rotondo, M.

    2005-10-12

    We report results from the BABAR Collaboration on the semileptonic B decays, highlighting the measurements of the magnitude of the Cabibbo-Kobayashi-Maskawa matrix elements Vub and Vcb. We describe the techniques used to obtain the matrix element |Vcb| using the measurement of the inclusive B {yields} Xclv process and a large sample of exclusive B {yields} D*lv decays. The vertical bar Vub vertical bar matrix elements has been measured studying different kinematic variables of the B {yields} Xulv process, and also with the exclusive reconstruction of B {yields} {pi}({rho})lv decays.

  6. Morphologies introduced by bistability in barred-spiral galactic potentials

    NASA Astrophysics Data System (ADS)

    Tsigaridi, L.; Patsis, P. A.

    2015-04-01

    We investigate the orbital dynamics of a barred-spiral model when the system is rotating slowly and corotation is located beyond the end of the spiral arms. In the characteristic of the central family of periodic orbits, we find a `bistable region'. In the response model, we observe a ring surrounding the bar and spiral arms starting tangential to the ring. This is a morphology resembling barred-spiral systems with inner rings. However, the dynamics associated with this structure in the case we study is different from that of a typical bar ending close to corotation. The ring of our model is round, or rather elongated perpendicular to the bar. It is associated with a folding (an `S'-shaped feature) of the characteristic of the central family, which is typical in bistable bifurcations. Along the `S' part of the characteristic, we have a change in the orientation of the periodic orbits from an x1-type to an x2-type morphology. The orbits populated in the response model change rather abruptly their orientation when reaching the lowest energy of the `S'. The spirals of the model follow a standard `precessing ellipses flow' and the orbits building them have energies beyond the `S' region. The bar is structured mainly by sticky orbits from regions around the stability islands of the central family. This leads to the appearance of X features in the bars on the galactic plane. Such a bar morphology appears in the unsharp-masked images of some moderately inclined galaxies.

  7. Bar formation and evolution in disc galaxies with gas and a triaxial halo: morphology, bar strength and halo properties

    NASA Astrophysics Data System (ADS)

    Athanassoula, E.; Machado, Rubens E. G.; Rodionov, S. A.

    2013-03-01

    particles that stay located relatively near the disc for long periods of time. Another part generates halo bulk rotation, which, contrary to that of the bar, increases with time but stays small. Thus, in our models there are two non-axisymmetric components rotating with different pattern speeds, namely the halo and the bar, so that the resulting dynamics have strong similarities to the dynamics of double bar systems.

  8. Breaking through the Bar

    ERIC Educational Resources Information Center

    Gray, Katti

    2011-01-01

    Howard University School of Law had a problem, and school officials knew it. Over a 20-year period, 40 percent of its graduates who took the Maryland bar exam failed it on their first try. During the next 24 months--the time frame required to determine its "eventual pass rate"--almost 90 percent of the students did pass. What they did not know was…

  9. Bar coded retroreflective target

    SciTech Connect

    Vann, C.S.

    2000-01-25

    This small, inexpensive, non-contact laser sensor can detect the location of a retroreflective target in a relatively large volume and up to six degrees of position. The tracker's laser beam is formed into a plane of light which is swept across the space of interest. When the beam illuminates the retroreflector, some of the light returns to the tracker. The intensity, angle, and time of the return beam is measured to calculate the three dimensional location of the target. With three retroreflectors on the target, the locations of three points on the target are measured, enabling the calculation of all six degrees of target position. Until now, devices for three-dimensional tracking of objects in a large volume have been heavy, large, and very expensive. Because of the simplicity and unique characteristics of this tracker, it is capable of three-dimensional tracking of one to several objects in a large volume, yet it is compact, light-weight, and relatively inexpensive. Alternatively, a tracker produces a diverging laser beam which is directed towards a fixed position, and senses when a retroreflective target enters the fixed field of view. An optically bar coded target can be read by the tracker to provide information about the target. The target can be formed of a ball lens with a bar code on one end. As the target moves through the field, the ball lens causes the laser beam to scan across the bar code.

  10. Bar coded retroreflective target

    DOEpatents

    Vann, Charles S.

    2000-01-01

    This small, inexpensive, non-contact laser sensor can detect the location of a retroreflective target in a relatively large volume and up to six degrees of position. The tracker's laser beam is formed into a plane of light which is swept across the space of interest. When the beam illuminates the retroreflector, some of the light returns to the tracker. The intensity, angle, and time of the return beam is measured to calculate the three dimensional location of the target. With three retroreflectors on the target, the locations of three points on the target are measured, enabling the calculation of all six degrees of target position. Until now, devices for three-dimensional tracking of objects in a large volume have been heavy, large, and very expensive. Because of the simplicity and unique characteristics of this tracker, it is capable of three-dimensional tracking of one to several objects in a large volume, yet it is compact, light-weight, and relatively inexpensive. Alternatively, a tracker produces a diverging laser beam which is directed towards a fixed position, and senses when a retroreflective target enters the fixed field of view. An optically bar coded target can be read by the tracker to provide information about the target. The target can be formed of a ball lens with a bar code on one end. As the target moves through the field, the ball lens causes the laser beam to scan across the bar code.

  11. Mechanics of dynamic fracture in notched polycarbonate

    NASA Astrophysics Data System (ADS)

    Faye, Anshul; Parmeswaran, Venkitanarayanan; Basu, Sumit

    2015-04-01

    Fracture toughness of brittle amorphous polymers (e.g. polymethyl methacrylate (PMMA)) has been reported to decrease with loading rate at moderate rates and increase abruptly thereafter to close to 5 times the static value at very high loading rates. Dynamic fracture toughness that is much higher than the static values has attractive technological possibilities. However, the reasons for the sharp increase remain unclear. Motivated by these observations, the present work focuses on the dynamic fracture behavior of polycarbonate (PC), which is also an amorphous polymer but unlike PMMA, is ductile at room temperature. Towards this end, a combined experimental and numerical approach is adopted. Dynamic fracture experiments at various loading rates are conducted on single edge notched (SEN) specimens with a notch of radius 150 μm, using a Hopkinson bar setup equipped with ultra high-speed imaging (>105 fps) for real-time observation of dynamic processes during fracture. Concurrently, 3D dynamic finite element simulations are performed using a well calibrated material model for PC. Experimentally, we were able to clearly capture the intricate details of the process, for both slowly and dynamically loaded samples, of damage nucleation and growth ahead of the notch tip followed by unstable crack propagation. These observations coupled with fractography and computer simulations led us to conclude that in PC, the fracture toughness remains invariant with loading rate at Jfrac = 12 ± 3 kN / m for the entire range of loading rates (J ˙) from static to 1 ×106 kN / m - s. However, the damage initiation toughness is significantly higher in dynamic loading compared to static situations. In dynamic situations, damage nucleation is quickly followed by initiation of radial crazes from around the void periphery that initiate and quickly bridge the ligament between the initial damaged region and the notch. Thus for PC, two criteria for two major stages in the failure process emerge

  12. Energy absorption behavior of polyurea coatings under laser-induced dynamic tensile and mixed-mode loading

    NASA Astrophysics Data System (ADS)

    Jajam, Kailash; Lee, Jaejun; Sottos, Nancy

    2015-06-01

    Energy absorbing, lightweight, thin transparent layers/coatings are desirable in many civilian and military applications such as hurricane resistant windows, personnel face-shields, helmet liners, aircraft canopies, laser shields, blast-tolerant sandwich structures, sound and vibration damping materials to name a few. Polyurea, a class of segmented block copolymer, has attracted recent attention for its energy absorbing properties. However, most of the dynamic property characterization of polyurea is limited to tensile and split-Hopkinson-pressure-bar compression loading experiments with strain rates on the order of 102 and 104 s-1, respectively. In the present work, we report the energy absorption behavior of polyurea thin films (1 to 2 μm) subjected to laser-induced dynamic tensile and mixed-mode loading. The laser-generated high amplitude stress wave propagates through the film in short time frames (15 to 20 ns) leading to very high strain rates (107 to 108 s-1) . The substrate stress, surface velocity and fluence histories are inferred from the displacement fringe data. On comparing input and output fluences, test results indicate significant energy absorption by the polyurea films under both tensile and mixed-mode loading conditions. Microscopic examination reveals distinct changes in failure mechanisms under mixed-mode loading from that observed under pure tensile loading. Office of Naval Research MURI.

  13. Grain size dependence of dynamic mechanical behavior of AZ31B magnesium alloy sheet under compressive shock loading

    SciTech Connect

    Asgari, H.; Odeshi, A.G.; Szpunar, J.A.; Zeng, L.J.; Olsson, E.

    2015-08-15

    The effects of grain size on the dynamic deformation behavior of rolled AZ31B alloy at high strain rates were investigated. Rolled AZ31B alloy samples with grain sizes of 6, 18 and 37 μm, were subjected to shock loading tests using Split Hopkinson Pressure Bar at room temperature and at a strain rate of 1100 s{sup −} {sup 1}. It was found that a double-peak basal texture formed in the shock loaded samples. The strength and ductility of the alloy under the high strain-rate compressive loading increased with decreasing grain size. However, twinning fraction and strain hardening rate were found to decrease with decreasing grain size. In addition, orientation imaging microscopy showed a higher contribution of double and contraction twins in the deformation process of the coarse-grained samples. Using transmission electron microscopy, pyramidal dislocations were detected in the shock loaded sample, proving the activation of pyramidal slip system under dynamic impact loading. - Highlights: • A double-peak basal texture developed in all shock loaded samples. • Both strength and ductility increased with decreasing grain size. • Twinning fraction and strain hardening rate decreased with decreasing grain size. • ‘g.b’ analysis confirmed the presence of dislocations in shock loaded alloy.

  14. The dynamic mechanical properties study on the sandwich panel of different thickness steel plate-foam aluminum core

    NASA Astrophysics Data System (ADS)

    Chang, Zhongliang; Zou, Guangping; Zhao, Weiling; Xia, Peixiu

    2009-12-01

    The foam aluminum belongs to multi-cell materials, and it has good mechanical performance, such as large deformation capacity and good energy absorption, and usually used as core material of sandwich panel, now it is widely used in automotive, aviation, aerospace and other fields, particularly suitable for various anti-collision structure and buffer structure. In this article, based on an engineering background, the INSTRON4505 electronic universal testing machine and split Hopkinson pressure bar (SHPB) were used for testing the static and dynamic mechanical properties of sandwich panel with different thickness steel plate- foam aluminum core, from the results we can see that the steel plate thickness has big influence on the stress-strain curve of the sandwich panel, and also takes the sandwich panel with 1mm steel panel to study the material strain rate dependence which under different high shock wave stress loaded, the results show that the sandwich panel is strain rate dependence material. And also, in order to get good waveforms in the SHPB experiment, the waveform shaped technique is used in the dynamic experiments, and the study of this paper will good to sandwich panel used in the engineering.

  15. Dynamic Properties of Polyurea

    NASA Astrophysics Data System (ADS)

    Youssef, George H.

    The aim of this thesis was to understand the dynamic behavior of polyurea at rates of loading that is outside the reach of plate impact and split-Hopkinson bar experiments. This was motivated by the desire to design polyurea-based armors against hypervelocity impacts such as those arising from shaped charges and explosively formed projectiles with speeds in the range of 9,000 to 30,000 ft/s. By employing the laser-induced stress waves, the tensile strength and fracture energy of polyurea were measured at peak strain rate of 10 7s-1. Tensile strength of 93.1 ±5 MPa and fracture energy values of 6.75 (± 0.5) J/m2 were measured. It was also shown that the Time Temperature Superposition Principle holds for polyurea even at strain rates as high as 105s-1. This strain rate is two orders of magnitude higher than those reported recently by the Caltech group (Zhao, et al.). This important finding suggests that blast simulations of large-scale structures and those of armors involving polyurea can be based on constitutive data gathered under quasi-static conditions. This is quite powerful. With a view towards future reach, preliminary experiments were performed to inquire how polyurca behaves in the presence of other armor materials when subjected to impacts in the nanoseconds timeframe. That is, does it synergistically add its intrinsic impact-mitigating properties to other known defeat mechanisms? To this end, sections in which I to 2 mm thick polyurea layers were sandwiched between glass, acrylic, polyurethane, Al, Steel, and PMMA plates were subjected to laser-generated stress waves. The sections were evaluated based on the amplitude and time profile of the stress wave that exited the sections. Both metal plates resulted in a significant reduction in the transmitted stress wave amplitude. This was due to the large impedance mismatch between the polyurea and the metal which essentially resulted in trapping of the stress wave within the incident substrate. An unexpected

  16. The Role of 2D Circulation in Sand Bar Migration

    NASA Astrophysics Data System (ADS)

    Splinter, K. D.; Holman, R. A.; Plant, N. G.; Holland, K. T.

    2006-12-01

    Models of bar dynamics typically involve moments of the cross-shore flow, with offshore movement associated with the strong offshore directed undertow and onshore migration related to wave asymmetry and skewness [Gallagher, et al., 1998]. Based on these hypotheses, models and laboratory studies have used the alongshore-mean bar position and alongshore-uniform wave conditions (a 1DH approach) to study bar response to varying wave conditions. Commonly, cases of offshore migration were reproduced with reasonable accuracy, but predictions of onshore migration were less successful. However, examination of time-exposure images of waves show that during periods of offshore migration, bars tend to be alongshore uniform and move rapidly offshore, but during onshore migration, sand bars are rarely straight, instead becoming very sinuous, violating the 1DH approach. We hypothesize that under milder wave conditions, the 2DH circulation associated with this alongshore-variable morphology is, in fact, largely responsible for increased onshore net sand transport and the resulting onshore bar movement. We extend the work of Plant et al. [in review] that relates bar position, sinuosity, and wave forcing within a dynamical feedback model. The model consists of coupled differential equations that govern the rates of change of cross-shore position and horizontal sinuosity as a function of the current cross-shore position and sinuosity and a proxy for wave forcing. Using a short data set from Duck, NC, they solve for the unknown coupling coefficients by doing a least-squares fit. They find that the coefficients for the self-interaction terms have a negative sign, indicating the overall system is stable. The coefficients of the cross-interaction terms (the effect of sinuosity on rate of change of bar position and visa versa), however, are non-zero and have opposite signs indicating the systems are coupled and stability is not affected by these terms. We expand this study, relating bar

  17. Shepherding tidal debris with the Galactic bar: the Ophiuchus stream

    NASA Astrophysics Data System (ADS)

    Hattori, Kohei; Erkal, Denis; Sanders, Jason L.

    2016-07-01

    The dynamics of stellar streams in rotating barred potentials is explained for the first time. Naturally, neighbouring stream stars reach pericentre at slightly different times. In the presence of a rotating bar, these neighbouring stream stars experience different bar orientations during pericentric passage and hence each star receives a different torque from the bar. These differing torques reshape the angular momentum and energy distribution of stars in the stream, which in turn changes the growth rate of the stream. For a progenitor orbiting in the same sense as the bar's rotation and satisfying a resonance condition, the resultant stream can be substantially shorter or longer than expected, depending on whether the pericentric passages of the progenitor occur along the bar's minor or major axis, respectively. We present a full discussion of this phenomenon focusing mainly on streams confined to the Galactic plane. In stark contrast with the evolution in static potentials, which give rise to streams that grow steadily in time, rotating barred potentials can produce dynamically old, short streams. This challenges the traditional viewpoint that the inner halo necessarily consists of well phase-mixed material whilst the tidally disrupted structures in the outer halo are more spatially coherent. We argue that this mechanism may play an important role in explaining the mysteriously short Ophiuchus stream that was recently discovered near the bulge region of the Milky Way.

  18. Quasi-static and dynamic responses of advanced high strength steels: Experiments and modeling

    SciTech Connect

    Khan, Akhtar; Baig, Muneer; Choi, Shi Hoon; Yang, Hoe Seok; Sun, Xin

    2012-03-01

    Measured responses of advanced high strength steels (AHSS) and their tailor welded blanks (TWBs), over a wide range of strain-rates (10*4 to 103 s*1) are presented. The steels investigated include transformation induced plasticity (TRIP), dual phase (DP), and drawing quality (DQ) steels. The TWBs include DQ-DQ and DP-DP laser welds. A tensile split Hopkinson pressure bar (SHPB) was used for the dynamic experiments. AHSS and their TWB's were found to exhibit positive strain-rate sensitivity. The Khan-Huang-Liang (KHL) constitutive model is shown to correlate and predict the observed responses reasonably well. Micro-texture characterization of DQ steels, DQ-DQ and DP-DP laser welds were performed to investigate the effect of strain-rate on texture evolution of these materials. Electron backscatter diffraction (EBSD) technique was used to analyze the micro-texture evolution and kernel average misorientation (KAM) map. Measurement of micro-hardness profile across the cross section of tensile samples was conducted to understand the effect of initial microstructure on ductility of laser weld samples.

  19. Bar piezoelectric ceramic transformers.

    PubMed

    Erhart, Jiří; Pulpan, Půlpán; Rusin, Luboš

    2013-07-01

    Bar-shaped piezoelectric ceramic transformers (PTs) working in the longitudinal vibration mode (k31 mode) were studied. Two types of the transformer were designed--one with the electrode divided into two segments of different length, and one with the electrodes divided into three symmetrical segments. Parameters of studied transformers such as efficiency, transformation ratio, and input and output impedances were measured. An analytical model was developed for PT parameter calculation for both two- and three-segment PTs. Neither type of bar PT exhibited very high efficiency (maximum 72% for three-segment PT design) at a relatively high transformation ratio (it is 4 for two-segment PT and 2 for three-segment PT at the fundamental resonance mode). The optimum resistive loads were 20 and 10 kΩ for two- and three-segment PT designs for the fundamental resonance, respectively, and about one order of magnitude smaller for the higher overtone (i.e., 2 kΩ and 500 Ω, respectively). The no-load transformation ratio was less than 27 (maximum for two-segment electrode PT design). The optimum input electrode aspect ratios (0.48 for three-segment PT and 0.63 for two-segment PT) were calculated numerically under no-load conditions.

  20. Dynamic crushing behaviour of aluminium tubes filled with cork

    NASA Astrophysics Data System (ADS)

    Gameiro, C. P.; Cirne, J.; Gary, G.

    2006-08-01

    Cork is a natural cellular material with unique remarkable properties such as low density, great elasticity, chemical stability and resilience, no permeability to liquid and gases and resistance to wear and fire. Besides, it is ecological, hygienic, easy to maintain and a very durable material. Unfortunately, there are still application fields that have not been explored yet for the use of cork, possibly due to the fact that it is a complex cellular material, characterized by very variable mechanical properties which clearly depend on its microstructure. The fundamental aspects of the static and dynamic mechanical behaviour of natural and agglomerate cork, used alone and as filler inside a tube with small dimensions, under axial compressive loading, have already been studied by the authors. Aluminium cork-filled tubes and their empty counterparts were tested experimentally and numerically at quasi-static and dynamic strain rates from 10 - 3s - 1 to 600 s - 1. Data from the Split-Hopkinson Pressure Bar and “deconvolution” techniques were used to generate stress-strain curves for the structures composed of natural and agglomerate cork. The numerical simulations of the dynamic compression of the specimens were carried out using the finite element method software LS-DYNA^TM and showed quite good agreement with the experimental results. Hence, in this work, in order to extend the study started previously and investigate the possible advantages of cork-filling in longer tubes with a different section, the authors simulate, using the same software, the influence of the introduction of agglomerate cork in square and circular aluminium tubes with a diameter/width of 80 mm, a length of 300mm and a variable thickness. The mechanical properties of the structures composed of cork may constitute a potential for this material to be used in innovative applications related to diverse fields such as automotive, transport, ships and military applications.

  1. Stellar bar in NGC 1068

    SciTech Connect

    Scoville, N.Z.; Matthews, K.; Carico, D.P.; Sanders, D.B.

    1988-04-01

    High-resolution 2-micron mapping of the inner disk of NGC 1068 reveals a bar extending to + or - 16 arcsec from the nucleus at position angle 48 deg. The stellar mass distribution, presumably traced by the near-infrared light, is therefore strongly nonaxisymmetric with a contrast of approximately 3:1 between the major and minor axes of the bar. This large-scale galactic structure is probably responsible for the concentration of molecular clouds in a ring just outside the bar. The massive bar may also drive noncircular motions in the inner disk of the galaxy as possibly seen in the gaseous emission lines. 21 references.

  2. Simulations of the quart (101-bar1)/water interface: A comparison of classical force fields, ab initi molecular dynamics, and x-ray reflectivity experiments.

    SciTech Connect

    Skelton, Adam; Fenter, Paul; Kubicki, James D.; Wesolowski, David J; Cummings, Peter T

    2011-01-01

    Classical molecular dynamics (CMD) simulations of the (1011) surface of quartz interacting with bulk liquid water are performed using three different classical force fields, Lopes et al., ClayFF, and CHARMM water contact angle (CWCA), and compared to ab initio molecular dynamics (AIMD) and X-ray reflectivity (XR) results. The axial densities of the water and surface atoms normal to the surface are calculated and compared to previous XR experiments. Favorable agreement is shown for all the force fields with respect to the position of the water atoms. Analyses such as the radial distribution functions between water and hydroxyl atoms and the average cosine of the angle between the water dipole vector and the normal of the surface are also calculated for each force field. Significant differences are found between the different force fields from such analyses, indicating differing descriptions of the structured water in the near vicinity of the surface. AIMD simulations are also performed to obtain the water and hydroxyl structure for comparison among the predictions of the three classical force fields to better understand which force field is most accurate. It is shown that ClayFF exhibits the best agreement with the AIMD simulations for water hydroxyl radial distribution functions, suggesting that ClayFF treats the hydrogen bonding more accurately.

  3. Variational Calculation of K-pp with Chiral SU(3)-BASED bar KN Interaction

    NASA Astrophysics Data System (ADS)

    Doté, A.; Hyodo, T.; Weise, W.

    The prototype of a bar K nuclear cluster, K-pp, has been investigated using effective bar KN potentials based on chiral SU(3) dynamics. Variational calculation shows a bound state solution with shallow binding energy B(K-pp) = 20 ± 3 MeV and broad mesonic decay width Γ (bar KNN -> π YN) = 40 - 70 {MeV}. The bar KN(I = 0) pair in the K-pp system exhibits a similar structure as the Λ(1405). We have also estimated the dispersive correction, p-wave bar KN interaction, and two-nucleon absorption width.

  4. Variational Calculation of K-pp with Chiral SU(3)-BASED bar KN Interaction

    NASA Astrophysics Data System (ADS)

    Doté, A.; Hyodo, T.; Weise, W.

    2010-10-01

    The prototype of a bar K nuclear cluster, K-pp, has been investigated using effective bar KN potentials based on chiral SU(3) dynamics. Variational calculation shows a bound state solution with shallow binding energy B(K-pp) = 20 ± 3 MeV and broad mesonic decay width Γ (bar KNN -> π YN) = 40 - 70 {MeV}. The bar KN(I = 0) pair in the K-pp system exhibits a similar structure as the Λ(1405). We have also estimated the dispersive correction, p-wave bar KN interaction, and two-nucleon absorption width.

  5. Gaseous Vortices in Barred Spiral Galaxies

    NASA Technical Reports Server (NTRS)

    England, Martin N.; Hunter, James H., Jr.

    1995-01-01

    During the course of examining many two-dimensional, as well as a smaller sample of three-dimensional, models of gas flows in barred spiral galaxies, we have been impressed by the ubiquitous presence fo vortex pairs, oriented roughly perpendicular to their bars, with one vortex on each side. The vortices are obvious only when viewed in the bar frame, and the centers of their velocity fields usually are near Lagrangian points L(sub 4,5). In all models that we have studied, the vortices form on essentially the same time scale as that for the development of gaseous spiral arms, typically two bar rotations. Usually the corotation radius, r(sub c), lies slightly beyond the end of the bar. Depending upon the mass distributions of the various components, gas spirals either into, or out of, the vortices: In the former case, the vortices become regions of high density, whereas the opposite is true if the gas spirals out of a vortex. The models described in this paper have low-density vortices, as do most of the models we have studied. Moreover, usually the vortex centers lie approximately within +/- 15 deg of L(sub 4,5). In the stellar dynamic limit, when pressure and viscous forces are absent, short-period orbits exist, centered on L(sub 4,5). These orbits need not cross and therefore their morphology is that of gas streamlines, that is, vortices. We believe that the gas vortices in our models are hydrodynamic analogues of closed, short-period, libration orbits centered on L(sub 4,5).

  6. Determination of Dynamic Flexural Tensile Strength of Thermally Treated Laurentian Granite Using Semi-Circular Specimens

    NASA Astrophysics Data System (ADS)

    Yin, Tubing; Wang, Pin; Li, Xibing; Wu, Bangbiao; Tao, Ming; Shu, Ronghua

    2016-10-01

    To understand the effects of increasing temperature and loading rate on the flexural tensile strength of Laurentian granite, dynamic flexural tensile strength experiments were carried out by means of a semi-circular bend specimen with a modified split Hopkinson pressure bar system. The tests were performed at different loading rates, specimens were treated from room temperature up to 850 °C, and a high-speed camera was utilized to monitor the failure process of the specimen. For samples in the same temperature group, a loading rate dependence of the flexural tensile strength was observed; it increased consistently with the increase of loading rate. Temperature effects on rock mechanical properties were investigated from the microscopic viewpoint, and the dynamic flexural tensile strength decreased with the treatment temperature. A formula relating dynamic flexural tensile strength to loading rate and temperature is presented to quantify the results. It was found that the change regulation of the dynamic flexural tensile strength of rock is very similar to that of its crack growth along with the increase of loading rate, which indicates that the essence of rock failure is the initiation and propagation of the internal cracks. Compared with our earlier work on dynamic tensile tests using the Brazilian test, it was observed that the flexural tensile strength is higher than the tensile strength. Non-local failure theory can be adopted to explain this discrepancy at low temperature conditions, but it is no longer effective at high temperatures. Under high loading rates, rock failure is initiated at the centre of the half circular disc, and finally it is separated completely into two equal parts.

  7. Improved Kolsky tension bar for high-rate tensile characterization of materials

    NASA Astrophysics Data System (ADS)

    Song, Bo; Antoun, Bonnie R.; Connelly, Kevin; Korellis, John; Lu, Wei-Yang

    2011-04-01

    A new Kolsky tension bar has been re-designed and developed at Sandia National Laboratories, CA. The new design uses the concept that a solid striker is fired to impact an end cap attached to the open end of the gun barrel to generate dynamic tensile loading. The gun barrel here serves as part of the loading device. The incident bar that is connected to the gun barrel and the transmission bar follow the design similar to the Kolsky compression bar. The bar supporting and aligning systems are the same as those in the Kolsky compression bar design described by Song et al (2009 Meas. Sci. Technol. 20 115701). Due to the connection complication among the gun barrel, bars and specimen, stress-wave propagation in the new Kolsky tension bar system is comprehensively analyzed. Based on the stress-wave analysis, the strain gage location on the incident bar needs to be carefully determined. A highly precise laser-beam measurement system is recommended to directly measure the displacement of the incident bar end. Dynamic tensile characterization of a 4330-V steel using this new Kolsky tension bar is presented as an example.

  8. Alluvial Bars of the Obed Wild and Scenic River, Tennessee

    USGS Publications Warehouse

    Wolfe, W.J.; Fitch, K.C.; Ladd, D.E.

    2007-01-01

    In 2004, the U.S. Geological Survey (USGS) and the National Park Service (NPS) initiated a reconnaissance study of alluvial bars along the Obed Wild and Scenic River (Obed WSR), in Cumberland and Morgan Counties, Tennessee. The study was partly driven by concern that trapping of sand by upstream impoundments might threaten rare, threatened, or endangered plant habitat by reducing the supply of sediment to the alluvial bars. The objectives of the study were to: (1) develop a preliminary understanding of the distribution, morphology, composition, stability, and vegetation structure of alluvial bars along the Obed WSR, and (2) determine whether evidence of human alteration of sediment dynamics in the Obed WSR warrants further, more detailed examination. This report presents the results of the reconnaissance study of alluvial bars along the Obed River, Clear Creek, and Daddys Creek in the Obed WSR. The report is based on: (1) field-reconnaissance visits by boat to 56 alluvial bars along selected reaches of the Obed River and Clear Creek; (2) analysis of aerial photographs, topographic and geologic maps, and other geographic data to assess the distribution of alluvial bars in the Obed WSR; (3) surveys of topography, surface particle size, vegetation structure, and ground cover on three selected alluvial bars; and (4) analysis of hydrologic records.

  9. Synchrotron X-ray diffraction study of texture evolution in 904L stainless steel under dynamic shock compression

    SciTech Connect

    Li, Nanan; Wang, Y. D.; Peng, R. Lin; Sun, Xin; Ren, Yang; Wang, L.; Cai, H. N.

    2011-01-01

    The influence of strain rate on development of deformation texture under a dynamic shock compression of a 904L stainless steel was quantitatively investigated using synchrotron X-ray diffraction and crystallographic orientation distribution function (ODF) analysis. Split-Hopkinson Pressure Bar technique was used to generate a high strain rate of > 103 s-1 for preparing the deformed samples. Starting with an almost random texture in a solution treatment condition, the deformed material developed several typical texture components, such as ‘Goss’ texture and ‘Brass’ texture. Compared to the texture components displayed in the state of quasi-static compression deformation, it was found that the high-speed deformation generated much weaker texture components. In combination with the change in microstructures observed by EBSD and TEM technique, the high-energy X-ray diffraction provides a powerful tool for characterizing the strain-rate dependence of grain rotation at each stage of deformation. The deformation heterogeneity evident in our experiment can be explained by a transition of deformation mechanism from the dislocation/twin-dominated mode to shear-band-dominated one with increasing strain rate.

  10. Influence of uniaxial, biaxial and plane strain pre-straining on the dynamic tensile properties of high strength sheet steels

    NASA Astrophysics Data System (ADS)

    Larour, P.; Verleysen, P.; Bleck, W.

    2006-08-01

    The influence of pre-straining and microstructure on the dynamic properties of car body high strength steels has been investigated at room temperature. The mechanical properties of a dual phase steel DP600, a TRIP steel TRIP700 and an austenitic steel AISI 301LN2B (1.4318) have been determined performing high speed servohydraulic and split-Hopkinson bar tensile tests in the strain rate range from 0.005s-1 up to 950s-1. The pre-straining modes and levels, respectively 10% uniaxial, 10% plane strain and 5% biaxial pre-straining, have been chosen in this investigation according to industrial use. 10% plane strain pre-straining brings the highest increase of yield and tensile strength values. 5% biaxial and 10% uniaxial pre-straining have similar effect on strength properties. The austenitic steel presents a pronounced minimum for tensile strength values at around 1/s. A combination of adiabatic heating and exothermic γ to α' transformation produces some significant softening effects in the austenitic steel grade.

  11. CULTURAL FACTORS RELATED TO SMOKING IN SAN FRANCISCO’S IRISH BARS

    PubMed Central

    Satterlund, Travis D.; Antin, Tamar M.J.; Lee, Juliet P.; Moore, Roland S.

    2009-01-01

    California’s Smoke-Free Workplace Act was extended to include bars in 1998. While the majority of bars in the state have become smoke free, in many bars patrons and staff continue to smoke despite the law. The authors present findings from a study which assessed cultural factors related to continued smoking in bars in the city of San Francisco. In bars serving primarily Irish migrants, tight-knit relations within the local Irish bar community together with a reluctance to be the first Irish bar to ban smoking were found to contribute to continued indoor smoking. The findings illustrate challenges to implementing tobacco control policies within ethnic subpopulations and particularly highlight the importance of considering how cultural dynamics within subpopulations may help or hinder such policies. PMID:19999704

  12. 'Light bar' attitude indicator

    NASA Technical Reports Server (NTRS)

    Enevoldson, E. K.; Horton, V. W.

    1982-01-01

    The development and evaluation of a light bar attitude indicator to help maintain proper aircraft attitude during high altitude night flying is described. A standard four-inch ADI was modified to project an artificial horizon across the instrument panel for pitch and roll information. A light bulb was put in the center of the ADI and a thin slit cut on the horizon, resulting in a thin horizontal sheet of light projecting from the instrument. The intensity of the projected beam is such that it can only be seen in a darkened room or at night. The beam on the instrument panel of the T-37 jet trainer is shown, depicting various attitudes. The favorable comments of about 50 pilots who evaluated the instrument are summarized, including recommendations for improving the instrument. Possible uses for the instrument to ease the pilot task are listed. Two potential problems in using the device are the development of pilot complacency and an upright-inverted ambiguity in the instrument.

  13. Longshore Bars and Bragg Resonance

    NASA Astrophysics Data System (ADS)

    Mei, C. C.; Hara, T.; Yu, J.

    Longshore bars are often found on many gently sloping beaches of large lakes, bays and sea coasts. A beautiful example can be seen in Fig. 20.1 which gives the aerial view of the Escambia Bay in Florida. Several other typical observations are summarized in Table 20.1. In contrast to bars found in rivers where the flows are essentially unidirectional and characterized by very long time scales (see Chap. 15), coastal bars are usually the products of waves. Of scientific interests are the detailed physics of their generation by waves, as well as their influence on the propagation of waves.

  14. Experimental serpentinization of dunite cores at 150-200ºC and 150 bar: Importance of open system dynamics for hydrogen generation and stabilization of ferric-rich serpentine

    NASA Astrophysics Data System (ADS)

    Luhmann, A. J.; Tutolo, B. M.; Bagley, B. C.; Mildner, D. F. R.; Seyfried, W. E., Jr.

    2015-12-01

    Tectonic processes often exhume mantle peridotite to environments near the Earth's surface, where serpentinization occurs and involves the hydration of peridotite at relatively low temperatures. This process oxidizes ferrous iron in olivine, which produces hydrogen (H2), creating environments that are conducive to abiotic synthesis of organic compounds and H2-based microbial communities. To understand better chemical and physical processes associated with serpentinization, two flow-through experiments (>30 days) were conducted at 150 and 200°C and 150 bar on intact dunite cores. Permeability decreased by a factor of 31 during the 200°C experiment, more than an order of magnitude larger than that at 150°C. Furthermore, H2 and methane concentrations exceeded 600 µmol/kg and 300 µmol/kg during the 200°C experiment, and were one and two orders of magnitude higher, respectively, than the 150°C experiment. H2 was primarily generated during the conversion of olivine to ferric serpentine at 200°C, since vibrating sample magnetometer analysis indicated little to no magnetite production. Secondary mineralization was identified on the core from this experiment, but X-ray computed tomography scans indicated little change. Furthermore, (ultra) small-angle neutron scattering datasets indicated that any change in nano-porosity and surface area was smaller than the natural variability of the dunite. Even though there was little evidence of alteration, the initial stage of serpentinization at 200°C was sufficient to produce a dramatic effect on flow fields in the core. Furthermore, this experiment generated significant dissolved H2 concentrations, while simulating open system dynamics. Thus, the experimental data provide insight on mass transfer processes in open geochemical systems, which effectively prevent highly elevated H2 concentrations due to continual loss. We speculate that this process is responsible for stabilizing unusually ferric-rich serpentine in nature.

  15. Triple bar, high efficiency mechanical sealer

    DOEpatents

    Pak, Donald J.; Hawkins, Samantha A.; Young, John E.

    2013-03-19

    A clamp with a bottom clamp bar that has a planar upper surface is provided. The clamp may also include a top clamp bar connected to the bottom clamp bar, and a pressure distribution bar between the top clamp bar and the bottom clamp bar. The pressure distribution bar may have a planar lower surface in facing relation to the upper surface of the bottom clamp bar. An object is capable of being disposed in a clamping region between the upper surface and the lower surface. The width of the planar lower surface may be less than the width of the upper surface within the clamping region. Also, the pressure distribution bar may be capable of being urged away from the top clamp bar and towards the bottom clamp bar.

  16. Processing, Dynamic Deformation and Fragmentation of Heterogeneous Materials (Aluminum-Tungsten Composites and Aluminum-Nickel Laminates)

    NASA Astrophysics Data System (ADS)

    Chiu, Po-Hsun

    Two types of heterogeneous reactive materials, Aluminum-Tungsten composites and Aluminum-Nickel laminates were investigated. The current interest in these materials is their ability to combine the high strength and energy output under critical condition of the mechanical deformation which may include their fragmentation. Mesoscale properties of reactive materials are very important for the generation of local hot spots to ignite reactions and generate critical size of debris suitable for fast oxidation kinetics. Samples with different mesostructures (e.g., coarse vs. fine W particles, bonded vs. non-bonded Al particles, W particles vs. W wires and concentric vs. corrugated Al-Ni laminates) were prepared by Cold Isostatic Pressing, Hot Isostatic Pressing and Swaging. Several dynamic tests were utilized including Split Hopkinson Pressure Bar, Drop Weight Test, Explosively Driven Fragmentation Test, and Thick-Walled Cylinder Method. A high speed camera was used to record images of the in situ behavior of materials under dynamic loading. Pre- and post-experiment analyses and characterization were done using Optical Microscopy, Scanning Electron Microscopy, X-ray Powder Diffraction, and Laser Diffraction. The numerical simulations were conducted to monitor the in situ dynamic behavior of materials and elucidate the mesoscale mechanisms of the plastic strain accommodation under high-strain, high-strain-rate conditions in investigated heterogeneous m aterials. Several interesting results should be specifically mentioned. They include observation that the fracture and dynamic properties of the Al-W composites are sensitive to porosity of samples, particles sizes of rigid inclusions (W particles or wires), and bonding strength between Al particles in the matrix. Soft Al particles were heavily deformed between the rigid W particles/wires during dynamic tests. Three plastic strain accommodation mechanisms are observed in Al-Ni laminates. They depend on the initial

  17. Property Control through Bar Coding.

    ERIC Educational Resources Information Center

    Kingma, Gerben J.

    1984-01-01

    A public utility company uses laser wands to read bar-coded labels on furniture and equipment. The system allows an 80 percent savings of the time required to create reports for inventory control. (MLF)

  18. Nanoporosity of Si (100) bars

    NASA Astrophysics Data System (ADS)

    Novikov, S. N.; Timoshenkov, S. P.; Minaev, V. S.; Goryunova, E. P.; Gerasimenko, N. N.; Smirnov, D. I.

    2016-09-01

    Si(100) samples cut from a typical bar (100 mm in diameter) prepared using industrial technology are studied. Measurements of the electron work function (EWF) show that the size effects in these samples (a reduction in thickness along with a sample's area and the EWF) detected earlier were due to nanostructure porosity that was buried by the technological treatment of a bar's surface. This hidden nanoporosity is assumed to be a manifestation of the secondary crystal structure.

  19. Bar Formation from Galaxy Flybys

    NASA Astrophysics Data System (ADS)

    Holley-Bockelmann, Kelly; Lang, Meagan; Sinha, Manodeep

    2016-05-01

    Both simulations and observations reveal that flybys—fast, one-time interactions between two galaxy halos—are surprisingly common, comparable to galaxy mergers. Since these are rapid, transient events with the closest approach well outside the galaxy disk, it is unclear if flybys can transform the galaxy in a lasting way. We conduct collisionless N-body simulations of three coplanar flyby interactions between pure-disk galaxies to take a first look at the effects flybys have on disk structure, with particular focus on stellar bar formation. We find that some flybys are capable of inciting a bar; bars form in both galaxies during our 1:1 interaction and in the secondary during our 10:1 interaction. The bars formed have ellipticities >0.5, sizes on the order of the scale length of the disk, and persist to the end of our simulations, ~5 Gyr after pericenter. The ability of flybys to incite bar formation implies that many processes associated with secular bar evolution may be more closely tied with flyby interactions than previously thought.

  20. Maximal dismounts from high bar.

    PubMed

    Hiley, Michael J; Yeadon, Maurice R

    2005-11-01

    In men's artistic gymnastics the triple straight somersault dismount from the high bar has yet to be performed in competition. The present study used a simulation model of a gymnast and the high bar apparatus (J. Appl. Biomech. 19(2003a) 119) to determine whether a gymnast could produce the required angular momentum and flight to complete a triple straight somersault dismount. Optimisations were carried out to maximise the margin for error in timing the bar release for a given number of straight somersaults in flight. The amount of rotation potential (number of straight somersaults) the model could produce whilst maintaining a realistic margin for error was determined. A simulation model of aerial movement (J. Biomech.23 (1990) 85) was used to find what would be possible with this amount of rotation potential. The model was able to produce sufficient angular momentum and time in the air to complete a triple straight somersault dismount. The margin for error when releasing the bar using the optimum technique was 28 ms, which is small when compared with the mean margin for error determined for high bar finalists at the 2000 Sydney Olympic Games (55 ms). Although the triple straight somersault dismount is theoretically possible, it would require close to maximum effort and precise timing of the release from the bar. However, when the model was required to have a realistic margin for error, it was able to produce sufficient angular momentum for a double twisting triple somersault dismount. PMID:16154409

  1. BAR FORMATION FROM GALAXY FLYBYS

    SciTech Connect

    Lang, Meagan; Holley-Bockelmann, Kelly; Sinha, Manodeep E-mail: k.holley@vanderbilt.edu

    2014-08-01

    Recently, both simulations and observations have revealed that flybys—fast, one-time interactions between two galaxy halos—are surprisingly common, nearing/comparable to galaxy mergers. Since these are rapid, transient events with the closest approach well outside the galaxy disk, it is unclear if flybys can transform the galaxy in a lasting way. We conduct collisionless N-body simulations of three coplanar flyby interactions between pure-disk galaxies to take a first look at the effects flybys have on disk structure, with particular focus on stellar bar formation. We find that some flybys are capable of inciting a bar with bars forming in both galaxies during our 1:1 interaction and in the secondary during our 10:1 interaction. The bars formed have ellipticities ≳ 0.5, sizes on the order of the host disk's scale length, and persist to the end of our simulations, ∼5 Gyr after pericenter. The ability of flybys to incite bar formation implies that many processes associated with secular bar evolution may be more closely tied with interactions than previously thought.

  2. A Kolsky tension bar technique using a hollow incident tube

    NASA Astrophysics Data System (ADS)

    Guzman, O.; Frew, D. J.; Chen, W.

    2011-04-01

    Load control of the incident pulse profiles in compression Kolsky bar experiments has been widely used to subject the specimen to optimal testing conditions. Tension Kolsky bars have been used to determine dynamic material behavior since the 1960s with limited capability to shape the loading pulses due to the pulse-generating mechanisms. We developed a modified Kolsky tension bar where a hollow incident tube is used to carry the incident stress waves. The incident tube also acts as a gas gun barrel that houses the striker for impact. The main advantage of this new design is that the striker impacts on an impact cap of the incident tube. Compression pulse shapers can be attached to the impact cap, thus fully utilizing the predictive compression pulse-shaping capability in tension experiments. Using this new testing technique, the dynamic tensile material behavior for Al 6061-T6511 and TRIP 800 (transformation-induced plasticity) steel has been obtained.

  3. Hercules and Wolf 630 stellar streams and galactic bar kinematics

    NASA Astrophysics Data System (ADS)

    Bobylev, V. V.; Bajkova, A. T.

    2016-04-01

    We have identified the four most significant features in the UV velocity distribution of solarneighborhood stars: H1, H2 in the Hercules stream and W1, W2 in the Wolf 630 stream. We have formulated the problemof determining several characteristics of the centralGalactic bar independently from each of the identified features by assuming that the Hercules and Wolf 630 streams are of a bar-induced dynamical nature. The problem has been solved by constructing 2: 1 resonant orbits in the rotating bar frame for each star in these streams. Analysis of the resonant orbits found has shown that the bar pattern speed is 45-55 km s-1 kpc-1, while the bar angle lies within the range 40°-60°. The results obtained are consistent with the view that the Hercules andWolf 630 streams could be formed by a long-term influence of the Galactic bar leading to a characteristic bimodal splitting of the UV velocity plane.

  4. The statistics and kinematics of transverse sand bars on an open coast

    USGS Publications Warehouse

    Konicki, K.M.; Holman, R.A.

    2000-01-01

    Ten years (1987-1996) of time exposure video images of the nearshore region at Duck, NC were used to study transverse sand bars, bathymetric features of intermediate length scales (10-200 m) oriented oblique or perpendicular to the shoreline. These transverse sand bars extend seaward from both the shoreline (trough transverse bars) and the shore-parallel sand bar (offshore transverse bars). Transverse bars had not previously been observed in an energetic Coastal environment such as that at Duck, and their dynamics and role in nearshore processes is unknown. Frequency of occurrence statistics and length scales of the transverse bars were calculated using the video images. Trough and offshore transverse bars appeared a mean of 39 and 73 days per year, respectively. The offshore bars were found to be much larger features than the trough bars, with mean wavelengths (alongshore spacing between consecutive crests) of 79 and 172 m for trough and offshore bars, respectively. Both the trough and offshore bars were found to persist for periods of days to months. The alongshore movement of the bars was measured and compared to estimates of surf zone longshore currents which were calculated from wave height and wave angle data. Both sets of bars were observed to move at rates up to 40 m/day. At times, both trough and offshore bars were observed shifting in the same direction as the current was flowing, and at other times, both sets of bars remained stationary, even under relatively strong longshore currents. Trough bars were also observed moving against the current. An hypothesis, proposed by Barcilon and Lau (1973) [J. Geophys. Res. 78(15): 2656-2664], that the transverse bars were created as a sea bed instability under longshore currents, was tested by comparing the magnitude of estimated surf zone longshore currents with times of formation or presence of transverse bars. There was no evidence to suggest that the bars were formed by this simple longshore current instability

  5. Applying Schwarzschild's orbit superposition method to barred or non-barred disc galaxies

    NASA Astrophysics Data System (ADS)

    Vasiliev, Eugene; Athanassoula, E.

    2015-07-01

    We present an implementation of the Schwarzschild orbit superposition method, which can be used for constructing self-consistent equilibrium models of barred or non-barred disc galaxies, or of elliptical galaxies with figure rotation. This is a further development of the publicly available code SMILE; its main improvements include a new efficient representation of an arbitrary gravitational potential using two-dimensional spline interpolation of Fourier coefficients in the meridional plane, as well as the ability to deal with rotation of the density profile and with multicomponent mass models. We compare several published methods for constructing composite axisymmetric disc-bulge-halo models and demonstrate that our code produces the models that are closest to equilibrium. We also apply it to create models of triaxial elliptical galaxies with cuspy density profiles and figure rotation, and find that such models can be found and are stable over many dynamical times in a wide range of pattern speeds and angular momenta, covering both slow- and fast-rotator classes. We then attempt to create models of strongly barred disc galaxies, using an analytic three-component potential, and find that it is not possible to make a stable dynamically self-consistent model for this density profile. Finally, we take snapshots of two N-body simulations of barred disc galaxies embedded in nearly-spherical haloes, and construct equilibrium models using only information on the density profile of the snapshots. We demonstrate that such reconstructed models are in near-stationary state, in contrast with the original N-body simulations, one of which displayed significant secular evolution.

  6. Novel experimental methods for investigating high speed friction of titanium-aluminum-vanadium/tool steel interface and dynamic failure of extrinsically toughened DRA composites

    NASA Astrophysics Data System (ADS)

    Irfan, Mohammad Abdulaziz

    effects the sliding resistance of the interface. The experimental results deduced from the response of the sliding interface to step changes in normal pressure and the applied shear stress reinforce the importance of including frictional memory in the development of rate dependent state variable friction models. The second part of the thesis presents an investigation into the dynamic deformation and failure of extrinsically toughened DRA composites. Experiments were conducted using the split Hopkinson pressure bar to investigate the deformation and flow behavior under dynamic compression loading. A modified Hopkinson bar apparatus was used to explore the dynamic fracture behavior of three different extrinsically toughened DRA composites. The study was paralleled by systematic exploration of the failure modes in each composite. For all the composites evaluated the dynamic crack propagation characteristics of the composites are observed to be strongly dependent on the volume fraction of the ductile phase reinforcement in the composite, the yield stress of the ductile phase reinforcement, the micro-structural arrangement of the ductile phase reinforcements with respect to the notch, and the impact velocity employed in the particular experiment.

  7. Gas flow models in the Milky Way embedded bars

    NASA Astrophysics Data System (ADS)

    Rodriguez-Fernandez, N. J.; Combes, F.

    2008-10-01

    Context: The gas distribution and dynamics in the inner Galaxy present many unknowns, such as the origin of the asymmetry of the lv-diagram of the Central Molecular Zone (CMZ). On the other hand, there is recent evidence in the stellar component of the presence of a nuclear bar that may be slightly lopsided. Aims: Our goal is to characterize the nuclear bar observed in 2MASS maps and to study the gas dynamics in the inner Milky Way taking into account this secondary bar. Methods: We have derived a realistic mass distribution by fitting the 2MASS star count map with a model including three components (disk, bulge and nuclear bar) and we have simulated the gas dynamics in the deduced gravitational potential using a sticky-particles code. Results: Our simulations of the gas dynamics successfully reproduce the main characteristics of the Milky Way for a bulge orientation of 20°-35°with respect to the Sun-Galactic Center (GC) line and a pattern speed of 30-40 km s-1 kpc-1. In our models the Galactic Molecular Ring (GMR) is not an actual ring but the inner parts of the spiral arms, while the 3-kpc arm and its far side counterpart are lateral arms that extend around the bar. Our simulations reproduce, for the first time, the parallelogram shape of the lv-diagram of the CMZ as the gas response to the nuclear bar. This bar should be oriented by an angle of ˜60°-75°with respect to the Sun-GC line and its mass amounts to (2-5.5) 109 M_⊙. We show that the observed asymmetry of the CMZ cannot be due to lopsidedness of the nuclear bar as suggested by the 2MASS maps. Conclusions: We do not find clear evidence of lopsidedness in the stellar potential. We propose that the observed asymmetry of the central gas layer can be due to the infalling of gas into the CMZ in the l = 1.3°-complex. Tables 3-6 are only available in electronic form at http://www.aanda.org

  8. Photometric Surveys of the Galactic Bulge and Long Bar

    NASA Astrophysics Data System (ADS)

    Gerhard, O.; Wegg, C.; Portail, M.

    The Galactic bar and box/peanut bulge can be studied in an unrivaled manner, star-by-star, with detailed chemical information and full 3D kinematics. Because of intervening dust this is greatly facilitated by the availability of wide field deep NIR photometric surveys. Here we summarize recent results on the three-dimensional structure of the bulge and the long bar region, based on 2MASS, UKIDSS, and particularly the ongoing VVV survey. We also summarize results from dynamical models for the Galactic bulge constructed with the Made-to-Measure method.

  9. BARS/SSC/SPHINX. BARS Bibliographic Data Retrieval System

    SciTech Connect

    Herrmann, W.

    1993-05-01

    BARS is a program which allows retrieval of information from suitable bibliographic databases. Two databases are included, SSC and SPHINX, which together list bibliographic information for some 12,000 references related to the fields of shock compression of condensed media, high rate deformation of solids, and detonation.

  10. BARS/SSC/SPHINX. BARS Bibliographic Data Retrieval System

    SciTech Connect

    Herrmann, W.

    1993-06-06

    BARS is a program which allows retrieval of information from suitable bibliographic databases. Two databases are included, SSC and SPHINX, which together list bibliographic information for some 12,000 references related to the fields of shock compression of condensed media, high rate deformation of solids, and detonation.

  11. Bar-spheroid interaction in galaxies

    NASA Technical Reports Server (NTRS)

    Hernquist, Lars; Weinberg, Martin D.

    1992-01-01

    N-body simulation and linear analysis is employed to investigate the secular evolution of barred galaxies, with emphasis on the interaction between bars and spheroidal components of galaxies. This interaction is argued to drive secular transfer of angular momentum from bars to spheroids, primarily through resonant coupling. A moderately strong bar, having mass within corotation about 0.3 times the enclosed spheroid mass, is predicted to shed all its angular momentum typically in less than about 10 exp 9 yr. Even shorter depletion time scales are found for relatively more massive bars. It is suggested either that spheroids around barred galaxies are structured so as to inhibit strong coupling with bars, or that bars can form by unknown processes long after disks are established. The present models reinforce the notion that bars can drive secular evolution in galaxies.

  12. Demographic response of northern spotted owls to barred owl removal

    USGS Publications Warehouse

    Diller, V. Lowell; Hamm, Keith A; Early, Desiree A; Lamphear, David W; Katie Dugger,; Yackulic, Charles B.; Schwarz, Carl J.; Carlson, Peter C.; McDonald, Trent L.

    2016-01-01

    Federally listed as threatened in 1990 primarily because of habitat loss, the northern spotted owl (Strix occidentalis caurina) has continued to decline despite conservation efforts resulting in forested habitat being reserved throughout its range. Recently, there is growing evidence the congeneric invasive barred owl (Strix varia) may be responsible for the continued decline primarily by excluding spotted owls from their preferred habitat. We used a long-term demographic study for spotted owls in coastal northern California as the basis for a pilot barred owl removal experiment. Our demography study used capture–recapture, reproductive output, and territory occupancy data collected from 1990 to 2013 to evaluate trends in vital rates and populations. We used a classic before-after-control-impact (BACI) experimental design to investigate the demographic response of northern spotted owls to the lethal removal of barred owls. According to the best 2-species dynamic occupancy model, there was no evidence of differences in barred or northern spotted owl occupancy prior to the initiation of the treatment (barred owl removal). After treatment, barred owl occupancy was lower in the treated relative to the untreated areas and spotted owl occupancy was higher relative to the untreated areas. Barred owl removal decreased spotted owl territory extinction rates but did not affect territory colonization rates. As a result, spotted owl occupancy increased in the treated area and continued to decline in the untreated areas. Prior to and after barred owl removal, there was no evidence that average fecundity differed on the 2 study areas. However, the greater number of occupied spotted owl sites on the treated areas resulted in greater productivity in the treated areas based on empirical counts of fledged young. Prior to removal, survival was declining at a rate of approximately 0.2% per year for treated and untreated areas. Following treatment, estimated survival was 0.859 for

  13. Mu-Synthesis robust control of 3D bar structure vibration using piezo-stack actuators

    NASA Astrophysics Data System (ADS)

    Mystkowski, Arkadiusz; Koszewnik, Andrzej Piotr

    2016-10-01

    This paper presents an idea for the Mu-Synthesis robust control of 3D bar structure vibration with using a piezo-stack actuators. A model of the 3D bar structure with uncertain parameters is presented as multi-input multi-output (MIMO) dynamics. Nominal stability and nominal performances of the open-loop 3D bar structure dynamic model is developed. The uncertain model-based robust controller is derived due to voltage control signal saturation and selected parameter perturbations. The robust control performances and robustness of the system due to uncertainties influence is evaluated by using singular values and a small gain theorem. Finally, simulation investigations and experimental results shown that system response of the 3D bar structure dynamic model with taken into account perturbed parameters met desired robust stability and system limits. The proposed robust controller ensures a good dynamics of the closed-loop system, robustness, and vibration attenuation.

  14. Dynamic testing of old and young baboon cortical bone with numerical validation

    NASA Astrophysics Data System (ADS)

    Chocron, S.; Nicolella, D.; Nicholls, A. E.; Bredbenner, T.; Havill, L.

    2012-08-01

    Cortical bone tensile mechanical properties at quasistatic and high rates (˜300s-1) were determined ex vivo using the right femurs of 12 female baboons, (Papio hamadryas spp.) from the Texas Biomedical Research Institute/Southwest National Primate Research Center in San Antonio, Texas. The animals were divided into two age groups: a young age group (6.63 ± 0.6 years) and an old age group (26.96 ± 1.3 years). Seven specimens per group were monotonically loaded to failure to determine their mechanical properties. The quasistatic strength of the bone for the old group was just a little (but not significantly) lower than the young group. High strain rate tests performed with the Hopkinson bar indicate that baboon bone from the older group was significantly weaker under impact loads than that from the younger group. This observation is particularly important due to the similarities between baboon and human bone tissue. Typical strain rates for these tests ranged from 130s-1 to 250s-1. A full-size 3-D simulation of the Hopkinson bar test was performed to confirm that the bone specimen was under stress equilibrium and to evaluate the consistency of the modulus and strength inferred from the tests. Simulations were performed in which the modulus, strength and failure strain were varied to see the sensitivity of the results. Additionally, simplified simulations were performed to estimate the strain rate environment of a femur during a fall at an impact velocity of 5 m/s, similar to a free fall velocity from a height of 1.3 meters. The simulations confirm that strain rates obtained in the Hopkinson bar are relevant because they are similar to those expected inr such a fall.

  15. Dynamical properties measurements for asteroid, comet and meteorite material applicable to impact modeling and mitigation calculations

    SciTech Connect

    Furnish, M.D.; Boslough, M.B.; Gray, G.T. III; Remo, J.L.

    1994-07-01

    We describe methods for measuring dynamical properties for two material categories of interest in understanding large-scale extraterrestrial impacts: iron-nickel and underdense materials (e.g. snow). Particular material properties measured by the present methods include Hugoniot release paths and constitutive properties (stress vs. strain). The iron-nickel materials lend themselves well to conventional shock and quasi-static experiments. As examples, a suite of experiments is described including six impact tests (wave profile compression/release) over the stress range 2--20 GPa, metallography, quasi-static and split Hopkinson pressure bar (SHPB) mechanical testing, and ultrasonic mapping and sound velocity measurements. Temperature sensitivity of the dynamic behavior was measured at high and low strain rates. Among the iron-nickel materials tested, an octahedrite was found to have behavior close to that of Armco iron under shock and quasi-static conditions, while an ataxite exhibited a significantly larger quasi-static yield strength than did the octahedrite or a hexahedrite. The underdense materials pose three primary experimental difficulties. First, the samples are friable; they can melt or sublimate during storage, preparation and testing. Second, they are brittle and crushable; they cannot withstand such treatment as traditional machining or launch in a gun system. Third, with increasing porosity the calculated Hugoniot density becomes rapidly more sensitive to errors in wave time-of-arrival measurements. Carefully chosen simulants eliminate preservation (friability) difficulties, but the other difficulties remain. A family of 36 impact tests was conducted on snow and snow simulants at Sandia, yielding reliable Hugoniot and reshock states, but limited release property information. Other methods for characterizing these materials are discussed.

  16. Dynamical properties measurements for asteroid, comet and meteorite material applicable to impact modeling and mitigation calculations

    NASA Astrophysics Data System (ADS)

    Furnish, M. D.; Boslough, M. B.; Gray, G. T., III; Remo, J. L.

    We describe methods for measuring dynamical properties for two material categories of interest in understanding large-scale extraterrestrial impacts: iron-nickel and underdense materials (e.g. snow). Particular material properties measured by the present methods include Hugoniot release paths and constitutive properties (stress vs. strain). The iron-nickel materials lend themselves well to conventional shock and quasi-static experiments. As examples, a suite of experiments is described including six impact tests (wave profile compression/release) over the stress range 2-20 GPa, metallography, quasi-static and split Hopkinson pressure bar (SHPB) mechanical testing, and ultrasonic mapping and sound velocity measurements. Temperature sensitivity of the dynamic behavior was measured at high and low strain rates. Among the iron-nickel materials tested, an octahedrite was found to have behavior close to that of Armco iron under shock and quasi-static conditions, while an ataxite exhibited a significantly larger quasi-static yield strength than did the octahedrite or a hexahedrite. The underdense materials pose three primary experimental difficulties. First, the samples are friable; they can melt or sublimate during storage, preparation and testing. Second, they are brittle and crushable; they cannot withstand such treatment as traditional machining or launch in a gun system. Third, with increasing porosity the calculated Hugoniot density becomes rapidly more sensitive to errors in wave time-of-arrival measurements. Carefully chosen simulants eliminate preservation (friability) difficulties, but the other difficulties remain. A family of 36 impact tests was conducted on snow and snow simulants at Sandia, yielding reliable Hugoniot and reshock states, but limited release property information. Other methods for characterizing these materials are discussed.

  17. Mass Distribution and Bar Formation in Growing Disk Galaxy Models

    NASA Astrophysics Data System (ADS)

    Berrier, Joel C.; Sellwood, J. A.

    2016-11-01

    We report idealized simulations that mimic the growth of galaxy disks embedded in responsive halos and bulges. The disks manifested an almost overwhelming tendency to form strong bars that we found very difficult to prevent. We found that fresh bars formed in growing disks after we had destroyed the original, indicating that bar formation also afflicts continued galaxy evolution, and not just the early stages of disk formation. This behavior raises still more insistently the previously unsolved question of how some galaxies avoid bars. Since our simulations included only collisionless star and halo particles, our findings may apply to gas-poor galaxies only; however, the conundrum persists for the substantial unbarred fraction of those galaxies. Our original objective was to study how internal dynamics rearranged the distribution of mass in the disk as a generalization of our earlier study with rigid spherical components. With difficulty, we were able to construct some models that were not strongly influenced by bars, and found that halo compression and angular momentum exchange with the disk did not alter our earlier conclusion that spiral activity is largely responsible for creating smooth density profiles and rotation curves.

  18. On loading velocity oscillations during dynamic tensile testing with flying wheel systems

    NASA Astrophysics Data System (ADS)

    Erice, Borja; Roth, Christian; Gary, Gerard; Mohr, Dirk

    2015-09-01

    Flying Wheels (FW) provide a space-saving alternative to Split Hopkinson Bar (SHB) systems for generating the loading pulse for intermediate and high strain rate material testing. This is particularly attractive in view of performing ductile fracture experiments at intermediate strain rates that require a several milliseconds long loading pulse. More than 50 m long Hopkinson bars are required in that case, whereas the same kinetic energy (for a given loading velocity) can be stored in rather compact flying wheels (e.g. diameter of less than 1.5 m). To gain more insight into the loading capabilities of FW tensile testing systems, a simple analytical model is presented to analyze the loading history applied by a FW system. It is found that due to the presence of a puller bar that transmits the tensile load from the rotating wheel to the specimen, the loading velocity applied onto the specimen oscillates between about zero and twice the tangential loading speed applied by the FW. The theoretical and numerical evaluation for a specific 1.1 m diameter FW system revealed that these oscillations occur at a frequency in the kHz range, thereby questioning the approximate engineering assumption of a constant strain rate in FW tensile experiments at strain rates of the order of 100/s.

  19. Effect of bars on the galaxy properties

    NASA Astrophysics Data System (ADS)

    Vera, Matias; Alonso, Sol; Coldwell, Georgina

    2016-10-01

    Aims: With the aim of assessing the effects of bars on disk galaxy properties, we present an analysis of different characteristics of spiral galaxies with strong bars, weak bars and without bars. Methods: We identified barred galaxies from the Sloan Digital Sky Survey (SDSS). By visual inspection of SDSS images we classified the face-on spiral galaxies brighter than g< 16.5 mag into strong-bar, weak-bar, and unbarred galaxies. With the goal of providing an appropriate quantification of the influence of bars on galaxy properties, we also constructed a suitable control sample of unbarred galaxies with similar redshifts, magnitudes, morphology, bulge sizes, and local density environment distributions to those of barred galaxies. Results: We found 522 strong-barred and 770 weak-barred galaxies; this represents a bar fraction of 25.82% with respect to the full sample of spiral galaxies, in good agreement with several previous studies. We also found that strong-barred galaxies show lower efficiency in star formation activity and older stellar populations (as derived with the Dn(4000) spectral index) with respect to weak-barred and unbarred spirals from the control sample. In addition, there is a significant excess of strong-barred galaxies with red colors. The color-color and color-magnitude diagrams show that unbarred and weak-barred galaxies are more extended towards the blue zone, while strong-barred disk objects are mostly grouped in the red region. Strong-barred galaxies present an important excess of high metallicity values compared to unbarred and weak-barred disk objects, which show similar distributions. Regarding the mass-metallicity relation, we found that weak-barred and unbarred galaxies are fitted by similar curves, while strong-barred ones show a curve that falls abruptly with more significance in the range of low stellar masses (log (M∗/M⊙) < 10.0). These results would indicate that prominent bars produced an accelerating effect on the gas processing

  20. Formation of membrane ridges and scallops by the F-BAR protein Nervous Wreck

    PubMed Central

    Becalska, Agata N.; Kelley, Charlotte F.; Berciu, Cristina; Stanishneva-Konovalova, Tatiana B.; Fu, Xiaofeng; Wang, ShiYu; Sokolova, Olga S.; Nicastro, Daniela; Rodal, Avital A.

    2013-01-01

    Eukaryotic cells are defined by extensive intracellular compartmentalization, which requires dynamic membrane remodeling. FER/Cip4 homology-Bin/amphiphysin/Rvs (F-BAR) domain family proteins form crescent-shaped dimers, which can bend membranes into buds and tubules of defined geometry and lipid composition. However, these proteins exhibit an unexplained wide diversity of membrane-deforming activities in vitro and functions in vivo. We find that the F-BAR domain of the neuronal protein Nervous Wreck (Nwk) has a novel higher-order structure and membrane-deforming activity that distinguishes it from previously described F-BAR proteins. The Nwk F-BAR domain assembles into zigzags, creating ridges and periodic scallops on membranes in vitro. This activity depends on structural determinants at the tips of the F-BAR dimer and on electrostatic interactions of the membrane with the F-BAR concave surface. In cells, Nwk-induced scallops can be extended by cytoskeletal forces to produce protrusions at the plasma membrane. Our results define a new F-BAR membrane-deforming activity and illustrate a molecular mechanism by which positively curved F-BAR domains can produce a variety of membrane curvatures. These findings expand the repertoire of F-BAR domain mediated membrane deformation and suggest that unique modes of higher-order assembly can define how these proteins sculpt the membrane. PMID:23761074

  1. Bar formation as driver of gas inflows in isolated disc galaxies

    NASA Astrophysics Data System (ADS)

    Fanali, R.; Dotti, M.; Fiacconi, D.; Haardt, F.

    2015-12-01

    Stellar bars are a common feature in massive disc galaxies. On a theoretical ground, the response of gas to a bar is generally thought to cause nuclear starbursts and, possibly, AGN activity once the perturbed gas reaches the central supermassive black hole. By means of high-resolution numerical simulations, we detail the purely dynamical effects that a forming bar exerts on the gas of an isolated disc galaxy. The galaxy is initially unstable to the formation of non-axisymmetric structures, and within ˜1 Gyr it develops spiral arms that eventually evolve into a central stellar bar on kpc scale. A first major episode of gas inflow occurs during the formation of the spiral arms while at later times, when the stellar bar is establishing, a low-density region is carved between the bar corotational and inner Lindblad resonance radii. The development of such `dead zone' inhibits further massive gas inflows. Indeed, the gas inflow reaches its maximum during the relatively fast bar-formation phase and not, as often assumed, when the bar is fully formed. We conclude that the low efficiency of long-lived, evolved bars in driving gas towards galactic nuclei is the reason why observational studies have failed to establish an indisputable link between bars and AGNs. On the other hand, the high efficiency in driving strong gas inflows of the intrinsically transient process of bar formation suggests that the importance of bars as drivers of AGN activity in disc galaxies has been overlooked so far. We finally prove that our conclusions are robust against different numerical implementations of the hydrodynamics routinely used in galaxy evolution studies.

  2. Effects of Added Rigid Vegetation on the Bar Formation: Results from Full-scale Experimental

    NASA Astrophysics Data System (ADS)

    Peng, K. Y.; Chen, S. C.; An, H. P.

    2015-12-01

    River corridors were characterized by island and floodplain development driven by the inter-play of flows, sediments and vegetation. This study used a natural stream as an experimental site with the site was 60m long by 30m wide, which was in downstream of Landao Creek, Huisun forest, Taiwan. The field experiment was designed to investigate the effects of river processes on bar, and the effects vegetation dynamics had on bar formation, which cause by upstream dam broke. To analysis how vegetation impact on bar-form and bar-stabilization, we used wood piles (4.4×4.4×80cm) as natural rigid vegetation, which inserted into the bar upstream. In the field site, we chose 6 site to set wood piles, each site was designed 4 row and were total 11 piles within, which set at in-row and in- line spacing of 50×20cm. According to the results, two primary phase of forming bar in the fluvial processes were discussed. First, in the flood period, presence of piles could trap large gravel in the front and turn the gravel into deposition. When the deposition gradually accreted, the front of deposition would induce flow to divide, let flow disperse into two branches around the deposition; some coarser particles rather are transported along the bar surface with momentum of flow movement and deposited at the top of bar, than are transported along the diversion channel around the bar (the median grain size of bar top were coarser 50% than before). Second, in the flood recession period, bar quickly accreted portions of passing bed load sheets and grew laterally and in the headward direction. Phenomenon showed that the composition of grain size were decreasing in the headward direction, which flow entrained were getting smaller with flood recession (the median grain size between top and the front of bar differed 30%).

  3. Bar morphodynamics in the tidally-influenced fluvial zone

    NASA Astrophysics Data System (ADS)

    Parsons, Daniel; Ashworth, Philip; Best, James; Nicholas, Andrew; Prokocki, Eric; Sambrook-Smith, Greg; Keevil, Claire; Sandbach, Steve

    2015-04-01

    The hydrodynamics and deposits of the Tidally-Influenced Fluvial Zone (TIFZ) are complex because it experiences competing fluvial and tidal flows and spatially and temporally variable rates of sediment transport and deposition. This paper presents a new integrated field dataset from the Columbia River Estuary, USA, that quantifies the morphodynamic response the bed morphology and bar stratigraphy to fluvial-tidal flows. A 3-year, field and modelling program that started in 2011, has been monitoring the dynamics and deposits of a 40 km-reach of the Columbia River Estuary. Data obtained so far throughout the TIFZ include: bathymetry using MBES, flow using ADCP, subsurface sedimentology using GPR and shallow coring to 5 m. Initial results from the programme suggest there is a complex spatial and temporal lag in the response of the bed morphology and deposits to the fluvial-tidal flows. Zones of strong ebb and flood flow do not necessarily produce channel beds dominated by bi-directional bedforms. Many mid-channel bars are stable over decadal time periods. This paper will illustrate the variety in bar morphologies and channel change throughout the fluvial-tidal zone and contrast these bar dynamics with examples from purely fluvial environments.

  4. Bar morphodynamics in the fluvial-tidal zone

    NASA Astrophysics Data System (ADS)

    Ashworth, P. J.; Best, J. L.; Nicholas, A.; Parsons, D. R.; Prokocki, E.; Sambrook Smith, G.; Simpson, C.

    2012-12-01

    The hydrodynamics and deposits of the Tidally-Influenced Fluvial Zone (TIFZ) are complex because it experiences competing fluvial and tidal flows, sometimes moderated by waves, and spatially and temporally variable rates of sediment transport and deposition. This paper presents a new integrated field dataset from the Columbia River Estuary, USA, that quantifies the response of the flow structure, bed morphology and bar stratigraphy to fluvial-tidal flows. A new 3-year, field and modelling program that started in 2011, has been monitoring the dynamics and deposits of a 40 km-reach of the Columbia River Estuary. Data obtained so far throughout the TIFZ include: bathymetry using MBES, flow using ADCP, subsurface sedimentology using GPR and shallow coring to 5 m. First results suggest there is a complex spatial and temporal lag in the response of the bed morphology and deposits to the fluvial-tidal flows. Zones of strong ebb and flood flow do not necessarily produce channel beds dominated by bi-directional bedforms. Many mid-channel bars are stable over decadal time periods. This paper will illustrate the variety in bar morphologies and channel change throughout the fluvial-tidal zone and contrast these bar dynamics with examples from purely fluvial environments.

  5. Galaxy Zoo: Observing secular evolution through bars

    SciTech Connect

    Cheung, Edmond; Faber, S. M.; Koo, David C.; Athanassoula, E.; Bosma, A.; Masters, Karen L.; Nichol, Robert C.; Melvin, Thomas; Bell, Eric F.; Lintott, Chris; Schawinski, Kevin; Skibba, Ramin A.; Willett, Kyle W.

    2013-12-20

    In this paper, we use the Galaxy Zoo 2 data set to study the behavior of bars in disk galaxies as a function of specific star formation rate (SSFR) and bulge prominence. Our sample consists of 13,295 disk galaxies, with an overall (strong) bar fraction of 23.6% ± 0.4%, of which 1154 barred galaxies also have bar length (BL) measurements. These samples are the largest ever used to study the role of bars in galaxy evolution. We find that the likelihood of a galaxy hosting a bar is anticorrelated with SSFR, regardless of stellar mass or bulge prominence. We find that the trends of bar likelihood and BL with bulge prominence are bimodal with SSFR. We interpret these observations using state-of-the-art simulations of bar evolution that include live halos and the effects of gas and star formation. We suggest our observed trends of bar likelihood with SSFR are driven by the gas fraction of the disks, a factor demonstrated to significantly retard both bar formation and evolution in models. We interpret the bimodal relationship between bulge prominence and bar properties as being due to the complicated effects of classical bulges and central mass concentrations on bar evolution and also to the growth of disky pseudobulges by bar evolution. These results represent empirical evidence for secular evolution driven by bars in disk galaxies. This work suggests that bars are not stagnant structures within disk galaxies but are a critical evolutionary driver of their host galaxies in the local universe (z < 1).

  6. In-Axis and Cross-Axid Accelerometer Response in Shock Environments

    SciTech Connect

    Bateman, V.I.; Brown, F.A.

    1999-03-10

    The characteristics of a piezoresistive accelerometer in shock environments have been studied at Sandia National Laboratories (SNL) in the Mechanical Shock Testing Laboratory for ten years The SNL Shock Laboratory has developed a capability to characterize accelerometers and other transducers with shocks aligned with the transducer's sensing axis and perpendicular to the transducer's sensing axis. This unique capability includes Hopkinson bars made of aluminum, steel, titanium, and beryllium. The bars are configured as both single and split Hopkinson bars. Four different areas that conclude this study are summarized in this paper: characterization of the cross-axis response of the accelerometer in the four environments of static compression, static strain on a beam, dynamic strain, and mechanical shock, the accelerometer's response on a titanium Hopkinson bar with two 45{degree} flats on the end of the bar; failure analysis of the accelerometer; and measurement of the accelerometer's self-generating cable response in a shock environment.

  7. Bar Coding and Tracking in Pathology.

    PubMed

    Hanna, Matthew G; Pantanowitz, Liron

    2015-06-01

    Bar coding and specimen tracking are intricately linked to pathology workflow and efficiency. In the pathology laboratory, bar coding facilitates many laboratory practices, including specimen tracking, automation, and quality management. Data obtained from bar coding can be used to identify, locate, standardize, and audit specimens to achieve maximal laboratory efficiency and patient safety. Variables that need to be considered when implementing and maintaining a bar coding and tracking system include assets to be labeled, bar code symbologies, hardware, software, workflow, and laboratory and information technology infrastructure as well as interoperability with the laboratory information system. This article addresses these issues, primarily focusing on surgical pathology.

  8. Recent developments in dynamic testing of materials

    NASA Astrophysics Data System (ADS)

    Gilat, A.; Seidt, J. D.

    2012-08-01

    Three new testing configurations that have been developed since the last DYMAT conference in 2009 are presented. The first is high strain rate testing of Kevlar cloth and Kevlar yarn in a tensile Split Hopkinson Bar (SHB) apparatus. The Kevlar cloth/yarn is attached to the bars by specially designed adaptors that keep the impedance constant. In addition to determining the specimen's stress and strain from the recorded waves in the bars the deformations are also measured with Digital Image Correlation (DIC). The second testing configuration is a high strain rate shear test for sheet metal. The experiment is done by using a flat notched specimen in a tensile SHB apparatus. The shear strain is measured using DIC within the notch and on the boundary. The third development is a compression apparatus for testing at intermediate strain rates ranging from 20 s-1 to 200 s-1. The apparatus is a combination of a hydraulic actuator and a compression SHB. The stress in the specimen is determined from the stress wave in a very long transmitter bar and the strain and strain rate is determined by using DIC. The results show clean stress strain curves (no ringing).

  9. Improved Kolsky-bar design for mechanical characterization of materials at high strain rates

    NASA Astrophysics Data System (ADS)

    Song, Bo; Connelly, Kevin; Korellis, John; Lu, Wei-Yang; Antoun, Bonnie R.

    2009-11-01

    A Kolsky apparatus with numerous modifications has been designed for mechanical characterization of materials at high strain rates. These modifications include employing a highly precise optical table, pillow blocks with Frelon®-coated linear bearings as bar supports and a laser system for better precision bar alignment, etc. In addition, the striker bars were coated with Teflon® to minimize the friction with the gun barrel after removal of the conventional plastic sabots. This new design significantly simplifies the alignment process, improving the final alignment and calibration in the bar system; both are critical for validity and accuracy of the resulting data. An example of a dynamic experiment on a 6061 aluminum specimen by using this newly designed Kolsky bar is also presented.

  10. [Nutritional characteristics of cereal and peanut bars].

    PubMed

    Escobar, B; Estévez, A M; Tepper, A; Aguayo, M

    1998-06-01

    Snack with good nutritional value could play an important role in the physical and mental development of children and teenagers since they show a great preference for them. The tendency is increasing their nutritional value by supplying proteins, carbohydrates, fiber, vitamins and minerals in a balanced form. The purpose of this research was to evaluate the chemical, sensorial and nutritional quality of cereal and peanut bars. Three types of bars using different ratios of oat, wheat germ, peanut, toasted and expanded amaranthus and wheat extrudate were prepared. Bars proximate composition was determined according the AOAC methods, and their acceptability according Hedonic Scale. In the biological assays, rats fed with 10% protein diets, were used to obtain the Protein Efficiency Ratio (PER) Net Protein Ratio (NPR) and Apparent Digestibility (AD). Corrected PER, relative PER, relative AD, PER and NPR values did not showed difference between bars CM1 and CM2 (PER: 2.59-2.57; NPR: 3.99-3.95 respectively); CM3 bar showed a lower quality. There were not differences among bars in relation to AD. CM1 and CM2 bars had a better biological quality of the protein being CM3 bar of lower quality. From a chemical and sensorial point of view CM1 bar shows the highest protein content (14.23%) and acceptability (6.8) and CM2 bar shows a high raw fiber content (2.27%). PMID:9830492

  11. Electrostatic precipatator construction having ladder bar spacers

    SciTech Connect

    Jonelis, J.A.

    1984-10-30

    The present invention relates to an improved construction for an electrostatic precipitator having ladder bar spacers. The electrostatic precipitator collects solid particles carried by a flue gas from a source of combustion. The precipitator includes a plurality of spaced plates for collecting solid particles from the flue gas by electrostatic attraction of the solid particles to the plates. A second plurality of elongated electrodes is positioned among the plates. Each of the electrodes is mounted between a pair of adjacent plates. Each of the electrodes is parallel to the other electrodes and is parallel to the plates. A third plurality of ladder bars is positioned between adjacent plates to hold the plates in a flat attitude and to maintain adjacent surfaces of adjacent plates substantially equidistantly spaced from one another. Each of the ladder bars has a connector bar secured to one of the pair of adjacent surfaces. Each of the ladder bars has a fourth plurality of holder bars. Each of the holder bars having one end connected to its respective connector bar and extending outwardly from the connector bar toward the other of the pair of adjacent surfaces. A contact on the other end of each holder bar engages the other of the pair of adjacent surfaces to hold the pair of adjacent surfaces apart.

  12. Bar-Halo Friction in Galaxies. I. Scaling Laws

    NASA Astrophysics Data System (ADS)

    Sellwood, J. A.

    2006-02-01

    It has been known for some time that rotating bars in galaxies slow due to dynamical friction against the halo. However, recent attempts to use this process to place constraints on the dark matter density in galaxies and possibly also to drive dark matter out of the center have been challenged. This paper uses simplified numerical experiments to clarify several aspects of the friction mechanism. I explicitly demonstrate the Chandrasekhar scaling of the friction force with bar mass, halo density, and halo velocity dispersion. I present direct evidence that exchanges between the bar and halo orbits at major resonances are responsible for friction and study both individual orbits and the net changes at these resonances. I also show that friction alters the phase space density of particles in the vicinity of a major resonance, which is the reason the magnitude of the friction force depends on the prior evolution. I demonstrate that bar slowdown can be captured correctly in simulations having modest spatial resolution and a practicable numbers of particles. Subsequent papers in this series delineate the dark matter density that can be tolerated in halos of different density profiles.

  13. Simulating a slow bar in the low surface brightness galaxy UGC 628

    NASA Astrophysics Data System (ADS)

    Chequers, Matthew H.; Spekkens, Kristine; Widrow, Lawrence M.; Gilhuly, Colleen

    2016-08-01

    We present a disc-halo N-body model of the low surface brightness galaxy UGC 628, one of the few systems that harbours a "slow" bar with a ratio of corotation radius to bar length of mathcal {R} equiv R_c/a_b ˜ 2. We select our initial conditions using SDSS DR10 photometry, a physically motivated radially variable mass-to-light ratio profile, and rotation curve data from the literature. A global bar instability grows in our submaximal disc model, and the disc morphology and dynamics agree broadly with the photometry and kinematics of UGC 628 at times between peak bar strength and the onset of buckling. Prior to bar formation, the disc and halo contribute roughly equally to the potential in the galaxy's inner region, giving the disc enough self gravity for bar modes to grow. After bar formation there is significant mass redistribution, creating a baryon dominated inner and dark matter dominated outer disc. This implies that, unlike most other low surface brightness galaxies, UGC 628 is not dark matter dominated everywhere. Our model nonetheless implies that UGC 628 falls on same the relationship between dark matter fraction and rotation velocity found for high surface brightness galaxies, and lends credence to the argument that the disc mass fraction measured at the location where its contribution to the potential peaks is not a reliable indicator of its dynamical importance at all radii.

  14. Optimization of the dynamic behavior of strongly nonlinear heterogeneous materials

    NASA Astrophysics Data System (ADS)

    Herbold, Eric B.

    New aspects of strongly nonlinear wave and structural phenomena in granular media are developed numerically, theoretically and experimentally. One-dimensional chains of particles and compressed powder composites are the two main types of materials considered here. Typical granular assemblies consist of linearly elastic spheres or layers of masses and effective nonlinear springs in one-dimensional columns for dynamic testing. These materials are highly sensitive to initial and boundary conditions, making them useful for acoustic and shock-mitigating applications. One-dimensional assemblies of spherical particles are examples of strongly nonlinear systems with unique properties. For example, if initially uncompressed, these materials have a sound speed equal to zero (sonic vacuum), supporting strongly nonlinear compression solitary waves with a finite width. Different types of assembled metamaterials will be presented with a discussion of the material's response to static compression. The acoustic diode effect will be presented, which may be useful in shock mitigation applications. Systems with controlled dissipation will also be discussed from an experimental and theoretical standpoint emphasizing the critical viscosity that defines the transition from an oscillatory to monotonous shock profile. The dynamic compression of compressed powder composites may lead to self-organizing mesoscale structures in two and three dimensions. A reactive granular material composed of a compressed mixture of polytetrafluoroethylene (PTFE), tungsten (W) and aluminum (Al) fine-grain powders exhibit this behavior. Quasistatic, Hopkinson bar, and drop-weight experiments show that composite materials with a high porosity and fine metallic particles exhibit a higher strength than less porous mixtures with larger particles, given the same mass fraction of constituents. A two-dimensional Eulerian hydrocode is implemented to investigate the mechanical deformation and failure of the compressed

  15. ON THE FRACTION OF BARRED SPIRAL GALAXIES

    SciTech Connect

    Nair, Preethi B.; Abraham, Roberto G. E-mail: abraham@astro.utoronto.c

    2010-05-10

    We investigate the stellar masses of strongly barred spiral galaxies. Our analysis is based on a sample of {approx}14,000 visually classified nearby galaxies given by Nair and Abraham. The fraction of barred spiral galaxies is found to be a strong function of stellar mass and star formation history, with a minimum near the characteristic mass at which bimodality is seen in the stellar populations of galaxies. We also find that bar fractions are very sensitive to the central concentration of galaxies below the transition mass but not above it. This suggests that whatever process is causing the creation of the red and blue sequences is either influencing, or being influenced by, structural changes which manifest themselves in the absence of bars. As a consequence of strong bar fractions being sensitive to the mass range probed, our analysis helps resolve discrepant results on the reported evolution of bar fractions with redshift.

  16. Boric Acid Reclamation System (BARS)

    SciTech Connect

    Kniazewycz, B.G.; Markind, J.

    1986-03-01

    KLM Technologies' personnel have identified a Boric Acid Reclamation System (BARS) utilizing reverse osmosis and ultrafiltration to produce a recyclable grade of otherwise waste boric acid at PWRs, thus reducing a major source of low-level radwaste. The design of a prototype BARS as a compact volume reduction system was the result of KLM's Phase 1 Program, and based upon a preliminary feasibility program, which assessed the applicability of membrane technology to refurbish and recycle waste boric acid from floor and equipment drain streams. The analysis of the overall program indicated a substantial savings regarding off-site disposal costs. Today's economic scenario indicates that optimization of volume reduction operation procedures could significantly reduce waste management costs, especially where burial penalties have become more severe. As a reaction to the economic burden imposed by final disposal, many nuclear plants are currently modifying their design and operating philosophies concerning liquid radwaste processing systems to meet stricter environmental regulations, and to derive potential economic benefits by reducing the ever-increasing volumes of wastes that are produced. To effect these changes, innovative practices in waste management and more efficient processing technologies are being successfully implemented.

  17. P{bar P} collider physics

    SciTech Connect

    Demarteau, M.

    1992-04-01

    A brief introduction to {bar p}p collider physics is given. Selected results from the collider experiments at the CERN S{bar p}pS and the Tevatron collider are described. The emphasis is on experimental aspects of {bar p}p collisions. Minimum bias physics and the production of jets, Intermediate Vector Bosons and heavy flavors is reviewed. The outlook for physics at hadron colliders for the near future is briefly discussed.

  18. DO BARS DRIVE SPIRAL DENSITY WAVES?

    SciTech Connect

    Buta, Ronald J.; Knapen, Johan H.; Elmegreen, Bruce G.; Salo, Heikki; Laurikainen, Eija; Elmegreen, Debra Meloy; Puerari, Ivanio; Block, David L. E-mail: jhk@iac.es E-mail: hsalo@sun3.oulu.fi E-mail: elmegreen@vassar.edu E-mail: David.Block@wits.ac.za

    2009-05-15

    We present deep near-infrared K{sub s} -band Anglo-Australian Telescope Infrared Imager and Spectrograph observations of a selected sample of nearby barred spiral galaxies, including some with the strongest known bars. The sample covers a range of Hubble types from SB0{sup -} to SBc. The goal is to determine if the torque strengths of the spirals correlate with those of the bars, which might be expected if the bars actually drive the spirals as has been predicted by theoretical studies. This issue has implications for interpreting bar and spiral fractions at high redshift. Analysis of previous samples suggested that such a correlation exists in the near-infrared, where effects of extinction and star formation are less important. However, the earlier samples had only a few excessively strong bars. Our new sample largely confirms our previous studies, but still any correlation is relatively weak. We find two galaxies, NGC 7513 and UGC 10862, where there is only a weak spiral in the presence of a very strong bar. We suggest that some spirals probably are driven by their bars at the same pattern speed, but that this may be only when the bar is growing or if there is abundant gas and dissipation.

  19. Basic physics of xylophone and marimba bars

    NASA Astrophysics Data System (ADS)

    Suits, B. H.

    2001-07-01

    The frequency-dependent wave velocity and nonsinusoidal spatial dependence found for transverse waves in finite vibrating bars stands in stark contrast to the solutions to the one-dimensional wave equation, for example for the idealized vibrating string. The difference is particularly important when the resulting vibrations are used to produce music. Here, the appropriate approximate equations for transverse vibrations on a uniform bar are developed and compared to measurements using wooden bars. The results are extended using a simple finite element model to provide a means to predict normal mode behavior in nonuniform wooden bars such as those used for xylophones, marimbas, and related musical instruments.

  20. Kinematic Properties of Double-barred Galaxies: Simulations versus Integral-field Observations

    NASA Astrophysics Data System (ADS)

    Du, Min; Debattista, Victor P.; Shen, Juntai; Cappellari, Michele

    2016-09-01

    Using high-resolution N-body simulations, we recently reported that a dynamically cool inner disk embedded in a hotter outer disk can naturally generate a steady double-barred (S2B) structure. Here we study the kinematics of these S2B simulations, and compare them to integral-field observations from ATLAS 3D and SAURON. We show that S2B galaxies exhibit several distinct kinematic features, namely: (1) significantly distorted isovelocity contours at the transition region between the two bars, (2) peaks in σ LOS along the minor axis of inner bars, which we term “σ-humps,” that are often accompanied by ring/spiral-like features of increased σ LOS, (3) {h}3{--}\\bar{v} anti-correlations in the region of the inner bar for certain orientations, and (4) rings of positive h 4 when viewed at low inclinations. The most impressive of these features are the σ-humps these evolve with the inner bar, oscillating in strength just as the inner bar does as it rotates relative to the outer bar. We show that, in cylindrical coordinates, the inner bar has similar streaming motions and velocity dispersion properties as normal large-scale bars, except for σ z , which exhibits peaks on the minor axis, i.e., humps. These σ z humps are responsible for producing the σ-humps. For three well-resolved early-type S2Bs (NGC 2859, NGC 2950, and NGC 3941) and a potential S2B candidate (NGC 3384), the S2B model qualitatively matches the integral-field data well, including the “σ-hollows” previously identified. We also discuss the kinematic effect of a nuclear disk in S2Bs.

  1. Kinematic Properties of Double-barred Galaxies: Simulations versus Integral-field Observations

    NASA Astrophysics Data System (ADS)

    Du, Min; Debattista, Victor P.; Shen, Juntai; Cappellari, Michele

    2016-09-01

    Using high-resolution N-body simulations, we recently reported that a dynamically cool inner disk embedded in a hotter outer disk can naturally generate a steady double-barred (S2B) structure. Here we study the kinematics of these S2B simulations, and compare them to integral-field observations from ATLAS 3D and SAURON. We show that S2B galaxies exhibit several distinct kinematic features, namely: (1) significantly distorted isovelocity contours at the transition region between the two bars, (2) peaks in σ LOS along the minor axis of inner bars, which we term “σ-humps,” that are often accompanied by ring/spiral-like features of increased σ LOS, (3) {h}3{--}\\bar{v} anti-correlations in the region of the inner bar for certain orientations, and (4) rings of positive h 4 when viewed at low inclinations. The most impressive of these features are the σ-humps these evolve with the inner bar, oscillating in strength just as the inner bar does as it rotates relative to the outer bar. We show that, in cylindrical coordinates, the inner bar has similar streaming motions and velocity dispersion properties as normal large-scale bars, except for σ z , which exhibits peaks on the minor axis, i.e., humps. These σ z humps are responsible for producing the σ-humps. For three well-resolved early-type S2Bs (NGC 2859, NGC 2950, and NGC 3941) and a potential S2B candidate (NGC 3384), the S2B model qualitatively matches the integral-field data well, including the “σ-hollows” previously identified. We also discuss the kinematic effect of a nuclear disk in S2Bs.

  2. The mass dependence of star formation histories in barred spiral galaxies

    NASA Astrophysics Data System (ADS)

    Carles, Christian; Martel, Hugo; Ellison, Sara L.; Kawata, Daisuke

    2016-11-01

    We performed a series of 29 gas dynamical simulations of disc galaxies, barred and unbarred, with various stellar masses, to study the impact of the bar on star formation history. Unbarred galaxies evolve very smoothly, with a star formation rate (SFR) that varies by at most a factor of 3 over a period of 2 Gyr. The evolution of barred galaxies is much more irregular, especially at high stellar masses. In these galaxies, the bar drives a substantial amount of gas towards the centre, resulting in a high SFR, and producing a starburst in the most massive galaxies. Most of the gas is converted into stars, and gas exhaustion leads to a rapid drop of star formation after the starburst. In massive barred galaxies (stellar mass M_{ast }>2{×} 10^{10} {M_{⊙}}) the large amount of gas funnelled towards the centre is completely consumed by the starburst, while in lower mass barred galaxies it is only partially consumed. Gas concentration is thus higher in lower mass barred galaxies than it is in higher mass ones. Even though unbarred galaxies funnelled less gas towards their centre, the lower SFR allows this gas to accumulate. At late times, the star formation efficiency is higher in barred galaxies than unbarred ones, enabling these galaxies to maintain a higher SFR with a smaller gas supply. Several properties, such as the global SFR, central SFR, or central gas concentration, vary monotonically with time for unbarred galaxies, but not for barred galaxies. Therefore one must be careful when comparing barred and unbarred galaxies that share one observational property, since these galaxies might be at very different stages of their respective evolution.

  3. The bar-halo interaction - II. Secular evolution and the religion of N-body simulations

    NASA Astrophysics Data System (ADS)

    Weinberg, Martin D.; Katz, Neal

    2007-02-01

    This paper explores resonance-driven secular evolution between a bar and dark matter halo using N-body simulations. We make direct comparisons to our analytic theory to demonstrate the great difficulty that an N-body simulation has representing these dynamics for realistic astronomical interactions. In a dark matter halo, the bar's angular momentum is coupled to the central density cusp (if present) by the inner Lindblad resonance. Owing to this angular momentum transfer and self-consistent re-equilibration, strong realistic bars WILL modify the cusp profile, lowering the central densities within about 30 per cent of the bar radius in a few bar orbits. Past results to the contrary may be the result of weak bars or numerical artefacts. The magnitude of the effect depends on many factors and we illustrate the sensitivity of the response to the dark matter profile, the bar shape and mass and the galaxy's evolutionary history. For example, if the bar length is comparable to the size of a central dark matter core, the bar may exchange angular momentum without changing its pattern speed significantly. We emphasize that this apparently simple example of secular evolution is remarkably subtle in detail and conclude that an N-body exploration of any astronomical scenario requires a deep investigation into the underlying dynamical mechanisms for that particular problem to set the necessary requirements for the simulation parameters and method (e.g. particle number and Poisson solver). Simply put, N-body simulations do not divinely reveal truth and hence their results are not infallible. They are unlikely to provide useful insight on their own, particularly for the study of even more complex secular processes such as the production of pseudo-bulges and disc heating.

  4. Too Much Bar and Not Enough Mitzvah? A Proposed Research Agenda on Bar/Bat Mitzvah

    ERIC Educational Resources Information Center

    Schoenfeld, Stuart

    2010-01-01

    Jewish educators are understandably interested in research on how bar/bat mitzvah affect Jewish education or research on what Jewish schools have done to avoid the distortions of a focus on bar/bat mitzvah. Research might also focus on the somewhat different and more ambitious topic of the role that bar/bat mitzvah play in contemporary Jewish…

  5. Taylor impact of glass bars

    NASA Astrophysics Data System (ADS)

    Murray, Natalie; Bourne, Neil; Field, John

    1997-07-01

    Brar and Bless pioneeered the use of plate impact upon bars as a technique for investigating the 1D stress loading of glass. We wish to extend this technique by applying VISAR and embedded stress gauge measurements to a symmetrical version of the test. In this configuration two rods impact one upon the other in a symmetrical version of the Taylor test geometry in which the impact is perfectly rigid in the centre of mass frame. Previous work in the laboratory has characterised the three glass types (float, borosilicate and a high density lead glass). These experiments will identify the 1D stress failure mechanisms from high-speed photography and the stress and particle velocity histories will be interpreted in the light of these results. The differences in response of the three glasses will be highlighted.

  6. Bars Triggered By Galaxy Flybys

    NASA Astrophysics Data System (ADS)

    Holley-Bockelmann, Kelly; Lang, Meagan; Sinha, Manodeep

    2015-05-01

    Galaxy mergers drive galaxy evolution and are a key mechanism by which galaxies grow and transform. Unlike galaxy mergers where two galaxies combine into one remnant, galaxy flybys occur when two independent galaxy halos interpenetrate but detach at a later time; these one-time events are surprisingly common and can even out-number galaxy mergers at low redshift for massive halos. Although these interactions are transient and occur far outside the galaxy disk, flybys can still drive a rapid and large pertubations within both the intruder and victim halos. We explored how flyby encounters can transform each galaxy using a suite of N-body simulations. We present results from three co-planar flybys between disk galaxies, demonstrating that flybys can both trigger strong bar formation and can spin-up dark matter halos.

  7. Gas flow in barred potentials

    NASA Astrophysics Data System (ADS)

    Sormani, Mattia C.; Binney, James; Magorrian, John

    2015-05-01

    We use a Cartesian grid to simulate the flow of gas in a barred Galactic potential and investigate the effects of varying the sound speed in the gas and the resolution of the grid. For all sound speeds and resolutions, streamlines closely follow closed orbits at large and small radii. At intermediate radii shocks arise and the streamlines shift between two families of closed orbits. The point at which the shocks appear and the streamlines shift between orbit families depends strongly on sound speed and resolution. For sufficiently large values of these two parameters, the transfer happens at the cusped orbit as hypothesized by Binney et al. over two decades ago. For sufficiently high resolutions, the flow downstream of the shocks becomes unsteady. If this unsteadiness is physical, as appears to be the case, it provides a promising explanation for the asymmetry in the observed distribution of CO.

  8. Experimental constraints on the energy budget of dynamic gouge formation: effects of rock strength, material heterogeneity, and initial flaw characteristics

    NASA Astrophysics Data System (ADS)

    Griffith, Ashley; Barber, Troy; Borjas, Christopher; Ghaffari, Hamed

    2016-04-01

    Fault core materials are characterized by substantial grain size reduction relative to host and damage zone rocks. The properties of these materials control fault strength and frictional behavior, and they record valuable information about rupture and slip processes. At high strain rates and large stress amplitudes characteristic of earthquake rupture tips, rock failure passes through a fragmentation transition from discrete fracture to pulverization; therefore much of the observed grain size reduction at the leading edge of propagating earthquake ruptures. Past examinations of particle size distributions in gouge formed in the cores of natural faults have led to contrasting conclusions that during a single event, the energy associated with creation of new surface area during this grain size reduction can be as large as 50%, or as little as <1% of the earthquake energy budget; however these estimates are difficult to confirm due to (A) challenges associated with accurate particle size measurement and (B) uncertainty regarding the variety of (not-necessarily coseismic) physico-chemical processes that may contribute to the observed grain size reduction. Here we study the micromechanics and energy budget of dynamic rock fragmentation under impulsive compressive loads using a Split Hopkinson Pressure Bar. We present new experimental results on Arkansas Novaculite and Westerly Granite coupled with microstructural observations and BET surface area measurements of post-mortem specimens. We show that the energy partitioned into creation of new surface areas approaches a significant portion of the total dissipated energy during our experiments, but this partitioning can be buffered by the presence of flaws and/or significant material heterogeneity. The results of this work have important implications for lithologic controls on gouge formation and energy partitioning during earthquakes.

  9. Outreach to bar workers in Bangkok.

    PubMed

    Sittitrai, W

    1990-12-01

    In the course of a campaign to provide AIDS education, information and related services to bar workers, outreach is a necessary strategy. This paper describes what "outreach" is, the direction it may take, who the bar workers are, where outreach is conducted, who performs the outreach, what "community preparation" or prior work is necessary, and useful tips for effective, ethical, outreach programmes.

  10. Adjustable drill bar replaces complex jigs

    NASA Technical Reports Server (NTRS)

    Coventry, J. H.

    1970-01-01

    Adjustable drill bar incorporates a micrometer screw which, when used in conjunction with standard gage blocks, provides rapid method of drill hole location and reduces time and skill requirements for precision drilling on large surfaces. Device picks up oddly dimensioned tool hole points and acts as sine drill bar.

  11. Bar Study Stories. Issues in Prevention

    ERIC Educational Resources Information Center

    Higher Education Center for Alcohol, Drug Abuse, and Violence Prevention, 2012

    2012-01-01

    This issue of "Issues in Prevention" focuses on the impact of the availability of drinks in licensed establishments, such as bars and taverns on student drinking. This issue contains the following articles: (1) Cheap Drinks at College Bars Can Escalate Student Drinking (John D. Clapp); (2) High Alcohol Outlet Density: A Problem for Campuses and…

  12. Conservative Groups Threaten to Sue Bar Association

    ERIC Educational Resources Information Center

    Jacobson, Jennifer

    2006-01-01

    A proposed revision in the American Bar Association's accrediting standards for law schools is coming under fire from the U.S. Commission on Civil Rights, which says the proposal seems to require the schools to use racial preferences in hiring and admissions despite federal and state laws limiting such policies. Although a bar-association official…

  13. Needle bar for warp knitting machines

    DOEpatents

    Hagel, Adolf; Thumling, Manfred

    1979-01-01

    Needle bar for warp knitting machines with a number of needles individually set into slits of the bar and having shafts cranked to such an extent that the head section of each needle is in alignment with the shaft section accommodated by the slit. Slackening of the needles will thus not influence the needle spacing.

  14. [Development of cereal bar with pineapple skin].

    PubMed

    Fonseca, Renata Siqueira; Del Santo, Victor Rogério; Souza, Gilberto Batista de; Pereira, Cíntia Alessandra Matiucci

    2011-06-01

    The cereal bars are multi-component products consisting of cereals, dried fruit and syrup binder and may be added to the consumable parts of fruits and vegetables which usually are not exploited and have high nutritional value, thereby reducing food waste. It was developed a jam with pineapple skin, which it was utilized in 13.5% in the cereal bar formulation. The cereal bar was sensorial evaluated and had its centesimal and mineral composition determined. The new product achieved average of 8.3 for global impression using 9 points hedonic scale, 91% of acceptance rate and 67% of purchase intent. In this first use of pineapple skin jam as food ingredient it can be concluded that its aggregation in the cereal bar formula is feasible, making an accepted product with fibers, proteins and minerals, as an alternative to traditional cereal bars.

  15. [Development of cereal bar with pineapple skin].

    PubMed

    Fonseca, Renata Siqueira; Del Santo, Victor Rogério; Souza, Gilberto Batista de; Pereira, Cíntia Alessandra Matiucci

    2011-06-01

    The cereal bars are multi-component products consisting of cereals, dried fruit and syrup binder and may be added to the consumable parts of fruits and vegetables which usually are not exploited and have high nutritional value, thereby reducing food waste. It was developed a jam with pineapple skin, which it was utilized in 13.5% in the cereal bar formulation. The cereal bar was sensorial evaluated and had its centesimal and mineral composition determined. The new product achieved average of 8.3 for global impression using 9 points hedonic scale, 91% of acceptance rate and 67% of purchase intent. In this first use of pineapple skin jam as food ingredient it can be concluded that its aggregation in the cereal bar formula is feasible, making an accepted product with fibers, proteins and minerals, as an alternative to traditional cereal bars. PMID:22308949

  16. Design and Evaluation of a Prosthetic Knee Joint Using the Geared Five-Bar Mechanism.

    PubMed

    Sun, Yuanxi; Ge, Wenjie; Zheng, Jia; Dong, Dianbiao

    2015-11-01

    This paper presents the mechanical design, dynamics analysis and ankle trajectory analysis of a prosthetic knee joint using the geared five-bar mechanism. Compared with traditional four-bar or six-bar mechanisms, the geared five-bar mechanism is better at performing diverse movements and is easy to control. This prosthetic knee joint with the geared five-bar mechanism is capable of fine-tuning its relative instantaneous center of rotation and ankle trajectory. The centrode of this prosthetic knee joint, which is mechanically optimized according to the centrode of human knee joint, is better in the bionic performance than that of a prosthetic knee joint using the four-bar mechanism. Additionally, the stability control of this prosthetic knee joint during the swing and stance phase is achieved by a motor. By adjusting the gear ratio of this prosthetic knee joint, the ankle trajectories of both unilateral and bilateral amputees show less deviations from expected than that of the four-bar knee joint.

  17. Dynamic fiber debonding and push-out in model composites

    NASA Astrophysics Data System (ADS)

    Bi, Xiaopeng

    2003-10-01

    When a crack propagates in a fiber-reinforced composite material, a substantial part of energy is dissipated in the debonding and sliding of the bridging fibers located behind the advancing crack front. Because of the important effect they have on the fracture toughness of a composite, these processes have been the subject of extensive experimental, analytical and numerical work. However, the vast majority of existing work on this topic has been limited to quasi-static loading situations. The few investigations performed on various composite systems involving higher loading rates seem to indicate that the fiber sliding process presents some unusual and sometimes contradictory rate-dependent characteristics. To enhance the current understanding of dynamic fiber debonding and push-out in model fiber-reinforced composites, a combined experimental and numerical investigation was carried out. A modified split Hopkinson pressure bar was used to perform high-rate fiber push-out experiments on an aluminum/epoxy model composite system. An axisymmetric cohesive/volumetric finite element scheme was developed to simulate the push-out process. Effects of several important parameters such as interfacial strength, interfacial fracture toughness and fiber/matrix friction coefficient were investigated. Interface cohesive properties were extracted by comparison between experimental and numerical results. The comparison between numerics and experiments was made as close as possible by (a) simulating the entire experimental apparatus; (b) using loading directly measured in the experiments as input to the finite element analysis (FEA) code; (c) using measured material properties in the FEA simulations; and (d) accounting for effects such as large deformations, residual stresses (through a quasi-static pre-loading scheme), spontaneous crack formation (through a cohesive failure formulation) and dynamic frictional sliding. Details of the physical process were discussed by numerically

  18. Projection techniques for iterative solution of A(bar x) equals (bar b) with successive right-hand sides

    NASA Technical Reports Server (NTRS)

    Fischer, Paul F.

    1993-01-01

    Two projection techniques for computing approximate solutions to linear systems of the form A(bar x)(sup n) = (bar b)(sup n), for a sequence n = 1, 2, ..., e.g., such as arises from time discretization of a partial differential equation, are presented. The inexpensive approximate solutions can be used as initial guesses for iterative solution of the system, resulting in significantly reduced computational expense. Examples of two- and three-dimensional incompressible Navier-Stokes calculations are presented in which x represents the pressure, and A is a discrete Poisson operator. In flows containing significant dynamic activity, these projection techniques lead to as much as a two-fold reduction in solution time.

  19. The Environment of Barred Galaxies Revisited

    NASA Astrophysics Data System (ADS)

    Cervantes Sodi, B.; Li, C.; Park, C.; Wang, L.

    We present a study of the environment of barred galaxies using galaxies drawn from the SDSS. We use several different statistics to quantify the environment: the projected two-point cross-correlation function, the background-subtracted number counts of neighbor galaxies, the overdensity of the local environment, the membership of our galaxies to galaxy groups to segregate central and satellite systems, and, for central galaxies, the stellar to halo mass ratio (M∗/Mh). When we split our sample into early- and late-type galaxies, we see a weak but significant trend for early-type galaxies with a bar to be more strongly clustered on scales from a few 100 kpc to 1 Mpc when compared to unbarred early-type galaxies. This indicates that the presence of a bar in early-type galaxies depends on the location within their host dark matter halos. This is confirmed by the group catalog in the sense that for early-types, the fraction of central galaxies is smaller if they have a bar. For late-type galaxies, we find fewer neighbors within ˜ 50 kpc around the barred galaxies when compared to unbarred galaxies from the control sample, suggesting that tidal forces from close companions suppress the formation/growth of bars. For central late-type galaxies, bars are more common on galaxies with high M∗/Mh values, as expected from early theoretical works which showed that systems with massive dark matter halos are more stable against bar instabilities. Finally, we find no obvious correlation between overdensity and the bars in our sample, showing that galactic bars are not obviously linked to the large-scale structure of the universe.

  20. Dissipation in barred galaxies - The growth of bulges and central mass concentrations

    SciTech Connect

    Pfenniger, D.; Norman, C. Johns Hopkins Univ. Space Telescope Science Institute, Baltimore, MD )

    1990-11-01

    Basic dynamical mechanisms that produce an amplification of the accretion rate of gas clouds into the central regions of barred galaxies, and their subsequent effects on the evolution of barred galaxies, are discussed. Weakly dissipative orbits, representing gas clouds, are computed in a barred galaxy model with a central mass concentration such as a black hole, or a secondary small inner bar. Amplified accretion across resonances that is especially rapid inside the inner Lindblad resonance, large excursions outside the galactic plane, and the existence of nontrivial attractors like strange (chaotic) attractors or limit cycles are found. The underlying physical mechanisms are, in general, due to the presence of broad horizontal and vertical resonances through which weakly dissipative particles can rapidly traverse. The principal physical implications of these findings are discussed. 65 refs.

  1. Galaxy Zoo 2: A Study of Bar Fraction Versus Stellar Mass and Environment

    NASA Astrophysics Data System (ADS)

    Fortson, Lucy; Bamford, S.; Lintott, C.; Schawinski, K.; Smith, A.; Whyte, L.; Galaxy Zoo Team

    2010-01-01

    Galaxy Zoo has involved ¼ million of the public through the Internet in providing morphological classifications of nearly a million galaxies from the Sloan Digital Sky Survey (SDSS). Galaxy Zoo 2 is a follow on project and has already recorded more than 40 million detailed morphological classifications on the brightest 250,000 galaxies in the SDSS. Among the most interesting products is a catalog of 10,000 barred spirals - an order of magnitude increase on the sample sizes used in most current population studies of barred spirals. In this poster we present a first look at the properties of this catalog focusing in particular on the fraction of spirals with bars as a function of environment, stellar mass and star formation history. Barred spirals are a sensitive indicator of the dynamical state of a galaxy and we discuss the implications for the evolution of the spiral population.

  2. 33 CFR 13.01-40 - Miniature medals and bars.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... GENERAL DECORATIONS, MEDALS, RIBBONS AND SIMILAR DEVICES Gold and Silver Lifesaving Medals, Bars, and Miniatures § 13.01-40 Miniature medals and bars. (a) Miniature Gold and Silver Lifesaving Medals and bars...

  3. 33 CFR 13.01-40 - Miniature medals and bars.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... GENERAL DECORATIONS, MEDALS, RIBBONS AND SIMILAR DEVICES Gold and Silver Lifesaving Medals, Bars, and Miniatures § 13.01-40 Miniature medals and bars. (a) Miniature Gold and Silver Lifesaving Medals and bars...

  4. 33 CFR 13.01-40 - Miniature medals and bars.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... GENERAL DECORATIONS, MEDALS, RIBBONS AND SIMILAR DEVICES Gold and Silver Lifesaving Medals, Bars, and Miniatures § 13.01-40 Miniature medals and bars. (a) Miniature Gold and Silver Lifesaving Medals and bars...

  5. 33 CFR 13.01-40 - Miniature medals and bars.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... GENERAL DECORATIONS, MEDALS, RIBBONS AND SIMILAR DEVICES Gold and Silver Lifesaving Medals, Bars, and Miniatures § 13.01-40 Miniature medals and bars. (a) Miniature Gold and Silver Lifesaving Medals and bars...

  6. 33 CFR 13.01-40 - Miniature medals and bars.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... GENERAL DECORATIONS, MEDALS, RIBBONS AND SIMILAR DEVICES Gold and Silver Lifesaving Medals, Bars, and Miniatures § 13.01-40 Miniature medals and bars. (a) Miniature Gold and Silver Lifesaving Medals and bars...

  7. A technique for relining bar-retained overdentures.

    PubMed

    Mosharraf, Ramin; Abolhasani, Majid; Givehchian, Pirooz

    2014-12-01

    This article describes a technique for relining a mandibular bar-retained overdenture that allows recording the soft tissue beneath the bar and makes it possible to replace or modify the retentive bar attachment simultaneously with the reline procedure.

  8. Distributary-mouth bar development and role of submarine landslides in delta growth, South Pass, Mississippi delta

    SciTech Connect

    Lindsay, J.F.; Coleman, J.M.; Prior, D.B.

    1984-11-01

    Submarine landslides play a major role in the development of distributary-mouth bars and are of major importance in transporting sediment from the bar front to deeper water along the Mississippi delta front. Historic maps of the South Pass of the Mississippi delta show that the bar advanced seaward more than 1 mi (1.6 km) between 1867 and 1953. Details of the growth of the bar have been elucidated using an elaborate computer modeling program to analyze these historic maps. The analysis has shown that the geometry of the bar was controlled by the dynamics of the freshwater plume of river water as it mixed with saline Gulf water. Approximately half the sediment deposited on the bar was moved into deeper water by submarine landslides. The underlying causes of bar failure were established during major floods with the deposition of thick blankets of unstable, watersaturated sediments on the bar front. Failure occurred one to four years later in response to a variety of triggering mechanisms, which either changed the shear strength of the sediment or modified local bottom slope. The triggering mechanisms include: major storms and hurricanes, mudlump activity, and possibly, increased pore pressures resulting from generation of biogenic gas. Bar growth and basinward movement of sediment thus represent a multilvariate problem that can be approached by means of a computer analysis of bathymetric data.

  9. Modeling and simulation framework for dynamic strain localization in elasto-viscoplastic metallic materials subject to large deformations

    DOE PAGES

    Mourad, Hashem Mourad; Bronkhorst, Curt Allan; Livescu, Veronica; Plohr, JeeYeon Nam; Cerreta, Ellen Kathleen

    2016-09-23

    geometry and the Split-Hopkinson Pressure Bar dynamic test system. Axi-symmetric finite element simulation results are compared to cross-sectional micrographs of recovered samples and experimental load–displacement results, in order to examine the performance of the proposed framework and demonstrate its effectiveness in treating the initiation and growth of adiabatic shear banding in dynamically loaded metallic materials. These comparisons demonstrate that thermal softening alone is insufficient to induce shear localization behaviors observed in some materials, such as stainless steel, and support the hypothesis that dynamic recrystallization and/or other softening mechanisms play an essential role in this process.« less

  10. The BaLROG project - II. Quantifying the influence of bars on the stellar populations of nearby galaxies

    NASA Astrophysics Data System (ADS)

    Seidel, M. K.; Falcón-Barroso, J.; Martínez-Valpuesta, I.; Sánchez-Blázquez, P.; Pérez, I.; Peletier, R.; Vazdekis, A.

    2016-08-01

    We continue the exploration of the BaLROG (Bars in Low Redshift Optical Galaxies) sample: 16 large mosaics of barred galaxies observed with the integral field unit Spectrographic Areal Unit for Research on Optical Nebulae. We quantify the influence of bars on the composition of the stellar component. We derive line-strength indices of H β, Fe5015 and Mgb. Based on single stellar population (SSP) models, we calculate ages, metallicities and [Mg/Fe] abundances and their gradients along the bar major and minor axes. The high spatial resolution of our data allows us to identify breaks among index and SSP profiles, commonly at 0.13 ± 0.06 bar length, consistent with kinematic features. Inner gradients are about 10 times steeper than outer gradients and become larger when there is a central rotating component, implying that the gradients are not independent of dynamics and orbits. Central ages appear to be younger for stronger bars. Yet, the bar regions are usually old. We find a flattening of the iron (Fe5015) and magnesium (Mgb) outer gradients along the bar major axis, translating into a flattening of the metallicity gradient. This gradient is found to be 0.03 ± 0.07 dex kpc-1 along the bar major axis while the mean value of the bar minor axis compares well with that of an unbarred control sample and is significantly steeper, namely -0.20 ± 0.04 dex kpc-1. These results confirm recent simulations and discern the important localized influence of bars. The elevated [Mg/Fe] abundances of bars and bulges compared to the lower values of discs suggest an early formation, in particular for early-type galaxies.

  11. Cam-controlled boring bar

    DOEpatents

    Glatthorn, Raymond H.

    1986-01-01

    A cam-controlled boring bar system (100) includes a first housing (152) which is rotatable about its longitudinal axis (154), and a second housing in the form of a cam-controlled slide (158) which is also rotatable about the axis (154) as well as being translatable therealong. A tool-holder (180) is mounted within the slide (158) for holding a single point cutting tool. Slide (158) has a rectangular configuration and is disposed within a rectangularly configured portion of the first housing (152). Arcuate cam slots (192) are defined within a side plate (172) of the housing (152), while cam followers (194) are mounted upon the cam slide (158) for cooperative engagement with the cam slots (192). In this manner, as the housing (152) and slide (158) rotate, and as the slide (158) also translates, a through-bore (14) having an hourglass configuration will be formed within a workpiece (16) which may be, for example, a nuclear reactor steam generator tube support plate.

  12. Tidally Induced Bars of Galaxies in Clusters

    NASA Astrophysics Data System (ADS)

    Łokas, Ewa L.; Ebrová, Ivana; del Pino, Andrés; Sybilska, Agnieszka; Athanassoula, E.; Semczuk, Marcin; Gajda, Grzegorz; Fouquet, Sylvain

    2016-08-01

    Using N-body simulations, we study the formation and evolution of tidally induced bars in disky galaxies in clusters. Our progenitor is a massive, late-type galaxy similar to the Milky Way, composed of an exponential disk and a Navarro-Frenk-White dark matter halo. We place the galaxy on four different orbits in a Virgo-like cluster and evolve it for 10 Gyr. As a reference case, we also evolve the same model in isolation. Tidally induced bars form on all orbits soon after the first pericenter passage and survive until the end of the evolution. They appear earlier, are stronger and longer, and have lower pattern speeds for tighter orbits. Only for the tightest orbit are the properties of the bar controlled by the orientation of the tidal torque from the cluster at pericenter. The mechanism behind the formation of the bars is the angular momentum transfer from the galaxy stellar component to its halo. All of the bars undergo extended periods of buckling instability that occur earlier and lead to more pronounced boxy/peanut shapes when the tidal forces are stronger. Using all simulation outputs of galaxies at different evolutionary stages, we construct a toy model of the galaxy population in the cluster and measure the average bar strength and bar fraction as a function of clustercentric radius. Both are found to be mildly decreasing functions of radius. We conclude that tidal forces can trigger bar formation in cluster cores, but not in the outskirts, and thus can cause larger concentrations of barred galaxies toward the cluster center.

  13. First Measurement of σ(gg → t$\\bar{t}$)/σ(p$\\bar{p}$ → t$\\bar{t}$)

    SciTech Connect

    Alamdari, Shabnaz Pashapour

    2008-01-01

    The work presented here is the first measurement of the fraction of top quark pair production through gluon-gluon fusion. We use an integrated luminosity of 0.96 ± 0.06 fb-1 of p{bar p} collisions at √s of 1.96 TeV collected by the CDF II detector. We select t$\\bar{t}$ candidates by identifying a high-pT lepton candidate, a large missing ET as evidence for a neutrino candidate and at least four high ET jets, one of which has to be identified as originating from a b quark. The challenge is to discriminate between the two production processes with the identical final state, gg → t$\\bar{t}$ and q$\\bar{p}$ → t$\\bar{t}$. We take advantage of the fact that compared to a quark, a gluon is more likely to radiate a low momentum gluon and therefore, one expects a larger number of charged particles with low pT in a process involving more gluons. Given the large uncertainties associated with the modeling of the low pT charged particle multiplicity, a data-driven technique was employed. Using calibration data samples, we show there exists a clear correlation between the observed average number of low pT charged particles and the average number of gluons involved in the production process predicted by Monte Carlo calculations. Given the correlation, one can identify low pT charged particle multiplicity distributions associated with specific average number of gluons. The W + 0 jet sample and dijets sample with leading jet ET in the range of 80-100 GeV are used to find no-gluon and gluon-rich low p{sub T} charged particle multiplicity distributions, respectively. Using these no-gluon and gluon-rich distributions in a likelihood fit, we find the fraction of gluon-rich events in t{bar t} candidates. This fraction has contributions from the signal and background events. Taking into account these contributions and the gg → t$\\bar{t}$ and q$\\bar{q}$ → t$\\bar

  14. Cooperation of phosphoinositides and BAR domain proteins in endosomal tubulation.

    PubMed

    Shinozaki-Narikawa, Naeko; Kodama, Tatsuhiko; Shibasaki, Yoshikazu

    2006-11-01

    Phosphorylated derivatives of phosphatidylinositol (PtdIns) regulate many intracellular events, including vesicular trafficking and actin remodeling, by recruiting proteins to their sites of function. PtdIns(4,5)-bisphosphate [PI(4,5)P2] and related phosphoinositides are mainly synthesized by type I PtdIns-4-phosphate 5-kinases (PIP5Ks). We found that PIP5K induces endosomal tubules in COS-7 cells. ADP-ribosylation factor (ARF) 6 has been shown to act upstream of PIP5K and regulate endocytic transport and tubulation. ARF GAP with coiled-coil, ankyrin repeat, and pleckstrin homology domains 1 (ACAP1) has guanosine triphosphatase-activating protein (GAP) activity for ARF6. While there were few tubules induced by the expression of ACAP1 alone, numerous endosomal tubules were induced by coexpression of PIP5K and ACAP1. ACAP1 has a pleckstrin homology (PH) domain known to bind phosphoinositide and a Bin/amphiphysin/Rvs (BAR) domain that has been reported to detect membrane curvature. Truncated and point mutations in the ACAP1 BAR and PH domains revealed that both BAR and PH domains are required for tubulation. These results suggest that two ARF6 downstream molecules, PIP5K and ACAP1, function together in endosomal tubulation and that phosphoinositide levels may regulate endosomal dynamics. PMID:17010122

  15. Orbital classification in an N-body bar

    NASA Astrophysics Data System (ADS)

    Wang, Yougang; Athanassoula, E.; Mao, Shude

    2016-09-01

    The dynamics and evolution of any galactic structure are strongly influenced by the properties of the orbits that constitute it. In this paper, we compare two orbit classification schemes, one by Laskar (NAFF) , and the other by Carpintero and Aguilar (CA), by applying both of them to orbits obtained by following individual particles in a numerical simulation of a barred galaxy. We find that, at least for our case and some provisos, the main frequencies calculated by the two methods are in good agreement: for 80% of the orbits the difference between the results of the two methods is less than 5% for all three main frequencies. However, it is difficult to evaluate the amount of regular or chaotic bar orbits in a given system. The fraction of regular orbits obtained by the NAFF method strongly depends on the critical frequency drift parameter, while in the CA method the number of fundamental frequencies strongly depends on the frequency difference parameter Lr and the maximum integer used for searching the linear independence of the fundamental frequencies. We also find that, for a given particle, in general the projection of its motion along the bar minor axis is more regular than the other two projections, while the projection along the intermediate axis is the least regular.

  16. The influence of stacking fault energy on the mechanical behavior of Cu and Cu-Al alloys: Deformation twinning, work hardening, and dynamic recovery

    NASA Astrophysics Data System (ADS)

    Rohatgi, Aashish; Vecchio, Kenneth S.; Gray, George T.

    2001-01-01

    The role of stacking fault energy (SFE) in deformation twinning and work hardening was systematically studied in Cu (SFE ˜78 ergs/cm2) and a series of Cu-Al solid-solution alloys (0.2, 2, 4, and 6 wt pct Al with SFE ˜75, 25, 13, and 6 ergs/cm2, respectively). The materials were deformed under quasi-static compression and at strain rates of ˜1000/s in a Split-Hopkinson pressure bar (SHPB). The quasi-static flow curves of annealed 0.2 and 2 wt pct Al alloys were found to be representative of solid-solution strengthening and well described by the Hall-Petch relation. The quasi-static flow curves of annealed 4 and 6 wt pct Al alloys showed additional strengthening at strains greater than 0.10. This additional strengthening was attributed to deformation twins and the presence of twins was confirmed by optical microscopy. The strengthening contribution of deformation twins was incorporated in a modified Hall-Petch equation (using intertwin spacing as the “effective” grain size), and the calculated strength was in agreement with the observed quasi-static flow stresses. While the work-hardening rate of the low SFE Cu-Al alloys was found to be independent of the strain rate, the work-hardening rate of Cu and the high SFE Cu-Al alloys (low Al content) increased with increasing strain rate. The different trends in the dependence of work-hardening rate on strain rate was attributed to the difference in the ease of cross-slip (and, hence, the ease of dynamic recovery) in Cu and Cu-Al alloys.

  17. Torsional vibration analysis of bars including secondary torsional shear deformation effect by the boundary element method

    NASA Astrophysics Data System (ADS)

    Sapountzakis, E. J.; Tsipiras, V. J.; Argyridi, A. K.

    2015-10-01

    In this paper a boundary element method (BEM) is developed for the torsional vibration problem of bars of arbitrary doubly symmetric constant cross section, taking into account the nonuniform warping and secondary torsional shear deformation effects (STSDE). The bar is subjected to arbitrarily distributed or concentrated dynamic torsional loading along its length, while its edges are subjected to the most general torsional and warping boundary conditions. Apart from the angle of twist, the primary angle of twist per unit length is considered as an additional 1-D degree of freedom in order to account for the STSDE in the equations of motion of the bar. The warping shear stress distribution and the pertinent secondary torsional rigidity are computed by satisfying local equilibrium considerations under dynamic conditions without adhering to assumptions of Thin Tube Theory (TTT). By employing a distributed mass model system accounting for rotatory and warping inertia, an initial boundary value and two boundary value problems with respect to the variable along the bar time-dependent 1-D kinematical components, to the primary and secondary warping functions, respectively, are formulated. The latter are solved employing a pure BE method, requiring exclusively boundary discretization of the bar's cross section. The numerical solution of the aforementioned initial boundary value problem is performed through a BE method leading to a system of differential equations with displacement only unknowns, which is solved using an efficient direct time integration technique. Additionally, for the free vibrations case, a generalized eigenvalue problem is formulated through a similar BE technique. The accuracy and reliability of the results is assessed by FEM solutions employing solid or shell modelling. Both open- and closed-shaped cross section bars are examined and the necessity to include nonuniform torsional and STSD effects in the dynamic analysis of bars is demonstrated.

  18. HOW DIFFERENT ARE NORMAL AND BARRED SPIRALS?

    SciTech Connect

    Van den Bergh, Sidney

    2011-06-15

    No significant color differences are found between normal and barred spirals over the range of Hubble stages a-ab-b-bc. Furthermore, no significant difference is seen between the luminosity distributions of normal and barred galaxies over the same range of Hubble stages. However, SBc galaxies are found to be systematically fainter than Sc galaxies at 99% confidence. The observation that normal and barred spirals with Hubble stages a-ab-b-bc have indistinguishable intrinsic colors hints at the possibility that the bars in such spiral galaxies might be ephemeral structures. Finally, it is pointed out that lenticular galaxies of types S0 and SB0 are systematically fainter than are other early-type galaxies, suggesting that such galaxies are situated on evolutionary tracks that differ systematically from those of galaxies that lie along the E-Sa-Sb-Sc and E-SBa-SBb-SBc sequences.

  19. ${{\\bar{d}} - {\\bar{u}}}$ Flavor Asymmetry in the Proton in Chiral Effective Field Theory

    SciTech Connect

    Salamu, Y.; Ji, Cheung-Ryong; Melnitchouk, Wally; Wang, P.

    2015-09-01

    The ${\\bar d - \\bar u}$ flavor asymmetry in the proton arising from pion loops is computed using chiral effective field theory. The calculation includes both nucleon and Δ intermediate states, and uses both the fully relativistic and heavy baryon frameworks. The x dependence of ${\\bar d - \\bar u}$ extracted from the Fermilab E866 Drell–Yan data can be well reproduced in terms of a single transverse momentum cutoff parameter regulating the ultraviolet behavior of the loop integrals. In addition to the distribution at x > 0, corrections to the integrated asymmetry from zero momentum contributions are computed, which arise from pion rainbow and bubble diagrams at x = 0. These have not been accounted for in previous analyses, and can make important contributions to the lowest moment of ${\\bar d-\\bar u}$ .

  20. THE DIRC Detector at BaBar

    SciTech Connect

    Ratcliff, Blair N

    1999-10-12

    A dedicated particle identification system based on the Detection of Internally Reflected Cherenkov (DIRC) light will be used in the BaBar detector. We provide an overview of the DIRC concept, design, and expected performance of the production device and a status report on its construction and commissioning. The DIRC is expected to be operating in the BaBar detector on beam line at the PEP-II B Factory in late spring 1999.

  1. Intelligent bar chart plagiarism detection in documents.

    PubMed

    Al-Dabbagh, Mohammed Mumtaz; Salim, Naomie; Rehman, Amjad; Alkawaz, Mohammed Hazim; Saba, Tanzila; Al-Rodhaan, Mznah; Al-Dhelaan, Abdullah

    2014-01-01

    This paper presents a novel features mining approach from documents that could not be mined via optical character recognition (OCR). By identifying the intimate relationship between the text and graphical components, the proposed technique pulls out the Start, End, and Exact values for each bar. Furthermore, the word 2-gram and Euclidean distance methods are used to accurately detect and determine plagiarism in bar charts.

  2. Intelligent Bar Chart Plagiarism Detection in Documents

    PubMed Central

    Al-Dabbagh, Mohammed Mumtaz; Salim, Naomie; Alkawaz, Mohammed Hazim; Saba, Tanzila; Al-Rodhaan, Mznah; Al-Dhelaan, Abdullah

    2014-01-01

    This paper presents a novel features mining approach from documents that could not be mined via optical character recognition (OCR). By identifying the intimate relationship between the text and graphical components, the proposed technique pulls out the Start, End, and Exact values for each bar. Furthermore, the word 2-gram and Euclidean distance methods are used to accurately detect and determine plagiarism in bar charts. PMID:25309952

  3. Phenomenological study of a cellular material behaviour under dynamic loadings

    NASA Astrophysics Data System (ADS)

    Bouix, R.; Viot, Ph.; Lataillade, J.-L.

    2006-08-01

    Polypropylene foams are cellular materials, which are often use to fill structures subjected to crash or violent impacts. Therefore, it is necessary to know and to characterise in experiments their mechanical behaviour in compression at high strain rates. So, several apparatus have been used in order to highlight the influence of strain rate, material density and also temperature. A split Hopkinson Pressure Bar has been used for impact tests, a fly wheel to test theses materials at medium strain rate and an electro-mechanical testing machine associated to a climatic chamber for temperature tests. Then, a rheological model has been used in order to describe the material behaviour. The mechanical response to compression of these foams presents three typical domains: a linear elastic step, a wide collapse plateau stress, which leads to a densification, which are related to a standard rheological model.

  4. $\\bar d - \\bar u$ asymmetry in the proton in chiral effective theory

    SciTech Connect

    Salamu, Yusupujiang; Ji, Chueng -Ryong; Melnitchouk, W.; Wang, P.

    2015-03-25

    We compute the $\\bar d - \\bar u$ asymmetry in the proton in chiral effective theory, including both nucleon and Δ degrees of freedom, within both relativistic and heavy baryon frameworks. In addition to the distribution at $x>0$, we estimate the correction to the integrated asymmetry arising from zero momentum contributions from pion rainbow and bubble diagrams at $x=0$, which have not been accounted for in previous analyses. In conclusion, we find that the empirical $x$ dependence of $\\bar d - \\bar u$ as well as the integrated asymmetry can be well reproduced in terms of a transverse momentum cutoff parameter.

  5. Possible Signatures of New Physics in e+e- and bar bar{p}p Collisions

    NASA Astrophysics Data System (ADS)

    Senju, H.

    1998-12-01

    A preon model with preonic charge predicts many unique new particles. Among them, several are expected to be relatively light, including the fermion lS, which is a stable WIMP, bosons U0 and U+ and the lepto-quark fermion q'. The production of these particles in e+e- and bar{p}p collisions is discussed, focusing on e+e- --> UlS(e) and bar{p}p --> bar{q}'q' + X. A signature of the latter is dilepton + 2 charm jets + missing energy. A discussion on reported unusual events in the dilepton + jets sample is made based on bar{q}'q' production.

  6. Cultural Factors Related to Smoking in San Francisco's Irish Bars

    ERIC Educational Resources Information Center

    Satterlund, Travis D.; Antin, Tamar M. J.; Lee, Juliet P.; Moore, Roland S.

    2009-01-01

    California's Smoke-Free Workplace Act was extended to include bars in 1998. While the majority of bars in the state have become smoke free, in many bars patrons and staff continue to smoke despite the law. The authors present findings from a study which assessed cultural factors related to continued smoking in bars in the city of San Francisco. In…

  7. 21 CFR 886.1650 - Ophthalmic bar prism.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Ophthalmic bar prism. 886.1650 Section 886.1650...) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1650 Ophthalmic bar prism. (a) Identification. An ophthalmic bar prism is a device that is a bar composed of fused prisms of gradually...

  8. 21 CFR 886.1650 - Ophthalmic bar prism.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Ophthalmic bar prism. 886.1650 Section 886.1650...) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1650 Ophthalmic bar prism. (a) Identification. An ophthalmic bar prism is a device that is a bar composed of fused prisms of gradually...

  9. Origin, structure, and evolution of a reattachment bar, Colorado River, Grand Canyon, Arizona

    USGS Publications Warehouse

    Rubin, David M.; Schmidt, John C.; Moore, Johnnie N.

    1990-01-01

    In a channel expansion, flow can separate from the bank, creating a zone of relatively weak recirculating current. Bars that accumulate in this weak flow near the point where flow reattaches to the bank are called reattachment bars. As a reattachment bar evolves, the recirculation zone may fill with sediment and restrict flow from the main channel. The increasingly restricted flow over the bar causes ripples to replace dunes and causes the sediment size to fine; the resulting vertical sequence resembles that of point bars. Seasonal and daily flow fluctuations in the Grand Canyon complicate this idealized sequence. Changes in discharge alter the geometry of recirculation zones, flow within the recirculation zones, the location of depositional and erosional sites, the kind of bedform and migration direction of bedforms on the bar, and the transported sediment size. Dunes and ripples within a recirculation zone migrate in a rotary pattern in response to the recirculating flow. Ripples near the reattachment point often resemble oscillation ripples in morphology and dynamics. The reversing flow that creates these ripples is caused by fluctuations in location of the reattachment point. These fluctuations cause flow near the reattachment point to reverse in an upstream-downstream direction, thereby producing symmetrical, reversing ripples with crests that trend normal to the bank. Low rates of ripple migration in the reversing flow, accompanied by rapid deposition, cause these ripples to climb at a high angle. At increasing distances from the reattachment point, the reversing flow is less balanced, and the ripples climb at lower angles as they migrate upstream and downstream. Although these observations were made in a bedrock canyon, the same processes operate in alluvial and tidal channels and are important in adjusting the shape of channels on point bars and concave benches and behind bedforms that become emergent at low stage. Reattachment bars can be recognized by the

  10. THE IMPACT OF BARS ON DISK BREAKS AS PROBED BY S{sup 4}G IMAGING

    SciTech Connect

    Munoz-Mateos, Juan Carlos; Sheth, Kartik; Kim, Taehyun; Meidt, Sharon; Athanassoula, E.; Bosma, Albert; Comeron, Sebastien; Laine, Jarkko; Laurikainen, Eija; Elmegreen, Bruce G.; Erroz-Ferrer, Santiago; Knapen, Johan H.; Gadotti, Dimitri A.; Hinz, Joannah L.; Ho, Luis C.; Madore, Barry F.; Holwerda, Benne; Jarrett, Thomas H.; and others

    2013-07-01

    We have analyzed the radial distribution of old stars in a sample of 218 nearby face-on disks, using deep 3.6 {mu}m images from the Spitzer Survey of Stellar Structure in Galaxies. In particular, we have studied the structural properties of those disks with a broken or down-bending profile. We find that, on average, disks with a genuine single-exponential profile have a scale length and a central surface brightness which are intermediate to those of the inner and outer components of a down-bending disk with the same total stellar mass. In the particular case of barred galaxies, the ratio between the break and the bar radii (R{sub br}/R{sub bar}) depends strongly on the total stellar mass of the galaxy. For galaxies more massive than 10{sup 10} M{sub Sun }, the distribution is bimodal, peaking at R{sub br}/R{sub bar} {approx} 2 and {approx}3.5. The first peak, which is the most populated one, is linked to the outer Lindblad resonance of the bar, whereas the second one is consistent with a dynamical coupling between the bar and the spiral pattern. For galaxies below 10{sup 10} M{sub Sun }, breaks are found up to {approx}10 R{sub bar}, but we show that they could still be caused by resonances given the rising nature of rotation curves in these low-mass disks. While not ruling out star formation thresholds, our results imply that radial stellar migration induced by non-axisymmetric features can be responsible not only for those breaks at {approx}2 R{sub bar}, but also for many of those found at larger radii.

  11. Decreased Frequency of Strong Bars in S0 Galaxies: Evidence for Secular Evolution?

    NASA Astrophysics Data System (ADS)

    Buta, R.; Laurikainen, E.; Salo, H.; Knapen, J. H.

    2010-09-01

    Using data from the Near-Infrared S0 Survey of nearby, early-type galaxies, we examine the distribution of bar strengths in S0 galaxies as compared to S0/a and Sa galaxies, and as compared to previously published bar strength data for Ohio State University Bright Spiral Galaxy Survey spiral galaxies. Bar strengths based on the gravitational torque method are derived from 2.2 μm Ks -band images for a statistical sample of 138 (98 S0, 40 S0/a,Sa) galaxies having a mean total blue magnitude lang BT rang <= 12.5 and generally inclined less than 65°. We find that S0 galaxies have weaker bars on average than spiral galaxies in general, even compared to their closest spiral counterparts, S0/a and Sa galaxies. The differences are significant and cannot be entirely due to uncertainties in the assumed vertical scale heights or in the assumption of constant mass-to-light ratios. Part of the difference is likely simply due to the dilution of the bar torques by the higher mass bulges seen in S0s. If spiral galaxies accrete external gas, as advocated by Bournaud & Combes, then the fewer strong bars found among S0s imply a lack of gas accretion according to this theory. If S0s are stripped former spirals, or else are evolved from former spirals due to internal secular dynamical processes which deplete the gas as well as grow the bulges, then the weaker bars and the prevalence of lenses in S0 galaxies could further indicate that bar evolution continues to proceed during and even after gas depletion.

  12. Social Organization in Bars: Implications for Tobacco Control Policy

    PubMed Central

    Lee, Juliet P.; Antin, Tamar M.J.; Moore, Roland S.

    2011-01-01

    This paper considers social roles and relationships of the patrons, staff and owners of bars as critical factors determining adherence to public health policies, and specifically California’s smokefree workplace law. Specific elements of social organization in bars affecting health policy include the community within which the bar is set, the unique identity the bar creates, the bar staff and patrons who enact this identity, and their bar society. These elements were found to contribute to the development of power relations within the bar and solidarity against the outside world, resulting in either resistance to or compliance with smokefree workplace policy. PMID:22522904

  13. pp-bar->LAMBDA{sub c}LAMBDA-bar{sub c} within a Handbag Picture - Section and Spin Observables

    SciTech Connect

    Goritschnig, A. T.; Schweiger, W.; Kroll, P.

    2009-08-04

    We study the process pp-bar->LAMBDA{sub c}LAMBDA-bar{sub c} within the generalized parton picture. Our starting point is the double handbag diagram which factorizes into soft generalized parton distributions and a hard subprocess amplitude for uu-bar->cc-bar. Our cross-section predictions may become interesting in view of forthcoming experiments at FAIR in Darmstadt.

  14. Bars, Lines, & Pies: A Graphing Skills Program. Expect the Unexpected with Math[R

    ERIC Educational Resources Information Center

    Actuarial Foundation, 2013

    2013-01-01

    "Bars, Lines, & Pies" is a dynamic math program designed to build graphing skills in students, while also showing them the relevance of math in their lives. Developed by The Actuarial Foundation along with Scholastic, the graphing lessons and activities involve engaging, real-world examples about the environment and recycling. In these lessons,…

  15. Method in calculating own vibration frequencies of open sections bars with thin walls

    NASA Astrophysics Data System (ADS)

    Mihuț, N.

    2016-08-01

    Dynamic stability of thin-walled bars of open sections, as well as the stability of elastic systems dynamics in general, is studying closely with their vibrations. This, because, areas of dynamics instability is around twice the frequency of free vibration of the bar or elastic system in all cases excitation parametric, on the one hand, and on the other hand matrices involved in the matrix equation of free vibration are matrices of matrix equation of dynamic stability. In this paper we settled differential equations of parametric vibrations of thin-walled straight bars open sections constant as a system with a triple infinity of second order differential equations, linear coefficients homogeneous and periodicals. In the end of work, by customizing differential equations of forced vibration parameters have been obtained differential equations of own vibration of bars with thin wall and open sections as a system with a triple infinity of differential equations of second order, linear, homogeneous with constant coefficients and, using it, the algebraic equation of own vibrations pulsations.

  16. Bar Admission--Default on Student Loan Warrants Denial of Admission to Minnesota Bar.

    ERIC Educational Resources Information Center

    William Mitchell Law Review, 1980

    1980-01-01

    The Minnesota Supreme Court upheld a decision that student loan default, and subsequent dismissal through bankruptcy, is sufficient reason to deny a law student's bar admission. The bar's requirement of good moral character was interpreted as financial integrity in the Gahan case. (MSE)

  17. Measurement of B0bar -> D(*)0 K(*)0bar BranchingFractions

    SciTech Connect

    Aubert, B.

    2006-04-10

    The authors present a study of the decays {bar B}{sup 0} {yields} D{sup (*)0}{bar K}{sup (*)0} using a sample of 226 million {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider at SLAC. They report evidence for the decay of B{sup 0} and {bar B}{sup 0} mesons to the D*{sup 0}K{sub S}{sup 0} final state with an average branching fraction {Beta}({bar B}{sup 0} {yields} D*{sup 0} {bar K}{sup 0}) {triple_bond} {Beta}({bar B}{sup 0} {yields} D*{sup 0} {bar K}{sup 0}) + {Beta}(B{sup 0} {yields} D*{sup 0}K{sup 0})/2 = (3.6 {+-} 1.2 {+-} 0.3) x 10{sup -5}.

  18. Measurements and efficient simulations of bowed bars

    PubMed

    Essl; Cook

    2000-07-01

    Bowing bar percussion instruments is an increasing part of the repertoire of modern composition and performance. Yet the system has not been studied systematically. In this paper experimental measurements of bars of bar percussion instruments bowed by a double bass bow and by a bowing machine are presented. They examine the relationships between performance parameters and perceptional parameters which are relevant for musical performance. In addition, a new efficient simulation method using a time-domain approach has been developed and the measured results are compared to the simulation. Most measurement results are in good qualitative agreement with the known results of the bowed string. The spectrum of the bowed bar is observed to be harmonic, independent of the harmonicity or inharmonicity of the eigenfrequencies of the bar. Important distinctions from the known results of the bowed string are the weakness or independence of bowing force and velocity on the fundamental frequency and the spectral content of the produced sound. Simulations show qualitative agreement with the measurements.

  19. Partial entrainment of gravel bars during floods

    USGS Publications Warehouse

    Konrad, C.P.; Booth, D.B.; Burges, S.J.; Montgomery, D.R.

    2002-01-01

    Spatial patterns of bed material entrainment by floods were documented at seven gravel bars using arrays of metal washers (bed tags) placed in the streambed. The observed patterns were used to test a general stochastic model that bed material entrainment is a spatially independent, random process where the probability of entrainment is uniform over a gravel bar and a function of the peak dimensionless shear stress ??*0 of the flood. The fraction of tags missing from a gravel bar during a flood, or partial entrainment, had an approximately normal distribution with respect to ??*0 with a mean value (50% of the tags entrained) of 0.085 and standard deviation of 0.022 (root-mean-square error of 0.09). Variation in partial entrainment for a given ??*0 demonstrated the effects of flow conditioning on bed strength, with lower values of partial entrainment after intermediate magnitude floods (0.065 < ??*0 < 0.08) than after higher magnitude floods. Although the probability of bed material entrainment was approximately uniform over a gravel bar during individual floods and independent from flood to flood, regions of preferential stability and instability emerged at some bars over the course of a wet season. Deviations from spatially uniform and independent bed material entrainment were most pronounced for reaches with varied flow and in consecutive floods with small to intermediate magnitudes.

  20. On the Galactic Spin of Barred Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Cervantes-Sodi, Bernardo; Li, Cheng; Park, Changbom; Wang, Lixin

    2013-09-01

    We present a study of the connection between the galactic spin parameter (λ d ) and the bar fraction in a volume-limited sample of 10,674 disk galaxies drawn from the Sloan Digital Sky Survey Data Release 7. The galaxies in our sample are visually classified into one of three groups: non-barred galaxies and galaxies hosting long or short bars, respectively. We find that the spin distributions of these three classes are statistically different, with galaxies hosting long bars having the lowest λ d values, followed by non-barred galaxies, while galaxies with short bars present typically high spin parameters. The bar fraction presents its maximum at low to intermediate λ d values for the case of long bars, while the maximum for short bars is at high λ d . This bimodality is in good agreement with previous studies finding longer bars hosted by luminous, massive, red galaxies with a low content of cold gas, while short bars were found in low luminosity, low mass, blue galaxies that were typically gas rich. In addition, the rise and fall of the bar fraction as a function of λ d , within the long-bar sample shown in our results, can be explained as a result of two competing factors: the self-gravity of the disk that enhances bar instabilities and the support by random motions, instead of ordered rotational motion, that prevents the formation/growth of bars.

  1. ON THE GALACTIC SPIN OF BARRED DISK GALAXIES

    SciTech Connect

    Cervantes-Sodi, Bernardo; Li, Cheng; Wang, Lixin; Park, Changbom

    2013-09-20

    We present a study of the connection between the galactic spin parameter (λ{sub d}) and the bar fraction in a volume-limited sample of 10,674 disk galaxies drawn from the Sloan Digital Sky Survey Data Release 7. The galaxies in our sample are visually classified into one of three groups: non-barred galaxies and galaxies hosting long or short bars, respectively. We find that the spin distributions of these three classes are statistically different, with galaxies hosting long bars having the lowest λ{sub d} values, followed by non-barred galaxies, while galaxies with short bars present typically high spin parameters. The bar fraction presents its maximum at low to intermediate λ{sub d} values for the case of long bars, while the maximum for short bars is at high λ{sub d}. This bimodality is in good agreement with previous studies finding longer bars hosted by luminous, massive, red galaxies with a low content of cold gas, while short bars were found in low luminosity, low mass, blue galaxies that were typically gas rich. In addition, the rise and fall of the bar fraction as a function of λ{sub d}, within the long-bar sample shown in our results, can be explained as a result of two competing factors: the self-gravity of the disk that enhances bar instabilities and the support by random motions, instead of ordered rotational motion, that prevents the formation/growth of bars.

  2. Rotational evolution of a symmetric gyrostat with visco-elastic bars around the center of mass in a circular orbit

    NASA Astrophysics Data System (ADS)

    Abd El-Hafiez Aly, Samy Ahmed

    1987-09-01

    The motion of a gyrostat in a circular orbit in a Newtonian field of force is considered. The gyrostat has four homogeneous viscoelastic bars attached to it. Rotation of the symmetric rotor inside the rigid body is statically and dynamically balanced. Bending deformations of the bars, accompanied by dissipation of energy, are the cause of the evolution of the system's rotational motion. Approximate equations describing this evolution are derived, together with averaged equations in Andoyer variables.

  3. Interpretation of the neutron electric dipole moment: Possible relationship to t bar. epsilon. prime t bar

    SciTech Connect

    Booth, M.J.; Briere, R.A.; Sachs, R.G. )

    1990-01-01

    Recent measurements of {ital D}{sub {ital n}} indicate that it {ital may} be of order {ital G}{sub {ital F}} (milliweak), which is much larger than predicted by the Kobayashi-Maskawa (KM) model. The predicted KM moment is shown to be small because it is of second order in {ital G}{sub {ital F}} (superweak) {ital and} suppressed by the Glashow-Iliopoulos-Maiani (GIM) mechanism. GIM cancellations have their largest effect on the calculation of the moment of a single quark so that {ital W}-exchange contributions between pairs of quarks dominate {ital D}{sub {ital n}} in the KM model. Experimental confirmation that {ital D}{sub {ital n}} is of order {ital G}{sub {ital F}} (in the range 10{sup {minus}27}--10{sup {minus}25} e cm) would require a {ital T}-violating phase between the {ital P}-conserving and {ital P}-violating first-order weak interactions, as occurs in the Weinberg model. Any such {ital T} violation would lead to a relationship between {epsilon}{prime} and {ital D}{sub {ital n}} of the form {vert bar}{ital D}{sub {ital n}}{vert bar}{similar to}{vert bar}{epsilon}{prime}{vert bar}. We estimate the ratio {vert bar}{ital D}{sub {ital n}}/{epsilon}{prime}{vert bar} for the Weinberg model, and show that it is consistent with current data on {ital D}{sub {ital n}}, {vert bar}{epsilon}{prime}/{epsilon}{vert bar}, and {vert bar}{epsilon}{vert bar}. However, the current data are also consistent with {ital D}{sub {ital n}}={epsilon}{prime}=0, so that a firm conclusion cannot be drawn now.

  4. Measuring the Fraction of Bars and Offset Bars Using the Spitzer Survey of Stellar Structure in Galaxies

    NASA Astrophysics Data System (ADS)

    Ross, Alexa

    2012-01-01

    Using the Spitzer Survey of Stellar Structure in Galaxies at 3.6 and 4.5μm, I have measured a preliminary bar fraction and offset bar fraction in the local universe by visually identifying bar structure within a sample of 2,140 local galaxies. A sample this large has not been used since 1963, when Gerard de Vaucouleurs found the bar fraction to be roughly fbar ˜ 0.6 in the Third Reference Catalog of Bright Galaxies. Since then, there has been much debate over the true value of the bar fraction. The purpose of finding a bar fraction using S4G is to provide a final say in this debate. I have found that the bar fraction in the local universe is fbar = 0.69 when including both definite bars (SB) and candidate bars (SAB). I have also measured a preliminary value for the fraction of offset bars using the same sample. Offset bars are a very rare phenomenon. Of the sample used, 91 galaxies are found to be definite offset bars while an additional 39 are found to be candidate offset bars. When including both definite offset bars and candidate offset bars, the offset bar fraction in the local universe becomes fob = 0.12. I also measure the fraction of offset bars as a function of Hubble type and stellar mass. We find that 54% of offset bars are found in disks having a stellar mass of M ≤ 108 M⊙. Late-type disks possess significantly more offset bars than early-type with 60% of offset bars being found in disks having a Hubble type t ≥ 6.

  5. Evidence for B+ -> K*0bar K*+

    SciTech Connect

    Aubert, B.; Bona, M.; Karyotakis, Y.; Lees, J.P.; Poireau, V.; Prencipe, E.; Prudent, X.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Lopez, L.; Palano, A.; Pappagallo, M.; Eigen, G.; Stugu, B.; Sun, L.; Battaglia, M.; Brown, D.N.; Kerth, L.T.; Kolomensky, Yu.G.; Lynch, G.; /LBL, Berkeley /UC, Berkeley /Birmingham U. /Ruhr U., Bochum /British Columbia U. /Brunel U. /Novosibirsk, IYF /UC, Irvine /UCLA /UC, Riverside /UC, San Diego /UC, Santa Barbara /UC, Santa Cruz /Caltech /Cincinnati U. /Colorado U. /Colorado State U. /Dortmund U. /Dresden, Tech. U. /Ecole Polytechnique /Edinburgh U. /INFN, Ferrara /Ferrara U. /INFN, Ferrara /INFN, Ferrara /Ferrara U. /INFN, Ferrara /INFN, Ferrara /Ferrara U. /Frascati /INFN, Genoa /Genoa U. /INFN, Genoa /Genoa U. /INFN, Genoa /INFN, Genoa /Genoa U. /INFN, Genoa /INFN, Genoa /Genoa U. /Harvard U. /Heidelberg U. /Humboldt U., Berlin /Imperial Coll., London /Iowa U. /Iowa State U. /Johns Hopkins U. /Orsay, LAL /LLNL, Livermore /Liverpool U. /Queen Mary, U. of London /Royal Holloway, U. of London /Louisville U. /Karlsruhe U., EKP /Manchester U. /Maryland U. /Massachusetts U., Amherst /MIT, LNS /McGill U. /INFN, Milan /Milan U. /INFN, Milan /INFN, Milan /Milan U. /Mississippi U. /Montreal U. /Mt. Holyoke Coll. /INFN, Naples /Naples U. /INFN, Naples /INFN, Naples /Naples U. /NIKHEF, Amsterdam /Notre Dame U. /Ohio State U. /Oregon U. /INFN, Padua /Padua U. /INFN, Padua /INFN, Padua /Padua U. /Paris U., VI-VII /Pennsylvania U. /INFN, Perugia /Perugia U. /INFN, Pisa /Pisa U. /INFN, Pisa /Pisa, Scuola Normale Superiore /INFN, Pisa /Pisa U. /INFN, Pisa /Princeton U. /INFN, Rome /INFN, Rome /Rome U. /INFN, Rome /INFN, Rome /Rome U. /INFN, Rome /INFN, Rome /Rome U. /INFN, Rome /INFN, Rome /Rome U. /INFN, Rome /Rostock U. /Rutherford /DSM, DAPNIA, Saclay /South Carolina U. /SLAC /Stanford U., Phys. Dept. /SUNY, Albany /Tennessee U. /Texas U. /Texas U., Dallas /INFN, Turin /Turin U. /INFN, Trieste /Trieste U. /Valencia U., IFIC /Victoria U. /Warwick U. /Wisconsin U., Madison

    2009-06-19

    We present measurements of the branching fraction and fraction of longitudinal polarization for the decay B{sup +} {yields} {bar K}*{sup 0} K*{sup +} with a sample of 467 {+-} 5 million B{bar B} pairs collected with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider at the SLAC National Accelerator Laboratory. We obtain the branching fraction {Beta}(B{sup +} {yields} {bar K}*{sup 0} K*{sup +}) = (1.2 {+-} 0.5 {+-} 0.1) x 10{sup ?6} with a significance of 3.7 standard deviations including systematic uncertainties. We measure the fraction of longitudinal polarization f{sub L} = 0.75{sub -0.26}{sup +0.16} {+-} 0.03. The first error quoted is statistical and the second is systematic.

  6. Subsurface Flow in Gravel River Bars

    NASA Astrophysics Data System (ADS)

    Bray, E. N.; Dunne, T.

    2014-12-01

    The geomorphic and hydraulic characteristics of gravel bars control the direction, magnitude and spatial patterns of infiltration and exfiltration between rivers and their immediate subsurface environments. Bed undulation, water-surface gradient, alluvial depth, and the spatial variation of hydraulic conductivity (both deterministic trends and stochastic variability) affect the hydrologically-driven groundwater-surface water exchange. In this paper, we use a set of field measurements of morphological and hydrological characteristics along two reaches of the San Joaquin River, California to motivate a systematic analysis of the factors that affect paths and residence times of flow through gravel bars under an observed range of streamflow values. In the field investigation, it is shown that asymmetry of bar morphology is a first-order control on the extent and magnitude of infiltration, which is often represented to produce approximately equal areas of infiltration and seepage under the assumption of sinusoidal bedforms. Infiltration over the length of a bar is shown to be greater at low flow than at high flow because of the effect of water-surface gradient. Hydraulic conductivity (ksat) varies by orders of magnitude and systematic downstream coarsening arises related to the process of bar evolution. The lowest values of ksat were observed where the difference between the topographic gradient and the water-surface gradient is at a maximum and thus where the infiltration would be greatest into a uniform bar of homogeneous gravel. Morphology and fine sediment accumulation in recharge zones exert an important control over the mechanisms driving subsurface fluid exchange. Simulations from a numerical groundwater flow model that isolate the signatures of morphology and streambed sediment patterns on subsurface flow corroborate our interpretation that the infiltration patterns and rates are primarily controlled by bed morphology, with ksat playing a secondary role.

  7. Multipole Field Effects for the Superconducting Parallel-Bar Deflecting/Crabbing Cavities

    SciTech Connect

    De Silva, Payagalage Subashini Uddika; Delayen, Jean Roger

    2012-09-01

    The superconducting parallel-bar deflecting/crabbing cavity is currently being considered as one of the design options in rf separation for the Jefferson Lab 12 GeV upgrade and for the crabbing cavity for the proposed LHC luminosity upgrade. Knowledge of multipole field effects is important for accurate beam dynamics study of rf structures. The multipole components can be accurately determined numerically using the electromagnetic surface field data in the rf structure. This paper discusses the detailed analysis of those components for the fundamental deflecting/crabbing mode and higher order modes in the parallel-bar deflecting/crabbing cavity.

  8. B Counting at BaBar

    SciTech Connect

    McGregor, Grant Duncan

    2008-12-16

    In this thesis we examine the method of counting B{bar B} events produced in the BABAR experiment. The original method was proposed in 2000, but improvements to track reconstruction and our understanding of the detector since that date make it appropriate to revisit the B Counting method. We propose a new set of cuts designed to minimize the sensitivity to time-varying backgrounds. We find the new method counts B{bar B} events with an associated systematic uncertainty of {+-} 0.6%.

  9. Newtorites in bar detectors of gravitational wave

    NASA Astrophysics Data System (ADS)

    Ronga, F.; ROG Collaboration

    2016-05-01

    The detection of particles with only gravitational interactions (Newtorites) in gravitational bar detectors was studied in 1984 by Bernard, De Rujula and Lautrup. The negative results of dark matter searches suggest to look to exotic possibilities like Newtorites. The limits obtained with the Nautilus bar detector will be presented and the possible improvements will be discussed. Since the gravitational coupling is very weak, the possible limits are very far from what is needed for dark matter, but for large masses are the best limits obtained on the Earth. An update of limits for MACRO particles will be given.

  10. Formation of q{bar q} resonances in the {bar N}N system

    SciTech Connect

    Ivanov, N.Ya.

    1995-11-01

    The formation of q{bar q} resonances lying on the leading Regge trajectories in the {bar N}N system is studied in the quark-gluon string model. The model predicts strong suppression of the decays of q{bar q} states into {bar N}N pairs in relation to two-meson modes. The author`s analysis shows that the contributions of the resonances f{sub 4}(2050) (I{sup G}J{sup PC}= 0{sup +}4{sup ++}), {rho}{sub 5}(2240) (I{sup G}J{sup PC} = 1{sup +}5{sup {minus}{minus}}), and f{sub 6}(2510) (I{sup G}J{sup PC} = 0{sup +}6{sup ++}) to the processes of two-meson {bar N}N annihilation ({bar p}p {yields} {pi}{pi}, {bar K}K, {hor_ellipsis}) are about 1% of the corresponding experimental integrated cross sections. 30 refs., 2 figs., 1 tab.

  11. Measurement of the forward-backward asymmetry of $$\\Lambda$$ and $$\\bar{\\Lambda}$$ production in $$p \\bar{p}$$ collisions

    DOE PAGES

    Abazov, Victor Mukhamedovich

    2016-02-09

    Here, we studymore » $$\\Lambda$$ and $$\\bar{\\Lambda}$$ production asymmetries in $$p \\bar{p} \\rightarrow \\Lambda (\\bar{\\Lambda}) X$$, $$p \\bar{p} \\rightarrow J/\\psi \\Lambda (\\bar{\\Lambda}) X$$, and $$p \\bar{p} \\rightarrow \\mu^\\pm \\Lambda (\\bar{\\Lambda}) X$$ events recorded by the D0 detector at the Fermilab Tevatron collider at $$\\sqrt{s} = 1.96$$ TeV. We find an excess of $$\\Lambda$$'s ($$\\bar{\\Lambda}$$'s) produced in the proton (antiproton) direction. This forward-backward asymmetry is measured as a function of rapidity. We confirm that the $$\\bar{\\Lambda}/\\Lambda$$ production ratio, measured by several experiments with various targets and a wide range of energies, is a universal function of "rapidity loss", i.e., the rapidity difference of the beam proton and the lambda.« less

  12. Paris [ital N[bar N

    SciTech Connect

    Pignone, M.; Lacombe, M.; Loiseau, B.; Vinh Mau, R. Division de Physique Theorique, Institut de Physique Nucleaire, 91406 Orsay Cedex LPTPE, Universite Pierre et Marie Curie, 4 Place Jussieu, 75252 Paris Cedex 05 )

    1994-12-01

    The inner part of the Paris nucleon-antinucleon optical potential has been reanalyzed in view of new experimental constraints. These are mainly provided by accurate measurements of the analyzing power in charge-exchange scattering, [ital [bar p]p][r arrow][ital [bar n]n], together with elastic [ital [bar p]p][r arrow][ital [bar p]p] polarization data, allowing a better determination of the isospin dependence of the short-range forces. The fit is performed with a set of 3632 data. The good quality of the fit is illustrated over a large sample of observables for laboratory momenta from 180 to 910 MeV/[ital c]. Curves of the potentials and of the phase shifts are shown as well as the parameters of the potentials and effective range formula coefficients for the [ital S] and [ital P] waves. The spectrum of resonances and bound states predicted by our potential is also displayed. In particular, a bound state having the [ital AX](1565) quantum numbers is found with the right mass.

  13. Spinners, Scroll Bars and Simpson's Rule

    ERIC Educational Resources Information Center

    Staples, Ed

    2005-01-01

    One of the most remarkable devices embedded in a Microsoft Excel spreadsheet is known as the spinner. Its staggering simplicity is undoubtedly its strength. As an incrementing device that allows graphs to dance across the screen, it gives the concept of variability a whole new meaning. Spinners and their close cousins scroll bars can be grabbed…

  14. A piezo-bar pressure probe

    NASA Technical Reports Server (NTRS)

    Friend, W. H.; Murphy, C. L.; Shanfield, I.

    1967-01-01

    Piezo-bar pressure type probe measures the impact velocity or pressure of a moving debris cloud. It measures pressures up to 200,000 psi and peak pressures may be recorded with a total pulse duration between 5 and 65 musec.

  15. My Bar Graph Tells a Story

    ERIC Educational Resources Information Center

    McMillen, Sue; McMillen, Beth

    2010-01-01

    Connecting stories to qualitative coordinate graphs has been suggested as an effective instructional strategy. Even students who are able to "create" bar graphs may struggle to correctly "interpret" them. Giving children opportunities to work with qualitative graphs can help them develop the skills to interpret, describe, and compare information…

  16. Divorce and Bar Mitzvah: A First Look.

    ERIC Educational Resources Information Center

    Geffen, Michael; Kaplan, Earl

    After an introductory discussion and review of literature on divorce among Jewish families, this document presents and analyzes two case studies which show the adverse effect of divorce and child-custody battles on the children of Jewish families who subsequently plan a B'nai Mitzvah (Bar or Bat Mitzvah) ceremony--a joyous ritual of initiation…

  17. Unitarity Triangles at BaBar

    SciTech Connect

    Martinez-Vidal, Fernando; /Valencia U., IFIC

    2011-11-23

    The BaBar experiment has used a variety of methods to determine the angles {alpha}, {beta}, and {gamma} of the Cabibbo-Kobayashi-Maskawa Unitarity Triangle, which give insight into the Standard Model description of CP violation in the quark sector of the electroweak interactions. Here we review the main experimental techniques and analyses, with emphasis in the most recent results.

  18. Star formation properties in barred galaxies. III. Statistical study of bar-driven secular evolution using a sample of nearby barred spirals

    SciTech Connect

    Zhou, Zhi-Min; Wu, Hong; Cao, Chen E-mail: hwu@bao.ac.cn

    2015-01-01

    Stellar bars are important internal drivers of secular evolution in disk galaxies. Using a sample of nearby spiral galaxies with weak and strong bars, we explore the relationships between the star formation feature and stellar bars in galaxies. We find that galaxies with weak bars tend coincide with low concentrical star formation activity, while those with strong bars show a large scatter in the distribution of star formation activity. We find enhanced star formation activity in bulges toward stronger bars, although not predominantly, consistent with previous studies. Our results suggest that different stages of the secular process and many other factors may contribute to the complexity of the secular evolution. In addition, barred galaxies with intense star formation in bars tend to have active star formation in their bulges and disks, and bulges have higher star formation densities than bars and disks, indicating the evolutionary effects of bars. We then derived a possible criterion to quantify the different stages of the bar-driven physical process, while future work is needed because of the uncertainties.

  19. Bar properties as seen in the Spitzer Survey of Stellar Structure in Galaxies

    NASA Astrophysics Data System (ADS)

    Sheth, Kartik

    2015-03-01

    Bars serve a crucial signpost in galaxy evolution because they form quickly once a disk is sufficiently massive and dynamically cold. Although the bar fraction in the local Universe is well-established since the mid-60s, a variety of studies have concluded varying bar fractions due to different definitions of bars, use of low quality data or different sample selection. The Spitzer Survey of Stellar Structure in Galaxies (S4G) offers us the ideal data set for resolving this outstanding issue once and for all. S4G consists of over 2000 nearby galaxies chosen based on optical brightness, distance, galactic latitude and size in a 40 Mpc volume. With a 4 minute integration time per pixel over >1.5 × D25 diameter for each galaxy, the data provide the deepest, homogenous, mid-infrared (3.6 and 4.5 microns) data on the nearby Universe. The data are so deep that we are tracing stellar surface densities << 1 solar mass per square parsec. With these data we can confidently constrain the bar fraction and thus shed important light on the evolutionary state of galaxies as a function of mass, environment and other galaxy host properties.

  20. Musculoskeletal work preceding the outward and inward Tkachev on uneven bars in artistic gymnastics.

    PubMed

    Kerwin, David G; Irwin, Gareth

    2010-03-01

    Outward facing Tkachevs on uneven bars have been the traditional technique employed by artistic gymnasts. Changes in bar spacing and judging have increased the popularity of the inward version of the skill, in which the gymnast faces towards the low bar as she straddles over the high bar. The purpose of this study was to compare these two variants of the women's Tkachev to examine the influence of the positioning of the low bar on the musculoskeletal demands placed on the gymnast. 3-D DLT reconstructed data sets from digitised video images of straddle Tkachevs performed at the 2000 Sydney Olympics were analysed. Five performances of each variant were compared using kinematics and inverse dynamics. Mean hip and shoulder kinematics were similar for both variants of the Tkachev, but for the inward, gymnasts released later, travelled higher and re-grasped earlier than for the outward. Hip joint moments were similar for both variants while shoulder moments were different. Total musculoskeletal demands were similar for both variants, although the distribution was markedly different with the shoulders contributing positively for the outward and negatively for the inward. Implications for training specificity, along with potential future developments for the inward variant, have been highlighted. PMID:20446636

  1. Physical and ecological connectivity among restored oyster bars in the Severn River (Maryland, USA)

    NASA Astrophysics Data System (ADS)

    Steppe, C. N.; Fredriksson, D. W.; Wallendorf, L.; Barlow, A.

    2008-12-01

    In an effort to improve water quality and enhance the Crassostrea virginica fishery, many oyster restoration bars have been placed in Chesapeake Bay tributaries. Nevertheless, bars are often placed in sub-estuaries with poorly described circulation dynamics. Therefore the potential for the restored bars to either re-seed themselves or serve as larval sources for other beds remains unclear. To address this problem we assessed connectivity among 3 restored oyster bars in the Severn River Estuary, (Maryland, USA) via a combination of weekly plankton tows at each bar (College Creek, Weems Creek, and Lake Ogleton; May-October 2007); predictions from a hydrodynamic model (ADCIRC) adapted for the study area; and satellite-tracked drifter deployments from the College Creek and Weems Creek sites (2007-2008). Planktonic assemblages were similar among sites, and shifted on a time scale of weeks. Preliminary model runs showed that connectivity between the Weems Creek site and the main-stem of the Severn River may be higher than between the College Creek site and the Severn. Finally, drifter trajectories indicated two distinct transport regimes; retention within the Severn River system, on a time scale pertinent to C. virginica larval development (about 3 weeks), and export to the main-stem of Chesapeake Bay, indicating loss of larvae from the local system, either by mortality or recruitment to another sub-estuary.

  2. X(5568) as a {su}\\bar{d}\\bar{b} tetraquark in a simple quark model

    NASA Astrophysics Data System (ADS)

    Stancu, Fl

    2016-10-01

    The S-wave eigenstates of tetraquarks of type {su}\\bar{d}\\bar{b} with J P = 0+, 1+ and 2+ are studied within a simple quark model with chromomagnetic interaction and effective quark masses extracted from meson and baryon spectra. It is tempting to see if this spectrum can accommodate the new narrow structure X(5568), observed by the DØ Collaboration, but not confirmed by the LHCb Collaboration. If it exists, such a tetraquark is a system with four different flavors and its study can improve our understanding of multiquark systems. The presently calculated mass of X(5568) agrees quite well with the experimental value of the DØ Collaboration. Predictions are also made for the spectrum of the charmed partner {su}\\bar{d}\\bar{c}. However we are aware of the difficulty of extracting effective quark masses, from mesons and baryons, to be used in multiquark systems.

  3. nu. (nu-bar)+d. --> nu. (nu-bar)+n+p at intermediate energies

    SciTech Connect

    Singh, S.K.; Khan, S.A.

    1981-03-01

    The deuteron disintegration processes ..nu..(nu-bar)+d..--> nu..(nu-bar)+n+p have been studied at intermediate energies in impulse approximation using closure over the final dinucleon states. The disintegration cross section sigma has been discussed as a function of neutrino (antineutrino) energy in various SU(2) x U(1) models for the helicity conserving weak neutral currents. A discussion on the helicity flipping weak neutral currents models of S, P, T couplings is also given.

  4. 11. Detail of horse lamp fixture in original Clubhouse bar. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. Detail of horse lamp fixture in original Clubhouse bar. Fixture is at north end of bar. Camera pointed up and NW. (July 1993) - Longacres, Clubhouse & Additions, 1621 Southwest Sixteenth Street, Renton, King County, WA

  5. Molecular Gas in NUclei of GAlaxies (NUGA). IX. The decoupled bars and gas inflow in NGC 2782

    NASA Astrophysics Data System (ADS)

    Hunt, L. K.; Combes, F.; García-Burillo, S.; Schinnerer, E.; Krips, M.; Baker, A. J.; Boone, F.; Eckart, A.; Léon, S.; Neri, R.; Tacconi, L. J.

    2008-04-01

    We present CO(1-0) and CO(2-1) maps of the starburst/Seyfert 1 galaxy NGC 2782 obtained with the IRAM interferometer, at 2.1 arcsec×1.5 arcsec and 0.7 arcsec×0.6 arcsec resolution respectively. The CO emission is aligned along the stellar nuclear bar of radius ~1 kpc, configured in an elongated structure with two spiral arms at high pitch angle ~90°. At the extremity of the nuclear bar, the CO changes direction to trace two more extended spiral features at a lower pitch angle. These are the beginning of two straight dust lanes, which are aligned parallel to an oval distortion, reminiscent of a primary bar, almost perpendicular to the nuclear one. The two embedded bars appear in Spitzer IRAC near-infrared images, and HST color images, although highly obscured by dust in the latter. We compute the torques exerted by the stellar bars on the gas, and find systematically negative average torques down to the resolution limit of the images, providing evidence of gas inflow tantalizingly close to the nucleus of NGC 2782. We propose a dynamical scenario based on numerical simulations to interpret coherently the radio, optical, and molecular gas features in the center of the galaxy. Star formation is occurring in a partial ring at ~1.3 kpc radius corresponding to the Inner Lindblad Resonance (ILR) of the primary bar; this ring-like structure encircles the nuclear bar, and is studded with Hα emission. The gas traced by CO emission is driven inward by the gravity torques of the decoupled nuclear bar, since most of it is inside its corotation. N-body simulations, including gas dissipation, predict the secondary bar decoupling, the formation of the elongated ring at the ~1 kpc-radius ILR of the primary bar, and the gas inflow to the ILR of the nuclear bar at a radius of ~200-300 pc. The presence of molecular gas inside the ILR of the primary bar, transported by a second nuclear bar, is a potential “smoking gun”; the gas there is certainly fueling the central starburst

  6. The F-BAR domain of srGAP2 induces membrane protrusions required for neuronal migration and morphogenesis

    PubMed Central

    Guerrier, Sabrice; Coutinho-Budd, Jaeda; Sassa, Takayuki; Gresset, Aurélie; Jordan, Nicole Vincent; Cheng, Ken; Jin, Wei-Lin; Frost, Adam; Polleux, Franck

    2009-01-01

    SUMMARY During brain development, proper neuronal migration and morphogenesis is critical for the establishment of functional neural circuits. Here we report that srGAP2 negatively regulates neuronal migration and induces neurite outgrowth and branching through the ability of its F-BAR domain to induce filopodia-like membrane protrusions resembling those induced by I-BAR domains in vivo and in vitro. Previous work has suggested that in non-neuronal cells, filopodia dynamics decreases the rate of cell migration and the persistence of leading edge protrusions. srGAP2 knockdown reduces leading process branching and increases the rate of neuronal migration in vivo. Overexpression of srGAP2 or its F-BAR domain has the opposite effects, increasing leading process branching and decreasing migration. These results (1) suggest that F-BAR domains are functionally diverse and (2) highlight the functional importance of proteins directly regulating membrane deformation for proper neuronal migration and morphogenesis. PMID:19737524

  7. Laboratory and workplace assessments of rivet bucking bar vibration emissions.

    PubMed

    McDowell, Thomas W; Warren, Christopher; Xu, Xueyan S; Welcome, Daniel E; Dong, Ren G

    2015-04-01

    Sheet metal workers operating rivet bucking bars are at risk of developing hand and wrist musculoskeletal disorders associated with exposures to hand-transmitted vibrations and forceful exertions required to operate these hand tools. New bucking bar technologies have been introduced in efforts to reduce workplace vibration exposures to these workers. However, the efficacy of these new bucking bar designs has not been well documented. While there are standardized laboratory-based methodologies for assessing the vibration emissions of many types of powered hand tools, no such standard exists for rivet bucking bars. Therefore, this study included the development of a laboratory-based method for assessing bucking bar vibrations which utilizes a simulated riveting task. With this method, this study evaluated three traditional steel bucking bars, three similarly shaped tungsten alloy bars, and three bars featuring spring-dampeners. For comparison the bucking bar vibrations were also assessed during three typical riveting tasks at a large aircraft maintenance facility. The bucking bars were rank-ordered in terms of unweighted and frequency-weighted acceleration measured at the hand-tool interface. The results suggest that the developed laboratory method is a reasonable technique for ranking bucking bar vibration emissions; the lab-based riveting simulations produced similar rankings to the workplace rankings. However, the laboratory-based acceleration averages were considerably lower than the workplace measurements. These observations suggest that the laboratory test results are acceptable for comparing and screening bucking bars, but the laboratory measurements should not be directly used for assessing the risk of workplace bucking bar vibration exposures. The newer bucking bar technologies exhibited significantly reduced vibrations compared to the traditional steel bars. The results of this study, together with other information such as rivet quality, productivity, tool

  8. Modelling of nonlinear wave scattering in a delaminated elastic bar

    PubMed Central

    Khusnutdinova, K. R.; Tranter, M. R.

    2015-01-01

    Integrity of layered structures, extensively used in modern industry, strongly depends on the quality of their interfaces; poor adhesion or delamination can lead to a failure of the structure. Can nonlinear waves help us to control the quality of layered structures? In this paper, we numerically model the dynamics of a long longitudinal strain solitary wave in a split, symmetric layered bar. The recently developed analytical approach, based on matching two asymptotic multiple-scales expansions and the integrability theory of the Korteweg–de Vries equation by the inverse scattering transform, is used to develop an effective semi-analytical numerical approach for these types of problems. We also employ a direct finite-difference method and compare the numerical results with each other, and with the analytical predictions. The numerical modelling confirms that delamination causes fission of an incident solitary wave and, thus, can be used to detect the defect. PMID:26730218

  9. 21 CFR 886.5800 - Ophthalmic bar reader.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...) MEDICAL DEVICES OPHTHALMIC DEVICES Therapeutic Devices § 886.5800 Ophthalmic bar reader. (a) Identification. An ophthalmic bar reader is a device that consists of a magnifying lens intended for use by a... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ophthalmic bar reader. 886.5800 Section...

  10. 21 CFR 886.5800 - Ophthalmic bar reader.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...) MEDICAL DEVICES OPHTHALMIC DEVICES Therapeutic Devices § 886.5800 Ophthalmic bar reader. (a) Identification. An ophthalmic bar reader is a device that consists of a magnifying lens intended for use by a... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Ophthalmic bar reader. 886.5800 Section...

  11. 21 CFR 886.5800 - Ophthalmic bar reader.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...) MEDICAL DEVICES OPHTHALMIC DEVICES Therapeutic Devices § 886.5800 Ophthalmic bar reader. (a) Identification. An ophthalmic bar reader is a device that consists of a magnifying lens intended for use by a... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Ophthalmic bar reader. 886.5800 Section...

  12. 21 CFR 886.5800 - Ophthalmic bar reader.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...) MEDICAL DEVICES OPHTHALMIC DEVICES Therapeutic Devices § 886.5800 Ophthalmic bar reader. (a) Identification. An ophthalmic bar reader is a device that consists of a magnifying lens intended for use by a... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Ophthalmic bar reader. 886.5800 Section...

  13. 21 CFR 886.5800 - Ophthalmic bar reader.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...) MEDICAL DEVICES OPHTHALMIC DEVICES Therapeutic Devices § 886.5800 Ophthalmic bar reader. (a) Identification. An ophthalmic bar reader is a device that consists of a magnifying lens intended for use by a... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Ophthalmic bar reader. 886.5800 Section...

  14. Chord, Tie Bar & Crossbracing Joint Detail in Plan; Crossbracing ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Chord, Tie Bar & Crossbracing Joint Detail in Plan; Crossbracing Center Joint Detail in Plan; Chord Joining Detail in Plan & Elevation; Chord, Panel Post, Tie Bar, & Diagonal Brace Joint Detail; Crossbracing Center Joint Detail in Section; Chord, Panel Post, Tie Bar & Horizontal Brace Joint Detail - Narrows Bridge, Spanning Sugar Creek at Old County Road 280 East, Marshall, Parke County, IN

  15. Access to Bathtub Grab Bars: Evidence of a Policy Gap

    ERIC Educational Resources Information Center

    Birkett, Nicholas; Nair, Rama; Murphy, Maureen; Roberge, Ginette; Lockett, Donna

    2006-01-01

    This paper examines access to bathtub grab bars in privately and publicly owned apartment buildings and explores the profile of seniors who have access to bathtub grab bars. Results indicate that bathtub grab bars were significantly more prevalent in apartments that were publicly owned (91.3%) as compared to privately owned (37.8%) (p lesser than…

  16. 21 CFR 201.25 - Bar code label requirements.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 4 2012-04-01 2012-04-01 false Bar code label requirements. 201.25 Section 201.25 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) DRUGS: GENERAL LABELING General Labeling Provisions § 201.25 Bar code label requirements. (a) Who is subject to these bar code...

  17. 21 CFR 201.25 - Bar code label requirements.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... drug product from the bar code label requirements set forth in this section. The exemption request must... 21 Food and Drugs 4 2014-04-01 2014-04-01 false Bar code label requirements. 201.25 Section 201.25...: GENERAL LABELING General Labeling Provisions § 201.25 Bar code label requirements. (a) Who is subject...

  18. 21 CFR 201.25 - Bar code label requirements.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... drug product from the bar code label requirements set forth in this section. The exemption request must... 21 Food and Drugs 4 2013-04-01 2013-04-01 false Bar code label requirements. 201.25 Section 201.25...: GENERAL LABELING General Labeling Provisions § 201.25 Bar code label requirements. (a) Who is subject...

  19. A Reading PR Reference for Bar Executive Staff and Officers.

    ERIC Educational Resources Information Center

    Georgia State Bar, Atlanta.

    This manual provides information to assist bar association staff and officers in explaining the role and function of the bar and in dealing with critical public-relations problems. Sections discuss the use and value of public relations, public relations and the role of the bar, public-relations problems, and major public-opinion problems…

  20. [Storage and use of antioxidants in cereal and peanut bars].

    PubMed

    Estévez, A M; Escobar, B; Tepper, A; Castillo, E

    1998-06-01

    The use of fatty materials in cereal bars gives to them a good energetic value; however they are exposed to oxidative rancidity which can affect their acceptability and nutritional value. So, the purpose of this research was to determine the stability in storage and the effect of antioxidants on three tipes of cereal bars with peanuts. Cereal bars with 18% of peanuts were prepared, with and without antioxidants (BHA + BHT; 100 ppm). Bars were packed in polyprolpilene-aluminium-polythilene bags, and were stored at room temperature (18-20 degrees C) for 90 days. Each 30 days, analysis of water activity (Aw); moisture content, peroxides index, sensory quality (flavor, aroma and appearance) and acceptability, were carried out. Moisture content was similar in all bars (7.6-9.6%) and Aw was higher in the bar which contained expanded amaranthus and antioxidant. At the 60th day of storage, the peroxide values were lower in the bars with antioxidants; only the bar which included expanded amaranthus showed significant differences (16.4 meq/kg in the bar with antioxidant and 25.7 meq/kg for the control bar). The sensory parameters were kept within normal status without differences between the bars with antioxidants and the control ones, along all the storage period. Shelf life of bars CM1 and CM2 was at least of 60 days when they are kept at 18-20 degrees C. PMID:9830493

  1. 33 CFR 13.01-10 - Gold and silver bars.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 1 2011-07-01 2011-07-01 false Gold and silver bars. 13.01-10... DECORATIONS, MEDALS, RIBBONS AND SIMILAR DEVICES Gold and Silver Lifesaving Medals, Bars, and Miniatures § 13.01-10 Gold and silver bars. No person shall receive more than one Gold Lifesaving Medal and...

  2. 33 CFR 13.01-10 - Gold and silver bars.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Gold and silver bars. 13.01-10... DECORATIONS, MEDALS, RIBBONS AND SIMILAR DEVICES Gold and Silver Lifesaving Medals, Bars, and Miniatures § 13.01-10 Gold and silver bars. No person shall receive more than one Gold Lifesaving Medal and...

  3. 33 CFR 13.01-10 - Gold and silver bars.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 1 2012-07-01 2012-07-01 false Gold and silver bars. 13.01-10... DECORATIONS, MEDALS, RIBBONS AND SIMILAR DEVICES Gold and Silver Lifesaving Medals, Bars, and Miniatures § 13.01-10 Gold and silver bars. No person shall receive more than one Gold Lifesaving Medal and...

  4. 33 CFR 13.01-10 - Gold and silver bars.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Gold and silver bars. 13.01-10... DECORATIONS, MEDALS, RIBBONS AND SIMILAR DEVICES Gold and Silver Lifesaving Medals, Bars, and Miniatures § 13.01-10 Gold and silver bars. No person shall receive more than one Gold Lifesaving Medal and...

  5. 33 CFR 13.01-10 - Gold and silver bars.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Gold and silver bars. 13.01-10... DECORATIONS, MEDALS, RIBBONS AND SIMILAR DEVICES Gold and Silver Lifesaving Medals, Bars, and Miniatures § 13.01-10 Gold and silver bars. No person shall receive more than one Gold Lifesaving Medal and...

  6. EAST ELEVATION, LTV STEEL (FORMERLY REPUBLIC STEEL), 8" BAR MILL, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    EAST ELEVATION, LTV STEEL (FORMERLY REPUBLIC STEEL), 8" BAR MILL, BUFFALO PLANT. VIEW LOOKING SOUTHWEST FROM ROLL SHOP. 8" BAR MILL DESIGNED AND BUILT BY DONNER STEEL CO. (PREDECESSOR OF REPUBLIC), 1919-1920. FOR DESCRIPTION OF ORIGINAL MILL SEE "IRON AGE", 116\\4 (23 JULY 1925): 201-204. - LTV Steel, 8-inch Bar Mill, Buffalo Plant, Buffalo, Erie County, NY

  7. 10 CFR 39.49 - Uranium sinker bars.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 1 2014-01-01 2014-01-01 false Uranium sinker bars. 39.49 Section 39.49 Energy NUCLEAR REGULATORY COMMISSION LICENSES AND RADIATION SAFETY REQUIREMENTS FOR WELL LOGGING Equipment § 39.49 Uranium sinker bars. The licensee may use a uranium sinker bar in well logging applications only if it is...

  8. 10 CFR 39.49 - Uranium sinker bars.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 1 2011-01-01 2011-01-01 false Uranium sinker bars. 39.49 Section 39.49 Energy NUCLEAR REGULATORY COMMISSION LICENSES AND RADIATION SAFETY REQUIREMENTS FOR WELL LOGGING Equipment § 39.49 Uranium sinker bars. The licensee may use a uranium sinker bar in well logging applications only if it is...

  9. 10 CFR 39.49 - Uranium sinker bars.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 1 2013-01-01 2013-01-01 false Uranium sinker bars. 39.49 Section 39.49 Energy NUCLEAR REGULATORY COMMISSION LICENSES AND RADIATION SAFETY REQUIREMENTS FOR WELL LOGGING Equipment § 39.49 Uranium sinker bars. The licensee may use a uranium sinker bar in well logging applications only if it is...

  10. 10 CFR 39.49 - Uranium sinker bars.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 1 2010-01-01 2010-01-01 false Uranium sinker bars. 39.49 Section 39.49 Energy NUCLEAR REGULATORY COMMISSION LICENSES AND RADIATION SAFETY REQUIREMENTS FOR WELL LOGGING Equipment § 39.49 Uranium sinker bars. The licensee may use a uranium sinker bar in well logging applications only if it is...

  11. 10 CFR 39.49 - Uranium sinker bars.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 1 2012-01-01 2012-01-01 false Uranium sinker bars. 39.49 Section 39.49 Energy NUCLEAR REGULATORY COMMISSION LICENSES AND RADIATION SAFETY REQUIREMENTS FOR WELL LOGGING Equipment § 39.49 Uranium sinker bars. The licensee may use a uranium sinker bar in well logging applications only if it is...

  12. Characterization of galactic bars from 3.6 μm S4G imaging

    NASA Astrophysics Data System (ADS)

    Díaz-García, S.; Salo, H.; Laurikainen, E.; Herrera-Endoqui, M.

    2016-03-01

    Context. Stellar bars play an essential role in the secular evolution of disk galaxies because they are responsible for the redistribution of matter and angular momentum. Dynamical models predict that bars become stronger and longer in time, while their rotation speed slows down. Aims: We use the Spitzer Survey of Stellar Structure in Galaxies (S4G) 3.6 μm imaging to study the properties (length and strength) and fraction of bars at z = 0 over a wide range of galaxy masses (M∗ ≈ 108-1011 M⊙) and Hubble types (-3 ≤ T ≤ 10). Methods: We calculated gravitational forces from the 3.6 μm images for galaxies with a disk inclination lower than 65°. We used the maximum of the tangential-to-radial force ratio in the bar region (Qb) as a measure of the bar-induced perturbation strength for a sample of ~600 barred galaxies. We also used the maximum of the normalized m = 2 Fourier density amplitude (A2max) to characterize the bar. Bar sizes were estimated i) visually; ii) from ellipse fitting; iii) from the radii of the strongest torque; and iv) from the radii of the largest m = 2 Fourier amplitude in the bar region. By combining our force calculations with the H i kinematics from the literature, we estimated the ratio of the halo-to-stellar mass (Mh/M∗) within the optical disk and by further using the universal rotation curve models, we obtained a first-order model of the rotation curve decomposition of 1128 disk galaxies. Results: We probe possible sources of uncertainty in our Qb measurements: the assumed scale height and its radial variation, the influence of the spiral arms torques, the effect of non-stellar emission in the bar region, and the dilution of the bar forces by the dark matter halo (our models imply that only ~10% of the disks in our sample are maximal). We find that for early- and intermediate-type disks (-3 ≤ T< 5), the relatively modest influence of the dark matter halo leads to a systematic reduction of the mean Qb by about 10-15%, which is

  13. A Local Reference For Bar Studies In The Distant Universe

    NASA Astrophysics Data System (ADS)

    Menéndez-Delmestre, Karín; Sheth, Kartik; S4G Team

    2015-08-01

    Stellar bars are present in ~2/3 of nearby spirals and play a critical role in the evolution of their hosts. With the advent of large high-resolution imaging surveys, bar studies are being extended to distant galaxies. However, photometric studies of the distant universe are invariably subject to the effects of band-shifting, the progressive shift of the photometric band to bluer rest-frame wavelengths. In order to reliably characterize the intrinsic evolution of bars with redshift, safe from band-shifting effects, it is necessary to establish a local anchor of how bar properties vary with wavelength. We present a detailed multi-band study of bar properties from UV through mid-infrared for a sample of 16 large nearby barred galaxies. Based on ellipticity and position angle profiles resulting from fitting elliptical isophotes to the 2D light distribution of each galaxy, we find that both the bar length and the bar ellipticity increase at bluer wavebands. We attribute the increase in bar length to the frequent presence of prominent star forming knots at the end of bars: these regions are significantly brighter in bluer bands, resulting in the “artificial” lengthening of the bar. The increase in bar ellipticity, on the other hand, is driven by the bulge size: the bulge, composed primarily of old/red stars, is less prominent at bluer bands, allowing for thinner ellipses to be fit within the bar region. The resulting effect is that bars appear longer and thinner at bluer bands. Although we find that ~50% of the bars disappear in the UV, the results on bar ellipticity and length extend to those cases in which the bar is still visible in the UV. These results imply that careful correction for band-shifting effects is necessary for high-z studies to reliably gauge any intrinsic evolution of the bar properties with redshift. In the light of the ample space-based optical data now available, this study may be used as a reference to implement band-shifting corrections to

  14. Bar-code automated waste tracking system

    SciTech Connect

    Hull, T.E.

    1994-10-01

    The Bar-Code Automated Waste Tracking System was designed to be a site-Specific program with a general purpose application for transportability to other facilities. The system is user-friendly, totally automated, and incorporates the use of a drive-up window that is close to the areas dealing in container preparation, delivery, pickup, and disposal. The system features ``stop-and-go`` operation rather than a long, tedious, error-prone manual entry. The system is designed for automation but allows operators to concentrate on proper handling of waste while maintaining manual entry of data as a backup. A large wall plaque filled with bar-code labels is used to input specific details about any movement of waste.

  15. Did liberalising bar hours decrease traffic accidents?

    PubMed

    Green, Colin P; Heywood, John S; Navarro, Maria

    2014-05-01

    Legal bar closing times in England and Wales have historically been early and uniform. Recent legislation liberalised closing times with the object of reducing social problems thought associated with drinking to "beat the clock." Indeed, using both difference in difference and synthetic control approaches we show that one consequence of this liberalisation was a decrease in traffic accidents. This decrease is heavily concentrated among younger drivers. Moreover, we provide evidence that the effect was most pronounced in the hours of the week directly affected by the liberalisation: late nights and early mornings on weekends. This evidence survives a series of robustness checks and suggests at least one socially positive consequence of extending bar hours.

  16. The Lifetimes of Spirals and Bars

    NASA Astrophysics Data System (ADS)

    Sellwood, J. A.

    2015-03-01

    Simulations of isolated galaxy disks that are stable against bar formation readily manifest multiple, transient spiral patterns. It therefore seems likely that some spirals in real galaxies are similarly self-excited, although others are clearly driven by tidal interactions or by bars. The rapidly changing appearance of simulated spirals does not, however imply that the patterns last only a fraction of an orbit. Power spectrum analysis reveals a few underlying, longer-lived spiral waves that turn at different rates, which when super-posed give the appearance of swing-amplified transients. These longer-lived waves are genuine unstable spiral modes; each grows vigorously, saturates and decays over a total of several orbit periods. As each mode decays, the wave action created as it grew drains away to the Lindblad resonances, where it scatters stars. The resulting changes to the disk create the conditions for a new instability, giving rise to a recurring cycle of unstable modes.

  17. [x, p] = i{h_bar} ?

    SciTech Connect

    Tang, Jau

    1996-03-01

    Heisenberg`s commutation relation for position x and momentum p, and its validity for relativistic harmonic oscillators are examined, using the techniques of Lie algebra and dual-bosonic representation of x, p and the Hamiltonian H. A modification with [x, p] =i{h_bar}({minus_plus} 1 + H/m{sub 0}c{sup 2}) is proposed for a particle and an antiparticle in a harmonic potential. For a 2 {times} 2 matrix representation for x, p and H operators, the quantized eigenenergy E is given by (E - m{sub 0}c{sup 2})/{h_bar}{omega} = 3/2, 5/2, 7/2, ..., where 1/2 is not allowed.

  18. ALIP with conducting bars in the channel

    NASA Astrophysics Data System (ADS)

    Krishbergs, R.

    2009-03-01

    Electromagnetic processes in the channel of a cylindrical induction pump having longitudinal copper bars of large electric conductivity have been analyzed. The possibility to increase the pressure developed by the pump if compared to the usual pump (ALIP) is considered as well as the increase of the coefficient of pressure head weakening k_{0 c} more than unity and its effects on the efficiency coefficient. Figs 5, Refs 5.

  19. Intersite comparison of interannual nearshore bar behavior

    NASA Astrophysics Data System (ADS)

    Ruessink, B. G.; Wijnberg, K. M.; Holman, R. A.; Kuriyama, Y.; van Enckevort, I. M. J.

    2003-08-01

    Long-term (>years) bathymetric data sets collected in six multiple near-shore sandbar systems were analyzed with complex empirical orthogonal function analysis to quantify intersite differences and similarities in cyclic offshore progressive bar behavior. The observations came from a 37-year annually sampled data set of four regions along the Dutch coast (spanning 70 km of coastline), an 18-year fortnightly to monthly sampled data set at Duck, North Carolina (alongshore extent ˜1 km), and a 7-year daily sampled data set of a single cross-shore profile at the Hasaki coast of Japan. The first complex mode, typically representing 50-70% of the total depth variance, described the long-term offshore progressive behavior and allowed for an objective separation of the barred part of the profile from the shoreward- and seaward-located nonbarred parts by considering a threshold bar amplitude below which the spatial results from the first mode were not considered reliable. The sandbars at the six examined sites share common lengths and nondimensional amplitude characteristics, which can be described by a negatively skewed Gaussian function. The absolute amplitude dimensions and the cycle return intervals differ, however, considerably between the sites. The key geometric parameters that steer this intersite variation are the time-averaged mean depths at the shoreward and seaward side of the bar zone (?shore and ?sea, respectively) as well as their difference ?bz. The degree to which intersite differences in ?shore, ?sea, and ?bz are related linearly to intersite differences in bulk statistics of external forcings (wave, tide, sediment, and bed profile characteristics) is inconclusive.

  20. Simulation of BaBar Drift Chamber

    SciTech Connect

    Anderson, Rachel; /Wisconsin U., Eau Claire /SLAC

    2006-09-27

    The BaBar drift chamber (DCH) is used to measure the properties of charged particles created from e{sup +}e{sup -} collisions in the PEP-II asymmetric-energy storage rings by making precise measurements of position, momentum and ionization energy loss (dE/dx). In October of 2005, the PEP-II storage rings operated with a luminosity of 10 x 10{sup 33} cm{sup -2}s{sup -1}; the goal for 2007 is a luminosity of 20 x 10{sup 33} cm{sup -2}s{sup -1}, which will increase the readout dead time, causing uncertainty in drift chamber measurements to become more significant in physics results. The research described in this paper aims to reduce position and dE/dx uncertainties by improving our understanding of the BaBar drift chamber performance. A simulation program--called GARFIELD--is used to model the behavior of the drift chamber with adjustable parameters such as gas mixture, wire diameter, voltage, and magnetic field. By exploring the simulation options offered in GARFIELD, we successfully produced a simulation model of the BaBar drift chamber. We compared the time-to-distance calibration from BaBar to that calculated by GARFIELD to validate our model as well as check for discrepancies between the simulated and calibrated time-to-distance functions, and found that for a 0{sup o} entrance angle there is a very good match between calibrations, but at an entrance angle of 90{sup o} the calibration breaks down. Using this model, we also systematically varied the gas mixture to find one that would optimize chamber operation, which showed that the gas mixture of 80:20 Helium:isobutane is a good operating point, though more calculations need to be done to confirm that it is the optimal mixture.

  1. Gas and Dust in the Orion Bar

    NASA Astrophysics Data System (ADS)

    Arab, H.; Compiègne, M.; Habart, E.; Abergel, A.

    2011-11-01

    We use the DustEM model coupled with a radiative transfer code to fit the Herschel and Spitzer emission of the Orion Bar. The thermal dust emission at the 250-μm peak position is well reproduced but we overestimate the stochastically heated grain emission. The dust model parameters are checked with the Meudon PDR code and are consistent with the spectroscopic data from the SPIRE FTS.

  2. Hadron Physics in BaBar

    SciTech Connect

    Lafferty, G.D.; /Manchester U.

    2005-08-29

    Some recent results in hadron physics from the BaBar experiment are discussed. In particular, the observation of two new charmed states, the D*{sub sJ}{sup +}(2317) and the D*{sub sJ}{sup +}(2457), is described, and results are presented on the first measurement of the rare decay mode of the B meson, B{sup 0} {pi}{sup 0}{pi}{sup 0}.

  3. Habitat Suitability Index Models: Barred Owl

    USGS Publications Warehouse

    Allen, Arthur W.

    1987-01-01

    A review and synthesis of existing information were used to develop a Habitat Suitability Index (HSI) model for the barred owl (Strix varia). The model consolidates habitat use information into a framework appropriate for field application, and is scaled to produce an index between 0.0 (unsuitable habitat) to 1.0 (optimum habitat). HSI models are designed to be used with Habitat Evaluation Procedures previously developed by the U.S. Fish and Wildlife Service.

  4. Leptonic B Decays at BaBar

    SciTech Connect

    Baracchini, Elisabetta; /Rome U. /INFN, Rome

    2011-11-10

    We will present the most recent results on leptonic B decays B{sup {+-}(0)} {yields} K*{sup {+-}(0)}{nu}{bar {nu}} and B{sup {+-}} {yields} {mu}{sup {+-}}{nu}, based on the data collected by the BaBar detector at PEP-II, an asymmetric e{sup +}e{sup -} collider at the center of mass energy of the {Upsilon}(4S) resonance. Rare B decays have always been a standard probe for New Physics (NP) searches. The very low Standard Model (SM) rate of these decays often make them unaccessible with the present experimental datasets, unless NP effects enhance the rate up to the current experimental sensitivity. Moreover, as NP effects can modify the decay kinematic, particular attention must be paid in order to perform a model independent analysis. A B-Factory provides an unique environment to investigate these processes. The high number of B{bar B} pairs produced by a B-Factory often allows to approach the needed experimental sensitivity. Moreover, the clean environment and the closed kinematic of the initial state enable to obtaining a very pure sample where to look for these decays.

  5. Discovering shared segments on the migration route of the bar-headed goose by time-based plane-sweeping trajectory clustering

    USGS Publications Warehouse

    Luo, Ze; Baoping, Yan; Takekawa, John Y.; Prosser, Diann J.

    2012-01-01

    We propose a new method to help ornithologists and ecologists discover shared segments on the migratory pathway of the bar-headed geese by time-based plane-sweeping trajectory clustering. We present a density-based time parameterized line segment clustering algorithm, which extends traditional comparable clustering algorithms from temporal and spatial dimensions. We present a time-based plane-sweeping trajectory clustering algorithm to reveal the dynamic evolution of spatial-temporal object clusters and discover common motion patterns of bar-headed geese in the process of migration. Experiments are performed on GPS-based satellite telemetry data from bar-headed geese and results demonstrate our algorithms can correctly discover shared segments of the bar-headed geese migratory pathway. We also present findings on the migratory behavior of bar-headed geese determined from this new analytical approach.

  6. The structure of the Milky Way's bar outside the bulge

    NASA Astrophysics Data System (ADS)

    Wegg, Christopher; Gerhard, Ortwin; Portail, Matthieu

    2015-07-01

    While it is incontrovertible that the inner Galaxy contains a bar, its structure near the Galactic plane has remained uncertain, where extinction from intervening dust is greatest. We investigate here the Galactic bar outside the bulge, the long bar, using red clump giant (RCG) stars from United Kingdom Infrared Deep Sky Survey, Two Micron All Sky Survey, Vista Variables in the Via Lactea and Galactic Legacy Infrared Midplane Survey Extraordinaire. We match and combine these surveys to investigate a wide area in latitude and longitude, |b| ≤ 9° and |l| ≤ 40°. We find (i) the bar extends to l ˜ 25° at |b| ˜ 5° from the Galactic plane, and to l ˜ 30° at lower latitudes; (ii) the long bar has an angle to the line-of-sight in the range (28°-33°), consistent with studies of the bulge at |l| < 10°; (iii) the scale height of RCG stars smoothly transitions from the bulge to the thinner long bar; (iv) there is evidence for two scale heights in the long bar; we find a ˜180 pc thin bar component reminiscent of the old thin disc near the Sun, and a ˜45 pc superthin bar components which exist predominantly towards the bar end; (v) constructing parametric models for the red clump magnitude distributions, we find a bar half-length of 5.0 ± 0.2 kpc for the two-component bar, and 4.6 ± 0.3 kpc for the thin bar component alone. We conclude that the Milky Way contains a central box/peanut bulge which is the vertical extension of a longer, flatter bar, similar as seen in both external galaxies and N-body models.

  7. Gas flow in barred potentials - II. Bar-driven spiral arms

    NASA Astrophysics Data System (ADS)

    Sormani, Mattia C.; Binney, James; Magorrian, John

    2015-08-01

    Spiral arms that emerge from the ends of a galactic bar are important in interpreting observations of our and external galaxies. It is therefore important to understand the physical mechanism that causes them. We find that these spiral arms can be understood as kinematic density waves generated by librations around underlying ballistic closed orbits. This is even true in the case of a strong bar, provided the librations are around the appropriate closed orbits and not around the circular orbits that form the basis of the epicycle approximation. An important consequence is that it is a potential's orbital structure that determines whether a bar should be classified as weak or strong, and not crude estimates of the potential's deviation from axisymmetry.

  8. Finite element analysis (FEA) studies in 2.5-mm round bar design: the effects of bar length and material composition on bar failure.

    PubMed

    Bidez, M W; Chen, Y; McLoughlin, S W; English, C E

    1992-01-01

    The round bar/overdenture prosthesis is commonly used in the restoration of the totally edentulous implant patient. The length of bar span and types of alloys used in clinical cases have raised questions related to beam flexure and its role as a possible etiology of reported clinical failures in cast alloy systems. Three-dimensional finite element analyses were thus conducted on a 2.5-mm round bar for investigation of mechanical performance with respect to failure potential as a function of bar length and bar material property. Specifically, three bar lengths (6 mm, 12 mm, and 18 mm) and three alloy materials were analyzed, representing a clinical range of usage. The ends of each bar were modeled fixed to a 2.5-mm coping which was attached to a 3.8-mm root-form-type implant. The implant was modeled rigidly fixed in a representative block of bone. A 200-N occlusal force was applied to the model, as would be transmitted through an attachment clip, 5 mm in length, for the three respective bar lengths. The results of these analyses suggested possible yielding (or failure) in the 18-mm case. Bar length was found to play a stronger role in the adequacy of the overall design as compared with changing material properties in the range of alloy stiffnesses tested. Factors of safety with respect to static yield strength ranged from 2.82 to 66.46 for the designs evaluated. Fatigue factors of safety ranged from 1.63 to 38.88. A factor of safety of 5 or greater is suggested for the design of round bar systems in order for bar failure to be prevented.

  9. Observation of B+ -> K0bar K+ and B0 -> K0 K0bar

    SciTech Connect

    Aubert, B.

    2006-08-16

    The authors report observations of the b {yields} d penguin-dominated decays B{sup +} {yields} {bar K}{sup 0}K{sup +} and B{sup 0} {yields} K{sup 0}{bar K}{sup 0} in approximately 350 million {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector. They measure the branching fractions {Beta}(B{sup +} {yields} {bar K}{sup 0}K{sup +}) = (1.61 {+-} 0.44 {+-} 0.09) x 10{sup -6} and {Beta}(B{sup 0} {yields} K{sup 0}{bar K}{sup 0}) = (1.08 {+-} 0.28 {+-} 0.11) x 10{sup -6}, and the CP-violating charge asymmetry {Alpha}{sub CP} ({bar K}{sup 0} K{sup +}) = 0.10 {+-} 0.26 {+-} 0.03. Using a vertexing technique previously employed in several analyses of all-neutral final states containing kaons, they report the first measurement of time-dependent CP-violating asymmetries in B{sup 0} {yields} K{sub S}{sup 0}K{sub S}{sup 0}, obtaining S = -1.28{sub -0.73 -0.16}{sup +0.80 +0.11} and C = -0.40 {+-} 0.41 {+-} 0.06. They also report improved measurements of the branching fraction {Beta}(B{sup +} {yields} K{sup 0} {pi}{sup +}) = (23.9 {+-} 1.1 {+-} 1.0) x 10{sup -6} and CP-violating charge asymmetry {Alpha}{sub CP} (K{sup 0} {pi}{sup +}) = -0.029 {+-} 0.039 {+-} 0.010.

  10. Galaxy Zoo: the effect of bar-driven fuelling on the presence of an active galactic nucleus in disc galaxies

    NASA Astrophysics Data System (ADS)

    Galloway, Melanie A.; Willett, Kyle W.; Fortson, Lucy F.; Cardamone, Carolin N.; Schawinski, Kevin; Cheung, Edmond; Lintott, Chris J.; Masters, Karen L.; Melvin, Thomas; Simmons, Brooke D.

    2015-04-01

    We study the influence of the presence of a strong bar in disc galaxies which host an active galactic nucleus (AGN). Using data from the Sloan Digital Sky Survey and morphological classifications from the Galaxy Zoo 2 project, we create a volume-limited sample of 19 756 disc galaxies at 0.01 < z < 0.05 which have been visually examined for the presence of a bar. Within this sample, AGN host galaxies have a higher overall percentage of bars (51.8 per cent) than inactive galaxies exhibiting central star formation (37.1 per cent). This difference is primarily due to known effects: that the presence of both AGN and galactic bars is strongly correlated with both the stellar mass and integrated colour of the host galaxy. We control for this effect by examining the difference in AGN fraction between barred and unbarred galaxies in fixed bins of mass and colour. Once this effect is accounted for, there remains a small but statistically significant increase that represents 16 per cent of the average barred AGN fraction. Using the L_{[O III]}/MBH ratio as a measure of AGN strength, we show that barred AGNs do not exhibit stronger accretion than unbarred AGNs at a fixed mass and colour. The data are consistent with a model in which bar-driven fuelling does contribute to the probability of an actively growing black hole, but in which other dynamical mechanisms must contribute to the direct AGN fuelling via smaller, non-axisymmetric perturbations.

  11. THE NATURE AND NURTURE OF BARS AND DISKS

    SciTech Connect

    Mendez-Abreu, J.; Aguerri, J. A. L.; Zarattini, S.; Corsini, E. M.

    2012-12-10

    The effects that interactions produce on galaxy disks and how they modify the subsequent formation of bars need to be distinguished to fully understand the relationship between bars and environment. To this aim we derive the bar fraction in three different environments ranging from the field to Virgo and Coma Clusters, covering an unprecedentedly large range of galaxy luminosities (or, equivalently, stellar masses). We confirm that the fraction of barred galaxies strongly depends on galaxy luminosity. We also show that the difference between the bar fraction distributions as a function of galaxy luminosity (and mass) in the field and Coma Cluster is statistically significant, with Virgo being an intermediate case. The fraction of barred galaxies shows a maximum of about 50% at M{sub r} {approx_equal} - 20.5 in clusters, whereas the peak is shifted to M{sub r} {approx_equal} - 19 in the field. We interpret this result as a variation of the effect of environment on bar formation depending on galaxy luminosity. We speculate that brighter disk galaxies are stable enough against interactions to keep their cold structure, thus, the interactions are able to trigger bar formation. For fainter galaxies, the interactions become strong enough to heat up the disks inhibiting bar formation and even destroying the disks. Finally, we point out that the controversy regarding whether the bar fraction depends on environment could be resolved by taking into account the different luminosity ranges probed by the galaxy samples studied so far.

  12. The Nature and Nurture of Bars and Disks

    NASA Astrophysics Data System (ADS)

    Méndez-Abreu, J.; Sánchez-Janssen, R.; Aguerri, J. A. L.; Corsini, E. M.; Zarattini, S.

    2012-12-01

    The effects that interactions produce on galaxy disks and how they modify the subsequent formation of bars need to be distinguished to fully understand the relationship between bars and environment. To this aim we derive the bar fraction in three different environments ranging from the field to Virgo and Coma Clusters, covering an unprecedentedly large range of galaxy luminosities (or, equivalently, stellar masses). We confirm that the fraction of barred galaxies strongly depends on galaxy luminosity. We also show that the difference between the bar fraction distributions as a function of galaxy luminosity (and mass) in the field and Coma Cluster is statistically significant, with Virgo being an intermediate case. The fraction of barred galaxies shows a maximum of about 50% at Mr ~= - 20.5 in clusters, whereas the peak is shifted to Mr ~= - 19 in the field. We interpret this result as a variation of the effect of environment on bar formation depending on galaxy luminosity. We speculate that brighter disk galaxies are stable enough against interactions to keep their cold structure, thus, the interactions are able to trigger bar formation. For fainter galaxies, the interactions become strong enough to heat up the disks inhibiting bar formation and even destroying the disks. Finally, we point out that the controversy regarding whether the bar fraction depends on environment could be resolved by taking into account the different luminosity ranges probed by the galaxy samples studied so far.

  13. Advances in bonding technology for high power diode laser bars

    NASA Astrophysics Data System (ADS)

    Wang, Jingwei; Li, Xiaoning; Hou, Dong; Feng, Feifei; Liu, Yalong; Liu, Xingsheng

    2015-02-01

    Due to their high electrical-optical conversion efficiency, compact size and long lifetime, high power diode lasers have found increased applications in many fields. As the improvement of device technology, high power diode laser bars with output power of tens or hundreds watts have been commercially available. With the increase of high current and output power, the reliability and lifetime of high power diode laser bars becomes a challenge, especially under harsh working conditions and hard-pulse operations. The bonding technology is still one of the bottlenecks of the advancement of high power diode laser bars. Currently, materials used in bonding high power diode laser bars are commonly indium and goldtin solders. Experimental and field application results indicates that the lifetime and reliability of high power diode laser bars bonded by gold-tin solder is much better than that bonded by indium solder which is prone to thermal fatigue, electro-migration and oxidization. In this paper, we review the bonding technologies for high power diode laser bars and present the advances in bonding technology for single bars, horizontal bar arrays and vertical bar stacks. We will also present the challenges and issues in bonding technology for high power diode laser bars and discuss some approaches and strategies in addressing the challenges and issues.

  14. Structure of Dimeric and Tetrameric Complexes of the BAR Domain Protein PICK1 Determined by Small-Angle X-Ray Scattering.

    PubMed

    Karlsen, Morten L; Thorsen, Thor S; Johner, Niklaus; Ammendrup-Johnsen, Ina; Erlendsson, Simon; Tian, Xinsheng; Simonsen, Jens B; Høiberg-Nielsen, Rasmus; Christensen, Nikolaj M; Khelashvili, George; Streicher, Werner; Teilum, Kaare; Vestergaard, Bente; Weinstein, Harel; Gether, Ulrik; Arleth, Lise; Madsen, Kenneth L

    2015-07-01

    PICK1 is a neuronal scaffolding protein containing a PDZ domain and an auto-inhibited BAR domain. BAR domains are membrane-sculpting protein modules generating membrane curvature and promoting membrane fission. Previous data suggest that BAR domains are organized in lattice-like arrangements when stabilizing membranes but little is known about structural organization of BAR domains in solution. Through a small-angle X-ray scattering (SAXS) analysis, we determine the structure of dimeric and tetrameric complexes of PICK1 in solution. SAXS and biochemical data reveal a strong propensity of PICK1 to form higher-order structures, and SAXS analysis suggests an offset, parallel mode of BAR-BAR oligomerization. Furthermore, unlike accessory domains in other BAR domain proteins, the positioning of the PDZ domains is flexible, enabling PICK1 to perform long-range, dynamic scaffolding of membrane-associated proteins. Together with functional data, these structural findings are compatible with a model in which oligomerization governs auto-inhibition of BAR domain function.

  15. VLA continuum observations of barred spiral galaxies

    NASA Technical Reports Server (NTRS)

    Garcia-Barreto, J. Antonio; Pismis, P.

    1987-01-01

    Observations of NGC 613, NGC 1300, NGC 4314 and NGC 5383 using the VLA at frequencies of 1464.9 and 4885.1 MHz are reported. These objects are a subset of galaxies from which radio emission were searched. The selection criteria were: (1) they are barred spiral galaxies preferentially with different Hubble type; (2) they have a peculiar or hot spot nucleus; (3) they have been observed at far infrared wavelengths by IRAS; and (4) they are observable from the northern hemisphere. Their radio and far infrared properties are summarized and their composite spectra are shown.

  16. Predicting Vertical Jump Height from Bar Velocity

    PubMed Central

    García-Ramos, Amador; Štirn, Igor; Padial, Paulino; Argüelles-Cienfuegos, Javier; De la Fuente, Blanca; Strojnik, Vojko; Feriche, Belén

    2015-01-01

    The objective of the study was to assess the use of maximum (Vmax) and final propulsive phase (FPV) bar velocity to predict jump height in the weighted jump squat. FPV was defined as the velocity reached just before bar acceleration was lower than gravity (-9.81 m·s-2). Vertical jump height was calculated from the take-off velocity (Vtake-off) provided by a force platform. Thirty swimmers belonging to the National Slovenian swimming team performed a jump squat incremental loading test, lifting 25%, 50%, 75% and 100% of body weight in a Smith machine. Jump performance was simultaneously monitored using an AMTI portable force platform and a linear velocity transducer attached to the barbell. Simple linear regression was used to estimate jump height from the Vmax and FPV recorded by the linear velocity transducer. Vmax (y = 16.577x - 16.384) was able to explain 93% of jump height variance with a standard error of the estimate of 1.47 cm. FPV (y = 12.828x - 6.504) was able to explain 91% of jump height variance with a standard error of the estimate of 1.66 cm. Despite that both variables resulted to be good predictors, heteroscedasticity in the differences between FPV and Vtake-off was observed (r2 = 0.307), while the differences between Vmax and Vtake-off were homogenously distributed (r2 = 0.071). These results suggest that Vmax is a valid tool for estimating vertical jump height in a loaded jump squat test performed in a Smith machine. Key points Vertical jump height in the loaded jump squat can be estimated with acceptable precision from the maximum bar velocity recorded by a linear velocity transducer. The relationship between the point at which bar acceleration is less than -9.81 m·s-2 and the real take-off is affected by the velocity of movement. Mean propulsive velocity recorded by a linear velocity transducer does not appear to be optimal to monitor ballistic exercise performance. PMID:25983572

  17. Predicting Error Bars for QSAR Models

    SciTech Connect

    Schroeter, Timon; Mika, Sebastian; Ter Laak, Antonius; Suelzle, Detlev; Ganzer, Ursula; Heinrich, Nikolaus; Mueller, Klaus-Robert

    2007-09-18

    Unfavorable physicochemical properties often cause drug failures. It is therefore important to take lipophilicity and water solubility into account early on in lead discovery. This study presents log D{sub 7} models built using Gaussian Process regression, Support Vector Machines, decision trees and ridge regression algorithms based on 14556 drug discovery compounds of Bayer Schering Pharma. A blind test was conducted using 7013 new measurements from the last months. We also present independent evaluations using public data. Apart from accuracy, we discuss the quality of error bars that can be computed by Gaussian Process models, and ensemble and distance based techniques for the other modelling approaches.

  18. Predicting vertical jump height from bar velocity.

    PubMed

    García-Ramos, Amador; Štirn, Igor; Padial, Paulino; Argüelles-Cienfuegos, Javier; De la Fuente, Blanca; Strojnik, Vojko; Feriche, Belén

    2015-06-01

    The objective of the study was to assess the use of maximum (Vmax) and final propulsive phase (FPV) bar velocity to predict jump height in the weighted jump squat. FPV was defined as the velocity reached just before bar acceleration was lower than gravity (-9.81 m·s(-2)). Vertical jump height was calculated from the take-off velocity (Vtake-off) provided by a force platform. Thirty swimmers belonging to the National Slovenian swimming team performed a jump squat incremental loading test, lifting 25%, 50%, 75% and 100% of body weight in a Smith machine. Jump performance was simultaneously monitored using an AMTI portable force platform and a linear velocity transducer attached to the barbell. Simple linear regression was used to estimate jump height from the Vmax and FPV recorded by the linear velocity transducer. Vmax (y = 16.577x - 16.384) was able to explain 93% of jump height variance with a standard error of the estimate of 1.47 cm. FPV (y = 12.828x - 6.504) was able to explain 91% of jump height variance with a standard error of the estimate of 1.66 cm. Despite that both variables resulted to be good predictors, heteroscedasticity in the differences between FPV and Vtake-off was observed (r(2) = 0.307), while the differences between Vmax and Vtake-off were homogenously distributed (r(2) = 0.071). These results suggest that Vmax is a valid tool for estimating vertical jump height in a loaded jump squat test performed in a Smith machine. Key pointsVertical jump height in the loaded jump squat can be estimated with acceptable precision from the maximum bar velocity recorded by a linear velocity transducer.The relationship between the point at which bar acceleration is less than -9.81 m·s(-2) and the real take-off is affected by the velocity of movement.Mean propulsive velocity recorded by a linear velocity transducer does not appear to be optimal to monitor ballistic exercise performance.

  19. CP Violation at BaBar

    SciTech Connect

    Yeche, Christophe; /DSM, DAPNIA, Saclay

    2011-11-15

    We report recent measurements of the three CKM angles of the Unitarity Triangle using about 383 millions b{bar b} pairs collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. The results of the angles ({beta}, {alpha}, {gamma}) of the unitarity triangle are consistent with Belle results, and with other CKM constraints such as the measurement of {epsilon}{sub K}, the length of the sides of the unitarity triangle determined from the measurements of {Delta}m{sub d}, {Delta}m{sub s}, |V{sub ub}|. This is an impressive confirmation of Standard Model in quark-flavor sector.

  20. Hadron Physics at BaBar

    SciTech Connect

    Muller, David; /SLAC

    2005-10-26

    The BaBar experiment at SLAC is designed to measure CP violation in the B meson system, however the very high statistics combined with the different e{sup +} and e{sup -} beam energies, the detector design and the open trigger allow a wide variety of spectroscopic measurements. We are beginning to tap this potential via several production mechanisms. Here we present recent results from initial state radiation, hadronic jets, few body B and D hadron decays, and interactions in the detector material. We also summarize measurements relevant to D{sub s} meson spectroscopy, pentaquarks and charmonium spectroscopy from multiple production mechanisms.

  1. Failure Waves in Cylindrical Glass Bars

    NASA Astrophysics Data System (ADS)

    Cazamias, James U.; Bless, Stephan J.; Marder, Michael P.

    1997-07-01

    Failure waves, a propagating front separating virgin and comminuted material, have been receiving a fair amount of attention the last couple of years. While most scientists have been looking at failure waves in plate impact geometries, we have conducted a series of experiments on Pyrex bars. In this paper, we present two types of photographic data from a series of tests. A streak camera was used to determine velocities of the failure front as a function of impact stress. A polaroid camera and a flash lamp provide detailed pictures of the actual event. Attempts were made to observe failure waves in amorphous quartz and acrylic.

  2. Predicting Error Bars for QSAR Models

    NASA Astrophysics Data System (ADS)

    Schroeter, Timon; Schwaighofer, Anton; Mika, Sebastian; Ter Laak, Antonius; Suelzle, Detlev; Ganzer, Ursula; Heinrich, Nikolaus; Müller, Klaus-Robert

    2007-09-01

    Unfavorable physicochemical properties often cause drug failures. It is therefore important to take lipophilicity and water solubility into account early on in lead discovery. This study presents log D7 models built using Gaussian Process regression, Support Vector Machines, decision trees and ridge regression algorithms based on 14556 drug discovery compounds of Bayer Schering Pharma. A blind test was conducted using 7013 new measurements from the last months. We also present independent evaluations using public data. Apart from accuracy, we discuss the quality of error bars that can be computed by Gaussian Process models, and ensemble and distance based techniques for the other modelling approaches.

  3. Manganese-oxide-coated redox bars as an indicator of reducing conditions in soils.

    PubMed

    Dorau, Kristof; Mansfeldt, Tim

    2015-03-01

    Identification of reducing conditions in soils is of concern not only for pedogenesis but also for nutrient and pollutant dynamics. We manufactured manganese (Mn)-oxide-coated polyvinyl chloride bars and proved their suitability for the identification of reducing soil conditions. Birnessite was synthesized and coated onto white polyvinyl chloride bars. The dark brown coatings were homogenous and durable. As revealed by microcosm devices with adjusted redox potentials (E), under oxidizing conditions (E ∼450 mV at pH 7) there was no Mn-oxide removal. Reductive dissolution of Mn-oxides, which is expressed by the removal of the coatings, started under weakly reducing conditions (E ∼175 mV) and was more intensive under moderately reducing conditions (∼80 mV). According to thermodynamics, the removal of Mn-oxide coatings (225 mm d) exceeded the removal of iron (Fe)-oxide coatings (118 mm d) in soil column experiments. This was confirmed in a soil with a shallow and strongly fluctuating water table where both types of redox bars were inserted. Consequently, it was possible to identify reducing conditions in soils using Mn-oxide-coated bars. We recommend this methodology for short-term monitoring because tri- and tetravalent Mn is the preferred electron acceptor compared with trivalent Fe, and this additionally offers the possibility of distinguishing between weakly and moderately reducing conditions. If dissolved Fe is abundant in soils, the possibility of nonenzymatic reduction of Mn has to be taken into account.

  4. a Study on the Alternative Technology Using Unsm Instead of the Presetting Method for Torsion Bar

    NASA Astrophysics Data System (ADS)

    Suh, Chang-Min; Kim, Min-Ho; Baek, Un-Bong; Pyoun, Young-Sik; Kim, Chang-Sik; Chi, Chong-Ho

    The torsion bar must be changed periodically due to its lack of durability and a phenomenon related to stress relaxation. Therefore technical development regarding the torsion bar's durability is urgently needed. In order to improve the fatigue life and durability of the dynamic components, new surface treatment technology such as ultrasonic shot peening, deep rolling, laser shock peening, etc. are developing widely. In this study, Ultrasonic Nanocrystal Surface Modification (UNSM) technology is applied as an advanced one to replace the presetting method (PM). UNSM and PM technology also induced the compressive residual stress on the surface layer of the torsion bar, which is the main improvement factor of fatigue life. DIN17221 material as a new MIL specification of torsion bar and SCM440 (as an alternative one to a old MIL-DTL-62567C) were processed with the UNSM technology to obtain the basic data and compare it between two, and then torsion fatigue tests of two materials were carried out to obtain the characteristics of torsion fatigue in this study.

  5. High-resolution spectral mapping of a lensed high power laser bar

    NASA Astrophysics Data System (ADS)

    Gannon, Caleb D.; Koenning, Tobias; Patterson, Steve G.; Leisher, Paul O.

    2014-03-01

    Alkali gas lasers based on rubidium vapor have an extremely narrow absorption band (<0.01 nm at STP) at 780 nm. Diode-pumped alkali lasers (DPALs) require high-power diode arrays having emission spectra which are closely matched to this absorption peak. There are several methods which can be used for narrowing and stabilizing the output spectrum of a diode laser bar including external locking via a volumetric holographic grating (VHG). While this approach offers several advantages over internal stabilization techniques, the effect of pointing error arising from bar smile can be detrimental to the locked performance of the lensed array. In order to investigate the effect of smile on wavelength locking, a system capable of mapping the emission spectrum of the lensed diode laser bar was developed. The approach utilizes an imaging system and spatial filter to couple light from individual emitters of the lensed array into a commercial optical spectrum analyzer. This approach offers a larger dynamic range than traditional spectral mapping techniques, with a resolved signal to noise ratio in excess of 60 dB. Results from the characterization of a VHG-locked 780 nm laser bar array will be presented.

  6. Moving Groups in the Milky Way Halo and Disk Induced by the Bar and Spiral Arms

    NASA Astrophysics Data System (ADS)

    Schuster, William John

    2015-08-01

    In a previous study (Moreno et al. 2015), the use of a detailed Milky Way potential (observationally and dynamically constrained) has shown that the Galactic bar is able to efficiently concentrate stars of the stellar halo and disk into several main resonances. With the tools introduced here, the Galactic bar is shown to produce significant phase-space structure attracting stars to several main resonances. This new study is dedicated to the study of known groups of the Galactic halo and disk, and their relation to these resonances. Stars belonging to some known halo and disk moving groups have settled down along these bar resonant families, showing, in some cases, a likely Galactic secular origin. In general, the 2D resonant orbits of the disk produced by the bar, seem to dominate at large scale-heights (several kiloparsecs) into the Galactic halo. In particular, provisionally six of the members of the Kapteyn halo moving group seem to be associated with one of these resonances, and also the Groombridge 1830 (Eggen 1996a; Eggen & Sandage 1959) and especially the newer halo moving groups G21-22 and G18-39 (Silva et al. 2012) show some correlation with these resonances suggesting possible secular origins, while the halo moving group Ross 451 (Eggen 1996b) does not show any such correlation, indicating a more probable cosmological (non-secular) ancestry. All Galactic disk moving groups (such as Arcturus, Hercules, Castor, IC 2391, Hyades, Pleiades, and Ursa Major) show considerable association with these resonances.

  7. Mapping the Anapa bay bar geosystems on the basis of satellite remote sensing and ground data

    NASA Astrophysics Data System (ADS)

    Kravtsova, Valentina I.; Tutubalina, Olga V.; Krylenko, Vyacheslav V.; Krylenko, Marina V.; Chalova, Ekaterina R.

    2015-06-01

    Our study is focused on the Anapa Bay Bar, a 43-km long body of sand on the Black Sea coast, which stretches from the Russian town of Anapa to the Zhelezny Rog Cape on the Taman' peninsula. It is a major recreational resource and a host to unique ecosystems of beaches and partially vegetated sand dunes. Due to large recreational pressure, it is important to identify features of the bay bar that have to be preserved in order to keep this resource sustainable. We have conducted landscape and morphological mapping with WorldView-2 images. Methods included field research, analysis of multitemporal stereopairs and automated image interpretation to create maps of key areas of the Anapa Bay Bar. In our paper we showcase the map for a section of the Anapa Bay Bar created through visual image interpretation. It presents all morphological elements such as beaches, sand dunes, sand ridges and lowlands adjoining lagoons. Each element has its specific vegetation and sustainability against recreational pressure. We also present results of automated image analysis of seasonal dynamics of the beach and dunes on the basis of multitemporal imagery.

  8. On the nature of high-mass states observed in {bar N}N annihilation at rest into 3 pseudoscalars

    SciTech Connect

    Grigoryan, A.A.; Montanet, L.

    1994-09-01

    The peaks at large masses of systems {pi}{pi}, {pi}{eta}, and {eta}{eta} produced in {bar N}N annihilation at rest into 3 pseudoscalars are shown to be connected to the dynamics of the nucleon-exchange mechanism. 13 refs., 4 figs.

  9. Boxy/Peanut/X Bulges, Barlenses and the Thick Part of Galactic Bars: What Are They and How Did They Form?

    NASA Astrophysics Data System (ADS)

    Athanassoula, E.

    Bars have a complex three-dimensional shape. In particular their inner part is vertically much thicker than the parts further out. Viewed edge-on, the thick part of the bar is what is commonly known as a boxy-, peanut-, or X- bulge and viewed face-on it is referred to as a barlens. These components are due to disc and bar instabilities and are composed of disc material. I review here their formation, evolution and dynamics, using simulations, orbital structure theory and comparisons to observations.

  10. Automated multisyringe stir bar sorptive extraction using robust montmorillonite/epoxy-coated stir bars.

    PubMed

    Ghani, Milad; Saraji, Mohammad; Maya, Fernando; Cerdà, Víctor

    2016-05-01

    Herein we present a simple, rapid and low cost strategy for the preparation of robust stir bar coatings based on the combination of montmorillonite with epoxy resin. The composite stir bar was implemented in a novel automated multisyringe stir bar sorptive extraction system (MS-SBSE), and applied to the extraction of four chlorophenols (4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol) as model compounds, followed by high performance liquid chromatography-diode array detection. The different experimental parameters of the MS-SBSE, such as sample volume, selection of the desorption solvent, desorption volume, desorption time, sample solution pH, salt effect and extraction time were studied. Under the optimum conditions, the detection limits were between 0.02 and 0.34μgL(-1). Relative standard deviations (RSD) of the method for the analytes at 10μgL(-1) concentration level ranged from 3.5% to 4.1% (as intra-day RSD) and from 3.9% to 4.3% (as inter-day RSD at 50μgL(-1) concentration level). Batch-to-batch reproducibility for three different stir bars was 4.6-5.1%. The enrichment factors were between 30 and 49. In order to investigate the capability of the developed technique for real sample analysis, well water, wastewater and leachates from a solid waste treatment plant were satisfactorily analyzed.

  11. Bar slowdown and the distribution of dark matter in barred galaxies

    NASA Astrophysics Data System (ADS)

    Athanassoula, E.

    2014-02-01

    `Conspiracy' between the dark and the baryonic matter prohibits an unambiguous decomposition of disc galaxy rotation curves into the corresponding components. Several methods have been proposed to counter this difficulty, but their results are widely discrepant. In this paper, I revisit one of these methods, which relies on the relation between the halo density and the decrease of the bar pattern speed. The latter is routinely characterized by the ratio R of the corotation radius RCR to the bar length Lb, R = R_CR/L_b. I use a set of N-body+SPH simulations, including subgrid physics, whose initial conditions cover a range of gas fractions and halo shapes. The models, by construction, have roughly the same azimuthally averaged circular velocity curve and halo density and they are all submaximal, i.e. according to previous works, they are expected to have all roughly the same R value, well outside the fast bar range (1.2 ± 0.2). Contrary to these expectations, however, these simulations end up having widely different R values, either within the fast bar range or well outside it. This shows that the R value cannot constrain the halo density, nor determine whether galactic discs are maximal or submaximal. I argue that this is true even for early-type discs (S0s and Sas).

  12. BARS/SSC/SPHINX4.0. BARS Bibliographic Data Retrieval System

    SciTech Connect

    Herrmann, W.

    1993-06-01

    BARS is a program which allows retrieval of information from suitable bibliographic databases. Two databases are included, SSC and SPHINX, which together list bibliographic information for some 12,000 references related to the fields of shock compression of condensed media, high rate deformation of solids, and detonation.

  13. $D^0 \\bar{D}^0$ Mixing at BaBar

    SciTech Connect

    Coleman, Jonathon; /SLAC

    2011-10-26

    This article reviews the recent measurement of D{sup 0}-{bar D}{sup 0} mixing with the D{sup 0} {yields} K{pi} decay channel from the BABAR experiment at the PEP-II B-Factory. Averages from the Heavy Flavor Averaging Group between this result and a previous result from BELLE are also presented.

  14. Tau Decays at BaBar

    SciTech Connect

    Hast, Carsten; /SLAC

    2009-01-22

    Recent results of tau lepton decay studies based on luminosities between 350 fb{sup -1} and 469 fb{sup -1} collected with the BABAR detector at the PEP-II e{sup +}e{sup -} collider at the SLAC National Accelerator Laboratory are presented. The analyses reported here are Charged Current Lepton Universality and measurements of |V{sub us}| using {tau}{sup -} {yields} e{sup -}{bar {nu}}{sub e}{nu}{sub {tau}}, {mu}{sup -}{bar {nu}}{sub {mu}}{nu}{sub {tau}}, {pi}{sup -} {nu}{sub {tau}}, and K{sup -}{nu}{sub {tau}} decays, as well as searches for Second Class Currents in {tau}{sup -} {yields} {omega}{pi}{sup -}{nu}{sub {tau}} decays, studies of Lepton Flavor Violations, and a tau mass measurement and CPT-Test. If not explicitly mentioned, charge conjugate decay modes are also implied. decays, as well as searches for Second Class Currents in {tau}{sup -} {yields} {omega}{pi}{sup -}{nu}{sub {tau}} decays, studies of Lepton Flavor Violations, and a tau mass measurement and CPT-Test. If not explicitly mentioned, charge conjugate decay modes are also implied.

  15. Recent developments in stir bar sorptive extraction.

    PubMed

    He, Man; Chen, Beibei; Hu, Bin

    2014-03-01

    As a crucial step in qualitative and quantitative analysis, sample pretreatment is commonly used to isolate the target analytes, concentrate them, or convert them into the forms tailored to the instrumental analysis. In recent years, there has been a trend for sample pretreatment techniques to become more miniaturized and more environmentally friendly. Stir bar sorptive extraction (SBSE), which was developed in 1999, is such an environmentally friendly microextraction technique. Compared with other microextraction techniques, including solid phase microextraction and liquid phase microextraction, SBSE provides a higher extraction efficiency and better reproducibility owing to the much greater amount of the extraction phase, and no special skills are required. However, there are some problems associated with SBSE, such as the limited applicable coatings, coating abrasion of the laboratory-made stir bar, and the difficulty in automation, which restrict the further improvement and application of SBSE. This review focuses on the development of SBSE in the past decade, in terms of coating preparation, automated systems, novel extraction modes, its use with various instruments, and applications in food, environmental, and biological samples.

  16. Sillicon Photomultiplier and Scintillator Bar Systems

    NASA Astrophysics Data System (ADS)

    Shelor, Mark; Elizondo, Leonardo; Ritt, Stefan

    2016-03-01

    To analyze extraterrestrial cosmic rays via precise measurements of airshower axes directions of penetrating particles such as muons, we constructed a model detector consisting of two 1-meter long scintillator bars. Each bar is fitted with green wavelength shifting fibers to modulate input for two silicon photomultiplier (SiPM) light detectors to record light produced by cosmic rays via scintillation. The purpose of the experiment is to determine the performance of these devices. Two makes of SiPMs were evaluated - from AdvanSiD and Hamamatsu. In order to filter out noise, timing measurements of the apparatus were performed under several trigger conditions such as coincidence trigger with 2 photomultiplier detectors, as well as SiPM detector arrays in self-triggered mode. The DRS4 Digitizer 4-channel fast waveform sampler digitized SiPM detector waveforms. Signals were analyzed with the CERN PAW package. The speed of light in the scintillator using the SiPM modules was found to be approximately 66% of the speed of light in a vacuum which is in accordance with the index of refraction for the fibers given by the manufacturer's specifications. The results of our timing measurements would be presented. Dept. of Ed. Title V Grant PO31S090007.

  17. A comparative study of mineralized biocomposites: Hierarchical structure, quasi-static and dynamic mechanical behavior, and toughening mechanisms

    NASA Astrophysics Data System (ADS)

    Chen, Po-Yu

    Antlers have a primary function in combat and are designed for sustaining high impact loading and bending moment without fracture. Learning from antler may shed a new light on traumatic bone fracture prevention and development of novel fracture-resistant, impact-absorbent materials. Antlers have a similar microstructure as bones, composed mainly of type-I collagen fibrils and carbonated apatite crystals, arranged in osteons in the compact bone and trabeculae in the cancellous bone. However, antlers have lower mineral content and consist mainly of primary osteons. The structure of antler at various hierarchical levels was thoroughly characterized and examined using various techniques and compared with bovine femur. Quasi-static mechanical tests (three-point bending, compression, and nanoindentation) were conducted on elk antlers and the results were compared to reported data. The flexural strength and elastic modulus are similar to other antlers but lower than bovine femur. However, the antler has much higher work of fracture and fracture toughness compared with bone. Dynamic behavior of antler was investigated using a split-Hopkinson pressure bar system. Results showed that antler can sustain large amount of deformation without catastrophic fracture. In situ mechanical testing under ESEM was performed to examine crack propagation in the longitudinal and transverse orientations in compact antler. Nonlinear-elastic fracture mechanics were applied to determine R-curves. The fracture toughness in the transverse orientation is much higher than that in the longitudinal orientation due to crack deflections/twists at the hypermineralized interface and the rising R-curve behavior was observed. Synchrotron X-ray computed tomography and SEM images showed toughening mechanisms, including crack deflections/twists, uncracked ligament and collagen fiber bridging. The structure and compressive mechanical properties of the mineral and protein constituents in cancellous antler and

  18. Cereal and nut bars, nutritional quality and storage stability.

    PubMed

    Estévez, A M; Escobar, B; Vásquez, M; Castillo, E; Araya, E; Zacarías, I

    1995-06-01

    Six snack-type bars were manufactured, to contain oat and wheat germ and two different walnut levels, agglutinated with natural sweeteners and fats. Two bars also contained toasted amaranth with brown sugar cover and wheat extrudate, while two others, contained puffed instead of toasted amaranth. Water activity (Aw) and moisture were determined in the manufactured products. Quality and sensory evaluation and proximate analysis were carried out on the bars containing highest levels of walnuts (18%). The caloric contribution of the bars was computed by Atwater methods. The nutritional quality of the bars was determined by means of the Protein Efficiency Ratio (PER) and Net Protein Ratio (NPR), and the results were used to obtain relative PER and relative NPR. Samples of the latter bars were kept under accelerated storage for 15 days at 37 degrees C and analyzed every 5 days to determine their Aw, moisture, peroxide and sensory acceptability. The drying time for the cereal - and walnut - based bars was 45 min at 120 degrees C. All bars presented a good fiber supply and the CN1 bar, containing only oat, wheat germ and walnut, had the greatest protein content. In the sensory evaluation, the walnut level with the greatest preference was 18%. PER and NPR values of the bars did not differ significantly showing values approximately 86% that of the casein value. During storage, the moisture and Aw decreased in all the bars. Peroxides remained within the acceptable ranges; acceptability based on sensory evaluation remained best in the bar with toasted amaranth.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8577648

  19. Kolkata Restaurant Problem as a Generalised El Farol Bar Problem

    NASA Astrophysics Data System (ADS)

    Chakrabarti, Bikas K.

    Generalisation of the El Farol bar problem to that of many bars here leads to the Kolkata restaurant problem, where the decision to go to any restaurant or not is much simpler (depending on the previous experience of course, as in the El Farol bar problem). This generalised problem can be exactly analysed in some limiting cases discussed here. The fluctuation in the restaurant service can be shown to have precisely an inverse cubic behavior, as widely seen in the stock market fluctuations.

  20. Uncertainties in the Deprojection of the Observed Bar Properties

    NASA Astrophysics Data System (ADS)

    Zou, Yanfei; Shen, Juntai; Li, Zhao-Yu

    2014-08-01

    In observations, it is important to deproject the two fundamental quantities characterizing a bar, i.e., its length (a) and ellipticity (e), to face-on values before any careful analyses. However, systematic estimation on the uncertainties of the commonly used deprojection methods is still lacking. Simulated galaxies are well suited in this study. We project two simulated barred galaxies onto a two-dimensional (2D) plane with different bar orientations and disk inclination angles (i). Bar properties are measured and deprojected with the popular deprojection methods in the literature. Generally speaking, deprojection uncertainties increase with increasing i. All of the deprojection methods behave badly when i is larger than 60°, due to the vertical thickness of the bar. Thus, future statistical studies of barred galaxies should exclude galaxies more inclined than 60°. At moderate inclination angles (i <= 60°), 2D deprojection methods (analytical and image stretching), and Fourier-based methods (Fourier decomposition and bar-interbar contrast) perform reasonably well with uncertainties ~10% in both the bar length and ellipticity, whereas the uncertainties of the one-dimensional (1D) analytical deprojection can be as high as 100% in certain extreme cases. We find that different bar measurement methods show systematic differences in the deprojection uncertainties. We further discuss the deprojection uncertainty factors with the emphasis on the most important one, i.e., the three-dimensional structure of the bar itself. We construct two triaxial toy bar models that can qualitatively reproduce the results of the 1D and 2D analytical deprojections; they confirm that the vertical thickness of the bar is the main source of uncertainties.

  1. Uncertainties in the deprojection of the observed bar properties

    SciTech Connect

    Zou, Yanfei; Shen, Juntai; Li, Zhao-Yu

    2014-08-10

    In observations, it is important to deproject the two fundamental quantities characterizing a bar, i.e., its length (a) and ellipticity (e), to face-on values before any careful analyses. However, systematic estimation on the uncertainties of the commonly used deprojection methods is still lacking. Simulated galaxies are well suited in this study. We project two simulated barred galaxies onto a two-dimensional (2D) plane with different bar orientations and disk inclination angles (i). Bar properties are measured and deprojected with the popular deprojection methods in the literature. Generally speaking, deprojection uncertainties increase with increasing i. All of the deprojection methods behave badly when i is larger than 60°, due to the vertical thickness of the bar. Thus, future statistical studies of barred galaxies should exclude galaxies more inclined than 60°. At moderate inclination angles (i ≤ 60°), 2D deprojection methods (analytical and image stretching), and Fourier-based methods (Fourier decomposition and bar-interbar contrast) perform reasonably well with uncertainties ∼10% in both the bar length and ellipticity, whereas the uncertainties of the one-dimensional (1D) analytical deprojection can be as high as 100% in certain extreme cases. We find that different bar measurement methods show systematic differences in the deprojection uncertainties. We further discuss the deprojection uncertainty factors with the emphasis on the most important one, i.e., the three-dimensional structure of the bar itself. We construct two triaxial toy bar models that can qualitatively reproduce the results of the 1D and 2D analytical deprojections; they confirm that the vertical thickness of the bar is the main source of uncertainties.

  2. An efficient approach to optimize the vibration mode of bar-type ultrasonic motors.

    PubMed

    Zhu, Hua; Li, Zhirong; Zhao, Chunsheng

    2010-04-01

    The electromechanical coupled dynamic model of the stator of the bar-type ultrasonic motor is derived based on the finite element method. The dynamical behavior of the stator is analyzed via this model and the theoretical result agrees with the experimental result of the stator of the prototype motor very well. Both the structural design principles and the approaches to meet the requirements for the mode of the stator are discussed. Based on the pattern search algorithm, an optimal model to meet the design requirements is established. The numerical simulation results show that this optimal model is effective for the structural design of the stator.

  3. Mechanical Engineering Safety Note PEPC Spreader Bar Assembly

    SciTech Connect

    Mason, D.

    2001-08-26

    The PEPC Spreader Bar Assembly consists of a spreader bar that will be attached to the PEPC Cell Housing or the Midplane Transportation Fixture during operation. While in use in the OAB (Optics Assembly Building), the Spreader Bar Assembly will be manipulated by the NOID (New Optics Insertion Device). The other critical components of the assembly are the three angular contact bearing swivels that attach the spreader bar to the lifting mechanism and the corner clamps which are used to capture the Cell Housing.

  4. Measurement of the B0-bar Lifetime and the B0B0-bar Oscillation Frequency Using Partially Reconstructed B0-bar to D*+ l- nu-bar Decays

    SciTech Connect

    Aubert, B.; Barate, R.; Boutigny, D.; Couderc, F.; Karyotakis, Y.; Lees, J.P.; Poireau, V.; Tisserand, V.; Zghiche, A.; Grauges, E.; Palano, A.; Pappagallo, M.; Pompili, A.; Chen, J.C.; Qi, N.D.; Rong, G.; Wang, P.; Zhu, Y.S.; Eigen, G.; Ofte, I.; Stugu, B. /Bergen U. /LBL, Berkeley /UC, Berkeley /Birmingham U. /Ruhr U., Bochum /Bristol U. /British Columbia U. /Brunel U. /Novosibirsk, IYF /UC, Irvine /UCLA /UC, Riverside /UC, San Diego /UC, Santa Barbara /UC, Santa Cruz /Caltech /Cincinnati U. /Colorado U. /Colorado State U. /Dortmund U. /Dresden, Tech. U. /Ecole Polytechnique /Edinburgh U. /Ferrara U. /INFN, Ferrara /Frascati /Genoa U. /INFN, Genoa /Harvard U. /Heidelberg U. /Imperial Coll., London /Iowa U. /Iowa State U. /Orsay, LAL /LLNL, Livermore /Liverpool U. /Queen Mary, U. of London /Royal Holloway, U. of London /Louisville U. /Manchester U. /Maryland U. /Massachusetts U., Amherst /MIT, LNS /McGill U. /Milan U. /INFN, Milan /Mississippi U. /Montreal U. /Mt. Holyoke Coll. /Naples U. /INFN, Naples /NIKHEF, Amsterdam /Notre Dame U. /Ohio State U. /Oregon U. /Padua U. /INFN, Padua /Paris U., VI-VII /Pennsylvania U. /Perugia U. /INFN, Perugia /Pisa U. /INFN, Pisa /Prairie View A-M /Princeton U. /Rome U. /INFN, Rome /Rostock U. /Rutherford /DAPNIA, Saclay /South Carolina U. /SLAC /Stanford U., Phys. Dept. /SUNY, Stony Brook /Tennessee U. /Texas U. /Texas U., Dallas /Turin U. /INFN, Turin /Trieste U. /INFN, Trieste /Valencia U., IFIC /Vanderbilt U. /Victoria U. /Warwick U. /Wisconsin U., Madison /Yale U.

    2005-07-27

    The authors present a simultaneous measurement of the {bar B}{sup 0} lifetime {tau}{sub B{sup 0}} and B{sup 0}{bar B}{sup 0} oscillation frequency {Delta}m{sub d}. We use a sample of about 50,000 partially reconstructed {bar B}{sup 0} {yields} D*{sup +}{ell}{sup -}{bar {nu}}{sub {ell}} decays identified with the BABAR detector at the PEP-II e{sup +}e{sup -} storage ring at SLAC. The flavor of the other B meson in the event is determined from the charge of another high-momentum lepton.

  5. An exploratory study of drug use in bar environments

    PubMed Central

    Trocki, Karen; Michalak, Laurence; McDaniel, Patricia

    2010-01-01

    The purpose of this paper is to explore the characteristics of bars where drug use was observed compared to those where no drug use was observed. The study was done through a combination of qualitative and quantitative techniques gleaned through observations and interviews. Among the most important of indicators were the type of activity (particularly dancing) and the level of rowdiness evident in the bars. In addition drug use bars had higher levels of other types of rule-breaking. Patron characteristics (more men) and behavioral patterns (more sexual risk-taking) also distinguished these bars. PMID:25221431

  6. Multipacting Analysis of the Superconducting Parallel-bar Cavity

    SciTech Connect

    S.U. De Silva, J.R. Delayen,

    2011-03-01

    The superconducting parallel-bar cavity is a deflecting/crabbing cavity with attractive properties, compared to other conventional designs, that is being considered for a number of applications. Multipacting can be a limiting factor to the performance of in any superconducting structure. In the parallel-bar cavity the main contribution to the deflection is due to the transverse deflecting voltage, between the parallel bars, making the design potentially prone to multipacting. This paper presents the results of analytical calculations and numerical simulations of multipacting in the parallel-bar cavity with resonant voltage, impact energies and corresponding particle trajectories.

  7. The Dependence of Bar Fraction on Galaxy Properties

    NASA Astrophysics Data System (ADS)

    Erwin, Peter

    2009-05-01

    I present an analysis of how the fraction of galaxies with bars depends on galaxy properties, using the optical bar classifications of the RC3 catalog and data from the literature. The most striking result is a strong anti-correlation between bars and galaxy mass: the more massive a galaxy is, the less likely it is to host a bar. The trend is strongest when rotation velocity is used, which suggests that the halo mass might be the most important factor. For example, almost 90% of early-type spirals with Vrot < 150 km/s are barred; but the fraction drops to 40% by the time Vrot > 300 km/s. Bar fractions are systematically lower for S0 galaxies, even when the mass dependence is taken into account. I find no dependence of bar fraction on gas mass fraction, which may put constraints on models where high gas fractions are either necessary for bar persistence, or enhance bar weakening and destruction.

  8. Interaction of Bar Morphology and Riparian Vegetation in Gravel-Bed Rivers

    NASA Astrophysics Data System (ADS)

    Francalanci, S.; Bertoldi, W.; Siviglia, A.; Solari, L.; Toffolon, M.; Vetsch, D.

    2013-12-01

    Gravel-bed rivers are often characterized by complex bed topography, including single- and multiple-row alternate bars, bed undulations associated with channel curvature, riffle and pool sequences, presence of riparian vegetation in the floodplain, etc. The interaction of these features results in different morphologies with complex patterns and dynamics. The present work investigates the effect of the riparian vegetation on the bar dynamics, in particular it is investigated how the vegetation, which grows during the dry season on the bars, can alter the topographic patterns evolution during flood conditions. Performing two-dimensional numerical simulations we try to answer to the following research questions: which is the interaction of vegetation with bar morphology? which are the changes in sediment discharge and flow resistance, at cross-sectional and reach scale? Which are the changes in distribution of emerged and submerged areas, and potential feedbacks for vegetation growth? Which is the effect of vegetation on bar wave-length? The code BASEMENT (Faeh et al., 2010) has been used for performing the numerical runs. It has been properly modified in order to deal with the numerical description of the vegetation. The vegetation was allowed to grow during the dry season on the top of dry emergent areas, and the vertical distribution of vegetation in equilibrium condition was modeled as a function of the bed elevation using a simple analytical formulation, following Marani et al (2013). Then, during the flood events we assume that the vegetation distribution does not change, and that it can only be uprooted if the bed is eroded.The flow resistance was divided into a resistance exerted by the soil and a resistance exerted by the plants (Crosato and Saleh, 2010; Li and Millar, 2011); in this way it was possible to reproduce both the decrease in bed shear stress, reducing the sediment transport capacity of the flow within the plants, and the increase in hydraulic

  9. Variable Dynamic Testbed Vehicle: Dynamics Analysis

    NASA Technical Reports Server (NTRS)

    Lee, A. Y.; Le, N. T.; Marriott, A. T.

    1997-01-01

    The Variable Dynamic Testbed Vehicle (VDTV) concept has been proposed as a tool to evaluate collision avoidance systems and to perform driving-related human factors research. The goal of this study is to analytically investigate to what extent a VDTV with adjustable front and rear anti-roll bar stiffnesses, programmable damping rates, and four-wheel-steering can emulate the lateral dynamics of a broad range of passenger vehicles.

  10. An Infrared Portrait of the Barred Spiral Galaxy Messier 83

    NASA Astrophysics Data System (ADS)

    2001-11-01

    Messier 83 (M83) is a relatively nearby spiral galaxy with a pronounced bar-like structure. It is located in the southern constellation Hydra (The Water-Snake) and is also known as NGC 5236 ; the distance is approximately 12 million light-years. Images of M83 obtained in visible light - like the VLT photo published exactly two years ago ( ESO PR 18/99 ) - show clumpy, well-defined spiral arms that are rich in young stars while the disk reveals a complex system of intricate dust lanes. This galaxy is known to be a site of vigorous star formation and no less than six supernovae (exploding stars) have been observed in M83 during the past century. It is a fairly symmetrical object and possesses no nearby companions. Gas dynamics and galaxy bars Investigations of gas motions in the nucleus and in the main disk play a key role in understanding the structure and evolution of barred spiral galaxies like M83. Inflow of gas towards the center caused by a mass distribution that is not circularly symmetric is often invoked to explain certain observed phenomena, e.g., the feeding of Active Galactic Nuclei (AGNs, see also the report about recent observations in three such galaxies in ESO PR 18/01 ), and the fueling of bursts of star formation in the nuclear region. Some astronomers think that this process may cause a change of a galaxy's (morphological) type, for instance from barred to normal spiral galaxy. It has also been suggested that the development of spiral structures in galactic disks may be due to central stellar bars. Interstellar gas that is subject to periodical perturbations by the non-circularly symmetrical gravitational field in a barred system will develop a "density wave" that attracts neighbouring stars and gas. The local density increases and once a certain ("critical") value is reached, star formation is "ignited" in this area. The mass distribution In order to better understand phenomena like these, it is essential to know in detail the distribution of

  11. Restoring Alternate Bar Sequences in Large Rivers: Flow, Sediment, and Elbow Room

    NASA Astrophysics Data System (ADS)

    Trush, W. J.; McBain, S. M.

    2006-12-01

    Large river management must rely on crucial premises that the river channel is a product of its watershed's hydrology and the space within which it moves, and that native plant and animal species have evolved with, and still depend on, the natural annual hydrograph. While interesting academically, these premises may appear to offer very limited utility as management tools, given few large rivers in the Pacific Northwest and elsewhere have escaped major hydrologic and geomorphic change. The opposite, however, is likely true. Without reconstructing and incorporating an historical perspective, large river restoration will fail. Healthy river ecosystems can be achieved without completely restoring the natural unregulated hydrology, sediment supply regime, and original migration corridor. Usually there is little choice. An historical perspective identifies crucial threshold streamflow, sediment, and corridor processes driving a healthy river ecosystem. Alternating point bar sequences are the building blocks of alluvial rivers that also function as the physical template for creating abundant, high quality habitat for fish, amphibians, and riparian plant. While alternating bars can be created with bulldozers, their evolution, longevity, and quality will endure only if key geomorphic and biological threshold processes are provided by naturally variable annual hydrographs. An historical perspective therefore must identify how unregulated annual hydrographs once created and fostered dynamic alternating bar sequences. Restoration practitioners must then devise ways to restore these processes while purposefully cheating Mother Nature of some of her flow, sediment, and corridor width (elbow room). Two commonly prescribed high flow releases, flushing flows and the bankfull discharge, address several geomorphic requirements yet neither, or the two combined, can restore and maintain alternating bar sequences. Higher flood peak magnitudes from winter floods and spring snowmelt

  12. Quark mass matrices presented by a power series expansion in t bar V sub u s t bar

    SciTech Connect

    Koide, Y. ); Fusaoka, H. ); Habe, C. )

    1992-12-01

    In a general three-family Hermitian quark mass matrix model ({ital M}{sub {ital u}},{ital M}{sub {ital d}}), if we take a quark basis on which {ital M}{sub {ital u}} takes a diagonal form {ital D}{sub {ital u}}, the structure of {ital M}{sub {ital d}}{equivalent to}{ital {cflx M}} is almost determined by three down-quark masses ({ital m}{sub {ital d}},{ital m}{sub {ital s}},{ital m}{sub {ital b}}) and three Kobayashi-Maskawa matrix parameters ({vert bar}{ital V}{sub {ital u}{ital s}}{vert bar},{vert bar}{ital V}{sub {ital c}{ital b}}{vert bar},{vert bar}{ital V}{sub {ital u}{ital b}}{vert bar}), except for phases of the matrix elements {ital {cflx M}}{sub {ital i}{ital j}}. By using the experimental facts {vert bar}{ital V}{sub {ital u}{ital s}}{vert bar}{similar to}{lambda}, {vert bar}{ital V}{sub {ital c}{ital b}}{vert bar}{similar to}{lambda}{sup 2}, {vert bar}{ital V}{sub {ital u}{ital b}}{vert bar}{similar to}{lambda}{sup 3}, and {ital m}{sub {ital d}}/{ital m}{sub {ital s}}{similar to}{ital m}{sub {ital s}}/{ital m}{sub {ital b}}{similar to}{lambda}{sup 2}, the mass matrices ({ital D}{sub {ital u}},{ital {cflx M}}) are presented in terms of a power series in {lambda}.

  13. Nutritional Evaluation of NASA's Rodent Food Bar Diet

    NASA Technical Reports Server (NTRS)

    Barrett, Joyce E.; Yu, Diane S.; Dalton, Bonnie P.

    2000-01-01

    Tests are being conducted on NASA's rodent Food Bar in preparation for long-term use as the rat and mouse diet aboard the International Space Station. Nutritional analyses are performed after the bars are manufactured and then repeated periodically to determine nutritional stability. The primary factors analyzed are protein, ash, fat, fiber, moisture, amino acids, fatty acids, and minerals. Nutrient levels are compared to values published in the National Research Council's dietary requirements for rodents, and also to those contained in several commonly used commercial rodent lab diets. The Food Bar is manufactured from a powdered diet to which moisture is added as it is processed through an extruder. The bars are dipped into potassium sorbate, vacuum-sealed, and irradiated. In order to determine nutrient changes during extrusion and irradiation, the powdered diet, the non-irradiated bars, and the irradiated bars are all analyzed. We have observed lower values for some nutrients (iodine, vitamin K, and iron) in the Food Bars compared with NRC requirements. Many nutrients in the Food Bars are contained at a higher level than levels in the NRC requirements. An additional factor we are investigating is the 26% moisture level in the Food Bars, which drops to about 15% within a week, compared to a stable 10% moisture in many standard lab chow diets. In addition to the nutritional analyses, the food bar is being fed to several strains of rats and mice, and feeding study and necropsy results are being observed (Barrett et al, unpublished data). Information from the nutritional analyses and from the rodent studies will enable us to recommend the formulation that will most adequately meet the rodent Food Bar requirements for long-term use aboard the Space Station.

  14. Charm Spectroscopy at BaBar

    SciTech Connect

    Poireau, Vincent; /Annecy, LAPP

    2007-12-21

    We present a mini-review on charm spectroscopy at the BABAR experiment. We first report on the c{bar s} meson spectrum, and present precise measurements of the D{sub s1}(2536) meson as well as the properties of the many new states discovered since 2003 (D*{sub s0}(2317), D{sub s1}(2460), D*{sub sJ}(2860), and D{sub sJ}(2700) mesons). We then discuss about charmed baryons observed recently in the BABAR experiment: {Omega}{sub c}{sup 0} and {Omega}*{sub c}{sup 0} css baryons, {Lambda}{sub c}(2940){sup +} udc baryon and the {Xi}{sub c} usc/dsc baryons.

  15. Symmetrical Taylor impact of glass bars

    NASA Astrophysics Data System (ADS)

    Murray, N. H.; Bourne, N. K.; Field, J. E.; Rosenberg, Z.

    1998-07-01

    Brar and Bless pioneered the use of plate impact upon bars as a technique for investigating the 1D stress loading of glass but limited their studies to relatively modest stresses (1). We wish to extend this technique by applying VISAR and embedded stress gauge measurements to a symmetrical version of the test in which two rods impact one upon the other. Previous work in the laboratory has characterised the glass types (soda-lime and borosilicate)(2). These experiments identify the failure mechanisms from high-speed photography and the stress and particle velocity histories are interpreted in the light of these results. The differences in response of the glasses and the relation of the fracture to the failure wave in uniaxial strain are discussed.

  16. Bus bar electrical feedthrough for electrorefiner system

    DOEpatents

    Williamson, Mark; Wiedmeyer, Stanley G; Willit, James L; Barnes, Laurel A; Blaskovitz, Robert J

    2013-12-03

    A bus bar electrical feedthrough for an electrorefiner system may include a retaining plate, electrical isolator, and/or contact block. The retaining plate may include a central opening. The electrical isolator may include a top portion, a base portion, and a slot extending through the top and base portions. The top portion of the electrical isolator may be configured to extend through the central opening of the retaining plate. The contact block may include an upper section, a lower section, and a ridge separating the upper and lower sections. The upper section of the contact block may be configured to extend through the slot of the electrical isolator and the central opening of the retaining plate. Accordingly, relatively high electrical currents may be transferred into a glovebox or hot-cell facility at a relatively low cost and higher amperage capacity without sacrificing atmosphere integrity.

  17. /bar p/p collider physics

    SciTech Connect

    Green, D.

    1989-03-01

    This note encompasses a set of six lectures given at the summer school held at Campos Do Jordao in January of 1989 near Sao Paulo, Brazil. The intent of the lectures was to describe the physics of /bar p/p at CERN and Fermilab. Particular attention has been paid to making a self contained presentation to a prospective audience of graduate students. Since large Monte Carlo codes might not be available to all members of this audience, great reliance was placed on ''back of the envelope estimates.'' Emphasis was also placed on experimental data rather than theoretical speculation, since predictions for, for example, supersymmetric particle production are easily obtained by transcription of formulae already obtained. 9 refs., 67 figs., 2 tabs.

  18. Anisakiasis - is the sushi bar guilty?

    PubMed

    Oshima, T

    1987-02-01

    Since 1972, Japan and some other countries such as the USA have seen a sudden increase in cases of anisakiasis (infection with Anisakis sp.) and codworm an isakiasis (infection with the codworm, Pseudoterranova [= Phocanema] decipiens). Larval stages of these nematodes occur in the muscles of a variety of fish and squid, and ingestion of raw and undercooked fish or squid is the prime route of human infection. Thus the Japanese style of eating sashimi (sliced raw fish fillet) and the increasing popularity of sushi bars where such dishes are served, has often been suggested as contributing to the spread of anisakid infections. In this article, Tomoo Oshima discusses the current status of anisakiasis and codworm anisakiasis, showing that the apparent increase in human cases is related more to advances in diagnosis than to the commercialization of sushi.

  19. High spatial resolution observations of Orion bright bar: CS (J = 1-0) and H51. cap alpha. emission

    SciTech Connect

    Omodaka, T.; Hayashi, M.; Hasegawa, T.

    1984-07-15

    High-resolution strip maps of CS (J = 1-0) and H51..cap alpha.. line emission across the Orion bright bar are presented. The intensity of CS emission is weaker in the H II region with a rapid increase at the optical bar, while the H51 ..cap alpha.. line was detected only on the side of the H II region. The variation of the CS intensity can be reproduced by a beam-convolved step function with the position of the step coincident with the ionization front. The molecular cloud associated with the bright bar is redshifted relative to the ambient molecular cloud by about 2 km s/sup -1/. This may suggest the dynamical interactions between the molecular cloud and the H II region excited by the Trapezium stars.

  20. Objectivity in Grading: The Promise of Bar Codes

    ERIC Educational Resources Information Center

    Jae, Haeran; Cowling, John

    2009-01-01

    This article proposes the use of a new technology to assure student anonymity and reduce bias hazards: identifying students by using bar codes. The limited finding suggests that the use of bar codes for assuring student anonymity could potentially cause students to perceive that grades are assigned more fairly and reassure teachers that they are…

  1. 27 CFR 70.266 - Credit against barred liability.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 2 2014-04-01 2014-04-01 false Credit against barred... Collection of Excise and Special (Occupational) Tax Limitations § 70.266 Credit against barred liability. Any credit against a liability in respect of any taxable year shall be void if the collection of...

  2. 27 CFR 70.266 - Credit against barred liability.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 2 2013-04-01 2013-04-01 false Credit against barred... Collection of Excise and Special (Occupational) Tax Limitations § 70.266 Credit against barred liability. Any credit against a liability in respect of any taxable year shall be void if the collection of...

  3. 32 CFR 1908.22 - Requests barred by res judicata.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 32 National Defense 6 2011-07-01 2011-07-01 false Requests barred by res judicata. 1908.22 Section 1908.22 National Defense Other Regulations Relating to National Defense CENTRAL INTELLIGENCE AGENCY... EXECUTIVE ORDER 12958 Agency Action on Mdr Requests § 1908.22 Requests barred by res judicata....

  4. 32 CFR 1908.22 - Requests barred by res judicata.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 32 National Defense 6 2010-07-01 2010-07-01 false Requests barred by res judicata. 1908.22 Section 1908.22 National Defense Other Regulations Relating to National Defense CENTRAL INTELLIGENCE AGENCY... EXECUTIVE ORDER 12958 Agency Action on Mdr Requests § 1908.22 Requests barred by res judicata....

  5. Researchers Misunderstand Confidence Intervals and Standard Error Bars

    ERIC Educational Resources Information Center

    Belia, Sarah; Fidler, Fiona; Williams, Jennifer; Cumming, Geoff

    2005-01-01

    Little is known about researchers' understanding of confidence intervals (CIs) and standard error (SE) bars. Authors of journal articles in psychology, behavioral neuroscience, and medicine were invited to visit a Web site where they adjusted a figure until they judged 2 means, with error bars, to be just statistically significantly different (p…

  6. 5 CFR 9701.305 - Bar on collective bargaining.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 5 Administrative Personnel 3 2010-01-01 2010-01-01 false Bar on collective bargaining. 9701.305 Section 9701.305 Administrative Personnel DEPARTMENT OF HOMELAND SECURITY HUMAN RESOURCES MANAGEMENT... HUMAN RESOURCES MANAGEMENT SYSTEM Pay and Pay Administration General § 9701.305 Bar on...

  7. 5 CFR 9701.205 - Bar on collective bargaining.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 5 Administrative Personnel 3 2010-01-01 2010-01-01 false Bar on collective bargaining. 9701.205 Section 9701.205 Administrative Personnel DEPARTMENT OF HOMELAND SECURITY HUMAN RESOURCES MANAGEMENT... HUMAN RESOURCES MANAGEMENT SYSTEM Classification General § 9701.205 Bar on collective bargaining....

  8. Sharing the Spotlight: Humane Education and Bar Graphs.

    ERIC Educational Resources Information Center

    Dewey, Paul

    1987-01-01

    Promotes the use of humane education as a vehicle for teaching students how to make bar graphs. Provides ideas for bar graph activities for both primary- and intermediate-grade children that focus on different kinds of domestic and wild animals. Suggests expanded types of graphing activities involving survey techniques. (TW)

  9. Energy Drinks and Food Bars: Power or Hype?

    MedlinePlus

    ... How Can I Help a Friend Who Cuts? Energy Drinks and Food Bars: Power or Hype? KidsHealth > ... nutritivas: ¿Energía o mera exageración? The Buzz on Energy Foods Energy drinks and nutrition bars often make ...

  10. Nutrition Education Strategies: A Trip to the Salad Bar.

    ERIC Educational Resources Information Center

    Nutter, June; Kotch, Anne

    1995-01-01

    Learning activities related to visiting a salad bar can help students apply basic nutrition concepts to real-life situations and make healthier choices at restaurants and in food preparation. The paper describes a class activity involving students in setting up a salad bar, making choices among ingredients and dressings, and taking home leftovers.…

  11. 21 CFR 610.67 - Bar code label requirements.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 7 2010-04-01 2010-04-01 false Bar code label requirements. 610.67 Section 610.67 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) BIOLOGICS GENERAL BIOLOGICAL PRODUCTS STANDARDS Labeling Standards § 610.67 Bar code label...

  12. 21 CFR 610.67 - Bar code label requirements.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 7 2012-04-01 2012-04-01 false Bar code label requirements. 610.67 Section 610.67 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) BIOLOGICS GENERAL BIOLOGICAL PRODUCTS STANDARDS Labeling Standards § 610.67 Bar code label...

  13. 21 CFR 610.67 - Bar code label requirements.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 7 2014-04-01 2014-04-01 false Bar code label requirements. 610.67 Section 610.67 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) BIOLOGICS GENERAL BIOLOGICAL PRODUCTS STANDARDS Labeling Standards § 610.67 Bar code label...

  14. 21 CFR 610.67 - Bar code label requirements.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 7 2013-04-01 2013-04-01 false Bar code label requirements. 610.67 Section 610.67 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) BIOLOGICS GENERAL BIOLOGICAL PRODUCTS STANDARDS Labeling Standards § 610.67 Bar code label...

  15. Calculation of error bars for laser damage observations

    NASA Astrophysics Data System (ADS)

    Arenberg, Jonathan W.

    2008-10-01

    The use of the error bar is a critical means of communicating the quality of individual data points and a processed result. Understanding the error bar for a processed measurement depends on the measurement technique being used and is the subject of many recent works, as such, the paper will confine its scope to the determination of the error bar on a single data point. Many investigators either ignore the error bar altogether or use a "one size error fits all" method, both of these approaches are poor procedure and misleading. It is the goal of this work to lift the veil of mysticism surrounding error bars for damage observations and make their description, calculation and use, easy and commonplace. This paper will rigorously derive the error bar size as a function of the experimental parameters and observed data and will concentrate on the dependent variable, the cumulative probability of damage. The paper will begin with a discussion of the error bar as a measure of data quality or reliability. The expression for the variance in the parameters is derived via standard methods and converted to a standard deviation. The concept of the coverage factor is introduced to scale the error bar to the desired confidence level, completing the derivation

  16. VIEW OF SHEAR (ELECTRIC POWERED), SCALE HOUSE TO LEFT. BARS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW OF SHEAR (ELECTRIC POWERED), SCALE HOUSE TO LEFT. BARS ARE PLACED ON WEIGHING SCALE SHOWN LOWER LEFT. 15-TON CLEVELAND CRANE HANDLES BARS FOR FINAL LOADING INTO RAILROAD CARS (12" BAY) AND FOR MOVING FROM TABLE TO SHEAR TABLE. - Cambria Iron Company, Gautier Works, 12" Mill, Clinton Street & Little Conemaugh River, Johnstown, Cambria County, PA

  17. 49 CFR 393.90 - Buses, standee line or bar.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 5 2010-10-01 2010-10-01 false Buses, standee line or bar. 393.90 Section 393.90... NECESSARY FOR SAFE OPERATION Miscellaneous Parts and Accessories § 393.90 Buses, standee line or bar. Except as provided below, every bus, which is designed and constructed so as to allow standees, shall...

  18. 49 CFR 393.90 - Buses, standee line or bar.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 5 2011-10-01 2011-10-01 false Buses, standee line or bar. 393.90 Section 393.90... NECESSARY FOR SAFE OPERATION Miscellaneous Parts and Accessories § 393.90 Buses, standee line or bar. Except as provided below, every bus, which is designed and constructed so as to allow standees, shall...

  19. 37. Tap room with bar, looking from east to west ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    37. Tap room with bar, looking from east to west showing part of the mural (on north wall) depicting nautical and whaling themes. (mural and bar were removed 1998 - 99 respectively.) - Fort Ord, Soldiers' Club, California State Highway 1 near Eighth Street, Seaside, Monterey County, CA

  20. Unitarity Triangle Angle Measurements at BaBar

    SciTech Connect

    Latham, Thomas E.; /SLAC

    2005-06-30

    We present recent results of measurements of the Unitarity Triangle angles alpha, beta and gamma made with the BaBar detector at the PEP-II asymmetric B factory. We present recent results of measurements of the Unitarity Triangle angles alpha, beta and gamma made with the BaBar detector at the PEP-II asymmetric B factory.

  1. 5 CFR 838.505 - Barring payment of refunds.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... REGULATIONS (CONTINUED) COURT ORDERS AFFECTING RETIREMENT BENEFITS Requirements for Court Orders Affecting Refunds of Employee Contributions § 838.505 Barring payment of refunds. A court order barring payment of a refund of employee contributions is not a court order acceptable for processing unless— (a) It...

  2. 5 CFR 838.505 - Barring payment of refunds.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... REGULATIONS (CONTINUED) COURT ORDERS AFFECTING RETIREMENT BENEFITS Requirements for Court Orders Affecting Refunds of Employee Contributions § 838.505 Barring payment of refunds. A court order barring payment of a refund of employee contributions is not a court order acceptable for processing unless— (a) It...

  3. 5 CFR 838.505 - Barring payment of refunds.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... REGULATIONS (CONTINUED) COURT ORDERS AFFECTING RETIREMENT BENEFITS Requirements for Court Orders Affecting Refunds of Employee Contributions § 838.505 Barring payment of refunds. A court order barring payment of a refund of employee contributions is not a court order acceptable for processing unless— (a) It...

  4. Detail of tension bars at end posts western truss. Shows ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Detail of tension bars at end posts western truss. Shows adjustable bars at top of structure; diagonal and vertical members on truss are not adjustable. Looking north from civilian land. - Naval Supply Annex Stockton, Rough & Ready Island, Stockton, San Joaquin County, CA

  5. Detail of tension bars at end posts western truss. Shows ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Detail of tension bars at end posts western truss. Shows adjustable bars at top of structure; diagonal and vertical members on truss are not adjustable. Looking north from civilian land. - Naval Supply Annex Stockton, Daggett Road Bridge, Daggett Road traversing Burns Cut Off, Stockton, San Joaquin County, CA

  6. Bar-Code System for a Microbiological Laboratory

    NASA Technical Reports Server (NTRS)

    Law, Jennifer; Kirschner, Larry

    2007-01-01

    A bar-code system has been assembled for a microbiological laboratory that must examine a large number of samples. The system includes a commercial bar-code reader, computer hardware and software components, plus custom-designed database software. The software generates a user-friendly, menu-driven interface.

  7. Sweet! Candy Bar Activity Teaches CAD, Math, and Graphics

    ERIC Educational Resources Information Center

    Granlund, George

    2009-01-01

    By far, the tastiest technology learning activity that the author's students work on is the development of the design of a chocolate candy bar. This article describes how the author implemented the candy bar activity. The activity gives students an opportunity to design a product and to take it from concept through to production.

  8. Spending Too Much Time at the Galactic Bar: Chaotic Fanning of the Ophiuchus Stream

    NASA Astrophysics Data System (ADS)

    Price-Whelan, Adrian M.; Sesar, Branimir; Johnston, Kathryn V.; Rix, Hans-Walter

    2016-06-01

    The Ophiuchus stellar stream is peculiar: (1) its length is short given the age of its constituent stars, and (2) several probable member stars have dispersions in sky position and velocity that far exceed those seen within the stream. The stream’s proximity to the Galactic center suggests that its dynamical history is significantly influenced by the Galactic bar. We explore this hypothesis with models of stream formation along orbits consistent with Ophiuchus’ properties in a Milky Way potential model that includes a rotating bar. In all choices for the rotation parameters of the bar, orbits fit to the stream are strongly chaotic. Mock streams generated along these orbits qualitatively match the observed properties of the stream: because of chaos, stars stripped early generally form low-density, high-dispersion “fans” leaving only the most recently disrupted material detectable as a strong over-density. Our models predict that there should be a significant amount of low-surface-brightness tidal debris around the stream with a complex phase-space morphology. The existence of or lack of these features could provide interesting constraints on the Milky Way bar and would rule out formation scenarios for the stream. This is the first time that chaos has been used to explain the properties of a stellar stream and is the first demonstration of the dynamical importance of chaos in the Galactic halo. The existence of long, thin streams around the Milky Way, presumably formed along non- or weakly chaotic orbits, may represent only a subset of the total population of disrupted satellites.

  9. A Pilot Study of Bar Codes in a Canadian Hospital

    PubMed Central

    Brisseau, Lionel; Chiveri, Andrei; Lebel, Denis; Bussières, Jean-François

    2011-01-01

    Background: In 2004, the US Food and Drug Administration issued a new rule requiring most prescription and some over-the-counter pharmaceutical products to carry bar codes down to the level of individual doses, with the intent of reducing the number of medication errors. Despite these regulatory changes in the United States, Health Canada has not yet adopted any mandatory bar-coding of drugs. Objective: To evaluate the feasibility of using commercial bar codes for receipt and preparation of drug products and to evaluate the readability of the bar codes printed on various levels of drug packaging. Methods: This cross-sectional observational pilot study was conducted in the Pharmacy Department of a Canadian mother–child university hospital centre in July 2010. For the purposes of the study, research drugs and cytotoxic drugs in various storage areas, as well as locally compounded medications with bar codes generated in house, were excluded. For all other drug products, the presence or absence of bar codes was documented for each level of packaging, along with the trade and generic names, content (i.e., drug product), quantity of doses or level of packaging, therapeutic class (if applicable), type of bar code (1- or 2-dimensional symbology), alphanumeric value contained in the bar code, standard of reference used to generate the alphanumeric value (Universal Product Code [UPC], Global Trade Item Number [GTIN], or unknown), and readability of the bar codes by 2 scanners. Results: Only 33 (1.9%) of the 1734 products evaluated had no bar codes on any level of packaging. Of the 2875 levels of packaging evaluated, 2021 (70.3%) had at least one bar code. Of the 2384 bar codes evaluated, 2353 (98.7%) were linear (1-dimensional) and 31 (1.3%) were 2-dimensional. Well over three-quarters (2112 or 88.6%) of the evaluated bar codes were readable by at least 1 of the 2 scanners used in the study. Conclusions: On the basis of these results, bar-coding could be used for receipt

  10. Nearshore bars and the break-point hypothesis

    USGS Publications Warehouse

    Sallenger, A.H., Jr.; Howd, P.A.

    1989-01-01

    The set of hypotheses calling for bar formation at the break point was tested with field data. During two different experiments, waves were measured across the surf zone coincident with the development of a nearshore bar. We use a criterion, based on the wave height to depth ratio, to determine the offshore limit of the inner surf zone. During the first experiment, the bar became better developed and migrated offshore while remaining well within the inner surf zone. During the second experiment, the surf zone was narrower and we cannot rule out the possibility of break point processes contributing to bar development. We conclude that bars are not necessarily coupled with the break point and can become better developed and migrate offshore while being in the inner surf zone landward from initial wave breaking in the outer surf zone. ?? 1989.

  11. Study of aging and embrittlement of microalloyed steel bars

    NASA Astrophysics Data System (ADS)

    Campillo, B.; Perez, R.; Martinez, L.

    1996-10-01

    The aging of hooks, anchors, and other bent reinforcing steel bars in concrete structures are considered in modern international standards. Rebend test procedures have been designed in order to predict the aging embrittlement susceptibility by submerging bent reinforcing bar specimens in boiling water. Subsequently the bars are rebent or straightened in order to determine the loss of ductility or embrittlement of the aged material. The present work considers the influence of carbon, sulfur, and niobium on the performance of reinforcing bars in rebend tests of 300 heats of microalloyed steel bars with a variety of compositions. The microstructural evidence and the statistical results clearly indicate the strong influence of carbon and sulfur on rebend failure, while niobium-rich precipitates contribute to the hardening of the ferrite grains during aging.

  12. Hader bar and clip attachment retained mandibular complete denture

    PubMed Central

    Singh, Kunwarjeet; Gupta, Nidhi; Kapoor, Vikram; Gupta, Ridhimaa

    2013-01-01

    Bar and clip attachments significantly improve the level of satisfaction of denture-wearing patients by enhancing the retention and stability of the prosthesis. These attachments have been most commonly used for connecting the prosthesis to implants, but they can be effectively used to retain tooth-supported prosthesis as well. The primary functions of bar attachments are splinting the abutments together, even distribution of forces to the abutments and supporting areas, guiding the prosthesis into place, improving the retention, stability, support and comfort of the patient. The primary requirement for the use of bar attachments is the availability of sufficient vertical and buccolingual space for the proper placement of the bar, sleeves, teeth arrangement and sufficient thickness of acrylic denture base to minimise incidence of denture fracture in the area of bar assembly. PMID:24145505

  13. Hydrodynamic and geomorphic controls on mouth bar evolution

    NASA Astrophysics Data System (ADS)

    Esposito, Christopher R.; Georgiou, Ioannis Y.; Kolker, Alexander S.

    2013-04-01

    While river deltas are one of the major repositories for sediments and carbon on Earth, there exists a paucity of field data on the formation of distributary mouth bars—one of their key features. Here we present results from an experiment that tested a model of mouth bar development using hydroacoustic, optical, sedimentary, and geochemical tools on a mouth bar in a crevasse splay near the mouth of the Mississippi River. Our results validate an existing model for mouth bar development, which we extend to explain mouth bar stratigraphy. We propose that changes across a hydrological cycle are important for mouth bar development, resulting in a stratigraphy that has alternating fine and coarse grain sediments. Results also indicate that sand is carried up to 6 km from the main stem of the Mississippi River, despite repeated channel bifurcations, which has important implications for our interpretation of the rock record, understanding of coastal sedimentary systems, and the restoration of large deltas.

  14. What is the Peak Stress in Ceramic Bar Impacts?

    NASA Astrophysics Data System (ADS)

    Manoj Simha, C. Hari; Bless, Stephan; Bedford, Anthony

    1999-06-01

    The bar impact experiment has been extensively used to characterize the high strain rate properties of high strength ceramics. In particular, alumina AD-99.5 has been widely studied; both stress gauge and VISAR bar impact data are available for this material. We have performed plate-on-bar impact experiments using this material in some novel configurations. An interface was introduced in the target bar (by cutting it) in the zone where the material fails by axial splitting. Such experiments resulted in a dramatic drop in the peak stress measured in the experiment, when compared to experiments with no interface. The measured stress levels were reproduced by a model that contains no explicit 1-D strength parameter. The main conclusion is that the bar impact experiment for a ceramic is a structural measurement, so the peak stress measurement cannot be correlated to some intrinsic strength of the ceramic.

  15. New States and Charmonium Spectroscopy at BaBar

    SciTech Connect

    Dunwoodie, W.; /SLAC

    2011-12-06

    Several charmonium-like states above D{bar D} threshold have been discovered at the Belle and BaBar B-factories. Some are produced via Initial State Radiation (e.g. Y(4260) and Y(4350)), and some are observed in B meson decays (e.g. X(3872), Y(3940), and Z-(4430)). The Z-(4430) state has generated a great deal of interest, having minimum quark content (c{bar c}d{bar u}) and, thus, representing the unequivocal manifestation of a four-quark meson state. Here we summarize recent BaBar results on the Y(4260), X(3872), Y(3940), and on a search for the Z-(4430).

  16. Revealing galactic scale bars with the help of Galaxy Zoo

    NASA Astrophysics Data System (ADS)

    Masters, Karen L.

    2015-03-01

    We use visual classifications of the brightest 250,000 galaxies in the Sloan Digital Sky Survey Main Galaxy Sample provided by citizen scientists via the Galaxy Zoo project (www.galaxyzoo.org, Lintott et al. 2008) to identify a sample of local disc galaxies with reliable bar identifications. These data, combined with information on the atomic gas content from the ALFALFA survey (Haynes et al. 2011) show that disc galaxies with higher gas content have lower bar fractions. We use a gas deficiency parameter to show that disc galaxies with more/less gas than expected for their stellar mass are less/more likely to host bars. Furthermore, we see that at a fixed gas content there is no residual correlation between bar fraction and stellar mass. We argue that this suggests previously observed correlations between galaxy colour/stellar mass and (strong) bar fraction (e.g. from the sample in Masters et al. 2011, and also see Nair & Abraham 2010) could be driven by the interaction between bars and the gas content of the disc, since more massive, optically redder disc galaxies are observed to have lower gas contents. Furthermore we see evidence that at a fixed gas content the global colours of barred galaxies are redder than those of unbarred galaxies. We suggest that this could be due to the exchange of angular momentum beyond co-rotation which might stop a replenishment of gas from external sources, and act as a source of feedback to temporarily halt or reduce the star formation in the outer parts of barred discs. These results (published as Masters et al. 2012) combined with those of Skibba et al. (2012), who use the same sample to show a clear (but subtle and complicated) environmental dependence of the bar fraction in disc galaxies, suggest that bars are intimately linked to the evolution of disc galaxies.

  17. Measurement of the Semileptonic B-bar->D{sup (*)}{tau}{nu}-bar{sub {tau}} Decays at BABAR

    SciTech Connect

    Lopes Pegna, David

    2010-02-10

    Semileptonic B meson decays into final states containing the tau lepton are of interesting as they provide information on the Standard Model as well as a window on new physics effects. We present results on B-bar->D{sup (*)}taunu-bar{sub tau} decays where the second B in the event is fully reconstructed.

  18. Lawyers for Literacy. A Bar Leadership Manual. A Special Service Publication of the American Bar Association's Task Force on Literacy.

    ERIC Educational Resources Information Center

    American Bar Association, Washington, DC.

    This manual is designed to provide materials to help state and local bar associations become involved with the literacy issue. Chapter 1 provides an overview of illiteracy as a very serious problem. Chapter 2 describes major public and private efforts to combat illiteracy. Chapter 3 explains why the bar associations should be involved. Chapter 4…

  19. A mathematical high bar-human body model for analysing and interpreting mechanical-energetic processes on the high bar.

    PubMed

    Arampatzis, A; Brüggemann, G P

    1998-12-01

    The aims of this study were: 1. To study the transfer of energy between the high bar and the gymnast. 2. To develop criteria from the utilisation of high bar elasticity and the utilisation of muscle capacity to assess the effectiveness of a movement solution. 3. To study the influence of varying segment movement upon release parameters. For these purposes a model of the human body attached to the high bar (high bar-human body model) was developed. The human body was modelled using a 15-segment body system. The joint-beam element method (superelement) was employed for modelling the high bar. A superelement consists of four rigid segments connected by joints (two Cardan joints and one rotational-translational joint) and springs (seven rotation springs and one tension-compression spring). The high bar was modelled using three superelements. The input data required for the high bar human body model were collected with video-kinematographic (50 Hz) and dynamometric (500 Hz) techniques. Masses and moments of inertia of the 15 segments were calculated using the data from the Zatsiorsky et al. (1984) model. There are two major phases characteristic of the giant swing prior to dismounts from the high bar. In the first phase the gymnast attempts to supply energy to the high bar-humanbody system through muscle activity and to store this energy in the high bar. The difference between the energy transferred to the high bar and the reduction in the total energy of the body could be adopted as a criterion for the utilisation of high bar elasticity. The energy previously transferred into the high bar is returned to the body during the second phase. An advantageous increase in total body energy at the end of the exercise could only be obtained through muscle energy supply. An index characterising the utilisation of muscle capacity was developed out of the difference between the increase in total body energy and the energy returned from the high bar. A delayed and initially slow but

  20. THE HST/ACS COMA CLUSTER SURVEY. VIII. BARRED DISK GALAXIES IN THE CORE OF THE COMA CLUSTER

    SciTech Connect

    Marinova, Irina; Jogee, Shardha; Weinzirl, Tim; Erwin, Peter; Trentham, Neil; Ferguson, Henry C.; Goudfrooij, Paul; Hammer, Derek; Den Brok, Mark; Peletier, Reynier F.; Kleijn, Gijs V.; Graham, Alister W.; Carter, David; Mouhcine, Mustapha; Balcells, Marc; Guzman, Rafael; Hoyos, Carlos; Mobasher, Bahram; Peng, Eric W. E-mail: sj@astro.as.utexas.edu

    2012-02-20

    -density environments for two reasons. First, S0s in rich clusters are less prone to bar instabilities as they are dynamically heated by harassment and are gas poor as a result of ram pressure stripping and accelerated star formation. Second, high-speed encounters in rich clusters may be less effective than slow, strong encounters in inducing bars. (3) We also take advantage of the high resolution of the ACS ({approx}50 pc) to analyze a sample of 333 faint (M{sub V} > -18) dwarf galaxies in the Coma core. Using visual inspection of unsharp-masked images, we find only 13 galaxies with bar and/or spiral structure. An additional eight galaxies show evidence for an inclined disk. The paucity of disk structures in Coma dwarfs suggests that either disks are not common in these galaxies or that any disks present are too hot to develop instabilities.