scholarly journals Anisotropic Psychophysical Trends in the Discrimination of Tactile Direction in a Precision Grip

2021 ◽  
Vol 14 ◽  
Author(s):  
Justin Tanner ◽  
Naomi Newman ◽  
Stephen Helms Tillery
Keyword(s):  
Reference Frames ◽  
Detection Threshold ◽  
Precision Grip ◽  
Arm Movement ◽  
Sensitivity Analyses ◽  
Gravity Modeling ◽  
Primary Stimulus ◽  
Safety Margins ◽  
The Subject ◽  
Radial Axis

Tactile cues arising from interactions with objects have a sense of directionality which affects grasp. Low latency responses to varied grip perturbations indicate that grasp safety margins are exaggerated in certain directions and conditions. In a grip with the ulnar-radial axis vertical, evidence suggests that distal and downward directions are more sensitive to task parameters and have larger safety margins. This suggests that, for the purpose of applying forces with the fingers, reference frames with respect to the hand and gravity are both in operation. In this experiment, we examined human sensitivities to the direction of tactile movement in the context of precision grip in orientations either orthogonal to or parallel to gravity. Subjects performed a two-alternative-forced-choice task involving a textured cube which moved orthogonal to their grip axis. Subjects’ arms were placed in a brace that allowed for finger movement but minimized arm movement. Movement of thumb and index joints were monitored via PhaseSpace motion capture. The subject was presented with a textured cube and instructed to lightly grasp the cube, as if it were slipping. In each trial the object was first translated 1 cm in 0° (proximal), 90° (radial), 180° (distal), or 270° (ulnar) and returned to its origin. This primary stimulus was immediately followed by a 10 mm secondary stimulus at a random 5° interval between −30° and 30° of the primary stimulus. Response from the subject after each pair of stimuli indicated whether the test direction felt the same as or different from the primary stimulus. Traditional bias and sensitivity analyses did not provide conclusive results but suggested that performance is best in the ulnar-radial axis regardless of gravity. Modeling of the response curve generated a detection threshold for each primary stimulus. Lower thresholds, indicating improved detection, persisted in the ulnar-radial axis. Anisotropic thresholds of increased detection appear to coincide with digit displacement and appear to be independent of the grasp orientation.

scholarly journals Vulnerability assessment and potential contamination of unconfined aquifers

2018 ◽  
Vol 19 (4) ◽  
pp. 1008-1016 ◽  
Author(s):  
J. Caprario ◽  
A. S. Rech ◽  
A. R. Finotti
Keyword(s):  
Vadose Zone ◽  
Vulnerability Index ◽  
The Other ◽  
Sensitivity Analyses ◽  
Drastic Model ◽  
Groundwater Availability ◽  
Unconfined Aquifers ◽  
Direct Infiltration ◽  
The Subject ◽  
The Impact

Abstract The decline in groundwater availability and quality has become a worldwide issue and has been the subject of several studies in recent decades. In this sense, the goal of this study is to assess the vulnerability of the Campeche Aquifer (Florianopolis, Brazil), identifying potential areas of possible contamination by the direct infiltration of runoff in drainage compensatory techniques. To achieve this goal, the following methodological steps were used: (1) data collection and preparation, (2) application of the DRASTIC model, (3) sensitivity analysis and (4) analysis of potential contamination by compensatory techniques. The results show that approximately 33% of the aquifer area presented moderate vulnerability to contamination. However, 29% of the remaining areas had high and extremely high vulnerability. Analysing the potential of contamination with drainage compensatory structures we verified that approximately 95% of them are located in areas of vulnerability classified as moderate and high. The other 5% were identified in areas with extremely high vulnerability. Sensitivity analyses indicated that the removal of topography, soil type and the impact of the vadose zone caused a large variation in vulnerability index. It is evident that there is a high potential of contamination of groundwater by direct infiltration of drainage compensatory structures.

General Relativity and Cosmology

2020 ◽  
pp. 227-360
Author(s):  
P. J. E. Peebles
Keyword(s):  
Constant Velocity ◽  
Large Scale ◽  
Reference Frames ◽  
Physical Sciences ◽  
Inertial Frames ◽  
Moving Body ◽  
History Of ◽  
The Subject ◽  
Freely Moving ◽  
The Universe

This chapter discusses the development of physical sciences in seemingly chaotic ways, by paths that are at best dimly seen at the time. It refers to the history of ideas as an important part of any science, and particularly worth examining in cosmology, where the subject has evolved over several generations. It also examines the puzzle of inertia, which traces the connection to Albert Einstein's bold idea that the universe is homogeneous in the large-scale average called “cosmological principle.” The chapter cites Newtonian mechanics that defines a set of preferred motions in space, the inertial reference frames, by the condition that a freely moving body has a constant velocity. It talks about Ernst Mach, who argued that inertial frames are determined relative to the motion of the rest of the matter in the universe.

scholarly journals CHEPECLETAS: UN COLECTIVO A FAVOR DE LA MOVILIDAD URBANA SOSTENIBLE

2021 ◽  
pp. 24-43
Author(s):  
Laura Parajeles-Jiménez ◽  
Cristian Silva-Jiménez
Keyword(s):  
Costa Rica ◽  
Reference Frames ◽  
Point Of View ◽  
Collective Actions ◽  
Public Intervention ◽  
Palabras Clave ◽  
Citizen Empowerment ◽  
The Subject ◽  
The City

En Costa Rica se encuentra el colectivo ChepeCletas que ha encauzado sus esfuerzos en mejorar la calidad del ambiente, a través del uso de bicicletas y las caminatas, así como la recuperación de espacios para la intervención pública, con el fn de convertir a la capital en un espacio para todas las personas. Por tanto, este artículo realizó un análisis dentro del colectivo, basado en los marcos de referencia de diagnóstico, pronóstico y motivo, dando como resultado mayor conciencia del impacto ambiental que genera el uso excesivo de vehículos privados, la construcción de un grupo que se siente como familia, incrementando el empoderamiento ciudadano para el cambio social, así como el interés por la ciudad y la necesidad de retomar los espacios que siempre fueron públicos; pero habían sido olvidados. Utilizar los marcos de referencia permite comprender, desde la visión de los integrantes, qué es, qué permite y qué se hace en dicho colectivo. Sumado a esto, se debe recalcar que este artículo aporta nuevos conocimientos respecto del tema, visualiza otra forma de hacer política desde abajo y crea  espacios que integran cada día a más personas. Palabras clave: Movilidad, acciones colectivas, ambiente, política. AbstractIn Costa Rica, where the ChepeCletas collective is  to be found, eforts have been channeled to improve the quality of the environment by  using bicycles and walking, as well as the recovery of spaces bound for public intervention to turn the capital into a space for all people. Therefore, this article conducts an analysis within the group based on the diagnostic, prognostic and motive reference frameworks which result in a greater awareness of the environmental impact than the excessive use of private vehicles generates. Additionally, the  onstruction of a group that feels like family increasing citizen empowerment for social change, as well as interest in the city and the need to retake spaces that were always public but had been forgotten. The use of reference frames allows us to understand, from the point of view of the members, it’s nature, what allows it to be and what is done in said group. In addition to this, it should be emphasized that this article provides new knowledge on the subject, visualizes another way of doing politics from below and creates spaces that integrate more people every day. Keywords: Mobility, collective actions, environment, politics

Accurate Determination of the Cold Detection Threshold with High-Speed Cooling of the Skin

Pain Medicine ◽  
2020 ◽  
Vol 21 (12) ◽  
pp. 3428-3436
Author(s):  
Segolene Lithfous ◽  
Olivier Després ◽  
Thierry Pebayle ◽  
Claudia Casadio ◽  
Andre Dufour
Keyword(s):  
High Speed ◽  
Accurate Determination ◽  
Detection Threshold ◽  
Detection Thresholds ◽  
Temperature Ramp ◽  
Temperature Ramps ◽  
The Subject ◽  
Order Four ◽  
Healthy Participants

Abstract Objective This study used high-speed cooling of the skin and exact control of stimulus duration to measure the cold detection threshold in healthy participants. The objective was to compare the method of limits, in which the temperature is slowly and gradually increased/decreased until the subject perceives the stimulation, and the method of levels, in which the subject must detect brief thermal stimulations close to the threshold of perception. Methods Twenty healthy volunteers (nine women, 11 men) aged 20–30 years participated in the study. The method of limits and method of levels were performed in all subjects in a counterbalanced order. Four cold detection thresholds were measured with the method of levels, with a temperature ramp of 300°C/sec and stimulus durations of 50 ms, 100 ms, 300 ms, and 500 ms. Three thresholds were measured with the method of limits, with temperature ramps of 1°C/sec, 2°C/sec, and 4°C/sec. Results On average, the cold detection thresholds were −0.47°C below skin temperature with the method of levels and −1.67°C the method of limits. Interindividual variability was significantly lower with the method of levels than with the method of limits. Conclusions These results suggest that the method of levels is more accurate than the method of limits for measuring cold detection threshold. The improvement of cold detection threshold measurement may provide new perspectives to more precisely assess the function of A-delta fibers and the spino-thalamic pathway.

Softness Discrimination With a Tool

2000 ◽  
Vol 83 (4) ◽  
pp. 1777-1786 ◽  
Author(s):  
Robert H. LaMotte
Keyword(s):  
Grip Force ◽  
Precision Grip ◽  
Sensory Information ◽  
Mechanical Contact ◽  
Experimental Conditions ◽  
Tactile Cues ◽  
The Subject ◽  
Kinesthetic Information ◽  
Contrast Discrimination ◽  
Anticipatory Motor Control

The abilities of humans to discriminate the softness of rubber objects of differing compliance with a hand-held tool (a stylus) was measured under experimental conditions that differed as to how the tool was used and the kind of sensory information available. When the subject actively tapped or pressed the compliant objects, they discriminated softness as well by means of a stylus as they did by contacting the objects directly with the fingerpad. Discrimination with the stylus was unaffected by whether the stylus was controlled by one or two fingers. While tapping or pressing a stylus held in a precision grip, the grip force increased before, reached a maximum at the same time as, and decreased in parallel with the compressional force. This relationship was suggestive of anticipatory motor control based on an internal model of the motor system and the physical properties of the object. Discrimination was significantly better when tapping as opposed to pressing the objects with the stylus. This was hypothesized as due to the presence of tactile cues generated by the rapid increase in force rate as the stylus struck and indented the object during tapping. During tapping, the magnitude and rate of compressional force produced by the stylus against the object were greater, the harder the object. An additional cue, possibly kinesthetic, during pressing and tapping was the magnitude of indentation of the specimen by the stylus that was greater, the softer the object. Subjects could discriminate differences on softness by tactile cues alone in the absence of kinesthetic when compliant objects were tapped at approximately the same velocity by the experimenter against a stylus in contact with the subject's passive fingerpad. Discrimination deteriorated if the softer specimen of a pair was tapped with a slightly greater velocity than the harder and not possible if the specimens were pressed against the stylus without generating tactile cues of mechanical contact. In contrast, discrimination was possible during active pressing and unaffected by variations in velocity during active tapping. It is concluded that during active movements, kinesthetic information and knowledge of central efferent commands provide useful cues that are not present during passive touch. These cues allow the observer to discriminate differences in object compliance not confounded by differences in applied velocity.

Sensitivity Analysis of 200 mm LOCA at Armenian NPP Unit 2

2004 ◽  
Author(s):  
Armen Amirjanyan ◽  
Tsolak Malakyan ◽  
Jae Jo
Keyword(s):  
Sensitivity Analysis ◽  
Safety Margin ◽  
Sensitivity Analyses ◽  
Equivalent Diameter ◽  
Diesel Generator ◽  
Acceptance Criteria ◽  
Safety Margins ◽  
Station Blackout ◽  
Diesel Generators ◽  
Safety Limit

This paper presents the results of sensitivity analyses of a loss-of-coolant accident (LOCA) with equivalent diameter of 200 mm on a cold leg at Armenian Nuclear Power Plant (ANPP) Unit 2. ANPP is a six-loop WWER-440/270 model of Russian design. Analyses performed for the Technical Assignment for WWER-440/270 reactors showed that this reactor had high safety margins with 100 mm LOCA, which may allow increasing the safety level for the maximum design base LOCA. To demonstrate the adequacy of the safety margin with equivalent diameter of 200 mm using the existing high-pressure injection (HPI) system, analyses of LOCAs with break sizes of the equivalent diameter of 200mm in the primary side were previously performed with highly conservative assumptions using the RELAP5 code (Mod3.2.2β). Results of this study were reported at ICONE 11. The results of LOCA analyses with highly conservative assumptions showed that the acceptance criteria were not exceeded in the cases of a surge line break and equivalent break on a hot leg. However, calculations for a break with equivalent diameter of 200 mm on a cold leg showed that the cladding temperature reached 1235 °C, narrowly exceeding the safety limit mentioned in acceptance criteria (1204 °C), and prompted to conduct additional sensitivity studies with slightly relaxed conservative assumptions. At ANPP, there are two trains of HPI systems with two diesel generators on each train and one additional generator in the reserve state. Each train of diesel generators supplies power to two HPI pumps. However, in the current ANPP configuration, only one HPI pump in each train is automatically switched on to diesel generators in case of a station blackout. Therefore, the previous analysis of LOCA with highly conservative assumptions took credit for only two HPI pumps available after station blackout (i.e., two of diesel generators and reserve diesel generator are not available). The current ANPP modernization plan includes automatic starts of four HPI pumps. For this sensitivity analysis we took credit for one additional HPI pump (namely, three HPI pumps all together). As in the previous calculations, a loss of off-site power was assumed at the moment of accident beginning and simultaneous reactor scram: diesel generators were assumed to be available 20 seconds after the off-site power loss. The results of this sensitivity calculation of LOCA with equivalent diameter of 200 mm on a cold leg show that the cladding temperature stayed far below the safety limit. The peak cladding temperature was 850°C, well below that of the original study (1235°C) and the safety limit in the acceptance criteria (1204°C).

Reaching to Grasp With a Multi-Jointed Arm. I. Computational Model

2002 ◽  
Vol 88 (5) ◽  
pp. 2355-2367 ◽  
Author(s):  
Elizabeth B. Torres ◽  
David Zipser
Keyword(s):  
Error Correction ◽  
Constraint Satisfaction ◽  
Degrees Of Freedom ◽  
Computational Models ◽  
Reference Frames ◽  
Dimensional Space ◽  
Arm Movement ◽  
Human Movement ◽  
Path Selection ◽  
Movement Trajectories

The generation of goal-directed movements requires the solution of many difficult computational problems. Among these are transformations from extrinsic to intrinsic reference frames, specifying solution paths, removing under-specification due to excess degrees of freedom and path multiplicity, constraint satisfaction, and error correction. There are no current motor-control computational models that address these issues in the context of realistic arm movement with redundant degrees of freedom. In this paper, we conjecture there is a geometric stage between sensory input and physical execution. The geometric stage determines movement trajectories independently of forces. It uses a gradient technique that relies on the metric of the space of postures to resolve endpoint path selection, posture-change specification, error correction, and multiple constraint satisfaction on-line without preplanning. The model is instantiated in an arm with seven degrees of freedom that moves in three-dimensional space. Simulated orientation-matching movements are compared with actual human movement data to assess the validity of several of the model's behavioral predictions.

Influence of fingertip contact on illusory arm movements

2004 ◽  
Vol 96 (4) ◽  
pp. 1555-1560 ◽  
Author(s):  
Ely Rabin ◽  
Andrew M. Gordon
Keyword(s):  
Contact Surface ◽  
A Priori ◽  
Point Contact ◽  
Arm Movement ◽  
Elbow Extension ◽  
Eyes Closed ◽  
Tactile Cues ◽  
The Subject ◽  
The Stability ◽  
The Right

Recent evidence suggests that reaching movements are more accurate when end point contact occurs, suggesting that fingertip contact contributes to a final estimation of arm position. In the present study we tested two hypotheses: 1) that fingertip contact influences illusions of arm movement produced by muscle vibration and 2) that this influence depends on the a priori context of the stability of the contact surface. Subjects sat with their elbows on a table and eyes closed. They demonstrated the perceived orientation of the left (cue) arm by mirroring the location with the right (report) arm. We manipulated deep proprioceptive cues by vibrating the left biceps brachia, causing illusions of elbow extension, and tested whether these illusions were altered when the fingertip remained in contact with a stable external surface. The context at this point represents a prior assumption that the external contact surface is stable. Midway through the experiment, the context was changed by challenging the prior assumption that the contact surface was stable by demonstrating that it could move. Unbeknownst to the subject, the external contact surface remained stable during data collection throughout the experiment. As expected, without tactile cues, biceps vibration caused illusory elbow extension. Conditions with fingertip contact and biceps vibration in the stable context demonstrated that contact largely eliminated the overestimation of cue arm elbow angle. However, in the context of a possibly unstable (movable) contact surface, the reports of elbow extension returned. Thus a priori notions about the stability context of an external contact surface influence how this tactile cue is integrated with proprioceptive sensory modalities to generate an estimate of arm location in space. These findings support the notion that tactile cues are used to calibrate proprioception against external spatial frameworks.

scholarly journals Reality in a few thermodynamic reference frames: Statistical thermodynamics from Boltzmann via Gibbs to Einstein

2020 ◽  
Author(s):  
Vasil Dinev Penchev
Keyword(s):  
Reference Frame ◽  
Reference Frames ◽  
Statistical Thermodynamics ◽  
Statistical Thermodynamic ◽  
Scientific Theories ◽  
Common Space ◽  
Starting Point ◽  
The Subject ◽  
The Many ◽  
Selection Of

The success of a few theories in statistical thermodynamics can be correlated with their selectivity to reality. These are the theories of Boltzmann, Gibbs, end Einstein.The starting point is Carnot’s theory, which defines implicitly the general selection of reality relevant to thermodynamics. The three other theories share this selection, but specify it further in detail. Each of them separates a few main aspects within the scope of the implicit thermodynamic reality. Their success grounds on that selection. Those aspects can be represented by corresponding oppositions. These are: macroscopic – microscopic; elements – states; relational – non-relational; and observable – theoretical. They can be interpreted as axes of independent qualities constituting a common qualitative reference frame shared by those theories. Each of them can be situated in this reference frame occupying a different place. This reference frame can be interpreted as an additional selection of reality within Carnot’s initial selection describable as macroscopic and both observable and theoretical. The deduced reference frame refers implicitly to many scientific theories independent of their subject therefore defining a general and common space or subspace for scientific theories (not for all).The immediate conclusion is: The examples of a few statistical thermodynamic theories demonstrate that the concept of “reality” is changed or generalized, or even exemplified (i.e. “de-generalized”) from a theory to another.Still a few more general suggestions referring the scientific realism debate can be added: One can admit that reality in scientific theories is some partially shared common qualitative space or subspace describable by relevant oppositions and rather independent of their subject quite different in general. Many or maybe all theories can be situated in that space of reality, which should develop adding new dimensions in it for still newer and newer theories. Its division of independent subspaces can represent the many-realities conception. The subject of a theory determines some relevant subspace of reality. This represents a selection within reality, relevant to the theory in question. The success of that theory correlates essentially with the selection within reality, relevant to its subject.

scholarly journals Summary of IAU Joint Discussion 16, “The International Celestial Reference System, Maintenance and Future Realizations

2005 ◽  
Vol 13 ◽  
pp. 595-600
Author(s):  
Dennis D. McCarthy
Keyword(s):  
Working Group ◽  
Reference System ◽  
Reference Frames ◽  
General Assembly ◽  
Division 1 ◽  
The Future ◽  
System Maintenance ◽  
The Subject ◽  
The One ◽  
Celestial Reference System

AbstractThe IAU Joint Discussion 16 (JD16) was held in conjunction with the XXVth General Assembly in July, 2003. Papers related to the maintenance of the International Celestial Reference System were presented in the one-day session, and these were followed by discussion that pointed out the need for standard nomenclature. This issue was addressed by the formation of a Division 1 Working Group on the subject. JD16 also pointed out the requirement for a dynamical expression for precession which was addressed by the creation of a Division 1 Working Group on Precession and the Ecliptic. It also showed that although plans are being implemented to provide reference frames for the future, there is a need for improved coordination of astrometric observations. Finally it should be noted that the discussion pointed out the concern for the future organization of IAU Division 1.

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