Kinematic Correlations Research Articles

Modelling the 20th and 21st century evolution of Hoffellsjökull glacier, SE-Vatnajökull, Iceland

Abstract. The Little Ice Age maximum extent of glaciers in Iceland was reached about 1890 AD and most glaciers in the country have retreated during the 20th century. A model for the surface mass balance and the flow of glaciers is used to reconstruct the 20th century retreat history of Hoffellsjökull, a south-flowing outlet glacier of the ice cap Vatnajökull, which is located close to the southeastern coast of Iceland. The bedrock topography was surveyed with radio-echo soundings in 2001. A wealth of data are available to force and constrain the model, e.g. surface elevation maps from ~1890, 1936, 1946, 1989, 2001, 2008 and 2010, mass balance observations conducted in 1936–1938 and after 2001, energy balance measurements after 2001, and glacier surface velocity derived by kinematic and differential GPS surveys and correlation of SPOT5 images. The approximately 20% volume loss of this glacier in the period 1895–2010 is realistically simulated with the model. After calibration of the model with past observations, it is used to simulate the future response of the glacier during the 21st century. The mass balance model was forced with an ensemble of temperature and precipitation scenarios derived from 10 global and 3 regional climate model simulations using the A1B emission scenario. If the average climate of 2000–2009 is maintained into the future, the volume of the glacier is projected to be reduced by 30% with respect to the present at the end of this century. If the climate warms, as suggested by most of the climate change scenarios, the model projects this glacier to almost disappear by the end of the 21st century. Runoff from the glacier is predicted to increase for the next 30–40 yr and decrease after that as a consequence of the diminishing ice-covered area.

Application of the Maggi Equations to Mathematical Modeling of a Robotic Underwater Vehicle as an Object with Superimposed Non-Holonomic Constraints Treated as Control Laws

Based on torpedoes, a universal mathematical model of a robotic underwater vehicle comprising coupling dynamics of a controlled object with superimposed guidance has been built. Using control laws as kinematic correlation of deviation from pre-defined parameters of ideal control, the control laws have been tied to the dynamic equations of motion.

Non-global structure of the $ \mathcal{O}\left( {\alpha_s^2} \right) $ dijet soft function

High energy scattering processes involving jets generically involve matrix elements of light- like Wilson lines, known as soft functions. These describe the structure of soft contributions to observables and encode color and kinematic correlations between jets. We compute the dijet soft function to O({\alpha}_s^2) as a function of the two jet invariant masses, focusing on terms not determined by its renormalization group evolution that have a non-separable dependence on these masses. Our results include non-global single and double logarithms, and analytic results for the full set of non-logarithmic contributions as well. Using a recent result for the thrust constant, we present the complete O({\alpha}_s^2) soft function for dijet production in both position and momentum space.

Kinematical correlations of dielectrons from semileptonic decays of heavy mesons and Drell-Yan processes at BNL RHIC

We discuss kinematical correlations between charged leptons from semileptonic decays of open charm/bottom, leptons produced in the Drell-Yan mechanism as well as some other mechanisms not included so far in the literature in proton-proton scattering at BNL RHIC. The distributions of charm and bottom quarks/antiquarks are calculated in the framework of the $k_t$-factorization approach. For this calculation we use the Kwieci\'nski unintegrated parton distributions. The hadronization of heavy quarks is done by means of Peterson et al. fragmentation function. We use semileptonic decay functions found by fitting recent semileptonic data obtained by the CLEO and BABAR collaborations. The Drell-Yan processes were calculated including transverse momenta of quarks and antiquarks, also using the Kwieci\'nski parton distributions. We have also took into consideration reactions initiated by purely QED $\gamma^*\gamma^*$-fusion in elastic and inelastic pp collisions as well as recently proposed diffractive mechanism of exclusive charm-anticharm production. The contribution of the later mechanism is rather small. We get good description of the dilepton invariant mass spectrum measured recently by the PHENIX collaboration and present predictions for the dilepton pair transverse momentum distribution as well as distribution in azimuthal angle between electron and positron.

PRODUCTION OF D AND B MESONS AND THEIR SEMILEPTONIC DECAYS

We have calculated the kinematical correlations between charged leptons from semileptonic decays of open charm/bottom as well as leptons produced in the Drell-Yan mechanism in proton-proton collisions at BNL RHIC. Presented production rates for open charm and bottom were estimated by a detailed analysis of so-called nonphotonic electrons. The distributions for charm and bottom quarks pairs are calculated in the kt-factorization approach with the help of the Kwieciński unintegrated parton distributions. The hadronization of heavy quarks is done by means of Peterson et al. fragmentation function. The semileptonic decay functions are found by fitting recent semileptonic data obtained by the CLEO and BABAR. We get good description of recent PHENIX data.

Adaptation to constant-magnitude assistive forces: kinematic and neural correlates

In many robot-assisted rehabilitation and motor skill learning applications, robots generate forces that facilitate movement performance. While there is some evidence that assistance is beneficial, the underlying mechanisms of action are largely unknown, and it is unclear what force patterns are more effective. Here, we investigate how reaching movements (and their neural correlates) are altered by 'assistive' forces. Subjects performed center-out reaching movements, under the influence of a robot-generated force, constant in magnitude and always directed toward the target. The experimental protocol included three phases: (1) baseline (no forces), (2) force field (with two different force levels, 3 N and 6 N, applied in random order), and (3) after-effect (no forces). EEG activity was recorded from motor and frontal cortical areas. In both movement kinematics and EEG activity, we looked at the effects of forces, of adaptation to such forces and at the aftereffects of such adaptation. Assistive forces initially induced a degraded performance and in general alterations in movement kinematics. However, subjects quickly adapted to the perturbation by improving their performance. With regard to EEG activity, we found (1) an increased beta band synchronization just before movements and an alpha band synchronization in the ipsilateral hemisphere, both proportional to force magnitude; (2) a gradual decrease in alpha band synchronization with practice in the contralateral hemisphere; (3) an increase in theta band synchronization in the later stage of the force epochs; and (4) an ipsilateral to contralateral shift (from baseline to aftereffect) of theta band synchronization. These results point to the need for a careful design of assistive forces to effectively facilitate motor performance and motor learning. Moreover, EEG signals exhibit distinct features related to force and adaptation. Therefore, at least in principle, the latter might be used to monitor the learning process and/or to regulate the amount of assistance.

Development and validation of pedestrian sedan bucks using finite-element simulations: a numerical investigation of the influence of vehicle automatic braking on the kinematics of the pedestrian involved in vehicle collisions

Previous vehicle-to-pedestrian impact simulations and experiments using pedestrian dummies and cadavers have shown that factors such as vehicle shape, pedestrian anthropometry and pre-impact conditions influence pedestrian kinematics and injury mechanisms. Generic pedestrian bucks, which approximate the geometrical and stiffness properties of current vehicles, would be useful in studying the influence of vehicle front-end structures on pedestrian kinematics and loading. This study explores the design of pedestrian bucks, intended to represent the basic vehicle front-end structures, consisting of five components: lower stiffener, bumper, hood leading edge and grille, hood and windshield. The deformable parts of the bucks were designed using types of currently manufactured materials, which allow fabricating the bucks in the future. The geometry of pedestrian bucks was approximated according to the contour cross-sections of two sedan vehicles used in previous pedestrian dummy and cadaver impact tests. Other cross-sectional dimensions and the stiffness of the buck components were determined by parameter identification using finite-element (FE) simulations of each sedan model. In the absence of a validated FE model of human, the FE model of the POLAR II pedestrian dummy was used to validate a mid-size sedan (MS) pedestrian buck. A good correlation of the pedestrian dummy kinematics and contact forces obtained in dummy–MS pedestrian buck with the corresponding data from dummy–MS vehicle simulation was achieved. A parametric study using the POLAR II FE model and different buck models – an MS buck and a large-size sedan (LS) buck – were run to study the influence of an automatic braking system for reducing the pedestrian injuries. The vehicle braking conditions showed reductions in the relative velocity of the head to the vehicle and increases in the time of head impact and in the wrap-around-distances (WAD) to primary head contact. The head impact velocity showed a greater sensitivity to the different buck shapes (e.g. LS buck versus MS buck) than to the braking deceleration. The buck FE models developed in this study are expected to be used in sensitivity and optimisation studies for the development of new pedestrian protection systems.

Two-phase interactions through turbulent events as described by fluid–particle correlations

An experimental investigation of a vertical upward, two-phase pipe flow was undertaken to measure kinematic parameters of the fluid and solid phases. The kinematic parameters included Reynolds stress distributions based on quadrant analyses that provided insight in understanding the behavior of two-phase kinematic correlation profiles. The data collected was based on a two-color digital particle image velocimetry (DPIV) technique that simultaneously measured the velocity fields of the fluid and solid phases. From quadrant analysis results, differences in Reynolds stress quadrant profiles between the single- and two-phase conditions were observed near the wall in the range 0.8> r/R>0.55, corresponding to wall distances between 35 and 75 viscous lengths ( y+). Correlation coefficients between the two phases were then calculated, using the fluctuating velocity components of each phase. The extent of the interaction between the two phases was tracked by the changing correlation values versus distance from the wall. The correlation of the fluid and solid phase velocities was highest in the core region of the pipe ( y+∼120), where the effect of turbulent events is reduced; low correlation coefficient values were found at y+<75, where differences of magnitudes, inflection points, etc. of burst and sweep event quadrant analysis profiles were observed. The extent of the influence of wall dynamic turbulent events on the solid phase was observed both by the differences in the relative Reynolds stress quadrant profiles and, more readily, by the changing values of two-phase axial and radial correlation coefficients determined from the simultaneous fluid and solid fluctuating velocities measured by the two-color DPIV methodology. These changing values of the correlation coefficients across the tube reflect the different responses of low inertia (fluid tracers) and high inertia (solid phase glass spheres) particles to the turbulent events. Similar profiles of the axial and radial correlation coefficients were observed, indicating that for the geometry and flow conditions considered, one velocity component of each phase was sufficient to track the spatial extent of turbulent event effects and their interactions with the fluid and solid phases. It is found that the two-color DPIV methodology and two-phase correlation results can give critical insight into the performance of thermal-fluid processes, as burst and sweep events have a large impact on the kinematics and dynamics of particles in the two-phase flow.

Same-sign W pair production as a probe of double-parton scattering at the LHC

We study the production of same-sign W boson pairs at the LHC in double parton interactions. Compared with simple factorised double parton distributions (dPDFs), we show that the recently developed dPDFs, GS09, lead to non-trivial kinematic correlations between the W bosons. A numerical study of the prospects for observing this process using same-sign dilepton signatures, including same-sign WWjj, di-boson and heavy flavour backgrounds, at 14 TeV centre-of-mass energy is then performed. It is shown that a small excess of same-sign dilepton events from double parton scattering over a background dominated by single scattering WZ(gamma*) production could be observed at the LHC.

Kinematic correlates of walking cadence in the foot

Evidence has frequently been reported of modifications in gait patterns within the lower limb related to the cadence of walking. Most reports have concerned relationships between cadence and kinematic and the kinetic changes occurring in the main joints and muscles of the lower limb as a whole. The aim of the present study was to assess whether significant changes are also measurable in kinematics of the foot segments. An existing 15 marker-set protocol allowed a four-segment foot and shank model to be defined for relative rotations between the segments to be calculated. Stereophotogrammetry was employed to record marker position data from ten subjects walking at three cadences. The slow- and normal cadence datasets showed similar profiles of joint rotation in three anatomical planes, but significant differences were found between these and the fast cadence. At all joints, frame-by-frame statistical analysis revealed increased dorsiflexion from heel-strike to midstance (p<0.05) and increased plantarflexion from midstance to toe-off (p<0.05) with increasing cadence. From foot-flat to heel-rise, the fast cadence kinematic data showed a decreased range of motion in the sagittal-plane between forefoot and rearfoot (3.2°±1.2° at slow cadence; 2.0°±0.8° at fast cadence; p<0.05). The cadences imposed and the multisegment protocol revealed significant kinematic changes in the joints of the foot during barefoot walking.

Correlation between preoperative and postoperative knee kinematics in total knee arthroplasty using cruciate retaining designs

The authors evaluated the relationships between preoperative and postoperative kinematics in 50 osteoarthritic knees scheduled for cruciate retaining total knee arthroplasty with regards to posterior femoral roll back and external femoral rotation using a navigation system from 10° to 120° of knee flexion. Although posterior femoral roll back was maintained, external femoral rotation was significantly decreased compared to those of the preoperative knee after total knee arthroplasty. However, the amount of posterior roll back and external femoral rotation after total knee arthroplasty were found to be significantly positively related to those measured preoperatively (r = 0.62 and 0.57, respectively). These significant kinematic correlations may explain why preoperative range of knee motion influences range of motion after total knee arthroplasty.

Spin Hall effect induced by a gravitational field

The experiment by Collela et al. (1975) [1] evidenced in a striking manner how the gravitational field appears in quantum mechanics. Within the modern framework of gauge theories, one can ascribe such effect as due to gauge fields originated from fundamental symmetries of spacetime: local transformations of the Lorentz–Poincaré group. When this gauge principle is applied to the Dirac equation, we obtain kinematical correlations between the gravitational field and the spin of the particles. The phenomenon is similar to the spin Hall effect found in condensed matter systems, although much smaller in magnitude. Actual measurements may require highly precision interferometric techniques with spin-polarized neutrons.

Drell-Yan process in the [formula omitted]-factorizations approach and its competition with semileptonic decays of heavy mesons

We discuss the main mechanisms for inclusive production of lepton pairs. Distributions of leptons in rapidity, azimuthal angle and transverse momentum are calculated in the k t -factorization approach. In our calculations we include not only Fermi motion of hadron constituents but also the emission from the ladders. We use unintegrated parton distributions which fulfill Kwiecinski evolution equations. We calculated both zeroth- and first-order contributions for pp collisions for different energies. These results are compared with experimental data. We have compared kinematic correlations between charged leptons for so-called “nonphotonic electrons” where electrons/positrons are obtained in semileptonic decays of heavy mesons (including c or b quark) and of charged leptons obtained in the Drell-Yan process.

Analysis of kinematic correlations in faults and focal mechanisms with GIS and Fortran programs

The kinematic correlation between faults and focal mechanisms can be quantified using scalar (vector and tensor product) or geometric (rotation pole and angle) measures of the similarity of their orientations. The statistical properties of the correlation may help characterise the spatio-temporal properties of natural datasets and test their congruence with theoretical models. This paper describes GIS and Fortran 90/95 tools for analysing the kinematic correlation of faults, and for simulating fault movements in a homogeneous stress field. As an example, we analyse the Umbria-Marche 1997 seismic sequence with these tools; our results show a positive spatial correlation of seismic events that increases with time following the mainshocks.

Chapter 7 Experimental Tests of QCD

The following sections are included: Inclusive Distributions Exclusive Cross Sections and Form Factors Multiplicity Distribution Kinematical and Dynamical Correlations Topological Event Shapes Bose-Einstein Correlations (BEC) Possible Fractal Structure of Final State Phase-Space

Structural evolution of the Day Nui Con Voi metamorphic complex: Implications on the development of the Red River Shear Zone, Northern Vietnam

The Day Nui Con Voi (DNCV) metamorphic complex in North Vietnam is the southernmost high-grade metamorphic zone along the NW–SE trending Red River Shear Zone (RRSZ) in Indochina. The RRSZ was considered as a classical large-scale continental strike-slip fault that had played a significant role in the continental extrusion of Southeast Asia since the collision of India and Eurasia. Earlier ideas determined the RRSZ as a steep shear zone that penetrated the entire lithosphere. Both metamorphism and structures within rocks along the DNCV metamorphic complex have been previously thought to be formed syn-tectonically by left-lateral shearing of the RRSZ during the Oligocene–Miocene continental escape tectonics. However, our meso- and microstructural re-examination of this region shows that these metamorphic rocks were formed during earlier tectonic episodes unrelated to strike-slip shearing. High angle to near orthogonal overprinting fabrics indicated that this region recorded three episodes of ductile deformation followed by brittle faulting events with different intensity spanning from the Triassic to the Tertiary. D 1 is preserved as NW–SE striking upright folds under garnet grade regional metamorphism during the Triassic Indosinian orogeny as South China block amalgamated with the Indochina block. The large-scale horizontal D 2 folds with a dominant top to N–NW bottom to S–SW sense of shear, and sub-horizontal fold axial planes suggest that the DNCV metamorphic complex remained at midcrustal depths since the Indosinian orogeny. The youngest ductile deformation event, D 3, refolded D 2 recumbent folds into a dome, and uplifted the DNCV as lower-temperature fabrics, S 3, indicated. Steep mylonite zones with left-lateral kinematic indicators and brittle faulting were developed on both limbs of the dome along the steep Song Hong and Song Chay faults during left-lateral movement of the RRSZ. Our new spatial, temporal and kinematic correlations of metamorphic fabrics within the DNCV metamorphic complex support the suggestion that the RRSZ developed after regional metamorphism and remained purely a crustal fault. The complicated deformation history recorded within the DNCV metamorphic complex provides an alternative interpretation and suggests that crustal scale strike-slip faults (such as the RRSZ) need not root from the mantle.

Kinematic Structure of the Orion Nebula Cluster and Its Surroundings1

We present results from 1351 high-resolution spectra of 1215 stars in the Orion Nebula Cluster (ONC) and the surrounding Orion 1c association, obtained with the Hectochelle multiobject echelle spectrograph on the 6.5 m MMT. We confirmed 1111 stars as members, based on their radial velocity and/or Hα emission. The radial velocity distribution of members shows a dispersion of σ = 3.1 km s−1. We found a substantial north-south velocity gradient and spatially coherent structure in the radial velocity distribution, similar to that seen in the molecular gas in the region. We also identified several binary and high velocity stars, a region exhibiting signs of triggered star formation, and a possible foreground population of stars somewhat older than the ONC. Stars without infrared excesses (as detected with the IRAC instrument on the Spitzer Space Telescope) exhibit a wider spread in radial velocity than the infrared excess stars; this spread is mostly due to a blueshifted population of stars that may constitute a foreground population. We also identify some accreting stars, based on Hα, that do not have detectable infrared excesses with IRAC, and thus are potential transitional disk systems (objects with inner disk holes). We propose that the substructure seen in both the stellar and gaseous components is the result of nonuniform gravitational collapse to a filamentary distribution of gas. The spatial and kinematic correlation between the stellar and gaseous components suggests that the region is very young, probably only ~1 crossing time old or less, to avoid shock dissipation and gravitational interactions which would tend to destroy the correlation between stars and gas.

On why the iron K-shell absorption in AGN is not a signature of the local warm/hot intergalactic medium

Abstract We present a comparison between the 2001 XMM–Newton and 2005 Suzaku observations of the quasar, PG 1211+143, at z = 0.0809. Variability is observed in the 7 keV iron K-shell absorption line (at 7.6 keV in the quasar frame), which is significantly weaker in 2005 than during the 2001 XMM–Newton observation. From a recombination time-scale of &amp;lt;4 yr, this implies an absorber density n &amp;gt; 4 × 103 cm−3, while the absorber column is 5 × 1022 &amp;lt; NH &amp;lt; 1 × 1024 cm−2. Thus, the size scale of the absorber is too compact (pc scale) and the surface brightness of the dense gas too high (by 9–10 orders of magnitude) to arise from local hot gas, such as the local bubble, group or warm/hot intergalactic medium (WHIM), as suggested by McKernan, Yaqoob &amp; Reynolds. Instead, the iron K-shell absorption must be associated with an active galactic nucleus (AGN) outflow with mildly relativistic velocities. Finally, we show that the association of the absorption in PG 1211+143 with local hot gas is simply a coincidence, and the comparison between the recession and iron K absorber outflow velocities in other AGN does not reveal a one-to-one kinematic correlation.

Three-body kinematical correlation in the dissociative recombination ofCH2+by three-dimensional imaging

A three-dimensional imaging technique installed at the Heidelberg Test Storage Ring (TSR) has been used to investigate the three-body breakup channels occurring in the dissociative recombination process of the methylene ion ${\text{CH}}_{2}^{+}$. By selecting dissociation planes perpendicular to the molecular beam direction the dissociation kinematics could be measured with unprecedented momentum resolution. Release energies, the relative branching ratio, and the kinematical correlations between the three fragments were determined for the two energetically allowed channels: $\text{C}(^{3}P)+\text{H}(^{2}S)+\text{H}(^{2}S)$ and $\text{C}(^{1}D)+\text{H}(^{2}S)+\text{H}(^{2}S)$.

Doping-dependent evolution of low-energy excitations and quantum phase transitions within an effective model for high-Tc copper oxides

In this paper a mean-field theory for the spin-liquid paramagnetic non-superconducting phase of the p- and n-type high-Tc cuprates is developed. This theory applied to the effective t-t'-t′′-J* model with the ab initio calculated parameters and with the three-site correlated hoppings. The static spin-spin and kinematic correlation functions beyond Hubbard-I approximation are calculated self-consistently. The evolution of the Fermi surface and band dispersion is obtained for the wide range of doping concentrations x. For p-type systems the three different types of behavior are found and the transitions between these types are accompanied by the changes in the Fermi surface topology. Thus a quantum phase transitions take place at x = 0.15 and at x = 0.23.Due to the different Fermi surface topology we found for n-type cuprates only one quantum critical concentration, x = 0.2. The calculated doping dependence of the nodal Fermi velocity and the effective mass are in good agreement with the experimental data.