scholarly journals Friction is preferred over grasp configuration in precision grip grasping

2021 ◽  
Author(s):  
Lina K. Klein ◽  
Guido Maiello ◽  
Roland W. Fleming ◽  
Dimitris Voudouris
Keyword(s):  
Precision Grip ◽  
Frontal Plane ◽  
Object Orientation ◽  
The Other ◽  
Surface Material ◽  
Grasp Stability ◽  
Surface Materials ◽  
Two Factors ◽  
Selection Of

ABSTRACTHow humans visually select where to grasp an object depends on many factors, including grasp stability and preferred grasp configuration. We examined how endpoints are selected when these two factors are brought into conflict: Do people favor stable grasps or do they prefer their natural grasp configurations? Participants reached to grasp one of three cuboids oriented so that its two corners were either aligned with, or rotated away from, each individual’s natural grasp axis (NGA). All objects were made of brass (mass: 420 g) but the surfaces of their sides were manipulated to alter friction: 1) all-brass, 2) two opposing sides covered with wood, while the other two remained of brass, or 3) two opposing sides covered with sandpaper, and the two remaining brass sides smeared with vaseline. Grasps were evaluated as either clockwise (thumb to the left of finger in frontal plane) or counterclockwise of the NGA. Grasp endpoints depended on both object orientation and surface material. For the all-brass object, grasps were bimodally distributed in the NGA-aligned condition but predominantly clockwise in the NGA-unaligned condition. These data reflected participants’ natural grasp configuration independently of surface material. When grasping objects with different surface materials, endpoint selection changed: Participants sacrificed their usual grasp configuration to choose the more stable object sides. A model in which surface material shifts participants’ preferred grip angle proportionally to the perceived friction of the surfaces accounts for our results. Our findings demonstrate that a stable grasp is more important than a biomechanically comfortable grasp configuration.NEW & NOTEWORTHYWhen grasping an object, humans can place their fingers at several positions on its surface. The selection of these endpoints depends on many factors, with two of the most important being grasp stability and grasp configuration. We put these two factors in conflict and examine which is considered more important. Our results highlight that humans are not reluctant to adopt unusual grasp configurations in order to satisfy grasp stability.

scholarly journals Friction is preferred over grasp configuration in precision grip grasping

2021 ◽  
Vol 125 (4) ◽  
pp. 1330-1338
Author(s):  
Lina K. Klein ◽  
Guido Maiello ◽  
Roland W. Fleming ◽  
Dimitris Voudouris
Keyword(s):  
Precision Grip ◽  
Grasp Stability ◽  
Two Factors ◽  
Selection Of

When grasping an object, humans can place their fingers at several positions on its surface. The selection of these endpoints depends on many factors, with two of the most important being grasp stability and grasp configuration. We put these two factors in conflict and examine which is considered more important. Our results highlight that humans are not reluctant to adopt unusual grasp configurations to satisfy grasp stability.

Control of Grasp Stability in Humans Under Different Frictional Conditions During Multidigit Manipulation

1999 ◽  
Vol 82 (5) ◽  
pp. 2393-2405 ◽  
Author(s):  
Magnus K. O. Burstedt ◽  
J. Randall Flanagan ◽  
Roland S. Johansson
Keyword(s):  
Load Distribution ◽  
Safety Margin ◽  
Middle Finger ◽  
The Other ◽  
Surface Material ◽  
Tangential Load ◽  
Normal Forces ◽  
Grasp Stability ◽  
Contact Surfaces ◽  
Lift Off

Control of grasp stability under different frictional conditions has primarily been studied in manipulatory tasks involving two digits only. Recently we found that many of the principles for control of forces originally demonstrated for two-digit grasping also apply to various three-digit grasps. Here we examine the control of grasp stability in a multidigit task in which subjects used the tips of the thumb, index, and middle finger to lift an object. The grasp resembled those used when lifting a cylindrical object from above. The digits either all contacted the same surface material or one of the digits contacted a surface material that was more, or less, slippery than that contacted by the other two digits. The three-dimensional forces and torques applied by each digit and the contact positions were measured along with the position and orientation of the object. The distribution of forces among the digits strongly reflected constraints imposed by the geometric relationship between the object's center of mass and the contact surfaces. On top of this distribution, we observed changes in force coordination related to changes in the combination of surface materials. When all digits contacted the same surface material, the ratio between the normal force and tangential load ( F n: L ratio) was similar across digits and scaled to provide an adequate safety margin against slip. With different contact surfaces subjects adapted the F n: L ratios at the individual digits to the local friction with only small influences by the friction at the other two digits. They accomplished this by scaling the normal forces similarly at all digits and changing the distribution of load among the digits. The surface combination did not, however, influence digit position, tangential torque, or object tilting systematically. The change in load distribution, rather, resulted from interplay between these factors, and the nature of this interplay varied between trials. That is, subjects achieved grasp stability with various combinations of fingertip actions and appeared to exploit the many degrees of freedom offered by the multidigit grasp. The results extend previous findings based on two-digit tasks to multidigit tasks by showing that subjects adjust fingertip forces at each digit to the local friction. Moreover, our findings suggest that subjects adapted the load distribution to the current frictional condition by regulating the normal forces to allow slips to occur early in the lift task, prior to object lift-off.

Investigation of the techniques decreasing the seam slippage in chenille fabrics (Part II)

2011 ◽  
Vol 81 (20) ◽  
pp. 2075-2081 ◽  
Author(s):  
Nazim Pasayev ◽  
Mahmut Korkmaz ◽  
Dilek Baspinar
Keyword(s):  
Theoretical Analysis ◽  
Experimental Studies ◽  
The Other ◽  
Woven Fabric ◽  
Mechanical Forces ◽  
Literature Analysis ◽  
Fabric Structure ◽  
Two Factors ◽  
Sewn Products ◽  
Selection Of

The seam slippage in woven fabric products is an adverse event in sewn products. The purpose of this study is to examine the seam slippage in chenille fabric products which are widely used as upholstery fabrics and to research ways to decrease seam slippage. In this study, the theoretical analysis of the seam slippage mechanism has been performed by the literature analysis and the results of experimental studies which were obtained in Part I. In this analysis, seam slippage is examined as the sum of two factors: the deformation of sewing stitch and the slippage of the fabric yarns by sewing stitch chains. According to the theoretical analysis of the processes, it can be inferred that it is possible to decrease seam slippage by driving the energy of applied mechanical forces to other tasks. Based on the results, the ways to decrease seam slippage, which occur in sewn products, have been determined. Two of them are related to the selection of sewing yarn and sewing parameters based on previous researches. The dependence of the other two ways on the fabric structure supported with adhesive interlining and the selection of sewing type were examined. The results of the experimental studies supported the results of the theoretical analysis.

XI.—The Inheritance of Complex Growth Forms, such as Stature, on Mendel's Theory

1912 ◽  
Vol 31 ◽  
pp. 251-256 ◽  
Author(s):  
John Brownlee
Keyword(s):  
The Other ◽  
Hand Dominance ◽  
Growth Forms ◽  
Other Hand ◽  
Two Factors ◽  
Selection Of

The inheritance of complexes is of great interest. The manner in which this arises on a Mendelian hasis can he most easily seen by the consideration of a simple case. Let two races of different stature mix in equal numbers. Let for simplicity stature depend on two elements (a, a), (c, c) in one race, and on (b, b), (d, d) corresponding elements in the other. Then the permanent race obtained by free mating without any special selection of one parent or another will consist of the following proportions:—Now two factors may come into play: either dominance may not exist and the hybrid be a blend, or, on the other hand, dominance may determine the result of the mating. If dominance does not exist we may rearrange the elements according as they contain one or more element from each original race.

Note on Selection of Coordinate Systems for Geodynamics

1975 ◽  
Vol 26 ◽  
pp. 395-407
Author(s):  
S. Henriksen
Keyword(s):  
Sea Level ◽  
The Other ◽  
Coordinate Systems ◽  
Mean Sea Level ◽  
The Earth ◽  
The One ◽  
Static Systems ◽  
Selection Of

The first question to be answered, in seeking coordinate systems for geodynamics, is: what is geodynamics? The answer is, of course, that geodynamics is that part of geophysics which is concerned with movements of the Earth, as opposed to geostatics which is the physics of the stationary Earth. But as far as we know, there is no stationary Earth – epur sic monere. So geodynamics is actually coextensive with geophysics, and coordinate systems suitable for the one should be suitable for the other. At the present time, there are not many coordinate systems, if any, that can be identified with a static Earth. Certainly the only coordinate of aeronomic (atmospheric) interest is the height, and this is usually either as geodynamic height or as pressure. In oceanology, the most important coordinate is depth, and this, like heights in the atmosphere, is expressed as metric depth from mean sea level, as geodynamic depth, or as pressure. Only for the earth do we find “static” systems in use, ana even here there is real question as to whether the systems are dynamic or static. So it would seem that our answer to the question, of what kind, of coordinate systems are we seeking, must be that we are looking for the same systems as are used in geophysics, and these systems are dynamic in nature already – that is, their definition involvestime.

INTERFERENSI GRAMATIKAL DALAM KUMPULAN CERPEN BIARKAN AKU MEMULAI KARYA NURUL F. HUDA

2019 ◽  
Vol 1 (01) ◽  
pp. 16-23
Author(s):  
Zimmatul Liviana
Keyword(s):  
Short Stories ◽  
Data Collection ◽  
Qualitative Method ◽  
Language Variation ◽  
The Other ◽  
Qualitative Descriptive ◽  
Ofthe Object ◽  
Selection Of ◽  
Descriptive Qualitative

The research grammatical interference in a collection ofshort stories Biarkan Aku Memula iwork Nurul F. Hudaisa collection ofshort storiesset in the back that Is start work Let Nurul F. Huda contains many grammatical interference.The problem of this   study were(1)how   the various morphologi calinterference containedin   a   collection of short stories Biarkan Aku Memulai work Nurul F. Huda. (2)how the various syntactic interference contained in a collection of short stories Biarkan Aku Memulai work Nurul F. Huda. The purposeof this studyis to describe the morphological and         Syntactic interference contained in a collection of short stories Biarkan Aku Memulai work Nurul F. Huda. Sociolinguistics is the study of language variation and use in society. Interference is the event of the use of language elements of one into the other language elements that occur in the speakers themselves. This research uses descriptive qualitative method because to describe the actual realityin order to obtainan accurateand objective. Qualitative descriptive methods were used to analyzethe elements ofa word orphrase that incorporated elements of other languages with the analysis and description of the formulation of the problem is the answer. Data collection techniques using observation techniques, the determination ofthe object of research, the selection of short stories.Based on the analysis of the data in this study can be found that there are six forms of interference morphology, namely (1) the prefix nasal N-sound, (2) the addition of the suffix, (3) the exchange prefix, (4) exchange suffixes, (5) exchange konfiks, (6) removal affixes. While the syntactic interference only on the words and phrases in a sentence. The results of the study it can be concluded that the interference morphology more common than syntactic interference.

Factor Structure of the Hellenic WISC-III for Children with Learning Disabilities

2018 ◽  
Vol 9 (03) ◽  
pp. 20445-20451
Author(s):  
Adam A ◽  
Kiosseoglou G ◽  
Abatzoglou G ◽  
Papaligoura Z.
Keyword(s):  
Learning Disabilities ◽  
Factor Structure ◽  
Factor Model ◽  
The Other ◽  
Clinical Value ◽  
Reasoning Abilities ◽  
Picture Arrangement ◽  
Factorial Model ◽  
Verbal Subtest ◽  
Two Factors

The present research aims to examine the factor structure of the Hellenic WISC-III in a sample of 50 children with learning disabilities. The results show the existence of a factorial model with two factors, one aggregating the Comprehension verbal subtest with four performance subtests and the other the Picture Arrangement performance subtest with four verbal subtests. This two-factor model includes loadings in two factors that relate to the sequencing abilities and the verbal reasoning abilities of children. These findings assert the clinical value of the intelligence evaluation in these children.

The Propaganda Feedback Loop

2018 ◽  
Author(s):  
Yochai Benkler ◽  
Robert Faris ◽  
Hal Roberts
Keyword(s):  
Case Studies ◽  
Feedback Loop ◽  
The Other ◽  
Hillary Clinton ◽  
Donald Trump ◽  
The Public ◽  
False Reporting ◽  
Media Ecosystem ◽  
Crowd Out ◽  
Selection Of

This chapter presents a model of the interaction of media outlets, politicians, and the public with an emphasis on the tension between truth-seeking and narratives that confirm partisan identities. This model is used to describe the emergence and mechanics of an insular media ecosystem and how two fundamentally different media ecosystems can coexist. In one, false narratives that reinforce partisan identity not only flourish, but crowd-out true narratives even when these are presented by leading insiders. In the other, false narratives are tested, confronted, and contained by diverse outlets and actors operating in a truth-oriented norms dynamic. Two case studies are analyzed: the first focuses on false reporting on a selection of television networks; the second looks at parallel but politically divergent false rumors—an allegation that Donald Trump raped a 13-yearold and allegations tying Hillary Clinton to pedophilia—and tracks the amplification and resistance these stories faced.

Visual and Tactile Information About Object-Curvature Control Fingertip Forces and Grasp Kinematics in Human Dexterous Manipulation

2000 ◽  
Vol 84 (6) ◽  
pp. 2984-2997 ◽  
Author(s):  
Per Jenmalm ◽  
Seth Dahlstedt ◽  
Roland S. Johansson
Keyword(s):  
Visual Processing ◽  
Visual Cues ◽  
Grip Force ◽  
Center Of Mass ◽  
Precision Grip ◽  
Sensory Information ◽  
Afferent Input ◽  
Dependent Manner ◽  
Tactile Sensibility ◽  
Grasp Stability

Most objects that we manipulate have curved surfaces. We have analyzed how subjects during a prototypical manipulatory task use visual and tactile sensory information for adapting fingertip actions to changes in object curvature. Subjects grasped an elongated object at one end using a precision grip and lifted it while instructed to keep it level. The principal load of the grasp was tangential torque due to the location of the center of mass of the object in relation to the horizontal grip axis joining the centers of the opposing grasp surfaces. The curvature strongly influenced the grip forces required to prevent rotational slips. Likewise the curvature influenced the rotational yield of the grasp that developed under the tangential torque load due to the viscoelastic properties of the fingertip pulps. Subjects scaled the grip forces parametrically with object curvature for grasp stability. Moreover in a curvature-dependent manner, subjects twisted the grasp around the grip axis by a radial flexion of the wrist to keep the desired object orientation despite the rotational yield. To adapt these fingertip actions to object curvature, subjects could use both vision and tactile sensibility integrated with predictive control. During combined blindfolding and digital anesthesia, however, the motor output failed to predict the consequences of the prevailing curvature. Subjects used vision to identify the curvature for efficient feedforward retrieval of grip force requirements before executing the motor commands. Digital anesthesia caused little impairment of grip force control when subjects had vision available, but the adaptation of the twist became delayed. Visual cues about the form of the grasp surface obtained before contact was used to scale the grip force, whereas the scaling of the twist depended on visual cues related to object movement. Thus subjects apparently relied on different visuomotor mechanisms for adaptation of grip force and grasp kinematics. In contrast, blindfolded subjects used tactile cues about the prevailing curvature obtained after contact with the object for feedforward adaptation of both grip force and twist. We conclude that humans use both vision and tactile sensibility for feedforward parametric adaptation of grip forces and grasp kinematics to object curvature. Normal control of the twist action, however, requires digital afferent input, and different visuomotor mechanisms support the control of the grasp twist and the grip force. This differential use of vision may have a bearing to the two-stream model of human visual processing.

scholarly journals Design Concepts for NiTiNOL Wires to Function as a Sensor

2021 ◽  
Author(s):  
D. Josephine Selvarani Ruth
Keyword(s):  
Shape Memory Alloy ◽  
Electrical Resistance ◽  
Nickel Titanium ◽  
The Other ◽  
Sensing Element ◽  
Proper Selection ◽  
Design Concepts ◽  
Mechanical Element ◽  
Selection Of ◽  
Inverse Hysteresis

AbstractNickel Titanium Naval Ordinance Laboratory (NiTiNOL) is widely called as a shape memory alloy (SMA), a class of nonlinear smart material inherited with the functionally programmed property of varying electrical resistance during the transformation enabling to be positioned as a sensing element. The major challenge to instrument the SMA wires is to suppress the wires’ nonlinearity by proper selection of two important factors. The first factor is influenced by the mechanical biasing element and the other is to identify the sensing current for the sensing device (SMA wires + biasing). This paper focuses on developing SMA wires for sensing in different orientation types and configurations by removing the non-linearity in the system’s output by introducing inverse hysteresis to the wires through the passive mechanical element.

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