Sequential Impulse Research Articles

Vibrotactile Spatiotemporal Pattern Recognition in Two-Dimensional Space Around Hand.

This study investigated vibrotactile spatiotemporal pattern recognition in the two-dimensional space around a hand. The participants placed their hands on the medium, and identified the recognized pattern presented in the medium. There were 64 rotational patterns, presented with sequential impulse vibrations. We investigated how well humans recognized the patterns presented around their hand, and identified the pattern factors (e.g., rotational direction) that affected recognition accuracy. The probability of obtaining correct answers was 48.9 %. It was observed that the start and end points, rotational direction, and the number of vibrations affected recognition accuracy. It was also found that patterns starting or ending on the ulnar side ( 0°) of the hand were difficult to recognize, whereas those starting or ending on the distal ( 90°) or proximal side ( 270°) of the hand were easily recognizable. Furthermore, we found a type of the oblique effect. Patterns starting or ending in the oblique direction were more difficult to recognize than those in the cardinal direction. We also found that the clockwise rotational pattern was slightly easier to recognize than the counterclockwise rotational pattern. Finally, the underestimation of the judgment of tactile numerosity explains how the number of vibrations in the patterns affected the recognition accuracy. This result can be used as a baseline when the recognition of spatiotemporal patterns outside the body under other conditions is examined in future studies.

Planck scale displacement of a connected mirror pair: An energy measurement in a gravitational field

The accuracy of a center of mass displacement measurement on a body that is under the influence of an external force is considered. Reflection of a photon from a mirror pair that is fixed to a platform which falls freely in a gravitational field is shown to infer displacement of the center of mass of this platform on the order of the Planck length. Such a displacement is a consequence of a quantum (but not a classical) treatment of the interaction: it occurs even though the reflection does not generate sequential impulses on the mirrors. The relationship between the wave and particle nature of reflection is elucidated using an external force that generates harmonic motion of the mirror pair.

Interactive simulation of realistic flexible and tearable membrane using virtual reality and haptic force-feedback interface

The paper deals with the description of a methodology for addressing the real-time simulation of a soft membrane that can be deformed and torn by the interactive two-way action of the user. The methodology makes use of the combination of an efficient real-time solver, a haptic interface with force feedback and it is implemented in a virtual reality environment in order to achieve a very high level of immersion. The elastic properties of the membrane and the corresponding haptic feedback are modelled using an accurate structural model based on a flexible-rigid (f-rigid) multibody model. The f-rigid approach is a trade-off between the accuracy of a full finite element model and the computational efficiency of a multibody model able to be solved using high efficiency sequential impulse solver. The f-rigid model is verified by dedicated experimental tests about nonlinear deformation and rupture. The proposed methodology can be the base of the development of interactive training environments, ergonomic and usability studies and for the assessment and optimization of product design.

Discretization of sequential impulse force of coherent flow structures and its impact on sediment entrainment at threshold conditions

In this paper, a new analysis of bursting events and their influences on bed sediment entrainment at threshold condition of motion is presented. A new concept of categorization, namely splitting bursting events into “group” and “single” cycles of bursting events is proposed. Categorization of these two cycles enables adequate estimation of the impulse force and its influence on the initiation of sediment motion. To achieve these outcomes, a Micro-ADV and a high-speed camera were concurrently used to assess the influence of “group” and “single” cycles of bursting events on the entrainment of sediment particles. At threshold condition, the contributions of sweep events as a “group” were found to be consistently more important than “single” sweep events. The ejection group events provided a secondary role after the sweep group events for particle entrainment. Additionally, the contributions of group outward interactions vary significantly with increasing the average shear stress. Finally, the contribution of inward interaction events was found to be insignificant for all experimental conditions.

Моделирование ограничений на относительное движение шарнирно связанных тел в системах виртуального окружения

The topic of this paper is a real-time simulation of the dynamics of a system of articulated rigid bodies with restrictions on their relative motion. Restrictions are set in the form of inequalities for the relative angles of rotation (for the rotational joints) or relative displacement (for the prismatic joints) of links. Examples of such systems are robots and manipulators, mobile vehicles with trailers, hinged doors, etc. This problem can be presented as a system of linear algebraic equations with linear complements. As a solution for this system the authors propose the method of sequential impulses utilizing a temporal coherence property, which means that the state of a multi-body system (their coordinates) varies slightly for a small period of time. The semi-implicit Euler method is used as the difference scheme. Since the problem presented in the form of a system of linear equations with linear complements is solved relative to velocities, it is necessary to ensure achievement of constraints relative to the body coordinates (task of constraint stabilization). For such a stabilization the authors propose to use the method of split impulses, which ensures stability of the dynamics simulation for a multi-body system. In this paper the authors consider methods used both for the open and closed kinematic chains. The proposed methods and algorithms are implemented in the program modules in the form of dynamic libraries for Windows OS. Their approbation was carried out in the subsystem of dynamics simulation performing simulation of the robots containing joints with restrictions on the parameters of the relative motion. Studies have shown that the proposed methods and algorithms meet the requirements for the dynamics simulation subsystems of the simulators for control of complex dynamic processes, and virtual environment systems. Such technologies can also be used in virtual labs, simulation complexes, systems of augmented virtual environment and other applications.

An impulse-based energy tracking method for collision resolution

Discrete element methods can be based on either penalties or impulses to resolve collisions. A generic impulse based method, the energy tracking method (ETM), is described to resolve collisions between multiple non-convex bodies in three dimensions. As opposed to the standard sequential impulse method (SQM) and simultaneous impulse method (SMM), which also apply impulses to avoid penetration, the energy tracking method changes the relative velocity between two colliding bodies iteratively yet simultaneously. Its main novelty is that impulses are applied gradually at multi-point contacts, and energy changes at the contact points are tracked to ensure conservation. Three main steps are involved in the propagation of the impulses during the single- and multi-contact resolution: compression, restitution-related energy loss, and separation. Numerical tests show that the energy tracking method captures the energy conservation property of perfectly elastic single- and multi-point collisions. ETM exhibits improved angular velocity estimation, as compared to SMM and SQM, as demonstrated by two numerical examples that model multi-point contact between box-shaped objects. Angles of repose estimated for multi-object pack repositioning of spheres, cubes, and crosses are in good agreement with the reported experimental values.

Calibration of an optical tweezer microrheometer by sequential impulse response

We report a robust method for calibrating optical tweezers in any viscoelastic medium. This approach uses two coupled measurements—one from a static experiment in which a trapped particle diffuses passively within the tweezer's harmonic potential and another from a dynamic experiment in which the trap is jumped discontinuously to a new position while the particle undergoes transient relaxation back into the minimum of the optical potential. Together, these are sufficient to determine the stiffness of the trap in a material of unknown rheology. The method is tested in a Newtonian fluid and compares favorably with other means of calibration. The calibration is also per- formed in a non-Newtonian fluid of which standard optical tweezer calibration methods may struggle to characterize. The correctly calibrated optical tweezer microrheometer measures the rheology of polymer solutions in agreement with macrorheological measurements.

Reconstruction of UWB Impulse Train by Parallel Sampling of Cascaded Identical RC Filters

In this framework we present a new method for measurement of the UWB impulse train based on the parallel sampling of the cascaded identical RC filters. We show that the amplitudes and time locations of p sequential impulses can be reconstructed from simultaneous measurement of the outputs from 2p cascaded identical RC filters. The parallel sampling scheme has a wide range of applications including the detection of the ultra wideband (UWB) impulses. Due to identical analog RC filters and buffer amplifiers, the parallel sampling scheme is flexible to implement in VLSI applications.

Numerical simulation of magnetospheric ULF waves excited by positive and negative impulses of solar wind dynamic pressure

The sources of ultra low frequency (ULF) waves in the magnetosphere are generally believed to be either the external solar wind perturbations or the internal plasma instabilities. When a sudden impulse of the solar wind dynamic pressure impinges on the magnetopause, ULF waves might be excited and thus the solar wind energy is transported into the earth’s magnetosphere. In this paper, we study the ULF waves excited by different kinds of sudden solar wind pressure impulses through an MHD simulation. We primarily focus on the responses of the earth’s magnetosphere to positive/negative impulses of solar wind dynamic pressure, and positive-negative impulse pairs. The simulation results show that the ULF waves excited by positive and negative impulse have the same amplitude and frequency, with 180° difference in phase, if the amplitude and durations of the input impulses are the same. In addition, it is found that field line resonances (FLRs) occur at certain L-shell regions of the earth’s magnetosphere after the impact of different positive-negative impulse pairs, which appear to be related to the duration of the impulses and the time interval between the sequential impulses. Another result is that the energy from the solar wind could be transported deeper into the inner magnetosphere by an impulse pair than by a single pulse impact. The results presented in this paper could help us to better understand how energy is transported from solar wind to the earth’s magnetosphere via ULF waves. Also, these results provide some new clues to understanding of how energetic particles in the inner magnetosphere response to different kinds of solar wind pressure impulse impacts including interplanetary shocks.

Two-dimensional kinematic model of piedmont steps formation

The essence of kinematic models is as follows: properties of the topographic substrate (soil ground or rocks), its response to forcing, and the forces are not considered; i.e., we do not introduce dynamic equations of motion. Instead, a dependence of the rate of slope surface subsidence on the slope morphology (its height, inclination, profile, and horizontal curvature) is specified. This can be supplemented by the effect of external factors unrelated to the slope processes. Kinematic models provide insight into the development mechanism of a configuration specified for a certain time moment at a certain dependence of the slope subsidence rate on the form of the slope at the given initial and boundary conditions and under the influence of external factors (for example, tectonic motions). Such an approach is justified by the fact that the laws of substrate deformation needed for composing dynamic equations are poorly known. Therefore, we usually have to specify them with a high degree of uncertainty. At the same time, kinematic models allow us to obtain easily various and clear patterns of slope evolution at different scenarios of the denudation rate. Some of the simplest cases are described in [1‐4] and many other publications. In this work, we suggest a model of the development of a series of piedmonts (piedmont steps) appearing as a result of sequential impulses of tectonic uplifts. For simplicity, we shall limit ourselves to the two-dimensional case and consider a slope the morphology of which does not change along its horizontal extension. We shall consider that the velocity of the slope displacement at each point depends on its morphological characteristics: inclination and profile curvature at each given point, as well as on external factors, such as tectonic motions or accumulation and erosion of material. The influence of the absolute height can appear only on megaslopes, when the difference in climatic conditions is manifested in the course of weathering of rocks. However, here we shall not consider this aspect. Let us consider these factors separately. If z ( x , t ) is the height of the slope ( x is the coordinate axis directed across the slope and t is time), the rate of slope surface subsidence is . The inclination angle of the slope is

Numerical Simulation of Rolling Dynamic Deflectometer Tests

The responses of typical flexible and rigid pavements to the dynamic loads imposed by the rolling dynamic deflectometer (RDD) were investigated. The RDD is a recently developed nondestructive testing vehicle that applies a steady-state harmonic force while continuously moving along the pavement. To find the pavement response to moving harmonic loads, a numerical method using the elastodynamics solution for stationary impulsive loads applied to layered media and the superposition of the effect of sequential loading impulses at different stations (spaced according to the advance velocity of the load) was implemented. The effects of RDD velocity, loading frequency, depth to bedrock, and layer stiffness on the deflection basins were investigated in the longitudinal and transverse directions. The results show that for the vehicle velocities and loading frequencies that will be used in conjunction with the RDD, dynamic effects caused by the motion of the vehicle are negligible, and the deflection basins at any instant of time essentially are the same as those that would be obtained with a stationary static or harmonic load, with the advantage to RDD testing being that the loading magnitude and loading frequency can be changed easily and that profiling is continuous along the pavement.

The muscle motor: `simultaneous' levers or sequential impulses?

We use the step-size distance equation z= u/ n developed in our two previous papers ( z is the step-size distance, u is the actin filament relative velocity and n is the rate of ATP splitting on a given actin filament), and introduce one additional concept: that the impulsive contractile forces developed on an actin filament should proceed sequentially along a given actin–myosin train. This enables us to elucidate some unexplained and puzzling data in the literature, and to predict the surprisingly high values of ATPase in intact muscle that have recently been found experimentally. It seems that a sequential impulsive model of the actin–myosin interaction may give a better explanation of many phenomena in muscle physiology than does the current model of the action of simultaneous levers.

Direct measurement of diffusion rates in high energy synchrotrons using longitudinal beam echoes.

We have made a direct determination of the diffusion rates in a stored, coasting antiproton beam by observing the decay rates associated with beam echoes in the longitudinal plane. The beam echoes, similar to those observed in other fields of physics, are generated by a sequential impulse excitation at harmonics of the beam revolution frequency. The echo envelope follows a characteristic response which, however, can be modified by the presence of even a very weak scattering process, permitting a sensitive determination of the longitudinal diffusion rate in the beam. {copyright} {ital 1996 The American Physical Society.}

Two hard sphere models for the reaction A+BC

In an attempt to understand the mechanism of chemical reactions such as A+BC→AB+C or AC+B, we have constructed two models based upon the assumption that A, B, and C are hard spheres with B and C initially touching. Both models include an accurate estimate of the total cross section for A+BC collisions, the proper angular dependence of the activation energy, and a set of reasonable procedures for selecting the product state (AB+C, AC+B, A+BC, or A+B+C) once the final velocities of the three atoms have been computed. The two models differ in that one uses the sequential impulse model to calculate the final velocities, whereas the other uses the direct interaction with product repulsion (DIPR) model to obtain the velocities. The two models are used to study the O(3P)+H2 system, and the results are compared with quasiclassical trajectory (QCT) calculations on this system. At high energies the DIPR model appears to give better overall agreement with the QCT results. In particular, the QCT calculations show that at high energy the major product channel is the knockout reaction, where the O atom first hits one H atom but then goes on to react with the other atom. This effect is predicted by the DIPR model, but not by the sequential impulse model.

Dynamics of rare-gas atom-diatom reactions

Quasiclassical trajectory calculations have been carried out for reactions between rare-gas atom-diatom pairs of Kr+Ar 2 , Fe+Ar 2 , and Kr+Fe 2 . A potential energy surface represented by pairwise additive diatomic Morse potentials plus a three-body Axilrod-Teller term was used. Experimental scattering angle distributions and the form of the excitation function (∞E -1.9 ) were nearly reproduced. A detailed analysis of time-dependent trajectories indicates that most reactive encounters involve either a knock-out or a sequential impulse collision, with virtually no stripping mechanism in action over the entire collision energy range studied

Reactive cross section for A+B 2→AB+B in the limit of high collision energy

The total cross section for the reaction A + B 2→AB + B has been calculated in closed form in the limit of high collision energy using the sequential impulse model. Only the case that A is heavier than B is considered. The cross section depends primarily on the hard-sphere bond length of the AB molecule and on the ratio D/E, where D is the dissociation energy of AB and E is the relative collision energy. There is a weak dependence on the mass ratio of A to B. The results should be valid for any reaction which takes place on a single potential energy surface at sufficiently high energy. We have also derived closed-form expressions for several differential and doubly differential reactive cross sections. The model agrees well with a hard-sphere trajectory study of the reaction Ar + + H 2→ArH + + H. A detailed comparison of the model predictions with a trajectory study of the reaction Cl − + H 2→ClH + H + e − is given in the companion paper.

A trajectory surface-hopping study of Cl − + H 2 reactive collisions. II. Results at high energy

A trajectory surface-hopping study has been carried out for collisions of Cl − + H 2 at relative collisions energies between 6 and 20 eV. In addition to total cross sections for producing the six product channels, we have computed a number of differential and doubly differential cross sections for the HCl products in reactive collisions at 20 eV. The results are compared with the predictions of a high-energy, sequential impulse model described in the companion paper.

A new mechanism for providing stable molecular products in high energy reactions

A new mechanism for stabilizing product molecules in high-energy chemical reactions is described. It was discovered in quasi-classical trajectory studies of the reactions of Cl −+H 2. It should apply to a wide range of reactions, and it may be the primary source of product molecules with internal energies well below the dissociation limit. It was quite different from the sequential impulse model, which can also give stable products.

Sequential impulse model for chemical reactions: a comparison of the reactive scattering contour diagrams for limiting cases

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSequential impulse model for chemical reactions: a comparison of the reactive scattering contour diagrams for limiting casesS. A. SafronCite this: J. Phys. Chem. 1985, 89, 26, 5713–5719Publication Date (Print):December 1, 1985Publication History Published online1 May 2002Published inissue 1 December 1985https://doi.org/10.1021/j100272a028RIGHTS & PERMISSIONSArticle Views19Altmetric-Citations11LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (770 KB) Get e-Alerts

Sequential impulse model for knockout reactions: a comparison with crossed beam scattering experiments

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSequential impulse model for knockout reactions: a comparison with crossed beam scattering experimentsS. A. SafronCite this: J. Phys. Chem. 1985, 89, 26, 5719–5722Publication Date (Print):December 1, 1985Publication History Published online1 May 2002Published inissue 1 December 1985https://doi.org/10.1021/j100272a029RIGHTS & PERMISSIONSArticle Views13Altmetric-Citations5LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (517 KB) Get e-Alerts