Can Gravity Probe B usefully constrain torsion gravity theories?
Flanagan, Eanna E.; Rosenthal, Eran
2007-06-15
In most theories of gravity involving torsion, the source for torsion is the intrinsic spin of matter. Since the spins of fermions are normally randomly oriented in macroscopic bodies, the amount of torsion generated by macroscopic bodies is normally negligible. However, in a recent paper, Mao et al. (arXiv:gr-qc/0608121) point out that there is a class of theories, including the Hayashi-Shirafuji (1979) theory, in which the angular momentum of macroscopic spinning bodies generates a significant amount of torsion. They further argue that, by the principle of action equals reaction, one would expect the angular momentum of test bodies to couple to a background torsion field, and therefore the precession of the Gravity Probe B gyroscopes should be affected in these theories by the torsion generated by the Earth. We show that in fact the principle of action equals reaction does not apply to these theories, essentially because the torsion is not an independent dynamical degree of freedom. We examine in detail a generalization of the Hayashi-Shirafuji theory suggested by Mao et al. called Einstein-Hayashi-Shirafuji theory. There are a variety of different versions of this theory, depending on the precise form of the coupling to matter chosen for the torsion. We show that, for any coupling to matter that is compatible with the spin transport equation postulated by Mao et al., the theory has either ghosts or an ill-posed initial-value formulation. These theoretical problems can be avoided by specializing the parameters of the theory and in addition choosing the standard minimal coupling to matter of the torsion tensor. This yields a consistent theory, but one in which the action equals reaction principle is violated, and in which the angular momentum of the gyroscopes does not couple to the Earth's torsion field. Thus, the Einstein-Hayashi-Shirafuji theory does not predict a detectable torsion signal for Gravity Probe B. There may be other torsion theories which do.
35. VERTICAL AND TORSIONAL MOTION FROM EAST TOWER SHOWING ANGULAR ...
35. VERTICAL AND TORSIONAL MOTION FROM EAST TOWER SHOWING ANGULAR DISTORTION APPROACHING 45 DEGREES WITH LAMP POSTS APPEARING TO BE AT EIGHT ANGLES, 7 NOVEMBER 1940, FROM 16MN FILM SHOT BY PROFESSOR F.B. FARQUHARSON, UNIVERSITY OF WASHINGTON. (LABORATORY STUDIES ON THE TACOMA NARROWS BRIDGE, AT UNIVERSITY OF WASHINGTON SEATTLE: UNIVERSITY OF WASHINGTON, DEPARTMENT OF CIVIL ENGINEERING, 1941) - Tacoma Narrows Bridge, Spanning Narrows at State Route 16, Tacoma, Pierce County, WA
Studies of torsional properties of DNA and nucleosomes using angular optical trapping
NASA Astrophysics Data System (ADS)
Sheinin, Maxim Y.
DNA in vivo is subjected to torsional stress due to the action of molecular motors and other DNA-binding proteins. Several decades of research have uncovered the fascinating diversity of DNA transformations under torsion and the important role they play in the regulation of vital cellular processes such as transcription and replication. Recent studies have also suggested that torsion can influence the structure and stability of nucleosomes---basic building blocks of the eukaryotic genome. However, our understanding of the impact of torsion is far from being complete due to significant experimental challenges. In this work we have used a powerful single-molecule experimental technique, angular optical trapping, to address several long-standing issues in the field of DNA and nucleosome mechanics. First, we utilized the high resolution and direct torque measuring capability of the angular optical trapping to precisely measure DNA twist-stretch coupling. Second, we characterized DNA melting under tension and torsion. We found that torsionally underwound DNA forms a left-handed structure, significantly more flexible compared to the regular B-DNA. Finally, we performed the first comprehensive investigation of the single nucleosome behavior under torque and force. Importantly, we discovered that positive torque causes significant dimer loss, which can have implications for transcription through chromatin.
Quan, Li-Di; Xue, Chao; Shao, Cheng-Gang; Yang, Shan-Qing; Tu, Liang-Cheng; Luo, Jun; Wang, Yong-Ji
2014-01-15
The performance of the feedback control system is of central importance in the measurement of the Newton's gravitational constant G with angular acceleration method. In this paper, a PID (Proportion-Integration-Differentiation) feedback loop is discussed in detail. Experimental results show that, with the feedback control activated, the twist angle of the torsion balance is limited to 7.3×10{sup −7} rad /√( Hz ) at the signal frequency of 2 mHz, which contributes a 0.4 ppm uncertainty to the G value.
On discrete symmetries and torsion homology in F-theory
NASA Astrophysics Data System (ADS)
Mayrhofer, Christoph; Palti, Eran; Till, Oskar; Weigand, Timo
2015-06-01
We study the relation between discrete gauge symmetries in F-theory compactifications and torsion homology on the associated Calabi-Yau manifold. Focusing on the simplest example of a symmetry, we show that there are two physically distinct ways that such a discrete gauge symmetry can arise. First, compactifications of M-Theory on Calabi-Yau threefolds which support a genus-one fibration with a bi-section are known to be dual to six-dimensional F-theory vacua with a gauge symmetry. We show that the resulting five-dimensional theories do not have a symmetry but that the latter emerges only in the F-theory decompactification limit. Accordingly the genus-one fibred Calabi-Yau manifolds do not exhibit torsion in homology. Associated to the bi-section fibration is a Jacobian fibration which does support a section. Compactifying on these related but distinct varieties does lead to a symmetry in five dimensions and, accordingly, we find explicitly an associated torsion cycle. We identify the expected particle and membrane system of the discrete symmetry in terms of wrapped M2 and M5 branes and present a field-theory description of the physics for both cases in terms of circle reductions of six-dimensional theories. Our results and methods generalise straightforwardly to larger discrete symmetries and to four-dimensional compactifications.
Nonlinear Fierz-Pauli theory from torsion and bigravity
NASA Astrophysics Data System (ADS)
Deffayet, C.; Randjbar-Daemi, S.
2011-08-01
The nonlinear aspects of a recently proposed model of massive spin-2 particles with propagating torsion are studied. We obtain a nonlinear equation which reduces at linear order to a generalized Fierz-Pauli equation in any background space-time with or without a vanishing torsion. We contrast those results with properties of a class of bigravity theories in an arbitrary background Einstein manifold. It is known that the nonperturbative spectrum of the bigravity model has 8 propagating physical degrees of freedom. This is identical to the physical propagating degrees of freedom of the massive spin-2 torsion model at the linearized order. The obtained nonlinear version of the Fierz-Pauli field equations, however, contains terms absent in the bigravity case which indicates that the curved space generalization of the unique flat space Fierz-Pauli equation is not unique. Moreover, in the torsion massive gravity model the Fierz-Pauli field appears as a derivative of fundamental fields. This, however, does not generate any unwanted pole once coupled to some external sources.
Can a macroscopic gyroscope feel torsion
NASA Technical Reports Server (NTRS)
Stoeger, W. R.; Yasskin, P. B.
1979-01-01
We demonstrate that for a large class of Lagrangian-based torsion theories a macroscopic gyroscope is insensitive to the torsion field: there can be no coupling of the torsion to the gyroscope's angular momentum of rotation. To detect torsion a polarized system with a net elementary particle spin is needed. These conclusions are evident from the conservation laws, which form the basis for deriving the equations of motion.
Thermal Properties of SiCp/Al Composites Consolidated by Equal Channel Angular Pressing and Torsion
NASA Astrophysics Data System (ADS)
Qian, Chen-hao; Li, Ping; Xue, Ke-min
2015-02-01
Powder mixture of pure Al and oxidized SiC was consolidated into SiCp/Al composites by equal channel angular pressing and torsion (ECAP-T). The influences of several parameters on the thermal expansions, the thermal conductivities, and the recrystallization temperatures of the as-consolidated composites were studied. These parameters are the number of ECAP-T passes (1, 2, and 4), the content of SiC (10, 20, and 40 wt.%), and the fabrication temperature (150, 250, and 350 °C). The results show that increasing the number of ECAP-T passes has a positive effect on depressing the coefficient of thermal expansion (CTE) of the composite within a certain temperature range, since the total variation amplitude of the CTE is enlarged. The CTE can also be decreased by increasing the content of SiC. The number of ECAP-T passes and the contents of SiC in the composites are both positively related with the thermal conductivity of the composites. No direct relationship between the fabrication temperature and the thermal properties was detected. However, the composite fabricated at too low temperature (150 °C) can not obtain full densification, leading to the appearance of low CTE and thermal conductivity. Finally, when the number of ECAP-T passes is elevated from 2 to 4, the recrystallization temperature of the composite has an obvious declination.
Constraining torsion with Gravity Probe B
Mao Yi; Guth, Alan H.; Cabi, Serkan; Tegmark, Max
2007-11-15
It is well-entrenched folklore that all torsion gravity theories predict observationally negligible torsion in the solar system, since torsion (if it exists) couples only to the intrinsic spin of elementary particles, not to rotational angular momentum. We argue that this assumption has a logical loophole which can and should be tested experimentally, and consider nonstandard torsion theories in which torsion can be generated by macroscopic rotating objects. In the spirit of action=reaction, if a rotating mass like a planet can generate torsion, then a gyroscope would be expected to feel torsion. An experiment with a gyroscope (without nuclear spin) such as Gravity Probe B (GPB) can test theories where this is the case. Using symmetry arguments, we show that to lowest order, any torsion field around a uniformly rotating spherical mass is determined by seven dimensionless parameters. These parameters effectively generalize the parametrized post-Newtonian formalism and provide a concrete framework for further testing Einstein's general theory of relativity (GR). We construct a parametrized Lagrangian that includes both standard torsion-free GR and Hayashi-Shirafuji maximal torsion gravity as special cases. We demonstrate that classic solar system tests rule out the latter and constrain two observable parameters. We show that Gravity Probe B is an ideal experiment for further constraining nonstandard torsion theories, and work out the most general torsion-induced precession of its gyroscope in terms of our torsion parameters.
Constraining torsion with Gravity Probe B
NASA Astrophysics Data System (ADS)
Mao, Yi; Tegmark, Max; Guth, Alan H.; Cabi, Serkan
2007-11-01
It is well-entrenched folklore that all torsion gravity theories predict observationally negligible torsion in the solar system, since torsion (if it exists) couples only to the intrinsic spin of elementary particles, not to rotational angular momentum. We argue that this assumption has a logical loophole which can and should be tested experimentally, and consider nonstandard torsion theories in which torsion can be generated by macroscopic rotating objects. In the spirit of action=reaction, if a rotating mass like a planet can generate torsion, then a gyroscope would be expected to feel torsion. An experiment with a gyroscope (without nuclear spin) such as Gravity Probe B (GPB) can test theories where this is the case. Using symmetry arguments, we show that to lowest order, any torsion field around a uniformly rotating spherical mass is determined by seven dimensionless parameters. These parameters effectively generalize the parametrized post-Newtonian formalism and provide a concrete framework for further testing Einstein’s general theory of relativity (GR). We construct a parametrized Lagrangian that includes both standard torsion-free GR and Hayashi-Shirafuji maximal torsion gravity as special cases. We demonstrate that classic solar system tests rule out the latter and constrain two observable parameters. We show that Gravity Probe B is an ideal experiment for further constraining nonstandard torsion theories, and work out the most general torsion-induced precession of its gyroscope in terms of our torsion parameters.
Baker, W.M.
1980-01-01
We examine the scale-invariant Lagrangian densities in Riemannian and non-Riemannian spacetimes. We find that the most general scale-invariant Lagrangian density of a Riemann-Cartan spacetime can also be reduced in a manner similar to that demonstrated earlier by Lanczos for the Riemannian case. However, this type of reduction process is not possible in a non-metric spacetime. Duality transformations of the type defined in electromagnetic theory are discussed and classified in terms of those transformations having a direct relationship to an internal symmetry structure of a given gauge theory and those that do not. We show that to build a satisfactory generalized electromagnetic type theory with local duality invariance into a gauge theory, as at least a part of its internal symmetry structure, requires a group no smaller than SO/sub 3/ or (SU/sub 2/). By considering a special metric geometry with torsion (U/sub 4/) we can describe the duality vector field of a duality invariant Maxwell theory in terms of a special form of torsion. This result indicates that the special U/sub 4/ geometry could play a role in the already unified field theory of Rainich, Misner, and Wheeler (RMW). We show how one could express the RMW conditions, together with their immediate generalizations in terms of geometric objects of the special U/sub 4/ theory. Conformal and projective transformations on the U/sub 4/ connection are examined. It is shown that an appropriate combination of these transformations have the effect of producing a special type of projective transformation on a metric connection with torsion. In the context of a gauge theory based on a U/sub 4/ spacetime, this special type of projective invariance has been interpreted as the underlying invariance principle for baryon number conservation in the same way that gauge changes on the Maxwell vector potential relate to charge conservation.
Micromechanical torsional digital-to-analog converter for open-loop angular positioning applications
NASA Astrophysics Data System (ADS)
Zhou, Guangya; Tay, Francis E. H.; Chau, Fook Siong; Zhao, Yi; Logeeswaran, VJ
2004-05-01
This paper reports a novel micromechanical torsional digital-to-analog converter (MTDAC), operated in open-loop with digitally controlled precise multi-level tilt angles. The MTDAC mechanism presented is analogous to that of an electrical binary-weighted-input digital-to-analog converter (DAC). It consists of a rigid tunable platform, an array of torsional microactuators, each operating in a two-state (on/off) mode, and a set of connection beams with binary-weighted torsional stiffnesses that connect the actuators to the platform. The feasibility of the proposed MTDAC mechanism was verified numerically by finite element simulations and experimentally with a commercial optical phase-shifting interferometric system. A prototype 2-bit MTDAC was implemented using the poly-MUMPS process achieving a full-scale output tilt angle of 1.92° with a rotation step of 0.64°. This mechanism can be configured for many promising applications, particularly in beam steering-based OXC switches.
Cosmological solutions of a quadratic theory of gravity with torsion
NASA Astrophysics Data System (ADS)
Canale, Anna; de Ritis, Ruggiero; Tarantino, Ciro
1984-01-01
Following the general approach of Hehl, and Hayashi and Shirafuji, we give the gravity equations for the lagrangian L=(e/2L2)(F+1/2×F2) + LM. We have found the explicit Einstein-de Sitter solutions for a spinless dust. We have discussed in this case the singularity problem for the metric and for the torsion.
PPN Metric and PPN torsion in the quadratic poincaré gauge theory of gravity
NASA Astrophysics Data System (ADS)
Gladchenko, M. S.; Ponomariov, V. N.; Zhytnikov, V. V.
1990-05-01
The post-newtonian approximation of the quadratic Poincaré gauge theory of gravity is studied. As a result of this investigation the modified PPN metric and PPN torsion is obtained. Post-newtonian equations of motion for different test bodies are analyzed and some restrictions on the parameters of the quadratic lagrangian are found.
REVIEW ARTICLE: Angular selective window coatings: theory and experiments
NASA Astrophysics Data System (ADS)
Mbise, G. W.; LeBellac, D.; Niklasson, G. A.; Granqvist, C. G.
1997-08-01
This review is devoted to the angular selectivity that can be obtained in thin films prepared under conditions such that they contain inclined absorbing regions of sizes much smaller than the wavelength of visible light. The films are of considerable interest as window coatings for energy-conscious architecture and, potentially, in the automotive sector. The theoretical basis for modelling the optical properties is presented, comprising rigorous bounds on the dielectric function, effective medium theories pertinent to different microgeometries and equations for treating the optics of anisotropic thin films. Experimental data are reported for films made by oblique-angle evaporation of Cr and for reactive and non-reactive oblique-angle sputtering of Cr, Al, Ti and W. The highest angular selectivity was obtained with evaporated Cr, whereas the highest luminous transmittance, combined with some angular selectivity, was found with reactively sputtered Al. Films made from Ti showed angular selectivity mainly in the infrared, whereas films made from W could display angular selective electrochromism. Samples of several types were subjected to elaborate theoretical analysis using effective-medium theories and it was seen that theory and experiment could be reconciled using plausible parameters to specify the microstructures of the films. Thus it appears that the angular, spectral and polarization dependences of obliquely deposited films can be understood, at least approximately, in terms of conceptually simple theoretical models.
Chern-Simons modified gravity as a torsion theory and its interaction with fermions
Alexander, Stephon; Yunes, Nicolas
2008-06-15
We study the tetrad formulation of Chern-Simons (CS) modified gravity, which adds a Pontryagin term to the Einstein-Hilbert action with a spacetime-dependent coupling field. We first verify that CS modified gravity leads to a theory with torsion, where this tensor is given by an antisymmetric product of the Riemann tensor and derivatives of the CS coupling. We then calculate the torsion in the far field of a weakly gravitating source within the parameterized post-Newtonian formalism, and specialize the result to Earth. We find that CS torsion vanishes only if the coupling vanishes, thus generically leading to a modification of gyroscopic precession, irrespective of the coupling choice. Perhaps most interestingly, we couple fermions to CS modified gravity via the standard Dirac action and find that these further correct the torsion tensor. Such a correction leads to two new results: (i) a generic enhancement of CS modified gravity by the Dirac equation and axial fermion currents; (ii) a new two-fermion interaction, mediated by an axial current and the CS correction. We conclude with a discussion of the consequences of these results in particle detectors and realistic astrophysical systems.
Some cosmological models coming from gravitational theories having torsional degrees of freedom
NASA Astrophysics Data System (ADS)
Espiro, J. Lorca; Vásquez, Yerko
2016-09-01
In this work we consider gravitational theories in which the effect of coupling characteristic classes, appropriately introduced as operators in the Einstein-Hilbert action, has been taken into account. As it is well known, this approach strays from the framework of general relativity since it results in theories in which torsion can be present. We consider here all the characteristic classes that are consistent with a four-dimensional space-time manifold. Then, we present explicit expressions for the contortion 1-form and torsion 2-form for a broad class of conditions in various cases of interest. Additionally, we use the same framework to study cosmological scenarios that are obtained mainly by selecting the flat FLRW metric and an ideal fluid.
All torsion-free spherical vacuum solutions of the quadratic Poincare gauge theory of gravity
NASA Astrophysics Data System (ADS)
Baekler, P.; Yasskin, P. B.
1984-12-01
The complete torsion-free spherically symmetric vacuum solutions of the theory of gravity proposed by Hehl et al. (1978) are obtained analytically and characterized. The solutions are shown to correspond to either Schwarzschild metrics (including a gravitational confinement potential when the cosmological constant Lambda is less than zero), Narai-Bertotti metrics, or conformally flat metrics (including some asymptotically flat but nonstationary solutions). The relationships of the theory of Hehl et al. to those of Eddington (1924), Nordstrom (1913), Einstein (1917, with cosmological constant), and Yang (1974) are explored.
Angular momentum theory applied to interactions in solids
NASA Astrophysics Data System (ADS)
Morrison, Clyde A.
1987-02-01
Concepts of group theory applied to the spectra of impurity ions in crystals are discussed. Beginning with the simple hydrogen atom, spectroscopic notation and angular momentum operators are discussed. This is followed by a general discussion of angular momentum theory including Clebsch Gordon coefficients, the Wigner Eckart theorem, unit spherical tensors, and Racah coefficients. The extension of these techniques to the electronic configuration, (nl to the Nth power), for N equivalent electrons is discussed. The theory of point groups as applied to ions in solids is introduced, along with the use of the International Tables of Crystallography and character tables. The phenomenological theory of crystal fields is discussed in some detail along with the so-called free ion parameters characterizing the Coulomb interaction, the spin-orbit interaction, and the interconfiguration interaction. The use of tables of 3-j and 6-j symbols in the calculation of the matrix elements of the various interactions is presented, along with other tables and aids in the computation of the energy levels. The point ion model of crystal-field interaction is discussed with particular emphasis on the work done at the Harry Diamond Laboratories (HDL) on its development. The earlier work at HDL was applied to triply ionized rare earth ions (l to the Nth power electronic configuration), and the preliminary extensions presently being undertaken at HDL are applied to the transit.
A Modified Theory of Gravity with Torsion and Its Applications to Cosmology and Particle Physics
NASA Astrophysics Data System (ADS)
Fabbri, Luca; Vignolo, Stefano
2012-10-01
In this paper we consider the most general least-order derivative theory of gravity in which not only curvature but also torsion is explicitly present in the Lagrangian, and where all independent fields have their own coupling constant: we will apply this theory to the case of ELKO fields, which is the acronym of the German Eigenspinoren des LadungsKonjugationsOperators designating eigenspinors of the charge conjugation operator, and thus they are a Majorana-like special type of spinors; and to the Dirac fields, the most general type of spinors. We shall see that because torsion has a coupling constant that is still undetermined, the ELKO and Dirac field equations are endowed with self-interactions whose coupling constant is undetermined: we discuss different applications according to the value of the coupling constants and the different properties that consequently follow. We highlight that in this approach, the ELKO and Dirac field's self-interactions depend on the coupling constant as a parameter that may even make these non-linearities manifest at subatomic scales.
Gyrokinetic theory and simulation of angular momentum transport
Waltz, R. E.; Staebler, G. M.; Candy, J.; Hinton, F. L.
2007-12-15
A gyrokinetic theory of turbulent toroidal angular momentum transport as well as modifications to neoclassical poloidal rotation from turbulence is formulated starting from the fundamental six-dimensional kinetic equation. The gyro-Bohm scaled transport is evaluated from toroidal delta-f gyrokinetic simulations using the GYRO code [Candy and Waltz, J. Comput. Phys. 186, 545 (2003)]. The simulations recover two pinch mechanisms in the radial transport of toroidal angular momentum: The slab geometry ExB shear pinch [Dominguez and Staebler, Phys. Fluids B 5, 387 (1993)] and the toroidal geometry 'Coriolis' pinch [Peeters, Angioni, and Strintzi, Phys. Rev. Lett. 98, 265003 (2007)]. The pinches allow the steady state null stress (or angular momentum transport flow) condition required to understand intrinsic (or spontaneous) toroidal rotation in heated tokamak without an internal source of torque [Staebler, Kinsey, and Waltz, Bull. Am. Phys. Soc. 46, 221 (2001)]. A predicted turbulent shift in the neoclassical poloidal rotation [Staebler, Phys. Plasmas 11, 1064 (2004)] appears to be small at the finite relative gyroradius (rho-star) of current experiments.
Singularity in the Laboratory Frame Angular Distribution Derived in Two-Body Scattering Theory
ERIC Educational Resources Information Center
Dick, Frank; Norbury, John W.
2009-01-01
The laboratory (lab) frame angular distribution derived in two-body scattering theory exhibits a singularity at the maximum lab scattering angle. The singularity appears in the kinematic factor that transforms the centre of momentum (cm) angular distribution to the lab angular distribution. We show that it is caused in the transformation by the…
Sokolovski, D.; Msezane, A.Z.
2004-09-01
A semiclassical complex angular momentum theory, used to analyze atom-diatom reactive angular distributions, is applied to several well-known potential (one-particle) problems. Examples include resonance scattering, rainbow scattering, and the Eckart threshold model. Pade reconstruction of the corresponding matrix elements from the values at physical (integral) angular momenta and properties of the Pade approximants are discussed in detail.
Weakly-Interacting Massive Particles in Torsionally-Gravitating Dirac Theory
NASA Astrophysics Data System (ADS)
Fabbri, Luca
2013-08-01
We shall consider the problem of Dark Matter (DM) in torsion gravity with Dirac matter fields; we will consider the fact that if Weakly-Interacting Massive Particles in a bath are allowed to form condensates then torsional effects may be relevant even at galactic scales: we show that torsionally-gravitating Dirac fields have interesting properties for the problem of DM. We discuss consequences.
Dark spinors with torsion in cosmology
Boehmer, Christian G.; Burnett, James
2008-11-15
We solve one of the open problems in Einstein-Cartan theory, namely, we find a natural matter source whose spin angular momentum tensor is compatible with the cosmological principle. We analyze the resulting evolution equations and find that an epoch of accelerated expansion is an attractor. The torsion field quickly decays in that period. Our results are interpreted in the context of the standard model of cosmology.
Kerr-Newman-dS/AdS solution and anti-evaporation in higher-order torsion scalar gravity theories
NASA Astrophysics Data System (ADS)
Nashed, Gamal G. L.
2016-03-01
We derive a null tetrad from axially-symmetric vierbein field. The f(T)f(T)-Maxwell field equations with cosmological constant, where T is the scalar torsion, are applied to the null tetrad. An exact non-vacuum solution having three constants of integration is derived which is a solution to the f (T) -Maxwell field equations provided that f(T)=T0f(T)=T0 and fT=df(T)dT=1fT=df(T)dT=1, where T0T0 is a constant. The scalar torsion related to this solution is constant, i.e., T=T0T=T0, and differs from the classical general relativity when f(T)≈T0f(T)≈T0. We study the singularities of this solution using curvature and torsion invariants. We consider a slow rotation and show that the derived solution behaves asymptotically as de Sitter spacetime and display the existence of Nariai spacetime as a background solution. We assume a perturbation of Nariai spacetime till the first order and investigate the behavior of the black hole horizon. Finally, we explain that the anti-evaporation occurs on the classical level in the f (T) gravitational theories.
NASA Astrophysics Data System (ADS)
Sabbaghianrad, Shima
A commercial Al-7075 alloy was processed by severe plastic deformation (SPD) techniques, namely equal-channel angular pressing (ECAP) and high-pressure torsion (HPT) or a combination of the two processes. After processing, the microstructural properties were examined, microhardness measurements were recorded across the disk diameters, and miniature tensile specimens were pulled to failure at a temperature of 623 K. Using TEM and EBSD techniques, it is demonstrated that the three SPD processing techniques have a potential for producing an ultrafine-grain structure containing reasonably equiaxed grains with high-angle grain boundary misorientations. However, microstructures were refined to different levels depending on the processing operation. It is shown that the most refined grain structure was achieved after processing by a combination of ECAP for 8 passes and HPT. The grain refinement mechanisms are primarily governed by dislocation activities. It is shown that the maximum saturation hardness achieved at high equivalent strains by different processing techniques increases with increasing amounts of deformation and it is the highest after processing by a combination of ECAP for 8 passes and HPT. The saturation hardness values were ˜231 after processing by HPT, ˜249 after processing by ECAP for 4 passes + HPT and ˜273 after processing by ECAP for 8 passes + HPT. Tensile testings show that the elongations to failure increase by increasing the amount of deformation. It is shown that after ECAP for 8 passes + HPT samples of the Al-7075 alloy have lower flow stresses and superplastic elongations up to >1000% when pulling to failure at 623 K. Superplastic elongations were not achieved after processing only by ECAP because of the non-uniform grain size and the presence of many larger grains.
Torsion cosmology of Poincaré gauge theory and the constraints of its parameters via SNeIa data
Ao, Xi-Chen; Li, Xin-Zhou E-mail: kychz@shnu.edu.cn
2012-02-01
Poincarè gauge theory (PGT) is an alternative gravity theory, which brings the gravity into the gauge-theoretic framework, where the Lagrangian includes both quadratic torsion and curvature terms. Recently, the cosmological models with torsion based on this theory, which explained the cosmic acceleration in a new way, have received much attention. Among these PGT cosmological models, the one with only even parity dynamical modes-SNY model, for its realistic meaning, is very attractive. In this paper, we first analyze the past-time cosmic evolution of SNY model analytically. And based on these results we fit this model to the most comprehensive SNeIa data (Union 2) and thus find the best-fit values of model parameters and initial conditions, whose related χ{sup 2} value is consistent with the one from ΛCMD at the 1σ level. Also by the χ{sup 2} estimate, we provide certain constraints on these parameters. Using these best-fit values for the Union 2 SNeIa dataset, we are able to predict the evolution of our real universe in late time. From this prediction, we know that the fate of our universe is that it would expand forever, slowly asymptotically to a halt, which is in accordance with the earlier works.
Propagating torsion in the Einstein frame
Poplawski, Nikodem J.
2006-11-15
The Einstein-Cartan-Saa theory of torsion modifies the spacetime volume element so that it is compatible with the connection. The condition of connection compatibility gives constraints on torsion, which are also necessary for the consistence of torsion, minimal coupling, and electromagnetic gauge invariance. To solve the problem of positivity of energy associated with the torsionic scalar, we reformulate this theory in the Einstein conformal frame. In the presence of the electromagnetic field, we obtain the Hojman-Rosenbaum-Ryan-Shepley theory of propagating torsion with a different factor in the torsionic kinetic term.
Belyaev, Mikhail A.; Rafikov, Roman R.; Stone, James M.
2013-06-10
The nature of angular momentum transport in the boundary layers of accretion disks has been one of the central and long-standing issues of accretion disk theory. In this work we demonstrate that acoustic waves excited by supersonic shear in the boundary layer serve as an efficient mechanism of mass, momentum, and energy transport at the interface between the disk and the accreting object. We develop the theory of angular momentum transport by acoustic modes in the boundary layer, and support our findings with three-dimensional hydrodynamical simulations, using an isothermal equation of state. Our first major result is the identification of three types of global modes in the boundary layer. We derive dispersion relations for each of these modes that accurately capture the pattern speeds observed in simulations to within a few percent. Second, we show that angular momentum transport in the boundary layer is intrinsically nonlocal, and is driven by radiation of angular momentum away from the boundary layer into both the star and the disk. The picture of angular momentum transport in the boundary layer by waves that can travel large distances before dissipating and redistributing angular momentum and energy to the disk and star is incompatible with the conventional notion of local transport by turbulent stresses. Our results have important implications for semianalytical models that describe the spectral emission from boundary layers.
Generalization of Equivalent Crystal Theory to Include Angular Dependence
NASA Technical Reports Server (NTRS)
Ferrante, John; Zypman, Fredy R.
2004-01-01
In the original Equivalent Crystal Theory, each atomic site in the real crystal is assigned an equivalent lattice constant, in general different from the ground state one. This parameter corresponds to a local compression or expansion of the lattice. The basic method considers these volumetric transformations and, in addition, introduces the possibility that the reference lattice is anisotropically distorted. These distortions however, were introduced ad-hoc. In this work, we generalize the original Equivalent Crystal Theory by systematically introducing site-dependent directional distortions of the lattice, whose corresponding distortions account for the dependence of the energy on anisotropic local density variations. This is done in the spirit of the original framework, but including a gradient term in the density. This approach is introduced to correct a deficiency in the original Equivalent Crystal Theory and other semiempirical methods in quantitatively obtaining the correct ratios of the surface energies of low index planes of cubic metals (100), (110), and (111). We develop here the basic framework, and apply it to the calculation of Fe (110) and Fe (111) surface energy formation. The results, compared with first principles calculations, show an improvement over previous semiempirical approaches.
Torsion of a cylinder of partially molten rock with a spherical inclusion: Theory and simulation
NASA Astrophysics Data System (ADS)
Alisic, Laura; Rhebergen, Sander; Rudge, John F.; Katz, Richard F.; Wells, Garth N.
2016-01-01
The processes that are involved in migration and extraction of melt from the mantle are not yet fully understood. Gaining a better understanding of material properties of partially molten rock could help shed light on the behavior of melt on larger scales in the mantle. In this study, we simulate three-dimensional torsional deformation of a partially molten rock that contains a rigid, spherical inclusion. We compare the computed porosity patterns to those found in recent laboratory experiments. The laboratory experiments show emergence of melt-rich bands throughout the rock sample, and pressure shadows around the inclusion. The numerical model displays similar melt-rich bands only for a small bulk-to-shear-viscosity ratio (five or less). The results are consistent with earlier two-dimensional numerical simulations; however, we show that it is easier to form melt-rich bands in three dimensions compared to two. The addition of strain-rate dependence of the viscosity causes a distinct change in the shape of pressure shadows around the inclusion. This change in shape presents an opportunity for experimentalists to identify the strain-rate dependence and therefore the dominant deformation mechanism in torsion experiments with inclusions.
Energy-Momentum and Angular Momentum in /line{Poincaré Gauge Theory of Gravity
NASA Astrophysics Data System (ADS)
Kawai, T.
1988-04-01
In /line{Poincaré gauge theory of gravity developed in previous papers, we examine energy-momentum and angular momentum for an isolated system by fixing the asymptotic form of the Higgs-type field psi = \\{psi(k}\\) to be psi(k) =~ e((0)k) _{mu}x(mu) + psi((0)k) with constants e((0)k}_{mu) and psi((0)k) . Conservations of energy-momentum and of total angular momentum both follow from the internal /line{Poincaré gauge invariance. The orbital part of the total angular momentum arises from a term, which Kibble-type ``Poincaré gauge'' theory lacks, in the expression for the ``spin'' angular momentum density. This resolves the mystery of the isolated conesrvation of spin in gauge theory of gravity. In the present scheme, the canonical energy-momentum density and the ``orbital angular momentum'' density, introduced by considering coordinate transformations, both turn out to be trivial when they are intergrated over a space-like surface. We need not invoke coordinate transformations to get physical quantities. An alternative asymptotic form of psi is also discussed.
Unexpectedly low angular extent of journal bearing pressures: experiment and theory
NASA Astrophysics Data System (ADS)
Sharma, Nikhil; Vimal, T.; Chatterjee, Anindya
2015-04-01
Journal bearings have been studied for a long time. Pressure solutions for the same, as presented in textbooks, typically have angular extents exceeding 150°. Here, for a bearing with a relatively larger clearance ratio (0.01 as opposed to, say, 0.001), our experiments show an angular extent of about 50° only. Such small angular extents cannot be predicted, even approximately, by the existing simple theories for journal bearing pressures. However, such theories are based on assumptions whereby only the relative speed between bearing and journal surfaces enters the governing equations. We discuss how these same assumptions motivate some new combinations of boundary conditions that allow reasonably simple numerical treatment. In this paper, the resulting families of possible solutions are computed semi-numerically using a Fourier series expansion in one direction and finite differences and numerical continuation in the other. We find that one such solution family contains small-extent solutions similar to those observed experimentally.
Dubhashi, Siddharth Pramod; Khadav, Bharat
2016-01-01
Torsion of the vermiform appendix is a rare condition detectable only at operation. It can be primary or secondary. This is a case report of 52-year-old female with 180° anti-clockwise rotation of the appendix. Torsion can further leads to strangulation and infarction of the organ. Appendicular torsion could be included in the differential diagnosis of pain in right iliac fossa. PMID:27013858
Zhou, Yun Pollak, Eli; Miret-Artés, Salvador
2014-01-14
A second order classical perturbation theory is developed and applied to elastic atom corrugated surface scattering. The resulting theory accounts for experimentally observed asymmetry in the final angular distributions. These include qualitative features, such as reduction of the asymmetry in the intensity of the rainbow peaks with increased incidence energy as well as the asymmetry in the location of the rainbow peaks with respect to the specular scattering angle. The theory is especially applicable to “soft” corrugated potentials. Expressions for the angular distribution are derived for the exponential repulsive and Morse potential models. The theory is implemented numerically to a simplified model of the scattering of an Ar atom from a LiF(100) surface.
Spin-torsion coupling and gravitational moments of Dirac fermions: Theory and experimental bounds
NASA Astrophysics Data System (ADS)
Obukhov, Yuri N.; Silenko, Alexander J.; Teryaev, Oleg V.
2014-12-01
We discuss the quantum dynamics of a Dirac fermion particle in the Poincaré gauge gravitational field. The minimal as well as the Pauli-type nonminimal coupling of a fermion with external fields is studied, bringing into consideration the notions of the translational and the Lorentz gravitational moments. The anomalous gravitomagnetic and gravitoelectric moments are ruled out on the basis of the covariance arguments. We derive the general Foldy-Wouthuysen transformation for an arbitrary configuration of the Poincaré gauge gravitational field without assuming it is weak. Making use of the Foldy-Wouthuysen Hamiltonian for the Dirac particle coupled to a magnetic field in a noninertial reference system, we analyze the recent experimental data and obtain bounds on the spacetime torsion.
Crystal Field Theory and the Angular Overlap Model Applied to Hydrides of Main Group Elements.
ERIC Educational Resources Information Center
Moore, E. A.
1990-01-01
Described is how crystal field theory and the angular overlap model can be applied to very simple molecules which can then be used to introduce such concepts as bonding orbitals, MO diagrams, and Walsh diagrams. The main-group compounds are used as examples and a switch to the transition metal complexes. (KR)
Flexural Torsional Guided Wave Pipe Inspection
NASA Astrophysics Data System (ADS)
Sun, Z.; Zhang, L.; Rose, J. L.
2006-03-01
Based on the flexural torsional guided wave theory and its focusing technique, this paper demonstrates the defect detection capability of flexural torsional guided waves on multiple defects with different shapes and axial, circumferential locations in pipe.
Derivation of Einstein-Cartan theory from general relativity
NASA Astrophysics Data System (ADS)
Petti, Richard
2016-03-01
This article presents a derivation of Einstein-Cartan theory from general relativity with no additional assumptions or parameters. The derivation begins with distributions of Kerr masses that converge to a continuum with constant densities of mass, momentum, and angular momentum. The limit includes torsion and the spin-torsion relationship of Einstein-Cartan theory. The construction of curvature and torsion is equivalent to definition of curvature with Cartan forms on fiber bundles. Advantages of Einstein-Cartan theory include accommodating exchange of classical intrinsic and orbital angular momentum and generation of inflation-like expansion in high density cosmological models.
Torsion and buckling of open sections
NASA Technical Reports Server (NTRS)
Wagner, H; Pretschner, W
1936-01-01
Following an abstract of the well-known theory of torsion in compression, the writers give directions for the practical calculation of the values of C(sub BT) (resistance to flexure and torsion) and i(sub SP(exp 2)), which determine the torsion. The second part treats the experiments in support of the theory of torsion of plain and flanged angle sections.
NASA Astrophysics Data System (ADS)
Dauth, M.; Kümmel, S.
2016-02-01
Photoemission spectroscopy is one of the most frequently used tools for characterizing the electronic structure of condensed matter systems. We discuss a scheme for simulating photoemission from finite systems based on time-dependent density-functional theory. It allows for the first-principles calculation of relative electron binding energies, ionization cross sections, and anisotropy parameters. We extract these photoemission spectroscopy observables from Kohn-Sham orbitals propagated in real time. We demonstrate that the approach is capable of estimating photoemission intensities, i.e., peak heights. It can also reliably predict the angular distribution of photoelectrons. For the example of benzene we contrast calculated angular distribution anisotropy parameters to experimental reference data. Self-interaction free Kohn-Sham theory yields meaningful outer valence single-particle states in the right energetic order. We discuss how to properly choose the complex absorbing potential that is used in the simulations.
Batishchev, Pavel A.; Tolstikhin, Oleg I.
2007-06-15
The Siegert pseudostate (SPS) formulation of scattering theory, originally developed by Tolstikhin, Ostrovsky, and Nakamura [Phys. Rev. A, 58, 2077 (1998)] for s-wave scattering in a spherically symmetric finite-range potential, is generalized to nonzero angular momenta. The orthogonality and completeness properties of SPSs are established and SPS expansions for the outgoing-wave Green's function, physical states, and scattering matrix are obtained. The present formulation completes the theory of SPSs in the one-channel case, making its application to three-dimensional problems possible. The results are illustrated by calculations for several model potentials.
Nonlinear Hysteretic Torsional Waves.
Cabaret, J; Béquin, P; Theocharis, G; Andreev, V; Gusev, V E; Tournat, V
2015-07-31
We theoretically study and experimentally report the propagation of nonlinear hysteretic torsional pulses in a vertical granular chain made of cm-scale, self-hanged magnetic beads. As predicted by contact mechanics, the torsional coupling between two beads is found to be nonlinear hysteretic. This results in a nonlinear pulse distortion essentially different from the distortion predicted by classical nonlinearities and in a complex dynamic response depending on the history of the wave particle angular velocity. Both are consistent with the predictions of purely hysteretic nonlinear elasticity and the Preisach-Mayergoyz hysteresis model, providing the opportunity to study the phenomenon of nonlinear dynamic hysteresis in the absence of other types of material nonlinearities. The proposed configuration reveals a plethora of interesting phenomena including giant amplitude-dependent attenuation, short-term memory, as well as dispersive properties. Thus, it could find interesting applications in nonlinear wave control devices such as strong amplitude-dependent filters. PMID:26274421
Nonlinear Hysteretic Torsional Waves
NASA Astrophysics Data System (ADS)
Cabaret, J.; Béquin, P.; Theocharis, G.; Andreev, V.; Gusev, V. E.; Tournat, V.
2015-07-01
We theoretically study and experimentally report the propagation of nonlinear hysteretic torsional pulses in a vertical granular chain made of cm-scale, self-hanged magnetic beads. As predicted by contact mechanics, the torsional coupling between two beads is found to be nonlinear hysteretic. This results in a nonlinear pulse distortion essentially different from the distortion predicted by classical nonlinearities and in a complex dynamic response depending on the history of the wave particle angular velocity. Both are consistent with the predictions of purely hysteretic nonlinear elasticity and the Preisach-Mayergoyz hysteresis model, providing the opportunity to study the phenomenon of nonlinear dynamic hysteresis in the absence of other types of material nonlinearities. The proposed configuration reveals a plethora of interesting phenomena including giant amplitude-dependent attenuation, short-term memory, as well as dispersive properties. Thus, it could find interesting applications in nonlinear wave control devices such as strong amplitude-dependent filters.
Quaternions, Torsion and the Physical Vacuum: Theories of M. Sachs and G. Shipov Compared
NASA Astrophysics Data System (ADS)
Cyganski, David; Page, William S.
Of several developments of unified field theories in the spirit of Einstein's original objective of a fully geometric description of all classical fields as well as quantum mechanics, two are particularly noteworthy. The works of Mendel Sachs and Gennady Shipov stand apart as major life works comprising tens of papers, several monographs and decades of effort. Direct comparison of these theories is hampered however by differences in notation and conceptual view-point. Despite these differences, there are many parallels between the fundamental mathematical structures appearing in each. In this paper we discuss the main tenets of the two approaches and demonstrate that they both give rise to a factorization of the invariant interval of general relativity.
Symmetry broken and restored coupled-cluster theory: I. Rotational symmetry and angular momentum
NASA Astrophysics Data System (ADS)
Duguet, T.
2015-02-01
We extend coupled-cluster (CC) theory performed on top of a Slater determinant breaking rotational symmetry to allow for the exact restoration of the angular momentum at any truncation order. The main objective relates to the description of near-degenerate finite quantum systems with an open-shell character. As such, the newly developed many-body formalism offers a wealth of potential applications and further extensions dedicated to the ab initio description of, e.g., doubly open-shell atomic nuclei and molecule dissociation. The formalism, which encompasses both single-reference CC theory and projected Hartree-Fock theory as particular cases, permits the computation of usual sets of connected diagrams while consistently incorporating static correlations through the highly non-perturbative restoration of rotational symmetry. Interestingly, the yrast spectroscopy of the system, i.e. the lowest energy associated with each angular momentum, is accessed within a single calculation. A key difficulty presently overcome relates to the necessity to handle generalized energy and norm kernels for which naturally terminating CC expansions could be eventually obtained. The present work focuses on SU(2) but can be extended to any (locally) compact Lie group and to discrete groups, such as most point groups. In particular, the formalism will be soon generalized to U(1) symmetry associated with particle number conservation. This is relevant to Bogoliubov CC theory that was recently applied to singly open-shell nuclei.
NASA Technical Reports Server (NTRS)
Hanson, Donald B.; Parzych, David J.
1993-01-01
This report presents the derivation of a frequency domain theory and working equations for radiation of propeller harmonic noise in the presence of angular inflow. In applying the acoustic analogy, integration over the tangential coordinate of the source region is performed numerically, permitting the equations to be solved without approximation for any degree of angular inflow. Inflow angle is specified in terms of yaw, pitch, and roll angles of the aircraft. Since these can be arbitrarily large, the analysis applies with equal accuracy to propellers and helicopter rotors. For thickness and loading, the derivation is given in complete detail with working equations for near and far field. However, the quadrupole derivation has been carried only far enough to show feasibility of the numerical approach. Explicit formulas are presented for computation of source elements, evaluation of Green's functions, and location of observer points in various visual and retarded coordinate systems. The resulting computer program, called WOBBLE has been written in FORTRAN and follows the notation of this report very closely. The new theory is explored to establish the effects of varying inflow angle on axial and circumferential directivity. Also, parametric studies were performed to evaluate various phenomena outside the capabilities of earlier theories, such as an unsteady thickness effect. Validity of the theory was established by comparison with test data from conventional propellers and Prop Fans in flight and in wind tunnels under a variety of operating conditions and inflow angles.
Empirical formula of crustal torsional oscillations
NASA Astrophysics Data System (ADS)
Sotani, Hajime
2016-02-01
Crustal torsional oscillations depend on not only crust properties but also the stellar mass and radius. Thus, one could extract stellar information by identifying the observed frequencies of stellar oscillations with the crustal torsional oscillations. Owing to the confinement of torsional oscillations inside the crust region of neutron stars, we successfully derive an empirical formula for the fundamental crustal torsional oscillations as a function of the stellar mass, radius, the so-called slope parameter of the nuclear symmetry energy, and the angular index of oscillations, with which one can estimate the frequencies with high accuracy. This empirical formula could be valuable in both the astrophysics and nuclear physics communities.
Abbasi, Mohammad; Karami Mohammadi, Ardeshir
2015-05-01
A relationship based on a nonlocal elasticity theory is developed to investigate the torsional sensitivity and resonant frequency of an atomic force microscope (AFM) with assembled cantilever probe (ACP). This ACP comprises a horizontal cantilever and a vertical extension, and a tip located at the free end of the extension, which makes the AFM capable of topography at sidewalls of microstructures. First, the governing differential equations of motion and boundary conditions for dynamic analysis are obtained by a combination of the basic equations of nonlocal elasticity theory and Hamilton's principle. Afterward, a closed-form expression for the sensitivity of vibration modes has been obtained using the relationship between the resonant frequency and contact stiffness of cantilever and sample. These analysis accounts for a better representation of the torsional behavior of an AFM with sidewall probe where the small-scale effect are significant. The results of the proposed model are compared with those of classical beam theory. The results show that the sensitivities and resonant frequencies of ACP predicted by the nonlocal elasticity theory are smaller than those obtained by the classical beam theory. PMID:25755027
Angular scale expansion theory and the misperception of egocentric distance in locomotor space
Durgin, Frank H.
2014-01-01
Perception is crucial for the control of action, but perception need not be scaled accurately to produce accurate actions. This paper reviews evidence for an elegant new theory of locomotor space perception that is based on the dense coding of angular declination so that action control may be guided by richer feedback. The theory accounts for why so much direct-estimation data suggests that egocentric distance is underestimated despite the fact that action measures have been interpreted as indicating accurate perception. Actions are calibrated to the perceived scale of space and thus action measures are typically unable to distinguish systematic (e.g., linearly scaled) misperception from accurate perception. Whereas subjective reports of the scaling of linear extent are difficult to evaluate in absolute terms, study of the scaling of perceived angles (which exist in a known scale, delimited by vertical and horizontal) provides new evidence regarding the perceptual scaling of locomotor space. PMID:25610539
Mass and angular momentum of black holes in low-energy heterotic string theory
NASA Astrophysics Data System (ADS)
Peng, Jun-Jin
2016-04-01
We investigate conserved charges in the low-energy effective field theory describing heterotic string theory. Starting with a general Lagrangian that consists of a metric, a scalar field, a vector gauge field, together with a two-form potential, we derive off-shell Noether potentials of the Lagrangian and generalize the Abbott-Deser-Tekin (ADT) formalism to the off-shell level by establishing one-to-one correspondence between the ADT potential and the off-shell Noether potential. It is proved that the off-shell generalized ADT formalism is conformally invariant. Then, we apply the formulation to compute mass and angular momentum of the four-dimensional Kerr-Sen black hole and the five-dimensional rotating charged black string in the string frame without a necessity to transform the metrics into the Einstein frame.
Bigoni, D.; Dal Corso, F.; Misseroni, D.; Bosi, F.
2014-01-01
One edge of an elastic rod is inserted into a friction-less and fitting socket head, whereas the other edge is subjected to a torque, generating a uniform twisting moment. It is theoretically shown and experimentally proved that, although perfectly smooth, the constraint realizes an expulsive axial force on the elastic rod, which amount is independent of the shape of the socket head. The axial force explains why screwdrivers at high torque have the tendency to disengage from screw heads and demonstrates torsional locomotion along a perfectly smooth channel. This new type of locomotion finds direct evidence in the realization of a ‘torsional gun’, capable of transforming torque into propulsive force. PMID:25383038
Torsional vibration isolator and method
Allen, C.A.; Durrett, V.D.
1986-10-21
This patent describes a multicylinder internal combustion engine having a rotatable crankshaft and a rotatable flywheel which together define an inertial system rotating about a predetermined axis of rotation. An improvement is described here which facilitates avoiding destructive effects on the crankshaft of stress induced by torsional vibration. The method comprises an elastomeric annulus coupling means operatively interposed between the crankshaft and flywheel for coupling the crankshaft and flywheel together for rotation of the flywheel with the crankshaft. The coupling means has a torsional spring rate of less than 20,000 in lb/radian effective to permit substantial angular displacement between the flywheel and the crankshaft for isolating the rotating inertia of the flywheel from the rotating inertia of the crankshaft after engine startup. The coupling means avoids dampening while preventing torsional vibration from being transferred between the flywheel and the crankshaft.
NASA Astrophysics Data System (ADS)
Wang, Guangjun; Wang, Huaying; Wang, Dayong; Xie, Jianjun; Zhao, Jie
2007-12-01
A simple holographic high-resolution imaging system without pre-magnification, which is based on off-axis lensless Fourier transform configuration, has been developed. Experimental investigations are performed on USAF resolution test target. The method based on angular spectrum theory for reconstructing lensless Fourier hologram is given. The reconstructed results of the same hologram at different reconstructing distances are presented for what is to our knowledge the first time. Approximate diffraction limited lateral resolution is achieved. The results show that the angular spectrum method has several advantages over more commonly used Fresnel transform method. Lossless reconstruction can be achieved for any numerical aperture holograms as long as the wave field is calculated at a special reconstructing distance, which is determined by the light wavelength and the chip size and the pixel size of the CCD sensor. This is very important for reconstructing an extremely large numerical aperture hologram. Frequency-domain spectrum filtering can be applied conveniently to remove the disturbance of zero-order. The reconstructed image wave field is accurate so long as the sampling theorem is not violated. The experimental results also demonstrate that for a high quality hologram, special image processing is unnecessary to obtain a high quality image.
Implementing torsional-mode Doppler ladar.
Fluckiger, David U
2002-08-20
Laguerre-Gaussian laser modes carry orbital angular momentum as a consequence of their helical-phase front screw dislocation. This torsional beam structure interacts with rotating targets, changing the orbital angular momentum (azimuthal Doppler) of the scattered beam because angular momentum is a conserved quantity. I show how to measure this change independently from the usual longitudinal momentum (normal Doppler shift) and derive the apropos coherent mixing efficiencies for monostatic, truncated Laguerre and Gaussian-mode ladar antenna patterns. PMID:12206220
NASA Astrophysics Data System (ADS)
Liu, Yuan; Ning, Chuangang
2015-10-01
Recently, the development of photoelectron velocity map imaging makes it much easier to obtain the photoelectron angular distributions (PADs) experimentally. However, explanations of PADs are only qualitative in most cases, and very limited works have been reported on how to calculate PAD of anions. In the present work, we report a method using the density-functional-theory Kohn-Sham orbitals to calculate the photodetachment cross sections and the anisotropy parameter β. The spherical average over all random molecular orientation is calculated analytically. A program which can handle both the Gaussian type orbital and the Slater type orbital has been coded. The testing calculations on Li-, C-, O-, F-, CH-, OH-, NH2-, O2-, and S2- show that our method is an efficient way to calculate the photodetachment cross section and anisotropy parameter β for anions, thus promising for large systems.
NASA Astrophysics Data System (ADS)
Singh, Abhishek K.; Pandey, K. Priyabrat; Singh, Sunita; Kar, Supriya
2013-05-01
The U(1) gauge dynamics on a D 4-brane is revisited, with a two form, to construct an effective curvature theory in a second order formalism. We exploit the local degrees in a two form, and modify its dynamics in a gauge invariant way, to incorporate a non-perturbative metric fluctuation in an effective D 4-brane. Interestingly, the near horizon D 4-brane is shown to describe an asymptotic Anti de Sitter (AdS) in a semi-classical regime. Using Weyl scaling(s), we obtain the emergent rotating geometries leading to primordial de Sitter (dS) and AdS vacua in a quantum regime. Under a discrete transformation, we re-arrange the mixed dS patches to describe a Schwazschild-like dS (SdS) and a topological-like dS (TdS) black holes. We analyze SdS vacuum for Hawking radiations to arrive at Nariai geometry, where a discrete torsion forms a condensate. We perform thermal analysis to identify Nariai vacuum with a TdS. Investigation reveals an AdS patch within a thermal dS brane, which may provide a clue to unfold dS/CFT. In addition, the role of dark energy, sourced by a discrete torsion, in the dS vacua is investigated using Painleve geometries. It is argued that a D-instanton pair is created by a discrete torsion, with a Big Bang/Crunch, at the past horizon in a pure dS. Nucleation, of brane/anti-brane pair(s), is qualitatively analyzed to construct an effective space-time on a D 4-brane and its anti brane. Analysis re-assures the significant role played by a non-zero mode, of NS-NS two form, to generalize the notion of branes within a brane.
Liu, Yuan; Ning, Chuangang
2015-10-14
Recently, the development of photoelectron velocity map imaging makes it much easier to obtain the photoelectron angular distributions (PADs) experimentally. However, explanations of PADs are only qualitative in most cases, and very limited works have been reported on how to calculate PAD of anions. In the present work, we report a method using the density-functional-theory Kohn-Sham orbitals to calculate the photodetachment cross sections and the anisotropy parameter β. The spherical average over all random molecular orientation is calculated analytically. A program which can handle both the Gaussian type orbital and the Slater type orbital has been coded. The testing calculations on Li{sup −}, C{sup −}, O{sup −}, F{sup −}, CH{sup −}, OH{sup −}, NH{sub 2}{sup −}, O{sub 2}{sup −}, and S{sub 2}{sup −} show that our method is an efficient way to calculate the photodetachment cross section and anisotropy parameter β for anions, thus promising for large systems.
Totenhofer, A J; Connor, J N L; Nyman, Gunnar
2016-03-01
The differential cross section (DCS) for the CH4 + Cl → CH3 + HCl reaction is studied at six total energies where all of the species are in their ground states. The scattering (S) matrix elements have been calculated by the rotating line umbrella method for a dual-level ab initio analytic potential energy surface. We make the first application to this reaction of nearside-farside (NF) and local angular momentum (LAM) techniques, including resummation orders (r) of 0, 1, 2, and 3 for the partial-wave series representation of the full scattering amplitude. We find that resummation usually cleans the NF r = 0 DCSs of unphysical oscillations, especially at small angles. This cleaning effect is typically most pronounced when changing from no resummation (r = 0) to r = 1; further resummations from r = 1 to r = 2 and from r = 2 to r = 3 have smaller effects. The NF DCS analyses show that the reaction is N-dominated at sideward and large angles, whereas at small angles there are oscillations caused by NF interference. The NF LAM analysis provides consistent and complementary information, in particular for the total angular momenta that contribute to the reaction at different scattering angles. The NF analyses also provide justification for simpler N-dominant dynamical theories such as the semiclassical optical model, which provides an explanation for the distorted mirror image effect for the moduli of the S matrix elements and the DCSs, as well as the use of a hard-sphere DCS over limited angular ranges. PMID:26625096
Face-seal lubrication. 2: Theory of response to angular misalignement
NASA Technical Reports Server (NTRS)
Ludwig, L. P.; Allen, G. P.
1976-01-01
A theoretical analysis was made of a hypothetical seal operating mode. The hypothetical seal model provides for three degrees of primary ring motion and includes the force and moments induced by primary ring response to seat angular misalignment. This ring response causes a relative angular misalignment between the faces of the primary seal. Hydrodynamic pressure generation is produced by this misalignment. The analysis is based on the Reynolds equation in short bearing form and on a balance of forces and moments that arise from hydrodynamic and secondary seal friction effects. A closed form solution was obtained that can be solved for film thickness and relative angular misalignment.
Torsional Oscillations of the Earths's Core
NASA Technical Reports Server (NTRS)
Hide, Raymond; Boggs, Dale H.; Dickey, Jean O.
1997-01-01
Torsional oscillations of the Earth's liquid metallic outer core are investigated by diving the core into twenty imaginary e1qui-volume annuli coaxial with the axis of ratation of the Earth and determining temproal fluctuations in the axial component of angular memonetum of each annulus under the assumption of iso-rotation on cylindrical surfaces.
NASA Astrophysics Data System (ADS)
Evans, M. W.
1992-07-01
Optical NMR and ESR is a recently introduced technique in which a circularly polarized laser (a "light magnet") is used in an NMR or ESR spectrometer to induce magnetization. The spectral consequencies are developed with a quantum theory similar to the rigorous theory of Zeeman splitting of Russell-Saunders states, a theory which is suitable for atoms and molecules with net electronic angular momentum, and in which the antisymmetric electronic polarizability is finite. The optical NMR and ESR Hamiltonians are developed with the Wigner-Eckhart Theorem. The circularly polarized laser shifts the original NMR or ESR resonance lines, and splits the shifted lines into analytically useful patterns. The theory gives Landé factors which are in agreement with an earlier, simple, semiclassical theory ( J. Phys. Chem.95, 2256-2260 (1991)).
Nonlinear management of the angular momentum of soliton clusters: Theory and experiment
Fratalocchi, Andrea; Piccardi, Armando; Peccianti, Marco; Assanto, Gaetano
2007-06-15
We demonstrate, both theoretically and experimentally, how to acquire nonlinear control over the angular momentum of a cluster of solitary waves. Our results, stemming from a universal theoretical model, show that the angular momentum can be adjusted by acting on the global energy input in the system. The phenomenon is experimentally ascertained in nematic liquid crystals by observing a power-dependent rotation of a two-soliton ensemble.
Variable stiffness torsion springs
NASA Technical Reports Server (NTRS)
Alhorn, Dean C. (Inventor); Polites, Michael E. (Inventor)
1994-01-01
In a torsion spring the spring action is a result of the relationships between the torque applied in twisting the spring, the angle through which the torsion spring twists, and the modulus of elasticity of the spring material in shear. Torsion springs employed industrially have been strips, rods, or bars, generally termed shafts, capabable of being flexed by twisting their axes. They rely on the variations in shearing forces to furnish an internal restoring torque. In the torsion springs herein the restoring torque is external and therefore independent of the shearing modulus of elasticity of the torsion spring shaft. Also provided herein is a variable stiffness torsion spring. This torsion spring can be so adjusted as to have a given spring constant. Such variable stiffness torsion springs are extremely useful in gimballed payloads such as sensors, telescopes, and electronic devices on such platforms as a space shuttle or a space station.
Variable stiffness torsion springs
NASA Technical Reports Server (NTRS)
Alhorn, Dean C. (Inventor); Polites, Michael E. (Inventor)
1995-01-01
In a torsion spring the spring action is a result of the relationships between the torque applied in twisting the spring, the angle through which the torsion spring twists, and the modulus of elasticity of the spring material in shear. Torsion springs employed industrially have been strips, rods, or bars, generally termed shafts, capabable of being flexed by twisting their axes. They rely on the variations in shearing forces to furnish an internal restoring torque. In the torsion springs herein the restoring torque is external and therefore independent of the shearing modulus of elasticity of the torsion spring shaft. Also provided herein is a variable stiffness torsion spring. This torsion spring can be so adjusted as to have a given spring constant. Such variable stiffness torsion springs are extremely useful in gimballed payloads such as sensors, telescopes, and electronic devices on such platforms as a space shuttle or a space station.
Torsionally mediated spin-rotation hyperfine splittings at moderate to high J values in methanol.
Belov, S P; Golubiatnikov, G Yu; Lapinov, A V; Ilyushin, V V; Alekseev, E A; Mescheryakov, A A; Hougen, J T; Xu, Li-Hong
2016-07-14
This paper presents an explanation based on torsionally mediated proton-spin-overall-rotation interaction for the observation of doublet hyperfine splittings in some Lamb-dip sub-millimeter-wave transitions between ground-state torsion-rotation states of E symmetry in methanol. These unexpected doublet splittings, some as large as 70 kHz, were observed for rotational quantum numbers in the range of J = 13 to 34, and K = - 2 to +3. Because they increase nearly linearly with J for a given branch, we confined our search for an explanation to hyperfine operators containing one nuclear-spin angular momentum factor I and one overall-rotation angular momentum factor J (i.e., to spin-rotation operators) and ignored both spin-spin and spin-torsion operators, since they contain no rotational angular momentum operator. Furthermore, since traditional spin-rotation operators did not seem capable of explaining the observed splittings, we constructed totally symmetric "torsionally mediated spin-rotation operators" by multiplying the E-species spin-rotation operator by an E-species torsional-coordinate factor of the form e(±niα). The resulting operator is capable of connecting the two components of a degenerate torsion-rotation E state. This has the effect of turning the hyperfine splitting pattern upside down for some nuclear-spin states, which leads to bottom-to-top and top-to-bottom hyperfine selection rules for some transitions, and thus to an explanation for the unexpectedly large observed hyperfine splittings. The constructed operator cannot contribute to hyperfine splittings in the A-species manifold because its matrix elements within the set of torsion-rotation A1 and A2 states are all zero. The theory developed here fits the observed large doublet splittings to a root-mean-square residual of less than 1 kHz and predicts unresolvable splittings for a number of transitions in which no doublet splitting was detected. PMID:27421405
Torsionally mediated spin-rotation hyperfine splittings at moderate to high J values in methanol
NASA Astrophysics Data System (ADS)
Belov, S. P.; Golubiatnikov, G. Yu.; Lapinov, A. V.; Ilyushin, V. V.; Alekseev, E. A.; Mescheryakov, A. A.; Hougen, J. T.; Xu, Li-Hong
2016-07-01
This paper presents an explanation based on torsionally mediated proton-spin-overall-rotation interaction for the observation of doublet hyperfine splittings in some Lamb-dip sub-millimeter-wave transitions between ground-state torsion-rotation states of E symmetry in methanol. These unexpected doublet splittings, some as large as 70 kHz, were observed for rotational quantum numbers in the range of J = 13 to 34, and K = - 2 to +3. Because they increase nearly linearly with J for a given branch, we confined our search for an explanation to hyperfine operators containing one nuclear-spin angular momentum factor I and one overall-rotation angular momentum factor J (i.e., to spin-rotation operators) and ignored both spin-spin and spin-torsion operators, since they contain no rotational angular momentum operator. Furthermore, since traditional spin-rotation operators did not seem capable of explaining the observed splittings, we constructed totally symmetric "torsionally mediated spin-rotation operators" by multiplying the E-species spin-rotation operator by an E-species torsional-coordinate factor of the form e±niα. The resulting operator is capable of connecting the two components of a degenerate torsion-rotation E state. This has the effect of turning the hyperfine splitting pattern upside down for some nuclear-spin states, which leads to bottom-to-top and top-to-bottom hyperfine selection rules for some transitions, and thus to an explanation for the unexpectedly large observed hyperfine splittings. The constructed operator cannot contribute to hyperfine splittings in the A-species manifold because its matrix elements within the set of torsion-rotation A1 and A2 states are all zero. The theory developed here fits the observed large doublet splittings to a root-mean-square residual of less than 1 kHz and predicts unresolvable splittings for a number of transitions in which no doublet splitting was detected.
Diez Muino, R.; Rolles, D.; Garcia de Abajo, F.J.; Fadley, C.S.; Van Hove, M.A.
2001-09-06
We use multiple scattering in non-spherical potentials (MSNSP) to calculate the angular distributions of electrons photoemitted from the 1s-shells of CO and N2 gas-phase molecules with fixed-in-space orientations. For low photoelectron kinetic energies (E<50 eV), as appropriate to certain shape-resonances, the electron scattering must be represented by non-spherical scattering potentials, which are naturally included in our formalism. Our calculations accurately reproduce the experimental angular patterns recently measured by several groups, including those at the shape-resonance energies. The MSNSP theory thus enhances the sensitivity to spatial electronic distribution and dynamics, paving the way toward their determination from experiment.
NASA Astrophysics Data System (ADS)
Maruyama, Tomoyuki; Cheoun, Myung-Ki; Kajino, Toshitaka; Mathews, Grant J.
2016-06-01
We study pion production by proton synchrotron radiation in the presence of a strong magnetic field when the Landau numbers of the initial and final protons are ni,f ∼104-105. We find in our relativistic field theory calculations that the pion decay width depends only on the field strength parameter which previously was only conjectured based upon semi-classical arguments. Moreover, we also find new results that the decay width satisfies a robust scaling relation, and that the polar angular distribution of emitted pion momenta is very narrow and can be easily obtained. This scaling implies that one can infer the decay width in more realistic magnetic fields of 1015 G, where ni,f ∼1012-1013, from the results for ni,f ∼104-105. The resultant pion intensity and angular distributions for realistic magnetic field strengths are presented and their physical implications discussed.
NASA Astrophysics Data System (ADS)
Maruyama, Tomoyuki; Cheoun, Myung-Ki; Kajino, Toshitaka; Mathews, Grant J.
2016-06-01
We study pion production by proton synchrotron radiation in the presence of a strong magnetic field when the Landau numbers of the initial and final protons are ni,f ∼104-105. We find in our relativistic field theory calculations that the pion decay width depends only on the field strength parameter which previously was only conjectured based upon semi-classical arguments. Moreover, we also find new results that the decay width satisfies a robust scaling relation, and that the polar angular distribution of emitted pion momenta is very narrow and can be easily obtained. This scaling implies that one can infer the decay width in more realistic magnetic fields of 1015 G, where ni,f ∼1012-1013, from the results for ni,f ∼104-105. The resultant pion intensity and angular distributions for realistic magnetic field strengths are presented and their physical implications discussed.
Theory and imaging applications of the angular correlation of multiply-scattered optical fields
NASA Astrophysics Data System (ADS)
Hoover, Brian Gilday
Through analysis of the field angular correlation the scattering of quasimonochromatic optical fields is considered as a coherence-based process well into the multiple scattering regime. Coherence analysis leads to the prediction of coherent effects in multiply-scattered light that can be applied to perform computed amplitude- phase imaging through turbid media and noninvasive laser material characterization. With the incentive of improved imaging through turbid media an experiment is described that directly compares the degradations, with the number of scattering mean free paths, of the field angular correlation and the correlation of the scattered wave with an unscattered reference wave, both of which can be used to form gates for imaging techniques in scattered light. Results for 20μ m polymer spheres show that the former correlation is consistently larger well into the multiple scattering regime (up to 10 mean free paths) for wavevector separations less than at least 50mm -1, and that the two correlations tend to merge in this scattering regime for larger wavevector separations. The implications of the results for imaging applications are considered. Complementary theoretical formulations of coherence effects in multiply-scattered fields are presented. Relations of the spatial coherence properties to the angular characteristics of the scattered field are established. A coherence-based model of multiple scattering processes is derived. The model predicts radiative-transfer-like behavior for restricted observational parameters, but also shows that the coherence-based process is required for an accurate description of the scattered field over an observational parameters. The applicability of the model to noninvasive laser material characterization is emphasized. A wavefront-sensor method is presented for measurement of the complex field angular correlation function of a three-dimensional turbid medium. The angular correlation function is measured at a series of
Torsion phenomenology at the CERN LHC
Belyaev, A. S.; Shapiro, I. L.; Vale, M. A. B. do
2007-02-01
We explore the potential of the CERN Large Hadron Collider (LHC) to test the dynamical torsion parameters. The form of the torsion action can be established from the requirements of consistency of effective quantum field theory. The most phenomenologically relevant part of the torsion tensor is dual to a massive axial vector field. This axial vector has geometric nature, that means it does not belong to any representation of the gauge group of the SM extension or GUT theory. At the same time, torsion should interact with all fermions, that opens the way for the phenomenological applications. We demonstrate that LHC collider can establish unique constraints on the interactions between fermions and torsion field considerably exceeding present experimental lower bounds on the torsion couplings and its mass. It is also shown how possible nonuniversal nature of torsion couplings due to the renormalization group running between the Planck and TeV energy scales can be tested via the combined analysis of Drell-Yan and tt production processes.
NASA Astrophysics Data System (ADS)
Hankel, Marlies; Connor, J. N. L.
2015-07-01
A valuable tool for understanding the dynamics of direct reactions is Nearside-Farside (NF) scattering theory. It makes a decomposition of the (resummed) partial wave series for the scattering amplitude, both for the differential cross section (DCS) and the Local Angular Momentum (LAM). This paper makes the first combined application of these techniques to complex-mode reactions. We ask if NF theory is a useful tool for their identification, in particular, can it distinguish complex-mode from direct-mode reactions? We also ask whether NF theory can identify NF interference oscillations in the full DCSs of complex-mode reactions. Our investigation exploits the fact that accurate quantum scattering matrix elements have recently become available for complex-mode reactions. We first apply NF theory to two simple models for the scattering amplitude of a complex-mode reaction: One involves a single Legendre polynomial; the other involves a single Legendre function of the first kind, whose form is suggested by complex angular momentum theory. We then study, at fixed translational energies, four state-to-state complex-mode reactions. They are: S(1D) + HD → SH + D, S(1D) + DH → SD + H, N(2D) +H2 → NH + H, and H+ + D2 → HD + D+. We compare the NF results for the DCSs and LAMs with those for a state-to-state direct reaction, namely, F + H2 → FH + H. We demonstrate that NF theory is a valuable tool for identifying and analyzing the dynamics of complex-mode reactions.
Hankel, Marlies E-mail: j.n.l.connor@manchester.ac.uk; Connor, J. N. L. E-mail: j.n.l.connor@manchester.ac.uk
2015-07-15
A valuable tool for understanding the dynamics of direct reactions is Nearside-Farside (NF) scattering theory. It makes a decomposition of the (resummed) partial wave series for the scattering amplitude, both for the differential cross section (DCS) and the Local Angular Momentum (LAM). This paper makes the first combined application of these techniques to complex-mode reactions. We ask if NF theory is a useful tool for their identification, in particular, can it distinguish complex-mode from direct-mode reactions? We also ask whether NF theory can identify NF interference oscillations in the full DCSs of complex-mode reactions. Our investigation exploits the fact that accurate quantum scattering matrix elements have recently become available for complex-mode reactions. We first apply NF theory to two simple models for the scattering amplitude of a complex-mode reaction: One involves a single Legendre polynomial; the other involves a single Legendre function of the first kind, whose form is suggested by complex angular momentum theory. We then study, at fixed translational energies, four state-to-state complex-mode reactions. They are: S({sup 1}D) + HD → SH + D, S({sup 1}D) + DH → SD + H, N({sup 2}D) +H{sub 2} → NH + H, and H{sup +} + D{sub 2} → HD + D{sup +}. We compare the NF results for the DCSs and LAMs with those for a state-to-state direct reaction, namely, F + H{sub 2} → FH + H. We demonstrate that NF theory is a valuable tool for identifying and analyzing the dynamics of complex-mode reactions.
Torsional Stability of Aluminum Alloy Seamless Tubing
NASA Technical Reports Server (NTRS)
Moore, R L; Paul, D A
1939-01-01
Torsion tests were made on 51ST aluminum-alloy seamless tubes having diameter-to-thickness ratios of from 77 to 139 and length-to-diameter ratios of from 1 to 60. The torsional strengths developed in the tubes which failed elastically (all tubes having lengths greater than 2 to 6 times the diameter) were in most cases within 10 percent of the value indicated by the theories of Donnel, Timoshenko, and Sturm, assuming a condition of simply supported ends.
NASA Astrophysics Data System (ADS)
Töws, W.; Pastor, G. M.
2015-11-01
Exact calculated time evolutions in the framework of a many-electron model of itinerant magnetism provide new insights into the laser-induced ultrafast demagnetization observed in ferromagnetic (FM) transition metal thin films. The interplay between local spin-orbit interactions and interatomic hopping is shown to be at the origin of the observed postexcitation breakdown of FM correlations between highly stable local magnetic moments. The mechanism behind spin- and angular-momentum transfer is revealed from a microscopic perspective by rigorously complying with all fundamental conservation laws. An energy-resolved analysis of the time evolution shows that the efficiency of the demagnetization process reaches almost 100% in the excited states.
Theory of neutrino emission from nucleon-hyperon matter in neutron stars: angular integrals
NASA Astrophysics Data System (ADS)
Kaminker, A. D.; Yakovlev, D. G.; Haensel, P.
2016-08-01
Investigations of thermal evolution of neutron stars with hyperon cores require neutrino emissivities for many neutrino reactions involving strongly degenerate particles (nucleons, hyperons, electrons, muons). We calculate the angular integrals In (over orientations of momenta of n degenerate particles) for major neutrino reactions with n=3, 4, 5 at all possible combinations of particle Fermi momenta. The integrals In are necessary ingredients for constructing a uniform database of neutrino emissivities in dense nucleon-hyperon matter. The results can also be used in many problems of physical kinetics of strongly degenerate systems.
Noncontact measurement of angular deflection
NASA Technical Reports Server (NTRS)
Bryant, E. L.
1978-01-01
Technique for measuring instantaneous angular deflection of object requires no physical contact. Technique utilizes two flat refractors, converging lens, and different photocell. Distinction of method is its combination of optical and electromechanical components into feedback system in which measurement error is made to approach zero. Application is foreseen in measurement of torsional strain.
Töws, W; Pastor, G M
2015-11-20
Exact calculated time evolutions in the framework of a many-electron model of itinerant magnetism provide new insights into the laser-induced ultrafast demagnetization observed in ferromagnetic (FM) transition metal thin films. The interplay between local spin-orbit interactions and interatomic hopping is shown to be at the origin of the observed postexcitation breakdown of FM correlations between highly stable local magnetic moments. The mechanism behind spin- and angular-momentum transfer is revealed from a microscopic perspective by rigorously complying with all fundamental conservation laws. An energy-resolved analysis of the time evolution shows that the efficiency of the demagnetization process reaches almost 100% in the excited states. PMID:26636871
Maruyama, Tomoyuki; Cheoun, Myung-Ki; Kajino, Toshitaka; Mathews, Grant J.
2016-03-26
We study pion production by proton synchrotron radiation in the presence of a strong magnetic field when the Landau numbers of the initial and final protons are n(i, f) similar to 10(4)-10(5). We find in our relativistic field theory calculations that the pion decay width depends only on the field strength parameter which previously was only conjectured based upon semi-classical arguments. Moreover, we also find new results that the decay width satisfies a robust scaling relation, and that the polar angular distribution of emitted pion momenta is very narrow and can be easily obtained. This scaling implies that one canmore » infer the decay width in more realistic magnetic fields of 10(15) G, where n(i, f) similar to 10(12)-10(13), from the results for n(i, f) similar to 10(4)-10(5). The resultant pion intensity and angular distributions for realistic magnetic field strengths are presented and their physical implications discussed. (C) 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP(3).« less
NASA Astrophysics Data System (ADS)
Kurian, P.; Verzegnassi, C.
2016-01-01
We consider in a quantum field theory framework the effects of a classical magnetic field on the spin and orbital angular momentum (OAM) of a free electron. We derive formulae for the changes in the spin and OAM due to the introduction of a general classical background field. We consider then a constant magnetic field, in which case the relevant expressions of the effects become much simpler and conversions between spin and OAM become readily apparent. An estimate of the expectation values for a realistic electron state is also given. Our findings may be of interest to researchers in spintronics and the field of quantum biology, where electron spin has been implicated on macroscopic time and energy scales.
Meana-Pañeda, Rubén; Fernández-Ramos, Antonio
2014-05-07
This work reports a detailed theoretical study of the hydrogen abstraction reactions from ethanol by atomic hydrogen. The calculated thermal rate constants take into account torsional anharmonicity and conformational flexibility, in addition to the variational and tunneling effects. Specifically, the kinetics calculations were performed by using multi-path canonical variational transition state theory with least-action path tunneling corrections, to which we have added the two-dimensional non-separable method to take into account torsional anharmonicity. The multi-path thermal rate constant is expressed as a sum over conformational reaction channels. Each of these channels includes all the transition states that can be reached by internal rotations. The results show that, in the interval of temperatures between 250 and 2500 K, the account for multiple paths leads to higher thermal rate constants with respect to the single path approach, mainly at low and at high temperatures. In addition, torsional anharmonicity enhances the slope of the Arrhenius plot in this range of temperatures. Finally, we show that the incorporation of tunneling into the hydrogen abstraction reactions substantially changes the contribution of each of the transition states to the conformational reaction channel.
Testicular Torsion (For Parents)
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Torsional oscillations in the solar convection zone
NASA Astrophysics Data System (ADS)
Covas, E.; Tavakol, R.; Moss, D.; Tworkowski, A.
2000-08-01
Recent analysis of the helioseismic observations indicate that the previously observed surface torsional oscillations extend significantly downwards into the solar convection zone. In an attempt to understand these oscillations, we study the nonlinear coupling between the magnetic field and the solar differential rotation in the context of a mean field dynamo model, in which the nonlinearity is due to the action of the azimuthal component of the Lorentz force of the dynamo generated magnetic field on the solar angular velocity. The underlying zero order angular velocity is chosen to be consistent with the most recent helioseismic data. The model produces butterfly diagrams which are in qualitative agreement with the observations. It displays torsional oscillations that penetrate into the convection zone, and which with time migrate towards the equator. The period of these oscillations is found to be half that of the period of the global magnetic fields. This is compatible with the observed period of the surface torsional oscillations. Inside the convection zone, this is a testable prediction that is not ruled out by the observations so far available.
Li, Zhi; Durgin, Frank H
2012-01-01
Two theories of distance perception—ie, the angular expansion hypothesis (Durgin and Li, 2011 Attention, Perception, & Psychophysics 73 1856–1870) and the intrinsic bias hypothesis (Ooi et al, 2006, Perception 35 605–624)—are compared. Both theories attribute exocentric distance foreshortening to an exaggeration in perceived slant, but their fundamental geometrical assumptions are very different. The intrinsic bias hypothesis assumes a constant bias in perceived geographical slant of the ground plane and predicts both perceived egocentric and exocentric distances are increasingly compressed. In contrast, the angular expansion hypothesis assumes exaggerations in perceived gaze angle and perceived optical slant. Because the bias functions of the two angular variables are different, it allows the angular expansion hypothesis to distinguish two types of distance foreshortening—the linear compression in perceived egocentric distance and the nonlinear compression in perceived exocentric distance. While the intrinsic bias is proposed only for explaining distance biases, the angular expansion hypothesis provides accounts for a broader range of spatial biases. PMID:22792434
DOE R&D Accomplishments Database
Schwinger, J.
1952-01-26
The commutation relations of an arbitrary angular momentum vector can be reduced to those of the harmonic oscillator. This provides a powerful method for constructing and developing the properties of angular momentum eigenvectors. In this paper many known theorems are derived in this way, and some new results obtained. Among the topics treated are the properties of the rotation matrices; the addition of two, three, and four angular momenta; and the theory of tensor operators.
Structural and torsional vibration analysis of a dry screw compressor
NASA Astrophysics Data System (ADS)
Willie, J.; Sachs, R.
2015-08-01
This paper investigates torsional vibration and pulsating noise in a dry screw compressor. The compressor is designed at Gardner Denver (GD) and is oil free and use for mounting on highway trucks. They are driven using a Power Take-Off (PTO) transmission and gear box on a truck. Torque peak fluctuation and noise measurements are done and their sources are investigated and reported in this work. To accurately predict the torsional response (frequency and relative angular deflection and torque amplitude), the Holzer method is used. It is shown that the first torsional frequency is manifested as sidebands in the gear train meshing frequencies and this can lead to noise that is the result of amplitude modulation. Sensitivity analysis of the drive train identifies the weakest link in the drive train that limits the first torsional frequency to a low value. Finally, the significance of higher mode shapes on inter-lobe clearance distribution of the rotors is investigated.
NASA Technical Reports Server (NTRS)
Ihrke, Chris A. (Inventor); Parsons, Adam H. (Inventor); Mehling, Joshua S. (Inventor); Griffith, Bryan Kristian (Inventor)
2012-01-01
A torsion spring comprises an inner mounting segment. An outer mounting segment is located concentrically around the inner mounting segment. A plurality of splines extends from the inner mounting segment to the outer mounting segment. At least a portion of each spline extends generally annularly around the inner mounting segment.
Lin, Chih-Ming; Angot, Ludovic
2008-06-15
The first Born approximation is applied to calculate the angular selectivity for different positions on the reconstructed image as a function of the object beam's optical axis angle theta(ob) and reference beam angle theta(rw) for a holographic data storage system that records the Fourier transform holograms in a medium with an infinite plane-wave reference beam. Results are compared with those calculated by the coupled-wave theory. PMID:18552937
Clark, G
2003-04-28
This report describes a feasibility study. We are interested in calculating the angular and linear velocities of a re-entry vehicle using six acceleration signals from a distributed accelerometer inertial measurement unit (DAIMU). Earlier work showed that angular and linear velocity calculation using classic nonlinear ordinary differential equation (ODE) solvers is not practically feasible, due to mathematical and numerical difficulties. This report demonstrates the theoretical feasibility of using model-based nonlinear state estimation techniques to obtain the angular and linear velocities in this problem. Practical numerical and calibration issues require additional work to resolve. We show that the six accelerometers in the DAIMU are not sufficient to provide observability, so additional measurements of the system states are required (e.g. from a Global Positioning System (GPS) unit). Given the constraint that our system cannot use GPS, we propose using the existing on-board 3-axis magnetometer to measure angular velocity. We further show that the six nonlinear ODE's for the vehicle kinematics can be decoupled into three ODE's in the angular velocity and three ODE's in the linear velocity. This allows us to formulate a three-state Gauss-Markov system model for the angular velocities, using the magnetometer signals in the measurement model. This re-formulated model is observable, allowing us to build an Extended Kalman Filter (EKF) for estimating the angular velocities. Given the angular velocity estimates from the EKF, the three ODE's for the linear velocity become algebraic, and the linear velocity can be calculated by numerical integration. Thus, we do not need direct measurements of the linear velocity to provide observability, and the technique is mathematically feasible. Using a simulation example, we show that the estimator adds value over the numerical ODE solver in the presence of measurement noise. Calculating the velocities in the presence of
Torsional fatigue of aramid fibers
Kawabata, S.; Sera, M.
1993-12-31
An experimental investigation on the shear fatigue process of aramid fibers is presented. Repeated cycles of the torsional deformation are applied on the aramid single fiber and the reduction of the shear modulus of the fiber with an increasing number of the cycles is observed for different strain amplitudes. It has been found that the reduction process of the shear modulus with an increasing number of the repeated cycles depends on the strain amplitude and the effect of the number of cycles is equivalent to that of the strain amplitude on the modulus reduction and they may be superposed like the time-temperature equivalence superposition observed in the viscoelasticity of amorphous polymeric solids. From this relation, the life prediction for the long term use of aramid fibers becomes possible by using this superimposed relation. A simple rate process theory is applied to interpret this fatigue process and to derive the equation for predicting the life cycle number of the loading.
NASA Technical Reports Server (NTRS)
Mattson, D. L.
1975-01-01
The effect of prolonged angular acceleration on choice reaction time to an accelerating visual stimulus was investigated, with 10 commercial airline pilots serving as subjects. The pattern of reaction times during and following acceleration was compared with the pattern of velocity estimates reported during identical trials. Both reaction times and velocity estimates increased at the onset of acceleration, declined prior to the termination of acceleration, and showed an aftereffect. These results are inconsistent with the torsion-pendulum theory of semicircular canal function and suggest that the vestibular adaptation is of central origin.
Femtosecond torsional relaxation
NASA Astrophysics Data System (ADS)
Clark, J.; Nelson, T.; Tretiak, S.; Cirmi, G.; Lanzani, G.
2012-03-01
Molecular conformational reorganization following photon absorption is a fundamental process driving reactions such as the cis-trans isomerization at the heart of the primary step of vision and can be exploited for switching in artificial systems using photochromics. In general, conformational change occurs on a timescale defined by the energy of the main vibrational mode and the rate of energy dissipation. Typically, for a conformational change such as a twist around the backbone of a conjugated molecule, this occurs on the tens of picoseconds timescale. However, here we demonstrate experimentally that in certain circumstances the molecule, in this case an oligofluorene, can change conformation over two orders of magnitude faster (that is sub-100fs) in a manner analogous to inertial solvent reorganization demonstrated in the 1990s. Theoretical simulations demonstrate that non-adiabatic transitions during internal conversion can efficiently convert electronic potential energy into torsional kinetic energy, providing the `kick' that prompts sub-100fs torsional reorganization.
Torsional Ratcheting Actuating System
BARNES,STEPHEN MATTHEW; MILLER,SAMUEL L.; RODGERS,M. STEVEN; BITSIE,FERNANDO
2000-01-24
A new type of surface micromachined ratcheting actuation system has been developed at the Microelectronics Development Laboratory at Sandia National Laboratories. The actuator uses a torsional electrostatic comb drive that is coupled to an external ring gear through a ratcheting scheme. The actuator can be operated with a single square wave, has minimal rubbing surfaces, maximizes comb finger density, and can be used for open-loop position control. The prototypes function as intended with a minimum demonstrated operating voltage of 18V. The equations of motion are developed for the torsional electrostatic comb drive. The resonant frequency, voltage vs. displacement and force delivery characteristics are predicted and compared with the fabricated device's performance.
NASA Technical Reports Server (NTRS)
Devries, P. L.; George, T. F.
1978-01-01
The problem of two atoms colliding in the presence of an intense radiation field, such as that of a laser, is investigated. The radiation field, which couples states of different electronic symmetry, is described by the number state representation while the electronic degrees of freedom (plus spin-orbit interaction) are discussed in terms of a diabatic representation. The total angular momentum of the field-free system and the angular momentum transferred by absorption (or emission) of a photon are explicitly considered in the derivation of the coupled scattering equations. A model calculation is discussed for the Xe + F collision system.
Torsional actuation with extension-torsion composite coupling and a magnetostrictive actuator
NASA Astrophysics Data System (ADS)
Bothwell, Christopher M.; Chandra, Ramesh; Chopra, Inderjit
1995-04-01
An analytical-experimental study of using magnetostrictive actuators in conjunction with an extension-torsion coupled composite tube to actuate a rotor blade trailing-edge flap to actively control helicopter vibration is presented. Thin walled beam analysis based on Vlasov theory was used to predict the induced twist and extension in a composite tube with magnetostrictive actuation. The study achieved good correlation between theory and experiment. The Kevlar-epoxy systems showed good correlation between measured and predicted twist values.
Constraining spacetime torsion with the Moon and Mercury
March, Riccardo; Bellettini, Giovanni; Tauraso, Roberto; Dell'Agnello, Simone
2011-05-15
We report a search for new gravitational physics phenomena based on Riemann-Cartan theory of general relativity including spacetime torsion. Starting from the parametrized torsion framework of Mao, Tegmark, Guth, and Cabi, we analyze the motion of test bodies in the presence of torsion, and, in particular, we compute the corrections to the perihelion advance and to the orbital geodetic precession of a satellite. We consider the motion of a test body in a spherically symmetric field, and the motion of a satellite in the gravitational field of the Sun and the Earth. We describe the torsion field by means of three parameters, and we make use of the autoparallel trajectories, which in general differ from geodesics when torsion is present. We derive the specific approximate expression of the corresponding system of ordinary differential equations, which are then solved with methods of celestial mechanics. We calculate the secular variations of the longitudes of the node and of the pericenter of the satellite. The computed secular variations show how the corrections to the perihelion advance and to the orbital de Sitter effect depend on the torsion parameters. All computations are performed under the assumptions of weak field and slow motion. To test our predictions, we use the measurements of the Moon's geodetic precession from lunar laser ranging data, and the measurements of Mercury's perihelion advance from planetary radar ranging data. These measurements are then used to constrain suitable linear combinations of the torsion parameters.
Primordial magnetic fields and dynamos from parity violated torsion
NASA Astrophysics Data System (ADS)
Garcia de Andrade, L. C.
2012-05-01
It is well known that torsion induced magnetic fields may seed galactic dynamos, but the price one pays for that is the conformal and gauge invariance breaks and a tiny photon mass. More recently I have shown [L.C. Garcia de Andrade, Phys. Lett. B 468 (2011) 28] that magnetic fields decay in a gauge invariant non-minimal coupling theory of torsion is slow down, which would allow for dynamo action to take place. In this Letter, by adding a parity violation term of the type Rɛ to the non-coupling term, a magnetic dynamo equation is obtained. From dynamo equation it is shown that torsion terms only appear in the dynamo equation when diffusion in the cosmic plasma is present. Torsion breaks the homogeneity of the magnetic field in the universe. Since Zeldovich anti-dynamo theorem assumes that the spacetime should be totally flat, torsion is responsible for violation of anti-dynamo theorem in 2D spatial dimensions. Contrary to previous results torsion induced primordial magnetic fields cannot seed galactic dynamos since from torsion and diffusion coefficient the decaying time of the magnetic field is 106yrs, which is much shorter than the galaxy age.
NASA Technical Reports Server (NTRS)
Bradas, James C.; Fennelly, Alphonsus J.; Smalley, Larry L.
1987-01-01
It is shown that a generalized (or 'power law') inflationary phase arises naturally and inevitably in a simple (Bianchi type-I) anisotropic cosmological model in the self-consistent Einstein-Cartan gravitation theory with the improved stress-energy-momentum tensor with the spin density of Ray and Smalley (1982, 1983). This is made explicit by an analytical solution of the field equations of motion of the fluid variables. The inflation is caused by the angular kinetic energy density due to spin. The model further elucidates the relationship between fluid vorticity, the angular velocity of the inertially dragged tetrads, and the precession of the principal axes of the shear ellipsoid. Shear is not effective in damping the inflation.
NASA Astrophysics Data System (ADS)
Bradas, James C.; Fennelly, Alphonsus J.; Smalley, Larry L.
1987-04-01
It is shown that a generalized (or 'power law') inflationary phase arises naturally and inevitably in a simple (Bianchi type-I) anisotropic cosmological model in the self-consistent Einstein-Cartan gravitation theory with the improved stress-energy-momentum tensor with the spin density of Ray and Smalley (1982, 1983). This is made explicit by an analytical solution of the field equations of motion of the fluid variables. The inflation is caused by the angular kinetic energy density due to spin. The model further elucidates the relationship between fluid vorticity, the angular velocity of the inertially dragged tetrads, and the precession of the principal axes of the shear ellipsoid. Shear is not effective in damping the inflation.
Randall-Sundrum scenario with bulk dilaton and torsion
Mukhopadhyaya, Biswarup; Sen, Somasri; SenGupta, Soumitra
2009-06-15
We consider a string-inspired torsion-dilaton-gravity action in a Randall-Sundrum braneworld scenario and show that, in an effective four-dimensional theory on the visible brane, the rank-2 antisymmetric Kalb-Ramond field (source of torsion) is exponentially suppressed. The result is similar to our earlier result in [B. Mukhopadhyaya, S. Sen, and S. SenGupta, Phys. Rev. Lett. 89, 121101 (2002); Phys. Rev. Lett. 89, 259902(E) (2002)], where no dilaton was present in the bulk. This offers an explanation of the apparent invisibility of torsion in our space-time. However, in this case the trilinear couplings {approx}TeV{sup -1} between the dilaton and torsion may lead to new signals in TeV-scale experiments, bearing the stamp of extra warped dimensions.
NASA Astrophysics Data System (ADS)
Coppi, B.
2007-11-01
Differentially rotating structures in the prevalent field of a central object have been shown to develop a ``crystal'' magnetic structure resulting from toroidal internal currents and leading to the formation of density ring sequencesootnotetextB. Coppi and F. Rousseau, Ap. J. 641, 458 (2006) rather than disks. Poloidal current densities with appropriate symmetries are found to be connected with angular momentum transport processes represented by an effective viscosity. Jets are suggested to consist of a series of stable ``smoke- rings'' ejected vertically in opposite directions from the central region of the considered ring sequence. A small inward flow velocity is shown to induce a spiral pattern in the magnetic field lines on a selected family of magnetic surfaces. The accretion theoryootnotetextB. Coppi, Nuc. Fus. 42, 1 (2002) of the spontaneous rotation phenomenon in toroidal laboratory plasmas relies on the ejection of angular momentum toward the surrounding material wall, by collisional ballooning modes excited at the edge, whose phase velocity depends on collisionality. The resulting recoil gives rise to the rotation of the main body of the plasma column as other plasma modes (called VTG) provide the needed inward transport of angular momentum. *Sponsored in part by the US D.O.E.
Autoparallel vs. Geodesic Trajectories in a Model of Torsion Gravity
NASA Astrophysics Data System (ADS)
Acedo, Luis
2015-11-01
We consider a parametrized torsion gravity model for Riemann-Cartan geometry around a rotating axisymmetric massive body. In this model, the source of torsion is given by a circulating vector potential following the celestial parallels around the rotating object. Ours is a variant of the Mao, Tegmark, Guth and Cabi (MTGC model) in which the total angular momentum is proposed as a source of torsion. We study the motion of bodies around the rotating object in terms of autoparallel trajectories and determine the leading perturbations of the orbital elements by using standard celestial mechanics techniques. We find that this torsion model implies new gravitational physical consequences in the Solar system and, in particular, secular variations of the semi-major axis of the planetary orbits. Perturbations on the longitude of the ascending node and the perihelion of the planets are already under discussion in the astronomical community, and if confirmed as truly non-zero effects at a statistically significant level, we might be at the dawn of an era of torsion phenomenology in the Solar system.
Testicular torsion: A surgical emergency
Prater, J.M.; Overdorf, B.S. )
1991-09-01
Testicular torsion is caused by twisting of the spermatic cord, which results in compromised testicular blood flow. The degree of ischemic injury is determined by the severity of arterial compression and the interval between the onset of symptoms and surgical intervention. Torsion usually occurs at puberty, and an anatomic defect known as bell-clapper deformity is usually present. Typical symptoms include acute scrotal pain with associated nausea and vomiting. Up to one-half of patients report previous similar episodes. On examination, the testis is high-riding, tender, swollen and firm. Testicular scan or Doppler ultrasound examination can be helpful in distinguishing torsion from acute epididymitis. Prompt surgical treatment is indicated to reduce the torsion, and bilateral orchiopexy is performed to prevent recurrence. Exocrine function, as determined by semen analysis, is often abnormal after unilateral torsion. 25 references.
NASA Technical Reports Server (NTRS)
Herakovich, C. T.
1978-01-01
Comparison between theory and experiment for buckling of laminated graphite-epoxy and boron-epoxy cylinders under combined compression and torsion are presented. The experimental results are compared to a theory by Wu. It is shown that there is excellent agreement between theory and experiment for pure torsional loading (positive and negative), experimental buckling loads for pure compression are well below the predicted values, and good correlation is exhibited between theory and experiment for buckling under combined loading when compared in the form of normalized buckling interaction diagrams in axial-torsional load space.
Torsion-rotation intensities in methanol
NASA Astrophysics Data System (ADS)
Pearson, John
Methanol exists in numerous kinds of astronomical objects featuring a wide range of local conditions. The light nature of the molecule coupled with the internal rotation of the methyl group with respect to the hydroxyl group results in a rich, strong spectrum that spans the entire far-infrared region. As a result, any modest size observational window will have a number of strong methanol transitions. This has made it the gas of choice for testing THz receivers and to extract the local physical conditions from observations covering small frequency windows. The latter has caused methanol to be dubbed the Swiss army knife of astrophysics. Methanol has been increasingly used in this capacity and will be used even more for subsequent investigations into the Herschel archive, and with SOFIA and ALMA. Interpreting physical conditions on the basis of a few methanol lines requires that the molecular data, line positions, intensities, and collision rates, be complete, consistent and accurate to a much higher level than previously required for astrophysics. The need for highly reliable data is even more critical for modeling the two classes of widespread maser action and many examples of optical pumping through the torsional bands. Observation of the torsional bands in the infrared will be a unique opportunity to directly connect JWST observations with those of Herschel, SOFIA, and ALMA. The theory for the intensities of torsion-rotation transitions in a molecule featuring a single internally rotating methyl group is well developed after 70 years of research. However, other than a recent very preliminary and not completely satisfactory investigation of a few CH3OH torsional bands, this theory has never been experimentally tested for any C3V internal rotor. More alarming is a set of recent intensity calibrated microwave measurements that showed deviations relative to calculations of up to 50% in some ground state rotational transitions commonly used by astronomers to extract
Coupled composite rotor blades under bending and torsional loads
NASA Astrophysics Data System (ADS)
Chandra, Ramesh; Chopra, Inderjit
This paper presents an analytical-cum-experimental study of the structural response of composite rotor blades with elastic couplings. Vlasov theory is expanded to analyze two-cell composite rotor blades made out of general composite laminates including the transverse shear deformation of the cross-section. In order to validate this analysis, two-cell graphite-epoxy composite blades with bending-torsion coupling were fabricated using matched-die molding technique. These blades were tested under tip bending and torsional loads, and their structural response in terms of bending slope and twist was measured with a laser optical system. Good correlation between theory and experiment is achieved.
Performance of an angular flange aeroelastic wind energy converter
Ahmadi, G.
1983-05-01
ALL conventional wind turbines operate on the principles of turbomachinaries, with wind being made to flow over a set of rotating vanes. Recently, a new concept for wind energy conversion based on aeroelastic instability was introduced. It is well known that couplings between the vibration of an elastic structure and fluid stream may lead to aeroelastic instability. Energy then is transferred from the airstream into the elastic structure, which results in a destructive monotonic increase of the vibration amplitude of the structure. The failure of the Tacoma Narrows Bridge is one of the well-known examples of such a disaster. The use of an aeroelastic instability (or flutter) mechanism for constructing a wind energy converter was suggested. The theory for a torsional wind energy converter and the results of some model tests were also presented. Recently, some studies on similar types of wind energy converters using oscillating airfoils were reported. In the present study an angular flange H-section model of a torsional aeroelastic wind energy converter is constructed, and its performances under various conditions are investigated. The effects of the variations of the flange angle and the flange width on the performance of the model are studied. The weight of the pendulum is also varied, and its effects on the power coefficient of the model are investigated. It is observed that the efficiency of energy conversion decreases with an increase in wind speed. A method for possible improvement of the theoretical prediction is suggested and discussed.
NASA Technical Reports Server (NTRS)
Stang, Ambrose H; Ramberg, Walter; Back, Goldie
1937-01-01
This report presents the results of tests of 63 chromium-molybdenum steel tubes and 102 17st aluminum-alloy tubes of various sizes and lengths made to study the dependence of the torsional strength on both the dimensions of the tube and the physical properties of the tube material. Three types of failure are found to be important for sizes of tubes frequently used in aircraft construction: (1) failure by plastic shear, in which the tube material reached its yield strength before the critical torque was reached; (2) failure by elastic two-lobe buckling, which depended only on the elastic properties of the tube material and the dimensions of the tube; and (3) failure by a combination of (1) and (2) that is, by buckling taking place after some yielding of the tube material.
NASA Astrophysics Data System (ADS)
Bialynicki-Birula, Iwo; RadoŻycki, Tomasz
2016-06-01
The motion of a neutral atom endowed with a magnetic moment interacting with the magnetic field is determined from the Ehrenfest-like equations of motion. These equations for the average values of the translational and spin degrees of freedom are derived from the Schrödinger-Pauli wave equation, and they form a set of nine coupled nonlinear evolution equations. The numerical and analytic solutions of these equations are obtained for the combination of the rotating magnetic field of a wave carrying orbital angular momentum and a static magnetic field. The running wave traps the atom only in the transverse direction, while the standing wave traps the atom also in the direction of the beam.
Saccular impact on ocular torsion.
De Graaf, B; Bos, J E; Groen, E
1996-01-01
When someone is tilted laterally, the shear force on the maculae of the utriculus and the sacculus is described by the sine and the cosine of the angle of tilt, respectively. So both the sacculus and the utriculus are stimulated, but in the literature, ocular torsion is normally attributed to utricular function alone (and, thus, seen as a response to y-axis linear acceleration). However, on the base of a series of experiments on a tilt chair, a linear track, human centrifuges, and during parabolic flights, we conclude that the sacculus contributes to ocular torsion as well (there is a response to z-axis linear acceleration). The data suggest that the ratio of the utricular and saccular impact on ocular torsion is 3:1. The utriculus generates conjugate and the sacculus disjunctive torsional eye movements. PMID:8886354
Isolated penile torsion in newborns
Eroglu, Egemen; Gundogdu, Gokhan
2015-01-01
Introduction: We reported on the incidence of isolated penile torsion among our healthy children and our approach to this anomaly. Methods: Between 2011 and 2014, newborn babies with penile torsion were classified according to the angle of torsion. Surgical correction (penile degloving and reattachment for moderate cases and dorsal dartos flap technique in case of resistance) after 6 months was advised to the babies with rotations more than 45°. Results: Among 1000 newborn babies, 200 isolated penile torsions were found, and among these, 43 had torsions more than 45°, and 4 of these had angles greater than 90°. The mean angle of the rotations was found 30.45° (median: 20°). In total, 8 children with 60° torsions were previously circumcised. Surgery was performed on 19 patients, with a mean patient age of 12 ± 2 months. Of these 19, 13 babies were corrected with degloving and reattachment. This technique was not enough on the remaining 6 patients; therefore, derotational dorsal dartos flap was added to correct the torsion. After a mean of 15.6 ± 9.8 months, residual penile rotation, less than 15°, was found only in 2 children. Conclusion: The incidence of isolated penile torsion is 20% in newborns. However, rotation more than 45° angles are seen in 4.3% of male babies. Correction is not necessary in mild degrees, and penile degloving with reattachment is enough in most cases. If the initial correction is insufficient, dorsal dartos flap rotation is easy and effective. Prior circumcision neither disturbs the operative procedure nor affects the outcomes. PMID:26600889
Torsional vibration of aircraft engines
NASA Technical Reports Server (NTRS)
Lurenbaum, Karl
1932-01-01
Exhaustive torsional-vibration investigations are required to determine the reliability of aircraft engines. A general outline of the methods used for such investigations and of the theoretical and mechanical means now available for this purpose is given, illustrated by example. True vibration diagrams are usually obtained from vibration measurements on the completed engine. Two devices for this purpose and supplementing each other, the D.V.L. torsiograph and the D.V.L. torsion recorder, are described in this report.
Torsion Stiffness of a Protein Pair Determined by Magnetic Particles
Janssen, X.J.A.; van Noorloos, J.M.; Jacob, A.; van IJzendoorn, L.J.; de Jong, A.M.; Prins, M.W.J.
2011-01-01
We demonstrate the ability to measure torsion stiffness of a protein complex by applying a controlled torque on a magnetic particle. As a model system we use protein G bound to an IgG antibody. The protein pair is held between a magnetic particle and a polystyrene substrate. The angular orientation of the magnetic particle shows an oscillating behavior upon application of a rotating magnetic field. The amplitude of the oscillation increases with a decreasing surface coverage of antibodies on the substrate and with an increasing magnitude of the applied field. For decreasing antibody coverage, the torsion spring constant converges to a minimum value of 1.5 × 103 pN·nm/rad that corresponds to a torsion modulus of 4.5 × 104 pN·nm2. This torsion stiffness is an upper limit for the molecular bond between the particle and the surface that is tentatively assigned to a single protein G–IgG protein pair. This assignment is supported by interpreting the measured stiffness with a simple mechanical model that predicts a two orders of magnitude larger stiffness for the protein G–IgG complex than values found for micrometer length dsDNA. This we understand from the structural properties of the molecules, i.e., DNA is a long and flexible chain-like molecule, whereas the antibody-antigen couple is orders of magnitude smaller and more globular in shape due to the folding of the molecules. PMID:21539795
Quick phases control ocular torsion during smooth pursuit.
Hess, Bernhard J M; Thomassen, Jakob S
2011-11-01
One of the open questions in oculomotor control of visually guided eye movements is whether it is possible to smoothly track a target along a curvilinear path across the visual field without changing the torsional stance of the eye. We show in an experimental study of three-dimensional eye movements in subhuman primates (Macaca mulatta) that although the pursuit system is able to smoothly change the orbital orientation of the eye's rotation axis, the smooth ocular motion was interrupted every few hundred milliseconds by a small quick phase with amplitude <1.5° while the animal tracked a target along a circle or ellipse. Specifically, during circular pursuit of targets moving at different angular eccentricities (5°, 10°, and 15°) relative to straight ahead at spatial frequencies of 0.067 and 0.1 Hz, the torsional amplitude of the intervening quick phases was typically around 1° or smaller and changed direction for clockwise vs. counterclockwise tracking. Reverse computations of the eye rotation based on the recorded angular eye velocity showed that the quick phases facilitate the overall control of ocular orientation in the roll plane, thereby minimizing torsional disturbances of the visual field. On the basis of a detailed kinematic analysis, we suggest that quick phases during curvilinear smooth tracking serve to minimize deviations from Donders' law, which are inevitable due to the spherical configuration space of smooth eye movements. PMID:21715669
ERIC Educational Resources Information Center
Shakur, Asif; Sinatra, Taylor
2013-01-01
The gyroscope in a smartphone was employed in a physics laboratory setting to verify the conservation of angular momentum and the nonconservation of rotational kinetic energy. As is well-known, smartphones are ubiquitous on college campuses. These devices have a panoply of built-in sensors. This creates a unique opportunity for a new paradigm in…
... the mouth. Overview Angular cheilitis (perlèche) is a chronic inflammatory condition of the corners of the mouth. Usually associated with a fungal ( Candidal ) or bacterial ( Staphylococcal ) infection, those ... people of all ages. Chronic pooling of saliva encourages fungal and bacterial growth, ...
Deligne-Beilinson cohomology and Abelian link invariants: Torsion case
Thuillier, F.
2009-12-15
For the Abelian Chern-Simons field theory, we consider the quantum functional integration over the Deligne-Beilinson cohomology classes and present an explicit path-integral nonperturbative computation of the Chern-Simons link invariants in SO(3){approx_equal}RP{sup 3}, a toy example of a 3-manifold with torsion.
Testing gravity-induced collapse models with torsion pendulums
NASA Astrophysics Data System (ADS)
Helou, Bassam; Wipf, Christopher; Chen, Yanbei
2016-03-01
Wavefunction collapse models have been proposed to resolve the measurement problem in QM. Some, , such as Diosi-Penrose model, are motivated by gravity. We first present the theory of such models, highlighting new results, such as fixing the only free paramater in the model. We then propose torsion pendulums as a promising optomechanical platform to test such models.
The Effect of Torsion-Torsion Interactions on the Tunneling Split Torsional Ground State.
NASA Astrophysics Data System (ADS)
Cameron, Ian George
In NMR studies of methyl groups it is normally assumed that the effects of inter-methyl group interactions (torsion-torsion interactions) are negligible. This is probably a reasonable assump- tion at high temperatures(, )(>50K), however, for lower temperatures this is no longer the case. This is clearly demonstrated with tetra- methylsilane (TMS) for which several important effects of torsion-torsion interactions are reported. The spin lattice relaxtion time, T(,1), was measured as a function of the Larmor frequency at several temperatures and it is shown that the observed recovery can be characterized by two exponential contributions. As anticipated, the frequency dependence of T(,ZT)('-1), the recovery rate for the faster of the two contributing processes, exhibited resonant-like peaks. In other ways, however, these results deviate quite substantially from the behavior expected. Firstly, the hindering potential experienced by each methyl group in TMS is perturbed by the other three methyl groups in the molecule. This leads to the appearance of four resonant peaks in the frequency dependence of T(,ZT)('-1) instead of just two. A perturbation calculation is presented to support this interpretation. Secondly, the contribu- tion to the measured linewidths from lifetime broadening, which dominates at high temperatures, becomes negligible at low tem- peratures compared with the underlying "inherent" width of the tunneling lines. We associate this inherent width with a relatively narrow ((TURN)1 MHz), quasi-continuous distribution of tunneling split- tings which occurs as a result of partially averaged torsion-torsion interactions. Thirdly, the intensity of the peaks, which is expected to be temperature independent, drops sharply as the temperature is lowered. This is a clear indication of the formation of a band of tunneling states of low temperatures where torsion-torsion interactions are strong.
Hypersymplectic structures with torsion on Lie algebroids
NASA Astrophysics Data System (ADS)
Antunes, P.; Nunes da Costa, J. M.
2016-06-01
Hypersymplectic structures with torsion on Lie algebroids are investigated. We show that each hypersymplectic structure with torsion on a Lie algebroid determines three Nijenhuis morphisms. From a contravariant point of view, these structures are twisted Poisson structures. We prove the existence of a one-to-one correspondence between hypersymplectic structures with torsion and hyperkähler structures with torsion. We show that given a Lie algebroid with a hypersymplectic structure with torsion, the deformation of the Lie algebroid structure by any of the transition morphisms does not affect the hypersymplectic structure with torsion. We also show that if a triplet of 2-forms is a hypersymplectic structure with torsion on a Lie algebroid A, then the triplet of the inverse bivectors is a hypersymplectic structure with torsion for a certain Lie algebroid structure on the dual A∗, and conversely. Examples of hypersymplectic structures with torsion are included.
New supersymmetric index of heterotic compactifications with torsion
NASA Astrophysics Data System (ADS)
Israël, Dan; Sarkis, Matthieu
2015-12-01
We compute the new supersymmetric index of a large class of N=2 heterotic compactifications with torsion, corresponding to principal two-torus bundles over warped K3 surfaces with H-flux. Starting from a UV description as a (0,2) gauged linear sigma-model with torsion, we use supersymmetric localization techniques to provide an explicit expression of the index as a sum over the Jeffrey-Kirwan residues of the one-loop determinant. We finally propose a geometrical formula that gives the new supersymmetric index in terms of bundle data, regardless of any particular choice of underlying two-dimensional theory.
On the interpretation of combined torsion and tension tests of thin-wall tubes
NASA Technical Reports Server (NTRS)
Prager, W
1948-01-01
General ways of testing thin-wall tubes under combined tension and torsion as a means of checking the various theories of plasticity are discussed. Suggestions also are given for the interpretation of the tests.
Torsional oscillations in dynamo simulations
NASA Astrophysics Data System (ADS)
Wicht, Johannes; Christensen, Ulrich R.
2010-06-01
Cylinders aligned with the planetary rotation axis have a special significance in the dynamics of planetary dynamo regions. The azimuthal Lorentz forces on these geostrophic cylinders is expected to cancel to a large degree, establishing the so-called Taylor state. Deviations from this state take the form of torsional oscillations (TOs) that are supposed to represent important fast flow variations. These oscillations have reportedly been identified in the secular variation signal from the top of Earth's core. We have performed several dynamo simulations at different parameters to check whether Taylor state and TOs can also be identified in a numerical model. Taylor states are approached when viscous effects are small at Ekman numbers of E = 3 × 10-5 or below and Reynolds stresses are kept low by choosing moderate Rayleigh numbers. One-dimensional magnetic Alfvén waves that travel towards the boundaries then become prominent in the motion of the geostrophic cylinders. These waves obey the TO theory but are also damped and modified by other effects. For example, fast variations of likely convective origin remain important in all our simulations. Reynolds stresses may play a more sizable role for the dynamics in Earth's dynamo region than commonly assumed. They may also contribute to the motions of geostrophic cylinders and severely reduce the significance of TOs for the fast core dynamics. The amplitude of TOs amounts to not more than a few percent of the total flow amplitude in the simulations, which renders these motions insignificant for the long-term dynamo process.
Transverse angular momentum of photons
Aiello, Andrea
2010-05-15
We develop the quantum theory of transverse angular momentum of light beams. The theory applies to paraxial and quasiparaxial photon beams in vacuum and reproduces the known results for classical beams when applied to coherent states of the field. Both the Poynting vector, alias the linear momentum, and the angular-momentum quantum operators of a light beam are calculated including contributions from first-order transverse derivatives. This permits a correct description of the energy flow in the beam and the natural emergence of both the spin and the angular momentum of the photons. We show that for collimated beams of light, orbital angular-momentum operators do not satisfy the standard commutation rules. Finally, we discuss the application of our theory to some concrete cases.
Torsional vibration transmissibility characteristics of reinforced viscoelastic flexible pipes
NASA Astrophysics Data System (ADS)
Kennedy, I.; Tomlinson, G. R.
1988-04-01
The dynamic complex shear moduli of fibre and steel reinforced viscoelastic flexible pipes are determined by using a torsional non-resonance method. Material property master curves as a function of frequency and temperature are obtained by using reduced modulus methods. In situations where the loss factor data is difficult to measure directly it is shown that these data can be obtained from the modulus data by using a stepwise Hilbert transform technique. Predictions of the torsional vibration transmissibility of reinforced pipes, by using a simple theory in conjunction with the material properties, results in a close comparison with experimental measurements of the torsional vibration transmissibility characteristics of the pipes over a wide frequency range.
Simple torsion test for shear moduli determination of orthotropic composites
NASA Technical Reports Server (NTRS)
Sumsion, H. T.; Rajapakse, Y. D. S.
1978-01-01
By means of torsion tests performed on test specimens of the same material having a minimum of two different cross sections (flat sheet of different widths), the effective in-plane (G13) and out-of-plane (G23) shear moduli were determined for two composite materials of uniaxial and angleply fiber orientations. Test specimens were 16 plies (nominal 2 mm) thick, 100 mm in length, and in widths of 6.3, 9.5, 12.5, and 15.8 mm. Torsion tests were run under controlled deflection (constant angle of twist) using an electrohydraulic servocontrolled test system. In-plane and out-of-plane shear moduli were calculated from an equation derived in the theory of elasticity which relates applied torque, the torsional angle of twist, the specimen width/thickness ratio, and the ratio of the two shear moduli G13/G23. Results demonstrate that torsional shear moduli, G23 as well as G13, can be determined by simple torsion tests of flat specimens of rectangular cross section. Neither the uniaxial nor angleply composite material were transversely isotropic.
Contribution to the theory of propeller vibrations
NASA Technical Reports Server (NTRS)
Liebers, F
1930-01-01
This report presents a calculation of the torsional frequencies of revolving bars with allowance for the air forces. Calculation of the flexural or bonding frequencies of revolving straight or tapered bars in terms of the angular velocity of revolution. Calculation on the basis of Rayleigh's principle of variation. There is also a discussion of error estimation and the accuracy of results. The author then provides an application of the theory to screw propellers for airplanes and the discusses the liability of propellers to damage through vibrations due to lack of uniform loading.
NASA Astrophysics Data System (ADS)
Murav'eva, O. V.; Len'kov, S. V.; Murashov, S. A.
2016-01-01
A theory of propagation of torsional waves excited by an electromagnetic-acoustic transducer in a pipe is proposed. This theory takes into account the excitation parameters, geometry, viscosity, and the elastic characteristics of an object. The main testing parameters (the frequency and geometry of the transducer) that determine the possibilities of guided-wave testing of pipelines of various dimensions using torsional waves are theoretically substantiated.
Torsional Carbon Nanotube Artificial Muscles
NASA Astrophysics Data System (ADS)
Foroughi, Javad; Spinks, Geoffrey M.; Wallace, Gordon G.; Oh, Jiyoung; Kozlov, Mikhail E.; Fang, Shaoli; Mirfakhrai, Tissaphern; Madden, John D. W.; Shin, Min Kyoon; Kim, Seon Jeong; Baughman, Ray H.
2011-10-01
Rotary motors of conventional design can be rather complex and are therefore difficult to miniaturize; previous carbon nanotube artificial muscles provide contraction and bending, but not rotation. We show that an electrolyte-filled twist-spun carbon nanotube yarn, much thinner than a human hair, functions as a torsional artificial muscle in a simple three-electrode electrochemical system, providing a reversible 15,000° rotation and 590 revolutions per minute. A hydrostatic actuation mechanism, as seen in muscular hydrostats in nature, explains the simultaneous occurrence of lengthwise contraction and torsional rotation during the yarn volume increase caused by electrochemical double-layer charge injection. The use of a torsional yarn muscle as a mixer for a fluidic chip is demonstrated.
NASA Astrophysics Data System (ADS)
Shakur, Asif; Sinatra, Taylor
2013-12-01
The gyroscope in a smartphone was employed in a physics laboratory setting to verify the conservation of angular momentum and the nonconservation of rotational kinetic energy. As is well-known, smartphones are ubiquitous on college campuses. These devices have a panoply of built-in sensors. This creates a unique opportunity for a new paradigm in the physics laboratory. Many traditional physics experiments can now be performed very conveniently in a pedagogically enlightening environment while simultaneously reducing the laboratory budget substantially by using student-owned smartphones.
Torsional waves operating in geodynamo and magnetoconvection simulations
NASA Astrophysics Data System (ADS)
Teed, Robert; Jones, Chris; Tobias, Steve
2015-04-01
Torsional waves are a principal feature of the dynamics of the fluid outer core where the Earth's magnetic field is generated. These oscillations are Alfvén waves operating about an equilibrium known as a Taylor state (Taylor, 1963) and they propagate in the cylindrical radial direction. The change in core angular momentum inferred from geomagnetic observations has a measurable impact on the length of the day, and the small decadal variations in the length-of-day signal confirm the existence of torsional oscillations (Holme & de Viron, 2013). Many questions remain unanswered about the exact nature of these waves and this presentation will attempt to address some of these. In order to gain insight we perform three-dimensional spherical dynamo and magnetoconvection simulations in parameter regimes where Earth-like magnetic fields are produced. Many of our simulations produce the desired torsional oscillations, identified by their movement at the correct Alfvén speed, and several show Earth-like core travel times of around 4 years. Our dynamo simulations (Teed et al., 2014) show torsional waves within the tangent cylinder region that also have the ability to pass through this theoretical cylinder. By calculating the driving terms for these waves we find that both the Reynolds force and ageostrophic convection acting through the Lorentz force can be important in driving torsional oscillations. Driven by a desire to reach smaller Ekman numbers and larger magnetic field strengths, which are computationally unattainable in dynamo simulations, we perform, in our follow up work, magnetoconvection simulations (Teed et al., 2015) by imposing a dipolar field on the core-mantle boundary. Under this configuration we find a transition, at low Ekman numbers, to regimes where excitation is found only at the tangent cylinder, is delivered by the Lorentz force and gives rise to a periodic Earth-like wave pattern. This pattern is approximately operating on a 4 to 5 year timescale
Optical activity caused by torsion stresses: the case of NaBi(MoO4)2 crystals.
Vasylkiv, Yuriy; Kvasnyuk, Oleksiy; Shopa, Yaroslav; Vlokh, Rostyslav
2013-05-01
We have found that torsion mechanical stresses induce the optical rotation effect in centrosymmetric NaBi(MoO4)2 crystals. We have suggested a description of the effect on the basis of nonlocal linear elasticity theory. It has been shown that the induced optical gyration is proportional to the stress gradient appearing due to the torsion. PMID:23695320
Non-linear torsional vibration characteristics of an internal combustion engine crankshaft assembly
NASA Astrophysics Data System (ADS)
Huang, Ying; Yang, Shouping; Zhang, Fujun; Zhao, Changlu; Ling, Qiang; Wang, Haiyan
2012-07-01
Crankshaft assembly failure is one of the main factors that affects the reliability and service life of engines. The linear lumped mass method, which has been universally applied to the dynamic modeling of engine crankshaft assembly, reveals obvious simulation errors. The nonlinear dynamic characteristics of a crankshaft assembly are instructionally significant to the improvement of modeling correctness. In this paper, a general expression for the non-constant inertia of a crankshaft assembly is derived based on the instantaneous kinetic energy equivalence method. The nonlinear dynamic equations of a multi-cylinder crankshaft assembly are established using the Lagrange rule considering nonlinear factors such as the non-constant inertia of reciprocating components and the structural damping of shaft segments. The natural frequency and mode shapes of a crankshaft assembly are investigated employing the eigenvector method. The forced vibration response of a diesel engine crankshaft assembly taking into account the non-constant inertia is studied using the numerical integral method. The simulation results are compared with a lumped mass model and a detailed model using the system matrix method. Results of non-linear torsional vibration analysis indicate that the additional excitation torque created by non-constant inertia activates the 2nd order rolling vibration, and the additional damping torque resulting from the non-constant inertia is the main nonlinear factor. The increased torsional angular displacement evoked by the high order excitation torque relates to the non-constant inertia. This research project is aimed at improving nonlinear dynamics theory, and the confirmed nonlinear parameters can be used for the structure design of a crankshaft assembly.
The dynamics and excitation of torsional waves in geodynamo simulations
NASA Astrophysics Data System (ADS)
Teed, R. J.; Jones, C. A.; Tobias, S. M.
2014-02-01
The predominant force balance in rapidly rotating planetary cores is between Coriolis, pressure, buoyancy and Lorentz forces. This magnetostrophic balance leads to a Taylor state where the spatially averaged azimuthal Lorentz force is compelled to vanish on cylinders aligned with the rotation axis. Any deviation from this state leads to a torsional oscillation, signatures of which have been observed in the Earth's secular variation and are thought to influence length of day variations via angular momentum conservation. In order to investigate the dynamics of torsional oscillations (TOs), we perform several 3-D dynamo simulations in a spherical shell. We find TOs, identified by their propagation at the correct Alfvén speed, in many of our simulations. We find that the frequency, location and direction of propagation of the waves are influenced by the choice of parameters. Torsional waves are observed within the tangent cylinder and also have the ability to pass through it. Several of our simulations display waves with core traveltimes of 4-6 yr. We calculate the driving terms for these waves and find that both the Reynolds force and ageostrophic convection acting through the Lorentz force are important in driving TOs.
Electrothermally-Actuated Micromirrors with Bimorph Actuators—Bending-Type and Torsion-Type
Tsai, Cheng-Hua; Tsai, Chun-Wei; Chang, Hsu-Tang; Liu, Shih-Hsiang; Tsai, Jui-Che
2015-01-01
Three different electrothermally-actuated MEMS micromirrors with Cr/Au-Si bimorph actuators are proposed. The devices are fabricated with the SOIMUMPs process developed by MEMSCAP, Inc. (Durham, NC, USA). A silicon-on-insulator MEMS process has been employed for the fabrication of these micromirrors. Electrothermal actuation has achieved a large angular movement in the micromirrors. Application of an external electric current 0.04 A to the bending-type, restricted-torsion-type, and free-torsion-type mirrors achieved rotation angles of 1.69°, 3.28°, and 3.64°, respectively. PMID:26110409
Electrothermally-Actuated Micromirrors with Bimorph Actuators--Bending-Type and Torsion-Type.
Tsai, Cheng-Hua; Tsai, Chun-Wei; Chang, Hsu-Tang; Liu, Shih-Hsiang; Tsai, Jui-Che
2015-01-01
Three different electrothermally-actuated MEMS micromirrors with Cr/Au-Si bimorph actuators are proposed. The devices are fabricated with the SOIMUMPs process developed by MEMSCAP, Inc. (Durham, NC, USA). A silicon-on-insulator MEMS process has been employed for the fabrication of these micromirrors. Electrothermal actuation has achieved a large angular movement in the micromirrors. Application of an external electric current 0.04 A to the bending-type, restricted-torsion-type, and free-torsion-type mirrors achieved rotation angles of 1.69°, 3.28°, and 3.64°, respectively. PMID:26110409
NASA Astrophysics Data System (ADS)
Krot, A. M.
2013-09-01
This work develops a statistical theory of gravitating spheroidal bodies to calculate the orbits of planets and explore forms of planetary orbits with regard to the Alfvén oscillating force [1] in the Solar system and other exoplanetary systems. The statistical theory of formation of gravitating spheroidal bodies has been proposed in [2]-[5]. Starting the conception for forming a spheroidal body inside a gas-dust protoplanetary nebula, this theory solves the problem of gravitational condensation of a gas-dust protoplanetary cloud with a view to planetary formation in its own gravitational field [3] as well as derives a new law of the Solar system planetary distances which generalizes the wellknown laws [2], [3]. This work also explains an origin of the Alfvén oscillating force modifying forms of planetary orbits within the framework of the statistical theory of gravitating spheroidal bodies [5]. Due to the Alfvén oscillating force moving solid bodies in a distant zone of a rotating spheroidal body have elliptic trajectories. It means that orbits for the enough remote planets from the Sun in Solar system are described by ellipses with focus in the origin of coordinates and with small eccentricities. The nearby planet to Sun named Mercury has more complex trajectory. Namely, in case of Mercury the angular displacement of a Newtonian ellipse is observed during its one rotation on an orbit, i.e. a regular (century) shift of the perihelion of Mercury' orbit occurs. According to the statistical theory of gravitating spheroidal bodies [2]-[5] under the usage of laws of celestial mechanics in conformity to cosmogonic bodies (especially, to stars) it is necessary to take into account an extended substance called a stellar corona. In this connection the stellar corona can be described by means of model of rotating and gravitating spheroidal body [5]. Moreover, the parameter of gravitational compression α of a spheroidal body (describing the Sun, in particular) has been
Some exact solutions with torsion in 5D Einstein-Gauss-Bonnet gravity
Canfora, F.; Giacomini, A.; Willison, S.
2007-08-15
Exact solutions with torsion in Einstein-Gauss-Bonnet gravity are derived. These solutions have a cross product structure of two constant curvature manifolds. The equations of motion give a relation for the coupling constants of the theory in order to have solutions with nontrivial torsion. This relation is not the Chern-Simons combination. One of the solutions has an AdS{sub 2}xS{sup 3} structure and is so the purely gravitational analogue of the Bertotti-Robinson space-time where the torsion can be seen as the dual of the covariantly constant electromagnetic field.
The torsional and rotation-torsion spectra of CD2HOH
NASA Astrophysics Data System (ADS)
Ndao, M.; Kwabia Tchana, F.; Coudert, L. H.; Motiyenko, R. A.; Margulès, L.; Barros, J.; Manceron, L.; Roy, P.
2016-08-01
The torsional and rotation-torsion spectra of the doubly deuterated species of methanol CD2HOH have been analyzed using submillimeter wave, terahertz, and far infrared spectra. 101 torsional subbands, with subband centers ranging from 2.3 to 626 cm-1, were assigned. Analysis of these yielded kinetic energy and hindering potential parameters of the torsional Hamiltonian describing the large amplitude internal rotation of the CD2H methyl group with respect to the hydroxyl group. 3271 rotation and rotation-torsion transitions, involving the 24 torsional levels up to e1 with 3 ⩽ K ⩽ 10 , were assigned and fitted approximating the rotational energy of each torsional level with a Taylor-type expansion in J (J + 1) . The rotational structure of 48 torsional subbands involving torsional levels higher than e1 has also been analyzed. In most cases, only the Q branch could be observed and assigned.
Simultaneous normal and torsional force measurement by cantilever surface contour analysis
NASA Astrophysics Data System (ADS)
Kumanchik, Lee; Schmitz, Tony; Pratt, Jon
2011-05-01
This study presents an alternative to the current Hooke's law-based force relation between rectangular cantilever deflection and applied force. In the new approach, a transduction constant is presented that (1) includes no cross-talk between torsion and normal force components, (2) is independent of the load application point, and (3) does not depend on the cantilever beam length. Rather than measuring the cantilever deformation at a single point (such as the tip location), it is measured at multiple adjacent points using scanning white light interferometry to provide a three-dimensional description of the cantilever deformation during loading. This measurement, processed by a force relation based on a superposition of deflections derived from Euler-Bernoulli bending theory and St Venant's torsion theory, provides the vertical, axial, and torsional force components simultaneously. Experimental results are compared to force predictions for the vertical and torsional components using macro-scale cantilevers under mass loading. An uncertainty analysis is also provided.
Combined bending-torsion fatigue reliability. III
NASA Technical Reports Server (NTRS)
Kececioglu, D.; Chester, L. B.; Nolf, C. F., Jr.
1975-01-01
Results generated by three, unique fatigue reliability research machines which can apply reversed bending loads combined with steady torque are presented. AISI 4340 steel, grooved specimens with a stress concentration factor of 1.42 and 2.34, and Rockwell C hardness of 35/40 were subjected to various combinations of these loads and cycled to failure. The generated cycles-to-failure and stress-to-failure data are statistically analyzed to develop distributional S-N and Goodman diagrams. Various failure theories are investigated to determine which one represents the data best. The effects of the groove, and of the various combined bending-torsion loads, on the S-N and Goodman diagrams are determined. Two design applications are presented which illustrate the direct useability and value of the distributional failure governing strength and cycles-to-failure data in designing for specified levels of reliability and in predicting the reliability of given designs.
Flap-Lag-Torsion Stability in Forward Flight
NASA Technical Reports Server (NTRS)
Panda, B.; Chopra, I.
1985-01-01
An aeroelastic stability of three-degree flap-lag-torsion blade in forward flight is examined. Quasisteady aerodynamics with a dynamic inflow model is used. The nonlinear time dependent periodic blade response is calculated using an iterative procedure based on Floquet theory. The periodic perturbation equations are solved for stability using Floquet transition matrix theory as well as constant coefficient approximation in the fixed reference frame. Results are presented for both stiff-inplane and soft-inplane blade configurations. The effects of several parameters on blade stability are examined, including structural coupling, pitch-flap and pitch-lag coupling, torsion stiffness, steady inflow distribution, dynamic inflow, blade response solution and constant coefficient approximation.
Hyttel, Trine E W; Bak, Geske S; Larsen, Solveig B; Løkkegaard, Ellen C L
2015-03-01
The increasing use of de-torsion of the ovaries may result in re-torsion. This review addresses risk of re-torsion and describes preventive strategies to avoid re-torsion in pre-menarcheal girls, and fertile and pregnant women. We clinically reviewed PubMed, Embase, Trip and Cochrane databases. The main outcome measures were re-torsion and viability of ovary with fixation measures. A total of 38 publications including 71 girls, 363 fertile women, and 69 pregnant women were found to be relevant. All studies were case reports or case series, sometimes with non-randomized controls. The studies show considerable heterogeneity in design, population, management and outcome. Only four studies included more than 50 cases. In pregnancy the risk of re-torsion was as high as 19.5-37.5%; among fertile women it was 28.6%. Most articles concluded that fixation of the ovaries to the pelvic sidewall or plication of the ovarian ligament after torsion may prevent re-torsion. In one case a girl experienced re-torsion after ovariopexy. Based on observational studies it seems that de-torsion and fixation of the ovary is a safe procedure that usually ensures maintenance of ovarian function and reduces the risk of recurrence, especially when there are no ovarian cysts or adnexal masses. PMID:25412114
Electric field in 3D gravity with torsion
Blagojevic, M.; Cvetkovic, B.
2008-08-15
It is shown that in static and spherically symmetric configurations of the system of Maxwell field coupled to 3D gravity with torsion, at least one of the Maxwell field components has to vanish. Restricting our attention to the electric sector of the theory, we find an interesting exact solution, corresponding to the azimuthal electric field. Its geometric structure is to a large extent influenced by the values of two different central charges, associated to the asymptotic AdS structure of spacetime.
Nonlinear electrodynamics in 3D gravity with torsion
Blagojevic, M.; Cvetkovic, B.; Miskovic, O.
2009-07-15
We study exact solutions of nonlinear electrodynamics coupled to three-dimensional gravity with torsion. We show that in any static and spherically symmetric configuration, at least one component of the electromagnetic field has to vanish. In the electric sector of the theory, we construct an exact solution, characterized by the azimuthal electric field. When the electromagnetic action is modified by a topological mass term, we find two types of the self-dual solutions.
Topological design of torsional metamaterials
NASA Astrophysics Data System (ADS)
Vitelli, Vincenzo; Paulose, Jayson; Meeussen, Anne; Topological Mechanics Lab Team
Frameworks - stiff elements with freely hinged joints - model the mechanics of a wide range of natural and artificial structures, including mechanical metamaterials with auxetic and topological properties. The unusual properties of the structure depend crucially on the balance between degrees of freedom associated with the nodes, and the constraints imposed upon them by the connecting elements. Whereas networks of featureless nodes connected by central-force springs have been well-studied, many real-world systems such as frictional granular packings, gear assemblies, and flexible beam meshes incorporate torsional degrees of freedom on the nodes, coupled together with transverse shear forces exerted by the connecting elements. We study the consequences of such torsional constraints on the mechanics of periodic isostatic networks as a foundation for mechanical metamaterials. We demonstrate the existence of soft modes of topological origin, that are protected against disorder or small perturbations of the structure analogously to their counterparts in electronic topological insulators. We have built a lattice of gears connected by rigid beams that provides a real-world demonstration of a torsional metamaterial with topological edge modes and mechanical Weyl modes.
An analysis of traction drive torsional stiffness
NASA Technical Reports Server (NTRS)
Rohn, D. A.; Loewenthal, S. H.
1983-01-01
The tangential compliance of elastic bodies in concentrated contact applied to traction drive elements to determine their torsional stiffness was analyzed. Static loading and rotating conditions are considered. The effects of several design variables are shown. The theoretical torsional stiffness of a fixed ratio multiroller drive is computed and compared to experimental values. It is shown that the torsional compliance of the traction contacts themselves is a relatively small portion of the overall drive system compliance.
The g - 2 muon anomaly in di-muon production with the torsion in LHC
NASA Astrophysics Data System (ADS)
Syromyatnikov, A. G.
2016-06-01
It was considered within the framework of the conformal gauge gravitational theory CGTG coupling of the standard model fermions to the axial torsion and preliminary discusses the impact of extra dimensions, in particular, in a five-dimensional space-time with Randall-Sundrum metric, where the fifth dimension is compactified on an S1/Z 2 orbifold, which as it turns out is conformally to the fifth dimension flat Euclidean space with permanent trace of torsion, with a compactification radius R in terms of the radius of a CGTG gravitational screening, through torsion in a process Z → μ+μ‑ and LHC data. In general, have come to the correct set of the conformal calibration curvature the Faddeev-Popov diagram technique type, that follows directly from dynamics. This leads to the effect of restrictions on neutral spin currents of gauge fields by helicity and the Regge’s form theory. The diagrams reveals the fact of opening of the fine spacetime structure in a process pp → γ/Z/T → μ+μ‑ with a center-of-mass energy of 14TeV, indicated by dotted lines and texture columns, as a result of p-p collision on 1.3 ṡ 10‑18cm scales from geometric shell gauge bosons of the SM continued by the heavy axial torsion resonance, and even by emerging from the inside into the outside of the ultra-light (freely-frozen in muon’s spin) axial torsion. We then evaluate the contribution of the torsion to the muon anomaly to derive new constraints on the torsion parameters. It was obtained that on the πN scattering through the exchange of axial torsion accounting, the nucleon anomalous magnetic moment in the eikonal phase leads to additive additives which is responsible for the spin-flip in the scattering process, the scattering amplitude is classical and characterized by a strong the torsion coupling ηT≅1. So the scattering of particles, occurs as on the Coulomb center with the charge fT This is the base model which is the g‑2 muon anomaly. The muon anomaly contribution
Useful angular selectivity in oblique columnar aluminum
NASA Astrophysics Data System (ADS)
Ditchburn, R. J.; Smith, G. B.
1991-03-01
A useful magnitude of angular selective transmittance of incident unpolarized light is demonstrated in obliquely deposited aluminum. Required deposition procedures and anisotropic optical properties are discussed. Angular selectivity is very strong at visible wavelengths but both experiment and theory indicate that a single oblique layer with well defined columns gives high transmittance at near-infrared wavelengths compared with normal films. There are ways of reducing this to enhance the energy control capability. Both solar and luminous angular selectivity are reported.
NASA Astrophysics Data System (ADS)
Ivanov, A. N.; Wellenzohn, M.
2016-02-01
We analyze a spin precession of slow neutrons in the Einstein-Cartan gravity with torsion, chameleon and magnetic field. For the derivation of the Heisenberg equation of motion of the neutron spin we use the effective low-energy potential, derived by Ivanov and Wellenzohn [Phys. Rev. D 92, 125004 (2015)] for slow neutrons, coupled to gravitational, chameleon, and torsion fields to order 1 /m , where m is the neutron mass. In addition to these low-energy interactions we switch on the interaction of slow neutrons with a magnetic field. We show that to linear order approximation with respect to gravitational, chameleon, and torsion fields the Dirac Hamilton operator for fermions (neutrons), moving in spacetimes created by rotating coordinate systems, contains the anti-Hermitian operators of torsion-fermion (neutron) interactions, caused by torsion scalar and tensor space-space-time and time-space-space degrees of freedom. Such anti-Hermitian operators violate C P and T invariance. In the low-energy approximation the C P and T violating torsion-fermion (neutron) interactions appear only to order O (1 /m ). One may assume that in the rotating Universe and galaxies the obtained anti-Hermitian torsion-fermion interactions might be an origin of (i) violation of C P and T invariance in the Universe and (ii) of baryon asymmetry. We show that anti-Hermitian torsion-fermion interactions of relativistic fermions, violating C P and T invariance, (i) cannot be removed by nonunitary transformations of the Dirac fermion wave functions and (ii) are conformal invariant. According to general requirements of conformal invariance of massive particle theories in gravitational fields [see R. H. Dicke, Phys. Rev. 125, 2163 (1962) and A. J. Silenko, Phys. Rev. D 91, 065012 (2015)], conformal invariance of anti-Hermitian torsion-fermion interactions is valid only if the fermion mass is changed by a conformal factor.
Premotor neurons encode torsional eye velocity during smooth-pursuit eye movements
NASA Technical Reports Server (NTRS)
Angelaki, Dora E.; Dickman, J. David
2003-01-01
Responses to horizontal and vertical ocular pursuit and head and body rotation in multiple planes were recorded in eye movement-sensitive neurons in the rostral vestibular nuclei (VN) of two rhesus monkeys. When tested during pursuit through primary eye position, the majority of the cells preferred either horizontal or vertical target motion. During pursuit of targets that moved horizontally at different vertical eccentricities or vertically at different horizontal eccentricities, eye angular velocity has been shown to include a torsional component the amplitude of which is proportional to half the gaze angle ("half-angle rule" of Listing's law). Approximately half of the neurons, the majority of which were characterized as "vertical" during pursuit through primary position, exhibited significant changes in their response gain and/or phase as a function of gaze eccentricity during pursuit, as if they were also sensitive to torsional eye velocity. Multiple linear regression analysis revealed a significant contribution of torsional eye movement sensitivity to the responsiveness of the cells. These findings suggest that many VN neurons encode three-dimensional angular velocity, rather than the two-dimensional derivative of eye position, during smooth-pursuit eye movements. Although no clear clustering of pursuit preferred-direction vectors along the semicircular canal axes was observed, the sensitivity of VN neurons to torsional eye movements might reflect a preservation of similar premotor coding of visual and vestibular-driven slow eye movements for both lateral-eyed and foveate species.
Dirac quasinormal modes of Chern-Simons and BTZ black holes with torsion
NASA Astrophysics Data System (ADS)
Bécar, Ramón; González, P. A.; Vásquez, Y.
2014-01-01
We study Chern-Simons black holes in d dimensions and we calculate analytically the quasinormal modes of fermionic perturbations. Also, we consider as background the five-dimensional Chern-Simons black hole with torsion and the BTZ black hole with torsion. We have found that the quasinormal modes depend on the highest power of curvature present in the Chern-Simons theory, such as that which occurs for the quasinormal modes of scalar perturbations. We also show that the effect of the torsion is to modify the real part of the quasinormal frequencies, which modify the oscillation frequency of the field for the five-dimensional case. However, for the BTZ black hole with torsion, the effect is to modify the imaginary part of these frequencies, that is, the relaxation time for the decay of the black hole perturbation. The imaginary part of the quasinormal frequencies is negative, which guarantees the stability of these black holes under fermionic field perturbations.
Torsional vibration of single-walled carbon nanotubes using doublet mechanics
NASA Astrophysics Data System (ADS)
Fatahi-Vajari, Alireza; Imam, Ali
2016-08-01
This paper investigates the torsional vibration of single-walled carbon nanotubes (SWCNTs) using a new approach based on doublet mechanics (DM) incorporating explicitly scale parameter and chiral effects. A fourth-order partial differential equation that governs the torsional vibration of nanotubes is derived. Using DM, an explicit equation for the natural frequency in terms of geometrical and mechanical property of CNTs is obtained for both the Zigzag and Armchair nanotube for the torsional vibration mode. It is shown that chiral effects along with the scale parameter play a significant role in the vibration behavior of SWCNTs in torsional vibration mode. Such effects decrease the natural frequency obtained by DM compared to the classical continuum mechanics and nonlocal theory predictions. However, with increase in the length and/or the radius of the tube, the effect of the chiral and scale parameter on the natural frequency decreases.
Angular Momentum Ejection and Recoil*
NASA Astrophysics Data System (ADS)
Ohia, O.; Coppi, B.
2009-11-01
The spontaneous rotation phenomenon observed in axisymmetric magnetically confined plasmas has been explained by the ``accretion theory'' [1] that considers the plasma angular momentum as gained from its interaction with the magnetic field and the surrounding material wall. The ejection of angular momentum to the wall, and the consequent recoil are attributed to modes excited at the edge while the transport of the (recoil) angular momentum from the edge toward the center is attributed to a different kind of mode. The toroidal phase velocity of the edge mode, to which the sign of the ejected angular momentum is related, is considered to change its direction in the transition from the H-regime to the L-regime. For the latter case, edge modes with phase velocity in the direction of vdi are driven by the temperature gradient of a cold ion population at the edge and damped on the ``hot'' ion population. The ``balanced'' double interaction [2] of the mode with the two populations, corresponding to a condition of marginal stability, leads to ejection of hot ions and loss of angular momentum in the direction of vdi while the cold population acquires angular momentum in the opposite direction. In the H-regime resistive ballooning modes with phase velocities in the direction of vde are viewed as the best candidates for the excited edge modes. *Sponsored in part by the U.S. DOE. [1] B. Coppi, Nucl. Fusion 42, 1 (2002) [2] B. Coppi and F. Pegoraro, Nucl. Fusion 17, 969 (1977)
Luebke, N H; Brantley, W A; Sabri, Z I; Luebke, J H
1992-01-01
A laboratory study was performed on Peeso drills to determine their physical dimensions, torsional performance, and metallurgical properties. Samples were measured from each of sizes #1 to #6 of Peeso drills (type P) and sizes #009 to #023 of Peeso drills (type B-1) from the two manufacturers that distribute these instruments in the United States. They were also tested in clockwise and counterclockwise torsion using a digital torque meter instrument. It was not possible to evaluate completely some type P drills of size #4 and larger or type B-1 drills of size #016 and larger because the torsional moments exceeded the capacity of the test instrument. Scanning electron microscopic examination confirmed visual observations that the stainless steel Peeso drills exhibited ductile torsional fracture, in contrast to the carbon steel Peeso drills which fractured in a relatively brittle manner. The carbon steel Peeso drills exhibited a much greater tendency for torsional fractures in the bur head, along with considerably smaller values of angular deflection at separation compared to the stainless steel Peeso drills. This study is part of a continuing investigation to establish standards for all rotary endodontic instruments. PMID:1402558
Torsional Buckling and Writhing Dynamics of Elastic Cables and DNA
Goyal, S; Perkins, N C; Lee, C L
2003-02-14
Marine cables under low tension and torsion on the sea floor can undergo a dynamic buckling process during which torsional strain energy is converted to bending strain energy. The resulting three-dimensional cable geometries can be highly contorted and include loops and tangles. Similar geometries are known to exist for supercoiled DNA and these also arise from the conversion of torsional strain energy to bending strain energy or, kinematically, a conversion of twist to writhe. A dynamic form of Kirchhoff rod theory is presented herein that captures these nonlinear dynamic processes. The resulting theory is discretized using the generalized-method for finite differencing in both space and time. The important kinematics of cross-section rotation are described using an incremental rotation ''vector'' as opposed to traditional Euler angles or Euler parameters. Numerical solutions are presented for an example system of a cable subjected to increasing twist at one end. The solutions show the dynamic evolution of the cable from an initially straight element, through a buckled element in the approximate form of a helix, and through the dynamic collapse of this helix through a looped form.
Bending stresses due to torsion in cantilever box beams
NASA Technical Reports Server (NTRS)
Kuhn, Paul
1935-01-01
The paper beings with a brief discussion on the origin of the bending stresses in cantilever box beams under torsion. A critical survey of existing theory is followed by a summary of design formulas; this summary is based on the most complete solution published but omits all refinements considered unnecessary at the present state of development. Strain-gage tests made by NACA to obtained some experimental verification of the formulas are described next. Finally, the formulas are applied to a series of box beams previously static-tested by the U.S. Army Air Corps; the results show that the bending stresses due to torsion are responsible to a large extent for the free-edge type of failure frequently experienced in these tests.
NASA Technical Reports Server (NTRS)
Plummer, G. M.; Herbst, E.; De Lucia, F.; Blake, G. A.
1984-01-01
Over 200 rotational lines of methyl formate in its ground (v sub t = 0), symmetric (A) torsional state have been measured in the frequency range 140-550 GHz. Analysis of these and lower frequency transitions permits accurate prediction (below 0.1 MHz) of over 10,000 transitions at frequencies below 600 GHz with angular momentum J lower than 50. The measured spectral lines have permitted identification of over 100 new methyl formate lines in Orion.
Ueki, T.; Larsen, E.W.
1998-09-01
The authors show that Monte Carlo simulations of neutral particle transport in planargeometry anisotropically scattering media, using the exponential transform with angular biasing as a variance reduction device, are governed by a new Boltzman Monte Carlo (BMC) equation, which includes particle weight as an extra independent variable. The weight moments of the solution of the BMC equation determine the moments of the score and the mean number of collisions per history in the nonanalog Monte Carlo simulations. Therefore, the solution of the BMC equation predicts the variance of the score and the figure of merit in the simulation. Also, by (1) using an angular biasing function that is closely related to the ``asymptotic`` solution of the linear Boltzman equation and (2) requiring isotropic weight changes as collisions, they derive a new angular biasing scheme. Using the BMC equation, they propose a universal ``safe`` upper limit of the transform parameter, valid for any type of exponential transform. In numerical calculations, they demonstrate that the behavior of the Monte Carlo simulations and the performance predicted by deterministically solving the BMC equation agree well, and that the new angular biasing scheme is always advantageous.
Torsion of Noncircular Composite Cylinders
NASA Technical Reports Server (NTRS)
Rouse, Marshall; Hyer, Michael W.; Haynie, Waddy T.
2005-01-01
The paper presents a brief overview of the predicted deformation and failure characteristics of noncircular composite cylinders subjected to torsion. Using a numerical analysis, elliptical cylinders with a minor-to-major diameter ratio of 0.7 are considered. Counterpart circular cylinders with the same circumference as the elliptical cylinders are included for comparison. The cylinders are constructed of a medium-modulus graphite-epoxy material in a quasi-isotropic lay-up. Imperfections generated from the buckling mode shapes are included in the initial cross-sectional geometry of the cylinders. Deformations until first fiber failure, as predicted using the maximum stress failure criterion and a material degradation scheme, are presented. For increasing levels of torsion, the deformations of the elliptical cylinders, in the form of wrinkling of the cylinder wall, occur primarily in the flatter regions of the cross section. By comparison the wrinkling deformations of the circular cylinders are more uniformly distributed around the circumference. Differences in the initial failure and damage progression and the overall torque vs. twist relationship between the elliptical and circular cylinders are presented. Despite differences in the response as the cylinders are being loaded, at first fiber failure the torque and twist for the elliptical and circular cylinders nearly coincide.
Gauge invariant coupling of fields to torsion: A string inspired model
Bhattacharjee, Srijit; Chatterjee, Ayan
2011-05-15
In a consistent heterotic string theory, the Kalb-Ramond field, which is the source of space-time torsion, is augmented by Yang-Mills and gravitational Chern-Simons terms. When compactified to 4 dimensions and in the field theory limit, such additional terms give rise to interactions with interesting astrophysical predictions like rotation of plane of polarization for electromagnetic and gravitational waves. On the other hand, if one is also interested in coupling 2- or 3-form (Abelian or non-Abelian) gauge fields to torsion, one needs another class of interaction. In this paper, we shall study this interaction and offer some astrophysical and cosmological predictions. We explicitly calculate the Coleman-Weinberg potential for this theory. We also comment on the possibility of such terms in loop quantum gravity where, if the Barbero-Immirzi parameter is promoted to a field, acts as a source for torsion.
Optically probing torsional superelasticity in spider silks
NASA Astrophysics Data System (ADS)
Kumar, Bhupesh; Thakur, Ashish; Panda, Biswajit; Singh, Kamal P.
2013-11-01
We investigate torsion mechanics of various spider silks using a sensitive optical technique. We find that spider silks are torsionally superelastic in that they can reversibly withstand great torsion strains of over 102-3 rotations per cm before failure. Among various silks from a spider, we find the failure twist-strain is greatest in the sticky capture silk followed by dragline and egg-case silk. Our in situ laser-diffraction measurements reveal that torsional strains on the silks induce a nano-scale transverse compression in its diameter that is linear and reversible. These unique torsional properties of the silks could find applications in silk-based materials and devices.
Torsion Profiling of Proteins Using Magnetic Particles
van Reenen, A.; Gutiérrez-Mejía, F.; van IJzendoorn, L.J.; Prins, M.W.J.
2013-01-01
We report a method to profile the torsional spring properties of proteins as a function of the angle of rotation. The torque is applied by superparamagnetic particles and has been calibrated while taking account of the magnetization dynamics of the particles. We record and compare the torsional profiles of single Protein G-Immunoglobulin G (IgG) and IgG-IgG complexes, sandwiched between a substrate and a superparamagnetic particle, for torques in the range between 0.5 × 103 and 5 × 103 pN·nm. Both molecular systems show torsional stiffening for increasing rotation angle, but the elastic and inelastic torsion stiffnesses are remarkably different. We interpret the results in terms of the structural properties of the molecules. The torsion profiling technique opens new dimensions for research on biomolecular characterization and for research on bio-nanomechanical structure-function relationships. PMID:23473490
Optically probing torsional superelasticity in spider silks
Kumar, Bhupesh; Thakur, Ashish; Panda, Biswajit; Singh, Kamal P.
2013-11-11
We investigate torsion mechanics of various spider silks using a sensitive optical technique. We find that spider silks are torsionally superelastic in that they can reversibly withstand great torsion strains of over 10{sup 2−3} rotations per cm before failure. Among various silks from a spider, we find the failure twist-strain is greatest in the sticky capture silk followed by dragline and egg-case silk. Our in situ laser-diffraction measurements reveal that torsional strains on the silks induce a nano-scale transverse compression in its diameter that is linear and reversible. These unique torsional properties of the silks could find applications in silk-based materials and devices.
Uncertainty principle for angular position and angular momentum
NASA Astrophysics Data System (ADS)
Franke-Arnold, Sonja; Barnett, Stephen M.; Yao, Eric; Leach, Jonathan; Courtial, Johannes; Padgett, Miles
2004-08-01
The uncertainty principle places fundamental limits on the accuracy with which we are able to measure the values of different physical quantities (Heisenberg 1949 The Physical Principles of the Quantum Theory (New York: Dover); Robertson 1929 Phys. Rev. 34 127). This has profound effects not only on the microscopic but also on the macroscopic level of physical systems. The most familiar form of the uncertainty principle relates the uncertainties in position and linear momentum. Other manifestations include those relating uncertainty in energy to uncertainty in time duration, phase of an electromagnetic field to photon number and angular position to angular momentum (Vaccaro and Pegg 1990 J. Mod. Opt. 37 17; Barnett and Pegg 1990 Phys. Rev. A 41 3427). In this paper, we report the first observation of the last of these uncertainty relations and derive the associated states that satisfy the equality in the uncertainty relation. We confirm the form of these states by detailed measurement of the angular momentum of a light beam after passage through an appropriate angular aperture. The angular uncertainty principle applies to all physical systems and is particularly important for systems with cylindrical symmetry.
NASA Astrophysics Data System (ADS)
Andrews, David L.; Babiker, Mohamed
2012-11-01
Preface D. L. Andrews and M. Babiker; 1. Light beams carrying orbital angular momentum J. B. Götte and S. M. Barnett; 2. Vortex transformation and vortex dynamics in optical fields G. Molina-Terriza; 3. Vector beams in free space E. J. Galvez; 4. Optical beams with orbital angular momentum in nonlinear media A. S. Desyatnikov and Y. S. Kivshar; 5. Ray optics, wave optics and quantum mechanics G. Nienhuis; 6. Quantum formulation of angle and orbital angular momentum J. B. Götte and S. M. Barnett; 7. Dynamic rotational frequency shift I. Bialynicki-Birula and Z. Bialynicka-Birula; 8. Spin-orbit interactions of light in isotropic media K. Y. Bliokh, A. Aiello and M. A. Alonso; 9. Quantum electrodynamics, angular momentum and chirality D. L. Andrews and M. Babiker; 10. Trapping of charged particles by Bessel beams I. Bialynicki-Birula, Z. Bialynicka-Birula and N. Drozd; 11. Theory of atoms in twisted light M. Babiker, D. L. Andrews and V. E. Lembessis; 12. An experimentalist's introduction to orbital angular momentum for quantum optics J. Romero, D. Giovannini, S. Franke-Arnold and M. J. Padgett; 13. Measurement of light's orbital angular momentum M. P. J. Lavery, J. Courtial and M. J. Padgett; 14. Efficient generation of optical twisters using helico-conical beams V. R. Daria, D. Palima and J. Glückstad; 15. Self similar modes of coherent diffusion with orbital angular momentum O. Firstenberg, M. Shuker, R. Pugatch and N. Davidson; 16. Dimensionality of azimuthal entanglement M. van Exter, E. Eliel and H. Woerdman; Index.
Spinning optical resonator sensor for torsional vibrational applications measurements
NASA Astrophysics Data System (ADS)
Ali, Amir R.; Gatherer, Andrew; Ibrahim, Mariam S.
2016-03-01
Spinning spherical resonators in the torsional vibrational applications could cause a shift in its whispering gallery mode (WGM). The centripetal force acting on the spinning micro sphere resonator will leads to these WGM shifts. An analysis and experiment were carried out in this paper to investigate and demonstrate this effect using different polymeric resonators. In this experiment, centripetal force exerted by the DC-Motor on the sphere induces an elastic deformation of the resonator. This in turn induces a shift in the whispering gallery modes of the sphere resonator. Materials used for the sphere are polydimethylsiloxane (PDMS 60:1 where 60 parts base silicon elastomer to 1 part polymer curing agent by volume) with shear modulus (G≍1kPa), (PDMS 10:1) with shear modulus (G≍300kPa), polymethylmethacrylate (PMMA, G≍2.6×109GPa) and silica (G≍3×1010 GPa). The sphere size was kept constant with 1mm in diameter for all above materials. The optical modes of the sphere exit using a tapered single mode optical fiber that is coupled to a distributed feedback laser. The transmission spectrum through the fiber is monitored to detect WGM shifts. The results showed the resonators with smaller shear modulus G experience larger WGM shift due to the larger mechanical deformation induced by the applied external centripetal force. Also, the results show that angular velocity sensors used in the torsional vibrational applications could be designed using this principle.
A Novel Permanent Magnetic Angular Acceleration Sensor
Zhao, Hao; Feng, Hao
2015-01-01
Angular acceleration is an important parameter for status monitoring and fault diagnosis of rotary machinery. Therefore, we developed a novel permanent magnetic angular acceleration sensor, which is without rotation angle limitations and could directly measure the instantaneous angular acceleration of the rotating system. The sensor rotor only needs to be coaxially connected with the rotating system, which enables convenient sensor installation. For the cup structure of the sensor rotor, it has a relatively small rotational inertia. Due to the unique mechanical structure of the sensor, the output signal of the sensor can be directed without a slip ring, which avoids signal weakening effect. In this paper, the operating principle of the sensor is described, and simulated using finite element method. The sensitivity of the sensor is calibrated by torsional pendulum and angle sensor, yielding an experimental result of about 0.88 mV/(rad·s−2). Finally, the angular acceleration of the actual rotating system has been tested, using both a single-phase asynchronous motor and a step motor. Experimental result confirms the operating principle of the sensor and indicates that the sensor has good practicability. PMID:26151217
A Novel Permanent Magnetic Angular Acceleration Sensor.
Zhao, Hao; Feng, Hao
2015-01-01
Angular acceleration is an important parameter for status monitoring and fault diagnosis of rotary machinery. Therefore, we developed a novel permanent magnetic angular acceleration sensor, which is without rotation angle limitations and could directly measure the instantaneous angular acceleration of the rotating system. The sensor rotor only needs to be coaxially connected with the rotating system, which enables convenient sensor installation. For the cup structure of the sensor rotor, it has a relatively small rotational inertia. Due to the unique mechanical structure of the sensor, the output signal of the sensor can be directed without a slip ring, which avoids signal weakening effect. In this paper, the operating principle of the sensor is described, and simulated using finite element method. The sensitivity of the sensor is calibrated by torsional pendulum and angle sensor, yielding an experimental result of about 0.88 mV/(rad·s(-2)). Finally, the angular acceleration of the actual rotating system has been tested, using both a single-phase asynchronous motor and a step motor. Experimental result confirms the operating principle of the sensor and indicates that the sensor has good practicability. PMID:26151217
Torsional directed walks, entropic elasticity, and DNA twist stiffness
Moroz, J. David; Nelson, Philip
1997-01-01
DNA and other biopolymers differ from classical polymers because of their torsional stiffness. This property changes the statistical character of their conformations under tension from a classical random walk to a problem we call the “torsional directed walk.” Motivated by a recent experiment on single lambda-DNA molecules [Strick, T. R., Allemand, J.-F., Bensimon, D., Bensimon, A. & Croquette, V. (1996) Science 271, 1835–1837], we formulate the torsional directed walk problem and solve it analytically in the appropriate force regime. Our technique affords a direct physical determination of the microscopic twist stiffness C and twist-stretch coupling D relevant for DNA functionality. The theory quantitatively fits existing experimental data for relative extension as a function of overtwist over a wide range of applied force; fitting to the experimental data yields the numerical values C = 120 nm and D = 50 nm. Future experiments will refine these values. We also predict that the phenomenon of reduction of effective twist stiffness by bend fluctuations should be testable in future single-molecule experiments, and we give its analytic form. PMID:9405627
Oligothiophene wires: impact of torsional conformation on the electronic structure.
Kislitsyn, D A; Taber, B N; Gervasi, C F; Zhang, L; Mannsfeld, S C B; Prell, J S; Briseno, A L; Nazin, G V
2016-02-14
Charge transport in polymer- and oligomer-based semiconductor materials depends strongly on the structural ordering of the constituent molecules. Variations in molecular conformations influence the electronic structures of polymers and oligomers, and thus impact their charge-transport properties. In this study, we used Scanning Tunneling Microscopy and Spectroscopy (STM/STS) to investigate the electronic structures of different alkyl-substituted oligothiophenes displaying varied torsional conformations on the Au(111) surface. STM imaging showed that on Au(111), oligothiophenes self-assemble into chain-like structures, binding to each other via interdigitated alkyl ligands. The molecules adopted distinct planar conformations with alkyl ligands forming cis- or trans- mutual orientations. For each molecule, by using STS mapping, we identify a progression of particle-in-a-box-like states corresponding to the LUMO, LUMO+1 and LUMO+2 orbitals. Analysis of STS data revealed very similar unoccupied molecular orbital energies for different possible molecular conformations. By using density functional theory calculations, we show that the lack of variation in molecular orbital energies among the different oligothiophene conformers implies that the effect of the Au-oligothiophene interaction on molecular orbital energies is nearly identical for all studied torsional conformations. Our results suggest that cis-trans torsional disorder may not be a significant source of electronic disorder and charge carrier trapping in organic semiconductor devices based on oligothiophenes. PMID:26804474
Magnetic Torsional Oscillations in Magnetars
Sotani, Hajime; Kokkotas, Kostas D.; Stergioulas, Nikolaos
2009-05-01
We investigate torsional Alfven oscillations of relativistic stars with a global dipole magnetic field, via 2D numerical simulations. We find that a) there exist two families of quasi-periodic oscillations (QPOs) with harmonics at integer multiples of the fundamental frequency, b) the QPOs are long-lived, c) for the chosen form of dipolar magnetic field, the frequency ratio of the lower to upper fundamental QPOs is about 0.6, independent of the equilibrium model or of the strength of the magnetic field, and d) within a representative sample of EOS and of various magnetar masses, the Alfven QPO frequencies are given by accurate empirical relations that depend only on the compactness of the star and on the magnetic field strength. Compared to the observational frequencies, we also obtain an upper limit on the strength of magnetic field of SGR 1806-20 (if is dominated by a dipolar component) between {approx}3 and 7x10{sup 15} Gauss.
Torsional oscillations of strange stars
NASA Astrophysics Data System (ADS)
Mannarelli, Massimo
2014-11-01
Strange stars are one of the hypothetical compact stellar objects that can be formed after a supernova explosion. The existence of these objects relies on the absolute stability of strange collapsed quark matter with respect to standard nuclear matter. We discuss simple models of strange stars with a bare quark matter surface, thus standard nuclear matter is completely absent. In these models an electric dipole layer a few hundreds Fermi thick should exist close to the star surface. Studying the torsional oscillations of the electrically charged layer we estimate the emitted power, finding that it is of the order of 1045 erg/s, meaning that these objects would be among the brightest compact sources in the heavens. The associated relaxation times are very uncertain, with values ranging between microseconds and minutes, depending on the crust thickness. Although part of the radiated power should be absorbed by the electrosphere surrounding the strange star, a sizable fraction of photons should escape and be detectable.
Euler angles as torsional flat spaces
NASA Astrophysics Data System (ADS)
Trejo-Mandujano, Hector A.
In this work we use general tensor calculus to compare the geodesic equation of motion and Newton's first law for force-free classical systems that are described by an arbitrary number of generalized coordinates in spaces with and without torsion. We choose as objects of study the flat torsional Euler angle metric spaces for rigid rotators. We tested the equivalence of the two motion equations using computational software that allowed algebraic manipulation. The main result is that the equivalence only holds for torsion-free spaces, and for isotropic force-free rotators. We present analytical calculations for the isotropic case and computational results for the general case.
Modification of gravity due to torsion
Nair, V. P.; Nikiforova, V.; Randjbar-Daemi, S.; Rubakov, V.
2010-01-01
Modifications of general relativity have been considered as one of the possible ways of addressing some of the outstanding problems related to the large scale gravitational physics. In this contribution we review some of the recent results which are due to the inclusion of dynamical torsion. More specifically we shall discuss the propagation of massive spin-2 particles in flat and curved space times. We shall show that, contrary to what is generally believed, spinning matter is not the sole source of torsion field. A symmetric energy momentum tensor can also couple to torsion degrees of freedom. The massive and massless spin-2 particles mix giving rise to an infrared modification of gravity.
Observation of coronal loop torsional oscillation
NASA Astrophysics Data System (ADS)
Zaqarashvili, T. V.
2003-02-01
We suggest that the global torsional oscillation of solar coronal loop may be observed by the periodical variation of a spectral line width. The amplitude of the variation must be maximal at the velocity antinodes and minimal at the nodes of the torsional oscillation. Then the spectroscopic observation as a time series at different heights above the active region at the solar limb may allow to determine the period and wavelength of global torsional oscillation and consequently the Alfvén speed in corona. From the analysis of early observation (Egan & Schneeberger \\cite{egan}) we suggest the value of coronal Alfvén speed as ~ 500 km s-1.
Testicular torsion in the older patient
Perry, S.; Hoopingarner, D.; Askins, D.
1983-05-01
A 40-year-old man presented with severe right-sided scrotal pain and was proven to have a 720-degree right testicular torsion. Fewer than 50 documented cases of testicular torsion have been reported in men over the age of thirty. The anatomical predisposition for torsion generally selects these individuals early in life. Rapid diagnosis allowed for surgical correction and testicular salvage. We outline an expedient diagnostic approach for these difficult cases with use of the Doppler ultrasound and the technetium (99mTc) testicular scan.
NASA Astrophysics Data System (ADS)
Czakó, Gábor
2014-06-01
Motivated by a recent experiment [H. Pan and K. Liu, J. Chem. Phys. 140, 191101 (2014)], we report a quasiclassical trajectory study of the O(3P) + CH4(vk = 0, 1) → OH + CH3 [k = 1 and 3] reactions on an ab initio potential energy surface. The computed angular distributions and cross sections correlated to the OH(v = 0, 1) + CH3(v = 0) coincident product states can be directly compared to experiment for O + CH4(v3 = 0, 1). Both theory and experiment show that the ground-state reaction is backward scattered, whereas the angular distributions shift toward sideways and forward directions upon antisymmetric stretching (v3) excitation of the reactant. Theory predicts similar behavior for the O + CH4(v1 = 1) reaction. The simulations show that stretching excitation enhances the reaction up to about 15 kcal/mol collision energy, whereas the O + CH4(vk = 1) reactions produce smaller cross sections for OH(v = 1) + CH3(v = 0) than those of O + CH4(v = 0) → OH(v = 0) + CH3(v = 0). The former finding agrees with experiment and the latter awaits for confirmation. The computed cold OH rotational distributions of O + CH4(v = 0) are in good agreement with experiment.
Torsion-induced effects in magnetic nanowires
NASA Astrophysics Data System (ADS)
Sheka, Denis D.; Kravchuk, Volodymyr P.; Yershov, Kostiantyn V.; Gaididei, Yuri
2015-08-01
A magnetic helix wire is one of the simplest magnetic systems which manifests properties of both curvature and torsion. Possible equilibrium magnetization states in the helix wire with different anisotropy directions are studied theoretically. There exist two equilibrium states in the helix wire with easy-tangential anisotropy: a quasitangential magnetization distribution in the case of relatively small curvatures and torsions, and an onion state in the opposite case. The curvature and torsion also essentially influence the spin-wave dynamics in the helix wire, acting as an effective magnetic field. Originated from a geometry-induced effective Dzyaloshinskii interaction, this magnetic field leads to a coupling between the helix chirality and the magnetochirality and breaks mirror symmetry in the spin-wave spectrum: the modification of magnon dispersion relation is linear with respect to the torsion and quadratic with respect to the curvature. All analytical predictions on magnetization statics and dynamics are well confirmed by direct spin-lattice simulations.
Inevitable inflation in Einstein-Cartan theory with improved energy-momentum tensor with spin
NASA Technical Reports Server (NTRS)
Fennelly, A. J.; Bradas, James C.; Smalley, Larry L.
1988-01-01
Generalized, or power-law, inflation is shown to necessarily exist for a simple, anisotropic, (Bianchi Type-1) cosmology in the Einstein-Cartan gravitational theory with the Ray-Smalley improved energy momentum tensor with spin. Formal solution of the EC field equations with the fluid equations of motion explicitly shows inflation caused by the RS spin angular kinetic energy density. Shear is not effective in preventing inflation in the ECRS model. The relation between fluid vorticity, torsion, reference axis rotation, and shear ellipsoid precession shows through clearly.
Torsion and buckling of open sections
NASA Technical Reports Server (NTRS)
Wagner, Herbert
1936-01-01
In this paper is a discussion of the general principles for open sections of any shape. In what follows the torsion will be computed and on the basis of the results it will be possible to obtain a proper design of section in each case. The torsion of buckling members for the case where they are centrally loaded, leads to a problem in pure stability and is similar to that of stressed beams.
Flow in a torsionally oscillating filled cylinder
NASA Technical Reports Server (NTRS)
Schafer, C. F.
1983-01-01
The flow of a liquid in a completely filled cylinder undergoing torsional oscillations about its longitudinal symmetry axis was studied analytically and experimentally. The objective of the studies was to determine the efficacy of the torsional oscillations in mixing the confined liquid. Flow was found to be confined primarily to toroidal cells at the ends of the cylinder. Cell thickness was about equal to the cylinder radius. The use of baffles at the end walls was shown to enhance the mixing process.
The Torsional Fundamental Band of Methylformate
NASA Astrophysics Data System (ADS)
Tudorie, M.; Ilyushin, V.; Vander Auwera, J.; Pirali, O.; Roy, P.; Huet, T. R.
2011-06-01
Methylformate (HCOOCH_3) is one of the most important molecules in astrophysics, first observed in 1975. The rotational structure of its ground and first excited torsional states are well known from millimeter wave measurements. However, some of the torsional parameters are still not precisely determined because information on the torsional vibrational frequency v_t = 1-0 is missing. To overcome that problem, the far infrared spectrum of HCOOCH_3 was recorded with a 150 m optical path in a White cell and a Bruker IFS 125 HR Fourier transform spectrometer at the AILES beamline of the synchrotron SOLEIL facility. The analysis of the very weak fundamental torsional band v_t = 1-0 observed around 130 Cm-1 was carried out. It led to the first precise determination of the torsional barrier height and the dipole moment induced by the torsional motion. This work is partly supported by the "Programme National de Physico-Chimie du Milieu Interstellaire" (PCMI-CNRS) and by the contract ANR-BLAN-08-0054. R.D. Brown, J.G. Crofts, P.D. Godfrey, F.F. Gardner, B.J. Robinson, J.B. Whiteoak, Astrophys. J. 197 (1975) L29-L31. See V. Ilyushin, A. Kryvda, E. Alekseev, J. Mol. Spectrosc. 255 (2009) 32-38, and references therein.
Attentional Modulation of Eye Torsion Responses
NASA Technical Reports Server (NTRS)
Stevenson, Scott B.; Mahadevan, Madhumitha S.; Mulligan, Jeffrey B.
2016-01-01
Eye movements generally have both reflexive and voluntary aspects, but torsional eye movements are usually thought of as a reflexive response to image rotation around the line of sight (torsional OKN) or to head roll (torsional VOR). In this study we asked whether torsional responses could be modulated by attention in a case where two stimuli rotated independently, and whether attention would influence the latency of responses. The display consisted of rear-projected radial "pinwheel" gratings, with an inner annulus segment extending from the center to 22 degrees eccentricity, and an outer annulus segment extending from 22 degrees out to 45 degrees eccentricity. The two segments rotated around the center in independent random walks, stepping randomly 4 degrees clockwise or counterclockwise at 60 Hz. Subjects were asked to attend to one or the other while keeping fixation steady at the center of the display. To encourage attention on one or the other segment of the display, subjects were asked to move a joystick in synchrony with the back and forth rotations of one part of the image while ignoring the other. Eye torsion was recorded with the scleral search coil technique, sampled at 500 Hz. All four subjects showed roughly 50% stronger torsion responses to the attended compared to unattended segments. Latency varied from 100 to 150 msec across subjects and was unchanged by attention. These findings suggest that attention can influence eye movement responses that are not typically under voluntary control.
NASA Astrophysics Data System (ADS)
Lattanzi, F.; di Lauro, C.; Horneman, V.-M.
The (ν4 + ν6) - ν4, (ν4 + ν8) - ν4 and (ν4 + ν9) - ν4 hot infrared systems of disilane (Si2H6) have been analysed at high resolution, and the values of the relative vibration-rotation-torsion parameters have been determined. The torsional splitting is about 0.500 cm-1 in the ν4 and ν4 + ν6 states, and decreases strongly in the vibrationally degenerate upper states ν4 + ν8 (about 0.0272 cm-1 on average) and ν4 + ν9 (about 0.3019 cm-1), consistent with theoretical predictions. Comparison between the vibrational wavenumbers of cold transitions and hot transitions originating in the excited torsional state v4 = 1 allows one to determine the change of the fundamental torsional frequency ν4 caused by the excitation of small amplitude vibrations. A remarkable increase in ν4 of about 8.599 cm-1 is found in the v9 = 1 state (E1d SiH3-rocking mode, asymmetric to inversion in the staggered geometry), and this corresponds to an increase in the torsional barrier height in this excited fundamental vibrational state by about 48.77 cm-1. The mechanism responsible for the decrease of the torsional splittings in the degenerate vibrational states is briefly outlined by means of second-order perturbation theory, using torsion-hindered vibrational basis functions of E1d and E2d symmetries for the degenerate modes.
NASA Astrophysics Data System (ADS)
Schaeffer, Nathanaël.; Jault, Dominique
2016-05-01
Torsional Alfvén waves propagating in the Earth's core have been inferred by inversion techniques applied to geomagnetic models. They appear to propagate across the core but vanish at the equator, exchanging angular momentum between core and mantle. Assuming axial symmetry, we find that an electrically conducting layer at the bottom of the mantle can lead to total absorption of torsional waves that reach the equator. We show that the reflection coefficient depends on GB_r, where Br is the strength of the radial magnetic field at the equator, and G the conductance of the lower mantle there. With Br=7×10-4 T, torsional waves are completely absorbed when they hit the equator if G≃1.3 × 108 S. For larger or smaller G, reflection occurs. As G is increased above this critical value, there is less attenuation and more angular momentum exchange. Our finding dissociates efficient core-mantle coupling from strong ohmic dissipation in the mantle.
NASA Astrophysics Data System (ADS)
Zheng, Jingjing; Meana-Pañeda, Rubén; Truhlar, Donald G.
2013-08-01
partition functions using the torsional eigenvalue summation method. Additional comments: The program package includes a manual, installation script, and input and output files for a test suite. Running time: There are 26 test runs. The running time of the test runs on a single processor of the Itasca computer is less than 2 s. References: [1] MS-T(C) method: Quantum Thermochemistry: Multi-Structural Method with Torsional Anharmonicity Based on a Coupled Torsional Potential, J. Zheng and D.G. Truhlar, Journal of Chemical Theory and Computation 9 (2013) 1356-1367, DOI: http://dx.doi.org/10.1021/ct3010722. [2] MS-T(U) method: Practical Methods for Including Torsional Anharmonicity in Thermochemical Calculations of Complex Molecules: The Internal-Coordinate Multi-Structural Approximation, J. Zheng, T. Yu, E. Papajak, I, M. Alecu, S.L. Mielke, and D.G. Truhlar, Physical Chemistry Chemical Physics 13 (2011) 10885-10907.
Williamson, M.M.; Pratt, G.A.
1999-06-08
The invention provides an elastic actuator consisting of a motor and a motor drive transmission connected at an output of the motor. An elastic element is connected in series with the motor drive transmission, and this elastic element is positioned to alone support the full weight of any load connected at an output of the actuator. A single force transducer is positioned at a point between a mount for the motor and an output of the actuator. This force transducer generates a force signal, based on deflection of the elastic element, that indicates force applied by the elastic element to an output of the actuator. An active feedback force control loop is connected between the force transducer and the motor for controlling the motor. This motor control is based on the force signal to deflect the elastic element an amount that produces a desired actuator output force. The produced output force is substantially independent of load motion. The invention also provides a torsional spring consisting of a flexible structure having at least three flat sections each connected integrally with and extending radially from a central section. Each flat section extends axially along the central section from a distal end of the central section to a proximal end of the central section. 30 figs.
Williamson, Matthew M.; Pratt, Gill A.
1999-06-08
The invention provides an elastic actuator consisting of a motor and a motor drive transmission connected at an output of the motor. An elastic element is connected in series with the motor drive transmission, and this elastic element is positioned to alone support the full weight of any load connected at an output of the actuator. A single force transducer is positioned at a point between a mount for the motor and an output of the actuator. This force transducer generates a force signal, based on deflection of the elastic element, that indicates force applied by the elastic element to an output of the actuator. An active feedback force control loop is connected between the force transducer and the motor for controlling the motor. This motor control is based on the force signal to deflect the elastic element an amount that produces a desired actuator output force. The produced output force is substantially independent of load motion. The invention also provides a torsional spring consisting of a flexible structure having at least three flat sections each connected integrally with and extending radially from a central section. Each flat section extends axially along the central section from a distal end of the central section to a proximal end of the central section.
Skokov, S.; Bowman, J.M.
1999-05-01
Complex L{sup 2} calculations of the variation of (very narrow) resonance widths of the 6{nu}{sub OH} state of HOCl with total angular momentum are reported, using a recently developed, accurate {ital ab initio} potential energy surface [S. Skokov, J. M. Bowman, and K. A. Peterson, J. Chem. Phys. {bold 109}, 2662 (1998)]. The calculations are carried out within the adiabatic rotation approximation for the overall rotation and a truncation/recoupling method for the vibrational states. Comparisons with recent double-resonance experiments of the Rizzo and Sinha groups are made. The variation of resonance width with {ital J} for {ital K}=0 is shown to be due to rotation-induced coupling of the 6{nu}{sub OH} state with a dense set of states with large excitation in the dissociative coordinate. {copyright} {ital 1999 American Institute of Physics.}
Strong field coherent control of molecular torsions--Analytical models.
Ashwell, Benjamin A; Ramakrishna, S; Seideman, Tamar
2015-08-14
We introduce analytical models of torsional alignment by moderately intense laser pulses that are applicable to the limiting cases of the torsional barrier heights. Using these models, we explore in detail the role that the laser intensity and pulse duration play in coherent torsional dynamics, addressing both experimental and theoretical concerns. Our results suggest strategies for minimizing the risk of off-resonant ionization, noting the qualitative differences between the case of torsional alignment subject to a field-free torsional barrier and that of torsional alignment of a barrier-less system (equivalent to a 2D rigid rotor). We also investigate several interesting torsional phenomena, including the onset of impulsive alignment of torsions, field-driven oscillations in quantum number space, and the disappearance of an alignment upper bound observed for a rigid rotor in the impulsive torsional alignment limit. PMID:26277138
NASA Astrophysics Data System (ADS)
He, Qing; Peng, Huichun; Zhai, Pengcheng; Zhen, Yaxin
2016-06-01
The angular acceleration is taken into the consideration for the modeling of equations of coupling vibration in rotational operation. The effects of angular acceleration on the amplitude of both lateral and torsion vibration of the breathing cracked rotor are studied for the first time. The torsion influence of unbalance orientation angles is especially studied during the modeling of the Breathing behavior model of the crack with the mass eccentricity. Different from the previous study, the effects of unbalance orientation angle on the lateral torsion coupling vibration of the breathing cracked rotor are compared by logarithmic spectrum diagrams. Parametric stability of the breathing cracked rotor associated with both unbalance orientation angle and accelerations in diverse level of mass eccentricity are presented, these works have not been seen before. The numerical parametrically stability results are verified by comparing with the dynamic response of the system.
No Effect of Steady Rotation on Solid ^4He in a Torsional Oscillator
NASA Astrophysics Data System (ADS)
Fear, M. J.; Walmsley, P. M.; Zmeev, D. E.; Mäkinen, J. T.; Golov, A. I.
2016-05-01
We have measured the response of a torsional oscillator containing polycrystalline hcp solid 4He to applied steady rotation in an attempt to verify the observations of several other groups that were initially interpreted as evidence for macroscopic quantum effects. The geometry of the cell was that of a simple annulus, with a fill line of relatively narrow diameter in the centre of the torsion rod. Varying the angular velocity of rotation up to 2 rad s^{-1} showed that there were no step-like features in the resonant frequency or dissipation of the oscillator and no history dependence, even though we achieved the sensitivity required to detect the various effects seen in earlier experiments on other rotating cryostats. All small changes during rotation were consistent with those occurring with an empty cell. We thus observed no effects on the samples of solid ^4He attributable to steady rotation.
Investigation of fluctuations in angular velocity in magnetic memory devices
NASA Technical Reports Server (NTRS)
Meshkis, Y. A.; Potsyus, Z. Y.
1973-01-01
The fluctuations in the angular velocity of individual assemblies of a precision mechanical system were analyzed. The system was composed of an electric motor and a magnetic drum which were connected by a flexible coupling. A dynamic model was constructed which took into account the absence of torsion in the rigid shafts of the electric motor drive rotor and the magnetic drum. The motion was described by Lagrange differential equations of the second kind. Curves are developed to show the nature of amplitude fluctuation of the magnetic drum angular velocity at a specific excitation frequency. Additional curves show the amplitudes of fluctuation of the magnetic drum angular velocity compared to the quantity of damping at specific frequencies.
Beam and Torsion Tests of Aluminum-alloy 61S-T Tubing
NASA Technical Reports Server (NTRS)
Moore, R L; Holt, Marshall
1942-01-01
Tests were made to determine the effect of length and the effect of ratios of diameter to wall thickness upon the flexural and torsional moduli of failure of 61S-T aluminum-alloy tubing. The moduli of failure in bending, as determined by tests in which the tubing was loaded on the neutral axis at the one-third points of the span, were found to bear an approximately linear relationship with diameter-thickness ratio and were practically independent of span within the limits investigated. Empirical equations are given describing the relations obtained. The moduli of failure in torsion were found to be dependent upon length as well as upon diameter-thickness ratios. Empirical equations are given for predicting strengths within the range of plastic buckling. Within the elastic range, available torsion theories were found to be satisfactory.
Vibration-Torsion Dynamics of Ethane-like Molecules in Degenerate Vibrational States
NASA Astrophysics Data System (ADS)
Dilauro, C.; Lattanzi, F.; Avellino, R.
1994-10-01
We examine the mechanisms of interaction between the deformations of the two identical halves of ethane-like molecules in degenerate vibrational states, in order to determine the most convenient symmetries of the degenerate vibrational wavefunctions, in the molecular symmetry group G36( EM). In moderate barrier molecules this is related to the problem of the vibration-torsion symmetry labeling of the tunneling split components, in the order of increasing energies, in given rotational states. Numerical calculations have been performed as a guide to explore several different situations. It has been proved that the torsional splittings in degenerate vibrational states of molecules with a moderate barrier depend dramatically on the value of the γ-Coriolis coefficient and, unlike the splittings in nondegenerate vibrational states, are not determined only by the effective torsional potential function. Theory and numerical predictions support the experimental result that all normal modes of ethane behave as E1 d, E2 d pairs.
Biophysical characterization of cofilin-induced extension-torsion coupling in actin filaments.
Kim, Jae In; Kwon, Junpyo; Baek, Inchul; Na, Sungsoo
2016-06-14
Cofilin makes the actin filament flexible and thermally unstable by disassembling the filament and inducing bending and torsional compliance. Actin monomers bound to cofilin are able to chemically and mechanically interact in response to external forces. In this study, we performed two molecular dynamics tensile tests for actin and cofilactin filaments under identical conditions. Surprisingly, cofilactin filaments were found to be twisted, generating shear stress caused by torsion. Additionally, analysis by plane stress assumption indicated that the extension-torsion coupling effect increases the amount of principal stress by 10%. Using elasticity and solid mechanics theories, our study elucidates the role of cofilin in the disassembly of actin filaments under tensile forces. PMID:27143106
Partonic orbital angular momentum
NASA Astrophysics Data System (ADS)
Arash, Firooz; Taghavi-Shahri, Fatemeh; Shahveh, Abolfazl
2013-04-01
Ji's decomposition of nucleon spin is used and the orbital angular momentum of quarks and gluon are calculated. We have utilized the so called valon model description of the nucleon in the next to leading order. It is found that the average orbital angular momentum of quarks is positive, but small, whereas that of gluon is negative and large. Individual quark flavor contributions are also calculated. Some regularities on the total angular momentum of the quarks and gluon are observed.
Endodontic instruments after torsional failure: nanoindentation test.
Jamleh, Ahmed; Sadr, Alireza; Nomura, Naoyuki; Ebihara, Arata; Yahata, Yoshio; Hanawa, Takao; Tagami, Junji; Suda, Hideaki
2014-01-01
This study aimed to evaluate effects of torsional loading on the mechanical properties of endodontic instruments using the nanoindentation technique. ProFile (PF; size 30, taper 04; Dentsply Maillefer, Switzerland) and stainless steel (SS; size 30, taper 02; Mani, Japan) instruments were subjected to torsional test. Nanoindentation was then performed adjacent to the edge of fracture (edge) and at the cutting part beside the shank (shank). Hardness and elastic modulus were measured under 100-mN force on 100 locations at each region, and compared to those obtained from the same regions on new instruments. It showed that PF and SS instruments failed at 559 ± 67 and 596 ± 73 rotation degrees and mean maximum torque of 0.90 ± 0.07 and 0.99 ± 0.05 N-cm, respectively. Hardness and elastic modulus ranged 4.8-6.7 and 118-339 GPa in SS, and 2.7-3.2 and 52-81 GPa in PF. Significant differences between torsion-fractured and new instruments in hardness and elastic modulus were detected in the SS system used. While in PF system, the edge region after torsional fracture had significantly lower hardness and elastic modulus compared to new instruments. The local hardness and modulus of elasticity of endodontic instruments adjacent to the fracture edge are significantly reduced by torsional loading. PMID:24610598
Torsion-Mediated Interaction between Adjacent Genes
Meyer, Sam; Beslon, Guillaume
2014-01-01
DNA torsional stress is generated by virtually all biomolecular processes involving the double helix, in particular transcription where a significant level of stress propagates over several kilobases. If another promoter is located in this range, this stress may strongly modify its opening properties, and hence facilitate or hinder its transcription. This mechanism implies that transcribed genes distant of a few kilobases are not independent, but coupled by torsional stress, an effect for which we propose the first quantitative and systematic model. In contrast to previously proposed mechanisms of transcriptional interference, the suggested coupling is not mediated by the transcription machineries, but results from the universal mechanical features of the double-helix. The model shows that the effect likely affects prokaryotes as well as eukaryotes, but with different consequences owing to their different basal levels of torsion. It also depends crucially on the relative orientation of the genes, enhancing the expression of eukaryotic divergent pairs while reducing that of prokaryotic convergent ones. To test the in vivo influence of the torsional coupling, we analyze the expression of isolated gene pairs in the Drosophila melanogaster genome. Their orientation and distance dependence is fully consistent with the model, suggesting that torsional gene coupling may constitute a widespread mechanism of (co)regulation in eukaryotes. PMID:25188032
Neoclassical Angular Momentum Flux Revisited
NASA Astrophysics Data System (ADS)
Wong, S. K.; Chan, V. S.
2004-11-01
The toroidal angular momentum flux in neoclassical transport theory of small rotations depends on the second order (in ion poloidal gyroradius over plasma scale length) ion distribution function. Owing to the complexity of the calculation, the result obtained a long time ago for circular cross-section tokamak plasmas in the banana regime [M.N. Rosenbluth, et al., Plasma Physics and Controlled Nuclear Fusion Research (IAEA, Vienna, 1971), Vol. 1, p. 495] has never been reproduced. Using a representation of the angular momentum flux based on the solution of an adjoint equation to the usual linearized drift kinetic equation, and performing systematically a large-aspect-ratio expansion, we have obtained the flux for flux surfaces of arbitrary shape. We have found the same analytic form for the temperature gradient driven part of the flux, but the overall numerical multiplier is different and has the opposite sign. Implications for rotations in discharges with no apparent momentum input will be discussed.
The metric on field space, functional renormalization, and metric-torsion quantum gravity
NASA Astrophysics Data System (ADS)
Reuter, Martin; Schollmeyer, Gregor M.
2016-04-01
Searching for new non-perturbatively renormalizable quantum gravity theories, functional renormalization group (RG) flows are studied on a theory space of action functionals depending on the metric and the torsion tensor, the latter parameterized by three irreducible component fields. A detailed comparison with Quantum Einstein-Cartan Gravity (QECG), Quantum Einstein Gravity (QEG), and "tetrad-only" gravity, all based on different theory spaces, is performed. It is demonstrated that, over a generic theory space, the construction of a functional RG equation (FRGE) for the effective average action requires the specification of a metric on the infinite-dimensional field manifold as an additional input. A modified FRGE is obtained if this metric is scale-dependent, as it happens in the metric-torsion system considered.
Passive torque wrench and angular position detection using a single-beam optical trap.
Inman, James; Forth, Scott; Wang, Michelle D
2010-09-01
The recent advent of angular optical trapping techniques has allowed for rotational control and direct torque measurement on biological substrates. Here we present a method that increases the versatility and flexibility of these techniques. We demonstrate that a single beam with a rapidly rotating linear polarization can be utilized to apply a constant controllable torque to a trapped particle without active feedback, while simultaneously measuring the particle angular position. In addition, this device can rapidly switch between a torque wrench and an angular trap. These features should make possible torsional measurements across a wide range of biological systems. PMID:20808379
NASA Astrophysics Data System (ADS)
Krak, Michael D.; Dreyer, Jason T.; Singh, Rajendra
2016-03-01
A vehicle clutch damper is intentionally designed to contain multiple discontinuous non-linearities, such as multi-staged springs, clearances, pre-loads, and multi-staged friction elements. The main purpose of this practical torsional device is to transmit a wide range of torque while isolating torsional vibration between an engine and transmission. Improved understanding of the dynamic behavior of the device could be facilitated by laboratory measurement, and thus a refined vibratory experiment is proposed. The experiment is conceptually described as a single degree of freedom non-linear torsional system that is excited by an external step torque. The single torsional inertia (consisting of a shaft and torsion arm) is coupled to ground through parallel production clutch dampers, which are characterized by quasi-static measurements provided by the manufacturer. Other experimental objectives address physical dimensions, system actuation, flexural modes, instrumentation, and signal processing issues. Typical measurements show that the step response of the device is characterized by three distinct non-linear regimes (double-sided impact, single-sided impact, and no-impact). Each regime is directly related to the non-linear features of the device and can be described by peak angular acceleration values. Predictions of a simplified single degree of freedom non-linear model verify that the experiment performs well and as designed. Accordingly, the benchmark measurements could be utilized to validate non-linear models and simulation codes, as well as characterize dynamic parameters of the device including its dissipative properties.
Influence of tungsten fiber's slow drift on the measurement of G with angular acceleration method
NASA Astrophysics Data System (ADS)
Luo, Jie; Wu, Wei-Huang; Xue, Chao; Shao, Cheng-Gang; Zhan, Wen-Ze; Wu, Jun-Fei; Milyukov, Vadim
2016-08-01
In the measurement of the gravitational constant G with angular acceleration method, the equilibrium position of torsion pendulum with tungsten fiber undergoes a linear slow drift, which results in a quadratic slow drift on the angular velocity of the torsion balance turntable under feedback control unit. The accurate amplitude determination of the useful angular acceleration signal with known frequency is biased by the linear slow drift and the coupling effect of the drifting equilibrium position and the room fixed gravitational background signal. We calculate the influences of the linear slow drift and the complex coupling effect on the value of G, respectively. The result shows that the bias of the linear slow drift on G is 7 ppm, and the influence of the coupling effect is less than 1 ppm.
Influence of tungsten fiber's slow drift on the measurement of G with angular acceleration method.
Luo, Jie; Wu, Wei-Huang; Xue, Chao; Shao, Cheng-Gang; Zhan, Wen-Ze; Wu, Jun-Fei; Milyukov, Vadim
2016-08-01
In the measurement of the gravitational constant G with angular acceleration method, the equilibrium position of torsion pendulum with tungsten fiber undergoes a linear slow drift, which results in a quadratic slow drift on the angular velocity of the torsion balance turntable under feedback control unit. The accurate amplitude determination of the useful angular acceleration signal with known frequency is biased by the linear slow drift and the coupling effect of the drifting equilibrium position and the room fixed gravitational background signal. We calculate the influences of the linear slow drift and the complex coupling effect on the value of G, respectively. The result shows that the bias of the linear slow drift on G is 7 ppm, and the influence of the coupling effect is less than 1 ppm. PMID:27587137
Li, Zhijie; Wang, Shengjie; Wang, Zhiguo; Zu, Xiaotao T.; Gao, Fei; Weber, William J.
2010-07-01
The mechanical behavior of twinned silicon carbide (SiC) nanowires under combined tension-torsion and compression-torsion is investigated using molecular dynamics simulations with an empirical potential. The simulation results show that both the tensile failure stress and buckling stress decrease under combined tension-torsional and combined compression-torsional strain, and they decrease with increasing torsional rate under combined loading. The torsion rate has no effect on the elastic properties of the twinned SiC nanowires. The collapse of the twinned nanowires takes place in a twin stacking fault of the nanowires.
Aeroelastic considerations for torsionally soft rotors
NASA Technical Reports Server (NTRS)
Mantay, W. R.; Yeager, W. T., Jr.
1985-01-01
A research study was initiated to systematically determine the impact of selected blade tip geometric parameters on conformable rotor performance and loads characteristics. The model articulated rotors included baseline and torsionally soft blades with interchangeable tips. Seven blade tip designs were evaluated on the baseline rotor and six tip designs were tested on the torsionally soft blades. The designs incorporated a systemmatic variation in geometric parameters including sweep, taper, and anhedral. The rotors were evaluated in the NASA Langley Transonic Dynamics Tunnel at several advance ratios, lift and propulsive force values, and tip Mach numbers. A track sensitivity study was also conducted at several advance ratios for both rotors. Based on the test results, tip parameter variations generated significant rotor performance and loads differences for both baseline and torsionally soft blades.
Surgical correction of torsion of the penis.
Azmy, A; Eckstein, H B
1981-08-01
Torsion of the penis is a rare anomaly, believed to be due to abnormal skin attachment and not to any structural abnormality of the corpora. The rotation is usually to the left in a counter-clockwise fashion. The urethral meatus is placed in a oblique position and the median raphe makes a spiral curve from the base of the penis towards the meatus. Three boys with congenital torsion of the penis are reported. A corrective operative for this condition is described. Penile torsion was first described by Verneuil in 1857, but in the past no operative correction was recommended, since attempts to move the skin around were believed not to correct the spiral alignment of the corpora cavernosa. PMID:7260553
Active structures to reduce torsional vibrations
NASA Astrophysics Data System (ADS)
Matthias, M.; Schlote, D.; Atzrodt, H.
2013-03-01
This paper describes the development of different active measures to reduce torsional vibrations in power trains. The measures are based on concepts developed for active mounts to reduce the transmission of structure-borne sound. To show the potential of these active measures and investigate their mode of operation to influence torsional vibrations, numerical simulations of powertrains with different active measures were done. First experimental results from tests on an experimental (reduced size) power train were used to align the numerical models. The work was done within the project 'LOEWE-Zentrum AdRIA: Adaptronik - Research, Innovation, Application' funded by the German federal state of Hessen, and the Project AKTos: 'Active control of torsional vibrations by coupling elements' placed in the research Framework program 'Navigation and Maritime Technology for the 21st Century' funded by the German Federal Ministry of Economics and Technology.
Torsional elasticity and energetics of F1-ATPase.
Czub, Jacek; Grubmüller, Helmut
2011-05-01
F(o)F(1)-ATPase is a rotary motor protein synthesizing ATP from ADP driven by a cross-membrane proton gradient. The proton flow through the membrane-embedded F(o) generates the rotary torque that drives the rotation of the asymmetric shaft of F(1). Mechanical energy of the rotating shaft is used by the F(1) catalytic subunit to synthesize ATP. It was suggested that elastic power transmission with transient storage of energy in some compliant part of the shaft is required for the observed high turnover rate. We used atomistic simulations to study the spatial distribution and structural determinants of the F(1) torsional elasticity at the molecular level and to comprehensively characterize the elastic properties of F(1)-ATPase. Our fluctuation analysis revealed an unexpected heterogeneity of the F(1) shaft elasticity. Further, we found that the measured overall torsional moduli of the shaft arise from two distinct contributions, the intrinsic elasticity and the effective potential imposed on the shaft by the catalytic subunit. Separation of these two contributions provided a quantitative description of the coupling between the rotor and the catalytic subunit. This description enabled us to propose a minimal quantitative model of the F(1) energetics along the rotary degrees of freedom near the resting state observed in the crystal structures. As opposed to the usually employed models where the motor mechanical progression is described by a single angular variable, our multidimensional treatment incorporates the spatially inhomogeneous nature of the shaft and its interactions with the stator and offers new insight into the mechanoenzymatics of F(1)-ATPase. PMID:21502534
Torsional elasticity and energetics of F1-ATPase
Czub, Jacek; Grubmüller, Helmut
2011-01-01
FoF1-ATPase is a rotary motor protein synthesizing ATP from ADP driven by a cross-membrane proton gradient. The proton flow through the membrane-embedded Fo generates the rotary torque that drives the rotation of the asymmetric shaft of F1. Mechanical energy of the rotating shaft is used by the F1 catalytic subunit to synthesize ATP. It was suggested that elastic power transmission with transient storage of energy in some compliant part of the shaft is required for the observed high turnover rate. We used atomistic simulations to study the spatial distribution and structural determinants of the F1 torsional elasticity at the molecular level and to comprehensively characterize the elastic properties of F1-ATPase. Our fluctuation analysis revealed an unexpected heterogeneity of the F1 shaft elasticity. Further, we found that the measured overall torsional moduli of the shaft arise from two distinct contributions, the intrinsic elasticity and the effective potential imposed on the shaft by the catalytic subunit. Separation of these two contributions provided a quantitative description of the coupling between the rotor and the catalytic subunit. This description enabled us to propose a minimal quantitative model of the F1 energetics along the rotary degrees of freedom near the resting state observed in the crystal structures. As opposed to the usually employed models where the motor mechanical progression is described by a single angular variable, our multidimensional treatment incorporates the spatially inhomogeneous nature of the shaft and its interactions with the stator and offers new insight into the mechanoenzymatics of F1-ATPase. PMID:21502534
Global axial-torsional dynamics during rotary drilling
NASA Astrophysics Data System (ADS)
Gupta, Sunit K.; Wahi, Pankaj
2016-08-01
We have studied the global dynamics of the bottom hole assembly (BHA) during rotary drilling with a lumped parameter axial-torsional model for the drill-string and a linear cutting force model. Our approach accounts for bit-bounce and stick-slip along with the regenerative effect and is independent of the drill-string and the bit-rock interaction model. Regenerative axial dynamics due to variable depth of cut is incorporated through a functional description of the cut surface profile instead of a delay differential equation with a state-dependent delay. The evolution of the cut surface is governed by a nonlinear partial differential equation (PDE) which is coupled with the ordinary differential equations (ODEs) governing the longitudinal and angular dynamics of the BHA. The boundary condition for the PDE captures multiple regeneration in the event of bit-bounce. Interruption in the torsional dynamics is included by considering separate evolution equations for the various states during the stick period. Finite-dimensional approximation for our coupled PDE-ODE model has been obtained and validated by comparing our results against existing results. Bifurcation analysis of our system reveals a supercritical Hopf bifurcation leading to periodic vibrations without bit-bounce and stick-slip which is followed by solutions involving bit-bounce or stick-slip depending on the operating parameters. Further inroads into the unstable regime leads to a variety of complex behavior including co-existence of periodic and chaotic solutions involving both bit-bounce and stick-slip.
Angular Acceleration Without Torque?
NASA Astrophysics Data System (ADS)
Kaufman, Richard D.
2012-01-01
Hardly. Just as Robert Johns qualitatively describes angular acceleration by an internal force in his article "Acceleration Without Force?" here we will extend the discussion to consider angular acceleration by an internal torque. As we will see, this internal torque is due to an internal force acting at a distance from an instantaneous center.2
Angular Acceleration without Torque?
ERIC Educational Resources Information Center
Kaufman, Richard D.
2012-01-01
Hardly. Just as Robert Johns qualitatively describes angular acceleration by an internal force in his article "Acceleration Without Force?" here we will extend the discussion to consider angular acceleration by an internal torque. As we will see, this internal torque is due to an internal force acting at a distance from an instantaneous center.
Helioseismic measurement of solar torsional oscillations.
Vorontsov, S V; Christensen-Dalsgaard, J; Schou, J; Strakhov, V N; Thompson, M J
2002-04-01
Bands of slower and faster rotation, the so-called torsional oscillations, are observed at the Sun's surface to migrate in latitude over the 11-year solar cycle. Here, we report on the temporal variations of the Sun's internal rotation from solar p-mode frequencies obtained over nearly 6 years by the Michelson Doppler Imager (MDI) instrument on board the Solar and Heliospheric Observatory (SOHO) satellite. The entire solar convective envelope appears to be involved in the torsional oscillations, with phase propagating poleward and equatorward from midlatitudes at all depths throughout the convective envelope. PMID:11935019
Cracked shells under skew-symmetric loading. [Reissner theory
NASA Technical Reports Server (NTRS)
Delale, F.
1981-01-01
The general problem of a shell containing a through crack in one of the principal planes of curvature and under general skew-symmetric loading is considered. By employing a Reissner type shell theory which takes into account the effect of transverse shear strains, all boundary conditions on the crack surfaces are satisfied separately. Consequently, unlike those obtained from the classical shell theory, the angular distributions of the stress components around the crack tips are shown to be identical to the distributions obtained from the plane and anti-plane elasticity solutions. Results are given for axially and circumferentially cracked cylindrical shells, spherical shells, and toroidal shells under uniform in-plane shearing, out of plane shearing, and torsion. The problem is formulated for specially orthostropic materials, therefore, the effect of orthotropy on the results is also studied.
NASA Astrophysics Data System (ADS)
de Andrade, L. C. G.
2016-01-01
A generalized dynamo equation in the first order torsion Garcia de Andrade L C (2012 Phys. Lett. B 711 143) has previously been derived. From this equation it is shown that for the 10 kpc scale, torsion gravity is not able to help seed galactic dynamos since the dynamo time is not long enough to take into account structure formation. In this paper, the dynamo equation is extended to second-order torsion terms—but unfortunately, the situation is even worse and the torsion does not seem to help dynamo efficiency. Nevertheless, in the intergalactic magnetic field scale of 1 mpc, the efficiency of the self-induction equation with torsion changes, and even in the first-order torsion case, one obtains large-scale magnetic fields with 109 yr dynamo efficiency. Dynamo efficiency in the case of interstellar matter (ISM) reaches a diffusion time of 1013 yr. This seems to be in contrast with a recent investigation by Bamba et al (2012 J. Cosmol. Astropart. Phys. JCAP05(2010)08) where they obtained, from another type of torsion theory called teleparallelism (A Einstein, Math Annalen (1922)), a large scale intergalactic magnetic field of 10-9 G. If this is not a model-dependent result, there is an apparent contradiction that has to be addressed. It is shown that for dynamo efficiency in astrophysical flow without shear, a strong seed field of 10-11 G is obtained, which is suitable for seeding galactic dynamos. As an example of a non-parity-violating dynamo equation, a magnetic field of the order of 10-27G is obtained as a seed field for the galactic dynamo from the theory of Einstein’s unified teleparallelism. This shows that in certain gravity models, torsion is able to enhance cosmological magnetic fields in view of obtaining better dynamo efficiency. To better compare our work with Bamba et al (2012 J. Cosmol. Astropart. Phys. JCAP05(2010)08), we consider the slow decay of magnetic fields in the teleparallel model. This observation is due to an anonymous referee who
Tussive syncope in a pug with lung-lobe torsion
Davies, John A.; Snead, Elisabeth C.R.; Pharr, John W.
2011-01-01
The most common presenting clinical signs of lung-lobe torsion include dyspnea, tachypnea, lethargy, and anorexia. Tussive syncope secondary to lung-lobe torsion has not been documented. This article describes the presentation, diagnosis, management, and outcome of a pug with tussive syncope secondary to lung-lobe torsion. PMID:22131584
Quantum gravity, torsion, parity violation, and all that
Freidel, Laurent; Minic, Djordje; Takeuchi, Tatsu
2005-11-15
We discuss the issue of parity violation in quantum gravity. In particular, we study the coupling of fermionic degrees of freedom in the presence of torsion and the physical meaning of the Immirzi parameter from the viewpoint of effective field theory. We derive the low-energy effective Lagrangian which turns out to involve two parameters: one measuring the nonminimal coupling of fermions in the presence of torsion, the other being the Immirzi parameter. In the case of nonminimal coupling the effective Lagrangian contains an axial-vector interaction leading to parity violation. Alternatively, in the case of minimal coupling there is no parity violation and the effective Lagrangian contains only the usual axial-axial interaction. In this situation the real values of the Immirzi parameter are not at all constrained. On the other hand, purely imaginary values of the Immirzi parameter lead to violations of unitarity for the case of nonminimal coupling. Finally, the effective Lagrangian blows up for the positive and negative unit imaginary values of the Immirzi parameter.
Matter-antimatter asymmetry and dark matter from torsion
Poplawski, Nikodem J.
2011-04-15
We propose a simple scenario which explains the observed matter-antimatter imbalance and the origin of dark matter in the Universe. We use the Einstein-Cartan-Sciama-Kibble theory of gravity which naturally extends general relativity to include the intrinsic spin of matter. Spacetime torsion produced by spin generates, in the classical Dirac equation, the Hehl-Datta term which is cubic in spinor fields. We show that under a charge-conjugation transformation this term changes sign relative to the mass term. A classical Dirac spinor and its charge conjugate therefore satisfy different field equations. Fermions in the presence of torsion have higher energy levels than antifermions, which leads to their decay asymmetry. Such a difference is significant only at extremely high densities that existed in the very early Universe. We propose that this difference caused a mechanism, according to which heavy fermions existing in such a Universe and carrying the baryon number decayed mostly to normal matter, whereas their antiparticles decayed mostly to hidden antimatter which forms dark matter. The conserved total baryon number of the Universe remained zero.
Matter-antimatter asymmetry and dark matter from torsion
NASA Astrophysics Data System (ADS)
Popławski, Nikodem J.
2011-04-01
We propose a simple scenario which explains the observed matter-antimatter imbalance and the origin of dark matter in the Universe. We use the Einstein-Cartan-Sciama-Kibble theory of gravity which naturally extends general relativity to include the intrinsic spin of matter. Spacetime torsion produced by spin generates, in the classical Dirac equation, the Hehl-Datta term which is cubic in spinor fields. We show that under a charge-conjugation transformation this term changes sign relative to the mass term. A classical Dirac spinor and its charge conjugate therefore satisfy different field equations. Fermions in the presence of torsion have higher energy levels than antifermions, which leads to their decay asymmetry. Such a difference is significant only at extremely high densities that existed in the very early Universe. We propose that this difference caused a mechanism, according to which heavy fermions existing in such a Universe and carrying the baryon number decayed mostly to normal matter, whereas their antiparticles decayed mostly to hidden antimatter which forms dark matter. The conserved total baryon number of the Universe remained zero.
Cryptorchid testis with torsion: Inguinoscrotal whirlpool sign
Indiran, Venkatraman
2016-01-01
Non contrast helical computed tomography (CT) study of the abdomen is frequently performed in evaluation of suspected ureteric colic. We present CT images of a young adult male patient who had torsion of an undescended, non-neoplastic testis and describe the “Inguinoscrotal whirlpool sign on CT”. PMID:27555688
Adnexal torsion: review of the literature.
Sasaki, Kirsten J; Miller, Charles E
2014-01-01
Adnexal torsion is one of a few gynecologic surgical emergencies. Misdiagnosis or delay in treatment can have permanent sequelae including loss of an ovary with effect on future fertility, peritonitis, and even death. A PubMed search was performed between 1985 and 2012 for reviews, comparative studies, and case reports to provide a review of the epidemiology, risk factors, clinical presentation, common laboratory and imaging findings, and treatments of adnexal torsion. Common symptoms of torsion include pain, nausea, and vomiting, with associated abdominal or pelvic tenderness, and may differ in premenarchal and pregnant patients. Laboratory and imaging findings including ultrasound with Doppler analysis, computed tomography, and magnetic resonance imaging can assist in making the diagnosis but should not trump clinical judgment; normal Doppler flow can be observed in up to 60% of adnexal torsion cases. Treatment depends on the individual patient but commonly includes detorsion, even if the adnexae initially seem necrotic, with removal of any associated cysts or salpingo-oophorectomy, because recurrence rates are higher with detorsion alone or detorsion with only cyst aspiration. PMID:24126258
Joining and forming using torsional ultrasonic principles.
Frost, M
2009-10-01
Developments in torsional ultrasonic joining mean that it is now used in a diverse range of joining, forming, selective weakening and "break-off" applications in the medical device industry.The principles and benefits of the technique are described together with application examples. PMID:20302140
Hepatic lobe torsion in a horse
Bentz, Kristin J.; Burgess, Brandy A.; Lohmann, Katharina L.; Shahriar, Farshid
2009-01-01
A 4-year-old Belgian mare was presented with a 1-week history of fever, suspected of being caused by peritonitis. The mare died before the diagnostic procedures had been completed; postmortem examination revealed torsion of the left medial lobe of the liver, resulting in diffuse necrosis of liver tissue and severe peritoneal effusion. PMID:19436480
NASA Technical Reports Server (NTRS)
Liebe, Wolfgang
1944-01-01
In many studies, especially of nonstationary flight motion, it is necessary to determine the angular velocities at which the airplane rotates about its various axes. The three-component recorder is designed to serve this purpose. If the angular velocity for one flight attitude is known, other important quantities can be derived from its time rate of change, such as the angular acceleration by differentiations, or - by integration - the angles of position of the airplane - that is, the angles formed by the airplane axes with the axis direction presented at the instant of the beginning of the motion that is to be investigated.
Angular velocity discrimination
NASA Technical Reports Server (NTRS)
Kaiser, Mary K.
1990-01-01
Three experiments designed to investigate the ability of naive observers to discriminate rotational velocities of two simultaneously viewed objects are described. Rotations are constrained to occur about the x and y axes, resulting in linear two-dimensional image trajectories. The results indicate that observers can discriminate angular velocities with a competence near that for linear velocities. However, perceived angular rate is influenced by structural aspects of the stimuli.
Design and analysis of a torsion braid pendulum displacement transducer
NASA Technical Reports Server (NTRS)
Rind, E.; Bryant, E. L.
1981-01-01
The dynamic properties at various temperatures of braids impregnated with polymer can be measured by using the braid as the suspension of a torsion pendulum. This report describes the electronic and mechanical design of a torsional braid pendulum displacement transducer which is an advance in the state of the art. The transducer uses a unique optical design consisting of refracting quartz windows used in conjunction with a differential photocell to produce a null signal. The release mechanism for initiating free torsional oscillation of the pendulum has also been improved. Analysis of the precision and accuracy of the transducer indicated that the maximum relative error in measuring torsional amplitude was approximately 0. A serious problem inherent in all instruments which use a torsional suspension was analyzed: misalignment of the physical and torsional axes of the torsional member which results in modulation of the amplitude of the free oscillation.
Evaluation of left ventricular torsion by cardiovascular magnetic resonance
2012-01-01
Recently there has been considerable interest in LV torsion and its relationship with symptomatic and pre-symptomatic disease processes. Torsion gives useful additional information about myocardial tissue performance in both systolic and diastolic function. CMR assessment of LV torsion is simply and efficiently performed. However, there is currently a wide variation in the reporting of torsional motion and the procedures used for its calculation. For example, torsion has been presented as twist (degrees), twist per length (degrees/mm), shear angle (degrees), and shear strain (dimensionless). This paper reviews current clinical applications and shows how torsion can give insights into LV mechanics and the influence of LV geometry and myocyte fiber architecture on cardiac function. Finally, it provides recommendations for CMR measurement protocols, attempts to stimulate standardization of torsion calculation, and suggests areas of useful future research. PMID:22827856
Development of a second generation torsion balance based on a spherical superconducting suspension.
Hammond, Giles D; Speake, Clive C; Matthews, Anthony J; Rocco, Emanuele; Peña-Arellano, Fabian
2008-02-01
This paper describes the development of a second generation superconducting torsion balance to be used for a precision measurement of the Casimir force and a short range test of the inverse square law of gravity at 4.2 K. The instrument utilizes niobium (Nb) as the superconducting element and employs passive damping of the parasitic modes of oscillation. Any contact potential difference between the torsion balance and its surroundings is nulled to within approximately 50 mV by applying known DC biases and fitting the resulting parabolic relationship between the measured torque and the applied voltage. A digital proportional-integral-derivative servo system has been developed and characterized in order to control the azimuthal position of the instrument. The angular acceleration and displacement noise are currently limited by the capacitive sensor at the level 3x10(-8) rad s(-2)/ squarerootHz and 30 nm/ squarerootHz at 100 mHz. The possibility of lossy dielectric coatings on the surface of the torsion balance test masses is also investigated. Our measurements show that the loss angles delta are (1.5+/-2.3)x10(-4) and (2.0+/-2.2)x10(-4) at frequencies of 5 and 10 mHz, respectively. These values of loss are not significant sources of error for measurements of the Casimir force using this experimental setup. PMID:18315325
Development of a second generation torsion balance based on a spherical superconducting suspension
NASA Astrophysics Data System (ADS)
Hammond, Giles D.; Speake, Clive C.; Matthews, Anthony J.; Rocco, Emanuele; Peña-Arellano, Fabian
2008-02-01
This paper describes the development of a second generation superconducting torsion balance to be used for a precision measurement of the Casimir force and a short range test of the inverse square law of gravity at 4.2K. The instrument utilizes niobium (Nb) as the superconducting element and employs passive damping of the parasitic modes of oscillation. Any contact potential difference between the torsion balance and its surroundings is nulled to within ≈50mV by applying known DC biases and fitting the resulting parabolic relationship between the measured torque and the applied voltage. A digital proportional-integral-derivative servo system has been developed and characterized in order to control the azimuthal position of the instrument. The angular acceleration and displacement noise are currently limited by the capacitive sensor at the level 3×10-8rads-2/√Hz and 30nm/√Hz at 100mHz. The possibility of lossy dielectric coatings on the surface of the torsion balance test masses is also investigated. Our measurements show that the loss angles δ are (1.5±2.3)×10-4 and (2.0±2.2)×10-4 at frequencies of 5 and 10mHz, respectively. These values of loss are not significant sources of error for measurements of the Casimir force using this experimental setup.
Sudden lateral asymmetry and torsional oscillations of section models of suspension bridges
NASA Astrophysics Data System (ADS)
Plaut, R. H.; Davis, F. M.
2007-11-01
Cable-supported bridges typically exhibit minimal torsional motion under traffic and wind loads. If symmetry of the bridge about the deck's centerline is suddenly lost, such as by the failure of one or more cables or hangers (suspenders), torsional motion of the deck may grow and angles of twist may become large. The initiation of the disastrous torsional oscillations of the original Tacoma Narrows Bridge involved a sudden lateral asymmetry due to loosening of a cable band at midspan. The effects of these types of events on two-degree-of-freedom and four-degree-of-freedom section models of suspension bridges are analyzed. Vertical and rotational motions of the deck, along with vertical motions of the cables, are considered. A harmonic vertical force and an aerodynamic moment proportional to angular velocity are applied to the deck. Resistance is provided by translational and rotational springs and dashpots. Flutter instability and large oscillations occur under the aerodynamic moment, which provides "negative damping." In order to model the occurrence of limit cycles, nonlinear damping of the van der Pol type is included in one case, and nonlinear stiffness of the hangers in others. The frequencies of the limit cycles are compared to the natural frequencies of the system.
Evidence for the distribution of angular velocity inside the sun and stars
NASA Technical Reports Server (NTRS)
1972-01-01
A round table discussion of problems of solar and stellar spindown and theory is presented. Observational evidence of the angular momentum of the solar wind is included, emphasizing the distribution of angular velocity inside the sun and stars.
Angular distribution of turbulence in wave space
NASA Technical Reports Server (NTRS)
Coleman, G.; Ferziger, J. H.; Bertoglio, J. P.
1987-01-01
An alternative to the one-point closure model for turbulence, the large eddy simulation (LES), together with its more exact relative, direct numerical simulation (DNS) are discussed. These methods are beginning to serve as partial substitutes for turbulence experiments. The eddy damped quasi-normal Markovian (EDQNM) theory is reviewed. Angular distribution of the converted data was examined in relationship to EDQNM.
Torsional oscillations of a sphere in a Stokes flow
NASA Astrophysics Data System (ADS)
Box, F.; Thompson, A. B.; Mullin, T.
2015-12-01
The results of an experimental investigation into a sphere performing torsional oscillations in a Stokes flow are presented. A novel experimental set-up was developed, which enabled the motion of the sphere to be remotely controlled through application of an oscillatory magnetic field. The response of the sphere to the applied field was characterised in terms of the viscous, magnetic and gravitational torques acting on the sphere. A mathematical model of the system was developed, and good agreement was found between experimental, numerical and theoretical results. The flow resulting from the motion of the sphere was measured, and the fluid velocity was found to have an inverse square dependence on radial distance from the sphere. The good agreement between measurements and the analytical solutions for both fluid velocity and angular displacement of the sphere indicates that the flow may be considered Stokesian, thus providing an excellent basis for experimental and theoretical characterisation of hydrodynamic interactions between multiple oscillating spheres at low Reynolds number.
Understanding Solar Torsional Oscillations from Global Dynamo Models
NASA Astrophysics Data System (ADS)
Guerrero, G.; Smolarkiewicz, P. K.; de Gouveia Dal Pino, E. M.; Kosovichev, A. G.; Mansour, N. N.
2016-09-01
The phenomenon of solar “torsional oscillations” (TO) represents migratory zonal flows associated with the solar cycle. These flows are observed on the solar surface and, according to helioseismology, extend through the convection zone. We study the origin of the TO using results from a global MHD simulation of the solar interior that reproduces several of the observed characteristics of the mean-flows and magnetic fields. Our results indicate that the magnetic tension (MT) in the tachocline region is a key factor for the periodic changes in the angular momentum transport that causes the TO. The torque induced by the MT at the base of the convection zone is positive at the poles and negative at the equator. A rising MT torque at higher latitudes causes the poles to speed up, whereas a declining negative MT torque at the lower latitudes causes the equator to slow-down. These changes in the zonal flows propagate through the convection zone up to the surface. Additionally, our results suggest that it is the magnetic field at the tachocline that modulates the amplitude of the surface meridional flow rather than the opposite as assumed by flux-transport dynamo models of the solar cycle.
Laser-Based Measurement Of Torsional Vibration
NASA Astrophysics Data System (ADS)
Eastwood, P. G.; Halliwell, N. A.
1986-07-01
Investigations of the torsional vibration characteristics of shaft systems which transmit pulsating torques are an important part of a machinery designer's responsibility. Satisfactory operation of such systems depends to a large extent on successful treatment of this vibration problem, since incorrectly or insufficiently controlled torsional oscillations can lead to fatigue failure, rapid bearing wear, gear hammer etc. The problem is particularly severe in engine crankshaft design where numerous failures have been traced to abnormal vibration at "critical" speeds. Traditionally, the monitoring of torsional oscillation has been performed using strain gauges, slip rings and a variety of mechanical and electrical "torsiographs". More recently systems employing slotted discs or toothed wheels together with proximity transducers have been preferred, but a disadvantage arises from all these methods in that they require contact with the rotating component which necessitates "downtime" for transducer attachment. Moreover, physical access to the rotating surface is often restricted thus making the use of such methods impractical. The "cross-beam" laser velocimeter provides a means of measuring torsional vibration by a non-contact method, thus effectively overcoming the disadvantages of previous measurement systems. This well established laser-based instrument provides a time-resolved voltage analogue of shaft tangential surface velocity and laboratory and field tests have shown it to be both accurate and reliable. The versatility of this instrument, however, is restricted by the need for accurate positioning, since the velocimeter must be arranged so that the rotating surface always traverses the beam intersection region, which is typically only a fraction of a millimetre in length. As a consequence use is restricted to components of circular cross section. This paper compares and contrasts the "cross-beam" system with a new laser instrument, the laser torsional vibrometer
Geometric absorption of electromagnetic angular momentum
NASA Astrophysics Data System (ADS)
Konz, C.; Benford, Gregory
2003-10-01
Circularly polarized electromagnetic fields carry both energy and angular momentum. We investigate the conditions under which a circularly polarized wave field transfers angular momentum to a perfectly conducting macroscopic object, using exact electromagnetic wave theory in a steady-state calculation. We find that axisymmetric perfect conductors cannot absorb or radiate angular momentum when illuminated. However, any asymmetry allows absorption. A rigorous, steady-state solution of the boundary value problem for the reflection from a perfectly conducting infinite wedge shows that waves convey angular momentum at the edges of asymmetries. Conductors can also radiate angular momentum, so their geometric absorption coefficient for angular momentum can be negative. Such absorption or radiation depends solely on the specific geometry of the conductor. The geometric absorption coefficient can be as high as 0.8, and the coefficient for radiation can be -0.4, larger than typical material absorption coefficients. We apply the results to recent experiments which spun roof-shaped aluminum sheets with polarized microwave beams. Applications of geometric, instead of material, absorption can be quite varied. Though experiments testing these ideas will be simpler at microwavelengths, the ideas work for optical ones as well.
Cosmology in Poincaré gauge gravity with a pseudoscalar torsion
NASA Astrophysics Data System (ADS)
Lu, Jianbo; Chee, Guoying
2016-05-01
A cosmology of Poincar é gauge theory is developed, where several properties of universe corresponding to the cosmological equations with the pseudoscalar torsion function are investigated. The cosmological constant is found to be the intrinsic torsion and curvature of the vacuum universe and is derived from the theory naturally rather than added artificially, i.e. the dark energy originates from geometry and includes the cosmological constant but differs from it. The cosmological constant puzzle, the coincidence and fine tuning problem are relieved naturally at the same time. By solving the cosmological equations, the analytic cosmological solution is obtained and can be compared with the ΛCDM model. In addition, the expressions of density parameters of the matter and the geometric dark energy are derived, and it is shown that the evolution of state equations for the geometric dark energy agrees with the current observational data. At last, the full equations of linear cosmological perturbations and the solutions are obtained.
Optomechanics based on angular momentum exchange between light and matter
NASA Astrophysics Data System (ADS)
Shi, H.; Bhattacharya, M.
2016-08-01
The subject of optomechanics involves interactions between optical and mechanical degrees of freedom, and is currently of great interest as an enabler of fundamental investigations in quantum mechanics, as well as a platform for ultrasensitive measurement devices. The majority of optomechanical configurations rely on the exchange of linear momentum between light and matter. We will begin this tutorial with a brief description of such systems. Subsequently, we will introduce optomechanical systems based on angular momentum exchange. In this context, optical fields carrying polarization and orbital angular momentum will be considered, while for the mechanics, torsional and free rotational motion will be of relevance. Our overall aims will be to supply basic analyses of some of the existing theoretical proposals, to provide functional descriptions of some of the experiments conducted thus far, and to consider some directions for future research. We hope this tutorial will be useful to both theorists and experimentalists interested in the subject.
Axial and torsional fatigue behavior of Waspaloy
NASA Technical Reports Server (NTRS)
Zamrik, S.; Mirdamadi, M.; Zahiri, F.
1986-01-01
The cyclic flow response and crack growth behavior of Waspaloy at room temperature and 650 C under tensile loading and torsional loading was studied, for two conditions of Waspaloy: fine grain, large gamma prime size; coarse grain, small gamma prime size. The fine grain material showed 5 to 10 percent hardening after about 10 percent of life, with sequent softening to failure at both themperature levels. The coarse grain material showed either stable response or monotonic softening to failure. Early crack initiation was observed on planes of maximum shear, with eventual branching to principle planes under torsional loading; cracks were always normal to load axis under tensile loading. Also, crack paths were intergranular at 650 C, mostly transgranular at room temperature.
Torsion and transverse bending of cantilever plates
NASA Technical Reports Server (NTRS)
Reissner, Eric; Stein, Manuel
1951-01-01
The problem of combined bending and torsion of cantilever plates of variable thickness, such as might be considered for solid thin high-speed airplane or missile wings, is considered in this paper. The deflections of the plate are assumed to vary linearly across the chord; minimization of the potential energy by means of the calculus of variations then leads to two ordinary linear differential equations for the bending deflections and the twist of the plate. Because the cantilever is analyzed as a plate rather than as a beam, the effect of constraint against axial warping in torsion is inherently included. The application of this method to specific problems involving static deflection, vibration, and buckling of cantilever plates is presented. In the static-deflection problems, taper and sweep are considered.
NASA Astrophysics Data System (ADS)
Thidé, B.; Tamburini, F.; Then, H.; Someda, C. G.; Mari, Elletra; Parisi, G.; Spinello, F.; Romanato, Fra
2014-02-01
Wireless communication amounts to encoding information onto physical observables carried by electromagnetic (EM) fields, radiating them into surrounding space, and detecting them remotely by an appropriate sensor connected to an informationdecoding receiver. Each observable is second order in the fields and fulfills a conservation law. In present-day radio only the EM linear momentum observable is fully exploited. A fundamental physical limitation of this observable, which represents the translational degrees of freedom of the charges (typically an oscillating current along a linear antenna) and the fields, is that it is single-mode. This means that a linear-momentum radio communication link comprising one transmitting and one receiving antenna, known as a single-input-single-output (SISO) link, can provide only one transmission channel per frequency (and polarization). In contrast, angular momentum, which represents the rotational degrees of freedom, is multi-mode, allowing an angular-momentum SISO link to accommodate an arbitrary number of independent transmission channels on one and the same frequency (and polarization). We describe the physical properties of EM angular momentum and how they can be exploited, discuss real-world experiments, and outline how the capacity of angular momentum links may be further enhanced by employing multi-port techniques, i.e., the angular momentum counterpart of linear-momentum multiple-input-multiple-output (MIMO).
Wang, Shibo; Niu, Chengchao
2016-01-01
In this work, the plane-on-plane torsional fretting tribological behavior of polytetrafluoroethylene (PTFE) was studied. A model of a rigid, flat-ended punch acting on an elastic half-space was built according to the experimental conditions. The results indicate that the shape of T–θ curves was influenced by both the torsional angle and the normal load. The torsion friction torque and wear rate of PTFE exponentially decreased when the torsion angle rose. The torsional torque increased from 0.025 N·m under a normal load of 43 N to 0.082 N·m under a normal load of 123 N. With sequentially increasing normal load, the value of torque was maintained. With rising normal load, the wear mass loss of PTFE disks was increased and the wear rate was decreased. Good agreement was found with the calculated torque according to the model and the experimental torque except for that under a normal load of 163 N. The difference under a normal load of 163 N was caused by the coefficient of friction. Usually the coefficient of friction of a polymer decreases with increasing normal load, whereas a constant coefficient of friction was applied in the model. PMID:26799324
Wang, Shibo; Niu, Chengchao
2016-01-01
In this work, the plane-on-plane torsional fretting tribological behavior of polytetrafluoroethylene (PTFE) was studied. A model of a rigid, flat-ended punch acting on an elastic half-space was built according to the experimental conditions. The results indicate that the shape of T-θ curves was influenced by both the torsional angle and the normal load. The torsion friction torque and wear rate of PTFE exponentially decreased when the torsion angle rose. The torsional torque increased from 0.025 N·m under a normal load of 43 N to 0.082 N·m under a normal load of 123 N. With sequentially increasing normal load, the value of torque was maintained. With rising normal load, the wear mass loss of PTFE disks was increased and the wear rate was decreased. Good agreement was found with the calculated torque according to the model and the experimental torque except for that under a normal load of 163 N. The difference under a normal load of 163 N was caused by the coefficient of friction. Usually the coefficient of friction of a polymer decreases with increasing normal load, whereas a constant coefficient of friction was applied in the model. PMID:26799324
Analytic Model for the Rototranslational Torsion Pendulum
NASA Astrophysics Data System (ADS)
De Marchi, F.; Bassan, M.; Pucacco, G.; Marconi, L.; Stanga, R.; Visco, M.
2013-01-01
We develop an analytic model to describe the motion of the RotoTranslational Torsion Pendulum PETER in a wide range of frequencies (from 1mHz up to 10-15Hz). We also try to explain some unexpected features we found in the data with only 1 soft degree of freedom and we estimate values for the misalignment angles and other parameters of the model.
Fluid driven torsional dipole seismic source
Hardee, Harry C.
1991-01-01
A compressible fluid powered oscillating downhole seismic source device capable of periodically generating uncontaminated horizontally-propagated, shear waves is provided. A compressible fluid generated oscillation is created within the device which imparts an oscillation to a housing when the device is installed in a housing such as the cylinder off an existing downhole tool, thereby a torsional seismic source is established. Horizontal waves are transferred to the surrounding bore hole medium through downhole clamping.