Rotation Of Principal Axes Research Articles

SANISAND‐FN: An evolving fabric‐based sand model accounting for stress principal axes rotation

SummarySANISAND is the name of a family of bounding surface plasticity constitutive models for sand within the framework of critical state theory, which have been able to realistically simulate the sand behavior under conventional monotonic and cyclic loading paths. In order to incorporate the important role of evolving fabric anisotropy, one such model was modified within the framework of the new anisotropic critical state theory and named SANISAND‐F model. Yet the response under continuous stress principal axes rotation requires further modification to account for the effect of ensuing noncoaxiality on the dilatancy and plastic modulus. This modification is simpler than what is often proposed in the literature, since it does not incorporate an additional plastic loading mechanism and/or multiple dilatancy and plastic modulus expressions. The new model named SANISAND‐FN is presented herein and is validated against published data for loading that includes drained stress principal axes rotation on Toyoura sand.

Coexistence of principal and tilted axis rotation in Ag110

The positive-parity band structure of $^{110}\mathrm{Ag}$ has been established for the first time. A new decay path to the isomeric ${6}^{+}$ state has been observed for this band. The lifetimes of the high spin levels have been measured using the Doppler-shift attenuation method. The comparison of the experimental data with the numerical results of the shears mechanism with principal axis cranking calculation indicates that this band originates due to the tilted axis rotation. On the other hand, it has already been established that the negative-parity levels in the same spin domain originate due to the principal axis rotation.

Spectral energy scaling in precessing turbulence.

We study precessing turbulence, which appears in several geophysical and astrophysical systems, by direct numerical simulations of homogeneous turbulence where precessional instability is triggered due to the imposed background flow. We show that the time development of kinetic energy K occurs in two main phases associated with different flow topologies: (i) an exponential growth characterizing three-dimensional turbulence dynamics and (ii) nonlinear saturation during which K remains almost time independent, the flow becoming quasi-two-dimensional. The latter stage, wherein the development of K remains insensitive to the initial state, shares an important common feature with other quasi-two-dimensional rotating flows such as rotating Rayleigh-Bénard convection, or the large atmospheric scales: in the plane k_{∥}=0, i.e., the plane associated to an infinite wavelength in the direction parallel to the principal rotation axis, the kinetic energy spectrum scales as k_{⊥}^{-3}. We show that this power law is observed for wave numbers ranging between the Zeman "precessional" and "rotational" scales, k_{S}^{-1} and k_{Ω}^{-1}, respectively, at which the associated background shear or inertial timescales are equal to the eddy turnover time. In addition, an inverse cascade develops for (k_{⊥},k)<k_{S}, and the spherically averaged kinetic energy spectrum exhibits a k^{-2} inertial scaling for k_{S}<k<k_{Ω}.

Spectral Deconvolution of the 6196 and 6614 Å Diffuse Interstellar Bands Supports a Common-carrier Origin

Abstract We explore the common-carrier hypothesis for the 6196 and 6614 Å diffuse interstellar bands (DIBs). The observed DIB spectra are sharpened using a spectral deconvolution algorithm. This reveals finer spectral features that provide tighter constraints on candidate carriers. We analyze a deconvolved λ6614 DIB spectrum and derive spectroscopic constants that are then used to model the λ6196 spectra. The common-carrier spectroscopic constants enable quantitative fits to the contrasting λ6196 and λ6614 spectra from two sightlines. Highlights of our analysis include (1) sharp cutoffs for the maximum values of the rotational quantum numbers, J max = K max, (2) the λ6614 DIB consisting of a doublet and a red-tail component arising from different carriers, (3) the λ6614 doublet and λ6196 DIBs sharing a common carrier, (4) the contrasting shapes of the λ6614 doublet and λ6196 DIBs arising from different vibration–rotation Coriolis coupling constants that originate from transitions from a common ground state to different upper electronic state degenerate vibrational levels, and (5) the different widths of the two DIBs arising from different effective rotational temperatures associated with principal rotational axes that are parallel and perpendicular to the highest-order symmetry axis. The analysis results suggest a puckered oblate symmetric top carrier with a dipole moment aligned with the highest-order symmetry axis. An example candidate carrier consistent with these specifications is corannulene (C20H10), or one of its symmetric ionic or dehydrogenated forms, whose rotational constants are comparable to those obtained from spectral modeling of the DIB profiles.

Multiaxial Fatigue Life Calculation Model for Engineering Components in Rolling-Sliding Contact

Number of important engineering components and elements such as gears, rollers, bearings operate in conditions of rolling-sliding contact loading. Determination of fatigue lives of such components and elements is very important for engineering practice but remains quite chalenging task due to complex states of stress and strain in the material in the vicinity of contact (multiaxiality, non-proportionality, rotation of principal axes, mean compressive stress) as well as complex contact conditions such as loading amplitude, complex geometry of bodies in contact, type of lubrication, value of coefficient of friction, etc. Proposed fatigue life calculation model for cases of rolling-sliding contact is based on critical plane approach in the form of Fatemi-Socie crack initiation criterion. Developed model was implemented in the case of gears teeth flanks in mesh and compared with results and fatigue lives of gears reported in literature. Good agreement was determined confirming validity of developed model. Further advantage of presented approach and developed model is obtained information on critical location(s) and critical plane(s) orientation which can subsequently be used for estimation of crack shapes in initial phases of their growth and later damage type into which they can be expected to develop.

Seismic Performance Study of Multistoried Buildings with Oblique Columns by using ETABS

Facing a large number of new-type complex structural system and progressively consummate earthquake-resistant theories, the conventional software can no longer meet the needs of calculation and analysis. Meanwhile, some international finite element programs, such as ETABS, were updating themselves but remained respective limitations. China has Circum-Pacific seismic belt and Europe-Asia seismic zone. These two are the largest seismic belts in the world. Densely populated and low seismic capacity buildings, in which the earthquake can be simply summarized as high frequency, wide distribution, high intensity and shallow focal depth was described as the world’s most earthquake disaster area. The seismic performance analysis and research of building structures look more indispensable. The Oblique Columns are neither parallel nor at right angles to a specified line means they are slanted or Rotated at an angle. In this present work, concerns with the elastic flexural buckling of doubly symmetric columns with oblique restraints under concentric loading. Oblique restraints cause coupling between the principal axis deflections and rotations, and the flexural buckling mode involves simultaneous bending about both principal axes. The present work deals with a study on the Oblique columns of different angles in high rise building. In this work, a high rise building with Normal Columns & at different locations of Oblique columns is considered for analysis. In this paper, response spectrum analysis was executed, which were also compared following the analysis results. The results of the analysis on the Story shear, Story stiffness, Storey drift and Displacements are compared. The results are presented in the tabular and graphical form.

The equivalence of multi-axis spine systems: Recommended stiffness limits using a standardized testing protocol

The complexity of multi-axis spine testing often makes it challenging to compare results from different studies. The aim of this work was to develop and implement a standardized testing protocol across three six-axis spine systems, compare them, and provide stiffness and phase angle limits against which other test systems can be compared. Standardized synthetic lumbar specimens (n=5), comprising three springs embedded in polymer at each end, were tested on each system using pure moments in flexion–extension, lateral bending, and axial rotation. Tests were performed using sine and triangle waves with an amplitude of 8Nm, a frequency of 0.1Hz, and with axial preloads of 0 and 500N. The stiffness, phase angle, and R2 value of the moment against rotation in the principal axis were calculated at the center of each specimen. The tracking error was adopted asa measure of each test system to minimize non-principal loads, defined as the root mean squared difference between actual and target loads. All three test systems demonstrated similar stiffnesses, with small (<14%) but significant differences in 4 of 12 tests. More variability was observed in the phase angle between the principal axis moment and rotation, with significant differences in 10 of 12 tests. Stiffness and phase angle limits were calculated based on the 95% confidence intervals from all three systems. These recommendations can be used with the standard specimen and testing protocol by other research institutions to ensure equivalence of different spine systems, increasing the ability to compare in vitro spine studies.

Band structures in Pd101

Excited states in the $^{101}\mathrm{Pd}$ nucleus were investigated through the $^{75}\mathrm{As}(^{31}\mathrm{P},2p3n)$ fusion-evaporation reaction at ${E}_{\mathrm{lab}}=125$ MeV by using the Indian National Gamma Array spectrometer equipped with 21 clover Ge detectors. The level scheme is considerably extended for medium spin values. New positive-parity band structures in $^{101}\mathrm{Pd}$ have been studied within the framework of the projected shell model and are found to undergo transition from single quasiparticle to high-$K$ three quasiparticle configuration after band crossing, i.e., from principal-axis rotation to tilted-axis rotation. The negative-parity band structures are discussed in the framework of the hybrid version of tilted-axis cranking shell model calculations. The observed alignment gain in the lowest excited $\ensuremath{\nu}{h}_{11/2}$ negative-parity band results from successive ${(\ensuremath{\nu}{g}_{7/2})}^{2}$ and ${(\ensuremath{\pi}{g}_{9/2})}^{2}$ pair alignments. The higher excited negative-parity bands are reproduced for the $\ensuremath{\nu}[{h}_{11/2}{({g}_{7/2}/{d}_{5/2})}^{2}]$ and ${(\ensuremath{\pi}{g}_{9/2})}^{\ensuremath{-}2}\ensuremath{\bigotimes}\ensuremath{\nu}{h}_{11/2}$ configurations.

Present-day kinematics in the Eastern Mediterranean and Caucasus from dense GPS observations

The Eastern Mediterranean and Caucasus are located among the Eurasian, African and Arabian plates, and tectonic activities are very complex. In this paper, the kinematics and strain distribution in these regions are determined and investigated from dense GPS observations with over 1000 stations and longer observations. The elastic block model is used to constrain present-day plate motions and crustal deformation. The relative Euler vectors between the Nubian, Arabian, Caucasus, Anatolian and Central Iranian plates are estimated. The Arabian-Eurasia, Anatolian-Eurasia, Nubian-Eurasia, Caucasus-Eurasia and Central Iranian Euler vectors are 0.584±0.1Myr−1, 0.825±0.064Myr−1, 0.35±0.175Myr−1, 0.85±0.086Myr−1 and 0.126±0.016Myr−1. The strain rate in the East Mediterranean and Caucasus has been estimated from the GPS velocity field. The results show that the thrust dominated areas, the eastern Mediterranean-Middle East-Caucasus and Zagros have negative dilatation and the western Anatolia region has positive 2D dilatation rate with significant rotation. The west Anatolian shows the extension in NW-SE with about 150–199nstrain/yr in the W-E direction. The Central Anatolia shows compression rate below 50nstrain/yr and extensional strain rate adjacent to East Anatolian Fault and Dead Sea Fault is about 0–100nstrain/yr. The contraction strain rate is higher in Zagros and Caucasus between 100–150nstrain/yr and contraction orientation is along the NE-SW direction in Caucasus. The north part of Iran shows less contraction rate below 50nstrain/yr but North-East Zagros Mountains, Tabriz fault and Chalderan fault show extensional rate between 50–110nstrain/yr and principal axes rotation in the N-S direction. The maximum contraction observed in the Kopek Dag is about 100–194nstrain/yr and orientated in the NE-SW direction. East Zagros Mountain and Makran subduction zone have a large clockwise rotation with 70–85nradian and principal axes remains mostly along the N-S direction. The observed extension is along N-S by about 0–100nstrain/yr with counter clockwise rotation in Dead Sea Fault. The Sinai block shows shortening rate in the range of 0–100nstrain/yr.

Modulation of unpolarized light in planar-aligned subwavelength-pitch deformed-helix ferroelectric liquid crystals.

We study the electro-optic properties of subwavelength-pitch deformed-helix ferroelectric liquid crystals (DHFLC) illuminated with unpolarized light. In the experimental setup based on the Mach-Zehnder interferometer, it was observed that the reference and the sample beams being both unpolarized produce the interference pattern which is insensitive to rotation of in-plane optical axes of the DHFLC cell. We find that the field-induced shift of the interference fringes can be described in terms of the electrically dependent Pancharatnam relative phase determined by the averaged phase shift, whereas the visibility of the fringes is solely dictated by the phase retardation.

Solvation Dynamics in Liquid Water. III. Energy Fluxes and Structural Changes.

In previous installments it has been shown how a detailed analysis of energy fluxes induced by electronic excitation of a solute can provide a quantitative understanding of the dominant molecular energy flow channels characterizing solvation-and in particular, hydration- relaxation dynamics. Here this work and power approach is complemented with a detailed characterization of the changes induced by such energy fluxes. We first examine the water solvent's spatial and orientational distributions and the assorted energy fluxes in the various hydration shells of the solute to provide a molecular picture of the relaxation. The latter analysis is also used to address the issue of a possible "inverse snowball" effect, an ansatz concerning the time scales of the different hydration shells to reach equilibrium. We then establish a link between the instantaneous torque, exerted on the water solvent neighbors' principal rotational axes immediately after excitation and the final energy transferred into those librational motions, which are the dominant short-time energy receptor.

Charge-ordering induces magnetic axes rotation in organic materials (TMTTF)2X (with X = SbF6, AsF6, and PF6)

We have performed a comprehensive EPR investigation of the quasi-one-dimensional organic systems (TMTTF)2X with centrosymmetrical anions X (X = SbF6, AsF6, and PF6). We observe a strong rotation of g-factor principal axes when the temperature decreases below charge-ordering temperature TCO. The possible origin of this rotation is analyzed on the basis of quantum chemical calculations performed using density functional theory method. A good agreement between theory and experiment is found.

Exotic rotations and triaxiality in Nd nuclei

We have recently studied the Nd nuclei up to very high spins and identified a multitude of bands which are interpreted as the manifestation of a nucleus with stable triaxial shape, presenting various types of collective motion: tilted axis and principal axis rotation, wobbling motion, chiral bands. Seniority isomers built on nearly spherical shapes up to very high spins, surrounded by coexisting triaxial bands, have also been observed. The new results obtained from the systematics of the high-spin bands of Nd nuclei are discussed.

Rotation of principal axes and changes of stress due to mine-induced stresses

This research project comprises stress monitoring, primarily of the changes induced by longwall mining or destress blasting, which was realized in a mine of the Ostrava-Karviná Coalfields (Upper Silesian Coal Basin). Verification of the stress field response to stresses induced by different geological or mining factors was the main aim of the research project. Stress change monitoring in the region of the advanced longwall was carried out using seven stress probes. In all, seven boreholes were instrumented with compact conical ended borehole monitoring (CCBM) probes for continuous stress monitoring of the stress–strain changes due to mining and the destress blasting effect. Compact conical-ended borehole overcoring (CCBO) and CCBM probe installation were carried out before the start of the longwall mining. Data of the stress changes in all seven probes were recorded weekly and, after the longwall advanced, daily. Analysis of the stress changes was based on the idea of original stress distribution, which is based on long-term experiences in rock mass behavior in similar geological and mining conditions. For all probes, the magnitude of stress changes and principal axis direction changes were investigated. Analysis results to date indicate that stress changes ahead of the longwall face present not only the changes of stress magnitude, but the rotation of the axes of the stress components as well. Rotations of the principal axes emerged as very important factors of the stress tensor changes and their influence on rock mass deformation and stability of the workings. In addition, results show that the vertical to horizontal stress component ratio converges to 1 and in many cases horizontal stresses are higher than vertical ones. This of course relates to the impact of mine-induced stresses. This knowledge is basic for the purpose of prevention of rock burst because the actual stress state is fundamental to its proper and operative planning.

Can a secondary isotope effect be larger than a primary?

Primary and secondary (18)O equilibrium isotope effects on the acidities of a variety of Brønsted and Lewis acids centered on carbon, boron, nitrogen, and phosphorus were computed by density-functional theory. For many of these acids, the secondary isotope effect was found to be larger than the primary isotope effect. This is a counterintuitive result, because the H atom that is lost is closer to the (18)O atom that is responsible for the primary isotope effect. The relative magnitudes of the isotope effects can be associated with the vibrational frequency and zero-point energy of the X═O vibrations, which are greater than those of the X-O vibrations. However, the difference between these contributions is small, and the major responsibility for the larger secondary isotope effect comes from the moment-of-inertia factor, which depends on the position of the (18)O atom relative to the principal axes of rotation.

Ultra-thin, planar, broadband, dual-polarity plasmonic metalens

An ultrathin, planar, broadband metalens composed of metal rectangular split-ring resonators (MRSRRs) has been designed, which shows dual-polarity characteristics for different types of circularly polarized (CP) light incidence. The designed metalens can be considered as the focusing lens and the diverging lens under left-handed CP and right-handed CP light incidence, respectively. The phase discontinuity of the cross-polarized transmission light is produced by optical-axis rotation through modulating two arms’ lengths of the MRSRR. The MRSRR metalens possesses a wavelength-controllable focal length and a relatively larger chromatic aberration compared with the conventional lenses. And the focal length changes from 9 to 7 μm with incident wavelength from 740 to 950 nm. The dual-polarity flat metalens opens a door for new applications of phase discontinuity devices, and it will promote the fabricating capability of on-chip or fiber-embedded optical devices.

Tumbling asteroid rotation with the YORP torque and inelastic energy dissipation

The Yarkovsky–O'Keefe–Radzievskii–Paddack (YORP) effect and rotational energy dissipation due to inelastic deformations are two key mechanisms affecting rotation of tumbling asteroids in long term. Each of the effects used to be discussed separately. We present the first results concerning a simulation of their joint action. Asteroids (3103) Eger and (99942) Apophis, as well as their scaled variants, are used as test bodies. Plugging in the dissipation destroys limit cycles of the pure YORP, but creates a new asymptotic state of stationary tumbling with a fixed rotation period. The present model does not contradict finding Eger in the principal axis rotation. For Apophis, the model suggests that its current rotation state should be relatively young. In general, the fraction of initial conditions leading to the principal axis rotation is too small, compared to the actual data. The model requires a stronger energy dissipation and weaker YORP components in the nutation angle and obliquity.

Particle mechanics approach to continuum constitutive modelling

A new type of constitutive model is proposed for soils, based on three foundations. The first foundation involves a new approach to Cauchy’s concept of stress, based on a way of organizing particle mechanical information. This leads to a description of effective stress that is consistent with Terzaghi’s principle but contains more information than a tensor. The second foundation involves the load-spreading and displacement-spreading effects of particles in an aggregate. The third foundation takes account of recent proposals in the thermomechanics of granular media. A simple model is then proposed based on expectations inferred from published data of asymptotic proportional straining. Validation calculations are presented showing realistic predictions for monotonic and cyclic plasticity, critical states, dilation, induced anisotropy and non-coaxiality as a result of principal axis rotation. The model suggests that a yield envelope, plastic flow and critical states are not fundamental properties but emergent ones. The paper concludes with a brief discussion of possibilities for further developments.

On the structural basis of the presence of two optical axes in α-HIO3 crystal

An X-ray diffraction study of α-HIO3 crystal has been performed with the following results: sp. gr. P212121, Z = 4, a = 5.5360(3) A, b = 5.8723(6) A, c = 7.7291(5) A, and R factors R(F)/wR(F) = 0.86/0.69%. Disordering of iodine site is revealed, which is described in terms of anharmonic atomic displacements. Packing (likely unique) of all structure atoms over two systems of planes rotated by an angle close to the rotation of optical axes (47°) is revealed. The rotation of the plane of polarization of light based on the structural data is calculated for the first time for the α-HIO3 crystal.

English

The study of fish diversity of Eastern and Western Doon Valley streams (2010-2012) viz., Baldi, Song and Suswa in East and Tons and Asan in West has revealed it to be represented by 56 species belonging to 5 Orders, 13 Families and 30 Genera. The present findings are the outcome of FactorAnalysis tool applied on 30 genera, fractionated into 2 categories viz., frequent (28 genera) and infrequent genera/species (2 genera + 12 species), with a view to find out determinants of associations amongst various genera. Four Factor groups (represented by 23 frequent genera + 1 set of infrequent genera/species) were obtained through oblique rotation of principal axes, factored from the number of individual’s data matrix of 480 collections, with heavy loadings of ≥ 0.70. The sake of convenience and easy understanding, various Factors have been named on the basis of genus/species showed the highest loading on each Factor. The distribution of fish genera according to their loading values in different Factors showed a specific pattern of association and vis-a-vis highlights meaningful interpretations about the ecological habitat characteristics of various genera.