Reference Orientation Research Articles

Fourientation activities and the Tutte polynomial

A fourientation of a graph G is a choice for each edge of the graph whether to orient that edge in either direction, leave it unoriented, or biorient it. We may naturally view fourientations as a mixture of subgraphs and graph orientations where unoriented and bioriented edges play the role of absent and present subgraph edges, respectively. Building on work of Backman and Hopkins (forthcoming), we show that given a linear order and a reference orientation of the edge set, one can define activities for fourientations of G which allow for a new 12 variable expansion of the Tutte polynomial TG. Our formula specializes to both an orientation activities expansion of TG due to Las Vergnas (1984) and a generalized activities expansion of TG due to Gordon and Traldi (1990).

Synthesis of arbitrary-shaped textures constrained by the structure tensor field

In this paper, a new algorithm is presented for the nonparametric synthesis of arbitrary-shaped textures from an initial texture sample, called the exemplar, and a reference orientation map, called the reference and intended to constrain the coarse scale orientation flow of the output texture. The synthesis process consists of three stages. First, a dictionary is constructed, composed of rotated versions of the exemplar and of their structure tensor fields. Then a synthetic structure tensor field is constructed from the exemplar’s one, under the constraint of the reference. Finally, the output texture is synthesized from the previously generated structure tensor field, again under the constraint of the reference. Synthesis experiments show that the proposed method is able to faithfully reproduce the visual aspect of input samples while respecting the large-scale orientation flow of the reference. This paves the way toward the synthesis of 3-D textures of arbitrary shapes from 2-D exemplars, with applications in virtual material design.

Propagation of errors in two methods for determining tibial contact locations using single-plane fluoroscopy following total knee arthroplasty

ABSTRACTAnalysis of anterior–posterior (A–P) tibial contact locations following total knee arthroplasty (TKA) provides an objective assessment of the relative motion of the tibia on the femur during activities of daily living. Determining A–P tibial contact locations using single-plane fluoroscopy requires input in the form of the relative 3D position and orientation of the components. Although errors in the relative 3D position and orientation of the components have been quantified, it is unknown how these errors propagate into errors in the A–P tibial contact locations. To assess the propagation of errors for two methods used to calculate A–P tibial contact locations, 1000-iteration Monte Carlo simulations were performed for different reference relative 3D positions and orientations of the femoral component. For each iteration, random errors were added to each of the six degrees of freedom of the reference relative 3D position and orientation and the A–P tibial contact locations were calculated using the closest point method and the penetration method. The root mean squared errors (RMSEs) for the closest point method and penetration method were 1.2 mm and 2.4 mm, respectively. Errors in the A–P tibial contact location due to errors in the relative 3D position and orientation of the components place a lower bound on the errors in computing A–P tibial contact location for each method. The RMSEs of 1.2 mm and 2.4 mm for the closest point and penetration methods, respectively, were due primarily to random errors and indicate that both methods have the potential to provide objective assessment of A-P tibial contact locations following TKA.

Fracture mode identification of low alloy steels and cast irons by electron back-scattered diffraction misorientation analysis

The fracture modes of low alloy steels and cast irons under tensile and fatigue conditions were identified by electron back-scattered diffraction (EBSD) misorientation analysis in this research. The curves of grain reference orientation deviation (GROD) distribution perpendicular to the fracture surface were obtained by EBSD observation, and the characteristics of each fracture mode were identified. The GROD value of the specimen fractured in tension decreases to a constant related to the elongation of corresponding specimen in the far field (farther than 5mm away from the fracture surface). The peak exhibits in GROD curves of two smooth specimens and a notched specimen near the fracture surface (within 5mm away from the fracture surface), and the formation mechanisms were discussed in detail based on the influences of specimen geometries (smooth or notched) and material toughness. The GROD value of fatigue fractured specimen is close to that at undeformed condition in the whole field, except the small area near the crack path. The loading conditions (constant stress amplitude loading or constant stress intensity factor range △K loading) and the EBSD striation formation during fatigue crack propagation were also studied by EBSD observation parallel to the crack path.

Work hardening characteristics and microstructural evolution during hot deformation of a nickel superalloy at moderate strain rates

Hot deformation behaviour of hot isostatically processed (HIPed) experimental nickel superalloy in the moderate strain rate regimes (0.01 s−1 & 0.1 s−1) is investigated by carrying out isothermal constant true strain rate compression experiments over wide temperature ranges (1000 °C, 1050 °C, 1100 °C and 1150 °C). From the experimentally obtained flow curves, the effect of deformation temperature on the work hardening behaviour is analyzed. Three stage behaviour exhibited by the work hardening characteristics is considerably influenced by deformation temperature and strain rate. The critical stress (σc) and critical strain (ec) for triggering dynamic recrystallization determined from the work hardening curves is related to Zener-Hollomon parameter through a power law relationship. Deformation microstructures investigated by Electron Backscattered Diffraction (EBSD) studies highlighted the dominance of discontinuous dynamic recrystallization (DDRX) evidenced by serrated/bulged grain boundaries and necklace type microstructure, although DRX volume fraction is strongly sensitive to deformation conditions. Dislocation accumulation studied by grain reference orientation deviation (GROD) maps corroborates to the observed deformation microstructures. Modest DRX is observed at the lowest deformation temperatures owing to the insufficient thermal energy; however, DDRX kinetics is enhanced at higher temperatures. Additionally, the grain boundary characteristics and misorientation angle distribution are studied and correlated with the microstructural evolution.

Chemical zoning and lattice distortion in uraninite from Olympic Dam, South Australia

Compositionally zoned uraninite from the Olympic Dam iron oxide-copper-gold deposit is rarely preserved, but represents an early product of in situ transformation of primary uraninite. Electron backscatter diffraction data (inverse pole figure, image quality, and grain reference orientation deviation mapping) reveal formation of zoned uraninite to be the result of a sequence of superimposed effects rather than from primary growth mechanisms alone. This is the first known microstructural analysis of uraninite showing crystal-plastic deformation of uraninite via formation and migration of defects and dislocations into tilt boundaries. Defining grain-scale characteristics and microstructural features in radiogenically modified minerals like uraninite carries implications in better understanding the processes involved in their formation, highlights limitations in the use of uraninite for U-Pb chemical ages, as well as for constraining the incorporation and release of daughter radioisotopes, especially where zoning, porosity, fractures, and microstructures are present.

Perceptual Learning of Motion Direction Discrimination Induced by True and False Feedback

Top-down factors such as feedback plays an important role in learning. However, in the literature of perceptual learning, only a few studies have focused on this topic. In the present study, we investigated how different types of feedback affect perceptual learning of motion direction discrimination. We trained participants for six days to discriminate whether the direction of moving dots was the same as the orientation of a fixed reference bar that preceded. The direction was either the same or deflected 1° to one side of the reference orientation during training. The participants were assigned to three groups based on the types of feedback they received during training: true feedback, false feedback, and random feedback. For the true feedback and false feedback groups, we analyzed the data from the learners who correctly reported the deflection and improved discrimination sensitivity, in accordance with their received feedback, after the training. A three-way repeated measure ANOVA for learners in both true and false feedback conditions revealed significant triple interactions among training, direction, and deflection (trueFB:F(1,11)= 13.512, p=0.004; falseFB: F(1,11)= 17.179, p=0.002). Additional analysis revealed that d' significantly changed only for trained direction and deflection after training, but not for other directions or deflections. These findings suggest that feedback can exert significant effect on the learning of motion direction discrimination. Particularly, the false feedback to the subthreshold stimuli during training led to wrong perception and such effect was limited to the trained condition. Meeting abstract presented at VSS 2016

On the nature of unintentional action: a study of force/moment drifts during multifinger tasks.

We explored the origins of unintentional changes in performance during accurate force production in isometric conditions seen after turning visual feedback off. The idea of control with referent spatial coordinates suggests that these phenomena could result from drifts of the referent coordinate for the effector. Subjects performed accurate force/moment production tasks by pressing with the fingers of a hand on force sensors. Turning the visual feedback off resulted in slow drifts of both total force and total moment to lower magnitudes of these variables; these drifts were more pronounced in the right hand of the right-handed subjects. Drifts in individual finger forces could be in different direction; in particular, fingers that produced moments of force against the required total moment showed an increase in their forces. The force/moment drift was associated with a drop in the index of synergy stabilizing performance under visual feedback. The drifts in directions that changed performance (non-motor equivalent) and in directions that did not (motor equivalent) were of about the same magnitude. The results suggest that control with referent coordinates is associated with drifts of those referent coordinates toward the corresponding actual coordinates of the hand, a reflection of the natural tendency of physical systems to move toward a minimum of potential energy. The interaction between drifts of the hand referent coordinate and referent orientation leads to counterdirectional drifts in individual finger forces. The results also demonstrate that the sensory information used to create multifinger synergies is necessary for their presence over the task duration.

Ultrasound imaging of the human medial gastrocnemius muscle: how to orient the transducer so that muscle fascicles lie in the image plane

The length and pennation of muscle fascicles are frequently measured using ultrasonography. Conventional ultrasonography imaging methods only provide two-dimensional images of muscles, but muscles have complex three-dimensional arrangements. The most accurate measurements will be obtained when the ultrasound transducer is oriented so that endpoints of a fascicle lie on the ultrasound image plane and the image plane is oriented perpendicular to the aponeurosis, but little is known about how to find this optimal transducer orientation in the frequently-studied medial gastrocnemius muscle. In the current study, we determined the optimal transducer orientation at 9 sites in the medial gastrocnemius muscle of 8 human subjects by calculating the angle of misalignment between three-dimensional muscle fascicles, reconstructed from diffusion tensor images, and the plane of a virtual ultrasound image. The misalignment angle was calculated for a range of tilts and rotations of the ultrasound transducer relative to a reference orientation that was perpendicular to the skin and parallel to the tibia. With the transducer in the reference orientation, the misalignment was substantial (mean across sites and subjects of 6.5°, range 1.4 to 20.2°). However for all sites and subjects a near-optimal alignment (on average 2.6°, range 0.5° to 6.0°) could be achieved by maintaining 0° tilt and applying a small rotation (typically less than 10°). On the basis of these data we recommend that ultrasonographic measurements of medial gastrocnemius muscle fascicle architecture be obtained, at least for relaxed muscles under static conditions, with the transducer oriented perpendicular to the skin and nearly parallel to the tibia.

A three-scale crystal plasticity model accounting for grain refinement in fcc metals subjected to severe plastic deformations

A new three-scale model of polycrystal accounting for grain refinement is proposed. The model is embedded into the crystal plasticity framework. With the experimental reference to the development of the dislocation induced cell substructure, a single crystallite in the representative grain aggregate is initially subdivided into subdomains with the crystallographic orientations slightly misoriented with respect to the nominal orientation of a parent grain. The predicted misorientation evolution of subgrains with respect to the reference orientation of a crystallite is an indicator of grain refinement. The correlation between the increase of a misorientation angle and a slip activity pattern is analyzed. The model predictions are compared with available experimental data.

Optimum kinematic design of a planar cable-driven parallel robot with wrench-closure gait trajectory

We report the design of a planar cable-driven parallel robot with four cables. The design can generate a wrench-closure trajectory of the lower limb, shank, with applications in gait rehabilitation. Using such a design, any external wrench on the target limb can be balanced using cables for all poses of the limb near to the trajectory in the gait cycle. We calculate the largest wrench-closure circular zone centered at an arbitrary point of the trajectory for a given range of orientations around a reference orientation of the limb. Taking the area of such zones into account for a set of points on a given trajectory, we optimize the robot kinematics with fixed cable attachment points. However, static evaluation of the robot in the trajectory indicates that, in some part of the trajectory, a general external wrench cannot be balanced. Therefore, a reconfigurable design of the robot is investigated in which the cable attachment points on the base can move with respect to the motion of the limb in its trajectory. The area of wrench-closure zones in the trajectory can be increased using different actuation schemes, which are obtained and compared. Finally, a redundant reconfigurable robot with an optimum wrench-closure gait trajectory is proposed.

Global orientation estimation in noisy conditions

The present paper studies the perceived orientation of line patterns with variable elongation, line length, orientation jitter, and presentation time. It evaluates whether the internal noise and sampling efficiency evaluated by equivalent noise paradigm (Pelli 1981) depend on the spatial configuration and temporal characteristics of the stimulation. The evaluated internal noise was compared to the results of double-pass noise estimation. In addition, the eye movements of the participants during active exploration of the line patterns were recorded and analyzed with respect to the stimulus characteristics. The results indicate the presence of late internal noise and show that the internal noise and sampling efficiency strongly depend on the elongation, duration and line length of the patterns. The response time increases with the orientation jitter and with the variability in line length of the patterns. It is longer also near the reference orientation for the low levels of added external noise. These results contradict some of the major assumptions of the variance-summation model and question its applicability in characterizing the perceived orientation of multi-element patterns.

Evaluating Deformation-Induced Grain Orientation Change in a Polycrystal During In Situ Tensile Deformation using EBSD.

Using an in situ load frame within a scanning electron microscope, a microstructural section on the surface of an annealed tantalum (Ta) polycrystalline specimen was mapped at successive tensile strain intervals, up to ~20% strain, using electron backscatter diffraction. A grain identification and correlation technique was developed for characterizing the evolving microstructure during loading. Presenting the correlated results builds on the reference orientation deviation (ROD) map concept where individual orientation measurements within a grain are compared with a reference orientation associated with that grain. In this case, individual orientation measurements in a deformed grain are measured relative to a reference orientation derived from the undeformed (initial) configuration rather than the current deformed configuration as has been done for previous ROD schemes. Using this technique helps reveal the evolution of crystallographic orientation gradients and development of deformation-induced substructure within grains. Although overall crystallographic texture evolved slowly during deformation, orientation spread within grains developed quickly. In some locations, misorientation relative to the original orientation of a grain exceeded 20° by 15% strain. The largest orientation changes often appeared near grain boundaries suggesting that these regions were preferred locations for the initial development of subgrains.

How to measure export performance? Scholars’ vs. practitioners’ answers

This paper investigates the conceptual domain of the export performance construct in a quest for higher content validity, taking into account the judgments of Brazilian managers. In-depth interviews helped elicit the domain of the construct from the meanings and routines of those actually involved with the concept in practice. Our findings suggest that Brazilian managers seem to take a shorter-term, narrower view in terms of the frame of reference and temporal orientation than do academicians. While the economic and market metrics seem to be important both for academicians and managers, the latter seem to assign much more importance to business process metrics than do the former.

Sensory substitution in bilateral vestibular a-reflexic patients.

Patients with bilateral vestibular loss have balance problems in darkness, but maintain spatial orientation rather effectively in the light. It has been suggested that these patients compensate for vestibular cues by relying on extravestibular signals, including visual and somatosensory cues, and integrating them with internal beliefs. How this integration comes about is unknown, but recent literature suggests the healthy brain remaps the various signals into a task-dependent reference frame, thereby weighting them according to their reliability. In this paper, we examined this account in six patients with bilateral vestibular a-reflexia, and compared them to six age-matched healthy controls. Subjects had to report the orientation of their body relative to a reference orientation or the orientation of a flashed luminous line relative to the gravitational vertical, by means of a two-alternative-forced-choice response. We tested both groups psychometrically in upright position (0°) and 90° sideways roll tilt. Perception of body tilt was unbiased in both patients and controls. Response variability, which was larger for 90° tilt, did not differ between groups, indicating that body somatosensory cues have tilt-dependent uncertainty. Perception of the visual vertical was unbiased when upright, but showed systematic undercompensation at 90° tilt. Variability, which was larger for 90° tilt than upright, did not differ between patients and controls. Our results suggest that extravestibular signals substitute for vestibular input in patients’ perception of spatial orientation. This is in line with the current status of rehabilitation programs in acute vestibular patients, targeting at recognizing body somatosensory signals as a reliable replacement for vestibular loss.

Honeybee linguistics—a comparative analysis of the waggle dance among species of Apis

All honeybees use the waggle dance to recruit nestmates. Studies on the dance precision of Apis mellifera have shown that the dance is often imprecise. Two hypotheses have been put forward aimed at explaining this imprecision. The first argues that imprecision in the context of foraging is adaptive as it ensures that the dance advertises the same patch size irrespective of distance. The second argues that the bees are constrained in their ability to be more precise, especially when the source is nearby. Recent studies have found support for the latter hypothesis but not for the ‘tuned-error’ hypothesis, as the adaptive hypothesis became known. Here we investigate intra-dance variation among Apis species. We analyse the dance precision of A. florea, A. dorsata and A. mellifera, in the context of foraging and swarming. A. mellifera performs forage dances in the dark, using gravity as point of reference, and in the light when dancing for nest sites, using the sun as point of reference. Both A. dorsata and A. florea are open-nesting species; they do not use a different point of reference depending on context. A. florea differs from both A. mellifera and A. dorsata in that it dances on a horizontal surface and does not use gravity but instead ‘points’ directly towards the goal when indicating direction. Previous work on A. mellifera has suggested that differences in dance orientation and point of reference can affect dance precision. We find that all three species improve dance precision with increasing dance duration, irrespective of differences in dance orientation and point of reference. When dancing for sources nearby, dances are highly variable. When the distance increases, dance precision converges. The exception is dances performed by A. mellifera on swarms. Here, dance precision decreases as the distance increases. We also show that the size of the patch advertised increases with increasing distance, contrary to what is predicted under the tuned-error hypothesis.

Pattern generation and compliant feedback control for quadrupedal dynamic trot-walking locomotion: experiments on RoboCat-1 and HyQ

In this paper, we introduce a method that synergistically combines an analytical pattern generator and a feedback controller frame, which are developed for the purpose of synthesizing dynamic quadrupedal trot-walking locomotion on flat and uneven surfaces. To begin with, the pattern generator analytically produces feasible and dynamically balanced joint motions in accordance with the desired trot-walking characteristics, with no empirical parameter tuning requirements. In concurrence with the pattern generation, a two-phased controller frame is constructed for closed-loop sensory feedback: (i) virtual admittance controller via force sensing, (ii) upper torso angular momentum regulation via gyro sensing. The former controller evaluates joint force errors and generates the corresponding joint displacement for a given set of virtual spring-damper couples. Together with the position constraints, these displacements are additionally fed-back to local servos for achieving compliant quadrupedal locomotion with which the position/force trade-off is addressed. The second controller, that is simultaneously used, evaluates the upper torso angular momentum rate change error using measured and reference orientation information. It then regulates the torso orientation in a dynamically consistent way as the rotational inertia is characterized. In order to validate the proposed methodology several experiments are conducted on both flat and uneven surfaces, using two robots with distinct properties; a $$\sim $$~7 kg cat-sized electrically actuated quadruped (RoboCat-1), and a $$\sim $$~80 kg Alpine Ibex-sized hydraulically actuated quadruped (HyQ). As a result we demonstrate continuous, repetitive, compliant and dynamically balanced trot-walking cycles in real-robot experiments, adequately confirming the effectiveness of the proposed approach.

SUS304HTB鋼のクリープ損傷過程における結晶粒内ひずみ分布のEBSDによる評価

Creep damage evaluation by EBSD(Electron BackScatter Diffraction pattern) method was conducted on the austenitic stainless steel SUS304HTB as the boiler tube material. Creep damage was imposed under the condition of 650℃/130MPa and 700℃/75MPa with various interruption hours. The longitudinal mid-section of specimen was cut and observed by EBSD equipment and then Phase maps, IPF(Inverse Pole Figure) maps, KAM(Kernel Average Misorientation) maps and GROD(Grain Reference Orientation Deviation) maps were obtained. Phase maps showed the increasing α-phase transformed from γ-phase at the grains oriented with (111) as the normal direction with the increasing time fraction or the accumulated macroscopic creep strain. The misorientation parameters obtained from KAM maps and GROD maps showed increasing trend with increasing time fraction. The distribution function of GROD was regressed on the basis of continuously distributed dislocation theory and its representative coefficient parameter AG showed the good correlation with time fraction or accumulated creep strain. By measuring AG value near creep voids, creep strains were evaluated in the vicinity of creep voids and did not show significant strain concentration compared with the non-voided area. However, the good correlation between the void length and the creep strain evaluated from AG was observed. The AG parameter was considered as an effective quantity obtained from EBSD observation to evaluate creep strain intensity at the grains with and without creep voids irrespectively.

The decision, not the decision task, causes repulsive biases away from the decision boundary

The perceived direction of a random-dot kinematogram in a fine discrimination task is systematically biased away from the decision boundary. Stimulus uncertainty combined with a neural read-out that is optimized for that specific discrimination task was thought to cause these biases (Jazayeri and Movshon, 2007). Based on this explanation, we would expect the biases to disappear if subjects did not have to perform the discrimination task. We conducted two experiments to test this prediction. Experiment 1 (control) was aimed to reproduce the effects of the original study, using stimuli that consisted of an array of line segments (length of 0.5 degs). The orientation of each line segment was drawn from a Gaussian around the array's mean orientation (stimulus orientation). Stimulus orientation was uniformly sampled from a range +/−21 degrees relative to a reference orientation. Black marks indicated the randomly chosen reference orientation. Gray wedges around the reference mark indicated the total range of stimulus orientations (prior). Subjects first had to indicate whether the stimulus orientation was clockwise (CW) or counter-clockwise (CCW) relative to reference orientation. Subsequently they had to estimate the stimulus orientation. Experiment 2 was identical to Experiment 1 except that subjects were given the stimulus' category (CW/CCW) before stimulus presentation. The results show very similar repulsive biases in both experiments. Hence, we conclude that the biases are not the result of a specific, task-dependent neural read-out as previously suggested, but instead are consistent with a “self-consistent“ Bayesian observer model (Stocker and Simoncelli, 2008).

Mechanisms of orientation sensitivity in the human visual system: Part I. Behavioral characteristics of orientation sensitivity. Influence of the task type, experimental conditions, and gender

Orientation sensitivity in the human visual system was studied in three experiments. In the first experiment, 134 subjects determined orientation of the segments of short lines by selecting it from a set of reference orientations (the Benton test). In the second experiment, 41 subjects of those who passed the Benton test determined the proximity of oblique lines to cardinal axes and to the angle of 45 degrees. In the third experiment, the same subjects identified the orientation of 0, 90, 45, and 135 degrees. It was shown that the cardinal orientations (vertical and horizontal) were determined more accurately and faster than the oblique ones. In this case, the erroneous estimates of oblique lines were associated with the effect of “tilt normalization,” which was manifested in the bias towards basic axes. The type of errors was dependent on test conditions: at normal illumination and availability of additional visual information about the cardinal axes, the errors towards horizontal prevailed; and at low light conditions, the errors towards vertical were dominated. Significant gender differences were found: women were worse than men in performing the tasks that require accurate estimation of orientation (the first and third experiments), which indicates the deficiency of metric abilities in them. It is assumed that in women the most pronounced effect of intermediate orientations is associated with gender differences in brain organization of internal reference frame.