Which Mechanical Invariants Are Associated With the Perception of Length and Heaviness of a Nonvisible Handheld Rod? Testing the Inertia Tensor Hypothesis.

It has been suggested that the inertia tensor governs many instances of haptic perception. However, the evidence is inconclusive because other candidate mechanical parameters (i.e., invariants) were not or were insufficiently controlled for in pertinent experiments. By independently varying all candidate mechanical parameters, the authors were able to test the role of the inertia tensor relative to that of other mechanical parameters. The results showed that length perception during rod wielding is not governed by the inertia tensor alone but also by the static moment. In contrast to previous reports, length perception during rod holding and heaviness perception during rod wielding were found to be unrelated to the inertia tensor and strongly related to the static moment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Haptically perceiving the distances reachable with hand-held objects.

Nine experiments are reported on the ability of people to perceive the distances reachable with hand-held rods that they could wield by movements about the wrist but not see. An observed linear relation between perceived and actual reaching distances with the rods held at one end was found to be unaffected by the density of the rods, the direction relative to the body in which they were wielded, and the frequency at which they were wielded. Manipulating (a) the position of an attached weight on an otherwise uniformly dense rod and (b) where a rod was grasped revealed that perceived reaching distance was governed by the principle movement(s) of inertia (I) of the hand-rod system about the axis of rotation. This dependency on moment of inertia (I) was found to hold even when the reaching distance was limited to the length of rod extending beyond an intermediate grasp. An account is given of the haptic subsystem (hand–muscles–joints–nerves) as a smart perceptual instrument in the Runeson (1977) sense, characterizable by an operator equation in which one operator functionally diagonalizes the inertia and strain tensors. Attunement to the invariants of the inertia tensor over major physical transformations may be the defining property of the haptic subsystem. This property is discussed from the Gibsonian (ecological) perspectives of information as invariants over transformations and of intentions as extraordinary constraints on natural law. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of the inertia tensor in perceiving object orientation by dynamic touch.

Ss wielded an occluded L-shaped rod and attempted to perceive the direction in which the rod was pointing with respect to the hand. The pattern of the rod's different resistances to rotation in different directions, quantified by the inertia tensor, changes systematically with the rod's orientation. Perception of orientation by wielding is possible if the tissue deformation consequences of the rod's inertia tensor are detectable. It was shown that perceived orientation was a linear function of actual orientation for both free and restricted wielding and for rods of different-size branches. The eigenvectors of the inertia tensor were implicated as the basis for this haptic perceptual capability. Results are discussed in reference to information–perception specificity and its implications for effortful or dynamic touch. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mechanical invariants are implicated in dynamic touch as a function of their salience in the stimulus flow.

The authors investigated the mechanical basis of length perception through dynamic touch using specially designed rods in which the various moments of mass distribution (mass, static moment, and rotational inertia) were varied independently. In a series of 4 experiments, exploration style and rod orientation were manipulated such that the relative salience of moments of mass distribution varied markedly. Results showed that perceived length was based on the most salient moments. The authors concluded that the notion of salience is crucial for understanding the implication of moments of mass distribution in length perception and that it should play a pivotal role in developing an encompassing theory of dynamic touch. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceiving extents of rods by wielding: Haptic diagonalization and decomposition of the inertia tensor.

We report two experiments on the length-perception capabilities of the hand-related haptic subsystem. On each trial, a visually occluded rod was wielded by the subject at a position intermediate between its two ends. The position was either ? or ? of the rod's length. On two-thirds of the trials, a weight was attached to the rod at a point either above or below its center of gravity and not coincident with the hand's position. In Experiment 1, the subject's task was to perceive the distance reachable with the portion of the rod extending beyond the position of the grasp. In the second experiment, the subject's task was to perceive the distance reachable with the entire rod if it were held at its proximal end. In Experiment 1, perceived reaching distance was a function of the moment of inertia of the amount of rod forward of the grasp about an axis through the proximal end of the rod segment. In Experiment 2, perceived reaching distance was a function of the moment of inertia of the entire rod about the given axis of rotation intermediate between the rod's ends. The results are discussed in terms of (a) the notion of smart perceptual instruments capitalizing on invariant properties of the inertia tensor and (b) how the haptic decomposition of moments of inertia follows the principle of equivalence of forces. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of the inertia tensor in haptically perceiving where an object is grasped.

When an object is held and wielded, a time-invariant quantity of the wielding dynamics is the inertia tensor Iij. Examination of Iij as a function of different locations at which a cylindrical object is grasped revealed that the off-diagonal components of Iij, the products of inertia, related most systematically to grip position. In 3 experiments, Ss wielded an occluded rod held at an intermediate point along its length and reproduced, with the other hand, the felt grip position on a visible rod. In Exp 1, the wielded rods were homogeneous; in Exps 2 and 3, weights were added on either side of the grasp, with different manners of grasp contrasted in Exp 3. In all 3 experiments, perceived hand position was predicted by Iij. Discussion is focused on the role of Iij's eigenvalues in perceiving the magnitudes of objects and Iij's eigenvectors in perceiving hand–object relations (e.g., position of grasp). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spinors and selective dynamic touch.

Nonvisual perception of a hand-held object's length through wielding is known to be a function of the object's inertia tensor about a fixed rotation point in the wrist. The tensor is insufficient, however, to support perceptions of 2 different extents of an object in 2 different directions. The attitude spinor represents the tilt of the object's inertia ellipsoid relative to the hand in 2 oppositely oriented directions of rotation. Predictions about selective dynamic touch based on the spinor's 2-orientedness were confirmed in experiments in which participants wielded in 1 hand either (a) 2 rods, and attempted to perceive the length of one of them, or (b) 1 rod, and attempted to perceive the length of a part. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Inertia tensor and weight-percept models of length perception by static holding.

S. J. Lederman, S. R. Ganeshan, and R. E. Ellis (1996) reported an experiment demonstrating that for occluded rods of equal mass and length but different diameters length perception by static holding was larger for rods of smaller diameter. They concluded that participants inferred length from illusory weight percepts. However, rods of equal mass and length that differ in diameter also differ in the eigenvalues of their respective inertia tensors. In the present experiments, the authors manipulated the diameters (Experiment 1) and the inertial eigenvalues (Experiments 4 and 5) of statically held objects. As has been shown with wielded objects, perceived length was a function of the eigenvalues. Additional experiments failed to confirm the expectation from the weight-percept model that perceived length maps to the estimated weight (Experiments 2 and 3). Physical quantities, not psychological quantities, seem to explain length perception by static holding. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective perception by dynamic touch

Perceiving the length of a rod by dynamic touch is tied to the inertia tensor Iij, a quantification of its resistance to rotational acceleration. Perception of the portion extending in front of the grasp has previously been ascribed to decomposing one component of Iij by attention. The tensorial nature of dynamic touch suggests that this ability must be anchored wholly in the tensor. Three experiments show that perceived partial length is a function of two components of the tensor, one tied primarily to magnitude and the other tied primarily to direction, whereas perceived whole length is a function of a magnitude component alone. Dynamic touch is characterized in terms of a haptic perceptual instrument that softly assembles to exploit Iij differently depending on the intention, producing 1:1 maps that are appropriately scaled for each intention.     

Effortful touch with minimum movement: Revisited.

The ecological static moment-torque model proposed by C. Carello, P. Fitzpatrick, I. Domaniewicz, T. C. Chan, and M. T. Turvey (see record 1992-18467-001) does not uniquely explain the perception of rod length by static holding. Guided by a mechanical analysis of the gravitational forces and torques produced in the hand as it statically holds rods of different lengths and materials at different orientations, we offer 2 additional theoretical explanations, the force-torque and weight-percept models. Experiment 1 demonstrates that all 3 models predict perceived rod length with considerable success. Experiment 2 provides clear experimental support for the force-torque and weight-percept models over the static moment-torque model. Experiment 3 pits the former 2 models against each other. Current results favor the weight-percept model. Implications for theories of haptic weight perception and design of a new tactile sensor are also considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Weight perception and the haptic size–weight illusion are functions of the inertia tensor.

The complex effects of mass and volume on weight perception (e.g., the size-weight illusion) were hypothesized to follow simply from invariants of rotational dynamics. In Experiments 1-3, the rotational inertia of wielded, occluded objects was varied independently of mass, size, and torque. Perceived heaviness depended only on rotational inertia. Reanalysis of J. C. Stevens and L. L. Rubin's (1970) study revealed that size's influence on weight perception depends on specific patterns of the eigenvalues of the inertia tensor. These patterns were simulated in Experiments 4-6 with objects of fixed mass, volume, and visible size. Perceived heaviness decreased and increased, respectively, over object sets with the eigenvalue patterns of (a) constant mass, increasing volume and (b) increasing mass, constant volume. Weight perception and the size-weight illusion depend on stimulus invariants, not inference. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effortful touch with minimal movement.

Perception of the extents of occluded rods was examined under conditions in which a rod was held as steadily as possible. A given rod was held horizontally, on 1 side of its center of mass, with 1 upward (U) and 1 downward (D) force. Extent was perceived when D and U were distributed over the surfaces of 1 hand, 2 hands, and a hand and a knee and if only D or only U was provided anatomically, the other being provided by an environmental support. Increasing the distance between D and U decreased perceived extent when both contact points were anatomical and when only 1 was anatomical. The 1st moment of the mass distribution, a constant, affected perceived extent more than gravitational torque, a variable. Rods of different lengths but of the same 1st moment were not distinguished. Results are discussed in terms of functionally equivalent, haptic perceptual instruments and the detection of invariants. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mechanism of Bond Behavior of Concrete Beams Strengthened with Near-Surface-Mounted CFRP Rods

Bond tests were conducted on concrete beams strengthened with near-surface-mounted (NSM) nonprestressed and prestressed carbon fiber-reinforced polymer (CFRP) rods under static loading. In the NSM technique, the CFRP rods are placed inside precut grooves and bonded to the concrete with epoxy adhesive. Six concrete beams were tested. The test variables included presence of internal tension steel reinforcement (unreinforced and reinforced), use of NSM CFRP strengthening (nonprestressed and prestressed), and type of CFRP rod (spirally wound and sand blasted). The beams were tested statically in four-point bending. Based on the test results, the transfer length for the prestressed CFRP rod in epoxied groove was 150 and 210 mm for the sand blasted and spirally wound rods, respectively. The main failure mode was debonding between the CFRP rod and the epoxy that starts at sections close to the midspan then, as the load increases, it propagates toward the supports. At failure, the beams strengthened with a given rod type showed the same CFRP strain at sections close to the support (29% of ultimate strain for spirally wound bars and 39% of ultimate strain for sand blasted bars). A cracked section analysis was carried out and compared well with the measured results.     

Control-related beliefs and self-reported depressive symptoms in late childhood

Research thus far links depressive symptoms in children to one type of control-related belief: low levels of perceived personal competence. However, child research, unlike adult research, has not supported a linkage between depressive symptoms and another theoretically important control-related belief: perceived noncontingency of outcomes. Here we reexamined the issue, adjusting for limitations in previous methodology by using (a) psychometrically stronger measures of control beliefs, and (b) a general population sample rather than children being treated in mental health clinics. In contrast to previous results, we found that both perceived incompetence and perceived noncontingency were strongly related to children's depression, together accounting for 40% of the variance in Child Depression Inventory scores. We also found, as in previous research, that depressive symptoms were correlated with uncertainty as to the causes of outcomes, especially successes. The findings suggest that children may be susceptible to both "personal helplessness" and "universal helplessness" forms of depression.     

Simulation of austenitic microstructure in rod and wire rolling of quenched and tempered steel grades

The determination of the microstructural and forming parameters of rods and wire from low to medium-alloy quenched and tempered as well as spring steel grades is a prerequisite for the mathematical modelling and optimization of the technology on the basis of process and material criteria. Using the boundary, heat balance and finite difference methods as well as visioplastic investigations, the most important forming parameters were determined in high-speed rolling. The rolling of such steel grades allowed to determine the material constants for the dynamic and static equations of recrystallization. Due to the inhibitive effect of the alloying elements (Mo, V) the investigated steel grades display a comparatively pronounced recrystallization inertia. Accordingly, the austenitic post-recrystallization grain size is very fine and relatively independent of the temperature. Temperature control during rod and wire rolling allows to influence and adjust the austenitic microstructure prior to phase transformation.     

Sufficiency of longitudinal moment of inertia for haptic cylinder length judgments.

Many studies invoke moment of inertia (Iii) as necessary and sufficient information to perceive cylinder length via wielding, yet some assert that Iii is neither necessary (weight, m, or static moment, M, are sufficient) nor sufficient for length judgments (m or M is necessary). Mathematical expressions for Iii not involving m or M imply length, so Iii could be sufficient for cylinder length judgments. In 5 experiments (N = 113), only longitudinal Iii (the smallest principal value) informed cylinder length estimates in a novel task, rolling. Experiment 1 yielded reliable length judgments. Varying diameter supported length scaling (Experiment 2); similar length estimates occurred with both rolling and wielding (Experiment 3); feedback improved rolling length judgments to levels commensurate with wielding (Experiment 4); and length judgments shifted predictably with added mass (Experiment 5). Contrary to proposals in the literature, Iii is sufficient information for cylinder length judgments, absent m or M information, even when Iii is of minimal magnitude and the task quite novel. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Structures,faults, and the rod-plate transition in eutectics

The microstructures of several eutectic alloys were examined by scanning electron microscopy. Eutectic alloys of Ni-W, NiAl-Cr, NiAl-Cr (Mo) were directionally solidified and selectively etched to reveal the microstructure in three dimensions. A variety of rod and plate structures was observed that illustrates the rod-plate transition. In a nonfaceted rod eutectic, a fault structure consisting of branched rods and rod terminations was observed, while in a faceted alloy faults consisted of a web connecting two faceted rods. During solidification, the web structure splits into two faceted rods producing a plate to rod transition. The formation of a web between two rods causes the transition from rods to plate. In Ni-W, the rod structure transformed to plates in grains where the growth direction deviated from being parallel to the facet planes. It was concluded that alignment is a principle factor in the rod plate transition.     

Evaluation of the genotoxic potential of alkylalkanolamines

The production of cell types in the vertebrate retina follows a stereotyped time course. We have focused on a component of the extracellular matrix that may guide this schedule: the laminin beta 2 chain. Here, we have asked directly whether heterotrimeric laminins containing the laminin beta 2 chain can promote the production of presumptive rod photoreceptors ("rods") and have correlated changes in rod production with changes in the production of other cell types. In cultures in which few rods, but many Müller and bipolar cells, are produced, the production of rods can be enhanced sixfold and that of bipolar cells can be reduced by 66%, by exposing cells to a laminin beta 2-rich matrix. Substitution of a laminin beta 2-depleted matrix (created with antisense RNA) returns the density of rods and bipolar cells to control levels. These linked alterations in phenotype expression suggest that laminins may control the choice between rod photoreceptor and rod bipolar cell fates.     

The Inversion-Torsion Potential Function for Hydrazine

The torsion-inversion potential surface for hydrazine has been determined from the rovibrational data using a new rotation-torsion-inversion Hamiltonian. All elements of the inverse moment of inertia tensor have been expanded into mixed Fourier series of large amplitude coordinates. That gives two major advantages: (i) no numerical integration is necessary at any step of calculation, and (ii) the three-dimensional integrals have been replaced by the products of one-dimensional integrals. It has been proven that the inversion-torsion coupling in hydrazine is negligible and the inversion-inversion coupling is very strong. The barrier to inversion of 2072 cm-1 is slightly higher than that in ammonia and the barrier to internal rotation of 934 cm-1 is relatively high but lower than that determined previously from one-dimensional models.